Statistical downscaling of general-circulation-model- simulated average monthly air temperature to the beginning of flowering of the dandelion (Taraxacum officinale) in Slovenia

NASA Astrophysics Data System (ADS)

Bergant, Klemen; Kajfež-Bogataj, Lučka; Črepinšek, Zalika

2002-02-01

Phenological observations are a valuable source of information for investigating the relationship between climate variation and plant development. Potential climate change in the future will shift the occurrence of phenological phases. Information about future climate conditions is needed in order to estimate this shift. General circulation models (GCM) provide the best information about future climate change. They are able to simulate reliably the most important mean features on a large scale, but they fail on a regional scale because of their low spatial resolution. A common approach to bridging the scale gap is statistical downscaling, which was used to relate the beginning of flowering of Taraxacum officinale in Slovenia with the monthly mean near-surface air temperature for January, February and March in Central Europe. Statistical models were developed and tested with NCAR/NCEP Reanalysis predictor data and EARS predictand data for the period 1960-1999. Prior to developing statistical models, empirical orthogonal function (EOF) analysis was employed on the predictor data. Multiple linear regression was used to relate the beginning of flowering with expansion coefficients of the first three EOF for the Janauary, Febrauary and March air temperatures, and a strong correlation was found between them. Developed statistical models were employed on the results of two GCM (HadCM3 and ECHAM4/OPYC3) to estimate the potential shifts in the beginning of flowering for the periods 1990-2019 and 2020-2049 in comparison with the period 1960-1989. The HadCM3 model predicts, on average, 4 days earlier occurrence and ECHAM4/OPYC3 5 days earlier occurrence of flowering in the period 1990-2019. The analogous results for the period 2020-2049 are a 10- and 11-day earlier occurrence.

Investigating the impact of diurnal cycle of SST on the intraseasonal and climate variability

NASA Astrophysics Data System (ADS)

Tseng, W. L.; Hsu, H. H.; Chang, C. W. J.; Keenlyside, N. S.; Lan, Y. Y.; Tsuang, B. J.; Tu, C. Y.

2016-12-01

The diurnal cycle is a prominent feature of our climate system and the most familiar example of externally forced variability. Despite this it remains poorly simulated in state-of-the-art climate models. A particular problem is the diurnal cycle in sea surface temperature (SST), which is a key variable in air-sea heat flux exchange. In most models the diurnal cycle in SST is not well resolved, due to insufficient vertical resolution in the upper ocean mixed-layer and insufficiently frequent ocean-atmosphere coupling. Here, we coupled a 1-dimensional ocean model (SIT) to two atmospheric general circulation model (ECHAM5 and CAM5). In particular, we focus on improving the representations of the diurnal cycle in SST in a climate model, and investigate the role of the diurnal cycle in climate and intraseasonal variability.

Evaluating the impact of chemical boundary conditions on near surface ozone in regional climate-air quality simulations over Europe

NASA Astrophysics Data System (ADS)

Akritidis, D.; Zanis, P.; Katragkou, E.; Schultz, M. G.; Tegoulias, I.; Poupkou, A.; Markakis, K.; Pytharoulis, I.; Karacostas, Th.

2013-12-01

A modeling system based on the air quality model CAMx driven off-line by the regional climate model RegCM3 is used for assessing the impact of chemical lateral boundary conditions (LBCs) on near surface ozone over Europe for the period 1996-2000. The RegCM3 and CAMx simulations were performed on a 50 km × 50 km grid over Europe with RegCM3 driven by the NCEP meteorological reanalysis fields and CAMx with chemical LBCs from ECHAM5/MOZART global model. The recent past period (1996-2000) was simulated in three experiments. The first simulation was forced using time and space invariant LBCs, the second was based on ECHAM5/MOZART chemical LBCs fixed for the year 1996 and the third was based on ECHAM5/MOZART chemical LBCs with interannual variability. Anthropogenic and biogenic emissions were kept identical for the three sensitivity runs.

High Frequency Chandler Wobble Excitation

NASA Astrophysics Data System (ADS)

Seitz, F.; Stuck, J.; Thomas, M.

2003-04-01

Variations of Earth rotation on sub-daily to secular timescales are caused by mass redistributions in the Earth system as a consequence of geophysical processes and gravitational influences. Forced oscillations of polar motion are superposed by free oscillations of the Earth, i.e. the Chandler wobble and the free core nutation. In order to study the interactions between externally induced polar motion and the Earth's free oscillations, a non-linear gyroscopic model has been developed. In most of the former investigations on polar motion, the Chandler wobble is introduced as a damped oscillation with predetermined frequency and amplitude. However, as the effect of rotational deformation is a backcoupling mechanism of polar motion on the Earth's rotational dynamics, both period and amplitude of the Chandler wobble are time-dependent when regarding additional excitations from, e.g., atmospheric or oceanic mass redistributions. The gyroscopic model is free of any explicit information concerning amplitude, phase, and period of free oscillations. The characteristics of the Earth's free oscillation is reproduced by the model from rheological and geometrical parameters and rotational deformation is taken into account. This enables to study the time variable Chandler oscillation when the gyro is forced with atmospheric and oceanic angular momentum from the global atmospheric ECHAM3-T21 general circulation model together with the ocean model for circulation and tides OMCT driven by ECHAM including surface pressure. Besides, mass redistributions in the Earth's body due to gravitational and loading deformations are regarded and external torques exerted by Moon and Sun are considered. The numerical results of the gyro are significantly related with the geodetically observed time series of polar motion published by the IERS. It is shown that the consistent excitation is capable to counteract the damping and thus to maintain the Chandler amplitude. Spectral analyses of the ECHAM and OMCT forcing fields give no hint for increased excitation power in the Chandler band. Thus it is assumed, that continuous high frequency excitation due to stochastic weather phenomena is responsible for the perpetuation of the Chandler wobble.

Downscaling of sea level and fluxes in the Malacca and Singapore Straits using A2 scenario projections of AR4 GCMs

NASA Astrophysics Data System (ADS)

Tkalich, Pavel; Koshebutsky, Volodymyr; Maderich, Vladimir; Thompson, Bijoy

2013-04-01

IPCC-coordinated work has been completed within Fourth Assessment Report (AR4) to project climate and ocean variables for the 21st century using coupled atmospheric-ocean General Circulation Models (GCMs). Resolution of the GCMs is not sufficient to resolve local features of narrow Malacca and Singapore Straits, having complex coastal line and bathymetry; therefore, dynamical downscaling of ocean variables from the global grid to the regional scale is advisable using ocean models, such as Regional Ocean Modeling System (ROMS). ROMS is customized for the domain centered on the Singapore and Malacca Straits, extending from 98°E to 109°E and 6°S to 14°N. Following IPCC methodology, the modelling is done for the past reference period 1961-1990, and then for the 21st century projections; subsequently, established past and projected trends and variability of ocean parameters are inter-compared. Boundary conditions for the past reference period are extracted from Simple Ocean Data Assimilation (SODA), while the projections are made using A2 scenario runs of ECHAM5 and CCSM3 GCMs. Atmospheric forcing for ROMS is downscaled with WRF using ERA-40 dataset for the past period, and outputs of atmospheric variables of respective GCMs for the projections. ROMS-downscaled regional sea level change during 1961-1990, corrected for the global thermosteric effect, land-ice melting and Global Isostatic Adjustment (GIA) effect, corresponds to a mean total trend of 1.52 mm/year, which is higher than the global estimate 1.25 mm/year and observed global sea-level rise (1.44 mm/year) for the same period. Local linear trend in the Singapore Strait (0.9 mm/year) corresponds to the observed trend at Victoria Dock tide gauge (1.1 mm/year) for the past period. Mean discharges through the Karimata, Malacca and Singapore Straits are 0.9, 0.21 and 0.12 Sv, respectively, fall in the range of observations and recent model estimates. A2 scenario projections using ROMS-ECHAM5 and ROMS-CCSM3 for 2011-2099 suggest that linear trends of sea level rise in Singapore Strait are 5.4 and 6.1 mm/year, respectively. These values fall in the range of global estimates of 3.0-8.5 mm/year. Mean sea level rise is expected around 0.43 m (ROMS-ECHAM5) and 0.47 m (ROMS-CCSM3) in 2099 relative to mean sea level in 2011. These values are greater than median estimation of global sea rise 0.32 under scenario A2. Mean discharge through Singapore Strait for scenario A2 during 2011 to 2099 is projected to be 0.062 Sv for ROMS-ECHAM5 and 0.11 Sv for ROMS-CCSM3. These projections are comparable to the discharges during 1961-1990 (0.065 and 0.11 Sv, respectively). The linear trend in discharges for the period 2011-2099 is relatively small with statistical confidence level being less than 95%. An important feature computationally discovered is the transient reversal of flow in the Singapore Strait during southwest monsoon. In general, the reversals of flow in ROMS-ECHAM5 and ROMS-CCSM3 are observed respectively to occur 1/3 and 1/5 of the whole period.

Impact of tropical Atlantic sea-surface temperature biases on the simulated atmospheric circulation and precipitation over the Atlantic region: An ECHAM6 model study

NASA Astrophysics Data System (ADS)

Eichhorn, Astrid; Bader, Jürgen

2017-09-01

As many coupled atmosphere-ocean general circulation models, the coupled Earth System Model developed at the Max Planck Institute for Meteorology suffers from severe sea-surface temperature (SST) biases in the tropical Atlantic. We performed a set of SST sensitivity experiments with its atmospheric model component ECHAM6 to understand the impact of tropical Atlantic SST biases on atmospheric circulation and precipitation. The model was forced by a climatology of observed global SSTs to focus on simulated seasonal and annual mean state climate. Through the superposition of varying tropical Atlantic bias patterns extracted from the MPI-ESM on top of the control field, this study investigates the relevance of the seasonal variation and spatial structure of tropical Atlantic biases for the simulated response. Results show that the position and structure of the Intertropical Convergence Zone (ITCZ) across the Atlantic is significantly affected, exhibiting a dynamically forced shift of annual mean precipitation maximum to the east of the Atlantic basin as well as a southward shift of the oceanic rain belt. The SST-induced changes in the ITCZ in turn affect seasonal rainfall over adjacent continents. However not only the ITCZ position but also other effects arising from biases in tropical Atlantic SSTs, e.g. variations in the wind field, change the simulation of precipitation over land. The seasonal variation and spatial pattern of tropical Atlantic SST biases turns out to be crucial for the simulated atmospheric response and is essential for analyzing the contribution of SST biases to coupled model mean state biases. Our experiments show that MPI-ESM mean-state biases in the Atlantic sector are mainly driven by SST biases in the tropical Atlantic while teleconnections from other basins seem to play a minor role.

Possible influence of dust on hurricane genesis

NASA Astrophysics Data System (ADS)

Bretl, Sebastian; Reutter, Philipp; Raible, Christoph C.; Ferrachat, Sylvaine; Lohmann, Ulrike

2014-05-01

Tropical Cyclones (TCs) belong to the most extreme events in nature. In the past decade, the possible impact of dust on Atlantic hurricanes receives growing interest. As mineral dust is able to absorb incoming solar radiation and therefore warm the surrounding air, the presence of dust can lead to a reduction of sea surface temperature (SST) and an increase in atmospheric stability. Furthermore, resulting baroclinic effects and the dry Saharan easterly jet lead to an enhanced vertical shear of the horizontal winds. SST, stability, moisture and vertical wind shear are known to potentially impact hurricane activity. But how Saharan dust influences these prerequisites for hurricane formation is not yet clear. Some dynamical mechanisms induced by the SAL might even strengthen hurricanes. An adequate framework for investigating the possible impact of dust on hurricanes is comparing high resolution simulations (~0.5°x0.5°, 31 vertical levels) with and without radiatively active dust aerosols. To accomplish this task, we are using the general circulation model ECHAM6 coupled to a modified version of the aerosol model HAM, ECHAM6-HAM-Dust. Instead of the five aerosol species HAM normally contains, the modified version takes only insoluble dust into account, but modifies the scavenging parameters in order to have a similar lifetime of dust as in the full ECHAM6-HAM. All remaining aerosols are prescribed. To evaluate the effects of dust on hurricanes, a TC detection and tracking method is applied on the results. ECHAM6-HAM-Dust was used in two configurations, one with radiatively active dust aerosols and one with dust being not radiatively active. For both set-ups, 10 Monte-Carlo simulations of the year 2005 were performed. A statistical method which identifies controlling parameters of hurricane genesis was applied on North Atlantic developing and non-developing disturbances in all simulations, comparing storms in the two sets of simulations. Hereby, dust can be assigned a more influencing role on TC genesis in the simulations with active dust. Despite dust is seeming to have a negative influence on TC genesis, the relative importance of dust compared to the sea surface temperature (SST) cannot be determined thoroughly. This is largely due to a similar pattern of SST and dust off the west coast of Africa, so that possible effects of dust and SST could hardly be separated.

Sensitivity of the summertime tropical Atlantic precipitation distribution to convective parameterization and model resolution in ECHAM6

DOE PAGES

Siongco, Angela Cheska; Hohenegger, Cathy; Stevens, Bjorn

2017-02-09

A realistic simulation of the tropical Atlantic precipitation distribution remains a challenge for atmospheric general circulation models, owing to their too coarse resolution that makes it necessary to parameterize convection. During boreal summer, models tend to underestimate the northward shift of the tropical Atlantic rain belt, leading to deficient precipitation over land and an anomalous precipitation maximum over the west Atlantic ocean. In this study, the model ECHAM6 is used to test the sensitivity of the precipitation biases to convective parameterization and horizontal resolution. Two sets of sensitivity experiments are performed. In the first set of experiments, modifications are appliedmore » to the convection scheme in order to investigate the relative roles of the trigger, entrainment, and closure formulations. In the second set, the model is run at high resolution with low-resolution boundary conditions in order to identify the relative contributions of a high-resolution atmosphere, orography, and surface. Results show that the dry bias over land in the model can be reduced by weakening the entrainment rate over land. Over ocean, it is found that the anomalous precipitation maximum occurs because of model choices that decrease the sensitivity of convection to the monsoon circulation in the east Atlantic. A reduction of the west Atlantic precipitation bias can be achieved by (i) using a moisture convergence closure, (ii) increasing the resolution of orography, or (iii) enhancing the production of deep convection in the east Atlantic. As a result, the biases over land and over ocean do not impact each other.« less

Heinrich events simulated across the glacial

NASA Astrophysics Data System (ADS)

Ziemen, F. A.; Mikolajewicz, U.

2015-12-01

Heinrich events are among the most prominent climate change events recorded in proxies across the northern hemisphere. They are the archetype of ice sheet — climate interactions on millennial time scales. Nevertheless, the exact mechanisms that cause Heinrich events are still under discussion, and their climatic consequences are far from being fully understood. We contribute to answering the open questions by studying Heinrich events in a coupled ice sheet model (ISM) atmosphere-ocean-vegetation general circulation model (AOVGCM) framework, where this variability occurs as part of the model generated internal variability. The setup consists of a northern hemisphere setup of the modified Parallel Ice Sheet Model (mPISM) coupled to the global AOVGCM ECHAM5/MPIOM/LPJ. The simulations were performed fully coupled and with transient orbital and greenhouse gas forcing. They span from several millennia before the last glacial maximum into the deglaciation. We analyze simulations where the ISM is coupled asynchronously to the AOVGCM and simulations where the ISM and the ocean model are coupled synchronously and the atmosphere model is coupled asynchronously to them. The modeled Heinrich events show a marked influence of the ice discharge on the Atlantic circulation and heat transport.

Model and Scenario Variations in Predicted Number of Generations of Spodoptera litura Fab. on Peanut during Future Climate Change Scenario

PubMed Central

Srinivasa Rao, Mathukumalli; Swathi, Pettem; Rama Rao, Chitiprolu Anantha; Rao, K. V.; Raju, B. M. K.; Srinivas, Karlapudi; Manimanjari, Dammu; Maheswari, Mandapaka

2015-01-01

The present study features the estimation of number of generations of tobacco caterpillar, Spodoptera litura. Fab. on peanut crop at six locations in India using MarkSim, which provides General Circulation Model (GCM) of future data on daily maximum (T.max), minimum (T.min) air temperatures from six models viz., BCCR-BCM2.0, CNRM-CM3, CSIRO-Mk3.5, ECHams5, INCM-CM3.0 and MIROC3.2 along with an ensemble of the six from three emission scenarios (A2, A1B and B1). This data was used to predict the future pest scenarios following the growing degree days approach in four different climate periods viz., Baseline-1975, Near future (NF) -2020, Distant future (DF)-2050 and Very Distant future (VDF)—2080. It is predicted that more generations would occur during the three future climate periods with significant variation among scenarios and models. Among the seven models, 1–2 additional generations were predicted during DF and VDF due to higher future temperatures in CNRM-CM3, ECHams5 & CSIRO-Mk3.5 models. The temperature projections of these models indicated that the generation time would decrease by 18–22% over baseline. Analysis of variance (ANOVA) was used to partition the variation in the predicted number of generations and generation time of S. litura on peanut during crop season. Geographical location explained 34% of the total variation in number of generations, followed by time period (26%), model (1.74%) and scenario (0.74%). The remaining 14% of the variation was explained by interactions. Increased number of generations and reduction of generation time across the six peanut growing locations of India suggest that the incidence of S. litura may increase due to projected increase in temperatures in future climate change periods. PMID:25671564

Understanding the Central Equatorial African long-term drought using AMIP-type simulations

NASA Astrophysics Data System (ADS)

Hua, Wenjian; Zhou, Liming; Chen, Haishan; Nicholson, Sharon E.; Jiang, Yan; Raghavendra, Ajay

2018-02-01

Previous studies show that Indo-Pacific sea surface temperature (SST) variations may help to explain the observed long-term drought during April-May-June (AMJ) since the 1990s over Central equatorial Africa (CEA). However, the underlying physical mechanisms for this drought are still not clear due to observation limitations. Here we use the AMIP-type simulations with 24 ensemble members forced by observed SSTs from the ECHAM4.5 model to explore the likely physical processes that determine the rainfall variations over CEA. We not only examine the ensemble mean (EM), but also compare the "good" and "poor" ensemble members to understand the intra-ensemble variability. In general, EM and the "good" ensemble member can simulate the drought and associated reduced vertical velocity and anomalous anti-cyclonic circulation in the lower troposphere. However, the "poor" ensemble members cannot simulate the drought and associated circulation patterns. These contrasts indicate that the drought is tightly associated with the tropical Walker circulation and atmospheric teleconnection patterns. If the observational circulation patterns cannot be reproduced, the CEA drought will not be captured. Despite the large intra-ensemble spread, the model simulations indicate an essential role of SST forcing in causing the drought. These results suggest that the long-term drought may result from tropical Indo-Pacific SST variations associated with the enhanced and westward extended tropical Walker circulation.

Consequences of changes in vegetation and snow cover for climate feedbacks in Alaska and northwest Canada

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Bennett, A. P.; Breen, A. L.; Genet, H.; Lindgren, M. A.; Kurkowski, T. A.; McGuire, A. D.; Rupp, T. S.

2016-10-01

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m-2 decade-1 regionally) compared to the CCCMA (+1.3 W m-2 decade-1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (-0.2 to -0.3 W m-2 decade-1). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m-2 decade regionally in the ECHAM scenario compared to +0.76 W m-2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Simulating Heinrich events in a coupled atmosphere-ocean-ice sheet model

NASA Astrophysics Data System (ADS)

Mikolajewicz, Uwe; Ziemen, Florian

2016-04-01

Heinrich events are among the most prominent events of long-term climate variability recorded in proxies across the northern hemisphere. They are the archetype of ice sheet - climate interactions on millennial time scales. Nevertheless, the exact mechanisms that cause Heinrich events are still under discussion, and their climatic consequences are far from being fully understood. We contribute to answering the open questions by studying Heinrich events in a coupled ice sheet model (ISM) atmosphere-ocean-vegetation general circulation model (AOVGCM) framework, where this variability occurs as part of the model generated internal variability without the need to prescribe external perturbations, as was the standard approach in almost all model studies so far. The setup consists of a northern hemisphere setup of the modified Parallel Ice Sheet Model (mPISM) coupled to the global coarse resolution AOVGCM ECHAM5/MPIOM/LPJ. The simulations used for this analysis were an ensemble covering substantial parts of the late Glacial forced with transient insolation and prescribed atmospheric greenhouse gas concentrations. The modeled Heinrich events show a marked influence of the ice discharge on the Atlantic circulation and heat transport, but none of the Heinrich events during the Glacial did show a complete collapse of the North Atlantic meridional overturning circulation. The simulated main consequences of the Heinrich events are a freshening and cooling over the North Atlantic and a drying over northern Europe.

Simulation of Rainfall Variability Over West Africa

NASA Astrophysics Data System (ADS)

Bader, J.; Latif, M.

The impact of sea surface temperature (SST) and vegetation on precipitation over West Africa is investigated with the atmospheric general circulation model ECHAM4.x/T42. Ensemble experiments -driven with observed SST- show that At- lantic SST has a significant influence on JJA precipitation over West Africa. Four- teen experiments were performed in which the climatological SST was enhanced or decreased by one Kelvin in certain ocean areas. Changing SST in the eastern tropi- cal Atlantic only caused significant changes along the Guinea Coast, with a positive SSTA increasing rainfall and a negative reducing it. The response was nearly linear. Changing SST in other ocean areas caused significant changes over West Africa, es- pecially in the Sahel area. The response is found to be non linear, with only negative SSTA leading to significant reduction in Sahel rainfall. Also, the impact of the SSTAs from the different ocean regions was not additive with respect to the rainfall. Four simulations with a coupled model (the simple dynamic vegetation model (SVege) and the ECHAM4-AGCM were coupled) were also performed, driven with observed SST from 1945 to 1998. The standard ECHAM-AGCM -forced by the same observed SST- was able to reproduce the drying trend from the fifties to the mid-eighties in the Sahel, but failed to mirror the magnitude of the rainfall anomalies. The coupled model was not only able to reproduce this drying trend, but was also able to better reproduce the amplitudes of the rainfall anomalies. The dynamic vegetation acted like an amplifier, increasing the SST induced rainfall anomalies.

Prognostic parameterization of cloud ice with a single category in the aerosol-climate model ECHAM(v6.3.0)-HAM(v2.3)

NASA Astrophysics Data System (ADS)

Dietlicher, Remo; Neubauer, David; Lohmann, Ulrike

2018-04-01

A new scheme for stratiform cloud microphysics has been implemented in the ECHAM6-HAM2 general circulation model. It features a widely used description of cloud water with two categories for cloud droplets and raindrops. The unique aspect of the new scheme is the break with the traditional approach to describe cloud ice analogously. Here we parameterize cloud ice by a single category that predicts bulk particle properties (P3). This method has already been applied in a regional model and most recently also in the Community Atmosphere Model 5 (CAM5). A single cloud ice category does not rely on heuristic conversion rates from one category to another. Therefore, it is conceptually easier and closer to first principles. This work shows that a single category is a viable approach to describe cloud ice in climate models. Prognostic representation of sedimentation is achieved by a nested approach for sub-stepping the cloud microphysics scheme. This yields good results in terms of accuracy and performance as compared to simulations with high temporal resolution. Furthermore, the new scheme allows for a competition between various cloud processes and is thus able to unbiasedly represent the ice formation pathway from nucleation to growth by vapor deposition and collisions to sedimentation. Specific aspects of the P3 method are evaluated. We could not produce a purely stratiform cloud where rime growth dominates growth by vapor deposition and conclude that the lack of appropriate conditions renders the prognostic parameters associated with the rime properties unnecessary. Limitations inherent in a single category are examined.

Reconciling the aerosol-liquid water path relationship in the ECHAM6-HAM GCM and the Aerosol_cci/Cloud_cci (A)ATSR dataset by minimizing the effect of aerosol swelling

NASA Astrophysics Data System (ADS)

Neubauer, D.; Christensen, M.; Lohmann, U.; Poulsen, C. A.

2016-12-01

Studies using present day variability to assess statistical relationships between aerosol and cloud properties find different strengths of these relationships between satellite data and general circulation model (GCM) data. This discrepancy can be explained by structural uncertainties due to differences in the analysis/observational scale and the process scale or spurious relationships between aerosol and cloud properties. Such spurious relationships are the growth of aerosol particles in the humid environment surrounding clouds, misclassification of partly cloudy satellite pixels as cloud free pixels, brightening of aerosol particles by sunlight reflected at cloud edges, or effects of clouds on aerosol like processing of aerosol particles in clouds by nucleation or impact scavenging and subsequent growth by heterogeneous chemistry and release by cloud droplet evaporation or wet scavenging of aerosol particles. To minimize the effects of spatial aggregation and spurious relationships we apply a new nearest neighbour approach to high resolution (A)ATSR datasets from the Aerosol_cci and Cloud_cci projects of the Climate Change Initiative (CCI) programme of ESA. For the ECHAM6-HAM GCM we quantify the impact of using dry aerosol (without aerosol water) in the analysis to mimic the effect of the nearest neighbour approach. The aerosol-liquid water path relationship in ECHAM6-HAM is systematically stronger than in (A)ATSR data and cannot be explained by an overestimation of autoconversion when using diagnostic precipitation but rather by aerosol swelling in regions where humidity is high and clouds are present. When aerosol water is removed from the analysis in ECHAM6-HAM the strength of the aerosol-liquid water path relationship agrees much better with the ones of (A)ATSR or MODIS. We further find that while the observed relationships of different satellite sensors ((A)ATSR vs. MODIS) are not always consistent for tested environmental conditions the relationships in ECHAM6-HAM are missing a strong dependence on environmental conditions which is critical for bridging the gap between satellite and model estimates of aerosol indirect forcing.

Tuning a climate model using nudging to reanalysis.

NASA Astrophysics Data System (ADS)

Cheedela, S. K.; Mapes, B. E.

2014-12-01

Tuning a atmospheric general circulation model involves a daunting task of adjusting non-observable parameters to adjust the mean climate. These parameters arise from necessity to describe unresolved flow through parametrizations. Tuning a climate model is often done with certain set of priorities, such as global mean temperature, net top of the atmosphere radiation. These priorities are hard enough to reach let alone reducing systematic biases in the models. The goal of currently study is to explore alternate ways to tune a climate model to reduce some systematic biases that can be used in synergy with existing efforts. Nudging a climate model to a known state is a poor man's inverse of tuning process described above. Our approach involves nudging the atmospheric model to state of art reanalysis fields thereby providing a balanced state with respect to the global mean temperature and winds. The tendencies derived from nudging are negative of errors from physical parametrizations as the errors from dynamical core would be small. Patterns of nudging are compared to the patterns of different physical parametrizations to decipher the cause for certain biases in relation to tuning parameters. This approach might also help in understanding certain compensating errors that arise from tuning process. ECHAM6 is a comprehensive general model, also used in recent Coupled Model Intercomparision Project(CMIP5). The approach used to tune it and effect of certain parameters that effect its mean climate are reported clearly, hence it serves as a benchmark for our approach. Our planned experiments include nudging ECHAM6 atmospheric model to European Center Reanalysis (ERA-Interim) and reanalysis from National Center for Environmental Prediction (NCEP) and decipher choice of certain parameters that lead to systematic biases in its simulations. Of particular interest are reducing long standing biases related to simulation of Asian summer monsoon.

Evaluation of stratospheric temperature simulation results by the global GRAPES model

NASA Astrophysics Data System (ADS)

Liu, Ningwei; Wang, Yangfeng; Ma, Xiaogang; Zhang, Yunhai

2017-12-01

Global final analysis (FNL) products and the general circulation spectral model (ECHAM) were used to evaluate the simulation of stratospheric temperature by the global assimilation and prediction system (GRAPES). Through a series of comparisons, it was shown that the temperature variations at 50 hPa simulated by GRAPES were significantly elevated in the southern hemisphere, whereas simulations by ECHAM and FNL varied little over time. The regional warming predicted by GRAPES seemed to be too distinct and uncontrolled to be reasonable. The temperature difference between GRAPES and FNL (GRAPES minus FNL) was small at the start time on the global scale. Over time, the positive values became larger in more locations, especially in parts of the southern hemisphere, where the warming predicted by GRAPES was dominant, with a maximal value larger than 24 K. To determine the reasons for the stratospheric warming, we considered the model initial conditions and ozone data to be possible factors; however, a comparison and sensitivity test indicated that the errors produced by GRAPES were not significantly related to either factor. Further research focusing on the impact of factors such as vapor, heating rate, and the temperature tendency on GRAPES simulations will be conducted.

Aerosol processing in mixed-phase clouds in ECHAM5-HAM: Model description and comparison to observations

NASA Astrophysics Data System (ADS)

Hoose, C.; Lohmann, U.; Stier, P.; Verheggen, B.; Weingartner, E.

2008-04-01

The global aerosol-climate model ECHAM5-HAM has been extended by an explicit treatment of cloud-borne particles. Two additional modes for in-droplet and in-crystal particles are introduced, which are coupled to the number of cloud droplet and ice crystal concentrations simulated by the ECHAM5 double-moment cloud microphysics scheme. Transfer, production, and removal of cloud-borne aerosol number and mass by cloud droplet activation, collision scavenging, aqueous-phase sulfate production, freezing, melting, evaporation, sublimation, and precipitation formation are taken into account. The model performance is demonstrated and validated with observations of the evolution of total and interstitial aerosol concentrations and size distributions during three different mixed-phase cloud events at the alpine high-altitude research station Jungfraujoch (Switzerland). Although the single-column simulations cannot be compared one-to-one with the observations, the governing processes in the evolution of the cloud and aerosol parameters are captured qualitatively well. High scavenged fractions are found during the presence of liquid water, while the release of particles during the Bergeron-Findeisen process results in low scavenged fractions after cloud glaciation. The observed coexistence of liquid and ice, which might be related to cloud heterogeneity at subgrid scales, can only be simulated in the model when assuming nonequilibrium conditions.

Global Warming In A Regional Model of The Atlantic Ocean - Echam4/opyc3 In Flame 4/3

NASA Astrophysics Data System (ADS)

Schweckendiek, U.; Willebrand, J.

The reaction of the Thermohaline Circulation (THC) in most climate models on global warming scenarios is a weakening of the THC. An exception is the ECHAM4/OPYC3 simulation whose stable behaviour is traced back to a strongly enhanced evaporation and as a consequence to a development of a salt anomaly in the tropics and subtropics of the Atlantic Ocean (Latif et al.,2000). This salt signal is advected into convection regions and compensates the reduction of surface density due to surface heating and freshening. To examine this scenario for a more realistic ocean model, data from this model is used to drive a reginal model of the Atlantic Ocean. In order to test the crucial mechanisms for the maintainance of the meridional overturning, we have performed sensitivity studies by focussing on different combinations of the anomalous freshwater and heat fluxes. The results demonstrate that for the stabilising effect to become effective the salt sig- nal has to enter the GIN-Seas and subsequently the overflow waters, underlining the importance of the overflows for the THC. The Labrador Sea Convection is however uneffected by this stabilising salt signal and its convection ultimatly breaks down un- der surface warming and freshening.

Consequences of changes in vegetation and snow cover for climate feedbacks in Alaska and northwest Canada

USGS Publications Warehouse

Euskirchen, Eugénie S.; Bennett, A. P.; Breen, Amy L.; Genet, Helene; Lindgren, Michael A.; Kurkowski, Tom; McGuire, A. David; Rupp, T. Scott

2016-01-01

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m−2 decade−1regionally) compared to the CCCMA (+1.3 W m−2 decade−1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (−0.2 to −0.3 W m−2 decade−1). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m−2decade regionally in the ECHAM scenario compared to +0.76 W m−2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Implementation of the MEGAN (v2.1) biogenic emission model in the ECHAM6-HAMMOZ chemistry climate model

NASA Astrophysics Data System (ADS)

Henrot, Alexandra-Jane; Stanelle, Tanja; Schröder, Sabine; Siegenthaler, Colombe; Taraborrelli, Domenico; Schultz, Martin G.

2017-02-01

A biogenic emission scheme based on the Model of Emissions of Gases and Aerosols from Nature (MEGAN) version 2.1 (Guenther et al., 2012) has been integrated into the ECHAM6-HAMMOZ chemistry climate model in order to calculate the emissions from terrestrial vegetation of 32 compounds. The estimated annual global total for the reference simulation is 634 Tg C yr-1 (simulation period 2000-2012). Isoprene is the main contributor to the average emission total, accounting for 66 % (417 Tg C yr-1), followed by several monoterpenes (12 %), methanol (7 %), acetone (3.6 %), and ethene (3.6 %). Regionally, most of the high annual emissions are found to be associated with tropical regions and tropical vegetation types. In order to evaluate the implementation of the biogenic model in ECHAM-HAMMOZ, global and regional biogenic volatile organic compound (BVOC) emissions of the reference simulation were compared to previous published experiment results with MEGAN. Several sensitivity simulations were performed to study the impact of different model input and parameters related to the vegetation cover and the ECHAM6 climate. BVOC emissions obtained here are within the range of previous published estimates. The large range of emission estimates can be attributed to the use of different input data and empirical coefficients within different setups of MEGAN. The biogenic model shows a high sensitivity to the changes in plant functional type (PFT) distributions and associated emission factors for most of the compounds. The global emission impact for isoprene is about -9 %, but reaches +75 % for α-pinene when switching from global emission factor maps to PFT-specific emission factor distributions. The highest sensitivity of isoprene emissions is calculated when considering soil moisture impact, with a global decrease of 12.5 % when the soil moisture activity factor is included in the model parameterization. Nudging ECHAM6 climate towards ERA-Interim reanalysis has an impact on the biogenic emissions, slightly lowering the global total emissions and their interannual variability.

Progress in Global Multicompartmental Modelling of DDT

NASA Astrophysics Data System (ADS)

Stemmler, I.; Lammel, G.

2009-04-01

Dichlorophenyltrichloroethane, DDT, and its major metabolite dichlorophenyldichloroethylene, DDE, are long-lived in the environment (persistent) and circulate since the 1950s. They accumulate along food chains, cause detrimental effects in marine and terrestrial wild life, and pose a hazard for human health. DDT was widely used as an insecticide in the past and is still in use in a number of tropical countries to combat vector borne diseases like malaria and typhus. It is a multicompartmental substance with only a small mass fraction residing in air. A global multicompartment chemistry transport model (MPI-MCTM; Semeena et al., 2006) is used to study the environmental distribution and fate of dichlorodiphenyltrichloroethane (DDT). For the first time a horizontally and vertically resolved global model was used to perform a long-term simulation of DDT and DDE. The model is based on general circulation models for the ocean (MPIOM; Marsland et al., 2003) and atmosphere (ECHAM5). In addition, an oceanic biogeochemistry model (HAMOCC5.1; Maier-Reimer et al., 2005 ) and a microphysical aerosol model (HAM; Stier et al., 2005 ) are included. Multicompartmental substances are cycling in atmosphere (3 phases), ocean (3 phases), top soil (3 phases), and vegetation surfaces. The model was run for 40 years forced with historical agricultural application data of 1950-1990. The model results show that the global environmental contamination started to decrease in air, soil and vegetation after the applications peaked in 1965-70. In some regions, however, the DDT mass had not yet reached a maximum in 1990 and was still accumulating mass until the end of the simulation. Modelled DDT and DDE concentrations in atmosphere, ocean and soil are evaluated by comparison with observational data. The evaluation of the model results indicate that degradation of DDE in air was underestimated. Also for DDT, the discrepancies between model results and observations are related to uncertainties of input parameters. Furthermore, better resolution of some processes could improve model performance. References: Marsland S.J., Haak H., Jungclaus J.H., Latif M., Röske F. (2003): The Max-Planck-Institute global ocean/sea ice model with orthogonal curvilinear coordinates. Ocean Modelling 5, 91-127 Maier-Reimer E. , Kriest I., Segschneider J., Wetzel P. : The HAMburg Ocean Carbon Cycle Model HAMOCC 5.1 - Technical Description Release 1.1 (2005),Reports on Earth System Science 14 Stier P. , Feichter J. (2005), Kinne S., Kloster S., Vignati E., Wilson J.Ganzeveld L., Tegen I., Werner M., Blakanski Y., Schulz M., Boucher O., Minikin A., Petzold A.: The aerosol-climate model ECHAM5-HAM. Atmos. Chem. Phys 5, 1125-1156 Semeena V.S., Feichter J., Lammel G. (2006): Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants - examples of DDT and γ-HCH. Atmos. Chem. Phys. 6, 1231-1248

Decomposition of Sources of Errors in Seasonal Streamflow Forecasting over the U.S. Sunbelt

NASA Technical Reports Server (NTRS)

Mazrooei, Amirhossein; Sinah, Tusshar; Sankarasubramanian, A.; Kumar, Sujay V.; Peters-Lidard, Christa D.

2015-01-01

Seasonal streamflow forecasts, contingent on climate information, can be utilized to ensure water supply for multiple uses including municipal demands, hydroelectric power generation, and for planning agricultural operations. However, uncertainties in the streamflow forecasts pose significant challenges in their utilization in real-time operations. In this study, we systematically decompose various sources of errors in developing seasonal streamflow forecasts from two Land Surface Models (LSMs) (Noah3.2 and CLM2), which are forced with downscaled and disaggregated climate forecasts. In particular, the study quantifies the relative contributions of the sources of errors from LSMs, climate forecasts, and downscaling/disaggregation techniques in developing seasonal streamflow forecast. For this purpose, three month ahead seasonal precipitation forecasts from the ECHAM4.5 general circulation model (GCM) were statistically downscaled from 2.8deg to 1/8deg spatial resolution using principal component regression (PCR) and then temporally disaggregated from monthly to daily time step using kernel-nearest neighbor (K-NN) approach. For other climatic forcings, excluding precipitation, we considered the North American Land Data Assimilation System version 2 (NLDAS-2) hourly climatology over the years 1979 to 2010. Then the selected LSMs were forced with precipitation forecasts and NLDAS-2 hourly climatology to develop retrospective seasonal streamflow forecasts over a period of 20 years (1991-2010). Finally, the performance of LSMs in forecasting streamflow under different schemes was analyzed to quantify the relative contribution of various sources of errors in developing seasonal streamflow forecast. Our results indicate that the most dominant source of errors during winter and fall seasons is the errors due to ECHAM4.5 precipitation forecasts, while temporal disaggregation scheme contributes to maximum errors during summer season.

Characteristics of the ocean simulations in the Max Planck Institute Ocean Model (MPIOM) the ocean component of the MPI-Earth system model

NASA Astrophysics Data System (ADS)

Jungclaus, J. H.; Fischer, N.; Haak, H.; Lohmann, K.; Marotzke, J.; Matei, D.; Mikolajewicz, U.; Notz, D.; von Storch, J. S.

2013-06-01

MPI-ESM is a new version of the global Earth system model developed at the Max Planck Institute for Meteorology. This paper describes the ocean state and circulation as well as basic aspects of variability in simulations contributing to the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The performance of the ocean/sea-ice model MPIOM, coupled to a new version of the atmosphere model ECHAM6 and modules for land surface and ocean biogeochemistry, is assessed for two model versions with different grid resolution in the ocean. The low-resolution configuration has a nominal resolution of 1.5°, whereas the higher resolution version features a quasiuniform, eddy-permitting global resolution of 0.4°. The paper focuses on important oceanic features, such as surface temperature and salinity, water mass distribution, large-scale circulation, and heat and freshwater transports. In general, these integral quantities are simulated well in comparison with observational estimates, and improvements in comparison with the predecessor system are documented; for example, for tropical variability and sea ice representation. Introducing an eddy-permitting grid configuration in the ocean leads to improvements, in particular, in the representation of interior water mass properties in the Atlantic and in the representation of important ocean currents, such as the Agulhas and Equatorial current systems. In general, however, there are more similarities than differences between the two grid configurations, and several shortcomings, known from earlier versions of the coupled model, prevail.

The on-line coupled atmospheric chemistry model system MECO(n) - Part 5: Expanding the Multi-Model-Driver (MMD v2.0) for 2-way data exchange including data interpolation via GRID (v1.0)

NASA Astrophysics Data System (ADS)

Kerkweg, Astrid; Hofmann, Christiane; Jöckel, Patrick; Mertens, Mariano; Pante, Gregor

2018-03-01

As part of the Modular Earth Submodel System (MESSy), the Multi-Model-Driver (MMD v1.0) was developed to couple online the regional Consortium for Small-scale Modeling (COSMO) model into a driving model, which can be either the regional COSMO model or the global European Centre Hamburg general circulation model (ECHAM) (see Part 2 of the model documentation). The coupled system is called MECO(n), i.e., MESSy-fied ECHAM and COSMO models nested n times. In this article, which is part of the model documentation of the MECO(n) system, the second generation of MMD is introduced. MMD comprises the message-passing infrastructure required for the parallel execution (multiple programme multiple data, MPMD) of different models and the communication of the individual model instances, i.e. between the driving and the driven models. Initially, the MMD library was developed for a one-way coupling between the global chemistry-climate ECHAM/MESSy atmospheric chemistry (EMAC) model and an arbitrary number of (optionally cascaded) instances of the regional chemistry-climate model COSMO/MESSy. Thus, MMD (v1.0) provided only functions for unidirectional data transfer, i.e. from the larger-scale to the smaller-scale models.Soon, extended applications requiring data transfer from the small-scale model back to the larger-scale model became of interest. For instance, the original fields of the larger-scale model can directly be compared to the upscaled small-scale fields to analyse the improvements gained through the small-scale calculations, after the results are upscaled. Moreover, the fields originating from the two different models might be fed into the same diagnostic tool, e.g. the online calculation of the radiative forcing calculated consistently with the same radiation scheme. Last but not least, enabling the two-way data transfer between two models is the first important step on the way to a fully dynamical and chemical two-way coupling of the various model instances.In MMD (v1.0), interpolation between the base model grids is performed via the COSMO preprocessing tool INT2LM, which was implemented into the MMD submodel for online interpolation, specifically for mapping onto the rotated COSMO grid. A more flexible algorithm is required for the backward mapping. Thus, MMD (v2.0) uses the new MESSy submodel GRID for the generalised definition of arbitrary grids and for the transformation of data between them.In this article, we explain the basics of the MMD expansion and the newly developed generic MESSy submodel GRID (v1.0) and show some examples of the abovementioned applications.

The chemistry-climate model ECHAM6.3-HAM2.3-MOZ1.0

NASA Astrophysics Data System (ADS)

Schultz, Martin G.; Stadtler, Scarlet; Schröder, Sabine; Taraborrelli, Domenico; Franco, Bruno; Krefting, Jonathan; Henrot, Alexandra; Ferrachat, Sylvaine; Lohmann, Ulrike; Neubauer, David; Siegenthaler-Le Drian, Colombe; Wahl, Sebastian; Kokkola, Harri; Kühn, Thomas; Rast, Sebastian; Schmidt, Hauke; Stier, Philip; Kinnison, Doug; Tyndall, Geoffrey S.; Orlando, John J.; Wespes, Catherine

2018-05-01

The chemistry-climate model ECHAM-HAMMOZ contains a detailed representation of tropospheric and stratospheric reactive chemistry and state-of-the-art parameterizations of aerosols using either a modal scheme (M7) or a bin scheme (SALSA). This article describes and evaluates the model version ECHAM6.3-HAM2.3-MOZ1.0 with a focus on the tropospheric gas-phase chemistry. A 10-year model simulation was performed to test the stability of the model and provide data for its evaluation. The comparison to observations concentrates on the year 2008 and includes total column observations of ozone and CO from IASI and OMI, Aura MLS observations of temperature, HNO3, ClO, and O3 for the evaluation of polar stratospheric processes, an ozonesonde climatology, surface ozone observations from the TOAR database, and surface CO data from the Global Atmosphere Watch network. Global budgets of ozone, OH, NOx, aerosols, clouds, and radiation are analyzed and compared to the literature. ECHAM-HAMMOZ performs well in many aspects. However, in the base simulation, lightning NOx emissions are very low, and the impact of the heterogeneous reaction of HNO3 on dust and sea salt aerosol is too strong. Sensitivity simulations with increased lightning NOx or modified heterogeneous chemistry deteriorate the comparison with observations and yield excessively large ozone budget terms and too much OH. We hypothesize that this is an impact of potential issues with tropical convection in the ECHAM model.

Impact of physical permafrost processes on hydrological change

NASA Astrophysics Data System (ADS)

Hagemann, Stefan; Blome, Tanja; Beer, Christian; Ekici, Altug

2015-04-01

Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. As it is a thermal phenomenon, its characteristics are highly dependent on climatic factors. The impact of the currently observed warming, which is projected to persist during the coming decades due to anthropogenic CO2 input, certainly has effects for the vast permafrost areas of the high northern latitudes. The quantification of these effects, however, is scientifically still an open question. This is partly due to the complexity of the system, where several feedbacks are interacting between land and atmosphere, sometimes counterbalancing each other. Moreover, until recently, many global circulation models (GCMs) and Earth system models (ESMs) lacked the sufficient representation of permafrost physics in their land surface schemes. Within the European Union FP7 project PAGE21, the land surface scheme JSBACH of the Max-Planck-Institute for Meteorology ESM (MPI-ESM) has been equipped with the representation of relevant physical processes for permafrost studies. These processes include the effects of freezing and thawing of soil water for both energy and water cycles, thermal properties depending on soil water and ice contents, and soil moisture movement being influenced by the presence of soil ice. In the present study, it will be analysed how these permafrost relevant processes impact projected hydrological changes over northern hemisphere high latitude land areas. For this analysis, the atmosphere-land part of MPI-ESM, ECHAM6-JSBACH, is driven by prescribed SST and sea ice in an AMIP2-type setup with and without the newly implemented permafrost processes. Observed SST and sea ice for 1979-1999 are used to consider induced changes in the simulated hydrological cycle. In addition, simulated SST and sea ice are taken from a MPI-ESM simulation conducted for CMIP5 following the RCP8.5 scenario. The corresponding simulations with ECHAM6-JSBACH are used to assess differences in projected hydrological changes induced by the permafrost relevant processes.

Distribution of N2O in the atmosphere under global warming - a simulation study with the MPI Earth System Model

NASA Astrophysics Data System (ADS)

Kracher, Daniela; Manzini, Elisa; Reick, Christian H.; Schultz, Martin; Stein, Olaf

2014-05-01

Climate change is driven by an increasing release of anthropogenic greenhouse gases (GHGs) such as carbon dioxide and nitrous oxide (N2O). Besides fossil fuel burning, also land use change and land management are anthropogenic sources of GHGs. Especially inputs of reactive nitrogen via fertilizer and deposition lead to enhanced emissions of N2O. One effect of a drastic future increase in surface temperature is a modification of atmospheric circulation, e.g. an accelerated Brewer Dobson circulation affecting the exchange between troposphere and stratosphere. N2O is inert in the troposphere and decayed only in the stratosphere. Thus, changes in atmospheric circulation, especially changes in the exchange between troposphere and stratosphere, will affect the atmospheric transport, decay, and distribution of N2O. In our study we assess the impact of global warming on atmospheric circulation and implied effects on the distribution and lifetime of atmospheric N2O. As terrestrial N2O emissions are highly determined by inputs of reactive nitrogen - the location of which being determined by human choice - we examine in particular the importance of latitudinal source regions of N2O for its global distribution. For this purpose we apply the Max Planck Institute Earth System Model, MPI-ESM. MPI-ESM consists of the atmospheric general circulation model ECHAM, the land surface model JSBACH, and MPIOM/HAMOCC representing ocean circulation and ocean biogeochemistry. Prognostic atmospheric N2O concentrations in MPI-ESM are determined by land N2O emissions, ocean N2O exchange and atmospheric tracer transport. As stratospheric chemistry is not explicitly represented in MPI-ESM, stratospheric decay rates of N2O are prescribed from a MACC MOZART simulation.

Unveiling aerosol-cloud interactions - Part 2: Minimising the effects of aerosol swelling and wet scavenging in ECHAM6-HAM2 for comparison to satellite data

NASA Astrophysics Data System (ADS)

Neubauer, David; Christensen, Matthew W.; Poulsen, Caroline A.; Lohmann, Ulrike

2017-11-01

Aerosol-cloud interactions (ACIs) are uncertain and the estimates of the ACI effective radiative forcing (ERFaci) magnitude show a large variability. Within the Aerosol_cci project the susceptibility of cloud properties to changes in aerosol properties is derived from the high-resolution AATSR (Advanced Along-Track Scanning Radiometer) data set using the Cloud-Aerosol Pairing Algorithm (CAPA) (as described in our companion paper) and compared to susceptibilities from the global aerosol climate model ECHAM6-HAM2 and MODIS-CERES (Moderate Resolution Imaging Spectroradiometer - Clouds and the Earth's Radiant Energy System) data. For ECHAM6-HAM2 the dry aerosol is analysed to mimic the effect of CAPA. Furthermore the analysis is done for different environmental regimes. The aerosol-liquid water path relationship in ECHAM6-HAM2 is systematically stronger than in AATSR-CAPA data and cannot be explained by an overestimation of autoconversion when using diagnostic precipitation but rather by aerosol swelling in regions where humidity is high and clouds are present. When aerosol water is removed from the analysis in ECHAM6-HAM2 the strength of the susceptibilities of liquid water path, cloud droplet number concentration and cloud albedo as well as ERFaci agree much better with those of AATSR-CAPA or MODIS-CERES. When comparing satellite-derived to model-derived susceptibilities, this study finds it more appropriate to use dry aerosol in the computation of model susceptibilities. We further find that the statistical relationships inferred from different satellite sensors (AATSR-CAPA vs. MODIS-CERES) as well as from ECHAM6-HAM2 are not always of the same sign for the tested environmental conditions. In particular the susceptibility of the liquid water path is negative in non-raining scenes for MODIS-CERES but positive for AATSR-CAPA and ECHAM6-HAM2. Feedback processes like cloud-top entrainment that are missing or not well represented in the model are therefore not well constrained by satellite observations. In addition to aerosol swelling, wet scavenging and aerosol processing have an impact on liquid water path, cloud albedo and cloud droplet number susceptibilities. Aerosol processing leads to negative liquid water path susceptibilities to changes in aerosol index (AI) in ECHAM6-HAM2, likely due to aerosol-size changes by aerosol processing. Our results indicate that for statistical analysis of aerosol-cloud interactions the unwanted effects of aerosol swelling, wet scavenging and aerosol processing need to be minimised when computing susceptibilities of cloud variables to changes in aerosol.

Representation of the West African Monsoon System in the aerosol-climate model ECHAM6-HAM2

NASA Astrophysics Data System (ADS)

Stanelle, Tanja; Lohmann, Ulrike; Bey, Isabelle

2017-04-01

The West African Monsoon (WAM) is a major component of the global monsoon system. The temperature contrast between the Saharan land surface in the North and the sea surface temperature in the South dominates the WAM formation. The West African region receives most of its precipitation during the monsoon season between end of June and September. Therefore the existence of the monsoon is of major social and economic importance. We discuss the ability of the climate model ECHAM6 as well as the coupled aerosol climate model ECHAM6-HAM2 to simulate the major features of the WAM system. The north-south temperature gradient is reproduced by both model versions but all model versions fail in reproducing the precipitation amount south of 10° N. A special focus is on the representation of the nocturnal low level jet (NLLJ) and the corresponding enhancement of low level clouds (LLC) at the Guinea Coast, which are a crucial factor for the regional energy budget. Most global climate models have difficulties to represent these features. The pure climate model ECHAM6 is able to simulate the existence of the NLLJ and LLC, but the model does not represent the pronounced diurnal cycle. Overall, the representation of LLC is worse in the coupled model. We discuss the model behaviors on the basis of outputted temperature and humidity tendencies and try to identify potential processes responsible for the model deficiencies.

Dynamics and transport in the stratosphere : Simulations with a general circulation mode

NASA Astrophysics Data System (ADS)

van Aalst, Maarten Krispijn

2005-01-01

The middle atmosphere is strongly affected by two of the world's most important environmental problems: global climate change and stratospheric ozone depletion, caused by anthropogenic emissions of greenhouse gases and chlorofluorocarbons (CFCs), respectively. General circulation models with coupled chemistry are a key tool to advance our understanding of the complex interplay between dynamics, chemistry and radiation in the middle atmosphere. A key problem of such models is that they generate their own meteorology, and thus cannot be used for comparisons with instantaneous measurements. This thesis presents the first application of a simple data assimilation method, Newtonian relaxation, to reproduce realistic synoptical conditions in a state-of-the-art middle atmosphere general circulation model, MA-ECHAM. By nudging the model's meteorology slightly towards analyzed observations from a weather forecasting system (ECMWF), we have simulated specific atmospheric processes during particular meteorological episodes, such as the 1999/2000 Arctic winter. The nudging technique is intended to interfere as little as possible with the model's own dynamics. In fact, we found that we could even limit the nudging to the troposphere, leaving the middle atmosphere entirely free. In that setup, the model realistically reproduced many aspects of the instantaneous meteorology of the middle atmosphere, such as the unusually early major warming and breakup of the 2002 Antarctic vortex. However, we found that this required careful interpolation of the nudging data, and a correct choice of nudging parameters. We obtained the best results when we first projected the nudging data onto the model's normal modes so that we could filter out the (spurious) fast components. In a four-year simulation, for which we also introduced an additional nudging of the stratospheric quasi-biennial oscillation, we found that the model reproduced much of the interannual variability throughout the stratosphere, including the Antarctic temperature minima crucial for polar ozone chemistry, but failed to capture the precise timing and evolution of Arctic stratospheric warmings. We also identified an important model deficiency regarding tracer transport in the lower polar stratosphere. The success of the runs with tropospheric nudging in simulating the right stratospheric conditions, including the model capability to forecast major stratospheric warming events, bodes well for the model's representation of the dynamic coupling between the troposphere and the stratosphere, an important element of realistic simulation of the future climate of the middle atmosphere (which will partly depend on a changing wave forcing from the troposphere). However, for some aspects of stratospheric dynamics, such as the quasi-biennial oscillation, a higher vertical resolution is required, which might also help to reduce some of the transport problems identified in the lower polar vortex. The nudging technique applied and developed in this thesis offers excellent prospects for applications in coupled-chemistry simulations of the middle atmosphere, including for the interpretation of instantaneous measurements. In particular, it can be used to test and improve the new MA-ECHAM5/MESSy/MECCA coupled chemistry climate model system, in preparation for more reliable simulations of past and future climates.

Trace gas variability within the Asian monsoon anticyclone on intraseasonal and interannual timescales

NASA Astrophysics Data System (ADS)

Nützel, Matthias; Dameris, Martin; Fierli, Federico; Stiller, Gabriele; Garny, Hella; Jöckel, Patrick

2016-04-01

The Asian monsoon and the associated monsoon anticyclone have the potential of substantially influencing the composition of the UTLS (upper troposphere/lower stratosphere) and hence global climate. Here we study the variability of the Asian summer monsoon anticyclone in the UTLS on intraseasonal and interannual timescales using results from long term simulations performed with the CCM EMAC (ECHAM5/MESSy Atmospheric Chemistry). In particular, we focus on specified dynamics simulations (Newtonian relaxation to ERA-Interim data) covering the period 1980-2013, which have been performed within the ESCiMo (Earth System Chemistry integrated Modelling) project (Jöckel et al., GMDD, 2015). Our main focus lies on variability of the anticyclone's strength (in terms of potential vorticity, geopotential and circulation) and variability in trace gas signatures (O3, H2O) within the anticyclone. To support our findings, we also include observations from satellites (MIPAS, MLS). Our work is linked to the EU StratoClim campaign in 2016.

Modes of North Atlantic Decadal Variability in the ECHAM1/LSG Coupled Ocean-Atmosphere General Circulation Model.

NASA Astrophysics Data System (ADS)

Zorita, Eduardo; Frankignoul, Claude

1997-02-01

The climate variability in the North Atlantic sector is investigated in a 325-yr integration of the ECHAM1/ LSG coupled ocean-atmosphere general circulation model. At the interannual timescale, the coupled model behaves realistically and sea surface temperature (SST) anomalies arise as a response of the oceanic surface layer to the stochastic forcing by the atmosphere, with the heat exchanges both generating and damping the SST anomalies. In the ocean interior, the temperature spectra are red up to a period of about 20 years, and substantial decadal fluctuations are found in the upper kilometer or so of the water column. Using extended empirical orthogonal function analysis, two distinct quasi-oscillatory modes of ocean-atmosphere variability are identified, with dominant periods of about 20 and 10 years, respectively. The oceanic changes in both modes reflect the direct forcing by the atmosphere through anomalous air-sea fluxes and Ekman pumping, which after some delay affects the intensity of the subtropical and subpolar gyres. The SST is also strongly modulated by the gyre currents. In the thermocline, the temperature and salinity fluctuations are in phase, as if caused by thermocline displacements, and they have no apparent connection with the thermohaline circulation. The 20-yr mode is the most energetic one; it is easily seen in the thermocline and can be found in SST data, but it is not detected in the atmosphere alone. As there is no evidence of positive ocean-atmosphere feedback, the 20-yr mode primarily reflects the passive response of the ocean to atmospheric fluctuations, which may be in part associated with climate anomalies appearing a few years earlier in the North Pacific. The 10-yr mode is more surface trapped in the ocean. Although the mode is most easily seen in the temperature variations of the upper few hundred meters of the ocean, it is also detected in the atmosphere alone and thus appears to be a coupled ocean-atmosphere mode. In both modes, the surface heat flux acts neutrally on the associated SST anomalies once they have been generated, so that their persistence appears to be due in part to an overall adjustment of the air-sea heat exchanges to the SST patterns.

Using in-situ observations of atmospheric water vapor isotopes to benchmark and isotope-enabled General Circulation Models and improve ice core paleo-climate reconstruction

NASA Astrophysics Data System (ADS)

Steen-Larsen, Hans Christian; Sveinbjörnsdottir, Arny; Masson-Delmotte, Valerie; Werner, Martin; Risi, Camille; Yoshimura, Kei

2016-04-01

We have since 2010 carried out in-situ continuous water vapor isotope observations on top of the Greenland Ice Sheet (3 seasons at NEEM), in Svalbard (1 year), in Iceland (4 years), in Bermuda (4 years). The expansive dataset containing high accuracy and precision measurements of δ18O, δD, and the d-excess allow us to validate and benchmark the treatment of the atmospheric hydrological cycle's processes in General Circulation Models using simulations nudged to reanalysis products. Recent findings from both Antarctica and Greenland have documented strong interaction between the snow surface isotopes and the near surface atmospheric water vapor isotopes on diurnal to synoptic time scales. In fact, it has been shown that the snow surface isotopes take up the synoptic driven atmospheric water vapor isotopic signal in-between precipitation events, erasing the precipitation isotope signal in the surface snow. This highlights the importance of using General or Regional Climate Models, which accurately are able to simulate the atmospheric water vapor isotopic composition, to understand and interpret the ice core isotope signal. With this in mind we have used three isotope-enabled General Circulation Models (isoGSM, ECHAM5-wiso, and LMDZiso) nudged to reanalysis products. We have compared the simulations of daily mean isotope values directly with our in-situ observations. This has allowed us to characterize the variability of the isotopic composition in the models and compared it to our observations. We have specifically focused on the d-excess in order to characterize why both the mean and the variability is significantly lower than our observations. We argue that using water vapor isotopes to benchmark General Circulation Models offers an excellent tool for improving the treatment and parameterization of the atmospheric hydrological cycle. Recent studies have documented a very large inter-model dispersion in the treatment of the Arctic water cycle under a future global warming and greenhouse gas emission scenario. Our results call for action to create an international pan-Arctic monitoring water vapor isotope network in order to improve future projections of Arctic climate.

The Stochastic Multicloud Model as part of an operational convection parameterisation in a comprehensive GCM

NASA Astrophysics Data System (ADS)

Peters, Karsten; Jakob, Christian; Möbis, Benjamin

2015-04-01

An adequate representation of convective processes in numerical models of the atmospheric circulation (general circulation models, GCMs) remains one of the grand challenges in atmospheric science. In particular, the models struggle with correctly representing the spatial distribution and high variability of tropical convection. It is thought that this model deficiency partly results from formulating current convection parameterisation schemes in a purely deterministic manner. Here, we use observations of tropical convection to inform the design of a novel convection parameterisation with stochastic elements. The novel scheme is built around the Stochastic MultiCloud Model (SMCM, Khouider et al 2010). We present the progress made in utilising SMCM-based estimates of updraft area fractions at cloud base as part of the deep convection scheme of a GCM. The updraft area fractions are used to yield one part of the cloud base mass-flux used in the closure assumption of convective mass-flux schemes. The closure thus receives a stochastic component, potentially improving modeled convective variability and coherence. For initial investigations, we apply the above methodology to the operational convective parameterisation of the ECHAM6 GCM. We perform 5-year AMIP simulations, i.e. with prescribed observed SSTs. We find that with the SMCM, convection is weaker and more coherent and continuous from timestep to timestep compared to the standard model. Total global precipitation is reduced in the SMCM run, but this reduces i) the overall error compared to observed global precipitation (GPCP) and ii) middle tropical tropospheric temperature biases compared to ERA-Interim. Hovmoeller diagrams indicate a slightly higher degree of convective organisation compared to the base case and Wheeler-Kiladis frequency wavenumber diagrams indicate slightly more spectral power in the MJO range.

Projected future wave climate in the NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Casas-Prat, M.; Sierra, J. P.

2013-07-01

Projected future regional wave climate scenarios at a high temporal-spatial scale were obtained for the NW Mediterranean Sea, using five combinations of regional-global circulation models. Changes in wave variables were analyzed and related to the variations of the forcing wind projections, while also evaluating the evolution of the presence of the different types of sea states. To assess the significance of the changes produced, a bootstrap-based method was proposed, which accounts for the autocorrelation of data and correctly reproduces the extremes. For the mean climate, relative changes of Hs up to ±10% were obtained, whereas they were around ±20% for the extreme climate. In mean terms, variations of Hs are similar to those associated with wind speed but are enhanced/attenuated, respectively, when fetch conditions are favorable/unfavorable. In general, most notable alterations are not in the Hs magnitude but rather in its direction. In this regard, during the winter season, it is interesting to note that the significant deviations between the results derived from the two global circulation models are larger than those between regional models. ECHAM5 simulated an enhanced west wind flow that is translated into more frequent W-NW waves, whereas the HadCM3Q3 global model gives rise to the east component, which contributes to a higher intensity and number of storms coming from such a direction and directly affects the wind-sea/swell distribution of coastal stretches that face east, like the Catalan coast. Different patterns of change were obtained during the summer when a common rise of NE-E waves was found.

Amplification of warming due to intensification of zonal circulation in the mid-latitudes

NASA Astrophysics Data System (ADS)

Alekseev, Genrikh; Ivanov, Nikolai; Kharlanenkova, Natalia; Kuzmina, Svetlana

2015-04-01

We propose a new index to evaluate the impact of atmospheric zonal transport oscillations on inter-annual variability and trends of average air temperature in mid-latitudes, Northern Hemisphere and globe. A simple model of mid-latitude channel "ocean-land-atmosphere" was used to produce the analytic relationship between the zonal circulation and the land-ocean temperature contrast which was used as a basis for index. An inverse relationship was found between indexes and average mid-latitude, hemisphere and global temperatures during the cold half of year and opposite one in summer. These relationships keep under 400 mb height. In winter relationship describes up to 70, 50 and 40 % of surface air temperature inter-annual variability of these averages, respectively. The contribution of zonal circulation to the increase in the average surface air temperature during warming period 1969-2008 reaches 75% in the mid-latitudes and 40% in the Northern Hemisphere. Proposed mid-latitude index correlates negatively with surface air temperature in the Arctic except summer. ECHAM4 projections with the A1B scenario show that increase of zonal circulation defines more than 74% of the warming in the Northern Hemisphere for 2001-2100. Our analysis confirms that the proposed index is an effective indicator of the climate change caused by variations of the zonal circulation that arise due to anthropogenic and/or natural global forcing mechanisms.

Heinrich events modeled in transient glacial simulations

NASA Astrophysics Data System (ADS)

Ziemen, Florian; Kapsch, Marie; Mikolajewicz, Uwe

2017-04-01

Heinrich events are among the most prominent events of climate variability recorded in proxies across the northern hemisphere. They are the archetype of ice sheet — climate interactions on millennial time scales. Nevertheless, the exact mechanisms that cause Heinrich events are still under debate, and their climatic consequences are far from being fully understood. We address open questions by studying Heinrich events in a coupled ice sheet model (ISM) atmosphere-ocean-vegetation general circulation model (AOVGCM) framework, where this variability occurs as part of the model generated internal variability. The framework consists of a northern hemisphere setup of the modified Parallel Ice Sheet Model (mPISM) coupled to the global AOVGCM ECHAM5/MPIOM/LPJ. The simulations were performed fully coupled and with transient orbital and greenhouse gas forcing. They span from several millennia before the last glacial maximum into the deglaciation. To make these long simulations feasible, the atmosphere is accelerated by a factor of 10 relative to the other model components using a periodical-synchronous coupling technique. To disentangle effects of the Heinrich events and the deglaciation, we focus on the events occurring before the deglaciation. The modeled Heinrich events show a peak ice discharge of about 0.05 Sv and raise the sea level by 2.3 m on average. The resulting surface water freshening reduces the Atlantic meridional overturning circulation and ocean heat release. The reduction in ocean heat release causes a sub-surface warming and decreases the air temperature and precipitation regionally and downstream into Eurasia. The surface elevation decrease of the ice sheet enhances moisture transport onto the ice sheet and thus increases precipitation over the Hudson Bay area, thereby accelerating the recovery after an event.

Climate Change, Public Health, and Decision Support: The New Threat of Vector-borne Disease

NASA Astrophysics Data System (ADS)

Grant, F.; Kumar, S.

2011-12-01

Climate change and vector-borne diseases constitute a massive threat to human development. It will not be enough to cut emissions of greenhouse gases-the tide of the future has already been established. Climate change and vector-borne diseases are already undermining the world's efforts to reduce extreme poverty. It is in the best interests of the world leaders to think in terms of concerted global actions, but adaptation and mitigation must be accomplished within the context of local community conditions, resources, and needs. Failure to act will continue to consign developed countries to completely avoidable health risks and significant expense. Failure to act will also reduce poorest of the world's population-some 2.6 billion people-to a future of diminished opportunity. Northrop Grumman has taken significant steps forward to develop the tools needed to assess climate change impacts on public health, collect relevant data for decision making, model projections at regional and local levels; and, deliver information and knowledge to local and regional stakeholders. Supporting these tools is an advanced enterprise architecture consisting of high performance computing, GIS visualization, and standards-based architecture. To address current deficiencies in local planning and decision making with respect to regional climate change and its effect on human health, our research is focused on performing a dynamical downscaling with the Weather Research and Forecasting (WRF) model to develop decision aids that translate the regional climate data into actionable information for users. For the present climate WRF was forced with the Max Planck Institute European Center/Hamburg Model version 5 (ECHAM5) General Circulation Model 20th century simulation. For the 21th century climate, we used an ECHAM5 simulation with the Special Report on Emissions (SRES) A1B emissions scenario. WRF was run in nested mode at spatial resolution of 108 km, 36 km and 12 km and 28 vertical levels. This model was examined relative to two mosquito vectors, both competent carriers of dengue fever, a viral, vector-borne disease. Models which incorporate public health considerations can enable decision makers to take proactive steps to mitigate the impacts and adapt to the changing environmental conditions. In this paper we provide a snapshot of our climate initiative and some examples relative to our public health practice work in vector-borne diseases to illustrate how integrated decision support could be of assistance to regional and local communities worldwide.

Influence of enhanced Asian NOx emissions on ozone in the upper troposphere and lower stratosphere in chemistry-climate model simulations

NASA Astrophysics Data System (ADS)

Roy, Chaitri; Fadnavis, Suvarna; Müller, Rolf; Ayantika, D. C.; Ploeger, Felix; Rap, Alexandru

2017-01-01

The Asian summer monsoon (ASM) anticyclone is the most pronounced circulation pattern in the upper troposphere and lower stratosphere (UTLS) during northern hemispheric summer. ASM convection plays an important role in efficient vertical transport from the surface to the upper-level anticyclone. In this paper we investigate the potential impact of enhanced anthropogenic nitrogen oxide (NOx) emissions on the distribution of ozone in the UTLS using the fully coupled aerosol-chemistry-climate model, ECHAM5-HAMMOZ. Ozone in the UTLS is influenced both by the convective uplift of ozone precursors and by the uplift of enhanced-NOx-induced tropospheric ozone anomalies. We performed anthropogenic NOx emission sensitivity experiments over India and China. In these simulations, covering the years 2000-2010, anthropogenic NOx emissions have been increased by 38 % over India and by 73 % over China with respect to the emission base year 2000. These emission increases are comparable to the observed linear trends of 3.8 % per year over India and 7.3 % per year over China during the period 2000 to 2010. Enhanced NOx emissions over India by 38 % and China by 73 % increase the ozone radiative forcing in the ASM anticyclone (15-40° N, 60-120° E) by 16.3 and 78.5 mW m-2 respectively. These elevated NOx emissions produce significant warming over the Tibetan Plateau and increase precipitation over India due to a strengthening of the monsoon Hadley circulation. However, increase in NOx emissions over India by 73 % (similar to the observed increase over China) results in large ozone production over the Indo-Gangetic Plain and Tibetan Plateau. The higher ozone concentrations, in turn, induce a reversed monsoon Hadley circulation and negative precipitation anomalies over India. The associated subsidence suppresses vertical transport of NOx and ozone into the ASM anticyclone.

Assessment of regional climate change and development of climate adaptation decision aids in the Southwestern US

NASA Astrophysics Data System (ADS)

Darmenova, K.; Higgins, G.; Kiley, H.; Apling, D.

2010-12-01

Current General Circulation Models (GCMs) provide a valuable estimate of both natural and anthropogenic climate changes and variability on global scales. At the same time, future climate projections calculated with GCMs are not of sufficient spatial resolution to address regional needs. Many climate impact models require information at scales of 50 km or less, so dynamical downscaling is often used to estimate the smaller-scale information based on larger scale GCM output. To address current deficiencies in local planning and decision making with respect to regional climate change, our research is focused on performing a dynamical downscaling with the Weather Research and Forecasting (WRF) model and developing decision aids that translate the regional climate data into actionable information for users. Our methodology involves development of climatological indices of extreme weather and heating/cooling degree days based on WRF ensemble runs initialized with the NCEP-NCAR reanalysis and the European Center/Hamburg Model (ECHAM5). Results indicate that the downscale simulations provide the necessary detailed output required by state and local governments and the private sector to develop climate adaptation plans. In addition we evaluated the WRF performance in long-term climate simulations over the Southwestern US and validated against observational datasets.

A dynamical perspective on the energetic particles precipitation-middle atmosphere interaction

NASA Astrophysics Data System (ADS)

Karami, Khalil; Sinnhuber, Miriam; Versick, Stefan; Braesicke, Peter

2015-04-01

Energetic particles including protons, electrons and heavier ions, enter the Earth's atmosphere over polar region of both hemispheres, where the geomagnetic lines are considered to be open and connected to the interplanetary medium. This condition allows direct access for energetic particles of solar or galactic origin to directly deposit their own energy into the middle and upper atmosphere. Such particle precipitations can greatly disturb the chemical composition of the upper and middle atmosphere. At polar latitudes, these particles have the potential to penetrate from thermosphere deep into the mesosphere and in rare occasions into the stratosphere. The most important are changes to the budget of atmospheric nitric oxides, NOy, and to atmospheric reactive hydrogen oxides, HOx, which both contribute to ozone loss in the stratosphere and mesosphere. The chemistry-climate general circulation model ECHAM5/MESSy is used to investigate the impact of changed ozone concentration due to energetic particles precipitation on temperatures and wind fields. The simulated anomalies of both zonal mean temperature and zonal wind suggest that these changes are very unlikely to be caused in situ by ozone depletion and indirect dynamical condition is important. The results of our simulations suggests that ozone perturbation is a starting point for a chain of processes resulting in temperature and circulation changes in many areas of the atmosphere. Different dynamical analysis (e.g., frequency of sudden stratospheric warming, dates of stratospheric final warming, divergence of Eliassen-Palm flux and refractive index of planetary waves) are performed to investigate the impact of ozone anomaly originated from high energetic particle precipitation on middle atmospheric temperature and circulation.

Simulated atmospheric response to Gulf Stream variability

NASA Astrophysics Data System (ADS)

Hand, Ralf; Keenlyside, Noel; Omrani, Nour-Eddine; Latif, Mojib; Minobe, Shoshiro

2010-05-01

Though the ocean variability has a distinct low-frequent component on interannual to interdecadal timescales, a better understanding of the main features of air-sea interaction in the extratropical ocean might increase the predictive skill of climate models significantly. An insufficiently understood region in this context are the sharp SST-fronts connected to western boundary currents, which interact with the overlaying atmosphere by forcing low-level winds and evaporation. Recent studies show, that this response extends beyond the marine boundary layer and so might influence also the large-scale atmospheric circulation. In this work a 5 member ensemble of model runs from the AGCM ECHAM5 was analyzed focussing on the atmospheric response to the Gulf Stream. The analyzed experiment covered a time period of 138 years from 1870 to 2007 and was forced by observed SSTs and sea-ice concentration from the HadISST dataset. The experiment was performed at T106 horizontal resolution (~100km) and with 31 vertical levels up to 1 hPa. Simulated seasonal mean circulation indicate a convective response of the atmosphere in the Gulf Stream region similar to observations, with distinct low-level wind convergence, strong upward motion, and low-pressure over the warm SST flank of the Gulf Stream. An analysis of variance (ANOVA) suggests, that up to 25-30% of the variability of the summer precipitation in the Gulf Stream region are connected to the boundary conditions. The link between oceanic and atmospheric variability on seasonal to interannual timescales is investigated with composite and linear regression analysis. Results indicate that increased (decreased) precipitation is associated with stronger (weaker) low-level wind convergence, enhanced (reduced) upward motion, low (high) pressure, and warm (cold) SST anomalies in the region of the Gulf Stream. Currently sensitivity experiments with the same AGCM configuration are in progress.

Predicting the Timing of Cherry Blossoms in Washington, DC and Mid-Atlantic States in Response to Climate Change

PubMed Central

Chung, Uran; Mack, Liz; Yun, Jin I.; Kim, Soo-Hyung

2011-01-01

Cherry blossoms, an icon of spring, are celebrated in many cultures of the temperate region. For its sensitivity to winter and early spring temperatures, the timing of cherry blossoms is an ideal indicator of the impacts of climate change on tree phenology. Here, we applied a process-based phenology model for temperate deciduous trees to predict peak bloom dates (PBD) of flowering cherry trees (Prunus×yedoensis ‘Yoshino’ and Prunus serrulata ‘Kwanzan’) in the Tidal Basin, Washington, DC and the surrounding Mid-Atlantic States in response to climate change. We parameterized the model with observed PBD data from 1991 to 2010. The calibrated model was tested against independent datasets of the past PBD data from 1951 to 1970 in the Tidal Basin and more recent PBD data from other locations (e.g., Seattle, WA). The model performance against these independent data was satisfactory (Yoshino: r2 = 0.57, RMSE = 6.6 days, bias = 0.9 days and Kwanzan: r2 = 0.76, RMSE = 5.5 days, bias = −2.0 days). We then applied the model to forecast future PBD for the region using downscaled climate projections based on IPCC's A1B and A2 emissions scenarios. Our results indicate that PBD at the Tidal Basin are likely to be accelerated by an average of five days by 2050 s and 10 days by 2080 s for these cultivars under a mid-range (A1B) emissions scenario projected by ECHAM5 general circulation model. The acceleration is likely to be much greater (13 days for 2050 s and 29 days for 2080s ) under a higher (A2) emissions scenario projected by CGCM2 general circulation model. Our results demonstrate the potential impacts of climate change on the timing of cherry blossoms and illustrate the utility of a simple process-based phenology model for developing adaptation strategies to climate change in horticulture, conservation planning, restoration and other related disciplines. PMID:22087317

Assessment of two physical parameterization schemes for desert dust emissions in an atmospheric chemistry general circulation model

NASA Astrophysics Data System (ADS)

Astitha, M.; Abdel Kader, M.; Pozzer, A.; Lelieveld, J.

2012-04-01

Atmospheric particulate matter and more specific desert dust has been the topic of numerous research studies in the past due to the wide range of impacts in the environment and climate and the uncertainty of characterizing and quantifying these impacts in a global scale. In this work we present two physical parameterizations of the desert dust production that have been incorporated in the atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy2.41 Atmospheric Chemistry). The scope of this work is to assess the impact of the two physical parameterizations in the global distribution of desert dust and highlight the advantages and disadvantages of using either technique. The dust concentration and deposition has been evaluated using the AEROCOM dust dataset for the year 2000 and data from the MODIS and MISR satellites as well as sun-photometer data from the AERONET network was used to compare the modelled aerosol optical depth with observations. The implementation of the two parameterizations and the simulations using relatively high spatial resolution (T106~1.1deg) has highlighted the large spatial heterogeneity of the dust emission sources as well as the importance of the input parameters (soil size and texture, vegetation, surface wind speed). Also, sensitivity simulations with the nudging option using reanalysis data from ECMWF and without nudging have showed remarkable differences for some areas. Both parameterizations have revealed the difficulty of simulating all arid regions with the same assumptions and mechanisms. Depending on the arid region, each emission scheme performs more or less satisfactorily which leads to the necessity of treating each desert differently. Even though this is a quite different task to accomplish in a global model, some recommendations are given and ideas for future improvements.

On the reduced lifetime of nitrous oxide due to climate change induced acceleration of the Brewer-Dobson circulation as simulated by the MPI Earth System Model

NASA Astrophysics Data System (ADS)

Kracher, D.; Manzini, E.; Reick, C. H.; Schultz, M. G.; Stein, O.

2014-12-01

Greenhouse gas induced climate change will modify the physical conditions of the atmosphere. One of the projected changes is an acceleration of the Brewer-Dobson circulation in the stratosphere, as it has been shown in many model studies. This change in the stratospheric circulation consequently bears an effect on the transport and distribution of atmospheric components such as N2O. Since N2O is involved in ozone destruction, a modified distribution of N2O can be of importance for ozone chemistry. N2O is inert in the troposphere and decays only in the stratosphere. Thus, changes in the exchange between troposphere and stratosphere can also affect the stratospheric sink of N2O, and consequently its atmospheric lifetime. N2O is a potent greenhouse gas with a global warming potential of currently approximately 300 CO2-equivalents in a 100-year perspective. A faster decay in atmospheric N2O mixing ratios, i.e. a decreased atmospheric lifetime of N2O, will also reduce its global warming potential. In order to assess the impact of climate change on atmospheric circulation and implied effects on the distribution and lifetime of atmospheric N2O, we apply the Max Planck Institute Earth System Model, MPI-ESM. MPI-ESM consists of the atmospheric general circulation model ECHAM, the land surface model JSBACH, and MPIOM/HAMOCC representing ocean circulation and ocean biogeochemistry. Prognostic atmospheric N2O concentrations in MPI-ESM are determined by land N2O emissions, ocean-atmosphere N2O exchange and atmospheric tracer transport. As stratospheric chemistry is not explicitly represented in MPI-ESM, stratospheric decay rates of N2O are prescribed from a MACC MOZART simulation. Increasing surface temperatures and CO2 concentrations in the stratosphere impact atmospheric circulation differently. Thus, we conduct a series of transient runs with the atmospheric model of MPI-ESM to isolate different factors governing a shift in atmospheric circulation. From those transient simulations we diagnose decreasing tropospheric N2O concentrations, increased transport of N2O from the troposphere to the stratosphere, and increasing stratospheric decay of N2O leading to a reduction in atmospheric lifetime of N2O, in dependency to climate change evolution.

GCM simulations of cold dry Snowball Earth atmospheres

NASA Astrophysics Data System (ADS)

Voigt, A.; Held, I.; Marotzke, J.

2009-12-01

We use the full-physics atmospheric general circulation model ECHAM5 to investigate cold and virtually dry Snowball Earth atmospheres. These result from specifying sea ice as the surface boundary condition everywhere, corresponding to a frozen aquaplanet, while keeping total solar irradiance at its present-day value of 1365 Wm-2 and setting atmospheric carbon dioxide to 300 ppmv. Here, we present four simulations corresponding to the four possible combinations of enabled or disabled diurnal and seasonal cycles. The aim of this study is twofold. First, we focus on the zonal-mean circulation of Snowball Earth atmospheres, which, due to missing moisture, might constitute an ideal though yet unexplored testbed for theories of atmospheric dynamics. Second, we investigate tropical surface temperatures with an emphasis on the impact of the diurnal and seasonal cycles. This will indicate whether the presence of the diurnal or seasonal cycle would facilitate or anticipate the escape from Snowball Earth conditions when total solar irradiance or atmospheric CO2 levels were increased. The dynamics of the tropical circulation in Snowball Earth atmospheres differs substantially from that in the modern atmosphere. The analysis of the mean zonal momentum budget reveals that the mean flow meridional advection of absolute vorticity is primarily balanced by vertical diffusion of zonal momentum. The contribution of eddies is found to be even smaller than the contribution of mean flow vertical advection of zonal momentum, the latter being usually neglected in theories for the Hadley circulation, at least in its upper tropospheric branch. Suppressing vertical diffusion of horizontal momentum above 850 hPa leads to a stronger Hadley circulation. This behaviour cannot be understood from axisymmetric models of the atmosphere, nor idealized atmospheric general circulation models, which both predict a weakening of the Hadley circulation when the vertical viscosity is decreased globally. We find that enabling the diurnal cycle does not change tropical annual-mean surface temperatures but significantly strengthens the Hadley circulation, which increases by 33% for equinoctial and by 50% during solstitial insolation conditions compared to simulations without diurnal cycle. Including the seasonal cycle results in a ''reversed'' annual-mean Hadley circulation with subsiding motion at the equator and ascending motion around 15N/S, a manifestation of the extreme seasonality of Snowball Earth atmospheres due to the low thermal inertia of the sea-ice surface. The impact of the seasonal cycle on the tropical annual-mean surface is a straightforward consequence of changes in insolation distribution: as annual-mean incoming shortwave radiation at the equator reduces by 18 Wm-2 for enabled seasonal cycle, tropical annual-mean surface temperatures decrease from 221 K to 217 K.

A multi-scale methodology for comparing GCM and RCM results over the Eastern Mediterranean

NASA Astrophysics Data System (ADS)

Samuels, Rana; Krichak, Simon; Breitgand, Joseph; Alpert, Pinhas

2010-05-01

The importance of skillful climate modeling is increasingly being realized as results are being incorporated into environmental, economic, and even business planning. Global circulation models (GCMs) employed by the IPCC provide results at spatial scales of hundreds of kilometers, which is useful for understanding global trends but not appropriate for use as input into regional and local impacts models used to inform policy and development. To address this shortcoming, regional climate models (RCMs) which dynamically downscale the results of the GCMs are used. In this study we present first results of a dynamically downscaled RCM focusing on the Eastern Mediterranean region. For the historical 1960-2000 time period, results at a spatial scale of both 25 km and 50 km are compared with historical station data from 5 locations across Israel as well as with the results of 3 GCM models (ECHAM5, NOAA GFDL, and CCCMA) at annual, monthly and daily time scales. Results from a recently completed Japanese GCM at a spatial scale of 20 km are also included. For the historical validation period, we show that as spatial scale increases the skill in capturing annual and inter-annual temperature and rainfall also increases. However, for intra-seasonal rainfall characteristics important for hydrological and agricultural planning (eg. dry and wet spells, number of rain days) the GCM results (including the 20 km Japanese model) capture the historical trends better than the dynamically downscaled RegCM. For future scenarios of temperature and precipitation changes, we compare results across the models for the available time periods, generating a range of future trends.

Simulation of a dust episode over Eastern Mediterranean using a high-resolution atmospheric chemistry general circulation model

NASA Astrophysics Data System (ADS)

Abdel Kader, Mohamed; Zittis, Georgios; Astitha, Marina; Lelieveld, Jos; Tymvios, Fillipos

2013-04-01

An extended episode of low visibility took place over the Eastern Mediterranean in late September 2011, caused by a strong increase in dust concentrations, analyzed from observations of PM10 (Particulate Matter with <10μm in diameter). A high-resolution version of the atmospheric chemistry general circulation model EMAC (ECHAM5/Messy2.41 Atmospheric Chemistry) was used to simulate the emissions, transport and deposition of airborne desert dust. The model configuration involves the spectral resolution of T255 (0.5°, ~50Km) and 31 vertical levels in the troposphere and lower stratosphere. The model was nudged towards ERA40 reanalysis data to represent the actual meteorological conditions. The dust emissions were calculated online at each model time step and the aerosol microphysics using the GMXe submodel (Global Modal-aerosol eXtension). The model includes a sulphur chemistry mechanism to simulate the transformation of the dust particles from the insoluble (at emission) to soluble modes, which promotes dust removal by precipitation. The model successfully reproduces the dust distribution according to observations by the MODIS satellite instruments and ground-based AERONET stations. The PM10 concentration is also compared with in-situ measurements over Cyprus, resulting in good agreement. The model results show two subsequent dust events originating from the Negev and Sahara deserts. The first dust event resulted from the transport of dust from the Sahara on the 21st of September and lasted only briefly (hours) as the dust particles were efficiently removed by precipitation simulated by the model and observed by the TRMM (Tropical Rainfall Measuring Mission) satellites. The second event resulted from dust transport from the Negev desert to the Eastern Mediterranean during the period 26th - 30th September with a peak concentration at 2500m elevation. This event lasted for four days and diminished due to dry deposition. The observed reduced visibility over Cyprus resulted from the sedimentation of dust originating from the Negev, followed by dry deposition at the surface. The dust particles were both pristine and polluted (sulphate coated), and we evaluate the role of mixing in the duration and extent of the episodes.

Impact of 3-D orographic gravity wave parameterisation on stratosphere dynamics

NASA Astrophysics Data System (ADS)

Eichinger, Roland; Garny, Hella; Cai, Duy; Jöckel, Patrick

2017-04-01

Stratosphere dynamics are strongly influenced by gravity waves (GWs) propagating upwards from the troposphere. Some of these GWs are generated through flow over small-scale orography and can not be resolved by common general circulation models (GCMs). Due to computational model designs, their parameterisation usually follows a one dimensional columnar approach that, among other simplifications, neglects the horizontal propagation of GWs on their way up into the Middle Atmosphere. This causes contradictions between models and observations in location and strength of GW drag force through their dissipation and as a consequence, also in stratospheric mean flow. In the EMAC (ECHAM MESSy Atmospheric Chemistry) model, we have found this deficiency to cause a too weak Antarctic polar vortex, which directly impacts stratospheric temperatures and thereby the chemical reactions that determine ozone depletion. For this reason, we adapt a three dimensional parameterisation for orographic GWs, that had been implemented and tested in the MIROC GCM, to the MESSy coding standard. This computationally light scheme can then be used in a modular and flexible way in a cascade of model setups from an idealised version for conceptional process analyses to full climate chemistry simulations for quantitative investigations. This model enhancement can help to reconcile models and observations in wave drag forcing itself, but in consequence, also in Brewer-Dobson Circulation trends across the recent decades. Furthermore, uncertainties in weather and climate predictions as well as in future ozone projections can be reduced.

Atmospheric winter response to Arctic sea ice changes in reanalysis data and model simulations

NASA Astrophysics Data System (ADS)

Jaiser, Ralf; Nakamura, Tetsu; Handorf, Dörthe; Romanowsky, Erik; Dethloff, Klaus; Ukita, Jinro; Yamazaki, Koji

2017-04-01

In recent years, Arctic regions showcased the most pronounced signals of a changing climate: Sea ice is reduced by more the ten percent per decade. At the same time, global warming trends have their maximum in Arctic latitudes often labled Arctic Amplification. There is strong evidence that amplified Arctic changes feed back into mid-latitudes in winter. We identified mechanisms that link recent Arctic changes through vertically propagating planetary waves to events of a weakened stratospheric polar vortex. Related anomalies propagate downward and lead to negative AO-like situations in the troposphere. European winter climate is sensitive to negative AO situations in terms of cold air outbreaks that are likely to occur more often in that case. These results based on ERA-Interim reanalysis data do not allow to dismiss other potential forcing factors leading to observed mid-latitude climate changes. Nevertheless, properly designed Atmospheric General Circulation Model (AGCM) experiments with AFES and ECHAM6 are able to reproduce observed atmospheric circulation changes if only observed sea ice changes in the Arctic are prescribed. This allows to deduce mechanisms that explain how Arctic Amplification can lead to a negative AO response via a stratospheric pathway. Further investigation of these mechanisms may feed into improved prediction systems.

Evaluation of a Mineral Dust Simulation in the Atmospheric-Chemistry General Circulation Model-EMAC

NASA Astrophysics Data System (ADS)

Abdel Kader, M.; Astitha, M.; Lelieveld, J.

2012-04-01

This study presents an evaluation of the atmospheric mineral dust cycle in the Atmospheric Chemistry General Circulation Model (AC-GCM) using new developed dust emissions scheme. The dust cycle, as an integral part of the Earth System, plays an important role in the Earth's energy balance by both direct and indirect ways. As an aerosol, it significantly impacts the absorption and scattering of radiation in the atmosphere and can modify the optical properties of clouds and snow/ice surfaces. In addition, dust contributes to a range of physical, chemical and bio-geological processes that interact with the cycles of carbon and water. While our knowledge of the dust cycle, its impacts and interactions with the other global-scale bio-geochemical cycles has greatly advanced in the last decades, large uncertainties and knowledge gaps still exist. Improving the dust simulation in global models is essential to minimize the uncertainties in the model results related to dust. In this study, the results are based on the ECHAM5 Modular Earth Submodel System (MESSy) AC-GCM simulations using T106L31 spectral resolution (about 120km ) with 31 vertical levels. The GMXe aerosol submodel is used to simulate the phase changes of the dust particles between soluble and insoluble modes. Dust emission, transport and deposition (wet and dry) are calculated on-line along with the meteorological parameters in every model time step. The preliminary evaluation of the dust concentration and deposition are presented based on ground observations from various campaigns as well as the evaluation of the optical properties of dust using AERONET and satellite (MODIS and MISR) observations. Preliminarily results show good agreement with observations for dust deposition and optical properties. In addition, the global dust emissions, load, deposition and lifetime is in good agreement with the published results. Also, the uncertainties in the dust cycle that contribute to the overall model performance will be briefly discussed as it is a subject of future work.

Multi-model projections of Indian summer monsoon climate changes under A1B scenario

NASA Astrophysics Data System (ADS)

Niu, X.; Wang, S.; Tang, J.

2016-12-01

As part of the Regional Climate Model Intercomparison Project for Asia, the projections of Indian summer monsoon climate changes are constructed using three global climate models (GCMs) and seven regional climate models (RCMs) during 2041-2060 based on the Intergovernmental Panel on Climate Change A1B emission scenario. For the control climate of 1981-2000, most nested RCMs show advantage over the driving GCM of European Centre/Hamburg Fifth Generation (ECHAM5) in the temporal-spatial distributions of temperature and precipitation over Indian Peninsula. Following the driving GCM of ECHAM5, most nested RCMs produce advanced monsoon onset in the control climate. For future climate widespread summer warming is projected over Indian Peninsula by all climate models, with the Multi-RCMs ensemble mean (MME) temperature increasing of 1°C to 2.5°C and the maximum warming center located in northern Indian Peninsula. While for the precipitation, a large inter-model spread is projected by RCMs, with wetter condition in MME projections and significant increase over southern India. Driven by the same GCM, most RCMs project advanced monsoon onset while delayed onset is found in two Regional Climate Model (RegCM3) projections, indicating uncertainty can be expected in the Indian Summer Monsoon onset. All climate models except Conformal-Cubic Atmospheric Model with equal resolution (referred as CCAMP) and two RegCM3 models project stronger summer monsoon during 2041-2060. The disagreement in precipitation projections by RCMs indicates that the surface climate change on regional scale is not only dominated by the large-scale forcing which is provided by driving GCM but also sensitive to RCM' internal physics.

Pinatubo eruption winter climate effects: Model versus observations

NASA Technical Reports Server (NTRS)

Graf, HANS-F.; Kirchner, Ingo; Schult, Ingrid; Robock, Alan

1992-01-01

Large volcanic eruptions, in addition to the well-known effect of producing global cooling for a year or two, have been observed to produce shorter-term responses in the climate system involving non-linear dynamical processes. In this paper, we use the ECHAM2 general circulation model forced with stratospheric aerosols to test some of these ideas. Run in a perpetual-January mode, with tropical stratospheric heating from the volcanic aerosols typical of the 1982 El Chichon eruption or the 1991 Pinatubo eruption, we find a dynamical response with an increased polar night jet in the Northern Hemisphere (NH) and stronger zonal winds which extended down into the troposphere. The Azores High shifts northward with increased tropospheric westerlies at 60N and increased easterlies at 30N. Surface temperatures are higher both in northern Eurasia and North America, in agreement with observations for the NH winters or 1982-83 and 1991-92 as well as the winters following the other 10 largest volcanic eruptions since 1883.

An "island" in the stratosphere - on the enhanced annual variation of water vapour in the middle and upper stratosphere in the southern tropics and subtropics

NASA Astrophysics Data System (ADS)

Lossow, Stefan; Garny, Hella; Jöckel, Patrick

2017-09-01

The amplitude of the annual variation in water vapour exhibits a distinct isolated maximum in the middle and upper stratosphere in the southern tropics and subtropics, peaking typically around 15° S in latitude and close to 3 hPa (˜ 40.5 km) in altitude. This enhanced annual variation is primarily related to the Brewer-Dobson circulation and hence also visible in other trace gases. So far this feature has not gained much attention in the literature and the present work aims to add more prominence. Using Envisat/MIPAS (Environmental Satellite/Michelson Interferometer for Passive Atmospheric Sounding) observations and ECHAM/MESSy (European Centre for Medium-Range Weather Forecasts Hamburg/Modular Earth Submodel System) Atmospheric Chemistry (EMAC) simulations we provide a dedicated illustration and a full account of the reasons for this enhanced annual variation.

Towards multi-resolution global climate modeling with ECHAM6-FESOM. Part II: climate variability

NASA Astrophysics Data System (ADS)

Rackow, T.; Goessling, H. F.; Jung, T.; Sidorenko, D.; Semmler, T.; Barbi, D.; Handorf, D.

2018-04-01

This study forms part II of two papers describing ECHAM6-FESOM, a newly established global climate model with a unique multi-resolution sea ice-ocean component. While part I deals with the model description and the mean climate state, here we examine the internal climate variability of the model under constant present-day (1990) conditions. We (1) assess the internal variations in the model in terms of objective variability performance indices, (2) analyze variations in global mean surface temperature and put them in context to variations in the observed record, with particular emphasis on the recent warming slowdown, (3) analyze and validate the most common atmospheric and oceanic variability patterns, (4) diagnose the potential predictability of various climate indices, and (5) put the multi-resolution approach to the test by comparing two setups that differ only in oceanic resolution in the equatorial belt, where one ocean mesh keeps the coarse 1° resolution applied in the adjacent open-ocean regions and the other mesh is gradually refined to 0.25°. Objective variability performance indices show that, in the considered setups, ECHAM6-FESOM performs overall favourably compared to five well-established climate models. Internal variations of the global mean surface temperature in the model are consistent with observed fluctuations and suggest that the recent warming slowdown can be explained as a once-in-one-hundred-years event caused by internal climate variability; periods of strong cooling in the model (`hiatus' analogs) are mainly associated with ENSO-related variability and to a lesser degree also to PDO shifts, with the AMO playing a minor role. Common atmospheric and oceanic variability patterns are simulated largely consistent with their real counterparts. Typical deficits also found in other models at similar resolutions remain, in particular too weak non-seasonal variability of SSTs over large parts of the ocean and episodic periods of almost absent deep-water formation in the Labrador Sea, resulting in overestimated North Atlantic SST variability. Concerning the influence of locally (isotropically) increased resolution, the ENSO pattern and index statistics improve significantly with higher resolution around the equator, illustrating the potential of the novel unstructured-mesh method for global climate modeling.

Climate change and watershed mercury export: a multiple projection and model analysis

USGS Publications Warehouse

Golden, Heather E.; Knightes, Christopher D.; Conrads, Paul; Feaster, Toby D.; Davis, Gary M.; Benedict, Stephen T.; Bradley, Paul M.

2013-01-01

Future shifts in climatic conditions may impact watershed mercury (Hg) dynamics and transport. An ensemble of watershed models was applied in the present study to simulate and evaluate the responses of hydrological and total Hg (THg) fluxes from the landscape to the watershed outlet and in-stream THg concentrations to contrasting climate change projections for a watershed in the southeastern coastal plain of the United States. Simulations were conducted under stationary atmospheric deposition and land cover conditions to explicitly evaluate the effect of projected precipitation and temperature on watershed Hg export (i.e., the flux of Hg at the watershed outlet). Based on downscaled inputs from 2 global circulation models that capture extremes of projected wet (Community Climate System Model, Ver 3 [CCSM3]) and dry (ECHAM4/HOPE-G [ECHO]) conditions for this region, watershed model simulation results suggest a decrease of approximately 19% in ensemble-averaged mean annual watershed THg fluxes using the ECHO climate-change model and an increase of approximately 5% in THg fluxes with the CCSM3 model. Ensemble-averaged mean annual ECHO in-stream THg concentrations increased 20%, while those of CCSM3 decreased by 9% between the baseline and projected simulation periods. Watershed model simulation results using both climate change models suggest that monthly watershed THg fluxes increase during the summer, when projected flow is higher than baseline conditions. The present study's multiple watershed model approach underscores the uncertainty associated with climate change response projections and their use in climate change management decisions. Thus, single-model predictions can be misleading, particularly in developmental stages of watershed Hg modeling.

Evaluation of Multi-Model Ensemble System for Seasonal and Monthly Prediction

NASA Astrophysics Data System (ADS)

Zhang, Q.; Van den Dool, H. M.

2013-12-01

Since August 2011, the realtime seasonal forecasts of U.S. National Multi-Model Ensemble (NMME) have been made on 8th of each month by NCEP Climate Prediction Center (CPC). During the first year, the participating models were NCEP/CFSv1&2, GFDL/CM2.2, NCAR/U.Miami/COLA/CCSM3, NASA/GEOS5, IRI/ ECHAM-a & ECHAM-f for the realtime NMME forecast. The Canadian Meteorological Center CanCM3 and CM4 replaced the CFSv1 and IRI's models in the second year. The NMME team at CPC collects three variables, including precipitation, 2-meter temperature and sea surface temperature from each modeling center on a 1x1 global grid, removes systematic errors, makes the grand ensemble mean with equal weight for each model and constructs a probability forecast with equal weight for each member. The team then provides the NMME forecast to the operational CPC forecaster responsible for the seasonal and monthly outlook each month. Verification of the seasonal and monthly prediction from NMME is conducted by calculating the anomaly correlation (AC) from the 30-year hindcasts (1982-2011) of individual model and NMME ensemble. The motivation of this study is to provide skill benchmarks for future improvements of the NMME seasonal and monthly prediction system. The experimental (Phase I) stage of the project already supplies routine guidance to users of the NMME forecasts.

Hydrogen peroxide in the marine boundary layer over the South Atlantic during the OOMPH cruise in March 2007

NASA Astrophysics Data System (ADS)

Fischer, H.; Pozzer, A.; Schmitt, T.; Jöckel, P.; Klippel, T.; Taraborrelli, D.; Lelieveld, J.

2015-06-01

In the OOMPH (Ocean Organics Modifying Particles in both Hemispheres) project a ship measurement cruise took place in the late austral summer from 01 to 23 March 2007. The French research vessel Marion Dufresne sailed from Punta Arenas, Chile (70.85° W, 53.12° S), to Réunion island (55.36° E, 21.06° S) across the South Atlantic Ocean. In situ measurements of hydrogen peroxide, methylhydroperoxide and ozone were performed and are compared to simulations with the atmospheric chemistry global circulation model EMAC (ECHAM/MESSy Atmospheric Chemistry). The model generally reproduces the measured trace gas levels, but it underestimates hydrogen peroxide mixing ratios at high wind speeds, indicating too-strong dry deposition to the ocean surface. An interesting feature during the cruise is a strong increase of hydrogen peroxide, methylhydroperoxide and ozone shortly after midnight off the west coast of Africa due to an increase in the boundary layer height, leading to downward transport from the free troposphere, which is qualitatively reproduced by the model.

Modeling the influence of atmospheric leading modes on the variability of the Arctic freshwater cycle

NASA Astrophysics Data System (ADS)

Niederdrenk, L.; Sein, D.; Mikolajewicz, U.

2013-12-01

Global general circulation models show remarkable differences in modeling the Arctic freshwater cycle. While they agree on the general sinks and sources of the freshwater budget, they differ largely in the magnitude of the mean values as well as in the variability of the freshwater terms. Regional models can better resolve the complex topography and small scale processes, but they are often uncoupled, thus missing the air-sea interaction. Additionally, regional models mostly use some kind of salinity restoring or flux correction, thus disturbing the freshwater budget. Our approach to investigate the Arctic hydrologic cycle and its variability is a regional atmosphere-ocean model setup, consisting of the global ocean model MPIOM with high resolution in the Arctic coupled to the regional atmosphere model REMO. The domain of the atmosphere model covers all catchment areas of the rivers draining into the Arctic. To account for all sinks and sources of freshwater in the Arctic, we include a discharge model providing terrestrial lateral waterflows. We run the model without salinity restoring but with freshwater correction, which is set to zero in the Arctic. This allows for the analysis of a closed freshwater budget in the Artic region. We perform experiments for the second half of the 20th century and use data from the global model MPIOM/ECHAM5 performed with historical conditions, that was used within the 4th Assessment Report of the IPCC, as forcing for our regional model. With this setup, we investigate how the dominant modes of large-scale atmospheric variability impact the variability in the freshwater components. We focus on the two leading empirical orthogonal functions of winter mean sea level pressure, as well as on the North Atlantic Oscillation and the Siberian High. These modes have a large impact on the Arctic Ocean circulation as well as on the solid and liquid export through Fram Strait and through the Canadian archipelago. However, they cannot explain the variability in river runoff. We find that not only winter conditions are responsible for increased river runoff, but also an enhanced summer cyclone activity, especially over Eurasia.

Improving groundwater predictions utilizing seasonal precipitation forecasts from general circulation models forced with sea surface temperature forecasts

USGS Publications Warehouse

Almanaseer, Naser; Sankarasubramanian, A.; Bales, Jerad

2014-01-01

Recent studies have found a significant association between climatic variability and basin hydroclimatology, particularly groundwater levels, over the southeast United States. The research reported in this paper evaluates the potential in developing 6-month-ahead groundwater-level forecasts based on the precipitation forecasts from ECHAM 4.5 General Circulation Model Forced with Sea Surface Temperature forecasts. Ten groundwater wells and nine streamgauges from the USGS Groundwater Climate Response Network and Hydro-Climatic Data Network were selected to represent groundwater and surface water flows, respectively, having minimal anthropogenic influences within the Flint River Basin in Georgia, United States. The writers employ two low-dimensional models [principle component regression (PCR) and canonical correlation analysis (CCA)] for predicting groundwater and streamflow at both seasonal and monthly timescales. Three modeling schemes are considered at the beginning of January to predict winter (January, February, and March) and spring (April, May, and June) streamflow and groundwater for the selected sites within the Flint River Basin. The first scheme (model 1) is a null model and is developed using PCR for every streamflow and groundwater site using previous 3-month observations (October, November, and December) available at that particular site as predictors. Modeling schemes 2 and 3 are developed using PCR and CCA, respectively, to evaluate the role of precipitation forecasts in improving monthly and seasonal groundwater predictions. Modeling scheme 3, which employs a CCA approach, is developed for each site by considering observed groundwater levels from nearby sites as predictands. The performance of these three schemes is evaluated using two metrics (correlation coefficient and relative RMS error) by developing groundwater-level forecasts based on leave-five-out cross-validation. Results from the research reported in this paper show that using precipitation forecasts in climate models improves the ability to predict the interannual variability of winter and spring streamflow and groundwater levels over the basin. However, significant conditional bias exists in all the three modeling schemes, which indicates the need to consider improved modeling schemes as well as the availability of longer time-series of observed hydroclimatic information over the basin.

The impact of Tibet and the Andes on the climate and isotopic composition of precipitation

NASA Astrophysics Data System (ADS)

Battisti, D. S.; Ding, Q.; Liu, X.; Roe, G.

2012-12-01

We summarize modeling and theoretical evidence for the impact of the high topography in Tibet and the Andes on the climate and the isotopic (δ18O) composition of precipitation, regionally and globally. Tibet controls the seasonal cycle of precipitation over eastern China, mainly via dynamical processes, and has little to no impact on the Indian and southeast Asian monsoons. Tibet is also responsible for the northwesterly winds and extraordinary cold winters in northern China, and contributes to the mid-winter suppression of storminess in the western and central Pacific. The Andes greatly shape the climatological precipitation over South America, and are an important contributor to the annual cycle in sea surface temperature, precipitation and atmospheric circulation throughout the eastern half of the tropical Pacific. We have performed a series of numerical experiments with the isotope-enabled ECHAM 4.6 atmospheric general circulation model to illuminate the impact of the Andes and Tibet on the regional distribution of oxygen isotopes in precipitation. Experiments to be discussed include a world without an elevated Andes circa 12 million years BP, and a series of experiments that prescribed a plausible evolution of the continental geometry and topography for the past 50 million years in and around the Indian Ocean basin. In the latter case, additional idealized experiments are performed to illuminate the separate impacts of topography and continental configuration.

Technical Note: On the use of nudging for aerosol–climate model intercomparison studies

DOE PAGES

Zhang, K.; Wan, H.; Liu, X.; ...

2014-08-26

Nudging as an assimilation technique has seen increased use in recent years in the development and evaluation of climate models. Constraining the simulated wind and temperature fields using global weather reanalysis facilitates more straightforward comparison between simulation and observation, and reduces uncertainties associated with natural variabilities of the large-scale circulation. On the other hand, the forcing introduced by nudging can be strong enough to change the basic characteristics of the model climate. In the paper we show that for the Community Atmosphere Model version 5 (CAM5), due to the systematic temperature bias in the standard model and the sensitivity ofmore » simulated ice formation to anthropogenic aerosol concentration, nudging towards reanalysis results in substantial reductions in the ice cloud amount and the impact of anthropogenic aerosols on long-wave cloud forcing. In order to reduce discrepancies between the nudged and unconstrained simulations, and meanwhile take the advantages of nudging, two alternative experimentation methods are evaluated. The first one constrains only the horizontal winds. The second method nudges both winds and temperature, but replaces the long-term climatology of the reanalysis by that of the model. Results show that both methods lead to substantially improved agreement with the free-running model in terms of the top-of-atmosphere radiation budget and cloud ice amount. The wind-only nudging is more convenient to apply, and provides higher correlations of the wind fields, geopotential height and specific humidity between simulation and reanalysis. Results from both CAM5 and a second aerosol–climate model ECHAM6-HAM2 also indicate that compared to the wind-and-temperature nudging, constraining only winds leads to better agreement with the free-running model in terms of the estimated shortwave cloud forcing and the simulated convective activities. This suggests nudging the horizontal winds but not temperature is a good strategy for the investigation of aerosol indirect effects since it provides well-constrained meteorology without strongly perturbing the model's mean climate.« less

Technical Note: On the use of nudging for aerosol-climate model intercomparison studies

NASA Astrophysics Data System (ADS)

Zhang, K.; Wan, H.; Liu, X.; Ghan, S. J.; Kooperman, G. J.; Ma, P.-L.; Rasch, P. J.; Neubauer, D.; Lohmann, U.

2014-08-01

Nudging as an assimilation technique has seen increased use in recent years in the development and evaluation of climate models. Constraining the simulated wind and temperature fields using global weather reanalysis facilitates more straightforward comparison between simulation and observation, and reduces uncertainties associated with natural variabilities of the large-scale circulation. On the other hand, the forcing introduced by nudging can be strong enough to change the basic characteristics of the model climate. In the paper we show that for the Community Atmosphere Model version 5 (CAM5), due to the systematic temperature bias in the standard model and the sensitivity of simulated ice formation to anthropogenic aerosol concentration, nudging towards reanalysis results in substantial reductions in the ice cloud amount and the impact of anthropogenic aerosols on long-wave cloud forcing. In order to reduce discrepancies between the nudged and unconstrained simulations, and meanwhile take the advantages of nudging, two alternative experimentation methods are evaluated. The first one constrains only the horizontal winds. The second method nudges both winds and temperature, but replaces the long-term climatology of the reanalysis by that of the model. Results show that both methods lead to substantially improved agreement with the free-running model in terms of the top-of-atmosphere radiation budget and cloud ice amount. The wind-only nudging is more convenient to apply, and provides higher correlations of the wind fields, geopotential height and specific humidity between simulation and reanalysis. Results from both CAM5 and a second aerosol-climate model ECHAM6-HAM2 also indicate that compared to the wind-and-temperature nudging, constraining only winds leads to better agreement with the free-running model in terms of the estimated shortwave cloud forcing and the simulated convective activities. This suggests nudging the horizontal winds but not temperature is a good strategy for the investigation of aerosol indirect effects since it provides well-constrained meteorology without strongly perturbing the model's mean climate.

Climate Downscaling over Nordeste, Brazil, Using the NCEP RSM97.

NASA Astrophysics Data System (ADS)

Sun, Liqiang; Ferran Moncunill, David; Li, Huilan; Divino Moura, Antonio; de Assis de Souza Filho, Francisco

2005-02-01

The NCEP Regional Spectral Model (RSM), with horizontal resolution of 60 km, was used to downscale the ECHAM4.5 AGCM (T42) simulations forced with observed SSTs over northeast Brazil. An ensemble of 10 runs for the period January-June 1971-2000 was used in this study. The RSM can resolve the spatial patterns of observed seasonal precipitation and capture the interannual variability of observed seasonal precipitation as well. The AGCM bias in displacement of the Atlantic ITCZ is partially corrected in the RSM. The RSM probability distribution function of seasonal precipitation anomalies is in better agreement with observations than that of the driving AGCM. Good potential prediction skills are demonstrated by the RSM in predicting the interannual variability of regional seasonal precipitation. The RSM can also capture the interannual variability of observed precipitation at intraseasonal time scales, such as precipitation intensity distribution and dry spells. A drought index and a flooding index were adopted to indicate the severity of drought and flooding conditions, and their interannual variability was reproduced by the RSM. The overall RSM performance in the downscaled climate of the ECHAM4.5 AGCM is satisfactory over Nordeste. The primary deficiency is a systematic dry bias for precipitation simulation.

Aerosol processing in stratiform clouds in ECHAM6-HAM

NASA Astrophysics Data System (ADS)

Neubauer, David; Lohmann, Ulrike; Hoose, Corinna

2013-04-01

Aerosol processing in stratiform clouds by uptake into cloud particles, collision-coalescence, chemical processing inside the cloud particles and release back into the atmosphere has important effects on aerosol concentration, size distribution, chemical composition and mixing state. Aerosol particles can act as cloud condensation nuclei. Cloud droplets can take up further aerosol particles by collisions. Atmospheric gases may also be transferred into the cloud droplets and undergo chemical reactions, e.g. the production of atmospheric sulphate. Aerosol particles are also processed in ice crystals. They may be taken up by homogeneous freezing of cloud droplets below -38° C or by heterogeneous freezing above -38° C. This includes immersion freezing of already immersed aerosol particles in the droplets and contact freezing of particles colliding with a droplet. Many clouds do not form precipitation and also much of the precipitation evaporates before it reaches the ground. The water soluble part of the aerosol particles concentrates in the hydrometeors and together with the insoluble part forms a single, mixed, larger particle, which is released. We have implemented aerosol processing into the current version of the general circulation model ECHAM6 (Stevens et al., 2013) coupled to the aerosol module HAM (Stier et al., 2005). ECHAM6-HAM solves prognostic equations for the cloud droplet number and ice crystal number concentrations. In the standard version of HAM, seven modes are used to describe the total aerosol. The modes are divided into soluble/mixed and insoluble modes and the number concentrations and masses of different chemical components (sulphate, black carbon, organic carbon, sea salt and mineral dust) are prognostic variables. We extended this by an explicit representation of aerosol particles in cloud droplets and ice crystals in stratiform clouds similar to Hoose et al. (2008a,b). Aerosol particles in cloud droplets are represented by 5 tracers for the chemical components as well as 5 tracers for aerosol particles in ice crystals. This allows simulations of aerosol processing in warm, mixed-phase (e.g. through the Bergeron-Findeisen process) and ice clouds. The fixed scavenging ratios used for wet deposition in clouds in standard HAM are replaced by an explicit treatment of collision of cloud droplets/ice crystals with interstitial aerosol particles. Nucleation scavenging of aerosol particles by acting as cloud condensation nuclei or ice nuclei, freezing and evaporation of cloud droplets and melting and sublimation of ice crystals are treated explicitly. In extension to previous studies, aerosol particles from evaporating precipitation are released to modes which correspond to their size. Cloud processing of aerosol particles changes their size distribution and hence influences cloud droplet and ice crystal number concentrations as well as precipitation rate, which in turn affects aerosol concentrations. Results will be presented at the conference. Hoose et al., JGR, 2008a, doi: 10.1029/2007JD009251 Hoose et al., ACP, 2008b, doi: 10.5194/acp-8-6939-2008 Stevens et al., 2013, submitted Stier et al., ACP, 2005, doi: 10.5194/acp-5-1125-2005

Future aerosol concentrations in Europe: Effects of changing meteorology and emissions

NASA Astrophysics Data System (ADS)

Coleman, Liz; Martin, Damien; Radalescu, Razvan; O'Dowd, Colin

2013-05-01

The ambient particulate matter concentrations are assessed using annual simulations for model validation period 2006, and for future time-slice years 2030, 2050 and 2100 under RCP scenario 6.0. Meteorological initial and boundary conditions are procured from ECHAM5-HAMMOC global simulations. The contribution of natural and anthropogenic processes to aerosol concentrations are assessed with particular emphasis on accumulation mode sea salt, organic enrichment thereof and future levels of secondary organic aerosol from isoprene.

Global radiative adjustment after a collapse of the Atlantic meridional overturning circulation

NASA Astrophysics Data System (ADS)

Drijfhout, Sybren S.

2015-10-01

The transient climate response to a collapse of the Atlantic meridional overturning circulation (AMOC) is analysed from the difference between two ensembles of climate model simulations with ECHAM5/MPI-OM, one with hosing and the other without hosing. The primary effect of the collapse is to redistribute heat over the two hemispheres. However, Northern Hemisphere sea ice increase in response to the AMOC collapse induces a hemisphere-wide cooling, amplified by atmospheric feedbacks, in particular water vapour. The Southern Hemisphere warming is governed by slower processes. After 25 years the global cooling peaks. Thereafter, the response is characterised by a gradual readjustment of global mean temperature. During the AMOC collapse a downward radiation anomaly arises at the top of the atmosphere (TOA), heating the earth's surface. The net downward radiation anomaly at TOA arises from reduced longwave emission by the atmosphere, overcompensating the increased net upward anomalies in shortwave and longwave radiation at the surface. This radiation anomaly is associated with net ocean heat uptake: cooling of the overlying atmosphere results from reduced ocean heat release through the increase of sea-ice cover in the North Atlantic. The change in energy flow arises from the reduction in latent and sensible heat flux, which dominate the surface radiation budget. Similar experiments with a climate model of intermediate complexity reveal a stronger shortwave response that acts to reduce the net downward radiation anomaly at TOA. The net shortwave and longwave radiation anomalies at TOA always decrease during the first 100 years after the AMOC collapse, but in the intermediate complexity model this is associated with a sign change after 90 years when the net radiation anomaly at TOA becomes upward, accompanied by net ocean heat loss. After several hundred years the longwave and shortwave anomalies increase again, while the net residual at TOA remains small. This radiative adjustment is associated with the transition to a colder climate.

Parameterization of dust emissions in the global atmospheric chemistry-climate model EMAC: impact of nudging and soil properties

NASA Astrophysics Data System (ADS)

Astitha, M.; Lelieveld, J.; Abdel Kader, M.; Pozzer, A.; de Meij, A.

2012-11-01

Airborne desert dust influences radiative transfer, atmospheric chemistry and dynamics, as well as nutrient transport and deposition. It directly and indirectly affects climate on regional and global scales. Two versions of a parameterization scheme to compute desert dust emissions are incorporated into the atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy2.41 Atmospheric Chemistry). One uses a globally uniform soil particle size distribution, whereas the other explicitly accounts for different soil textures worldwide. We have tested these two versions and investigated the sensitivity to input parameters, using remote sensing data from the Aerosol Robotic Network (AERONET) and dust concentrations and deposition measurements from the AeroCom dust benchmark database (and others). The two versions are shown to produce similar atmospheric dust loads in the N-African region, while they deviate in the Asian, Middle Eastern and S-American regions. The dust outflow from Africa over the Atlantic Ocean is accurately simulated by both schemes, in magnitude, location and seasonality. Approximately 70% of the modelled annual deposition data and 70-75% of the modelled monthly aerosol optical depth (AOD) in the Atlantic Ocean stations lay in the range 0.5 to 2 times the observations for all simulations. The two versions have similar performance, even though the total annual source differs by ~50%, which underscores the importance of transport and deposition processes (being the same for both versions). Even though the explicit soil particle size distribution is considered more realistic, the simpler scheme appears to perform better in several locations. This paper discusses the differences between the two versions of the dust emission scheme, focusing on their limitations and strengths in describing the global dust cycle and suggests possible future improvements.

Climate change and watershed mercury export: a multiple projection and model analysis.

PubMed

Golden, Heather E; Knightes, Christopher D; Conrads, Paul A; Feaster, Toby D; Davis, Gary M; Benedict, Stephen T; Bradley, Paul M

2013-09-01

Future shifts in climatic conditions may impact watershed mercury (Hg) dynamics and transport. An ensemble of watershed models was applied in the present study to simulate and evaluate the responses of hydrological and total Hg (THg) fluxes from the landscape to the watershed outlet and in-stream THg concentrations to contrasting climate change projections for a watershed in the southeastern coastal plain of the United States. Simulations were conducted under stationary atmospheric deposition and land cover conditions to explicitly evaluate the effect of projected precipitation and temperature on watershed Hg export (i.e., the flux of Hg at the watershed outlet). Based on downscaled inputs from 2 global circulation models that capture extremes of projected wet (Community Climate System Model, Ver 3 [CCSM3]) and dry (ECHAM4/HOPE-G [ECHO]) conditions for this region, watershed model simulation results suggest a decrease of approximately 19% in ensemble-averaged mean annual watershed THg fluxes using the ECHO climate-change model and an increase of approximately 5% in THg fluxes with the CCSM3 model. Ensemble-averaged mean annual ECHO in-stream THg concentrations increased 20%, while those of CCSM3 decreased by 9% between the baseline and projected simulation periods. Watershed model simulation results using both climate change models suggest that monthly watershed THg fluxes increase during the summer, when projected flow is higher than baseline conditions. The present study's multiple watershed model approach underscores the uncertainty associated with climate change response projections and their use in climate change management decisions. Thus, single-model predictions can be misleading, particularly in developmental stages of watershed Hg modeling. Copyright © 2013 SETAC.

Impacts of deforestation and afforestation in the Mediterranean region as simulated by the MPI atmospheric GCM

NASA Astrophysics Data System (ADS)

Dümenil Gates, Lydia; Ließ, Stefan

2001-10-01

For two reasons it is important to study the sensitivity of the global climate to changes in the vegetation cover over land. First, in the real world, changes in the vegetation cover may have regional and global implications. Second, in numerical simulations, the sensitivity of the simulated climate may depend on the specific parameterization schemes employed in the model and on the model's large-scale systematic errors. The Max-Planck-Institute's global general circulation model ECHAM4 has been used to study the sensitivity of the local and global climate during a full annual cycle to deforestation and afforestation in the Mediterranean region. The deforestation represents an extreme desertification scenario for this region. The changes in the afforestation experiment are based on the pattern of the vegetation cover 2000 years before present when the climate in the Mediterranean was more humid. The comparison of the deforestation integration to the control shows a slight cooling at the surface and reduced precipitation during the summer as a result of less evapotranspiration of plants and less evaporation from the assumption of eroded soils. There is no significant signal during the winter season due to the stronger influence of the mid-latitude baroclinic disturbances. In general, the results of the afforestation experiment are opposite to those of the deforestation case. A significant response was found in the vicinity of grid points where the land surface characteristics were modified. The response in the Sahara in the afforestation experiment is in agreement with the results from other general circulation model studies.

Modelling absorbing aerosol with ECHAM-HAM: Insights from regional studies

NASA Astrophysics Data System (ADS)

Tegen, Ina; Heinold, Bernd; Schepanski, Kerstin; Banks, Jamie; Kubin, Anne; Schacht, Jacob

2017-04-01

Quantifying distributions and properties of absorbing aerosol is a basis for investigations of interactions of aerosol particles with radiation and climate. While evaluations of aerosol models by field measurements can be particularly successful at the regional scale, such results need to be put into a global context for climate studies. We present an overview over studies performed at the Leibniz Institute for Tropospheric Research aiming at constraining the properties of mineral dust and soot aerosol in the global aerosol model ECHAM6-HAM2 based on different regional studies. An example is the impact of different sources for dust transported to central Asia, which is influenced, by far-range transport of dust from Arabia and the Sahara together with dust from local sources. Dust types from these different source regions were investigated in the context of the CADEX project and are expected to have different optical properties. For Saharan dust, satellite retrievals from MSG SEVIRI are used to constrain Saharan dust sources and optical properties. In the Arctic region, on one hand dust aerosol is simulated in the framework of the PalMod project. On the other hand aerosol measurements that will be taken during the DFG-funded (AC)3 field campaigns will be used to evaluate the simulated transport pathways of soot aerosol from European, North American and Asian sources, as well as the parameterization of soot ageing processes in ECHAM6-HAM2. Ultimately, results from these studies will improve the representation of aerosol absorption in the global model.

Impact of climate change on ozone-related mortality and morbidity in Europe.

PubMed

Orru, Hans; Andersson, Camilla; Ebi, Kristie L; Langner, Joakim; Aström, Christofer; Forsberg, Bertil

2013-02-01

Ozone is a highly oxidative pollutant formed from precursors in the presence of sunlight, associated with respiratory morbidity and mortality. All else being equal, concentrations of ground-level ozone are expected to increase due to climate change. Ozone-related health impacts under a changing climate are projected using emission scenarios, models and epidemiological data. European ozone concentrations are modelled with the model of atmospheric transport and chemistry (MATCH)-RCA3 (50×50 km). Projections from two climate models, ECHAM4 and HadCM3, are applied under greenhouse gas emission scenarios A2 and A1B, respectively. We applied a European-wide exposure-response function to gridded population data and country-specific baseline mortality and morbidity. Comparing the current situation (1990-2009) with the baseline period (1961-1990), the largest increase in ozone-associated mortality and morbidity due to climate change (4-5%) have occurred in Belgium, Ireland, the Netherlands and the UK. Comparing the baseline period and the future periods (2021-2050 and 2041-2060), much larger increases in ozone-related mortality and morbidity are projected for Belgium, France, Spain and Portugal, with the impact being stronger using the climate projection from ECHAM4 (A2). However, in Nordic and Baltic countries the same magnitude of decrease is projected. The current study suggests that projected effects of climate change on ozone concentrations could differentially influence mortality and morbidity across Europe.

Evaluation of Oceanic Surface Observation for Reproducing the Upper Ocean Structure in ECHAM5/MPI-OM

NASA Astrophysics Data System (ADS)

Luo, Hao; Zheng, Fei; Zhu, Jiang

2017-12-01

Better constraints of initial conditions from data assimilation are necessary for climate simulations and predictions, and they are particularly important for the ocean due to its long climate memory; as such, ocean data assimilation (ODA) is regarded as an effective tool for seasonal to decadal predictions. In this work, an ODA system is established for a coupled climate model (ECHAM5/MPI-OM), which can assimilate all available oceanic observations using an ensemble optimal interpolation approach. To validate and isolate the performance of different surface observations in reproducing air-sea climate variations in the model, a set of observing system simulation experiments (OSSEs) was performed over 150 model years. Generally, assimilating sea surface temperature, sea surface salinity, and sea surface height (SSH) can reasonably reproduce the climate variability and vertical structure of the upper ocean, and assimilating SSH achieves the best results compared to the true states. For the El Niño-Southern Oscillation (ENSO), assimilating different surface observations captures true aspects of ENSO well, but assimilating SSH can further enhance the accuracy of ENSO-related feedback processes in the coupled model, leading to a more reasonable ENSO evolution and air-sea interaction over the tropical Pacific. For ocean heat content, there are still limitations in reproducing the long time-scale variability in the North Atlantic, even if SSH has been taken into consideration. These results demonstrate the effectiveness of assimilating surface observations in capturing the interannual signal and, to some extent, the decadal signal but still highlight the necessity of assimilating profile data to reproduce specific decadal variability.

Decomposition of Sources of Errors in Seasonal Streamflow Forecasts in a Rainfall-Runoff Dominated Basin

NASA Astrophysics Data System (ADS)

Sinha, T.; Arumugam, S.

2012-12-01

Seasonal streamflow forecasts contingent on climate forecasts can be effectively utilized in updating water management plans and optimize generation of hydroelectric power. Streamflow in the rainfall-runoff dominated basins critically depend on forecasted precipitation in contrast to snow dominated basins, where initial hydrological conditions (IHCs) are more important. Since precipitation forecasts from Atmosphere-Ocean-General Circulation Models are available at coarse scale (~2.8° by 2.8°), spatial and temporal downscaling of such forecasts are required to implement land surface models, which typically runs on finer spatial and temporal scales. Consequently, multiple sources are introduced at various stages in predicting seasonal streamflow. Therefore, in this study, we addresses the following science questions: 1) How do we attribute the errors in monthly streamflow forecasts to various sources - (i) model errors, (ii) spatio-temporal downscaling, (iii) imprecise initial conditions, iv) no forecasts, and (iv) imprecise forecasts? and 2) How does monthly streamflow forecast errors propagate with different lead time over various seasons? In this study, the Variable Infiltration Capacity (VIC) model is calibrated over Apalachicola River at Chattahoochee, FL in the southeastern US and implemented with observed 1/8° daily forcings to estimate reference streamflow during 1981 to 2010. The VIC model is then forced with different schemes under updated IHCs prior to forecasting period to estimate relative mean square errors due to: a) temporally disaggregation, b) spatial downscaling, c) Reverse Ensemble Streamflow Prediction (imprecise IHCs), d) ESP (no forecasts), and e) ECHAM4.5 precipitation forecasts. Finally, error propagation under different schemes are analyzed with different lead time over different seasons.

ECHMERIT: A new on-line global mercury-chemistry model

NASA Astrophysics Data System (ADS)

Jung, G.; Hedgecock, I. M.; Pirrone, N.

2009-04-01

Mercury is a volatile metal, that is of concern because when deposited and transformed to methylmercury accumulates within the food-web. Due to the long lifetime of elemental mercury, which is the dominant fraction of mercury species in the atmosphere, mercury is prone to long-range transport and therefore distributed over the globe, transported and hence deposited even in regions far from anthropogenic emission sources. Mercury is released to the atmosphere from a variety of natural and anthropogenic sources, in elementary and oxidised forms, and as particulate mercury. It is then transported, but also transformed chemically in the gaseous phase, as well as in aqueous phase within cloud and rain droplets. Mercury (particularly its oxidised forms) is removed from the atmosphere though wet and dry deposition processes, a large fraction of deposited mercury is, after chemical or biological reduction, re-emitted to the atmosphere as elementary mercury. To investigate mercury chemistry and transport processes on the global scale, the new, global model ECHMERIT has been developed. ECHMERIT simulates meteorology, transport, deposition, photolysis and chemistry on-line. The general circulation model on which ECHMERIT is based is ECHAM5. Sophisticated chemical modules have been implemented, including gas phase chemistry based on the CBM-Z chemistry mechanism, as well as aqueous phase chemistry, both of which have been adapted to include Hg chemistry and Hg species gas-droplet mass transfer. ECHMERIT uses the fast-J photolysis routine. State-of-the-art procedures simulating wet and dry deposition and emissions were adapted and included in the model as well. An overview of the model structure, development, validation and sensitivity studies is presented.

Technical Note: The Modular Earth Submodel System (MESSy) - a new approach towards Earth System Modeling

NASA Astrophysics Data System (ADS)

Jöckel, P.; Sander, R.; Kerkweg, A.; Tost, H.; Lelieveld, J.

2005-02-01

The development of a comprehensive Earth System Model (ESM) to study the interactions between chemical, physical, and biological processes, requires coupling of the different domains (land, ocean, atmosphere, ...). One strategy is to link existing domain-specific models with a universal coupler, i.e. an independent standalone program organizing the communication between other programs. In many cases, however, a much simpler approach is more feasible. We have developed the Modular Earth Submodel System (MESSy). It comprises (1) a modular interface structure to connect to a , (2) an extendable set of such for miscellaneous processes, and (3) a coding standard. MESSy is therefore not a coupler in the classical sense, but exchanges data between a and several within one comprehensive executable. The internal complexity of the is controllable in a transparent and user friendly way. This provides remarkable new possibilities to study feedback mechanisms (by two-way coupling). Note that the MESSy and the coupler approach can be combined. For instance, an atmospheric model implemented according to the MESSy standard could easily be coupled to an ocean model by means of an external coupler. The vision is to ultimately form a comprehensive ESM which includes a large set of submodels, and a base model which contains only a central clock and runtime control. This can be reached stepwise, since each process can be included independently. Starting from an existing model, process submodels can be reimplemented according to the MESSy standard. This procedure guarantees the availability of a state-of-the-art model for scientific applications at any time of the development. In principle, MESSy can be implemented into any kind of model, either global or regional. So far, the MESSy concept has been applied to the general circulation model ECHAM5 and a number of process boxmodels.

The added value of dynamical downscaling in a climate change scenario simulation:A case study for European Alps and East Asia

NASA Astrophysics Data System (ADS)

Im, Eun-Soon; Coppola, Erika; Giorgi, Filippo

2010-05-01

Since anthropogenic climate change is a rather important factor for the future human life all over the planet and its effects are not globally uniform, climate information at regional or local scales become more and more important for an accurate assessment of the potential impact of climate change on societies and ecosystems. High resolution information with suitably fine-scale for resolving complex geographical features could be a critical factor for successful linkage between climate models and impact assessment studies. However, scale mismatch between them still remains major problem. One method for overcoming the resolution limitations of global climate models and for adding regional details to coarse-grid global projections is to use dynamical downscaling by means of a regional climate model. In this study, the ECHAM5/MPI-OM (1.875 degree) A1B scenario simulation has been dynamically downscaled by using two different approaches within the framework of RegCM3 modeling system. First, a mosaic-type parameterization of subgrid-scale topography and land use (Sub-BATS) is applied over the European Alpine region. The Sub-BATS system is composed of 15 km coarse-grid cell and 3 km sub-grid cell. Second, we developed the RegCM3 one-way double-nested system, with the mother domain encompassing the eastern regions of Asia at 60 km grid spacing and the nested domain covering the Korean Peninsula at 20 km grid spacing. By comparing the regional climate model output and the driving global model ECHAM5/MPI-OM output, it is possible to estimate the added value of physically-based dynamical downscaling when for example impact studies at hydrological scale are performed.

Ajustement statistique des simulations climatiques : l'exemple des précipitations saisonnières de l'Amérique tropicaleStatistical adjustment of simulated climate: example of seasonal rainfall of tropical America.

NASA Astrophysics Data System (ADS)

Moron, Vincent; Navarra, Antonio

2000-05-01

This study presents the skill of the seasonal rainfall of tropical America from an ensemble of three 34-year general circulation model (ECHAM 4) simulations forced with observed sea surface temperature between 1961 and 1994. The skill gives a first idea of the amount of potential predictability if the sea surface temperatures are perfectly known some time in advance. We use statistical post-processing based on the leading modes (extracted from Singular Value Decomposition of the covariance matrix between observed and simulated rainfall fields) to improve the raw skill obtained by simple comparison between observations and simulations. It is shown that 36-55 % of the observed seasonal variability is explained by the simulations on a regional basis. Skill is greatest for Brazilian Nordeste (March-May), but also for northern South America or the Caribbean basin in June-September or northern Amazonia in September-November for example.

Interannual tropical Pacific sea surface temperature anomalies teleconnection to Northern Hemisphere atmosphere in November

NASA Astrophysics Data System (ADS)

King, Martin P.; Herceg-Bulić, Ivana; Kucharski, Fred; Keenlyside, Noel

2018-03-01

We investigate the Northern Hemisphere atmospheric circulation anomalies associated to the sea surface temperature (SST) anomalies that are related to the eastern-Pacific and central-Pacific El Nino-Southern Oscillations in the late autumn (November). This research is motivated by the need for improving understanding of the autumn climate conditions which can impact on winter climate, as well as the relative lack of study on the boreal autumn climate processes compared to winter. Using reanalysis and SST datasets available from the late nineteenth century through the recent years, we found that there are two major atmospheric responses; one is a hemispheric-wide wave number-4 pattern, another has a more annular pattern. Both of these project on the East Atlantic pattern (southward-shifted North Atlantic Oscillation) in the Atlantic sector. Which of the patterns is active is suggested to depend on the background mean flow, with the annular anomaly active in the most recent decades, while the wave-4 pattern in the decades before. This switch is associated with a change of correlation sign in the North Pacific. We discuss the robustness of this finding. The ability of two atmospheric general circulation models (ICTP-AGCM and ECHAM-AGCM) to reproduce the teleconnections is also examined. Evidence provided shows that the wave-4 pattern and the East Atlantic pattern signals can be reproduced by the models, while the shift from this to an annular response for the recent years is not found conclusively.

A COMPARATIVE STUDY ON SPECTRAL ENERGETICS BETWEEN THE NCEP reanalysisII in current climate AND MODEL ECHAM5 in future scenarios

NASA Astrophysics Data System (ADS)

Aranha, A. F.; Veiga, J. P.

2013-12-01

Saltzman (1957) starting Lorenz Cycle (1955) derived a set of equations that show the energy contained in the basic state and the disturbed atmosphere, decomposing in various fields disturbance wave type, so as to quantify and analyze the energy of these disorders according to their number or wavelength. Based on the methodology Saltzman, this paper aims a comparative study between the energy of the disturbed state between the NCEP reanalysis-II for the current weather conditions and model ECHAM5 scenarios for future conditions of increased concentration of greenhouse gases (RCP26, RCP45 and RCP85), considering the terms of the generation of available potential energy to nth wave due to diabatic heating, represented by (Gn), the potential energy of nth wave (Pn) and kinetic energy of nth wave (Kn), as well as the conversion of energy between kinetic energy and potential energy nth wave of nth wave, given by (Cn). Two data sets were used in the calculation of the aforementioned terms. For the data set of NCEP and ECHAM5 were used variables, temperature (T), orthogonal wind components (u, v, w) and geopotential height (L), considering daily shared values on a regular grid with spatial resolutions of 2,5 x 2.5 and 1.875 x 1.875 graus, distributed on 12 and 15 levels of pressure (1000.0, 925.0, 850.0, 700.0, 600.0, 500.0, 400.0, 300.0, 250.0, 200.0, 150.0, 100.0 hPa), (1000.0, 850.0, 700.0, 500.0, 250.0, 150.0, 100.0, 70.0, 50.0, 30.0, 10.0, 3.0, 1.0, 0.3, 0.1 hPa) for the period of 1979-1999 and 2090-2100, respectively. The results show that most of the kinetic energy of disturbance to nth waves is concentrated in the first 15 wave numbers, both for the weather-NCEP II as to ECHAM5, having more significant increase in the profile and having a RCP85 energy cascade. This increase in kinetic energy was expected due to the increased energy in the system. For Pn, increasing the potential energy is also expected in view of the increased diabatic heating, but the energy jump is large spectrum in the range of 1 a 5, growth or accumulation of energy is visible in the figure wave, almost double the energy accumulated by the wave number 2, a derivative obeying the strong energy in the wave spectrum. We can conclude that the energy contained in a nonlinear way on the biggest waves are not shared aplenty. According to the results, the term conversion in Kn Pn, represented by Cn, reveals important characteristics in the energy spectrum. This we note that Pn feeds both the planetary waves and intermediate waves as synoptic scale. However, the production of Kn from Pn is added to the first wave specifically. It is also observed that Cn does not show large variations along the spectral profile. It is noteworthy that the energy conversions of RCP's are much smaller than the energy conversions NCEP-II, indicating that when there are increased concentrations of greenhouse gases is increasing Gen. therefore increased Pn and fall in Cn. Negative values of Cn are likely to occur, which would represent the conversion of kinetic energy into potential energy of the waves of the basic state.

Sensitivity simulations of superparameterised convection in a general circulation model

NASA Astrophysics Data System (ADS)

Rybka, Harald; Tost, Holger

2015-04-01

Cloud Resolving Models (CRMs) covering a horizontal grid spacing from a few hundred meters up to a few kilometers have been used to explicitly resolve small-scale and mesoscale processes. Special attention has been paid to realistically represent cloud dynamics and cloud microphysics involving cloud droplets, ice crystals, graupel and aerosols. The entire variety of physical processes on the small-scale interacts with the larger-scale circulation and has to be parameterised on the coarse grid of a general circulation model (GCM). Since more than a decade an approach to connect these two types of models which act on different scales has been developed to resolve cloud processes and their interactions with the large-scale flow. The concept is to use an ensemble of CRM grid cells in a 2D or 3D configuration in each grid cell of the GCM to explicitly represent small-scale processes avoiding the use of convection and large-scale cloud parameterisations which are a major source for uncertainties regarding clouds. The idea is commonly known as superparameterisation or cloud-resolving convection parameterisation. This study presents different simulations of an adapted Earth System Model (ESM) connected to a CRM which acts as a superparameterisation. Simulations have been performed with the ECHAM/MESSy atmospheric chemistry (EMAC) model comparing conventional GCM runs (including convection and large-scale cloud parameterisations) with the improved superparameterised EMAC (SP-EMAC) modeling one year with prescribed sea surface temperatures and sea ice content. The sensitivity of atmospheric temperature, precipiation patterns, cloud amount and types is observed changing the embedded CRM represenation (orientation, width, no. of CRM cells, 2D vs. 3D). Additionally, we also evaluate the radiation balance with the new model configuration, and systematically analyse the impact of tunable parameters on the radiation budget and hydrological cycle. Furthermore, the subgrid variability (individual CRM cell output) is analysed in order to illustrate the importance of a highly varying atmospheric structure inside a single GCM grid box. Finally, the convective transport of Radon is observed comparing different transport procedures and their influence on the vertical tracer distribution.

Will climate change affect weather types associated with flooding in the Elbe river basin?

NASA Astrophysics Data System (ADS)

Nissen, Katrin M.; Pardowitz, Tobias; Ulbrich, Uwe; Nied, Manuela

2013-04-01

This study investigates the effects of anthropogenic climate change on weather types associated with flooding in the Elbe river basin. The study is based on an ensemble of 3 simulations with the ECHAM5 MPIOM coupled model forced with historical and SRES A1B greenhouse gas concentrations. Relevant weather types, occuring in association with recent flood events, are identified in the ERA40 reanalysis data set. The weather types are classified with the SANDRA cluster algorithm. Distributions of tropospheric humidity content, 500 hPa geopotential height and 500 hPa temperature over Europe are taken as input parameters. 8 (out of 40) weather types are found to be associated with flooding events in the Elbe river basin. The majority of these (6) typically occur during winter, while 2 are warm season patterns. Downscaling reveals characteristic precipitation anomalies associated with the individual patterns. The 8 flood relevant weather types are then identified in the ECHAM5 simulations. The effect of climate change on these patterns is investigated by comparing the last 30 years of the previous century to the last 30 years of the 21st century. According to the model the frequency of most patterns will not change. 5 patterns may experience a statistically significant increase in the mean precipitation over the catchment area and 4 patterns an increase in extreme precipitation. Persistence may slightly decrease for 2 patterns and remain unchanged for the others. Overall, this indicates a moderate increase in the risk for Elbe river flooding, related to changes in the weather patterns, in the coming decades.

Uncertainty associated with convective wet removal of entrained aerosols in a global climate model

NASA Astrophysics Data System (ADS)

Croft, B.; Pierce, J. R.; Martin, R. V.; Hoose, C.; Lohmann, U.

2012-11-01

The uncertainties associated with the wet removal of aerosols entrained above convective cloud bases are investigated in a global aerosol-climate model (ECHAM5-HAM) under a set of limiting assumptions for the wet removal of the entrained aerosols. The limiting assumptions for the wet removal of entrained aerosols are negligible scavenging and vigorous scavenging (either through activation, with size-dependent impaction scavenging, or with the prescribed fractions of the standard model). To facilitate this process-based study, an explicit representation of cloud-droplet-borne and ice-crystal-borne aerosol mass and number, for the purpose of wet removal, is introduced into the ECHAM5-HAM model. This replaces and is compared with the prescribed cloud-droplet-borne and ice-crystal-borne aerosol fraction scavenging scheme of the standard model. A 20% to 35% uncertainty in simulated global, annual mean aerosol mass burdens and optical depth (AOD) is attributed to different assumptions for the wet removal of aerosols entrained above convective cloud bases. Assumptions about the removal of aerosols entrained above convective cloud bases control modeled upper tropospheric aerosol concentrations by as much as one order of magnitude. Simulated aerosols entrained above convective cloud bases contribute 20% to 50% of modeled global, annual mean aerosol mass convective wet deposition (about 5% to 10% of the total dry and wet deposition), depending on the aerosol species, when including wet scavenging of those entrained aerosols (either by activation, size-dependent impaction, or with the prescribed fraction scheme). Among the simulations, the prescribed fraction and size-dependent impaction schemes yield the largest global, annual mean aerosol mass convective wet deposition (by about two-fold). However, the prescribed fraction scheme has more vigorous convective mixed-phase wet removal (by two to five-fold relative to the size-dependent impaction scheme) since nearly all entrained accumulation and coarse mode aerosols are assumed to be cloud-droplet borne or ice-crystal borne, and evaporation due to the Bergeron-Findeisen process is neglected. The simulated convective wet scavenging of entrained accumulation and coarse mode aerosols has feedbacks on new particle formation and the number of Aitken mode aerosols, which control stratiform and convective cloud droplet number concentrations and yield precipitation changes in the ECHAM5-HAM model. However, the geographic distribution of aerosol annual mean convective wet deposition change in the model is driven by changes to the assumptions regarding the scavenging of aerosols entrained above cloud bases rather than by precipitation changes, except for sea salt deposition in the tropics. Uncertainty in the seasonal, regional cycles of AOD due to assumptions about entrained aerosol wet scavenging is similar in magnitude to the estimated error in the AOD retrievals. The uncertainty in aerosol concentrations, burdens, and AOD attributed to different assumptions for the wet scavenging of aerosols entrained above convective cloud bases in a global model motivates the ongoing need to better understand and model the activation and impaction processes that aerosols undergo after entrainment into convective updrafts.

Projected Changes on the Global Surface Wave Drift Climate towards the END of the Twenty-First Century

NASA Astrophysics Data System (ADS)

Carrasco, Ana; Semedo, Alvaro; Behrens, Arno; Weisse, Ralf; Breivik, Øyvind; Saetra, Øyvind; Håkon Christensen, Kai

2016-04-01

The global wave-induced current (the Stokes Drift - SD) is an important feature of the ocean surface, with mean values close to 10 cm/s along the extra-tropical storm tracks in both hemispheres. Besides the horizontal displacement of large volumes of water the SD also plays an important role in the ocean mix-layer turbulence structure, particularly in stormy or high wind speed areas. The role of the wave-induced currents in the ocean mix-layer and in the sea surface temperature (SST) is currently a hot topic of air-sea interaction research, from forecast to climate ranges. The SD is mostly driven by wind sea waves and highly sensitive to changes in the overlaying wind speed and direction. The impact of climate change in the global wave-induced current climate will be presented. The wave model WAM has been forced by the global climate model (GCM) ECHAM5 wind speed (at 10 m height) and ice, for present-day and potential future climate conditions towards the end of the end of the twenty-first century, represented by the Intergovernmental Panel for Climate Change (IPCC) CMIP3 (Coupled Model Inter-comparison Project phase 3) A1B greenhouse gas emission scenario (usually referred to as a ''medium-high emissions'' scenario). Several wave parameters were stored as output in the WAM model simulations, including the wave spectra. The 6 hourly and 0.5°×0.5°, temporal and space resolution, wave spectra were used to compute the SD global climate of two 32-yr periods, representative of the end of the twentieth (1959-1990) and twenty-first (1969-2100) centuries. Comparisons of the present climate run with the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-40 reanalysis are used to assess the capability of the WAM-ECHAM5 runs to produce realistic SD results. This study is part of the WRCP-JCOMM COWCLIP (Coordinated Ocean Wave Climate Project) effort.

Factors controlling the initiation of Snowball Earth events

NASA Astrophysics Data System (ADS)

Voigt, A.

2012-12-01

During the Neoproterozoic glaciations tropical continents were covered by active glaciers that extended down to sea level. To explain these glaciers, the Snowball Earth hypothesis assumes that oceans were completely sea-ice covered during these glaciation, but there is an ongoing debate whether or not some regions of the tropical oceans remained open. In this talk, I will describe past and ongoing climate modelling activities with the comprehensive coupled climate model ECHAM5/MPI-OM that identify and compare factors that control the initiation of Snowball Earth events. I first show that shifting the continents from their present-day location to their Marinoan (635 My BP) low-latitude location increases the planetary albedo, cools the climate, and thereby allows Snowball Earth initiation at higher levels of total solar irradiance and atmospheric CO2. I then present simulations with successively lowered bare sea-ice albedo, disabled sea-ice dynamics, and switched-off ocean heat transport. These simulations show that both lowering the bare sea-ice albedo and disabling sea-ice dynamics increase the critical sea-ice cover in ECHAM5/MPI-OM, but sea-ice dynamics due to strong equatorward sea-ice transport have a much larger influence on the critical CO2. Disabling sea-ice transport allows a state with sea-ice margin at 10 deg latitude by virtue of the Jormungand mechanism. The accumulation of snow on land, in combination with tropical land temperatures below or close to freezing, suggests that tropical land glaciers could easily form in such a state. However, in contrast to aquaplanet simulations without ocean heat transport, there is no sign of a Jormungand hysteresis in the coupled simulations. Ocean heat transport is not responsible for the lack of a Jormungand hysteresis in the coupled simulations. By relating the above findings to previous studies, I will outline promising future avenues of research on the initiation of Snowball Earth events. In particular, an improved understanding and modelling of sea-ice dynamics is needed.ea-ice cover as a function of CO2 for ECHAM5/MPI-OM simulations with high bare sea-ice albedo (black circles), low bare sea-ice albedo (blue squares), low bare sea-ice albedo and disabled sea-ice dynamics (red triangles), and low bare sea-ice albedo, disabled sea-ice dynamics and zero ocean heat transport (green diamonds). All simulations use Marinoan low-latitude continents and a solar constant reduced to 94% of its modern value.

Assessing modelled spatial distributions of ice water path using satellite data

NASA Astrophysics Data System (ADS)

Eliasson, S.; Buehler, S. A.; Milz, M.; Eriksson, P.; John, V. O.

2010-05-01

The climate models used in the IPCC AR4 show large differences in monthly mean cloud ice. The most valuable source of information that can be used to potentially constrain the models is global satellite data. For this, the data sets must be long enough to capture the inter-annual variability of Ice Water Path (IWP). PATMOS-x was used together with ISCCP for the annual cycle evaluation in Fig. 7 while ECHAM-5 was used for the correlation with other models in Table 3. A clear distinction between ice categories in satellite retrievals, as desired from a model point of view, is currently impossible. However, long-term satellite data sets may still be used to indicate the climatology of IWP spatial distribution. We evaluated satellite data sets from CloudSat, PATMOS-x, ISCCP, MODIS and MSPPS in terms of monthly mean IWP, to determine which data sets can be used to evaluate the climate models. IWP data from CloudSat cloud profiling radar provides the most advanced data set on clouds. As CloudSat data are too short to evaluate the model data directly, it was mainly used here to evaluate IWP from the other satellite data sets. ISCCP and MSPPS were shown to have comparatively low IWP values. ISCCP shows particularly low values in the tropics, while MSPPS has particularly low values outside the tropics. MODIS and PATMOS-x were in closest agreement with CloudSat in terms of magnitude and spatial distribution, with MODIS being the best of the two. As PATMOS-x extends over more than 25 years and is in fairly close agreement with CloudSat, it was chosen as the reference data set for the model evaluation. In general there are large discrepancies between the individual climate models, and all of the models show problems in reproducing the observed spatial distribution of cloud-ice. Comparisons consistently showed that ECHAM-5 is the GCM from IPCC AR4 closest to satellite observations.

Kinematic and diabatic vertical velocity climatologies from a chemistry climate model

NASA Astrophysics Data System (ADS)

Marinke Hoppe, Charlotte; Ploeger, Felix; Konopka, Paul; Müller, Rolf

2016-05-01

The representation of vertical velocity in chemistry climate models is a key element for the representation of the large-scale Brewer-Dobson circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic vertical velocities in the ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model. The calculation of kinematic vertical velocity is based on the continuity equation, whereas diabatic vertical velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of vertical velocity from a 10-year simulation are provided for both kinematic and diabatic vertical velocity representations. In general, both vertical velocity patterns show the main features of the stratospheric circulation, namely, upwelling at low latitudes and downwelling at high latitudes. The main difference in the vertical velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic vertical velocity. Diabatic vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two vertical velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different vertical velocities and analyze the impact of residual circulation and mixing processes on the age of air. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic vertical velocities. Further, the age of air climatology from the transport scheme using diabatic vertical velocities shows a younger mean age of air in the inner tropical upwelling branch and an older mean age in the extratropical tropopause region.

Response of North American freshwater lakes to simulated future climates

USGS Publications Warehouse

Hostetler, S.W.; Small, E.E.

1999-01-01

We apply a physically based lake model to assess the response of North American lakes to future climate conditions as portrayed by the transient trace-gas simulations conducted with the Max Planck Institute (ECHAM4) and the Canadian Climate Center (CGCM1) atmosphere-ocean general circulation models (A/OGCMs). To quantify spatial patterns of lake responses (temperature, mixing, ice cover, evaporation) we ran the lake model for theoretical lakes of specified area, depth, and transparency over a uniformly spaced (50 km) grid. The simulations were conducted for two 10-year periods that represent present climatic conditions and those around the time of CO2 doubling. Although the climate model output produces simulated lake responses that differ in specific regional details, there is broad agreement with regard to the direction and area of change. In particular, lake temperatures are generally warmer in the future as a result of warmer climatic conditions and a substantial loss (> 100 days/yr) of winter ice cover. Simulated summer lake temperatures are higher than 30??C ever the Midwest and south, suggesting the potential for future disturbance of existing aquatic ecosystems. Overall increases in lake evaporation combine with disparate changes in A/OGCM precipitation to produce future changes in net moisture (precipitation minus evaporation) that are of less fidelity than those of lake temperature.

The role of shallow convection in promoting the northward propagation of boreal summer intraseasonal oscillation

NASA Astrophysics Data System (ADS)

Liu, Fei; Zhao, Jiuwei; Fu, Xiouhua; Huang, Gang

2018-02-01

By conducting idealized experiments in a general circulation model (GCM) and in a toy theoretical model, we test the hypothesis that shallow convection (SC) is responsible for explaining why the boreal summer intraseasonal oscillation (BSISO) prefers propagating northward. Two simulations are performed using ECHAM4, with the control run using a standard detrainment rate of SC and the sensitivity run turning off the detrainment rate of SC. These two simulations display dramatically different BSISO characteristics. The control run simulates the realistic northward propagation (NP) of the BSISO, while the sensitivity run with little SC only simulates stationary signals. In the sensitivity run, the meridional asymmetries of vorticity and humidity fields are simulated under the monsoon vertical wind shear (VWS); thus, the frictional convergence can be excited to the north of the BSISO. However, the lack of SC makes the lower and middle troposphere very dry, which prohibits further development of deeper convection. A theoretical BSISO model is also constructed, and the result shows that SC is a key to convey the asymmetric vorticity effect to induce the BSISO to move northward. Thus, both the GCM and theoretical model results demonstrate the importance of SC in promoting the NP of the BSISO.

Megadroughts in Southwestern North America in ECHO-G Millennial Simulations and Their Comparison to Proxy Drought Reconstructions

NASA Technical Reports Server (NTRS)

Coats, Sloan; Smerdon, Jason E.; Seager, Richard; Cook, Benjamin I.; Gozalez-Rouco, J. F.

2013-01-01

Simulated hydroclimate variability in millennium-length forced transient and control simulations from the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled atmosphere-ocean general circulation model (AOGCM) is analyzed and compared to 1000 years of reconstructed Palmer drought severity index (PDSI) variability from the North American Drought Atlas (NADA). The ability of the model to simulate megadroughts in the North American southwest is evaluated. (NASW: 25deg42.5degN, 125deg-105degW). Megadroughts in the ECHO-G AOGCM are found to be similar in duration and magnitude to those estimated from the NADA. The droughts in the forced simulation are not, however, temporally synchronous with those in the paleoclimate record, nor are there significant differences between the drought features simulated in the forced and control runs. These results indicate that model-simulated megadroughts can result from internal variability of the modeled climate system rather than as a response to changes in exogenous forcings. Although the ECHO-G AOGCM is capable of simulating megadroughts through persistent La Nina-like conditions in the tropical Pacific, other mechanisms can produce similarly extreme NASW moisture anomalies in the model. In particular, the lack of low-frequency coherence between NASW soil moisture and simulated modes of climate variability like the El Nino-Southern Oscillation, Pacific decadal oscillation, and Atlantic multidecadal oscillation during identified drought periods suggests that stochastic atmospheric variability can contribute significantly to the occurrence of simulated megadroughts in the NASW. These findings indicate that either an expanded paradigm is needed to understand multidecadal hydroclimate variability in the NASW or AOGCMs may incorrectly simulate the strength and/or dynamics of the connection between NASW hydroclimate variability and the tropical Pacific.

Evaluation of the North American Multi-Model Ensemble System for Monthly and Seasonal Prediction

NASA Astrophysics Data System (ADS)

Zhang, Q.

2014-12-01

Since August 2011, the real time seasonal forecasts of the U.S. National Multi-Model Ensemble (NMME) have been made on 8th of each month by NCEP Climate Prediction Center (CPC). The participating models were NCEP/CFSv1&2, GFDL/CM2.2, NCAR/U.Miami/COLA/CCSM3, NASA/GEOS5, IRI/ ECHAM-a & ECHAM-f in the first year of the real time NMME forecast. Two Canadian coupled models CMC/CanCM3 and CM4 joined in and CFSv1 and IRI's models dropped out in the second year. The NMME team at CPC collects monthly means of three variables, precipitation, temperature at 2m and sea surface temperature from each modeling center on a 1x1 global grid, removes systematic errors, makes the grand ensemble mean in equal weight for each model mean and probability forecast with equal weight for each member of each model. This provides the NMME forecast locked in schedule for the CPC operational seasonal and monthly outlook. The basic verification metrics of seasonal and monthly prediction of NMME are calculated as an evaluation of skill, including both deterministic and probabilistic forecasts for the 3-year real time (August, 2011- July 2014) period and the 30-year retrospective forecast (1982-2011) of the individual models as well as the NMME ensemble. The motivation of this study is to provide skill benchmarks for future improvements of the NMME seasonal and monthly prediction system. We also want to establish whether the real time and hindcast periods (used for bias correction in real time) are consistent. The experimental phase I of the project already supplies routine guidance to users of the NMME forecasts.

Effect of Interactive River Routing on North Atlantic Overturning in a Simulation of the last Deglaciation

NASA Astrophysics Data System (ADS)

Mikolajewicz, Uwe; Ziemen, Florian; Kapsch, Marie; Meccia, Virna

2017-04-01

One of the major challenges in climate modeling is the simulation of glacial-interglacial transitions. A few models of intermediate complexity have been successful in simulating the last termination. Complex atmosphere-ocean general circulation models (AOGCMs) with prescribed ice sheets are able to yield realistic climate changes. Here we present results from our first attempt to simulate a substantial part of the last glacial cycle with an AOGCM coupled interactively with a state-of-the-art ice sheet model. The ECHAM5/MPIOM AOGCM is interactively coupled to the dynamical ice sheet model PISM and the dynamical vegetation model LPJ. The model is integrated from the late Glacial into the Holocene using insolation and greenhouse gas concentrations as transient forcing. To make the long simulations feasible, the atmosphere is accelerated by a factor of 10 relative to the other components using a periodical-synchronous coupling technique. The land sea mask remains fixed at the LGM state. River routing and surface elevation are calculated interactively. A mini-ensemble with different initial conditions is performed. Additionally, one fully synchronously simulation, without acceleration in the atmosphere, is run. In all simulations the northern hemisphere deglaciation starts between 18 and 17 kyr BP, consistent with the onset of global warming. The model produces Heinrich event like variability. These rapid ice discharge events have a strong impact on the North Atlantic meridional overturning circulation (NAMOC). The interactive river routing has a strong impact on the simulated NAMOC during the deglaciation. The retreat of the Laurentide Ice Sheet together with the depressed topography due to the former ice load leads to a redirection of the river routes.. In particular, the discharge route for runoff from the melting southwestern Laurentide shifts from the Gulf of Mexico to the Arctic. The consequence is a rapid reduction/suppression of the North Atlantic deep water (NADW) formation. When the Laurentide Ice Sheet retreats from the Hudson Strait, this becomes the new drainage route. Hence, fresh water is released into the Labrador Sea and is less effective in suppressing the deep water formation in the North Atlantic. As a consequence, the NADW formation recovers within a few decades. Our results show the potential importance of interactive river routing for rapid changes in NAMOC strength during the deglaciation.

Ozone impacts of gas-aerosol uptake in global chemistry transport models

NASA Astrophysics Data System (ADS)

Stadtler, Scarlet; Simpson, David; Schröder, Sabine; Taraborrelli, Domenico; Bott, Andreas; Schultz, Martin

2018-03-01

The impact of six heterogeneous gas-aerosol uptake reactions on tropospheric ozone and nitrogen species was studied using two chemical transport models, the Meteorological Synthesizing Centre-West of the European Monitoring and Evaluation Programme (EMEP MSC-W) and the European Centre Hamburg general circulation model combined with versions of the Hamburg Aerosol Model and Model for Ozone and Related chemical Tracers (ECHAM-HAMMOZ). Species undergoing heterogeneous reactions in both models include N2O5, NO3, NO2, O3, HNO3, and HO2. Since heterogeneous reactions take place at the aerosol surface area, the modelled surface area density (Sa) of both models was compared to a satellite product retrieving the surface area. This comparison shows a good agreement in global pattern and especially the capability of both models to capture the extreme aerosol loadings in east Asia. The impact of the heterogeneous reactions was evaluated by the simulation of a reference run containing all heterogeneous reactions and several sensitivity runs. One reaction was turned off in each sensitivity run to compare it with the reference run. The analysis of the sensitivity runs confirms that the globally most important heterogeneous reaction is the one of N2O5. Nevertheless, NO2, HNO3, and HO2 heterogeneous reactions gain relevance particularly in east Asia due to the presence of high NOx concentrations and high Sa in the same region. The heterogeneous reaction of O3 itself on dust is of minor relevance compared to the other heterogeneous reactions. The impacts of the N2O5 reactions show strong seasonal variations, with the biggest impacts on O3 in springtime when photochemical reactions are active and N2O5 levels still high. Evaluation of the models with northern hemispheric ozone surface observations yields a better agreement of the models with observations in terms of concentration levels, variability, and temporal correlations at most sites when the heterogeneous reactions are incorporated. Our results are loosely consistent with results from earlier studies, although the magnitude of changes induced by N2O5 reaction is at the low end of estimates, which seems to fit a trend, whereby the more recent the study the lower the impacts of these reactions.

Effects of mixing on resolved and unresolved scales on stratospheric age of air

NASA Astrophysics Data System (ADS)

Dietmüller, Simone; Garny, Hella; Plöger, Felix; Jöckel, Patrick; Cai, Duy

2017-06-01

Mean age of air (AoA) is a widely used metric to describe the transport along the Brewer-Dobson circulation. We seek to untangle the effects of different processes on the simulation of AoA, using the chemistry-climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) and the Chemical Lagrangian Model of the Stratosphere (CLaMS). Here, the effects of residual transport and two-way mixing on AoA are calculated. To do so, we calculate the residual circulation transit time (RCTT). The difference of AoA and RCTT is defined as aging by mixing. However, as diffusion is also included in this difference, we further use a method to directly calculate aging by mixing on resolved scales. Comparing these two methods of calculating aging by mixing allows for separating the effect of unresolved aging by mixing (which we term aging by diffusion in the following) in EMAC and CLaMS. We find that diffusion impacts AoA by making air older, but its contribution plays a minor role (order of 10 %) in all simulations. However, due to the different advection schemes of the two models, aging by diffusion has a larger effect on AoA and mixing efficiency in EMAC, compared to CLaMS. Regarding the trends in AoA, in CLaMS the AoA trend is negative throughout the stratosphere except in the Northern Hemisphere middle stratosphere, consistent with observations. This slight positive trend is neither reproduced in a free-running nor in a nudged simulation with EMAC - in both simulations the AoA trend is negative throughout the stratosphere. Trends in AoA are mainly driven by the contributions of RCTT and aging by mixing, whereas the contribution of aging by diffusion plays a minor role.

Climate impacts of deforestation/land-use changes in Central South America in the PRECIS regional climate model: mean precipitation and temperature response to present and future deforestation scenarios.

PubMed

Canziani, Pablo O; Carbajal Benitez, Gerardo

2012-01-01

Deforestation/land-use changes are major drivers of regional climate change in central South America, impacting upon Amazonia and Gran Chaco ecoregions. Most experimental and modeling studies have focused on the resulting perturbations within Amazonia. Using the Regional Climate Model PRECIS, driven by ERA-40 reanalysis and ECHAM4 Baseline model for the period 1961-2000 (40-year runs), potential effects of deforestation/land-use changes in these and other neighboring ecoregions are evaluated. Current 2002 and estimated 2030 land-use scenarios are used to assess PRECIS's response during 1960-2000. ERA-40 and ECHAM4 Baseline driven runs yield similar results. Precipitation changes for 2002 and 2030 land-use scenarios, while significant within deforested areas, do not result in significant regional changes. For temperature significant changes are found within deforested areas and beyond, with major temperature enhancements during winter and spring. Given the current climate, primary effects of deforestation/land-use changes remain mostly confined to the tropical latitudes of Gran Chaco, and Amazonia.

Climate Impacts of Deforestation/Land-Use Changes in Central South America in the PRECIS Regional Climate Model: Mean Precipitation and Temperature Response to Present and Future Deforestation Scenarios

PubMed Central

Canziani, Pablo O.; Carbajal Benitez, Gerardo

2012-01-01

Deforestation/land-use changes are major drivers of regional climate change in central South America, impacting upon Amazonia and Gran Chaco ecoregions. Most experimental and modeling studies have focused on the resulting perturbations within Amazonia. Using the Regional Climate Model PRECIS, driven by ERA-40 reanalysis and ECHAM4 Baseline model for the period 1961–2000 (40-year runs), potential effects of deforestation/land-use changes in these and other neighboring ecoregions are evaluated. Current 2002 and estimated 2030 land-use scenarios are used to assess PRECIS's response during 1960–2000. ERA-40 and ECHAM4 Baseline driven runs yield similar results. Precipitation changes for 2002 and 2030 land-use scenarios, while significant within deforested areas, do not result in significant regional changes. For temperature significant changes are found within deforested areas and beyond, with major temperature enhancements during winter and spring. Given the current climate, primary effects of deforestation/land-use changes remain mostly confined to the tropical latitudes of Gran Chaco, and Amazonia. PMID:22645487

Regional Climate Change and Development of Public Health Decision Aids

NASA Astrophysics Data System (ADS)

Hegedus, A. M.; Darmenova, K.; Grant, F.; Kiley, H.; Higgins, G. J.; Apling, D.

2011-12-01

According to the World Heath Organization (WHO) climate change is a significant and emerging threat to public health, and changes the way we must look at protecting vulnerable populations. Worldwide, the occurrence of some diseases and other threats to human health depend predominantly on local climate patterns. Rising average temperatures, in combination with changing rainfall patterns and humidity levels, alter the lifecycle and regional distribution of certain disease-carrying vectors, such as mosquitoes, ticks and rodents. In addition, higher surface temperatures will bring heat waves and heat stress to urban regions worldwide and will likely increase heat-related health risks. A growing body of scientific evidence also suggests an increase in extreme weather events such as floods, droughts and hurricanes that can be destructive to human health and well-being. Therefore, climate adaptation and health decision aids are urgently needed by city planners and health officials to determine high risk areas, evaluate vulnerable populations and develop public health infrastructure and surveillance systems. To address current deficiencies in local planning and decision making with respect to regional climate change and its effect on human health, our research is focused on performing a dynamical downscaling with the Weather Research and Forecasting (WRF) model to develop decision aids that translate the regional climate data into actionable information for users. WRF model is initialized with the Max Planck Institute European Center/Hamburg Model version 5 (ECHAM5) General Circulation Model simulations forced with the Special Report on Emissions (SRES) A1B emissions scenario. Our methodology involves development of climatological indices of extreme weather, quantifying the risk of occurrence of water/rodent/vector-borne diseases as well as developing various heat stress related decision aids. Our results indicate that the downscale simulations provide the necessary detailed output required by state and local governments and the private sector to develop climate adaptation plans with respect to human health.

Use of Moderate-Resolution Imaging Spectroradiometer bidirectional reflectance distribution function products to enhance simulated surface albedos

NASA Astrophysics Data System (ADS)

Roesch, Andreas; Schaaf, Crystal; Gao, Feng

2004-06-01

Moderate-Resolution Imaging Spectroradiometer (MODIS) surface albedo at high spatial and spectral resolution is compared with other remotely sensed climatologies, ground-based data, and albedos simulated with the European Center/Hamburg 4 (ECHAM4) global climate model at T42 resolution. The study demonstrates the importance of MODIS data in assessing and improving albedo parameterizations in weather forecast and climate models. The remotely sensed PINKER surface albedo climatology follows the MODIS estimates fairly well in both the visible and near-infrared spectra, whereas ECHAM4 simulates high positive albedo biases over snow-covered boreal forests and the Himalayas. In contrast, the ECHAM4 albedo is probably too low over the Sahara sand desert and adjacent steppes. The study clearly indicates that neglecting albedo variations within T42 grid boxes leads to significant errors in the simulated regional climate and horizontal fluxes, mainly in mountainous and/or snow-covered regions. MODIS surface albedo at 0.05 resolution agrees quite well with in situ field measurements collected at Baseline Surface Radiation Network (BSRN) sites during snow-free periods, while significant positive biases are found under snow-covered conditions, mainly due to differences in the vegetation cover at the BSRN site (short grass) and the vegetation within the larger MODIS grid box. Black sky (direct beam) albedo from the MODIS bidirectional reflectance distribution function model captures the diurnal albedo cycle at BSRN sites with sufficient accuracy. The greatest negative biases are generally found when the Sun is low. A realistic approach for relating albedo and zenith angle has been proposed. Detailed evaluations have demonstrated that ignoring the zenith angle dependence may lead to significant errors in the surface energy balance.

GPU-accelerated atmospheric chemical kinetics in the ECHAM/MESSy (EMAC) Earth system model (version 2.52)

NASA Astrophysics Data System (ADS)

Alvanos, Michail; Christoudias, Theodoros

2017-10-01

This paper presents an application of GPU accelerators in Earth system modeling. We focus on atmospheric chemical kinetics, one of the most computationally intensive tasks in climate-chemistry model simulations. We developed a software package that automatically generates CUDA kernels to numerically integrate atmospheric chemical kinetics in the global climate model ECHAM/MESSy Atmospheric Chemistry (EMAC), used to study climate change and air quality scenarios. A source-to-source compiler outputs a CUDA-compatible kernel by parsing the FORTRAN code generated by the Kinetic PreProcessor (KPP) general analysis tool. All Rosenbrock methods that are available in the KPP numerical library are supported.Performance evaluation, using Fermi and Pascal CUDA-enabled GPU accelerators, shows achieved speed-ups of 4. 5 × and 20. 4 × , respectively, of the kernel execution time. A node-to-node real-world production performance comparison shows a 1. 75 × speed-up over the non-accelerated application using the KPP three-stage Rosenbrock solver. We provide a detailed description of the code optimizations used to improve the performance including memory optimizations, control code simplification, and reduction of idle time. The accuracy and correctness of the accelerated implementation are evaluated by comparing to the CPU-only code of the application. The median relative difference is found to be less than 0.000000001 % when comparing the output of the accelerated kernel the CPU-only code.The approach followed, including the computational workload division, and the developed GPU solver code can potentially be used as the basis for hardware acceleration of numerous geoscientific models that rely on KPP for atmospheric chemical kinetics applications.

Improving microphysics in a convective parameterization: possibilities and limitations

NASA Astrophysics Data System (ADS)

Labbouz, Laurent; Heikenfeld, Max; Stier, Philip; Morrison, Hugh; Milbrandt, Jason; Protat, Alain; Kipling, Zak

2017-04-01

The convective cloud field model (CCFM) is a convective parameterization implemented in the climate model ECHAM6.1-HAM2.2. It represents a population of clouds within each ECHAM-HAM model column, simulating up to 10 different convective cloud types with individual radius, vertical velocities and microphysical properties. Comparisons between CCFM and radar data at Darwin, Australia, show that in order to reproduce both the convective cloud top height distribution and the vertical velocity profile, the effect of aerodynamic drag on the rising parcel has to be considered, along with a reduced entrainment parameter. A new double-moment microphysics (the Predicted Particle Properties scheme, P3) has been implemented in the latest version of CCFM and is compared to the standard single-moment microphysics and the radar retrievals at Darwin. The microphysical process rates (autoconversion, accretion, deposition, freezing, …) and their response to changes in CDNC are investigated and compared to high resolution CRM WRF simulations over the Amazon region. The results shed light on the possibilities and limitations of microphysics improvements in the framework of CCFM and in convective parameterizations in general.

Climate and land use changes effects on soil organic carbon stocks in a Mediterranean semi-natural area.

PubMed

Lozano-García, Beatriz; Muñoz-Rojas, Miriam; Parras-Alcántara, Luis

2017-02-01

A thorough knowledge of the effects of climate and land use changes on the soil carbon pool is critical to planning effective strategies for adaptation and mitigation in future scenarios of global climate and land use change. In this study, we used CarboSOIL model to predict changes in soil organic carbon stocks in a semi-natural area of Southern Spain in three different time horizons (2040, 2070, 2100), considering two general circulation models (BCM2 and ECHAM5) and three IPCC scenarios (A1b, A2, B2). The effects of potential land use changes from natural vegetation (Mediterranean evergreen oak woodland) to agricultural land (olive grove and cereal) on soil organic carbon stocks were also evaluated. Predicted values of SOC contents correlated well those measured (R2 ranging from 0.71 at 0-25cm to 0.97 at 50-75cm) showing the efficiency of the model. Results showed substantial differences among time horizons, climate and land use scenarios and soil depth with larger decreases of soil organic carbon stocks in the long term (2100 time horizon) and particularly in olive groves. The combination of climate and land use scenarios (in particular conversion from current 'dehesa' to olive groves) resulted in yet higher losses of soil organic carbon stocks, e.g. -30, -15 and -33% in the 0-25, 25-50 and 50-75cm sections respectively. This study shows the importance of soil organic carbon stocks assessment under both climate and land use scenarios at different soil sections and point towards possible directions for appropriate land use management in Mediterranean semi natural areas. Copyright © 2016 Elsevier B.V. All rights reserved.

Hadley cell dynamics of a cold and virtually dry Snowball Earth atmosphere

NASA Astrophysics Data System (ADS)

Voigt, Aiko; Held, Isaac; Marotzke, Jochem

2010-05-01

We use the full-physics atmospheric general circulation model ECHAM5 to investigate a cold and virtually dry Snowball Earth atmosphere that results from specifying sea ice as the surface boundary condition everywhere, corresponding to a frozen aquaplanet, while keeping total solar irradiance at its present-day value of 1365 Wm-2. The aim of this study is the investigation of the zonal-mean circulation of a Snowball Earth atmosphere, which, due to missing moisture, might constitute an ideal though yet unexplored testbed for theories of atmospheric dynamics. To ease comparison with theories, incoming solar insolation follows permanent equinox conditions with disabled diurnal cycle. The meridional circulation consists of a thermally direct cell extending from the equator to 45 N/S with ascent in the equatorial region, and a weak thermally indirect cell with descent between 45 and 65 N/S and ascent in the polar region. The former cell corresponds to the present-day Earth's Hadley cell, while the latter can be viewed as an eddy-driven Ferrell cell; the present-day Earth's direct polar cell is missing. The Hadley cell itself is subdivided into a vigorous cell confined to the troposphere and a weak deep cell reaching well into the stratosphere. The dynamics of the vigorous Snowball Earth Hadley cell differ substantially from the dynamics of the present-day Hadley cell. The zonal momentum balance shows that in the poleward branch of the vigorous Hadley cell, mean flow meridional advection of absolute vorticity is not only balanced by eddy momentum flux convergence but also by vertical diffusion. Inside the poleward branch, eddies are more important in the upper part and vertical diffusion is more important in the lower part. Vertical diffusion also contributes to the meridional momentum balance as it decelerates the vigorous Hadley cell by downgradient momentum mixing between its poleward and equatorward branch. Zonal winds, therefore, are not in thermal wind balance in the vigorous Hadley cell. Suppressing vertical momentum diffusion above 870 hPa results in a doubling of the vigorous Hadley cell strength. Simulations where we only suppress either vertical diffusion of zonal or meridional momentum show that this doubling can be understood from the decelerating effect of vertical diffusion in the meridional momentum balance. Comparing our simulations with theories, we conclude that neither the axisymmetric Hadley cell model of Held & Hou (1980) nor the eddy-permitting model of T. Schneider et al. (2005, 2006, 2008) are applicable to a Snowball Earth atmosphere since both assume an inviscid upper Hadley cell branch.

Exceptional warming in the Western Pacific-Indian Ocean warm pool has contributed to more frequent droughts in eastern Africa

USGS Publications Warehouse

Funk, Christopher C.; Peterson, Thomas C.; Stott, Peter A.; Herring, Stephanie

2012-01-01

In 2011, East Africa faced a tragic food crisis that led to famine conditions in parts of Somalia and severe food shortages in parts of Ethiopia and Somalia. While many nonclimatic factors contributed to this crisis (high global food prices, political instability, and chronic poverty, among others) failed rains in both the boreal winter of 2010/11 and the boreal spring of 2011 played a critical role. The back-to-back failures of these rains, which were linked to the dominant La Niña climate and warm SSTs in the central and southeastern Indian Ocean, were particularly problematic since they followed poor rainfall during the spring and summer of 2008 and 2009. In fact, in parts of East Africa, in recent years, there has been a substantial increase in the number of below-normal rainy seasons, which may be related to the warming of the western Pacific and Indian Oceans (for more details, see Funk et al. 2008; Williams and Funk 2011; Williams et al. 2011; Lyon and DeWitt 2012). The basic argument of this work is that recent warming in the Indian–Pacific warm pool (IPWP) enhances the export of geopotential height energy from the warm pool, which tends to produce subsidence across eastern Africa and reduce onshore moisture transports. The general pattern of this disruption has been supported by canonical correlation analyzes and numerical experiments with the Community Atmosphere Model (Funk et al. 2008), diagnostic evaluations of reanalysis data (Williams and Funk 2011; Williams et al. 2011), and SST-driven experiments with ECHAM4.5, ECHAM5, and the Community Climate Model version 3 (CCM3.6) (Lyon and DeWitt 2012).

Origin and Variability of Upper Tropospheric Nitrogen Oxides and Ozone at Northern Mid-Latitudes

NASA Technical Reports Server (NTRS)

Grewe, V.; Brunner, D.; Dameris, M.; Grenfell, J. L.; Hein, R.; Shindell, D.; Staehelin, J.

1999-01-01

Measurements of NO(x) and ozone performed during the NOXAR project are compared with results from the coupled chemistry-climate models ECHAM4.L39(DLR)/CHEM and GISS-model. The measurements are based on flights between Europe and the East coast of America and between Europe and the Far East in the latitude range 40 deg N to 65 deg N. The comparison concentrates on tropopause altitudes and reveals strong longitudinal variations of seasonal mean NO,, of 200 pptv. Either model reproduced strong variations 3 km below but not at the tropopause, indicating a strong missing NO(x) or NO(y) sink over remote areas, e.g. NO(x) to HNO3 conversion by OH from additional OH sources or HNO3 wash-out. Vertical profiles show maximum NO(x) values 2-3 km below the tropopause with a strong seasonal cycle. ECHAM4.L39(DLR)/CHEM reproduces a maximum, although located at the tropopause with a less pronounced seasonal cycle, whereas the GISS model reproduces the seasonal cycle but not the profile's shape due to its coarser vertical resolution. A comparison of NO(x) frequency distributions reveals that both models are capable of reproducing the observed variability, except that ECHAM4.L39(DLR)/CHEM shows no very high NO(x) mixing ratios. Ozone mean values, vertical profiles and frequency distributions are much better reproduced in either model, indicating that the NO(x) frequency distribution, namely the most frequent NO(x) mixing ratio, is more important for the tropospheric photochemical ozone production than its mean value. Both models show that among all sources, NO(x) from lightning contributes most to the seasonal cycle of NO(x) at tropopause altitudes. The impact of lightning in the upper troposphere on NO(x) does not vary strongly with altitude, whereas the impact of surface emissions decreases with altitude. However, the models show significant differences in lightning induced NO(x) concentrations, especially in winter, which may be related to the different treatment of the lower stratospheric coupling between dynamics and chemistry.

Global tropospheric hydroxyl distribution, budget and reactivity

NASA Astrophysics Data System (ADS)

Lelieveld, Jos; Gromov, Sergey; Pozzer, Andrea; Taraborrelli, Domenico

2016-10-01

The self-cleaning or oxidation capacity of the atmosphere is principally controlled by hydroxyl (OH) radicals in the troposphere. Hydroxyl has primary (P) and secondary (S) sources, the former mainly through the photodissociation of ozone, the latter through OH recycling in radical reaction chains. We used the recent Mainz Organics Mechanism (MOM) to advance volatile organic carbon (VOC) chemistry in the general circulation model EMAC (ECHAM/MESSy Atmospheric Chemistry) and show that S is larger than previously assumed. By including emissions of a large number of primary VOC, and accounting for their complete breakdown and intermediate products, MOM is mass-conserving and calculates substantially higher OH reactivity from VOC oxidation compared to predecessor models. Whereas previously P and S were found to be of similar magnitude, the present work indicates that S may be twice as large, mostly due to OH recycling in the free troposphere. Further, we find that nighttime OH formation may be significant in the polluted subtropical boundary layer in summer. With a mean OH recycling probability of about 67 %, global OH is buffered and not sensitive to perturbations by natural or anthropogenic emission changes. Complementary primary and secondary OH formation mechanisms in pristine and polluted environments in the continental and marine troposphere, connected through long-range transport of O3, can maintain stable global OH levels.

Numerical Issues Associated with Compensating and Competing Processes in Climate Models: an Example from ECHAM-HAM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Hui; Rasch, Philip J.; Zhang, Kai

2013-06-26

The purpose of this paper is to draw attention to the need for appropriate numerical techniques to represent process interactions in climate models. In two versions of the ECHAM-HAM model, different time integration methods are used to solve the sulfuric acid (H2SO4) gas evolution equation, which lead to substantially different results in the H2SO4 gas concentration and the aerosol nucleation rate. Using convergence tests and sensitivity simulations performed with various time stepping schemes, it is confirmed that numerical errors in the second model version are significantly smaller than those in version one. The use of sequential operator splitting in combinationmore » with long time step is identified as the main reason for the large systematic biases in the old model. The remaining errors in version two in the nucleation rate, related to the competition between condensation and nucleation, have a clear impact on the simulated concentration of cloud condensation nuclei in the lower troposphere. These errors can be significantly reduced by employing an implicit solver that handles production, condensation and nucleation at the same time. Lessons learned in this work underline the need for more caution when treating multi-time-scale problems involving compensating and competing processes, a common occurrence in current climate models.« less

Evaluation of East Asian climatology as simulated by seven coupled models

NASA Astrophysics Data System (ADS)

Jiang, Dabang; Wang, Huijun; Lang, Xianmei

2005-07-01

Using observation and reanalysis data throughout 1961 1990, the East Asian surface air temperature, precipitation and sea level pressure climatology as simulated by seven fully coupled atmosphere-ocean models, namely CCSR/NIES, CGCM2, CSIRO-Mk2, ECHAM4/OPYC3, GFDL-R30, HadCM3, and NCAR-PCM, are systematically evaluated in this study. It is indicated that the above models can successfully reproduce the annual and seasonal surface air temperature and precipitation climatology in East Asia, with relatively good performance for boreal autumn and annual mean. The models’ ability to simulate surface air temperature is more reliable than precipitation. In addition, the models can dependably capture the geographical distribution pattern of annual, boreal winter, spring and autumn sea level pressure in East Asia. In contrast, relatively large simulation errors are displayed when simulated boreal summer sea level pressure is compared with reanalysis data in East Asia. It is revealed that the simulation errors for surface air temperature, precipitation and sea level pressure are generally large over and around the Tibetan Plateau. No individual model is best in every aspect. As a whole, the ECHAM4/OPYC3 and HadCM3 performances are much better, whereas the CGCM2 is relatively poorer in East Asia. Additionally, the seven-model ensemble mean usually shows a relatively high reliability.

Modelling carbon cycle in boreal wetlands with the Earth System Model ECHAM6/MPIOM

NASA Astrophysics Data System (ADS)

Getzieh, Robert J.; Brovkin, Victor; Kleinen, Thomas; Raivonen, Maarit; Sevanto, Sanna

2010-05-01

Wetlands of the northern high latitudes provide excellent conditions for peat accumulation and methanogenesis. High moisture and low O2 content in the soils lead to effective preservation of soil organic matter and methane emissions. Boreal Wetlands contain about 450 PgC and currently constitute a significant natural source of methane (CH4) even though they cover only 3% of the global land surface. While storing carbon and removing CO2 from the atmosphere, boreal wetlands have contributed to global cooling on millennial timescales. Undisturbed boreal wetlands are likely to continue functioning as a net carbon sink. On the other hand these carbon pools might be destabilised in future since they are sensitive to climate change. Given that processes of peat accumulation and decay are closely dependent on hydrology and temperature, this balance may be altered significantly in the future. As a result, northern wetlands could have a large impact on carbon cycle-climate feedback mechanisms and therefore play an important role in global carbon cycle dynamics. However global biogeochemistry models used for simulations of CO2 dynamics in past and future climates usually neglect carbon cycle in wetlands. We investigate the potential for positive or negative feedbacks to the climate system through fluxes of greenhouse gases (CO2 and CH4) with the general circulation model ECHAM6/MPIOM. A generic model of peat accumulation and decay has been developed and implemented into the land surface module JSBACH. We consider anaerobic biogeochemical processes which lead to formation of thick organic soils. Furthermore we consider specific wetland plant functional types (PFTs) in our model such as vascular plants (sedges) which impact methane transport and oxidation processes and non vascular plants (sphagnum mosses) which are promoting peat growth. As prototypes we use the modelling approaches by Frolking et al. (2001) as well as Walter & Heimann (2001) for the peat dynamics, and the wetland model by Wania (2008) for vegetation cover and methane emissions. An initial distribution of wetlands follows the GLWD-3 map by Lehner and Döll (2004). A dynamical wetlands hydrology scheme (T. Stacke) and a methane transport and emission model (M. Raivonen) are at the moment also under development at the MPI for Meteorology respectively in close cooperation with the University of Helsinki. First results of our modelling approach will be presented. REFERENCES S. Frolking et al., Ecosystems 4, 479-498 (2001). B. Lehner et al., Journal of Hydrology 296, 1-22 (2004). B. P. Walter et al., J. Geophys. Res. 106, D24, 34189-34206 and 34207-34219 (2001). R. Wania et al., Global Biogeochem. Cycles 23, GB3014 and GB3015 (2009).

Projection of North Atlantic Oscillation and its effect on tracer transport

NASA Astrophysics Data System (ADS)

Bacer, Sara; Christoudias, Theodoros; Pozzer, Andrea

2016-12-01

The North Atlantic Oscillation (NAO) plays an important role in the climate variability of the Northern Hemisphere, with significant consequences on long-range pollutant transport. We investigate the evolution of pollutant transport in the 21st century influenced by the NAO under a global climate change scenario. We use a free-running simulation performed by the ECHAM/MESSy Atmospheric Chemistry (EMAC) model coupled with the ocean general circulation model MPIOM, covering the period from 1950 until 2100. Similarly to other works, the model shows a future northeastward shift of the NAO centres of action and a weak positive trend of the NAO index (over 150 years). Moreover, we find that NAO trends (computed over periods shorter than 30 years) will continue to oscillate between positive and negative values in the future. To investigate the NAO effects on transport we consider carbon monoxide tracers with exponential decay and constant interannual emissions. We find that at the end of the century, the south-western Mediterranean and northern Africa will, during positive NAO phases, see higher pollutant concentrations with respect to the past, while a wider part of northern Europe will, during positive NAO phases, see lower pollutant concentrations. Such results are confirmed by the changes observed in the future for tracer concentration and vertically integrated tracer transport, differentiating the cases of "high NAO" and "low NAO" events.

The 1-way on-line coupled model system MECO(n) - Part 4: Chemical evaluation (based on MESSy v2.52)

NASA Astrophysics Data System (ADS)

Mertens, Mariano; Kerkweg, Astrid; Jöckel, Patrick; Tost, Holger; Hofmann, Christiane

2016-10-01

For the first time, a simulation incorporating tropospheric and stratospheric chemistry using the newly developed MECO(n) model system is performed. MECO(n) is short for MESSy-fied ECHAM and COSMO models nested n times. It features an online coupling of the COSMO-CLM model, equipped with the Modular Earth Submodel System (MESSy) interface (called COSMO/MESSy), with the global atmospheric chemistry model ECHAM5/MESSy for Atmospheric Chemistry (EMAC). This online coupling allows a consistent model chain with respect to chemical and meteorological boundary conditions from the global scale down to the regional kilometre scale. A MECO(2) simulation incorporating one regional instance over Europe with 50 km resolution and one instance over Germany with 12 km resolution is conducted for the evaluation of MECO(n) with respect to tropospheric gas-phase chemistry. The main goal of this evaluation is to ensure that the chemistry-related MESSy submodels and the online coupling with respect to the chemistry are correctly implemented. This evaluation is a prerequisite for the further usage of MECO(n) in atmospheric chemistry-related studies. Results of EMAC and the two COSMO/MESSy instances are compared with satellite, ground-based and aircraft in situ observations, focusing on ozone, carbon monoxide and nitrogen dioxide. Further, the methane lifetimes in EMAC and the two COSMO/MESSy instances are analysed in view of the tropospheric oxidation capacity. From this evaluation, we conclude that the chemistry-related submodels and the online coupling with respect to the chemistry are correctly implemented. In comparison with observations, both EMAC and COSMO/MESSy show strengths and weaknesses. Especially in comparison to aircraft in situ observations, COSMO/MESSy shows very promising results. However, the amplitude of the diurnal cycle of ground-level ozone measurements is underestimated. Most of the differences between COSMO/MESSy and EMAC can be attributed to differences in the dynamics of both models, which are subject to further model developments.

Atmospheric and Oceanic Response to Southern Ocean Deep Convection Oscillations on Decadal to Centennial Time Scales in Climate Models

NASA Astrophysics Data System (ADS)

Martin, T.; Reintges, A.; Park, W.; Latif, M.

2014-12-01

Many current coupled global climate models simulate open ocean deep convection in the Southern Ocean as a recurring event with time scales ranging from a few years to centennial (de Lavergne et al., 2014, Nat. Clim. Ch.). The only observation of such event, however, was the occurrence of the Weddell Polynya in the mid-1970s, an open water area of 350 000 km2 within the Antarctic sea ice in three consecutive winters. Both the wide range of modeled frequency of occurrence and the absence of deep convection in the Weddell Sea highlights the lack of understanding concerning the phenomenon. Nevertheless, simulations indicate that atmospheric and oceanic responses to the cessation of deep convection in the Southern Ocean include a strengthening of the low-level atmospheric circulation over the Southern Ocean (increasing SAM index) and a reduction in the export of Antarctic Bottom Water (AABW), potentially masking the regional effects of global warming (Latif et al., 2013, J. Clim.; Martin et al., 2014, Deep Sea Res. II). It is thus of great importance to enhance our understanding of Southern Ocean deep convection and clarify the associated time scales. In two multi-millennial simulations with the Kiel Climate Model (KCM, ECHAM5 T31 atmosphere & NEMO-LIM2 ~2˚ ocean) we showed that the deep convection is driven by strong oceanic warming at mid-depth periodically overriding the stabilizing effects of precipitation and ice melt (Martin et al., 2013, Clim. Dyn.). Sea ice thickness also affects location and duration of the deep convection. A new control simulation, in which, amongst others, the atmosphere grid resolution is changed to T42 (~2.8˚), yields a faster deep convection flip-flop with a period of 80-100 years and a weaker but still significant global climate response similar to CMIP5 simulations. While model physics seem to affect the time scale and intensity of the phenomenon, the driving mechanism is a rather robust feature. Finally, we compare the atmospheric and oceanic responses among CMIP5 models. Since open ocean convection is the dominant mode of AABW formation in these models, the northward extent and strength of the AABW cell in the Atlantic correlates with the deep convection intensity but varies between models. Likewise, atmospheric response patterns outside the Southern Ocean region are not consistent among models.

Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter - a model study with ECHAM6-HAM

NASA Astrophysics Data System (ADS)

Joos, Hanna; Madonna, Erica; Witlox, Kasja; Ferrachat, Sylvaine; Wernli, Heini; Lohmann, Ulrike

2017-05-01

While there is a clear impact of aerosol particles on the radiation balance, whether and how aerosol particles influence precipitation is controversial. Here we use the ECHAM6-HAM global climate model coupled to an aerosol module to analyse whether an impact of anthropogenic aerosol particles on the timing and amount of precipitation can be detected in North Pacific warm conveyor belts. Warm conveyor belts are the strongest precipitation-producing airstreams in extratropical cyclones and are identified here with a Lagrangian technique, i.e. by objectively identifying the most strongly ascending trajectories in North Pacific cyclones. These conveyor belts have been identified separately in 10-year ECHAM6-HAM simulations with present-day and pre-industrial aerosol conditions. Then, the evolution of aerosols and cloud properties has been analysed in detail along the identified warm conveyor belt trajectories. The results show that, under present-day conditions, some warm conveyor belt trajectories are strongly polluted (i.e. high concentrations of black carbon and sulfur dioxide) due to horizontal transport from eastern Asia to the oceanic region where warm conveyor belts start their ascent. In these polluted trajectories a weak delay and reduction of precipitation formation occurs compared to clean warm conveyor belt trajectories. However, all warm conveyor belts consist of both polluted and clean trajectories at the time they start their ascent, and the typically more abundant clean trajectories strongly reduce the aerosol impact from the polluted trajectories. The main conclusion then is that the overall amount of precipitation is comparable in pre-industrial conditions, when all warm conveyor belt trajectories are clean, and in present-day conditions, when warm conveyor belts consist of a mixture of clean and polluted trajectories.

Assessment of impacts of climate change on surface water availability using coupled SWAT and WEAP models: case of upper Pangani River Basin, Tanzania

NASA Astrophysics Data System (ADS)

Kishiwa, Peter; Nobert, Joel; Kongo, Victor; Ndomba, Preksedis

2018-05-01

This study was designed to investigate the dynamics of current and future surface water availability for different water users in the upper Pangani River Basin under changing climate. A multi-tier modeling technique was used in the study, by coupling the Soil and Water Assessment Tool (SWAT) and Water Evaluation And Planning (WEAP) models, to simulate streamflows under climate change and assess scenarios of future water availability to different socio-economic activities by year 2060. Six common Global Circulation Models (GCMs) from WCRP-CMIP3 with emissions Scenario A2 were selected. These are HadCM3, HadGEM1, ECHAM5, MIROC3.2MED, GFDLCM2.1 and CSIROMK3. They were downscaled by using LARS-WG to station scale. The SWAT model was calibrated with observed data and utilized the LARS-WG outputs to generate future streamflows before being used as input to WEAP model to assess future water availability to different socio-economic activities. GCMs results show future rainfall increase in upper Pangani River Basin between 16-18 % in 2050s relative to 1980-1999 periods. Temperature is projected to increase by an average of 2 °C in 2050s, relative to baseline period. Long-term mean streamflows is expected to increase by approximately 10 %. However, future peak flows are estimated to be lower than the prevailing average peak flows. Nevertheless, the overall annual water demand in Pangani basin will increase from 1879.73 Mm3 at present (2011) to 3249.69 Mm3 in the future (2060s), resulting to unmet demand of 1673.8 Mm3 (51.5 %). The impact of future shortage will be more severe in irrigation where 71.12 % of its future demand will be unmet. Future water demands of Hydropower and Livestock will be unmet by 27.47 and 1.41 % respectively. However, future domestic water use will have no shortage. This calls for planning of current and future surface water use in the upper Pangani River Basin.

The influence of land cover change in the Asian monsoon region on present-day and mid-Holocene climate

NASA Astrophysics Data System (ADS)

Dallmeyer, A.; Claussen, M.

2011-02-01

Using the general circulation model ECHAM5/JSBACH, we investigate the biogeophysical effect of large-scale afforestation and deforestation in the Asian monsoon domain on present-day and mid-Holocene climate. We demonstrate that the applied land cover change does not only modify the local climate but also change the climate in North Africa and the Middle East via teleconnections. Deforestation in the Asian monsoon domain enhances the rainfall in North Africa. In parts of the Sahara summer precipitation is more than doubled. In contrast, afforestation strongly decreases summer rainfall in the Middle East and even leads to the cessation of the rainfall-activity in some parts of this region. Regarding the local climate, deforestation results in a reduction of precipitation and a cooler climate as grass mostly has a higher albedo than forests. However, in the core region of the Asian monsoon the decrease of evaporative cooling in the monsoon season overcompensates this signal and results in a net warming. Afforestation has mainly the opposite effect, although the pattern of change is less clear. It leads to more precipitation in most parts of the Asian monsoon domain and a warmer climate except for the southern regions where a stronger evaporation decreases near-surface temperatures in the monsoon season. When prescribing mid-Holocene insolation, the pattern of local precipitation change differs. Afforestation particularly increases monsoon rainfall in the region along the Yellow River which was the settlement area of major prehistoric cultures. In this region, the effect of land cover change on precipitation is half as large as the orbitally-induced precipitation change. Thus, our model results reveal that mid- to late-Holocene land cover change could strongly have contributed to the decreasing Asian monsoon precipitation during the Holocene known from reconstructions.

The influence of land cover change in the Asian monsoon region on present-day and mid-Holocene climate

NASA Astrophysics Data System (ADS)

Dallmeyer, A.; Claussen, M.

2011-06-01

Using the general circulation model ECHAM5/JSBACH, we investigate the biogeophysical effect of large-scale afforestation and deforestation in the Asian monsoon domain on present-day and mid-Holocene climate. We demonstrate that the applied land cover change does not only modify the local climate but also change the climate in North Africa and the Middle East via teleconnections. Deforestation in the Asian monsoon domain enhances the rainfall in North Africa. In parts of the Sahara summer precipitation is more than doubled. In contrast, afforestation strongly decreases summer rainfall in the Middle East and even leads to the cessation of the rainfall-activity in some parts of this region. Regarding the local climate, deforestation results in a reduction of precipitation and a cooler climate as grass mostly has a higher albedo than forests. However, in the core region of the Asian monsoon the decrease in evaporative cooling in the monsoon season overcompensates this signal and results in a net warming. Afforestation has mainly the opposite effect, although the pattern of change is less clear. It leads to more precipitation in most parts of the Asian monsoon domain and a warmer climate except for the southern regions where a stronger evaporation decreases near-surface temperatures in the monsoon season. When prescribing mid-Holocene insolation, the pattern of local precipitation change differs. Afforestation particularly increases monsoon rainfall in the region along the Yellow River which was the settlement area of major prehistoric cultures. In this region, the effect of land cover change on precipitation is half as large as the orbitally-induced precipitation change. Thus, our model results reveal that mid- to late-Holocene land cover change could strongly have contributed to the decreasing Asian monsoon precipitation during the Holocene known from reconstructions.

Hydroclimatic sustainability assessment of changing climate on cholera in the Ganges-Brahmaputra basin

NASA Astrophysics Data System (ADS)

Nasr-Azadani, Fariborz; Khan, Rakibul; Rahimikollu, Javad; Unnikrishnan, Avinash; Akanda, Ali; Alam, Munirul; Huq, Anwar; Jutla, Antarpreet; Colwell, Rita

2017-10-01

The association of cholera and climate has been extensively documented. However, determining the effects of changing climate on the occurrence of disease remains a challenge. Bimodal peaks of cholera in Bengal Delta are hypothesized to be linked to asymmetric flow of the Ganges and Brahmaputra rivers. Spring cholera is related to intrusion of bacteria-laden coastal seawater during low flow seasons, while autumn cholera results from cross-contamination of water resources when high flows in the rivers cause massive inundation. Coarse resolution of General Circulation Model (GCM) output (usually at 100 - 300 km)cannot be used to evaluate variability at the local scale(10-20 km),hence the goal of this study was to develop a framework that could be used to understand impacts of climate change on occurrence of cholera. Instead of a traditional approach of downscaling precipitation, streamflow of the two rivers was directly linked to GCM outputs, achieving reasonable accuracy (R2 = 0.89 for the Ganges and R2 = 0.91 for the Brahmaputra)using machine learning algorithms (Support Vector Regression-Particle Swarm Optimization). Copula methods were used to determine probabilistic risks of cholera under several discharge conditions. Key results, using model outputs from ECHAM5, GFDL, andHadCM3for A1B and A2 scenarios, suggest that the combined low flow of the two rivers may increase in the future, with high flows increasing for first half of this century, decreasing thereafter. Spring and autumn cholera, assuming societal conditions remain constant e.g., at the current rate, may decrease. However significant shifts were noted in the magnitude of river discharge suggesting that cholera dynamics of the delta may well demonstrate an uncertain predictable pattern of occurrence over the next century.

Late quaternary climate, precipitation δ18O, and Indian monsoon variations over the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Li, Jingmin; Ehlers, Todd A.; Werner, Martin; Mutz, Sebastian G.; Steger, Christian; Paeth, Heiko

2017-01-01

The Himalaya-Tibet orogen contains one of the largest modern topographic and climate gradients on Earth. Proxy data from the region provide a basis for understanding Tibetan Plateau paleo climate and paleo elevation reconstructions. Paleo climate model comparisons to proxy data compliment sparsely located data and can improve climate reconstructions. This study investigates temporal changes in precipitation, temperature and precipitation δ18O (δO18p) over the Himalaya-Tibet from the Last Glacial Maximum (LGM) to present. We conduct a series of atmospheric General Circulation Model (GCM, ECHAM5-wiso) experiments at discrete time slices including a Pre-industrial (PI, Pre-1850 AD), Mid Holocene (MH, 6 ka BP) and LGM (21 ka BP) simulations. Model predictions are compared with existing proxy records. Model results show muted climate changes across the plateau during the MH and larger changes occurring during the LGM. During the LGM surface temperatures are ∼ 2.0- 4.0 °C lower across the Himalaya and Tibet, and >5.0 °C lower at the northwest and northeast edge of the Tibetan Plateau. LGM mean annual precipitation is 200-600 mm/yr lower over on the Tibetan Plateau. Model and proxy data comparison shows a good agreement for the LGM, but large differences for the MH. Large differences are also present between MH proxy studies near each other. The precipitation weighted annual mean δ18Op lapse rate at the Himalaya is about 0.4 ‰ /km larger during the MH and 0.2 ‰ /km smaller during the LGM than during the PI. Finally, rainfall associated with the continental Indian monsoon (between 70°E-110°E and 10°N-30°N) is about 44% less in the LGM than during PI times. The LGM monsoon period is about one month shorter than in PI times. Taken together, these results document significant spatial and temporal changes in temperature, precipitation, and δ18Op over the last ∼21 ka. These changes are large enough to impact interpretations of proxy data and the intensity of the Indian monsoon.

Water Isotopes in Precipitation: Data/Model Comparison for Present-Day and Past Climates

NASA Technical Reports Server (NTRS)

Jouzel, J.; Hoffmann, G.; Masson, V.

1998-01-01

Variations of HDO and H2O-18 concentrations are observed in precipitation both on a geographical and on a temporal basis. These variations, resulting from successive isotopic fractionation processes at each phase change of water during its atmospheric cycle, are well documented through the IAEA/WMO network and other sources. Isotope concentrations are, in middle and high latitudes, linearly related to the annual mean temperature at the precipitation site. Paleoclimatologists have used this relationship to infer paleotemperatures from isotope paleodata extractable from ice cores, deep groundwater and other such sources. For this application to be valid, however, the spatial relationship must also hold in time at a given location as the location undergoes a series of climatic changes. Progress in water isotope modeling aimed at examining and evaluating this assumption has been recently reviewed with a focus on polar regions and, more specifically, on Greenland. This article was largely based on the results obtained using the isotopic version of the NASA/GISS Atmospheric General Circulation Model (AGCM) fitted with isotope tracer diagnostics. We extend this review in comparing the results of two different isotopic AGCMs (NASA/GISS and ECHAM) and in examining, with a more global perspective, the validity of the above assumption, i.e. the equivalence of the spatial and temporal isotope-temperature relationship. We also examine recent progress made in modeling the relationship between the conditions prevailing in moisture source regions for precipitation and the deuterium-excess of that precipitation.

Initializing decadal climate predictions over the North Atlantic region

NASA Astrophysics Data System (ADS)

Matei, Daniela Mihaela; Pohlmann, Holger; Jungclaus, Johann; Müller, Wolfgang; Haak, Helmuth; Marotzke, Jochem

2010-05-01

Decadal climate prediction aims to predict the internally-generated decadal climate variability in addition to externally-forced climate change signal. In order to achieve this it is necessary to start the predictions from the current climate state. In this study we investigate the forecast skill of the North Atlantic decadal climate predictions using two different ocean initialization strategies. First we apply an assimilation of ocean synthesis data provided by the GECCO project (Köhl and Stammer, 2008) as initial conditions for the coupled model ECHAM5/MPI-OM. Hindcast experiments are then performed over the period 1952-2001. An alternative approach is one in which the subsurface ocean temperature and salinity are diagnosed from an ensemble of ocean model runs forced by the NCEP-NCAR atmospheric reanalyzes for the period 1948-2007, then nudge into the coupled model to produce initial conditions for the hindcast experiments. An anomaly coupling scheme is used in both approaches to avoid the hindcast drift and the associated initial shock. Differences between the two assimilation approaches are discussed by comparing them with the observational data in key regions and processes. We asses the skill of the initialized decadal hindcast experiments against the prediction skill of the non-initialized hindcasts simulation. We obtain an overview of the regions with the highest predictability from the regional distribution of the anomaly correlation coefficients and RMSE for the SAT. For the first year the hindcast skill is increased over almost all ocean regions in the NCEP-forced approach. This increase in the hindcast skill for the 1 year lead time is somewhat reduced in the GECCO approach. At lead time 5yr and 10yr, the skill enhancement is still found over the North Atlantic and North Pacific regions. We also consider the potential predictability of the Atlantic Meridional Overturning Circulation (AMOC) and Nordic Seas Overflow by comparing the predicted values to the respective assimilation experiments. Hindcasts of Atlantic MOC and Denmark Strait Overflow show higher predictability than the comparison experiments without initialization and damped persistence predictions up to about 5-6 years.

Ocean Dynamics in the Key Regions of North Atlantic-Arctic Exchanges: Evaluation of Global Multi-Resolution FESOM and CMIP-type INMCM Models with Long-Term Observations

NASA Astrophysics Data System (ADS)

Beszczynska-Moeller, A.; Gürses, Ö.; Sidorenko, D.; Goessling, H.; Volodin, E. M.; Gritsun, A.; Iakovlev, N. G.; Andrzejewski, J.

2017-12-01

Enhancing the fidelity of climate models in the Arctic and North Atlantic in order to improve Arctic predictions requires better understanding of the underlying causes of common biases. The main focus of the ERA.Net project NAtMAP (Amending North Atlantic Model Biases to Improve Arctic Predictions) is on the dynamics of the key regions connecting the Arctic and the North Atlantic climate. The study aims not only at increased model realism, but also at a deeper understanding of North Atlantic-Arctic links and their contribution to Arctic predictability. Two complementary approaches employing different global coupled climate models, ECHAM6-FESOM and INMCM4/5, were adopted. The first approach is based on a recent development of climate models with ocean components based on unstructured meshes, allowing to resolve eddies and narrow boundary currents in the most crucial regions while keeping a moderate resolution elsewhere. The multi-resolution sea ice-ocean component of ECHAM6-FESOM allows studying the benefits of very high resolution in key areas of the North Atlantic. An alternative approach to address the North Atlantic and Arctic biases is also tried by tuning the performance of the relevant sub-grid-scale parameterizations in eddy resolving version the CMIP5 climate model INMCM4. Using long-term in situ and satellite observations and available climatologies we attempt to evaluate to what extent a higher resolution, allowing the explicit representation of eddies and narrow boundary currents in the North Atlantic and Nordic Seas, can alleviate the common model errors. The effects of better resolving the Labrador Sea area on reducing the model bias in surface hydrography and improved representation of ocean currents are addressed. Resolving eddy field in the Greenland Sea is assessed in terms of reducing the deep thermocline bias. The impact of increased resolution on the modeled characteristics of Atlantic water transport into the Arctic is examined with a special focus on separation of Atlantic inflow between Fram Strait and the Barents Sea, lateral exchanges in the Nordic Seas, and a role of eddies in modulating the poleward flow of Atlantic water. We also explore the effects of resolving boundary currents in the Arctic basin on the representation of the adjacent sea ice.

Return periods of losses associated with European windstorm series in a changing climate

NASA Astrophysics Data System (ADS)

Karremann, Melanie K.; Pinto, Joaquim G.; Reyers, Mark; Klawa, Matthias

2015-04-01

During the last decades, several windstorm series hit Europe leading to large aggregated losses. Such storm series are examples of serial clustering of extreme cyclones, presenting a considerable risk for the insurance industry. Clustering of events and return periods of storm series affecting Europe are quantified based on potential losses using empirical models. Moreover, possible future changes of clustering and return periods of European storm series with high potential losses are quantified. Historical storm series are identified using 40 winters of NCEP reanalysis data (1973/1974 - 2012/2013). Time series of top events (1, 2 or 5 year return levels) are used to assess return periods of storm series both empirically and theoretically. Return periods of historical storm series are estimated based on the Poisson and the negative binomial distributions. Additionally, 800 winters of ECHAM5/MPI-OM1 general circulation model simulations for present (SRES scenario 20C: years 1960- 2000) and future (SRES scenario A1B: years 2060- 2100) climate conditions are investigated. Clustering is identified for most countries in Europe, and estimated return periods are similar for reanalysis and present day simulations. Future changes of return periods are estimated for fixed return levels and fixed loss index thresholds. For the former, shorter return periods are found for Western Europe, but changes are small and spatially heterogeneous. For the latter, which combines the effects of clustering and event ranking shifts, shorter return periods are found everywhere except for Mediterranean countries. These changes are generally not statistically significant between recent and future climate. However, the return periods for the fixed loss index approach are mostly beyond the range of preindustrial natural climate variability. This is not true for fixed return levels. The quantification of losses associated with storm series permits a more adequate windstorm risk assessment in a changing climate.

Significance of hydrological model choice and land use changes when doing climate change impact assessment

NASA Astrophysics Data System (ADS)

Bjørnholt Karlsson, Ida; Obel Sonnenborg, Torben; Refsgaard, Jens Christian; Høgh Jensen, Karsten

2014-05-01

Uncertainty in impact studies arises both from Global Climate Models (GCM), emission projections, statistical downscaling, Regional Climate Models (RCM), hydrological models and calibration techniques (Refsgaard et al. 2013). Some of these uncertainties have been evaluated several times in the literature; however few studies have investigated the effect of hydrological model choice on the assessment results (Boorman & Sefton 1997; Jiang et al. 2007; Bastola et al. 2011). These studies have found that model choice results in large differences, up to 70%, in the predicted discharge changes depending on the climate input. The objective of the study is to investigate the impact of climate change on hydrology of the Odense catchment, Denmark both in response to (a) different climate projections (GCM-RCM combinations); (b) different hydrological models and (c) different land use scenarios. This includes: 1. Separation of the climate model signal; the hydrological model signal and the land use signal 2. How do the different hydrological components react under different climate and land use conditions for the different models 3. What land use scenario seems to provide the best adaptation for the challenges of the different future climate change scenarios from a hydrological perspective? Four climate models from the ENSEMBLES project (Hewitt & Griggs 2004): ECHAM5 - HIRHAM5, ECHAM5 - RCA3, ARPEGE - RM5.1 and HadCM3 - HadRM3 are used, assessing the climate change impact in three periods: 1991-2010 (present), 2041-2060 (near future) and 2081-2100 (far future). The four climate models are used in combination with three hydrological models with different conceptual layout: NAM, SWAT and MIKE SHE. Bastola, S., C. Murphy and J. Sweeney (2011). "The role of hydrological modelling uncertainties in climate change impact assessments of Irish river catchments." Advances in Water Resources 34: 562-576. Boorman, D. B. and C. E. M. Sefton (1997). "Recognising the uncertainty in the quantification of the effects of climate change on hydrological response." Climate Change 35: 415-434. Hewitt, C. D. and D. J. Griggs (2004). "Ensembles-based predictions of climate changes and their impacts." Eos, Transactions American Geophysical Union 85: 1-566. Jiang, T., Y. D. Chen, C. Xu, X. Chen, X. Chen and V. P. Singh (2007). "Comparison of hydrological impacts of climate change simulated by six hydrological models in the Dongjiang Basin, South China." Journal of hydrology 336: 316-333. Refsgaard, J. C., K. Arnbjerg-Nielsen, M. Drews, K. Halsnæs, E. Jeppesen, H. Madsen, A. Markandya, J. E. Olesen, J. R. Porter and J. H. Christensen (2013). "The role of uncertainty in climate change adaptation strategies - A Danish water management example." Mitigation and Adaptation Strategies for Global Change 18: 337-359.

Land-Climate Feedbacks in Indian Summer Monsoon Rainfall

NASA Astrophysics Data System (ADS)

Asharaf, Shakeel; Ahrens, Bodo

2016-04-01

In an attempt to identify how land surface states such as soil moisture influence the monsoonal precipitation climate over India, a series of numerical simulations including soil moisture sensitivity experiments was performed. The simulations were conducted with a nonhydrostatic regional climate model (RCM), the Consortium for Small-Scale Modeling (COSMO) in climate mode (CCLM) model, which was driven by the European Center for Medium-Range Weather Forecasts (ECMWF) Interim reanalysis (ERA-Interim) data. Results showed that pre-monsoonal soil moisture has a significant impact on monsoonal precipitation formation and large-scale atmospheric circulations. The analysis revealed that even a small change in the processes that influence precipitation via changes in local evapotranspiration was able to trigger significant variations in regional soil moisture-precipitation feedback. It was observed that these processes varied spatially from humid to arid regions in India, which further motivated an examination of soil-moisture memory variation over these regions and determination of the ISM seasonal forecasting potential. A quantitative analysis indicated that the simulated soil-moisture memory lengths increased with soil depth and were longer in the western region than those in the eastern region of India. Additionally, the subsequent precipitation variance explained by soil moisture increased from east to west. The ISM rainfall was further analyzed in two different greenhouse gas emission scenarios: the Special Report on Emissions Scenario (SRES: B1) and the new Representative Concentration Pathways (RCPs: RCP4.5). To that end, the CCLM and its driving global-coupled atmospheric-oceanic model (GCM), ECHAM/MPIOM were used in order to understand the driving processes of the projected inter-annual precipitation variability and associated trends. Results inferred that the projected rainfall changes were the result of two largely compensating processes: increase of remotely induced precipitation and decrease of precipitation efficiency. However, the complementing precipitation components and their simulation uncertainties rendered climate projections of the Indian summer monsoon rainfall as an ongoing, highly ambiguous challenge for both the GCM and the RCM.

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

NASA Astrophysics Data System (ADS)

Niemeier, Ulrike; Schmidt, Hauke

2017-12-01

The injection of sulfur dioxide (SO2) into the stratosphere to form an artificial stratospheric aerosol layer is discussed as an option for solar radiation management. Sulfate aerosol scatters solar radiation and absorbs infrared radiation, which warms the stratospheric sulfur layer. Simulations with the general circulation model ECHAM5-HAM, including aerosol microphysics, show consequences of this warming, including changes of the quasi-biennial oscillation (QBO) in the tropics. The QBO slows down after an injection of 4 Tg(S) yr-1 and completely shuts down after an injection of 8 Tg(S) yr-1. Transport of species in the tropics and sub-tropics depends on the phase of the QBO. Consequently, the heated aerosol layer not only impacts the oscillation of the QBO but also the meridional transport of the sulfate aerosols. The stronger the injection, the stronger the heating and the simulated impact on the QBO and equatorial wind systems. With increasing injection rate the velocity of the equatorial jet streams increases, and the less sulfate is transported out of the tropics. This reduces the global distribution of sulfate and decreases the radiative forcing efficiency of the aerosol layer by 10 to 14 % compared to simulations with low vertical resolution and without generated QBO. Increasing the height of the injection increases the radiative forcing only for injection rates below 10 Tg(S) yr-1 (8-18 %), a much smaller value than the 50 % calculated previously. Stronger injection rates at higher levels even result in smaller forcing than the injections at lower levels.

Dynamics and composition of the Asian summer monsoon anticyclone

NASA Astrophysics Data System (ADS)

Gottschaldt, Klaus-Dirk; Schlager, Hans; Baumann, Robert; Sinh Cai, Duy; Eyring, Veronika; Graf, Phoebe; Grewe, Volker; Jöckel, Patrick; Jurkat-Witschas, Tina; Voigt, Christiane; Zahn, Andreas; Ziereis, Helmut

2018-04-01

This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth System Model Validation (ESMVal) campaign in September 2012. Observed and simulated tracer-tracer relations reflect photochemical O3 production as well as in-mixing from the lower troposphere and the tropopause layer. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from those in the rest of the year, and the measurements reflect the main processes acting throughout the monsoon season. Net photochemical O3 production is significantly enhanced in the ASMA, where uplifted precursors meet increased NOx, mainly produced by lightning. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank and then transported in the southern fringe around the interior region. Radial transport barriers of the circulation are effectively overcome by subseasonal dynamical instabilities of the anticyclone, which occur quite frequently and are of paramount importance for the trace gas composition of the ASMA. Both the isentropic entrainment of O3-rich air and the photochemical conversion of uplifted O3-poor air tend to increase O3 in the ASMA outflow.

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

NASA Astrophysics Data System (ADS)

Salameh, Josiane; Popp, Max; Marotzke, Jochem

2018-04-01

We investigate the influence of the rotation period (P_{rot}) on the mean climate of an aquaplanet, with a focus on the role of sea-ice albedo. We perform aquaplanet simulations with the atmospheric general circulation model ECHAM6 for various rotation periods from one Earth-day to 365 Earth-days in which case the planet is synchronously rotating. The global-mean surface temperature decreases with increasing P_{rot} and sea ice expands equatorwards. The cooling of the mean climate with increasing P_{rot} is caused partly by the high surface albedo of sea ice on the dayside and partly by the high albedo of the deep convective clouds over the substellar region. The cooling caused by these deep convective clouds is weak for non-synchronous rotations compared to synchronous rotation. Sensitivity simulations with the sea-ice model switched off show that the global-mean surface temperature is up to 27 K higher than in our main simulations with sea ice and thus highlight the large influence of sea ice on the climate. We present the first estimates of the influence of the rotation period on the transition of an Earth-like climate to global glaciation. Our results suggest that global glaciation of planets with synchronous rotation occurs at substantially lower incoming solar irradiation than for planets with slow but non-synchronous rotation.

Scales of variability of black carbon plumes and their dependence on resolution of ECHAM6-HAM

NASA Astrophysics Data System (ADS)

Weigum, Natalie; Stier, Philip; Schutgens, Nick; Kipling, Zak

2015-04-01

Prediction of the aerosol effect on climate depends on the ability of three-dimensional numerical models to accurately estimate aerosol properties. However, a limitation of traditional grid-based models is their inability to resolve variability on scales smaller than a grid box. Past research has shown that significant aerosol variability exists on scales smaller than these grid-boxes, which can lead to discrepancies between observations and aerosol models. The aim of this study is to understand how a global climate model's (GCM) inability to resolve sub-grid scale variability affects simulations of important aerosol features. This problem is addressed by comparing observed black carbon (BC) plume scales from the HIPPO aircraft campaign to those simulated by ECHAM-HAM GCM, and testing how model resolution affects these scales. This study additionally investigates how model resolution affects BC variability in remote and near-source regions. These issues are examined using three different approaches: comparison of observed and simulated along-flight-track plume scales, two-dimensional autocorrelation analysis, and 3-dimensional plume analysis. We find that the degree to which GCMs resolve variability can have a significant impact on the scales of BC plumes, and it is important for models to capture the scales of aerosol plume structures, which account for a large degree of aerosol variability. In this presentation, we will provide further results from the three analysis techniques along with a summary of the implication of these results on future aerosol model development.

Comparison of aerosol optical properties above clouds between POLDER and AeroCom models over the South East Atlantic Ocean during the fire season: POLDER/AeroCom Comparison Above Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peers, F.; Bellouin, N.; Waquet, F.

Aerosol properties above clouds have been retrieved over the South East Atlantic Ocean during the fire season 2006 using satellite observations from POLDER (Polarization and Directionality of Earth Reflectances). From June to October, POLDER has observed a mean Above-Cloud Aerosol Optical Thickness (ACAOT) of 0.28 and a mean Above-Clouds Single Scattering Albedo (ACSSA) of 0.87 at 550nm. These results have been used to evaluate the simulation of aerosols above clouds in 5 AeroCom (Aerosol Comparisons between Observations and Models) models (GOCART, HadGEM3, ECHAM5-HAM2, OsloCTM2 and SPRINTARS). Most models do not reproduce the observed large aerosol load episodes. The comparison highlightsmore » the importance of the injection height and the vertical transport parameterizations to simulate the large ACAOT observed by POLDER. Furthermore, some models overestimate the ACSSA. In accordance with recent recommendations of the black carbon refractive index, a higher prescription of the imaginary part allows a better comparison with POLDER’s ACSSA.« less

In vitro nematicidal effect of Chenopodium ambrosioides and Castela tortuosa n-hexane extracts against Haemonchus contortus (Nematoda) and their anthelmintic effect in gerbils.

PubMed

Zamilpa, A; García-Alanís, C; López-Arellano, M E; Hernández-Velázquez, V M; Valladares-Cisneros, M G; Salinas-Sánchez, D O; Mendoza-de Gives, P

2018-05-06

The in vitro nematicidal effect of Chenopodium ambrosioides and Castela tortuosa n-hexane extracts (E-Cham and E-Cato, respectively) on Haemonchus contortus infective larvae (L3) and the anthelmintic effect of these extracts against the pre-adult stage of the parasite in gerbils were evaluated using both individual and combined extracts. The in vitro confrontation between larvae and extracts was performed in 24-well micro-titration plates. The results were considered 24 and 72 h post confrontation. The in vivo nematicidal effect was examined using gerbils as a study model. The extracts from the two assessed plants were obtained through maceration using n-hexane as an organic agent. Gerbils artificially infected with H. contortus L3 were treated intraperitoneally with the corresponding extract either individually or in combination. The results showed that the highest individual lethal in vitro effect (96.3%) was obtained with the E-Cham extract at 72 h post confrontation at 40 mg/ml, followed by E-Cato (78.9%) at 20 mg/ml after 72 h. The highest combined effect (98.7%) was obtained after 72 h at 40 mg/ml. The in vivo assay showed that the individual administration of the E-Cato and E-Cham extracts reduced the parasitic burden in gerbils by 27.1% and 45.8%, respectively. Furthermore, the anthelmintic efficacy increased to 57.3% when both extracts were administered in combination. The results of the present study show an important combined nematicidal effect of the two plant extracts assessed against L3 in gerbils.

Consequences of Changes in Vegetation and Snow Cover for Climate Feedbacks in Alaska and Northwest Canada

NASA Astrophysics Data System (ADS)

Euskirchen, E. S.; Breen, A. L.; Bennett, A.; Genet, H.; Lindgren, M.; Kurkowski, T. A.; McGuire, A. D.; Rupp, S. T.

2016-12-01

A continuing challenge in global change studies is to determine how land surface changes may impact atmospheric heating. Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90-year period from 2010- 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We consider a more comprehensive suite of possible feedbacks to climate due to shifts in vegetation than previous studies, including both boreal and tundra fire, an advance of treeline, reduction in forest cover due to drought, and increases in the distribution of shrub tundra. However, changes in snow cover still provided the dominant positive land surface feedback to atmospheric heating. This positive feedback was partially moderated by an increase in area burned in spruce forests and shrub tundra. Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks, we can reach a more integrated understanding of the vulnerability of this region to changes in climate.

Comparison of aerosol optical properties above clouds between POLDER and AeroCom models over the South East Atlantic Ocean during the fire season

NASA Astrophysics Data System (ADS)

Peers, F.; Bellouin, N.; Waquet, F.; Ducos, F.; Goloub, P.; Mollard, J.; Myhre, G.; Skeie, R. B.; Takemura, T.; Tanré, D.; Thieuleux, F.; Zhang, K.

2016-04-01

Aerosol properties above clouds have been retrieved over the South East Atlantic Ocean during the fire season 2006 using satellite observations from POLDER (Polarization and Directionality of Earth Reflectances). From June to October, POLDER has observed a mean Above-Cloud Aerosol Optical Thickness (ACAOT) of 0.28 and a mean Above-Clouds Single Scattering Albedo (ACSSA) of 0.87 at 550 nm. These results have been used to evaluate the simulation of aerosols above clouds in five Aerosol Comparisons between Observations and Models (Goddard Chemistry Aerosol Radiation and Transport (GOCART), Hadley Centre Global Environmental Model 3 (HadGEM3), European Centre Hamburg Model 5-Hamburg Aerosol Module 2 (ECHAM5-HAM2), Oslo-Chemical Transport Model 2 (OsloCTM2), and Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS)). Most models do not reproduce the observed large aerosol load episodes. The comparison highlights the importance of the injection height and the vertical transport parameterizations to simulate the large ACAOT observed by POLDER. Furthermore, POLDER ACSSA is best reproduced by models with a high imaginary part of black carbon refractive index, in accordance with recent recommendations.

Tuning the climate sensitivity of a global model to match 20th Century warming

NASA Astrophysics Data System (ADS)

Mauritsen, T.; Roeckner, E.

2015-12-01

A climate models ability to reproduce observed historical warming is sometimes viewed as a measure of quality. Yet, for practical reasons historical warming cannot be considered a purely empirical result of the modelling efforts because the desired result is known in advance and so is a potential target of tuning. Here we explain how the latest edition of the Max Planck Institute for Meteorology Earth System Model (MPI-ESM1.2) atmospheric model (ECHAM6.3) had its climate sensitivity systematically tuned to about 3 K; the MPI model to be used during CMIP6. This was deliberately done in order to improve the match to observed 20th Century warming over the previous model generation (MPI-ESM, ECHAM6.1) which warmed too much and had a sensitivity of 3.5 K. In the process we identified several controls on model cloud feedback that confirm recently proposed hypotheses concerning trade-wind cumulus and high-latitude mixed-phase clouds. We then evaluate the model fidelity with centennial global warming and discuss the relative importance of climate sensitivity, forcing and ocean heat uptake efficiency in determining the response as well as possible systematic biases. The activity of targeting historical warming during model development is polarizing the modeling community with 35 percent of modelers stating that 20th Century warming was rated very important to decisive, whereas 30 percent would not consider it at all. Likewise, opinions diverge as to which measures are legitimate means for improving the model match to observed warming. These results are from a survey conducted in conjunction with the first WCRP Workshop on Model Tuning in fall 2014 answered by 23 modelers. We argue that tuning or constructing models to match observed warming to some extent is practically unavoidable, and as such, in many cases might as well be done explicitly. For modeling groups that have the capability to tune both their aerosol forcing and climate sensitivity there is now a unique opportunity to explore the bounds of our understanding - a low sensitivity model could be sustained by weak aerosol forcing, and a highly sensitive model could potentially be constructed to match observed warming by strong compensating aerosol cooling. This next natural step could constitute a new paradigm in climate modeling.

Lightning Forcing in Global Fire Models: The Importance of Temporal Resolution

NASA Astrophysics Data System (ADS)

Felsberg, A.; Kloster, S.; Wilkenskjeld, S.; Krause, A.; Lasslop, G.

2018-01-01

In global fire models, lightning is typically prescribed from observational data with monthly mean temporal resolution while meteorological forcings, such as precipitation or temperature, are prescribed in a daily resolution. In this study, we investigate the importance of the temporal resolution of the lightning forcing for the simulation of burned area by varying from daily to monthly and annual mean forcing. For this, we utilize the vegetation fire model JSBACH-SPITFIRE to simulate burned area, forced with meteorological and lightning data derived from the general circulation model ECHAM6. On a global scale, differences in burned area caused by lightning forcing applied in coarser temporal resolution stay below 0.55% compared to the use of daily mean forcing. Regionally, however, differences reach up to 100%, depending on the region and season. Monthly averaged lightning forcing as well as the monthly lightning climatology cause differences through an interaction between lightning ignitions and fire prone weather conditions, accounted for by the fire danger index. This interaction leads to decreased burned area in the boreal zone and increased burned area in the Tropics and Subtropics under the coarser temporal resolution. The exclusion of interannual variability, when forced with the lightning climatology, has only a minor impact on the simulated burned area. Annually averaged lightning forcing causes differences as a direct result of the eliminated seasonal characteristics of lightning. Burned area is decreased in summer and increased in winter where fuel is available. Regions with little seasonality, such as the Tropics and Subtropics, experience an increase in burned area.

Modeling the water isotopes in Greenland precipitation 1959-2001 with the meso-scale model REMO-iso

NASA Astrophysics Data System (ADS)

Sjolte, J.; Hoffmann, G.; Johnsen, S. J.; Vinther, B. M.; Masson-Delmotte, V.; Sturm, C.

2011-09-01

Ice core studies have proved the δ18O in Greenland precipitation to be correlated to the phase of the North Atlantic Oscillation (NAO). This subject has also been investigated in modeling studies. However, these studies have either had severe biases in the δ18O levels, or have not been designed to be compared directly with observations. In this study we nudge a meso-scale climate model fitted with stable water isotope diagnostics (REMO-iso) to follow the actual weather patterns for the period 1959-2001. We evaluate this simulation using meteorological observations from stations along the Greenland coast, and δ18O from several Greenland ice core stacks and Global Network In Precipitation (GNIP) data from Greenland, Iceland and Svalbard. The REMO-iso output explains up to 40% of the interannual δ18O variability observed in ice cores, which is comparable to the model performance for precipitation. In terms of reproducing the observed variability the global model, ECHAM4-iso performs on the same level as REMO-iso. However, REMO-iso has smaller biases in δ18O and improved representation of the observed spatial δ18O-temperature slope compared to ECHAM4-iso. Analysis of the main modes of winter variability of δ18O shows a coherent signal in Central and Western Greenland similar to results from ice cores. The NAO explains 20% of the leading δ18O pattern. Based on the model output we suggest that methods to reconstruct the NAO from Greenland ice cores employ both δ18O and accumulation records.

Simulating the Snowball Stratosphere and Its Influence On CO2 Inference

NASA Astrophysics Data System (ADS)

Graham, R. J.; Shaw, T.; Abbot, D. S.

2017-12-01

According to the snowball Earth hypothesis, a large quantity of CO2 must build up during an event in order to cause eventual deglaciation. One prediction of this model is a depletion in atmospheric oxygen-17 as a result of stratospheric chemical reactions, which has been observed in preserved barite minerals. This represents one of the most dramatic and compelling pieces of evidence in support of the snowball Earth hypothesis. The inference of anomalous atmospheric oxygen-17 based on measurements of barite minerals, however, was made by assuming that the stratosphere-troposphere mass exchange rate and mixing within the stratosphere were the same as the present. In this contribution we test these assumptions with simulations of modern and snowball atmospheric conditions using the global climate model ECHAM5. Our simulations are still running, but we will have results to report by December.

Potential Carbon Stock Changes in Arizona's Ecosystems Due to Projected Climate Change

NASA Astrophysics Data System (ADS)

Finley, B. K.; Ironside, K.; Hungate, B. A.; Hurteau, M.; Koch, G. W.

2011-12-01

Climate change can alter the role of plants and soils as sources or sinks of atmospheric carbon dioxide and result in changes in long-term carbon storage. To understand the sensitivity of Arizona's ecosystems to climate change, we quantified the present carbon stocks in Arizona's major ecosystem types using the NASA-CASA (Carnegie Ames Stanford Approach) model. Carbon stocks for each vegetation type included surface mineral soil, dead wood litter, standing wood and live leaf biomass. The total Arizona ecosystem carbon stock is presently 1775 MMtC, 545 MMtC of which is in Pinus ponderosa and Pinus edulis forests and woodlands. Evergreen forest vegetation, predominately Pinus ponderosa, has the largest current C density at 11.3 kgC/m2, while Pinus edulis woodlands have a C density of 6.0 kgC/m2. A change in climate will impact the suitable range for each tree species, and consequentially the amount of C stored. Present habitat ranges for these tree species are projected to have widespread mortality and likely will be replaced by herbaceous species, resulting in a loss of C stored. We evaluated the C storage implications over the 2010 to 2099 period of climate change based on output from GCMs with contrasting projections for the southwestern US: MPI-ECHAM5, which projects warming and reduced precipitation, and UKMO-HadGEM, which projects warming and increased precipitation. These projected changes are end points of a spectrum of possible future climate scenarios. The vegetation distribution models used describe potential suitable habitat, and we assumed that the growth rate for each vegetation type would be one-third of the way to full C density for each 30 year period up to 2099. With increasing temperature and decreasing precipitation predictions under the MPI-ECHAM5 model, P. ponderosa and P. edulis vegetation show a decrease in carbon stored from 545 MMtC presently to 116 MMtC. With the combined increase in temperature and precipitation, C storage in these vegetation types is projected to increase to 808 MMtC. Our results indicate that future C storage in Arizona is highly dependent on precipitation. Given that most climate models for the Southwest predict a more arid future, it is likely that C storage will decrease in Arizona ecosystems, as it has in response to recent droughts, reducing mitigation of rising human emissions.

Predicting and attributing recent East African Spring droughts with dynamical-statistical climate model ensembles

NASA Astrophysics Data System (ADS)

Funk, C. C.; Shukla, S.; Hoerling, M. P.; Robertson, F. R.; Hoell, A.; Liebmann, B.

2013-12-01

During boreal spring, eastern portions of Kenya and Somalia have experienced more frequent droughts since 1999. Given the region's high levels of food insecurity, better predictions of these droughts could provide substantial humanitarian benefits. We show that dynamical-statistical seasonal climate forecasts, based on the latest generation of coupled atmosphere-ocean and uncoupled atmospheric models, effectively predict boreal spring rainfall in this area. Skill sources are assessed by comparing ensembles driven with full-ocean forcing with ensembles driven with ENSO-only sea surface temperatures (SSTs). Our analysis suggests that both ENSO and non-ENSO Indo-Pacific SST forcing have played an important role in the increase in drought frequencies. Over the past 30 years, La Niña drought teleconnections have strengthened, while non-ENSO Indo-Pacific convection patterns have also supported increased (decreased) Western Pacific (East African) rainfall. To further examine the relative contribution of ENSO, low frequency warming and the Pacific Decadal Oscillation, we present decompositions of ECHAM5, GFS, CAM4 and GMAO AMIP simulations. These decompositions suggest that rapid warming in the western Pacific and steeper western-to-central Pacific SST gradients have likely played an important role in the recent intensification of the Walker circulation, and the associated increase in East African aridity. A linear combination of time series describing the Pacific Decadal Oscillation and the strength of Indo-Pacific warming are shown to track East African rainfall reasonably well. The talk concludes with a few thoughts linking the potentially important interplay of attribution and prediction. At least for recent East African droughts, it appears that a characteristic Indo-Pacific SST and precipitation anomaly pattern can be linked statistically to support forecasts and attribution analyses. The combination of traditional AGCM attribution analyses with simple yet physically plausible statistical estimation procedures may help us better untangle some climate mysteries.

Extreme weather events in southern Germany - Climatological risk and development of a large-scale identification procedure

NASA Astrophysics Data System (ADS)

Matthies, A.; Leckebusch, G. C.; Rohlfing, G.; Ulbrich, U.

2009-04-01

Extreme weather events such as thunderstorms, hail and heavy rain or snowfall can pose a threat to human life and to considerable tangible assets. Yet there is a lack of knowledge about present day climatological risk and its economic effects, and its changes due to rising greenhouse gas concentrations. Therefore, parts of economy particularly sensitve to extreme weather events such as insurance companies and airports require regional risk-analyses, early warning and prediction systems to cope with such events. Such an attempt is made for southern Germany, in close cooperation with stakeholders. Comparing ERA40 and station data with impact records of Munich Re and Munich Airport, the 90th percentile was found to be a suitable threshold for extreme impact relevant precipitation events. Different methods for the classification of causing synoptic situations have been tested on ERA40 reanalyses. An objective scheme for the classification of Lamb's circulation weather types (CWT's) has proved to be most suitable for correct classification of the large-scale flow conditions. Certain CWT's have been turned out to be prone to heavy precipitation or on the other side to have a very low risk of such events. Other large-scale parameters are tested in connection with CWT's to find out a combination that has the highest skill to identify extreme precipitation events in climate model data (ECHAM5 and CLM). For example vorticity advection in 700 hPa shows good results, but assumes knowledge of regional orographic particularities. Therefore ongoing work is focused on additional testing of parameters that indicate deviations of a basic state of the atmosphere like the Eady Growth Rate or the newly developed Dynamic State Index. Evaluation results will be used to estimate the skill of the regional climate model CLM concerning the simulation of frequency and intensity of the extreme weather events. Data of the A1B scenario (2000-2050) will be examined for a possible climate change signal.

Diversity in the representation of large-scale circulation associated with ENSO-Indian summer monsoon teleconnections in CMIP5 models

NASA Astrophysics Data System (ADS)

Ramu, Dandi A.; Chowdary, Jasti S.; Ramakrishna, S. S. V. S.; Kumar, O. S. R. U. B.

2018-04-01

Realistic simulation of large-scale circulation patterns associated with El Niño-Southern Oscillation (ENSO) is vital in coupled models in order to represent teleconnections to different regions of globe. The diversity in representing large-scale circulation patterns associated with ENSO-Indian summer monsoon (ISM) teleconnections in 23 Coupled Model Intercomparison Project Phase 5 (CMIP5) models is examined. CMIP5 models have been classified into three groups based on the correlation between Niño3.4 sea surface temperature (SST) index and ISM rainfall anomalies, models in group 1 (G1) overestimated El Niño-ISM teleconections and group 3 (G3) models underestimated it, whereas these teleconnections are better represented in group 2 (G2) models. Results show that in G1 models, El Niño-induced Tropical Indian Ocean (TIO) SST anomalies are not well represented. Anomalous low-level anticyclonic circulation anomalies over the southeastern TIO and western subtropical northwest Pacific (WSNP) cyclonic circulation are shifted too far west to 60° E and 120° E, respectively. This bias in circulation patterns implies dry wind advection from extratropics/midlatitudes to Indian subcontinent. In addition to this, large-scale upper level convergence together with lower level divergence over ISM region corresponding to El Niño are stronger in G1 models than in observations. Thus, unrealistic shift in low-level circulation centers corroborated by upper level circulation changes are responsible for overestimation of ENSO-ISM teleconnections in G1 models. Warm Pacific SST anomalies associated with El Niño are shifted too far west in many G3 models unlike in the observations. Further large-scale circulation anomalies over the Pacific and ISM region are misrepresented during El Niño years in G3 models. Too strong upper-level convergence away from Indian subcontinent and too weak WSNP cyclonic circulation are prominent in most of G3 models in which ENSO-ISM teleconnections are underestimated. On the other hand, many G2 models are able to represent most of large-scale circulation over Indo-Pacific region associated with El Niño and hence provide more realistic ENSO-ISM teleconnections. Therefore, this study advocates the importance of representation/simulation of large-scale circulation patterns during El Niño years in coupled models in order to capture El Niño-monsoon teleconnections well.

Scenarios of the spatiotemporal variability of precipitation for West Africa on the continental to local scale including ghg forcing and land use change

NASA Astrophysics Data System (ADS)

Krüger, A.; Born, K.; Brücher, T.; Fink, A.; Ludwig, P.; Paeth, H.; Kerschgens, M.

2009-04-01

In the present study the influence of SST variability and land use change on the spatiotemporal rainfall variability in West Africa is investigated. The research is embedded in multidisciplinary Project IMPETUS (An integrated approach to the efficient management of scarce water resources in West Africa), which develops various decision support systems for local stakeholders to mitigate the impacts of the ongoing and projected climate change. There is increasing evidence that in some regions, particularly in the tropics, land use changes may play an equally or even more important role in future climate change compared with enhanced greenhouse conditions. Particularly, tropical Africa appears to be a paradigm for the prominent link between land surface conditions and changes in the hydrological cycle and energy budget. Recently, complex scenarios of future land cover changes are elaborated and combined with radiative forcing according to the IPCC scenarios A1B and B1. Based on these more realistic scenarios, ensemble simulations with the regional climate model REMO are carried out, nested in global ECHAM5 simulations between 1960 and 2050 (IMPETUS model chain). The results reveal some remarkable changes in near-surface climate. In a broad band between the Guinean coast and 15°N as well as in the Congo basin annual precipitation is decreasing by 100 to 500 mm until the middle of the 21st century. At the same time, near-surface temperature increases by 2 to 5 K. The warming rate is much more pronounced in tropical Africa than in northern Africa and southern Europe, where greenhouse-gas concentrations are equally rising, and basically reflects the pattern of enhanced land degradation. The large-scale monsoon circulation and the occurrence of extreme events are affected as well. Differences between the A1B and B1 ensembles are small. By means of the high resolution models of the IMPETUS model chain (LM and FOOT3DK) the effect of interactions between the Earth's surface and the atmosphere on fresh water availability is investigated on the local scale (the river catchment of the upper Ouémé in Benin). It is planned to use model rainfall simulations to construct a generator for future rainy seasons with a statistical-dynamical regionalisation approach for the regarded area. For this purposes simulations with the non-hydrostatic mesoscale meteorological model FOOT3DK are conducted. First, on basis of the 3-D modelling several sensitivity studies for a certain episode of 54 hours were executed, which hint at a substantial risk of precipitation decrease in case of unfavourable land surface change i.e. the reduction of vegetation cover and/or decreasing of initial soil moisture. In a further step accumulated precipitation for the rainy season 2002 for the HVO (Haute Vallée de l'Ouémé) was estimated with a satellite based approach for the detection of rainfall generating cloud systems (cf. Fink et al., 2006) in combination with episode simulations of FOOT3DK. The simulations with LM for 2002 are forced with analysis-data provided by the German Weather Service. The LM data serves as the input for FOOT3DK. The latter model is used for a double nesting procedure with horizontal resolutions of 9 km and 3 km. Land use is provided from other IMPETUS working groups and is mainly assessed on basis of Landsat and GLCC data. A comparison of observations and simulations leads to satisfactory results. Finally, the entire model chain (ECHAM5-REMO-LM-FOOT3DK) is used to calculate scenario simulations with respect to the regarded IPCC scenarios. Simulations with LM are undertaken for the year 2025. Again episodes of 54 to 72 hours are calculated with FOOT3DK and an IMPETUS generated projection for the land use of 2025 to overcome the limited calculating capacity. The forty chosen dry and wet episodes shall enable the estimation of future rainy seasons (rainy season generator) by assigning them to meteorological parameters derived from REMO output.

Estimating the uncertainty of the impact of climate change on alluvial aquifers. Case study in central Italy

NASA Astrophysics Data System (ADS)

Romano, Emanuele; Camici, Stefania; Brocca, Luca; Moramarco, Tommaso; Pica, Federico; Preziosi, Elisabetta

2014-05-01

There is evidence that the precipitation pattern in Europe is trending towards more humid conditions in the northern region and drier conditions in the southern and central-eastern regions. However, a great deal of uncertainty concerns how the changes in precipitations will have an impact on water resources, particularly on groundwater, and this uncertainty should be evaluated on the basis of that coming from 1) future climate scenarios of Global Circulation Models (GCMs) and 2) modeling chains including the downscaling technique, the infiltration model and the calibration/validation procedure used to develop the groundwater flow model. With the aim of quantifying the uncertainty of these components, the Valle Umbra porous aquifer (Central Italy) has been considered as a case study. This aquifer, that is exploited for human consumption and irrigation, is mainly fed by the effective infiltration from the ground surface and partly by the inflow from the carbonate aquifers bordering the valley. A numerical groundwater flow model has been developed through the finite difference MODFLOW2005 code and it has been calibrated and validated considering the recharge regime computed through a Thornthwaite-Mather infiltration model under the climate conditions observed in the period 1956-2012. Future scenarios (2010-2070) of temperature and precipitation have been obtained from three different GMCs: ECHAM-5 (Max Planck Institute, Germany), PCM (National Centre Atmospheric Research) and CCSM3 (National Centre Atmospheric Research). Each scenario has been downscaled (DSC) to the data of temperature and precipitation collected in the baseline period 1960-1990 at the stations located in the study area through two different statistical techniques (linear rescaling and quantile mapping). Then, stochastic rainfall and temperature time series are generated through the Neyman-Scott Rectangular Pulses model (NSRP) for precipitation and the Fractionally Differenced ARIMA model (FARIMA) for temperature. Such a procedure has allowed to estimate, through the Thornthwaite-Mather model, the uncertainty related to the future scenarios of recharge to the aquifer. Finally, all the scenarios of recharge have been used as input to the groundwater flow model and the results have been evaluated in terms of the uncertainty on the computed aquifer heads and total budget. The main results have indicated that most of the uncertainty on the impact to the aquifer arise from the uncertainty on the first part of the processing chain GCM-DSC.

Understanding scale dependency of climatic processes with diarrheal disease

NASA Astrophysics Data System (ADS)

Nasr Azadani, F.; Jutla, A.; Akanda, A. S. S.; Colwell, R. R.

2015-12-01

The issue of scales in linking climatic processes with diarrheal diseases is perhaps one of the most challenging aspect to develop any predictive algorithm for outbreaks and to understand impacts of changing climate. Majority of diarrheal diseases have shown to be strongly associated with climate modulated environmental processes where pathogens survive. Using cholera as an example of characteristic diarrheal diseases, this study will provide methodological insights on dominant scale variability in climatic processes that are linked with trigger and transmission of disease. Cholera based epidemiological models use human to human interaction as a main transmission mechanism, however, environmental conditions for creating seasonality in outbreaks is not explicitly modeled. For example, existing models cannot create seasonality, unless some of the model parameters are a-priori chosen to vary seasonally. A systems based feedback approach will be presented to understand role of climatic processes on trigger and transmission disease. In order to investigate effect of changing climate on cholera, a downscaling approach using support vector machine will be used. Our preliminary results using three climate models, ECHAM5, GFDL, and HADCM show that varying modalities in future cholera outbreaks.

Revised mineral dust emissions in the atmospheric chemistry-climate model EMAC (MESSy 2.52 DU_Astitha1 KKDU2017 patch)

NASA Astrophysics Data System (ADS)

Klingmüller, Klaus; Metzger, Swen; Abdelkader, Mohamed; Karydis, Vlassis A.; Stenchikov, Georgiy L.; Pozzer, Andrea; Lelieveld, Jos

2018-03-01

To improve the aeolian dust budget calculations with the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC), which combines the Modular Earth Submodel System (MESSy) with the ECMWF/Hamburg (ECHAM) climate model developed at the Max Planck Institute for Meteorology in Hamburg based on a weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF), we have implemented new input data and updates of the emission scheme.The data set comprises land cover classification, vegetation, clay fraction and topography. It is based on up-to-date observations, which are crucial to account for the rapid changes of deserts and semi-arid regions in recent decades. The new Moderate Resolution Imaging Spectroradiometer (MODIS)-based land cover and vegetation data are time dependent, and the effect of long-term trends and variability of the relevant parameters is therefore considered by the emission scheme. All input data have a spatial resolution of at least 0.1° compared to 1° in the previous version, equipping the model for high-resolution simulations.We validate the updates by comparing the aerosol optical depth (AOD) at 550 nm wavelength from a 1-year simulation at T106 (about 1.1°) resolution with Aerosol Robotic Network (AERONET) and MODIS observations, the 10 µm dust AOD (DAOD) with Infrared Atmospheric Sounding Interferometer (IASI) retrievals, and dust concentration and deposition results with observations from the Aerosol Comparisons between Observations and Models (AeroCom) dust benchmark data set. The update significantly improves agreement with the observations and is therefore recommended to be used in future simulations.

Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM

NASA Astrophysics Data System (ADS)

Kazil, J.; Stier, P.; Zhang, K.; Quaas, J.; Kinne, S.; O'Donnell, D.; Rast, S.; Esch, M.; Ferrachat, S.; Lohmann, U.; Feichter, J.

2010-05-01

Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative budget. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are -1.15 W/m2 for charged H2SO4/H2O nucleation, -0.235 W/m2 for cluster activation, and -0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is -2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with -2.18 W/m2 to total absorbed solar short-wave radiation, compared to -0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative budget over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations.

Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM

NASA Astrophysics Data System (ADS)

Kazil, J.; Stier, P.; Zhang, K.; Quaas, J.; Kinne, S.; O'Donnell, D.; Rast, S.; Esch, M.; Ferrachat, S.; Lohmann, U.; Feichter, J.

2010-11-01

Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are -1.15 W/m2 for charged H2SO4/H2O nucleation, -0.235 W/m2 for cluster activation, and -0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is -2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with -2.18 W/m2 to total absorbed solar short-wave radiation, compared to -0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations.

10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

NASA Astrophysics Data System (ADS)

Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

2013-10-01

This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 yr time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 BP and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather or climate driven noise in the 10Be deposition flux during different stages of climate. The production signal varies on lower frequencies, dominated by the 11yr solar cycle within the 30 yr time scale of these experiments. The climatic noise is of higher frequencies. We first apply empirical orthogonal functions (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis on the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low frequency components and the long term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high frequency components represent climate driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that the 10Be atmospheric production signal is preserved in the deposition flux to surface even during climates very different from today's both in global data and at two specific locations. Secondly, noise can be effectively reduced from 10Be deposition data by simply applying the EOF analysis in the case of a reasonably large number of available data sets, or by decomposing the individual data sets to filter out high-frequency fluctuations.

Rainfall-aerosol relationships explained by wet scavenging and humidity

NASA Astrophysics Data System (ADS)

Grandey, Benjamin S.; Gururaj, Anisha; Stier, Philip; Wagner, Till M.

2014-08-01

Relationships between precipitation rate and aerosol optical depth, the extinction of light by aerosol in an atmospheric column, have been observed in satellite-retrieved data. What are the reasons for these precipitation-aerosol relationships? We investigate relationships between convective precipitation rate (Rconv) and aerosol optical depth (τtot) using the ECHAM5-HAM aerosol-climate model. We show that negative Rconv-τtot relationships arise due to wet scavenging of aerosol. The apparent lack of negative Rconv-τtot relationships in satellite-retrieved data is likely because the satellite data do not sample wet scavenging events. When convective wet scavenging is excluded in the model, we find positive Rconv-τtot relationships in regions where convective precipitation is the dominant form of model precipitation. The spatial distribution of these relationships is in good agreement with satellite-based results. We further demonstrate that a substantial component of these positive relationships arises due to covariation with large-scale relative humidity. Although the interpretation of precipitation-aerosol relationships remains a challenging question, we suggest that progress can be made through a synergy between observations and models.

Projections of increased and decreased dengue incidence under climate change.

PubMed

Williams, C R; Mincham, G; Faddy, H; Viennet, E; Ritchie, S A; Harley, D

2016-10-01

Dengue is the world's most prevalent mosquito-borne disease, with more than 200 million people each year becoming infected. We used a mechanistic virus transmission model to determine whether climate warming would change dengue transmission in Australia. Using two climate models each with two carbon emission scenarios, we calculated future dengue epidemic potential for the period 2046-2064. Using the ECHAM5 model, decreased dengue transmission was predicted under the A2 carbon emission scenario, whereas some increases are likely under the B1 scenario. Dengue epidemic potential may decrease under climate warming due to mosquito breeding sites becoming drier and mosquito survivorship declining. These results contradict most previous studies that use correlative models to show increased dengue transmission under climate warming. Dengue epidemiology is determined by a complex interplay between climatic, human host, and pathogen factors. It is therefore naive to assume a simple relationship between climate and incidence, and incorrect to state that climate warming will uniformly increase dengue transmission, although in general the health impacts of climate change will be negative.

A more accurate scheme for calculating Earth's skin temperature

NASA Astrophysics Data System (ADS)

Tsuang, Ben-Jei; Tu, Chia-Ying; Tsai, Jeng-Lin; Dracup, John A.; Arpe, Klaus; Meyers, Tilden

2009-02-01

The theoretical framework of the vertical discretization of a ground column for calculating Earth’s skin temperature is presented. The suggested discretization is derived from the evenly heat-content discretization with the optimal effective thickness for layer-temperature simulation. For the same level number, the suggested discretization is more accurate in skin temperature as well as surface ground heat flux simulations than those used in some state-of-the-art models. A proposed scheme (“op(3,2,0)”) can reduce the normalized root-mean-square error (or RMSE/STD ratio) of the calculated surface ground heat flux of a cropland site significantly to 2% (or 0.9 W m-2), from 11% (or 5 W m-2) by a 5-layer scheme used in ECMWF, from 19% (or 8 W m-2) by a 5-layer scheme used in ECHAM, and from 74% (or 32 W m-2) by a single-layer scheme used in the UCLA GCM. Better accuracy can be achieved by including more layers to the vertical discretization. Similar improvements are expected for other locations with different land types since the numerical error is inherited into the models for all the land types. The proposed scheme can be easily implemented into state-of-the-art climate models for the temperature simulation of snow, ice and soil.

Simulation climate change impact on runoff and sediment yield in a small watershed in the basque country, northern Spain.

PubMed

Zabaleta, Ane; Meaurio, Maite; Ruiz, Estilita; Antigüedad, Iñaki

2014-01-01

Climate change is likely to have an impact on runoff and fluvial sediments in watersheds. These factors are among those used to characterize water bodies in relation to the European Water Framework Directive (WFD). Hence, it is important to investigate the extent to which climate change may hinder the achievement of the objectives of the WFD. We explored the potential impact of climate change on runoff and sediment yield for the Aixola watershed using the Soil and Water Assessment Tool (SWAT). The model calibration (2007-2010) and validation (2005-2006) results were rated as satisfactory. Subsequently, simulations were run for four climate change model-scenario combinations based on two general circulation models (CGCM2 and ECHAM4) under two emissions scenarios (A2 and B2) from 2011 to 2100. All combinations predicted that runoff and sediment yield would decrease compared with baseline (1961-1990). Three combinations suggested that runoff and sediments would decrease by 0.13 to 0.45 m s and 0.11 to 0.43 t every year from 2011 to 2100. However, the CGCM2-B2 scenario resulted in an "extremely likely" increase in runoff and sediments of 0.94 m s and 0.57 t every year. These variations in annual sediment yield are closely related to changes in precipitation. The high degree of uncertainty in the results must be considered when assessing potential impacts and making decisions about adaptation measures. Nevertheless, this first attempt to estimate future sediment yields in our region could be a useful starting point to explore future hydrological impacts in the area. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Large-Scale Transport Responses to Tropospheric Circulation Changes Using GEOS-5

NASA Technical Reports Server (NTRS)

Orbe, Clara; Molod, Andrea; Arnold, Nathan; Waugh, Darryn W.; Yang, Huang

2017-01-01

The mean age since air was last at the Northern Hemisphere midlatitude surface is a fundamental property of tropospheric transport. Recent comparisons among chemistry climate models, however, reveal that there are large differences in the mean age among models and that these differences are most likely related to differences in tropical (parameterized) convection. Here we use aquaplanet simulations of the Goddard Earth Observing System Model Version 5 (GEOS-5) to explore the sensitivity of the mean age to changes in the tropical circulation. Tropical circulation changes are forced by prescribed localized off-equatorial warm sea surface temperature anomalies that (qualitatively) reproduce the convection and circulation differences among the comprehensive models. Idealized chemical species subject to prescribed OH loss are also integrated in parallel in order to illustrate the impact of tropical transport changes on interhemispheric constituent transport.

Simulation of Tropical Rainfall Variability

NASA Astrophysics Data System (ADS)

Bader, J.; Latif, M.

2002-12-01

The impact of sea surface temperature (SST) - especially the role of the tropical Atlantic meridional SST gradient and the El Nino-Southern Oscillation - on precipitation is investigated with the atmospheric general circulation model ECHAM4/T42. Ensemble experiments - driven with observed SST - show that Atlantic SST has a significant influence on precipitation over West Africa and northeast Brazil. SST sensitivity experiments were performed in which the climatological SST was enhanced or decreased by one Kelvin in certain ocean areas. Changing SST in the eastern tropical Atlantic caused only significant changes along the Guinea Coast, with a positive anomaly (SSTA) increasing rainfall and a negative SSTA reducing it. The response was nearly linear. Changing SST in other ocean areas caused significant changes over West Africa, especially in the Sahel area. The response is found to be non linear, with only negative SSTA leading to significant reduction in Sahel rainfall. Also, the impact of the SSTAs from the different ocean regions was not additive with respect to the rainfall. The influence of SST on precipitation over northeast Brazil (Nordeste) was also investigated. Three experiments were performed in which the climatological SST was enhanced/decreased or decreased/enhanced by one Kelvin in the North/South Atlantic and increased by two Kelvin in the Nino3 ocean area. All experiments caused significant changes over Nordeste, with an enhanced/reduced SST gradient in the Atlantic increasing/reducing rainfall. The response was nearly linear. The main effect of the Atlantic SST gradient was a shift of the ITCZ, caused by trade wind changes. The ''El Nino'' event generates a significant reduction in Nordeste rainfall. A significant positive SLP anomaly occurs in northeast Brazil which may be associated with the descending branch of the Walker circulation. Also a significant positive SLP over the Atlantic from 30S to 10N north occurs. This results in a reduced SLP gradient from the subtropical highs to the equator and a weakening of the trade winds.

The impacts of climate, land use, and demography on fires during the 21st century simulated by CLM-CN

NASA Astrophysics Data System (ADS)

Kloster, S.; Mahowald, N. M.; Randerson, J. T.; Lawrence, P. J.

2012-01-01

Landscape fires during the 21st century are expected to change in response to multiple agents of global change. Important controlling factors include climate controls on the length and intensity of the fire season, fuel availability, and fire management, which are already anthropogenically perturbed today and are predicted to change further in the future. An improved understanding of future fires will contribute to an improved ability to project future anthropogenic climate change, as changes in fire activity will in turn impact climate. In the present study we used a coupled-carbon-fire model to investigate how changes in climate, demography, and land use may alter fire emissions. We used climate projections following the SRES A1B scenario from two different climate models (ECHAM5/MPI-OM and CCSM) and changes in population. Land use and harvest rates were prescribed according to the RCP 45 scenario. In response to the combined effect of all these drivers, our model estimated, depending on our choice of climate projection, an increase in future (2075-2099) fire carbon emissions by 17 and 62% compared to present day (1985-2009). The largest increase in fire emissions was predicted for Southern Hemisphere South America for both climate projections. For Northern Hemisphere Africa, a region that contributed significantly to the global total fire carbon emissions, the response varied between a decrease and an increase depending on the climate projection. We disentangled the contribution of the single forcing factors to the overall response by conducting an additional set of simulations in which each factor was individually held constant at pre-industrial levels. The two different projections of future climate change evaluated in this study led to increases in global fire carbon emissions by 22% (CCSM) and 66% (ECHAM5/MPI-OM). The RCP 45 projection of harvest and land use led to a decrease in fire carbon emissions by -5%. The RCP 26 and RCP 60 harvest and landuse projections caused decreases around -20%. Changes in human ignition led to an increase of 20%. When we also included changes in fire management efforts to suppress fires in densely populated areas, global fire carbon emission decreased by -6% in response to changes in population density. We concluded from this study that changes in fire emissions in the future are controlled by multiple interacting factors. Although changes in climate led to an increase in future fire emissions this could be globally counterbalanced by coupled changes in land use, harvest, and demography.

Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

NASA Astrophysics Data System (ADS)

Lohmann, U.; Hoose, C.

2009-11-01

Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m-2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

NASA Astrophysics Data System (ADS)

Lohmann, U.; Hoose, C.

2009-07-01

Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m-2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

Cirrus clouds as seen by the CALIPSO satellite and ECHAM-HAM global climate model

NASA Astrophysics Data System (ADS)

Gasparini, Blaz; Meyer, Angela; Neubauer, David; Münch, Steffen; Lohmann, Ulrike

2017-04-01

Ice clouds impact the planetary energy balance and upper tropospheric water vapour transport and are therefore relevant for climate. In this study ice clouds at temperatures below -40°C simulated by the ECHAM-HAM global climate model are compared to CALIPSO/CALIOP satellite data. The model reproduces well the mean occurrence of ice clouds, while the ice water path, ice crystal radius, cloud optical depth and extinction are overestimated in terms of annual means and temperature dependent frequency histograms. Two distinct types of cirrus clouds are found: in-situ formed cirrus dominating at temperatures below -60°C and liquid-origin cirrus, dominating at temperatures warmer than -55°C. The latter form in anvils of deep convective clouds or by glaciation of mixed-phase clouds. They are associated with ice water contents of up to 0.1 g m-3 and extinctions of up to 0.1 km-1, while the in-situ formed cirrus are optically thinner and contain at least an order of magnitude less ice. The ice cloud properties do not differ significantly between the southern and the northern hemisphere. In-situ formed ice clouds are further divided into homogeneously and heterogeneously nucleated ones. The simulated liquid-origin ice crystals mainly form in convective outflow in large number concentrations, similar to in-situ homogeneously nucleated ice crystals. On the contrary, heterogeneously nucleated ice crystals are associated with smaller number concentrations. However, ice crystal aggregation and depositional growth smooth the differences between several formation mechanisms making the attribution to a specific ice nucleation mechanism challenging.

Effect of Vortex Circulation on Injectant from a Single Film-Cooling Hole and a Row of Film-Cooling Holes in a Turbulent Boundary Layer. Part 1. Injection Beneath the Vortex Downwash

DTIC Science & Technology

1989-06-01

coefficients vortex circulation, symbols used in vorticity plots representing circulation values derived from different vortex core models injection...derived from different vortex core models dimensionless core size parameter: t wice the a verage core radius divided by t h e i n jection hole...Wall Heating, xjd=109.2, m=0.5, Single Injection Hole Vortex w, Temp. Difference Range (.5- 2.5) degree s 91. Local Temperature Distribution

AOD trends during 2001-2010 from observations and model simulations

NASA Astrophysics Data System (ADS)

Pozzer, A.; de Meij, A.; Yoon, J.; Tost, H.; Georgoulias, A. K.; Astitha, M.

2015-05-01

The aerosol optical depth (AOD) trend between 2001 and 2010 is estimated globally and regionally from observations and results from simulations with the EMAC (ECHAM5/MESSy Atmospheric Chemistry) model. Although interannual variability is applied only to anthropogenic and biomass-burning emissions, the model is able to quantitatively reproduce the AOD trends as observed by the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite sensor, while some discrepancies are found when compared to MISR (Multi-angle Imaging SpectroRadiometer) and SeaWIFS (Sea-viewing Wide Field-of-view Sensor) observations. Thanks to an additional simulation without any change in emissions, it is shown that decreasing AOD trends over the US and Europe are due to the decrease in the emissions, while over the Sahara Desert and the Middle East region, the meteorological changes play a major role. Over Southeast Asia, both meteorology and emissions changes are equally important in defining AOD trends. Additionally, decomposing the regional AOD trends into individual aerosol components reveals that the soluble components are the most dominant contributors to the total AOD, as their influence on the total AOD is enhanced by the aerosol water content.

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

NASA Astrophysics Data System (ADS)

Zhang, K.; O'Donnell, D.; Kazil, J.; Stier, P.; Kinne, S.; Lohmann, U.; Ferrachat, S.; Croft, B.; Quaas, J.; Wan, H.; Rast, S.; Feichter, J.

2012-03-01

This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Sensitivity experiments are carried out to analyse the effects of these improvements in the process representation on the simulated aerosol properties and global distribution. The new parameterizations that have largest impact on the global mean aerosol optical depth and radiative effects turn out to be the water uptake scheme and cloud microphysics. The former leads to a significant decrease of aerosol water contents in the lower troposphere, and consequently smaller optical depth; the latter results in higher aerosol loading and longer lifetime due to weaker in-cloud scavenging. The combined effects of the new/updated parameterizations are demonstrated by comparing the new model results with those from the earlier version, and against observations. Model simulations are evaluated in terms of aerosol number concentrations against measurements collected from twenty field campaigns as well as from fixed measurement sites, and in terms of optical properties against the AERONET measurements. Results indicate a general improvement with respect to the earlier version. The aerosol size distribution and spatial-temporal variance simulated by HAM2 are in better agreement with the observations. Biases in the earlier model version in aerosol optical depth and in the Ångström parameter have been reduced. The paper also points out the remaining model deficiencies that need to be addressed in the future.

South Asian Summer Monsoon and Its Relationship with ENSO in the IPCC AR4 Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annamalai, H; Hamilton, K; Sperber, K R

In this paper we use the extensive integrations produced for the IPCC Fourth Assessment Report (AR4) to examine the relationship between ENSO and the monsoon at interannual and decadal timescales. We begin with an analysis of the monsoon simulation in the 20th century integrations. Six of the 18 models were found to have a reasonably realistic representation of monsoon precipitation climatology. For each of these six models SST and anomalous precipitation evolution along the equatorial Pacific during El Nino events display considerable differences when compared to observations. Out of these six models only four (GFDL{_}CM{_}2.0, GFDL{_}CM{_}2.1, MRI, and MPI{_}ECHAM5) exhibitmore » a robust ENSO-monsoon contemporaneous teleconnection, including the known inverse relationship between ENSO and rainfall variations over India. Lagged correlations between the all-India rainfall (AIR) index and Nino3.4 SST reveal that three models represent the timing of the teleconnection, including the spring predictability barrier which is manifested as the transition from positive to negative correlations prior to the monsoon onset. Furthermore, only one of these three models (GFDL{_}CM{_}2.1) captures the observed phase lag with the strongest anticorrelation of SST peaking 2-3 months after the summer monsoon, which is partially attributable to the intensity of simulated El Nino itself. We find that the models that best capture the ENSO-monsoon teleconnection are those that correctly simulate the timing and location of SST and diabatic heating anomalies in the equatorial Pacific, and the associated changes to the equatorial Walker Circulation during El Nino events. The strength of the AIR-Nino3.4 SST correlation in the model runs waxes and wanes to some degree on decadal timescales. The overall magnitude and timescale for this decadal modulation in most of the models is similar to that seen in observations. However, there is little consistency in the phase among the realizations, suggesting a lack of predictability of the decadal modulation of the monsoon-ENSO relationship. The analysis was repeated for each of the four models using results from integrations in which the atmospheric CO{sub 2} concentration was raised to twice pre-industrial values. From these ''best'' models in the double CO{sub 2} simulations there are increases in both the mean monsoon rainfall over the Indian sub-continent (by 5-25%) and in its interannual variability (5-10%). We find for each model that the ENSO-monsoon correlation in the global warming runs is very similar to that in the 20th century runs, suggesting that the ENSO-monsoon connection will not weaken as global climate warms. This result, though plausible, needs to be taken with some caution because of the diversity in the simulation of ENSO variability in the coupled models we have analyzed. The implication of the present results for monsoon prediction are discussed.« less

Aerosol effect on climate extremes in Europe under different future scenarios

NASA Astrophysics Data System (ADS)

Sillmann, J.; Pozzoli, L.; Vignati, E.; Kloster, S.; Feichter, J.

2013-05-01

This study investigates changes in extreme temperature and precipitation events under different future scenarios of anthropogenic aerosol emissions (i.e., SO2 and black and organic carbon) simulated with an aerosol-climate model (ECHAM5-HAM) with focus on Europe. The simulations include a maximum feasible aerosol reduction (MFR) scenario and a current legislation emission (CLEmod) scenario where Europe implements the MFR scenario, but the rest of the world follows the current legislation scenario and a greenhouse gas scenario. The strongest changes relative to the year 2000 are projected for the MFR scenario, in which the global aerosol reduction greatly enforces the general warming effect due to greenhouse gases and results in significant increases of temperature and precipitation extremes in Europe. Regional warming effects can also be identified from aerosol reductions under the CLEmodscenario. This becomes most obvious in the increase of the hottest summer daytime temperatures in Northern Europe.

Influence of prolonged Anomalies in North Atlantic Sea Surface Temperature on Winter Windstorms

NASA Astrophysics Data System (ADS)

Höschel, Ines; Schuster, Mareike; Grieger, Jens; Ulbrich, Uwe

2016-04-01

The focus of this presentation is on decadal scale variations in the frequency and in the intensity of mid-latitude winter windstorms. Projections for the end of the next century are often beyond the time horizon of business, thus there is an increasing interest on decadal prediction, especially for infrastructural planning and in the insurance industry. One source of decadal predictability is the Atlantic multidecadal variability (AMV), a change in the sea surface temperature of the North Atlantic, strongly linked to the meridional overturning circulation. Correlation patterns between annual AMV-indices and annual mean of geopotential height at 500 hPa in reanalysis data show an anti-correlation in the North Atlantic. That is, during AMV warm phases the North Atlantic Oscillation (NAO) is more negative. Consequently, AMV should influence the characteristics of winter windstorms at multi-year scales. For the presented investigations a 10-member ensemble of 38-year-long idealized simulations with the atmosphere model ECHAM6 with lower boundary conditions, representing warm and cool phases of the AMV, is used. In the idealized simulations, the anti-correlation between AMV and NAO is well represented. For the identification of winter windstorms an objective wind tracking algorithm based on the exceedance of the local 98th percentile of 10m wind speed is applied. Storms under AMV-warm and AMV-cool conditions will be compared in terms of storm track density and probability distribution of storm characteristics.

Quantifying the effect of varying GHG's concentration in Regional Climate Models

NASA Astrophysics Data System (ADS)

López-Romero, Jose Maria; Jerez, Sonia; Palacios-Peña, Laura; José Gómez-Navarro, Juan; Jiménez-Guerrero, Pedro; Montavez, Juan Pedro

2017-04-01

Regional Climate Models (RCMs) are driven at the boundaries by Global Circulation Models (GCM), and in the particular case of Climate Change projections, such simulations are forced by varying greenhouse gases (GHGs) concentrations. In hindcast simulations driven by reanalysis products, the climate change signal is usually introduced in the assimilation process as well. An interesting question arising in this context is whether GHGs concentrations have to be varied within the RCMs model itself, or rather they should be kept constant. Some groups keep the GHGs concentrations constant under the assumption that information about climate change signal is given throughout the boundaries; sometimes certain radiation parameterization schemes do not permit such changes. Other approaches vary these concentrations arguing that this preserves the physical coherence respect to the driving conditions for the RCM. This work aims to shed light on this topic. For this task, various regional climate simulations with the WRF model for the 1954-2004 period have been carried out for using a Euro-CORDEX compliant domain. A series of simulations with constant and variable GHGs have been performed using both, a GCM (ECHAM6-OM) and a reanalysis product (ERA-20C) data. Results indicate that there exist noticeable differences when introducing varying GHGs concentrations within the RCM domain. The differences in 2-m temperature series between the experiments with varying or constant GHGs concentration strongly depend on the atmospheric conditions, appearing a strong interannual variability. This suggests that short-term experiments are not recommended if the aim is to assess the role of varying GHGs. In addition, and consistently in both GCM and reanalysis-driven experiments, the magnitude of temperature trends, as well as the spatial pattern represented by varying GHGs experiment, are closer to the driving dataset than in experiments keeping constant the GHGs concentration. These results point towards the need for the inclusion of varying GHGs concentration within the RCM itself when dynamically downscaling global datasets, both in GCM and hindcast simulations.

Climate model uncertainty in impact assessments for agriculture: A multi-ensemble case study on maize in sub-Saharan Africa

NASA Astrophysics Data System (ADS)

Dale, Amy; Fant, Charles; Strzepek, Kenneth; Lickley, Megan; Solomon, Susan

2017-03-01

We present maize production in sub-Saharan Africa as a case study in the exploration of how uncertainties in global climate change, as reflected in projections from a range of climate model ensembles, influence climate impact assessments for agriculture. The crop model AquaCrop-OS (Food and Agriculture Organization of the United Nations) was modified to run on a 2° × 2° grid and coupled to 122 climate model projections from multi-model ensembles for three emission scenarios (Coupled Model Intercomparison Project Phase 3 [CMIP3] SRES A1B and CMIP5 Representative Concentration Pathway [RCP] scenarios 4.5 and 8.5) as well as two "within-model" ensembles (NCAR CCSM3 and ECHAM5/MPI-OM) designed to capture internal variability (i.e., uncertainty due to chaos in the climate system). In spite of high uncertainty, most notably in the high-producing semi-arid zones, we observed robust regional and sub-regional trends across all ensembles. In agreement with previous work, we project widespread yield losses in the Sahel region and Southern Africa, resilience in Central Africa, and sub-regional increases in East Africa and at the southern tip of the continent. Spatial patterns of yield losses corresponded with spatial patterns of aridity increases, which were explicitly evaluated. Internal variability was a major source of uncertainty in both within-model and between-model ensembles and explained the majority of the spatial distribution of uncertainty in yield projections. Projected climate change impacts on maize production in different regions and nations ranged from near-zero or positive (upper quartile estimates) to substantially negative (lower quartile estimates), highlighting a need for risk management strategies that are adaptive and robust to uncertainty.

The effect of the East Atlantic pattern on the precipitation δ18O-NAO relationship in Europe

NASA Astrophysics Data System (ADS)

Comas-Bru, L.; McDermott, F.; Werner, M.

2016-10-01

The North Atlantic Oscillation (NAO) is known to influence precipitation δ18O (δ18Op) through its control on air temperature and on the trajectory of the westerly winds that carry moisture onto Europe during boreal winters. Hence, paleoclimate studies seeking to reconstruct the NAO can exploit the δ18O signal that is commonly preserved in natural archives such as stalagmites, ice cores, tree rings and lake sediments. However, such reconstructions should consider the uncertainties that arise from non-stationarities in the δ18Op-NAO relationship. Here, new insights into the causes of these temporal non-stationarities are presented for the European region using both observations (GNIP database) and the output of an isotope-enabled general circulation model (ECHAM5-wiso). The results show that, although the East Atlantic (EA) pattern is generally uncorrelated to δ18Op during the instrumental period, its polarity affects the δ18Op-NAO relationship. Non-stationarities in this relationship result from spatial shifts of the δ18Op-NAO correlated areas as a consequence of different NAO/EA combinations. These shifts are consistent with those reported previously for NAO-winter climate variables and the resulting non-stationarities mean that δ18O-based NAO reconstructions could be compromised if the balance of positive and negative NAO/EA states differs substantially in a calibration period compared with the period of interest in the past. The same approach has been followed to assess the relationships between δ18Op and both winter total precipitation and winter mean surface air temperature, with similar results. Crucially, this study also identifies regions within Europe where temporal changes in the NAO, air temperature and precipitation can be more robustly reconstructed using δ18O time series from natural archives, irrespective of concomitant changes in the EA.

The transition of North Atlantic dust deposition and Saharan landscape during the Holocene

NASA Astrophysics Data System (ADS)

Egerer, S.; Claussen, M.; Stanelle, T.; Reick, C. H.

2017-12-01

The sudden increase in North Atlantic dust deposition about 5 ka BP indicated by sediment records along the West African margin has been associated with an abrupt end of the African Humid Period (AHP). We perform several time slice simulations from 8 ka BP until the pre-industrial era to explore changes in the Holocene dust cycle. To do so, we use the coupled aerosol-climate model ECHAM6-HAM2 including interactive vegetation and dust, whereas ocean conditions and lakes are prescribed. The interactive coupling of vegetation, dust and atmosphere allows to set the dynamics of North Atlantic dust deposition in context to Holocene climate and landscape change in North Africa.In agreement with marine sediment records, we find an abrupt increase in simulated dust deposition at the location of the core sites roughly between 6 and 4 ka BP. Accordingly, dust emission in the North-west Sahara increases rapidly indicating that dust was transported by the same wind systems throughout the Holocene. The sudden increase in dust emission in the North-west Sahara is partly a consequence of a fast decline of vegetation cover from 22°N to 18°N due to vegetation-climate feedbacks and the rapid replacement of shrubs by grasses. Additionally, the prescribed strong but gradual reduction of lake surface area enforces accelerated dust release as former areas covered by lakes turn into highly productive dust sources. Changes in the Saharan landscape and dust emission south of 18°N and in the eastern Sahara as well as changes in atmospheric circulation play a minor role in driving the dynamics of North Atlantic dust deposition at the specific core sites. Our study emphasizes spatial and temporal differences in the transition of North African landscape implying that implications from local data records to large scales have to be treated with caution.

Effects of high-frequency activity on latent heat flux of MJO

NASA Astrophysics Data System (ADS)

Gao, Yingxia; Hsu, Pang-Chi; Li, Tim

2018-04-01

The effect of high-frequency (HF) variability on latent heat flux (LHF) associated with the Madden-Julian Oscillation (MJO) during the boreal winter is investigated through diagnosis using two reanalysis datasets and numerical experiments of an atmospheric general circulation model (AGCM). The diagnostic results show that the HF activities exert an impact on the variability of MJO LHF mainly through their interactions with the longer than 90-day low-frequency background state (LFBS). The contribution of intraseasonal LHF induced by the interactions between LFBS and HF activities accounts for more than 20% of the total intraseasonal LHF over active MJO regions. The intraseasonal LHF induced by the LFBS-HF interaction is in phase with the MJO convection, while the total intraseasonal LHF appears at and to the west of the MJO convection center. This suggests that the intraseasonal LHF via the feedback of HF activity interacting with LFBS is conducive to the maintenance and eastward propagation of MJO convection. To confirm the role of HF disturbances in MJO convection activity, we carry out a series of experiments using the AGCM of ECHAM4, which captures well the general features of MJO. We select a number of MJO cases with enhanced convective signals and significant eastward propagation from a 30-year climatological simulation. Once the HF components of surface wind and moisture fields in LHF are excluded in model integration for each MJO case, most of the simulated MJO convection shows weakened activity and a slower propagation speed compared to the simulations containing all time-scale components. The outputs of these sensitivity experiments support the diagnostic results that HF activities contribute to the maintenance and propagation of MJO convection through the intraseasonal LHF induced by the scale interaction of HF activities with lower frequency variability.

Multimodel Evidence for an Atmospheric Circulation Response to Arctic Sea Ice Loss in the CMIP5 Future Projections

NASA Astrophysics Data System (ADS)

Zappa, G.; Pithan, F.; Shepherd, T. G.

2018-01-01

Previous single-model experiments have found that Arctic sea ice loss can influence the atmospheric circulation. To evaluate this process in a multimodel ensemble, a novel methodology is here presented and applied to infer the influence of Arctic sea ice loss in the CMIP5 future projections. Sea ice influence is estimated by comparing the circulation response in the RCP8.5 scenario against the circulation response to sea surface warming and CO2 increase inferred from the AMIPFuture and AMIP4xCO2 experiments, where sea ice is unperturbed. Multimodel evidence of the impact of sea ice loss on midlatitude atmospheric circulation is identified in late winter (January-March), when the sea ice-related surface heat flux perturbation is largest. Sea ice loss acts to suppress the projected poleward shift of the North Atlantic jet, to increase surface pressure in northern Siberia, and to lower it in North America. These features are consistent with previous single-model studies, and the present results indicate that they are robust to model formulation.

Multimodel Evidence for an Atmospheric Circulation Response to Arctic Sea Ice Loss in the CMIP5 Future Projections.

PubMed

Zappa, G; Pithan, F; Shepherd, T G

2018-01-28

Previous single-model experiments have found that Arctic sea ice loss can influence the atmospheric circulation. To evaluate this process in a multimodel ensemble, a novel methodology is here presented and applied to infer the influence of Arctic sea ice loss in the CMIP5 future projections. Sea ice influence is estimated by comparing the circulation response in the RCP8.5 scenario against the circulation response to sea surface warming and CO 2 increase inferred from the AMIPFuture and AMIP4xCO2 experiments, where sea ice is unperturbed. Multimodel evidence of the impact of sea ice loss on midlatitude atmospheric circulation is identified in late winter (January-March), when the sea ice-related surface heat flux perturbation is largest. Sea ice loss acts to suppress the projected poleward shift of the North Atlantic jet, to increase surface pressure in northern Siberia, and to lower it in North America. These features are consistent with previous single-model studies, and the present results indicate that they are robust to model formulation.

Going with the flow: the role of ocean circulation in global marine ecosystems under a changing climate.

PubMed

van Gennip, Simon J; Popova, Ekaterina E; Yool, Andrew; Pecl, Gretta T; Hobday, Alistair J; Sorte, Cascade J B

2017-07-01

Ocean warming, acidification, deoxygenation and reduced productivity are widely considered to be the major stressors to ocean ecosystems induced by emissions of CO 2 . However, an overlooked stressor is the change in ocean circulation in response to climate change. Strong changes in the intensity and position of the western boundary currents have already been observed, and the consequences of such changes for ecosystems are beginning to emerge. In this study, we address climatically induced changes in ocean circulation on a global scale but relevant to propagule dispersal for species inhabiting global shelf ecosystems, using a high-resolution global ocean model run under the IPCC RCP 8.5 scenario. The ¼ degree model resolution allows improved regional realism of the ocean circulation beyond that of available CMIP5-class models. We use a Lagrangian approach forced by modelled ocean circulation to simulate the circulation pathways that disperse planktonic life stages. Based on trajectory backtracking, we identify present-day coastal retention, dominant flow and dispersal range for coastal regions at the global scale. Projecting into the future, we identify areas of the strongest projected circulation change and present regional examples with the most significant modifications in their dominant pathways. Climatically induced changes in ocean circulation should be considered as an additional stressor of marine ecosystems in a similar way to ocean warming or acidification. © 2017 John Wiley & Sons Ltd.

Does coupled ocean enhance ozone-hole-induced Southern Hemisphere circulation changes?

NASA Astrophysics Data System (ADS)

Son, S. W.; Han, B. R.; Kim, S. Y.; Park, R.

2017-12-01

The ozone-hole-induced Southern Hemisphere (SH) circulation changes, such as poleward shift of westerly jet and Hadley cell widening, have been typically explored with either coupled general circulation models (CGCMs) prescribing stratospheric ozone or chemistry-climate models (CCMs) prescribing surface boundary conditions. Only few studies have utilized ocean-coupled CCMs with a relatively coarse resolution. To better quantify the role of interactive chemistry and coupled ocean in the ozone-hole-induced SH circulation changes, the present study examines a set of CGCM and CCM simulations archived for the Coupled Model Intercomparison Project phase 5 (CMIP5) and CCM initiative (CCMI). Although inter-model spread of Antarctic ozone depletion is substantially large especially in the austral spring, both CGCMs with relatively simple ozone chemistry and CCMs with fully interactive comprehensive chemistry reasonably well reproduce long-term trends of Antarctic ozone and the associated polar-stratospheric temperature changes. Most models reproduce a poleward shift of SH jet and Hadley-cell widening in the austral summer in the late 20th century as identified in reanalysis datasets. These changes are quasi-linearly related with Antarctic ozone changes, confirming the critical role of Antarctic ozone depletion in the austral-summer zonal-mean circulation changes. The CGCMs with simple but still interactive ozone show slightly stronger circulation changes than those with prescribed ozone. However, the long-term circulation changes in CCMs are largely insensitive to the coupled ocean. While a few models show the enhanced circulation changes when ocean is coupled, others show essentially no changes or even weakened circulation changes. This result suggests that the ozone-hole-related stratosphere-troposphere coupling in the late 20th century may be only weakly sensitive to the coupled ocean.

Modeling The Hydrology And Water Allocation Under Climate Change In Rural River Basins: A Case Study From Nam Ngum River Basin, Laos

NASA Astrophysics Data System (ADS)

Jayasekera, D. L.; Kaluarachchi, J.; Kim, U.

2011-12-01

Rural river basins with sufficient water availability to maintain economic livelihoods can be affected with seasonal fluctuations of precipitation and sometimes by droughts. In addition, climate change impacts can also alter future water availability. General Circulation Models (GCMs) provide credible quantitative estimates of future climate conditions but such estimates are often characterized by bias and coarse scale resolution making it necessary to downscale the outputs for use in regional hydrologic models. This study develops a methodology to downscale and project future monthly precipitation in moderate scale basins where data are limited. A stochastic framework for single-site and multi-site generation of weekly rainfall is developed while preserving the historical temporal and spatial correlation structures. The spatial correlations in the simulated occurrences and the amounts are induced using spatially correlated yet serially independent random numbers. This method is applied to generate weekly precipitation data for a 100-year period in the Nam Ngum River Basin (NNRB) that has a land area of 16,780 km2 located in Lao P.D.R. This method is developed and applied using precipitation data from 1961 to 2000 for 10 selected weather stations that represents the basin rainfall characteristics. Bias-correction method, based on fitted theoretical probability distribution transformations, is applied to improve monthly mean frequency, intensity and the amount of raw GCM precipitation predicted at a given weather station using CGCM3.1 and ECHAM5 for SRES A2 emission scenario. Bias-correction procedure adjusts GCM precipitation to approximate the long-term frequency and the intensity distribution observed at a given weather station. Index of agreement and mean absolute error are determined to assess the overall ability and performance of the bias correction method. The generated precipitation series aggregated at monthly time step was perturbed by the change factors estimated using the corrected GCM and baseline scenarios for future time periods of 2011-2050 and 2051-2090. A network based hydrologic and water resources model, WEAP, was used to simulate the current water allocation and management practices to identify the impacts of climate change in the 20th century. The results of this work are used to identify the multiple challenges faced by stakeholders and planners in water allocation for competing demands in the presence of climate change impacts.

Regional climates in the GISS global circulation model - Synoptic-scale circulation

NASA Technical Reports Server (NTRS)

Hewitson, B.; Crane, R. G.

1992-01-01

A major weakness of current general circulation models (GCMs) is their perceived inability to predict reliably the regional consequences of a global-scale change, and it is these regional-scale predictions that are necessary for studies of human-environmental response. For large areas of the extratropics, the local climate is controlled by the synoptic-scale atmospheric circulation, and it is the purpose of this paper to evaluate the synoptic-scale circulation of the Goddard Institute for Space Studies (GISS) GCM. A methodology for validating the daily synoptic circulation using Principal Component Analysis is described, and the methodology is then applied to the GCM simulation of sea level pressure over the continental United States (excluding Alaska). The analysis demonstrates that the GISS 4 x 5 deg GCM Model II effectively simulates the synoptic-scale atmospheric circulation over the United States. The modes of variance describing the atmospheric circulation of the model are comparable to those found in the observed data, and these modes explain similar amounts of variance in their respective datasets. The temporal behavior of these circulation modes in the synoptic time frame are also comparable.

Climate change and Mediterranean storm tracks: present and future climate simulations of a high-resolution Mediterranean model

NASA Astrophysics Data System (ADS)

Hatzaki, M.; Flocas, H. A.; Simmonds, I.; Keay, K.; Giannakopoulos, C.; Brikolas, V.; Kouroutzoglou, J.

2010-09-01

A number of studies suggest that cyclone activity over both hemispheres has changed over the second half of the 20th century. General features include a reduction in the number of cyclones but with an increase in the number of more intense cyclones; as well as a poleward shift in the tracks. Moreover, these features are expected to be projected in the future under global warming conditions. The assessment of the future changes of the cyclonic activity as imposed by global warming conditions is very important since these cyclones can be associated with extreme precipitation conditions, severe storms and floods. This is more important for the Mediterranean that has been found to be more vulnerable to climate change. The main objective of the current study is to better understand and assess future changes in the main characteristics of cyclonic tracks in the Mediterranean. The climatology of the cyclonic tracks includes temporal and spatial variations of frequency, and dynamic and kinematic parameters, such as intensity, size, propagation velocity, as well as trend analysis. For this purpose, the ENEA high resolution model is employed, based on PROTHEUS system composed of the RegCM atmospheric regional model and the MITgcm ocean model, coupled through the OASIS3 flux coupler. These model data became available through the EU Project CIRCE which aims to perform, for the first time, climate change projections with a realistic representation of the Mediterranean Sea. Two experiments are employed; a) the EH5OM_20C3M present climate simulation, where the lateral boundary conditions for the atmosphere (1951-2000) are taken from the ECHAM5-MPIOM 20c3m global simulation (run3) included in the IPCC-AR4, and b) the EH5OM_A1B scenario simulation, where the IPCC-AR4 ECHAM5-MPIOM SRESA1B global simulation (run3) has been used for the period 2001-2050. The identification and tracking of cyclones is performed with the aid of the Melbourne University algorithm (MS algorithm), according to the Lagrangian perspective. MS algorithm characterizes a cyclone only if a vorticity maximum could be connected with a local pressure minimum. This approach is considered to be crucial, since open lows are also incorporated into the storm life-cycle, preventing possible inappropriate time series breaks, if a temporary weakening to an open-low state occurs. According to the results, a decrease of the storm number and a tendency towards deeper cyclones is expected in the future, in general agreement with the results of previous studies. However, new findings reveal with respect to the dynamic/kinematic characteristics of the cyclonic tracks. ACKNOWLEDGMENTS: M. Hatzaki would like to thank the Greek State Scholarships Foundation for financial support through the program of postdoctoral research. The support of EU-FP6 project CIRCE Integrated Project-Climate Change and Impact Research: the Mediterranean Environment (http://www.circeproject.eu) for climate model data provision is also greatly acknowledged.

10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

NASA Astrophysics Data System (ADS)

Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

2014-04-01

This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 year time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea-surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather- or climate-driven noise in the 10Be deposition flux during different stages of climate. The production signal varies at lower frequencies, dominated by the 11 year solar cycle within the 30 year timescale of these experiments. The climatic noise is of higher frequencies than 11 years during the 30 year period studied. We first apply empirical orthogonal function (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis to the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low-frequency components and the long-term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high-frequency components represent climate-driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that the 10Be atmospheric production signal is preserved in the deposition flux to surface even during climates very different from today's both in global data and at two specific locations. Secondly, noise can be effectively reduced from 10Be deposition data by simply applying the EOF analysis in the case of a reasonably large number of available data sets, or by decomposing the individual data sets to filter out high-frequency fluctuations.

Quantifying the role of ocean initial conditions in decadal prediction

NASA Astrophysics Data System (ADS)

Matei, D.; Pohlmann, H.; Müller, W.; Haak, H.; Jungclaus, J.; Marotzke, J.

2009-04-01

The forecast skill of decadal climate predictions is investigated using two different initialization strategies. First we apply an assimilation of ocean synthesis data provided by the GECCO project (Köhl and Stammer 2008) as initial conditions for the coupled model ECHAM5/MPI-OM. The results show promising skill up to decadal time scales particularly over the North Atlantic (see also Pohlmann et al. 2009). However, mismatches between the ocean climates of GECCO and the MPI-OM model may lead to inconsistencies in the representation of water masses. Therefore, we pursue an alternative approach to the representation of the observed North Atlantic climate for the period 1948-2007. Using the same MPI-OM ocean model as in the coupled system, we perform an ensemble of four NCEP integrations. The ensemble mean temperature and salinity anomalies are then nudged into the coupled model, followed by hindcast/forecast experiments. The model gives dynamically consistent three-dimensional temperature and salinity fields, thereby avoiding the problems of model drift that were encountered when the assimilation experiment was only driven by reconstructed SSTs (Keenlyside et al. 2008, Pohlmann et al. 2009). Differences between the two assimilation approaches are discussed by comparing them with the observational data in key regions and processes, such as North Atlantic and Tropical Pacific climate, MOC variability, Subpolar Gyre variability.

An improved ice cloud formation parameterization in the EMAC model

NASA Astrophysics Data System (ADS)

Bacer, Sara; Pozzer, Andrea; Karydis, Vlassis; Tsimpidi, Alexandra; Tost, Holger; Sullivan, Sylvia; Nenes, Athanasios; Barahona, Donifan; Lelieveld, Jos

2017-04-01

Cirrus clouds cover about 30% of the Earth's surface and are an important modulator of the radiative energy budget of the atmosphere. Despite their importance in the global climate system, there are still large uncertainties in understanding the microphysical properties and interactions with aerosols. Ice crystal formation is quite complex and a variety of mechanisms exists for ice nucleation, depending on aerosol characteristics and environmental conditions. Ice crystals can be formed via homogeneous nucleation or heterogeneous nucleation of ice-nucleating particles in different ways (contact, immersion, condensation, deposition). We have implemented the computationally efficient cirrus cloud formation parameterization by Barahona and Nenes (2009) into the EMAC (ECHAM5/MESSy Atmospheric Chemistry) model in order to improve the representation of ice clouds and aerosol-cloud interactions. The parameterization computes the ice crystal number concentration from precursor aerosols and ice-nucleating particles accounting for the competition between homogeneous and heterogeneous nucleation and among different freezing modes. Our work shows the differences and the improvements obtained after the implementation with respect to the previous version of EMAC.

Stability of the Atlantic meridional overturning circulation: A model intercomparison

NASA Astrophysics Data System (ADS)

Weaver, Andrew J.; Sedláček, Jan; Eby, Michael; Alexander, Kaitlin; Crespin, Elisabeth; Fichefet, Thierry; Philippon-Berthier, Gwenaëlle; Joos, Fortunat; Kawamiya, Michio; Matsumoto, Katsumi; Steinacher, Marco; Tachiiri, Kaoru; Tokos, Kathy; Yoshimori, Masakazu; Zickfeld, Kirsten

2012-10-01

The evolution of the Atlantic Meridional Overturning Circulation (MOC) in 30 models of varying complexity is examined under four distinct Representative Concentration Pathways. The models include 25 Atmosphere-Ocean General Circulation Models (AOGCMs) or Earth System Models (ESMs) that submitted simulations in support of the 5th phase of the Coupled Model Intercomparison Project (CMIP5) and 5 Earth System Models of Intermediate Complexity (EMICs). While none of the models incorporated the additional effects of ice sheet melting, they all projected very similar behaviour during the 21st century. Over this period the strength of MOC reduced by a best estimate of 22% (18%-25% 5%-95% confidence limits) for RCP2.6, 26% (23%-30%) for RCP4.5, 29% (23%-35%) for RCP6.0 and 40% (36%-44%) for RCP8.5. Two of the models eventually realized a slow shutdown of the MOC under RCP8.5, although no model exhibited an abrupt change of the MOC. Through analysis of the freshwater flux across 30°-32°S into the Atlantic, it was found that 40% of the CMIP5 models were in a bistable regime of the MOC for the duration of their RCP integrations. The results support previous assessments that it is very unlikely that the MOC will undergo an abrupt change to an off state as a consequence of global warming.

Ocean Circulation-Cloud Interactions Reduce the Pace of Transient Climate Change

NASA Astrophysics Data System (ADS)

Trossman, D.; Palter, J. B.; Merlis, T. M.; Huang, Y.; Xia, Y.

2016-12-01

We argue that a substantial fraction of the uncertainty in the cloud radiative feedback during transient climate change may be due to uncertainty in the ocean circulation perturbation. A suite of climate model simulations in which the ocean circulation, the cloud radiative feedback, or a combination of both are held fixed while CO2 doubles, shows that changes in the ocean circulation reduce the amount of transient global warming caused by the radiative cloud feedback. Specifically, a slowdown in the Atlantic Meridional Overturning Circulation (AMOC) helps to maintain low cloud cover in the Northern Hemisphere extratropics. We propose that the AMOC decline increases the meridional SST gradient, strengthening the storm track, its attendant clouds and the amount of shortwave radiation they reflect back to space. If the results of our model were to scale proportionately in the CMIP5 models, whose AMOC decline ranges from 15 to 60% under RCP8.5, then as much as 70% of the intermodel spread in the cloud radiative feedback and 35% of the spread in the transient climate response could possibly stem from the model representations of AMOC decline.

Developing Novel Therapeutic Approaches in Small Cell Lung Carcinoma Using Genetically Engineered Mouse Models and Human Circulating Tumor Cells

DTIC Science & Technology

2014-10-01

AD_________________ Award Number: W81XWH-13-1-0325 TITLE: Developing Novel Therapeutic Approaches in Small Cell Lung Carcinoma Using ...Genetically Engineered Mouse Models and Human Circulating Tumor Cells PRINCIPAL INVESTIGATOR: Jeffrey Engelman MD PhD CONTRACTING ORGANIZATION ...Novel Therapeutic Approaches in Small Cell Lung 5a. CONTRACT NUMBER W81XWH-13-1-0325 Carcinoma Using Genetically Engineered Mouse Models and 5b

The Pattern and Dynamics of the Meridional Overturning Circulation in the Upper Ocean

DTIC Science & Technology

2008-09-01

Atlantic . Figure 4a shows that the center of meridional overturning circulation occurs at a level of about one kilometer. Circulation is weak at...maintenance of the meridional overturning circulation in the Atlantic Ocean. 5. Global Simulation The most exciting experiment would be to fully model the...mechanisms responsible for the strength and maintenance of the meridional overturning circulation in the Atlantic Ocean are not

Seasonal climate information preserved within West Antarctic ice cores and its relation to large-scale atmospheric circulation and regional sea ice variations

NASA Astrophysics Data System (ADS)

Küttel, M.; Steig, E. J.; Ding, Q.; Battisti, D. S.

2010-12-01

Recent evidence suggests that West Antarctica has been warming since at least the 1950s. With the instrumental record being limited to the mid-20th century, indirect information from stable isotopes (δ18O and δD, hereafter collectively δ) preserved within ice cores have commonly been used to place this warming into a long term context. Here, using a large number of δ records obtained during the International Trans-Antarctic Scientific Expedition (ITASE), past variations in West Antarctic δ are not only investigated over time but also in space. This study therefore provides an important complement to longer records from single locations as e.g. the currently being processed West Antarctic ice sheet (WAIS) Divide ice core. Although snow accumulation rates at the ITASE sites in West Antarctica are variable, they are generally high enough to allow studies on sub-annual scale over the last 50-100 years. Here, we show that variations in δ in this region are strongly related to the state of the large-scale atmospheric circulation as well as sea ice variations in the adjacent Southern Ocean, with important seasonal changes. While a strong relationship to sea ice changes in the Ross and Amundsen Sea as well as to the atmospheric circulation offshore is found during austral fall (MAM) and winter (JJA), only modest correlations are found during spring (SON) and summer (DJF). Interestingly, the correlations with the atmospheric circulation in the latter two seasons have the strongest signal over the Antarctic continent, but not offshore - an important difference to MAM and JJA. These seasonal changes are in good agreement with the seasonally varying predominant circulation: meridional with more frequent storms in the Amundsen Sea during MAM and JJA and more zonal and stable during SON and DJF. The relationship to regional temperature is similarly seasonally variable with highest correlations found during MAM and JJA. Notably, the circulation pattern found to be strongest related to West Antarctic MAM and JJA δ variations is comparable to the tropical-polar wave train found by Ding et al. (this meeting, and in review) during JJA, a pattern which appears to be the dominant forcing behind the West Antarctic JJA temperature increase since the 1950s or earlier (Steig et al. 2009). The coupled atmosphere/sea ice influence can be observed for most of the large δ anomalies with, however, 1980 standing out as the prime example with a record-high δ anomaly of up to 3 standard deviations in the ITASE cores. While the anomalously strong northerly onshore winds certainly are a relevant factor, the spatial pattern and seasonal evolution of the δ peaks in the spatial ITASE network indicates that the record-low sea ice concentration in the Ross/Amundsen Sea during 1980 is an important contributor to this δ anomaly. Using observational evidence as well as model simulations from the ECHAM4.6 AGCM, a general framework for the atmosphere/sea ice coupling and its influence on West Antarctic δ is established and presented.

Impact of climate change on soil thermal and moisture regimes in Serbia: An analysis with data from regional climate simulations under SRES-A1B.

PubMed

Mihailović, D T; Drešković, N; Arsenić, I; Ćirić, V; Djurdjević, V; Mimić, G; Pap, I; Balaž, I

2016-11-15

We considered temporal and spatial variations to the thermal and moisture regimes of the most common RSGs (Reference Soil Groups) in Serbia under the A1B scenario for the 2021-2050 and 2071-2100 periods, with respect to the 1961-1990 period. We utilized dynamically downscaled global climate simulations from the ECHAM5 model using the coupled regional climate model EBU-POM (Eta Belgrade University-Princeton Ocean Model). We analysed the soil temperature and moisture time series using simple statistics and a Kolmogorov complexity (KC) analysis. The corresponding metrics were calculated for 150 sites. In the future, warmer and drier regimes can be expected for all RSGs in Serbia. The calculated soil temperature and moisture variations include increases in the mean annual soil temperature (up to 3.8°C) and decreases in the mean annual soil moisture (up to 11.3%). Based on the KC values, the soils in Serbia are classified with respect to climate change impacts as (1) less sensitive (Vertisols, Umbrisols and Dystric Cambisols) or (2) more sensitive (Chernozems, Eutric Cambisols and Planosols). Copyright © 2016 Elsevier B.V. All rights reserved.

Recent intensification of the Walker Circulation and the role of natural sea surface temperature variability

NASA Astrophysics Data System (ADS)

Zhao, X.; Allen, R.

2017-12-01

In a warming world, the tropical atmospheric overturning circulation-including the Walker Circulation-is expected to weaken due to thermodynamic constraints. Tropical precipitation increases at a slower rate than water vapor-which increases according to Clausius Clapeyron scaling, assuming constant relative humidity-so the tropical overturning circulation slows down. This is supported by both observations and model simulations, which show a slowdown of the Walker Circulation over the 20th century. Model projections suggest a further weakening of the Walker Circulation in the 21st century. However, over the last several decades (1979-2014), multiple observations reveal a robust strengthening of the Walker Circulation. Although coupled CMIP5 simulations are unable to reproduce this strengthening, AMIP simulations-which feature the observed evolution of SSTs-are generally able to reproduce it. Assuming the ensemble mean sea surface temperatures (SSTs) from historical CMIP5 simulations accurately represent the externally forced SST response, the observed SSTs can be decomposed into a forced and an unforced component. CAM5 AMIP-type simulations driven by the unforced component of observed SSTs reproduce the observed strengthening of the Walker Circulation. Corresponding simulations driven by the forced component of observed SSTs yield a weaker Walker Circulation. These results are consistent with the zonal tropical SST gradient and the Bjerknes feedback. The unforced component of SSTs yield an increased SST gradient over tropical Pacific (a La Nina like pattern) and strengthening of the tropical trade winds, which constitute the lower branch of the Walker Circulation. The forced component of SSTs yields a zonally uniform tropical Pacific SST warming and a marginal weakening of the Walker Circulation. Our results suggest significant modulation of the tropical Walker Circulation by natural SST variability over the last several decades.

Uncertainties in the Modelled CO2 Threshold for Antarctic Glaciation

NASA Technical Reports Server (NTRS)

Gasson, E.; Lunt, D. J.; DeConto, R.; Goldner, A.; Heinemann, M.; Huber, M.; LeGrande, A. N.; Pollard, D.; Sagoo, N.; Siddall, M.;

Mars atmospheric circulation - Aspects from Viking Landers

NASA Technical Reports Server (NTRS)

Ryan, J. A.

1985-01-01

Winds measured by the two Viking Landers have been filtered and then compared with predictions from the general circulation model and to Orbiter observations of clouds and surface phenomena that indicate wind direction. This was done to determine the degree to which filtered winds may represent aspects of the general circulation. Excellent agreement was found between wind direction data from Lander 1 and the model predictions and Orbiter observations. For Lander 2, agreement was generally good, but there were periods of disagreement which indicate that the filtering did not remove other extraneous effects. It is concluded that Lander 1 gives a good representation of the general circulation at 22.5 deg N latitude but that Lander 2 is suspect. Most wind data from Lander 1 have yet to be analyzed. It appears that when analyzed these Lander 1 data (covering 3.5 Mars years) can provide information about interannual variations in the general circulation at the Lander latitude.

Simulated and Observed Circulation in the Indonesian Seas: 1/12 degree Global HYCOM and the INSTANT Observations

DTIC Science & Technology

2010-01-01

Circulation in the Indonesian Seas: 1/12 degree Global HYCOM and the INSTANT Observations 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM...SUPPLEMENTARY NOTES 14. ABSTRACT A l/l 2 global version of the HYbrid Coordinate Ocean Model (HYCOM) using 3-hourly atmospheric forcing is analyzed and...TERMS Indonesian Throughflow, global HYCOM, INSTANT, Inter-ocean exchange, ocean modeling 16. SECURITY CLASSIFICATION OF: a. REPORT Unclassified b

Concurrent Simulation of the Eddying General Circulation and Tides in a Global Ocean Model

DTIC Science & Technology

2010-01-01

Eddying General Circulation and Tides in a Global Ocean Model 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 0602435N 6...STATEMENT Approved for public release, distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT This paper presents a five-year global ...running 25-h average to approximately separate tidal and non-tidal components of the near-bottom flow. In contrast to earlier high-resolution global

10Be in ice at high resolution: Solar activity and climate signals observed and GCM-modeled in Law Dome ice cores

NASA Astrophysics Data System (ADS)

Pedro, Joel; Heikkilä, Ulla; van Ommen, T. D.; Smith, A. M.

2010-05-01

Changes in solar activity modulate the galactic cosmic ray flux, and in turn, the production rate of 10Be in the earth's atmosphere. The best archives of past changes in 10Be production rate are the polar ice cores. Key challenges in interpreting these archives as proxies for past solar activity lie in separating the useful solar activity (or production) signal from the interfering meteorological (or climate) signal, and furthermore, in determining the atmospheric source regions of 10Be deposited to the ice core site. In this study we use a new monthly resolution composite 10Be record, which spans the past decade, and a general circulation model (ECHAM5-HAM), to constrain both the production and climate signals in 10Be concentrations at the Law Dome ice core site, East Antarctica. This study differs from most previous work on 10Be in Antarctica due to the very high sample resolution achieved. This high resolution, through a time period where accurate instrumental measurements of solar activity and climate are available, allows us to examine the response of 10Be concentrations in ice to short-term (monthly to annual) variations in solar activity, and to short-term variations in climate, including seasonality. We find a significant correlation (r2 = 0.56, P < 0.005, n = 92) between observed 10Be concentrations and solar activity (represented by the neutron counting rate). The most pervasive climate influence is a seasonal cycle, which shows maximum concentrations in mid-to-late-summer and minimum concentrations in winter. Model results show reasonable agreement with observations; both a solar activity signal and seasonal cycle in 10Be are captured. However, the modeled snow accumulation rate is too high by approximately 60%. According to the model, the main atmospheric source region of 10Be deposited to Law Dome is the 30-90°S stratosphere (~50%), followed by the 30-90°S troposphere (~30%). An enhancement in the fraction of 10Be arriving to Law Dome from the stratosphere is found by the model during the mid-to-late summer, we suggest this pattern is implicated in the seasonality of observed 10Be concentrations in ice. Our results have implications for interpretation of longer term records of 10Be from ice cores. Firstly, the strong production signal supports the use of 10Be as a solar proxy. Secondly, the short term climate processes operating here, may provide clues to how longer term shifts in climate impact on ice core 10Be.

Enhanced basal lubrication and the contribution of the Greenland ice sheet to future sea-level rise

PubMed Central

Shannon, Sarah R.; Payne, Antony J.; Bartholomew, Ian D.; van den Broeke, Michiel R.; Edwards, Tamsin L.; Fettweis, Xavier; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Goelzer, Heiko; Hoffman, Matthew J.; Huybrechts, Philippe; Mair, Douglas W. F.; Nienow, Peter W.; Perego, Mauro; Price, Stephen F.; Smeets, C. J. P. Paul; Sole, Andrew J.; van de Wal, Roderik S. W.; Zwinger, Thomas

2013-01-01

We assess the effect of enhanced basal sliding on the flow and mass budget of the Greenland ice sheet, using a newly developed parameterization of the relation between meltwater runoff and ice flow. A wide range of observations suggest that water generated by melt at the surface of the ice sheet reaches its bed by both fracture and drainage through moulins. Once at the bed, this water is likely to affect lubrication, although current observations are insufficient to determine whether changes in subglacial hydraulics will limit the potential for the speedup of flow. An uncertainty analysis based on our best-fit parameterization admits both possibilities: continuously increasing or bounded lubrication. We apply the parameterization to four higher-order ice-sheet models in a series of experiments forced by changes in both lubrication and surface mass budget and determine the additional mass loss brought about by lubrication in comparison with experiments forced only by changes in surface mass balance. We use forcing from a regional climate model, itself forced by output from the European Centre Hamburg Model (ECHAM5) global climate model run under scenario A1B. Although changes in lubrication generate widespread effects on the flow and form of the ice sheet, they do not affect substantial net mass loss; increase in the ice sheet’s contribution to sea-level rise from basal lubrication is projected by all models to be no more than 5% of the contribution from surface mass budget forcing alone. PMID:23940337

Enhanced basal lubrication and the contribution of the Greenland ice sheet to future sea-level rise.

PubMed

Shannon, Sarah R; Payne, Antony J; Bartholomew, Ian D; van den Broeke, Michiel R; Edwards, Tamsin L; Fettweis, Xavier; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Goelzer, Heiko; Hoffman, Matthew J; Huybrechts, Philippe; Mair, Douglas W F; Nienow, Peter W; Perego, Mauro; Price, Stephen F; Smeets, C J P Paul; Sole, Andrew J; van de Wal, Roderik S W; Zwinger, Thomas

2013-08-27

We assess the effect of enhanced basal sliding on the flow and mass budget of the Greenland ice sheet, using a newly developed parameterization of the relation between meltwater runoff and ice flow. A wide range of observations suggest that water generated by melt at the surface of the ice sheet reaches its bed by both fracture and drainage through moulins. Once at the bed, this water is likely to affect lubrication, although current observations are insufficient to determine whether changes in subglacial hydraulics will limit the potential for the speedup of flow. An uncertainty analysis based on our best-fit parameterization admits both possibilities: continuously increasing or bounded lubrication. We apply the parameterization to four higher-order ice-sheet models in a series of experiments forced by changes in both lubrication and surface mass budget and determine the additional mass loss brought about by lubrication in comparison with experiments forced only by changes in surface mass balance. We use forcing from a regional climate model, itself forced by output from the European Centre Hamburg Model (ECHAM5) global climate model run under scenario A1B. Although changes in lubrication generate widespread effects on the flow and form of the ice sheet, they do not affect substantial net mass loss; increase in the ice sheet's contribution to sea-level rise from basal lubrication is projected by all models to be no more than 5% of the contribution from surface mass budget forcing alone.

What Drives Hydrogen Isotopic Variability Recorded by Biomarkers in Sediments of Lake Karakul, Pamir?

NASA Astrophysics Data System (ADS)

Aichner, B.; Mischke, S.; Pausata, F. S. R.; Werner, M.; Zhang, Q.; Heinecke, L.; Feakins, S. J.; Sachse, D.; Mahmoudov, Z.; Rajabov, I.

2017-12-01

Central Asia is a climate sensitive region located at the boundary of large scale atmospheric circulation systems. To examine glacial to interglacial hydrological changes in the region, we analysed the hydrogen isotopic composition (δD values) of n-alkanes in a 30-ka record from Lake Karakul, eastern Pamir (altitude: 3,915m, MAT: -3.9 °C, MAP: 82 mm). δD values of both aquatic and terrestrial compounds showed distinct trends throughout the studied time interval, with generally higher values during the glacial and lower values during the Holocene, and variability of up to 60‰. In particular shifts towards higher δD values were observed for aquatic biomarkers at ca. 30, 27, and 15 ka BP. Temperature and precipitation effects alone cannot explain the higher δD values during the glacial and the large isotopic amplitudes. To explain these observations we conducted a set of experiments using atmospheric models with embedded isotope modules (CAM3iso- and ECHAM5-wiso). We assume that terrestrial n-alkanes mainly record the isotopic signature of summer precipitation within the lower elevated parts of the Karakul Basin. Based on the model output we hypothesize that shifts between local and more distant vapour sources are the reason behind the trends within isotopic data. Data derived from aquatic biomarkers are more difficult to explain due to multiple influencing factors on δD of the lake water. Assuming that the lake water integrates an annual isotopic signal from the whole lake catchment, we suggest that a change in precipitation seasonality drives the large variability of hydrogen isotopic values. This is in agreement with the models, which suggest reduced winter (more negative δD) and slightly higher summer precipitation (more positive δD) during the glacial compared to the Holocene. Consequently, a net-increase of isotopically enriched inflow into the lake could explain the three distinct shifts towards higher δD values. Expansion of terrestrial vegetation, indicated by increasing biomarker concentrations, during these periods is another indicator for wetter summers in an arid environment. We conclude that δD values of terrestrial compounds reflect major shifts of vapour sources which are driven by insolation, while aquatic biomarkers are additionally influenced by changes of precipitation seasonality.

Estimation of the climate change impact on a catchment water balance using an ensemble of GCMs

NASA Astrophysics Data System (ADS)

Reshmidevi, T. V.; Nagesh Kumar, D.; Mehrotra, R.; Sharma, A.

2018-01-01

This work evaluates the impact of climate change on the water balance of a catchment in India. Rainfall and hydro-meteorological variables for current (20C3M scenario, 1981-2000) and two future time periods: mid of the 21st century (2046-2065) and end of the century (2081-2100) are simulated using Modified Markov Model-Kernel Density Estimation (MMM-KDE) and k-nearest neighbor downscaling models. Climate projections from an ensemble of 5 GCMs (MPI-ECHAM5, BCCR-BCM2.0, CSIRO-mk3.5, IPSL-CM4, and MRI-CGCM2) are used in this study. Hydrologic simulations for the current as well as future climate scenarios are carried out using Soil and Water Assessment Tool (SWAT) integrated with ArcGIS (ArcSWAT v.2009). The results show marginal reduction in runoff ratio, annual streamflow and groundwater recharge towards the end of the century. Increased temperature and evapotranspiration project an increase in the irrigation demand towards the end of the century. Rainfall projections for the future shows marginal increase in the annual average rainfall. Short and moderate wet spells are projected to decrease, whereas short and moderate dry spells are projected to increase in the future. Projected reduction in streamflow and groundwater recharge along with the increase in irrigation demand is likely to aggravate the water stress in the region under the future scenario.

Dynamical Evaluation of Ocean Models using the Gulf Stream as an Example

DTIC Science & Technology

2010-01-01

transport for the Atlantic meridional overturning circulation (AMOC) as the 3 nonlinear solutions discussed in Section 2. The model boundary is...Hellerman and Rosenstein (1983) wind stress climatology and the northward upper ocean flow (14 Sv) of the Atlantic meridional overturning circulation ... overturning circulation (AMOC) streamfunction with a 5 Sv contour interval from (a) 1/12° Atlantic MICOM, (b) 1/12° Atlantic HYCOM, and (c) 1/12

Spatiotemporal Variability of Mountain Block Recharge in Three Semiarid Watersheds along the U.S.-Mexico Border Region

NASA Astrophysics Data System (ADS)

Robles-Morua, A.; Vivoni, E. R.; Mascaro, G.; Dominguez, F.; Rivera-fernandez, E. R.

2015-12-01

Groundwater recharge in semiarid mountains of the western U.S. remains a critical component of the regional water balance and has significant repercussions on water resources management, in particular during periods of drought. The bimodal distribution of annual precipitation in the southwest United States and northwest Mexico present a challenge as differential climate impacts during the winter and summer seasons are not currently well understood. In this work, we focus on the predictions of Mountain Block Recharge (MBR) using precipitation forcing from a reanalysis product, regional climate model-based precipitation products and available ground observations. MBR estimates in the Santa Cruz, San Pedro and Sonora River basins (>40,000 km2) are compared along a north to south gradient crossing the U.S.-Mexico border. As a result of the influence of the North American monsoon, the impact of seasonality in each of these systems is evaluated. Simulated precipitation fields under historical (1991-2000) conditions and climate change (2031-2040 and 2070-2080) scenarios are compared at resolutions of 10-km and 35-km as generated from the Weather Research and Forecast (WRF) model using boundary conditions from two general circulation models (MPI-ECHAM and HadCM3). Mountain subbasins to apply a seasonal MBR method were delineated using a threshold in terrain slope that matched official boundaries of known aquifers in these transboundary watersheds. We evaluated the MBR outcomes from the various precipitation products to quantify biases involved in the historical estimates and to inform groundwater management on the uncertainties inherent in future projections. We also inspect the variability of MBR across pluvial and drought periods lasting several years. Seasonal comparisons across a north to south spatial gradient yield a valuable assessment on the impacts of climate change on MBR for important basins in the U.S.-Mexico border region.

A new Geoengineering Model Intercomparison Project (GeoMIP) experiment designed for climate and chemistry models

DOE PAGES

Tilmes, S.; Mills, Mike; Niemeier, Ulrike; ...

2015-01-15

A new Geoengineering Model Intercomparison Project (GeoMIP) experiment "G4 specified stratospheric aerosols" (short name: G4SSA) is proposed to investigate the impact of stratospheric aerosol geoengineering on atmosphere, chemistry, dynamics, climate, and the environment. In contrast to the earlier G4 GeoMIP experiment, which requires an emission of sulfur dioxide (SO₂) into the model, a prescribed aerosol forcing file is provided to the community, to be consistently applied to future model experiments between 2020 and 2100. This stratospheric aerosol distribution, with a total burden of about 2 Tg S has been derived using the ECHAM5-HAM microphysical model, based on a continuous annualmore » tropical emission of 8 Tg SO₂ yr⁻¹. A ramp-up of geoengineering in 2020 and a ramp-down in 2070 over a period of 2 years are included in the distribution, while a background aerosol burden should be used for the last 3 decades of the experiment. The performance of this experiment using climate and chemistry models in a multi-model comparison framework will allow us to better understand the impact of geoengineering and its abrupt termination after 50 years in a changing environment. The zonal and monthly mean stratospheric aerosol input data set is available at https://www2.acd.ucar.edu/gcm/geomip-g4-specified-stratospheric-aerosol-data-set.« less

Near-inertial Wave Studies using Historical Mooring Records and a High-Resolution General Circulation Model

DTIC Science & Technology

2009-01-01

Mooring Records and a High- Resolution General Circulation Model Harper Simmons School of Fisheries and Ocean Sciences 903 Koyukuk Drive Fairbanks AK...oceanographic community has been to develop a global internal wave prediction system analogous to those already in place for surface waves. Early steps have...AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) School of Fisheries and Ocean

Understanding the Asian summer monsoon response to greenhouse warming: the relative roles of direct radiative forcing and sea surface temperature change

NASA Astrophysics Data System (ADS)

Li, Xiaoqiong; Ting, Mingfang

2017-10-01

Future hydroclimate projections from state-of-the-art climate models show large uncertainty and model spread, particularly in the tropics and over the monsoon regions. The precipitation and circulation responses to rising greenhouse gases involve a fast component associated with direct radiative forcing and a slow component associated with sea surface temperature (SST) warming; the relative importance of the two may contribute to model discrepancies. In this study, regional hydroclimate responses to greenhouse warming are assessed using output from coupled general circulation models in the Coupled Model Intercomparison Project-Phase 5 (CMIP5) and idealized atmospheric general circulation model experiments from the Atmosphere Model Intercomparison Project. The thermodynamic and dynamic mechanisms causing the rainfall changes are examined using moisture budget analysis. Results show that direct radiative forcing and SST change exert significantly different responses both over land and ocean. For most part of the Asian monsoon region, the summertime rainfall changes are dominated by the direct CO2 radiative effect through enhanced monsoon circulation. The response to SST warming shows a larger model spread compared to direct radiative forcing, possibly due to the cancellation between the thermodynamical and dynamical components. While the thermodynamical response of the Asian monsoon is robust across the models, there is a lack of consensus for the dynamical response among the models and weak multi-model mean responses in the CMIP5 ensemble, which may be related to the multiple physical processes evolving on different time scales.

Trends of atmospheric circulation during singular hot days in Europe

NASA Astrophysics Data System (ADS)

Jézéquel, Aglaé; Cattiaux, Julien; Naveau, Philippe; Radanovics, Sabine; Ribes, Aurélien; Vautard, Robert; Vrac, Mathieu; Yiou, Pascal

2018-05-01

The influence of climate change on mid-latitudes atmospheric circulation is still very uncertain. The large internal variability makes it difficult to extract any statistically significant signal regarding the evolution of the circulation. Here we propose a methodology to calculate dynamical trends tailored to the circulation of specific days by computing the evolution of the distances between the circulation of the day of interest and the other days of the time series. We compute these dynamical trends for two case studies of the hottest days recorded in two different European regions (corresponding to the heat-waves of summer 2003 and 2010). We use the NCEP reanalysis dataset, an ensemble of CMIP5 models, and a large ensemble of a single model (CESM), in order to account for different sources of uncertainty. While we find a positive trend for most models for 2003, we cannot conclude for 2010 since the models disagree on the trend estimates.

Responses of dune activity and desertification in China to global warming in the twenty-first century

NASA Astrophysics Data System (ADS)

Wang, Xunming; Yang, Yi; Dong, Zhibao; Zhang, Caixia

2009-06-01

Most areas of arid and semiarid China are covered by aeolian sand dunes, sand sheets, and desert steppes, and the existence of the nearly 80 million people who live in this region could be seriously jeopardized if climate change increases desertification. However, the expected trends in desertification during the 21st century are poorly understood. In the present study, we selected the ECHAM4 and HadCM3 global climate models (after comparing them with the results of the GFDL-R30, CGCM2, and CSIRO-Mk2b models) and used simulations of a dune mobility index under IPCC SRES climate scenarios A1FI, A2a, A2b, A2c, B1a, B2a, and B2b to estimate future trends in dune activity and desertification in China. Although uncertainties in climate predictions mean that there is still far to go before we can develop a comprehensive dune activity estimation system, HadCM3 simulations with most greenhouse forcing scenarios showed decreased desertification in most western region of arid and semiarid China by 2039, but increased desertification thereafter, whereas ECHAM4 simulation results showed that desertification will increase during this period. Inhabitants of thecentral region will benefit from reversed desertification from 2010 to 2099, whereas inhabitants of the eastern region will suffer from increased desertification from 2010 to 2099. From 2010 to 2039, most regions will not be significantly affected by desertification, but from 2040 to 2099, the environments of the western and eastern regions will deteriorate due to the significant effects of global warming (particularly the interaction between precipitation and potential evapotranspiration), leading to decreased livestock and grain yields and possibly threatening China's food security.

Model-free adaptive control of supercritical circulating fluidized-bed boilers

DOEpatents

Cheng, George Shu-Xing; Mulkey, Steven L

2014-12-16

A novel 3-Input-3-Output (3.times.3) Fuel-Air Ratio Model-Free Adaptive (MFA) controller is introduced, which can effectively control key process variables including Bed Temperature, Excess O2, and Furnace Negative Pressure of combustion processes of advanced boilers. A novel 7-input-7-output (7.times.7) MFA control system is also described for controlling a combined 3-Input-3-Output (3.times.3) process of Boiler-Turbine-Generator (BTG) units and a 5.times.5 CFB combustion process of advanced boilers. Those boilers include Circulating Fluidized-Bed (CFB) Boilers and Once-Through Supercritical Circulating Fluidized-Bed (OTSC CFB) Boilers.

Tropospheric Distribution of Trace Species during the Oxidation Mechanism Observations (OMO-2015) campaign: Model Evaluation and sensitivity simulations

NASA Astrophysics Data System (ADS)

Ojha, Narendra; Pozzer, Andrea; Jöckel, Patrick; Fischer, Horst; Zahn, Andreas; Tomsche, Laura; Lelieveld, Jos

2017-04-01

The Asian monsoon convection redistributes trace species, affecting the tropospheric chemistry and radiation budget over Asia and downwind as far as the Mediterranean. It remains challenging to model these impacts due to uncertainties, e.g. associated with the convection parameterization and input emissions. Here, we perform a series of numerical experiments using the global ECHAM5/MESSy atmospheric chemistry model (EMAC) to investigate the tropospheric distribution of O3 and related tracers measured during the Oxidation Mechanism Observations (OMO) conducted during July-August 2015. The reference simulation can reproduce the spatio-temporal variations to some extent (e.g. r2 = 0.7 for O3, 0.6 for CO). However, this simulation underestimates mean CO in the lower troposphere by about 30 ppbv and overestimates mean O3 up to 35 ppbv, especially in the middle-upper troposphere. Interestingly, sensitivity simulations with 50% higher biofuel emissions of CO over South Asia had insignificant effect on CO underestimation, pointing to sources upwind of South Asia. Use of an alternative convection parameterization is found to significantly improve simulated O3. The study reveals the abilities as well as the limitations of the model to reproduce observations and study atmospheric chemistry and climate implications of the monsoon.

Sensitivity of amplitude-phase characteristics of the surface air temperature annual cycle to variations in annual mean temperature

NASA Astrophysics Data System (ADS)

Eliseev, A. V.; Mokhov, I. I.; Guseva, M. S.

2006-05-01

The ERA40 and NCEP/NCAR data over 1958 1998 were used to estimate the sensitivity of amplitude-phase characteristics (APCs) of the annual cycle (AC) of the surface air temperature (SAT) T s. The results were compared with outputs of the ECHAM4/OPYC3, HadCM3, and INM RAS general circulation models and the IAP RAS climate model of intermediate complexity, which were run with variations in greenhouse gases and sulfate aerosol specified over 1860 2100. The analysis was performed in terms of the linear regression coefficients b of SAT AC APCs on the local annual mean temperature and in terms of the sensitivity characteristic D = br 2, which takes into account not only the linear regression coefficient but also its statistical significance (via the correlation coefficient r). The reanalysis data were used to reveal the features of the tendencies of change in the SAT AC APCs in various regions, including areas near the snow-ice boundary, storm-track ocean regions, large desert areas, and the tropical Pacific. These results agree with earlier observations. The model computations are in fairly good agreement with the reanalysis data in regions of statistically significant variations in SAT AC APCs. The differences between individual models and the reanalysis data can be explained, in particular, in terms of the features of the sea-ice schemes used in the models. Over the land in the middle and high latitudes of the Northern Hemisphere, the absolute values of D for the fall phase time and the interval of exceeding exhibit a positive intermodel correlation with the absolute value of D for the annual-harmonic amplitude. Over the ocean, the models reproducing larger (in modulus) sensitivity parameters of the SAT annual-harmonic amplitude are generally characterized by larger (in modulus) negative sensitivity values of the semiannual-harmonic amplitude T s, 2, especially at latitudes characteristic of the sea-ice boundary. In contrast to the averaged fields of AC APCs and their interannual standard deviations, the sensitivity parameters of the SAT AC APCs on a regional scale vary noticeably for various types of anthropogenic forcing.

Relationships between hormones and aggressive behavior in green anole lizards: an analysis using structural equation modeling.

PubMed

Yang, Eun-Jin; Wilczynski, Walter

2002-09-01

We investigated the relationship between aggressive behavior and circulating androgens in the context of agonistic social interaction and examined the effect of this interaction on the androgen-aggression relationship in response to a subsequent social challenge in male Anolis carolinensis lizards. Individuals comprising an aggressive encounter group were exposed to an aggressive conspecific male for 10 min per day during a 5-day encounter period, while controls were exposed to a neutral stimulus for the same period. On the sixth day, their responses to an intruder test were observed. At intervals, individuals were sacrificed to monitor plasma androgen levels. Structural equation modeling (SEM) was used to test three a priori interaction models of the relationship between social stimulus, aggressive behavior, and androgen. Model 1 posits that exposure to a social stimulus influences androgen and aggressive behavior independently. In Model 2, a social stimulus triggers aggressive behavior, which in turn increases circulating levels of androgen. In Model 3, exposure to a social stimulus influences circulating androgen levels, which in turn triggers aggressive behavior. During the 5 days of the encounter period, circulating testosterone (T) levels of the aggressive encounter group followed the same pattern as their aggressive behavioral responses, while the control group did not show significant changes in their aggressive behavior or T level. Our SEM results supported Model 2. A means analysis showed that during the intruder test, animals with 5 days of aggressive encounters showed more aggressive responses than did control animals, while their circulating androgen levels did not differ. This further supports Model 2, suggesting that an animal's own aggressive behavior may trigger increases in levels of plasma androgen. Copyright 2002 Elsevier Science (USA)

Tropospheric jet response to Antarctic ozone depletion: An update with Chemistry-Climate Model Initiative (CCMI) models

NASA Astrophysics Data System (ADS)

Son, Seok-Woo; Han, Bo-Reum; Garfinkel, Chaim I.; Kim, Seo-Yeon; Park, Rokjin; Abraham, N. Luke; Akiyoshi, Hideharu; Archibald, Alexander T.; Butchart, N.; Chipperfield, Martyn P.; Dameris, Martin; Deushi, Makoto; Dhomse, Sandip S.; Hardiman, Steven C.; Jöckel, Patrick; Kinnison, Douglas; Michou, Martine; Morgenstern, Olaf; O’Connor, Fiona M.; Oman, Luke D.; Plummer, David A.; Pozzer, Andrea; Revell, Laura E.; Rozanov, Eugene; Stenke, Andrea; Stone, Kane; Tilmes, Simone; Yamashita, Yousuke; Zeng, Guang

2018-05-01

The Southern Hemisphere (SH) zonal-mean circulation change in response to Antarctic ozone depletion is re-visited by examining a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models reasonably well reproduce Antarctic ozone depletion in the late 20th century. The related SH-summer circulation changes, such as a poleward intensification of westerly jet and a poleward expansion of the Hadley cell, are also well captured. All experiments exhibit quantitatively the same multi-model mean trend, irrespective of whether the ocean is coupled or prescribed. Results are also quantitatively similar to those derived from the Coupled Model Intercomparison Project phase 5 (CMIP5) high-top model simulations in which the stratospheric ozone is mostly prescribed with monthly- and zonally-averaged values. These results suggest that the ozone-hole-induced SH-summer circulation changes are robust across the models irrespective of the specific chemistry-atmosphere-ocean coupling.

Nonhydrostatic icosahedral atmospheric model (NICAM) for global cloud resolving simulations

NASA Astrophysics Data System (ADS)

Satoh, M.; Matsuno, T.; Tomita, H.; Miura, H.; Nasuno, T.; Iga, S.

2008-03-01

A new type of ultra-high resolution atmospheric global circulation model is developed. The new model is designed to perform "cloud resolving simulations" by directly calculating deep convection and meso-scale circulations, which play key roles not only in the tropical circulations but in the global circulations of the atmosphere. Since cores of deep convection have a few km in horizontal size, they have not directly been resolved by existing atmospheric general circulation models (AGCMs). In order to drastically enhance horizontal resolution, a new framework of a global atmospheric model is required; we adopted nonhydrostatic governing equations and icosahedral grids to the new model, and call it Nonhydrostatic ICosahedral Atmospheric Model (NICAM). In this article, we review governing equations and numerical techniques employed, and present the results from the unique 3.5-km mesh global experiments—with O(10 9) computational nodes—using realistic topography and land/ocean surface thermal forcing. The results show realistic behaviors of multi-scale convective systems in the tropics, which have not been captured by AGCMs. We also argue future perspective of the roles of the new model in the next generation atmospheric sciences.

Regional climate simulations over complex topography using WRF: Andalusian present climate

NASA Astrophysics Data System (ADS)

Argüeso, D.; Hidalgo-Muñoz, J. M.; Calandria-Hernández, D.; Gámiz-Fortis, S. R.; Esteban-Parra, M. J.; Castro-Díez, Y.

2010-09-01

In this study three WRF simulations were carried out and analyzed to assess its accuracy to describe the main climate features of Southern Spain in terms of maximum temperature, minimum temperature and precipitation. Present climate was represented by the last 30 year of the 20th Century (1970-1999). The model was evaluated using an observational network distributed throughout Andalusia that comprised both temperatures and precipitation. Since comparison between site-specific measurements and model grid points is definitely troublesome due to differences in spatial-scale, a multi-step regionalization strategy was adopted to upscale observational information. This is of particular importance when studying complex topography regions such as Andalusia, with a wide range of climate conditions in a relative small area. Additionally, WRF outputs were also compared with SPAIN02, a 20-km resolution gridded dataset of precipitation for further validation of the model performance. The model set up consisted in two domains with one-way nesting and spectral nudging. The target domain has a resolution of 10km with 136 by 136 points covering the whole Iberian Peninsula and nested in a coarser domain of 30-km resolution and 130 by 120 grid points. Both domains have 35 vertical levels. Three different driving data were used to provide the boundary conditions, one reanalysis (ERA-40) and two control runs from different General Circulation Models (ECHAM5 and CCSM 3.0). A conservative 7-month spin-up period was added to the 30-year simulation so that dependence on initial conditions can be completely removed. Physics options were chosen on the basis of previous parameterization sensitivity tests over Andalusia that led to a compromise configuration that adequately describes the different subclimates. Probability distributions of daily values as well as monthly statistics were examined to determine the uncertainties associated to each variable and take them into consideration for future regional high-resolution projections of climate change scenarios. These analyses permitted to conclude that WRF is an extremely useful tool due to the significant value-added information produced with respect to the driving data. Nonetheless, according to differences in performance between regions it has also been shown that results must be interpreted carefully depending on the region characteristics. Acknowledgements: The Spanish Ministry of Science and Innovation, with additional support from the European Community Funds (FEDER), project CGL2007-61151/CLI, and the Regional Government of Andalusia project P06-RNM-01622, have financed this study.

Analyzing the future climate change of Upper Blue Nile River basin using statistical downscaling techniques

NASA Astrophysics Data System (ADS)

Fenta Mekonnen, Dagnenet; Disse, Markus

2018-04-01

Climate change is becoming one of the most threatening issues for the world today in terms of its global context and its response to environmental and socioeconomic drivers. However, large uncertainties between different general circulation models (GCMs) and coarse spatial resolutions make it difficult to use the outputs of GCMs directly, especially for sustainable water management at regional scale, which introduces the need for downscaling techniques using a multimodel approach. This study aims (i) to evaluate the comparative performance of two widely used statistical downscaling techniques, namely the Long Ashton Research Station Weather Generator (LARS-WG) and the Statistical Downscaling Model (SDSM), and (ii) to downscale future climate scenarios of precipitation, maximum temperature (Tmax) and minimum temperature (Tmin) of the Upper Blue Nile River basin at finer spatial and temporal scales to suit further hydrological impact studies. The calibration and validation result illustrates that both downscaling techniques (LARS-WG and SDSM) have shown comparable and good ability to simulate the current local climate variables. Further quantitative and qualitative comparative performance evaluation was done by equally weighted and varying weights of statistical indexes for precipitation only. The evaluation result showed that SDSM using the canESM2 CMIP5 GCM was able to reproduce more accurate long-term mean monthly precipitation but LARS-WG performed best in capturing the extreme events and distribution of daily precipitation in the whole data range. Six selected multimodel CMIP3 GCMs, namely HadCM3, GFDL-CM2.1, ECHAM5-OM, CCSM3, MRI-CGCM2.3.2 and CSIRO-MK3 GCMs, were used for downscaling climate scenarios by the LARS-WG model. The result from the ensemble mean of the six GCM showed an increasing trend for precipitation, Tmax and Tmin. The relative change in precipitation ranged from 1.0 to 14.4 % while the change for mean annual Tmax may increase from 0.4 to 4.3 °C and the change for mean annual Tmin may increase from 0.3 to 4.1 °C. The individual result of the HadCM3 GCM has a good agreement with the ensemble mean result. HadCM3 from CMIP3 using A2a and B2a scenarios and canESM2 from CMIP5 GCMs under RCP2.6, RCP4.5 and RCP8.5 scenarios were downscaled by SDSM. The result from the two GCMs under five different scenarios agrees with the increasing direction of three climate variables (precipitation, Tmax and Tmin). The relative change of the downscaled mean annual precipitation ranges from 2.1 to 43.8 % while the change for mean annual Tmax and Tmin may increase in the range from 0.4 to 2.9 °C and from 0.3 to 1.6 °C respectively.

Responses of East Asian Summer Monsoon to Natural and Anthropogenic Forcings in the 17 Latest CMIP5 Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Fengfei; Zhou, Tianjun; Qian, Yun

2014-01-31

In this study, we examined the responses of East Asian Summer Monsoon (EASM) to natural (solar variability and volcanic aerosols) and anthropogenic (greenhouse gasses and aerosols) forcings simulated in the 17 latest Coupled Model Intercomparison Program phase 5 (CMIP5) models with 105 realizations. The observed weakening trend of low-level EASM circulation during 1958-2001 is partly reproduced under all-forcing runs. A comparison of separate forcing experiments reveals that the aerosol-forcing plays a primary role in driving the weakened low-level monsoon circulation. The preferential cooling over continental East Asia caused by aerosol affects the monsoon circulation through reducing the land-sea thermal contrastmore » and results in higher sea level pressure over northern China. In the upper-level, both natural-forcing and aerosol-forcing contribute to the observed southward shift of East Asian subtropical jet through changing the meridional temperature gradient.« less

The role of the uncertainty in assessing future scenarios of water shortage in alluvial aquifers

NASA Astrophysics Data System (ADS)

Romano, Emanuele; Camici, Stefania; Brocca, Luca; Moramarco, Tommaso; Guyennon, Nicolas; Preziosi, Elisabetta

2015-04-01

There are many evidences that the combined effects of variations in precipitation and temperature due to climate change can result in a significant change of the recharge to groundwater at different time scales. A possible reduction of effective infiltration can result in a significant decrease, temporary or permanent, of the availability of the resource and, consequently, the sustainable pumping rate should be reassessed. In addition to this, one should also consider the so called indirect impacts of climate change, resulting from human intervention (e.g. augmentation of abstractions) which are feared to be even more important than the direct ones in the medium term: thus, a possible increase of episodes of shortage (i.e. the inability of the groundwater system to completely supply the water demand) can result both from change in the climate forcing and change in the demand. In order to assess future scenarios of water shortage a modelling chain is often used. It includes: 1) the use of General Circulation Models to estimate changes in temperature and precipitation; 2) downscaling procedures to match modeling scenarios to the observed meteorological time series; 3) soil-atmosphere modelling to estimate the time variation of the recharge to the aquifer; 4) groundwater flow models to simulate the water budget and piezometric head evolution; 5) future scenarios of groundwater quantitative status that include scenarios of demand variation. It is well known that each of these processing steps is affected by an intrinsic uncertainty that propagates through the whole chain leading to a final uncertainty on the piezometric head scenarios. The estimate of such an uncertainty is a key point for a correct management of groundwater resources, in case of water shortage due to prolonged droughts as well as for planning purposes. This study analyzes the uncertainty of the processing chain from GCM scenarios to its impact on an alluvial aquifer in terms of exploitation sustainability. To this goal, three GCMs (ECHAM5, PCM and CCSM3) and two downscaling methods (Linear Rescaling and Quantile Mapping) are used to generate future scenarios of precipitation and temperature; the Thornthwaite-Mather soil water balance model is used to estimate the recharge to the aquifer; the evolution in time of the piezometric heads is estimated through a numerical model developed using the MODFLOW2005 code. Finally, different scenarios of water demand are applied. Final results show that the uncertainty due to the groundwater flow model calibration/validation in steady-state conditions is comparable to that arising from the whole processing chain from the GCM choice to the effective infiltration estimates. Simulations in transient conditions show the high impact of the uncertainty related to the calibration of the storage coefficient, that significantly drives the resilience of the system, thus the ability of the aquifer to sustain the demand during the periods of prolonged drought.

Aerosol- and greenhouse gas-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations

NASA Astrophysics Data System (ADS)

Rotstayn, L. D.; Jeffrey, S. J.; Collier, M. A.; Dravitzki, S. M.; Hirst, A. C.; Syktus, J. I.; Wong, K. K.

2012-07-01

We use a coupled atmosphere-ocean global climate model (CSIRO-Mk3.6) to investigate the drivers of trends in summer rainfall and circulation in the vicinity of northern Australia. As part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), we perform a 10-member 21st century ensemble driven by Representative Concentration Pathway 4.5 (RCP4.5). To investigate the roles of different forcing agents, we also perform multiple 10-member ensembles of historical climate change, which are analysed for the period 1951-2010. The historical runs include ensembles driven by "all forcings" (HIST), all forcings except anthropogenic aerosols (NO_AA) and forcing only from long-lived greenhouse gases (GHGAS). Anthropogenic aerosol-induced effects in a warming climate are calculated from the difference of HIST minus NO_AA. CSIRO-Mk3.6 simulates a strong summer rainfall decrease over north-western Australia (NWA) in RCP4.5, whereas simulated trends in HIST are weakly positive (but insignificant) during 1951-2010. The weak rainfall trends in HIST are due to compensating effects of different forcing agents: there is a significant decrease in GHGAS, offset by an aerosol-induced increase. Observations show a significant increase of summer rainfall over NWA during the last few decades. The large magnitude of the observed NWA rainfall trend is not captured by 440 unforced 60-yr trends calculated from a 500-yr pre-industrial control run, even though the model's decadal variability appears to be realistic. This suggests that the observed trend includes a forced component, despite the fact that the model does not simulate the magnitude of the observed rainfall increase in response to "all forcings" (HIST). We investigate the mechanism of simulated and observed NWA rainfall changes by exploring changes in circulation over the Indo-Pacific region. The key circulation feature associated with the rainfall increase in reanalyses is a lower-tropospheric cyclonic circulation trend off the coast of NWA, which enhances the monsoonal flow. The model shows an aerosol-induced cyclonic circulation trend off the coast of NWA in HIST minus NO_AA, whereas GHGAS shows an anticyclonic circulation trend. This explains why the aerosol-induced effect is an increase of rainfall over NWA, and the greenhouse gas-induced effect is of opposite sign. Possible explanations for the cyclonic (anticyclonic) circulation trend in HIST minus NO_AA (GHGAS) involve changes in the Walker circulation or the local Hadley circulation. In either case, a plausible atmospheric mechanism is that the circulation anomaly is a Rossby wave response to convective heating anomalies south of the Equator. We also discuss the possible role of air-sea interactions, e.g. an increase (decrease) of sea-surface temperatures off the coast of NWA in HIST minus NO_AA (GHGAS). Further research is needed to better understand the mechanisms and the extent to which these are model-dependent. In summary, our results suggest that anthropogenic aerosols may have "masked" greenhouse gas-induced changes in rainfall over NWA and in circulation over the wider Indo-Pacific region. Due to the opposing effects of greenhouse gases and anthropogenic aerosols, future trends may be very different from trends observed over the last few decades.

More robust regional precipitation projection from selected CMIP5 models based on multiple-dimensional metrics

NASA Astrophysics Data System (ADS)

Qian, Y.; Wang, L.; Leung, L. R.; Lin, G.; Lu, J.; Gao, Y.; Zhang, Y.

2017-12-01

Projecting precipitation changes is challenging because of incomplete understanding of the climate system and biases and uncertainty in climate models. In East Asia where summer precipitation is dominantly influenced by the monsoon circulation and the global models from Coupled Model Intercomparison Project Phase 5 (CMIP5), however, give various projection of precipitation change for 21th century. It is critical for community to know which models' projection are more reliable in response to natural and anthropogenic forcings. In this study we defined multiple-dimensional metrics, measuring the model performance in simulating the present-day of large-scale circulation, regional precipitation and relationship between them. The large-scale circulation features examined in this study include the lower tropospheric southwesterly winds, the western North Pacific subtropical high, the South China Sea Subtropical High, and the East Asian westerly jet in the upper troposphere. Each of these circulation features transport moisture to East Asia, enhancing the moist static energy and strengthening the Meiyu moisture front that is the primary mechanism for precipitation generation in eastern China. Based on these metrics, 30 models in CMIP5 ensemble are classified into three groups. Models in the top performing group projected regional precipitation patterns that are more similar to each other than the bottom or middle performing group and consistently projected statistically significant increasing trends in two of the large-scale circulation indices and precipitation. In contrast, models in the bottom or middle performing group projected small drying or no trends in precipitation. We also find the models that only reasonably reproduce the observed precipitation climatology does not guarantee more reliable projection of future precipitation because good simulation skill could be achieved through compensating errors from multiple sources. Herein the potential for more robust projections of precipitation changes at regional scale is demonstrated through the use of discriminating metric to subsample the multi-model ensemble. The results from this study provides insights for how to select models from CMIP ensemble to project regional climate and hydrological cycle changes.

How Will Aerosol-Cloud Interactions Change in an Ice-Free Arctic Summer?

NASA Astrophysics Data System (ADS)

Gilgen, Anina; Katty Huang, Wan Ting; Ickes, Luisa; Lohmann, Ulrike

2016-04-01

Future temperatures in the Arctic are expected to increase more than the global mean temperature, which will lead to a pronounced retreat in Arctic sea ice. Before mid-century, most sea ice will likely have vanished in late Arctic summers. This will allow ships to cruise in the Arctic Ocean, e.g. to shorten their transport passage or to extract oil. Since both ships and open water emit aerosol particles and precursors, Arctic clouds and radiation may be affected via aerosol-cloud and cloud-radiation interactions. The change in radiation feeds back on temperature and sea ice retreat. In addition to aerosol particles, also the temperature and the open ocean as a humidity source should have a strong effect on clouds. The main goal of this study is to assess the impact of sea ice retreat on the Arctic climate with focus on aerosol emissions and cloud properties. To this purpose, we conducted ensemble runs with the global climate model ECHAM6-HAM2 under present-day and future (2050) conditions. ECHAM6-HAM2 was coupled with a mixed layer ocean model, which includes a sea ice model. To estimate Arctic aerosol emissions from ships, we used an elaborated ship emission inventory (Peters et al. 2011); changes in aerosol emissions from the ocean are calculated online. Preliminary results show that the sea salt aerosol and the dimethyl sulfide burdens over the Arctic Ocean significantly increase. While the ice water path decreases, the total water path increases. Due to the decrease in surface albedo, the cooling effect of the Arctic clouds becomes more important in 2050. Enhanced Arctic shipping has only a very small impact. The increase in the aersol burden due to shipping is less pronounced than the increase due to natural emissions even if the ship emissions are increased by a factor of ten. Hence, there is hardly an effect on clouds and radiation caused by shipping. References Peters et al. (2011), Atmos. Chem. Phys., 11, 5305-5320

Simulating Climate Change in Ireland

NASA Astrophysics Data System (ADS)

Nolan, P.; Lynch, P.

2012-04-01

At the Meteorology & Climate Centre at University College Dublin, we are using the CLM-Community's COSMO-CLM Regional Climate Model (RCM) and the WRF RCM (developed at NCAR) to simulate the climate of Ireland at high spatial resolution. To address the issue of model uncertainty, a Multi-Model Ensemble (MME) approach is used. The ensemble method uses different RCMs, driven by several Global Climate Models (GCMs), to simulate climate change. Through the MME approach, the uncertainty in the RCM projections is quantified, enabling us to estimate the probability density function of predicted changes, and providing a measure of confidence in the predictions. The RCMs were validated by performing a 20-year simulation of the Irish climate (1981-2000), driven by ECMWF ERA-40 global re-analysis data, and comparing the output to observations. Results confirm that the output of the RCMs exhibit reasonable and realistic features as documented in the historical data record. Projections for the future Irish climate were generated by downscaling the Max Planck Institute's ECHAM5 GCM, the UK Met Office HadGEM2-ES GCM and the CGCM3.1 GCM from the Canadian Centre for Climate Modelling. Simulations were run for a reference period 1961-2000 and future period 2021-2060. The future climate was simulated using the A1B, A2, B1, RCP 4.5 & RCP 8.5 greenhouse gas emission scenarios. Results for the downscaled simulations show a substantial overall increase in precipitation and wind speed for the future winter months and a decrease during the summer months. The predicted annual change in temperature is approximately 1.1°C over Ireland. To date, all RCM projections are in general agreement, thus increasing our confidence in the robustness of the results.

From nuclear power to coal power: Aerosol-induced health and radiative effects

NASA Astrophysics Data System (ADS)

Mielonen, Tero; Laakso, Anton; Karhunen, Anni; Kokkola, Harri; Partanen, Antti-Ilari; Korhonen, Hannele; Romakkaniemi, Sami; Lehtinen, Kari E. J.

2015-12-01

We have investigated what would be the climate and PM-induced air quality consequences if all nuclear reactors worldwide were closed down and replaced by coal combustion. In a way, this presents a "worst-case scenario" since less polluting energy sources are available. We studied simultaneously the radiative and health effects of coal power emissions using a global 3-D aerosol-climate model (ECHAM-HAMMOZ). This approach allowed us to estimate the effects of a major global energy production change from low carbon source to a high carbon one using detailed spatially resolved population density information. We included the radiative effects of both CO2 and PM2.5 but limited the study of health effects to PM2.5 only. Our results show that the replacement of nuclear power with coal power would have globally caused an average of 150,000 premature deaths per year during the period 2005-2009 with two thirds of them in Europe. For 37 years the aerosol emissions from the additional coal power plants would cool the climate but after that the accumulating CO2 emissions would accelerate the warming of the climate.

Potential modulations of pre-monsoon aerosols during El Niño: impact on Indian summer monsoon

NASA Astrophysics Data System (ADS)

Fadnavis, S.; Roy, Chaitri; Sabin, T. P.; Ayantika, D. C.; Ashok, K.

2017-10-01

The potential role of aerosol loading on the Indian summer monsoon rainfall during the El Niño years are examined using satellite-derived observations and a state of the art fully interactive aerosol-chemistry-climate model. The Aerosol Index (AI) from TOMS (1978-2005) and Aerosol Optical Depth (AOD) from MISR spectroradiometer (2000-2010) indicate a higher-than-normal aerosol loading over the Indo-Gangetic plain (IGP) during the pre-monsoon season with a concurrent El Niño. Sensitivity experiments using ECHAM5-HAMMOZ climate model suggests that this enhanced loading of pre-monsoon absorbing aerosols over the Indo-Gangetic plain can reduce the drought during El Niño years by invoking the `Elevated-Heat-Pump' mechanism through an anomalous aerosol-induced warm core in the atmospheric column. This anomalous heating upshot the relative strengthening of the cross-equatorial moisture inflow associated with the monsoon and eventually reduces the severity of drought during El Niño years. The findings are subject to the usual limitations such as the uncertainties in observations, and limited number of El Niño years (during the study period).

Rodent heart failure models do not reflect the human circulating microRNA signature in heart failure.

PubMed

Vegter, Eline L; Ovchinnikova, Ekaterina S; Silljé, Herman H W; Meems, Laura M G; van der Pol, Atze; van der Velde, A Rogier; Berezikov, Eugene; Voors, Adriaan A; de Boer, Rudolf A; van der Meer, Peter

2017-01-01

We recently identified a set of plasma microRNAs (miRNAs) that are downregulated in patients with heart failure in comparison with control subjects. To better understand their meaning and function, we sought to validate these circulating miRNAs in 3 different well-established rat and mouse heart failure models, and correlated the miRNAs to parameters of cardiac function. The previously identified let-7i-5p, miR-16-5p, miR-18a-5p, miR-26b-5p, miR-27a-3p, miR-30e-5p, miR-199a-3p, miR-223-3p, miR-423-3p, miR-423-5p and miR-652-3p were measured by means of quantitative real time polymerase chain reaction (qRT-PCR) in plasma samples of 8 homozygous TGR(mREN2)27 (Ren2) transgenic rats and 8 (control) Sprague-Dawley rats, 6 mice with angiotensin II-induced heart failure (AngII) and 6 control mice, and 8 mice with ischemic heart failure and 6 controls. Circulating miRNA levels were compared between the heart failure animals and healthy controls. Ren2 rats, AngII mice and mice with ischemic heart failure showed clear signs of heart failure, exemplified by increased left ventricular and lung weights, elevated end-diastolic left ventricular pressures, increased expression of cardiac stress markers and reduced left ventricular ejection fraction. All miRNAs were detectable in plasma from rats and mice. No significant differences were observed between the circulating miRNAs in heart failure animals when compared to the healthy controls (all P>0.05) and no robust associations with cardiac function could be found. The previous observation that miRNAs circulate in lower levels in human patients with heart failure could not be validated in well-established rat and mouse heart failure models. These results question the translation of data on human circulating miRNA levels to experimental models, and vice versa the validity of experimental miRNA data for human heart failure.

Climate model biases in jet streams, blocking and storm tracks resulting from missing orographic drag

NASA Astrophysics Data System (ADS)

Pithan, Felix; Shepherd, Theodore G.; Zappa, Giuseppe; Sandu, Irina

2016-07-01

State-of-the art climate models generally struggle to represent important features of the large-scale circulation. Common model deficiencies include an equatorward bias in the location of the midlatitude westerlies and an overly zonal orientation of the North Atlantic storm track. Orography is known to strongly affect the atmospheric circulation and is notoriously difficult to represent in coarse-resolution climate models. Yet how the representation of orography affects circulation biases in current climate models is not understood. Here we show that the effects of switching off the parameterization of drag from low-level orographic blocking in one climate model resemble the biases of the Coupled Model Intercomparison Project Phase 5 ensemble: An overly zonal wintertime North Atlantic storm track and less European blocking events, and an equatorward shift in the Southern Hemispheric jet and increase in the Southern Annular Mode time scale. This suggests that typical circulation biases in coarse-resolution climate models may be alleviated by improved parameterizations of low-level drag.

The Mean State and Inter-annual Variability of East Asian Summer Monsoon in CMIP5 Coupled Models: Does Air-Sea Coupling Improve the Simulations?

NASA Astrophysics Data System (ADS)

Zhou, T.; Song, F.

2014-12-01

The climatology and inter-annual variability of East Asian summer monsoon (EASM) simulated by 34 Coupled Model Intercomparison Project phase 5 (CMIP5) coupled general circulation models (CGCMs) are evaluated. To estimate the role of air-sea coupling, 17 CGCMs are compared to their corresponding atmospheric general circulation models (AGCMs). The climatological low-level monsoon circulation and mei-yu/changma/baiu rainfall band are improved in CGCMs from AGCMs. The improvement is at the cost of the local cold sea surface temperature (SST) biases in CGCMs, since they decrease the surface evaporation and enhance the circulation. The inter-annual EASM pattern is evaluated by a skill formula and the highest/lowest 8 models are selected to investigate the skill origins. The observed Indian Ocean (IO) warming, tropical eastern Indian Ocean (TEIO) rainfall anomalies and Kelvin wave response are captured well in high-skill models, while these features are not present in low-skill models. Further, the differences in the IO warming between high-skill and low-skill models are rooted in the preceding ENSO simulation. Hence, the IO-WPAC teleconnection is important for CGCMs, similar to AGCMs. However, compared to AGCMs, the easterly anomalies in the southern flank of the WPAC make the TEIO warmer in CGCMs by reducing the climatological monsoon westerlies and decreasing the surface evaporation. The warmer TEIO induces the stronger precipitation anomalies and intensifies the teleconnection. Hence, the inter-annual EASM pattern is better simulated in CGCMs than that in AGCMs. Key words: CMIP5, CGCMs, air-sea coupling, AGCMs, inter-annual EASM pattern, ENSO, IO-WPAC teleconnection

An ocean dynamical thermostat—dominant in observations, absent in climate models

NASA Astrophysics Data System (ADS)

Coats, S.; Karnauskas, K. B.

2016-12-01

The pattern of sea surface temperature (SST) in the tropical Pacific Ocean is coupled to the Walker circulation, necessitating an understanding of how this pattern will change in response to anthropogenic radiative forcing. State-of-the-art climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) overwhelmingly project a decrease in the tropical Pacific zonal SST gradient over the coming century. This decrease in the zonal SST gradient is a response of the ocean to a weakening Walker circulation in the CMIP5 models, a consequence of the mass and energy balances of the hydrologic cycle identified by Held and Soden (2006). CMIP5 models, however, are not able to reproduce the observed increase in the zonal SST gradient between 1900-2013 C.E., which we argue to be robust using advanced statistical techniques and new observational datasets. While the observed increase in the zonal SST gradient is suggestive of the ocean dynamical thermostat mechanism of Clement et al. (1996), a strengthening Equatorial Undercurrent (EUC) also contributes to eastern equatorial Pacific cooling. Importantly, the strengthening EUC is a response of the ocean to a seasonal weakening of the Walker circulation and thus can reconcile disparate observations of changes to the atmosphere and ocean in the equatorial Pacific. CMIP5 models do not capture the magnitude of this response of the EUC to anthropogenic radiative forcing potentially because of biases in the sensitivity of the EUC to changes in zonal wind stress, like the weakening Walker circulation. Consequently, they project a continuation of the opposite to what has been observed in the real world, with potentially serious consequences for projected climate impacts that are influenced by the tropical Pacific.

Climate Prediction for Brazil's Nordeste: Performance of Empirical and Numerical Modeling Methods.

NASA Astrophysics Data System (ADS)

Moura, Antonio Divino; Hastenrath, Stefan

2004-07-01

Comparisons of performance of climate forecast methods require consistency in the predictand and a long common reference period. For Brazil's Nordeste, empirical methods developed at the University of Wisconsin use preseason (October January) rainfall and January indices of the fields of meridional wind component and sea surface temperature (SST) in the tropical Atlantic and the equatorial Pacific as input to stepwise multiple regression and neural networking. These are used to predict the March June rainfall at a network of 27 stations. An experiment at the International Research Institute for Climate Prediction, Columbia University, with a numerical model (ECHAM4.5) used global SST information through February to predict the March June rainfall at three grid points in the Nordeste. The predictands for the empirical and numerical model forecasts are correlated at +0.96, and the period common to the independent portion of record of the empirical prediction and the numerical modeling is 1968 99. Over this period, predicted versus observed rainfall are evaluated in terms of correlation, root-mean-square error, absolute error, and bias. Performance is high for both approaches. Numerical modeling produces a correlation of +0.68, moderate errors, and strong negative bias. For the empirical methods, errors and bias are small, and correlations of +0.73 and +0.82 are reached between predicted and observed rainfall.

Effects of trade-wind strength and direction on the leeside circulations and rainfall of the island of Hawaii

Treesearch

Yang Yang; Yi-Leng Chen; Francis M. Fujioka

2009-01-01

The leeside circulations and weather of the island of Hawaii were studied from the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) land surface model simulations for eight strong (∼7.9 m s−1) and eight weak (∼5.2 m s−1) trade-wind days and for five days with southeasterly trades (∼7.1 m s

MUSICA MetOp/IASI {H2O,δD} pair retrieval simulations for validating tropospheric moisture pathways in atmospheric models

NASA Astrophysics Data System (ADS)

Schneider, Matthias; Borger, Christian; Wiegele, Andreas; Hase, Frank; García, Omaira E.; Sepúlveda, Eliezer; Werner, Martin

2017-02-01

The project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) has shown that the sensor IASI aboard the satellite MetOp can measure the free tropospheric {H2O,δD} pair distribution twice per day on a quasi-global scale. Such data are very promising for investigating tropospheric moisture pathways, however, the complex data characteristics compromise their usage in the context of model evaluation studies. Here we present a tool that allows for simulating MUSICA MetOp/IASI {H2O,δD} pair remote sensing data for a given model atmosphere, thereby creating model data that have the remote sensing data characteristics assimilated. This model data can then be compared to the MUSICA data. The retrieval simulation method is based on the physical principles of radiative transfer and we show that the uncertainty of the simulations is within the uncertainty of the MUSICA MetOp/IASI products, i.e. the retrieval simulations are reliable enough. We demonstrate the working principle of the simulator by applying it to ECHAM5-wiso model data. The few case studies clearly reveal the large potential of the MUSICA MetOp/IASI {H2O,δD} data pairs for evaluating modelled moisture pathways. The tool is made freely available in form of MATLAB and Python routines and can be easily connected to any atmospheric water vapour isotopologue model.

Estimates of late Cenozoic climate change relevant to Earth surface processes in tectonically active orogens

NASA Astrophysics Data System (ADS)

Mutz, Sebastian G.; Ehlers, Todd A.; Werner, Martin; Lohmann, Gerrit; Stepanek, Christian; Li, Jingmin

2018-04-01

The denudation history of active orogens is often interpreted in the context of modern climate gradients. Here we address the validity of this approach and ask what are the spatial and temporal variations in palaeoclimate for a latitudinally diverse range of active orogens? We do this using high-resolution (T159, ca. 80 × 80 km at the Equator) palaeoclimate simulations from the ECHAM5 global atmospheric general circulation model and a statistical cluster analysis of climate over different orogens (Andes, Himalayas, SE Alaska, Pacific NW USA). Time periods and boundary conditions considered include the Pliocene (PLIO, ˜ 3 Ma), the Last Glacial Maximum (LGM, ˜ 21 ka), mid-Holocene (MH, ˜ 6 ka), and pre-industrial (PI, reference year 1850). The regional simulated climates of each orogen are described by means of cluster analyses based on the variability in precipitation, 2 m air temperature, the intra-annual amplitude of these values, and monsoonal wind speeds where appropriate. Results indicate the largest differences in the PI climate existed for the LGM and PLIO climates in the form of widespread cooling and reduced precipitation in the LGM and warming and enhanced precipitation during the PLIO. The LGM climate shows the largest deviation in annual precipitation from the PI climate and shows enhanced precipitation in the temperate Andes and coastal regions for both SE Alaska and the US Pacific Northwest. Furthermore, LGM precipitation is reduced in the western Himalayas and enhanced in the eastern Himalayas, resulting in a shift of the wettest regional climates eastward along the orogen. The cluster-analysis results also suggest more climatic variability across latitudes east of the Andes in the PLIO climate than in other time slice experiments conducted here. Taken together, these results highlight significant changes in late Cenozoic regional climatology over the last ˜ 3 Myr. Comparison of simulated climate with proxy-based reconstructions for the MH and LGM reveal satisfactory to good performance of the model in reproducing precipitation changes, although in some cases discrepancies between neighbouring proxy observations highlight contradictions between proxy observations themselves. Finally, we document regions where the largest magnitudes of late Cenozoic changes in precipitation and temperature occur and offer the highest potential for future observational studies that quantify the impact of climate change on denudation and weathering rates.

Direct Radiative Effect of Aerosols Based on PARASOL and OMI Satellite Observations

NASA Technical Reports Server (NTRS)

Lacagnina, Carlo; Hasekamp, Otto P.; Torres, Omar

2017-01-01

Accurate portrayal of the aerosol characteristics is crucial to determine aerosol contribution to the Earth's radiation budget. We employ novel satellite retrievals to make a new measurement-based estimate of the shortwave direct radiative effect of aerosols (DREA), both over land and ocean. Global satellite measurements of aerosol optical depth, single-scattering albedo (SSA), and phase function from PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) are used in synergy with OMI (Ozone Monitoring Instrument) SSA. Aerosol information is combined with land-surface bidirectional reflectance distribution function and cloud characteristics from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite products. Eventual gaps in observations are filled with the state-of-the-art global aerosol model ECHAM5-HAM2. It is found that our estimate of DREA is largely insensitive to model choice. Radiative transfer calculations show that DREA at top-of-atmosphere is -4.6 +/- 1.5 W/sq m for cloud-free and -2.1 +/- 0.7 W/sq m for all-sky conditions, during year 2006. These fluxes are consistent with, albeit generally less negative over ocean than, former assessments. Unlike previous studies, our estimate is constrained by retrievals of global coverage SSA, which may justify different DREA values. Remarkable consistency is found in comparison with DREA based on CERES (Clouds and the Earth's Radiant Energy System) and MODIS observations.

THE ATMOSPHERIC CIRCULATION OF THE HOT JUPITER WASP-43b: COMPARING THREE-DIMENSIONAL MODELS TO SPECTROPHOTOMETRIC DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kataria, Tiffany; Showman, Adam P.; Fortney, Jonathan J.

The hot Jupiter WASP-43b (2 M{sub J}, 1 R{sub J}, T {sub orb} = 19.5 hr) has now joined the ranks of transiting hot Jupiters HD 189733b and HD 209458b as an exoplanet with a large array of observational constraints. Because WASP-43b receives a similar stellar flux as HD 209458b but has a rotation rate four times faster and a higher gravity, studying WASP-43b probes the effect of rotation rate and gravity on the circulation when stellar irradiation is held approximately constant. Here we present three-dimensional (3D) atmospheric circulation models of WASP-43b, exploring the effects of composition, metallicity, and frictional drag. We find thatmore » the circulation regime of WASP-43b is not unlike other hot Jupiters, with equatorial superrotation that yields an eastward-shifted hotspot and large day-night temperature variations (∼600 K at photospheric pressures). We then compare our model results to Hubble Space Telescope (HST)/WFC3 spectrophotometric phase curve measurements of WASP-43b from 1.12 to 1.65 μm. Our results show the 5× solar model light curve provides a good match to the data, with a peak flux phase offset and planet/star flux ratio that is similar to observations; however, the model nightside appears to be brighter. Nevertheless, our 5× solar model provides an excellent match to the WFC3 dayside emission spectrum. This is a major success, as the result is a natural outcome of the 3D dynamics with no model tuning. These results demonstrate that 3D circulation models can help interpret exoplanet atmospheric observations, even at high resolution, and highlight the potential for future observations with HST, James Webb Space Telescope, and other next-generation telescopes.« less

Implications of Water Budget Deficits on Socio-Economic Stability and Food Security in the Arabian Peninsula and in North Africa

NASA Astrophysics Data System (ADS)

Mazzoni, A.; Heggy, E.; Scabbia, G.

2017-12-01

Water scarcity in the Arabian Peninsula and North Africa is accentuated by forecasted climatic variability, decreasing precipitation volumes and projected population growth, urbanization and economic development, increasing water demand. These factors impose uncertainties on food security and socio-economic stability in the region. We develop a water-budget model combining hydrologic, climatic and economic data to quantify water deficit volumes and groundwater depletion rates for the main aquifer systems in the area, taking into account three different climatic scenarios, and calculated from the precipitation forecast elaborated in the CSIRO, ECHAM4 and HADCM3 global circulation models from 2016 to 2050 over 1-year intervals. Water demand comprises water requirements for each economic sector, derived from data such as population, GDP, cropland cover and electricity production, and is based upon the five different SSPs. Conventional and non-conventional water resource supply data are retrieved from FAO Aquastat and institutional databases. Our results suggest that in the next 35 years, in North Africa, only Egypt and Libya will exhibit severe water deficits with respectively 44% and 89.7% of their current water budgets by 2050 (SSP2-AVG climatic scenario), while all the countries in the Arabian Peninsula will be subjected to water stress; the majority of small-size aquifers in the Arabian Peninsula will reach full depletion by 2050. In North Africa, the fossil aquifers' volume loss will be 1-15% by 2050, and total depletion within 200-300 years. Our study suggests that (1) anthropogenic drivers on water resources are harsher than projected climatic variability; (2) the estimated water deficit will induce substantial rise in domestic food production's costs, causing higher dependency on food imports; and (3) projected water deficits will most strongly impact the nations with the lowest GDPP, namely Egypt, Yemen and Libya.

The thermal environment of the human being on the global scale.

PubMed

Jendritzky, Gerd; Tinz, Birger

2009-11-11

The close relationship between human health, performance, well-being and the thermal environment is obvious. Nevertheless, most studies of climate and climate change impacts show amazing shortcomings in the assessment of the environment. Populations living in different climates have different susceptibilities, due to socio-economic reasons, and different customary behavioural adaptations. The global distribution of risks of hazardous thermal exposure has not been analysed before. To produce maps of the baseline and future bioclimate that allows a direct comparison of the differences in the vulnerability of populations to thermal stress across the world. The required climatological data fields are obtained from climate simulations with the global General Circulation Model ECHAM4 in T106-resolution. For the thermo-physiologically relevant assessment of these climate data a complete heat budget model of the human being, the 'Perceived Temperature' procedure has been applied which already comprises adaptation by clothing to a certain degree. Short-term physiological acclimatisation is considered via Health Related Assessment of the Thermal Environment. The global maps 1971-1980 (control run, assumed as baseline climate) show a pattern of thermal stress intensities as frequencies of heat. The heat load for people living in warm-humid climates is the highest. Climate change will lead to clear differences in health-related thermal stress between baseline climate and the future bioclimate 2041-2050 based on the 'business-as-usual' greenhouse gas scenario IS92a. The majority of the world's population will be faced with more frequent and more intense heat strain in spite of an assumed level of acclimatisation. Further adaptation measures are crucial in order to reduce the vulnerability of the populations. This bioclimatology analysis provides a tool for various questions in climate and climate change impact research. Considerations of regional or local scale require climate simulations with higher resolution. As adaptation is the key term in understanding the role of climate/climate change for human health, performance and well-being, further research in this field is crucial.

Role of absorbing aerosols on hot extremes in India in a GCM

NASA Astrophysics Data System (ADS)

Mondal, A.; Sah, N.; Venkataraman, C.; Patil, N.

2017-12-01

Temperature extremes and heat waves in North-Central India during the summer months of March through June are known for causing significant impact in terms of human health, productivity and mortality. While greenhouse gas-induced global warming is generally believed to intensify the magnitude and frequency of such extremes, aerosols are usually associated with an overall cooling, by virtue of their dominant radiation scattering nature, in most world regions. Recently, large-scale atmospheric conditions leading to heat wave and extreme temperature conditions have been analysed for the North-Central Indian region. However, the role of absorbing aerosols, including black carbon and dust, is still not well understood, in mediating hot extremes in the region. In this study, we use 30-year simulations from a chemistry-coupled atmosphere-only General Circulation Model (GCM), ECHAM6-HAM2, forced with evolving aerosol emissions in an interactive aerosol module, along with observed sea surface temperatures, to examine large-scale and mesoscale conditions during hot extremes in India. The model is first validated with observed gridded temperature and reanalysis data, and is found to represent observed variations in temperature in the North-Central region and concurrent large-scale atmospheric conditions during high temperature extremes realistically. During these extreme events, changes in near surface properties include a reduction in single scattering albedo and enhancement in short-wave solar heating rate, compared to climatological conditions. This is accompanied by positive anomalies of black carbon and dust aerosol optical depths. We conclude that the large-scale atmospheric conditions such as the presence of anticyclones and clear skies, conducive to heat waves and high temperature extremes, are exacerbated by absorbing aerosols in North-Central India. Future air quality regulations are expected to reduce sulfate particles and their masking of GHG warming. It is concurrently important to mitigate emissions of warming black carbon particles, to manage future climate change-induced hot extremes.

The impact of aerosol emissions on the 1.5 °C pathways

NASA Astrophysics Data System (ADS)

Hienola, Anca; Partanen, Antti-Ilari; Pietikäinen, Joni-Pekka; O’Donnell, Declan; Korhonen, Hannele; Damon Matthews, H.; Laaksonen, Ari

2018-04-01

To assess the impact of anthropogenic aerosol emission reduction on limiting global temperature increase to 1.5 °C or 2 °C above pre-industrial levels, two climate modeling approaches have been used (MAGICC6, and a combination of ECHAM-HAMMOZ and the UVic ESCM), with two aerosol control pathways under two greenhouse gas (GHG) reduction scenarios. We found that aerosol emission reductions associated with CO2 co-emissions had a significant warming effect during the first half of the century and that the near-term warming is dependent on the pace of aerosol emission reduction. The modeling results show that these aerosol emission reductions account for about 0.5 °C warming relative to 2015, on top of the 1 °C above pre-industrial levels that were already reached in 2015. We found also that the decreases in aerosol emissions lead to different decreases in the magnitude of the aerosol radiative forcing in the two models. By 2100, the aerosol forcing is projected by ECHAM–UVic to diminish in magnitude by 0.96 W m‑2 and by MAGICC6 by 0.76 W m‑2 relative to 2000. Despite this discrepancy, the climate responses in terms of temperature are similar. Aggressive aerosol control due to air quality legislation affects the peak temperature, which is 0.2 °C–0.3 °C above the 1.5 °C limit even within the most ambitious CO2/GHG reduction scenario. At the end of the century, the temperature differences between aerosol reduction scenarios in the context of ambitious CO2 mitigation are negligible.

North Atlantic deep water formation and AMOC in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Wåhlin, Anna

2017-04-01

North Atlantic deep water formation processes and properties in climate models are indicative of their ability to simulate future ocean circulation, ventilation, carbon and heat uptake, and sea level rise. Historical time series of temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to reveal the causes and consequences of North Atlantic deep water formation in models. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. The trigger of deep convection varies among models; for one third it is intense surface cooling only, while the remaining two thirds also need upward mixing of subsurface warm salty water. The models with the most intense deep convection have the most accurate deep water properties, which are warmer and fresher than in the other models. They also have the strongest Atlantic Meridional Overturning Circulation (AMOC). For over half of the models, 40% of the variability of the AMOC is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas, with 3 and 4 years lag respectively. Understanding the dynamical drivers of the AMOC in models is key to realistically forecast a possible slow down and its consequences on the global circulation and marine life.

Southern Hemisphere extratropical circulation: Recent trends and natural variability

NASA Astrophysics Data System (ADS)

Thomas, Jordan L.; Waugh, Darryn W.; Gnanadesikan, Anand

2015-07-01

Changes in the Southern Annular Mode (SAM), Southern Hemisphere (SH) westerly jet location, and magnitude are linked with changes in ocean circulation along with ocean heat and carbon uptake. Recent trends have been observed in these fields but not much is known about the natural variability. Here we aim to quantify the natural variability of the SH extratropical circulation by using Coupled Model Intercomparison Project Phase 5 (CMIP5) preindustrial control model runs and compare with the observed trends in SAM, jet magnitude, and jet location. We show that trends in SAM are due partly to external forcing but are not outside the natural variability as described by these models. Trends in jet location and magnitude, however, lie outside the unforced natural variability but can be explained by a combination of natural variability and the ensemble mean forced trend. These results indicate that trends in these three diagnostics cannot be used interchangeably.

Northern Winter Climate Change: Assessment of Uncertainty in CMIP5 Projections Related to Stratosphere-Troposphere Coupling

NASA Technical Reports Server (NTRS)

Manzini, E.; Karpechko, A.Yu.; Anstey, J.; Shindell, Drew Todd; Baldwin, M.P.; Black, R.X.; Cagnazzo, C.; Calvo, N.; Charlton-Perez, A.; Christiansen, B.;

On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East

NASA Astrophysics Data System (ADS)

Akritidis, Dimitris; Pozzer, Andrea; Zanis, Prodromos; Tyrlis, Evangelos; Škerlak, Bojan; Sprenger, Michael; Lelieveld, Jos

2016-11-01

We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle and lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the southeast and decreasing altitude. We find that the interannual variability of near-surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

Analysis of a general circulation model product. I - Frontal systems in the Brazil/Malvinas and Kuroshio/Oyashio regions

NASA Technical Reports Server (NTRS)

Garzoli, Silvia L.; Garraffo, Zulema; Podesta, Guillermo; Brown, Otis

1992-01-01

The general circulation model (GCM) of Semtner and Chervin (1992) is tested by comparing the fields produced by this model with available observations in two western boundary current regions, the Brazil/Malvinas and the Kuroshio/Oyashio confluences. The two sets of data used are the sea surface temperature from satellite observations and the temperature field product from the GCM at levels 1 (12.5 m), 2 (37.5 m), and 6 (160 m). It is shown that the model reproduces intense thermal fronts at the sea surface and in the upper layers (where they are induced by the internal dynamics of the model). The location of the fronts are reproduced in the model within 4 to 5 deg, compared with observations. However, the variability of these fronts was found to be less pronounced in the model than in the observations.

Eddy Resolving Global Ocean Prediction including Tides

DTIC Science & Technology

2013-09-30

atlantic meridional overturning circulation in the subpolar North Atlantic . Journal of Geophysical Research vol 118, doi:10.1002/jgrc,20065. [published, refereed] ...global ocean circulation model was examined using results from years 2005-2009 of a seven and a half year 1/12.5° global simulation that resolves...internal tides, along with barotropic tides and the eddying general circulation . We examined tidal amplitudes computed using 18 183-day windows that

Interannual to decadal variability of circulation in the northern Japan/East Sea, 1958-2006

NASA Astrophysics Data System (ADS)

Stepanov, Dmitry; Stepanova, Victoriia; Gusev, Anatoly

2015-04-01

We use a numerical ocean model INMOM (Institute of Numerical Mathematics Ocean Model) and atmospheric forcing data extracted from the CORE (Coordinated Ocean Reference Experiments) dataset and reconstruct a circulation in the Japan/East Sea (JES) from 1958 to 2006 and its interannual and decadal variability in the intermediate and abyssal layers in the northern JES. It is founded that the circulation is cyclonic over the course of a climatological year. The circulation increases in spring and decreases in autumn. We analyzes the relative vorticity (RV) averaged over the Japan Basin (JB) and show that the variability is characterized by the interannual oscillations (2.3, 3.7 and 4.7 years) and decadal variability (9.5 and 14.3 years). The spectrum structure of the average RV variability does not change with depth; however, the energy of the decadal oscillations decreases in contrast to that of the interannual oscillations. We analyze monthly anomalies of the wind stress curl and sensible heat flux and reveal that interannual variability (3-4 years) of the circulation over the JB result from 4-year variability of the wind stress curl. In contrast, the decadal variability (period of 9.5 years) of the circulation over the JB is generated by both the wind stress curl and the decadal variability in deep convection.

Astronomically paced middle Eocene deepwater circulation in the western North Atlantic

NASA Astrophysics Data System (ADS)

Vahlenkamp, Maximilian; Niezgodzki, Igor; De Vleeschouwer, David; Bickert, Torsten; Harper, Dustin; Lohmann, Gerrit; Pälike, Heiko; Zachos, James C.

2017-04-01

The role of the Atlantic Meridional Overturning Circulation (AMOC) as a key player for abrupt climatic changes (e.g. Heinrich Stadials) during the Pleistocene is relatively well constrained. However, the timing of the onset of a „modern" North Atlantic Deepwater (NADW) formation are still debated: Recent estimates range from the middle Miocene to the Early Eocene [Davies et al., 2001, Stoker et al., 2005, Hohbein et al., 2012] and are mainly based on the seismic interpretation contourite drifts. Another understudied aspect of the AMOC is its behavior during climatic variations on orbital time scales and under different climatic boundary conditions (icehouse vs hothouse). IODP Expedition 342 drilled carbonate-rich sequences from sediment drifts offshore Newfoundland that cover the middle Eocene with high sedimentation rates ( 3 cm/ kyr). We present a 2 Myr long stable carbon and oxygen isotope record of benthic foraminifera nuttalides truempyi spanning magnetochron C20r in unprecedented resolution (< 2 kyr/sample), sufficient to resolve dominant Milankovic frequencies. Data from Site U1410 (3400m water depth) indicate an active overturning in the North Atlantic during the middle Eocene, sensitively responding to variations in Earth's axial tilt (obliquity). Experiments in a GCM (ECHAM5 - MPIOM, OASIS 3 coupled) indicate that temperatures in the Norwegian and Labrador Sea could have allowed for sea ice during winter in a minimal obliquity setting (22.1°), whereas temperatures are too high to allow sea ice formation under maximum obliquity (24.5°) winter conditions depending on Eocene boundary conditions (atmospheric CO2 concentration). We hypothesize that the combined effect of low temperatures in the sinking areas, an increased latitudinal SST gradient seasonal, and the potential formation of sea ice during obliquity minima results in an initial shallow NADW formation during the middle Eocene. This hypothesis is in accordance with the astronomical imprint observed in the data from IODP Site U1410. Davies, R., Cartwright, J., Pike, J., and Line, C., 2001, Early Oligocene initiation of North Atlantic deep water formation: Nature, v. 410, no. 6831, p. 917-920. Stoker, M. S., Praeg, D., Hjelstuen, B. O., Laberg, J. S., Nielsen, T., and Shannon, P. M., 2005, Neogene stratigraphy and the sedimentary and oceanographic development of the NW European Atlantic margin: Marine and Petroleum Geology, v. 22, no. 9, p. 977-1005. Hohbein, M. W., Sexton, P. F., and Cartwright, J. A., 2012, Onset of North Atlantic Deep Water production coincident with inception of the Cenozoic global cooling trend: Geology, v. 40, no. 3, p. 255-258.

Documentation of a ground hydrology parameterization for use in the GISS atmospheric general circulation model

NASA Technical Reports Server (NTRS)

Lin, J. D.; Aleano, J.; Bock, P.

1978-01-01

The moisture transport processes related to the earth's surface relevant to the ground circulation model GCM are presented. The GHM parametrizations considered are: (1) ground wetness and soil parameters; (2) precipitation; (3) evapotranspiration; (4) surface storage of snow and ice; and (5) runout. The computational aspects of the GHM using computer programs and flow charts are described.

Red Sea circulation during marine isotope stage 5e

NASA Astrophysics Data System (ADS)

Siccha, Michael; Biton, Eli; Gildor, Hezi

2015-04-01

We have employed a regional Massachusetts Institute of Technology oceanic general circulation model of the Red Sea to investigate its circulation during marine isotope stage (MIS) 5e, the peak of the last interglacial, approximately 125 ka before present. Compared to present-day conditions, MIS 5e was characterized by higher Northern Hemisphere summer insolation, accompanied by increases in air temperature of more than 2°C and global sea level approximately 8 m higher than today. As a consequence of the increased seasonality, intensified monsoonal conditions with increased winds, rainfall, and humidity in the Red Sea region are evident in speleothem records and supported by model simulations. To assess the dominant factors responsible for the observed changes, we conducted several sensitivity experiments in which the MIS 5 boundary conditions or forcing parameters were used individually. Overall, our model simulation for the last interglacial maximum reconstructs a Red Sea that is colder, less ventilated and probably more oligotrophic than at present day. The largest alteration in Red Sea circulation and properties was found for the simulation of the northward displacement and intensification of the African tropical rain belt during MIS 5e, leading to a notable increase in the fresh water flux into the Red Sea. Such an increase significantly reduced the Red Sea salinity and exchange volume of the Red Sea with the Gulf of Aden. The Red Sea reacted to the MIS 5e insolation forcing by the expected increase in seasonal sea surface temperature amplitude and overall cooling caused by lower temperatures during deep water formation in winter.

Vegetation and Carbon Cycle Dynamics in the High-Resolution Transient Holocene Simulations Using the MPI Earth System Model

NASA Astrophysics Data System (ADS)

Brovkin, V.; Lorenz, S.; Raddatz, T.; Claussen, M.; Dallmeyer, A.

2017-12-01

One of the interesting periods to investigate a climatic role of terrestrial biosphere is the Holocene, when, despite of the relatively steady global climate, the atmospheric CO2 grew by about 20 ppm from 7 kyr BP to pre-industrial. We use a new setup of the Max Planck Institute Earth System Model MPI-ESM1 consisting of the latest version of the atmospheric model ECHAM6, including the land surface model JSBACH3 with carbon cycle and vegetation dynamics, coupled to the ocean circulation model MPI-OM, which includes the HAMOCC model of ocean biogeochemistry. The model has been run for several simulations over the Holocene period of the last 8000 years under the forcing data sets of orbital insolation, atmospheric greenhouse gases, volcanic aerosols, solar irradiance and stratospheric ozone, as well as land-use changes. In response to this forcing, the land carbon storage increased by about 60 PgC between 8 and 4 kyr BP, stayed relatively constant until 2 kyr BP, and decreased by about 90 PgC by 1850 AD due to land use changes. At 8 kyr BP, vegetation cover was much denser in Africa, mainly due to increased rainfall in response to the orbital forcing. Boreal forests moved northward in both, North America and Eurasia. The boreal forest expansion in North America is much less pronounced than in Eurasia. Simulated physical ocean fields, including surface temperatures and meridional overturning, do not change substantially in the Holocene. Carbonate ion concentration in deep ocean decreases in both, prescribed and interactive CO2simulations. Comparison with available proxies for terrestrial vegetation and for the ocean carbonate chemistry will be presented. Vegetation and soil carbon changes significantly affected atmospheric CO2 during the periods of strong volcanic eruptions. In response to the eruption-caused cooling, the land initially stores more carbon as respiration decreases, but then it releases even more carbon die to productivity decrease. This decadal-scale variability helps to quantify the vegetation and land carbon feedbacks during the past periods when the temporal resolution of the ice-core CO2 record is not sufficient to capture fast CO2 variations. From a set of Holocene simulations with prescribed or interactive atmospheric CO2, we get estimates of climate-carbon feedback useful for future climate studies.

Potential impacts of a future Grand Solar Minimum on decadal regional climate change and interannual hemispherical climate variability

NASA Astrophysics Data System (ADS)

Spiegl, Tobias; Langematz, Ulrike

2016-04-01

The political, technical and socio-economic developments of the next decades will determine the magnitude of 21st century climate change, since they are inextricably linked to future anthropogenic greenhouse gas emissions. To assess the range of uncertainty that is related to these developments, it is common to assume different emission scenarios for 21st climate projections. While the uncertainties associated with the anthropogenic greenhouse gas forcing have been studied intensely, the contribution of natural climate drivers (particularly solar variability) to recent and future climate change are subject of intense debate. The past 1,000 years featured at least 5 excursions (lasting 60-100 years) of exceptionally low solar activity, induced by a weak magnetic field of the Sun, so called Grand Solar Minima. While the global temperature response to such a decrease in solar activity is assumed to be rather small, nonlinear mechanisms in the climate system might amplify the regional temperature signal. This hypothesis is supported by the last Grand Solar Minimum (the Maunder Minimum, 1645-1715) which coincides with the Little Ice Age, an epoch which is characterized by severe cold and hardship over Europe, North America and Asia. The long-lasting minimum of Solar Cycle 23 as well as the overall weak maximum of Cycle 24 reveal the possibility for a return to Grand Solar Minimum conditions within the next decades. The quantification of the implications of such a projected decrease in solar forcing is of ultimate importance, given the on-going public discussion of the role of carbon dioxide emissions for global warming, and the possible role a cooling due to decreasing solar activity could be ascribed to. Since there is still no clear consensus about the actual strength of the Maunder Minimum, we used 3 acknowledged solar reconstruction datasets that show significant differences in both, total solar irradiance (TSI) and spectral irradiance (SSI) to simulate a future Grand Solar Minimum under RCP6.0 conditions. The results obtained were compared to a RCP6.0 simulation that was carried out using the CCMI recommendations for a 21st century solar forcing. We used the ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry-climate model that incorporates interactive ozone chemistry, a high-resolution shortwave radiation scheme, a high model top (0.01 hPa) and is coupled to a 3D ocean general circulation model. We focused on the regional responses to a future Grand Solar Minimum and interannual variability patterns (i.e. the Northern and Southern Annular Mode (NAM/SAM)).

Stratosphere-resolving CMIP5 models simulate different changes in the Southern Hemisphere

NASA Astrophysics Data System (ADS)

Rea, Gloria; Riccio, Angelo; Fierli, Federico; Cairo, Francesco; Cagnazzo, Chiara

2018-03-01

This work documents long-term changes in the Southern Hemisphere circulation in the austral spring-summer season in the Coupled Intercomparison Project Phase 5 models, showing that those changes are larger in magnitude and closer to ERA-Interim and other reanalyses if models include a dynamical representation of the stratosphere. Specifically, models with a high-top and included dynamical and—in some cases—chemical feedbacks within the stratosphere better simulate the lower stratospheric cooling observed over 1979-2001 and strongly driven by ozone depletion, when compared to the other models. This occurs because high-top models can fully capture the stratospheric large scale circulation response to the ozone-induced cooling. Interestingly, this difference is also found at the surface for the Southern Annular Mode (SAM) changes, even though all model categories tend to underestimate SAM trends over those decades. In this analysis, models including a proper dynamical stratosphere are more sensitive to lower stratospheric cooling in their tropospheric circulation response. After a brief discussion of two RCP scenarios, our study confirms that at least for large changes in the extratropical regions, stratospheric changes induced by external forcing have to be properly simulated, as they are important drivers of tropospheric climate variations.

Impact of cloud radiative heating on East Asian summer monsoon circulation

DOE PAGES

Guo, Zhun; Zhou, Tianjun; Wang, Minghuai; ...

2015-07-17

The impacts of cloud radiative heating on East Asian Summer Monsoon (EASM) over the southeastern China (105°-125°E, 20°-35°N) are explained by using the Community Atmosphere Model version 5 (CAM5). Sensitivity experiments demonstrate that the radiative heating of clouds leads to a positive effect on the local EASM circulation over southeastern China. Without the radiative heating of cloud, the EASM circulation and precipitation would be much weaker than that in the normal condition. The longwave heating of clouds dominates the changes of EASM circulation. The positive effect of clouds on EASM circulation is explained by the thermodynamic energy equation, i.e. themore » different heating rate between cloud base and cloud top enhances the convective instability over southeastern China, which enhances updraft consequently. The strong updraft would further result in a southward meridional wind above the center of the updraft through Sverdrup vorticity balance.« less

Implementing microscopic charcoal in a global climate-aerosol model

NASA Astrophysics Data System (ADS)

Gilgen, Anina; Lohmann, Ulrike; Brügger, Sandra; Adolf, Carole; Ickes, Luisa

2017-04-01

Information about past fire activity is crucial to validate fire models and to better understand their deficiencies. Several paleofire records exist, among them ice cores and sediments, which preserve fire tracers like levoglucosan, vanillic acid, or charcoal particles. In this work, we implement microscopic charcoal particles (maximum dimension 10-100 μm) into the global climate-aerosol model ECHAM6.3HAM2.3. Since we are not aware of any reliable estimates of microscopic charcoal emissions, we scaled black carbon emissions from GFAS to capture the charcoal fluxes from a calibration dataset. After that, model results were compared with a validation dataset. The coarse model resolution (T63L31; 1.9°x1.9°) impedes the model to capture local variability of charcoal fluxes. However, variability on the global scale is pronounced due to highly-variable fire emissions. In future, we plan to model charcoal fluxes in the past 1-2 centuries using fire emissions provided from fire models. Furthermore, we intend to compare modelled charcoal fluxes from prescribed fire emissions with those calculated by an interactive fire model.

North Atlantic deep water formation and AMOC in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, Céline

2017-07-01

Deep water formation in climate models is indicative of their ability to simulate future ocean circulation, carbon and heat uptake, and sea level rise. Present-day temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to assess the biases, causes and consequences of North Atlantic deep convection in models. The majority of models convect too deep, over too large an area, too often and too far south. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. Half of the models convect in response to local cooling or salinification of the surface waters; only a third have a dynamic relationship between freshwater coming from the Arctic and deep convection. The models with the most intense deep convection have the warmest deep waters, due to a redistribution of heat through the water column. For the majority of models, the variability of the Atlantic Meridional Overturning Circulation (AMOC) is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas up to 2 years before. In turn, models with the strongest AMOC have the largest heat export to the Arctic. Understanding the dynamical drivers of deep convection and AMOC in models is hence key to realistically forecasting Arctic oceanic warming and its consequences for the global ocean circulation, cryosphere and marine life.

Shock competition and circulation deposition in shock interactions with heavy prolate cylinders

NASA Astrophysics Data System (ADS)

Ray, Jaideep; Samtaney, R.; Zabusky, Norman J.

1998-11-01

We investigate the interaction of a shock wave with elliptical heavier-than-ambient gaseous cylinders. We identify two different modes of interaction between the incident and transmitted shocks on the leeward side of the cylinder which yeild different mechanisms for the baroclinic vorticity generation. We model the net baroclinic circulation generated on the interface by both the shocks and validate the model via numerical simulations of the Euler equations. The principal parameters governing the interaction are the Mach number of the shock (M), the density ratio of the two gases (η, η > 1), λ (the aspect ratio) and the ratio of specific heats of the two gases. We derive a time ratio which uniquely characterizes the mode of interaction. In the range 1.2 <= M <= 3.5, 1.54 <= η <= 5.04 and λ = 1.5 and 3.0, our model predicts circulation within 10 % of the simulation results. Further developments on this topic will be posted on the Web at http://www.caip.rutgers.edu/ ~jaray/ellipse/RM_ellipse.html.

Climatic change impacts on water balance of the Upper Jordan River

NASA Astrophysics Data System (ADS)

Heckl, A.; Kunstmann, H.

2009-04-01

The Eastern Mediterranean and Near East (EM/NE) is an extremely water scarce environment. It is expected that problems will increase due to climate change and population growth. The impact of climate change on water availability in EM/NE and in particular the Jordan River catchment is investigated in this study. Focus is set on the Upper Jordan River catchment (UJC) as it provides 1/3rd of freshwater resources in Israel and Palestine. It is a hydro-geologically extremely complex region with karstic groundwater flow and an orography with steep gradients. The methods used are high resolution coupled regional climate - hydrology simulations. Two IPCC scenarios (A2 and B2) of the global climate model ECHAM4 have been dynamically downscaled using the non-hydrostatic meteorological model MM5 in two nesting steps with resolutions of 54x54 km2 and 18x18 km2 for the period 1961-2099, whereby the time slice 1961-1989 represents the current climate. The meteorological fields are used to drive the physically based hydrological model WaSiM applied to the UJC. The hydrological model computes in detail the surface and subsurface water flow and water balance in a horizontal resolution of 450 x 450 m2 and dynamically couples to a 2-dim numerical groundwater model. Parameters like surface runoff, groundwater recharge, soil moisture and evapotranspiration can be extracted. Results show in both scenarios increasing yearly mean temperatures up to 4-5 K until 2099 and decreasing yearly precipitation amounts up to 25% (scenario A2). The effect on the water balance of the UJC are reduced discharge and groundwater recharge, increased evaporation and reduction of snow cover in the mountains which usually serves as an important freshwater reservoir for the summer discharge.

ENSO-related Interannual Variability of Southern Hemisphere Atmospheric Circulation: Assessment and Projected Changes in CMIP5 Models

NASA Astrophysics Data System (ADS)

Frederiksen, Carsten; Grainger, Simon; Zheng, Xiaogu; Sisson, Janice

2013-04-01

ENSO variability is an important driver of the Southern Hemisphere (SH) atmospheric circulation. Understanding the observed and projected changes in ENSO variability is therefore important to understanding changes in Australian surface climate. Using a recently developed methodology (Zheng et al., 2009), the coherent patterns, or modes, of ENSO-related variability in the SH atmospheric circulation can be separated from modes that are related to intraseasonal variability or to changes in radiative forcings. Under this methodology, the seasonal mean SH 500 hPa geopotential height is considered to consist of three components. These are: (1) an intraseasonal component related to internal dynamics on intraseasonal time scales; (2) a slow-internal component related to internal dynamics on slowly varying (interannual or longer) time scales, including ENSO; and (3) a slow-external component related to external (i.e. radiative) forcings. Empirical Orthogonal Functions (EOFs) are used to represent the modes of variability of the interannual covariance of the three components. An assessment is first made of the modes in models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) dataset for the SH summer and winter seasons in the 20th century. In reanalysis data, two EOFs of the slow component (which includes the slow-internal and slow-external components) have been found to be related to ENSO variability (Frederiksen and Zheng, 2007). In SH summer, the CMIP5 models reproduce the leading ENSO mode very well when the structures of the EOF and the associated SST, and associated variance are considered. There is substantial improvement in this mode when compared with the CMIP3 models shown in Grainger et al. (2012). However, the second ENSO mode in SH summer has a poorly reproduced EOF structure in the CMIP5 models, and the associated variance is generally underestimated. In SH winter, the performance of the CMIP5 models in reproducing the structure and variance is similar for both ENSO modes, with the associated variance being generally underestimated. Projected changes in the modes in the 21st century are then investigated using ensembles of CMIP5 models that reproduce well the 20th century slow modes. The slow-internal and slow-external components are examined separately, allowing the projected changes in the response to ENSO variability to be separated from the response to changes in greenhouse gas concentrations. By using several ensembles, the model-dependency of the projected changes in the ENSO-related slow-internal modes is examined. Frederiksen, C. S., and X. Zheng, 2007: Variability of seasonal-mean fields arising from intraseasonal variability. Part 3: Application to SH winter and summer circulations. Climate Dyn., 28, 849-866. Grainger, S., C. S. Frederiksen, and X. Zheng, 2012: Modes of interannual variability of Southern Hemisphere atmospheric circulation in CMIP3 models: Assessment and Projections. Climate Dyn., in press. Zheng, X., D. M. Straus, C. S. Frederiksen, and S. Grainger, 2009: Potentially predictable patterns of extratropical tropospheric circulation in an ensemble of climate simulations with the COLA AGCM. Quart. J. Roy. Meteor. Soc., 135, 1816-1829.

High resolution simulations on the North Aegean Sea seasonal circulation

NASA Astrophysics Data System (ADS)

Kourafalou, V. H.; Barbopoulos, K.

2003-01-01

The seasonal characteristics of the circulation in the North Aegean Sea are examined with the aid of a climatological type simulation (three-year run with perpetual year forcing) on a fine resolution grid (2.5 km by 2.5 km). The model is based on the Princeton Ocean Model with a parameterisation of plume dynamics that is employed for the input of waters with hydrographic properties that are different than the properties of basin waters, as the Black Sea Water (BSW) outflow through the Dardanelles Strait and riverine sources. The model is nested with a sequence of coarser regional and basin-wide models that provide for the long-term interaction between the study area and the Eastern Mediterranean at large. The results are employed to discuss the response of the North Aegean to the important circulation forcing mechanisms in the region, namely wind stress, heat and salt fluxes, buoyancy due to rivers and the BSW outflow (which is low in salinity and occasionally low in temperature) and the interaction with the Southern Aegean. The high resolution allows for the detailed representation of the complicated topography that presides in the region. This helps produce a rich eddy field and it allows for variability in the pathways of BSW that has implications in the basin hydrography and circulation.

Forcing mechanism of the seasonally asymmetric quasi-biennial oscillation secondary circulation in ERA-40 and MAECHAM5

NASA Astrophysics Data System (ADS)

Peña-Ortiz, C.; Ribera, P.; García-Herrera, R.; Giorgetta, M. A.; García, R. R.

2008-08-01

The seasonality of the quasi-biennial oscillation (QBO) and its secondary circulation is analyzed in the European Reanalysis (ERA-40) and Middle Atmosphere European Centre Hamburg Model (MAECHAM5) general circulation model data sets through the multitaper method-singular value decomposition (MTM-SVD). In agreement with previous studies, the results reveal a strong seasonal dependence of the QBO secondary circulation. This is characterized by a two-cell structure symmetric about the equator during autumn and spring. However, anomalies strongly weaken in the summer hemisphere and strengthen in the winter hemisphere, leading to an asymmetric QBO secondary circulation characterized by a single-cell structure displaced into the winter hemisphere during the solstices. In ERA-40, this asymmetry is more pronounced during the northern than during the southern winter. These results provide the first observation of the QBO secondary circulation asymmetries in the ERA-40 reanalysis data set across the full stratosphere and the lower mesosphere, up to 0.1 hPa. The MTM-SVD reconstruction of the seasonal QBO signals in the residual circulation and the QBO signals in Eliassen Palm (EP) flux divergences suggest a particular mechanism for the seasonal asymmetries of the QBO secondary circulation and its extension across the midlatitudes. The analysis shows that the QBO modulates the EP flux in the winter hemispheric surf zone poleward of the QBO jets. The zonal wind forcing by EP flux divergence is transformed by the Coriolis effect into a meridional wind signal. The seasonality in the stratospheric EP flux and the hemispheric differences in planetary wave forcing cause the observed seasonality in the QBO secondary circulation and its hemispheric differences.

Constrained parameterisation of photosynthetic capacity causes significant increase of modelled tropical vegetation surface temperature

NASA Astrophysics Data System (ADS)

Kattge, J.; Knorr, W.; Raddatz, T.; Wirth, C.

2009-04-01

Photosynthetic capacity is one of the most sensitive parameters of terrestrial biosphere models whose representation in global scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Due to its coupling to stomatal conductance changes in the parameterisation of photosynthetic capacity may potentially influence transpiration rates and vegetation surface temperature. Here, we provide a constrained parameterisation of photosynthetic capacity for different plant functional types in the context of the photosynthesis model proposed by Farquhar et al. (1980), based on a comprehensive compilation of leaf photosynthesis rates and leaf nitrogen content. Mean values of photosynthetic capacity were implemented into the coupled climate-vegetation model ECHAM5/JSBACH and modelled gross primary production (GPP) is compared to a compilation of independent observations on stand scale. Compared to the current standard parameterisation the root-mean-squared difference between modelled and observed GPP is substantially reduced for almost all PFTs by the new parameterisation of photosynthetic capacity. We find a systematic depression of NUE (photosynthetic capacity divided by leaf nitrogen content) on certain tropical soils that are known to be deficient in phosphorus. Photosynthetic capacity of tropical trees derived by this study is substantially lower than standard estimates currently used in terrestrial biosphere models. This causes a decrease of modelled GPP while it significantly increases modelled tropical vegetation surface temperatures, up to 0.8°C. These results emphasise the importance of a constrained parameterisation of photosynthetic capacity not only for the carbon cycle, but also for the climate system.

Maritime Continent seasonal climate biases in AMIP experiments of the CMIP5 multimodel ensemble

NASA Astrophysics Data System (ADS)

Toh, Ying Ying; Turner, Andrew G.; Johnson, Stephanie J.; Holloway, Christopher E.

2018-02-01

The fidelity of 28 Coupled Model Intercomparison Project phase 5 (CMIP5) models in simulating mean climate over the Maritime Continent in the Atmospheric Model Intercomparison Project (AMIP) experiment is evaluated in this study. The performance of AMIP models varies greatly in reproducing seasonal mean climate and the seasonal cycle. The multi-model mean has better skill at reproducing the observed mean climate than the individual models. The spatial pattern of 850 hPa wind is better simulated than the precipitation in all four seasons. We found that model horizontal resolution is not a good indicator of model performance. Instead, a model's local Maritime Continent biases are somewhat related to its biases in the local Hadley circulation and global monsoon. The comparison with coupled models in CMIP5 shows that AMIP models generally performed better than coupled models in the simulation of the global monsoon and local Hadley circulation but less well at simulating the Maritime Continent annual cycle of precipitation. To characterize model systematic biases in the AMIP runs, we performed cluster analysis on Maritime Continent annual cycle precipitation. Our analysis resulted in two distinct clusters. Cluster I models are able to capture both the winter monsoon and summer monsoon shift, but they overestimate the precipitation; especially during the JJA and SON seasons. Cluster II models simulate weaker seasonal migration than observed, and the maximum rainfall position stays closer to the equator throughout the year. The tropics-wide properties of these clusters suggest a connection between the skill of simulating global properties of the monsoon circulation and the skill of simulating the regional scale of Maritime Continent precipitation.

Arctic Ocean Pathways in the 21st century

NASA Astrophysics Data System (ADS)

Aksenov, Yevgeny; van Gennip, Simon J.; Kelly, Stephen J.; Popova, Ekaterina E.; Yool, Andrew

2017-04-01

In the last three decades, changes in the Arctic environment have been occurring at an increasing rate. The opening up of large areas of previously sea ice-covered ocean affects the marine environment with potential impacts on Arctic ecosystems, including through changes in Arctic access, industries and societies. Changes to sea ice and surface winds result in large-scale shifts in ocean circulation and oceanic pathways. This study presents a high-resolution analysis of the projected ocean circulation and pathways of the Arctic water masses across the 21st century. The analysis is based on an eddy-permitting high-resolution global simulation of the ocean general circulation model NEMO (Nucleus for European Modelling of the Ocean) at the 1/4-degree horizontal resolution. The atmospheric forcing is from HadGEM2-ES model output from IPCC Assessment Report 5 (AR5) simulations performed for Coupled Model Intercomparison Project 5 (CMIP5), and follow the Representative Concentration Pathway 8.5 (RCP8.5) scenario. During the 21st century the AO experiences a significant warming, with sea surface temperature increased by in excess of 4 deg. C. Annual mean Arctic sea ice thickness drops to less than 0.5m, and the Arctic Ocean is ice-free in summer from the mid-century. We use an off-line tracer technique to investigate Arctic pathways of the Atlantic and Pacific waters (AW and PW respectively) under this future climate. The AW tracers have been released in the eastern Fram Strait and in the western Barents Sea, whereas the PW tracer has been seeded in the Bering Strait. In the second half of the century the upper 1000 m ocean circulation shows a reduction in the eastward AW flow along the continental slopes towards the Makarov and Canada basins and a deviation of the PW flow away from the Beaufort Sea towards the Siberian coast. Strengthening of Arctic boundary current and intensification of the cyclonic gyre in the Nansen basin of the Arctic Ocean is accompanied by weakening of the current and an anti-cyclonic gyre spin-up in the Makarov Basin. This presents a shift of the Arctic circulation "dipole" and of the Transpolar Drift, with the consequence that the PW flow towards Fram Strait is significantly reduced by the end of the century, weakening the Pacific-Atlantic connection via the Arctic Ocean, and reducing the Arctic freshwater outflow into the North Atlantic. Examination of the simulations suggests that these circulation changes are primarily due to the shift in the wind.

How robust is the atmospheric circulation response to Arctic sea-ice loss in isolation?

NASA Astrophysics Data System (ADS)

Kushner, P. J.; Hay, S. E.; Blackport, R.; McCusker, K. E.; Oudar, T.

2017-12-01

It is now apparent that active dynamical coupling between the ocean and atmosphere determines a good deal of how Arctic sea-ice loss changes the large-scale atmospheric circulation. In coupled ocean-atmosphere models, Arctic sea-ice loss indirectly induces a 'mini' global warming and circulation changes that extend into the tropics and the Southern Hemisphere. Ocean-atmosphere coupling also amplifies by about 50% Arctic free-tropospheric warming arising from sea-ice loss (Deser et al. 2015, 2016). The mechanisms at work and how to separate the response to sea-ice loss from the rest of the global warming process remain poorly understood. Different studies have used distinctive numerical approaches and coupled ocean-atmosphere models to address this problem. We put these studies on comparable footing using pattern scaling (Blackport and Kushner 2017) to separately estimate the part of the circulation response that scales with sea-ice loss in the absence of low-latitude warming from the part that scales with low-latitude warming in the absence of sea-ice loss. We consider well-sampled simulations from three different coupled ocean-atmosphere models (CESM1, CanESM2, CNRM-CM5), in which greenhouse warming and sea-ice loss are driven in different ways (sea ice albedo reduction/transient RCP8.5 forcing for CESM1, nudged sea ice/CO2 doubling for CanESM2, heat-flux forcing/constant RCP8.5-derived forcing for CNRM-CM5). Across these different simulations, surprisingly robust influences of Arctic sea-ice loss on atmospheric circulation can be diagnosed using pattern scaling. For boreal winter, the isolated sea-ice loss effect acts to increase warming in the North American Sub-Arctic, decrease warming of the Eurasian continent, enhance precipitation over the west coast of North America, and strengthen the Aleutian Low and the Siberian High. We will also discuss how Arctic free tropospheric warming might be enhanced via midlatitude ocean surface warming induced by sea-ice loss. Less robust is the part of the response that scales with low-latitude warming, which, depending on the model, can reinforce or cancel the response to sea-ice loss. The extent to which a "tug of war" exists between tropical and high-latitude influences on the general circulation might thus be model dependent.

Evaluating Antarctic sea ice predictability at seasonal to interannual timescales in global climate models

NASA Astrophysics Data System (ADS)

Marchi, Sylvain; Fichefet, Thierry; Goosse, Hugues; Zunz, Violette; Tietsche, Steffen; Day, Jonny; Hawkins, Ed

2016-04-01

Unlike the rapid sea ice losses reported in the Arctic, satellite observations show an overall increase in Antarctic sea ice extent over recent decades. Although many processes have already been suggested to explain this positive trend, it remains the subject of current investigations. Understanding the evolution of the Antarctic sea ice turns out to be more complicated than for the Arctic for two reasons: the lack of observations and the well-known biases of climate models in the Southern Ocean. Irrespective of those issues, another one is to determine whether the positive trend in sea ice extent would have been predictable if adequate observations and models were available some decades ago. This study of Antarctic sea ice predictability is carried out using 6 global climate models (HadGEM1.2, MPI-ESM-LR, GFDL CM3, EC-Earth V2, MIROC 5.2 and ECHAM 6-FESOM) which are all part of the APPOSITE project. These models are used to perform hindcast simulations in a perfect model approach. The predictive skill is estimated thanks to the PPP (Potential Prognostic Predictability) and the ACC (Anomaly Correlation Coefficient). The former is a measure of the uncertainty of the ensemble while the latter assesses the accuracy of the prediction. These two indicators are applied to different variables related to sea ice, in particular the total sea ice extent and the ice edge location. This first model intercomparison study about sea ice predictability in the Southern Ocean aims at giving a general overview of Antarctic sea ice predictability in current global climate models.

Assessment and simulation of global terrestrial latent heat flux by synthesis of CMIP5 climate models and surface eddy covariance observations

Treesearch

Yunjun Yao; Shunlin Liang; Xianglan Li; Shaomin Liu; Jiquan Chen; Xiaotong Zhang; Kun Jia; Bo Jiang; Xianhong Xie; Simon Munier; Meng Liu; Jian Yu; Anders Lindroth; Andrej Varlagin; Antonio Raschi; Asko Noormets; Casimiro Pio; Georg Wohlfahrt; Ge Sun; Jean-Christophe Domec; Leonardo Montagnani; Magnus Lund; Moors Eddy; Peter D. Blanken; Thomas Grunwald; Sebastian Wolf; Vincenzo Magliulo

2016-01-01

The latent heat flux (LE) between the terrestrial biosphere and atmosphere is a major driver of the globalhydrological cycle. In this study, we evaluated LE simulations by 45 general circulation models (GCMs)in the Coupled Model Intercomparison Project Phase 5 (CMIP5) by a comparison...

Clinical CVVH model removes endothelium-derived microparticles from circulation

PubMed Central

Abdelhafeez, Abdelhafeez H.; Jeziorczak, Paul M.; Schaid, Terry R.; Hoefs, Susan L.; Kaul, Sushma; Nanchal, Rahul; Jacobs, Elizabeth R.; Densmore, John C.

2014-01-01

Background Endothelium-derived microparticles (EMPs) are submicron vesicles released from the plasma membrane of endothelial cells in response to injury, apoptosis or activation. We have previously demonstrated EMP-induced acute lung injury (ALI) in animal models and endothelial barrier dysfunction in vitro. Current treatment options for ALI are limited and consist of supportive therapies. We hypothesize that standard clinical continuous venovenous hemofiltration (CVVH) reduces serum EMP levels and may be adapted as a potential therapeutic intervention. Materials and methods EMPs were generated from plasminogen activation inhibitor-1 (PAI-1)-stimulated human umbilical vein endothelial cells (HUVECs). Flow cytometric analysis was used to characterize EMPs as CD31- and annexin V-positive events in a submicron size gate. Enumeration was completed against a known concentration of latex beads. Ultimately, a concentration of ~650,000 EMP/mL perfusate fluid (total 470 mL) was circulated through a standard CVVH filter (pore size 200 μm, flow rate 250 mL/hr) for a period of 70 minutes. 0.5 mL aliquots were removed at 5- to 10-minute intervals for flow cytometric analysis. EMP concentration in the dialysate was measured at the end of 4 hours to better understand the fate of EMPs. Results A progressive decrease in circulating EMP concentration was noted using standard CVVH at 250 mL/hr (a clinical standard rate) from a 470 mL volume modelling a patient's circulation. A 50% reduction was noted within the first 30 minutes. EMPs entering the dialysate after 4 hours were 5.7% of the EMP original concentration. Conclusion These data demonstrate that standard CVVH can remove EMPs from circulation in a circuit modelling a patient. An animal model of hemofiltration with induction of EMP release is required to test the therapeutic potential of this finding and potential of application in early treatment of ALI. PMID:24596654

A Study of the Climate Change during 21st Century over Peninsular Malaysia Watersheds

NASA Astrophysics Data System (ADS)

Kavvas, M. L.; Ercan, A.; Ishida, K.; Chen, Z. R.; Jang, S.; Amin, M. Z. M.; Shaaban, A. J.

2016-12-01

15 coarse-resolution (150 - 300 km) climate projections for the 21st century by 3 different coupled land-atmosphere-ocean GCMs (ECHAM5 of the Max Planck Institute of Meteorology of Germany, CCSM3 of the National Center for Atmospheric Research (NCAR) of the United States, and MRI-CGCM2.3.2 of the Meteorological Research Institute of Japan) under 4 different greenhouse gas emission scenarios (B1, A1B, A2, A1FI) were dynamically downscaled at hourly intervals by a regional hydro-climate model of Peninsular Malaysia (RegHCM-PM) that consisted of Regional Atmospheric Model MM5 that was coupled with WEHY watershed hydrology model over Peninsular Malaysia (PM), at the scale of the hillslopes of 13 selected watersheds (Batu Pahat, Johor, Muda, Kelang, Kelantan, Linggi, Muar, Pahang, Perak, Selangor, Dungun, Kemaman and Kuantan) and 12 selected intervening coastal regions in order to assess the impact of climate change on the climate conditions at the selected watersheds and coastal regions of PM. From the downscaled climate projections it can be concluded that the mean annual precipitation gradually increases toward the end of the 21st century over each of the 13 watersheds and the 12 coastal regions. The basin-average mean annual temperature increases in the range of 2.50C - 2.950C over PM during the 2010 -2100 period when compared to the 1970-2000 historical period. The ensemble average basin-average annual potential evapotranspiration increases gradually throughout the 21st century over all watersheds.

Single-Particle Measurements of Midlatitude Black Carbon and Light-Scattering Aerosols from the Boundary Layer to the Lower Stratosphere

NASA Technical Reports Server (NTRS)

Schwartz, J. P.; Gao, R. S.; Fahey, D. W.; Thomson, D. S.; Watts, L. A.; Wilson, J. C.; Reeves, J. M.; Darbeheshti, M.; Baumgardner, D. G.; Kok, G. L.;

Projected changes of the low-latitude north-western Pacific wind-driven circulation under global warming

NASA Astrophysics Data System (ADS)

Duan, Jing; Chen, Zhaohui; Wu, Lixin

2017-05-01

Based on the outputs of 25 models participating in the Coupled Model Intercomparison Project Phase 5, the projected changes of the wind-driven circulation in the low-latitude north-western Pacific are evaluated. Results demonstrate that there will be a decrease in the mean transport of the North Equatorial Current (NEC), Mindanao Current, and Kuroshio Current in the east of the Philippines, accompanied by a northward shift of the NEC bifurcation Latitude (NBL) off the Philippine coast with over 30% increase in its seasonal south-north migration amplitude. Numerical simulations using a 1.5-layer nonlinear reduced-gravity ocean model show that the projected changes of the upper ocean circulation are predominantly determined by the robust weakening of the north-easterly trade winds and the associated wind stress curl under the El Niño-like warming pattern. The changes in the wind forcing and intensified upper ocean stratification are found equally important in amplifying the seasonal migration of the NBL.

A numerical study of circulation in the Gulf of Riga, Baltic Sea. Part I: Whole-basin gyres and mean currents

NASA Astrophysics Data System (ADS)

Lips, Urmas; Zhurbas, Victor; Skudra, Maris; Väli, Germo

2016-01-01

A regional model of the Gulf of Riga (GoR) with horizontal grid spacing of 0.5 nautical miles was applied to study the features and driving forces of the whole-basin circulation in the GoR. The initial conditions and atmospheric forcing were taken from the operational models High Resolution Operational Model for the Baltic (HIROMB) and High Resolution Limited Area Model (HIRLAM), respectively. The wind stress curl is shown to be a major contributor to the whole-basin circulation pattern. An anticyclonic circulation pattern in the summer is determined by a combined effect of the negative wind stress curl, thermal density stratification and bottom topography. Positive values of the wind stress curl and a cyclonic circulation pattern prevail during the cold period of the year when seasonal thermocline is absent. During calm periods, the anticyclonic type of circulation is established due to a combined effect of the river runoff, saltier water inflow into and mixed water outflow from the GoR. Two seasonal baroclinic jet-like currents are identified in the summer: the Northward Longshore Current in the western GoR and Southward Subsurface Longshore Current in the eastern GoR. The alteration of the circulation pattern in the GoR from cyclonic in the cold period of the year to anticyclonic in the summer, and vice versa, was shown to be observed not every year due to inter-annual variability of wind forcing.

Stratospheric wind errors, initial states and forecast skill in the GLAS general circulation model

NASA Technical Reports Server (NTRS)

Tenenbaum, J.

1983-01-01

Relations between stratospheric wind errors, initial states and 500 mb skill are investigated using the GLAS general circulation model initialized with FGGE data. Erroneous stratospheric winds are seen in all current general circulation models, appearing also as weak shear above the subtropical jet and as cold polar stratospheres. In this study it is shown that the more anticyclonic large-scale flows are correlated with large forecast stratospheric winds. In addition, it is found that for North America the resulting errors are correlated with initial state jet stream accelerations while for East Asia the forecast winds are correlated with initial state jet strength. Using 500 mb skill scores over Europe at day 5 to measure forecast performance, it is found that both poor forecast skill and excessive stratospheric winds are correlated with more anticyclonic large-scale flows over North America. It is hypothesized that the resulting erroneous kinetic energy contributes to the poor forecast skill, and that the problem is caused by a failure in the modeling of the stratospheric energy cycle in current general circulation models independent of vertical resolution.

Influence of North Atlantic modes on European climate extremes

NASA Astrophysics Data System (ADS)

Proemmel, K.; Cubasch, U.

2017-12-01

It is well known that the North Atlantic strongly influences European climate. Only few studies exist that focus on its impact on climate extremes. We are interested in these extremes and the processes and mechanisms behind it. For the analysis of the North Atlantic Oscillation (NAO) we use simulations performed with the Max Planck Institute for Meteorology Earth System Model (MPI-ESM). The NAO has a strong impact especially on European winter and the changes in minimum temperature are even larger than in maximum temperature. The impact of the Atlantic Multi-decadal Variability (AMV) on climate extremes is analyzed in ECHAM6 simulations forced with AMV warm and AMV cold sea surface temperature patterns. We analyze different extreme indices and try to understand the processes.

Reducing the Uncertainty in Atlantic Meridional Overturning Circulation Projections Using Bayesian Model Averaging

NASA Astrophysics Data System (ADS)

Olson, R.; An, S. I.

2016-12-01

Atlantic Meridional Overturning Circulation (AMOC) in the ocean might slow down in the future, which can lead to a host of climatic effects in North Atlantic and throughout the world. Despite improvements in climate models and availability of new observations, AMOC projections remain uncertain. Here we constrain CMIP5 multi-model ensemble output with observations of a recently developed AMOC index to provide improved Bayesian predictions of future AMOC. Specifically, we first calculate yearly AMOC index loosely based on Rahmstorf et al. (2015) for years 1880—2004 for both observations, and the CMIP5 models for which relevant output is available. We then assign a weight to each model based on a Bayesian Model Averaging method that accounts for differential model skill in terms of both mean state and variability. We include the temporal autocorrelation in climate model errors, and account for the uncertainty in the parameters of our statistical model. We use the weights to provide future weighted projections of AMOC, and compare them to un-weighted ones. Our projections use bootstrapping to account for uncertainty in internal AMOC variability. We also perform spectral and other statistical analyses to show that AMOC index variability, both in models and in observations, is consistent with red noise. Our results improve on and complement previous work by using a new ensemble of climate models, a different observational metric, and an improved Bayesian weighting method that accounts for differential model skill at reproducing internal variability. Reference: Rahmstorf, S., Box, J. E., Feulner, G., Mann, M. E., Robinson, A., Rutherford, S., & Schaffernicht, E. J. (2015). Exceptional twentieth-century slowdown in atlantic ocean overturning circulation. Nature Climate Change, 5(5), 475-480. doi:10.1038/nclimate2554

Impact of a statistical bias correction on the projected simulated hydrological changes obtained from three GCMs and two hydrology models

NASA Astrophysics Data System (ADS)

Hagemann, Stefan; Chen, Cui; Haerter, Jan O.; Gerten, Dieter; Heinke, Jens; Piani, Claudio

2010-05-01

Future climate model scenarios depend crucially on their adequate representation of the hydrological cycle. Within the European project "Water and Global Change" (WATCH) special care is taken to couple state-of-the-art climate model output to a suite of hydrological models. This coupling is expected to lead to a better assessment of changes in the hydrological cycle. However, due to the systematic model errors of climate models, their output is often not directly applicable as input for hydrological models. Thus, the methodology of a statistical bias correction has been developed, which can be used for correcting climate model output to produce internally consistent fields that have the same statistical intensity distribution as the observations. As observations, global re-analysed daily data of precipitation and temperature are used that are obtained in the WATCH project. We will apply the bias correction to global climate model data of precipitation and temperature from the GCMs ECHAM5/MPIOM, CNRM-CM3 and LMDZ-4, and intercompare the bias corrected data to the original GCM data and the observations. Then, the orginal and the bias corrected GCM data will be used to force two global hydrology models: (1) the hydrological model of the Max Planck Institute for Meteorology (MPI-HM) consisting of the Simplified Land surface (SL) scheme and the Hydrological Discharge (HD) model, and (2) the dynamic vegetation model LPJmL operated by the Potsdam Institute for Climate Impact Research. The impact of the bias correction on the projected simulated hydrological changes will be analysed, and the resulting behaviour of the two hydrology models will be compared.

Mechanisms and detectability of oxygen depletion in the North Atlantic

NASA Astrophysics Data System (ADS)

Tjiputra, J. F.; Goris, N.; Lauvset, S. K.; Schwinger, J.

2016-12-01

Dissolved oxygen is a key tracer in models used to represent the tight interaction between ocean biogeochemical cycle and circulation. Future ocean warming and stratification are projected, leading to a reduced oxygen concentration. Reduction in export production, in contrast, is projected to increase subsurface concentration by lowering the oxygen consumption during organic matter remineralization. In this exercise, we use a suite of CMIP5 models to study the oxygen evolution under the RCP8.5 scenario focusing on the North Atlantic, a region of rapid and steady circulation change. Most models agree with a large reduction in the deep North Atlantic (north of 40N), whereas an increase is projected in the upper subtropical ocean region. We attribute the former to weakening of the net primary production due to stronger stratification and the latter to less air-sea oxygen flux owing to less ventilation. The models also show that interior oxygen could provide earlier indicator of climate change than surface tracers. Sustained observation of oxygen is therefore crucial to reaffirm the ongoing circulation change due to global warming.

Predicting the Arctic Ocean Environment in the 21st century

NASA Astrophysics Data System (ADS)

Aksenov, Yevgeny; Popova, Ekaterina; Yool, Andrew; Nurser, George

2015-04-01

Recent environmental changes in the Arctic have clearly demonstrated that climate change is faster and more vigorously in the Polar Regions than anywhere else. Significantly, change in the Arctic Ocean (AO) environment presents a variety of impacts, from ecological to social-economic and political. Mitigation of this change and adaptation to it requires detailed and robust environmental predictions. Here we present a detailed projection of ocean circulation and sea ice from the present until 2099, based on an eddy-permitting high-resolution global simulation of the NEMO ¼ degree ocean model. The model is forced at the surface with HadGEM2-ES atmosphere model output from the UK Met. Office IPCC Assessment Report 5 (AR5) Representative Concentration Pathways 8.5 (RCP8.5) scenario. The HadGEM2-ES simulations span 1860-2099 and are one of an ensemble of runs performed for the Coupled Model Intercomparison Project 5 (CMIP5) and IPCC AR5. Between 2000-2009 and 2090-2099 the AO experiences a significant warming, with sea surface temperature increasing on average by about 4° C, particularly in the Barents and Kara Seas, and in the Greenland Sea and Hudson Bay. By the end of the simulation, Arctic sea ice has an average annual thickness of less than 10 cm in the central AO, and less than 0.5 m in the East-Siberian Sea and Canadian Archipelago, and disappears entirely during the Arctic summer. In summer, opening of large areas of the Arctic Ocean to the wind and surface waves leads to the Arctic pack ice cover evolving into the Marginal Ice Zone (MIZ). In winter, sea ice persists until the 2030s; then it sharply declines and disappears from the Central Arctic Ocean by the end of the 21st century, with MIZ provinces remaining in winter along the Siberian, Alaskan coasts and in the Canadian Arctic Archipelago. Analysis of the AO circulation reveals evidence of (i) the reversal of the Arctic boundary currents in the Canadian Basin, from a weak cyclonic current in 2040-2049 to a strong anti-cyclonic current in 2090-2099, and (ii) increased anti-cyclonic surface ocean circulation in the eastern part of the AO, while the surface circulation in the western Arctic becomes more cyclonic. We relate the shift in the circulation to changes in the winds and reduction of sea ice cover, which modify momentum transfer from atmosphere to the ocean. Our simulation suggests a potentially complex picture of future AO change, and highlights the importance of high resolution modelling in forecasting it.

Baroclinic stabilization effect of the Atlantic-Arctic water exchange simulated by the eddy-permitting ocean model and global atmosphere-ocean model

NASA Astrophysics Data System (ADS)

Moshonkin, Sergey; Bagno, Alexey; Gritsun, Andrey; Gusev, Anatoly

2017-04-01

Numerical experiments were performed with the global atmosphere-ocean model INMCM5 (for version of the international project CMIP6, resolution for atmosphere is 2°x1.5°, 21 level) and with the three-dimensional, free surface, sigma coordinate eddy-permitting ocean circulation model for Atlantic (from 30°S) - Arctic and Bering sea domain (0.25 degrees resolution, Institute of Numerical Mathematics Ocean Model or INMOM). Spatial resolution of the INMCM5 oceanic component is 0.5°x0.25°. Both models have 40 s-levels in ocean. Previously, the simulations were carried out for INMCM5 to generate climatic system stable state. Then model was run for 180 years. In the experiment with INMOM, CORE-II data for 1948-2009 were used. As the goal for comparing results of two these numerical models, we selected evolution of the density and velocity anomalies in the 0-300m active ocean layer near Fram Strait in the Greenland Sea, where oceanic cyclonic circulation influences Atlantic-Arctic water exchange. Anomalies were count without climatic seasonal cycle for time scales smaller than 30 years. We use Singular Value Decomposition analysis (SVD) for density-velocity anomalies with time lag from minus one to six months. Both models perform identical stable physical result. They reveal that changes of heat and salt transports by West Spitsbergen and East Greenland currents, caused by atmospheric forcing, produce the baroclinic modes of velocity anomalies in 0-300m layer, thereby stabilizing ocean response on the atmospheric forcing, which stimulates keeping water exchange between the North Atlantic and Arctic Ocean at the certain climatological level. The first SVD-mode of density-velocity anomalies is responsible for the cyclonic circulation variability. The second and third SVD-modes stabilize existing ocean circulation by the anticyclonic vorticity generation. The second and third SVD-modes give 35% of the input to the total dispersion of density anomalies and 16-18% of the input to the total dispersion of velocity anomalies for numerical results as in INMCM5 so in INMOM models. Input to the total dispersion of velocity anomalies for the first SVD-mode is equal to 50% for INMCM5 and only 19% for INMOM. The research was done in the INM RAS. The model INMOM was supported by Russian Foundation for Basic Research (grant №16-05-00534), and the model INMCM was supported by the Russian Scientific Foundation (grant №14-27-00126).

Risk mapping of West Nile virus circulation in Spain, 2015.

PubMed

Sánchez-Gómez, Amaya; Amela, Carmen; Fernández-Carrión, Eduardo; Martínez-Avilés, Marta; Sánchez-Vizcaíno, José Manuel; Sierra-Moros, María José

2017-05-01

West Nile fever is an emergent disease in Europe. The objective of this study was to conduct a predictive risk mapping of West Nile Virus (WNV) circulation in Spain based on historical data of WNV circulation. Areas of Spain with evidence of WNV circulation were mapped based on data from notifications to the surveillance systems and a literature review. A logistic regression-based spatial model was used to assess the probability of WNV circulation. Data were analyzed at municipality level. Mean temperatures of the period from June to October, presence of wetlands and presence of Special Protection Areas for birds were considered as potential predictors. Two predictors of WNV circulation were identified: higher temperature [adjusted odds ratio (AOR) 2.07, 95% CI 1.82-2.35, p<0.01] and presence of wetlands (3.37, 95% CI 1.89-5.99, p<0.01). Model validations indicated good predictions: area under the ROC curve was 0.895 (95% CI 0.870-0.919) for internal validation and 0.895 (95% CI 0.840-0.951) for external validation. This model could support improvements of WNV risk- based surveillance in Spain. The importance of a comprehensive surveillance for WNF, including human, animal and potential vectors is highlighted, which could additionally result in model refinements. Copyright © 2017 Elsevier B.V. All rights reserved.

Large-scale drivers of local precipitation extremes in convection-permitting climate simulations

NASA Astrophysics Data System (ADS)

Chan, Steven C.; Kendon, Elizabeth J.; Roberts, Nigel M.; Fowler, Hayley J.; Blenkinsop, Stephen

2016-04-01

The Met Office 1.5-km UKV convective-permitting models (CPM) is used to downscale present-climate and RCP8.5 60-km HadGEM3 GCM simulations. Extreme UK hourly precipitation intensities increase with local near-surface temperatures and humidity; for temperature, the simulated increase rate for the present-climate simulation is about 6.5% K**-1, which is consistent with observations and theoretical expectations. While extreme intensities are higher in the RCP8.5 simulation as higher temperatures are sampled, there is a decline at the highest temperatures due to circulation and relative humidity changes. Extending the analysis to the broader synoptic scale, it is found that circulation patterns, as diagnosed by MSLP or circulation type, play an increased role in the probability of extreme precipitation in the RCP8.5 simulation. Nevertheless for both CPM simulations, vertical instability is the principal driver for extreme precipitation.

Field estimates of groundwater circulation depths in two mountainous watersheds in the western U.S. and the effect of deep circulation on solute concentrations in streamflow

NASA Astrophysics Data System (ADS)

Frisbee, Marty D.; Tolley, Douglas G.; Wilson, John L.

2017-04-01

Estimates of groundwater circulation depths based on field data are lacking. These data are critical to inform and refine hydrogeologic models of mountainous watersheds, and to quantify depth and time dependencies of weathering processes in watersheds. Here we test two competing hypotheses on the role of geology and geologic setting in deep groundwater circulation and the role of deep groundwater in the geochemical evolution of streams and springs. We test these hypotheses in two mountainous watersheds that have distinctly different geologic settings (one crystalline, metamorphic bedrock and the other volcanic bedrock). Estimated circulation depths for springs in both watersheds range from 0.6 to 1.6 km and may be as great as 2.5 km. These estimated groundwater circulation depths are much deeper than commonly modeled depths suggesting that we may be forcing groundwater flow paths too shallow in models. In addition, the spatial relationships of groundwater circulation depths are different between the two watersheds. Groundwater circulation depths in the crystalline bedrock watershed increase with decreasing elevation indicative of topography-driven groundwater flow. This relationship is not present in the volcanic bedrock watershed suggesting that both the source of fracturing (tectonic versus volcanic) and increased primary porosity in the volcanic bedrock play a role in deep groundwater circulation. The results from the crystalline bedrock watershed also indicate that relatively deep groundwater circulation can occur at local scales in headwater drainages less than 9.0 km2 and at larger fractions than commonly perceived. Deep groundwater is a primary control on streamflow processes and solute concentrations in both watersheds.

The Mpi-M Aerosol Climatology (MAC)

NASA Astrophysics Data System (ADS)

Kinne, S.

2014-12-01

Monthly gridded global data-sets for aerosol optical properties (AOD, SSA and g) and for aerosol microphysical properties (CCN and IN) offer a (less complex) alternate path to include aerosol radiative effects and aerosol impacts on cloud-microphysics in global simulations. Based on merging AERONET sun-/sky-photometer data onto background maps provided by AeroCom phase 1 modeling output and AERONET sun-/the MPI-M Aerosol Climatology (MAC) version 1 was developed and applied in IPCC simulations with ECHAM and as ancillary data-set in satellite-based global data-sets. An updated version 2 of this climatology will be presented now applying central values from the more recent AeroCom phase 2 modeling and utilizing the better global coverage of trusted sun-photometer data - including statistics from the Marine Aerosol network (MAN). Applications include spatial distributions of estimates for aerosol direct and aerosol indirect radiative effects.

The GEOS-5 Atmospheric General Circulation Model: Mean Climate and Development from MERRA to Fortuna

NASA Technical Reports Server (NTRS)

Molod, Andrea; Takacs, Lawrence; Suarez, Max; Bacmeister, Julio; Song, In-Sun; Eichmann, Andrew

2012-01-01

This report is a documentation of the Fortuna version of the GEOS-5 Atmospheric General Circulation Model (AGCM). The GEOS-5 AGCM is currently in use in the NASA Goddard Modeling and Assimilation Office (GMAO) for simulations at a wide range of resolutions, in atmosphere only, coupled ocean-atmosphere, and data assimilation modes. The focus here is on the development subsequent to the version that was used as part of NASA s Modern-Era Retrospective Analysis for Research and Applications (MERRA). We present here the results of a series of 30-year atmosphere-only simulations at different resolutions, with focus on the behavior of the 1-degree resolution simulation. The details of the changes in parameterizations subsequent to the MERRA model version are outlined, and results of a series of 30-year, atmosphere-only climate simulations at 2-degree resolution are shown to demonstrate changes in simulated climate associated with specific changes in parameterizations. The GEOS-5 AGCM presented here is the model used for the GMAO s atmosphere-only and coupled CMIP-5 simulations.

A case study of sea breeze circulation at Thumba Coast through observations and modelling

NASA Astrophysics Data System (ADS)

Kunhikrishnan, P. K.; Ramachandran, Radhika; Alappattu, Denny P.; Kiran Kumar, N. V. P.; Balasubrahamanyam, D.

2006-12-01

A case study of sea breeze circulation at a coastal region Thumba (8.5°N, 76.9°E) was carried out using Doppler Sodar, surface wind, temperature, humidity measurements and radiosonde ascents. The analysis of surface meteorological data showed that the onset of sea breeze on 12th April 2006 was at 0945 hrs. GPS sonde observation over sea at 1425 hrs and Radiosonde observation over land at 1730 showed a well developed sea breeze circulation over Thumba coast by afternoon hours. The vertical extent of sea breeze circulation was ~1000m over sea as well as on land. The Thermal Internal Boundary Layer (TIBL) depth associated with sea breeze circulation was about 400m at 8 km away from coast. The marine mixed layer height was ~500m about 12 km away from the coast. Numerical simulation of sea breeze was made using HRM (High Resolution Model) and compared the results with the observations.

A Forecast Skill Comparison between CliPAS One-Tier and Two-Tier Hindcast Experiments

NASA Astrophysics Data System (ADS)

Lee, J.; Wang, B.; Kang, I.

2006-05-01

A 24-year (1981-2004) MME hindcast experimental dataset is produced under the "Climate Prediction and Its Application to Society" (CliPAS) project sponsored by Korean Meteorological Administration (KMA). This dataset consists of 5 one-tier model systems from National Aeronautics and Space Administration (NASA), National Center for Environmental Prediction (NCEP), Frontier Research Center for Global Change (FRCGC), Seoul National University (SNU), and University of Hawaii (UH) and 5 two-tier model systems from Florida State University (FSU), Geophysical Fluid Dynamic Lab (GFDL), SNU, and UH. Multi-model Ensemble (MME) Forecast skills of seasonal precipitation and atmospheric circulation are compared between CliPAS one-tier and two-tier hindcast experiments for seasonal mean precipitation and atmospheric circulation. For winter prediction, two-tier MME has a comparable skill to one-tier MME. However, it is demonstrated that in the Asian-Australian monsoon (A-AM) heavy precipitation regions, one-tier systems are superior to two-tier systems in summer season. The reason is that inclusion of the local warm pool- monsoon interaction in the one-tier system improves the ENSO teleconnection with monsoon regions. Both one-tier and two-tier MME fail to predict Indian monsoon circulation, while they have a significantly good skill for the broad scale monsoon circulation defined by Webster and Yang index. One-tier system has a much better skill to predict the monsoon circulation over the western North pacific where air-sea interaction plays an important role than two-tier system.

Earth system modelling on system-level heterogeneous architectures: EMAC (version 2.42) on the Dynamical Exascale Entry Platform (DEEP)

NASA Astrophysics Data System (ADS)

Christou, Michalis; Christoudias, Theodoros; Morillo, Julián; Alvarez, Damian; Merx, Hendrik

2016-09-01

We examine an alternative approach to heterogeneous cluster-computing in the many-core era for Earth system models, using the European Centre for Medium-Range Weather Forecasts Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model as a pilot application on the Dynamical Exascale Entry Platform (DEEP). A set of autonomous coprocessors interconnected together, called Booster, complements a conventional HPC Cluster and increases its computing performance, offering extra flexibility to expose multiple levels of parallelism and achieve better scalability. The EMAC model atmospheric chemistry code (Module Efficiently Calculating the Chemistry of the Atmosphere (MECCA)) was taskified with an offload mechanism implemented using OmpSs directives. The model was ported to the MareNostrum 3 supercomputer to allow testing with Intel Xeon Phi accelerators on a production-size machine. The changes proposed in this paper are expected to contribute to the eventual adoption of Cluster-Booster division and Many Integrated Core (MIC) accelerated architectures in presently available implementations of Earth system models, towards exploiting the potential of a fully Exascale-capable platform.

Simulation of the global ocean thermohaline circulation with an eddy-resolving INMIO model configuration

NASA Astrophysics Data System (ADS)

Ushakov, K. V.; Ibrayev, R. A.

2017-11-01

In this paper, the first results of a simulation of the mean World Ocean thermohaline characteristics obtained by the INMIO ocean general circulation model configured with 0.1 degree resolution in a 5-year long numerical experiment following the CORE-II protocol are presented. The horizontal and zonal mean distributions of the solution bias against the WOA09 data are analyzed. The seasonal cycle of heat content at a specified site of the North Atlantic is also discussed. The simulation results demonstrate a clear improvement in the quality of representation of the upper ocean compared to the results of experiments with 0.5 and 0.25 degree model configurations. Some remaining biases of the model solution and possible ways of their overcoming are highlighted.

Major modes of short-term climate variability in the newly developed NUIST Earth System Model (NESM)

NASA Astrophysics Data System (ADS)

Cao, Jian; Wang, Bin; Xiang, Baoqiang; Li, Juan; Wu, Tianjie; Fu, Xiouhua; Wu, Liguang; Min, Jinzhong

2015-05-01

A coupled earth system model (ESM) has been developed at the Nanjing University of Information Science and Technology (NUIST) by using version 5.3 of the European Centre Hamburg Model (ECHAM), version 3.4 of the Nucleus for European Modelling of the Ocean (NEMO), and version 4.1 of the Los Alamos sea ice model (CICE). The model is referred to as NUIST ESM1 (NESM1). Comprehensive and quantitative metrics are used to assess the model's major modes of climate variability most relevant to subseasonal-to-interannual climate prediction. The model's assessment is placed in a multi-model framework. The model yields a realistic annual mean and annual cycle of equatorial SST, and a reasonably realistic precipitation climatology, but has difficulty in capturing the spring-fall asymmetry and monsoon precipitation domains. The ENSO mode is reproduced well with respect to its spatial structure, power spectrum, phase locking to the annual cycle, and spatial structures of the central Pacific (CP)-ENSO and eastern Pacific (EP)-ENSO; however, the equatorial SST variability, biennial component of ENSO, and the amplitude of CP-ENSO are overestimated. The model captures realistic intraseasonal variability patterns, the vertical-zonal structures of the first two leading predictable modes of Madden-Julian Oscillation (MJO), and its eastward propagation; but the simulated MJO speed is significantly slower than observed. Compared with the T42 version, the high resolution version (T159) demonstrates improved simulation with respect to the climatology, interannual variance, monsoon-ENSO lead-lag correlation, spatial structures of the leading mode of the Asian-Australian monsoon rainfall variability, and the eastward propagation of the MJO.

Aerosol-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations

NASA Astrophysics Data System (ADS)

Rotstayn, L. D.; Jeffrey, S. J.; Collier, M. A.; Dravitzki, S. M.; Hirst, A. C.; Syktus, J. I.; Wong, K. K.

2012-02-01

We use a coupled atmosphere-ocean global climate model (CSIRO-Mk3.6) to investigate the roles of different forcing agents as drivers of summer rainfall trends in the Australasian region. Our results suggest that anthropogenic aerosols have contributed to the observed multi-decadal rainfall increase over north-western Australia. As part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), we performed multiple 10-member ensembles of historical climate change, which are analysed for the period 1951-2010. The historical runs include ensembles driven by "all forcings" (HIST), all forcings except anthropogenic aerosols (NO_AA) and forcing only from long-lived greenhouse gases (GHGAS). Anthropogenic aerosol-induced effects in a warming climate are calculated from the difference of HIST minus NO_AA. We also compare a 10-member 21st century ensemble driven by Representative Concentration Pathway 4.5 (RCP4.5). Simulated aerosol-induced rainfall trends over the Indo-Pacific region for austral summer and boreal summer show a distinct contrast. In boreal summer, there is a southward shift of equatorial rainfall, consistent with the idea that anthropogenic aerosols have suppressed Asian monsoonal rainfall, and caused a southward shift of the local Hadley circulation. In austral summer, the aerosol-induced response more closely resembles a westward shift and strengthening of the upward branch of the Walker circulation, rather than a coherent southward shift of regional tropical rainfall. Thus the mechanism by which anthropogenic aerosols may affect Australian summer rainfall is unclear. Focusing on summer rainfall trends over north-western Australia (NWA), we find that CSIRO-Mk3.6 simulates a strong rainfall decrease in RCP4.5, whereas simulated trends in HIST are weak and insignificant during 1951-2010. The weak rainfall trends in HIST are due to compensating effects of different forcing agents: there is a significant decrease in GHGAS, offset by an aerosol-induced increase in HIST minus NO_AA. However, the magnitude of the observed NWA rainfall trend is not captured by the ensemble mean of HIST minus NO_AA, or by 440 unforced 60-yr trends calculated from a 500-yr pre-industrial control run. This suggests that the observed trend includes both a forced and unforced component. We investigate the mechanism of simulated and observed NWA rainfall changes by exploring changes in circulation over the Indo-Pacific region. The key circulation feature associated with the rainfall increase is a lower-tropospheric cyclonic circulation trend off the coast of NWA. In the model, it induces moisture convergence and upward motion over NWA. The cyclonic anomaly is present in trends calculated from HIST minus NO_AA and from reanalyses. Further analysis suggests that the cyclonic circulation trend in HIST minus NO_AA may be initiated as a Rossby wave response to positive convective heating anomalies south of the equator during November, when the aerosol-induced response of the model over the Indian Ocean still resembles that in boreal summer (i.e. a southward shift of equatorial rainfall). The aerosol-induced enhancement of the cyclonic circulation and associated monsoonal rainfall becomes progressively stronger from December to March, suggesting that there is a positive feedback between the source of latent heat (the Australian monsoon) and the cyclonic circulation. CSIRO-Mk3.6 indicates that anthropogenic aerosols may have masked greenhouse gas-induced changes in rainfall over NWA and in circulation over the wider Indo-Pacific region: simulated trends in RCP4.5 resemble a stronger version of those in GHGAS, and are very different from those in HIST. Further research is needed to better understand the mechanisms and the extent to which these findings are model-dependent.

The influence of placental metabolism on fatty acid transfer to the fetus[S

PubMed Central

Perazzolo, Simone; Hirschmugl, Birgit; Wadsack, Christian; Desoye, Gernot; Lewis, Rohan M.; Sengers, Bram G.

2017-01-01

The factors determining fatty acid transfer across the placenta are not fully understood. This study used a combined experimental and computational modeling approach to explore placental transfer of nonesterified fatty acids and identify the rate-determining processes. Isolated perfused human placenta was used to study the uptake and transfer of 13C-fatty acids and the release of endogenous fatty acids. Only 6.2 ± 0.8% of the maternal 13C-fatty acids taken up by the placenta was delivered to the fetal circulation. Of the unlabeled fatty acids released from endogenous lipid pools, 78 ± 5% was recovered in the maternal circulation and 22 ± 5% in the fetal circulation. Computational modeling indicated that fatty acid metabolism was necessary to explain the discrepancy between uptake and delivery of 13C-fatty acids. Without metabolism, the model overpredicts the fetal delivery of 13C-fatty acids 15-fold. Metabolic rate was predicted to be the main determinant of uptake from the maternal circulation. The microvillous membrane had a greater fatty acid transport capacity than the basal membrane. This study suggests that incorporation of fatty acids into placental lipid pools may modulate their transfer to the fetus. Future work needs to focus on the factors regulating fatty acid incorporation into lipid pools. PMID:27913585

Ocean Hydrodynamics Numerical Model in Curvilinear Coordinates for Simulating Circulation of the Global Ocean and its Separate Basins.

NASA Astrophysics Data System (ADS)

Gusev, Anatoly; Diansky, Nikolay; Zalesny, Vladimir

2010-05-01

The original program complex is proposed for the ocean circulation sigma-model, developed in the Institute of Numerical Mathematics (INM), Russian Academy of Sciences (RAS). The complex can be used in various curvilinear orthogonal coordinate systems. In addition to ocean circulation model, the complex contains a sea ice dynamics and thermodynamics model, as well as the original system of the atmospheric forcing implementation on the basis of both prescribed meteodata and atmospheric model results. This complex can be used as the oceanic block of Earth climate model as well as for solving the scientific and practical problems concerning the World ocean and its separate oceans and seas. The developed program complex can be effectively used on parallel shared memory computational systems and on contemporary personal computers. On the base of the complex proposed the ocean general circulation model (OGCM) was developed. The model is realized in the curvilinear orthogonal coordinate system obtained by the conformal transformation of the standard geographical grid that allowed us to locate the system singularities outside the integration domain. The horizontal resolution of the OGCM is 1 degree on longitude, 0.5 degree on latitude, and it has 40 non-uniform sigma-levels in depth. The model was integrated for 100 years starting from the Levitus January climatology using the realistic atmospheric annual cycle calculated on the base of CORE datasets. The experimental results showed us that the model adequately reproduces the basic characteristics of large-scale World Ocean dynamics, that is in good agreement with both observational data and results of the best climatic OGCMs. This OGCM is used as the oceanic component of the new version of climatic system model (CSM) developed in INM RAS. The latter is now ready for carrying out the new numerical experiments on climate and its change modelling according to IPCC (Intergovernmental Panel on Climate Change) scenarios in the scope of the CMIP-5 (Coupled Model Intercomparison Project). On the base of the complex proposed the Pacific Ocean circulation eddy-resolving model was realized. The integration domain covers the Pacific from Equator to Bering Strait. The model horizontal resolution is 0.125 degree and it has 20 non-uniform sigma-levels in depth. The model adequately reproduces circulation large-scale structure and its variability: Kuroshio meandering, ocean synoptic eddies, frontal zones, etc. Kuroshio high variability is shown. The distribution of contaminant was simulated that is admittedly wasted near Petropavlovsk-Kamchatsky. The results demonstrate contaminant distribution structure and provide us understanding of hydrological fields formation processes in the North-West Pacific.

Atmosphere, ocean, and land: Critical gaps in Earth system models

NASA Technical Reports Server (NTRS)

Prinn, Ronald G.; Hartley, Dana

1992-01-01

We briefly review current knowledge and pinpoint some of the major areas of uncertainty for the following fundamental processes: (1) convection, condensation nuclei, and cloud formation; (2) oceanic circulation and its coupling to the atmosphere and cryosphere; (3) land surface hydrology and hydrology-vegetation coupling; (4) biogeochemistry of greenhouse gases; and (5) upper atmospheric chemistry and circulation.

NWP model forecast skill optimization via closure parameter variations

NASA Astrophysics Data System (ADS)

Järvinen, H.; Ollinaho, P.; Laine, M.; Solonen, A.; Haario, H.

2012-04-01

We present results of a novel approach to tune predictive skill of numerical weather prediction (NWP) models. These models contain tunable parameters which appear in parameterizations schemes of sub-grid scale physical processes. The current practice is to specify manually the numerical parameter values, based on expert knowledge. We developed recently a concept and method (QJRMS 2011) for on-line estimation of the NWP model parameters via closure parameter variations. The method called EPPES ("Ensemble prediction and parameter estimation system") utilizes ensemble prediction infra-structure for parameter estimation in a very cost-effective way: practically no new computations are introduced. The approach provides an algorithmic decision making tool for model parameter optimization in operational NWP. In EPPES, statistical inference about the NWP model tunable parameters is made by (i) generating an ensemble of predictions so that each member uses different model parameter values, drawn from a proposal distribution, and (ii) feeding-back the relative merits of the parameter values to the proposal distribution, based on evaluation of a suitable likelihood function against verifying observations. In this presentation, the method is first illustrated in low-order numerical tests using a stochastic version of the Lorenz-95 model which effectively emulates the principal features of ensemble prediction systems. The EPPES method correctly detects the unknown and wrongly specified parameters values, and leads to an improved forecast skill. Second, results with an ensemble prediction system emulator, based on the ECHAM5 atmospheric GCM show that the model tuning capability of EPPES scales up to realistic models and ensemble prediction systems. Finally, preliminary results of EPPES in the context of ECMWF forecasting system are presented.

A world ocean model for greenhouse sensitivity studies: resolution intercomparison and the role of diagnostic forcing

NASA Astrophysics Data System (ADS)

Washington, Warren M.; Meehl, Gerald A.; Verplank, Lynda; Bettge, Thomas W.

1994-05-01

We have developed an improved version of a world ocean model with the intention of coupling to an atmospheric model. This article documents the simulation capability of this 1° global ocean model, shows improvements over our earlier 5° version, and compares it to features simulated with a 0.5° model. These experiments use a model spin-up methodology whereby the ocean model can subsequently be coupled to an atmospheric model and used for order 100-year coupled model integrations. With present-day computers, 1° is a reasonable compromise in resolution that allows for century-long coupled experiments. The 1° ocean model is derived from a 0.5°-resolution model developed by A. Semtner (Naval Postgraduate School) and R. Chervin (National Center for Atmospheric Research) for studies of the global eddy-resolving world ocean circulation. The 0.5° bottom topography and continental outlines have been altered to be compatible with the 1° resolution, and the Arctic Ocean has been added. We describe the ocean simulation characteristics of the 1° version and compare the result of weakly constraining (three-year time scale) the three-dimensional temperature and salinity fields to the observations below the thermocline (710 m) with the model forced only at the top of the ocean by observed annual mean wind stress, temperature, and salinity. The 1° simulations indicate that major ocean circulation patterns are greatly improved compared to the 5° version and are qualitatively reproduced in comparison to the 0.5° version. Using the annual mean top forcing alone in a 100-year simulation with the 1° version preserves the general features of the major observed temperature and salinity structure with most climate drift occurring mainly beneath the thermocline in the first 50 75 years. Because the thermohaline circulation in the 1° version is relatively weak with annual mean forcing, we demonstrate the importance of the seasonal cycle by performing two sensitivity experiments. Results show a dramatic intensification of the meridional overturning circulation (order of magnitude) with perpetual winter surface temperature forcing in the North Atlantic and strong intensification (factor of three) with perpetual early winter temperatures in that region. These effects are felt throughout the Atlantic (particularly an intensified and northward-shifted Gulf Stream outflow). In the Pacific, the temperature gradient strengthens in the thermocline, thus helping counter the systematic error of a thermocline that is too diffuse.

Reduced connection between the East Asian Summer Monsoon and Southern Hemisphere Circulation on interannual timescales under intense global warming

NASA Astrophysics Data System (ADS)

Yu, Tianlei; Guo, Pinwen; Cheng, Jun; Hu, Aixue; Lin, Pengfei; Yu, Yongqiang

2018-03-01

Previous studies show a close relationship between the East Asian Summer Monsoon (EASM) and Southern Hemisphere (SH) circulation on interannual timescales. In this study, we investigate whether this close relationship will change under intensive greenhouse-gas effect by analyzing simulations under two different climate background states: preindustrial era and Representative Concentration Pathway (RCP) 8.5 stabilization from the Community Climate System Model Version 4 (CCSM4). Results show a significantly reduced relationship under stabilized RCP8.5 climate state, such a less correlated EASM with the sea level pressure in the southern Indian Ocean and the SH branch of local Hadley Cell. Further analysis suggests that the collapse of the Atlantic Meridional Overturning Circulation (AMOC) due to this warming leads to a less vigorous northward meridional heat transport, a decreased intertropical temperature contrast in boreal summer, which produces a weaker cross-equatorial Hadley Cell in the monsoonal region and a reduced Interhemispheric Mass Exchange (IME). Since the monsoonal IME acts as a bridge connecting EASM and SH circulation, the reduced IME weakens this connection. By performing freshwater hosing experiment using the Flexible Global Ocean—Atmosphere—Land System model, Grid-point Version 2 (FGOALS-g2), we show a weakened relationship between the EASM and SH circulation as in CCSM4 when AMOC collapses. Our results suggest that a substantially weakened AMOC is the main driver leading to the EASM, which is less affected by SH circulation in the future warmer climate.

Assessment of local and regional climate signals in water stable isotopes and chemistry records from new high resolution shallow ice cores in Adélie Land, Antarctica

NASA Astrophysics Data System (ADS)

Goursaud, Sentia; Masson Delmotte, Valerie; Preunkert, Susanne; Legrand, Michel; Werner, Martin

2017-04-01

Documenting climatic variations in Antarctica is important to characterize natural climate variability and to provide a long-term context for recent changes. For this purpose, ice cores are unique archives providing a variety of proxy records. While water stable isotopes are commonly used to reconstruct past temperatures, their variability may also reflect changes in moisture origin and evaporation conditions. Further information on the origin of air masses can be obtained from aerosols, through the chemical analyses of ice cores. In high accumulation regions, such as the coastal Adélie Land area, the combination of water stable isotope and chemical records is crucial to date ice cores by annual layer counting and assess the associated uncertainty on annual accumulation rates, but may also help to unveil past changes in regional atmospheric circulation. In order to document accumulation in the area from Dumont d'Urville station to the central Antarctic plateau, towards Dome C, the Agence Nationale de la Recherche ASUMA project (Improving the Accuracy of the Surface Mass Balance of Antarctica, 2014-2018) initiated new field campaigns and was successful in obtaining a network of new shallow ice cores in a previously undocumented region. Here, we will present new results from two shallow ice cores drilled in Adélie Land, the S1C1 ice core (67.71 °S, 139.83 °E ,279 m a.s.l.) drilled in January 2007 and the TA192A ice core (66.78 °S, 139.56 °E, 602 m a.s.l.). We have dated the ice cores by combining multi-parameter annual layer counting using major ions and δ18O, as well as reference horizons. This allowed us to estimate very contrasted accumulation rates (respectively 21.8 ± 6.9 cm w.e. y-1 and 73.38±21.9 cm w.e. y-1), averaged respectively over the period from 1946 to 2006 and from 1998 to 2014 . As a result, we have reconstructed annual accumulation rates, isotopic and ion time series, and investigated their characteristics (mean values, trends and periodicities). The high accumulation rates enables us to compare the ice core seasonal variations in δ18O and deuterium excess with outputs from the ECHAM5-wiso atmospheric general circulation model equipped with water stable isotopes and nudged to ERA reanalyses. We have investigated through statistical analyses the relationships between inter-annual variations in our new ice core records with local climatic parameters (near-surface temperature, wind speed and direction, local sea-ice extent), and with large-scale modes of variability (ENSO and PSA2). The first results rule out any significant multi-decadal trend and evidence decadal periodicities already documented in instrumental records. Remarkable years identified in one shallow ice core do not coincide with those identified in the other ice core. No significant correlation with local or regional climate parameters is identified. This suggests that either the ice core signals are dominated by changes in regional atmospheric circulation or that they are strongly affected very local effects of deposition and post deposition, in an area marked by strong katabatic winds.

Modeling tides and their influence on the circulation in Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Wang, Xiaochun; Chao, Yi; Zhang, Hongchun; Farrara, John; Li, Zhijin; Jin, Xin; Park, Kyungeen; Colas, Francois; McWilliams, James C.; Paternostro, Chris; Shum, C. K.; Yi, Yuchan; Schoch, Carl; Olsson, Peter

2013-07-01

In the process of developing a real-time data-assimilating coastal ocean forecasting system for Prince William Sound, Alaska, tidal signal was added to a three-domain nested model for the region. The model, which is configured from the Regional Ocean Modeling System (ROMS), has 40 levels in the vertical direction and horizontal resolutions of 10.6km, 3.6km and 1.2km for its three nested domains, respectively. In the present research, the ROMS tidal solution was validated using data from coastal tide gauges, satellite altimeters, high-frequency coastal radars, and Acoustic Doppler Current Profiler (ADCP) current surveys. The error of barotropic tides, as measured by the total root mean square discrepancy of eight major tidal constituents is 5.3cm, or 5.6% of the tidal sea surface height variability in the open ocean. Along the coastal region, the total discrepancy is 9.6cm, or 8.2% of the tidal sea surface height variability. Model tidal currents agree reasonably well with the observations. The influence of tides on the circulation was also investigated using numerical experiments. Besides tides, other types of forcing fields (heat flux, wind stress, evaporation minus precipitation, and freshwater discharge) were also included in the model. Our results indicate that tides play a significant role in shaping the mean circulation of the region. For the summer months, the tidal residual circulation tends to generate a cyclonic gyre in the central Sound. The net transport into the Sound through Hinchinbrook Entrance is reduced. Tides also increase the mixed layer depth in the Sound, especially during the winter months.

Impacts of Large-Scale Circulation on Convection: A 2-D Cloud Resolving Model Study

NASA Technical Reports Server (NTRS)

Li, X; Sui, C.-H.; Lau, K.-M.

1999-01-01

Studies of impacts of large-scale circulation on convection, and the roles of convection in heat and water balances over tropical region are fundamentally important for understanding global climate changes. Heat and water budgets over warm pool (SST=29.5 C) and cold pool (SST=26 C) were analyzed based on simulations of the two-dimensional cloud resolving model. Here the sensitivity of heat and water budgets to different sizes of warm and cold pools is examined.

Clouds and the extratropical circulation response to global warming in a hierarchy of global atmosphere models

NASA Astrophysics Data System (ADS)

Voigt, A.

2017-12-01

Climate models project that global warming will lead to substantial changes in extratropical jet streams. Yet, many quantitative aspects of warming-induced jet stream changes remain uncertain, and recent work has indicated an important role of clouds and their radiative interactions. Here, I will investigate how cloud-radiative changes impact the zonal-mean extratropical circulation response under global warming using a hierarchy of global atmosphere models. I will first focus on aquaplanet setups with prescribed sea-surface temperatures (SSTs), which reproduce the model spread found in realistic simulations with interactive SSTs. Simulations with two CMIP5 models MPI-ESM and IPSL-CM5A and prescribed clouds show that half of the circulation response can be attributed to cloud changes. The rise of tropical high-level clouds and the upward and poleward movement of midlatitude high-level clouds lead to poleward jet shifts. High-latitude low-level cloud changes shift the jet poleward in one model but not in the other. The impact of clouds on the jet operates via the atmospheric radiative forcing that is created by the cloud changes and is qualitatively reproduced in a dry Held-Suarez model, although the latter is too sensitive because of its simplified treatment of diabatic processes. I will then show that the aquaplanet results also hold when the models are used in a realistic setup that includes continents and seasonality. I will further juxtapose these prescribed-SST simulations with interactive-SST simulations and show that atmospheric and surface cloud-radiative interactions impact the jet poleward jet shifts in about equal measure. Finally, I will discuss the cloud impact on regional and seasonal circulation changes.

Present and future connection of Asian-Pacific Oscillation to large-scale atmospheric circulations and East Asian rainfall: results of CMIP5

NASA Astrophysics Data System (ADS)

Zhou, Botao; Xu, Ying; Shi, Ying

2018-01-01

The summer Asian-Pacific oscillation (APO), one of the major modes of climate variability over the Asian-Pacific sector, has a pronounced effect on variations of large-scale atmospheric circulations and climate. This study evaluated the capability of 30 state-of-the-art climate models among the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating its association with the atmospheric circulations over the Asian-Pacific region and the precipitation over East Asia. Furthermore, their future connections under the RCP8.5 scenario were examined. The evaluation results show that 5 out of 30 climate models can well capture the observed APO-related features in a comprehensive way, including the strengthened South Asian high (SAH), deepened North Pacific trough (NPT) and northward East Asian jet (EAJ) in the upper troposphere; an intensification of the Asian low and the North Pacific subtropical high (NPSH) as well as a northward shift of the western Pacific subtropical high (WPSH) in the lower troposphere; and a decrease in East Asian summer rainfall (EASR) under the positive APO phase. Based on the five CMIP5 models' simulations, the dynamic linkages of the APO to the SAH, NPT, AL, and NPSH are projected to maintain during the second half of the twenty-first century. However, its connection with the EASR tends to reduce significantly. Such a reduction might result from the weakening of the linkage of the APO to the meridional displacement of the EAJ and WPSH as a response to the warming scenario.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Zhun; Zhou, Tianjun; Wang, Minghuai

The impacts of cloud radiative heating on East Asian Summer Monsoon (EASM) over the southeastern China (105°-125°E, 20°-35°N) are explained by using the Community Atmosphere Model version 5 (CAM5). Sensitivity experiments demonstrate that the radiative heating of clouds leads to a positive effect on the local EASM circulation over southeastern China. Without the radiative heating of cloud, the EASM circulation and precipitation would be much weaker than that in the normal condition. The longwave heating of clouds dominates the changes of EASM circulation. The positive effect of clouds on EASM circulation is explained by the thermodynamic energy equation, i.e. themore » different heating rate between cloud base and cloud top enhances the convective instability over southeastern China, which enhances updraft consequently. The strong updraft would further result in a southward meridional wind above the center of the updraft through Sverdrup vorticity balance.« less

Multivariate Bias Correction Procedures for Improving Water Quality Predictions from the SWAT Model

NASA Astrophysics Data System (ADS)

Arumugam, S.; Libera, D.

2017-12-01

Water quality observations are usually not available on a continuous basis for longer than 1-2 years at a time over a decadal period given the labor requirements making calibrating and validating mechanistic models difficult. Further, any physical model predictions inherently have bias (i.e., under/over estimation) and require post-simulation techniques to preserve the long-term mean monthly attributes. This study suggests a multivariate bias-correction technique and compares to a common technique in improving the performance of the SWAT model in predicting daily streamflow and TN loads across the southeast based on split-sample validation. The approach is a dimension reduction technique, canonical correlation analysis (CCA) that regresses the observed multivariate attributes with the SWAT model simulated values. The common approach is a regression based technique that uses an ordinary least squares regression to adjust model values. The observed cross-correlation between loadings and streamflow is better preserved when using canonical correlation while simultaneously reducing individual biases. Additionally, canonical correlation analysis does a better job in preserving the observed joint likelihood of observed streamflow and loadings. These procedures were applied to 3 watersheds chosen from the Water Quality Network in the Southeast Region; specifically, watersheds with sufficiently large drainage areas and number of observed data points. The performance of these two approaches are compared for the observed period and over a multi-decadal period using loading estimates from the USGS LOADEST model. Lastly, the CCA technique is applied in a forecasting sense by using 1-month ahead forecasts of P & T from ECHAM4.5 as forcings in the SWAT model. Skill in using the SWAT model for forecasting loadings and streamflow at the monthly and seasonal timescale is also discussed.

Heat flow in the flanks of the Oceanographer-Hayes segment of the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Le Gal, V.; Lucazeau, F.; Cannat, M.; Battani, A.; Poort, J.; Guichet, X.; Monnin, C.; Fontaine, F. J.; Leroy, S. D.

2016-12-01

It is currently estimated that a third of the oceanic heat loss is due to fluid circulation in the oceanic crust. Besides high and low temperature fluid discharge at ridge axis, off-axis low temperature fluid circulations can affect large volumes of the oceanic crust. Long term investigations of the Eastern Juan de Fuca ridge flank (Hutnak et al.2006) have established a circulation pattern where hydrothermal discharge and recharge occur at basement outcrops and where sediment is mostly impermeable. Here, we present results from the recent Oceanograflu cruise (2013), on the Oceanographer-Hayes segment ridge flanks of the Mid-Atlantic ridge in crust 5 and 12 myrs in age. On both flanks, we obtained 185 temperature gradients and conductivities in-situ, 30 Küllenberg cores (3 to 5 meters long) coupled with temperature gradients in-situ and conductivity measurements onboard. These data are interpreted in terms of heat flow values and are generally lower than the conductive cooling model. Several temperature-depth profiles don't show linear gradients, but rather sigmoid shapes or inverse gradients suggesting superficial circulations through the first meters of sediments. The corresponding heat flow pattern is not similar to the one observed at Juan de Fuca. No systematic links have been observed between basement outcrops and lower or higher heat flow which would point to discharge or recharge sites. Instead, the pattern recalls studies in the North Pond area (Langseth et al.1992), with a clear predominance of low heat flow values over the site. We propose that the North Pond circulation model is applicable to large portions of slow-spreading ridge flanks such as the Atlantic. In this model, seawater cools the uppermost crust below sediments in basins that are typically tens of kms wide, reducing the surface heat flow under cooling model values. Based on subsidence rates, these shallow hydrothermal circulations have a minor impact on the cooling of the diverging plates.

Polycyclic aromatic hydrocarbons - fate and long-range atmospheric transport studied using a global model, EMAC-SVOC

NASA Astrophysics Data System (ADS)

Octaviani, Mega; Tost, Holger; Lammel, Gerhard

2017-04-01

Polycyclic aromatic hydrocarbons (PAHs) are emitted by incomplete combustion from fossil fuel, vehicles, and biomass burning. They may persist in environmental compartments, pose a health hazard and may bio accumulate along food chains. The ECHAM/MESSy Atmospheric Chemistry (EMAC) model had been used to simulate global tropospheric, stratospheric chemistry and climate. In this study, we improve the model to include simulations of the transport and fate of semi-volatile organic compounds (SVOC). The EMAC-SVOC model takes into account essential environmental processes including gas-particle partitioning, dry and wet deposition, chemical and bio-degradation, and volatilization from sea surface, soils, vegetation, and snow. The model was evaluated against observational data in the Arctic, mid-latitudes, and tropics, and further applied to study total environmental lifetime and long-range transport potential (LRTP) of PAHs. We selected four compounds for study, spanning a wide range of volatility, i.e., phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene. Several LRTP indicators were investigated, including the Arctic contamination potential, meridional spreading, and zonal and meridional fluxes to remote regions.

Global-scale combustion sources of organic aerosols: sensitivity to formation and removal mechanisms

NASA Astrophysics Data System (ADS)

Tsimpidi, Alexandra P.; Karydis, Vlassis A.; Pandis, Spyros N.; Lelieveld, Jos

2017-06-01

Organic compounds from combustion sources such as biomass burning and fossil fuel use are major contributors to the global atmospheric load of aerosols. We analyzed the sensitivity of model-predicted global-scale organic aerosols (OA) to parameters that control primary emissions, photochemical aging, and the scavenging efficiency of organic vapors. We used a computationally efficient module for the description of OA composition and evolution in the atmosphere (ORACLE) of the global chemistry-climate model EMAC (ECHAM/MESSy Atmospheric Chemistry). A global dataset of aerosol mass spectrometer (AMS) measurements was used to evaluate simulated primary (POA) and secondary (SOA) OA concentrations. Model results are sensitive to the emission rates of intermediate-volatility organic compounds (IVOCs) and POA. Assuming enhanced reactivity of semi-volatile organic compounds (SVOCs) and IVOCs with OH substantially improved the model performance for SOA. The use of a hybrid approach for the parameterization of the aging of IVOCs had a small effect on predicted SOA levels. The model performance improved by assuming that freshly emitted organic compounds are relatively hydrophobic and become increasingly hygroscopic due to oxidation.

The 0.125 degree finite-volume General Circulation Model on the NASA Columbia Supercomputer: Preliminary Simulations of Mesoscale Vortices

NASA Technical Reports Server (NTRS)

Shen, B.-W.; Atlas, R.; Chern, J.-D.; Reale, O.; Lin, S.-J.; Lee, T.; Chang, J.

2005-01-01

The NASA Columbia supercomputer was ranked second on the TOP500 List in November, 2004. Such a quantum jump in computing power provides unprecedented opportunities to conduct ultra-high resolution simulations with the finite-volume General Circulation Model (fvGCM). During 2004, the model was run in realtime experimentally at 0.25 degree resolution producing remarkable hurricane forecasts [Atlas et al., 2005]. In 2005, the horizontal resolution was further doubled, which makes the fvGCM comparable to the first mesoscale resolving General Circulation Model at the Earth Simulator Center [Ohfuchi et al., 2004]. Nine 5-day 0.125 degree simulations of three hurricanes in 2004 are presented first for model validation. Then it is shown how the model can simulate the formation of the Catalina eddies and Hawaiian lee vortices, which are generated by the interaction of the synoptic-scale flow with surface forcing, and have never been reproduced in a GCM before.)

Improved Understanding of the Modeled QBO Using MLS Observations and MERRA Reanalysis

NASA Technical Reports Server (NTRS)

Oman, Luke David; Douglass, Anne Ritger; Hurwitz, Maggie M.; Garfinkel, Chaim I.

2013-01-01

The Quasi-Biennial Oscillation (QBO) dominates the variability of the tropical stratosphere on interannual time scales. The QBO has been shown to extend its influence into the chemical composition of this region through dynamical mechanisms. We have started our analysis using the realistic QBO internally generated by the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 33 years. We will show targeted comparisons with observations from NASAs Aura satellite Microwave Limb Sounder (MLS) and the Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis to provide insight into the simulation of the primary and secondary circulations associated with the QBO. Using frequency spectrum analysis and multiple linear regression we can illuminate the resulting circulations and deduce the strengths and weaknesses in their modeled representation. Inclusion of the QBO in our simulation improves the representation of the subtropical barriers and overall tropical variability. The QBO impact on tropical upwelling is important to quantify when calculating trends in sub-decadal scale datasets.

Meridional overturning and large-scale circulation of the Indian Ocean

NASA Astrophysics Data System (ADS)

Ganachaud, Alexandre; Wunsch, Carl; Marotzke, Jochem; Toole, John

2000-11-01

The large scale Indian Ocean circulation is estimated from a global hydrographic inverse geostrophic box model with a focus on the meridional overturning circulation (MOC). The global model is based on selected recent World Ocean Circulation Experiment (WOCE) sections which in the Indian Basin consist of zonal sections at 32°S, 20°S and 8°S, and a section between Bali and Australia from the Java-Australia Dynamic Experiment (JADE). The circulation is required to conserve mass, salinity, heat, silica and "PO" (170PO4+O2). Near-conservation is imposed within layers bounded by neutral surfaces, while permitting advective and diffusive exchanges between the layers. Conceptually, the derived circulation is an estimate of the average circulation for the period 1987-1995. A deep inflow into the Indian Basin of 11±4 Sv is found, which is in the lower range of previous estimates, but consistent with conservation requirements and the global data set. The Indonesian Throughflow (ITF) is estimated at 15±5 Sv. The flow in the Mozambique Channel is of the same magnitude, implying a weak net flow between Madagascar and Australia. A net evaporation of -0.6±0.4 Sv is found between 32°S and 8°S, consistent with independent estimates. No net heat gain is found over the Indian Basin (0.1 ± 0.2PW north of 32°S) as a consequence of the large warm water influx from the ITF. Through the use of anomaly equations, the average dianeutral upwelling and diffusion between the sections are required and resolved, with values in the range 1-3×10-5 cm s-1 for the upwelling and 2-10 cm2 s-1 for the diffusivity.

Climate services for an urban area (Baia Mare City, Romania) with a focus on climate extremes

NASA Astrophysics Data System (ADS)

Sima, Mihaela; Micu, Dana; Dragota, Carmen-Sofia; Mihalache, Sorin

2013-04-01

The Baia Mare Urban System is located in the north-western part of Romania, with around 200,000 inhabitants and represents one of the most important former mining areas in the country, whose socioeconomic profile and environmental conditions have greatly changed over the last 20 years during the transition and post-transition period. Currently the mining is closed in the area, but the historical legacy of this activity has implications in terms of economic growth, social and cultural developments and environmental quality. Baia Mare city lies in an extended depression, particularly sheltered by the mountain and hilly regions located in the north and respectively, in the south-south-eastern part of it, which explains the high frequency of calm conditions and low airstream channeling occurrences. This urban system has a typically moderate temperate-continental climate, subject to frequent westerly airflows (moist), which moderate the thermal regime (without depicting severe extremes, both positive and negative) and enhance the precipitation one (entailing a greater frequency of wet extremes). During the reference period (1971-2000), the climate change signal in the area is rather weak and not statistically significant. However, since the mid 1980s, the warming signal became more evident from the observational data (Baia Mare station), showing a higher frequency of dry spells and positive extremes. The modelling experiments covering the 2021-2050 time horizon using regional (RM5.1/HadRM3Q0/RCA3) and global (ARPEGE/HadCM3Q0/BCM/ECHAM5) circulation models carried out within the ECLISE FP7 project suggest an ongoing temperature rise, associated to an intensification of temperature and precipitation extremes. In this context, the aim of this study was to evaluate how the local authorities consider and include climate change in their activity, as well as in the development plans (e.g. territorial, economic and social development plans). Individual interviews have been undertaken with key institutions focusing on environmental, health and urban development issues. The survey was conducted in order to identify the local authorities' perception and needs on climate change information and the importance of climate services for the city and institution's activity. Generally, the results suggest that the selected institutions are poorly aware of the potential impacts of climate change and associated extremes in the area, but they showed a real interest for future climate estimations necessary to undertake reliable adaptation measures. At institutional level, do not exist specialized departments (job positions) to tackle or manage climate information and climate-related aspects, this not being a pressing or priority issue for the city. The climate services aspects are seen with interest mainly in supplying climate scenarios and models for a relatively short term (next 10 or 15 years), the climate information being in this way included in the local planning strategies.

Bathymetric Changes Shaped by Longshore Currents on a Natural Beach

NASA Astrophysics Data System (ADS)

Reilly, W. L.; Slinn, D.; Plant, N.

2004-12-01

The goal of the project is to simulate beach morphology on time scales of hours to days. Our approach is to develop finite difference solutions from a coupled modeling system consisting of existing nearshore circulation, wave, and sediment flux models. We initialize the model with bathymetry from a dense data set north of the pier at the Field Research Facility (FRF) in Duck, NC. We integrate the model system forward in time and compare the results of the hind-cast of the beach evolution with the field observations. The model domain extends 1000 meters in the alongshore direction and 500 meters in the cross-shore direction with 5 meter grid spacing. The bathymetry is interpolated and filtered from CRAB transects. A second-degree exponential smoothing method is used to return the cross-shore beach profile near the edges of the modeled domain back to the mean alongshore profile, because the circulation model implements periodic boundary conditions in the alongshore direction. The offshore wave height and direction are taken from the 8-meter bipod at the FRF and input to the wave-model, SWAN (Spectral Wave Nearshore), with a Gaussian-shaped frequency spectrum and a directional spreading of 5 degrees. A constant depth induced wave breaking parameter of 0.73 is used. The resulting calculated wave induced force per unit surface area (gradient of the radiation stress) output from SWAN is used to drive the currents in the circulation model. The circulation model is based on the free-surface non-linear shallow water equations and uses the fourth order compact scheme to calculate spatial derivatives and a third order Adams-Bashforth time discretization scheme. Free slip, symmetry boundary conditions are applied at both the shoreline and offshore boundaries. The time averaged sediment flux is calculated at each location after one hour of circulation. The sediment flux model is based on the approach of Bagnold and includes approximations for both bed-load and suspended load. The bathymetry is then updated by computing the divergence of the time averaged sediment fluxes. The process is then repeated using the updated bathymetry in both SWAN and the circulation model. The cycle continues for a simulation of 10 hours. The results of bathymetric change vary for different time-dependent wave conditions and initial bathymetric profiles. Typical results indicate that for wave heights on the order of one meter, shoreline advancement and sandbar evolution is observed on the order of tens of centimeters.

The impact of resolution on the dynamics of the martian global atmosphere: Varying resolution studies with the MarsWRF GCM

NASA Astrophysics Data System (ADS)

Toigo, Anthony D.; Lee, Christopher; Newman, Claire E.; Richardson, Mark I.

2012-09-01

We investigate the sensitivity of the circulation and thermal structure of the martian atmosphere to numerical model resolution in a general circulation model (GCM) using the martian implementation (MarsWRF) of the planetWRF atmospheric model. We provide a description of the MarsWRF GCM and use it to study the global atmosphere at horizontal resolutions from 7.5° × 9° to 0.5° × 0.5°, encompassing the range from standard Mars GCMs to global mesoscale modeling. We find that while most of the gross-scale features of the circulation (the rough location of jets, the qualitative thermal structure, and the major large-scale features of the surface level winds) are insensitive to horizontal resolution over this range, several major features of the circulation are sensitive in detail. The northern winter polar circulation shows the greatest sensitivity, showing a continuous transition from a smooth polar winter jet at low resolution, to a distinct vertically “split” jet as resolution increases. The separation of the lower and middle atmosphere polar jet occurs at roughly 10 Pa, with the split jet structure developing in concert with the intensification of meridional jets at roughly 10 Pa and above 0.1 Pa. These meridional jets appear to represent the separation of lower and middle atmosphere mean overturning circulations (with the former being consistent with the usual concept of the “Hadley cell”). Further, the transition in polar jet structure is more sensitive to changes in zonal than meridional horizontal resolution, suggesting that representation of small-scale wave-mean flow interactions is more important than fine-scale representation of the meridional thermal gradient across the polar front. Increasing the horizontal resolution improves the match between the modeled thermal structure and the Mars Climate Sounder retrievals for northern winter high latitudes. While increased horizontal resolution also improves the simulation of the northern high latitudes at equinox, even the lowest model resolution considered here appears to do a good job for the southern winter and southern equinoctial pole (although in detail some discrepancies remain). These results suggest that studies of the northern winter jet (e.g., transient waves and cyclogenesis) will be more sensitive to global model resolution that those of the south (e.g., the confining dynamics of the southern polar vortex relevant to studies of argon transport). For surface winds, the major effect of increased horizontal resolution is in the superposition of circulations forced by local-scale topography upon the large-scale surface wind patterns. While passive predictions of dust lifting are generally insensitive to model horizontal resolution when no lifting threshold is considered, increasing the stress threshold produces significantly more lifting in higher resolution simulations with the generation of finer-scale, higher-stress winds due primarily to better-resolved topography. Considering the positive feedbacks expected for radiatively active dust lifting, we expect this bias to increase when such feedbacks are permitted.

Chemistry-Climate Interactions in the Goddard Institute for Space Studies General Circulation Model. 2; New Insights into Modeling the Pre-Industrial Atmosphere

NASA Technical Reports Server (NTRS)

Grenfell, J. Lee; Shindell, D. T.; Koch, D.; Rind, D.; Hansen, James E. (Technical Monitor)

2002-01-01

We investigate the chemical (hydroxyl and ozone) and dynamical response to changing from present day to pre-industrial conditions in the Goddard Institute for Space Studies General Circulation Model (GISS GMC). We identify three main improvements not included by many other works. Firstly, our model includes interactive cloud calculations. Secondly we reduce sulfate aerosol which impacts NOx partitioning hence Ox distributions. Thirdly we reduce sea surface temperatures and increase ocean ice coverage which impact water vapor and ground albedo respectively. Changing the ocean data (hence water vapor and ozone) produces a potentially important feedback between the Hadley circulation and convective cloud cover. Our present day run (run 1, control run) global mean OH value was 9.8 x 10(exp 5) molecules/cc. For our best estimate of pre-industrial conditions run (run 2) which featured modified chemical emissions, sulfate aerosol and sea surface temperatures/ocean ice, this value changed to 10.2 x 10(exp 5) molecules/cc. Reducing only the chemical emissions to pre-industrial levels in run 1 (run 3) resulted in this value increasing to 10.6 x 10(exp 5) molecules/cc. Reducing the sulfate in run 3 to pre-industrial levels (run 4) resulted in a small increase in global mean OH (10.7 x 10(exp 5) molecules/cc). Changing the ocean data in run 4 to pre-industrial levels (run 5) led to a reduction in this value to 10.3 x 10(exp 5) molecules/cc. Mean tropospheric ozone burdens were 262, 181, 180, 180, and 182 Tg for runs 1-5 respectively.

Timeslice experiments for understanding regional climate projections: applications to the tropical hydrological cycle and European winter circulation

NASA Astrophysics Data System (ADS)

Chadwick, Robin; Douville, Hervé; Skinner, Christopher B.

2017-11-01

A set of atmosphere-only timeslice experiments are described, designed to examine the processes that cause regional climate change and inter-model uncertainty in coupled climate model responses to CO_2 forcing. The timeslice experiments are able to reproduce the pattern of regional climate change in the coupled models, and are applied here to two cases where inter-model uncertainty in future projections is large: the tropical hydrological cycle, and European winter circulation. In tropical forest regions, the plant physiological effect is the largest cause of hydrological cycle change in the two models that represent this process. This suggests that the CMIP5 ensemble mean may be underestimating the magnitude of water cycle change in these regions, due to the inclusion of models without the plant effect. SST pattern change is the dominant cause of precipitation and circulation change over the tropical oceans, and also appears to contribute to inter-model uncertainty in precipitation change over tropical land regions. Over Europe and the North Atlantic, uniform SST increases drive a poleward shift of the storm-track. However this does not consistently translate into an overall polewards storm-track shift, due to large circulation responses to SST pattern change, which varies across the models. Coupled model SST biases influence regional rainfall projections in regions such as the Maritime Continent, and so projections in these regions should be treated with caution.

Shaping climate change in the North Atlantic sector: The role of the atmospheric response to local SST changes vs. large-scale changes

NASA Astrophysics Data System (ADS)

Hand, Ralf; Keenlyside, Noel; Omrani, Nour-Eddine; Greatbatch, Richard; Bader, Jürgen

2017-04-01

Climate change simulations robustly show a warming hole in the sub-polar North Atlantic that results from slowing of the AMOC countering the global warming signal. Here we investigate how the distinct SST spatial structures, which include a sharpening of the Gulf Stream SST gradients, influence climate change in the NA sector in winter. For this we analyse the RCP8.5 scenario simulation of the MPI Earth System Model. Additional sensitivity experiments with the atmospheric model component, ECHAM5, are performed to deconstruct the effect of the local spatial structure of the SST change from those arising from large-scale warming of the ocean, remote SST pattern changes and changed radiative forcings. The MPI model simulation shows a signifcant decrease in precipitation to the south of the GS extension region in the future, despite a strong increase in underlying SST. While directly to the north there is a significant increase in precipitation. These distinct features in the precipitation response over the North Atlantic result from the local SST. Over the Gulf Stream, the differential structure of the precipitation changes reflects the changes of the local SST gradients there. Over the subpolar gyre the increase in precipitation is partly suppressed. In this region the Subpolar Gyre the weakened AMOC causes a SST warming, that is much weaker than the warming other regions of the ocean show at the same latitude. The large-scale response, which includes the overall increase in precipitation over the NA is due to the overall warming, remote SSTs and/or directly connected to the radiative forcing.

Projected changes to South Atlantic boundary currents and confluence region in the CMIP5 models: the role of wind and deep ocean changes

NASA Astrophysics Data System (ADS)

Pontes, G. M.; Gupta, A. Sen; Taschetto, A. S.

2016-09-01

The South Atlantic (SA) circulation plays an important role in the oceanic teleconnections from the Indian, Pacific and Southern oceans to the North Atlantic, with inter-hemispheric exchanges of heat and salt. Here, we show that the large-scale features of the SA circulation are projected to change significantly under ‘business as usual’ greenhouse gas increases. Based on 19 models from the Coupled Model Intercomparison Project phase 5 there is a projected weakening in the upper ocean interior transport (<1000 m) between 15° and ˜32°S, largely related to a weakening of the wind stress curl over this region. The reduction in ocean interior circulation is largely compensated by a decrease in the net deep southward ocean transport (>1000 m), mainly related to a decrease in the North Atlantic deep water transport. Between 30° and 40°S, there is a consistent projected intensification in the Brazil current strength of about 40% (30%-58% interquartile range) primarily compensated by an intensification of the upper interior circulation across the Indo-Atlantic basin. The Brazil-Malvinas confluence is projected to shift southwards, driven by a weakening of the Malvinas current. Such a change could have important implications for the distribution of marine species in the southwestern SA in the future.

Trend estimates of AERONET-observed and model-simulated AOT percentiles between 1993 and 2013

NASA Astrophysics Data System (ADS)

Yoon, Jongmin; Pozzer, Andrea; Chang, Dong Yeong; Lelieveld, Jos

2016-04-01

Recent Aerosol Optical thickness (AOT) trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope±2σ = 0.75 ± 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires.

HEPPA-II model-measurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008-2009

NASA Astrophysics Data System (ADS)

Funke, Bernd; Ball, William; Bender, Stefan; Gardini, Angela; Harvey, V. Lynn; Lambert, Alyn; López-Puertas, Manuel; Marsh, Daniel R.; Meraner, Katharina; Nieder, Holger; Päivärinta, Sanna-Mari; Pérot, Kristell; Randall, Cora E.; Reddmann, Thomas; Rozanov, Eugene; Schmidt, Hauke; Seppälä, Annika; Sinnhuber, Miriam; Sukhodolov, Timofei; Stiller, Gabriele P.; Tsvetkova, Natalia D.; Verronen, Pekka T.; Versick, Stefan; von Clarmann, Thomas; Walker, Kaley A.; Yushkov, Vladimir

2017-03-01

We compare simulations from three high-top (with upper lid above 120 km) and five medium-top (with upper lid around 80 km) atmospheric models with observations of odd nitrogen (NOx = NO + NO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, and SMR on Odin) during the Northern Hemisphere (NH) polar winter 2008/2009. The models included in the comparison are the 3-D chemistry transport model 3dCTM, the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the modelling tools for SOlar Climate Ozone Links studies (SOCOL and CAO-SOCOL), and the Whole Atmosphere Community Climate Model (WACCM4). The comparison focuses on the energetic particle precipitation (EPP) indirect effect, that is, the polar winter descent of NOx largely produced by EPP in the mesosphere and lower thermosphere. A particular emphasis is given to the impact of the sudden stratospheric warming (SSW) in January 2009 and the subsequent elevated stratopause (ES) event associated with enhanced descent of mesospheric air. The chemistry climate model simulations have been nudged toward reanalysis data in the troposphere and stratosphere while being unconstrained above. An odd nitrogen upper boundary condition obtained from MIPAS observations has further been applied to medium-top models. Most models provide a good representation of the mesospheric tracer descent in general, and the EPP indirect effect in particular, during the unperturbed (pre-SSW) period of the NH winter 2008/2009. The observed NOx descent into the lower mesosphere and stratosphere is generally reproduced within 20 %. Larger discrepancies of a few model simulations could be traced back either to the impact of the models' gravity wave drag scheme on the polar wintertime meridional circulation or to a combination of prescribed NOx mixing ratio at the uppermost model layer and low vertical resolution. In March-April, after the ES event, however, modelled mesospheric and stratospheric NOx distributions deviate significantly from the observations. The too-fast and early downward propagation of the NOx tongue, encountered in most simulations, coincides with a temperature high bias in the lower mesosphere (0.2-0.05 hPa), likely caused by an overestimation of descent velocities. In contrast, upper-mesospheric temperatures (at 0.05-0.001 hPa) are generally underestimated by the high-top models after the onset of the ES event, being indicative for too-slow descent and hence too-low NOx fluxes. As a consequence, the magnitude of the simulated NOx tongue is generally underestimated by these models. Descending NOx amounts simulated with medium-top models are on average closer to the observations but show a large spread of up to several hundred percent. This is primarily attributed to the different vertical model domains in which the NOx upper boundary condition is applied. In general, the intercomparison demonstrates the ability of state-of-the-art atmospheric models to reproduce the EPP indirect effect in dynamically and geomagnetically quiescent NH winter conditions. The encountered differences between observed and simulated NOx, CO, and temperature distributions during the perturbed phase of the 2009 NH winter, however, emphasize the need for model improvements in the dynamical representation of elevated stratopause events in order to allow for a better description of the EPP indirect effect under these particular conditions.

The thermal environment of the human being on the global scale

PubMed Central

Jendritzky, Gerd; Tinz, Birger

2009-01-01

Background The close relationship between human health, performance, well-being and the thermal environment is obvious. Nevertheless, most studies of climate and climate change impacts show amazing shortcomings in the assessment of the environment. Populations living in different climates have different susceptibilities, due to socio-economic reasons, and different customary behavioural adaptations. The global distribution of risks of hazardous thermal exposure has not been analysed before. Objective To produce maps of the baseline and future bioclimate that allows a direct comparison of the differences in the vulnerability of populations to thermal stress across the world. Design The required climatological data fields are obtained from climate simulations with the global General Circulation Model ECHAM4 in T106-resolution. For the thermo-physiologically relevant assessment of these climate data a complete heat budget model of the human being, the ‘Perceived Temperature’ procedure has been applied which already comprises adaptation by clothing to a certain degree. Short-term physiological acclimatisation is considered via Health Related Assessment of the Thermal Environment. Results The global maps 1971–1980 (control run, assumed as baseline climate) show a pattern of thermal stress intensities as frequencies of heat. The heat load for people living in warm–humid climates is the highest. Climate change will lead to clear differences in health-related thermal stress between baseline climate and the future bioclimate 2041–2050 based on the ‘business-as-usual’ greenhouse gas scenario IS92a. The majority of the world's population will be faced with more frequent and more intense heat strain in spite of an assumed level of acclimatisation. Further adaptation measures are crucial in order to reduce the vulnerability of the populations. Conclusions This bioclimatology analysis provides a tool for various questions in climate and climate change impact research. Considerations of regional or local scale require climate simulations with higher resolution. As adaptation is the key term in understanding the role of climate/climate change for human health, performance and well-being, further research in this field is crucial. PMID:20052427

Modelling Local Sea-Breeze Flow and Associated Dispersion Patterns Over a Coastal Area in North-East Spain: A Case Study

NASA Astrophysics Data System (ADS)

Soler, M. R.; Arasa, R.; Merino, M.; Olid, M.; Ortega, S.

2011-07-01

The structure and evolution of the sea breeze in the north-west part of the Mediterranean (Catalonia, north-east Spain) is studied both experimentally and, predominantly, using numerical models to increase understanding of sea-breeze structure and three-dimensional (3D) pollution distributions in coastal environments. Sea-breeze components are modelled and analyzed using the fifth-generation Pennsylvania State University-National Centre for Atmospheric Research Mesoscale Model (MM5). The results show that the growth and structure of the sea-breeze circulation is modulated by the synoptic flow and especially by the complex topography of the area. 3D pollution transport in a sea breeze is modelled by coupling the MM5 to the Community Multiscale Air Quality (CMAQ) model, with results indicating that topography and synoptic flow are the main factors modulating horizontal and vertical pollutant transport in sea-breeze episodes. In this way, horizontal dispersion is limited by the complex topography of the area, whilst the sea-breeze flow is intensified by anabatic upslope winds that contribute to vertical pollutant transport. The numerical model results also indicate that the sea-breeze circulation with a weak return flow at upper levels grows due to a synoptic onshore wind component. However, such a sea-breeze circulation is capable of transporting pollutants towards the coast.

Electrical Lumped Model Examination for Load Variation of Circulation System

NASA Astrophysics Data System (ADS)

Koya, Yoshiharu; Ito, Mitsuyo; Mizoshiri, Isao

Modeling and analysis of the circulation system enables the characteristic decision of circulation system in the body to be made. So, many models of circulation system have been proposed. But, they are complicated because the models include a lot of elements. Therefore, we proposed a complete circulation model as a lumped electrical circuit, which is comparatively simple. In this paper, we examine the effectiveness of the complete circulation model as a lumped electrical circuit. We use normal, angina pectoris, dilated cardiomyopathy and myocardial infarction for evaluation of the ventricular contraction function.

Combined effects of projected sea level rise, storm surge, and peak river flows on water levels in the Skagit Floodplain

USGS Publications Warehouse

Hamman, Josheph J; Hamlet, Alan F.; Fuller, Roger; Grossman, Eric E.

2016-01-01

Current understanding of the combined effects of sea level rise (SLR), storm surge, and changes in river flooding on near-coastal environments is very limited. This project uses a suite of numerical models to examine the combined effects of projected future climate change on flooding in the Skagit floodplain and estuary. Statistically and dynamically downscaled global climate model scenarios from the ECHAM-5 GCM were used as the climate forcings. Unregulated daily river flows were simulated using the VIC hydrology model, and regulated river flows were simulated using the SkagitSim reservoir operations model. Daily tidal anomalies (TA) were calculated using a regression approach based on ENSO and atmospheric pressure forcing simulated by the WRF regional climate model. A 2-D hydrodynamic model was used to estimate water surface elevations in the Skagit floodplain using resampled hourly hydrographs keyed to regulated daily flood flows produced by the reservoir simulation model, and tide predictions adjusted for SLR and TA. Combining peak annual TA with projected sea level rise, the historical (1970–1999) 100-yr peak high water level is exceeded essentially every year by the 2050s. The combination of projected sea level rise and larger floods by the 2080s yields both increased flood inundation area (+ 74%), and increased average water depth (+ 25 cm) in the Skagit floodplain during a 100-year flood. Adding sea level rise to the historical FEMA 100-year flood resulted in a 35% increase in inundation area by the 2040's, compared to a 57% increase when both SLR and projected changes in river flow were combined.

NOy and O3 in the Asian Monsoon Anticyclone: Uncertainties associated with the Convection and Lightning in a Global Model

NASA Astrophysics Data System (ADS)

Pozzer, A.; Ojha, N.; Tost, H.; Joeckel, P.; Fischer, H.; Ziereis, H.; Zahn, A.; Tomsche, L.; Lelieveld, J.

2017-12-01

The impacts of Asian monsoon on the tropospheric chemistry are difficult to simulate in numerical models due to the lack of accurate emission inventories over the Asian region and the strong influence of parameterized processes such as convection and lightning. Further, the lack of observational data over the region during the monsoon period reduce drastically the capability to evaluate numerical models. Here, we combine simulations using the global EMAC (ECHAM5/MESSy2 Atmospheric Chemistry) model with the observational dataset based on the OMO campaign (July-August 2015) to study the tropospheric composition in the Asian monsoon anticyclone. The results of the simulations capture the C-shape of the CO vertical profiles, typically observed during the summer monsoon. The observed spatio-temporal variations in O3, CO, and NOy are reproduced by EMAC, with a better correlation in the upper troposphere (UT). However, the model overestimates NOy and O3 mixing ratios in the anticyclone by 25% and 35%, respectively. A series of numerical experiments showed the strong lightning emissions in the model as the source of this overestimation, with the anthropogenic NOx sources (in Asia) and global soil emissions having lower impact in the UT. A reduction of the lightning NOx emission by 50% leads to a better agreement between the model and OMO observations of NOy and O3. The uncertainties in the lightning emissions are found to considerably influence the OH distribution in the UT over India and downwind. The study reveals existing uncertainties in the estimations of monsoon impact on the tropospheric composition, and highlights the need to constrain numerical simulations with state-of-the-art observations for deriving the budget of trace species of climatic relevance.

Vegetation and land carbon feedbacks in the high-resolution transient Holocene simulations using the MPI Earth system model

NASA Astrophysics Data System (ADS)

Brovkin, Victor; Lorenz, Stephan; Raddatz, Thomas

2017-04-01

Plants influence climate through changes in the land surface biophysics (albedo, transpiration) and concentrations of the atmospheric greenhouse gases. One of the interesting periods to investigate a climatic role of terrestrial biosphere is the Holocene, when, despite of the relatively steady global climate, the atmospheric CO2 grew by about 20 ppm from 7 kyr BP to pre-industrial. We use a new setup of the Max Planck Institute Earth System Model MPI-ESM1 consisting of the latest version of the atmospheric model ECHAM6, including the land surface model JSBACH3 with carbon cycle and vegetation dynamics, coupled to the ocean circulation model MPI-OM, which includes the HAMOCC model of ocean biogeochemistry. The model has been run for several simulations over the Holocene period of the last 8000 years under the forcing data sets of orbital insolation, atmospheric greenhouse gases, volcanic aerosols, solar irradiance and stratospheric ozone, as well as land-use changes. In response to this forcing, the land carbon storage increased by about 60 PgC between 8 and 4 kyr BP, stayed relatively constant until 2 kyr BP, and decreased by about 90 PgC by 1850 AD due to land use changes. Vegetation and soil carbon changes significantly affected atmospheric CO2 during the periods of strong volcanic eruptions. In response to the eruption-caused cooling, the land initially stores more carbon as respiration decreases, but then it releases even more carbon due to productivity decrease. This decadal- scale variability helps to quantify the vegetation and land carbon feedbacks during the past periods when the temporal resolution of the ice-core CO2 record is not sufficient to capture fast CO2 variations. From a set of Holocene simulations with prescribed or interactive atmospheric CO2, we get estimates of climate-carbon feedback useful for future climate studies. Members of the Hamburg Holocene Team: Jürgen Bader1, Sebastian Bathiany2, Victor Brovkin1, Martin Claussen1,3, Traute Crüger1, Roberta D'agostino1, Anne Dallmeyer1, Sabine Egerer1, Vivienne Groner1, Matthias Heinze1, Tatiana Ilyina1, Johann Jungclaus1, Thomas Kleinen1, Alexander Lemburg1, Stephan Lorenz1, Thomas Raddatz1, Hauke Schmidt1, Gerhard Schmiedl3, Bjorn Stevens1, Claudia Timmreck1, Matthew Toohey4 1Max-Planck-Institut für Meteorologie, D 2Wageningen University, NL 3CEN, Universität Hamburg, D 4GEOMAR Helmholtz Zentrum für Ozeanforschung Kiel, D

Mesoscale mixing of the Denmark Strait Overflow in the Irminger Basin

NASA Astrophysics Data System (ADS)

Koszalka, Inga M.; Haine, Thomas W. N.; Magaldi, Marcello G.

2017-04-01

The Denmark Strait Overflow (DSO) is a major export route for dense waters from the Nordic Seas forming the lower limb of the Atlantic Meridional Overturning Circulation, an important element of the climate system. Mixing processes along the DSO pathway influence its volume transport and properties contributing to the variability of the deep overturning circulation. They are poorly sampled by observations, however, which hinders development of a proper DSO representation in global circulation models. We employ a high resolution regional ocean model of the Irminger Basin to quantify impact of the mesoscale flows on DSO mixing focusing on geographical localization and the time-modulation of water property changes. The model reproduces the observed bulk warming of the DSO plume 100-200 km downstream of the Denmark Strait sill. It also reveals that mesoscale variability of the overflow ('DSO-eddies', of 20-30 km extent and a time scale of 2-5 day) modulates water property changes and turbulent mixing, diagnosed with the vertical shear of horizontal velocity and the eddy heat flux divergence. The space-time localization of the DSO mixing and warming and the role of coherent mesoscale structures should be explored by turbulence measurements and factored into the coarse circulation models.

Diagnostic calculations of the circulation in the Martian atmosphere

NASA Technical Reports Server (NTRS)

Santee, Michelle L.; Crisp, David

1995-01-01

The circulation of the Martian atmosphere during late southern summer is derived from atmospheric temperature and dust distributions retrieved from a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra (L(sub s) = 343-348 deg). Zonal-mean zonal winds are calculated by assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense midlatitude westerly jets with velocities of 80-90 m/s near 50 km; in the southern tropics the winds are easterly with velocities of 40 m/s near 50 km. The net effect of the zonal mean meridional circulation and large-scale waves can be approximated by the diabatic circulation, which is defined from the atmospheric thermal structure and net radiative heating rates. The radiative transfer model described by Crisp (1990) and Santee (1993) is used to compute solar heating and thermal cooling rates from diurnal averages of the retrieved IRIS temperature and dust distributions. At pressures below 4 mbar, there are large net radiative heating rates (up to 5 K/d) in the equatorial region and large net radiative cooling rates (up to 12 K/d) in the polar regions. These net radiative heating rates are used in a diagnostic stream function model which solves for the meridional and vertical components of the diabatic circulation simultaneously. We find a two-cell circulation, with rising motion over the equator, poleward flow in both hemispheres, sinking motion over both polar regions, and return flow in the lowest atmospheric levels. The maximum poleward velocity is 3 m/s in the tropics at approx. 55 km altitude, and the maximum vertical velocity is 2.5 cm/s downward over the north pole at approx. 60 km altitude. If these large transport rates are sustained for an entire season, the Martian atmosphere above the 1-mbar level is overturned in about 38 days. This diabatic circulation is qualitatively similar to the terrestrial diabatic circulation at the comparable season, but is more vigorous.

The characterization of a full-thickness excision open foot wound model in n5-streptozotocin (STZ)-induced type 2 diabetic rats that mimics diabetic foot ulcer in terms of reduced blood circulation, higher C-reactive protein, elevated inflammation, and reduced cell proliferation.

PubMed

Yu, Caroline Oi-Ling; Leung, Kwok-Sui; Fung, Kwok-Pui; Lam, Francis Fu-Yuen; Ng, Ethel Sau-Kuen; Lau, Kit-Man; Chow, Simon Kwoon-Ho; Cheung, Wing-Hoi

2017-08-05

Delayed foot wound healing is a major complication attributed to hyperglycemia in type 2 diabetes mellitus (DM) patients, and these wounds may develop into foot ulcers. There are at least two types of DM wound models used in rodents to study delayed wound healing. However, clinically relevant animal models are not common. Most models use type 1 DM rodents or wounds created on the back rather than on the foot. An open full-thickness excision wound on the footpad of type 2 DM rats is more clinically relevant, but such a model has not yet been characterized systematically. The objective of this study was to investigate and characterize how DM affected a full-thickness excision open foot wound in n5-streptozotocin (n5-STZ)-induced type 2 DM rats. We hypothesized that elevated inflammation, reduced blood circulation, and cell proliferation due to hyperglycemia could delay the wound healing of DM rats. The wounds of DM rats were compared with those of non-DM rats (Ctrl) at Days 1 and 8 post wounding. The wound healing process of the DM rats was significantly delayed compared with that of the Ctrl rats. The DM rats also had higher C-reactive protein (CRP) and lower blood circulation and proliferating cell nuclear antigen (PCNA) in DM wounds. This confirmed that elevated inflammation and reduced blood flow and cell proliferation delayed foot wound healing in the n5-STZ rats. Hence, this open foot wound animal model provides a good approach to study the process of delayed wound healing.

The characterization of a full-thickness excision open foot wound model in n5-streptozotocin (STZ)-induced type 2 diabetic rats that mimics diabetic foot ulcer in terms of reduced blood circulation, higher C-reactive protein, elevated inflammation, and reduced cell proliferation

PubMed Central

Yu, Caroline Oi-Ling; Leung, Kwok-Sui; Fung, Kwok-Pui; Lam, Francis Fu-Yuen; Ng, Ethel Sau-Kuen; Lau, Kit-Man; Chow, Simon Kwoon-Ho; Cheung, Wing-Hoi

2017-01-01

Delayed foot wound healing is a major complication attributed to hyperglycemia in type 2 diabetes mellitus (DM) patients, and these wounds may develop into foot ulcers. There are at least two types of DM wound models used in rodents to study delayed wound healing. However, clinically relevant animal models are not common. Most models use type 1 DM rodents or wounds created on the back rather than on the foot. An open full-thickness excision wound on the footpad of type 2 DM rats is more clinically relevant, but such a model has not yet been characterized systematically. The objective of this study was to investigate and characterize how DM affected a full-thickness excision open foot wound in n5-streptozotocin (n5-STZ)-induced type 2 DM rats. We hypothesized that elevated inflammation, reduced blood circulation, and cell proliferation due to hyperglycemia could delay the wound healing of DM rats. The wounds of DM rats were compared with those of non-DM rats (Ctrl) at Days 1 and 8 post wounding. The wound healing process of the DM rats was significantly delayed compared with that of the Ctrl rats. The DM rats also had higher C-reactive protein (CRP) and lower blood circulation and proliferating cell nuclear antigen (PCNA) in DM wounds. This confirmed that elevated inflammation and reduced blood flow and cell proliferation delayed foot wound healing in the n5-STZ rats. Hence, this open foot wound animal model provides a good approach to study the process of delayed wound healing. PMID:28413186

Tumor-derived exosomes promote tumor self-seeding in hepatocellular carcinoma by transferring miRNA-25-5p to enhance cell motility.

PubMed

Liu, Hao; Chen, Wei; Zhi, Xiao; Chen, En-Jiang; Wei, Tao; Zhang, Jian; Shen, Jian; Hu, Li-Qiang; Zhao, Bin; Feng, Xin-Hua; Bai, Xue-Li; Liang, Ting-Bo

2018-05-22

Tumor self-seeding occurs when circulating malignant cells reinfiltrate the original tumor. The process may breed more aggressive tumor cells, which may contribute to cancer progression. In this study, we observed tumor self-seeding in mouse xenograft models of hepatocellular carcinoma (HCC) for the first time. We confirmed that circulating tumor cell uptake of tumor-derived exosomes, which are increasingly recognized as key instigators of cancer progression by facilitating cell-cell communication, promoted tumor self-seeding by enhancing the invasive and migration capability of recipient HCC cells. Horizontal transfer of exosomal microRNA-25-5p to anoikis-resistant HCC cells significantly enhanced their migratory and invasive abilities, whereas inhibiting microRNA-25-5p alleviated these effects. Our experiments delineate an exosome-based novel pathway employed by functional microRNA from the original tumor cells that can influence the biological fate of circulating tumor cells.

Thermal Pollution Mathematical Model. Volume 5: User's Manual for Three-Dimensional Rigid-Lid Model. [environment impact of thermal discharges from power plants

NASA Technical Reports Server (NTRS)

Lee, S. S.; Sengupta, S.; Nwadike, E. V.; Sinha, S. K.

1980-01-01

A user's manual for a three dimensional, rigid lid model used for hydrothermal predictions of closed basins subjected to a heated discharge together with various other inflows and outflows is presented. The model has the capability to predict (1) wind driven circulation; (2) the circulation caused by inflows and outflows to the domain; and (3) the thermal effects in the domain, and to combine the above processes. The calibration procedure consists of comparing ground truth corrected airborne radiometer data with surface isotherms predicted by the model. The model was verified for accuracy at various sites and results are found to be fairly accurate in all verification runs.

Ocean Circulation Modeling for Aquatic Dispersion of Liquid Radioactive Effluents from Nuclear Power Plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Y.G.; Lee, G.B.; Bang, S.Y.

2006-07-01

Recently, three-dimensional models have been used for aquatic dispersion of radioactive effluents in relation to nuclear power plant siting based on the Notice No. 2003-12 'Guideline for investigating and assessing hydrological and aquatic characteristics of nuclear facility site' of the Ministry of Science and Technology (MOST) in Korea. Several nuclear power plants have been under construction or planed, which are Shin-Kori Unit 1 and 2, Shin-Wolsong Unit 1 and 2, and Shin-Ulchin Unit 1 and 2. For assessing the aquatic dispersion of radionuclides released from the above nuclear power plants, it is necessary to know the coastal currents around sitesmore » which are affected by circulation of East Sea. In this study, a three dimensional hydrodynamic model for the circulation of the East Sea of Korea has been developed as the first phase, which is based on the RIAMOM (Research Institute of Applied Mechanics' Ocean Model, Kyushu University, Japan). The model uses the primitive equation with hydrostatic approximation, and uses Arakawa-B grid system horizontally and Z coordinate vertically. Model domain is 126.5 deg. E to 142.5 deg. E of east longitude and 33 deg. N and 52 deg. N of the north latitude. The space of the horizontal grid was 1/12 deg. to longitude and latitude direction and vertical level was divided to 20. This model uses Generalized Arakawa Scheme, Slant Advection, and Mode-Splitting Method. The input data were from JODC (Japan Oceanographic Data Center), KNFRDI (Korea National Fisheries Research and Development Institute), and ECMWF (European Center for Medium-Range Weather Forecasts). The modeling results are in fairly good agreement with schematic patterns of the surface circulation in the East Sea/Japan Sea. The local current model and aquatic dispersion model of the coastal region will be developed as the second phase. The oceanic dispersion experiments will be also carried out by using ARGO Drifter around a nuclear power plant site. (authors)« less

Quantifying the Aerosol Semi-Direct Effect in the NASA GEOS-5 AGCM

NASA Technical Reports Server (NTRS)

Randles, Cynthia A.; Colarco, Peter R.; daSilva, Arlindo

2011-01-01

Aerosols such as black carbon, dust, and some organic carbon species both scatter and absorb incoming solar radiation. This direct aerosol radiative forcing (DARF) redistributes solar energy both by cooling the surface and warming the atmosphere. As a result, these aerosols affect atmospheric stability and cloud cover (the semi-direct effect, or SDE). Furthermore, in regions with persistent high loadings of absorbing aerosols (e.g. Asia), regional circulation patterns may be altered, potentially resulting in changes in precipitation patterns. Here we investigate aerosol-climate coupling using the NASA Goddard Earth Observing System model version 5 (GEOS-5) atmospheric general circulation model (AGCM), in which we have implemented an online version of the Goddard Chemistry, Aerosol, Radiation and Transport (GOCART) model. GOCART includes representations of the sources, sinks, and chemical transformation of externally mixed dust, sea salt, sulfate, and carbonaceous aerosols. We examine a series of free-running ensemble climate simulations of the present-day period (2000-2009) forced by observed sea surface temperatures to determine the impact of aerosols on the model climate. The SDE and response of each simulation is determined by differencing with respect to the control simulation (no aerosol forcing). In a free-running model, any estimate of the SDE includes changes in clouds due both to atmospheric heating from aerosols and changes in circulation. To try and quantify the SDE without these circulation changes we then examine the DARF and SDE in GEOS-5 with prescribed meteorological analyses introduced by the MERRA analysis. By doing so, we are able to examine changes in model clouds that occur on shorter scales (six hours). In the GEOS-5 data assimilation system (DAS), the analysis is defined as the best estimate of the atmospheric state at any given time, and it is determined by optimally combining a first-guess short-term GCM forecast with all available observations. The Incremental Analysis Update (IAU) is added to the model forecast tendencies to align them with the analysis every six hours, thus preventing longer timescale feedbacks due to the aerosol forcing. We calculate the SDE by comparing model runs with and without aerosols, and the difference in the IAU between these runs is a useful metric with which to evaluate the impact of the SDE on the model atmosphere and clouds. Decreasing the IAU indicates that the aerosol direct and semi-direct effects act to reduce the bias between the model and observations and vice versa.

Aerosol specification in single-column Community Atmosphere Model version 5

DOE PAGES

Lebassi-Habtezion, B.; Caldwell, P. M.

2015-03-27

Single-column model (SCM) capability is an important tool for general circulation model development. In this study, the SCM mode of version 5 of the Community Atmosphere Model (CAM5) is shown to handle aerosol initialization and advection improperly, resulting in aerosol, cloud-droplet, and ice crystal concentrations which are typically much lower than observed or simulated by CAM5 in global mode. This deficiency has a major impact on stratiform cloud simulations but has little impact on convective case studies because aerosol is currently not used by CAM5 convective schemes and convective cases are typically longer in duration (so initialization is less important).more » By imposing fixed aerosol or cloud-droplet and crystal number concentrations, the aerosol issues described above can be avoided. Sensitivity studies using these idealizations suggest that the Meyers et al. (1992) ice nucleation scheme prevents mixed-phase cloud from existing by producing too many ice crystals. Microphysics is shown to strongly deplete cloud water in stratiform cases, indicating problems with sequential splitting in CAM5 and the need for careful interpretation of output from sequentially split climate models. Droplet concentration in the general circulation model (GCM) version of CAM5 is also shown to be far too low (~ 25 cm −3) at the southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site.« less

The Southern Ocean in the Coupled Model Intercomparison Project phase 5

PubMed Central

Meijers, A. J. S.

2014-01-01

The Southern Ocean is an important part of the global climate system, but its complex coupled nature makes both its present state and its response to projected future climate forcing difficult to model. Clear trends in wind, sea-ice extent and ocean properties emerged from multi-model intercomparison in the Coupled Model Intercomparison Project phase 3 (CMIP3). Here, we review recent analyses of the historical and projected wind, sea ice, circulation and bulk properties of the Southern Ocean in the updated Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble. Improvements to the models include higher resolutions, more complex and better-tuned parametrizations of ocean mixing, and improved biogeochemical cycles and atmospheric chemistry. CMIP5 largely reproduces the findings of CMIP3, but with smaller inter-model spreads and biases. By the end of the twenty-first century, mid-latitude wind stresses increase and shift polewards. All water masses warm, and intermediate waters freshen, while bottom waters increase in salinity. Surface mixed layers shallow, warm and freshen, whereas sea ice decreases. The upper overturning circulation intensifies, whereas bottom water formation is reduced. Significant disagreement exists between models for the response of the Antarctic Circumpolar Current strength, for reasons that are as yet unclear. PMID:24891395

Circulatory shear flow alters the viability and proliferation of circulating colon cancer cells

NASA Astrophysics Data System (ADS)

Fan, Rong; Emery, Travis; Zhang, Yongguo; Xia, Yuxuan; Sun, Jun; Wan, Jiandi

2016-06-01

During cancer metastasis, circulating tumor cells constantly experience hemodynamic shear stress in the circulation. Cellular responses to shear stress including cell viability and proliferation thus play critical roles in cancer metastasis. Here, we developed a microfluidic approach to establish a circulatory microenvironment and studied circulating human colon cancer HCT116 cells in response to a variety of magnitude of shear stress and circulating time. Our results showed that cell viability decreased with the increase of circulating time, but increased with the magnitude of wall shear stress. Proliferation of cells survived from circulation could be maintained when physiologically relevant wall shear stresses were applied. High wall shear stress (60.5 dyne/cm2), however, led to decreased cell proliferation at long circulating time (1 h). We further showed that the expression levels of β-catenin and c-myc, proliferation regulators, were significantly enhanced by increasing wall shear stress. The presented study provides a new insight to the roles of circulatory shear stress in cellular responses of circulating tumor cells in a physiologically relevant model, and thus will be of interest for the study of cancer cell mechanosensing and cancer metastasis.

Multimillennium changes in dissolved oxygen under global warming: results from an AOGCM and offline ocean biogeochemical model

NASA Astrophysics Data System (ADS)

Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y.

2016-12-01

Long-term oceanic oxygen change due to global warming is still unclear; most future projections (such as CMIP5) are only performed until 2100. Indeed, few previous studies using conceptual models project oxygen change in the next thousands of years, showing persistent global oxygen reduction by about 30% in the next 2000 years, even after atmospheric carbon dioxide stops rising. Yet, these models cannot sufficiently represent the ocean circulation change: the key driver of oxygen change. Moreover, considering serious effect oxygen reduction has on marine life and biogeochemical cycling, long-term oxygen change should be projected for higher validity. Therefore, we used a coupled atmosphere-ocean general circulation model (AOGCM) and an offline ocean biogeochemical model, investigating realistic long-term changes in oceanic oxygen concentration and ocean circulation. We integrated these models for 2000 years under atmospheric CO2 doubling and quadrupling. After global oxygen reduction in the first 500 years, oxygen concentration in deep ocean globally recovers and overshoots, despite surface oxygen decrease and weaker Atlantic Meridional Overturning Circulation. Deep ocean convection in the Weddell Sea recovers and overshoots, after initial cessation. Thus, enhanced deep convection and associated Antarctic Bottom Water supply oxygen-rich surface waters to deep ocean, resulting global deep ocean oxygenation. We conclude that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in the deep ocean; contrary to past reported long-term oxygen reduction and general expectation. In presentation, we will discuss the mechanism of response of deep ocean convection in the Weddell Sea and show the volume changes of hypoxic waters.

Regional variability of the frequency distribution of daily precipitation and the synoptic characteristics of heavy precipitation events in present and future climate simulations

NASA Astrophysics Data System (ADS)

DeAngelis, Anthony M.

Changes in the characteristics of daily precipitation in response to global warming may have serious impacts on human life and property. An analysis of precipitation in climate models is performed to evaluate how well the models simulate the present climate and how precipitation may change in the future. Models participating in phase 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5) have substantial biases in their simulation of heavy precipitation intensity over parts of North America during the 20th century. Despite these biases, the large-scale atmospheric circulation accompanying heavy precipitation is either simulated realistically or the strength of the circulation is overestimated. The biases are not related to the large-scale flow in a simple way, pointing toward the importance of other model deficiencies, such as coarse horizontal resolution and convective parameterizations, for the accurate simulation of intense precipitation. Although the models may not sufficiently simulate the intensity of precipitation, their realistic portrayal of the large-scale circulation suggests that projections of future precipitation may be reliable. In the CMIP5 ensemble, the distribution of daily precipitation is projected to undergo substantial changes in response to future atmospheric warming. The regional distribution of these changes was investigated, revealing that dry days and days with heavy-extreme precipitation are projected to increase at the expense of light-moderate precipitation over much of the middle and low latitudes. Such projections have serious implications for future impacts from flood and drought events. In other places, changes in the daily precipitation distribution are characterized by a shift toward either wetter or drier conditions in the future, with heavy-extreme precipitation projected to increase in all but the driest subtropical subsidence regions. Further analysis shows that increases in heavy precipitation in midlatitudes are largely explained by thermodynamics, including increases in atmospheric water vapor. However, in low latitudes and northern high latitudes, changes in vertical velocity accompanying heavy precipitation are also important. The strength of the large-scale atmospheric circulation is projected to change in accordance with vertical velocity in many places, though the circulation patterns, and therefore physical mechanisms that generate heavy precipitation, may remain the same.

Final Technical Report for DE-SC0005467

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broccoli, Anthony J.

2014-09-14

The objective of this project is to gain a comprehensive understanding of the key atmospheric mechanisms and physical processes associated with temperature extremes in order to better interpret and constrain uncertainty in climate model simulations of future extreme temperatures. To achieve this objective, we first used climate observations and a reanalysis product to identify the key atmospheric circulation patterns associated with extreme temperature days over North America during the late twentieth century. We found that temperature extremes were associated with distinctive signatures in near-surface and mid-tropospheric circulation. The orientations and spatial scales of these circulation anomalies vary with latitude, season,more » and proximity to important geographic features such as mountains and coastlines. We next examined the associations between daily and monthly temperature extremes and large-scale, recurrent modes of climate variability, including the Pacific-North American (PNA) pattern, the northern annular mode (NAM), and the El Niño-Southern Oscillation (ENSO). The strength of the associations are strongest with the PNA and NAM and weaker for ENSO, and also depend upon season, time scale, and location. The associations are stronger in winter than summer, stronger for monthly than daily extremes, and stronger in the vicinity of the centers of action of the PNA and NAM patterns. In the final stage of this project, we compared climate model simulations of the circulation patterns associated with extreme temperature days over North America with those obtained from observations. Using a variety of metrics and self-organizing maps, we found the multi-model ensemble and the majority of individual models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) generally capture the observed patterns well, including their strength and as well as variations with latitude and season. The results from this project indicate that current models are capable of simulating the large-scale meteorological patterns associated with daily temperature extremes and they suggest that such models can be used to evaluate the extent to which changes in atmospheric circulation will influence future changes in temperature extremes.« less

GEOS-5 Chemistry Transport Model User's Guide

NASA Technical Reports Server (NTRS)

Kouatchou, J.; Molod, A.; Nielsen, J. E.; Auer, B.; Putman, W.; Clune, T.

2015-01-01

The Goddard Earth Observing System version 5 (GEOS-5) General Circulation Model (GCM) makes use of the Earth System Modeling Framework (ESMF) to enable model configurations with many functions. One of the options of the GEOS-5 GCM is the GEOS-5 Chemistry Transport Model (GEOS-5 CTM), which is an offline simulation of chemistry and constituent transport driven by a specified meteorology and other model output fields. This document describes the basic components of the GEOS-5 CTM, and is a user's guide on to how to obtain and run simulations on the NCCS Discover platform. In addition, we provide information on how to change the model configuration input files to meet users' needs.

Three-pattern decomposition of global atmospheric circulation: part I—decomposition model and theorems

NASA Astrophysics Data System (ADS)

Hu, Shujuan; Chou, Jifan; Cheng, Jianbo

2018-04-01

In order to study the interactions between the atmospheric circulations at the middle-high and low latitudes from the global perspective, the authors proposed the mathematical definition of three-pattern circulations, i.e., horizontal, meridional and zonal circulations with which the actual atmospheric circulation is expanded. This novel decomposition method is proved to accurately describe the actual atmospheric circulation dynamics. The authors used the NCEP/NCAR reanalysis data to calculate the climate characteristics of those three-pattern circulations, and found that the decomposition model agreed with the observed results. Further dynamical analysis indicates that the decomposition model is more accurate to capture the major features of global three dimensional atmospheric motions, compared to the traditional definitions of Rossby wave, Hadley circulation and Walker circulation. The decomposition model for the first time realized the decomposition of global atmospheric circulation using three orthogonal circulations within the horizontal, meridional and zonal planes, offering new opportunities to study the large-scale interactions between the middle-high latitudes and low latitudes circulations.

Development of an Accident Reproduction Simulator System Using a Hemodialysis Extracorporeal Circulation System.

PubMed

Nishite, Yoshiaki; Takesawa, Shingo

2016-01-01

Accidents that occur during dialysis treatment are notified to the medical staff via alarms raised by the dialysis apparatus. Similar to such real accidents, apparatus activation or accidents can be reproduced by simulating a treatment situation. An alarm that corresponds to such accidents can be utilized in the simulation model. The aim of this study was to create an extracorporeal circulation system (hereinafter, the circulation system) for dialysis machines so that it sets off five types of alarms for: 1) decreased arterial pressure, 2) increased arterial pressure, 3) decreased venous pressure, 4) increased venous pressure, and 5) blood leakage, according to the five types of accidents chosen based on their frequency of occurrence and the degree of severity. In order to verify the alarm from the dialysis apparatus connected to the circulation system and the accident corresponding to it, an evaluation of the alarm for its reproducibility of an accident was performed under normal treatment circumstances. The method involved testing whether the dialysis apparatus raised the desired alarm from the moment of control of the circulation system, and measuring the time it took until the desired alarm was activated. This was tested on five main models from four dialyzer manufacturers that are currently used in Japan. The results of the tests demonstrated successful activation of the alarms by the dialysis apparatus, which were appropriate for each of the five types of accidents. The time between the control of the circulatory system to the alarm signal was as follows, 1) venous pressure lower limit alarm: 7 seconds; 2) venous pressure lower limit: 8 seconds; 3) venous pressure upper limit: 7 seconds; 4) venous pressure lower limit alarm: 2 seconds; and 5) blood leakage alarm: 19 seconds. All alarms were set off in under 20 seconds. Thus, we can conclude that a simulator system using an extracorporeal circulation system can be set to different models of dialyzers, and that the reproduced treatment scenarios can be used for simulation training.

The millennium water vapour drop in chemistry-climate model simulations

NASA Astrophysics Data System (ADS)

Brinkop, Sabine; Dameris, Martin; Jöckel, Patrick; Garny, Hella; Lossow, Stefan; Stiller, Gabriele

2016-07-01

This study investigates the abrupt and severe water vapour decline in the stratosphere beginning in the year 2000 (the "millennium water vapour drop") and other similarly strong stratospheric water vapour reductions by means of various simulations with the state-of-the-art Chemistry-Climate Model (CCM) EMAC (ECHAM/MESSy Atmospheric Chemistry Model). The model simulations differ with respect to the prescribed sea surface temperatures (SSTs) and whether nudging is applied or not. The CCM EMAC is able to most closely reproduce the signature and pattern of the water vapour drop in agreement with those derived from satellite observations if the model is nudged. Model results confirm that this extraordinary water vapour decline is particularly obvious in the tropical lower stratosphere and is related to a large decrease in cold point temperature. The drop signal propagates under dilution to the higher stratosphere and to the poles via the Brewer-Dobson circulation (BDC). We found that the driving forces for this significant decline in water vapour mixing ratios are tropical sea surface temperature (SST) changes due to a coincidence with a preceding strong El Niño-Southern Oscillation event (1997/1998) followed by a strong La Niña event (1999/2000) and supported by the change of the westerly to the easterly phase of the equatorial stratospheric quasi-biennial oscillation (QBO) in 2000. Correct (observed) SSTs are important for triggering the strong decline in water vapour. There are indications that, at least partly, SSTs contribute to the long period of low water vapour values from 2001 to 2006. For this period, the specific dynamical state of the atmosphere (overall atmospheric large-scale wind and temperature distribution) is important as well, as it causes the observed persistent low cold point temperatures. These are induced by a period of increased upwelling, which, however, has no corresponding pronounced signature in SSTs anomalies in the tropics. Our free-running simulations do not capture the drop as observed, because a) the cold point temperature has a low bias and thus the water vapour variability is reduced and b) because they do not simulate the appropriate dynamical state. Large negative water vapour declines are also found in other years and seem to be a feature which can be found after strong combined El Niño/La Niña events if the QBO west phase during La Niña changes to the east phase.

Downscaled climate change projections with uncertainty assessment over India using a high resolution multi-model approach.

PubMed

Kumar, Pankaj; Wiltshire, Andrew; Mathison, Camilla; Asharaf, Shakeel; Ahrens, Bodo; Lucas-Picher, Philippe; Christensen, Jens H; Gobiet, Andreas; Saeed, Fahad; Hagemann, Stefan; Jacob, Daniela

2013-12-01

This study presents the possible regional climate change over South Asia with a focus over India as simulated by three very high resolution regional climate models (RCMs). One of the most striking results is a robust increase in monsoon precipitation by the end of the 21st century but regional differences in strength. First the ability of RCMs to simulate the monsoon climate is analyzed. For this purpose all three RCMs are forced with ECMWF reanalysis data for the period 1989-2008 at a horizontal resolution of ~25 km. The results are compared against independent observations. In order to simulate future climate the models are driven by lateral boundary conditions from two global climate models (GCMs: ECHAM5-MPIOM and HadCM3) using the SRES A1B scenario, except for one RCM, which only used data from one GCM. The results are presented for the full transient simulation period 1970-2099 and also for several time slices. The analysis concentrates on precipitation and temperature over land. All models show a clear signal of gradually wide-spread warming throughout the 21st century. The ensemble-mean warming over India is 1.5°C at the end of 2050, whereas it is 3.9°C at the end of century with respect to 1970-1999. The pattern of projected precipitation changes shows considerable spatial variability, with an increase in precipitation over the peninsular of India and coastal areas and, either no change or decrease further inland. From the analysis of a larger ensemble of global climate models using the A1B scenario a wide spread warming (~3.2°C) and an overall increase (~8.5%) in mean monsoon precipitation by the end of the 21st century is very likely. The influence of the driving GCM on the projected precipitation change simulated with each RCM is as strong as the variability among the RCMs driven with one. Copyright © 2013 Elsevier B.V. All rights reserved.

Seasonal Variability of Salt Transport During the Indian Ocean Monsoons

DTIC Science & Technology

2011-08-27

Wunsch, J. Marotzkc, and J. Toolc (2000). Meridional overturning and large-scale circulation of the Indian Ocean, J. Geophvs Res., W5(C\\ 1), 26,117...and II. Hasumi (2006), Effects of model resolution on salt transport through northern high-latitude passages and Atlantic meridional overturning ...affects meridional circulation and aids the transport of salt [Sevellec et ai, 2008; Czaja, 2009]. Deep convection could be inhibited by the freshening

Trends in winter circulation over the British Isles and central Europe in twenty-first century projections by 25 CMIP5 GCMs

NASA Astrophysics Data System (ADS)

Stryhal, Jan; Huth, Radan

2018-03-01

Winter midlatitude atmospheric circulation has been extensively studied for its tight link to surface weather, and automated circulation classifications have often been used to this end. Here, eight such classifications are applied to daily sea level pressure patterns simulated by an ensemble of CMIP5 GCMs twenty-first century projections for the British Isles and central Europe in order to robustly estimate future changes in frequency, persistence, and strength of synoptic-scale circulation there. All methods are able to identify present-day biases of models reported before, such as an overestimated occurrence of zonal flow and underestimation of anticyclonic conditions and easterly advection, although the strength of these biases varies among the methods. In future, models show that the zonal flow will become more frequent while the strength of the mean flow is not projected to change. Over the British Isles, the models that better simulate the latitude of zonal flow over the historical period indicate a slight equatorward shift of westerlies in their projections, while the poleward expansion of circulation—expected in future at global scale—is apparent in those models that have large errors. Over central Europe, some classifications indicate an increase in persistence and especially in frequency of anticyclonic types, which is, however, shown to be rather an artifact of some methods than a real feature. On the other hand, the easterly flow is robustly projected to become markedly weaker in central Europe, which we hypothesize might be an important factor contributing to the projected decrease of cold extremes there.

Process Analysis of Lignite Circulating Fluidized Bed Boiler Coupled with Pyrolysis Topping

NASA Astrophysics Data System (ADS)

Wang, Baoqun; Dong, Li; Wang, Yin; Matsuzawa, Y.; Xu, Guangwen

We developed a comprehensive process model in ASPEN Plus to simulate the energy and mass balances of a lignite-fueled atmospheric circulating fluidized bed (CFB) boiler integrated with coal predrying and pyrolysis topping. In this model, it is assumed that the heat from exhausted flue gas was employed for coal predrying, and the sensible heat derived from circulated bed material was used for the pyrolysis topping (endothermic process). The simulation was conducted with respectto the Yunnan Kaiyuan CFB boiler, and two representative lignite coals from Xiao Long Tan (XLT) and Xin Shao (XS) were considered. The result shows that the predrying of coal with the sensible heat of above 363 K from flue gas, the amount of coal consumed in the boiler can be reduced by 3.5% and 5.3% for XLT lignite and XS lignite, respectively. It was also found that integration of pyrolysis topping with the boiler increased the coal consumption of the boiler, and the extent of consumption-increase varies with the yields of tar and gas in the pyrolysis topping process. For agas yield of 5.2% and a tar yield of 5-6%, the consumption of XS lignite increased by about 20% comparing to that in the case without topping.

Low-dose endotoxemia and human neuropsychological functions.

PubMed

Krabbe, Karen Suárez; Reichenberg, Abraham; Yirmiya, Raz; Smed, Annelise; Pedersen, Bente Klarlund; Bruunsgaard, Helle

2005-09-01

Epidemiological data demonstrate an association between systemic low-grade inflammation defined as 2- to 3-fold increases in circulating inflammatory mediators and age-related decline in cognitive function. However, it is not known whether small elevations of circulating cytokine levels cause direct effects on human neuropsychological functions. We investigated changes in emotional, cognitive, and inflammatory parameters in an experimental in vivo model of low-grade inflammation. In a double-blind crossover study, 12 healthy young males completed neuropsychological tests before as well as 1.5, 6, and 24 h after an intravenous injection of Escherichia coli endotoxin (0.2 ng/kg) or saline in two experimental sessions. Endotoxin administration had no effect on body temperature, cortisol levels, blood pressure or heart rate, but circulating levels of tumor necrosis factor (TNF) and interleukin (IL)-6 increased 2- and 7-fold, respectively, reaching peak values at 3 h, whereas soluble TNF-receptors and IL-1 receptor antagonist peaked at 4.5 h. The neutrophil count increased and the lymphocyte count declined. In this model, low-dose endotoxemia did not affect cognitive performance significantly but declarative memory performance was inversely correlated with cytokine increases. In conclusion, our findings demonstrate a negative association between circulating IL-6 and memory functions during very low-dose endotoxemia independently of physical stress symptoms, and the hypothalamo-pituitary-adrenal axis.

The Dependence of Cloud-SST Feedback on Circulation Regime and Timescale

NASA Astrophysics Data System (ADS)

Middlemas, E.; Clement, A. C.; Medeiros, B.

2017-12-01

Studies suggest cloud radiative feedback amplifies internal variability of Pacific sea surface temperature (SST) on interannual-and-longer timescales, though only a few modeling studies have tested the quantitative importance of this feedback (Bellomo et al. 2014b, Brown et al. 2016, Radel et al. 2016 Burgman et al. 2017). We prescribe clouds from a previous control run in the radiation module in Community Atmospheric Model (CAM5-slab), a method called "cloud-locking". By comparing this run to a control run, in which cloud radiative forcing can feedback on the climate system, we isolate the effect of cloud radiative forcing on SST variability. Cloud-locking prevents clouds from radiatively interacting with atmospheric circulation, water vapor, and SST, while maintaining a similar mean state to the control. On all timescales, cloud radiative forcing's influence on SST variance is modulated by the circulation regime. Cloud radiative forcing amplifies SST variance in subsiding regimes and dampens SST variance in convecting regimes. In this particular model, a tug of war between latent heat flux and cloud radiative forcing determines the variance of SST, and the winner depends on the timescale. On decadal-and-longer timescales, cloud radiative forcing plays a relatively larger role than on interannual-and-shorter timescales, while latent heat flux plays a smaller role. On longer timescales, the absence of cloud radiative feedback changes SST variance in a zonally asymmetric pattern in the Pacific Ocean that resembles an IPO-like pattern. We also present an analysis of cloud feedback's role on Pacific SST variability among preindustrial control CMIP5 models to test the model robustness of our results. Our results suggest that circulation plays a crucial role in cloud-SST feedbacks across the globe and cloud radiative feedbacks cannot be ignored when studying SST variability on decadal-and-longer timescales.

The diagnosis and forecast system of hydrometeorological characteristics for the White, Barents, Kara and Pechora Seas

NASA Astrophysics Data System (ADS)

Fomin, Vladimir; Diansky, Nikolay; Gusev, Anatoly; Kabatchenko, Ilia; Panasenkova, Irina

2017-04-01

The diagnosis and forecast system for simulating hydrometeorological characteristics of the Russian Western Arctic seas is presented. It performs atmospheric forcing computation with the regional non-hydrostatic atmosphere model Weather Research and Forecasting model (WRF) with spatial resolution 15 km, as well as computation of circulation, sea level, temperature, salinity and sea ice with the marine circulation model INMOM (Institute of Numerical Mathematics Ocean Model) with spatial resolution 2.7 km, and the computation of wind wave parameters using the Russian wind-wave model (RWWM) with spatial resolution 5 km. Verification of the meteorological characteristics is done for air temperature, air pressure, wind velocity, water temperature, currents, sea level anomaly, wave characteristics such as wave height and wave period. The results of the hydrometeorological characteristic verification are presented for both retrospective and forecast computations. The retrospective simulation of the hydrometeorological characteristics for the White, Barents, Kara and Pechora Seas was performed with the diagnosis and forecast system for the period 1986-2015. The important features of the Kara Sea circulation are presented. Water exchange between Pechora and Kara Seas is described. The importance is shown of using non-hydrostatic atmospheric circulation model for the atmospheric forcing computation in coastal areas. According to the computation results, extreme values of hydrometeorological characteristics were obtained for the Russian Western Arctic seas.

Understanding and Portraying the Global Atmospheric Circulation.

ERIC Educational Resources Information Center

Harrington, John, Jr.; Oliver, John E.

2000-01-01

Examines teaching models of atmospheric circulation and resultant surface pressure patterns, focusing on the three-cell model and the meaning of meridional circulation as related to middle and high latitudes. Addresses the failure of the three-cell model to explain seasonal variations in atmospheric circulation. Suggests alternative models. (CMK)

Circulating tumour DNA and CT monitoring in patients with untreated diffuse large B-cell lymphoma: a correlative biomarker study.

PubMed

Roschewski, Mark; Dunleavy, Kieron; Pittaluga, Stefania; Moorhead, Martin; Pepin, Francois; Kong, Katherine; Shovlin, Margaret; Jaffe, Elaine S; Staudt, Louis M; Lai, Catherine; Steinberg, Seth M; Chen, Clara C; Zheng, Jianbiao; Willis, Thomas D; Faham, Malek; Wilson, Wyndham H

2015-05-01

Diffuse large-B-cell lymphoma is curable, but when treatment fails, outcome is poor. Although imaging can help to identify patients at risk of treatment failure, they are often imprecise, and radiation exposure is a potential health risk. We aimed to assess whether circulating tumour DNA encoding the clonal immunoglobulin gene sequence could be detected in the serum of patients with diffuse large-B-cell lymphoma and used to predict clinical disease recurrence after frontline treatment. We used next-generation DNA sequencing to retrospectively analyse cell-free circulating tumour DNA in patients assigned to one of three treatment protocols between May 8, 1993, and June 6, 2013. Eligible patients had diffuse large-B-cell lymphoma, no evidence of indolent lymphoma, and were previously untreated. We obtained serial serum samples and concurrent CT scans at specified times during most treatment cycles and up to 5 years of follow-up. VDJ gene segments of the rearranged immunoglobulin receptor genes were amplified and sequenced from pretreatment specimens and serum circulating tumour DNA encoding the VDJ rearrangements was quantitated. Tumour clonotypes were identified in pretreatment specimens from 126 patients who were followed up for a median of 11 years (IQR 6·8-14·2). Interim monitoring of circulating tumour DNA at the end of two treatment cycles in 108 patients showed a 5-year time to progression of 41·7% (95% CI 22·2-60·1) in patients with detectable circulating tumour DNA and 80·2% (69·6-87·3) in those without detectable circulating tumour DNA (p<0·0001). Detectable interim circulating tumour DNA had a positive predictive value of 62·5% (95% CI 40·6-81·2) and a negative predictive value of 79·8% (69·6-87·8). Surveillance monitoring of circulating tumour DNA was done in 107 patients who achieved complete remission. A Cox proportional hazards model showed that the hazard ratio for clinical disease progression was 228 (95% CI 51-1022) for patients who developed detectable circulating tumour DNA during surveillance compared with patients with undetectable circulating tumour DNA (p<0·0001). Surveillance circulating tumour DNA had a positive predictive value of 88·2% (95% CI 63·6-98·5) and a negative predictive value of 97·8% (92·2-99·7) and identified risk of recurrence at a median of 3·5 months (range 0-200) before evidence of clinical disease. Surveillance circulating tumour DNA identifies patients at risk of recurrence before clinical evidence of disease in most patients and results in a reduced disease burden at relapse. Interim circulating tumour DNA is a promising biomarker to identify patients at high risk of treatment failure. National Cancer Institute and Adaptive Biotechnologies. Copyright © 2015 Elsevier Ltd. All rights reserved.

The accuracy of estimates of the overturning circulation from basin-wide mooring arrays

NASA Astrophysics Data System (ADS)

Sinha, B.; Smeed, D. A.; McCarthy, G.; Moat, B. I.; Josey, S. A.; Hirschi, J. J.-M.; Frajka-Williams, E.; Blaker, A. T.; Rayner, D.; Madec, G.

2018-01-01

Previous modeling and observational studies have established that it is possible to accurately monitor the Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N using a coast-to-coast array of instrumented moorings supplemented by direct transport measurements in key boundary regions (the RAPID/MOCHA/WBTS Array). The main sources of observational and structural errors have been identified in a variety of individual studies. Here a unified framework for identifying and quantifying structural errors associated with the RAPID array-based AMOC estimates is established using a high-resolution (eddy resolving at low-mid latitudes, eddy permitting elsewhere) ocean general circulation model, which simulates the ocean state between 1978 and 2010. We define a virtual RAPID array in the model in close analogy to the real RAPID array and compare the AMOC estimate from the virtual array with the true model AMOC. The model analysis suggests that the RAPID method underestimates the mean AMOC by ∼1.5 Sv (1 Sv = 106 m3 s-1) at ∼900 m depth, however it captures the variability to high accuracy. We examine three major contributions to the streamfunction bias: (i) due to the assumption of a single fixed reference level for calculation of geostrophic transports, (ii) due to regions not sampled by the array and (iii) due to ageostrophic transport. A key element in (i) and (iii) is use of the model sea surface height to establish the true (or absolute) geostrophic transport. In the upper 2000 m, we find that the reference level bias is strongest and most variable in time, whereas the bias due to unsampled regions is largest below 3000 m. The ageostrophic transport is significant in the upper 1000 m but shows very little variability. The results establish, for the first time, the uncertainty of the AMOC estimate due to the combined structural errors in the measurement design and suggest ways in which the error could be reduced. Our work has applications to basin-wide circulation measurement arrays at other latitudes and in other basins as well as quantifying systematic errors in ocean model estimates of the AMOC at 26.5°N.

Re-examination of the I-5 dust storm

NASA Astrophysics Data System (ADS)

Kaplan, Michael L.; Vellore, Ramesh K.; Lewis, John M.; Underwood, S. Jeffrey; Pauley, Patricia M.; Martin, Jonathan E.; Krishnan, R.

2013-01-01

The infamous dust storm over the thanksgiving holiday of 1991 that led to loss of life from numerous automobile accidents on Interstate 5 (I-5) has been re-examined. Pauley et al. (1996) conducted an earlier investigation of this dust storm following the tenets of Danielsen's paradigm—a paradigm that links the tropopause fold phenomenon and a balanced thermally indirect circulation about the upper level jet stream. However, a cursory examination of mesoscale structures in the storm from the North American Regional Reanalysis (NARR) indicated evidence of a low-level unbalanced thermally direct circulation that demanded further investigation using a high-resolution Weather Research and Forecasting (WRF) model simulation. Principal results from the present study follow: (1) Although the model simulation showed evidence of a weak indirect circulation in the upper troposphere in support of the Danielsen's paradigm, the dynamic control of the storm stemmed from the lower tropospheric mesoscale response to geostrophic imbalance. (2) A lower tropospheric direct circulation led to mass/temperature adjustments that were confirmed by upper air observations at locations in proximity to the accident site, and (3) boundary layer deepening and destabilization due to these mesoscale processes pinpointed the timing and location of the dust storm. Although the present study does not underestimate the value of analyses that focus on the larger/synoptic scales of motion, it does bring to light the value of investigation that makes use of the mesoscale resources in order to clarify synoptic-mesoscale interactions.

Soil frost-induced soil moisture precipitation feedback and effects on atmospheric states

NASA Astrophysics Data System (ADS)

Hagemann, Stefan; Blome, Tanja; Ekici, Altug; Beer, Christian

2016-04-01

Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. As it is a thermal phenomenon, its characteristics are highly dependent on climatic factors. The impact of the currently observed warming, which is projected to persist during the coming decades due to anthropogenic CO2 input, certainly has effects for the vast permafrost areas of the high northern latitudes. The quantification of these effects, however, is scientifically still an open question. This is partly due to the complexity of the system, where several feedbacks are interacting between land and atmosphere, sometimes counterbalancing each other. Moreover, until recently, many global circulation models (GCMs) and Earth system models (ESMs) lacked the sufficient representation of permafrost physics in their land surface schemes. Within the European Union FP7 project PAGE21, the land surface scheme JSBACH of the Max-Planck-Institute for Meteorology ESM (MPI-ESM) has been equipped with the representation of relevant physical processes for permafrost studies. These processes include the effects of freezing and thawing of soil water for both energy and water cycles, thermal properties depending on soil water and ice contents, and soil moisture movement being influenced by the presence of soil ice. In the present study, it will be analysed how these permafrost relevant processes impact large-scale hydrology and climate over northern hemisphere high latitude land areas. For this analysis, the atmosphere-land part of MPI-ESM, ECHAM6-JSBACH, is driven by prescribed observed SST and sea ice in an AMIP2-type setup with and without the newly implemented permafrost processes. Results show a large improvement in the simulated discharge. On one hand this is related to an improved snowmelt peak of runoff due to frozen soil in spring. On the other hand a subsequent reduction of soil moisture leads to a positive land atmosphere feedback to precipitation over the high latitudes, which reduces the model's wet biases in precipitation and evapotranspiration during the summer. This is noteworthy as soil moisture - atmosphere feedbacks have previously not been in the research focus over the high latitudes. These results point out the importance of high latitude physical processes at the land surface for the regional climate.

Impact of seasonal synoptic weather types on local PM10 concentrations in Bavaria/Germany: recent conditions and future projections

NASA Astrophysics Data System (ADS)

Weitnauer, Claudia; Beck, Christoph; Jacobeit, Jucundus

2015-04-01

It is a matter of common knowledge that local concentrations of PM10 (fine particles in the air with a medium diameter less than 10 μm) vary with the seasons in Europe. These concentrations are influenced on the one hand by the amount of natural and anthropogenic emissions and on the other hand by large-scale and local meteorological conditions. In Bavaria (part of southern Germany) as the target region of the present study, the PM10 concentrations are particularly high in winter time. One reason for this are increased particle emissions due to domestic heating and traffic load in December, January and February. As several studies in other European regions indicated, a distinct effect of the large-scale synoptic weather situation in winter on local PM10 concentrations should be considered as another reason. The main task of this study is to use seasonal synoptic weather types, which are optimized with respect to daily mean PM10 data at 16 Bavarian cities, and therefore are classified by using daily gridded NCEP/NCAR reanalysis data (2.5° x 2.5° horizontal resolution) for the recent period 1980 - 2011 over a Central European spatial domain, to describe the impact of the large-scale meteorological conditions on the local particle concentrations. The weather types are related to monthly PM10 indices by using different transfer techniques like direct synoptic downscaling, multiple regression and generalized linear models as well as random forests. The PM10 indices are determined by averaging daily to monthly data (PMmean) or by counting the daily exceedances of a particular threshold (> 50 μg/m3, PMe50). The generated transfer models are evaluated in calibration and validation periods using several forecast skills, for example the mean squared skill score (MSSS) or the Heidke Skill Score (HSS). The sufficiently performing models are then applied to weather types derived from future climate change scenarios of the global climate model ECHAM 6 for the IPCC scenarios RCP 4.5 and 8.5 in order to estimate future climate-change induced modifications of local PM10 concentrations in Bavaria.

The effects of global change upon United States air quality

NASA Astrophysics Data System (ADS)

Gonzalez-Abraham, R.; Avise, J.; Chung, S. H.; Lamb, B.; Salathé, E. P., Jr.; Nolte, C. G.; Loughlin, D.; Guenther, A.; Wiedinmyer, C.; Duhl, T.; Zhang, Y.; Streets, D. G.

2014-12-01

To understand more fully the effects of global changes on ambient concentrations of ozone and particulate matter with aerodynamic diameter smaller than 2.5 μm (PM2.5) in the US, we conducted a comprehensive modeling effort to evaluate explicitly the effects of changes in climate, biogenic emissions, land use, and global/regional anthropogenic emissions on ozone and PM2.5 concentrations and composition. Results from the ECHAM5 global climate model driven with the A1B emission scenario from the Intergovernmental Panel on Climate Change (IPCC) were downscaled using the Weather Research and Forecasting (WRF) model to provide regional meteorological fields. We developed air quality simulations using the Community Multiscale Air Quality Model (CMAQ) chemical transport model for two nested domains with 220 and 36 km horizontal grid cell resolution for a semi-hemispheric domain and a continental United States (US) domain, respectively. The semi-hemispheric domain was used to evaluate the impact of projected Asian emissions changes on US air quality. WRF meteorological fields were used to calculate current (2000s) and future (2050s) biogenic emissions using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). For the semi-hemispheric domain CMAQ simulations, present-day global emissions inventories were used and projected to the 2050s based on the IPCC A1B scenario. Regional anthropogenic emissions were obtained from the US Environmental Protection Agency National Emission Inventory 2002 (EPA NEI2002) and projected to the future using the MARKet ALlocation (MARKAL) energy system model assuming a business as usual scenario that extends current decade emission regulations through 2050. Our results suggest that daily maximum 8 h average ozone (DM8O) concentrations will increase in a range between 2 to 12 ppb across most of the continental US, with the highest increase in the South, Central, and Midwest regions of the US, due to increases in temperature, enhanced biogenic emissions, and changes in land use. The effects of these factors are only partially offset by reductions in DM8O associated with decreasing US anthropogenic emissions. Increases in PM2.5 levels between 2 and 4 μg m-3 in the Northeast, Southeast, and South regions are mostly a result of enhanced biogenic emissions and land use changes. Little change in PM2.5 in the Central, Northwest, and Southwest regions was found, even when PM precursors are reduced with regulatory curtailment. Changes in temperature, relative humidity, and boundary conditions shift the composition but do not alter overall PM2.5 mass concentrations.

Polyethylene Glycol Modified, Cross-Linked Starch Coated Iron Oxide Nanoparticles for Enhanced Magnetic Tumor Targeting

PubMed Central

Cole, Adam J.; David, Allan E.; Wang, Jianxin; Galbán, Craig J.; Hill, Hannah L.; Yang, Victor C.

2010-01-01

While successful magnetic tumor targeting of iron oxide nanoparticles has been achieved in a number of models, the rapid blood clearance of magnetically suitable particles by the reticuloendothelial system (RES) limits their availability for targeting. This work aimed to develop a long-circulating magnetic iron oxide nanoparticle (MNP) platform capable of sustained tumor exposure via the circulation and, thus, enhanced magnetic tumor targeting. Aminated, cross-linked starch (DN) and aminosilane (A) coated MNPs were successfully modified with 5 kDa (A5, D5) or 20 kDa (A20, D20) polyethylene glycol (PEG) chains using simple N-Hydroxysuccinimide (NHS) chemistry and characterized. Identical PEG-weight analogues between platforms (A5 & D5, A20 & D20) were similar in size (140–190 nm) and relative PEG labeling (1.5% of surface amines – A5/D5, 0.4% – A20/D20), with all PEG-MNPs possessing magnetization properties suitable for magnetic targeting. Candidate PEG-MNPs were studied in RES simulations in vitro to predict long-circulating character. D5 and D20 performed best showing sustained size stability in cell culture medium at 37°C and 7 (D20) to 10 (D5) fold less uptake in RAW264.7 macrophages when compared to previously targeted, unmodified starch MNPs (D). Observations in vitro were validated in vivo, with D5 (7.29 hr) and D20 (11.75 hr) showing much longer half-lives than D (0.12 hr). Improved plasma stability enhanced tumor MNP exposure 100 (D5) to 150 (D20) fold as measured by plasma AUC0-∞ Sustained tumor exposure over 24 hours was visually confirmed in a 9L-glioma rat model (12 mg Fe/kg) using magnetic resonance imaging (MRI). Findings indicate that both D5 and D20 are promising MNP platforms for enhanced magnetic tumor targeting, warranting further study in tumor models. PMID:21176955

Application of Land Surface Data Assimilation to Simulations of Sea Breeze Circulations

NASA Technical Reports Server (NTRS)

Mackaro, Scott; Lapenta, William M.; Blackwell, Keith; Suggs, Ron; McNider, Richard T.; Jedlovec, Gary; Kimball, Sytske

2003-01-01

A technique has been developed for assimilating GOES-derived skin temperature tendencies and insolation into the surface energy budget equation of a mesoscale model so that the simulated rate of temperature change closely agrees with the satellite observations. A critical assumption of the technique is that the availability of moisture (either from the soil or vegetation) is the least known term in the model's surface energy budget. Therefore, the simulated latent heat flux, which is a function of surface moisture availability, is adjusted based upon differences between the modeled and satellite- observed skin temperature tendencies. An advantage of this technique is that satellite temperature tendencies are assimilated in an energetically consistent manner that avoids energy imbalances and surface stability problems that arise from direct assimilation of surface shelter temperatures. The fact that the rate of change of the satellite skin temperature is used rather than the absolute temperature means that sensor calibration is not as critical. The sea/land breeze is a well-documented mesoscale circulation that affects many coastal areas of the world including the northern Gulf Coast of the United States. The focus of this paper is to examine how the satellite assimilation technique impacts the simulation of a sea breeze circulation observed along the Mississippi/Alabama coast in the spring of 2001. The technique is implemented within the PSUNCAR MM5 V3-5 and applied at spatial resolutions of 12- and 4-km. It is recognized that even 4-km grid spacing is too coarse to explicitly resolve the detailed, mesoscale structure of sea breezes. Nevertheless, the model can forecast certain characteristics of the observed sea breeze including a thermally direct circulation that results from differential low-level heating across the land-sea interface. Our intent is to determine the sensitivity of the circulation to the differential land surface forcing produced via the assimilation of GOES skin temperature tendencies. Results will be quantified through statistical verification techniques.

Mock Circulatory System of the Fontan Circulation to Study Respiration Effects on Venous Flow Behavior

PubMed Central

Vukicevic, M.; Chiulli, J.A.; Conover, T.; Pennati, G.; Hsia, T.Y.; Figliola, R.S.

2013-01-01

We describe an in vitro model of the Fontan circulation with respiration to study subdiaphragmatic venous flow behavior. The venous and arterial connections of a total cavopulmonary connection (TCPC) test section were coupled with a physical lumped parameter (LP) model of the circulation. Intrathoracic and subdiaphragmatic pressure changes associated with normal breathing were applied. This system was tuned for two patients (5 years, 0.67 m2; 10 years, 1.2 m2) to physiological values. System function was verified by comparison to the analytical model on which it was based and by consistency with published clinical measurements. Overall, subdiaphragmatic venous flow was influenced by respiration. Flow within the arteries and veins increased during inspiration but decreased during expiration with retrograde flow in the inferior venous territories. System pressures and flows showed close agreement with the analytical LP model (p < 0.05). The ratio of the flow rates occurring during inspiration to expiration were within the clinical range of values reported elsewhere. The approach used to setup and control the model was effective and provided reasonable comparisons with clinical data. PMID:23644612

Secondary Gravity Waves in the Winter Mesosphere: Results From a High-Resolution Global Circulation Model

NASA Astrophysics Data System (ADS)

Becker, Erich; Vadas, Sharon L.

2018-03-01

This study analyzes a new high-resolution general circulation model with regard to secondary gravity waves in the mesosphere during austral winter. The model resolves gravity waves down to horizontal and vertical wavelengths of 165 and 1.5 km, respectively. The resolved mean wave drag agrees well with that from a conventional model with parameterized gravity waves up to the midmesosphere in winter and up to the upper mesosphere in summer. About half of the zonal-mean vertical flux of westward momentum in the southern winter stratosphere is due to orographic gravity waves. The high intermittency of the primary orographic gravity waves gives rise to secondary waves that result in a substantial eastward drag in the winter mesopause region. This induces an additional eastward maximum of the mean zonal wind at z ˜ 100 km. Radar and lidar measurements at polar latitudes and results from other high-resolution global models are consistent with this finding. Hence, secondary gravity waves may play a significant role in the general circulation of the winter mesopause region.

Circulation in the South China Sea during summer 2000 as obtained from observations and a generalized topography-following ocean model

NASA Astrophysics Data System (ADS)

Wang, Huiqun; Yuan, Yaochu; Guan, Weibing; Lou, Ruyun; Wang, Kangshan

2004-07-01

On the basis of the recently obtained hydrographic data in the South China Sea, the improved Princeton Ocean Model with a generalized topography-following coordinate system is used to study the circulation in the region during summer 2000. Several sensitivity experiments are carried out to achieve reasonable model parameters for the South China Sea (SCS). It is shown from the resting stratification experiments that the generalized topography-following coordinate scheme is better than the standard sigma grid scheme for reducing the pressure gradient errors. The combination of sea surface height anomaly derived from TOPEX/Poseidon and numerical results with both diagnostic and semidiagnostic simulations provides a consistent circulation pattern for the SCS in August, and the main circulation features can be summarized as follows: (1) There is a notable anticyclonic warm eddy southeast of Vietnam with a horizontal scale of ˜300 km, and there is a cyclonic cold eddy. The simultaneous existence of these cold and warm eddies is one of the important circulation characteristics in the SCS during summer 2000. (2) A secondary cold eddy is found east of Vietnam. (3) The northwestern part of the SCS is dominated by an anticyclonic circulation system. (4) There is also a secondary warm eddy southwest off the Luzon Island. (5) A cyclonic eddy is found west off the Borneo Island. (6) A western intensification phenomenon obviously occurs in the SCS. The dynamical mechanisms of the above-mentioned circulation pattern in the SCS are the interaction between the wind stress and bottom topography and the joint effect of baroclinicity and relief.

Large-Scale Stratospheric Transport Processes

NASA Technical Reports Server (NTRS)

Plumb, R. Alan

2001-01-01

The paper discusses the following: 1. The Brewer-Dobson circulation: tropical upwelling. 2. Mixing into polar vortices. 3. The latitudinal structure of "age" in the stratosphere. 4. The subtropical "tracer edges". 5. Transport in the lower troposphere. 6. Tracer modeling during SOLVE. 7. 3D modeling of "mean age". 8. Models and measurements II.

An in-depth investigation of the life cycle of sulfate from the Kilauea volcano using satellite observations and EMAC model calculations

NASA Astrophysics Data System (ADS)

Penning de Vries, Marloes; Beirle, Steffen; Brühl, Christoph; Hörmann, Christoph; Wagner, Thomas

2015-04-01

The Kilauea volcano (Hawaii), currently perhaps the most active volcano on Earth, has been continuously erupting since the beginning of 1983. A pronounced degassing phase in March-November 2008 caused the formation of an extensive SO2 plume, which in turn led to the formation of sulfate aerosols. The steady trade winds and lack of interfering sources previously allowed us to determine the life time of SO2 using only satellite-based measurements (no a priori or model information). The current investigation is focused on improving our understanding of the processes contributing to sulfate aerosol formation, processing, and loss. We use space-based aerosol measurements by MODIS, MISR, and CALIOP to characterize the aerosols (amount, size, altitude) and study the evolution of aerosol optical depth as a function of distance from the volcano to determine formation and loss rates. The outcome is compared to results from calculations using the EMAC (ECHAM/MESSy Atmospheric Chemistry) model to test the state of understanding of the sulfate aerosol life cycle.

Chemistry and dynamics of the Arctic winter 2015/2016: Simulations with the Chemistry-Climate Model EMAC

NASA Astrophysics Data System (ADS)

Khosrawi, Farahnaz; Kirner, Ole; Sinnhuber, Bjoern-Martin; Ruhnke, Roland; Hoepfner, Michael; Woiwode, Wolfgang; Oelhaf, Hermann; Santee, Michelle L.; Manney, Gloria L.; Froidevaux, Lucien; Murtagh, Donal; Braesicke, Peter

2016-04-01

Model simulations of the Arctic winter 2015/2016 were performed with the atmospheric chemistry-climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) for the POLSTRACC (Polar Stratosphere in a Changing Climate) project. The POLSTRACC project is a HALO mission (High Altitude and LOng Range Research Aircraft) that aims to investigate the structure, composition and evolution of the Arctic Upper Troposphere Lower Stratosphere (UTLS) in a changing climate. Especially, the chemical and physical processes involved in Arctic stratospheric ozone depletion, transport and mixing processes in the UTLS at high latitudes, polar stratospheric clouds as well as cirrus clouds are investigated. The model simulations were performed with a resolution of T42L90, corresponding to a quadratic Gaussian grid of approximately 2.8°× 2.8° degrees in latitude and longitude, and 90 vertical layers from the surface up to 0.01 hPa (approx. 80 km). A Newtonian relaxation technique of the prognostic variables temperature, vorticity, divergence and surface pressure towards ECMWF data was applied above the boundary layer and below 10 hPa, in order to nudge the model dynamics towards the observed meteorology. During the Arctic winter 2015/2016 a stable vortex formed in early December, with a cold pool where temperatures reached below the Nitric Acid Trihydrate (NAT) existence temperature of 195 K, thus allowing Polar Stratospheric Clouds (PSCs) to form. The early winter has been exceptionally cold and satellite observations indicate that sedimenting PSC particles have lead to denitrification as well as dehydration of stratospheric layers. In this presentation an overview of the chemistry and dynamics of the Arctic winter 2015/2016 as simulated with EMAC will be given and comparisons to satellite observations such as e.g. Aura/MLS and Odin/SMR will be shown.

Land cover maps, BVOC emissions, and SOA burden in a global aerosol-climate model

NASA Astrophysics Data System (ADS)

Stanelle, Tanja; Henrot, Alexandra; Bey, Isaelle

2015-04-01

It has been reported that different land cover representations influence the emission of biogenic volatile organic compounds (BVOC) (e.g. Guenther et al., 2006). But the land cover forcing used in model simulations is quite uncertain (e.g. Jung et al., 2006). As a consequence the simulated emission of BVOCs depends on the applied land cover map. To test the sensitivity of global and regional estimates of BVOC emissions on the applied land cover map we applied 3 different land cover maps into our global aerosol-climate model ECHAM6-HAM2.2. We found a high sensitivity for tropical regions. BVOCs are a very prominent precursor for the production of Secondary Organic Aerosols (SOA). Therefore the sensitivity of BVOC emissions on land cover maps impacts the SOA burden in the atmosphere. With our model system we are able to quantify that impact. References: Guenther et al. (2006), Estimates of global terrestrial isoprene emissions using MEGAN, Atmos. Chem. Phys., 6, 3181-3210, doi:10.5194/acp-6-3181-2006. Jung et al. (2006), Exploiting synergies of global land cover products for carbon cycle modeling, Rem. Sens. Environm., 101, 534-553, doi:10.1016/j.rse.2006.01.020.

Recent and possible future variations in the North American Monsoon

USGS Publications Warehouse

Hoell, Andrew; Funk, Chris; Barlow, Mathew; Shukla, Shraddhanand

2016-01-01

The dynamics and recent and possible future changes of the June–September rainfall associated with the North American Monsoon (NAM) are reviewed in this chapter. Our analysis as well as previous analyses of the trend in June–September precipitation from 1948 until 2010 indicate significant precipitation increases over New Mexico and the core NAM region, and significant precipitation decreases over southwest Mexico. The trends in June–September precipitation have been forced by anomalous cyclonic circulation centered at 15°N latitude over the eastern Pacific Ocean. The anomalous cyclonic circulation is responsible for changes in the flux of moisture and the divergence of moisture flux within the core NAM region. Future climate projections using the Coupled Model Intercomparison Project Phase 5 (CMIP5) models, as part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5), support the observed analyses of a later shift in the monsoon season in the presence of increased greenhouse gas concentrations in the atmosphere under the RCP8.5 scenario. The CMIP5 models under the RCP8.5 scenario predict significant NAM-related rainfall decreases during June and July and predict significant NAM-related rainfall increases during September and October.

Diagnostic calculations of the circulation in the Martian atmosphere

NASA Technical Reports Server (NTRS)

Santee, Michelle L.; Crisp, David

1995-01-01

The circulation of the Martian atmosphere during late southern summer is derived from atmospheric temperature and dust distributions retrieved from a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra (LS = 343-348 deg) (Santee and Crisp, 1933). Zonal-mean zonal winds are calculated by assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense midlatitude westerly jets with velocities of 80-90 m/s near 50 km; in the southern tropics the winds are easterly with velocities of 40 m/s near 50 km. The net effect of the zonal-mean meridional circulation and large-scale waves can be approximated by the diabatic ciculation, which is defined from the atmospheric thermal structure and net radiative heating rates. The radiative transfer model described by Crisp (1990) and Santee (1993) is used to compute solar heating and thermal cooling rates from diurnal averages of the retrieved IRIS temperature and dust distributions. At pressures below 4 mbar, there are large net radiative heating rates (up to 5 K/d) in the equatorial region and large net radiative cooling rates (up to 12 K/d) in the polar regions. These net radiative heating rates are used in a diagnostic stream function model which solves for the meridonal and vertical components of the diabatic circulation simultaneously. We find a two cell circulation, with rising motion over the equator, poleward flow in both hemispheres, sinking motion over both polar regions, and return flow in the lowest atmospheric levels. The maximum poleward velocity is 3 m/s in the tropics at approximately 55 km altitude, and the maximum vertical velocity is 2.5 cm/s downward over the north pole at approximately 60 km altitude. If these large transport rates are sustained for an entire season, the Martian atmosphere above the 1-mbar level is overturned in about 38 days. This diabatic circulation is qualitatively similar to the terrestial diabatic circulation at the comparable season, but is more vigorous.

Diagnostic calculations of the circulation in the Martian atmosphere

NASA Astrophysics Data System (ADS)

Santee, Michelle L.; Crisp, David

1995-03-01

The circulation of the Martian atmosphere during late southern summer is derived from atmospheric temperature and dust distributions retrieved from a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra (LS = 343-348 deg) (Santee and Crisp, 1933). Zonal-mean zonal winds are calculated by assuming gradient wind balance and zero surface zonal wind. Both hemispheres have intense midlatitude westerly jets with velocities of 80-90 m/s near 50 km; in the southern tropics the winds are easterly with velocities of 40 m/s near 50 km. The net effect of the zonal-mean meridional circulation and large-scale waves can be approximated by the diabatic ciculation, which is defined from the atmospheric thermal structure and net radiative heating rates. The radiative transfer model described by Crisp (1990) and Santee (1993) is used to compute solar heating and thermal cooling rates from diurnal averages of the retrieved IRIS temperature and dust distributions. At pressures below 4 mbar, there are large net radiative heating rates (up to 5 K/d) in the equatorial region and large net radiative cooling rates (up to 12 K/d) in the polar regions. These net radiative heating rates are used in a diagnostic stream function model which solves for the meridonal and vertical components of the diabatic circulation simultaneously. We find a two cell circulation, with rising motion over the equator, poleward flow in both hemispheres, sinking motion over both polar regions, and return flow in the lowest atmospheric levels. The maximum poleward velocity is 3 m/s in the tropics at approximately 55 km altitude, and the maximum vertical velocity is 2.5 cm/s downward over the north pole at approximately 60 km altitude. If these large transport rates are sustained for an entire season, the Martian atmosphere above the 1-mbar level is overturned in about 38 days. This diabatic circulation is qualitatively similar to the terrestial diabatic circulation at the comparable season, but is more vigorous.

Polyethylene glycol modified, cross-linked starch-coated iron oxide nanoparticles for enhanced magnetic tumor targeting.

PubMed

Cole, Adam J; David, Allan E; Wang, Jianxin; Galbán, Craig J; Hill, Hannah L; Yang, Victor C

2011-03-01

While successful magnetic tumor targeting of iron oxide nanoparticles has been achieved in a number of models, the rapid blood clearance of magnetically suitable particles by the reticuloendothelial system (RES) limits their availability for targeting. This work aimed to develop a long-circulating magnetic iron oxide nanoparticle (MNP) platform capable of sustained tumor exposure via the circulation and, thus, potentially enhanced magnetic tumor targeting. Aminated, cross-linked starch (DN) and aminosilane (A) coated MNPs were successfully modified with 5 kDa (A5, D5) or 20 kDa (A20, D20) polyethylene glycol (PEG) chains using simple N-Hydroxysuccinimide (NHS) chemistry and characterized. Identical PEG-weight analogues between platforms (A5 & D5, A20 & D20) were similar in size (140-190 nm) and relative PEG labeling (1.5% of surface amines - A5/D5, 0.4% - A20/D20), with all PEG-MNPs possessing magnetization properties suitable for magnetic targeting. Candidate PEG-MNPs were studied in RES simulations in vitro to predict long-circulating character. D5 and D20 performed best showing sustained size stability in cell culture medium at 37 °C and 7 (D20) to 10 (D5) fold less uptake in RAW264.7 macrophages when compared to previously targeted, unmodified starch MNPs (D). Observations in vitro were validated in vivo, with D5 (7.29 h) and D20 (11.75 h) showing much longer half-lives than D (0.12 h). Improved plasma stability enhanced tumor MNP exposure 100 (D5) to 150 (D20) fold as measured by plasma AUC(0-∞). Sustained tumor exposure over 24 h was visually confirmed in a 9L-glioma rat model (12 mg Fe/kg) using magnetic resonance imaging (MRI). Findings indicate that a polyethylene glycol modified, cross-linked starch-coated MNP is a promising platform for enhanced magnetic tumor targeting, warranting further study in tumor models. Copyright © 2010 Elsevier Ltd. All rights reserved.

Impact of lateral boundary conditions on regional analyses

NASA Astrophysics Data System (ADS)

Chikhar, Kamel; Gauthier, Pierre

2017-04-01

Regional and global climate models are usually validated by comparison to derived observations or reanalyses. Using a model in data assimilation results in a direct comparison to observations to produce its own analyses that may reveal systematic errors. In this study, regional analyses over North America are produced based on the fifth-generation Canadian Regional Climate Model (CRCM5) combined with the variational data assimilation system of the Meteorological Service of Canada (MSC). CRCM5 is driven at its boundaries by global analyses from ERA-interim or produced with the global configuration of the CRCM5. Assimilation cycles for the months of January and July 2011 revealed systematic errors in winter through large values in the mean analysis increments. This bias is attributed to the coupling of the lateral boundary conditions of the regional model with the driving data particularly over the northern boundary where a rapidly changing large scale circulation created significant cross-boundary flows. Increasing the time frequency of the lateral driving and applying a large-scale spectral nudging improved significantly the circulation through the lateral boundaries which translated in a much better agreement with observations.

Understanding the West African Monsoon from the analysis of diabatic heating distributions as simulated by climate models

NASA Astrophysics Data System (ADS)

Martin, G. M.; Peyrillé, P.; Roehrig, R.; Rio, C.; Caian, M.; Bellon, G.; Codron, F.; Lafore, J.-P.; Poan, D. E.; Idelkadi, A.

2017-03-01

Vertical and horizontal distributions of diabatic heating in the West African monsoon (WAM) region as simulated by four model families are analyzed in order to assess the physical processes that affect the WAM circulation. For each model family, atmosphere-only runs of their CMIP5 configurations are compared with more recent configurations which are on the development path toward CMIP6. The various configurations of these models exhibit significant differences in their heating/moistening profiles, related to the different representation of physical processes such as boundary layer mixing, convection, large-scale condensation and radiative heating/cooling. There are also significant differences in the models' simulation of WAM rainfall patterns and circulations. The weaker the radiative cooling in the Saharan region, the larger the ascent in the rainband and the more intense the monsoon flow, while the latitude of the rainband is related to heating in the Gulf of Guinea region and on the northern side of the Saharan heat low. Overall, this work illustrates the difficulty experienced by current climate models in representing the characteristics of monsoon systems, but also that we can still use them to understand the interactions between local subgrid physical processes and the WAM circulation. Moreover, our conclusions regarding the relationship between errors in the large-scale circulation of the WAM and the structure of the heating by small-scale processes will motivate future studies and model development.

Seasonal cycle of circulation in the Antarctic Peninsula and the off-shelf transport of shelf waters into southern Drake Passage and Scotia Sea

NASA Astrophysics Data System (ADS)

Jiang, Mingshun; Charette, Matthew A.; Measures, Christopher I.; Zhu, Yiwu; Zhou, Meng

2013-06-01

The seasonal cycle of circulation and transport in the Antarctic Peninsula shelf region is investigated using a high-resolution (˜2 km) regional model based on the Regional Oceanic Modeling System (ROMS). The model also includes a naturally occurring tracer with a strong source over the shelf (radium isotope 228Ra, t1/2=5.8 years) to investigate the sediment Fe input and its transport. The model is spun-up for three years using climatological boundary and surface forcing and then run for the 2004-2006 period using realistic forcing. Model results suggest a persistent and coherent circulation system throughout the year consisting of several major components that converge water masses from various sources toward Elephant Island. These currents are largely in geostrophic balance, driven by surface winds, topographic steering, and large-scale forcing. Strong off-shelf transport of the Fe-rich shelf waters takes place over the northeastern shelf/slope of Elephant Island, driven by a combination of topographic steering, extension of shelf currents, and strong horizontal mixing between the ACC and shelf waters. These results are generally consistent with recent and historical observational studies. Both the shelf circulation and off-shelf transport show a significant seasonality, mainly due to the seasonal changes of surface winds and large-scale circulation. Modeled and observed distributions of 228Ra suggest that a majority of Fe-rich upper layer waters exported off-shelf around Elephant Island are carried by the shelfbreak current and the Bransfield Strait Current from the shallow sills between Gerlache Strait and Livingston Island, and northern shelf of the South Shetland Islands, where strong winter mixing supplies much of the sediment derived nutrients (including Fe) input to the surface layer.

Mixing parametrizations for ocean climate modelling

NASA Astrophysics Data System (ADS)

Gusev, Anatoly; Moshonkin, Sergey; Diansky, Nikolay; Zalesny, Vladimir

2016-04-01

The algorithm is presented of splitting the total evolutionary equations for the turbulence kinetic energy (TKE) and turbulence dissipation frequency (TDF), which is used to parameterize the viscosity and diffusion coefficients in ocean circulation models. The turbulence model equations are split into the stages of transport-diffusion and generation-dissipation. For the generation-dissipation stage, the following schemes are implemented: the explicit-implicit numerical scheme, analytical solution and the asymptotic behavior of the analytical solutions. The experiments were performed with different mixing parameterizations for the modelling of Arctic and the Atlantic climate decadal variability with the eddy-permitting circulation model INMOM (Institute of Numerical Mathematics Ocean Model) using vertical grid refinement in the zone of fully developed turbulence. The proposed model with the split equations for turbulence characteristics is similar to the contemporary differential turbulence models, concerning the physical formulations. At the same time, its algorithm has high enough computational efficiency. Parameterizations with using the split turbulence model make it possible to obtain more adequate structure of temperature and salinity at decadal timescales, compared to the simpler Pacanowski-Philander (PP) turbulence parameterization. Parameterizations with using analytical solution or numerical scheme at the generation-dissipation step of the turbulence model leads to better representation of ocean climate than the faster parameterization using the asymptotic behavior of the analytical solution. At the same time, the computational efficiency left almost unchanged relative to the simple PP parameterization. Usage of PP parametrization in the circulation model leads to realistic simulation of density and circulation with violation of T,S-relationships. This error is majorly avoided with using the proposed parameterizations containing the split turbulence model. The high sensitivity of the eddy-permitting circulation model to the definition of mixing is revealed, which is associated with significant changes of density fields in the upper baroclinic ocean layer over the total considered area. For instance, usage of the turbulence parameterization instead of PP algorithm leads to increasing circulation velocity in the Gulf Stream and North Atlantic Current, as well as the subpolar cyclonic gyre in the North Atlantic and Beaufort Gyre in the Arctic basin are reproduced more realistically. Consideration of the Prandtl number as a function of the Richardson number significantly increases the modelling quality. The research was supported by the Russian Foundation for Basic Research (grant № 16-05-00534) and the Council on the Russian Federation President Grants (grant № MK-3241.2015.5)

ENSO-Related Precipitation and Its Statistical Relationship with the Walker Circulation Trend in CMIP5 AMIP Models

DOE PAGES

Yim, Bo; Yeh, Sang -Wook; Sohn, Byung -Ju

2016-01-29

Observational evidence shows that the Walker circulation (WC) in the tropical Pacific has strengthened in recent decades. In this study, we examine the WC trend for 1979–2005 and its relationship with the precipitation associated with the El Niño Southern Oscillation (ENSO) using the sea surface temperature (SST)-constrained Atmospheric Model Intercomparison Project (AMIP) simulations of the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. All of the 29 models show a strengthening of the WC trend in response to an increase in the SST zonal gradient along the equator. Despite the same SST-constrained AMIP simulations, however, a large diversity ismore » found among the CMIP5 climate models in the magnitude of the WC trend. The relationship between the WC trend and precipitation anomalies (PRCPAs) associated with ENSO (ENSO-related PRCPAs) shows that the longitudinal position of the ENSO-related PRCPAs in the western tropical Pacific is closely related to the magnitude of the WC trend. Specifically, it is found that the strengthening of the WC trend is large (small) in the CMIP5 AMIP simulations in which the ENSO-related PRCPAs are located relatively westward (eastward) in the western tropical Pacific. Furthermore, the zonal shift of the ENSO-related precipitation in the western tropical Pacific, which is associated with the climatological mean precipitation in the tropical Pacific, could play an important role in modifying the WC trend in the CMIP5 climate models.« less

Contribution of different PSC types to Arctic ozone depletion caused by chlorine activation and denitrification

NASA Astrophysics Data System (ADS)

Kirner, Oliver; Khosrawi, Farah; Müller, Rolf; Weimer, Michael; Ruhnke, Roland

2017-04-01

Heterogeneous reactions on the surfaces of PSC particles and denitrification of the stratosphere are the cause for polar ozone depletion in spring. In a former study we investigated the impact of different types of PSCs on Antarctic ozone depletion with the help of the chemistry-climate model ECHAM5/MESSy Atmospheric chemistry (EMAC). In this study, we investigate the impact of PSCs on Arctic ozone loss. One standard and four sensitivity EMAC simulations (nudged with ERA-Interim) have been performed to evaluate the contribution of liquid, NAT and ice particles to ozone depletion in the Arctic winters 2010/2011 and 2015/2016 due to chlorine activation by heterogeneous chemistry on their surfaces and due to denitrification of the stratosphere. In the first three sensitivity simulations, we changed the heterogeneous chemistry on PSC particles by switching on and off the chemistry on liquid, NAT and ice particles. One further sensitivity simulation without NAT formation (only liquid and ice particles) was performed to evaluate the contribution of NAT to Arctic ozone depletion due to denitrification of the stratosphere. With the help of these different EMAC simulations, we will show the significance of liquid, NAT and ice particles to Arctic ozone depletion caused by chlorine activation and denitrification.

Assessing the Tangent Linear Behaviour of Common Tracer Transport Schemes and Their Use in a Linearised Atmospheric General Circulation Model

NASA Technical Reports Server (NTRS)

Holdaway, Daniel; Kent, James

2015-01-01

The linearity of a selection of common advection schemes is tested and examined with a view to their use in the tangent linear and adjoint versions of an atmospheric general circulation model. The schemes are tested within a simple offline one-dimensional periodic domain as well as using a simplified and complete configuration of the linearised version of NASA's Goddard Earth Observing System version 5 (GEOS-5). All schemes which prevent the development of negative values and preserve the shape of the solution are confirmed to have nonlinear behaviour. The piecewise parabolic method (PPM) with certain flux limiters, including that used by default in GEOS-5, is found to support linear growth near the shocks. This property can cause the rapid development of unrealistically large perturbations within the tangent linear and adjoint models. It is shown that these schemes with flux limiters should not be used within the linearised version of a transport scheme. The results from tests using GEOS-5 show that the current default scheme (a version of PPM) is not suitable for the tangent linear and adjoint model, and that using a linear third-order scheme for the linearised model produces better behaviour. Using the third-order scheme for the linearised model improves the correlations between the linear and non-linear perturbation trajectories for cloud liquid water and cloud liquid ice in GEOS-5.

Projections of Southern Hemisphere atmospheric circulation interannual variability

NASA Astrophysics Data System (ADS)

Grainger, Simon; Frederiksen, Carsten S.; Zheng, Xiaogu

2017-02-01

An analysis is made of the coherent patterns, or modes, of interannual variability of Southern Hemisphere 500 hPa geopotential height field under current and projected climate change scenarios. Using three separate multi-model ensembles (MMEs) of coupled model intercomparison project phase 5 (CMIP5) models, the interannual variability of the seasonal mean is separated into components related to (1) intraseasonal processes; (2) slowly-varying internal dynamics; and (3) the slowly-varying response to external changes in radiative forcing. In the CMIP5 RCP8.5 and RCP4.5 experiments, there is very little change in the twenty-first century in the intraseasonal component modes, related to the Southern annular mode (SAM) and mid-latitude wave processes. The leading three slowly-varying internal component modes are related to SAM, the El Niño-Southern oscillation (ENSO), and the South Pacific wave (SPW). Structural changes in the slow-internal SAM and ENSO modes do not exceed a qualitative estimate of the spatial sampling error, but there is a consistent increase in the ENSO-related variance. Changes in the SPW mode exceed the sampling error threshold, but cannot be further attributed. Changes in the dominant slowly-varying external mode are related to projected changes in radiative forcing. They reflect thermal expansion of the tropical troposphere and associated changes in the Hadley Cell circulation. Changes in the externally-forced associated variance in the RCP8.5 experiment are an order of magnitude greater than for the internal components, indicating that the SH seasonal mean circulation will be even more dominated by a SAM-like annular structure. Across the three MMEs, there is convergence in the projected response in the slow-external component.

ELABELA/APELA levels are not decreased in the maternal circulation or placenta among women with preeclampsia.

PubMed

Pritchard, Natasha; Kaitu'u-Lino, Tu'uhevaha J; Gong, Sungsam; Dopierala, Justyna; Smith, Gordon C S; Charnock-Jones, D Stephen; Tong, Stephen

2018-05-24

The genetic deletion of Elabela (official name APELA, encoding the peptide hormone apelin receptor early endogenous ligand) produces a preeclampsia-like phenotype in mice. However, evidence linking ELABELA with human disease is lacking. Therefore, we measured placental mRNA and circulating ELABELA in human samples. ELABELA mRNA (measured by RNA-Seq) was unchanged in 82 preeclamptic placentas compared to 82 matched controls (mean difference 0.53 %; 95% CI, -25.9 to 27.0, P = 0.78). We measured circulating ELABELA in 32 women with preterm preeclampsia (delivered <34 weeks' gestation) and 32 matched controls sampled at the same gestational age. There was no difference in circulating ELABELA concentration (median (95% CI) in the preeclamptic cohort 28.5 pg/mL (5.3 to 63.2) vs 20.5 pg/mL (9.2 to 58.0) controls; median difference (95% CI) was 8.0 pg/mL (CI -17.7 to 12.1), P = 0.43). In contrast, soluble FLT1 (sFLT1, a protein with an established association with preeclampsia) mRNA was elevated in placental tissue (mean difference 34.9%; 95% CI, 16.6 to 53.1, P = 0.001), and circulating concentrations were 16.8-fold higher among the preeclamptic cohort (P < 0.0001). In conclusion, we were able to recapitulate the well-recognized association between circulating sFLT1 and preeclampsia but there was no such association with ELABELA. Hence, the speculated clinical relevance of observations in the murine model linking ELABELA to preeclampsia are likely incorrect. Copyright © 2018. Published by Elsevier Inc.

Atlantic Meridional Overturning Circulation Influence on North Atlantic Sector Surface Air Temperature and its Predictability in the Kiel Climate Model

NASA Astrophysics Data System (ADS)

Latif, M.

2017-12-01

We investigate the influence of the Atlantic Meridional Overturning Circulation (AMOC) on the North Atlantic sector surface air temperature (SAT) in two multi-millennial control integrations of the Kiel Climate Model (KCM). One model version employs a freshwater flux correction over the North Atlantic, while the other does not. A clear influence of the AMOC on North Atlantic sector SAT only is simulated in the corrected model that depicts much reduced upper ocean salinity and temperature biases in comparison to the uncorrected model. Further, the model with much reduced biases depicts significantly enhanced multiyear SAT predictability in the North Atlantic sector relative to the uncorrected model. The enhanced SAT predictability in the corrected model is due to a stronger and more variable AMOC and its enhanced influence on North Atlantic sea surface temperature (SST). Results obtained from preindustrial control integrations of models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) support the findings obtained from the KCM: models with large North Atlantic biases tend to have a weak AMOC influence on SST and exhibit a smaller SAT predictability over the North Atlantic sector.

Ecosystem behavior at Bermuda Station [open quotes]S[close quotes] and ocean weather station [open quotes]India[close quotes]: A general circulation model and observational analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fasham, M.J.R.; Sarmiento, J.L.; Slater, R.D.

1993-06-01

One important theme of modern biological oceanography has been the attempt to develop models of how the marine ecosystem responds to variations in the physical forcing functions such as solar radiation and the wind field. The authors have addressed the problem by embedding simple ecosystem models into a seasonally forced three-dimensional general circulation model of the North Atlantic ocean. In this paper first, some of the underlying biological assumptions of the ecosystem model are presented, followed by an analysis of how well the model predicts the seasonal cycle of the biological variables at Bermuda Station s' and Ocean Weather Stationmore » India. The model gives a good overall fit to the observations but does not faithfully model the whole seasonal ecosystem model. 57 refs., 25 figs., 5 tabs.« less

Introducing a boreal wetland model within the Earth System model framework

NASA Astrophysics Data System (ADS)

Getzieh, R. J.; Brovkin, V.; Reick, C.; Kleinen, T.; Raddatz, T.; Raivonen, M.; Sevanto, S.

2009-04-01

Wetlands of the northern high latitudes with their low temperatures and waterlogged conditions are prerequisite for peat accumulation. They store at least 25% of the global soil organic carbon and constitute currently the largest natural source of methane. These boreal and subarctic peat carbon pools are sensitive to climate change since the ratio of carbon sequestration and emission is closely dependent on hydrology and temperature. Global biogeochemistry models used for simulations of CO2 dynamics in the past and future climates usually ignore changes in the peat storages. Our approach aims at the evaluation of the boreal wetland feedback to climate through the CO2 and CH4 fluxes on decadal to millennial time scales. A generic model of organic matter accumulation and decay in boreal wetlands is under development in the MPI for Meteorology in cooperation with the University of Helsinki. Our approach is to develop a wetland model which is consistent with the physical and biogeochemical components of the land surface module JSBACH as a part of the Earth System model framework ECHAM5-MPIOM-JSBACH. As prototypes, we use modelling approach by Frolking et al. (2001) for the peat dynamics and the wetland model by Wania (2007) for vegetation cover and plant productivity. An initial distribution of wetlands follows the GLWD-3 map by Lehner and Döll (2004). First results of the modelling approach will be presented. References: Frolking, S. E., N. T. Roulet, T. R. Moore, P. J. H. Richard, M. Lavoie and S. D. Muller (2001): Modeling Northern Peatland Decomposition and Peat Accumulation, Ecosystems, 4, 479-498. Lehner, B., Döll P. (2004): Development and validation of a global database of lakes, reservoirs and wetlands. Journal of Hydrology 296 (1-4), 1-22. Wania, R. (2007): Modelling northern peatland land surface processes, vegetation dynamics and methane emissions. PhD thesis, University of Bristol, 122 pp.

Black Carbon Measurement and Modeling in the Arabian Peninsula

NASA Astrophysics Data System (ADS)

Zawad, Faisal Al; Khoder, Mamdouh; Almazroui, Mansour; Alghamdi, Mansour; Lihavainen, Heikki; Hyvarinen, Antti; Henriksson, Svante

2017-04-01

Black carbon is an important atmospheric aerosol as an effective factor in public health, changing the global and regional climate, and reducing visibility. Black carbon absorbs light, warms the atmosphere, and modifies cloud droplets and the amount of precipitation. In spite of this significance, knowledge of black carbon over the Arabian Peninsula is hard to find in literature until recently. The total mass of black carbon and wind direction and speeds were measured continuously at Hada Al-Sham, Saudi Arabia for the year 2013. In addition, a state of the art global aerosol - climate model (ECHAM5-HAM) was used to determine black carbon climatology over the Arabian Peninsula. Simulation of the model was carried out for the years eight years (2004 - 2011). The daily mean values of the concentrations of black carbon had a minimum of 15.0 ng/m3 and a maximum of 6372 ng/m3 with a mean of at 1899 ng/m3. The diurnal pattern of black carbon showed higher values overnight, and steady low values during daytimes caused by sea and land breezes. Seasons of black carbon vary over the Arabian Peninsula, and the longest is in the Northern Region where it lasts from July to October. High concentrations of black carbon at Hada Al-Sham was observed with a mean of 1.9 µm/m3, and seasons of black carbon vary widely across the Arabian Peninsula. Assessment of the effects of black carbon over the Arabian Peninsula on the global radiation balance. Initiating a black carbon monitoring network is highly recommended to assess its impacts on health, environment, and climate.

Variability of hydrological extreme events in East Asia and their dynamical control: a comparison between observations and two high-resolution global climate models

NASA Astrophysics Data System (ADS)

Freychet, N.; Duchez, A.; Wu, C.-H.; Chen, C.-A.; Hsu, H.-H.; Hirschi, J.; Forryan, A.; Sinha, B.; New, A. L.; Graham, T.; Andrews, M. B.; Tu, C.-Y.; Lin, S.-J.

2017-02-01

This work investigates the variability of extreme weather events (drought spells, DS15, and daily heavy rainfall, PR99) over East Asia. It particularly focuses on the large scale atmospheric circulation associated with high levels of the occurrence of these extreme events. Two observational datasets (APHRODITE and PERSIANN) are compared with two high-resolution global climate models (HiRAM and HadGEM3-GC2) and an ensemble of other lower resolution climate models from CMIP5. We first evaluate the performance of the high resolution models. They both exhibit good skill in reproducing extreme events, especially when compared with CMIP5 results. Significant differences exist between the two observational datasets, highlighting the difficulty of having a clear estimate of extreme events. The link between the variability of the extremes and the large scale circulation is investigated, on monthly and interannual timescales, using composite and correlation analyses. Both extreme indices DS15 and PR99 are significantly linked to the low level wind intensity over East Asia, i.e. the monsoon circulation. It is also found that DS15 events are strongly linked to the surface temperature over the Siberian region and to the land-sea pressure contrast, while PR99 events are linked to the sea surface temperature anomalies over the West North Pacific. These results illustrate the importance of the monsoon circulation on extremes over East Asia. The dependencies on of the surface temperature over the continent and the sea surface temperature raise the question as to what extent they could affect the occurrence of extremes over tropical regions in future projections.

Three-pattern decomposition of global atmospheric circulation: part II—dynamical equations of horizontal, meridional and zonal circulations

NASA Astrophysics Data System (ADS)

Hu, Shujuan; Cheng, Jianbo; Xu, Ming; Chou, Jifan

2018-04-01

The three-pattern decomposition of global atmospheric circulation (TPDGAC) partitions three-dimensional (3D) atmospheric circulation into horizontal, meridional and zonal components to study the 3D structures of global atmospheric circulation. This paper incorporates the three-pattern decomposition model (TPDM) into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal, meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved, as in the primitive equations. The physical significance of the newly established equations is demonstrated. Our findings reveal that the new equations are essentially the 3D vorticity equations of atmosphere and that the time evolution rules of the horizontal, meridional and zonal circulations can be described from the perspective of 3D vorticity evolution. The new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large-scale atmospheric circulation variations. A simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the Rossby, Hadley and Walker circulations. The model shows that the horizontal air temperature anomaly gradient (ATAG) induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation. The simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved, and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations. Moreover, the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature. The simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal, meridional and zonal components of global atmospheric circulation.

Implications of summertime marine stratocumulus on the North American climate

NASA Technical Reports Server (NTRS)

Clark, John H. E.

1994-01-01

This study focuses on the effects of summertime stratocumulus over the eastern Pacific. This cloud is linked to the semi-permanent sub-tropical highs that dominate the low-level circulation over the Pacific and Atlantic. Subsidence on the eastern flank of these highs creates an inversion based about 800 m above sea level that caps moist air near the surface. This air overlies cool waters driven by upwelling along the coastal regions of North America. Strong surface north-westerlies mix the boundary layer enough to saturate the air just below the capping inversion. Widespread stratocumulus is thus formed. All calculations were carried out using the GENESIS general circulation model that was run at MSFC. Among the more important properties of the model is that it includes radiative forcing due to absorption of solar radiation and the emission of infrared radiation, interactive clouds (both stratocumulus and cumulus types), exchanges of heat and moisture with the lower boundary. Clouds are interactive in the sense that they impact the circulation by modifying the fields of radiative heating and turbulent fluxes of heat and moisture in the boundary layer. In turn, clouds are modified by the winds through the advection of moisture. In order to isolate the effects of mid- and high-latitude stratocumulus, two runs were made with the model: one with and the other without stratocumulus. The runs were made for a year, but with perpetual July conditions, i.e., solar forcing was fixed. The diurnal solar cycle, however, was allowed for. The sea surface temperature distribution was fixed in both runs to represent climatological July conditions. All dependent variables were represented at 12 surfaces of constant sigma = p/p(sub O), where p is pressure and p(sub O) is surface pressure. To facilitate analysis, model output was transformed to constant pressure surfaces. Structures no smaller in size than 7.5 degrees longitude and 4.5 degrees in latitude were resolved. Smaller features of the circulation were parameterized. The model thus captures synoptic- and planetary-scale circulation features.

Secondary ozone peaks in the troposphere over the Himalayas

NASA Astrophysics Data System (ADS)

Ojha, Narendra; Pozzer, Andrea; Akritidis, Dimitris; Lelieveld, Jos

2017-06-01

Layers with strongly enhanced ozone concentrations in the middle-upper troposphere, referred to as secondary ozone peaks (SOPs), have been observed in different regions of the world. Here we use the global ECHAM5/MESSy atmospheric chemistry model (EMAC) to (i) investigate the processes causing SOPs, (ii) explore both their frequency of occurrence and seasonality, and (iii) assess their effects on the tropospheric ozone budget over the Himalayas. The vertical profiles of potential vorticity (PV) and a stratospheric ozone tracer (O3s) in EMAC simulations, in conjunction with the structure of SOPs, suggest that SOPs over the Himalayas are formed by stratosphere-to-troposphere transport (STT) of ozone. The spatial distribution of O3s further shows that such effects are in general most pronounced in the northern part of India. Model simulated ozone distributions and backward air trajectories show that ozone rich air masses, associated with STT, originate as far as northern Africa and the North Atlantic Ocean, the Middle East, as well as in nearby regions in Afghanistan and Pakistan, and are rapidly (within 2-3 days) transported to the Himalayas. Analysis of a 15-year (2000-2014) EMAC simulation shows that the frequency of SOPs is highest during the pre-monsoon season (e.g. 11 % of the time in May), while no intense SOP events are found during the July-October period. The SOPs are estimated to enhance the tropospheric column ozone (TCO) over the central Himalayas by up to 21 %.

Statistical downscaling and future scenario generation of temperatures for Pakistan Region

NASA Astrophysics Data System (ADS)

Kazmi, Dildar Hussain; Li, Jianping; Rasul, Ghulam; Tong, Jiang; Ali, Gohar; Cheema, Sohail Babar; Liu, Luliu; Gemmer, Marco; Fischer, Thomas

2015-04-01

Finer climate change information on spatial scale is required for impact studies than that presently provided by global or regional climate models. It is especially true for regions like South Asia with complex topography, coastal or island locations, and the areas of highly heterogeneous land-cover. To deal with the situation, an inexpensive method (statistical downscaling) has been adopted. Statistical DownScaling Model (SDSM) employed for downscaling of daily minimum and maximum temperature data of 44 national stations for base time (1961-1990) and then the future scenarios generated up to 2099. Observed as well as Predictors (product of National Oceanic and Atmospheric Administration) data were calibrated and tested on individual/multiple basis through linear regression. Future scenario was generated based on HadCM3 daily data for A2 and B2 story lines. The downscaled data has been tested, and it has shown a relatively strong relationship with the observed in comparison to ECHAM5 data. Generally, the southern half of the country is considered vulnerable in terms of increasing temperatures, but the results of this study projects that in future, the northern belt in particular would have a possible threat of increasing tendency in air temperature. Especially, the northern areas (hosting the third largest ice reserves after the Polar Regions), an important feeding source for Indus River, are projected to be vulnerable in terms of increasing temperatures. Consequently, not only the hydro-agricultural sector but also the environmental conditions in the area may be at risk, in future.

Midlatitude atmospheric circulation responses under 1.5 and 2.0 °C warming and implications for regional impacts

NASA Astrophysics Data System (ADS)

Li, Camille; Michel, Clio; Seland Graff, Lise; Bethke, Ingo; Zappa, Giuseppe; Bracegirdle, Thomas J.; Fischer, Erich; Harvey, Ben J.; Iversen, Trond; King, Martin P.; Krishnan, Harinarayan; Lierhammer, Ludwig; Mitchell, Daniel; Scinocca, John; Shiogama, Hideo; Stone, Dáithí A.; Wettstein, Justin J.

2018-04-01

This study investigates the global response of the midlatitude atmospheric circulation to 1.5 and 2.0 °C of warming using the HAPPI (Half a degree Additional warming, Prognosis and Projected Impacts) ensemble, with a focus on the winter season. Characterising and understanding this response is critical for accurately assessing the near-term regional impacts of climate change and the benefits of limiting warming to 1.5 °C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the circulation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model mean response of the jet streams, storm tracks, and stationary waves across most of the midlatitudes; larger signals in these features are mostly consistent with those seen in more strongly forced warming scenarios. Signals that emerge in the 1.5 °C experiment are a weakening of storm activity over North America, an inland shift of the North American stationary ridge, an equatorward shift of the North Pacific jet exit, and an equatorward intensification of the South Pacific jet. Signals that emerge under an additional 0.5 °C of warming include a poleward shift of the North Atlantic jet exit, an eastward extension of the North Atlantic storm track, and an intensification on the flanks of the Southern Hemisphere storm track. Case studies explore the implications of these circulation responses for precipitation impacts in the Mediterranean, in western Europe, and on the North American west coast, paying particular attention to possible outcomes at the tails of the response distributions. For example, the projected weakening of the Mediterranean storm track emerges in the 2 °C warmer world, with exceptionally dry decades becoming 5 times more likely.

Using a Gravity Model to Predict Circulation in a Public Library System.

ERIC Educational Resources Information Center

Ottensmann, John R.

1995-01-01

Describes the development of a gravity model based upon principles of spatial interaction to predict the circulation of libraries in the Indianapolis-Marion County Public Library (Indiana). The model effectively predicted past circulation figures and was tested by predicting future library circulation, particularly for a new branch library.…

Weakening of tropical Pacific atmospheric circulation due to anthropogenic forcing

NASA Astrophysics Data System (ADS)

Vecchi, Gabriel A.; Soden, Brian J.; Wittenberg, Andrew T.; Held, Isaac M.; Leetmaa, Ants; Harrison, Matthew J.

2006-05-01

Since the mid-nineteenth century the Earth's surface has warmed, and models indicate that human activities have caused part of the warming by altering the radiative balance of the atmosphere. Simple theories suggest that global warming will reduce the strength of the mean tropical atmospheric circulation. An important aspect of this tropical circulation is a large-scale zonal (east-west) overturning of air across the equatorial Pacific Ocean-driven by convection to the west and subsidence to the east-known as the Walker circulation. Here we explore changes in tropical Pacific circulation since the mid-nineteenth century using observations and a suite of global climate model experiments. Observed Indo-Pacific sea level pressure reveals a weakening of the Walker circulation. The size of this trend is consistent with theoretical predictions, is accurately reproduced by climate model simulations and, within the climate models, is largely due to anthropogenic forcing. The climate model indicates that the weakened surface winds have altered the thermal structure and circulation of the tropical Pacific Ocean. These results support model projections of further weakening of tropical atmospheric circulation during the twenty-first century.

Mediterranean summer climate and the importance of Middle-East Topography

NASA Astrophysics Data System (ADS)

Simpson, Isla; Seager, Richard; Shaw, Tiffany; Ting, Mingfang

2015-04-01

In summer, the atmospheric circulation over the Mediterranean is characterized by localized intense subsidence and low level northerlies over the central- to eastern portion of the basin. Here, simulations with the Community Atmosphere Model, version 5 are used to investigate the influence of the elevated terrain of North Africa and the Middle East on this summertime circulation. This builds on previous work that recognized a role for North African topography in localizing the Mediterranean subsidence. By flattening the two regions of elevated terrain in the model it is demonstrated that, while they both conspire to produce about 30% of the summertime subsidence, contrary to previous work, the mountains of the Middle-East dominate in this topographic contribution by far. This topography, consisting primarily of the Zagros Mountain range, alters the circulation throughout the depth of the troposphere over the Mediterranean, and further East. The model results suggest that about 20% of the Mediterranean summertime moisture deficit can be attributed to this mountain induced circulation. This topography, therefore, plays an important role in the climate of the Mediterranean and the large scale circulation over the rest of Eurasia during the summer. Further stationary wave modelling reveals that the mountain influence is produced via mechanical forcing of the flow. The greatest influence of the topography occurs when the low level incident flow is easterly, as happens during the summer, primarily due to the presence of condensational heating over Asia. During other seasons, when the low level incident flow is westerly, the influence of Middle-East topography on the Mediterranean is negligible.

Evaluating wave-current interaction in an urban estuary and flooding implications for coastal communities

NASA Astrophysics Data System (ADS)

Cifuentes-Lorenzen, A.; O'Donnell, J.; Howard-Strobel, M. M.; Fake, T.; McCardell, G.

2016-12-01

Accurate hydrodynamic-wave coupled coastal circulation models aid the prediction of storm impacts, particularly in areas where data is absent, and can inform mitigation options. They are essential everywhere to account for the effects of climate change. Here, the Finite Volume Community Ocean Model (FVCOM) was used to estimate the residual circulation inside a small urban estuary, Long Island Sound, during three severe weather events of different magnitude (i.e. 1/5, 1/25 and 1/50 year events). The effect of including wave coupling using a log-layer bottom boundary and the bottom wave-current coupling, following the approach of Madsen (1994) on the simulated residual circulation was assessed. Significant differences in the solutions were constrained to the near surface (s>-0.3) region. No significant difference in the depth-averaged residual circulation was detected. When the Madsen (1994) bottom boundary layer model for wave-current interaction was employed, differences in residual circulation resulted. The bottom wave-current interaction also plays an important role in the wave dynamics. Significant wave heights along the northern Connecticut shoreline were enhanced by up to 15% when the bottom wave-current interaction was included in the simulations. The wave-induced bottom drag enhancement has a substantial effect on tides in the Sound, possibly because it is nearly resonant at semidiurnal frequencies. This wave-current interaction current leads to severe tidal dampening ( 40% amplitude reduction) at the Western end of the estuary in the modeled sea surface displacement. The potential magnitude of these effects means that wave current interaction should be included and carefully evaluated in models of estuaries that are useful.

Impact of four-dimensional data assimilation (FDDA) on urban climate analysis

NASA Astrophysics Data System (ADS)

Pan, Linlin; Liu, Yubao; Liu, Yuewei; Li, Lei; Jiang, Yin; Cheng, Will; Roux, Gregory

2015-12-01

This study investigates the impact of four-dimensional data assimilation (FDDA) on urban climate analysis, which employs the NCAR (National Center for Atmospheric Research) WRF (the weather research and forecasting model) based on climate FDDA (CFDDA) technology to develop an urban-scale microclimatology database for the Shenzhen area, a rapidly developing metropolitan located along the southern coast of China, where uniquely high-density observations, including ultrahigh-resolution surface AWS (automatic weather station) network, radio sounding, wind profilers, radiometers, and other weather observation platforms, have been installed. CFDDA is an innovative dynamical downscaling regional climate analysis system that assimilates diverse regional observations; and has been employed to produce a 5 year multiscale high-resolution microclimate analysis by assimilating high-density observations at Shenzhen area. The CFDDA system was configured with four nested-grid domains at grid sizes of 27, 9, 3, and 1 km, respectively. This research evaluates the impact of assimilating high-resolution observation data on reproducing the refining features of urban-scale circulations. Two experiments were conducted with a 5 year run using CFSR (climate forecast system reanalysis) as boundary and initial conditions: one with CFDDA and the other without. The comparisons of these two experiments with observations indicate that CFDDA greatly reduces the model analysis error and is able to realistically analyze the microscale features such as urban-rural-coastal circulation, land/sea breezes, and local-hilly terrain thermal circulations. It is demonstrated that the urbanization can produce 2.5 k differences in 2 m temperatures, delays/speeds up the land/sea breeze development, and interacts with local mountain-valley circulations.

Adrenaline, terlipressin, and corticoids versus adrenaline in the treatment of experimental pediatric asphyxial cardiac arrest.

PubMed

González, Rafael; Urbano, Javier; Botrán, Marta; López, Jorge; Solana, Maria J; García, Ana; Fernández, Sarah; López-Herce, Jesús

2014-07-01

To analyze if treatment with adrenaline (epinephrine) plus terlipressin plus corticoids achieves higher return of spontaneous circulation than adrenaline in an experimental infant animal model of asphyxial cardiac arrest. Prospective randomized animal study. Experimental department in a University Hospital. Forty-nine piglets were studied. Cardiac arrest was induced by at least 10 minutes of removal of mechanical ventilation and was followed by manual external chest compressions and mechanical ventilation. After 3 minutes of resuscitation, piglets that did not achieve return of spontaneous circulation were randomized to two groups: adrenaline 0.02 mg kg every 3 minutes (20 animals) and adrenaline 0.02 mg kg every 3 minutes plus terlipressin 20 μg kg every 6 minutes plus hydrocortisone 30 mg kg one dose (22 animals). Resuscitation was discontinued when return of spontaneous circulation was achieved or after 24 minutes. Return of spontaneous circulation was achieved in 14 piglets (28.5%), 14.2% with only cardiac massage and ventilation. Return of spontaneous circulation was achieved in 25% of piglets treated with adrenaline and in 9.1% of those treated with adrenaline plus terlipressin plus hydrocortisone (p = 0.167). Return of spontaneous circulation was achieved in 45.4% of animals with pulseless electric activity, 20% with asystole, and 0% with ventricular fibrillation (p = 0.037). Shorter duration of cardiac arrest, higher mean blood pressure and EtCO2 and lower PaCO2 before resuscitation, and higher mean blood pressure during resuscitation were associated with higher return of spontaneous circulation. Treatment with adrenaline plus terlipressin plus corticoids does not achieve higher return of spontaneous circulation than that with adrenaline in an infant animal model of asphyxial cardiac arrest.

Updated Results for the Wake Vortex Inverse Model

NASA Technical Reports Server (NTRS)

Robins, Robert E.; Lai, David Y.; Delisi, Donald P.; Mellman, George R.

2008-01-01

NorthWest Research Associates (NWRA) has developed an Inverse Model for inverting aircraft wake vortex data. The objective of the inverse modeling is to obtain estimates of the vortex circulation decay and crosswind vertical profiles, using time history measurements of the lateral and vertical position of aircraft vortices. The Inverse Model performs iterative forward model runs using estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Iterations are performed until a user-defined criterion is satisfied. Outputs from an Inverse Model run are the best estimates of the time history of the vortex circulation derived from the observed data, the vertical crosswind profile, and several vortex parameters. The forward model, named SHRAPA, used in this inverse modeling is a modified version of the Shear-APA model, and it is described in Section 2 of this document. Details of the Inverse Model are presented in Section 3. The Inverse Model was applied to lidar-observed vortex data at three airports: FAA acquired data from San Francisco International Airport (SFO) and Denver International Airport (DEN), and NASA acquired data from Memphis International Airport (MEM). The results are compared with observed data. This Inverse Model validation is documented in Section 4. A summary is given in Section 5. A user's guide for the inverse wake vortex model is presented in a separate NorthWest Research Associates technical report (Lai and Delisi, 2007a).

Evaluation of the Surface Representation of the Greenland Ice Sheet in a General Circulation Model

NASA Technical Reports Server (NTRS)

Cullather, Richard I.; Nowicki, Sophie M. J.; Zhao, Bin; Suarez, Max J.

2014-01-01

Simulated surface conditions of the Goddard Earth Observing System model, version 5 (GEOS 5) atmospheric general circulation model (AGCM) are examined for the contemporary Greenland Ice Sheet (GrIS). A surface parameterization that explicitly models surface processes including snow compaction, meltwater percolation and refreezing, and surface albedo is found to remedy an erroneous deficit in the annual net surface energy flux and provide an adequate representation of surface mass balance (SMB) in an evaluation using simulations at two spatial resolutions. The simulated 1980-2008 GrIS SMB average is 24.7+/-4.5 cm yr(- 1) water-equivalent (w.e.) at.5 degree model grid spacing, and 18.2+/-3.3 cm yr(- 1) w.e. for 2 degree grid spacing. The spatial variability and seasonal cycle of the simulation compare favorably to recent studies using regional climate models, while results from 2 degree integrations reproduce the primary features of the SMB field. In comparison to historical glaciological observations, the coarser resolution model overestimates accumulation in the southern areas of the GrIS, while the overall SMB is underestimated. These changes relate to the sensitivity of accumulation and melt to the resolution of topography. The GEOS-5 SMB fields contrast with available corresponding atmospheric models simulations from the Coupled Model Intercomparison Project (CMIP5). It is found that only a few of the CMIP5 AGCMs examined provide significant summertime runoff, a dominant feature of the GrIS seasonal cycle. This is a condition that will need to be remedied if potential contributions to future eustatic change from polar ice sheets are to be examined with GCMs.

Thermal-hydraulic simulation of natural convection decay heat removal in the High Flux Isotope Reactor (HFIR) using RELAP5 and TEMPEST: Part 2, Interpretation and validation of results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruggles, A.E.; Morris, D.G.

The RELAP5/MOD2 code was used to predict the thermal-hydraulic behavior of the HFIR core during decay heat removal through boiling natural circulation. The low system pressure and low mass flux values associated with boiling natural circulation are far from conditions for which RELAP5 is well exercised. Therefore, some simple hand calculations are used herein to establish the physics of the results. The interpretation and validation effort is divided between the time average flow conditions and the time varying flow conditions. The time average flow conditions are evaluated using a lumped parameter model and heat balance. The Martinelli-Nelson correlations are usedmore » to model the two-phase pressure drop and void fraction vs flow quality relationship within the core region. Systems of parallel channels are susceptible to both density wave oscillations and pressure drop oscillations. Periodic variations in the mass flux and exit flow quality of individual core channels are predicted by RELAP5. These oscillations are consistent with those observed experimentally and are of the density wave type. The impact of the time varying flow properties on local wall superheat is bounded herein. The conditions necessary for Ledinegg flow excursions are identified. These conditions do not fall within the envelope of decay heat levels relevant to HFIR in boiling natural circulation. 14 refs., 5 figs., 1 tab.« less

A sigma-coordinate primitive equation model for studying the circulation in the South Atlantic Part II: Meridional transports and seasonal variability

NASA Astrophysics Data System (ADS)

Marchesiello, P.; Barnier, B.; de Miranda, A. P.

1998-04-01

The mean and seasonal variability of the circulation and meridional heat transport in the South Atlantic are investigated using a set of numerical experiments. The primitive equation model uses a topography-following (sigma) coordinate. The model domain is limited to the South Atlantic basin. Artificial boundaries at Drake Passage, between Brazil and Angola, and between South Africa and Antarctica are treated as open boundaries. Finally, recent and self-consistent estimates of seasonal fluxes are used to define a model-dependent atmospheric forcing. Quasi-diagnostic simulations forced by constant climatological winds are first conducted to determine the sensitivity of model solutions to bottom topography smoothing, and to diagnose meridional fluxes from a mass field that is relaxed to the annual climatology of Levitus (1982). Model results show good agreement with known climatological circulation features in this basin, especially in the Confluence Region, where coarse resolution models usually give smooth structures. Sensitivity studies show that the more detailed features of the circulation are influenced by the model bathymetry. The model simulates a meridional circulation whose upper branch (the return flow that balances the southward flow of North Atlantic Deep Water) is composed of Intermediate (IW) and Thermocline (TW) Waters. The transport of IW is found to be predominant, and the value of meridional heat transport consequently falls within the low estimates. We notice that the meridional heat balance is sensitive to the position of the Confluence. When this region occurs too far south, the amount of IW contributing to the return flow of the overturning cell is reduced. Prognostic simulations forced by seasonal winds and heat fluxes are studied to quantify the impact of wind forcing on the circulation in the South Atlantic. Particular attention is focused on meridional transports at 30°S. Analysis of the mean annual circulation confirms that the upper branch of the meridional circulation is predominantly composed of IW (9 Sv), rather than TW (5.3 Sv). The mean transport of the lower branch is 16 Sv, in agreement with recent estimates by Schlitzer (1996). The annual meridional heat transport (0.29 PW) is still within the low estimates, but agrees well with other estimates that give a dominant role to IW (Rintoul, 1991). Original results also concern the variability of the upper branch of the meridional circulation. It is shown that the wind creates seasonal variability in the Subtropical Gyre, which has a marked impact on the water mass balance in the South Atlantic. In winter, a large convergence to the north of the Subtropical Gyre (27°S) reduces the northward flow of IW, whereas stronger Ekman pumping favors an equatorward transport of TW. In summer, this convergence disappears and a larger transport of IW is allowed. Thus a more complex scheme is proposed for the meridional circulation, in which local wind forcing in the South Atlantic Basin has a significant role in preconditioning the surface waters of the global overturning cell.

Greenland ice sheet surface mass-balance modeling in a 131-year perspective, 1950-2080

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mernild, Sebastian Haugard; Liston, Glen; Hiemstra, Christopher

2009-01-01

Fluctuations in the Greenland Ice Sheet (GrIS) surface mass-balance (SMB) and freshwater influx to the surrounding oceans closely follow climate fluctuations and are of considerable importance to the global eustatic sea level rise. SnowModel, a state-of-the-art snow-evolution modeling system, was used to simulate variations in the GrIS melt extent, surface water balance components, changes in SMB, and freshwater influx to the ocean. The simulations are based on the IPCC scenario AlB modeled by the HIRHAM4 RCM (using boundary conditions from ECHAM5 AOGCM) from 1950 through 2080. In-situ meteorological station (GC-Net and WMO DMI) observations from inside and outside the GrISmore » were used to validate and correct RCM output data before it was used as input for SnowModel. Satellite observations and independent SMB studies were used to validate the SnowModel output and confirm the model's robustness. We simulated a {approx}90% increase in end-of-summer surface melt extent (0.483 x 10{sup 6} km{sup 2}) from 1950 to 2080, and a melt index (above 2,000-m elevation) increase of 138% (1.96 x 10{sup 6} km{sup 2} x days). The greatest difference in melt extent occured in the southern part of the GrIS, and the greatest changes in the number of melt days was seen in the eastern part of the GrIS ({approx}50-70%) and was lowest in the west ({approx}20-30%). The rate of SMB loss, largely tied to changes in ablation processes, lead to an enhanced average loss of 331 km{sup 3} from 1950 to 2080, an average 5MB level of -99 km{sup 3} for the period 2070-2080. GrIS surface freshwater runoff yielded an eustatic rise in sea level from 0.8 {+-} 0.1 (1950-1959) to 1.9 {+-} 0.1 mm (2070-2080) sea level equivalent (SLE) y{sup -1}. The accumulated GrIS freshwater runoff contribution from surface melting equaled 160 mm SLE from 1950 through 2080.« less

Projecting Future Changes in Extreme Weather During the North American Monsoon in the Southwest with High Resolution, Convective-Permitting Regional Atmospheric Modeling

NASA Astrophysics Data System (ADS)

Chang, H. I.; Castro, C. L.; Luong, T. M.; Lahmers, T.; Jares, M.; Carrillo, C. M.

2014-12-01

Most severe weather during the North American monsoon in the Southwest U.S. occurs in association with organized convection, including microbursts, dust storms, flash flooding and lightning. Our objective is to project how monsoon severe weather is changing due to anthropogenic global warming. We first consider a dynamically downscaled reanalysis (35 km grid spacing), generated with the Weather Research and Forecasting (WRF) model during the period 1948-2010. Individual severe weather events, identified by favorable thermodynamic conditions of instability and precipitable water, are then simulated for short-term, numerical weather prediction-type simulations of 24h at a convective-permitting scale (2 km grid spacing). Changes in the character of severe weather events within this period likely reflect long-term climate change driven by anthropogenic forcing. Next, we apply the identical model simulation and analysis procedures to several dynamically downscaled CMIP3 and CMIP5 models for the period 1950-2100, to assess how monsoon severe weather may change in the future and if these changes correspond with what is already occurring per the downscaled renalaysis and available observational data. The CMIP5 models we are downscaling (HadGEM and MPI-ECHAM6) will be included as part of North American CORDEX. The regional model experimental design for severe weather event projection reasonably accounts for the known operational forecast prerequisites for severe monsoon weather. The convective-permitting simulations show that monsoon convection appears to be reasonably well captured with the use of the dynamically downscaled reanalysis, in comparison to Stage IV precipitation data. The regional model tends to initiate convection too early, though correctly simulates the diurnal maximum in convection in the afternoon and subsequent westward propagation of thunderstorms. Projected changes in extreme event precipitation will be described in relation to the long-term changes in thermodynamic and dynamic forcing mechanisms for severe weather. Results from this project will be used for climate change impacts assessment for U.S. military installations in the region.

Development of an Accident Reproduction Simulator System Using a Hemodialysis Extracorporeal Circulation System

PubMed Central

Nishite, Yoshiaki; Takesawa, Shingo

2016-01-01

Background: Accidents that occur during dialysis treatment are notified to the medical staff via alarms raised by the dialysis apparatus. Similar to such real accidents, apparatus activation or accidents can be reproduced by simulating a treatment situation. An alarm that corresponds to such accidents can be utilized in the simulation model. Objectives: The aim of this study was to create an extracorporeal circulation system (hereinafter, the circulation system) for dialysis machines so that it sets off five types of alarms for: 1) decreased arterial pressure, 2) increased arterial pressure, 3) decreased venous pressure, 4) increased venous pressure, and 5) blood leakage, according to the five types of accidents chosen based on their frequency of occurrence and the degree of severity. Materials and Methods: In order to verify the alarm from the dialysis apparatus connected to the circulation system and the accident corresponding to it, an evaluation of the alarm for its reproducibility of an accident was performed under normal treatment circumstances. The method involved testing whether the dialysis apparatus raised the desired alarm from the moment of control of the circulation system, and measuring the time it took until the desired alarm was activated. This was tested on five main models from four dialyzer manufacturers that are currently used in Japan. Results: The results of the tests demonstrated successful activation of the alarms by the dialysis apparatus, which were appropriate for each of the five types of accidents. The time between the control of the circulatory system to the alarm signal was as follows, 1) venous pressure lower limit alarm: 7 seconds; 2) venous pressure lower limit: 8 seconds; 3) venous pressure upper limit: 7 seconds; 4) venous pressure lower limit alarm: 2 seconds; and 5) blood leakage alarm: 19 seconds. All alarms were set off in under 20 seconds. Conclusions: Thus, we can conclude that a simulator system using an extracorporeal circulation system can be set to different models of dialyzers, and that the reproduced treatment scenarios can be used for simulation training. PMID:26981503

The contrasting response of Hadley circulation to different meridional structure of sea surface temperature in CMIP5

NASA Astrophysics Data System (ADS)

Feng, Juan; Li, Jianping; Zhu, Jianlei; Li, Yang; Li, Fei

2018-02-01

The response of the Hadley circulation (HC) to the sea surface temperature (SST) is determined by the meridional structure of SST and varies according to the changing nature of this meridional structure. The capability of the models from the phase 5 of the Coupled Model Intercomparison Project (CMIP5) is utilized to represent the contrast response of the HC to different meridional SST structures. To evaluate the responses, the variations of HC and SST were linearly decomposed into two components: the equatorially asymmetric (HEA for HC, and SEA for SST) and equatorially symmetric (HES for HC, and SES for SST) components. The result shows that the climatological features of HC and tropical SST (including the spatial structures and amplitude) are reasonably simulated in all the models. However, the response contrast of HC to different SST meridional structures shows uncertainties among models. This may be due to the fact that the long-term temporal variabilities of HEA, HES, and SEA are limited reproduced in the models, although the spatial structures of their long-term variabilities are relatively reasonably simulated. These results indicate that the performance of the CMIP5 models to simulate long-term temporal variability of different meridional SST structures and related HC variations plays a fundamental role in the successful reproduction of the response of HC to different meridional SST structures.

El Nino-southern oscillation simulated in an MRI atmosphere-ocean coupled general circulation model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagai, T.; Tokioka, T.; Endoh, M.

A coupled atmosphere-ocean general circulation model (GCM) was time integrated for 30 years to study interannual variability in the tropics. The atmospheric component is a global GCM with 5 levels in the vertical and 4[degrees]latitude X 5[degrees] longitude grids in the horizontal including standard physical processes (e.g., interactive clouds). The oceanic component is a GCM for the Pacific with 19 levels in the vertical and 1[degrees]x 2.5[degrees] grids in the horizontal including seasonal varying solar radiation as forcing. The model succeeded in reproducing interannual variations that resemble the El Nino-Southern Oscillation (ENSO) with realistic seasonal variations in the atmospheric andmore » oceanic fields. The model ENSO cycle has a time scale of approximately 5 years and the model El Nino (warm) events are locked roughly in phase to the seasonal cycle. The cold events, however, are less evident in comparison with the El Nino events. The time scale of the model ENSO cycle is determined by propagation time of signals from the central-eastern Pacific to the western Pacific and back to the eastern Pacific. Seasonal timing is also important in the ENSO time scale: wind anomalies in the central-eastern Pacific occur in summer and the atmosphere ocean coupling in the western Pacific operates efficiently in the first half of the year.« less

A large ozone-circulation feedback and its implications for global warming assessments.

PubMed

Nowack, Peer J; Abraham, N Luke; Maycock, Amanda C; Braesicke, Peter; Gregory, Jonathan M; Joshi, Manoj M; Osprey, Annette; Pyle, John A

2015-01-01

State-of-the-art climate models now include more climate processes which are simulated at higher spatial resolution than ever 1 . Nevertheless, some processes, such as atmospheric chemical feedbacks, are still computationally expensive and are often ignored in climate simulations 1,2 . Here we present evidence that how stratospheric ozone is represented in climate models can have a first order impact on estimates of effective climate sensitivity. Using a comprehensive atmosphere-ocean chemistry-climate model, we find an increase in global mean surface warming of around 1°C (~20%) after 75 years when ozone is prescribed at pre-industrial levels compared with when it is allowed to evolve self-consistently in response to an abrupt 4×CO 2 forcing. The difference is primarily attributed to changes in longwave radiative feedbacks associated with circulation-driven decreases in tropical lower stratospheric ozone and related stratospheric water vapour and cirrus cloud changes. This has important implications for global model intercomparison studies 1,2 in which participating models often use simplified treatments of atmospheric composition changes that are neither consistent with the specified greenhouse gas forcing scenario nor with the associated atmospheric circulation feedbacks 3-5 .

The Venus nitric oxide night airglow - Model calculations based on the Venus Thermospheric General Circulation Model

NASA Technical Reports Server (NTRS)

Bougher, S. W.; Gerard, J. C.; Stewart, A. I. F.; Fesen, C. G.

1990-01-01

The mechanism responsible for the Venus nitric oxide (0,1) delta band nightglow observed in the Pioneer Venus Orbiter UV spectrometer (OUVS) images was investigated using the Venus Thermospheric General Circulation Model (Dickinson et al., 1984), modified to include simple odd nitrogen chemistry. Results obtained for the solar maximum conditions indicate that the recently revised dark-disk average NO intensity at 198.0 nm, based on statistically averaged OUVS measurements, can be reproduced with minor modifications in chemical rate coefficients. The results imply a nightside hemispheric downward N flux of (2.5-3) x 10 to the 9th/sq cm sec, corresponding to the dayside net production of N atoms needed for transport.

Turbulent Convection in an Anelastic Rotating Sphere: A Model for the Circulation on the Giant Planets

DTIC Science & Technology

2008-06-01

exterior weather layer, using a quasigeostrophic two layer channel model on a beta plane , where the colum- nar interior is therefore represented by a...116 5.4 The evolution of the ’it’ field in the weakly nonlinear run ........ .. 117 5.5 The zonal mean zonal velocity on the equatorial plane in...turbulence on a 8 plane . These two approaches have been in debate ever since. 1.3.1 Shallow Models The first to apply the "shallow" approach to

Robust Hadley Circulation changes and increasing global dryness due to CO2 warming from CMIP5 model projections.

PubMed

Lau, William K M; Kim, Kyu-Myong

2015-03-24

In this paper, we investigate changes in the Hadley Circulation (HC) and their connections to increased global dryness (suppressed rainfall and reduced tropospheric relative humidity) under CO2 warming from Coupled Model Intercomparison Project Phase 5 (CMIP5) model projections. We find a strengthening of the HC manifested in a "deep-tropics squeeze" (DTS), i.e., a deepening and narrowing of the convective zone, enhanced ascent, increased high clouds, suppressed low clouds, and a rise of the level of maximum meridional mass outflow in the upper troposphere (200-100 hPa) of the deep tropics. The DTS induces atmospheric moisture divergence and reduces tropospheric relative humidity in the tropics and subtropics, in conjunction with a widening of the subsiding branches of the HC, resulting in increased frequency of dry events in preferred geographic locations worldwide. Among various water-cycle parameters examined, global dryness is found to have the highest signal-to-noise ratio. Our results provide a physical basis for inferring that greenhouse warming is likely to contribute to the observed prolonged droughts worldwide in recent decades.

5 CFR 2634.403 - Qualified blind trusts.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Qualified blind trusts. 2634.403 Section... Qualified blind trusts. (a) Definition. A qualified blind trust is a trust in which the filer, his spouse... instrument which establishes a blind trust must adhere substantively to model drafts circulated by the Office...

Evaluation of the new EMAC-SWIFT chemistry climate model

NASA Astrophysics Data System (ADS)

Scheffler, Janice; Langematz, Ulrike; Wohltmann, Ingo; Rex, Markus

2016-04-01

It is well known that the representation of atmospheric ozone chemistry in weather and climate models is essential for a realistic simulation of the atmospheric state. Including atmospheric ozone chemistry into climate simulations is usually done by prescribing a climatological ozone field, by including a fast linear ozone scheme into the model or by using a climate model with complex interactive chemistry. While prescribed climatological ozone fields are often not aligned with the modelled dynamics, a linear ozone scheme may not be applicable for a wide range of climatological conditions. Although interactive chemistry provides a realistic representation of atmospheric chemistry such model simulations are computationally very expensive and hence not suitable for ensemble simulations or simulations with multiple climate change scenarios. A new approach to represent atmospheric chemistry in climate models which can cope with non-linearities in ozone chemistry and is applicable to a wide range of climatic states is the Semi-empirical Weighted Iterative Fit Technique (SWIFT) that is driven by reanalysis data and has been validated against observational satellite data and runs of a full Chemistry and Transport Model. SWIFT has recently been implemented into the ECHAM/MESSy (EMAC) chemistry climate model that uses a modular approach to climate modelling where individual model components can be switched on and off. Here, we show first results of EMAC-SWIFT simulations and validate these against EMAC simulations using the complex interactive chemistry scheme MECCA, and against observations.

Risk Assessment of Hurricane Storm Surge for Tampa Bay

NASA Astrophysics Data System (ADS)

Lin, N.; Emanuel, K.

2011-12-01

Hurricane storm surge presents a major hazard for the United States and many other coastal areas around the world. Risk assessment of current and future hurricane storm surge provides the basis for risk mitigation and related decision making. This study investigates the hurricane surge risk for Tampa Bay, located on the central west coast of Florida. Although fewer storms have made landfall in the central west Florida than in regions farther west in the Gulf of Mexico and the east coast of U.S., Tampa Bay is highly vulnerable to storm surge due to its geophysical features. It is surrounded by low-lying lands, much of which may be inundated by a storm tide of 6 m. Also, edge waves trapped on the west Florida shelf can propagate along the coastline and affect the sea level outside the area of a forced storm surge; Tampa Bay may be affected by storms traversing some distance outside the Bay. Moreover, when the propagation speed of the edge wave is close to that of a storm moving parallel to the coast, resonance may occur and the water elevation in the Bay may be greatly enhanced. Therefore, Tampa Bay is vulnerable to storms with a broad spectrum of characteristics. We apply a model-based risk assessment method to carry out the investigation. To estimate the current surge risk, we apply a statistical/deterministic hurricane model to generate a set of 1500 storms for the Tampa area, under the observed current climate (represented by 1981-2000 statistics) estimated from the NCAR/NCEP reanalysis. To study the effect of climate change, we use four climate models, CNRM-CM3, ECHAM, GFDL-CM2.0, and MIROC3.2, respectively, to drive the hurricane model to generate four sets of 1500 Tampa storms under current climate conditions (represented by 1981-2000 statistics) and another four under future climate conditions of the IPCC-AR4 A1B emission scenario (represented by 2081-2100 statistics). Then, we apply two hydrodynamic models, the Advanced Circulation (ADCIRC) model and the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model with grids of various resolutions to simulate the surges induced by the synthetic storms. The surge risk under each of the climate scenarios is depicted by a surge return level curve (exceedance probability curve). For the city of Tampa, the heights of the 100-year, 500-year, and 1000-year surges under the current climate are estimated to be 3.85, 5.66, and 6.31 m, respectively. Two of the four climate models predict that surge return periods will be significantly shortened in the future climates due to the change of storm climatology; the current 100-year surge may happen every 50 years or less, the 500-year surge every 200 years or less, and the 1000-year surge every 300 years or less. The other two climate models predict that the surge return periods will become moderately shorter or remain almost unchanged in the future climates. Extreme surges up to 12 m at Tampa appear in our simulations. Although occurring with very small probabilities, these extreme surges would have a devastating impact on the Tampa Bay area. By examining the generated synthetic surge database, we study the characteristics of the extreme storms at Tampa Bay, especially for the storms that may interact with edge waves along the Florida west coast.

An approach for modeling thermal destruction of hazardous wastes in circulating fluidized bed incinerator.

PubMed

Patil, M P; Sonolikar, R L

2008-10-01

This paper presents a detailed computational fluid dynamics (CFD) based approach for modeling thermal destruction of hazardous wastes in a circulating fluidized bed (CFB) incinerator. The model is based on Eular - Lagrangian approach in which gas phase (continuous phase) is treated in a Eularian reference frame, whereas the waste particulate (dispersed phase) is treated in a Lagrangian reference frame. The reaction chemistry hasbeen modeled through a mixture fraction/ PDF approach. The conservation equations for mass, momentum, energy, mixture fraction and other closure equations have been solved using a general purpose CFD code FLUENT4.5. Afinite volume method on a structured grid has been used for solution of governing equations. The model provides detailed information on the hydrodynamics (gas velocity, particulate trajectories), gas composition (CO, CO2, O2) and temperature inside the riser. The model also allows different operating scenarios to be examined in an efficient manner.

Projecting Climate Change Impacts on Wildfire Probabilities

NASA Astrophysics Data System (ADS)

Westerling, A. L.; Bryant, B. P.; Preisler, H.

2008-12-01

We present preliminary results of the 2008 Climate Change Impact Assessment for wildfire in California, part of the second biennial science report to the California Climate Action Team organized via the California Climate Change Center by the California Energy Commission's Public Interest Energy Research Program pursuant to Executive Order S-03-05 of Governor Schwarzenegger. In order to support decision making by the State pertaining to mitigation of and adaptation to climate change and its impacts, we model wildfire occurrence monthly from 1950 to 2100 under a range of climate scenarios from the Intergovernmental Panel on Climate Change. We use six climate change models (GFDL CM2.1, NCAR PCM1, CNRM CM3, MPI ECHAM5, MIROC3.2 med, NCAR CCSM3) under two emissions scenarios--A2 (C02 850ppm max atmospheric concentration) and B1(CO2 550ppm max concentration). Climate model output has been downscaled to a 1/8 degree (~12 km) grid using two alternative methods: a Bias Correction and Spatial Donwscaling (BCSD) and a Constructed Analogues (CA) downscaling. Hydrologic variables have been simulated from temperature, precipitation, wind and radiation forcing data using the Variable Infiltration Capacity (VIC) Macroscale Hydrologic Model. We model wildfire as a function of temperature, moisture deficit, and land surface characteristics using nonlinear logistic regression techniques. Previous work on wildfire climatology and seasonal forecasting has demonstrated that these variables account for much of the inter-annual and seasonal variation in wildfire. The results of this study are monthly gridded probabilities of wildfire occurrence by fire size class, and estimates of the number of structures potentially affected by fires. In this presentation we will explore the range of modeled outcomes for wildfire in California, considering the effects of emissions scenarios, climate model sensitivities, downscaling methods, hydrologic simulations, statistical model specifications for california wildfire, and their intersection with a range of development scenarios for California.

The climatic effects of nuclear war

NASA Technical Reports Server (NTRS)

Turco, R. P.; Toon, O. B.; Ackerman, T. P.; Pollack, J. B.; Sagan, C.

1984-01-01

The effects of various US-USSR nuclear-exchange scenarios on global climate are investigated by means of computer simulations, summarizing the results of Turco et al. (1983) and follow-up studies using 3D global-circulation models. A nuclear-scenario model is used to determine the amounts of dust, smoke, radioactivity, and pyrotoxins generated by a particular type of nuclear exchange (such as a general 5,000-Mt exchange, a 1,000-Mt limited exchange, a 5,000-Mt hard-target counterforce attack, and a 100-Mt attack on cities only): a particle-microphysics model predicts the evolution of the dust and smoke particles; and a radiative-convective climate model estimates the effects of the dust and smoke clouds on the global radiation budget. The findings are presented in graphs, diagrams, and a table. Thick clouds blocking most sunlight over the Northern Hemisphere midlatitudes for weeks or months and producing ground-temperature reductions of 20-40 C, disruption of global circulation patterns, and rapid spread of clouds to the Southern Hemisphere are among the 'nuclear-winter' effects predicted for the 5,000-Mt baseline case. The catastrophic consequences for plant, animal, and human populations are considered, and the revision of superpower nuclear strategies is urged.

Hydrodynamic characteristics of airlift nitrifying reactor using carrier-induced granular sludge.

PubMed

Jin, Ren-Cun; Zheng, Ping; Mahmood, Qaisar; Zhang, Lei

2008-09-15

Since nitrification is the rate-limiting step in the biological nitrogen removal from wastewater, many studies have been conducted on the immobilization of nitrifying bacteria. A laboratory-scale investigation was carried out to scrutinize the effectiveness of activated carbon carrier addition for granulation of nitrifying sludge in a continuous-flow airlift bioreactor and to study the hydrodynamics of the reactor with carrier-induced granules. The results showed that the granular sludge began to appear and matured 60 and 108 days, respectively, after addition of carriers, while no granule was observed in the absence of carriers in the control test. The mature granules had a diameter of 0.5-5 mm (1.6 mm in average), settling velocity 22.3-55.8 m h(-1) and specific gravity of 1.086. The relationship between the two important hydrodynamic coefficients, i.e. gas holdup and liquid circulation velocity, and the superficial gas velocity were established by a simple model and were confirmed experimentally. The model also could predict the critical superficial gas velocity for liquid circulation and that for granules circulation, with respective values of 1.017 and 2.662 cm min(-1), accurately.

Metabolomic markers of fatigue: Association between circulating metabolome and fatigue in women with chronic widespread pain.

PubMed

Freidin, Maxim B; Wells, Helena R R; Potter, Tilly; Livshits, Gregory; Menni, Cristina; Williams, Frances M K

2018-02-01

Fatigue is a sensation of unbearable tiredness that frequently accompanies chronic widespread musculoskeletal pain (CWP) and inflammatory joint disease. Its mechanisms are poorly understood and there is a lack of effective biomarkers for diagnosis and onset prediction. We studied the circulating metabolome in a population sample characterised for CWP to identify biomarkers showing specificity for fatigue. Untargeted metabolomic profiling was conducted on fasting plasma and serum samples of 1106 females with and without CWP from the TwinsUK cohort. Linear mixed-effects models accounting for covariates were used to determine relationships between fatigue and metabolites. Receiver operating curve (ROC)-analysis was used to determine predictive value of metabolites for fatigue. While no association between fatigue and metabolites was identified in twins without CWP (n=711), in participants with CWP (n=395), levels of eicosapentaenoate (EPA) ω-3 fatty acid were significantly reduced in those with fatigue (β=-0.452±0.116; p=1.2×10 -4 ). A significant association between fatigue and two other metabolites also emerged when BMI was excluded from the model: 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), and C-glycosyltryptophan (p=1.5×10 -4 and p=3.1×10 -4 , respectively). ROC analysis has identified a combination of 15 circulating metabolites with good predictive potential for fatigue in CWP (AUC=75%; 95% CI 69-80%). The results of this agnostic metabolomics screening show that fatigue is metabolically distinct from CWP, and is associated with a decrease in circulating levels of EPA. Our panel of circulating metabolites provides the starting point for a diagnostic test for fatigue in CWP. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Characteristics of atmospheric circulation patterns associated with extreme temperatures over North America in observations and climate models

NASA Astrophysics Data System (ADS)

Loikith, Paul C.

Motivated by a desire to understand the physical mechanisms involved in future anthropogenic changes in extreme temperature events, the key atmospheric circulation patterns associated with extreme daily temperatures over North America in the current climate are identified. Several novel metrics are used to systematically identify and describe these patterns for the entire continent. The orientation, physical characteristics, and spatial scale of these circulation patterns vary based on latitude, season, and proximity to important geographic features (i.e., mountains, coastlines). The anomaly patterns associated with extreme cold events tend to be similar to, but opposite in sign of, those associated with extreme warm events, especially within the westerlies, and tend to scale with temperature in the same locations. The influence of the Pacific North American (PNA) pattern, the Northern Annular Mode (NAM), and the El Niño-Southern Oscillation (ENSO) on extreme temperature days and months shows that associations between extreme temperatures and the PNA and NAM are stronger than associations with ENSO. In general, the association with extremes tends to be stronger on monthly than daily time scales. Extreme temperatures are associated with the PNA and NAM in locations typically influenced by these circulation patterns; however many extremes still occur on days when the amplitude and polarity of these patterns do not favor their occurrence. In winter, synoptic-scale, transient weather disturbances are important drivers of extreme temperature days; however these smaller-scale events are often concurrent with amplified PNA or NAM patterns. Associations are weaker in summer when other physical mechanisms affecting the surface energy balance, such as anomalous soil moisture content, are associated with extreme temperatures. Analysis of historical runs from seventeen climate models from the CMIP5 database suggests that most models simulate realistic circulation patterns associated with extreme temperature days in most places. Model-simulated patterns tend to resemble observed patterns better in the winter than the summer and at 500 hPa than at the surface. There is substantial variability among the suite of models analyzed and most models simulate circulation patterns more realistically away from influential features such as large bodies of water and complex topography.

The computation of the post-stall behavior of a circulation controlled airfoil

NASA Technical Reports Server (NTRS)

Linton, Samuel W.

1993-01-01

The physics of the circulation controlled airfoil is complex and poorly understood, particularly with regards to jet stall, which is the eventual breakdown of lift augmentation by the jet at some sufficiently high blowing rate. The present paper describes the numerical simulation of stalled and unstalled flows over a two-dimensional circulation controlled airfoil using a fully implicit Navier-Stokes code, and the comparison with experimental results. Mach numbers of 0.3 and 0.5 and jet total to freestream pressure ratios of 1.4 and 1.8 are investigated. The Baldwin-Lomax and k-epsilon turbulence models are used, each modified to include the effect of strong streamline curvature. The numerical solutions of the post-stall circulation controlled airfoil show a highly regular unsteady periodic flowfield. This is the result of an alternation between adverse pressure gradient and shock induced separation of the boundary layer on the airfoil trailing edge.

Climate and health implications of future aerosol emission scenarios

NASA Astrophysics Data System (ADS)

Partanen, Antti-Ilari; Landry, Jean-Sébastien; Damon Matthews, H.

2018-02-01

Anthropogenic aerosols have a net cooling effect on climate and also cause adverse health effects by degrading air quality. In this global-scale sensitivity study, we used a combination of the aerosol-climate model ECHAM-HAMMOZ and the University of Victoria Earth System Climate Model to assess the climate and health effects of aerosols emissions from three Representative Concentration Pathways (RCP2.6, RCP4.5, and RCP8.5) and two new (LOW and HIGH) aerosol emission scenarios derived from RCP4.5, but that span a wider spectrum of possible future aerosol emissions. All simulations had CO2 emissions and greenhouse gas forcings from RCP4.5. Aerosol forcing declined similarly in the standard RCP aerosol emission scenarios: the aerosol effective radiative forcing (ERF) decreased from -1.3 W m-2 in 2005 to between -0.1 W m-2 and -0.4 W m-2 in 2100. The differences in ERF were substantially larger between LOW (-0.02 W m-2 in 2100) and HIGH (-0.8 W m-2) scenarios. The global mean temperature difference between the simulations with standard RCP aerosol emissions was less than 0.18 °C, whereas the difference between LOW and HIGH reached 0.86 °C in 2061. In LOW, the rate of warming peaked at 0.48 °C per decade in the 2030s, whereas in HIGH it was the lowest of all simulations and never exceeded 0.23 °C per decade. Using present-day population density and baseline mortality rates for all scenarios, PM2.5-induced premature mortality was 2 371 800 deaths per year in 2010 and 525 700 in 2100 with RCP4.5 aerosol emissions; in HIGH, the premature mortality reached its maximum value of 2 780 800 deaths per year in 2030, whereas in LOW the premature mortality at 2030 was below 299 900 deaths per year. Our results show potential trade-offs in aerosol mitigation with respect to climate change and public health as ambitious reduction of aerosol emissions considerably increased warming while decreasing mortality.

A High-Resolution WRF Tropical Channel Simulation Driven by a Global Reanalysis

NASA Astrophysics Data System (ADS)

Holland, G.; Leung, L.; Kuo, Y.; Hurrell, J.

2006-12-01

Since 2003, NCAR has invested in the development and application of Nested Regional Climate Model (NRCM) based on the Weather Research and Forecasting (WRF) model and the Community Climate System Model, as a key component of the Prediction Across Scales Initiative. A prototype tropical channel model has been developed to investigate scale interactions and the influence of tropical convection on large scale circulation and tropical modes. The model was developed based on the NCAR Weather Research and Forecasting Model (WRF), configured as a tropical channel between 30 ° S and 45 ° N, wide enough to allow teleconnection effects over the mid-latitudes. Compared to the limited area domain that WRF is typically applied over, the channel mode alleviates issues with reflection of tropical modes that could result from imposing east/west boundaries. Using a large amount of available computing resources on a supercomputer (Blue Vista) during its bedding in period, a simulation has been completed with the tropical channel applied at 36 km horizontal resolution for 5 years from 1996 to 2000, with large scale circulation provided by the NCEP/NCAR global reanalysis at the north/south boundaries. Shorter simulations of 2 years and 6 months have also been performed to include two-way nests at 12 km and 4 km resolution, respectively, over the western Pacific warm pool, to explicitly resolve tropical convection in the Maritime Continent. The simulations realistically captured the large-scale circulation including the trade winds over the tropical Pacific and Atlantic, the Australian and Asian monsoon circulation, and hurricane statistics. Preliminary analysis and evaluation of the simulations will be presented.

Measured and Modelled Tidal Circulation Under Ice Covered Van Mijenforden

NASA Astrophysics Data System (ADS)

Nilsen, F.

The observation and model area Van Mijenfjorden is situated at the west coast of Spits- bergen. An area of 533 km2 makes it the second largest fjord on Spitsbergen and the distance from the head to the mouth of the fjord is approximately 70 km. An 8.5km long and 1km wide island, Akseløya, is lying across the fjord mouth and blocking exchanges between the fjord and the coastal water masses outside. The sound Aksel- sundet on the northern side of the island is 1km wide and has a sill at 34m depth. On the southern side an islet, Mariaholmen, is between two sounds that are 200m wide and 2m deep, and 500m wide and 12m deep. Strong tidal currents exist in these sounds. Van Mijenfjorden has special ice conditions in that Akseløya almost closes the fjord, and comparatively little ice comes in from west. On the other hand, there are periods with fast ice in the fjord inside Akseløya longer than in other places, as the sea waves have little chance to break up fast ice here, or delay ice formation in autumn/winter. Van Mijenfjorden is often separated into two basins by a sill at 30m depth. The inner basin is typical 5km wide and has a maximum depth of 80m, while the outer basin is on average 10 km wide and has a maximum depth of 115m. Hydrographic measurements have been conducted since 1958 and up to the present. Through the last decade, The University Courses on Svalbard (UNIS) has used this fjord as a laboratory for their student excursions, in connection to courses in air-ice- ocean interaction and master programs, and build up an oceanographic data base. In this work, focus is put on the wintertime situation and the circulation under an ice covered fjord. Measurements show a mean cyclonic circulation pattern in the outer basin with tidal oscillation (mainly M2) superposed on this mean vector. A three- dimensional sigma layered numerical model called Bergen Ocean Model (BOM) was used to simulate the circulation in Van Mijenfjorden with only tidal forcing. The four most pronounced tidal components were used to force the model area outside Ak- seløya. The calculated cyclonic circulation pattern fits the measurements, proving that the fjord circulation is controlled by tides in periods when the ice cover shade the fjord water masses from direct wind forcing.

Simulation of seasonal anomalies of atmospheric circulation using coupled atmosphere-ocean model

NASA Astrophysics Data System (ADS)

Tolstykh, M. A.; Diansky, N. A.; Gusev, A. V.; Kiktev, D. B.

2014-03-01

A coupled atmosphere-ocean model intended for the simulation of coupled circulation at time scales up to a season is developed. The semi-Lagrangian atmospheric general circulation model of the Hydrometeorological Centre of Russia, SLAV, is coupled with the sigma model of ocean general circulation developed at the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), INMOM. Using this coupled model, numerical experiments on ensemble modeling of the atmosphere and ocean circulation for up to 4 months are carried out using real initial data for all seasons of an annual cycle in 1989-2010. Results of these experiments are compared to the results of the SLAV model with the simple evolution of the sea surface temperature. A comparative analysis of seasonally averaged anomalies of atmospheric circulation shows prospects in applying the coupled model for forecasts. It is shown with the example of the El Niño phenomenon of 1997-1998 that the coupled model forecasts the seasonally averaged anomalies for the period of the nonstationary El Niño phase significantly better.

Library Circulation Systems: An Overview

ERIC Educational Resources Information Center

Surace, Cecily J.

1972-01-01

The model circulation system outlined is an on-line real time system in which the circulation file is created from the shelf list. The model extends beyond the operational limits of most existing circulation systems and can be considered a reflection of the current state of the art. (36 references) (Author/NH)

Isoprene derived secondary organic aerosol in a global aerosol chemistry climate model

NASA Astrophysics Data System (ADS)

Stadtler, Scarlet; Kühn, Thomas; Taraborrelli, Domenico; Kokkola, Harri; Schultz, Martin

2017-04-01

Secondary organic aerosol (SOA) impacts earth's climate and human health. Since its precursor chemistry and its formation are not fully understood, climate models cannot catch its direct and indirect effects. Global isoprene emissions are higher than any other non-methane hydrocarbons. Therefore, SOA from isoprene-derived, low volatile species (iSOA) is simulated using a global aerosol chemistry climate model ECHAM6-HAM-SALSA-MOZ. Isoprene oxidation in the chemistry model MOZ is following a novel semi-explicit scheme, embedded in a detailed atmospheric chemical mechanism. For iSOA formation four low volatile isoprene oxidation products were identified. The group method by Nanoonlal et al. 2008 was used to estimate their evaporation enthalpies ΔHvap. To calculate the saturation concentration C∗(T) the sectional aerosol model SALSA uses the gas phase concentrations simulated by MOZ and their corresponding ΔHvap to obtain the saturation vapor pressure p∗(T) from the Clausius Clapeyron equation. Subsequently, the saturation concentration is used to calculate the explicit kinetic partitioning of these compounds forming iSOA. Furthermore, the irreversible heterogeneous reactions of IEPOX and glyoxal from isoprene were included. The possibility of reversible heterogeneous uptake was ignored at this stage, leading to an upper estimate of the contribution of glyoxal to iSOA mass.

Analyses of Projected Changes in Climate for Sub-Saharan Africa Using a Variable-Resolution Atmospheric Model

NASA Astrophysics Data System (ADS)

Adegoke, J.; Engelbrecht, F.; Vezhapparambu, S.

2012-12-01

The conformal-cubic atmospheric model (CCAM) is employed in this study as a flexible downscaling tool at the climate-change time scale. In the downscaling procedure, the sea-ice and bias-corrected SSTs of 6 CGCMs (CSIRO Mk 3.5, GFDL2.1, GFDL2.0, HadCM2, ECHAM5 and Miroc-Medres) from AR4 of the IPCC were first used as lower-boundary forcing in CCAM simulations performed at a quasi-uniform resolution (about 200 km in the horizontal), which were subsequently downscaled to a resolution of about 60 km over southern and tropical Africa. All the simulations were for the A2 scenario of the Special Report on Emission Scenarios (SRES), and for the period 1961-2100. The SST biases were derived by comparing the simulated and observed present-day climatol¬ogy of SSTs for 1979-1999 for each month of the year; the same monthly bias corrections were applied for the duration of the simulations. CCAM ensemble projected change in annual average temperature and Rainfall for 2071-2100 vs 1961-1990 for tropical Africa will be presented and discussed. In summary, a robust signal of drastic increases in surface temperature (more than 3 degrees C for the period 2071-2100 relative to 1961-1990) is projected across the domain. Temperature increases as large as 5 degrees C are projected over the subtropical regions in the north of the domain. Increase in rainfall over tropical Africa (for the period 2071-2100 relative to 1961-1990) is projected across the domain. This is consistent with an increase in moisture in a generally warmer atmosphere. There is a robust signal of drying along the West African coast - however, the CMIP3 CGCM projections indicate a wide range of possible rainfall futures over this region The projections of East Africa becoming wetter is robust across the CCAM ensemble, consistent with the CGCM projections of CMIP3 and AR4.

Agro-Environmental Determinants of Avian Influenza Circulation: A Multisite Study in Thailand, Vietnam and Madagascar

PubMed Central

Paul, Mathilde C.; Gilbert, Marius; Desvaux, Stéphanie; Rasamoelina Andriamanivo, Harena; Peyre, Marisa; Khong, Nguyen Viet; Thanapongtharm, Weerapong; Chevalier, Véronique

2014-01-01

Outbreaks of highly pathogenic avian influenza have occurred and have been studied in a variety of ecological systems. However, differences in the spatial resolution, geographical extent, units of analysis and risk factors examined in these studies prevent their quantitative comparison. This study aimed to develop a high-resolution, comparative study of a common set of agro-environmental determinants of avian influenza viruses (AIV) in domestic poultry in four different environments: (1) lower-Northern Thailand, where H5N1 circulated in 2004–2005, (2) the Red River Delta in Vietnam, where H5N1 is circulating widely, (3) the Vietnam highlands, where sporadic H5N1 outbreaks have occurred, and (4) the Lake Alaotra region in Madagascar, which features remarkable similarities with Asian agro-ecosystems and where low pathogenic avian influenza viruses have been found. We analyzed H5N1 outbreak data in Thailand in parallel with serological data collected on the H5 subtype in Vietnam and on low pathogenic AIV in Madagascar. Several agro-environmental covariates were examined: poultry densities, landscape dominated by rice cultivation, proximity to a water body or major road, and human population density. Relationships between covariates and AIV circulation were explored using spatial generalized linear models. We found that AIV prevalence was negatively associated with distance to the closest water body in the Red River Delta, Vietnam highlands and Madagascar. We also found a positive association between AIV and duck density in the Vietnam highlands and Thailand, and with rice landscapes in Thailand and Madagascar. Our findings confirm the important role of wetlands-rice-ducks ecosystems in the epidemiology of AI in diverse settings. Variables influencing circulation of the H5 subtype in Southeast Asia played a similar role for low pathogenic AIV in Madagascar, indicating that this area may be at risk if a highly virulent strain is introduced. PMID:25029441

Agro-environmental determinants of avian influenza circulation: a multisite study in Thailand, Vietnam and Madagascar.

PubMed

Paul, Mathilde C; Gilbert, Marius; Desvaux, Stéphanie; Andriamanivo, Harena Rasamoelina; Peyre, Marisa; Khong, Nguyen Viet; Thanapongtharm, Weerapong; Chevalier, Véronique

2014-01-01

Outbreaks of highly pathogenic avian influenza have occurred and have been studied in a variety of ecological systems. However, differences in the spatial resolution, geographical extent, units of analysis and risk factors examined in these studies prevent their quantitative comparison. This study aimed to develop a high-resolution, comparative study of a common set of agro-environmental determinants of avian influenza viruses (AIV) in domestic poultry in four different environments: (1) lower-Northern Thailand, where H5N1 circulated in 2004-2005, (2) the Red River Delta in Vietnam, where H5N1 is circulating widely, (3) the Vietnam highlands, where sporadic H5N1 outbreaks have occurred, and (4) the Lake Alaotra region in Madagascar, which features remarkable similarities with Asian agro-ecosystems and where low pathogenic avian influenza viruses have been found. We analyzed H5N1 outbreak data in Thailand in parallel with serological data collected on the H5 subtype in Vietnam and on low pathogenic AIV in Madagascar. Several agro-environmental covariates were examined: poultry densities, landscape dominated by rice cultivation, proximity to a water body or major road, and human population density. Relationships between covariates and AIV circulation were explored using spatial generalized linear models. We found that AIV prevalence was negatively associated with distance to the closest water body in the Red River Delta, Vietnam highlands and Madagascar. We also found a positive association between AIV and duck density in the Vietnam highlands and Thailand, and with rice landscapes in Thailand and Madagascar. Our findings confirm the important role of wetlands-rice-ducks ecosystems in the epidemiology of AI in diverse settings. Variables influencing circulation of the H5 subtype in Southeast Asia played a similar role for low pathogenic AIV in Madagascar, indicating that this area may be at risk if a highly virulent strain is introduced.

Walker circulation in a transient climate

NASA Astrophysics Data System (ADS)

Plesca, Elina; Grützun, Verena; Buehler, Stefan A.

2016-04-01

The tropical overturning circulations modulate the heat exchange across the tropics and between the tropics and the poles. The anthropogenic influence on the climate system will affect these circulations, impacting the dynamics of the Earth system. In this work we focus on the Walker circulation. We investigate its temporal and spatial dynamical changes and their link to other climate features, such as surface and sea-surface temperature patterns, El-Niño Southern Oscillation (ENSO), and ocean heat-uptake, both at global and regional scale. In order to determine the impact of anthropogenic climate change on the tropical circulation, we analyze the outputs of 28 general circulation models (GCMs) from the CMIP5 project. We use the experiment with 1% year-1 increase in CO2 concentration from pre-industrial levels to quadrupling of the concentration. Consistent with previous studies (ex. Ma and Xie 2013), we find that for this experiment most GCMs associate a weakening Walker circulation to a warming transient climate. Due to the role of the Walker Pacific cell in the meridional heat and moisture transport across the tropical Pacific and also the connection to ENSO, we find that a weakened Walker circulation correlates with more extreme El-Niño events, although without a change in their frequency. The spatial analysis of the Pacific Walker cell suggests an eastward displacement of the ascending branch, which is consistent with positive SST anomalies over the tropical Pacific and the link of the Pacific Walker cell to ENSO. Recent studies (ex. England et al. 2014) have linked a strengthened Walker circulation to stronger ocean heat uptake, especially in the western Pacific. The inter-model comparison of the correlation between Walker circulation intensity and ocean heat uptake does not convey a robust response for the investigated experiment. However, there is some evidence that a stronger weakening of the Walker circulation is linked to a higher transient climate response (temperature change by the time of CO2 doubling), which in turn might be related to a decreased ocean heat uptake. This uncertainty across the models we attribute to the multitude of factors controlling ocean and atmosphere heat exchange, both at global and regional scales, as well as to the present capabilities of GCMs in simulating this exchange. References: England, M. H., McGregor, S., Spence, P., Meehl, G. A., Timmermann, A., Cai, W., Gupta, A. S., McPhaden, M. J., Purich, A., and Santoso, A., 2014. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nature Climate Change 4 (3): 222-227. Ma, J., and Xie, S. P., 2013. Regional Patterns of Sea Surface Temperature Change: A Source of Uncertainty in Future Projections of Precipitation and Atmospheric Circulation*. Journal of Climate, 26 (8): 2482-2501

Statistical downscaling of sub-daily (6-hour) temperature in Romania, by means of artificial neural networks

NASA Astrophysics Data System (ADS)

Birsan, Marius-Victor; Dumitrescu, Alexandru; Cǎrbunaru, Felicia

2016-04-01

The role of statistical downscaling is to model the relationship between large-scale atmospheric circulation and climatic variables on a regional and sub-regional scale, making use of the predictions of future circulation generated by General Circulation Models (GCMs) in order to capture the effects of climate change on smaller areas. The study presents a statistical downscaling model based on a neural network-based approach, by means of multi-layer perceptron networks. Sub-daily temperature data series from 81 meteorological stations over Romania, with full data records are used as predictands. As large-scale predictor, the NCEP/NCAD air temperature data at 850 hPa over the domain 20-30E / 40-50N was used, at a spatial resolution of 2.5×2.5 degrees. The period 1961-1990 was used for calibration, while the validation was realized over the 1991-2010 interval. Further, in order to estimate future changes in air temperature for 2021-2050 and 2071-2100, air temperature data at 850 hPa corresponding to the IPCC A1B scenario was extracted from the CNCM33 model (Meteo-France) and used as predictor. This work has been realized within the research project "Changes in climate extremes and associated impact in hydrological events in Romania" (CLIMHYDEX), code PN II-ID-2011-2-0073, financed by the Romanian Executive Agency for Higher Education Research, Development and Innovation Funding (UEFISCDI).

Future projections of insured losses in the German private building sector following the A1B climatic change scenario

NASA Astrophysics Data System (ADS)

Held, H.; Gerstengarbe, F.-W.; Hattermann, F.; Pinto, J. G.; Ulbrich, U.; Böhm, U.; Born, K.; Büchner, M.; Donat, M. G.; Kücken, M.; Leckebusch, G. C.; Nissen, K.; Nocke, T.; Österle, H.; Pardowitz, T.; Werner, P. C.; Burghoff, O.; Broecker, U.; Kubik, A.

2012-04-01

We present an overview of a complementary-approaches impact project dealing with the consequences of climate change for the natural hazard branch of the insurance industry in Germany. The project was conducted by four academic institutions together with the German Insurance Association (GDV) and finalized in autumn 2011. A causal chain is modeled that goes from global warming projections over regional meteorological impacts to regional economic losses for private buildings, hereby fully covering the area of Germany. This presentation will focus on wind storm related losses, although the method developed had also been applied in part to hail and flood impact losses. For the first time, the GDV supplied their collected set of insurance cases, dating back for decades, for such an impact study. These data were used to calibrate and validate event-based damage functions which in turn were driven by three different types of regional climate models to generate storm loss projections. The regional models were driven by a triplet of ECHAM5 experiments following the A1B scenario which were found representative in the recent ENSEMBLES intercomparison study. In our multi-modeling approach we used two types of regional climate models that conceptually differ at maximum: a dynamical model (CCLM) and a statistical model based on the idea of biased bootstrapping (STARS). As a third option we pursued a hybrid approach (statistical-dynamical downscaling). For the assessment of climate change impacts, the buildings' infrastructure and their economic value is kept at current values. For all three approaches, a significant increase of average storm losses and extreme event return levels in the German private building sector is found for future decades assuming an A1B-scenario. However, the three projections differ somewhat in terms of magnitude and regional differentiation. We have developed a formalism that allows us to express the combined effect of multi-source uncertainty on return levels within the framework of a generalized Pareto distribution.

AOD trends during 2001-2010 from observations and model simulations

NASA Astrophysics Data System (ADS)

Pozzer, Andrea; de Meij, Alexander; Yoon, Jongmin; Astitha, Marina

2016-04-01

The trend of aerosol optical depth (AOD) between 2001 and 2010 is estimated globally and regionally from remote sensed observations by the MODIS (Moderate Resolution Imaging Spectroradiometer), MISR (Multi-angle Imaging SpectroRadiometer) and SeaWIFS (Sea-viewing Wide Field-of-view Sensor) satellite sensor. The resulting trends have been compared to model results from the EMAC (ECHAM5/MESSy Atmospheric Chemistry {[1]}), model. Although interannual variability is applied only to anthropogenic and biomass-burning emissions, the model is able to quantitatively reproduce the AOD trends as observed by MODIS, while some discrepancies are found when compared to MISR and SeaWIFS. An additional numerical simulation with the same model was performed, neglecting any temporal change in the emissions, i.e. with no interannual variability for any emission source. It is shown that decreasing AOD trends over the US and Europe are due to the decrease in the (anthropogenic) emissions. On contrary over the Sahara Desert and the Middle East region, the meteorological/dynamical changes in the last decade play a major role in driving the AOD trends. Further, over Southeast Asia, both meteorology and emissions changes are equally important in defining AOD trends {[2]}. Finally, decomposing the regional AOD trends into individual aerosol components reveals that the soluble components are the most dominant contributors to the total AOD, as their influence on the total AOD is enhanced by the aerosol water content. {[1]}: Jöckel, P., Kerkweg, A., Pozzer, A., Sander, R., Tost, H., Riede, H., Baumgaertner, A., Gromov, S., and Kern, B.: Development cycle 2 of the Modular Earth Submodel System (MESSy2), Geosci. Model Dev., 3, 717-752, doi:10.5194/gmd-3-717-2010, 2010. {[2]}: Pozzer, A., de Meij, A., Yoon, J., Tost, H., Georgoulias, A. K., and Astitha, M.: AOD trends during 2001-2010 from observations and model simulations, Atmos. Chem. Phys., 15, 5521-5535, doi:10.5194/acp-15-5521-2015, 2015.

Global ionospheric and thermospheric response to the 5 April 2010 geomagnetic storm: An integrated data-model investigation

NASA Astrophysics Data System (ADS)

Lu, G.; Hagan, M. E.; Häusler, K.; Doornbos, E.; Bruinsma, S.; Anderson, B. J.; Korth, H.

2014-12-01

We present a case study of the 5 April 2010 geomagnetic storm using observations and numerical simulations. The event was driven by a fast-moving coronal mass ejection and despite being a moderate storm with a minimum Dst near -50 nT, the event exhibited elevated thermospheric density and surges of traveling atmospheric disturbances (TADs) more typically seen during major storms. The Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) was used to assess how these features were generated and developed during the storm. The model simulations gave rise to TADs that were highly nonuniform with strong latitude and longitude/local time dependence. The TAD phase speeds ranged from 640 m/s to 780 m/s at 400 km and were ~5% lower at 300 km and approximately 10-15% lower at 200 km. In the lower thermosphere around 100 km, the TAD signatures were nearly unrecognizable due to much stronger influence of upward propagating atmospheric tides. The thermosphere simulation results were compared to observations available from the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites. Comparison with GOCE data shows that the TIMEGCM reproduced the cross-track winds over the polar region very well. The model-data comparison also revealed some differences, specifically, the simulations underestimated neutral mass density in the upper thermosphere above ~300 km and overestimated the storm recovery tome by 6 h. These discrepancies indicate that some heating or circulation dynamics and potentially cooling processes are not fully represented in the simulations, and also that updates to some parameterization schemes in the TIMEGCM are warranted.

NEIGHBORHOOD SCALE AIR QUALITY MODELING IN HOUSTON USING URBAN CANOPY PARAMETERS IN MM5 AND CMAQ WITH IMPROVED CHARACTERIZATION OF MESOSCALE LAKE-LAND BREEZE CIRCULATION

EPA Science Inventory

Advanced capability of air quality simulation models towards accurate performance at finer scales will be needed for such models to serve as tools for performing exposure and risk assessments in urban areas. It is recognized that the impact of urban features such as street and t...

Regional climate change predictions from the Goddard Institute for Space Studies high resolution GCM

NASA Technical Reports Server (NTRS)

Crane, Robert G.; Hewitson, B. C.

1991-01-01

A new diagnostic tool is developed for examining relationships between the synoptic scale circulation and regional temperature distributions in GCMs. The 4 x 5 deg GISS GCM is shown to produce accurate simulations of the variance in the synoptic scale sea level pressure distribution over the U.S. An analysis of the observational data set from the National Meteorological Center (NMC) also shows a strong relationship between the synoptic circulation and grid point temperatures. This relationship is demonstrated by deriving transfer functions between a time-series of circulation parameters and temperatures at individual grid points. The circulation parameters are derived using rotated principal components analysis, and the temperature transfer functions are based on multivariate polynomial regression models. The application of these transfer functions to the GCM circulation indicates that there is considerable spatial bias present in the GCM temperature distributions. The transfer functions are also used to indicate the possible changes in U.S. regional temperatures that could result from differences in synoptic scale circulation between a 1XCO2 and a 2xCO2 climate, using a doubled CO2 version of the same GISS GCM.

Upper-Ocean Heat Balance Processes and the Walker Circulation in CMIP5 Model Projections

NASA Technical Reports Server (NTRS)

Robertson, F. R.; Roberts, J. B.; Funk, C.; Lyon, B.; Ricciardulli, L.

2012-01-01

Considerable uncertainty remains as to the importance of mechanisms governing decadal and longer variability of the Walker Circulation, its connection to the tropical climate system, and prospects for tropical climate change in the face of anthropogenic forcing. Most contemporary climate models suggest that in response to elevated CO2 and a warmer but more stratified atmosphere, the required upward mass flux in tropical convection will diminish along with the Walker component of the tropical mean circulation as well. Alternatively, there is also evidence to suggest that the shoaling and increased vertical stratification of the thermocline in the eastern Pacific will enable a muted SST increase there-- preserving or even enhancing some of the dynamical forcing for the Walker cell flow. Over the past decade there have been observational indications of an acceleration in near-surface easterlies, a strengthened Pacific zonal SST gradient, and globally-teleconnected dislocations in precipitation. But is this evidence in support of an ocean dynamical thermostat process posited to accompany anthropogenic forcing, or just residual decadal fluctuations associated with variations in warm and cold ENSO events and other stochastic forcing? From a modeling perspective we try to make headway on this question by examining zonal variations in surface energy fluxes and dynamics governing tropical upper ocean heat content evolution in the WCRP CMIP5 model projections. There is some diversity among model simulations; for example, the CCSM4 indicates net ocean warming over the IndoPacific region while the CSIRO model concentrates separate warming responses over the central Pacific and Indian Ocean regions. The models, as with observations, demonstrate strong local coupling between variations in column water vapor, downward surface longwave radiation and SST; but the spatial patterns of changes in the sign of this relationship differ among models and, for models as a whole, with observations. Our analysis focuses initially on probing the inter-model differences in energy fluxes / transports and Walker Circulation response to forcing. We then attempt to identify statistically the El Nino- / La Nina-related ocean heat content variability unique to each model and regress out the associated energy flux, ocean heat transport and Walker response on these shorter time scales for comparison to that of the anthropogenic signals.

Future projections of active-break spells of Indian summer monsoon in a climate change perspective

NASA Astrophysics Data System (ADS)

Sudeepkumar, B. L.; Babu, C. A.; Varikoden, Hamza

2018-02-01

The effect of global climate change on Indian summer monsoon has been analysed with special emphasis on active-break cycle. The changes in intensity and duration of active and break monsoon conditions towards the end of the century are studied by using 850 hPa zonal circulations. The analysis is carried out using twenty year climatology of historical period (1986-2005) and future projections (2080-2099) simulated as part of Coupled Model Intercomparison Project phase 5 (CMIP5). Models are compared with NCEP/NCAR reanalysis data. The models that effectively capture the circulation pattern of monsoon (JJAS) are considered for assessing the future climate in RCP 4.5 scenario. They are CanESM2, CNRM-CM5, GFDL-ESM2M, MIROC5 and MPI-ESM-LR. During the southwest monsoon period, the ensemble mean of models projects a strengthening of the wind speed towards north (north of 15°N) and weakening to the southern region (especially south of 12°N) which facilitates wetting of northern Indian regions and drying of southern peninsular regions. In the case of active-break conditions, the active spells are found to be strengthening over northern India and weakening over the peninsular India, the break spells intensify over southern tip of peninsular India indicating intense breaks. Increased propensity of short intense active days and decreased propensity of long active days are also projected by the models. The number of break spells does not show any significant changes.

Aerosol as a player in the Arctic Amplification - an aerosol-climate model evaluation study

NASA Astrophysics Data System (ADS)

Schacht, Jacob; Heinold, Bernd; Tegen, Ina

2017-04-01

Climate warming is much more pronounced in the Arctic than in any other region on Earth - a phenomenon referred to as the "Arctic Amplification". This is closely related to a variety of specific feedback mechanisms, which relative importance, however, is not yet sufficiently understood. The local changes in the Arctic climate are far-reaching and affect for example the general atmospheric circulation and global energy transport. Aerosol particles from long-range transport and local sources play an important role in the Arctic system by modulating the energy balance (directly by interaction with solar and thermal infrared radiation and indirectly by changing cloud properties and atmospheric dynamics). The main source regions of anthropogenic aerosol are Europe and East Asia, but also local shipping and oil/gas extraction may contribute significantly. In addition, important sources are widespread, mainly natural boreal forest fires. Most of the European aerosol is transported through the lower atmospheric layers in wintertime. The Asian aerosol is transported through higher altitudes. Because of the usually pristine conditions in the Arctic even small absolute changes in aerosol concentration can have large impacts on the Arctic climate. Using global and Arctic-focused model simulations, we aim at investigating the sources and transport pathways of natural and anthropogenic aerosol to the Arctic region, as well as their impact on radiation and clouds. Here, we present first results from an aerosol-climate model evaluation study. Simulations were performed with the global aerosol-climate model ECHAM6-HAM2, using three different state-of-the-art emission inventories (ACCMIP, ACCMIP + GFAS emissions for wildfires and ECLIPSE). The runs were performed in nudged mode at T63 horizontal resolution (approximately 1.8°) with 47 vertical levels for the 10-year period 2006-2015. Black carbon (BC) and sulphate (SO4) are of particular interest. BC is highly absorbing in the solar spectrum, an effect that is enhanced by the contrast between the bright snow/ice surfaces and the dark BC. When deposited on snow and ice, BC also accelerates melting and lowers the surface albedo. SO4 however is more scattering and, therefore, cooling. The model results are compared among each other and evaluated against ground-based in-situ and remote sensing, as well as active satellite observations. The following questions are addressed in the evaluation: 1) Are the sources and transport pathways of aerosol to the Arctic region captured? 2) Is the annual cycle of aerosol conditions reproduced? 3) What are uncertainties related to the emission database? After thorough evaluation, the model results will provide a state-of-the-art estimate of the aerosol budget and the effective radiative forcing by anthropogenic aerosols in the Arctic region.

A numerical circulation model with topography for the Martian Southern Hemisphere

NASA Technical Reports Server (NTRS)

Mass, C.; Sagan, C.

1975-01-01

A quasi-geostrophic numerical model, including friction, radiation, and the observed planetary topography, is applied to the general circulation of the Martian atmosphere in the Southern Hemisphere at latitudes south of about 35 deg. Near equilibrium weather systems developed after about 5 model days. To avoid violating the quasi-geostrophic approximation, only 0.8 of the already smoothed relief was employed. Weather systems and velocity fields are strikingly tied to topography. A 2mb middle latitude jet stream is found of remarkably terrestrial aspect. Highest surface velocities, both horizontal and vertical, are predicted in western Hellas Planitia and eastern Argyre Planitia, which are observed to be preferred sites of origin of major Martian dust storms. Mean horizontal velocities and vertical velocities are found just above the surface velocity boundary layer.

Earth System Chemistry integrated Modelling (ESCiMo) with the Modular Earth Submodel System (MESSy) version 2.51

NASA Astrophysics Data System (ADS)

Jöckel, Patrick; Tost, Holger; Pozzer, Andrea; Kunze, Markus; Kirner, Oliver; Brenninkmeijer, Carl A. M.; Brinkop, Sabine; Cai, Duy S.; Dyroff, Christoph; Eckstein, Johannes; Frank, Franziska; Garny, Hella; Gottschaldt, Klaus-Dirk; Graf, Phoebe; Grewe, Volker; Kerkweg, Astrid; Kern, Bastian; Matthes, Sigrun; Mertens, Mariano; Meul, Stefanie; Neumaier, Marco; Nützel, Matthias; Oberländer-Hayn, Sophie; Ruhnke, Roland; Runde, Theresa; Sander, Rolf; Scharffe, Dieter; Zahn, Andreas

2016-03-01

Three types of reference simulations, as recommended by the Chemistry-Climate Model Initiative (CCMI), have been performed with version 2.51 of the European Centre for Medium-Range Weather Forecasts - Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model: hindcast simulations (1950-2011), hindcast simulations with specified dynamics (1979-2013), i.e. nudged towards ERA-Interim reanalysis data, and combined hindcast and projection simulations (1950-2100). The manuscript summarizes the updates of the model system and details the different model set-ups used, including the on-line calculated diagnostics. Simulations have been performed with two different nudging set-ups, with and without interactive tropospheric aerosol, and with and without a coupled ocean model. Two different vertical resolutions have been applied. The on-line calculated sources and sinks of reactive species are quantified and a first evaluation of the simulation results from a global perspective is provided as a quality check of the data. The focus is on the intercomparison of the different model set-ups. The simulation data will become publicly available via CCMI and the Climate and Environmental Retrieval and Archive (CERA) database of the German Climate Computing Centre (DKRZ). This manuscript is intended to serve as an extensive reference for further analyses of the Earth System Chemistry integrated Modelling (ESCiMo) simulations.

Reduction of circulating and selective limbic brain levels of (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) following forced swim stress in C57BL/6J mice

PubMed Central

Maldonado-Devincci, Antoniette M.; Beattie, Matthew C.; Morrow, Danielle H.; McKinley, Raechel E.; Cook, Jason B.; O’Buckley, Todd K.

2014-01-01

Rationale Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, and GABAergic neuroactive steroids contribute to homeostatic regulation of this circuitry. Acute forced swim stress (FSS) increases plasma, cortical, and hypothalamic (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) levels in rats. However, there have not been systemic investigations of acute stress on changes in plasma and brain levels of 3α,5α-THP in mouse models. Objectives The present experiments aimed to assess circulating and local brain levels of 3α,5α-THP following acute FSS in C57BL/6J mice. Methods Mice were exposed to FSS (10 min), and 50 min later, blood and brains were collected. Circulating pregnenolone and 3α,5α-THP levels were assessed in serum. Free-floating brain sections (40 µm, four to five sections/region) were immunostained and analyzed in cortical and limbic brain structures. Results FSS decreased circulating 3α,5α-THP (−41.6± 10.4 %) and reduced 3α,5α-THP immunolabeling in the paraventricular nucleus of the hypothalamus (−15.2±5.7 %), lateral amygdala (LA, −31.1±13.4 %), and nucleus accumbens (NAcc) shell (−31.9±14.6). Within the LA, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter were localized in 3α,5α-THP-positively stained cells, while in the NAcc shell, only VGLUT1 was localized in 3α,5α-THP-positively stained cells, suggesting that both glutamatergic and GABAergic cells within the LA are 3α,5α-THP-positive, while in the NAcc shell, 3α,5α-THP only localizes to glutamatergic cells. Conclusions The decrease in circulating and brain levels of 3α,5α-THP may be due to alterations in the biosynthesis/ metabolism or changes in the regulation of the HPA axis following FSS. Changes in GABAergic neuroactive steroids in response to stress likely mediate functional adaptations in neuronal activity. This may provide a potential targeted therapeutic avenue to address maladaptive stress responsivity. PMID:24744202

The effects of global change upon United States air quality

NASA Astrophysics Data System (ADS)

Gonzalez-Abraham, R.; Chung, S. H.; Avise, J.; Lamb, B.; Salathé, E. P., Jr.; Nolte, C. G.; Loughlin, D.; Guenther, A.; Wiedinmyer, C.; Duhl, T.; Zhang, Y.; Streets, D. G.

2015-11-01

To understand more fully the effects of global changes on ambient concentrations of ozone and particulate matter with aerodynamic diameter smaller than 2.5 μm (PM2.5) in the United States (US), we conducted a comprehensive modeling effort to evaluate explicitly the effects of changes in climate, biogenic emissions, land use and global/regional anthropogenic emissions on ozone and PM2.5 concentrations and composition. Results from the ECHAM5 global climate model driven with the A1B emission scenario from the Intergovernmental Panel on Climate Change (IPCC) were downscaled using the Weather Research and Forecasting (WRF) model to provide regional meteorological fields. We developed air quality simulations using the Community Multiscale Air Quality Model (CMAQ) chemical transport model for two nested domains with 220 and 36 km horizontal grid cell resolution for a semi-hemispheric domain and a continental United States (US) domain, respectively. The semi-hemispheric domain was used to evaluate the impact of projected global emissions changes on US air quality. WRF meteorological fields were used to calculate current (2000s) and future (2050s) biogenic emissions using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). For the semi-hemispheric domain CMAQ simulations, present-day global emissions inventories were used and projected to the 2050s based on the IPCC A1B scenario. Regional anthropogenic emissions were obtained from the US Environmental Protection Agency National Emission Inventory 2002 (EPA NEI2002) and projected to the future using the MARKet ALlocation (MARKAL) energy system model assuming a business as usual scenario that extends current decade emission regulations through 2050. Our results suggest that daily maximum 8 h average ozone (DM8O) concentrations will increase in a range between 2 to 12 parts per billion (ppb) across most of the continental US. The highest increase occurs in the South, Central and Midwest regions of the US due to increases in temperature, enhanced biogenic emissions and changes in land use. The model predicts an average increase of 1-6 ppb in DM8O due to projected increase in global emissions of ozone precursors. The effects of these factors are only partially offset by reductions in DM8O associated with decreasing US anthropogenic emissions. Increases in PM2.5 levels between 4 and 10 μg m-3 in the Northeast, Southeast, Midwest and South regions are mostly a result of increase in primary anthropogenic particulate matter (PM), enhanced biogenic emissions and land use changes. Changes in boundary conditions shift the composition but do not alter overall simulated PM2.5 mass concentrations.

Climate Simulations based on a different-grid nested and coupled model

NASA Astrophysics Data System (ADS)

Li, Dan; Ji, Jinjun; Li, Yinpeng

2002-05-01

An atmosphere-vegetation interaction model (A VIM) has been coupled with a nine-layer General Cir-culation Model (GCM) of Institute of Atmospheic Physics/State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (IAP/LASG), which is rhomboidally truncated at zonal wave number 15, to simulate global climatic mean states. A VIM is a model having inter-feedback between land surface processes and eco-physiological processes on land. As the first step to couple land with atmosphere completely, the physiological processes are fixed and only the physical part (generally named the SVAT (soil-vegetation-atmosphere-transfer scheme) model) of AVIM is nested into IAP/LASG L9R15 GCM. The ocean part of GCM is prescribed and its monthly sea surface temperature (SST) is the climatic mean value. With respect to the low resolution of GCM, i.e., each grid cell having lon-gitude 7.5° and latitude 4.5°, the vegetation is given a high resolution of 1.5° by 1.5° to nest and couple the fine grid cells of land with the coarse grid cells of atmosphere. The coupling model has been integrated for 15 years and its last ten-year mean of outputs was chosen for analysis. Compared with observed data and NCEP reanalysis, the coupled model simulates the main characteris-tics of global atmospheric circulation and the fields of temperature and moisture. In particular, the simu-lated precipitation and surface air temperature have sound results. The work creates a solid base on coupling climate models with the biosphere.

Why is the simulated climatology of tropical cyclones so sensitive to the choice of cumulus parameterization scheme in the WRF model?

NASA Astrophysics Data System (ADS)

Zhang, Chunxi; Wang, Yuqing

2018-01-01

The sensitivity of simulated tropical cyclones (TCs) to the choice of cumulus parameterization (CP) scheme in the advanced Weather Research and Forecasting Model (WRF-ARW) version 3.5 is analyzed based on ten seasonal simulations with 20-km horizontal grid spacing over the western North Pacific. Results show that the simulated frequency and intensity of TCs are very sensitive to the choice of the CP scheme. The sensitivity can be explained well by the difference in the low-level circulation in a height and sorted moisture space. By transporting moist static energy from dry to moist region, the low-level circulation is important to convective self-aggregation which is believed to be related to genesis of TC-like vortices (TCLVs) and TCs in idealized settings. The radiative and evaporative cooling associated with low-level clouds and shallow convection in dry regions is found to play a crucial role in driving the moisture-sorted low-level circulation. With shallow convection turned off in a CP scheme, relatively strong precipitation occurs frequently in dry regions. In this case, the diabatic cooling can still drive the low-level circulation but its strength is reduced and thus TCLV/TC genesis is suppressed. The inclusion of the cumulus momentum transport (CMT) in a CP scheme can considerably suppress genesis of TCLVs/TCs, while changes in the moisture-sorted low-level circulation and horizontal distribution of precipitation are trivial, indicating that the CMT modulates the TCLVs/TCs activities in the model by mechanisms other than the horizontal transport of moist static energy.

Field-wind Distribution and Eruption Columns: Colima Volcano, México.

NASA Astrophysics Data System (ADS)

Fonseca, R.; Martin, A. L.; Perez, I.

2006-12-01

Colima Volcano (19º51'N 103º62'W) is characterized by explosive behaviour. Recently this volcano has shown an increase in explosive activity suggesting the possibility of a subplinian event in the next future like the ones occurred in 1818 and 1913. They were characterized by eruptive columns higher than 20 Km. Considering the possibility of a new explosive event we carried out a wind study based on the radiosonde balloon data set (1980-1995) with 15 atmospheric levels. This data set was collected by Global Gridded Upper Air Statistics (GGUAS) of the European Centre for Médium Range Weather Forecast (ECMRWF). The data was processed with a cinematic model for the study of global atmospheric wind circulation. In this model the current function (vorticity) and a potential function (convergency and/or divergency) was calculated with the Poison equation, utilizing a spectral numeric model. Dominant wind direction in January-May and October-December is toward the East with variations to the East/South East. On the contrary during July-September the dominant wind direction is toward the West, South-West, North-East; East and North-East. The fluctuations related to anticyclonic circulation occur in May, July, September and November at the altitude between 5 and 18 Km. The wind model allows identification of the wind horizontal circulation during the whole year at different atmospheric levels. Moreover, the perturbations of the normal circulation have also been identified. These results are applied to an a ash fall map for ash-fall hazard zonification.

Combined ice core and climate-model evidence for the collapse of the West Antarctic Ice Sheet during Marine Isotope Stage 5e.

NASA Astrophysics Data System (ADS)

Steig, Eric J.; Huybers, Kathleen; Singh, Hansi A.; Steiger, Nathan J.; Frierson, Dargan M. W.; Popp, Trevor; White, James W. C.

2015-04-01

It has been speculated that collapse of the West Antarctic Ice Sheet explains the very high eustatic sea level rise during the last interglacial period, marine isotope stage (MIS) 5e, but the evidence remains equivocal. Changes in atmospheric circulation resulting from a collapse of the West Antarctic Ice Sheet (WAIS) would have significant regional impacts that should be detectable in ice core records. We conducted simulations using general circulation models (GCMs) at varying levels of complexity: a gray-radiation aquaplanet moist GCM (GRaM), the slab ocean version of GFDL-AM2 (also as an aquaplanet), and the fully-coupled version of NCAR's CESM with realistic topography. In all the experiments, decreased elevation from the removal of the WAIS leads to greater cyclonic circulation over the West Antarctic region. This creates increased advection of relatively warm marine air from the Amundsen-Bellingshausen Seas towards the South Pole, and increased cold-air advection from the East Antarctic plateau towards the Ross Sea and coastal Marie Byrd Land. The result is anomalous warming in some areas of the East Antarctic interior, and significant cooling in Marie Byrd Land. Comparison of ice core records shows good agreement with the model predictions. In particular, isotope-paleotemperature records from ice cores in East Antarctica warmed more between the previous glacial period (MIS 6) and MIS 5e than coastal Marie Byrd Land. These results add substantial support to other evidence for WAIS collapse during the last interglacial period.

Endotoxin-induced shock in the rat. A role for C5a.

PubMed Central

Smedegård, G.; Cui, L. X.; Hugli, T. E.

1989-01-01

Administration of endotoxin from gram-negative bacteria to rats results in systemic hypotension, an increased hematocrit, and decreased numbers of circulating leukocytes (polymorphonuclear), monocytes, and platelets. These potentially lethal physiologic changes may be partially attributed to complement activation and generation of anaphylatoxins by the endotoxin (LPS). We demonstrated an elevation in the plasma levels of both C3a and C5a in LPS-treated rats. Injection of 5 micrograms C5ades Arg (rat) into rats produced effects similar to those induced by LPS, including decreased mean arterial pressure (systemic hypotension) and decreased numbers of circulating polymorphonuclear leukocytes, monocytes, and platelets. Unlike the response to LPS, C5a did not increase the hematocrit, indicating little effect on vascular permeability at the doses used. When LPS-treated animals were pretreated with F(ab')2 fragments of rabbit anti-rat C5a, no changes were measured in the circulating cell counts compared with LPS alone; however a significant improvement in the mean arterial pressure and a decrease in hematocrit was observed. We conclude that LPS-induced (septic) shock in the rat may result, in part, from the effects of complement activation and particularly from the generation of C5a. The influence of C5a on the LPS effect in the rat appears to enhance both the hypotensive (mean arterial pressure) and vascular permeability (hematocrit) responses. These results appear to support and confirm earlier observations that anti-human C5a increased survival in a septic-shock monkey model by eliminating circulating C5a and presumably thereby reducing the effects of endotoxin on blood pressure. Our results demonstrate that C5a plays a significant role in the hemodynamic changes associated with endotoxin-induced shock. Neutralization of C5a with specific antibodies may reduce the hypotensive response to endotoxin sufficiently to prevent lethal septic shock both in animals and in man. PMID:2789475

Effects of mineral dust on global atmospheric nitrate concentrations

NASA Astrophysics Data System (ADS)

Karydis, V. A.; Tsimpidi, A. P.; Pozzer, A.; Astitha, M.; Lelieveld, J.

2016-02-01

This study assesses the chemical composition and global aerosol load of the major inorganic aerosol components, focusing on mineral dust and aerosol nitrate. The mineral dust aerosol components (i.e., Ca2+, Mg2+, K+, Na+) and their emissions are included in the ECHAM5/MESSy Atmospheric Chemistry model (EMAC). Gas/aerosol partitioning is simulated using the ISORROPIA-II thermodynamic equilibrium model that considers K+, Ca2+, Mg2+, NH4+, Na+, SO42-, NO3-, Cl-, and H2O aerosol components. Emissions of mineral dust are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. Presence of metallic ions can substantially affect the nitrate partitioning into the aerosol phase due to thermodynamic interactions. The model simulates highest fine aerosol nitrate concentration over urban and industrialized areas (1-3 µg m-3), while coarse aerosol nitrate is highest close to deserts (1-4 µg m-3). The influence of mineral dust on nitrate formation extends across southern Europe, western USA, and northeastern China. The tropospheric burden of aerosol nitrate increases by 44 % when considering interactions of nitrate with mineral dust. The calculated global average nitrate aerosol concentration near the surface increases by 36 %, while the coarse- and fine-mode concentrations of nitrate increase by 53 and 21 %, respectively. Other inorganic aerosol components are affected by reactive dust components as well (e.g., the tropospheric burden of chloride increases by 9 %, ammonium decreases by 41 %, and sulfate increases by 7 %). Sensitivity tests show that nitrate aerosol is most sensitive to the chemical composition of the emitted mineral dust, followed by the soil size distribution of dust particles, the magnitude of the mineral dust emissions, and the aerosol state assumption.

Sensitivity of Statistical Downscaling Techniques to Reanalysis Choice and Implications for Regional Climate Change Scenarios

NASA Astrophysics Data System (ADS)

Manzanas, R., Sr.; Brands, S.; San Martin, D., Sr.; Gutiérrez, J. M., Sr.

2014-12-01

This work shows that local-scale climate projections obtained by means of statistical downscaling are sensitive to the choice of reanalysis used for calibration. To this aim, a Generalized Linear Model (GLM) approach is applied to downscale daily precipitation in the Philippines. First, the GLMs are trained and tested -under a cross-validation scheme- separately for two distinct reanalyses (ERA-Interim and JRA-25) for the period 1981-2000. When the observed and downscaled time-series are compared, the attained performance is found to be sensitive to the reanalysis considered if climate change signal bearing variables (temperature and/or specific humidity) are included in the predictor field. Moreover, performance differences are shown to be in correspondence with the disagreement found between the raw predictors from the two reanalyses. Second, the regression coefficients calibrated either with ERA-Interim or JRA-25 are subsequently applied to the output of a Global Climate Model (MPI-ECHAM5) in order to assess the sensitivity of local-scale climate change projections (up to 2100) to reanalysis choice. In this case, the differences detected in present climate conditions are considerably amplified, leading to "delta-change" estimates differing by up to a 35% (on average for the entire country) depending on the reanalysis used for calibration. Therefore, reanalysis choice is shown to importantly contribute to the uncertainty of local-scale climate change projections, and, consequently, should be treated with equal care as other, well-known, sources of uncertainty -e.g., the choice of the GCM and/or downscaling method.- Implications of the results for the entire tropics, as well as for the Model Output Statistics downscaling approach are also briefly discussed.

A blood circulation model for reference man

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leggett, R.W.; Eckerman, K.F.; Williams, L.R.

This paper describes a dynamic blood circulation model that predicts the movement and gradual dispersal of a bolus of material in the circulation after its intravascular injection into an adult human. The main purpose of the model is to improve the dosimetry of internally deposited radionuclides that decay in the circulation to a significant extent. The total blood volume is partitioned into the blood contents of 24 separate organs or tissues, right heart chambers, left heart chambers, pulmonary circulation, arterial outflow to the systemic tissues (aorta and large arteries), and venous return from the systemic tissues (large veins). As amore » compromise between physical reality and computational simplicity, the circulation of blood is viewed as a system of first-order transfers between blood pools, with the delay time depending on the mean transit time across the pool. The model allows consideration of incomplete, tissue-dependent extraction of material during passage through the circulation and return of material from tissues to plasma.« less

Solar related waves in the Venusian atmosphere from the cloud tops to 100 km

NASA Technical Reports Server (NTRS)

Elson, L. S.

1983-01-01

A quasi-linear diagnostic model using observed solar-related temperatures and a specified solar mean circulation and surface structure to find the solar-related circulation above the clouds of Venus is presented. Despite the greater dependence of model-derived, solar-related circulation on the mean flow than is the case for terrestrial tides, as well as the uncertainty concerning this mean flow, significant conclusions are drawn for the solar-related circulation and thermal structure of Venus. An anomalously large response is found in the polar regions, due to the model's requirement of a process such as dissipation which will act as a major sink for momentum. Dissipation is specified in the model as Rayleigh friction with an unknown free parameter coefficient. In view of this, dissipation is either very efficient by terrestrial standards and accompanied by small solar-related circulation, or similar to that of earth and possessed of a circulation large enough to have an impact on the mean circulation.

Fundamental characteristics of degradation-recoverable solid-state DFB polymer laser.

PubMed

Yoshioka, Hiroaki; Yang, Yu; Watanabe, Hirofumi; Oki, Yuji

2012-02-13

A novel solid-state dye laser with degradation recovery was proposed and demonstrated. Polydimethylsiloxane was used as a nanoporous solid matrix to enable the internal circulation of dye molecules in the solid state. An internal circulation model for the dye molecules was also proposed and verified numerically by assuming molecular mobility and using a proposed diffusion equation. The durability of the laser was increased 20.5-fold compared with that of a conventional polymethylmethacrylate laser. This novel laser solves the low-durability problem of dye-doped polymer lasers.

Potential Seasonal Predictability for Winter Storms over Europe

NASA Astrophysics Data System (ADS)

Wild, Simon; Befort, Daniel J.; Leckebusch, Gregor C.

2017-04-01

Reliable seasonal forecasts of strong extra-tropical cyclones and windstorms would have great social and economical benefits, as these events are the most costly natural hazards over Europe. In a previous study we have shown good agreement of spatial climatological distributions of extra-tropical cyclones and wind storms in state-of-the-art multi-member seasonal prediction systems with reanalysis. We also found significant seasonal prediction skill of extra-tropical cyclones and windstorms affecting numerous European countries. We continue this research by investigating the mechanisms and precursor conditions (primarily over the North Atlantic) on a seasonal time scale leading to enhanced extra-tropical cyclone activity and winter storm frequency over Europe. Our results regarding mechanisms show that an increased surface temperature gradient at the western edge of the North Atlantic can be related to enhanced winter storm frequency further downstream causing for example a greater number of storms over the British Isles, as observed in winter 2013-14.The so-called "Horseshoe Index", a SST tripole anomaly pattern over the North Atlantic in the summer months can also cause a higher number of winter storms over Europe in the subsequent winter. We will show results of AMIP-type sensitivity experiments using an AGCM (ECHAM5), supporting this hypothesis. Finally we will analyse whether existing seasonal forecast systems are able to capture these identified mechanisms and precursor conditions affecting the models' seasonal prediction skill.

AN INITIAL ASSESSMENT OF THE CLIMATE IMPACT OF SECONDARY ORGANIC AEROSOLS

NASA Astrophysics Data System (ADS)

O'Donnell, D.; Feichter, J.

2009-12-01

Atmospheric aerosols influence the Earth’s climate by absorbing and scattering solar radiation (the direct effect) and by altering the properties of clouds (indirect effects). Measurements have shown that a substantial fraction of the tropospheric aerosol burden consists of organic compounds. Hundreds of different organic species have been identified. While progress has been made in the understanding of the role of certain aerosol types in the climate system, that of organic aerosols remains poorly understood and the climate influences resulting from their presence poorly constrained. Organic aerosols are emitted directly from the surface (primary organic aerosols, POA) and are also formed in the atmosphere from gaseous precursors by oxidation reactions (secondary organic aerosols, SOA). Both biogenic and anthropogenic precursors have been identified. Biogenic emissions of aerosol precursors are known to be climate-dependent. Thus, a bi-directional dependency exists between the biosphere and the atmosphere, whereby aerosols of biogenic origin influence the climate system, which in turn affects biogenic aerosol precursor production. This study builds upon the global aerosol-climate model ECHAM5/HAM and adds techniques to model SOA as well as the necessary global emission inventories. Emission of biogenic precursors is calculated online. Formation of SOA is modeled by the well-known two-product model of SOA formation. SOA is subject to the same aerosol microphysics and sink processes as other modeled species (sulphate, black carbon, primary organic carbon, sea salt and dust). The aerosol radiative effects are calculated on a size resolved basis, and the aerosol scheme is coupled to the model cloud microphysics, permitting estimation of both direct and indirect aerosol effects. The following results will be discussed: (i) Estimation of the direct and indirect effects of biogenic and anthropogenic SOA, (ii) Estimation of the sign and magnitude of the biospheric feedback (through biogenic aerosol precursor emission) on the climate system, and (iii) Identification of physical processes and aerosol physical properties that need further experimental investigation in order to improve our understanding of the climate impact of SOA

Current and future background ozone simulations for Mexico using a multi-scale regional climate modeling system

NASA Astrophysics Data System (ADS)

Lamb, B. K.; Gonzalez Abraham, R.; Avise, J. C.; Chung, S. H.; Salathe, E. P.; Zhang, Y.; Guenther, A. B.; Wiedinmyer, C.; Duhl, T.; Streets, D. G.

2013-05-01

Global change will clearly have a significant impact on the environment. Among the concerns for future air quality in North America, intercontinental transport of pollution has become increasingly important. In this study, we examined the effect of projected changes in Asian emissions and emissions from lightning and wildfires to produce ozone background concentrations within Mexico and the continental US. This provides a basis for developing an understanding of North American background levels and how they may change in the future. Meteorological fields were downscaled from the results of the ECHAM5 global climate model using the Weather Research Forecast (WRF) model. Two nested domains were employed, one covering most of the Northern Hemisphere from eastern Asia to North America using 220 km grid cells (semi-hemispheric domain) and one covering the continental US and northern Mexico using 36 km grid cells. Meteorological results from WRF were used to drive the MEGAN biogenic emissions model, the SMOKE emissions processing tool, and the CMAQ chemical transport model to predict ozone concentrations for current (1995-2004) and future (2045-2054) summertime conditions. The MEGAN model was used to calculate biogenic emissions for all simulations. For the semi-hemispheric domain, year 2000 global emissions of gases (ozone precursors) from anthropogenic (outside of North America), natural, and biomass burning sources from the POET and EDGAR emission inventories were used. The global tabulation for black and organic carbon (BC and OC respectively) was obtained from Bond et al. (2004) For the future decade, the current emissions were projected to the year 2050 following the Intergovernmental Panel for Climate Change (IPCC) A1B emission scenario. Anthropogenic emissions from the US, Canada, and Mexico were omitted so that only global background concentrations, and local biogenic, wildfire, and lightning emissions were treated. In this paper, we focus on background ozone levels in Mexico due to changes in future climate, local biogenic emissions and global emissions.

Isolated transient vertigo: posterior circulation ischemia or benign origin?

PubMed

Blasberg, Tobias F; Wolf, Lea; Henke, Christian; Lorenz, Matthias W

2017-06-14

Isolated transient vertigo can be the only symptom of posterior circulation ischemia. Thus, it is important to differentiate isolated vertigo of a cerebrovascular origin from that of more benign origins, as patients with cerebral ischemia have a much higher risk for future stroke than do those with 'peripheral' vertigo. The current study aims to identify risk factors for cerebrovascular origin of isolated transient vertigo, and for future cerebrovascular events. From the files of 339 outpatients with isolated transient vertigo we extracted history, clinical and technical findings, diagnosis, and follow-up information on subsequent stroke or transient ischemic attack (TIA). Risk factors were analyzed using multivariate regression models (logistic or Cox) and reconfirmed in univariate analyses. On first presentation, 48 (14.2%) patients received the diagnosis 'probable or definite cerebrovascular vertigo'. During follow-up, 41 patients suffered stroke or TIA (event rate 7.9 per 100 person years, 95% confidence interval (CI) 5.5-10.4), 26 in the posterior circulation (event rate 4.8 per 100 person years, 95% CI 3.0-6.7). The diagnosis was not associated with follow-up cerebrovascular events. In multivariate models testing multiple potential determinants, only the presentation mode was consistently associated with the diagnosis and stroke risk: patients who presented because of vertigo (rather than reporting vertigo when they presented for other reasons) had a significantly higher risk for future stroke or TIA (p = 0.028, event rate 13.4 vs. 5.4 per 100 person years) and for future posterior circulation stroke or TIA (p = 0.044, event rate 7.8 vs. 3.5 per 100 person years). We here report for the first time follow-up stroke rates in patients with transient isolated vertigo. In such patients, the identification of those with cerebrovascular origin remains difficult, and presentation mode was found to be the only consistent risk factor. Confirmation in an independent prospective sample is needed.

Prognostic impact of circulating plasma cells in patients with multiple myeloma: implications for plasma cell leukemia definition

PubMed Central

Granell, Miquel; Calvo, Xavier; Garcia-Guiñón, Antoni; Escoda, Lourdes; Abella, Eugènia; Martínez, Clara Mª; Teixidó, Montserrat; Gimenez, Mª Teresa; Senín, Alicia; Sanz, Patricia; Campoy, Desirée; Vicent, Ana; Arenillas, Leonor; Rosiñol, Laura; Sierra, Jorge; Bladé, Joan; de Larrea, Carlos Fernández

2017-01-01

The presence of circulating plasma cells in patients with multiple myeloma is considered a marker for highly proliferative disease. In the study herein, the impact of circulating plasma cells assessed by cytology on survival of patients with multiple myeloma was analyzed. Wright-Giemsa stained peripheral blood smears of 482 patients with newly diagnosed myeloma or plasma cell leukemia were reviewed and patients were classified into 4 categories according to the percentage of circulating plasma cells: 0%, 1–4%, 5–20%, and plasma cell leukemia with the following frequencies: 382 (79.2%), 83 (17.2%), 12 (2.5%) and 5 (1.0%), respectively. Median overall survival according to the circulating plasma cells group was 47, 50, 6 and 14 months, respectively. At multivariate analysis, the presence of 5 to 20% circulating plasma cells was associated with a worse overall survival (relative risk 4.9, 95% CI 2.6–9.3) independently of age, creatinine, the Durie-Salmon system stage and the International Staging System (ISS) stage. Patients with ≥5% circulating plasma cells had lower platelet counts (median 86×109/L vs. 214×109/L, P<0.0001) and higher bone marrow plasma cells (median 53% vs. 36%, P=0.004). The presence of ≥5% circulating plasma cells in patients with multiple myeloma has a similar adverse prognostic impact as plasma cell leukemia. PMID:28255016

Role of Equatorial Pacific SST Anomalies in Precipitation over Western Americas

NASA Astrophysics Data System (ADS)

Jong, B. T.; Ting, M.; Seager, R.; Henderson, N.; Lee, D.

2017-12-01

El Niño, as the prime source of seasonal to interannual climate predictability, could impose impacts on the Americas from tropical to mid-latitude regions. The teleconnection patterns are sensitive to the longitudinal location of the maximum tropical sea surface temperature anomalies (SSTA). Meanwhile, slight differences in the location and configuration of the anomalous atmospheric circulations could differentiate between a wet and dry season regionally. For example, the 2015/16 strong El Niño event did not bring excessive precipitation to California despite expectations based on observational and model-based analyses. Whether the westward shift in the tropical SSTA pattern played a key role during this event is examined. We conduct two SSTA-forced experimental runs in three NCAR GCMs (CCM3, CAM4, and CAM5): one forced by the observed February-March-April 2016 SSTA and the other forced by the model-ensemble mean forecast FMA 2016 SSTA from the North America Multi-Model Ensemble. The observed SSTAs, compared to the forecast SSTAs, are colder in the central-eastern tropical Pacific and slightly warmer in the westernmost tropical Pacific. In response, all three models have a weaker and westward shifted low-pressure anomaly over the North Pacific and west coast of North America when the observed SSTA is prescribed. As the result, northern California is either about the same or drier in the observed SSTA runs than in the forecast SSTA runs. However, the precipitation over southern California responds differently across models. One of the possible explanations is that in CCM3 the teleconnections respond mainly to the SSTA differences in the eastern tropical Pacific; while in CAM4 and CAM5, the teleconnections are also sensitive to the small SSTA differences in the western tropical Pacific. The results suggest that the tropical SSTA differences matter for atmospheric circulations and precipitation over western Americas even though models disagree on the details of the circulation responses and subsequently the sign of regional precipitation responses. Further work on the sensitivity of circulations and precipitation to the tropical Pacific SSTA forcing will be conducted to improve the prediction of precipitation over western Americas.

Numerical simulations of island-scale airflow over Maui and the Maui vortex under summer trade wind conditions

Treesearch

DaNa L. Carlis; Yi-Leng Chen; Vernon R. Morris

2010-01-01

The fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) coupled with the Noah land surface model (LSM) is employed to simulate island-scale airflow and circulations over Maui County, Hawaii, under summer trade wind conditions, during July–August 2005. The model forecasts are validated by surface observations with good agreement.

Assessing the Global Climate Response to Freshwater Forcing from the Antarctic Ice Sheet Under Future Climate Scenarios

NASA Astrophysics Data System (ADS)

Rogstad, S.; Condron, A.; DeConto, R.; Pollard, D.

2017-12-01

Observational evidence indicates that the West Antarctic Ice Sheet (WAIS) is losing mass at an accelerating rate. Impacts to global climate resulting from changing ocean circulation patterns due to increased freshwater runoff from Antarctica in the future could have significant implications for global heat transport, but to-date this topic has not been investigated using complex numerical models with realistic freshwater forcing. Here, we present results from a high resolution fully coupled ocean-atmosphere model (CESM 1.2) forced with runoff from Antarctica prescribed from a high resolution regional ice sheet-ice shelf model. Results from the regional simulations indicate a potential freshwater contribution from Antarctica of up to 1 m equivalent sea level rise by the end of the century under RCP 8.5 indicating that a substantial input of freshwater into the Southern Ocean is possible. Our high resolution global simulations were performed under IPCC future climate scenarios RCP 4.5 and 8.5. We will present results showing the impact of WAIS collapse on global ocean circulation, sea ice, air temperature, and salinity in order to assess the potential for abrupt climate change triggered by WAIS collapse.

A meridional dipole in premonsoon Bay of Bengal tropical cyclone activity induced by ENSO: TROPICAL CYCLONES, MONSOON AND ENSO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balaguru, Karthik; Leung, L. Ruby; Lu, Jian

2016-06-27

Analysis of Bay of Bengal tropical cyclone (TC) track data for the month of May during 1980-2013 reveals a meridional dipole in TC intensification: TC intensification rates increased in the northern Bay and decreased in the southern Bay. The dipole was driven by an increase in low-level vorticity and atmospheric humidity in the northern Bay, making the environment more favorable for TC intensification, and enhanced vertical wind shear in the southern Bay, tending to reduce TC development. These environmental changes were associated with a strengthening of the monsoon circulation for the month of May, driven by a La Nin˜a-like shiftmore » in tropical Pacific SSTs andassociated tropical wave dynamics. Analysis of a suite of climate models fromthe CMIP5 archive for the 150-year historical period shows that most models correctly reproduce the link between ENSO and Bay of Bengal TC activity through the monsoon at interannual timescales. Under the RCP 8.5 scenario the same CMIP5 models produce an El Nin˜o like warming trend in the equatorial Pacific, tending to weaken the monsoon circulation. These results suggest« less

1-D transient numerical model of a regenerator in a novel sub Kelvin Active Magnetic Regenerative Refrigerator

NASA Astrophysics Data System (ADS)

Jahromi, Amir E.; Miller, Franklin K.

2016-03-01

A sub Kelvin Active Magnetic Regenerative Refrigerator (AMRR) is being developed at the University of Wisconsin - Madison. This AMRR consists of two circulators, two regenerators, one superleak, one cold heat exchanger, and two warm heat exchangers. The circulators are novel non-moving part pumps that reciprocate a superfluid mixture of 4He-3He in the system. Heat from the mixture is removed within the two regenerators of this tandem system. An accurate model of the regenerators in this AMRR is necessary in order to predict the performance of these components, which in turn helps predicting the overall performance of the AMRR system. This work presents modeling methodology along with results from a 1-D transient numerical model of the regenerators of an AMRR capable of removing 2.5 mW at 850 mK at cyclic steady state.

Complex mean circulation over the inner shelf south of Martha's Vineyard revealed by observations and a high-resolution model

USGS Publications Warehouse

Ganju, Neil K.; Lentz, Steven J.; Kirincich, Anthony R.; Farrar, J. Thomas

2011-01-01

Inner-shelf circulation is governed by the interaction between tides, baroclinic forcing, winds, waves, and frictional losses; the mean circulation ultimately governs exchange between the coast and ocean. In some cases, oscillatory tidal currents interact with bathymetric features to generate a tidally rectified flow. Recent observational and modeling efforts in an overlapping domain centered on the Martha's Vineyard Coastal Observatory (MVCO) provided an opportunity to investigate the spatial and temporal complexity of circulation on the inner shelf. ADCP and surface radar observations revealed a mean circulation pattern that was highly variable in the alongshore and cross-shore directions. Nested modeling incrementally improved representation of the mean circulation as grid resolution increased and indicated tidal rectification as the generation mechanism of a counter-clockwise gyre near the MVCO. The loss of model skill with decreasing resolution is attributed to insufficient representation of the bathymetric gradients (Δh/h), which is important for representing nonlinear interactions between currents and bathymetry. The modeled momentum balance was characterized by large spatial variability of the pressure gradient and horizontal advection terms over short distances, suggesting that observed inner-shelf momentum balances may be confounded. Given the available observational and modeling data, this work defines the spatially variable mean circulation and its formation mechanism—tidal rectification—and illustrates the importance of model resolution for resolving circulation and constituent exchange near the coast. The results of this study have implications for future observational and modeling studies near the MVCO and other inner-shelf locations with alongshore bathymetric variability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Gang

Mid-latitude extreme weather events are responsible for a large part of climate-related damage. Yet large uncertainties remain in climate model projections of heat waves, droughts, and heavy rain/snow events on regional scales, limiting our ability to effectively use these projections for climate adaptation and mitigation. These uncertainties can be attributed to both the lack of spatial resolution in the models, and to the lack of a dynamical understanding of these extremes. The approach of this project is to relate the fine-scale features to the large scales in current climate simulations, seasonal re-forecasts, and climate change projections in a very widemore » range of models, including the atmospheric and coupled models of ECMWF over a range of horizontal resolutions (125 to 10 km), aqua-planet configuration of the Model for Prediction Across Scales and High Order Method Modeling Environments (resolutions ranging from 240 km – 7.5 km) with various physics suites, and selected CMIP5 model simulations. The large scale circulation will be quantified both on the basis of the well tested preferred circulation regime approach, and very recently developed measures, the finite amplitude Wave Activity (FAWA) and its spectrum. The fine scale structures related to extremes will be diagnosed following the latest approaches in the literature. The goal is to use the large scale measures as indicators of the probability of occurrence of the finer scale structures, and hence extreme events. These indicators will then be applied to the CMIP5 models and time-slice projections of a future climate.« less

An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

1998-01-01

This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical 'cores' of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. The two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical 'simple physics' parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

1998-01-01

This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Cen- ter and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical "cores" of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. ne two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical "simple physics" parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

Recent slowing of Atlantic overturning circulation as a recovery from earlier strengthening

NASA Astrophysics Data System (ADS)

Jackson, Laura C.; Peterson, K. Andrew; Roberts, Chris D.; Wood, Richard A.

2016-07-01

The Atlantic meridional overturning circulation (AMOC) has weakened substantially over the past decade. Some weakening may already have occurred over the past century, and global climate models project further weakening in response to anthropogenic climate change. Such a weakening could have significant impacts on the surface climate. However, ocean model simulations based on historical conditions have often found an increase in overturning up to the mid-1990s, followed by a decrease. It is therefore not clear whether the observed weakening over the past decade is part of decadal variability or a persistent weakening. Here we examine a state-of-the-art global-ocean reanalysis product, GloSea5, which covers the years 1989 to 2015 and closely matches observations of the AMOC at 26.5° N, capturing the interannual variability and decadal trend with unprecedented accuracy. The reanalysis data place the ten years of observations--April 2004 to February 2014--into a longer-term context and suggest that the observed decrease in the overturning circulation is consistent with a recovery following a previous increase. We find that density anomalies that propagate southwards from the Labrador Sea are the most likely cause of these variations. We conclude that decadal variability probably played a key role in the decline of the AMOC observed over the past decade.

Circulation and rainfall climatology of a 10-year (1979 - 1988) integration with the Goddard Laboratory for atmospheres general circulation model

NASA Technical Reports Server (NTRS)

Kim, J.-H.; Sud, Y. C.

1993-01-01

A 10-year (1979-1988) integration of Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) under Atmospheric Model Intercomparison Project (AMIP) is analyzed and compared with observation. The first momentum fields of circulation variables and also hydrological variables including precipitation, evaporation, and soil moisture are presented. Our goals are (1) to produce a benchmark documentation of the GLA GCM for future model improvements; (2) to examine systematic errors between the simulated and the observed circulation, precipitation, and hydrologic cycle; (3) to examine the interannual variability of the simulated atmosphere and compare it with observation; and (4) to examine the ability of the model to capture the major climate anomalies in response to events such as El Nino and La Nina. The 10-year mean seasonal and annual simulated circulation is quite reasonable compared to the analyzed circulation, except the polar regions and area of high orography. Precipitation over tropics are quite well simulated, and the signal of El Nino/La Nina episodes can be easily identified. The time series of evaporation and soil moisture in the 12 biomes of the biosphere also show reasonable patterns compared to the estimated evaporation and soil moisture.

Climate Simulations from Super-parameterized and Conventional General Circulation Models with a Third-order Turbulence Closure

NASA Astrophysics Data System (ADS)

Xu, Kuan-Man; Cheng, Anning

2014-05-01

A high-resolution cloud-resolving model (CRM) embedded in a general circulation model (GCM) is an attractive alternative for climate modeling because it replaces all traditional cloud parameterizations and explicitly simulates cloud physical processes in each grid column of the GCM. Such an approach is called "Multiscale Modeling Framework." MMF still needs to parameterize the subgrid-scale (SGS) processes associated with clouds and large turbulent eddies because circulations associated with planetary boundary layer (PBL) and in-cloud turbulence are unresolved by CRMs with horizontal grid sizes on the order of a few kilometers. A third-order turbulence closure (IPHOC) has been implemented in the CRM component of the super-parameterized Community Atmosphere Model (SPCAM). IPHOC is used to predict (or diagnose) fractional cloudiness and the variability of temperature and water vapor at scales that are not resolved on the CRM's grid. This model has produced promised results, especially for low-level cloud climatology, seasonal variations and diurnal variations (Cheng and Xu 2011, 2013a, b; Xu and Cheng 2013a, b). Because of the enormous computational cost of SPCAM-IPHOC, which is 400 times of a conventional CAM, we decided to bypass the CRM and implement the IPHOC directly to CAM version 5 (CAM5). IPHOC replaces the PBL/stratocumulus, shallow convection, and cloud macrophysics parameterizations in CAM5. Since there are large discrepancies in the spatial and temporal scales between CRM and CAM5, IPHOC used in CAM5 has to be modified from that used in SPCAM. In particular, we diagnose all second- and third-order moments except for the fluxes. These prognostic and diagnostic moments are used to select a double-Gaussian probability density function to describe the SGS variability. We also incorporate a diagnostic PBL height parameterization to represent the strong inversion above PBL. The goal of this study is to compare the simulation of the climatology from these three models (CAM5, CAM5-IPHOC and SPCAM-IPHOC), with emphasis on low-level clouds and precipitation. Detailed comparisons of scatter diagrams among the monthly-mean low-level cloudiness, PBL height, surface relative humidity and lower tropospheric stability (LTS) reveal the relative strengths and weaknesses for five coastal low-cloud regions among the three models. Observations from CloudSat and CALIPSO and ECMWF Interim reanalysis are used as the truths for the comparisons. We found that the standard CAM5 underestimates cloudiness and produces small cloud fractions at low PBL heights that contradict with observations. CAM5-IPHOC tends to overestimate low clouds but the ranges of LTS and PBL height variations are most realistic. SPCAM-IPHOC seems to produce most realistic results with relatively consistent results from one region to another. Further comparisons with other atmospheric environmental variables will be helpful to reveal the causes of model deficiencies so that SPCAM-IPHOC results will provide guidance to the other two models.

Influence of Sea Ice on the Thermohaline Circulation in the Arctic-North Atlantic Ocean

NASA Technical Reports Server (NTRS)

Mauritzen, Cecilie; Haekkinen, Sirpa

1997-01-01

A fully prognostic coupled ocean-ice model is used to study the sensitivity of the overturning cell of the Arctic-North-Atlantic system to sea ice forcing. The strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the Arctic to the Greenland Sea and further to the subpolar gyre. The model produces a 2-3 Sv increase of the meridional circulation cell at 25N (at the simulation year 15) corresponding to a decrease of 800 cu km in the sea ice export from the Arctic. Previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic, implying that sea ice induced variability in the overturning cell can reach 5-6 Sv from peak to peak.

Future projections of synoptic weather types over the Arabian Peninsula during the twenty-first century using an ensemble of CMIP5 models

NASA Astrophysics Data System (ADS)

El Kenawy, Ahmed M.; McCabe, Matthew F.

2017-10-01

An assessment of future change in synoptic conditions over the Arabian Peninsula throughout the twenty-first century was performed using 20 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) database. We employed the mean sea level pressure (SLP) data from model output together with NCEP/NCAR reanalysis data and compared the relevant circulation types produced by the Lamb classification scheme for the base period 1975-2000. Overall, model results illustrated good agreement with the reanalysis, albeit with a tendency to underestimate cyclonic (C) and southeasterly (SE) patterns and to overestimate anticyclones and directional flows. We also investigated future projections for each circulation-type during the rainy season (December-May) using three Representative Concentration Pathways (RCPs), comprising RCP2.6, RCP4.5, and RCP8.5. Overall, two scenarios (RCP4.5 and RCP 8.5) revealed a statistically significant increase in weather types favoring above normal rainfall in the region (e.g., C and E-types). In contrast, weather types associated with lower amounts of rainfall (e.g., anticyclones) are projected to decrease in winter but increase in spring. For all scenarios, there was consistent agreement on the sign of change (i.e., positive/negative) for the most frequent patterns (e.g., C, SE, E and A-types), whereas the sign was uncertain for less recurrent types (e.g., N, NW, SE, and W). The projected changes in weather type frequencies in the region can be viewed not only as indicators of change in rainfall response but may also be used to inform impact studies pertinent to water resource planning and management, extreme weather analysis, and agricultural production.

An Isopycnal Box Model with predictive deep-ocean structure for biogeochemical cycling applications

NASA Astrophysics Data System (ADS)

Goodwin, Philip

2012-07-01

To simulate global ocean biogeochemical tracer budgets a model must accurately determine both the volume and surface origins of each water-mass. Water-mass volumes are dynamically linked to the ocean circulation in General Circulation Models, but at the cost of high computational load. In computationally efficient Box Models the water-mass volumes are simply prescribed and do not vary when the circulation transport rates or water mass densities are perturbed. A new computationally efficient Isopycnal Box Model is presented in which the sub-surface box volumes are internally calculated from the prescribed circulation using a diffusive conceptual model of the thermocline, in which upwelling of cold dense water is balanced by a downward diffusion of heat. The volumes of the sub-surface boxes are set so that the density stratification satisfies an assumed link between diapycnal diffusivity, κd, and buoyancy frequency, N: κd = c/(Nα), where c and α are user prescribed parameters. In contrast to conventional Box Models, the volumes of the sub-surface ocean boxes in the Isopycnal Box Model are dynamically linked to circulation, and automatically respond to circulation perturbations. This dynamical link allows an important facet of ocean biogeochemical cycling to be simulated in a highly computationally efficient model framework.

Tradeoffs between Maize Silage Yield and Nitrate Leaching in a Mediterranean Nitrate-Vulnerable Zone under Current and Projected Climate Scenarios

PubMed Central

Basso, Bruno; Giola, Pietro; Dumont, Benjamin; Migliorati, Massimiliano De Antoni; Cammarano, Davide; Pruneddu, Giovanni; Giunta, Francesco

2016-01-01

Future climatic changes may have profound impacts on cropping systems and affect the agronomic and environmental sustainability of current N management practices. The objectives of this work were to i) evaluate the ability of the SALUS crop model to reproduce experimental crop yield and soil nitrate dynamics results under different N fertilizer treatments in a farmer’s field, ii) use the SALUS model to estimate the impacts of different N fertilizer treatments on NO3- leaching under future climate scenarios generated by twenty nine different global circulation models, and iii) identify the management system that best minimizes NO3- leaching and maximizes yield under projected future climate conditions. A field experiment (maize-triticale rotation) was conducted in a nitrate vulnerable zone on the west coast of Sardinia, Italy to evaluate N management strategies that include urea fertilization (NMIN), conventional fertilization with dairy slurry and urea (CONV), and no fertilization (N0). An ensemble of 29 global circulation models (GCM) was used to simulate different climate scenarios for two Representative Circulation Pathways (RCP6.0 and RCP8.5) and evaluate potential nitrate leaching and biomass production in this region over the next 50 years. Data collected from two growing seasons showed that the SALUS model adequately simulated both nitrate leaching and crop yield, with a relative error that ranged between 0.4% and 13%. Nitrate losses under RCP8.5 were lower than under RCP6.0 only for NMIN. Accordingly, levels of plant N uptake, N use efficiency and biomass production were higher under RCP8.5 than RCP6.0. Simulations under both RCP scenarios indicated that the NMIN treatment demonstrated both the highest biomass production and NO3- losses. The newly proposed best management practice (BMP), developed from crop N uptake data, was identified as the optimal N fertilizer management practice since it minimized NO3- leaching and maximized biomass production over the long term. PMID:26784113

Computational models of the pulmonary circulation: Insights and the move towards clinically directed studies

PubMed Central

Tawhai, Merryn H.; Clark, Alys R.; Burrowes, Kelly S.

2011-01-01

Biophysically-based computational models provide a tool for integrating and explaining experimental data, observations, and hypotheses. Computational models of the pulmonary circulation have evolved from minimal and efficient constructs that have been used to study individual mechanisms that contribute to lung perfusion, to sophisticated multi-scale and -physics structure-based models that predict integrated structure-function relationships within a heterogeneous organ. This review considers the utility of computational models in providing new insights into the function of the pulmonary circulation, and their application in clinically motivated studies. We review mathematical and computational models of the pulmonary circulation based on their application; we begin with models that seek to answer questions in basic science and physiology and progress to models that aim to have clinical application. In looking forward, we discuss the relative merits and clinical relevance of computational models: what important features are still lacking; and how these models may ultimately be applied to further increasing our understanding of the mechanisms occurring in disease of the pulmonary circulation. PMID:22034608

Simulation and Prediction of Warm Season Drought in North America

NASA Technical Reports Server (NTRS)

Wang, Hailan; Chang, Yehui; Schubert, Siegfried D.; Koster, Randal D.

2018-01-01

This presentation presents our recent work on model simulation and prediction of warm season drought in North America. The emphasis will be on the contribution from the leading modes of subseasonal atmospheric circulation variability, which are often present in the form of stationary Rossby waves. Here we take advantage of the results from observations, reanalyses, and simulations and reforecasts performed using the NASA Goddard Earth Observing System (GEOS-5) atmospheric and coupled General Circulation Model (GCM). Our results show that stationary Rossby waves play a key role in Northern Hemisphere (NH) atmospheric circulation and surface meteorology variability on subseasonal timescales. In particular, such waves have been crucial to the development of recent short-term warm season heat waves and droughts over North America (e.g. the 1988, 1998, and 2012 summer droughts) and northern Eurasia (e.g., the 2003 summer heat wave over Europe and the 2010 summer drought and heat wave over Russia). Through an investigation of the physical processes by which these waves lead to the development of warm season drought in North America, it is further found that these waves can serve as a potential source of drought predictability. In order to properly represent their effect and exploit this source of predictability, a model needs to correctly simulate the Northern Hemisphere (NH) mean jet streams and be able to predict the sources of these waves. Given the NASA GEOS-5 AGCM deficiency in simulating the NH jet streams and tropical convection during boreal summer, an approach has been developed to artificially remove much of model mean biases, which leads to considerable improvement in model simulation and prediction of stationary Rossby waves and drought development in North America. Our study points to the need to identify key model biases that limit model simulation and prediction of regional climate extremes, and diagnose the origin of these biases so as to inform modeling group for model improvement.

Prognostic impact of circulating plasma cells in patients with multiple myeloma: implications for plasma cell leukemia definition.

PubMed

Granell, Miquel; Calvo, Xavier; Garcia-Guiñón, Antoni; Escoda, Lourdes; Abella, Eugènia; Martínez, Clara Mª; Teixidó, Montserrat; Gimenez, Mª Teresa; Senín, Alicia; Sanz, Patricia; Campoy, Desirée; Vicent, Ana; Arenillas, Leonor; Rosiñol, Laura; Sierra, Jorge; Bladé, Joan; de Larrea, Carlos Fernández

2017-06-01

The presence of circulating plasma cells in patients with multiple myeloma is considered a marker for highly proliferative disease. In the study herein, the impact of circulating plasma cells assessed by cytology on survival of patients with multiple myeloma was analyzed. Wright-Giemsa stained peripheral blood smears of 482 patients with newly diagnosed myeloma or plasma cell leukemia were reviewed and patients were classified into 4 categories according to the percentage of circulating plasma cells: 0%, 1-4%, 5-20%, and plasma cell leukemia with the following frequencies: 382 (79.2%), 83 (17.2%), 12 (2.5%) and 5 (1.0%), respectively. Median overall survival according to the circulating plasma cells group was 47, 50, 6 and 14 months, respectively. At multivariate analysis, the presence of 5 to 20% circulating plasma cells was associated with a worse overall survival (relative risk 4.9, 95% CI 2.6-9.3) independently of age, creatinine, the Durie-Salmon system stage and the International Staging System (ISS) stage. Patients with ≥5% circulating plasma cells had lower platelet counts (median 86×10 9 /L vs 214×10 9 /L, P <0.0001) and higher bone marrow plasma cells (median 53% vs 36%, P =0.004). The presence of ≥5% circulating plasma cells in patients with multiple myeloma has a similar adverse prognostic impact as plasma cell leukemia. Copyright© Ferrata Storti Foundation.

Posttransfusion Increase of Hematocrit per se Does Not Improve Circulatory Oxygen Delivery due to Increased Blood Viscosity.

PubMed

Zimmerman, Robert; Tsai, Amy G; Salazar Vázquez, Beatriz Y; Cabrales, Pedro; Hofmann, Axel; Meier, Jens; Shander, Aryeh; Spahn, Donat R; Friedman, Joel M; Tartakovsky, Daniel M; Intaglietta, Marcos

2017-05-01

Blood transfusion is used to treat acute anemia with the goal of increasing blood oxygen-carrying capacity as determined by hematocrit (Hct) and oxygen delivery (DO2). However, increasing Hct also increases blood viscosity, which may thus lower DO2 if the arterial circulation is a rigid hydraulic system as the resistance to blood flow will increase. The net effect of transfusion on DO2 in this system can be analyzed by using the relationship between Hct and systemic blood viscosity of circulating blood at the posttransfusion Hct to calculate DO2 and comparing this value with pretransfusion DO2. We hypothesized that increasing Hct would increase DO2 and tested our hypothesis by mathematically modeling DO2 in the circulation. Calculations were made assuming a normal cardiac output (5 L/min) with degrees of anemia ranging from 5% to 80% Hct deficit. We analyzed the effects of transfusing 0.5 or more units of 300 cc of packed red blood cells (PRBCs) at an Hct of 65% and calculated microcirculatory DO2 after accounting for increased blood viscosity and assuming no change in blood pressure. Our model accounts for O2 diffusion out of the circulation before blood arriving to the nutritional circulation and for changes in blood flow velocity. The immediate posttransfusion DO2 was also compared with DO2 after the transient increase in volume due to transfusion has subsided. Blood transfusion of up to 3 units of PRBCs increased DO2 when Hct (or hemoglobin) was 60% lower than normal, but did not increase DO2 when administered before this threshold. After accounting for the effect of increasing blood viscosity on blood flow owing to increasing Hct, we found in a mathematical simulation of DO2 that transfusion of up to 3 units of PRBCs does not increase DO2, unless anemia is the result of an Hct deficit greater than 60%. Observations that transfusions occasionally result in clinical improvement suggest that other mechanisms possibly related to increased blood viscosity may compensate for the absence of increase in DO2.

A zonally averaged, three-basin ocean circulation model for climate studies

NASA Astrophysics Data System (ADS)

Hovine, S.; Fichefet, T.

1994-09-01

A two-dimensional, three-basin ocean model suitable for long-term climate studies is developed. The model is based on the zonally averaged form of the primitive equations written in spherical coordinates. The east-west density difference which arises upon averaging the momentum equations is taken to be proportional to the meridional density gradient. Lateral exchanges of heat and salt between the basins are explicitly resolved. Moreover, the model includes bottom topography and has representations of the Arctic Ocean and of the Weddell and Ross seas. Under realistic restoring boundary conditions, the model reproduces the global conveyor belt: deep water is formed in the Atlantic between 60 and 70°N at a rate of about 17 Sv (1 Sv=106 m3 s-1) and in the vicinity of the Antarctic continent, while the Indian and Pacific basins show broad upwelling. Superimposed on this thermohaline circulation are vigorous wind-driven cells in the upper thermocline. The simulated temperature and salinity fields and the computed meridional heat transport compare reasonably well with the observational estimates. When mixed boundary conditions (i.e., a restoring condition on sea-surface temperature and flux condition on sea-surface salinity) are applied, the model exhibits an irregular behavior before reaching a steady state characterized by self-sustained oscillations of 8.5-y period. The conveyor-belt circulation always results at this stage. A series of perturbation experiments illustrates the ability of the model to reproduce different steady-state circulations under mixed boundary conditions. Finally, the model sensitivity to various factors is examined. This sensitivity study reveals that the bottom topography and the presence of a submarine meridional ridge in the zone of the Drake Passage play a crucial role in determining the properties of the model bottom-water masses. The importance of the seasonality of the surface forcing is also stressed.

Understanding hydrothermal circulation patterns at a low-enthalpy thermal spring using audio-magnetotelluric data: A case study from Ireland

NASA Astrophysics Data System (ADS)

Blake, Sarah; Henry, Tiernan; Muller, Mark R.; Jones, Alan G.; Moore, John Paul; Murray, John; Campanyà, Joan; Vozar, Jan; Walsh, John; Rath, Volker

2016-09-01

Kilbrook spring is a thermal spring in east-central Ireland. The temperatures in the spring are the highest recorded for any thermal spring in Ireland (maximum of 25 °C). The temperature is elevated with respect to average Irish groundwater temperatures (9.5-10.5 °C), and represents a geothermal energy potential, which is currently under evaluation. A multi-disciplinary investigation based upon an audio-magnetotelluric (AMT) survey, and hydrochemical analysis including time-lapse temperature and chemistry measurements, has been undertaken with the aims of investigating the provenance of the thermal groundwater and characterising the geological structures facilitating groundwater circulation in the bedrock. The three-dimensional (3-D) electrical resistivity model of the subsurface at Kilbrook spring was obtained by the inversion of AMT impedances and vertical magnetic transfer functions. The model is interpreted alongside high resolution temperature and electrical conductivity measurements, and a previous hydrochemical analysis. The hydrochemical analysis and time-lapse measurements suggest that the thermal waters have a relatively stable temperature and major ion hydrochemistry, and flow within the limestones of the Carboniferous Dublin Basin at all times. The 3-D resistivity model of the subsurface reveals a prominent NNW aligned structure within a highly resistive limestone lithology that is interpreted as a dissolutionally enhanced strike-slip fault, of Cenozoic age. The karstification of this structure, which extends to depths of at least 500 m directly beneath the spring, has provided conduits that facilitate the operation of a relatively deep hydrothermal circulation pattern (likely estimated depths between 560 and 1000 m) within the limestone succession of the Dublin Basin. The results of this study support the hypothesis that the winter thermal maximum and simultaneous increased discharge at Kilbrook spring is the result of rapid infiltration, heating and re-circulation of meteoric waters within this structurally controlled hydrothermal circulation system. This paper illustrates how AMT may be useful in a multi-disciplinary investigation of an intermediate-depth (100-1000 m), low-enthalpy, geothermal target, and shows how the different strands of inquiry from a multi-disciplinary investigation may be woven together to gain a deeper understanding of a complex hydrothermal system.

Behavioral alterations in autism model induced by valproic acid and translational analysis of circulating microRNA.

PubMed

Hirsch, Mauro Mozael; Deckmann, Iohanna; Fontes-Dutra, Mellanie; Bauer-Negrini, Guilherme; Della-Flora Nunes, Gustavo; Nunes, Walquiria; Rabelo, Bruna; Riesgo, Rudimar; Margis, Rogerio; Bambini-Junior, Victorio; Gottfried, Carmem

2018-05-01

Autism spectrum disorder (ASD) is characterized by difficulties in social interaction, communication and language, and restricted repertoire of activities and interests. The etiology of ASD remains unknown and no clinical markers for diagnosis were identified. Environmental factors, including prenatal exposure to valproic acid (VPA), may contribute to increased risk of developing ASD. MicroRNA (miRNA) are small noncoding RNA that regulate gene expression and are frequently linked to biological processes affected in neurodevelopmental disorders. In this work, we analyzed the effects of resveratrol (an antioxidant and anti-inflammatory molecule) on behavioral alterations of the VPA model of autism, as well as the levels of circulating miRNA. We also evaluated the same set of miRNA in autistic patients. Rats of the VPA model of autism showed reduced total reciprocal social interaction, prevented by prenatal treatment with resveratrol (RSV). The levels of miR134-5p and miR138-5p increased in autistic patients. Interestingly, miR134-5p is also upregulated in animals of the VPA model, which is prevented by RSV. In conclusion, our findings revealed important preventive actions of RSV in the VPA model, ranging from behavior to molecular alterations. Further evaluation of preventive mechanisms of RSV can shed light in important biomarkers and etiological triggers of ASD. Copyright © 2018 Elsevier Ltd. All rights reserved.

Circulating CXCR5+CD4+ T cells participate in the IgE accumulation in allergic asthma.

PubMed

Gong, Fang; Zhu, Hua-Yan; Zhu, Jie; Dong, Qiao-Jing; Huang, Xuan; Jiang, Dong-Jin

2018-05-01

The pathogenesis of allergic asthma is primarily characterized by abnormality in immunoglobin(Ig)E pathway, suggesting a possible role for follicular helper T cells (Tfh) in the genesis of excessive IgE accumulation. The blood chemokine (C-X-C motif) receptor 5 (CXCR)5 + CD4 + T cells, known as "circulating" Tfh, share common functional characteristics with Tfh cells from germinal centers. The aim of this study was to determine the phenotypes and functions of circulating CXCR5 + CD4 + T cells in allergic asthmatics. Here we found the frequency of the circulating CXCR5 + CD4 + T cells was raised in allergic asthma compared with healthy control (HC). Phenotypic assays showed that activated circulating CXCR5 + CD4 + T cells display the key features of Tfh cells, including invariably coexpressed programmed cell death (PD)-1 and inducible costimulator (ICOS). The frequency of interleukin IL-4 + -, IL-21 + -producing CXCR5 + CD4 + T cells was increased in allergic asthma patients compared with HC. Furthermore, sorted circulating CXCR5 + CD4 + T cells from allergic asthma patients boosted IgE production in coculture assay which could be inhibited by IL-4 or IL-21 blockage. Interestingly, IL-4 + -, IL-21 + -CXCR5 + CD4 + T cells positively correlated with total IgE in the blood. Our data indicated that circulating CXCR5 + CD4 + T cells may have a significant role in facilitating IgE production in allergic asthma patients. Copyright © 2018 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

Seasonal overturning circulation in the Red Sea: 2. Winter circulation

NASA Astrophysics Data System (ADS)

Yao, Fengchao; Hoteit, Ibrahim; Pratt, Larry J.; Bower, Amy S.; Köhl, Armin; Gopalakrishnan, Ganesh; Rivas, David

2014-04-01

The shallow winter overturning circulation in the Red Sea is studied using a 50 year high-resolution MITgcm (MIT general circulation model) simulation with realistic atmospheric forcing. The overturning circulation for a typical year, represented by 1980, and the climatological mean are analyzed using model output to delineate the three-dimensional structure and to investigate the underlying dynamical mechanisms. The horizontal model circulation in the winter of 1980 is dominated by energetic eddies. The climatological model mean results suggest that the surface inflow intensifies in a western boundary current in the southern Red Sea that switches to an eastern boundary current north of 24°N. The overturning is accomplished through a cyclonic recirculation and a cross-basin overturning circulation in the northern Red Sea, with major sinking occurring along a narrow band of width about 20 km along the eastern boundary and weaker upwelling along the western boundary. The northward pressure gradient force, strong vertical mixing, and horizontal mixing near the boundary are the essential dynamical components in the model's winter overturning circulation. The simulated water exchange is not hydraulically controlled in the Strait of Bab el Mandeb; instead, the exchange is limited by bottom and lateral boundary friction and, to a lesser extent, by interfacial friction due to the vertical viscosity at the interface between the inflow and the outflow.

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

NASA Astrophysics Data System (ADS)

Zhang, K.; O'Donnell, D.; Kazil, J.; Stier, P.; Kinne, S.; Lohmann, U.; Ferrachat, S.; Croft, B.; Quaas, J.; Wan, H.; Rast, S.; Feichter, J.

2012-10-01

This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation. Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker in-cloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This leads to a general increase in the number concentration of smaller particles over the oceans in HAM2, as reflected by the higher Ångström parameters. Evaluation against observation reveals that in terms of model performance, main improvements in HAM2 include a marked decrease of the systematic negative bias in the absorption aerosol optical depth, as well as smaller biases over the oceans in Ångström parameter and in the accumulation mode number concentration. The simulated geographical distribution of aerosol optical depth (AOD) is better correlated with the MODIS data, while the surface aerosol mass concentrations are very similar to those in the old version. The total aerosol water content in HAM2 is considerably closer to the multi-model average from Phase I of the AeroCom intercomparison project. Model deficiencies that require further efforts in the future include (i) positive biases in AOD over the ocean, (ii) negative biases in AOD and aerosol mass concentration in high-latitude regions, and (iii) negative biases in particle number concentration, especially that of the Aitken mode, in the lower troposphere in heavily polluted regions.

Newly developed photon-cell interactive Monte Carlo (pciMC) simulation for non-invasive and continuous diagnosis of blood during extracorporeal circulation support

NASA Astrophysics Data System (ADS)

Sakota, Daisuke; Takatani, Setsuo

2011-07-01

We have sought for non-invasive diagnosis of blood during the extracorporeal circulation support. To achieve the goal, we have newly developed a photon-cell interactive Monte Carlo (pciMC) model for optical propagation through blood. The pciMC actually describes the interaction of photons with 3-dimentional biconcave RBCs. The scattering is described by micro-scopical RBC boundary condition based on geometric optics. By using pciMC, we modeled the RBCs inside the extracorporeal circuit will be oriented by the blood flow. The RBCs' orientation was defined as their long axis being directed to the center of the circulation tube. Simultaneously the RBCs were allowed to randomly rotate about the long axis direction. As a result, as flow rate increased, the orientation rate increased and converged to approximately 22% at 0.5 L/min flow rate and above. And finally, by using this model, the pciMC non-invasively and absolutely predicted Hct and hemoglobin with the accuracies of 0.84+/-0.82 [HCT%] and 0.42+/-0.28 [g/dL] respectively against measurements by a blood gas analyzer.

Tracer transport by the diabatic circulation deduced from satellite observations

NASA Technical Reports Server (NTRS)

Solomon, S.; Kiehl, J. T.; Garcia, R. R.; Grose, W.

1986-01-01

Nimbus-7 sensor data were used to track the diabatic circulation in the stratosphere to study the advective transport of CH4 and N2O as tracer species. Advective transport by the mean circulation was found to be a function of the temperature field and associated deviations from radiative equilibrium. A photochemical model was applied to account for the disappearance of the tracer species from the stratosphere. Comparisons between the SAMS data and modeling on the basis of the chemical loss rates of the tracers and the LIMS circulation data showed that the model predictions underestimated the resident abundances, although the global distributions and circulations exhibited a good match.

Composition Changes After the "Halloween" Solar Proton Event: The High-Energy Particle Precipitation in the Atmosphere (HEPPA) Model Versus MIPAS Data Intercomparison Study

NASA Technical Reports Server (NTRS)

Funke, B.; Baumgaertner, A.; Calisto, M.; Egorova, T.; Jackman, C. H.; Kieser, J.; Krivolutsky, A.; Lopez-Puertas, M.; Marsh. D. R.; Reddmann, T.;

Circulating Irisin Levels Are Not Regulated by Nutritional Status, Obesity, or Leptin Levels in Rodents.

PubMed

Quiñones, Mar; Folgueira, Cintia; Sánchez-Rebordelo, Estrella; Al-Massadi, Omar

2015-01-01

Irisin is a cleaved and secreted fragment of fibronectin type III domain containing 5 (FNDC5) that is mainly released by skeletal muscle and was proposed to mediate the beneficial effects of exercise on metabolism. In the present study we aim to investigate the regulation of the circulating levels of irisin in obese animal models (diet-induced obese (DIO) rats and leptin-deficient (ob/ob) mice), as well as the influence of nutritional status and leptin. Irisin levels were measured by Enzyme-Linked Immunosorbent Assay (ELISA) and Radioimmunoassay (RIA). Serum irisin levels remained unaltered in DIO rats and ob/ob mice. Moreover, its circulating levels were also unaffected by fasting, leptin deficiency, and exogenous leptin administration in rodents. In spite of these negative results we find a negative correlation between irisin and insulin in DIO animals and a positive correlation between irisin and glucose under short-term changes in nutritional status. Our findings indicate that serum irisin levels are not modulated by different physiological settings associated to alterations in energy homeostasis. These results suggest that in rodents circulating levels of irisin are not involved in the pathophysiology of obesity and could be unrelated to metabolic status; however, further studies should clarify its precise role in states of glucose homeostasis imbalance.

Characterising the hydrothermal circulation patterns beneath thermal springs in the limestones of the Carboniferous Dublin Basin, Ireland: a geophysical and geochemical approach.

NASA Astrophysics Data System (ADS)

Blake, Sarah; Henry, Tiernan; Muller, Mark R.; Jones, Alan G.; Moore, John Paul; Murray, John; Campanyà, Joan; Vozár, Jan; Walsh, John; Rath, Volker

2016-04-01

A hydrogeological conceptual model of the sources, circulation pathways and temporal variations of two low-enthalpy thermal springs is derived from a multi-disciplinary approach. The springs are situated in the Carboniferous limestones of the Dublin Basin, in east-central Ireland. Kilbrook spring (Co. Kildare) has the highest recorded temperatures for any thermal spring in Ireland (maximum of 25.0 °C), and St. Gorman's Well (Co. Meath) has a complex and variable temperature profile (maximum of 21.8 °C). These temperatures are elevated with respect to average Irish groundwater temperatures (9.5 - 10.5 °C), and represent a geothermal energy potential, which is currently under evaluation. A multi-disciplinary investigation based upon audio-magnetotelluric (AMT) surveys, time-lapse temperature and chemistry measurements, and hydrochemical analysis, has been undertaken with the aims of investigating the provenance of the thermal groundwater and characterising the geological structures facilitating groundwater circulation in the bedrock. The hydrochemical analysis indicates that the thermal waters flow within the limestones of the Dublin Basin, and there is evidence that Kilbrook spring receives a contribution from deep-basinal fluids. The time-lapse temperature, electrical conductivity and water level records for St. Gorman's Well indicate a strongly non-linear response to recharge inputs to the system, suggestive of fluid flow in karst conduits. The 3-D electrical resistivity models of the subsurface revealed two types of geological structure beneath the springs; (1) Carboniferous normal faults, and (2) Cenozoic strike-slip faults. These structures are dissolutionally enhanced, particularly where they intersect. The karstification of these structures, which extend to depths of at least 500 m, has provided conduits that facilitate the operation of a relatively deep hydrothermal circulation pattern (likely estimated depths between 240 and 1,000 m) within the Dublin Basin. The results of this study support a hypothesis that the thermal maximum and simultaneous increased discharge observed each winter at both springs is the result of rapid infiltration, heating and re-circulation of meteoric waters within a structurally- and recharge-controlled hydrothermal circulation system.

Future Changes in Autumn Flood Type and Frequency in Pacific Northwest North America

NASA Astrophysics Data System (ADS)

Menounos, B.; Cannon, A. J.; Radic, V.; Moore, R. D.; Dery, S. J.; Jackson, P. L.; Anslow, F. S.

2013-12-01

During the 20th and early 21st century, autumn storms in the Pacific Northwest of North America - PNWNA (coastal British Columbia and Washington) caused widespread flooding and landslides. Understanding how these intense storms are likely to change in the future is important given their potential to harm people and cause widespread damage, but assessing these changes using climate models is difficult. Parameterization of precipitation in general circulation and regional climate models (GCM, RCM) is prone to error, especially in the mountainous terrain of the PNWNA. High computational demands of RCMs also limits their use in assessing changes in flood type and frequency for a suite of GCM and emission scenarios. We instead focus our efforts on understanding atmospheric circulation patterns responsible for historical autumn flooding (15 August - 31 December) and examine how these synoptic conditions are likely to change under future emission scenarios. Our analysis includes identification of extreme events (runoff and precipitation) in streamflow and precipitation records from coastal Washington and British Columbia for the period 1948-2010. Our methods to link the instrumental record of extreme autumn events to atmospheric conditions (500 and 850 hPa geopotential height and integrated vapor transport obtained from NCEP and CFSR reanalysis) include: (1) compositing of streamflow and precipitation events (environment-to-circulation); (2) self organizing map synoptic classification (circulation-to-environment); and (3) regression tree synoptic classification (hybrid of environment-to-circulation and circulation-to-environment). We then evaluate changes in flood-generating synoptic types in the CMIP5 ensemble over the period 2010-2100. Our analysis indicates that, as expected, most floods are associated with atmospheric river events that are commonly associated with upper level, quasi stationary low- and high-pressure systems respectively located in the Gulf of Alaska and east of the PNWNA. Based on our initial analysis of the CMIP5 data, we note an increase in autumn flood-producing synoptic weather types for the PNWNA. We discuss the implications of increased autumn flooding to communities and infrastructure.

Scaling and Numerical Model Evaluation of Snow-Cover Effects on the Generation and Modification of Daytime Mesoscale Circulations.

NASA Astrophysics Data System (ADS)

Segal, M.; Garratt, J. R.; Pielke, R. A.; Ye, Z.

1991-04-01

Consideration of the sensible heat flux characteristics over a snow surface suggests a significant diminution in the magnitude of the flux, compared to that over a snow-free surface under the same environmental conditions. Consequently, the existence of snow-covered mesoscale areas adjacent to snow-free areas produces horizontal thermal gradients in the lower atmosphere during the daytime, possibly resulting in a `snow breeze.' In addition, suppression of the daytime thermally induced upslope flow over snow-covered slopes is likely to occur. The present paper provides scaling and modeling evaluations of these situations, with quantification of the generated and modified circulations. These evaluations suggest that under ideal situations involved with uniform snow cover over large areas, particularly in late winter and early spring, a noticeable `snow breeze' is likely to develop. Additionally: suppression of the daytime thermally induced upslope flow is significant and may even result in a daytime drainage flow. The effects of bare ground patchiness in the snow cover on these circulations are also explored, both for flat terrain and slope-flow situations. A patchiness fraction greater than 0.5 is found to result in a noticeably reduced snow-breeze circulation, while a patchiness fraction of only 0.1 caused the simulated daytime drainage flow over slopes to he reversed.