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Sample records for coupled ocean-atmosphere gcm

  1. Variability in North Atlantic heat content and heat transport in a coupled ocean-atmosphere GCM

    NASA Astrophysics Data System (ADS)

    Dong, B.; Sutton, R. T.

    2002-06-01

    A coupled ocean-atmosphere general circulation model has been used to study the variations of North Atlantic upper ocean heat content (OHC), sea surface temperature (SST) and ocean heat transport (OHT), and the relationships between these three quantities. We find that OHC anomalies, and salinity anomalies, propagate anti-cyclonically around the North Atlantic subtropical gyre. They propagate eastward in midlatitudes and westward in low latitudes. Both the advection of mean temperature by anomalous currents and the advection of temperature anomalies by mean currents are responsible for these zonal propagations. In addition to zonal propagations, upper ocean temperature anomalies propagate southward in the eastern North Atlantic, where subduction plays a dominant role. Variability in the northward OHT in the Atlantic is primarily governed by variability in the ocean circulation rather than variability in temperatures. Fluctuations in OHT are the major cause of anomalies in OHC and SST in the Gulf Stream extension region. This is true both for interannual variability and for decadal variability. On interannual time scales, however, surface fluxes also make a significant contribution. Analysis of the relationships of OHT with OHC and SST suggests that a knowledge of OHT fluctuations could be used to predict variations in OHC, and therefore sea surface temperatures, several years in advance.

  2. The dominant mechanisms of variability in Atlantic Ocean Heat Transport in a Coupled Ocean-Atmosphere GCM

    NASA Astrophysics Data System (ADS)

    Dong, B.-W.; Sutton, R. T.

    The variability of the Atlantic meridional ocean heat transport (OHT) has been diagnosed from a simulation of a coupled ocean-atmosphere general circulation model (GCM), and the mechanisms responsible for this variability have been elucidated. Interannual variability is dominated by windstress-driven Ekman fluctuations, which account for 50.3% of the OHT variance. By contrast, decadal and multidecadal variability in Atlantic OHT is dominated by a mixed thermohaline/gyre mode driven by variations in buoyancy fluxes and windstress curl. It accounts for 55.6% of low pass filtered OHT variance. The North Atlantic Oscillation (NAO) has a significant role in both the interannual mode and the low frequency mode, but it is not the only important driver. A notable feature of both modes is significant changes in the tropical atmosphere and ocean. We highlight a number of potential mechanisms involved in the tropical-extratropical teleconnections.

  3. Impact of resolving the diurnal cycle in an ocean-atmosphere GCM. Part 2: A diurnally coupled CGCM

    NASA Astrophysics Data System (ADS)

    Bernie, D. J.; Guilyardi, E.; Madec, G.; Slingo, J. M.; Woolnough, S. J.; Cole, J.

    2008-12-01

    Coupled ocean atmosphere general circulation models (GCM) are typically coupled once every 24 h, excluding the diurnal cycle from the upper ocean. Previous studies attempting to examine the role of the diurnal cycle of the upper ocean and particularly of diurnal SST variability have used models unable to resolve the processes of interest. In part 1 of this study a high vertical resolution ocean GCM configuration with modified physics was developed that could resolve the diurnal cycle in the upper ocean. In this study it is coupled every 3 h to atmospheric GCM to examine the sensitivity of the mean climate simulation and aspects of its variability to the inclusion of diurnal ocean-atmosphere coupling. The inclusion of the diurnal cycle leads to a tropics wide increase in mean sea surface temperature (SST), with the strongest signal being across the equatorial Pacific where the warming increases from 0.2°C in the central and western Pacific to over 0.3°C in the eastern equatorial Pacific. Much of this warming is shown to be a direct consequence of the rectification of daily mean SST by the diurnal variability of SST. The warming of the equatorial Pacific leads to a redistribution of precipitation from the Inter tropical convergence zone (ITCZ) toward the equator. In the western Pacific there is an increase in precipitation between Papa new guinea and 170°E of up to 1.2 mm/day, improving the simulation compared to climatology. Pacific sub tropical cells are increased in strength by about 10%, in line with results of part 1 of this study, due to the modification of the exchange of momentum between the equatorially divergent Ekman currents and the geostropic convergence at depth, effectively increasing the dynamical response of the tropical Pacific to zonal wind stresses. During the spring relaxation of the Pacific trade winds, a large diurnal cycle of SST increases the seasonal warming of the equatorial Pacific. When the trade winds then re-intensify, the increase

  4. Sea level changes under increasing atmospheric CO[sub 2] in a transient coupled ocean-atmosphere GCM experiment

    SciTech Connect

    Gregory, J.M. )

    1993-12-01

    Climate change resulting from the enhanced greenhouse effect of increasing atmospheric CO[sub 2] concentrations is expected to bring about global and local changes in sea level. A global rise in sea level would result from thermal expansion of seawater and from melting of land ice, while changes in ocean dynamics and atmospheric pressure patterns could alter relative sea surface topography. Global and local seal level changes have been diagnosed from a 75-yr experiment with a version of the U.K. Meteorological Office coupled ocean-atmosphere general circulation model in which the CO[sub 2] concentration increases at 1% per year. Over the final decade, the component of mean global average sea level rise caused by thermal expansion is 90 mm; on this time scale, a significant contribution is expected from melting of mountain glaciers, but the model does not represent these. Sea level rises over practically the entire ocean area, but there is considerable variation in the magnitude, showing that the global figure by itself gives only a rough idea of the local effect; the largest rises are found in the northwest Atlantic. It is illustrated how this local variation makes it difficult to estimate global sea level rise from a limited number of coastal stations, as must usually be done in practice. 26 refs., 10 figs., 2 tabs.

  5. Modelling the oxygen isotope distribution of ancient seawater using a coupled ocean-atmosphere GCM: Implications for reconstructing early Eocene climate

    NASA Astrophysics Data System (ADS)

    Tindall, Julia; Flecker, Rachel; Valdes, Paul; Schmidt, Daniela N.; Markwick, Paul; Harris, Jim

    2010-04-01

    One of the motivations for studying warm climates of the past such as the early Eocene, is the enhanced understanding this brings of possible future greenhouse conditions. Traditionally, climate information deduced from biological or chemical proxies have been used to "test" computer model simulations of past climatic conditions and hence establish some of the uncertainties associated with model-based predictions. However, extracting climate information from proxies is itself an interpretative process and discrepancies between climate information inferred from different types of proxy undermines the assumption that model-data conflicts automatically mean that the model is inherently flawed. A new approach which both acknowledges and reduces the uncertainties associated with both model and data is required. Although the oxygen isotopic ratio ( δ18O) preserved in calcareous marine fossils has been used to reconstruct past seawater temperature for several decades, significant uncertainties associated with this method persist. These include assumptions about past seawater δ18O for which no proxy exists and which is a key control on the temperature inferred from fossil carbonate. Here we present the results of an early Eocene simulation made using a state-of-the-art General Circulation Model (GCM; HadCM3) with CO 2 set at six times pre-industrial values and which has oxygen isotopes incorporated into the full hydrological cycle and hence simulates the δ18O of past seawater. This allows us to explore the implications of the different seawater δ18O correction factors commonly used for δ18O-based temperature reconstruction. It also allows us to focus model-data comparison on δ18O rather than interpret ocean temperature, an approach that reduces uncertainties in model-data comparison since the effects of both the temperature and the isotopic composition of ocean water on δ18O of carbonate are accounted for. The good agreement between model and data for both modern

  6. The Influence of Midlatitude Ocean-Atmosphere Coupling on the Low-Frequency Variability of a GCM. Part I: No Tropical SST Forcing*.

    NASA Astrophysics Data System (ADS)

    Bladé, Ileana

    1997-08-01

    This study examines the extent to which the thermodynamic interactions between the midlatitude atmosphere and the underlying oceanic mixed layer contribute to the low-frequency atmospheric variability. A general circulation model, run under perpetual northern winter conditions, is coupled to a motionless constant-depth mixed layer in midlatitudes, while elsewhere the sea surface temperature (SST) is kept fixed; interannual tropical SST forcing is not included. It is found that coupling does not modify the spatial organization of the variability. The influence of coupling is manifested as a slight reddening of the spectrum of 500-mb geopotential height and a significant enhancement of the lower-tropospheric thermal variance over the oceans at very low frequencies by virtue of the mixed-layer adjustment to surface air temperature variations that occurs on those timescales. This adjustment effectively reduces the thermal damping of the atmosphere associated with surface heat fluxes (or negative oceanic feedback), thus increasing the thermal variance and the persistence of circulation anomalies.In studying the covariability between ocean and atmosphere it is found that the dominant mode of natural atmospheric variability is coupled to the leading mode of SST in each ocean, with the atmosphere leading the ocean by about one month. The cross-correlation function between oceanic and atmospheric anomalies is strongly asymmetric about zero lag. The SST structures are consistent with direct forcing by the anomalous heat fluxes implied by the concurrent surface air temperature and wind fluctuations. Additionally, composites based on large amplitude SST anomaly events contain no evidence of direct driving of atmospheric perturbations by these SST anomalies. Thus, in terms of the spatial organization of the covariability and the evolution of the coupled system from one regime to another, large-scale air-sea interaction in the model is characterized by one-way atmospheric

  7. Coupled Oceanic / Atmospheric Variability and United States Streamflow

    NASA Astrophysics Data System (ADS)

    Tootle, G.; Piechota, T.

    2005-12-01

    A study of the influence of interdecadal, decadal and interannual oceanic / atmospheric influences on streamflow in the U.S. is presented. Unimpaired streamflow was identified for 639 stations in the U.S. for the period 1951 - 2002. The phase (cold / negative or warm / positive) of Pacific Ocean [El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)] and Atlantic Ocean [Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO)] oceanic / atmospheric influences were identified for the year prior to the streamflow year (i.e., long lead-time). Statistical significance testing of streamflow, based on the interdecadal, decadal and interannual oceanic / atmospheric phase (warm / positive or cold / negative), was performed applying the nonparametric rank-sum test. The results show that, in addition to the well-established ENSO signal, the PDO, AMO and NAO influence streamflow variability in the United States. The warm phase of the PDO is associated with increased streamflow in the central and southwest U.S. while the warm phase of the AMO is associated with reduced streamflow in these regions. The positive phase of the NAO and the cold phase of the AMO are associated with increased streamflow in the central United States. Additionally, the coupled effects of the oceanic / atmospheric influences were evaluated, based on the long-term phase (cold / negative or warm / positive) of the interdecadal (PDO and AMO) and decadal (NAO) influences and ENSO. Streamflow regions in the U.S. were identified that respond to these climatic couplings. The results show that the AMO may influence La Niña impacts in the Southeast while the NAO may influence La Niña impacts in the Midwest. By utilizing the streamflow water year and the long lead-time for the oceanic / atmospheric variables, useful information can be provided to streamflow forecasters and water managers.

  8. Coupled oceanic-atmospheric variability and U.S. streamflow

    NASA Astrophysics Data System (ADS)

    Tootle, Glenn A.; Piechota, Thomas C.; Singh, Ashok

    2005-12-01

    A study of the influence of interdecadal, decadal, and interannual oceanic-atmospheric influences on streamflow in the United States is presented. Unimpaired streamflow was identified for 639 stations in the United States for the period 1951-2002. The phases (cold/negative or warm/positive) of Pacific Ocean (El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) and Atlantic Ocean (Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO)) oceanic-atmospheric influences were identified for the year prior to the streamflow year (i.e., long lead time). Statistical significance testing of streamflow, based on the interdecadal, decadal, and interannual oceanic-atmospheric phase (warm/positive or cold/negative), was performed by applying the nonparametric rank-sum test. The results show that in addition to the well-established ENSO signal the PDO, AMO, and NAO influence streamflow variability in the United States. The warm phase of the PDO is associated with increased streamflow in the central and southwest United States, while the warm phase of the AMO is associated with reduced streamflow in these regions. The positive phase of the NAO and the cold phase of the AMO are associated with increased streamflow in the central United States. Additionally, the coupled effects of the oceanic-atmospheric influences were evaluated on the basis of the long-term phase (cold/negative or warm/positive) of the interdecadal (PDO and AMO) and decadal (NAO) influences and ENSO. Streamflow regions in the United States were identified that respond to these climatic couplings. The results show that the AMO may influence La Niña impacts in the Southeast, while the NAO may influence La Niña impacts in the Midwest. By utilizing the streamflow water year and the long lead time for the oceanic-atmospheric variables, useful information can be provided to streamflow forecasters and water managers.

  9. Predictability of a coupled ocean-atmosphere model

    NASA Technical Reports Server (NTRS)

    Goswami, B. N.; Shukla, J.

    1991-01-01

    A study is presented to determine the limits on the predictability of the coupled ocean-atmosphere system. Following the classical methods developed for atmospheric predictability studies, the model used is one of the simplest that realistically reproduces many of the important features of the observed interannual variability of sea surface temperature in the tropical Pacific Ocean when forced by observed wind stresses. As no reasonable analysis is available for all the fields, initial conditions for these prediction experiments were taken from a model control run in which the ocean model was forced by the observed surface winds. The atmospheric component of the coupled model is not capable of accurately simulating the large-scale components of the observed wind stress.

  10. Studies of regional-scale climate variability and change. Hidden Markov models and coupled ocean-atmosphere modes

    SciTech Connect

    Ghil, M.; Kravtsov, S.; Robertson, A. W.; Smyth, P.

    2008-10-14

    This project was a continuation of previous work under DOE CCPP funding, in which we had developed a twin approach of probabilistic network (PN) models (sometimes called dynamic Bayesian networks) and intermediate-complexity coupled ocean-atmosphere models (ICMs) to identify the predictable modes of climate variability and to investigate their impacts on the regional scale. We had developed a family of PNs (similar to Hidden Markov Models) to simulate historical records of daily rainfall, and used them to downscale GCM seasonal predictions. Using an idealized atmospheric model, we had established a novel mechanism through which ocean-induced sea-surface temperature (SST) anomalies might influence large-scale atmospheric circulation patterns on interannual and longer time scales; we had found similar patterns in a hybrid coupled ocean-atmosphere-sea-ice model. The goal of the this continuation project was to build on these ICM results and PN model development to address prediction of rainfall and temperature statistics at the local scale, associated with global climate variability and change, and to investigate the impact of the latter on coupled ocean-atmosphere modes. Our main results from the grant consist of extensive further development of the hidden Markov models for rainfall simulation and downscaling together with the development of associated software; new intermediate coupled models; a new methodology of inverse modeling for linking ICMs with observations and GCM results; and, observational studies of decadal and multi-decadal natural climate results, informed by ICM results.

  11. Mesoscale Coupled Ocean-Atmosphere Feedbacks in Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Putrasahan, Dian Ariyani

    The focus of this dissertation is on studying ocean-atmosphere (OA) interactions in the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using satellite observations and the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This technique provides insights to spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean. For the HCS, the use of downscaled forcing from SCOAR, as compared to NCEP Reanalysis 2, proves to be more appropriate in quantifying wind-driven upwelling indices along the coast of Peru and Chile. The difference in their wind stress distribution has significant impact on the wind-driven upwelling processes and total upwelling transport along the coast. Although upwelling induced by coastal Ekman transport dominates the wind-driven upwelling along coastal areas, Ekman pumping can account for 30% of the wind-driven upwelling in several coastal locations. Control SCOAR shows significant SST-wind stress coupling during fall and winter, while Smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air-sea coupling in HCS. The SST-wind stress coupling however, did not produce any rectified response on the ocean eddies. Coupling between SST, wind speed and latent heat flux is insignificant on large-scale coupling and full coupling mode. On the other hand, coupling between these three variables are significant on the mesoscale for most of the model run, which suggests that mesoscale SST affects latent heat through direct flux anomalies as well as indirectly through stability changes on the

  12. A parallel coupled oceanic-atmospheric general circulation model

    SciTech Connect

    Wehner, M.F.; Bourgeois, A.J.; Eltgroth, P.G.; Duffy, P.B.; Dannevik, W.P.

    1994-12-01

    The Climate Systems Modeling group at LLNL has developed a portable coupled oceanic-atmospheric general circulation model suitable for use on a variety of massively parallel (MPP) computers of the multiple instruction, multiple data (MIMD) class. The model is composed of parallel versions of the UCLA atmospheric general circulation model, the GFDL modular ocean model (MOM) and a dynamic sea ice model based on the Hiber formulation extracted from the OPYC ocean model. The strategy to achieve parallelism is twofold. One level of parallelism is accomplished by applying two dimensional domain decomposition techniques to each of the three constituent submodels. A second level of parallelism is attained by a concurrent execution of AGCM and OGCM/sea ice components on separate sets of processors. For this functional decomposition scheme, a flux coupling module has been written to calculate the heat, moisture and momentum fluxes independent of either the AGCM or the OGCM modules. The flux coupler`s other roles are to facilitate the transfer of data between subsystem components and processors via message passing techniques and to interpolate and aggregate between the possibly incommensurate meshes.

  13. A parallel coupled oceanic-atmospheric general circulation model

    NASA Astrophysics Data System (ADS)

    Wehner, Michael F.; Bourgeois, Al J.; Eltgroth, Peter G.; Duffy, Phillip B.; Dannevik, William P.

    1994-12-01

    The Climate Systems Modeling group at Lawrence Liwermore National Laboratory (LLNL) has developed a portable coupled oceanic-atmospheric general circulation model suitable for use on a variety of massively parallel (MPP) computers of the multiple instruction, multiple data (MIMD) class. The model is composed of parallel versions of the UCLA atmospheric general circulation model, the GFDL modular ocean model (MOM) and a dynamic sea ice model based on the Hiber formulation extracted from the OPYC ocean model. The strategy to achieve parallelism is twofold. One level of parallelism is accomplished by applying two dimensional domain decomposition techniques to each of the three constituent submodels. A second level of parallelism is attained by a concurrent execution of AGCM and OGCM/sea ice components on separate sets of processors. For this functional decomposition scheme, a flux coupling module has been written to calculate the heat, moisture and momentum fluxes independent of either the AGCM or the OGCM modules. The flux coupler's other roles are to facilitate the transfer of data between subsystem components and processors via message passing techniques and to interpolate and aggregate between the possibly incommensurate meshes.

  14. Coupled Ocean-Atmosphere 4D-Var: Formulation and Sensitivity Analysis Results

    NASA Astrophysics Data System (ADS)

    Ngodock, Hans; Carrier, Matthew; Xu, Liang; Amerault, Clark; Campbell, Tim; Rowley, Clark

    2016-04-01

    The US Navy is currently developing the first coupled ocean-atmosphere four-dimensional variational (4D-Var) data assimilation system to be used for short-term regional forecasting. This project merges the 4D-Var capabilities of the atmospheric component of the Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS©) with the Navy Coastal Ocean Model (NCOM) through the Earth System Modeling Framework (ESMF). This will provide the coupled ocean-atmosphere forecast with a fully balanced analysis that accounts for all combined observations in both primary fluids (i.e. ocean and atmosphere). In this present work, the formulation of the system is presented in detail along with a series of adjoint sensitivity analysis results using the coupled ocean-atmosphere adjoint model. The sensitivity of the atmosphere (ocean) to each ocean (atmosphere) model variable is analyzed in detail in order to illustrate the usefulness of this approach in the coupled data assimilation system.

  15. ENSO Bred Vectors in Coupled Ocean-Atmosphere General Circulation Models

    NASA Technical Reports Server (NTRS)

    Yang, S. C.; Cai, Ming; Kalnay, E.; Rienecker, M.; Yuan, G.; Toth, ZA.

    2004-01-01

    The breeding method has been implemented in the NASA Seasonal-to-Interannual Prediction Project (NSIPP) Coupled General Circulation Model (CGCM) with the goal of improving operational seasonal to interannual climate predictions through ensemble forecasting and data assimilation. The coupled instability as cap'tured by the breeding method is the first attempt to isolate the evolving ENSO instability and its corresponding global atmospheric response in a fully coupled ocean-atmosphere GCM. Our results show that the growth rate of the coupled bred vectors (BV) peaks at about 3 months before a background ENSO event. The dominant growing BV modes are reminiscent of the background ENSO anomalies and show a strong tropical response with wind/SST/thermocline interrelated in a manner similar to the background ENSO mode. They exhibit larger amplitudes in the eastern tropical Pacific, reflecting the natural dynamical sensitivity associated with the presence of the shallow thermocline. Moreover, the extratropical perturbations associated with these coupled BV modes reveal the variations related to the atmospheric teleconnection patterns associated with background ENSO variability, e.g. over the North Pacific and North America. A similar experiment was carried out with the NCEP/CFS03 CGCM. Comparisons between bred vectors from the NSIPP CGCM and NCEP/CFS03 CGCM demonstrate the robustness of the results. Our results strongly suggest that the breeding method can serve as a natural filter to identify the slowly varying, coupled instabilities in a coupled GCM, which can be used to construct ensemble perturbations for ensemble forecasts and to estimate the coupled background error covariance for coupled data assimilation.

  16. Coupled Ocean-Atmosphere Modeling of the Coastal Zone

    DTIC Science & Technology

    2010-09-30

    response of the ocean/atmosphere. Results from cloud resolving LES experiments are also presented for cases with fog and stratus . 1 Report... stratus cloud layer. An example showing this effect is presented in Figure 5 where the atmospheric stratification is initialized with two different...inversion strengths. For the fog case, the boundary layer top is capped by 5 a potential temperature increase of about 8 oC, whereas the stratus case

  17. The seasonal cycle over the tropical Pacific in coupled ocean-atmosphere General Circulation Models

    SciTech Connect

    Mechoso, C.R.; Robertson, A.W.; Neelin, J.D.

    1995-09-01

    The seasonal cycle over the tropical Pacific simulated by 11 coupled ocean-atmosphere general circulation models (GCMs) is examined. Each model consists of a high-resolution ocean GCM of either the tropical Pacific or near-global oceans coupled to a moderate- or high-resolution atmospheric GCM, without the use of flux correction. The seasonal behavior of sea surface temperature (SST) and eastern Pacific rainfall is presented for each model. The results show that current state-of-the-art coupled GCMs share important successes and troublesome systematic errors. All 11 models are able to simulate the mean zonal gradient in SST at the equator over the central Pacific. The simulated equatorial cold tongue generally tends to be strong, too narrow, and extend too far west. SSTs are generally too warm in a broad region west of Peru and in a band near 10{degrees}S. This is accompanied in some models by a double intertropical convergence zone (ITCZ) straddling the equator over the eastern Pacific, and in others by an ITCZ that migrates across the equator with the seasons; neither behavior is realistic. There is considerable spread in the simulated seasonal cycles of equatorial SST in the eastern Pacific. Some simulations do capture the annual harmonic quite realistically, although the seasonal cold tongue tends to appear prematurely. Others overestimate the amplitude of the semiannual harmonic. Nonetheless, the results constitute a marked improvement over the simulations of only a few years ago when serious climate drift was still widespread and simulated zonal gradients of SST along the equator were often very weak. 41 refs., 5 figs., 4 tabs.

  18. Predicting Coupled Ocean-Atmosphere Modes with a Climate Modeling Hierarchy -- Final Report

    SciTech Connect

    Michael Ghil, UCLA; Andrew W. Robertson, IRI, Columbia Univ.; Sergey Kravtsov, U. of Wisconsin, Milwaukee; Padhraic Smyth, UC Irvine

    2006-08-04

    The goal of the project was to determine midlatitude climate predictability associated with tropical-extratropical interactions on interannual-to-interdecadal time scales. Our strategy was to develop and test a hierarchy of climate models, bringing together large GCM-based climate models with simple fluid-dynamical coupled ocean-ice-atmosphere models, through the use of advanced probabilistic network (PN) models. PN models were used to develop a new diagnostic methodology for analyzing coupled ocean-atmosphere interactions in large climate simulations made with the NCAR Parallel Climate Model (PCM), and to make these tools user-friendly and available to other researchers. We focused on interactions between the tropics and extratropics through atmospheric teleconnections (the Hadley cell, Rossby waves and nonlinear circulation regimes) over both the North Atlantic and North Pacific, and the ocean’s thermohaline circulation (THC) in the Atlantic. We tested the hypothesis that variations in the strength of the THC alter sea surface temperatures in the tropical Atlantic, and that the latter influence the atmosphere in high latitudes through an atmospheric teleconnection, feeding back onto the THC. The PN model framework was used to mediate between the understanding gained with simplified primitive equations models and multi-century simulations made with the PCM. The project team is interdisciplinary and built on an existing synergy between atmospheric and ocean scientists at UCLA, computer scientists at UCI, and climate researchers at the IRI.

  19. The Monsoon as a Self-regulating Coupled Ocean-Atmosphere System

    NASA Astrophysics Data System (ADS)

    Webster, P. J.; Clark, C.; Cherikova, G.; Fasullo, J.; Han, W.; Loschnigg, J.; Sahami, K.

    INTRODUCTION REGULATION OF THE MONSOON ANNUAL CYCLE The Climatological Annual Cycle Processes Determining the Annual Cycle of the Monsoon Role of Ocean Dynamics in the Annual Heat Balance of the Indian - Ocean Regulation of the Annual Cycle of the Monsoon: an Ocean-Atmosphere - Feedback System INTERANNUAL VARIABILITY OF THE MONSOON Modes of Interannual Variability in the Monsoon Interannual Modes in Ocean Heat Transport Interannual Regulation of the Monsoon GENERAL THEORY OF REGULATION OF THE COUPLED OCEAN-ATMOSPHERIC MONSOON - SYSTEM CONCLUSIONS REFERENCES

  20. Ocean-Atmosphere Coupled Model Simulations of Precipitation in the Central Andes

    NASA Technical Reports Server (NTRS)

    Nicholls, Stephen D.; Mohr, Karen I.

    2015-01-01

    The meridional extent and complex orography of the South American continent contributes to a wide diversity of climate regimes ranging from hyper-arid deserts to tropical rainforests to sub-polar highland regions. In addition, South American meteorology and climate are also made further complicated by ENSO, a powerful coupled ocean-atmosphere phenomenon. Modelling studies in this region have typically resorted to either atmospheric mesoscale or atmosphere-ocean coupled global climate models. The latter offers full physics and high spatial resolution, but it is computationally inefficient typically lack an interactive ocean, whereas the former offers high computational efficiency and ocean-atmosphere coupling, but it lacks adequate spatial and temporal resolution to adequate resolve the complex orography and explicitly simulate precipitation. Explicit simulation of precipitation is vital in the Central Andes where rainfall rates are light (0.5-5 mm hr-1), there is strong seasonality, and most precipitation is associated with weak mesoscale-organized convection. Recent increases in both computational power and model development have led to the advent of coupled ocean-atmosphere mesoscale models for both weather and climate study applications. These modelling systems, while computationally expensive, include two-way ocean-atmosphere coupling, high resolution, and explicit simulation of precipitation. In this study, we use the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST), a fully-coupled mesoscale atmosphere-ocean modeling system. Previous work has shown COAWST to reasonably simulate the entire 2003-2004 wet season (Dec-Feb) as validated against both satellite and model analysis data when ECMWF interim analysis data were used for boundary conditions on a 27-9-km grid configuration (Outer grid extent: 60.4S to 17.7N and 118.6W to 17.4W).

  1. Global coupled ocean-atmosphere general circulation models in LASG/IAP

    NASA Astrophysics Data System (ADS)

    Yongqiang, Yu; Xuehong, Zhang; Yufu, Guo

    2004-06-01

    Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working to develop a global OGCM and a global coupled ocean-atmosphere general circulation model (CGCM). From the original flux anomaly-coupling model developed in the beginning of the 1990s to the latest directly-coupling model, LASG scientists have developed four global coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs and selected applications. Strengths and weaknesses of these models are highlighted.

  2. Ocean-Atmosphere State Estimation and Targeted Observing using Coupled Model Ensembles

    DTIC Science & Technology

    2013-09-30

    1 Ocean-Atmosphere State Estimation and Targeted Observing using Coupled Model Ensembles Craig H. Bishop, PI Naval Research Laboratory...Targeted Observing using Coupled Model Ensembles 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e...forecast error covariance model for this coupled system is based solely on ensemble covariances because the pre-existing covariance model does not

  3. Upscalling processes in an ocean-atmosphere multiscale coupled model

    NASA Astrophysics Data System (ADS)

    Masson, S. G.; Berthet, S.; Samson, G.; Crétat, J.; Colas, F.; Echevin, V.; Jullien, S.; Hourdin, C.

    2015-12-01

    This work explores new pathways toward a better representation of the multi-scale physics that drive climate variability. We are analysing the key upscaling processes by which small-scale localized errors have a knock-on effect onto global climate. We focus on the Peru-Chilli coastal upwelling, an area known to hold among the strongest models biases in the Tropics. Our approach is based on the development of a multiscale coupling interface allowing us to couple WRF with the NEMO oceanic model in a configuration including 2-way nested zooms in the oceanic and/or the atmospheric component of the coupled model. Upscalling processes are evidenced and quantified by comparing three 20-year long simulations of a tropical channel (45°S-45°N), which differ by their horizontal resolution: 0.75° everywhere, 0.75°+0.25° zoom in the southeastern Pacific or 0.25° everywhere. This set of three 20-year long simulations was repeated with 3 different sets of parameterizations to assess the robustness of our results. Our results show that adding an embedded zoom over the southeastern Pacific only in the atmosphere cools down the SST along the Peru-Chili coast, which is a clear improvement. This change is associated with a displacement of the low-level cloud cover, which moves closer to the coast cooling further the coastal area SST. Offshore, we observe the opposite effect with a reduction of the cloud cover with higher resolution, which increases solar radiation and warms the SST. Increasing the resolution in the oceanic component show contrasting results according to the different set parameterization used in the experiments. Some experiment shows a coastal cooling as expected, whereas, in other cases, we observe a counterintuitive response with a warming of the coastal SST. Using at the same time an oceanic and an atmospheric zoom mostly combines the results obtained when using the 2-way nesting in only one component of the coupled model. In the best case, we archive by this

  4. MJO simulation in a cloud-system-resolving global ocean-atmosphere coupled model

    NASA Astrophysics Data System (ADS)

    Sasaki, Wataru; Onishi, Ryo; Fuchigami, Hiromitsu; Goto, Koji; Nishikawa, Shiro; Ishikawa, Yoichi; Takahashi, Keiko

    2016-09-01

    An observed Madden-Julian Oscillation (MJO) propagating from the central Indian Ocean to the western Pacific from 15 December 2006 to 10 January 2007 was successfully simulated by a cloud-system-resolving global ocean-atmosphere coupled model without parameterization of cumulus convection. We found that the ocean coupling has significant impacts on the MJO simulation, e.g., strength of the moisture convergence, and the timing and strength of the westerly wind burst over the Maritime Continent. The model also generally well simulated the decay of the MJO in the western Pacific, as well as the changes in sea surface temperature. These results demonstrate that the cloud-system-resolving global ocean-atmosphere coupled model can be used for realistic MJO simulation.

  5. Simulated ENSO in a global coupled ocean-atmosphere model: Multidecadal amplitude modulation and CO{sub 2} sensitivity

    SciTech Connect

    Knutson, T.R.; Manabe, S.

    1997-01-01

    An analysis is presented of simulated ENSO phenomena occurring in three 1000-yr experiments with a low-resolution (R15) global coupled ocean-atmosphere GCM. Although the model ENSO is much weaker than the observed one, the model ENSO`s life cycle is qualitatively similar to the {open_quotes}delayed oscillator{close_quotes} ENSO life cycle simulated using much higher resolution ocean models. Thus, the R15 coupled model appears to capture the essential physical mechanism of ENSO despite its coarse ocean model resolution. Several observational studies have shown that the amplitude of ENSO has varied substantially between different multidecadal periods during the past century. A wavelet analysis of a multicentury record of eastern tropical Pacific SST inferred from {delta}{sup 18}O measurements suggests that a similar multidecadal amplitude modulation of ENSO has occurred for at least the past three centuries. A similar multidecadal amplitude modulation occurs for the model ENSO (2-7-yr band), which suggests that much of the past amplitude modulation of the observed ENSO could be attributable to internal variability of the coupled ocean-atmosphere system. In two 1000-yr CO{sub 2} sensitivity experiments, the amplitude of the model ENSO decreases slightly relative to the control run in response to either a doubling or quadrupling of CO{sub 2}. This decreased variability is due in part to CO{sub 2}-induced changes in the model`s time-mean basic state, including a reduced time-mean zonal SST gradient. In contrast to the weaker overall amplitude, the multidecadal amplitude modulations become more pronounced with increased CO{sub 2}. The frequency of ENSO in the model does not appear to be strongly influenced by increased CO{sub 2}. 41 refs., 14 figs.

  6. An intimate coupling of ocean-atmospheric interaction over the extratropical North Atlantic and Pacific

    NASA Astrophysics Data System (ADS)

    Li, Chun; Wu, Lixin; Wang, Qi; Qu, Liwei; Zhang, Liping

    2009-05-01

    The inter-basin teleconnection between the North Atlantic and the North Pacific ocean-atmosphere interaction is studied using a coupled ocean-atmosphere general circulation model. In the model, an idealized oceanic temperature anomaly is initiated over the Kuroshio and the Gulf Stream extension region to track the coupled evolution of ocean and atmosphere interaction, respectively. The experiments explicitly demonstrate that both the North Pacific and the North Atlantic ocean-atmosphere interactions are intimately coupled through an inter-basin atmospheric teleconnection. This fast inter-basin communication can transmit oceanic variability between the North Atlantic and the North Pacific through local ocean-to-atmosphere feedbacks. The leading mode of the extratropical atmospheric internal variability plays a dominant role in shaping the hemispheric-scale response forced by oceanic variability over the North Atlantic and Pacific. Modeling results also suggest that a century (two centuries) long observations are necessary for the detection of Pacific response to Atlantic forcings (Atlantic response to Pacific forcing).

  7. Evidence of coupling in ocean-atmosphere dynamics over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Vannitsem, Stéphane; Ghil, Michael

    2017-04-01

    The investigation of low-frequency variability (LFV) in the mid-latitude atmosphere, for instance of the North Atlantic Oscillation (NAO), is currently attracting considerable interest. One of the main reasons is LFV's potential to enable predictions beyond the generally accepted upper bound of weather forecasting skill of 10-15 days in mid-latitudes. To understand the development of the LFV in the atmosphere, it is necessary to clarify how it interacts with the other components of the climate system, in particular the ocean. The usual strategy to clarify the coupling between the ocean and the atmosphere is to analyze the one-way sensitivity of either component to forcing by the other. In the present work, we adopt a different strategy by investigating the projections of atmospheric and oceanic fields, based on reanalysis datasets, onto a reduced phase space. The latter ocean-atmosphere subspace is dynamically defined here by relying on the leading modes of the Vannitsem et al. (2015) idealized low-order model. This approach allows one to isolate the dominant modes of the coupled system's observed variability. The coupled projection is then analyzed using multichannel singular spectrum analysis (M-SSA). The results suggest that a dominant low-frequency signal with a 25-30-yr period already mentioned in the literature is a common mode of variability of the atmosphere and the ocean. A new score for evaluating the internal nature of the common variability is then introduced and it confirms the presence of coupled dynamics in the ocean-atmosphere system that includes a significant large-scale atmospheric component. The physical nature of this coupled dynamics is also discussed. Reference Vannitsem S., J. Demaeyer, L. de Cruz, and M. Ghil, Low-frequency variability and heat transport in a low-order nonlinear coupled ocean-atmosphere model, Physica D, 309, 71-85, 2015.

  8. State and Parameter Estimation for a Coupled Ocean--Atmosphere Model

    NASA Astrophysics Data System (ADS)

    Ghil, M.; Kondrashov, D.; Sun, C.

    2006-12-01

    The El-Nino/Southern-Oscillation (ENSO) dominates interannual climate variability and plays, therefore, a key role in seasonal-to-interannual prediction. Much is known by now about the main physical mechanisms that give rise to and modulate ENSO, but the values of several parameters that enter these mechanisms are an important unknown. We apply Extended Kalman Filtering (EKF) for both model state and parameter estimation in an intermediate, nonlinear, coupled ocean--atmosphere model of ENSO. The coupled model consists of an upper-ocean, reduced-gravity model of the Tropical Pacific and a steady-state atmospheric response to the sea surface temperature (SST). The model errors are assumed to be mainly in the atmospheric wind stress, and assimilated data are equatorial Pacific SSTs. Model behavior is very sensitive to two key parameters: (i) μ, the ocean-atmosphere coupling coefficient between SST and wind stress anomalies; and (ii) δs, the surface-layer coefficient. Previous work has shown that δs determines the period of the model's self-sustained oscillation, while μ measures the degree of nonlinearity. Depending on the values of these parameters, the spatio-temporal pattern of model solutions is either that of a delayed oscillator or of a westward propagating mode. Estimation of these parameters is tested first on synthetic data and allows us to recover the delayed-oscillator mode starting from model parameter values that correspond to the westward-propagating case. Assimilation of SST data from the NCEP-NCAR Reanalysis-2 shows that the parameters can vary on fairly short time scales and switch between values that approximate the two distinct modes of ENSO behavior. Rapid adjustments of these parameters occur, in particular, during strong ENSO events. Ways to apply EKF parameter estimation efficiently to state-of-the-art coupled ocean--atmosphere GCMs will be discussed.

  9. Coupled ocean/atmosphere modeling on high-performance computing systems

    SciTech Connect

    Eltgroth, P.G.; Bolstad, J.H.; Duffy, P.B.; Mirin, A.A.; Wang, H.; Wehner, M.F.

    1996-12-01

    We investigate performance of a coupled ocean/atmosphere general circulation model on high-performance computing systems. Our programming paradigm has been domain decomposition with message- passing for distributed memory. With the emergence of SMP clusters we are investigating how to best support shaped memory as well. We consider how to assign processes to the major model components so as to obtain optimal load balance. We examine throughput on contemporary parallel architectures, such as the Cray-I3D, I3B, and the IBM-SP family.

  10. Coupled ocean/atmosphere modeling on high-performance computing systems

    SciTech Connect

    Eltgroth, P.G.; Bolstad, J.H.; Duffy, P.B.; Mirin, A.A.; Wang, H.; Wehner, M.F.

    1997-03-01

    We investigate performance of a coupled ocean/atmosphere general circulation model on high-performance computing systems. Our programming paradigm has been domain decomposition with message- passing for distributed memory. With the emergence of SMP clusters we are investigating how to best support shared memory as well. We consider how to assign processors to the major model components so as to obtain optimal load balance. We examine throughput on contemporary parallel architectures, such as the Cray-T3D/T3E and the IBM-SP family.

  11. An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

    NASA Technical Reports Server (NTRS)

    Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

    1991-01-01

    An atmospheric convective boundary layer (CBL) model is coupled to an ocean mixed-layer (OML) model in order to study the equilibrium state of the coupled system in the tropics, particularly in the Pacific region. The equilibrium state of the coupled system is solved as a function of sea-surface temperature (SST) for a given surface wind and as a function of surface wind for a given SST. It is noted that in both cases, the depth of the CBL and OML increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The coupled ocean-atmosphere model is solved iteratively as a function of surface wind for a fixed upwelling and a fixed OML depth, and it is observed that SST falls with increasing wind in both cases. Realistic gradients of mixed-layer depth and upwelling are observed in experiments with surface wind and SST prescribed as a function of longitude.

  12. Intercomparison of present and future climates simulated by coupled ocean-atmosphere GCMs

    SciTech Connect

    Covey, C; AchutaRao, K M; Lambert, S J

    2000-09-06

    We present an overview of results from the most recent phase of the Coupled Model Intercomparison Project (CMIP). This phase of CMIP has archived output from both unforced (''control run'') and perturbed (1% per year increasing atmospheric carbon dioxide) simulations by 15 modern coupled ocean-atmosphere general circulation models. The models are about equally divided between those employing and those not employing ad hoc flux corrections at the ocean-atmosphere interface. The new generation of non-flux-connected control runs are nearly as stable and agree with observations nearly as well as the flux-corrected models. This development represents significant progress in the state of the art of climate modeling since the Second (1995) Scientific Assessment Report of the Intergovernmental Panel on Climate Change (IPCC; see Gates et al. 1996). From the increasing-CO{sub 2} runs, we find that differences between different models, while substantial, are not as great as would be expected from earlier assessments that relied on equilibrium climate sensitivity.

  13. Interdecadal variations of the thermohaline circulation in a coupled ocean-atmosphere model

    SciTech Connect

    Delworth, T.; Manabe, S.; Stouffer, R.J. )

    1993-11-01

    A fully coupled ocean-atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the NOrth Atlantic Ocean with a time scale of approximately 50 years. The irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation (approximately 52[degrees]N to 72[degrees]N) combined with much smaller density anomalies of opposite sign in the broad, rising region. The spatial pattern of sea surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the North Atlantic. The anomalies of sea surface temperature induce model surface air temperature anomalies over the northern North Atlantic, Arctic, and northwestern Europe. 21 refs., 28 figs.

  14. Response of a Coupled Ocean-Atmosphere Model to Greenland Ice Melting

    NASA Astrophysics Data System (ADS)

    Stammer, D.; Agarwal, N.; Herrmann, P.; Köhl, A.; Mechoso, C. R.

    2011-09-01

    We investigate the transient response of the global coupled ocean-atmosphere system to enhanced freshwater forcing representative of melting of the Greenland ice sheets. A 50-year long simulation by a coupled atmosphere-ocean general circulation model (CGCM) is compared with another of the same length in which Greenland melting is prescribed. To highlight the importance of coupled atmosphere-ocean processes, the CGCM results are compared with those of two other experiments carried out with the oceanic general circulation model (OGCM). In one of these OGCM experiments, the prescribed surface fluxes of heat, momentum and freshwater correspond to the unperturbed simulation by the CGCM; in the other experiment, Greenland melting is added to the freshwater flux. The responses by the CGCM and OGCM to the Greenland melting have similar patterns in the Atlantic, albeit the former having five times larger amplitudes in sea surface height anomalies. The CGCM shows likewise stronger variability in all state variables in all ocean basins because the impact of Greenland melting is quickly communicated to all ocean basins via atmospheric bridges. We conclude that the response of the global climate to Greenland ice melting is highly dependent on coupled atmosphere-ocean processes. These lead to reduced latent heat flux into the atmosphere and an associated increase in net freshwater flux into the ocean, especially in the subpolar North Atlantic. The combined result is a stronger response of the coupled system to Greenland ice sheet melting.

  15. An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

    NASA Astrophysics Data System (ADS)

    Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

    A coupled model is used to study the equilibrium state of the ocean-atmosphere boundary layer in the tropics. The atmospheric model is a one-dimensional thermodynamic model for a partially mixed, partly cloudy convective boundary layer (CBL), including the effects of cloud-top subsidence, surface momentum and heat (latent and sensible) fluxes, and realistic radiative transfer for both shortwaves and longwaves (Betts and Ridgway, 1988; 1989). The oceanic model is a thermodynamic model for a well-mixed layer, with a closure constraint based on a one-dimensional turbulent kinetic energy (TKE) equation following Kraus and Turner (1967). Results of several sets of experiments are reported in this paper. In the first two sets of experiments, with sea surface temperature (SST) specified, we solve the equilibrium state of the coupled system as a function of SST for a given surface wind (case 1) and as a function of surface wind for a given SST (case 2). In both cases the depth of the CBL and the ocean mixed layer (OML) increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The deepening of the equilibrium CBL is primarily linked to the increase of CBL moisture with increasing SST and surface wind. The increase of OML depth and decrease of upwelling are due to a decrease of net downward heat flux with increasing SST and the generation of TKE by increasing wind. In another two sets of experiments, we solve for the coupled ocean-atmosphere model iteratively as a function of surface wind for a fixed upwelling (case 3) and a fixed OML depth (case 4). SST falls with increasing wind in both cases, but the fall is steeper in case 4, because the OML depth is fixed, whereas in case 3 the depth is allowed to deepen and the cooling is spread over a larger mass of water. The decrease of evaporation with increasing wind in case 4 leads to a very dry and shallow CBL. Results of further experiments with surface wind and SST

  16. Wintertime atmospheric response to Atlantic multidecadal variability: effect of stratospheric representation and ocean-atmosphere coupling

    NASA Astrophysics Data System (ADS)

    Peings, Yannick; Magnusdottir, Gudrun

    2016-08-01

    The impact of the Atlantic multidecadal variability (AMV) on the wintertime atmosphere circulation is investigated using three different configurations of the Community Atmospheric Model version 5 (CAM5). Realistic SST and sea ice anomalies associated with the AMV in observations are prescribed in CAM5 (low-top model) and WACCM5 (high-top model) to assess the dependence of the results on the representation of the stratosphere. In a third experiment, the role of ocean-atmosphere feedback is investigated by coupling CAM5 to a slab-ocean model in which the AMV forcing is prescribed through oceanic heat flux anomalies. The three experiments give consistent results concerning the response of the NAO in winter, with a negative NAO signal in response to a warming of the North Atlantic ocean. This response is found in early winter when the high-top model is used, and in late winter with the low-top model. With the slab-ocean, the negative NAO response is more persistent in winter and shifted eastward over the continent due to the damping of the atmospheric response over the North Atlantic ocean. Additional experiments suggest that both tropical and extratropical SST anomalies are needed to obtain a significant modulation of the NAO, with small influence of sea ice anomalies. Warm tropical SST anomalies induce a northward shift of the ITCZ and a Rossby-wave response that is reinforced in the mid-latitudes by the extratropical SST anomalies through eddy-mean flow interactions. This modeling study supports that the positive phase of the AMV promotes the negative NAO in winter, while illustrating the impacts of the stratosphere and of the ocean-atmosphere feedbacks in the spatial pattern and timing of this response.

  17. Coupled ocean-atmosphere modeling on horizontally icosahedral and vertically hybrid-isentropic/isopycnic grids.

    NASA Astrophysics Data System (ADS)

    Bleck, Rainer; Sun, Shan; Li, Haiqin; Benjamin, Stan

    2016-04-01

    Current efforts to close the gap between weather prediction and climate models have led to the construction of a coupled ocean-atmosphere system consisting of two high-resolution component models, operating on matching icosahedral grids and utilizing adaptive, near-isentropic/isopycnic vertical coordinates. The two components models, FIM and HYCOM (the latter converted to an icosahedral mesh for this purpose), have been tested extensively in twice-daily global medium-range weather prediction (http://fim.noaa.gov) and in real-time ocean data assimilation (http://hycom.org), respectively. The use of matching horizontal grids, currently at resolutions of 15km, 30km and 60km, avoids coastline ambiguities and interpolation errors at the air-sea interface. The intended purpose of the coupled model being subseasonal-to-seasonal prediction, our focus is on mid-term precipitation biases and the statistical steadiness of the atmospheric circulation (blocking frequency, Rossby wave breaking, meridional heat transport, etc.), as well as on possible causes of ocean model drift. An attempt is made to isolate the weather model's role in modifying water mass properties and ocean circulations (including meridional overturning) by comparing coupled model results to ocean-only experiments forced by observed atmospheric boundary conditions. A multi-decadal run at 60km resolution is used to illustrate ENSO variability in the coupled system.

  18. Improvement of the Cloud Physics Formulation in the U.S. Navy Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS)

    DTIC Science & Technology

    2005-09-30

    following tasks: 1. Investigation of aerosol-cloud-precipitation interactions in COAMPS using the CIMMS bulk drizzle parameterization 2...Naval Research Laboratory’s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) equipped with the CIMMS bulk drizzle scheme. In an...activation parameterization, giant CCN parameterization, SGS variability) developed at CIMMS /OU will be made available to NRL and registered COAMPS users

  19. Secular Trends and Climate Drift in Coupled Ocean-Atmosphere General Circulation Models

    SciTech Connect

    Covey, C C; Gleckler, P J; Phillips, T J; Bader, D C

    2004-11-23

    Coupled ocean-atmosphere general circulation models (coupled GCMs) with interactive sea ice are the primary tool for investigating possible future global warming and numerous other issues in climate science. A long-standing problem with such models is that when different components of the physical climate system are linked together, the simulated climate can drift away from observations unless constrained by ad hoc adjustments to interface fluxes. However, eleven modern coupled GCMs--including three that do not employ flux adjustments--behave much better in this respect than the older generation of models. Surface temperature trends in control run simulations (with external climate forcing such as solar brightness and atmospheric carbon dioxide held constant) are small compared with observed trends, which include 20th century climate change due to both anthropogenic and natural factors. Sea ice changes in the models are dominated by interannual variations. Deep ocean temperature and salinity trends are small enough for model control runs to extend over 1000 simulated years or more, but trends in some regions, most notably the Arctic, are inconsistent among the models and may be problematic.

  20. Toward understanding the double Intertropical Convergence Zone pathology in coupled ocean-atmosphere general circulation models

    NASA Astrophysics Data System (ADS)

    Zhang, Xuehong; Lin, Wuyin; Zhang, Minghua

    2007-06-01

    This paper first analyzes structures of the double Intertropical Convergence Zone (ITCZ) in the central equatorial Pacific simulated by three coupled ocean-atmosphere general circulation models in terms of sea surface temperatures, surface precipitation, and surface winds. It then describes the projection of the double ITCZ in the equatorial upper ocean. It is shown that the surface wind convergences, associated with the zonally oriented double rainbands on both sides of the equator, also correspond to surface wind curls that are favorable to Ekman pumping immediately poleward of the rainbands. The pumping results in a thermocline ridge south of the equator in the central equatorial Pacific, causing a significant overestimation of the eastward South Equatorial Counter Current that advects warm water eastward. A positive feedback mechanism is then described for the amplification of the double ITCZ in the coupled models from initial biases in stand-alone atmospheric models through the following chain of interactions: precipitation (atmospheric latent heating), surface wind convergences, surface wind curls, Ekman pumping, South Equatorial Counter Current, and eastward advection of ocean temperature. This pathology provides a possible means to address the longstanding double ITCZ problem in coupled models.

  1. Stochastic modelling and predictability: analysis of a low-order coupled ocean-atmosphere model.

    PubMed

    Vannitsem, Stéphane

    2014-06-28

    There is a growing interest in developing stochastic schemes for the description of processes that are poorly represented in atmospheric and climate models, in order to increase their variability and reduce the impact of model errors. The use of such noise could however have adverse effects by modifying in undesired ways a certain number of moments of their probability distributions. In this work, the impact of developing a stochastic scheme (based on stochastic averaging) for the ocean is explored in the context of a low-order coupled (deterministic) ocean-atmosphere system. After briefly analysing its variability, its ability in predicting the oceanic flow generated by the coupled system is investigated. Different phases in the error dynamics are found: for short lead times, an initial overdispersion of the ensemble forecast is present while the ensemble mean follows a dynamics reminiscent of the combined amplification of initial condition and model errors for deterministic systems; for longer lead times, a reliable diffusive ensemble spread is observed. These different phases are also found for ensemble-oriented skill measures like the Brier score and the rank histogram. The implications of these features on building stochastic models are then briefly discussed.

  2. Simulation of global warming with a simple coupled ocean-atmosphere model

    SciTech Connect

    Jin Xiangze; Zhang Xuehong

    1994-12-31

    A highly simplified ocean-atmosphere coupling system is established based on a two-dimensional oceanic thermohaline circulation model and an energy balance atmospheric model. Transient responses of the coupled system to a radiation forcing corresponding to the doubling of the atmospheric CO{sub 2} concentration have been investigated with an emphasis on the role of the model`s thermohaline circulation in the warming processes of the system. The results show that there are some significant differences between the Pacific and the Atlantic in their transient responses. On the whole, the warming in the Atlantic is slower in the surface and faster in the deep layers than those in the Pacific due to the process of the deep water formation in the northern North Atlantic, where the active convection and the downward vertical advection transport the surface thermal anomalies into the lower layers efficiently. On a hundred-year time scale, the thermohaline circulation in the North Atlantic is weakened. As a result, the warming in the upper layer of the northern North Atlantic will be further delayed because of the reduction of the northward heat transport.

  3. Climate variability in a coupled GCM. Part II: The Indian Ocean and monsoon

    SciTech Connect

    Latif, M.; Sterl, A.; Assenbaum, M.; Junge, M.M.; Maier-Reimer, E.

    1994-10-01

    We have investigated the seasonal cycle and the interannual variability of the tropical Indian Ocean circulation and the Indian summer monsoon simulated by a coupled ocean-atmosphere general circulation model in a 26-year integration. Although the model exhibits significant climate drift, overall, the coupled GCM simulates realistically the seasonal changes in the tropical Indian Ocean and the onset and evolution of the Indian summer monsoon. The amplitudes of the seasonal changes, however, are underestimated. The coupled GCM also simulates considerable interannual variability in the tropical Indian Ocean circulation, which is partly related to the El Nino/Southern Oscillation phenomenon and the associated changes in the Walker circulation. Changes in the surface wind stress appear to be crucial in forcing interannual variations in the Indian Ocean SST. As in the Pacific Ocean, the net surface heat flux acts as a negative feedback on the SST anomalies. The interannual variability in monsoon rainfall, simulated by the coupled GCM, is only about half as strong as observed. The reason for this is that the simulated interannual variability in the Indian monsoon appears to be related to internal processes within the atmosphere only. In contrast, an investigation based on observations shows a clear lead-lag relationship between interannual variations in the monsoon rainfall and tropical Pacific SST anomalies. Furthermore, the atmospheric GCM also fails to reproduce this lead-lag relationship between monsoon rainfall and tropical Pacific SST when run in a stand-alone integration with observed SSTs prescribed during the period 1970-1988. These results indicate that important physical processes relating tropical Pacific SST to Indian monsoon rainfall are not adequately modeled in our atmospheric GCM. Monsoon rainfall predictions appear therefore premature. 24 refs., 13 figs, 2 tabs.

  4. Development and applications of a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System

    NASA Astrophysics Data System (ADS)

    Warner, J. C.; Armstrong, B. N.; He, R.; Zambon, J. B.; Olabarrieta, M.; Voulgaris, G.; Kumar, N.; Haas, K. A.

    2012-12-01

    Understanding processes responsible for coastal change is important for managing both our natural and economic coastal resources. Coastal processes respond from both local scale and larger regional scale forcings. Understanding these processes can lead to significant insight into how the coastal zone evolves. Storms are one of the primary driving forces causing coastal change from a coupling of wave and wind driven flows. Here we utilize a numerical modeling approach to investigate these dynamics of coastal storm impacts. We use the Coupled Ocean - Atmosphere - Wave - Sediment Transport (COAWST) Modeling System that utilizes the Model Coupling Toolkit to exchange prognostic variables between the ocean model ROMS, atmosphere model WRF, wave model SWAN, and the Community Sediment Transport Modeling System (CSTMS) sediment routines. The models exchange fields of sea-surface temperature, ocean currents, water levels, bathymetry, wave heights, lengths, periods, bottom orbital velocities, and atmospheric surface heat and momentum fluxes, atmospheric pressure, precipitation, and evaporation. Data fields are exchanged using regridded flux conservative sparse matrix interpolation weights computed from the SCRIP spherical coordinate remapping interpolation package. We describe the modeling components and the model field exchange methods. As part of the system, the wave and ocean models run with cascading, refined, spatial grids to provide increased resolution, scaling down to resolve nearshore wave driven flows simulated by the vortex force formulation, all within selected regions of a larger, coarser-scale coastal modeling system. The ocean and wave models are driven by the atmospheric component, which is affected by wave dependent ocean-surface roughness and sea surface temperature which modify the heat and momentum fluxes at the ocean-atmosphere interface. We describe the application of the modeling system to several regions of multi-scale complexity to identify the

  5. Data Assimilation Into a Coupled Ocean Atmosphere Model: Application to the 1997-1998 El Nino

    NASA Technical Reports Server (NTRS)

    Lee, Tong

    1999-01-01

    As part of JPL's ocean data assimilation effort to study ocean circulation and seasonal-interannual climate variability, sea level anomaly observed by TOPEX altimeter, together with sea surface temperature and wind stress data, are assimilated into a simple coupled ocean atmosphere model of the tropical Pacific. Model-data consistency is examined. Impact of the assimilation (as initialization) on El Nino Southern Oscillation (ENSO) forecasts is evaluated. The coupled model consists of a shallow water component with two baroclinic modes, an Ekman shear layer, a simplified mixed-layer temperature equation, and a statistical atmosphere based on dominant correlations between historical surface temperature and wind stress anomaly data. The adjoins method is used to fit the coupled model to the data over various six-month periods from late 1996 to early 1998 by optimally adjusting the initial state, model parameters, and basis functions of the statistical atmosphere. On average, the coupled model can be fitted to the data to approximately within the data and representation errors (5 cm, 0.5 C, and 10 sq m/sq m for sea level, surface temperature, and pseudo wind stress anomalies, respectively). The estimated fields resemble observed spatio-temporal structure reasonably well. Hindcasts/forecasts of the 1997/1998 El Nino initialized from forced estimated ocean states and parameters are much more realistic than those simply initialized from ocean states (see figure below). In particular, the ability of the model to produce significant warming beyond the initial state is dramatically improved. Parameter estimation, which compensates for some model errors, is found to be important to obtaining better fits of the model to data and to improving forecasts.

  6. Data Assimilation Into a Coupled Ocean Atmosphere Model: Application to the 1997-1998 El Nino

    NASA Technical Reports Server (NTRS)

    Lee, Tong

    1999-01-01

    As part of JPL's ocean data assimilation effort to study ocean circulation and seasonal-interannual climate variability, sea level anomaly observed by TOPEX altimeter, together with sea surface temperature and wind stress data, are assimilated into a simple coupled ocean atmosphere model of the tropical Pacific. Model-data consistency is examined. Impact of the assimilation (as initialization) on El Nino Southern Oscillation (ENSO) forecasts is evaluated. The coupled model consists of a shallow water component with two baroclinic modes, an Ekman shear layer, a simplified mixed-layer temperature equation, and a statistical atmosphere based on dominant correlations between historical surface temperature and wind stress anomaly data. The adjoins method is used to fit the coupled model to the data over various six-month periods from late 1996 to early 1998 by optimally adjusting the initial state, model parameters, and basis functions of the statistical atmosphere. On average, the coupled model can be fitted to the data to approximately within the data and representation errors (5 cm, 0.5 C, and 10 sq m/sq m for sea level, surface temperature, and pseudo wind stress anomalies, respectively). The estimated fields resemble observed spatio-temporal structure reasonably well. Hindcasts/forecasts of the 1997/1998 El Nino initialized from forced estimated ocean states and parameters are much more realistic than those simply initialized from ocean states (see figure below). In particular, the ability of the model to produce significant warming beyond the initial state is dramatically improved. Parameter estimation, which compensates for some model errors, is found to be important to obtaining better fits of the model to data and to improving forecasts.

  7. How much of the NAO monthly variability is from ocean-atmospheric coupling: results from an interactive ensemble climate model

    NASA Astrophysics Data System (ADS)

    Xin, Xiaoge; Xue, Wei; Zhang, Minghua; Li, Huimin; Zhang, Tao; Zhang, Jie

    2015-02-01

    The chaotic atmospheric circulations and the ocean-atmosphere coupling may both cause variations in the North Atlantic Oscillation (NAO). This study uses an interactive ensemble (IE) coupled model to study the contribution of the atmospheric noise and coupling to the monthly variability of the NAO. In the IE model, seven atmospheric general circulation model (AGCM) realizations with different initial states are coupled with a single realization of the land, ocean and ice component models. The chaotic noise from the atmosphere at the air-sea interface is therefore reduced. The time variances of monthly NAO index in the ensemble AGCM mean of the IE model is found to be about 20.1 % of that in the SC model. Therefore, more than 79.9 % of the simulated monthly variability of NAO is caused by atmospheric noise. The coupling between sea surface temperature (SST) and NAO is only found in regions south of about 40°N in the North Atlantic Ocean. The IE strategy highlighted the interaction between the NAO and the SST in the region (28°-38°N, 20°W-50°W) to the southeast of the Gulf Stream extension. While the ocean-atmosphere coupling explains <1/5th of the NAO variability in the IE model, it shows slightly larger persistence than the SC model, consistent with the hypothesis of a slower mode of variability from ocean-atmosphere coupling that has larger predictability than the variability driven by the atmosphere.

  8. Coupled Ocean-Atmosphere Loss of Refractory Marine Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Kieber, D. J.; Keene, W. C.; Frossard, A. A.; Long, M. S.; Russell, L. M.; Maben, J. R.; Kinsey, J. D.; Tyssebotn, I. M.; Quinn, P.; Bates, T. S.

    2013-12-01

    Marine aerosol produced in the oceans from bursting bubbles and breaking waves is number dominated by submicron aerosol that are highly enriched in marine organic matter relative to seawater. Recent studies suggest that these organic-rich, submicron aerosol have a major impact on tropospheric chemistry and climate. It has been assumed this marine-derived aerosol organic matter is of recent origin stemming from biological activity in the photic zone. However, we deployed a marine aerosol generator on a recent cruise in the Sargasso Sea with seawater collected from 2500 m and showed that the aerosol generated from this seawater was enriched with organic matter to the same level as observed in surface Sargasso seawater, implying that the marine organic matter flux from the oceans into atmospheric aerosol is partly due to marine organic matter not of recent origin. We propose that marine aerosol production and subsequent physical and photochemical atmospheric evolution is the main process whereby old, refractory organic matter is removed from the oceans, thereby closing the carbon budget in the oceans and solving a long-standing conundrum regarding the removal mechanism for this organic matter in the sea. The implications of this study for couplings in the ocean-atmosphere cycling of organic matter will be discussed.

  9. Seasonal climate hindcasts with Eta model nested in CPTEC coupled ocean-atmosphere general circulation model

    NASA Astrophysics Data System (ADS)

    Pilotto, Isabel L.; Chou, Sin Chan; Nobre, Paulo

    2012-12-01

    This work evaluates the added value of the downscaling technique employed with the Eta model nested in the CPTEC atmospheric general circulation model and in the CPTEC coupled ocean-atmosphere general circulation model (CGCM). The focus is on the austral summer season, December-January-February, with three members each year. Precipitation, latent heat flux, and shortwave radiation flux at the surface hindcast by the models are compared with observational data and model analyses. The global models generally overestimate the precipitation over South America and tropical Atlantic. The CGCM and the nested Eta (Eta + C) both produce a split in the ITCZ precipitation band. The Eta + C produces better precipitation pattern for the studied season. The Eta model reduces the excessive latent heat flux generated by these global models, in particular the Eta + C. Comparison against PIRATA buoys data shows that the Eta + C results in the smallest precipitation and shortwave radiation forecast errors. The Eta + C comparatively best results are though as a consequence of both: the regional model resolution/physics and smaller errors on the lateral boundary conditions provided by the CGCM.

  10. Coupling submesoscale physics to seabirds behaviour at the ocean-atmosphere interface

    NASA Astrophysics Data System (ADS)

    De Monte, S.; Cotté, C.; d'Ovidio, F.; Lévy, M.; Le Corre, M.; Weimerskirch, H.

    2012-04-01

    During their journeys, seabirds are faced to environmental heterogeneity of the scale of tens of Kms in extension and of days in duration, that are induced in the open ocean by mesoscale and submesoscale turbulence. We combine tracking of frigatebirds in the Mozambique channel - available for the first time with 3-D resolution - and multisatellite-based nonlinear diagnostics to inquire how birds respond to the coupled ocean-atmosphere physics. Birds behaviour along their flight trajectory are categorized in 5 classes of vertical displacement, e.g. slow or fast descents, and are superimposed with the submesoscale structures obtained by a Lagrangian reanalysis or remote-sensing measures. We show that frigatebirds modify their behaviour at such scale over and outside transport and thermal fronts. We suggest that birds colocalization with structures generated by horizontal transport is a consequence of their quest for food (preferentially located on thermal fronts) but also for upward vertical wind. Our multidisciplinary method can be applied to forthcoming high-resolution animal tracking data and contribute to elucidate the response of marine ecosystems to environmental change.

  11. Simulation of ENSO with a global atmospheric GCM coupled to a high-resolution, tropical Pacific ocean GCM

    SciTech Connect

    Philander, S.G.H.; Pacanowski, R.C.; Lau, N.C.; Nath, M.J. )

    1992-04-01

    A global atmospheric general circulation model (GCM) coupled to an oceanic GCM that is dynamically active only in the tropical Pacific simulates variability over a broad spectrum of frequencies. Of special interest is the simulation of a realistically irregular Southern Oscillation between warm El Nino and cold La Nino states with time scale of 5 years. The spatial structure is different in the eastern and western halves of the ocean basin. Sea surface temperature changes have their largest amplitude in the central and eastern tropical Pacific, but the low-frequency zonal wind fluctuations are displaced westward and are large over the western half of the basin. During El Nino the associated curl contributes to a pair of pronounced minima in thermocline depth, symmetrically about the equator in the west. In the east the deepening of the thermodine in response to the winds in the west has an approximate Gaussian shape centered on the equator. The low-frequency sea surface temperature and zonal wind anomalies wax and wane practically in place and in phase without significant zonal phase propagation. Thermocline depth variations have phase propagation, a property of the oceanic response to the quasi-periodic winds that force currents and excite a host of waves with periods near 5 years, This indicates that the ocean-atmosphere interactions that cause El Nino to develop at a certain time are countered and reversed by the delayed response of the ocean to earlier winds. Kelvin and Rossby waves cannot be identified in the low-frequency fluctuations of this model, but they are energetic at relatively short periods and are of vital importance to a quasi-resonant oceanic mode with a period near 7 months that is excited in the model. The similarities and differences between the results of this simulation and those with other models are discussed.

  12. Indian Ocean and Indian summer monsoon: relationships without ENSO in ocean-atmosphere coupled simulations

    NASA Astrophysics Data System (ADS)

    Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll

    2017-08-01

    The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (ENSO) in two partially decoupled global experiments. ENSO is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between ENSO, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of ENSO and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of ENSO. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and Hadley cells. This meridional circulation is masked in the presence of ENSO. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker circulation despite the absence of ENSO. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon circulation when ENSO is removed. On the contrary, the monsoon circulation significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by ENSO in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of ENSO, favoring moisture convergence over India.

  13. Indian Ocean and Indian summer monsoon: relationships without ENSO in ocean-atmosphere coupled simulations

    NASA Astrophysics Data System (ADS)

    Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll

    2016-10-01

    The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (ENSO) in two partially decoupled global experiments. ENSO is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between ENSO, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of ENSO and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of ENSO. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and Hadley cells. This meridional circulation is masked in the presence of ENSO. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker circulation despite the absence of ENSO. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon circulation when ENSO is removed. On the contrary, the monsoon circulation significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by ENSO in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of ENSO, favoring moisture convergence over India.

  14. Antarctic Circumpolar Wave dynamics in a simplified ocean- atmosphere coupled model

    NASA Astrophysics Data System (ADS)

    Maze, G.; D'Andrea, F.; Colin de Verdiere, A.

    2004-12-01

    The Antarctic Circumpolar Wave (ACW) is one of the main pattern of variability in the Ocean-Atmosphere system in the southern Hemisphere extratropics. It involves sea surface temperature (SST), sea level pressure (SLP) and other variables, and consists of a wave train of zonal number 2, travelling around Antarctica at the speed of 6-8 cm s-1, hence taking around 8 years to complete a circle. A fundamental feature of this observed pattern is that anomalies are eastward propagating and seem to be phase locked: for example SST and SLP are in quadrature (high downstream of warm SST). Nevertheless the atmospheric part of the wave has been questioned by some observational studies. Different analytical and numerical studies have veen proposed, but a convincing theoretical explanation for the ACW is still missing. In this work we study the ACW as simulated by a simple dynamical model, in order to determine the basic physical processes that characterize it. The model used is an atmospheric quasi-geostrophic tridimensional model coupled to an ocean "slab" mixed layer, which includes mean geostrophic advection by the antarctic circumpolar current (ACC). The atmosphere-ocean coupling is obtained via surface sensible heat fluxes. We analyse three configuration of the model, a "passive ocean" one, where the ocean responds to the atmopheric forcing but does not feeds back to the atmosphere; a "passive atmosphere" one, where the stationary reponse of the atmosphere to prescribed SST anomalies; and a fully coupled one. The two forced experiment show separately a positive feedback in the coupled system.The passive ocean experiment shows an ACW-type low frequency variability in the ocean, ie a propagating SST anomaly with 4 years period. SSTa amplitude created were around 0.5C wich is less than observed anomalies (1.5oC). This means that the stochastic focing of the atmosphere is sufficient to substain a variability of the SST whose periodicity is set by the mean advection

  15. Dynamics and predictability of a low-order wind-driven ocean-atmosphere coupled model

    NASA Astrophysics Data System (ADS)

    Vannitsem, Stéphane

    2014-04-01

    The dynamics of a low-order coupled wind-driven ocean-atmosphere system is investigated with emphasis on its predictability properties. The low-order coupled deterministic system is composed of a baroclinic atmosphere for which 12 dominant dynamical modes are only retained (Charney and Straus in J Atmos Sci 37:1157-1176, 1980) and a wind-driven, quasi-geostrophic and reduced-gravity shallow ocean whose field is truncated to four dominant modes able to reproduce the large scale oceanic gyres (Pierini in J Phys Oceanogr 41:1585-1604, 2011). The two models are coupled through mechanical forcings only. The analysis of its dynamics reveals first that under aperiodic atmospheric forcings only dominant single gyres (clockwise or counterclockwise) appear, while for periodic atmospheric solutions the double gyres emerge. In the present model domain setting context, this feature is related to the level of truncation of the atmospheric fields, as indicated by a preliminary analysis of the impact of higher wavenumber ("synoptic" scale) modes on the development of oceanic gyres. In the latter case, double gyres appear in the presence of a chaotic atmosphere. Second the dynamical quantities characterizing the short-term predictability (Lyapunov exponents, Lyapunov dimension, Kolmogorov-Sinaï (KS) entropy) displays a complex dependence as a function of the key parameters of the system, namely the coupling strength and the external thermal forcing. In particular, the KS-entropy is increasing as a function of the coupling in most of the experiments, implying an increase of the rate of loss of information about the localization of the system on its attractor. Finally the dynamics of the error is explored and indicates, in particular, a rich variety of short term behaviors of the error in the atmosphere depending on the (relative) amplitude of the initial error affecting the ocean, from polynomial ( at 2 + bt 3 + ct 4) up to exponential-like evolutions. These features are explained

  16. Shortwave feedbacks and El Nino-Southern Oscillation: Forced ocean coupled ocean-atmosphere experiments

    NASA Technical Reports Server (NTRS)

    Waliser, Duane E.; Blanke, Bruno; Neelin, J. David; Gautier, C.

    1994-01-01

    Changes in tropical sea surface temperature (SST) can produce changes in cloudiness that modify incoming solar shortwave (SW) radiation, which in turn affects SST. The effects of this negative feedback on Pacific interannual variability are examined in forced ocean model and hybrid coupled ocean-atmosphere model simulations. Two empirical schemes are used to model the large-scale, low-frequency response of surface SW to SST anomalies. The first scheme attempts to account for the nonlocal nature of the atmospheric response to SST based patterns of covariability analyzed through singular value decomposition. In the observations the primary coupled mode of variability is composed of a SW anomaly in the central Pacific that covaries with anomalous SST in the eastern Pacific. This is applied in the model as a nonlocal feedback. The second scheme examines the effects of a purely local feedback with a spatially varying coefficient of magnitude chosen similar to the first scheme. In almost all cases the second scheme behaved similarly to the first, presumably because the correlation scale of SST is large enough for El Nino-Southern Oscillation (ENSO) dynamics that there is little sensitivity to the local approximation in the SW feedback. In simulations forced by time series of observed wind stress the SW feedback induced very minor SST damping. Results for a simpified heat budget analysis showed that while the SW feedback increased the local heat flux damping on SST, it also induced a mean shallowing of the mixed layer. The resulting changes in both the local mean vertical temperature gradient and the zonal velocity response to the wind stress acted to oppose the local heat flux damping effects. When the observed SW anomalies were applied to forced simulations, the simulated SST anomalies were modified as expected, and agreement with observed SST improved. In coupled simulations the SW feedbacks had greater impact than in the case of specified stress. The main effects were

  17. Coupled ocean-atmosphere surface variability and its climate impacts in the tropical Atlantic region

    NASA Astrophysics Data System (ADS)

    Fontaine, B.; Janicot, Serge; Roucou, P.

    This study examines time evolution and statistical relationships involving the two leading ocean-atmosphere coupled modes of variability in the tropical Atlantic and some climate anomalies over the tropical 120°W-60°W region using selected historical files (75-y near global SSTs and precipitation over land), more recent observed data (30-y SST and pseudo wind stress in the tropical Atlantic) and reanalyses from the US National Centers for Environmental Prediction (NCEP/NCAR) reanalysis System on the period 1968-1997: surface air temperature, sea level pressure, moist static energy content at 850 hPa, precipitable water and precipitation. The first coupled mode detected through singular value decomposition of the SST and pseudo wind-stress data over the tropical Atlantic (30°N-20°S) expresses a modulation in the thermal transequatorial gradient of SST anomalies conducted by one month leading wind-stress anomalies mainly in the tropical north Atlantic during northern winter and fall. It features a slight dipole structure in the meridional plane. Its time variability is dominated by a quasi-decadal signal well observed in the last 20-30 ys and, when projected over longer-term SST data, in the 1920s and 1930s but with shorter periods. The second coupled mode is more confined to the south-equatorial tropical Atlantic in the northern summer and explains considerably less wind-stress/SST cross-covariance. Its time series features an interannual variability dominated by shorter frequencies with increased variance in the 1960s and 1970s before 1977. Correlations between these modes and the ENSO-like Nino3 index lead to decreasing amplitude of thermal anomalies in the tropical Atlantic during warm episodes in the Pacific. This could explain the nonstationarity of meridional anomaly gradients on seasonal and interannual time scales. Overall the relationships between the oceanic component of the coupled modes and the climate anomaly patterns denote thermodynamical

  18. Ocean-atmosphere dynamics during Hurricane Ida and Nor'Ida: An application of the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system

    USGS Publications Warehouse

    Olabarrieta, M.; Warner, J.C.; Armstrong, B.; Zambon, J.B.; He, R.

    2012-01-01

    The coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system was used to investigate atmosphere-ocean-wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor'Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor'easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor'Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness

  19. Ocean-atmosphere dynamics during Hurricane Ida and Nor'Ida: An application of the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system

    NASA Astrophysics Data System (ADS)

    Olabarrieta, Maitane; Warner, John C.; Armstrong, Brandy; Zambon, Joseph B.; He, Ruoying

    The coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system was used to investigate atmosphere-ocean-wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor'Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor'easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor'Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness

  20. Parallel Computation of Ocean-Atmosphere-Wave Coupled Storm Surge Model

    NASA Astrophysics Data System (ADS)

    Kim, K.; Yamashita, T.

    2003-12-01

    Ocean-atmosphere interactions are very important in the formation and development of tropical storms. These interactions are dominant in exchanging heat, momentum, and moisture fluxes. Heat flux is usually computed using a bulk equation. In this equation air-sea interface supplies heat energy to the atmosphere and to the storm. Dynamical interaction is most often one way in which it is the atmosphere that drives the ocean. The winds transfer momentum to both ocean surface waves and ocean current. The wind wave makes an important role in the exchange of the quantities of motion, heat and a substance between the atmosphere and the ocean. Storm surges can be considered as the phenomena of mean sea-level changes, which are the result of the frictional stresses of strong winds blowing toward the land and causing the set level and the low atmospheric pressure at the centre of the cyclone can additionally raise the sea level. In addition to the rise in water level itself, another wave factor must be considered. A rise of mean sea level due to white-cap wave dissipation should be considered. In bounded bodies of water, such as small seas, wind driven sea level set up is much serious than inverted barometer effects, in which the effects of wind waves on wind-driven current play an important role. It is necessary to develop the coupled system of the full spectral third-generation wind-wave model (WAM or WAVEWATCH III), the meso-scale atmosphere model (MM5) and the coastal ocean model (POM) for simulating these physical interactions. As the component of coupled system is so heavy for personal usage, the parallel computing system should be developed. In this study, first, we developed the coupling system of the atmosphere model, ocean wave model and the coastal ocean model, in the Beowulf System, for the simulation of the storm surge. It was applied to the storm surge simulation caused by Typhoon Bart (T9918) in the Yatsushiro Sea. The atmosphere model and the ocean model have

  1. An ENSO prediction approach based on ocean conditions and ocean-atmosphere coupling

    NASA Astrophysics Data System (ADS)

    Tseng, Yu-heng; Hu, Zeng-Zhen; Ding, Ruiqiang; Chen, Han-ching

    2017-03-01

    A simple statistical model for the El Niño-Southern Oscillation (ENSO) prediction is derived based on the evolution of the ocean heat condition and the oceanic Kelvin wave propagation associated with westerly wind events (WWEs) and easterly wind surges (EWSs) in the tropical Pacific. The multivariate linear regression model solely relies on the pentad thermocline depth anomaly evolution in 25 days along with the zonal surface wind modulation. It successfully hindcasts all ENSOs except for the 2000/01 La Niña, using the pentad (or monthly) mean tropical atmosphere ocean array data since 1994 with an averaged skill (measured by anomaly correlation) of 0.62 (or 0.67) with a 6-month lead. The exception is mainly due to the long-lasting cold sea surface temperature anomalies in the subtropics resulting from the strong 1998/99 La Niña, even though the tropical warm water volume (WWV) had rebounded and turned phases after 2000. We also note that the hindcast skill is comparable using pentad or monthly mean NCEP global ocean data assimilation system data for the same time period. The hindcast skill of the proposed statistical model is better than that based on the WWV index in terms of the monthly correlation, normalized RMSEs and ENSO occurrences, which suggest that including the evolution of the subsurface ocean temperature anomaly and the WWEs/EWSs in the central tropical Pacific can enhance the ability to predict ENSO. The hindcast skill is also comparable to the predictions using other dynamical and statistical models, indicating that these processes are the keys to ENSO development. The dynamics behind the statistical model are consistent with the physical processes of ENSO development as follows: the tropical WWV resulting from the interannually-varying meridional subtropical cell transport provides a sufficient heat source. When the seasonal phase lock of ocean-atmosphere coupling triggers the positive (negative) zonal wind anomaly in boreal summer and fall, an

  2. A study on air-sea interaction on the simulated seasonal climate in an ocean-atmosphere coupled model

    NASA Astrophysics Data System (ADS)

    Ham, Suryun; Hong, Song-You; Park, Suhee

    2014-03-01

    This study investigates the effects of air-sea interaction upon simulated tropical climatology, focusing on the boreal summer mean precipitation and the embedded intra-seasonal oscillation (ISO) signal. Both the daily coupling of ocean-atmosphere and the diurnal variation of sea surface temperature (SST) at every time step by accounting for the ocean mixed layer and surface-energy budget at the ocean surface are considered. The ocean-atmosphere coupled model component of the global/regional integrated model system has been utilized. Results from the coupled model show better precipitation climatology than those from the atmosphere-only model, through the inclusion of SST-cloudiness-precipitation feedback in the coupled system. Cooling the ocean surface in the coupled model is mainly responsible for the improved precipitation climatology, whereas neither the coupling itself nor the diurnal variation in the SST influences the simulated climatology. However, the inclusion of the diurnal cycle in the SST shows a distinct improvement of the simulated ISO signal, by either decreasing or increasing the magnitude of spectral powers, as compared to the simulation results that exclude the diurnal variation of the SST in coupled models.

  3. Comparing the effect of low wind spead parameterization on heat fluxes in atmosphere only and coupled ocean-atmosphere simulations

    NASA Astrophysics Data System (ADS)

    Torres, Olivier; Braconnot, Pascale; Marti, Olivier

    2017-04-01

    The turbulent fluxes across the ocean/atmosphere interface represent one of the principal driving forces of the global atmospheric and oceanic circulation. Representation of these fluxes presents a challenge due to the small scale acting turbulent processes compared to the resolved scales of the models. Beyond this subgrid parameterization issue, a comprehensive understanding of the impact of air-sea interactions on the system is still lacking. We are developing a methodology to investigate how differences in the parameterizations affect the water supply of the atmospheric column in the tropics, the ocean heat content and the equator-pole redistribution of heat and water by the oceanic and atmospheric circulation. We focus on the representation of the latent heat fluxes in the tropics. We investigate how the representation of the heat transfer coefficient in weak winds affect the climate response considering both atmosphere only and ocean-atmosphere coupled simulations with the IPSL climate model. We compare simulations where the only difference is the activation of a function that increases latent heat fluxes during periods of weak wind. This allows us to isolate the behavior of the Pacific warmpool region where low winds occurs frequently. Although the heat transfer coefficients are very similar for a given parameterization between atmosphere only and ocean-atmosphere coupled simulation the surface heat fluxes are very different. We analyze in detail the ocean feedbacks and the role of the latent heat fluxes by looking at the energy transport carried out by the atmosphere considering the divergent part of the moist static energy. Differences appear between the coupled and uncoupled models due to the role of the ocean which dampens a large part of the disturbance caused by the modification of parameterization.

  4. 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

  5. Structure and predictability of the El Nino/Southern Oscillation phenomenon in a coupled ocean-atmosphere general circulation model

    SciTech Connect

    Latif, M.; Sterl, A.; Maier-Reimer, E.; Junge, M.M. )

    1993-04-01

    The space-time structure and predictability of the El Nino/Southern Oscillation (ENSO) phenomenon was investigated. Two comprehensive datasets were analyzed by means of an advanced statistical method, one based on observational data and other on data derived from an extended-range integration performed with a coupled ocean atmosphere general circulation model. It is shown that a considerable portion of the ENSO related low-frequency climate variability in both datasets is associated with a cycle implies the possibility of climate predictions in the tropics up to lead times of about one year. This is shown by conducting an ensemble of predictions with our coupled general circulation model. For the first time a coupled model of this type was successfully applied to ENSO predictions. 34 refs., 6 figs.

  6. Role of the Ocean-Atmosphere interactions for the Atlantic Multidecadal Variability in an idealized coupled model

    NASA Astrophysics Data System (ADS)

    Jamet, Quentin; Huck, Thierry; de Verdière, Alain Colin; Arzel, Olivier; Campin, Jean-Michel

    2015-04-01

    The role of the ocean-atmosphere interactions in the multidecadal variability of the Atlantic Meridional Overturning Circulation (AMOC) is investigated in an idealized coupled configuration of the MIT General Circulation Model. The flat-bottom ocean, composed of an Atlantic-like small basin, a Pacific-like large basin, and an unblocked Antarctic-like circumpolar channel, is coupled to a global atmospheric model (SPEEDY). In order to better represent the atmospheric dynamics and its interactions with the ocean, three set-ups, with horizontal resolution of about 4°, 2° and 1° (at the equator) in both the ocean and atmosphere models, are compared. They show a linearly increasing North Atlantic Oscillation-like variability. At all resolutions, the AMOC undergoes a spontaneous variability on multidecadal time scales between 30-40 yr, with an additional higher frequency in the highest resolution set-up. The AMOC variability responds to temperature anomalies along the western boundary through the thermal wind relationship. These temperature anomalies result from the propagation of large-scale baroclinic Rossby waves across the small basin. The unstable region responsible for the growth of Rossby waves through baroclinic instability, diagnosed using a temperature variance budget, shifts from the eastern boundary at coarse resolution (4°) to the western boundary at higher resolution (2° and 1°). An earlier study, performed with the same coarse resolution set-up (4°), has shown that the AMOC does not participate to the growth of Rossby waves, but passively reacts to these waves. The AMOC being mainly connected to the western boundary dynamics, its role in setting large scale baroclinic Rossby waves might be different between the coarse resolution set-ups (4°) and the higher resolution set-ups (2° and 1°). The ocean-atmosphere interactions are strongly enhanced in the highest resolution set-up (1°), with the development of a significant correlation of about 0

  7. Coupled Oceanic-Atmospheric Variability at Different Temporal Scales and U.S. Precipitation Characteristics

    NASA Astrophysics Data System (ADS)

    Goly, A.; Teegavarapu, R. S.

    2013-12-01

    A comprehensive examination of the influences of interdecadal, decadal and interannual oceanic-atmospheric oscillations on U.S. precipitation characteristics and extremes is carried out in this study. Four major oscillations affecting the precipitation patterns in the U.S. are evaluated within two phases (cool/negative and warm/positive phases) for each of the oscillations: El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO). Nine extreme precipitation indices, Inter-Event Time Definition (IETD) parameters, dry and wet spell transitions and correlations are analyzed along with parametric statistical hypothesis tests to validate significant changes from one phase to another. The analysis is carried out for the entire continental U.S. at a spatial resolution of 0.125 degree for the period 1950-1999. Analyses confirm spatially non-uniform changes in the influence of the oscillations on precipitation characteristics along with temporal variations over major hydrological basins of the U.S.

  8. Ocean-Atmosphere coupling and CO2 exchanges in the Southwestern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Souza, R.; Pezzi, L. P.; Carmargo, R.; Acevedo, O. C.

    2013-05-01

    The establishment of the INTERCONF Program (Air-Sea Interactions at the Brazil-Malvinas Confluence Zone) in 2004 and subsequent developing of projects such as the SIMTECO (Integrated System for Monitoring the Weather, the Climate and the Ocean in the South of Brazil) and ACEx (Atlantic Ocean Carbon Experiment) from 2010 in Brazil brought to light the importance of understanding the impact of the Southwestern Atlantic Ocean's mesoscale variability on the modulation of the atmospheric boundary layer (ABL) at the synoptic scale. Recent results of all these projects showed that the ABL modulation, as well as the ocean-atmosphere turbulent (heat, momentum and CO2) fluxes are dependent on the behavior of the ocean's surface thermal gradients, especially those found in the Brazil-Malvinas Confluence Zone and at the southern coast off Brazil during the winter. As expected, when atmospheric large scale systems are not present over the study area, stronger heat fluxes are found over regions of higher sea surface temperature (SST) including over warm core eddies shed towards the subantarctic (cold) environment. In the coastal region off southern Brazil, the wintertime propagation of the Brazilian Costal Current (La Plata Plume) acts rising the chlorophyll concentration over the continental shelf as well as diminishing considerably the SST - hence producing prominent across-shore SST gradients towards the offshore region dominated by the Brazil Current waters. Owing to that, heat fluxes are directed towards the ocean in coastal waters that are also responsible for the carbon sinking off Brazil in wintertime. All this description is dependent on the synoptic atmospheric cycle and strongly perturbed when transient systems (cold fronts, subtropical cyclones) are present in the area. However, remote sensing data used here suggest that the average condition of the atmosphere directly responding to the ocean's mesoscale variability appears to imprint a signal that extends from the

  9. Finding the driver of local ocean-atmosphere coupling in reanalyses and CMIP5 climate models

    NASA Astrophysics Data System (ADS)

    Ruiz-Barradas, Alfredo; Kalnay, Eugenia; Peña, Malaquías; BozorgMagham, Amir E.; Motesharrei, Safa

    2016-06-01

    Identification of the driver of coupled anomalies in the climate system is of great importance for a better understanding of the system and for its use in predictive efforts with climate models. The present analysis examines the robustness of a physical method proposed three decades ago to identify coupled anomalies as of atmospheric or oceanic origin by analyzing 850 mb vorticity and sea surface temperature anomalies. The method is then used as a metric to assess the coupling in climate simulations and a 30-year hindcast from models of the CMIP5 project. Analysis of the frequency of coupled anomalies exceeding one standard deviation from uncoupled NCEP/NCAR and ERA-Interim and partially coupled CFSR reanalyses shows robustness in the main results: anomalies of oceanic origin arise inside the deep tropics and those of atmospheric origin outside of the tropics. Coupled anomalies occupy similar regions in the global oceans independently of the spatiotemporal resolution. Exclusion of phenomena like ENSO, NAO, or AMO has regional effects on the distribution and origin of coupled anomalies; the absence of ENSO decreases anomalies of oceanic origin and favors those of atmospheric origin. Coupled model simulations in general agree with the distribution of anomalies of atmospheric and oceanic origin from reanalyses. However, the lack of the feedback from the atmosphere to the ocean in the AMIP simulations reduces substantially the number of coupled anomalies of atmospheric origin and artificially increases it in the tropics while the number of those of oceanic origin outside the tropics is also augmented. Analysis of a single available 30-year hindcast surprisingly indicates that coupled anomalies are more similar to AMIP than to coupled simulations. Differences in the frequency of coupled anomalies between the AMIP simulations and the uncoupled reanalyses, and similarities between the uncoupled and partially coupled reanalyses, support the notion that the nature of the

  10. Finding the driver of local ocean-atmosphere coupling in reanalyses and CMIP5 climate models

    NASA Astrophysics Data System (ADS)

    Ruiz-Barradas, Alfredo; Kalnay, Eugenia; Peña, Malaquías; BozorgMagham, Amir E.; Motesharrei, Safa

    2017-04-01

    Identification of the driver of coupled anomalies in the climate system is of great importance for a better understanding of the system and for its use in predictive efforts with climate models. The present analysis examines the robustness of a physical method proposed three decades ago to identify coupled anomalies as of atmospheric or oceanic origin by analyzing 850 mb vorticity and sea surface temperature anomalies. The method is then used as a metric to assess the coupling in climate simulations and a 30-year hindcast from models of the CMIP5 project. Analysis of the frequency of coupled anomalies exceeding one standard deviation from uncoupled NCEP/NCAR and ERA-Interim and partially coupled CFSR reanalyses shows robustness in the main results: anomalies of oceanic origin arise inside the deep tropics and those of atmospheric origin outside of the tropics. Coupled anomalies occupy similar regions in the global oceans independently of the spatiotemporal resolution. Exclusion of phenomena like ENSO, NAO, or AMO has regional effects on the distribution and origin of coupled anomalies; the absence of ENSO decreases anomalies of oceanic origin and favors those of atmospheric origin. Coupled model simulations in general agree with the distribution of anomalies of atmospheric and oceanic origin from reanalyses. However, the lack of the feedback from the atmosphere to the ocean in the AMIP simulations reduces substantially the number of coupled anomalies of atmospheric origin and artificially increases it in the tropics while the number of those of oceanic origin outside the tropics is also augmented. Analysis of a single available 30-year hindcast surprisingly indicates that coupled anomalies are more similar to AMIP than to coupled simulations. Differences in the frequency of coupled anomalies between the AMIP simulations and the uncoupled reanalyses, and similarities between the uncoupled and partially coupled reanalyses, support the notion that the nature of the

  11. Coupled ocean-atmosphere models feature systematic delay in Indian monsoon onset compared to their atmosphere-only component

    NASA Astrophysics Data System (ADS)

    Turner, Andrew

    2014-05-01

    In this study we examine monsoon onset characteristics in 20th century historical and AMIP integrations of the CMIP5 multi-model database. We use a period of 1979-2005, common to both the AMIP and historical integrations. While all available observed boundary conditions, including sea-surface temperature (SST), are prescribed in the AMIP integrations, the historical integrations feature ocean-atmosphere models that generate SSTs via air-sea coupled processes. The onset of Indian monsoon rainfall is shown to be systematically earlier in the AMIP integrations when comparing groups of models that provide both experiments, and in the multi-model ensemble means for each experiment in turn. We also test some common circulation indices of the monsoon onset including the horizontal shear in the lower troposphere and wind kinetic energy. Since AMIP integrations are forced by observed SSTs and CMIP5 models are known to have large cold SST biases in the northern Arabian Sea during winter and spring that limits their monsoon rainfall, we relate the delayed onset in the coupled historical integrations to cold Arabian Sea SST biases. This study provides further motivation for solving cold SST biases in the Arabian Sea in coupled models.

  12. Thirty-two-year ocean-atmosphere coupled downscaling of global reanalysis over the Intra-American Seas

    NASA Astrophysics Data System (ADS)

    Li, Haiqin; Misra, Vasubandhu

    2014-11-01

    This study examines the oceanic and atmospheric variability over the Intra-American Seas (IAS) from a 32-year integration of a 15-km coupled regional climate model consisting of the Regional Spectral Model (RSM) for the atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean. It is forced at the lateral boundaries by National Centers for Environmental Prediction-Department of Energy (NCEP-DOE R-2) atmospheric global reanalysis and Simplified Ocean Data Assimilation global oceanic reanalysis. This coupled downscaling integration is a free run without any heat flux correction and is referred as the Regional Ocean-Atmosphere coupled downscaling of global Reanalysis over the Intra-American Seas (ROARS). The paper examines the fidelity of ROARS with respect to independent observations that are both satellite based and in situ. In order to provide a perspective on the fidelity of the ROARS simulation, we also compare it with the Climate Forecast System Reanalysis (CFSR), a modern global ocean-atmosphere reanalysis product. Our analysis reveals that ROARS exhibits reasonable climatology and interannual variability over the IAS region, with climatological SST errors less than 1 °C except along the coastlines. The anomaly correlation of the monthly SST and precipitation anomalies in ROARS are well over 0.5 over the Gulf of Mexico, Caribbean Sea, Western Atlantic and Eastern Pacific Oceans. A highlight of the ROARS simulation is its resolution of the loop current and the episodic eddy events off of it. This is rather poorly simulated in the CFSR. This is also reflected in the simulated, albeit, higher variance of the sea surface height in ROARS and the lack of any variability in the sea surface height of the CFSR over the IAS. However the anomaly correlations of the monthly heat content anomalies of ROARS are comparatively lower, especially over the Gulf of Mexico and the Caribbean Sea. This is a result of ROARS exhibiting a bias of underestimation

  13. Surface Wind and Upper-Ocean Variability Associated with the Madden-Julian Oscillation Simulated by the Coupled Ocean-Atmosphere Mesoscale Prediction System

    DTIC Science & Technology

    2013-07-01

    Madden- Julian Oscillation Simulated by the Coupled Ocean-Atmosphere Mesoscale Prediction System 0601153N 73-4347-22-5 Toshiaki Shinoda, Tommy G...unlimited. Simulation of surface wind and upper-ocean variability associated with the Madden - Julian oscillation (MJO) by a regional coupled model, the...based on the comparison with the spatial variation of surface forcing fields. Indian Ocean, diurnal effects, Madden- Julian oscillation, coupled

  14. Impact of two-way ocean atmosphere coupling on precipitation forecast for the coastal Adriatic region

    NASA Astrophysics Data System (ADS)

    Smerkol, Peter; Cedilnik, Jure; Fettich, Anja; Licer, Matjaz; Strajnar, Benedikt; Jerman, Jure

    2017-04-01

    A two-way coupled ocean and atmosphere modeling system has been developed at Slovenian Environment Agency and the National Institute of Biology (Ličer at al., 2016). The system comprises 4.4 km ALADIN/ALARO limited-area numerical weather prediction model and Princeton Ocean Model (POM) for Adriatic sea and uses Mediterranean Forecasting System (MFS) as ocean component outside the POM model domain. The heat and momentum fluxes between sea surface and atmosphere as estimated by ALADIN model are transferred into POM every model time stamp, and sea surface temperature (SST) is returned from POM to ALADIN. A positive impact of such a coupling system with respect to one-way coupling was demonstrated mainly for sea surface variables. In this contribution we study the impact on atmospheric variables, mainly precipitation. Unlike in the previous work where the atmospheric part of the system was reinitialized every day from external (non-coupled) data assimilation cycle, we implement the two-way coupling in the data assimilation cycle for ALADIN. Rather than running long-term simulations which would presumably lack observational information given no data assimilation for the ocean component, we focus on several precipitation events and assess performance of the atmospheric model by running the coupled system for a short warm-up periods beforehand the events. We evaluate several approaches to applying the one- or two-way coupling (in the warm-up period, during the main forecast, or both) and several approaches to using SST information in ALADIN in the one-way coupled mode (POM, MFS, global atmospheric model). Preliminary results suggest that it is important that two-way coupling is applied not only during the long term (e.g. 72 h) forecast but also already in the data assimilation cycle prior to event.

  15. Investigation of hurricane Ivan using the coupled ocean-atmosphere-wave-sediment transport (COAWST) model

    USGS Publications Warehouse

    Zambon, Joseph B.; He, Ruoying; Warner, John C.

    2014-01-01

    The coupled ocean–atmosphere–wave–sediment transport (COAWST) model is used to hindcast Hurricane Ivan (2004), an extremely intense tropical cyclone (TC) translating through the Gulf of Mexico. Sensitivity experiments with increasing complexity in ocean–atmosphere–wave coupled exchange processes are performed to assess the impacts of coupling on the predictions of the atmosphere, ocean, and wave environments during the occurrence of a TC. Modest improvement in track but significant improvement in intensity are found when using the fully atmosphere–ocean-wave coupled configuration versus uncoupled (e.g., standalone atmosphere, ocean, or wave) model simulations. Surface wave fields generated in the fully coupled configuration also demonstrates good agreement with in situ buoy measurements. Coupled and uncoupled model-simulated sea surface temperature (SST) fields are compared with both in situ and remote observations. Detailed heat budget analysis reveals that the mixed layer temperature cooling in the deep ocean (on the shelf) is caused primarily by advection (equally by advection and diffusion).

  16. A zonally averaged, coupled ocean-atmosphere model for paleoclimate studies

    SciTech Connect

    Stocker, T.F.; Mysak, L.A. ); Wright, D.G. )

    1992-08-01

    A zonally averaged ocean model for the thermohaline circulation is coupled to a zonally averaged, one-layer energy balance model of the atmosphere to form a climate model for paleoclimate studies. The emphasis of the coupled model is on the ocean's thermohaline circulation in the Pacific, Atlantic, and Indian oceans. Under present-day conditions, the global conveyor belt is simulated. Latitude-depth structures of modeled temperature and salinity fields, as well as depth-integrated meridional transports of heat and freshwater, compare well with estimates from observations when wind stress is included. Ekman cells are present in the upper ocean and contribute substantially to the meridional fluxes at low latitudes.The atmospheric component of the coupled climate model consists of a classical balance model. When the two components are coupled after being spun up individually, the system remains steady. If intermittent convection is operating, the coupled model shows systematic deviations of the surface salinity, which may result in reversals of the thermohaline circulation. This climate drift can be inhibited by removing intermittent convection prior to coupling. The climate model is applied to investigate the effect of excess freshwater discharge into the North Atlantic, and the influence of the parameterization of precipitation is tested. The Atlantic thermohalinc flow is sensitive to anomalous freshwater input. Reversals of the deep circulation can occur in the Atlantic, leading to a state where deep water is formed only in the Southern Ocean. A feedback mechanism is identified that may also trigger the reversal of the Pacific thermobaline circulation yielding the inverse conveyor bell as an additional steady state. In total, four different stable equilibria of the coupled model were realized.

  17. Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS), Version 5.0 (User’s Guide)

    DTIC Science & Technology

    2010-03-30

    Operational Flowchart (Based On HPC BABBAGE Usage) .................................. 38  4.0   FUNCTIONAL DESCRIPTION ...FILE DESCRIPTIONS . .................................................................................................................... 35  FIGURE 6...acoustic products . Coupling can be both one-way and two-way, as well as with or without data assimilation. Data assimilation is facilitated through the

  18. Dynamics of Quasi-biennial Oscillations in Tropical Ocean-Atmosphere Coupled System

    NASA Technical Reports Server (NTRS)

    Kim, K.-M.; Lau, K.-M.

    1999-01-01

    In this study, quasi-biennial oscillation (QBO) in atmosphere-ocean coupled system is investigated using intermediate coupled model. Observation studies show that the easterly zonal winds anomalies prevail over the equatorial western Pacific during the warm phase of El Nino/Southern Oscillation (ENSO). At the time scale of QBO, SST variations and east Asia Summer monsoon rainfall are closely linked to the eastward propagating zonal winds anomalies originated from Indian ocean. To investigate the effect of zonal wind anomalies over western Pacific on the evolution of ENSO, simple anomalous winds are added to the western part of model domain as external forcing. Wind forcing is parameterized as a function of SST anomalies in the eastern Pacific with time lag. Time lag is adopted to mimic the relation between east Asian monsoon and ENSO. The results shows that the winds anomalies make coupled system oscillate through generating forced Kelvin waves even without the western boundary reflection of Rossby waves. Kelvin waves generated by external forcing are also crucial for the model to oscillate as well as Rossby wave reflections at the western boundary. When the monsoon forced Kelvin wave is strong during the northern winter, the coupled system damped out very quickly. In certain range of external winds amplitude and time lag, the model El Nino shows QBO features. It is suggested that the external wind forcing which is related to summer monsoon flow over western Pacific intensify the negative feedback process of off-equatorial Rossby waves and modify the ENSO periodicity.

  19. On the dependence of hindcast skill on ocean thermodynamics in a coupled ocean-atmosphere model

    SciTech Connect

    Kleeman, R. )

    1993-11-01

    Three different mechanisms for the generation of ENSO SST anomalies within a simplified tropical Pacific Ocean model are examined: thermocline depth changes, Ekman-induced upwelling anomalies, and zonal advection changes. The effect of varying the relative influence of these terms on the realism of tropical pacific coupled models is analyzed. The principal tool used to assess such realism is hindcast skill, with forced ocean and oscillatory behavior also being examined. Of the mechanisms considered, thermocline perturbations are shown to be crucially important for high coupled-model hindcast skills. Furthermore, it is concluded that the realism of the model (as measured by hindcast skill) deteriorates markedly when the influence on SST of Ekman upwelling becomes greater than a small fraction of the thermocline influence. This provides strong evidence for the hypothesis that Ekman upwelling anomalies (which are essentially a local response to wind stress anomalies) have only a small influence on the creation of real world SST anomalies. The implications of this latter point for coupled models involving ocean general circulation models is briefly discussed. It is also demonstrated that western boundary reflections provide a vital role by means of a negative feedback in ensuring realistic performance. The hindcast skill (as measured by NINO3 anomaly correlation) demonstrated by a model involving only the thermocline mechanism can be tuned to exceed that of the benchmark Cane and Zebiak model for hindcast lags up to 7 months (from 7 to 12 months the model skills are roughly equal). 47 refs., 32 figs.

  20. Large-scale ocean-atmosphere interactions in a simplified coupled model of the midlatitude wintertime circulation

    NASA Technical Reports Server (NTRS)

    Miller, Arthur J.

    1992-01-01

    Midlatitude ocean-atmosphere interactions are studied in simulations from a simplified coupled model that includes synoptic-scale atmospheric variability, ocean current advection of SST, and air-sea heat exchange. Although theoretical dynamical ('identical twin') predictions using this model have shown that the SST anomalies in this model indeed influence the atmosphere, it is found here that standard cross correlation and empirical orthogonal function analyses of monthly mean model output yield the standard result, familiar from observational studies, that the atmosphere forces the ocean with little or no feedback. Therefore, these analyses are inconclusive and leave open the question of whether anomalous SST is influencing the atmosphere. In contrast, it is found that compositing strong warm events of model SST is a useful indicator of ocean forcing the atmosphere. Additional evidence is presented for oceanic influence on the atmosphere, namely, that ocean current advection appears to enhance the persistence of model SST anomalies through a feedback effect that is absent when only heat flux is allowed to influence SST anomaly evolution.

  1. Evaluation of climate sensitivity to the representation of aerosols in a coupled ocean-atmosphere global model

    NASA Astrophysics Data System (ADS)

    Watson, Laura; Michou, Martine; Nabat, Pierre; Saint-Martin, David

    2017-04-01

    Aerosol radiative forcing is one of the greatest sources of uncertainty when projecting future climate change. Aerosols vary in time and in space and alter the Earth's radiative balance directly, by absorbing and scattering radiation, and indirectly, by interacting with clouds and altering cloud microphysics. A series of sensitivity tests were performed using the coupled ocean-atmosphere general circulation model CNRM-CM in order to investigate how the representation of aerosols within the model can affect climate. These tests included looking at the difference between using constant emissions versus using emissions that evolve over a period of thirty years; examining the impacts of including indirect effects from sea salt and organics; altering the aerosol optical properties; altering the vertical distribution of aerosols, and using an interactive aerosol scheme versus using 2-D climatologies. The results of these sensitivity tests show how modifying certain aspects of the aerosol scheme can significantly affect radiative flux, the cloud radiative effect and global surface temperatures. Of particular note is the importance of the indirect effect of sea salt aerosols, which has more of a significant impact upon climate than the direct radiative forcing of sea salt aerosols; and the impact of using an interactive aerosol scheme instead of 2-D climatologies, which results in more net radiative flux at the top of the atmosphere and slightly warmer temperatures at land surfaces.

  2. Multiple-century response of a coupled ocean-atmosphere model to an increase of atmospheric carbon dioxide

    SciTech Connect

    Manabe, S.; Stouffer, R.J. )

    1994-01-01

    To speculate on the future change of climate over several centuries, three 500-year integrations of a coupled ocean-atmosphere model were performed. In addition, to the standard integration in which the atmospheric concentration of carbon dioxide remains unchanged, two integrations are conducted. In one integration, the CO[sub 2] concentration increases by 1% yr[sup [minus]1] (compounded) until it reaches four times the initial value at the 140th year and remains unchanged thereafter. In another integration, the CO[sub 2] concentration also increases at the rate of 1% yr[sup [minus]1] until it reaches twice the initial value of the 70th year and remains unchanged thereafter. One of the most notable features of the CO[sub 2]-quadrupoling integration is the gradual disappearance of thermohaline circulations in most of the model oceans during the first 250-year period, leaving behind wind-driven cells. For example, thermohaline circulation nearly vanished in the North Atlantic during the first 200 years of the integration. In the Weddell and Ross seas, thermohaline circulation becomes weaker and shallower, thereby reducing the rate of bottom water formation and weakening the northward flow of bottom water in the Pacific and Atlantic oceans. The weakening or near disappearance of thermohaline circulation described above is attributable mainly to the capping of the model oceans by relatively fresh water in high latitudes where the excess of precipitation over evaporation increases markedly due to the enhanced poleward moisture transport in the warmer model troposphere.

  3. CO/sub 2/-induced change in a coupled ocean-atmosphere model and its paleoclimatic implications

    SciTech Connect

    Manabe, S.; Bryan, K. Jr.

    1985-11-20

    The effect of large changes of atmospheric CO/sub 2/ was studied, using the coupled ocean-atmosphere model of Bryan et al. (1982), for derivation of six climatic equilibria (cases with 1/2 to 8 times the present CO/sub 2/ concentration). An increase of atmospheric CO/sub 2/ to the level of 8 times the normal concentration is accompanied by a decrease in the meridional gradient of surface air temperature (SAT) (the CO/sub 2/-induced increase of SAT is particularly large at high latitudes), with no changes in the intensity or the latitudinal placement of the atmospheric jet. The meridional density gradient of the ocean surface water changes little because of an increased in thermal expansion coefficient of seawater with increased temperature; thus, the intensity of thermohaline circulation does not diminish as expected. On the other hand, reduction of atmospheric CO/sub 2/ causes a dramatic change in the thermohaline circulation at half the normal CO/sub 2/ concentration, the sea water is held at the freezing point from pole down to 45 deg latitude because of the formation of sea ice.

  4. Double ITCZ in Coupled Ocean-Atmosphere Models: From CMIP3 to CMIP5

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxiao; Liu, Hailong; Zhang, Minghua

    2015-10-01

    Recent progress in reducing the double Intertropical Convergence Zone bias in coupled climate models is examined based on multimodel ensembles of historical climate simulations from Phase 3 and Phase 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). Biases common to CMIP3 and CMIP5 models include spurious precipitation maximum in the southeastern Pacific, warmer sea surface temperature (SST), weaker easterly, and stronger meridional wind divergences away from the equator relative to observations. It is found that there is virtually no improvement in all these measures from the CMIP3 ensemble to the CMIP5 ensemble models. The five best models in the two ensembles as measured by the spatial correlations are also assessed. No progress can be identified in the subensembles of the five best models from CMIP3 to CMIP5 even though more models participated in CMIP5; the biases of excessive precipitation and overestimated SST in southeastern Pacific are even worse in the CMIP5 models.

  5. Investigating the effects of a summer storm on the North Sea stratification using a regional coupled ocean-atmosphere model

    NASA Astrophysics Data System (ADS)

    Gronholz, Alexandra; Gräwe, Ulf; Paul, André; Schulz, Michael

    2017-01-01

    The influence of a summer storm event in 2007 on the North Sea and its effects on the ocean stratification are investigated using a regional coupled ocean (Regional Ocean Modeling System, ROMS)-atmosphere (Weather Research & Forecasting model, WRF) modeling system. An analysis of potential energy anomaly (PEA, Φ) and its temporal development reveals that the loss of stratification due to the storm event is dominated by vertical mixing in almost the entire North Sea. For specific regions, however, a considerable contribution of depth-mean straining is observed. Vertical mixing is highly correlated with wind induced surface stresses. However, peak mixing values are observed in combination with incoming flood currents. Depending on the phase between winds and tides, the loss of stratification differs strongly over the North Sea. To study the effects of interactive ocean-atmosphere exchange, a fully coupled simulation is compared with two uncoupled ones for the same vertical mixing parameters to identify the impact of spatial resolution as well as of SST feedback. While the resulting new mixed layer depth after the storm event in the uncoupled simulation with lower spatial and temporal resolution of the surface forcing data can still be located in the euphotic zone, the coupled simulation is capable to mix the entire water column and the vertical mixing in the uncoupled simulation with higher resolution of the surface forcing data is strongly amplified. These differences might have notable implications for ecosystem modeling since it could determine the development of new phytoplankton blooms after the storm and for sediment modeling in terms of sediment mobilization. An investigation of restratification after the extreme event illustrates the persistent effect of this summer storm.

  6. Investigating the effects of a summer storm on the North Sea stratification using a regional coupled ocean-atmosphere model

    NASA Astrophysics Data System (ADS)

    Gronholz, Alexandra; Gräwe, Ulf; Paul, André; Schulz, Michael

    2017-02-01

    The influence of a summer storm event in 2007 on the North Sea and its effects on the ocean stratification are investigated using a regional coupled ocean (Regional Ocean Modeling System, ROMS)-atmosphere (Weather Research & Forecasting model, WRF) modeling system. An analysis of potential energy anomaly (PEA, Φ) and its temporal development reveals that the loss of stratification due to the storm event is dominated by vertical mixing in almost the entire North Sea. For specific regions, however, a considerable contribution of depth-mean straining is observed. Vertical mixing is highly correlated with wind induced surface stresses. However, peak mixing values are observed in combination with incoming flood currents. Depending on the phase between winds and tides, the loss of stratification differs strongly over the North Sea. To study the effects of interactive ocean-atmosphere exchange, a fully coupled simulation is compared with two uncoupled ones for the same vertical mixing parameters to identify the impact of spatial resolution as well as of SST feedback. While the resulting new mixed layer depth after the storm event in the uncoupled simulation with lower spatial and temporal resolution of the surface forcing data can still be located in the euphotic zone, the coupled simulation is capable to mix the entire water column and the vertical mixing in the uncoupled simulation with higher resolution of the surface forcing data is strongly amplified. These differences might have notable implications for ecosystem modeling since it could determine the development of new phytoplankton blooms after the storm and for sediment modeling in terms of sediment mobilization. An investigation of restratification after the extreme event illustrates the persistent effect of this summer storm.

  7. On the use of ocean-atmosphere-wave models during an extreme CAO event: the importance of being coupled

    NASA Astrophysics Data System (ADS)

    Carniel, Sandro; Barbariol, Francesco; Benetazzo, Alvise; Bonaldo, Davide; Falcieri, Francesco M.; Miglietta, Mario M.; Ricchi, Antonio; Sclavo, Mauro

    2015-04-01

    During winter 2012 an extreme meteorological event stroke the whole Europe and particularly its central-southern sector. A strong and persistent spit of cold air coming from Siberian region (a Cold Air Outbreak, CAO) insisted on northern Italy and the Adriatic sea basin, leading to decreases in the sea temperatures up to 6 °C in less than two weeks, ice formation on the Venice lagoon and an exceptional snow fall in the Apennine region. In the sea the CAO was associated to a significant episode of dense water formation (DWF), a crucial phenomenon that heavily impacts the whole Adriatic Sea (from the sinking of water masses and associated ventilation of the northernmost shelf, to the flow along the western coast, until the flushing of southern Adriatic open slope and submarine canyons, with associated sediment transport and bottom reshaping). The extent of the DWF event in the Northern Adriatic sub-basin was estimated by means of coastal observatories, ad hoc measurements and, until now, results from existing one-way coupled atmosphere-ocean models. These are characterized by no SST feedback from the ocean to the atmosphere, and therefore by turbulent heat fluxes that may heavily reflect a non-consistent ocean state. The study proposes an investigation of the 2012 CAO using a fully coupled, three components, ocean-atmosphere-wave system (COAWST). Results highlight that, although the energy interplays between air and sea do not seem to significantly impact the wind forecasts, when providing heat fluxes that are consistent with the ocean temperature we find modified heat fluxes and air sea temperatures figures. Moreover, the consistent description of thermal exchanges adopted in the fully coupled model can affect the basin circulation, the quantification of dense water produced mass, and the description of its migration pathways and rates of off-shelf descent.

  8. Sensitivity of ocean-atmosphere multiscale coupled model to oceanic parameterizations.

    NASA Astrophysics Data System (ADS)

    Masson, S. G.; Berthet, S.; Samson, G.; Crétat, J.; Colas, F.; Echevin, V.; Jullien, S.; Hourdin, C.

    2016-02-01

    This work explores new pathways toward a better representation of the multi-scale physics that drive climate variability. We are targeting key upscaling processes by which small-scale localized errors have a knock-on effect onto global climate. We focus on the Peru-Chile coastal upwelling, an area known to hold among the strongest models biases in the Tropics. Our approach is based on the development of a multiscale coupling interface allowing us to couple WRF with the NEMO oceanic model in a configuration including 2-way nested zooms in the oceanic and/or the atmospheric component of the coupled model. Upscalling processes are evidenced and quantified by comparing 20-year long simulations of a tropical channel (45°S-45°N), which differ by their horizontal resolution: 0.75° everywhere, 0.75°+0.25° zoom in the southeastern Pacific either in the ocean alone, in the atmosphere alone or in both, ocean and atmosphere. This group of 20-year long simulations was repeated with different sets of parameterizations to assess the robustness of our results. In this presentation, we will underline the difficulty to disentangle the impact of the increase of resolution from the changes in the parameterizations required by each resolution. Our results show that adding an embedded zoom over the southeastern Pacific only in the atmosphere cools down the SST along the Peru-Chili coast, which is a clear improvement. However, increasing the resolution only in the oceanic component show contrasting results according to the different set parameterization used in the experiments. Some experiment shows a coastal cooling as expected, whereas, in other cases, we observe a counterintuitive response with a warming of the coastal SST. Using a zoom in both ocean and atmosphere mostly combines the results obtained with a zoom in only one component. In the best case, we archive by this means a reduction of the coastal SST of several degrees in agreement with the observations.

  9. Evaluating Physical Processes during the Freeze-Up Season using a Coupled Sea Ice-Ocean-Atmosphere Forecast Model

    NASA Astrophysics Data System (ADS)

    Solomon, Amy; Intrieri, Janet; Persson, Ola; Cox, Christopher; Hughes, Mimi; Grachev, Andrey; Capotondi, Antonietta; de Boer, Gijs

    2017-04-01

    Improved sea ice forecasting must be based on improved model representation of coupled system processes that impact the sea ice thermodynamic and dynamic state. Pertinent coupled system processes remain uncertain and include surface energy fluxes, clouds, precipitation, boundary layer structure, momentum transfer and sea-ice dynamics, interactions between large-scale circulation and local processes, and others. In this presentation, we use a fully-coupled ocean-sea ice-atmosphere forecast system as a testbed for investigating biases in 0-10 day forecasts, with a focus on processes that determine fluxes at the ocean-ice-air interface. Model results and validation examples from an experimental, weather-scale, coupled ice-ocean-atmosphere model for 2015 and 2016 fall, sea ice freeze-up season will be presented. The model, a limited-area, fully-coupled atmosphere-ice-ocean model (named, RASM-ESRL), was developed from the larger-scale Regional Arctic System Model (RASM) architecture. RASM-ESRL includes the Weather Research and Forecasting (WRF) atmospheric model, Parallel Ocean Program (POP2) model, Community Ice Model (CICE5) and the NCAR Community Land Model. The domain is limited to the Arctic and all components are run with 10 km horizontal resolution. Components are coupled using a regionalized version of the CESM flux coupler (CPL7), which includes modifications important for resolving the sea ice pack's inertial response to transient (i.e. weather) events. The model is initialized with a GFS atmosphere, satellite-derived sea ice analyses using AMSR-2, and forced by 3-hourly GFS forecasts at the lateral boundaries. Experimental forecasts were run daily from late-July through mid-November in 2015 and 2016. These daily forecasts have been compared with observations of surface fluxes and vertical atmospheric profiles at the International Arctic Systems for Observing the Atmosphere (IASOA) stations, and with atmospheric and oceanic observations obtained within the sea

  10. The sensitivity of the regional coupled ocean-atmosphere simulations over the Intra-Americas seas to the prescribed bathymetry

    NASA Astrophysics Data System (ADS)

    Misra, Vasubandhu; Mishra, A.; Li, Haiqin

    2016-12-01

    This study examines the sensitivity of the coupled ocean-atmosphere climate of the Intra-Americas Seas (IAS; which includes the Gulf of Mexico and the Caribbean Sea) and parts of the western tropical and sub-tropical Atlantic Ocean to the prescribed bathymetry in three independent multi-decadal, high-resolution (15 km grid interval), regional coupled ocean-atmosphere model (RCM) integrations centered over the IAS. All of these RCM integrations with different prescribed bathymetries are forced by identical global atmospheric and oceanic reanalysis at the lateral boundaries. It is observed that the model integration with a smoother and coarser bathymetry in the region (RCM-C) results in more widespread sea surface temperature (SST) bias across the IAS. We also note that the bias displayed by the RCM-C simulation is analogous to the bias in the IAS ocean circulation of some Coupled Model Intercomparison Project version 5 (CMIP5) models. The models with an intermediate bathymetry (RCM-I) and finest bathymetry (RCM-F) rectify the bias in ocean transport through the Yucatan Channel relative to RCM-C but display mixed results with respect to SST bias. The RCM-C integration uses a bathymetry with a shallower Yucatan Channel, which tends to produce unrealistically weak flow through the Yucatan Channel and a weak Loop Current. However, the stronger heat transport through the Yucatan Channel in RCM-F results in significant warming of the northwestern tropical Atlantic Ocean and associated weakening of the surface easterly atmospheric winds relative to the other RCM integrations. Due to the weaker surface wind-induced shelf currents, the area comprised of western Gulf of Mexico and southern Caribbean Sea have a severe cold SST bias over the IAS in RCM-F relative to either RCM-I or RCM-C. RCM-I on the other hand significantly warms the western Gulf of Mexico. RCM-I displays the least SST bias over the IAS and the ocean transport through the Yucatan Channel is most comparable to

  11. Aperiodic variability in the Zebiak-Cane coupled ocean-atmosphere model: Air-sea interactions in the western equatorial Pacific

    SciTech Connect

    Mantua, N.J.; Battisti, D.S.

    1995-12-01

    The behavior of two coupled ocean-atmosphere models of intermediate complexity, the Zebiak-Cane (ZC hereafter) and Battisti version (B88 hereafter) of the ZC coupled ocean-atmosphere model, are reviewed and compared to the observed climate record from the tropical Pacific region. A major difference between each system lies in the modes of variability that each supports. IIt is demonstrated that differences in the basic-state climatology and thermodynamic parameters are keys to understanding the differences between the ZC and B88 coupled model behaviors. It is found that interactions between the ENSO and the mobile mode is the cause for irregular variability in standard ZC model simulations. The timescale of the recurrence of the mobile instability is that of the free-equatorial-wave basin mode, which is about 9 months. Interactions between the ENSO and mobile modes play an important role in the behavior of the standard ZC model. The phase (cold versus warm) of the model ENSO cycle determines the strength of the mobile mode instability, while ocean disturbances generated by the mobile mode interfere with the model ENSO regularity. It is demonstrated that the coexistence of these distinct, unstable, coupled ocean-atmosphere instabilities is key in producing aperiodic behavior in the ZC coupled model. By explicitly suppressing the air-sea interactions in the far western Pacific, the ZC model ENSO cycle becomes much more periodic than that in the standard model. There is no convincing evidence for robust coupled ocean-atmosphere interactions in the observed western Pacific region. However, uncoupled atmospheric variability associated with intraseasonal oscillations and the south Asian monsoon are very energetic features in this region. The results imply that wind stress variability in the western equatorial Pacific may act as a stochastic forcing that interrupts what might otherwise be a pure ENSO cycle.

  12. ENSO Simulation in Coupled Ocean-Atmosphere Models: Are the Current Models Better?

    SciTech Connect

    AchutaRao, K; Sperber, K R

    2005-04-29

    Maintaining a multi-model database over a generation or more of model development provides an important framework for assessing model improvement. Using control integrations, we compare the simulation of the El Nino/Southern Oscillation (ENSO), and its extratropical impact, in models developed for the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report with models developed in the late 1990's (the so-called Coupled Model Intercomparison Project-2 [CMIP2] models). The IPCC models tend to be more realistic in representing the frequency with which ENSO occurs, and they are better at locating enhanced temperature variability over the eastern Pacific Ocean. When compared with reanalyses, the IPCC models have larger pattern correlations of tropical surface air temperature than do the CMIP2 models during the boreal winter peak phase of El Nino. However, for sea-level pressure and precipitation rate anomalies, a clear separation in performance between the two vintages of models is not as apparent. The strongest improvement occurs for the modeling groups whose CMIP2 model tended to have the lowest pattern correlations with observations. This has been checked by subsampling the multi-century IPCC simulations in a manner to be consistent with the single 80-year time segment available from CMIP2. Our results suggest that multi-century integrations may be required to statistically assess model improvement of ENSO. The quality of the El Nino precipitation composite is directly related to the fidelity of the boreal winter precipitation climatology, highlighting the importance of reducing systematic model error. Over North America distinct improvement of El Nino forced boreal winter surface air temperature, sea-level pressure, and precipitation rate anomalies in the IPCC models occurs. This improvement, is directly proportional to the skill of the tropical El Nino forced precipitation anomalies.

  13. A Model Study on the Role of Ocean-Atmosphere Coupling for the 11-year Solar Signal in the Troposphere

    NASA Astrophysics Data System (ADS)

    Kubin, Anne; Abalichin, Janna; Langematz, Ulrike

    2017-04-01

    The 11-year solar cycle is known to influence the stratospheric circulation and even tropospheric conditions on a hemispheric and seasonal scale. However, large uncertainties exist with respect to the top-down influence of radiative-chemical interactions as well as bottom-up ocean-atmosphere interactions for the tropospheric signal. Here, effects of the 11-year solar cycle on the tropospheric climate are studied by analyzing integrations of the chemistry climate model EMAC that has been coupled to the MPIOM ocean model. A series of experiments has been tailored to investigate the role of atmosphere-ocean coupling for the formation of the near-surface response to the 11-year solar irradiance variability. The focus is on the north Atlantic region in the northern winter season. The model output is analyzed with a multiple linear regression technique. It is found that there is a tendency towards a positive phase of the North-Atlantic Oscillation (NAO) at maxima of the Sunspot cycle. The signal is enhanced when the atmosphere-ocean interaction is suppressed by prescribed sea surface temperatures. Additional sensitivity simulations with either the sea surface temperatures or the middle atmosphere being free from 11-year solar influence reveal a key role for the stratospheric forcing in shaping the tropospheric response in the North Atlantic-European region. The robustness of the signals is tested by varying the length of the analyzed time series as well as by varying the set of basis functions used in the regression. The NAO response shows substantial variation of magnitude and even sign when subsets of the analysis period are examined.

  14. A regional ocean-atmosphere coupled model developed for CORDEX East Asia: assessment of Asian summer monsoon simulation

    NASA Astrophysics Data System (ADS)

    Zou, Liwei; Zhou, Tianjun

    2016-12-01

    In this study, a developed regional ocean-atmosphere coupled model FROALS was applied to the CORDEX East Asia domain. The performance of FROALS in the simulation of Asian summer monsoon during 1989-2010 was assessed using the metrics developed by the CLIVAR Asian-Australian Monsoon Panel Diagnostics Task Team. The results indicated that FROALS exhibited good performance in simulating Asian summer monsoon climatology. The simulated JJA mean SST biases were weaker than those of the CMIP5 multi-model ensemble mean (MMEM). The skill of FROALS approached that of CMIP5 MMEM in terms of the annual cycle of Asian summer monsoon. The simulated monsoon duration matched the observed counterpart well (with a spatial pattern correlation coefficient of 0.59). Some biases of CMIP5 MMEM were also found in FROALS, highlighting the importance of local forcing and model physics within the Asian monsoon domain. Corresponding to a strong East Asian summer monsoon, an anomalous anticyclone was found over western North Pacific in both observation and simulation. However, the simulated strength was weaker than the observed due to the responses to incorrect sea surface anomalies over the key regions. The model also accurately captured the spatial pattern of the intraseasonal variability variance and the extreme climate indices of Asian summer monsoons, although with larger amplitude. The results suggest that FROALS could be used as a dynamical downscaling tool nested within the global climate model with coarse resolution to develop high-resolution regional climate change projections over the CORDEX East Asia domain.

  15. Intrinsic Coupled Ocean-Atmosphere Modes of the Asian Summer Monsoon: A Re-assessment of Monsoon-ENSO Relationships

    NASA Technical Reports Server (NTRS)

    Lau, K.-M.; Wu, H. T.

    2000-01-01

    Using global rainfall and sea surface temperature (SST) data for the past two decades (1979-1998), we have investigated the intrinsic modes of Asian summer monsoon (ASM) and ENSO co-variability. Three recurring ASM rainfall-SST coupled modes were identified. The first is a basin scale mode that features SST and rainfall variability over the entire tropics (including the ASM region), identifiable with those occurring during El Nino or La Nina. This mode is further characterized by a pronounced biennial variation in ASM rainfall and SST associated with fluctuations of the anomalous Walker circulation that occur during El Nino/La Nina transitions. The second mode comprises mixed regional and basin-scale rainfall and SST signals, with pronounced intraseasonal and interannual variabilities. This mode features a SST pattern associated with a developing La Nina, with a pronounced low level anticyclone in the subtropics of the western Pacific off the coast of East Asia. The third mode depicts an east-west rainfall and SST dipole across the southern equatorial Indian Ocean, most likely stemming from coupled ocean-atmosphere processes within the ASM region. This mode also possesses a decadal time scale and a linear trend, which are not associated with El Nino/La Nina variability. Possible causes of year-to-year rainfall variability over the ASM and sub-regions have been evaluated from a reconstruction of the observed rainfall from singular eigenvectors of the coupled modes. It is found that while basin-scale SST can account for portions of ASM rainfall variability during ENSO events (up to 60% in 1998), regional processes can accounts up to 20-25% of the rainfall variability in typical non-ENSO years. Stronger monsoon-ENSO relationship tends to occur in the boreal summer immediately preceding a pronounced La Nina, i.e., 1998, 1988 and 1983. Based on these results, we discuss the possible impacts of the ASM on ENSO variability via the west Pacific anticyclone and articulate a

  16. A comparison of surface air temperature variability in three 1000-Yr. coupled ocean-atmosphere model integrations

    SciTech Connect

    Stouffer, R.J.; Hegerl, G.; Tett, S.

    2000-02-01

    This study compares the variability of surface air temperature in three long coupled ocean-atmosphere general circulation model integrations. It is shown that the annual mean climatology of the surface air temperatures (SAT) in all three models is realistic and the linear trends over the 1,000-yr integrations are small over most areas of the globe. Second, although there are notable differences among the models, the models' SAT variability is fairly realistic on annual to decadal timescales, both in terms of the geographical distribution and of the global mean values. A notable exception is the poor simulation of observed tropical Pacific variability. In the HadCM2 model, the tropical variability is overestimated, while in the GFDL and HAM3L models, it is underestimated. Also, the ENSO-related spectral peak in the globally averaged observed SAT differs from that in any of the models. The relatively low resolution required to integrate models for long time periods inhibits the successful simulation of the variability in this region. On timescales longer than a few decades, the largest variance in the models is generally located near sea ice margins in high latitudes, which are also regions of deep oceanic convection and variability related to variations in the thermohaline circulation. However, the exact geographical location of these maxima varies from model to model. The preferred patterns of interdecadal variability that are common to all three coupled models can be isolated by computing empirical orthogonal functions (EOFs) of all model data simultaneously using the common EOF technique. A comparison of the variance each model associated with these common EOF patterns shows that the models generally agree on the most prominent patterns of variability. However, the amplitudes of the dominant models of variability differ to some extent between the models and between the models and observations. For example, two of the models have a mode with relatively large

  17. Response of a coupled ocean-atmosphere model to increasing atmospheric carbon dioxide: Sensitivity to the rate of increase

    SciTech Connect

    Stouffer, R.J.

    1999-08-01

    The influence of differing rates of increase of the atmospheric CO{sub 2} concentration on the climatic response is investigated using a coupled ocean-atmosphere model. Five transient integrations are performed each using a different constant exponential rate of CO{sub 2} increase ranging from 4% yr{sup {minus}1} to 0.25% yr{sup {minus}1}. By the time of CO{sub 2} doubling, the surface air temperature response in all the transient integrations is locally more than 50% and globally more than 35% of the equilibrium response. The land-sea contrast in the warming, which is evident in the equilibrium results, is larger in all the transient experiments. The land-sea difference in the response increases with the rate of increase in atmospheric CO{sub 2} concentration. The thermohaline circulation (THC) weakens in response to increasing atmospheric CO{sub 2} concentration in all the transient integrations, confirming earlier work. The results also indicate that the slower the rate of increase, the larger the weakening of the THC by the time of doubling. Two of the transient experiments are continued beyond the time of CO{sub 2} doubling with the CO{sub 2} concentration maintained at that level. The amount of weakening of the THC after the CO{sub 2} stops increasing is smaller in the experiment with the slower rate of CO{sub 2} increase, indicating that the coupled system has more time to adjust to the forcing when the rate of CO{sub 2} increase is slower. After a period of slow overturning, the THC gradually recovers and eventually regains the intensity found in the control integration, so that the equilibrium THC is very similar in the control and doubled CO{sub 2} integrations. Considering only the sea level changes due to the thermal expansion of seawater, the integration with the slowest rate of increase in CO{sub 2} concentration has the largest globally averaged sea level rise by the time of CO{sub 2} doubling. However, only a relatively small fraction of the

  18. Two Types of El Niño Events Simulated in the SNU Coupled GCM

    NASA Astrophysics Data System (ADS)

    Lim, M.; Kang, I.; Kug, J.; Ham, Y.

    2010-12-01

    Recent studies have reported that there exist more than one type of El Niño. One is the cold tongue (CT) El Niño, which shows stronger sea surface temperature anomalies (SSTA) in the eastern Pacific, and the other is the warm pool (WP) El Niño, which features SSTA in the central Pacific. The WP El Niño is different from the CT El Niño, not only the action center but also developing and transition mechanisms. In addition, WP El Niño occurs more frequently in recent decades. Furthermore, Yeh et al. (2009) suggests that WP El Niño occurrence will increase in future climate under global warming . Given the importance of correct simulations and predictions of the two types of El Niño events, it is required to better understand mechanisms which control them in numerical models. The present study investigates the CT and WP El Niño events simulated by two different versions of the SNU coupled GCM (SNUCGCM). The SNUCGCM is an ocean-atmosphere coupled model which couples the SNU Atmospheric GCM (SNUAGCM) to the Modular Ocean Model ver. 2.2 (MOM 2.2) Ocean GCM developed at Geophysical Fluid Dynamics Laboratory (GFDL). Two versions are control version (CNTL), second version (CTOK) includes the cumulus momentum transport parameterization and minimum entrainment rate. All two versions of the SNUCGCM used in this study reasonably simulate ENSO variability, with center of positive SSTA shifted slightly to the west compared to the observation. It is worthwhile to note that models simulate the major observed features of the WP El Niño distinguished from the CT El Niño. Furthermore, all versions of model simulate the occurrence of the CT El Niño more frequently than that of the WP El Niño as the observation. The CNTL shows interannual variability of SSTA over the tropical Pacific weaker than that in the CTOK, while the intensity of the WP El Niño event in the CNTL is stronger than that of the CTOK. In addition, the WP El Niño frequently occurs in the CNTL compared to

  19. ARM tropical pacific experiment (ATPEX): Role of cloud, water vapor and convection feedbacks in the coupled ocean/atmosphere system

    SciTech Connect

    Ramanathan, V.; Barnett, T.P.

    1992-03-05

    We have initiated studies that include radiation model validation, improved treatment of the three-dimensional structure of cloud-radiation interactions, and sensitivity runs that will unravel the role of cloud-convection-radiation interactions in the Pacific Sear Surface Temperatures and the overlying Walker and Hadley circulation. The research program is divided into three phases: (1) radiation, (2) cloud parameterization issues; (3) feedback and ocean-atmosphere interactions.

  20. Interactions between the seasonal cycle and the southern oscillation-frequency entrainment and chaos in a coupled ocean-atmosphere model

    SciTech Connect

    Chang, P.; Ji, L.; Wang, B.; Li, T.

    1994-12-15

    Nonlinear interactions between the seasonal cycle and interannual variations in the coupled ocean-atmosphere system have recently been proposed as the cause of irregularity of El Nino - Southern Oscillation (ENSO). The authors investigated such a hypothesis using a coupled ocean-atmosphere model which allows coupling between total sea surface temperature (SST) and total surface winds. Numerical simulations indicate that the model is capable of capturing the essential SST variability on seasonal-to-interannual time scale. Furthermore, it is shown that, as the seasonal forcing amplitude is gradually increased from zero, the coupled model undergoes several transitions between periodic (frequency-locking) and chaotic states before it finally {open_quotes}gives up{close_quotes} its intrinsic ENSO mode of oscillation entirely and acquires the frequency of the seasonal forcing. Chaotic response is found as the forcing amplitude approaches the observed value and the route to ENSO chaos is identified to be the period-doubling cascade. The study suggests that the response of a coupled system, coupled General Circulation Models of the ocean and atmosphere for example, can be very sensitive not only to changes in the internal model parameters but also to changes in the external forcing conditions. 15 refs., 3 figs.

  1. Regional Variability of the 20th century sea level rise from Ocean-Atmosphere Coupled Climate Models

    NASA Astrophysics Data System (ADS)

    Chevrier, Robin; Meyssignac, Benoit; Bourgeois, Elsa; Marzeion, Ben; Cazenave, Anny

    2014-05-01

    Regional Variability of the 20th century sea level rise from Ocean-Atmosphere Coupled Climate Models. R.Chevrier, B. Meyssignac, E. Bourgeois, B. Marzeion and A.Cazenave Over the 20th century, tide gauge records indicate a rise in global mean sea level of 1.7 mm.y-1 (Church and White 2011). This rise is essentially due to the warming of the ocean (which made the ocean water expand and sea level rise by ˜0.6 mm.yr-1) and the melt of mountain glaciers (which added more water to the ocean and made sea level rise by ˜,0.6 mm.yr-1 Gregory et al. 2013). Land water changes and Greenland surface mass balance changes also played a role but of lesser importance ( ˜0.1 mm.yr-1 for the land water storage and ˜0.2 mm.yr-1 for the Greenland mass balance since 1900, Gregory et al. 2013). Each of these different contributors to the 20th century global mean sea level rise had also an impact on the regional sea level changes. This regional signal, which must be added to the global sea level rise to compute the total sea level signal, is essential when we want to assess the impacts of the 20th century sea level rise on coastal areas and low lying islands. In this study we aim to estimate this 20th century regional sea level changes. We use historical runs of the CMIP5 (Coupled Model Intercomparison Project Phase 5) coupled climate models, which cover the period 1850-2006, to estimate the different contributors to the regional sea level changes since 1900. The ocean warming contribution is directly computed from the Temperature and Salinity outputs of the CMIP5 models while the mountain glaciers and the Greenland contributions are computed from offline models using the surface temperature output of CMIP5 models. Concerning the landwater storage contribution, it is actually mainly of anthropogenic origin over the 20th century (Ngoduc et al. 2005, Meyssignac et Cazenave 2012) so it is not modeled in CMIP5 models. Consequently, we use here estimates of the landwater storage

  2. Teleconnections of the Southern Oscillation in the tropical Atlantic sector in the OSU coupled upper ocean-atomosphere GCM

    SciTech Connect

    Hameed, S.; Meinster, A. ); Sperber, K.R. )

    1993-03-01

    The Oregon State University coupled upper ocean-atmosphere GCM has been shown to qualitatively simulate the Southern Oscillation. A composite analysis of the warm and cold events simulated in this 23-year integration has been performed. During the low phase of the Southern Oscillation, when warm anomalies occur in the eastern Pacific, the model simulates for the Atlantic region during March-May (1) a deficit of precipitation over the tropical South American continent, (2) Caribbean and Gulf of Mexico sea level pressure and sea surface temperature are in phase with the eastern Pacific anomalies, while those east of the Nordeste region are out of phase, and (3) northeast trade winds are anomalously weak and southwest trade winds are anomalously strong (as inferred from surface current anomalies). The anomalies in the oceanic processes are induced by perturbations in the atmospheric circulation over the Atlantic and are coupled to changes in the Walker circulation. During the high phase of the simulated Southern Oscillation, conditions in the atmosphere and ocean are essentially the reverse of the low phase. The model produces a response in the South American region during the opposing phases of the Southern Oscillation that is in general agreement with observations. The interannual variation of Nordeste rainfall is shown to be dominated by a few band-limited frequencies. These frequencies are found in the SST series of those regions of the Atlantic and Pacific oceans where strong correlations with Nordeste precipitation exist.

  3. Future summer precipitation changes over CORDEX-East Asia domain downscaled by a regional ocean-atmosphere coupled model: A comparison to the stand-alone RCM

    NASA Astrophysics Data System (ADS)

    Zou, Liwei; Zhou, Tianjun

    2016-03-01

    Climate changes under the RCP8.5 scenario over the Coordinated Regional Downscaling Experiment (CORDEX)-East Asia domain downscaled by a regional ocean-atmosphere coupled model Flexible Regional Ocean-Atmosphere Land System (FROALS) are compared to those downscaled by the corresponding atmosphere-only regional climate model driven by a global climate system model. Changes in the mean and interannual variability of summer rainfall were discussed for the period of 2051-2070 with respect to the present-day period of 1986-2005. Followed by an enhanced western North Pacific subtropical high and an intensified East Asian summer monsoon, an increase in total rainfall over north China, the Korean Peninsula, and Japan but a decrease in total rainfall over southern China are observed in the FROALS projection. Homogeneous increases of extreme rainfall amounts were found over the CORDEX-East Asia domain. A predominant increase in the interannual variability was evident for both total rainfall and the extreme rainfall amount. The spatial patterns of the projected rainfall changes by FROALS were generally consistent with those from the driving global model at a broad scale due to similar projected circulation changes. In both models, the enhanced southerlies over east China increased the moisture divergences over southern China and enhanced the moisture advection over north China. However, the atmosphere-only regional climate model (RCM) exhibited responses to the underlying sea surface temperature (SST) warming anomalies that were too strong, which induced an anomalous cyclone over the north South China Sea, followed by increases (decreases) of total and extreme rainfall over southern China (central China). The differences of the projected changes in both rainfall and circulation between FROALS and the atmosphere-only RCM were partly affected by the differences in the projected SST changes. The results recommend the employment of a regional ocean-atmosphere coupled model in the

  4. Coupled ocean-atmosphere model system for studies of interannual-to-decadal climate variability over the North Pacific Basin and precipitation over the Southwestern United States

    SciTech Connect

    Lai, Chung-Chieng A.

    1997-10-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The ultimate objective of this research project is to make understanding and predicting regional climate easier. The long-term goals of this project are (1) to construct a coupled ocean-atmosphere model (COAM) system, (2) use it to explore the interannual-to-decadal climate variability over the North Pacific Basin, and (3) determine climate effects on the precipitation over the Southwestern United States. During this project life, three major tasks were completed: (1) Mesoscale ocean and atmospheric model; (2) global-coupled ocean and atmospheric modeling: completed the coupling of LANL POP global ocean model with NCAR CCM2+ global atmospheric model; and (3) global nested-grid ocean modeling: designed the boundary interface for the nested-grid ocean models.

  5. On Verifying Currents and Other Features in the Hawaiian Islands Region Using Fully Coupled Ocean/Atmosphere Mesoscale Prediction System Compared to Global Ocean Model and Ocean Observations

    NASA Astrophysics Data System (ADS)

    Jessen, P. G.; Chen, S.

    2014-12-01

    This poster introduces and evaluates features concerning the Hawaii, USA region using the U.S. Navy's fully Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS-OS™) coupled to the Navy Coastal Ocean Model (NCOM). It also outlines some challenges in verifying ocean currents in the open ocean. The system is evaluated using in situ ocean data and initial forcing fields from the operational global Hybrid Coordinate Ocean Model (HYCOM). Verification shows difficulties in modelling downstream currents off the Hawaiian islands (Hawaii's wake). Comparing HYCOM to NCOM current fields show some displacement of small features such as eddies. Generally, there is fair agreement from HYCOM to NCOM in salinity and temperature fields. There is good agreement in SSH fields.

  6. The impact of coastal phytoplankton blooms on ocean-atmosphere thermal energy exchange: Evidence from a two-way coupled numerical modeling system

    NASA Astrophysics Data System (ADS)

    Jolliff, Jason K.; Smith, Travis A.; Barron, Charlie N.; deRada, Sergio; Anderson, Stephanie C.; Gould, Richard W.; Arnone, Robert A.

    2012-12-01

    A set of sensitivity experiments are performed with a two-way coupled and nested ocean-atmosphere forecasting system in order to deconvolve how dense phytoplankton stocks in a coastal embayment may impact thermal energy exchange processes. Monterey Bay simulations parameterizing solar shortwave transparency in the surface ocean as an invariant oligotrophic oceanic water type estimate consistently colder sea surface temperature (SST) than simulations utilizing more realistic, spatially varying shortwave attenuation terms based on satellite estimates of surface algal pigment concentration. These SST differences lead to an ∼88% increase in the cumulative turbulent thermal energy transfer from the ocean to the atmosphere over the three month simulation period. The result is a warmer simulated atmospheric boundary layer with respective local air temperature differences approaching ∼2°C. This study suggests that the retention of shortwave solar flux by ocean flora may directly impact even short-term forecasts of coastal meteorological variables.

  7. Impact of diurnal atmosphere-ocean coupling on tropical climate simulations using a coupled GCM

    NASA Astrophysics Data System (ADS)

    Ham, Yoo-Geun; Kug, Jong-Seong; Kang, In-Sik; Jin, Fei-Fei; Timmermann, Axel

    2009-05-01

    The impacts of diurnal atmosphere-ocean (air-sea) coupling on tropical climate simulations are investigated using the SNU coupled GCM. To investigate the effect of the atmospheric and oceanic diurnal cycles on a climate simulation, a 1-day air-sea coupling interval experiment is compared to a 2-h coupling experiment. As previous studies have suggested, cold temperature biases over equatorial western Pacific regions are significantly reduced when diurnal air-sea coupling strategy is implemented. This warming is initiated by diurnal rectification and amplified further by the air-sea coupled feedbacks. In addition to its effect on the mean climatology, the diurnal coupling has also a distinctive impact on the amplitude of the El Nino-Southern Oscillation (ENSO). It is demonstrated that a weakening of the ENSO magnitude is caused by reduced (increased) surface net heat fluxes into the ocean during El Nino (La Nina) events. Primarily, decreased (increased) incoming shortwave radiation during El Nino (La Nina) due to cloud shading is responsible for the net heat fluxes associated with ENSO.

  8. Simulation of ENSO-like phenomena with a low-resolution coupled GCM of the global ocean and atmosphere

    SciTech Connect

    Lau, Ngarcheung; Philander, S.G.H.; Nath, M.J. )

    1992-04-01

    A 140-year simulation of the ocean-atmosphere climate system has been performed by the GFDL Climate Dynamics Project using a low-resolution coupled general circulation model (GCM). The model was subjected to annually averaged insolation throughout the integration. This coupled system exhibits well-defined fluctuations in the tropical Pacific, with a preferred time scale of 3-4 years. The characteristics of these recurrent anomalies were examined by applying an extended empirical orthogonal function (EEOF) analysis to selected model variables. These results indicate that the simulated oscillations are accompanied by coherent changes in the atmospheric and oceanic circulation. The spatial patterns associated with the leading EEOF mode indicate that SST anomalies make their first appearance off the Peru-Ecuador coast and then migrate steadily westward, with an average transit time of 12-15 months. The arrival and eventual decay of SST fluctuations in the western Pacific is typically followed by the initiation of anomalies of the opposite polarity along the American coasts. The space-time evolution of various meteorological and oceanographic signals exhibits well-defined phase relationships with the SST perturbations. Some aspects of the model behavior during these warm and cold episodes are reminiscent of observed phenomena associated with the El Nino-Southern Oscillation (ENSO). Analysis of the climatological heat budget for the top ocean layer indicates a near balance between horizontal and vertical temperature advection by the time-mean flow, vertical diffusion, and heat input from the overlying atmosphere. The principal mechanisms associated with the simulated ENSO-like cycles were then studied by examining the local heat budget for the SST perturbations. The relative importance of various linear advective processes in the heat budget exhibits a notable dependence on geographical location and on the specific phase of the ENSO-like cycle.

  9. Simulation of medicanes over the Mediterranean Sea in a regional climate model ensemble: impact of ocean-atmosphere coupling and increased resolution

    NASA Astrophysics Data System (ADS)

    Gaertner, Miguel Ángel; González-Alemán, Juan Jesús; Romera, Raquel; Domínguez, Marta; Gil, Victoria; Sánchez, Enrique; Gallardo, Clemente; Miglietta, Mario Marcello; Walsh, Kevin J. E.; Sein, Dmitry V.; Somot, Samuel; Dell'Aquila, Alessandro; Teichmann, Claas; Ahrens, Bodo; Buonomo, Erasmo; Colette, Augustin; Bastin, Sophie; van Meijgaard, Erik; Nikulin, Grigory

    2016-11-01

    Medicanes are cyclones over the Mediterranean Sea having a tropical-like structure but a rather small size, that can produce significant damage due to the combination of intense winds and heavy precipitation. Future climate projections, performed generally with individual atmospheric climate models, indicate that the intensity of the medicanes could increase under climate change conditions. The availability of large ensembles of high resolution and ocean-atmosphere coupled regional climate model (RCM) simulations, performed in MedCORDEX and EURO-CORDEX projects, represents an opportunity to improve the assessment of the impact of climate change on medicanes. As a first step towards such an improved assessment, we analyze the ability of the RCMs used in these projects to reproduce the observed characteristics of medicanes, and the impact of increased resolution and air-sea coupling on their simulation. In these storms, air-sea interaction plays a fundamental role in their formation and intensification, a different mechanism from that of extra-tropical cyclones, where the baroclinic instability mechanism prevails. An observational database, based on satellite images combined with high resolution simulations (Miglietta et al. in Geophys Res Lett 40:2400-2405, 2013), is used as a reference for evaluating the simulations. In general, the simulated medicanes do not coincide on a case-by-case basis with the observed medicanes. However, observed medicanes with a high intensity and relatively long duration of tropical characteristics are better replicated in simulations. The observed spatial distribution of medicanes is generally well simulated, while the monthly distribution reveals the difficulty of simulating the medicanes that first appear in September after the summer minimum in occurrence. Increasing the horizontal resolution has a systematic and generally positive impact on the frequency of simulated medicanes, while the general underestimation of their intensity is

  10. Dynamical downscaling of historical climate over CORDEX East Asia domain: A comparison of regional ocean-atmosphere coupled model to stand-alone RCM simulations

    NASA Astrophysics Data System (ADS)

    Zou, Liwei; Zhou, Tianjun; Peng, Dongdong

    2016-02-01

    The FROALS (flexible regional ocean-atmosphere-land system) model, a regional ocean-atmosphere coupled model, has been applied to the Coordinated Regional Downscaling Experiment (CORDEX) East Asia domain. Driven by historical simulations from a global climate system model, dynamical downscaling for the period from 1980 to 2005 has been conducted at a uniform horizontal resolution of 50 km. The impacts of regional air-sea couplings on the simulations of East Asian summer monsoon rainfall have been investigated, and comparisons have been made to corresponding simulations performed using a stand-alone regional climate model (RCM). The added value of the FROALS model with respect to the driving global climate model was evident in terms of both climatology and the interannual variability of summer rainfall over East China by the contributions of both the high horizontal resolution and the reasonably simulated convergence of the moisture fluxes. Compared with the stand-alone RCM simulations, the spatial pattern of the simulated low-level monsoon flow over East Asia and the western North Pacific was improved in the FROALS model due to its inclusion of regional air-sea coupling. The results indicated that the simulated sea surface temperature (SSTs) resulting from the regional air-sea coupling were lower than those derived directly from the driving global model over the western North Pacific north of 15°N. These colder SSTs had both positive and negative effects. On the one hand, they strengthened the western Pacific subtropical high, which improved the simulation of the summer monsoon circulation over East Asia. On the other hand, the colder SSTs suppressed surface evaporation and favored weaker local interannual variability in the SST, which led to less summer rainfall and weaker interannual rainfall variability over the Korean Peninsula and Japan. Overall, the reference simulation performed using the FROALS model is reasonable in terms of rainfall over the land area of

  11. Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

    NASA Astrophysics Data System (ADS)

    Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

    The coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST) enables simulations that integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean. Within the modeling system, the three-dimensional ocean circulation module (ROMS) is coupled with the wave generation and propagation model (SWAN) to allow full integration of the effect of waves on circulation and vice versa. The existing wave-current coupling component utilizes a depth dependent radiation stress approach. In here we present a new approach that uses the vortex force formalism. The formulation adopted and the various parameterizations used in the model as well as their numerical implementation are presented in detail. The performance of the new system is examined through the presentation of four test cases. These include obliquely incident waves on a synthetic planar beach and a natural barred beach (DUCK' 94); normal incident waves on a nearshore barred morphology with rip channels; and wave-induced mean flows outside the surf zone at the Martha's Vineyard Coastal Observatory (MVCO). Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from Garcez Faria et al. (1998, 2000). Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction

  12. The role of ocean-atmosphere interaction in Typhoon Sinlaku (2008) using a regional coupled data assimilation system

    NASA Astrophysics Data System (ADS)

    Wada, Akiyoshi; Kunii, Masaru

    2017-05-01

    For improving analyses of tropical cyclone (TC) and sea surface temperature (SST) and thereby TC simulations, a regional mesoscale strongly coupled atmosphere-ocean data assimilation system was developed with the local ensemble transform Kalman filter (LETKF) implemented with the Japan Meteorological Agency's nonhydrostatic model (NHM) coupled with a multilayer ocean model and the third-generation ocean wave model. The NHM-LETKF coupled data assimilation system was applied to Typhoon Sinlaku (2008) along with the original NHM-LETKF system to investigate the sensitivity of Sinlaku to SST assimilation with the Level 2 Pre-processed (L2P) standard product of satellite SST. SST calculated in the coupled-assimilation experiment with the coupled data assimilation system and the satellite SST (CPL) showed a better correlation with Optimally Interpolated SST than SST used in the control experiment with the original NHM-LETKF (CNTL) and SST calculated in the succession experiment with the coupled system without satellite SST (SUCC). The time series in the CPL experiment well captured the variation in the SST observed at the Kuroshio Extension Observation buoy site. In addition, TC-induced sea surface cooling was analyzed more realistically in the CPL experiment than that in the CNTL and SUCC experiments. However, the central pressure analyzed in each three experiments was overestimated compared with the Regional Specialized Meteorological Center Tokyo best-track central pressure, mainly due to the coarse horizontal resolution of 15 km. The 96 h TC simulations indicated that the CPL experiment provided more favorable initial and boundary conditions than the CNTL experiment to simulate TC tracks more accurately.

  13. Dynamical downscaling of historical climate over CORDEX Central America domain with a regionally coupled ocean-atmosphere model

    NASA Astrophysics Data System (ADS)

    Quintanar, Arturo I.; Sein, Dmitry; Martinez-Lopez, Benjamin; Cabos, William; Ochoa-Moya, Carlos-Abraham

    2017-04-01

    ABSTRACT Recently, there has been a concerted effort by several research groups to model precipitation variability for North America and Central America in the context of the Coordinated Regional Climate Downscaling Experiment (CORDEX). One important objective of CORDEX is to dynamically downscale global output from coupled and non-coupled models and to objectively gauge a measure of added value from higher resolution boundary conditions forcing regional atmospheric and ocean models at their lateral walls. Up to now, a sufficiently large computational domain covering from the southern US to the north of South America including the eastern Pacific Ocean, the southern Atlantic and the Caribbean Seas has been lacking. Such a computational domain permits the analysis of an ample range of inter-annual and intra-seasonal time-scales phenomena and the possibility of exploring sensitivity to horizontal resolution. To date, most simulations performed for the region remain too coarse to be of any use at the regional scale but also, and most importantly, most modeling studies of the region rely on regional atmospheric models forced at their lower boundaries by prescribed sea surface temperature. In this work we explore both, climate sensitivity to coupling and, to the choice of horizontal resolution, using a regional atmospheric model (REMO) coupled to a global ocean model (MPI-OM). External atmospheric forcing is applied to REMO at its lateral walls and over the ocean surface that is not coupled to REMO. In order to gain insight into the sensitivity to the choice of the atmospheric forcing, two sources are used: 1) ERA-Interim and 2) a global free run of the MPI-ESM coupled system. Preliminary results suggest that the original biases between the ERA-Interim and the MPI-ESM forcing data tend to become similar when comparing the downscaled simulations at 50 km and 25 km atmospheric resolutions. Additionally, biases at 25 km tend to become smaller over most of the computational

  14. The impact of ocean-atmosphere interaction and atmospheric model resolution on the Mediterranean climate as simulated by regionally coupled ESM ROM

    NASA Astrophysics Data System (ADS)

    Sein, Dmitry; Cabos, William; Jacob, Daniela

    2017-04-01

    The Mediterranean Sea and adjacent land is located in a transitional area between tropical and mid-latitudes and presents a complex orography and coastlines where intense local air-sea and land-sea interactions take place. These intense local air-sea interactions together with the inflow of Atlantic water drive the Mediterranean thermohaline circulation. The resolution of global climate models in general is too coarse to correctly describe air-sea fluxes of energy and mass that play a key role in the process of deep water formation in the Mediterranean Sea. From the other hand stand-alone atmospheric models can be inadequate to simulate the air-sea fluxes correctly. For these reasons, the Mediterranean Sea is a region where atmosphere-ocean regional climate models (AORCM) are critical for the study of the processes in the atmosphere and ocean. In this work we use the regionally coupled atmosphere-ocean model ROM and its atmospheric component REMO in standalone configuration in order to assess the role of ocean-atmosphere feedbacks and the ocean and atmosphere models resolution in the simulation of both the ocean and atmospheric features of the Mediterranean hydrological cycle. To this end, a number of coupled and uncoupled simulations forced by ERA-Interim boundary conditions have been carried out. Namely, four different sets of coupled and uncoupled simulations with different atmospheric resolutions (25 and 12.5 km) are used to estimate the impact of resolution and coupling on the mass and heat budget as well as deep water formation in the Mediterranean Sea.

  15. Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) Version 5.0, Rev. 2.0 (User’s Guide)

    DTIC Science & Technology

    2012-05-03

    moisture, sea surface heights, currents, Stokes’ drift currents, and wave radiation stress gradients are exchanged across the air- sea -wave interface... Sea /Wave Run with Atmosphere and Ocean Assimilation .......................... 49 3.2.2 Two-way, Fully Coupled Run with Data Assimilation on DSRC...momentum are exchanged across the air- sea interface. COAMPS receives input from the Navy Operational Global Atmospheric Prediction System

  16. Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS), Version 5.0, Revision 2.0 (User’s Guide)

    DTIC Science & Technology

    2012-05-03

    moisture, sea surface heights, currents, Stokes’ drift currents, and wave radiation stress gradients are exchanged across the air- sea -wave interface... Sea /Wave Run with Atmosphere and Ocean Assimilation .......................... 49 3.2.2 Two-way, Fully Coupled Run with Data Assimilation on DSRC...momentum are exchanged across the air- sea interface. COAMPS receives input from the Navy Operational Global Atmospheric Prediction System (NOGAPS

  17. Transient response of the Hadley Centre coupled ocean-atmosphere model to increasing carbon dioxide. Part I: Control climate and flux adjustment

    SciTech Connect

    Murphy, J.M.

    1995-01-01

    This paper describes the initialization of an experiment to study the time-dependent response of a high-resolution global coupled ocean-atmosphere general circulation model to a gradual increase in carbon dioxide. The stability of the control integration with respect to climate drift is assessed, and aspects of the model climatology relevant to the simulation of climate change are discussed. The observed variation of oceanic temperature with latitude and depth is basically well simulated, although, in common with other ocean models, the main thermocline is too diffuse. Nevertheless, it is found that large heat and water flux adjustments must be added to the surface layer of the ocean in order to prevent the occurrence of unacceptable climate drift. The ocean model appears to achieve insufficient meridional heat transport, and this is supported by the pattern of the heat flux adjustment term, although errors in the simulated atmosphere-ocean heat flux also contribute to the latter. The application of the flux adjustments restricts climate drift during the 75-year control experiment. However, a gradual warming still occurs in the surface layers of the Southern Ocean because the flux adjustments are inserted as additive terms in this integration and cannot therefore be guaranteed to prevent climate drift completely. 68 refs., 29 figs., 1 tab.

  18. Transient response of the Hadley Centre coupled ocean-atmosphere model to increasing carbon dioxide. Part II: Spatial and temporal structure of response

    SciTech Connect

    Murphy, J.M.; Mitchell, J.F.B.

    1995-01-01

    A high-resolution (2.75{degrees} lat x 3.75{degrees} long) coupled ocean-atmosphere model has been used to simulate the transient response of climate to a gradual increase in atmospheric carbon dioxide concentrations. Although the radiative forcing increases linearly, there is a delay of about 30 yr before the ocean warms appreciably. This {open_quotes}cold start{close_quotes} is, at least partly, an artifact of the experimental design. At the time of doubling (after 70 yr), the patterns of change are similar to those found in comparable studies of the equilibrium response, except in the high latitudes of the Southern Ocean and the North Atlantic, where the warming is considerably reduced. The mechanisms leading to this reduction are discussed. After two to three decades, the pattern of warming is well established. The warming over land is substantially larger than that over the sea, with a consequent lowering of surface pressure over the northern continents in summer. The patterns of changes in precipitation and soil moisture take longer to establish themselves, although locally there are consistent changes after the third decade. 55 refs., 30 figs., 6 tabs.

  19. Comparison of a Coupled Ocean-Atmosphere Model with and without Oceanic Eddy-Induced Advection. Part I: Ocean Spinup and Control Integrations.

    NASA Astrophysics Data System (ADS)

    Hirst, Anthony C.; O'Farrell, Siobhan P.; Gordon, Hal B.

    2000-01-01

    The Gent and McWilliams (GM) parameterization for large-scale water transport caused by mesoscale oceanic eddies is introduced into the oceanic component of the Commonwealth Scientific and Industrial Research Organisation global coupled ocean-atmosphere model. Parallel simulations with and without the GM scheme are performed to examine the effect of this parameterization on the model behavior for integrations lasting several centuries under conditions of constant atmospheric CO2. The solution of the version with GM shows several significant improvements over that of the earlier version. First, the generally beneficial effects of the GM scheme found previously in studies of stand-alone ocean models, including more realistic deep water properties, increased stratification, reduced high-latitude convection, elimination of fictitious horizontal diffusive heat transport, and more realistic surface fluxes in some regions, are all maintained during the coupled integration. These improvements are especially pronounced in the high-latitude Southern Ocean. Second, the magnitude of flux adjustment is reduced in the GM version, mainly because of smaller surface fluxes at high southern latitudes in the GM ocean spinup. Third, the GM version displays markedly reduced climate drift in comparison to the earlier version. Analysis in the present study verifies previous indications that changes in the pattern of convective heat flux are central to the drift in the earlier version, supporting the view that reduced convective behavior in the GM version contributes to the reduction in drift. Based on the satisfactory behavior of the GM model version, the GM coupled integration is continued for a full 1000 yr. Key aspects of the model behavior during this longer period are also presented. Interannual variability of surface air temperature in the two model versions is briefly examined using some simple measures of magnitude. The variability differs between the two versions regionally, but

  20. Predictability of weather and climate in a coupled ocean-atmosphere model: A dynamical systems approach. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Nese, Jon M.

    1989-01-01

    A dynamical systems approach is used to quantify the instantaneous and time-averaged predictability of a low-order moist general circulation model. Specifically, the effects on predictability of incorporating an active ocean circulation, implementing annual solar forcing, and asynchronously coupling the ocean and atmosphere are evaluated. The predictability and structure of the model attractors is compared using the Lyapunov exponents, the local divergence rates, and the correlation, fractal, and Lyapunov dimensions. The Lyapunov exponents measure the average rate of growth of small perturbations on an attractor, while the local divergence rates quantify phase-spatial variations of predictability. These local rates are exploited to efficiently identify and distinguish subtle differences in predictability among attractors. In addition, the predictability of monthly averaged and yearly averaged states is investigated by using attractor reconstruction techniques.

  1. Simulation of the Pinatubo Impact on the Red Sea Using Coupled Regional Ocean/Atmosphere Modeling System

    NASA Astrophysics Data System (ADS)

    Stenchikov, G. L.; Osipov, S.

    2016-12-01

    This study focuses on the Middle East regional climate response to the Mt. Pinatubo volcanic eruption of 1991. It is motivated by the observed severe winter cooling in the Middle East during the winter of 1991/92. The Red Sea surface temperature dropped by more than 1K and deep water mixing caused coral bleaching for a few years. To better understand the mechanisms of the Middle East climate response and evaluate the effects of radiative cooling and regional meteorological processes on the Red Sea, we employ the Regional Ocean Modeling system (ROMS) fully coupled with the Weather Research and Forecasting (WRF) model. The WRF model parent and nested domains are configured over the Middle East and North Africa (MENA) region and over the Red Sea with 30 and 10 km resolution, respectively. The ROMS model over the Red Sea has 2 km grid spacing. The WRF code was modified to interactively account for the radiative effect of volcanic aerosols. Spectral optical properties of sulfate aerosols are computed using Mie based on the Sato's optical depth. Both atmosphere and ocean models capture the main features of the MENA climate response and correctly reproduce the anomalous winter cooling of 1991/92. We find that the sea surface cooling associated with meteorological effects prevails that caused by the direct radiative forcing of volcanic aerosols. The overturning circulation in the Red Sea strengthens. The salinity distribution and deep water formation are significantly perturbed.

  2. On the use of a coupled ocean-atmosphere-wave model during an extreme cold air outbreak over the Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Ricchi, Antonio; Miglietta, Mario Marcello; Falco, Pier Paolo; Benetazzo, Alvise; Bonaldo, Davide; Bergamasco, Andrea; Sclavo, Mauro; Carniel, Sandro

    2016-05-01

    An intense cold air outbreak affected the northern Adriatic Sea during winter 2012, determining an exceptional persistence of northeasterly Bora wind over the basin, which lasted for about 3 weeks. The cold air coming from the Balkans produced icing in the Venice lagoon and very intense snowfall in the Apennines Mountains and even near the coasts. In order to understand the importance and role of air-sea interactions for the evolution of the atmospheric fields, simulations with the Weather Research and Forecasting (WRF) model encompassing the whole period have been performed using sea surface temperature (SST) fields with an increasing level of complexity. Starting from a large-scale static sea temperature, the SST in the initial and boundary conditions has been progressively made more realistic. First, a more refined field, retrieved from a satellite radiometer was used; then, the same field was updated every 6 h. Next, the effect of including a simplified 1D ocean model reproducing the Oceanic Mixed Layer (OML) evolution has been tested. Finally, the potential improvements coming from a coupled description of atmosphere-ocean and atmosphere-ocean-waves interactions have been explored within the Coupled Ocean-Atmosphere-Wave Sediment Transport (COAWST) modeling system. Results highlight that the energy exchange between air and sea does not significantly impact the atmospheric fields, in particular 10 m wind and 2 m temperature, also because of the geography of the basin and the predominance of synoptic-scale flow in intense events of Bora, in the northern Adriatic. However, when sensible and latent heat fluxes, which are dependent on atmospheric and oceanic variables, are analyzed, the more realistic representation of SST drastically improves the model performances.

  3. Roles of land surface albedo and horizontal resolution on the Indian summer monsoon biases in a coupled ocean-atmosphere tropical-channel model

    NASA Astrophysics Data System (ADS)

    Samson, Guillaume; Masson, Sébastien; Durand, Fabien; Terray, Pascal; Berthet, Sarah; Jullien, Swen

    2017-03-01

    The Indian summer monsoon (ISM) simulated over the 1989-2009 period with a new 0.75° ocean-atmosphere coupled tropical-channel model extending from 45°S to 45°N is presented. The model biases are comparable to those commonly found in coupled global climate models (CGCMs): the Findlater jet is too weak, precipitations are underestimated over India while they are overestimated over the southwestern Indian Ocean, South-East Asia and the Maritime Continent. The ISM onset is delayed by several weeks, an error which is also very common in current CGCMs. We show that land surface temperature errors are a major source of the ISM low-level circulation and rainfall biases in our model: a cold bias over the Middle-East (ME) region weakens the Findlater jet while a warm bias over India strengthens the monsoon circulation over the southern Bay of Bengal. A surface radiative heat budget analysis reveals that the cold bias is due to an overestimated albedo in this desertic ME region. Two new simulations using a satellite-observed land albedo show a significant and robust improvement in terms of ISM circulation and precipitation. Furthermore, the ISM onset is shifted back by 1 month and becomes in phase with observations. Finally, a supplementary set of simulations at 0.25°-resolution confirms the robustness of our results and shows an additional reduction of the warm and dry bias over India. These findings highlight the strong sensitivity of the simulated ISM rainfall and its onset timing to the surface land heating pattern and amplitude, especially in the ME region. It also illustrates the key-role of land surface processes and horizontal resolution for improving the ISM representation, and more generally the monsoons, in current CGCMs.

  4. Using InterComm Enhanced ESMF to Couple TIME-GCM and CAM

    NASA Astrophysics Data System (ADS)

    Oehmke, R.; Wiltberger, M.; Sussman, A.; Wang, W.; Lo, N.

    2008-12-01

    This project uses the Earth System Modeling Framework (ESMF) and InterComm to produce a TIME-GCM and CAM coupled model. This project will demonstrate a new ESMF capability for coupling models running as separate executables. This capability is based on the InterComm library. InterComm is a runtime library and programming model for coupling separately executing parallel (and sequential programs), and is being used as the component coupling technology within the NSF Center for Integrated Space Weather Modeling. ESMF interfaces to InterComm have been contributed to the ESMF code repository, making it easy to use InterComm to transfer data into and out of ESMF components such as CAM. This project's work to couple TIME-GCM and CAM is motivated by the goal of understanding the day-to-day behavior of the ionosphere-thermosphere system. Doing this requires unraveling the relative strengths of forcing mechanisms of the I-T system, including solar ultraviolet, extreme-ultraviolet, and X-ray fluxes, magnetospheric processes resulting in geomagnetic activity and auroral effects, and propagation of dynamical variations driven by lower atmosphere weather and middle atmosphere tides. The National Center for Atmospheric Research (NCAR) Thermosphere - Ionosphere - Mesosphere -Electrodynamic - Global Circulation Model (TIME-GCM) is used to simulate this region depending on its forcing by the Sun. Recent work on improving the forcing of this model by including an improved description of the Extreme Ultra Violet (EUV) radiation has increased its ability to predict observed parameters such as satellite drag, but it does not capture all the observed hemispheric asymmetries. The implication is that forcing from the lower atmosphere, which is clearly asymmetric due to the location of continental masses, and is known to have very different dynamical features at solstices, is controlling the thermosphere. However, the TIME-GCM, with its 30-km lower boundary, does not contain these effects

  5. Transient response of the Hadley Centre coupled ocean-atmosphere model to increasing carbon dioxide. Part 3: Analysis of global-mean response using simple models

    SciTech Connect

    Murphy, J.M.

    1995-03-01

    The roles of surface, atmospheric, and oceanic feedbacks in controlling the global-mean transient response of a coupled ocean-atmosphere general circulation model (AOGCM) to increasing carbon dioxide are investigated. The analysis employs a four-box energy balance model (EBM) and an oceanic box-diffusion model (BDM) both tuned to the simulated general circulation model response. The land-sea contrast in the surface warming is explained almost entirely by the shortwave radiative feedbacks associated with changes in cloud and surface albedo. The oceanic thermal inertia delays the response; however, the initial delay is enhanced by increases in Anarctic sea-ice cover, which substantially reduce the effective climate sensitivity of the model in the first half of the 75-year experiment. When driven by the observed anthropogenic greenhouse forcing from the pre-industrial period to present day, the energy balance model overestimates the warming observed over land. However, inclusion of the direct forcing due to anthropogenic tropospheric sulphate aerosol eliminates the land/sea contrast in the response at 1990, leaving the simulated warming over land slightly below the observed value, although the rapid warming observed during the 1980s is well reproduced. The vertical penetration of the oceanic response is small below 1000 m. Within the top 1000 m the effective diffusivities are substantially enhanced by reduced convection and thermohaline overturning, driven by increased precipitation minus evaporation at high latitudes. These changes in ocean heat transport become significant after year 30, whereupon the effective oceanic heat capacity increases substantially, although this increase is partially offset by the effect of changes in the sea-ice margin.

  6. Simulation of medicanes over the Mediterranean Sea in regional climate model ensembles: impact of ocean-atmosphere coupling and increased resolution

    NASA Astrophysics Data System (ADS)

    Gaertner, Miguel Angel; Jesús González-Alemán, Juan; Romera, Raquel; Domínguez, Marta; Gil, Victoria; Sánchez, Enrique; Gallardo, Clemente

    2017-04-01

    Some cyclones over the Mediterranean Sea occasionally develop a tropical structure. These cyclones, also called medicanes, can produce significant damage due to the combination of intense winds and heavy precipitation. The small size of medicanes and the importance of air-sea interaction in their formation and intensification represents a challenge for RCMs. Large ensembles of high resolution and ocean-atmosphere coupled RCM simulations are now available from MedCORDEX and EURO-CORDEX. We use these ensembles to analyze the ability of RCMs to reproduce the observed characteristics of medicanes, and to assess the impact of increasing resolution and using air-sea coupling on its simulation. As a reference for evaluating the simulations, we take the observational database of Miglietta et al. (2013), based on satellite images combined with very high resolution simulations. The simulated medicanes do not coincide in general on a case-by-case basis with the observed medicanes. This can be expected in climate mode simulations due to the small size of medicanes and the fact that they develop within the RCM domain. Therefore, the evaluation of medicanes in RCM simulations has to be done statistically. The observed spatial distribution of medicanes is well simulated in general. Regarding the monthly distribution, RCMs have difficulties in simulating the first medicanes appearing in September after the summer minimum. The use of higher horizontal resolution clearly increases the simulated frequency of medicanes, resulting in generally better frequency values. But the intensity, which is underestimated in low resolution runs, is not improved by most increased resolution simulations. A few RCMs show a clear intensity increase in the higher resolution runs, suggesting that model formulation is more important in this respect than high resolution alone. Air-sea interaction frequently produces a negative intensity feedback for tropical cyclones, which depends on the oceanic mixed

  7. ARM tropical pacific experiment (ATPEX): Role of cloud, water vapor and convection feedbacks in the coupled ocean/atmosphere system. Progress report, September 1, 1991--August 31, 1992

    SciTech Connect

    Ramanathan, V.; Barnett, T.P.

    1992-03-05

    We have initiated studies that include radiation model validation, improved treatment of the three-dimensional structure of cloud-radiation interactions, and sensitivity runs that will unravel the role of cloud-convection-radiation interactions in the Pacific Sear Surface Temperatures and the overlying Walker and Hadley circulation. The research program is divided into three phases: (1) radiation, (2) cloud parameterization issues; (3) feedback and ocean-atmosphere interactions.

  8. A Coupled GCM-Cloud Resolving Modeling System to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Chern, Jiundar; Atlas, Robert; Peters-Lidard, Christa; Hou, Arthur; Lin, Xin

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud resolving models (CRMs) agree with observations better than traditional single column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA Satellite and field campaign cloud related data sets can provide initial conditions as well as validation for both the MMF and CRMs. Also we have implemented a Land Information System (LIS that includes the CLM and NOAH land surface models into the MMF. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM) This modeling system has been applied and tested its performance for two different climate scenarios, El Nino (1998) and La Nina (1999). The coupled new modeling system produced more realistic propagation and intensity of tropical rainfall systems and intraseasonal oscillations, and diurnal variation of precipitation that are very difficult to forecast using even the state-of-the-art GCMs. In this talk I will present: (1) a brief review on GCE model and its applications on precipitation processes (both Microphysical and land processes) and (2) The Goddard MMF and the Major difference between two existing MMFs (CSU MMF and Goddard MMF) and preliminary results (the comparison with traditional GCMs).

  9. A Coupled GCM-Cloud Resolving Modeling System to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Chern, Jiundar; Atlas, Robert; Peters-Lidard, Christa; Hou, Arthur; Lin, Xin

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud resolving models (CRMs) agree with observations better than traditional single column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA Satellite and field campaign cloud related data sets can provide initial conditions as well as validation for both the MMF and CRMs. Also we have implemented a Land Information System (LIS that includes the CLM and NOAH land surface models into the MMF. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM) This modeling system has been applied and tested its performance for two different climate scenarios, El Nino (1998) and La Nina (1999). The coupled new modeling system produced more realistic propagation and intensity of tropical rainfall systems and intraseasonal oscillations, and diurnal variation of precipitation that are very difficult to forecast using even the state-of-the-art GCMs. In this talk I will present: (1) a brief review on GCE model and its applications on precipitation processes (both Microphysical and land processes) and (2) The Goddard MMF and the Major difference between two existing MMFs (CSU MMF and Goddard MMF) and preliminary results (the comparison with traditional GCMs).

  10. Numerical studies of the air-sea interaction processes in intense tropical systems using the Coupled Ocean/Atmosphere Mesoscale Prediction System

    NASA Astrophysics Data System (ADS)

    Hong, Xiaodong

    1998-07-01

    The purpose of this study is to further our understanding of the air-sea interaction processes in intense tropical systems through numerical modeling. Three well-documented intense tropical systems are selected to study several aspects of the air-sea processes. First, the ocean response (one-way interaction) to an idealized representation of Hurricane Gilbert (1988) using the GFDL's Modular Ocean Model version 2 (MOM2) is given. Then the two-way interactions between a TOGA COARE squall line and the tropical ocean in an idealized setting using the NRL's original Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) are shown. Finally, the mutual responses between Hurricane Opal (1995) and a Warm Core Eddy (WCE) in the Gulf of Mexico using a more recent version of COAMPS, of which the MOM2 is used as an oceanic component, are presented. Results show that the Hurricane Gilbert increases the local speed of Loop Current over 55%. The maximum increase of WCE F surface current speed is approximate 133%. The near-inertial oscillation in the WCE F persists for at least 7 IP and propagated downward to 400 m. With the effect of Gilbert, the simulated translation of WCE F to the Mexican coast is more realistic. With the WCE F effect, the storm-induced surface current speed reduces by about 50%. The near-inertial oscillation and the vertical structure in the along-track direction are also influenced. The storm-induced sea surface temperature (SST) decrease in Gilbert's wake is over 2.5oC. The simulated TOGA COARE squall line from idealized conditions reproduces most of the features as observed. The squall line-induced SST decrease is about 0.21oC, resulting in about 10% less surface heat fluxes and weaker convective motions. The coupled system using real data is capable of reproducing the observed Hurricane Opal intensity. The simulated track is located directly over the simulated WCE. Maximum induced SST cooling behind the storm is 2oC, whereas this cooling is

  11. Coupled fvGCM-GCE Modeling System, TRMM Latent Heating and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2004-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to imiprove the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D GCE model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF will be developed by the end of 2004 and production runs will be conducted at the beginning of 2005. The purpose of this proposal is to augment the current Goddard MMF and other cloud modeling activities. I this talk, I will present: (1) A summary of the second Cloud Modeling Workshop took place at NASA Goddard, (2) A summary of the third TRMM Latent Heating Workshop took place at Nara Japan, (3) A brief discussion on the Goddard research plan of using Weather Research Forecast (WRF) model, and (4) A brief discussion on the GCE model on developing a global cloud simulator.

  12. Coupled fvGCM-GCE Modeling System: TRMM Latent Heating and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D GCE model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF will be developed by the end of 2004 and production runs will be conducted at the beginning of 2005. The purpose of this proposal is to augment the current Goddard MMF and other cloud modeling activities. In this talk, I will present: (1) A summary of the second Cloud Modeling Workshop took place at NASA Goddard, (2) A summary of the third TRMM Latent Heating Workshop took place at Nara Japan, (3) A brief discussion on the GCE model on developing a global cloud simulator.

  13. Coupled fvGCM-GCE Modeling System, 3D Cloud-Resolving Model and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional singlecolumn models in simulating various types of clouds and cloud systems from Merent geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloudscale model (termed a super-parameterization or multiscale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameteridon NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D Goddard cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF in being developed and production nms will be conducted at the beginning of 2005. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes, (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), (3) A cloud library generated by Goddard MMF, and 3D GCE model, and (4) A brief discussion on the GCE model on developing a global cloud simulator.

  14. Coupled fvGCM-GCE Modeling System, 3D Cloud-Resolving Model and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud- resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF in being developed and production runs will be conducted at the beginning of 2005. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes, ( 2 ) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), (3) A cloud library generated by Goddard MMF, and 3D GCE model, and (4) A brief discussion on the GCE model on developing a global cloud simulator.

  15. Coupled fvGCM-GCE Modeling System, TRMM Latent Heating and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2004-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to imiprove the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D GCE model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF will be developed by the end of 2004 and production runs will be conducted at the beginning of 2005. The purpose of this proposal is to augment the current Goddard MMF and other cloud modeling activities. I this talk, I will present: (1) A summary of the second Cloud Modeling Workshop took place at NASA Goddard, (2) A summary of the third TRMM Latent Heating Workshop took place at Nara Japan, (3) A brief discussion on the Goddard research plan of using Weather Research Forecast (WRF) model, and (4) A brief discussion on the GCE model on developing a global cloud simulator.

  16. Coupled fvGCM-GCE Modeling System, 3D Cloud-Resolving Model and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud- resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF in being developed and production runs will be conducted at the beginning of 2005. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes, ( 2 ) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), (3) A cloud library generated by Goddard MMF, and 3D GCE model, and (4) A brief discussion on the GCE model on developing a global cloud simulator.

  17. Coupled fvGCM-GCE Modeling System, 3D Cloud-Resolving Model and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional singlecolumn models in simulating various types of clouds and cloud systems from Merent geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloudscale model (termed a super-parameterization or multiscale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameteridon NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D Goddard cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF in being developed and production nms will be conducted at the beginning of 2005. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes, (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), (3) A cloud library generated by Goddard MMF, and 3D GCE model, and (4) A brief discussion on the GCE model on developing a global cloud simulator.

  18. Coupled fvGCM-GCE Modeling System: TRMM Latent Heating and Cloud Library

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. A seed fund is available at NASA Goddard to build a MMF based on the 2D GCE model and the Goddard finite volume general circulation model (fvGCM). A prototype MMF will be developed by the end of 2004 and production runs will be conducted at the beginning of 2005. The purpose of this proposal is to augment the current Goddard MMF and other cloud modeling activities. In this talk, I will present: (1) A summary of the second Cloud Modeling Workshop took place at NASA Goddard, (2) A summary of the third TRMM Latent Heating Workshop took place at Nara Japan, (3) A brief discussion on the GCE model on developing a global cloud simulator.

  19. A System of Conservative Regridding for Ice-Atmosphere Coupling in a General Circulation Model (GCM)

    NASA Technical Reports Server (NTRS)

    Fischer, R.; Nowicki, S.; Kelley, M.; Schmidt, G. A.

    2014-01-01

    The method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields for use in one-way studies coupling atmospheres and ice flow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded and five transformations between those grids required by a typical coupled atmosphere-ice flow model. This paper develops a theoretical framework for the problem and shows how each of these transformations may be achieved in a consistent, conservative manner. These transformations are implemented in Glint2, a library used to couple atmosphere models with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

  20. Technical Report Series on Global Modeling and Data Assimilation. Volume 22; A Coupled Ocean-Atmosphere Radiative Model for Global Ocean Biogeochemical Models

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Suarez, Max J. (Editor)

    2002-01-01

    An ocean-atmosphere radiative model (OARM) evaluates irradiance availability and quality in the water column to support phytoplankton growth and drive ocean thermodynamics. An atmospheric component incorporates spectral and directional effects of clear and cloudy skies as a function of atmospheric optical constituents, and spectral reflectance across the air-sea interface. An oceanic component evaluates the propagation of spectral and directional irradiance through the water column as a function of water, five phytoplankton groups, and chromophoric dissolved organic matter. It tracks the direct and diffuse streams from the atmospheric component, and a third stream, upwelling diffuse irradiance. The atmospheric component of OARM was compared to data sources at the ocean surface with a coefficient of determination (r2) of 0.97 and a root mean square of 12.1%.

  1. Climatic impacts of stochastic air-sea fluxes in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Williams, P. D.

    2009-04-01

    Air-sea fluxes of heat and moisture contain structures too small to be explicitly resolved by global coupled atmosphere-ocean general circulation models (GCMs). In the air-sea moisture flux, for example, small-scale precipitation structures could be caused by unresolved clouds and small-scale evaporation structures could be caused by unresolved turbulence in the surface wind field. In an attempt to capture the climatic impacts of such structures, coupled GCM experiments are performed in which the air-sea fluxes are stochastically perturbed. Stochastic approaches are used increasingly widely by climate modellers (e.g. Palmer and Williams, 2008). The stochasticity impacts significantly upon the simulated mean climate, especially in the tropics. A physical mechanism to explain the impacts is proposed: the ocean responds asymmetrically to random positive and negative surface buoyancy perturbations, systematically deepening the mixed layer, cooling the equatorial surface ocean, and weakening the atmospheric Hadley circulation. The experiments therefore yield a new mechanistic understanding of the detailed climatic impacts of stochastic air-sea fluxes. Reference Tim Palmer and Paul Williams (Editors), Stochastic Physics and Climate Modelling, special issue of Philosophical Transactions of the Royal Society A, 366(1875), pp 2419-2641, 2008. http://publishing.royalsociety.org/stochastic-climate

  2. Mechanisms of Internally Generated Multidecadal Variability of SST in the Atlantic Ocean in a Coupled GCM

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Schneider, Edwin; Wu, Zhiwei

    2015-04-01

    Mechanisms of the internally generated multidecadal variability of SST in the Atlantic Ocean are investigated in a long control simulation of the Community Climate System Model version 3 with constant external forcing. The interactive ensemble (IE) coupling strategy, with an ensemble of atmospheric GCMs (AGCM) coupled to an ocean model, a sea-ice model and a land model, is used to diagnose the roles of various processes in the coupled GCM (CGCM). The noise components of heat flux, wind stress and fresh water flux of the control simulation, determined from the CGCM surface fluxes by subtracting the SST-forced surface fluxes, estimated as the ensemble mean of AGCM simulations, are applied at the ocean surface of the IE in different regions and in different combinations. The IE simulations demonstrate that the climate variability in the control simulation is predominantly forced by noise. The local noise forcing is found to be responsible for the SST variability in the Atlantic Ocean, with noise heat flux and noise wind stress playing a critical role. The control run Atlantic multidecadal variability (AMV) index is decomposed into interannual, decadal, multidecadal and centennial modes based on the ensemble empirical mode decomposition, and the multidecadal mode of 50-year period is examined in detail. The North Atlantic Oscillation (NAO) pattern in the atmosphere, dominated by the noise component, forces the AMV 50-year mode through noise heat flux and noise wind stress. The noise wind stress forcing on AMV is associated with ocean dynamics, including gyre adjustment and the Atlantic Meridional Overturning Circulation. The atmospheric response to SST, including the SST-forced heat flux and SST-forced wind stress, acts as a damping on AMV.

  3. Atmospheric Heat Transport Feedbacks to Freshwater Forcing in the Coupled GCM GISS Model

    NASA Astrophysics Data System (ADS)

    Legrande, A. N.; Schmidt, G. A.

    2005-12-01

    We perform a range of North Atlantic fresh water forcing simulations in the GISS ModelE coupled GCM. Here we present results from two sets of experiments designed to explore the sensitivity of the model to varying fresh water pulses: (1) 12 relatively small simulations emulate the magnitude and placement of 8kyr event and (2) much larger and longer PhosMIP2 hosing experiments (0.1 Sv rate and 1 Sv rate). We find that within the first set of simulations, the modeled THC response to the freshwater forcing is stochastic - the largest volume of fresh water produces neither the largest response, nor the longest perturbation of THC. We evaluate the nature of modeled THC response given (1) a range of volumes, rates, and lengths of freshwater forcing; (2) two locations of fresh water input; and (3) two base states prior to the freshwater forcing. In all simulations, reduced overturning circulation in the Atlantic results in reduced northward heat transport by the ocean (OHT); we evaluate the response of heat transport in the atmosphere (AHT) and address to what extent the rest of the climate system compensates for the reduced OHT.

  4. Tropical Pacific impacts of convective momentum transport in the SNU coupled GCM

    NASA Astrophysics Data System (ADS)

    Kim, Daehyun; Kug, Jong-Seong; Kang, In-Sik; Jin, Fei-Fei; Wittenberg, Andrew T.

    2008-08-01

    Impacts of convective momentum transport (CMT) on tropical Pacific climate are examined, using an atmospheric (AGCM) and coupled GCM (CGCM) from Seoul National University. The CMT scheme affects the surface mainly via a convection-compensating atmospheric subsidence which conveys momentum downward through most of the troposphere. AGCM simulations—with SSTs prescribed from climatological and El Nino Southern Oscillation (ENSO) conditions—show substantial changes in circulation when CMT is added, such as an eastward shift of the climatological trade winds and west Pacific convection. The CMT also alters the ENSO wind anomalies by shifting them eastward and widening them meridionally, despite only subtle changes in the precipitation anomaly patterns. During ENSO, CMT affects the low-level winds mainly via the anomalous convection acting on the climatological westerly wind shear over the central Pacific—so that an eastward shift of convection transfers more westerly momentum toward the surface than would occur without CMT. By altering the low-level circulation, the CMT further alters the precipitation, which in turn feeds back on the CMT. In the CGCM, CMT affects the simulated climatology by shifting the mean convection and trade winds eastward and warming the equatorial SST; the ENSO period and amplitude also increase. In contrast to the AGCM simulations, CMT substantially alters the El Nino precipitation anomaly patterns in the CGCM. Also discussed are possible impacts of the CMT-induced changes in climatology on the simulated ENSO.

  5. Performance of an upper-ocean model coupled to an atmospheric GCM: preliminary results. Vol. 2

    SciTech Connect

    Pollard, D.

    1982-02-01

    A global dynamical model of the upper ocean and sea ice is coupled to the OSU atmospheric general circulation model. Preliminary results are described from a 16-month simulation with seasonally-varying insolation, and compared with both observations and the results from two earlier experiments with simpler upper-ocean models. The present ocean model consists of two vertically homogeneous layers of variable thickness: the upper layer represents the well-mixed layer and can entrain or detrain fluid locally with the lower layer, as in standard mixed-layer models. The second layer typically has thicknesses of approx.100 to approx.400 meters and crudely represents the seasonal thermocline and the part of the main thermocline involved in the subtropical gyres; it rests immiscibly on deep water of no motion where the density contrast is prescribed. Horizontal advection is predicted in both layers by the primitive momentum equations. Sea ice can form if the upper-layer temperature (SST) drops to freezing, after which the local ice thickness is predicted thermo-dynamically with ice dynamics neglected. The 16-month simulation is started from relatively realistic conditions obtained by spinning up the atmospheric and oceanic models separately. After several months of the coupled run, errors of up to 4/sup 0/C in the SST appear in the western oceans, probably due to the underestimate of the western boundary currents inherent in coarse-grid oceanic models. Equatorial upwelling and undercurrents are simulated but extend basin-wide, producing SSTs up to 6/sup 0/C too cold in the western equatorial Pacific. The large-scale seasonal variation of sea-ice thickness and extent are fairly realistic. Surface heat fluxes are compared with observations and with an earlier control integration of the atmospheric GCM, in an effort to distinguish between errors in the SST caused by the upper-ocean model and those caused by the atmospheric model. 38 refs., 11 figs.

  6. Oceanic-atmospheric variability and western U.S. snowfall

    NASA Astrophysics Data System (ADS)

    Hunter, Thad; Tootle, Glenn; Piechota, Thomas

    2006-07-01

    A study of the influences of interdecadal and interannual oceanic-atmospheric influences on April 1 Snow-Water Equivalent (SWE) in the western U.S. is presented. SWE data was identified at 323 Natural Resources Conservation Service (NRCS) SNOTEL (SNOwpack TELemetrysites) stations for the period of 1961 to 2004 and for 121 SNOTEL stations for the period 1941 to 2004. The phases (cold/negative or warm/positive) of Pacific Ocean [El Niño -Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)] and Atlantic Ocean [Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO)] oceanic-atmospheric influences were identified for the year prior to the SWE data set. Statistical significance testing of SWE data set, based on the interdecadal and interannual oceanic-atmospheric phase (warm/positive or cold/negative) was performed by applying the nonparametric rank-sum test. The results show that in addition to the well established ENSO signal in the northwest, the PDO and AMO influence SWE variability. Additionally, the coupled effects of the oceanic-atmospheric influences were evaluated on the basis of the long-term phase (cold/negative or warm/positive) of the interdecadal (PDO, AMO, NAO) influences and the interannual ENSO. Finally, the coupled effects of the oceanic-atmospheric influences were evaluated on the basis of the long-term phase (cold/negative or warm/positive) of the interdecadal (AMO, PDO, NAO) phenomena. Regions in the west were identified that responded to the interdecadal/decadal climatic coupling. By utilizing the April 1 SWE and the long lead-time approach for the oceanic-atmospheric variables, useful information can be provided to snow forecasters and water managers.

  7. Wave Coupling in the Earth's Atmosphere: TIME-GCM Simulations of Variable Tidal Effects

    NASA Astrophysics Data System (ADS)

    Hagan, Maura; Maute, Astrid; Zhang, Xiaoli; Forbes, Jeffrey M.; Roble, Raymond; Oberheide, Jens

    We report on the tidal characteristics and their impact on the Earth's atmosphere as determined from a series of National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) simulations. We assess the TIME-GCM performance by comparing the model results with extant observational tidal diagnostics. We also investigate the sensitivity of TIME-GCM performance to variable tro-pospheric forcing schemes with particular attention to their impact on upper atmospheric tidal signatures. Toward this end, we introduce tidal perturbations associated with Interna-tional Satellite Cloud Climatology Project (ISCCP) and Tropical Rainfall Measuring Mission (TRMM) data, as well as tidal components inferred from Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite observations, at the model lower boundary (ca. 30 km). Finally, we investigate the role of mean winds and wave-wave interactions on the tidal components that propagate into the upper atmosphere by contrasting them with linear tidal model results.

  8. Performance of a Dynamic Initialization Scheme in the Coupled Ocean-Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS-TC)

    DTIC Science & Technology

    2011-10-01

    Performance of a Dynamic Initialization Scheme in the Coupled Ocean –Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS-TC) ERIC A...initialization scheme was tested on multiple tropical cyclones during 2008 and 2009 in the North Atlantic and western North Pacific Ocean basins using the...Naval Research Laboratory’s tropical cyclone version of the Coupled Ocean –Atmosphere Mesoscale Prediction System (COAMPS-TC). The use of this

  9. Coupling of a Simple 3-Layer Snow Model to GISS GCM

    NASA Astrophysics Data System (ADS)

    Aleinov, I.

    2001-12-01

    Appropriate simulation of the snow cover dynamics is an important issue for the General Circulation Models (GCMs). The presence of snow has a significant impact on ground albedo and on heat and moisture balance. A 3-layer snow model similar to the one proposed by Lynch-Stieglitz was developed with the purpose of using it inside the GCM developed in the NASA Goddard Institute for Space Studies (GISS). The water transport between the layers is modeled explicitly while the heat balance is computed implicitly between the snow layers and semi-implicitly on the surface. The processes of melting and refreezing and compactification of layers under the gravitational force are modeled appropriately. It was noticed that implicit computation of the heat transport can cause a significant under- or over-estimation of the incoming heat flux when the temperature of the upper snow layer is equal to 0 C. This may lead in particular to delayed snow melting in spring. To remedy this problem a special flux-control algorithm was added to the model, which checks computed flux for possible errors and if such are detected the heat transport is recomputed again with the appropriate corrections. The model was tested off-line with Sleepers River forcing data and exhibited a good agreement between simulated and observed quantities for snow depth, snow density and snow temperature. The model was then incorporated into the GISS GCM. Inside the GCM the model is driven completely by the data simulated by other parts of the GCM. The screening effect of the vegetation is introduced by means of masking depth. For a thin snowpack a fractional cover is implemented so that the total thickness of the the snow is never less then 10 cm (rather, the areal fraction of the snow cover decreases when it melts). The model was tested with 6 year long GCM speed-up runs. It proved to be stable and produced reasonable results for the global snow cover. In comparison to the old GISS GCM snow model (which was

  10. A Coupled GCM-Cloud Resolving Modeling System, and A Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1 998 and 1999).

  11. Modeling the Effects of Tropospheric Tides on the Ionosphere using SAMI3 Coupled with TIME-GCM

    NASA Astrophysics Data System (ADS)

    McDonald, S. E.; Huba, J.; Hagan, M. E.; Maute, A. I.; Basu, S.

    2009-12-01

    Recent modeling studies performed with the NCAR thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) have shown that tides of tropospheric origin are capable of affecting the thermosphere and ionosphere and can explain the wave-four longitudinal structure that has been observed in the equatorial ionization anomaly (EIA). The eastward propagating zonal wavenumber-3 diurnal tide (DE3) has a particularly strong signature that peaks near 110 km and penetrates into the upper thermosphere. In this study, we couple the TIME-GCM thermosphere with NRL’s comprehensive 3D ionosphere model, SAMI3, in order to investigate the impact of non-migrating tides on the E- and F-region ionosphere. SAMI3 includes a potential equation to self-consistently solve for the electric field. Simulation runs have been performed for March equinox and June solstice conditions at solar minimum (F10.7 = 75.) The SAMI3 results are compared with TIME-GCM as well as with measurements of electron density and electric fields.

  12. Validation Test Report for the Coupled Ocean/Atmosphere MesoscalePrediction System (COAMPS) Version 5.0: Ocean/Wave Component Validation

    DTIC Science & Technology

    2012-12-31

    to ocean model NCOM. The ocean model passes surface currents and water levels to the wave model SWAN . Ocean-wave coupling shows improvement and...NEARSHORE ( SWAN ) MODEL ................................................................................................. 4  2.4  EARTH SYSTEM MODELING...COUPLING AND  SWAN  SENSITIVITY TO WAVE DISSIPATION AND DRAG COEFFICIENT ..................................... 7  2.7  DOCUMENT OVERVIEW

  13. Assessment of an ensemble of ocean-atmosphere coupled and uncoupled regional climate models to reproduce the climatology of Mediterranean cyclones

    NASA Astrophysics Data System (ADS)

    Flaounas, Emmanouil; Kelemen, Fanni Dora; Wernli, Heini; Gaertner, Miguel Angel; Reale, Marco; Sanchez-Gomez, Emilia; Lionello, Piero; Calmanti, Sandro; Podrascanin, Zorica; Somot, Samuel; Akhtar, Naveed; Romera, Raquel; Conte, Dario

    2016-11-01

    This study aims to assess the skill of regional climate models (RCMs) at reproducing the climatology of Mediterranean cyclones. Seven RCMs are considered, five of which were also coupled with an oceanic model. All simulations were forced at the lateral boundaries by the ERA-Interim reanalysis for a common 20-year period (1989-2008). Six different cyclone tracking methods have been applied to all twelve RCM simulations and to the ERA-Interim reanalysis in order to assess the RCMs from the perspective of different cyclone definitions. All RCMs reproduce the main areas of high cyclone occurrence in the region south of the Alps, in the Adriatic, Ionian and Aegean Seas, as well as in the areas close to Cyprus and to Atlas mountains. The RCMs tend to underestimate intense cyclone occurrences over the Mediterranean Sea and reproduce 24-40 % of these systems, as identified in the reanalysis. The use of grid nudging in one of the RCMs is shown to be beneficial, reproducing about 60 % of the intense cyclones and keeping a better track of the seasonal cycle of intense cyclogenesis. Finally, the most intense cyclones tend to be similarly reproduced in coupled and uncoupled model simulations, suggesting that modeling atmosphere-ocean coupled processes has only a weak impact on the climatology and intensity of Mediterranean cyclones.

  14. Assimilation of satellite color observations in a coupled ocean GCM-ecosystem model

    NASA Technical Reports Server (NTRS)

    Sarmiento, Jorge L.

    1992-01-01

    Monthly average coastal zone color scanner (CZCS) estimates of chlorophyll concentration were assimilated into an ocean global circulation model(GCM) containing a simple model of the pelagic ecosystem. The assimilation was performed in the simplest possible manner, to allow the assessment of whether there were major problems with the ecosystem model or with the assimilation procedure. The current ecosystem model performed well in some regions, but failed in others to assimilate chlorophyll estimates without disrupting important ecosystem properties. This experiment gave insight into those properties of the ecosystem model that must be changed to allow data assimilation to be generally successful, while raising other important issues about the assimilation procedure.

  15. Decadal to multi-decadal scale variability of Indian summer monsoon rainfall in the coupled ocean-atmosphere-chemistry climate model SOCOL-MPIOM

    NASA Astrophysics Data System (ADS)

    Malik, Abdul; Brönnimann, Stefan; Stickler, Alexander; Raible, Christoph C.; Muthers, Stefan; Anet, Julien; Rozanov, Eugene; Schmutz, Werner

    2017-01-01

    The present study is an effort to deepen the understanding of Indian summer monsoon rainfall (ISMR) on decadal to multi-decadal timescales. We use ensemble simulations for the period AD 1600-2000 carried out by the coupled Atmosphere-Ocean-Chemistry-Climate Model (AOCCM) SOCOL-MPIOM. Firstly, the SOCOL-MPIOM is evaluated using observational and reanalyses datasets. The model is able to realistically simulate the ISMR as well as relevant patterns of sea surface temperature and atmospheric circulation. Further, the influence of Atlantic Multi-decadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) variability on ISMR is realistically simulated. Secondly, we investigate the impact of internal climate variability and external climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that AMO, PDO, and Total Solar Irradiance (TSI) play a considerable role in controlling the wet and dry decades of ISMR. Resembling observational findings most of the dry decades of ISMR occur during a negative phase of AMO and a simultaneous positive phase of PDO. The observational and simulated datasets reveal that on decadal to multi-decadal timescales the ISMR has consistent negative correlation with PDO whereas its correlation with AMO and TSI is not stationary over time.

  16. On the connection between continental-scale land surface processes and the tropical climate in a coupled ocean-atmosphere-land system

    NASA Astrophysics Data System (ADS)

    Ma, H.; Mechoso, C. R.; Xue, Y.; Xiao, H.; Neelin, J.; Ji, X.

    2013-12-01

    An evaluation is presented of the impact on tropical climate of continental-scale perturbations given by different representations of land surface processes (LSP) in a general circulation model that includes atmosphere-ocean interactions. One representation is a simple land scheme, which specifies climatological albedos and soil moisture availability. The other representation is the more comprehensive Simplified Simple Biosphere Model, which allows for interactive soil moisture and vegetation biophysical processes. The results demonstrate that such perturbations have strong impacts on the seasonal mean states and seasonal cycles of global precipitation, clouds, and surface air temperature. The impact is especially significant over the tropical Pacific Ocean. To explore the mechanisms for such impact, model experiments are performed with different LSP representations confined to selected continental-scale regions where strong interactions of climate-vegetation biophysical processes are present. The largest impact found over the tropical Pacific is mainly from perturbations in the tropical African continent where convective heating anomalies associated with perturbed surface heat fluxes trigger global teleconnections through equatorial wave dynamics. In the equatorial Pacific, the remote impacts of the convection anomalies are further enhanced by strong air-sea coupling between surface wind stress and upwelling, as well as by the effects of ocean memory. LSP perturbations over South America and Asia-Australia have much weaker global impacts. The results further suggest that correct representations of LSP, land use change, and associated changes in the deep convection over tropical Africa are crucial to reducing the uncertainty of future climate projections with global climate models under various climate change scenarios. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA

  17. On the connection between continental-scale land surface processes and the tropical climate in a coupled ocean-atmosphere-land system

    SciTech Connect

    Ma, Hsi-Yen; Mechoso, C. R.; Xue, Yongkang; Xiao, Heng; Neelin, David; Ji, Xuan

    2013-11-15

    The impact of global tropical climate to perturbations in land surface processes (LSP) are evaluated using perturbations given by different LSP representations of continental-scale in a global climate model that includes atmosphere-ocean interactions. One representation is a simple land scheme, which specifies climatological albedos and soil moisture availability. The other representation is the more comprehensive Simplified Simple Biosphere Model, which allows for interactive soil moisture and vegetation biophysical processes. The results demonstrate that LSP processes such as interactive soil moisture and vegetation biophysical processes have strong impacts on the seasonal mean states and seasonal cycles of global precipitation, clouds, and surface air temperature. The impact is especially significant over the tropical Pacific. To explore the mechanisms for such impact, different LSP representations are confined to selected continental-scale regions where strong interactions of climate-vegetation biophysical processes are present. We find that the largest impact is mainly from LSP perturbations over the tropical African continent. The impact is through anomalous convective heating in tropical Africa due to changes in the surface heat fluxes, which in turn affect basinwide teleconnections in the Pacific through equatorial wave dynamics. The modifications in the equatorial Pacific climate are further enhanced by strong air-sea coupling between surface wind stress and upwelling, as well as effect of ocean memory. Our results further suggest that correct representations of land surface processes, land use change and the associated changes in the deep convection over tropical Africa are crucial to reducing the uncertainty when performing future climate projections under different climate change scenarios.

  18. Ocean-atmosphere dynamics during Hurricane Ida and Nor'Ida: An application of the coupled ocean-;atmosphere–wave–sediment transport (COAWST) modeling system

    USGS Publications Warehouse

    Olabarrieta, Maitane; Warner, John C.; Armstrong, Brandy N.; Zambon, Joseph B.; He, Ruoying

    2012-01-01

    The coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system was used to investigate atmosphere–ocean–wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor'Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor'easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor'Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness

  19. A Coupled GCM-Cloud Resolving Modeling System, and a Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CFWs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1 998 and 1999). In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) A discussion on the Goddard WRF version (its developments and applications).

  20. A Coupled fcGCM-GCE Modeling System: A 3D Cloud Resolving Model and a Regional Scale Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and ore sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1998 and 1999). Also, at Goddard, we have implemented several Goddard microphysical schemes (21CE, several 31CE), Goddard radiation (including explicity calculated cloud optical properties), and Goddard Land Information (LIS, that includes the CLM and NOAH land surface models) into a next generation regional scale model, WRF. In this talk, I will present: (1) A Brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), (3) A discussion on the Goddard WRF version (its developments and applications), and (4) The characteristics of the four-dimensional cloud data

  1. A Coupled GCM-Cloud Resolving Modeling System, and a Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2007-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a superparameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1998 and 1999). Also, at Goddard, we have implemented several Goddard microphysical schemes (2ICE, several 31CE), Goddard radiation (including explicitly calculated cloud optical properties), and Goddard Land Information (LIS, that includes the CLM and NOAH land surface models) into a next generatio11 regional scale model, WRF. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) A discussion on the Goddard WRF version (its developments and applications).

  2. A Coupled GCM-Cloud Resolving Modeling System, and A Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1998 and 1999). Also, at Goddard, we have implemented several Goddard microphysical schemes (21CE, several 31CE), Goddard radiation (including explicitly calculated cloud optical properties), and Goddard Land Information (LIS, that includes the CLM and NOAH land surface models) into a next generation regional scale model, WRF. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) A discussion on the Goddard WRF version (its developments and applications).

  3. A Coupled fcGCM-GCE Modeling System: A 3D Cloud Resolving Model and a Regional Scale Model

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2005-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and ore sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1998 and 1999). Also, at Goddard, we have implemented several Goddard microphysical schemes (21CE, several 31CE), Goddard radiation (including explicity calculated cloud optical properties), and Goddard Land Information (LIS, that includes the CLM and NOAH land surface models) into a next generation regional scale model, WRF. In this talk, I will present: (1) A Brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), (3) A discussion on the Goddard WRF version (its developments and applications), and (4) The characteristics of the four-dimensional cloud data

  4. A Coupled GCM-Cloud Resolving Modeling System, and a Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2007-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a superparameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1998 and 1999). Also, at Goddard, we have implemented several Goddard microphysical schemes (2ICE, several 31CE), Goddard radiation (including explicitly calculated cloud optical properties), and Goddard Land Information (LIS, that includes the CLM and NOAH land surface models) into a next generatio11 regional scale model, WRF. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) A discussion on the Goddard WRF version (its developments and applications).

  5. A Coupled GCM-Cloud Resolving Modeling System, and a Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CFWs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1 998 and 1999). In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) A discussion on the Goddard WRF version (its developments and applications).

  6. A Coupled GCM-Cloud Resolving Modeling System, and A Regional Scale Model to Study Precipitation Processes

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo

    2006-01-01

    Recent GEWEX Cloud System Study (GCSS) model comparison projects have indicated that cloud-resolving models (CRMs) agree with observations better than traditional single-column models in simulating various types of clouds and cloud systems from different geographic locations. Current and future NASA satellite programs can provide cloud, precipitation, aerosol and other data at very fine spatial and temporal scales. It requires a coupled global circulation model (GCM) and cloud-scale model (termed a super-parameterization or multi-scale modeling framework, MMF) to use these satellite data to improve the understanding of the physical processes that are responsible for the variation in global and regional climate and hydrological systems. The use of a GCM will enable global coverage, and the use of a CRM will allow for better and more sophisticated physical parameterization. NASA satellite and field campaign cloud related datasets can provide initial conditions as well as validation for both the MMF and CRMs. The Goddard MMF is based on the 2D Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume general circulation model (fvGCM), and it has started production runs with two years results (1998 and 1999). Also, at Goddard, we have implemented several Goddard microphysical schemes (21CE, several 31CE), Goddard radiation (including explicitly calculated cloud optical properties), and Goddard Land Information (LIS, that includes the CLM and NOAH land surface models) into a next generation regional scale model, WRF. In this talk, I will present: (1) A brief review on GCE model and its applications on precipitation processes (microphysical and land processes), (2) The Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) A discussion on the Goddard WRF version (its developments and applications).

  7. Simulation of the tropical oceans with an ocean GCM coupled to an atmospheric mixed-layer model

    SciTech Connect

    Murtugudde, R.; Seager, R.; Busalacchi, A.

    1996-08-01

    A reduced gravity, primitive equation, ocean general circulation model (GCM) is coupled to an advective atmospheric mixed-layer (AML) model to demonstrate the importance of a nonlocal atmospheric mixed-layer parameterization for a proper simulation of surface heat fluxes and sea surface temperatures (SST). Seasonal variability of the model SSTs and the circulation are generally in good agreement with the observations in each of the tropical oceans. These results are compared to other simulations that use a local equilibrium mixed-layer model. Inclusion of the advective AML model is demonstrated to lead to a significant improvement in the SST simulation in all three oceans. Advection and diffusion of the air humidity play significant roles in determining SSTs even in the tropical Pacific where the local equilibrium assumption was previously deemed quite accurate. The main, and serious, model flaw is an inadequate representation of the seasonal cycle in the upwelling regions of the eastern Atlantic and Pacific Oceans. The results indicate that the feedback between mixed-layer depths and SSTs can amplify SST errors, implying that increased realism in the modeling of the ocean mixed layer increases the demand for realism in the representation of the surface heat fluxes. The performance of the GCM with a local-equilibrium mixed-layer model in the Atlantic is as poor as previous simple ocean model simulations of the Atlantic. The conclusion of earlier studies that the simple ocean model was at fault may, in fact, not be correct. Instead the local-equilibrium heat flux parameterization appears to have been the major source of error. Accurate SST predictions may, hence, be feasible by coupling the AML model to computationally efficient simple ocean models. 69 refs., 18 figs., 1 tab.

  8. Earth's Climate: The Ocean-Atmosphere Interaction

    NASA Astrophysics Data System (ADS)

    Lifland, Jonathan

    2004-11-01

    A new AGU book, Earth's Climate: The Ocean-Atmosphere Interaction, edited by Chunzai Wang, Shang-Ping Xie, and James A. Carton, presents current observations, theories, and models of ocean-atmosphere interaction that helps shape climate and its variations over the global ocean. The book represents the climate community's first effort to summarize the modern science of ocean-atmosphere interaction and the roles that the interaction play in climate variability in the Pacific, Atlantic, and Indian Oceans as well as interactions across basins and between the tropics and extratropics. In this issue, Eos talks with lead editor Chunzai Wang. Wang is a research oceanographer at the Physical Oceanography Division of the National Oceanic and Atmospheric Administration's Atlantic Oceanographic and Meteorological Laboratory, in Miami, Florida.

  9. A comparison of observed extreme water levels at the German Bight elaborated through an extreme value analysis (EVA) with extremes derived from a regionally coupled ocean-atmospheric climate model (MPI-OM)

    NASA Astrophysics Data System (ADS)

    Möller, Jens; Heinrich, Hartmut

    2017-04-01

    As a consequence of climate change atmospheric and oceanographic extremes and their potential impacts on coastal regions are of growing concern for governmental authorities responsible for the transportation infrastructure. Highest risks for shipping as well as for rail and road traffic originate from combined effects of extremes of storm surges and heavy rainfall which sometimes lead to insufficient dewatering of inland waterways. The German Ministry of Transport and digital Infrastructure therefore has tasked its Network of Experts to investigate the possible evolutions of extreme threats for low lands and especially for Kiel Canal, which is an important shortcut for shipping between the North and Baltic Seas. In this study we present results of a comparison of an Extreme Value Analysis (EVA) carried out on gauge observations and values derived from a coupled Regional Ocean-Atmosphere Climate Model (MPI-OM). High water levels at the coasts of the North and Baltic Seas are one of the most important hazards which increase the risk of flooding of the low-lying land and prevents such areas from an adequate dewatering. In this study changes in the intensity (magnitude of the extremes) and duration of extreme water levels (above a selected threshold) are investigated for several gauge stations with data partly reaching back to 1843. Different methods are used for the extreme value statistics, (1) a stationary general Pareto distribution (GPD) model as well as (2) an instationary statistical model for better reproduction of the impact of climate change. Most gauge stations show an increase of the mean water level of about 1-2 mm/year, with a stronger increase of the highest water levels and a decrease (or lower increase) of the lowest water levels. Also, the duration of possible dewatering time intervals for the Kiel-Canal was analysed. The results for the historical gauge station observations are compared to the statistics of modelled water levels from the coupled

  10. The impacts of precipitating cloud radiative effects on ocean surface evaporation, precipitation, and ocean salinity in coupled GCM simulations

    NASA Astrophysics Data System (ADS)

    Li, J.-L. F.; Wang, Yi-Hui; Lee, Tong; Waliser, Duane; Lee, Wei-Liang; Yu, Jia-Yuh; Chen, Yi-Chun; Fetzer, Eric; Hasson, Audrey

    2016-08-01

    The coupled global climate model (GCM) fidelity in representing upper ocean salinity including near sea surface bulk salinity (SSS) is evaluated in this study, with a focus on the Pacific Ocean. The systematic biases in ocean surface evaporation (E) minus precipitation (P) and SSS are found to be fairly similar in the twentieth century simulations of the Coupled Model Intercomparison Phase 3 (CMIP3) and Phase 5 (CMIP5) relative to the observations. One of the potential causes of the CMIP model biases is the missing representation of the radiative effects of precipitating hydrometeors (i.e., snow) in most CMIP models. To examine the radiative effect of cloud snow on SSS, sensitivity experiments with and without such effect are conducted by the National Center for Atmospheric Research-coupled Community Earth System Model (CESM). This study investigates the difference in SSS between sensitivity experiments and its relationship with atmospheric circulation, E - P and air-sea heat fluxes. It is found that the exclusion of the cloud snow radiative effect in CESM produces weaker Pacific trade winds, resulting in enhanced precipitation, reduced evaporation, and a reduction of the upper ocean salinity in the tropical and subtropical Pacific. The latter results in an improved comparison with climatological upper ocean bulk salinity. The introduction of cloud snow also altered the budget terms that maintain the time-mean salinity in the mixed layer.

  11. A Discussion on the Errors in the Surface Heat Fluxes Simulated by a Coupled GCM.

    NASA Astrophysics Data System (ADS)

    Yu, Jin-Yi; Mechoso, Carlos R.

    1999-02-01

    This paper contrasts the sea surface temperature (SST) and surface heat flux errors in the Tropical Pacific simulated by the University of California, Los Angeles, coupled atmosphere-ocean general circulation model (CGCM) and by its atmospheric component (AGCM) using prescribed SSTs. The usefulness of such a comparison is discussed in view of the sensitivities of the coupled system.Off the equator, the CGCM simulates more realistic surface heat fluxes than the AGCM, except in the eastern Pacific south of the equator where the coupled model produces a spurious intertropical convergence zone. The AGCM errors are dominated by excessive latent heat flux, except in the stratus regions along the coasts of California and Peru where errors are dominated by excessive shortwave flux. The CGCM tends to balance the AGCM errors by either correctly decreasing the evaporation at the expense of cold SST biases or erroneously increasing the evaporation at the expense of warm SST biases.At the equator, errors in simulated SSTs are amplified by the feedbacks of the coupled system. Over the western equatorial Pacific, the CGCM produces a cold SST bias that is a manifestation of a spuriously elongated cold tongue. The AGCM produces realistic values of surface heat flux. Over the cold tongue in the eastern equatorial Pacific, the CGCM simulates realistic annual variations in SST. In the simulation, however, the relationship between variations in SST and surface latent heat flux corresponds to a negative feedback, while in the observation it corresponds to a positive feedback. Such an erroneous feature of the CGCM is linked to deficiencies in the simulation of the cross-equatorial component of the surface wind. The reasons for the success in the simulation of SST in the equatorial cold tongue despite the erroneous surface heat flux are examined.

  12. Sensitivity of the thermohaline circulation in coupled oceanic GCM — atmospheric EBM experiments

    NASA Astrophysics Data System (ADS)

    Lohmann, Gerrit; Gerdes, Rüdiger; Chen, Deliang

    1996-05-01

    We analyze the sensitivity of the oceanic thermohaline circulation (THC) regarding perturbations in fresh water flux for a range of coupled oceanic general circulation — atmospheric energy balance models. The energy balance model (EBM) predicts surface air temperature and fresh water flux and contains the feedbacks due to meridional transports of sensible and latent heat. In the coupled system we examine a negative perturbation in run-off into the southern ocean and analyze the role of changed atmospheric heat transports and fresh water flux. With mixed boundary conditions (fixed air temperature and fixed surface fresh water fluxes) the response is characterized by a completely different oceanic heat transport than in the reference case. On the other hand, the surface heat flux remains roughly constant when the air temperature can adjust in a model where no anomalous atmospheric transports are allowed. This gives an artificially stable system with nearly unchanged oceanic heat transport. However, if meridional heat transports in the atmosphere are included, the sensitivity of the system lies between the two extreme cases. We find that changes in fresh water flux are unimportant for the THC in the coupled system.

  13. Tropical Cyclones-Ocean Interactions in a High Resolution GCM: the Role of the Coupling Frequency

    NASA Astrophysics Data System (ADS)

    Scoccimarro, E.; Fogli, P. G.; Masina, S.; Gualdi, S.; Navarra, A.

    2015-12-01

    The interaction between Tropical Cyclones (TCs) and ocean is a major mechanism responsible for energy exchange between the atmosphere and the ocean. TCs affect the thermal and dynamical structure of the ocean, but the magnitude of the impact is still uncertain. Very few CMIP5 models demonstrated ability in representing TCs, mainly due to their horizontal resolution. We aim to improve TCs representation in next CMIPs experiments through the new CMCC-CESM-NEMO General Circulation Model, having a horizontal resolution of ¼ degree in both atmospheric and ocean components. The model is capable to represent realistically TCs up to Cat-4 Typhoons. The wind structure associated with TCs is responsible for two important atmosphere-ocean feedbacks: the first feedback — positive — is driven by the latent heat associated with the enhanced evaporation rate and leads to an increase of the available energy for TC. The second feedback — negative — is due to the cold water upwelling induced by the increased wind stress at the ocean surface and by the shear-induced mixing at the base of the mixed layer. The second feedback is responsible for a significant cooling of the sea surface, leading to a weakening of the cyclone intensity due to the reduction of the total heat flux into the atmosphere. Furthermore TC intensification, intensity, and lifetime strongly depend on their transitional speed. A good representation of the TC-Ocean interaction strongly depends on the coupling frequency between the atmospheric and the ocean components, especially when simulating fast moving TCs. In this work, we investigate the role of the coupling frequency in representing the two mentioned feedbacks using the new fully coupled General Circulation Model developed at CMCC.

  14. Tropical Pacific internal atmospheric dynamics and resolution in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Lopez, Hosmay; Kirtman, Ben P.

    2015-01-01

    A noise reduction technique, namely the interactive ensemble (IE) approach is adopted to reduce noise at the air-sea interface due to internal atmospheric dynamics in a state-of-the-art coupled general circulation model (CGCM). The IE technique uses multiple realization of atmospheric general circulation models coupled to a single ocean general circulation model. The ensembles mean fluxes from the atmospheric simulations are communicated to the ocean component. Each atmospheric simulation receives the same SST coming from the ocean component. The only difference among the atmospheric simulations comes from perturbed initial conditions, thus the atmospheric states are, in principle synoptically independent. The IE technique can be used to better understand the importance of weather noise forcing of natural variability such as El Niño Southern Oscillation (ENSO). To study the impact of weather noise and resolution in the context of a CGCM, two IE experiments are performed at different resolutions. Atmospheric resolution is an important issue since the noise statistics will depend on the spatial scales resolved. A simple formulation to extract atmospheric internal variability is presented. The results are compared to their respective control cases where internal atmospheric variability is left unchanged. The noise reduction has a major impact on the coupled simulation and the magnitude of this effect strongly depends on the horizontal resolution of the atmospheric component model. Specifically, applying the noise reduction technique reduces the overall climate variability more effectively at higher resolution. This suggests that "weather noise" is more important in sustaining climate variability as resolution increases. ENSO statistics, dynamics, and phase asymmetry are all modified by the noise reduction, in particular ENSO becomes more regular with less phase asymmetry when noise is reduced. All these effects are more marked for the higher resolution case. In

  15. Ensemble-Based Parameter Estimation in a Coupled GCM Using the Adaptive Spatial Average Method

    DOE PAGES

    Liu, Y.; Liu, Z.; Zhang, S.; ...

    2014-05-29

    Ensemble-based parameter estimation for a climate model is emerging as an important topic in climate research. And for a complex system such as a coupled ocean–atmosphere general circulation model, the sensitivity and response of a model variable to a model parameter could vary spatially and temporally. An adaptive spatial average (ASA) algorithm is proposed to increase the efficiency of parameter estimation. Refined from a previous spatial average method, the ASA uses the ensemble spread as the criterion for selecting “good” values from the spatially varying posterior estimated parameter values; these good values are then averaged to give the final globalmore » uniform posterior parameter. In comparison with existing methods, the ASA parameter estimation has a superior performance: faster convergence and enhanced signal-to-noise ratio.« less

  16. Ensemble-Based Parameter Estimation in a Coupled GCM Using the Adaptive Spatial Average Method

    SciTech Connect

    Liu, Y.; Liu, Z.; Zhang, S.; Rong, X.; Jacob, R.; Wu, S.; Lu, F.

    2014-05-29

    Ensemble-based parameter estimation for a climate model is emerging as an important topic in climate research. And for a complex system such as a coupled ocean–atmosphere general circulation model, the sensitivity and response of a model variable to a model parameter could vary spatially and temporally. An adaptive spatial average (ASA) algorithm is proposed to increase the efficiency of parameter estimation. Refined from a previous spatial average method, the ASA uses the ensemble spread as the criterion for selecting “good” values from the spatially varying posterior estimated parameter values; these good values are then averaged to give the final global uniform posterior parameter. In comparison with existing methods, the ASA parameter estimation has a superior performance: faster convergence and enhanced signal-to-noise ratio.

  17. Sensitivity of a coupled atmosphere-dynamic upper ocean GCM to variations of CO2, solar constant, and orbital forcing

    NASA Astrophysics Data System (ADS)

    Syktus, Jozef; Gordon, Hal; Chappell, John

    1994-07-01

    Sensitivity of a coupled atmosphere-dynamic upper ocean general circulation model (GCM) to varying CO2, solar constant, and orbital forcing was examined. Response to atmospheric CO2 concentrations ranging from 100-3500 ppm is logarithmic at all latitudes and seasons, with highest sensitivity at high latitudes, during the winter season. Solar constant response is approximately linear over the range of values +2%, but the sensitivity at high latitudes is less than for equivalent CO2 forcing. Sensitivity to 'cold northern summer' orbital forcing, which occurred at the start of the last glacial cycle, is strongly affected by CO2. For CO2 at or below the present level, perennial snow cover in the northern hemisphere expands dramatically with 'cold summer' orbital forcing, but this effect becomes very small for CO2 levels in the range 410-460 ppm. This result suggests that the Quaternary 'ice age' mode of climatic behavior may have been initiated by an atmospheric CO2 decrease below a critical value, probably around 350-450 ppm.

  18. On the Decadal Modes of Oscillation of an Idealized Ocean-atmosphere System

    NASA Technical Reports Server (NTRS)

    Mehta, Vikram M.

    1990-01-01

    Axially-symmetric, linear, free modes of global, primitive equation, ocean-atmosphere models are examined to see if they contain decadal (10 to 30 years) oscillation time scale modes. A two-layer ocean model and a two-level atmospheric model are linearized around axially-symmetric basic states containing mean meridional circulations in the ocean and the atmosphere. Uncoupled and coupled, axially-symmetric modes of oscillation of the ocean-atmosphere system are calculated. The main conclusion is that linearized, uncoupled and coupled, ocean-atmosphere systems can contain axially-symmetric, free modes of variability on decadal time scales. These results have important implications for externally-forced decadal climate variability.

  19. Mechanisms of internally generated decadal-to-multidecadal variability of SST in the Atlantic Ocean in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Schneider, Edwin K.; Wu, Zhiwei

    2016-03-01

    Mechanisms of the internally generated decadal-to-multidecadal variability of SST in the Atlantic Ocean are investigated in a long control simulation of the Community Climate System Model version 3 with constant external forcing. The interactive ensemble (IE) coupling strategy, with an ensemble of atmospheric GCMs (AGCM) coupled to an ocean model, a sea-ice model and a land model, is used to diagnose the roles of various processes in the coupled GCM (CGCM). The noise components of heat flux, wind stress and fresh water flux of the control simulation, determined from the CGCM surface fluxes by subtracting the SST-forced surface fluxes, estimated as the ensemble mean of AGCM simulations, are applied at the ocean surface of the IE in different regions and in different combinations. The IE simulations demonstrate that the climate variability in the control simulation is predominantly forced by noise. The local noise forcing is found to be responsible for the SST variability in the Atlantic Ocean, with noise heat flux and noise wind stress playing a critical role. The control run Atlantic multidecadal variability (AMV) index is decomposed into interannual, decadal and multidecadal modes based on the ensemble empirical mode decomposition. The AMV multidecadal mode, a combination of 50- and 100-year modes, is examined in detail. The North Atlantic Oscillation (NAO) pattern in the atmosphere, dominated by the noise component, forces the multidecadal mode through noise heat flux and noise wind stress. The noise wind stress forcing on the multidecadal mode is associated with ocean dynamics, including gyre adjustment and the Atlantic Meridional Overturning Circulation (AMOC). The AMV decadal mode is also found to be related to noise NAO forcing. The associated ocean dynamics are connected with both noise heat flux and noise wind stress, but the AMOC related to the decadal mode is more likely to be forced by noise heat flux. For both multidecadal and decadal modes, the

  20. Mechanisms of interannual ocean-atmosphere interactions

    NASA Technical Reports Server (NTRS)

    Frankignoul, C.

    1984-01-01

    Results of an investigation to study the interaction between ocean and atmosphere on the annual to decadal time scale are reported. Separate studies of the ocean response to atmospheric forcing, and of atmospheric response to ocean forcing were also conducted. The main findings are the dynamics of sea surface temperature anomalies, the role of short time scale weather fluctuations in the seasonal cycle of the upper ocean variability, and the planetary wave response to sea surface temperature anomalies. A numerical model of the ocean atmosphere continent system and a two layer quasi-geostropic ocean model is discussed.

  1. The Modular Arbitrary-Order Ocean-Atmosphere Model of the RMIB: MAOOAM

    NASA Astrophysics Data System (ADS)

    De Cruz, Lesley; Demaeyer, Jonathan; Vannitsem, Stéphane

    2016-04-01

    The coupled ocean-atmosphere system exhibits a decadal variability at midlatitudes, which gives rise to the North-Atlantic Oscillation (NOA). The driving mechanism behind this variability has been the subject of much interest and debate in recent years. This conundrum was addressed using several low-order coupled ocean-atmosphere models for midlatitudes, with an increasing level of physical realism: OA-QG-WS v1 [1], v2 [2], and most recently, VDDG [3]. The VDDG-model was designed to capture the key dynamics of the coupled ocean-atmosphere system, featuring a two-layer atmosphere over a shallow-water ocean layer with passively advected temperature. It incorporates both frictional coupling and an energy balance scheme which accounts for radiative and heat fluxes between ocean and atmosphere. The spectral expansion was truncated at 10 atmospheric and 8 oceanic modes, and a coupled low-frequency variability was found. We present an extended version of the VDDG model, in which an arbitrary number of atmospheric and oceanic modes can be retained. The modularity of the new model version allows one to easily modify the model physics. Using this new model, named the "Modular Arbitrary-Order Ocean-Atmosphere Model" (MAOOAM), we analyse the dependence of the model dynamics on the truncation level of the spectral expansion. Indeed, previous studies have shown that spurious behaviour may exist in low-resolution models, which can be unveiled by a comparison with their high-resolution counterparts [4]. In particular, we assess the robustness of the coupled low-frequency variability when the number of modes is increased. References [1] Vannitsem, S.: Dynamics and predictability of a low-order wind-driven ocean-atmosphere coupled model, Climate dynamics, 42, 1981-1998, 2014. [2] Vannitsem, S. and De Cruz, L.: A 24-variable low-order coupled ocean-atmosphere model: OA-QG-WS v2, Geoscientific Model Development, 7, 649-662, 2014. [3] Vannitsem, S., Demaeyer, J., De Cruz, L., and Ghil

  2. Eight centuries of north atlantic ocean atmosphere variability

    PubMed

    Black; Peterson; Overpeck; Kaplan; Evans; Kashgarian

    1999-11-26

    Climate in the tropical North Atlantic is controlled largely by variations in the strength of the trade winds, the position of the Intertropical Convergence Zone, and sea surface temperatures. A high-resolution study of Caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years. These results confirm the importance of a decadal (12- to 13-year) mode of Atlantic variability believed to be driven by coupled tropical ocean-atmosphere dynamics. Although a well-defined interdecadal mode of variability does not appear to be characteristic of the tropical Atlantic, there is evidence that century-scale variability is substantial. The tropical Atlantic may also have been involved in a major shift in Northern Hemisphere climate variability that took place about 700 years ago.

  3. A mass flux closure function in a GCM based on the Richardson number

    NASA Astrophysics Data System (ADS)

    Yang, Young-Min; Kang, In-Sik; Almazroui, Mansour

    2014-03-01

    A mass flux closure in a general circulation model (GCM) was developed in terms of the mean gradient Richardson number (GRN), which is defined as the ratio between the buoyancy and the shear-driven kinetic energy in the planetary boundary layer. The cloud resolving model (CRM) simulations using the tropical ocean and global atmosphere-coupled ocean-atmosphere response experiment forcing show that cloud-base mass flux is well correlated with the GRN. Using the CRM simulations, a mass flux closure function is formulated as an exponential function of the GRN and it is implemented in the Arakawa-Schubert convective scheme. The GCM simulations with the new mass flux closure are compared to those of the GCM with the conventional mass flux closure based on convective available potential energy. Because of the exponential function, the new closure permits convective precipitation only when the GRN has a sufficiently large value. When the GRN has a relatively small value, the convection is suppressed while the convective instability is released by large-scale precipitation. As a result, the ratio of convective precipitation to total precipitation is reduced and there is an increase in the frequency of heavy precipitation, more similar to the observations. The new closure also improves the diurnal cycle of precipitation due to a time delay of the large GRN with respect to convective instability.

  4. Continental Moisture Availability and Planetary Temperature in an Idealized GCM

    NASA Astrophysics Data System (ADS)

    Scheff, J.; Frierson, D. M.

    2014-12-01

    In CMIP-class GCMs, land tends to "dry out" with greenhouse warming outside of the high latitudes, as evaporative demand consistently increases but mean precipitation does not. Soil moisture, relative humidity, and common water-availability indices tend to decline. Yet, paleoclimate evidence is usually interpreted to imply that past greenhouse climates were generally well-watered on land, while glacial periods were generally arid - just the opposite. Motivated by this apparent discrepancy, we perform greenhouse warming experiments over a wide range of planetary temperatures with a slab-ocean atmospheric GCM coupled to a simple land-surface water/energy balance model in idealized continental geometry. We assess the results using several nondimensional measures. The mean-state terrestrial aridity strongly depends on the extent of subtropical seaways and on the prescribed ocean heat transport. Unexpectedly, the aridity responses to warming can dramatically differ from the canonical CMIP story. In very wet terrestrial settings, including much of the mid-latitudes and sometimes the tropics as well, precipitation can increase enough to stop evaporative demand from increasing at all. This is a tantalizing analog to the paleo-evidence. However, when the terrestrial tropics are drier, precipitation there declines very strongly with greenhouse warming even as tropical ocean precipitation increases, causing strong aridification. Future work will seek to understand these and other surprising results, and to explain why they do not generally occur in the full GCMs.

  5. GCM response of northern winter stationary waves and storm tracks to increasing amounts of carbon dioxide

    SciTech Connect

    Stephenson, D.B.; Held, I.M. )

    1993-10-01

    The response of the Geophysical Fluid Dynamics Laboratory (GFDL) coupled ocean-atmosphere R15, 9-level GCM to gradually increasing CO[sub 2] amounts is analyzed with emphasis on the changes in the stationary waves and storm tracks in the Northern Hemisphere wintertime troposphere. A large part of the change is described by an equivalent-barotropic stationary wave with a high over eastern Canada and a low over southern Alaska. Consistent with this, the Atlantic jet weakens near the North American coast. Perpetual winter runs of an R15, nine-level atmospheric GCM with sea surface temperature, sea ice thickness, and soil moisture values prescribed from the coupled GCM results are able to reproduce the coupled model's response qualitatively. Consistent with the weakened baroclinicity associated with the stationary wave change, the Atlantic storm track weakens with increasing CO[sub 2] concentrations while the Pacific storm track does not change in strength substantially. An R15, nine-level atmospheric model linearized about the zonal time-mean state is used to analyze the contributions to the stationary wave response. With mountains, diabatic heating, and transient forcings the linear model gives a stationary wave change in qualitative agreement with the change seen in the coupled and perpetual models. Transients and diabatic heating appear to be the major forcing terms, while changes in zonal-mean basic state and topographic forcing play only a small role. A substantial part of the diabatic response is due to changes in tropical latent heating. 25 refs., 36 figs.

  6. A study of a self-generated stratospheric sudden warming and its mesospheric-lower thermospheric impacts using the coupled TIME-GCM/CCM3

    NASA Astrophysics Data System (ADS)

    Liu, H.-L.; Roble, R. G.

    2002-12-01

    A stratospheric sudden warming episode was self-consistently generated in the coupled National Center for Atmospheric Research Thermosphere, Ionosphere, Mesosphere, and Electrodynamics General Circulation Model/Climate Community Model version 3 (TIME-GCM/CCM3). Taking advantage of the unique vertical range of the coupled model (ground to 500 km), we were able to study the coupling of the lower and upper atmosphere in this warming episode. Planetary wave 1 is the dominant wave component in this warming event. Analysis of the wave phase structure and the wave amplitude indicates that the wave may experience resonant amplification prior to the peak warming. The mean wind in the high-latitude winter stratopause and mesosphere decelerates and reverses to westward due to planetary wave forcing and forms a critical layer near the zero wind lines. The wind deceleration and reversal also change the filtering of gravity waves by allowing more eastward gravity waves to propagate into the mesosphere and lower thermosphere (MLT), which causes eastward forcing and reverses the westward jet in the MLT. This also changes the meridional circulation in the upper mesosphere from poleward/downward to equatorward/upward, causing a depletion of the peak atomic oxygen layer at 97 km and significant reduction of green line airglow emission at high latitudes and midlatitudes. Planetary waves forced in situ by filtered gravity waves in the MLT grow in the warming episode. Their growth and interaction with tides create diurnal and semidiurnal variabilities in the zonal mean zonal wind.

  7. Modeling oxygenation of an ocean-atmosphere system during the Late Ordovician-Devonian

    NASA Astrophysics Data System (ADS)

    Ozaki, K.

    2013-12-01

    Throughout the Earth's history, the redox state of surface environments, biogeochemical cycles, and biological innovation/extinction have been intimately related. Therefore, understanding the long-term (over millions of years) evolution of the redox state of an ocean-atmosphere system and its controlling factors is one of the fundamental topics of Earth Sciences. In particular, Early Paleozoic is marked by the prominent biological evolution/diversification events (Cambrian explosion and Great Ordovician Biodiversification Event), implying the causal linkage between ocean oxygenation and biological innovation. On the other hand, multiple lines of evidence (such as black shale deposition, low C/S ratio of buried sediments, low molybdenum isotopic value, and iron speciation data) suggest that ocean interior had been kept in low oxygen condition until the Devonian. Dahl et al. (2010) PNAS found an increase in molybdenum isotopic value from ~1.4‰ to ~2.0‰ between ~440 Ma and ~390 Ma, implying the oceanic redox transition to a well-oxygenated condition. It was proposed that this ocean oxygenation event correlates with the diversification of vascular land plants; an enhanced burial of terrigenous organic matter increases the oxygen supply rate to an ocean-atmosphere system. Although this hypothesis for a causal linkage between the diversification of land plants and oxidation event of an ocean-atmosphere system is intriguing, it remains unclear whether the radiation of land plant is necessary to cause such redox transition. Because oxygen is most likely regulated by a combination of several feedbacks in the Earth system, it is essential to evaluate the impact of plant diversification on the oxygenation state of an ocean-atmosphere system by use of a numerical model in which C-N-P-O-S coupled biogeochemical cycles between ocean-atmosphere-sediment systems are take into account. In this study, the paleoredox history of an ocean-atmosphere system during the Paleozoic is

  8. The effect of large-scale model time step and multiscale coupling frequency on cloud climatology, vertical structure, and rainfall extremes in a superparameterized GCM

    DOE PAGES

    Yu, Sungduk; Pritchard, Michael S.

    2015-12-17

    The effect of global climate model (GCM) time step—which also controls how frequently global and embedded cloud resolving scales are coupled—is examined in the Superparameterized Community Atmosphere Model ver 3.0. Systematic bias reductions of time-mean shortwave cloud forcing (~10 W/m2) and longwave cloud forcing (~5 W/m2) occur as scale coupling frequency increases, but with systematically increasing rainfall variance and extremes throughout the tropics. An overarching change in the vertical structure of deep tropical convection, favoring more bottom-heavy deep convection as a global model time step is reduced may help orchestrate these responses. The weak temperature gradient approximation is more faithfullymore » satisfied when a high scale coupling frequency (a short global model time step) is used. These findings are distinct from the global model time step sensitivities of conventionally parameterized GCMs and have implications for understanding emergent behaviors of multiscale deep convective organization in superparameterized GCMs. Lastly, the results may also be useful for helping to tune them.« less

  9. The effect of large-scale model time step and multiscale coupling frequency on cloud climatology, vertical structure, and rainfall extremes in a superparameterized GCM

    SciTech Connect

    Yu, Sungduk; Pritchard, Michael S.

    2015-12-17

    The effect of global climate model (GCM) time step—which also controls how frequently global and embedded cloud resolving scales are coupled—is examined in the Superparameterized Community Atmosphere Model ver 3.0. Systematic bias reductions of time-mean shortwave cloud forcing (~10 W/m2) and longwave cloud forcing (~5 W/m2) occur as scale coupling frequency increases, but with systematically increasing rainfall variance and extremes throughout the tropics. An overarching change in the vertical structure of deep tropical convection, favoring more bottom-heavy deep convection as a global model time step is reduced may help orchestrate these responses. The weak temperature gradient approximation is more faithfully satisfied when a high scale coupling frequency (a short global model time step) is used. These findings are distinct from the global model time step sensitivities of conventionally parameterized GCMs and have implications for understanding emergent behaviors of multiscale deep convective organization in superparameterized GCMs. Lastly, the results may also be useful for helping to tune them.

  10. Estimating annual precipitation for the Colorado River Basin using oceanic-atmospheric oscillations

    NASA Astrophysics Data System (ADS)

    Kalra, Ajay; Ahmad, Sajjad

    2012-06-01

    Estimating long-lead time precipitation under the stress of increased climatic variability is a challenging task in the field of hydrology. A modified Support Vector Machine (SVM) based framework is proposed to estimate annual precipitation using oceanic-atmospheric oscillations. Oceanic-atmospheric oscillations, consisting of Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and El Niño-Southern Oscillation (ENSO) for a period of 1900-2008, are used to generate annual precipitation estimates with a 1 year lead time. The SVM model is applied to 17 climate divisions encompassing the Colorado River Basin in the western United States. The overall results revealed that the annual precipitation in the Colorado River Basin is significantly influenced by oceanic-atmospheric oscillations. The long-term precipitation predictions for the Upper Colorado River Basin can be successfully obtained using a combination of PDO, NAO, and AMO indices, whereas coupling AMO and ENSO results in improved precipitation predictions for the Lower Colorado River Basin. The results also show that the SVM model provides better precipitation estimates compared to the Artificial Neural Network and Multivariate Linear Regression models. The annual precipitation estimates obtained using the modified SVM modeling framework may assist water managers in statistically understanding the hydrologic response in relation to large scale climate patterns within the Colorado River Basin.

  11. Quasi-two-day wave coupling of the mesosphere and lower thermosphere-ionosphere in the TIME-GCM: Two-day oscillations in the ionosphere

    NASA Astrophysics Data System (ADS)

    Yue, Jia; Wang, Wenbin; Richmond, Arthur D.; Liu, Han-Li

    2012-07-01

    The Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) is used to simulate the quasi-two-day wave (QTDW) modulation of the ionospheric dynamo and electron density. The QTDW can directly penetrate into the lower thermosphere and modulate the neutral winds at a period of two days. The QTDW modulation of the tidal amplitudes is not evident. The QTDW in zonal and meridional winds results in a quasi-two-day oscillation (QTDO) of the dynamo electric fields at southern midlatitudes, which is mapped into the conjugate northern magnetic midlatitudes. The QTDO of the electric fields in the E region is transmitted along the magnetic field lines to the F region and leads to the QTDOs of the vertical ion drift and total electron content (TEC) at low and mid latitudes. The QTDO of the vertical ion drift near the magnetic equator leads to the 2-day oscillation of the fountain effect. The QTDO of the TEC has two peaks at ±25 magnetic latitude (Mlat) and one near the dip equator. The equatorial peak is nearly out of phase with the ones at ±25 Mlat. The vertical ion drift at midlatitudes extends the QTDW response of the TEC to midlatitudes from the Equatorial Ionospheric Anomaly (EIA). Most differently from previous reports, we discover that the QTDW winds couple into the F region ionosphere through both the fountain effect and the middle latitude dynamos.

  12. Impact of seas/lakes on polar meteorology of Titan: Simulation by a coupled GCM-Sea model

    NASA Astrophysics Data System (ADS)

    Tokano, Tetsuya

    2009-12-01

    The detection of large hydrocarbon seas/lakes near the poles by the Cassini spacecraft raises the question as to whether and how polar seas affect the meteorology on Titan. The polar meteorology and methane hydrological cycle in the presence of seas are investigated by a three-dimensional atmospheric general circulation model coupled to a one-dimensional sea energy balance model considering the observed sea/lake geography. The sea composition has a large control on the seasonal evolution of seas, temperature and wind system in the polar region, particularly in the north where large seas are located. The surface of ethane-rich seas, which do not evaporate methane, undergo a large seasonal temperature variation and the sea surface is often warmer than the surrounding land surface. Land breeze in summer towards the seas causes a moisture convergence over the seas, which leads to enhanced summer precipitation in the sea area. On the other hand, methane-rich seas evaporate some methane and are therefore colder than the surroundings. This causes a sea breeze across the north pole in summer, which blows away the moisture from the polar region, so precipitation becomes scarce in the north polar region. The breeze can become stronger than the tidal wind. Sea evaporation peaks in winter, when the temperature and average methane mixing ratio in the planetary boundary layer become lowest. The sea level predominantly rises in summer by precipitation and retreats in winter by evaporation. The meteorology in the south polar region is less sensitive to the composition of the lakes because of the paucity and smallness of southern lakes. Lake-effect precipitation can occur either by moisture convergence by the breeze or humidity enhancement over the seas, but is more characteristic of warm seasons than of cold seasons.

  13. Contrasting Indian Ocean SST Variability With and Without ENSO Influence: A Coupled Atmosphere-Ocean GCM Study

    NASA Technical Reports Server (NTRS)

    Yu, Jin-Yi; Lau, K. M.

    2004-01-01

    In this study, we perform experiments with a coupled atmosphere-ocean general circulation model (CGCM) to examine ENSO's influence on the interannual sea surface temperature (SST) variability of the tropical Indian Ocean. The control experiment includes both the Indian and Pacific Oceans in the ocean model component of the CGCM (the Indo-Pacific Run). The anomaly experiment excludes ENSOs influence by including only the Indian Ocean while prescribing monthly-varying climatological SSTs for the Pacific Ocean (the Indian-Ocean Run). In the Indo-Pacific Run, an oscillatory mode of the Indian Ocean SST variability is identified by a multi-channel singular spectral analysis (MSSA). The oscillatory mode comprises two patterns that can be identified with the Indian Ocean Zonal Mode (IOZM) and a basin-wide warming/cooling mode respectively. In the model, the IOZM peaks about 3-5 months after ENSO reaches its maximum intensity. The basin mode peaks 8 months after the IOZM. The timing and associated SST patterns suggests that the IOZM is related to ENSO, and the basin- wide warming/cooling develops as a result of the decay of the IOZM spreading SST anomalies from western Indian Ocean to the eastern Indian Ocean. In contrast, in the Indian-Ocean Run, no oscillatory modes can be identified by the MSSA, even though the Indian Ocean SST variability is characterized by east-west SST contrast patterns similar to the IOZM. In both control and anomaly runs, IOZM-like SST variability appears to be associated with forcings from fluctuations of the Indian monsoon. Our modeling results suggest that the oscillatory feature of the IOZM is primarily forced by ENSO.

  14. Characterizing unforced multi-decadal variability of ENSO: a case study with the GFDL CM2.1 coupled GCM

    NASA Astrophysics Data System (ADS)

    Atwood, A. R.; Battisti, D. S.; Wittenberg, A. T.; Roberts, W. H. G.; Vimont, D. J.

    2016-12-01

    Large multi-decadal fluctuations of El Niño-Southern Oscillation (ENSO) variability simulated in a 4000-year pre-industrial control run of GFDL CM2.1 have received considerable attention due to implications for constraining the causes of past and future changes in ENSO. We evaluated the mechanisms of this low-frequency ENSO modulation through analysis of the extreme epochs of CM2.1 as well as through the use of a linearized intermediate-complexity model of the tropical Pacific, which produces reasonable emulations of observed ENSO variability. We demonstrate that the low-frequency ENSO modulation can be represented by the simplest model of a linear, stationary process, even in the highly nonlinear CM2.1. These results indicate that CM2.1's ENSO modulation is driven by transient processes that operate at interannual or shorter time scales. Nonlinearities and/or multiplicative noise in CM2.1 likely exaggerate the ENSO modulation by contributing to the overly active ENSO variability. In contrast, simulations with the linear model suggest that intrinsically-generated tropical Pacific decadal mean state changes do not contribute to the extreme-ENSO epochs in CM2.1. Rather, these decadal mean state changes actually serve to damp the intrinsically-generated ENSO modulation, primarily by stabilizing the ENSO mode during strong-ENSO epochs. Like most coupled General Circulation Models, CM2.1 suffers from large biases in its ENSO simulation, including ENSO variance that is nearly twice that seen in the last 50 years of observations. We find that CM2.1's overly strong ENSO variance directly contributes to its strong multi-decadal modulation through broadening the distribution of epochal variance, which increases like the square of the long-term variance. These results suggest that the true spectrum of unforced ENSO modulation is likely substantially narrower than that in CM2.1. However, relative changes in ENSO modulation are similar between CM2.1, the linear model tuned to

  15. Multiple equilibria, natural variability, and climate transitions in an idealized ocean-atmosphere model

    SciTech Connect

    Saravanan, R.; McWilliams, J.C.

    1995-10-01

    An idealized coupled ocean-atmosphere is constructed to study climatic equilibria and variability. The model focuses on the role of large-scale fluid motions in the climate system. The atmospheric component is an eddy-resolving two-level global primitive equation model with simplified physical parameterizations. The oceanic component is a zonally averaged sector model of the thermohaline circulation. The two components exchange heat and freshwater fluxes synchonously. Coupled integrations are carried out over periods of several centuries to identify the equilibrium states of the ocean-atmosphere system. It is shown that there exist at least three types of equilibria, which are distinguished by whether they have upwelling or downwelling in the polar regions. Each oceanic circulation in the coupled model exhibits natural variability on interdecadal and longer timescales. The dominant interdecadal mode of variability is associated with the advection of oceanic temperature anomalies in the sinking regions. The sensitivity of the coupled model to climatic perturbations is studied. A rapid increase in the greenhouse gas concentrations leads to a collapse of the meridional overtuning in the ocean. Introduction of a large positive surface freshwater anomaly in the high latitudes leads to a temporary suppression of the sinking motion, followed by a rapid recovery, due primarily to the high latitude cooling associated with the reduction of oceanic heat transport. In this evolution, the secondary roles played by the atmospheric heat transport and moisture transport in destablizing the thermohaline circulation are compared, and the former is found to be dominant.

  16. Midlatitude Ocean-Atmosphere Interactions in a Warming Climate

    NASA Astrophysics Data System (ADS)

    Hand, Ralf; Keenlyside, Noel S.; Greatbatch, Richard J.; Omrani, Nour-Eddine

    2014-05-01

    Recent studies have shown that mid-latitude regions with strong SST gradients as they can be found in the Gulf Stream and it's extension are a key-region for midlatitude ocean-atmosphere interactions; SST variability on inter-annual to decadal timescales in this region has a distinct impact on the overlying atmosphere. Climate projections with coupled general circulation models show strong indications, that the strength and the shape of the ocean circulation might underly crucial changes in a warming climate. This work presents an analysis of the atmospheric part of a long-term (covering the period until 2300) RCP 8.5 scenario run of a coupled general circulation model (MPI-ESM-LR) with focus on the North Atlantic. The ocean component of the model shows a strong decrease in the meridional overturning circulation and a northward-shift of the boundary between the subpolar and the subtropical gyre. This leads to significant changes of the ocean surface conditions in the Gulf Stream and the Gulf Stream extension. The weakened MOC and the northward shift of the SST front leads to a weakening of the SST gradients in the historical Gulf Stream area and a strengthening of the gradients east of Newfoundland. We analysed the impact of the changes in the ocean on precipitation, a quantity which has been shown to be highly sensitive to the position of the SST front and the absolute value of SST in that region in previous studies. In winter the model shows a large region with strongly enhanced precipitation southeast off Newfoundland, likely related to a slight intensification of the North-Atlantic storm track present in the future projection. In summer the most prominent feature in terms of precipitation is a decrease in the region off the US east coast, where the historical control experiment had the strongest SST gradients, but shows weaker gradients in the future. A preliminary analysis of the hydrological cycle gives indications, that the precipitation changes are induced

  17. Skill Assessment of a Spectral Ocean-Atmosphere Radiative Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson, W.; Casey, Nancy W.

    2009-01-01

    Ocean phytoplankton, detrital material, and water absorb and scatter light spectrally. The Ocean- Atmosphere Spectral Irradiance Model (OASIM) is intended to provide surface irradiance over the oceans with sufficient spectral resolution to support ocean ecology, biogeochemistry, and heat exchange investigations, and of sufficient duration to support inter-annual and decadal investigations. OASIM total surface irradiance (integrated 200 nm to 4 microns) was compared to in situ data and three publicly available global data products at monthly 1-degree resolution. OASIM spectrally-integrated surface irradiance had root mean square (RMS) difference= 20.1 W/sq m (about 11%), bias=1.6 W/sq m (about 0.8%), regression slope= 1.01 and correlation coefficient= 0.89, when compared to 2322 in situ observations. OASIM had the lowest bias of any of the global data products evaluated (ISCCP-FD, NCEP, and ISLSCP 11), and the best slope (nearest to unity). It had the second best RMS, and the third best correlation coefficient. OASIM total surface irradiance compared well with ISCCP-FD (RMS= 20.7 W/sq m; bias=-11.4 W/sq m, r=0.98) and ISLSCP II (RMS =25.2 W/sq m; bias= -13.8 W/sq m; r=0.97), but less well with NCEP (RMS =43.0 W/sq m ;bias=-22.6 W/sq m; x=0.91). Comparisons of OASIM photosynthetically available radiation (PAR) with PAR derived from SeaWiFS showed low bias (-1.8 mol photons /sq m/d, or about 5%), RMS (4.25 mol photons /sq m/d ' or about 12%), near unity slope (1.03) and high correlation coefficient (0.97). Coupled with previous estimates of clear sky spectral irradiance in OASIM (6.6% RMS at 1 nm resolution), these results suggest that OASIM provides reasonable estimates of surface broadband and spectral irradiance in the oceans, and can support studies on ocean ecosystems, carbon cycling, and heat exchange.

  18. Skill Assessment of a Spectral Ocean-Atmosphere Radiative Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson, W.; Casey, Nancy W.

    2009-01-01

    Ocean phytoplankton, detrital material, and water absorb and scatter light spectrally. The Ocean- Atmosphere Spectral Irradiance Model (OASIM) is intended to provide surface irradiance over the oceans with sufficient spectral resolution to support ocean ecology, biogeochemistry, and heat exchange investigations, and of sufficient duration to support inter-annual and decadal investigations. OASIM total surface irradiance (integrated 200 nm to 4 microns) was compared to in situ data and three publicly available global data products at monthly 1-degree resolution. OASIM spectrally-integrated surface irradiance had root mean square (RMS) difference= 20.1 W/sq m (about 11%), bias=1.6 W/sq m (about 0.8%), regression slope= 1.01 and correlation coefficient= 0.89, when compared to 2322 in situ observations. OASIM had the lowest bias of any of the global data products evaluated (ISCCP-FD, NCEP, and ISLSCP 11), and the best slope (nearest to unity). It had the second best RMS, and the third best correlation coefficient. OASIM total surface irradiance compared well with ISCCP-FD (RMS= 20.7 W/sq m; bias=-11.4 W/sq m, r=0.98) and ISLSCP II (RMS =25.2 W/sq m; bias= -13.8 W/sq m; r=0.97), but less well with NCEP (RMS =43.0 W/sq m ;bias=-22.6 W/sq m; x=0.91). Comparisons of OASIM photosynthetically available radiation (PAR) with PAR derived from SeaWiFS showed low bias (-1.8 mol photons /sq m/d, or about 5%), RMS (4.25 mol photons /sq m/d ' or about 12%), near unity slope (1.03) and high correlation coefficient (0.97). Coupled with previous estimates of clear sky spectral irradiance in OASIM (6.6% RMS at 1 nm resolution), these results suggest that OASIM provides reasonable estimates of surface broadband and spectral irradiance in the oceans, and can support studies on ocean ecosystems, carbon cycling, and heat exchange.

  19. Ocean-Atmosphere Interactions Modulate Irrigation's Climate Impacts

    NASA Technical Reports Server (NTRS)

    Krakauer, Nir Y.; Puma, Michael J.; Cook, Benjamin I.; Gentine, Pierre; Nazarenko, Larissa

    2016-01-01

    Numerous studies have focused on the local and regional climate effects of irrigated agriculture and other land cover and land use change (LCLUC) phenomena, but there are few studies on the role of ocean- atmosphere interaction in modulating irrigation climate impacts. Here, we compare simulations with and without interactive sea surface temperatures of the equilibrium effect on climate of contemporary (year 2000) irrigation geographic extent and intensity. We find that ocean-atmosphere interaction does impact the magnitude of global-mean and spatially varying climate impacts, greatly increasing their global reach. Local climate effects in the irrigated regions remain broadly similar, while non-local effects, particularly over the oceans, tend to be larger. The interaction amplifies irrigation-driven standing wave patterns in the tropics and mid-latitudes in our simulations, approximately doubling the global-mean amplitude of surface temperature changes due to irrigation. The fractions of global area experiencing significant annual-mean surface air temperature and precipitation change also approximately double with ocean-atmosphere interaction. Subject to confirmation with other models, these findings imply that LCLUC is an important contributor to climate change even in remote areas such as the Southern Ocean, and that attribution studies should include interactive oceans and need to consider LCLUC, including irrigation, as a truly global forcing that affects climate and the water cycle over ocean as well as land areas.

  20. Ocean-atmosphere interactions modulate irrigation's climate impacts

    NASA Astrophysics Data System (ADS)

    Krakauer, Nir Y.; Puma, Michael J.; Cook, Benjamin I.; Gentine, Pierre; Nazarenko, Larissa

    2016-11-01

    Numerous studies have focused on the local and regional climate effects of irrigated agriculture and other land cover and land use change (LCLUC) phenomena, but there are few studies on the role of ocean-atmosphere interaction in modulating irrigation climate impacts. Here, we compare simulations with and without interactive sea surface temperatures of the equilibrium effect on climate of contemporary (year 2000) irrigation geographic extent and intensity. We find that ocean-atmosphere interaction does impact the magnitude of global-mean and spatially varying climate impacts, greatly increasing their global reach. Local climate effects in the irrigated regions remain broadly similar, while non-local effects, particularly over the oceans, tend to be larger. The interaction amplifies irrigation-driven standing wave patterns in the tropics and midlatitudes in our simulations, approximately doubling the global-mean amplitude of surface temperature changes due to irrigation. The fractions of global area experiencing significant annual-mean surface air temperature and precipitation change also approximately double with ocean-atmosphere interaction. Subject to confirmation with other models, these findings imply that LCLUC is an important contributor to climate change even in remote areas such as the Southern Ocean, and that attribution studies should include interactive oceans and need to consider LCLUC, including irrigation, as a truly global forcing that affects climate and the water cycle over ocean as well as land areas.

  1. Ocean-Atmosphere Interactions Modulate Irrigation's Climate Impacts

    NASA Technical Reports Server (NTRS)

    Krakauer, Nir Y.; Puma, Michael J.; Cook, Benjamin I.; Gentine, Pierre; Nazarenko, Larissa

    2016-01-01

    Numerous studies have focused on the local and regional climate effects of irrigated agriculture and other land cover and land use change (LCLUC) phenomena, but there are few studies on the role of ocean- atmosphere interaction in modulating irrigation climate impacts. Here, we compare simulations with and without interactive sea surface temperatures of the equilibrium effect on climate of contemporary (year 2000) irrigation geographic extent and intensity. We find that ocean-atmosphere interaction does impact the magnitude of global-mean and spatially varying climate impacts, greatly increasing their global reach. Local climate effects in the irrigated regions remain broadly similar, while non-local effects, particularly over the oceans, tend to be larger. The interaction amplifies irrigation-driven standing wave patterns in the tropics and mid-latitudes in our simulations, approximately doubling the global-mean amplitude of surface temperature changes due to irrigation. The fractions of global area experiencing significant annual-mean surface air temperature and precipitation change also approximately double with ocean-atmosphere interaction. Subject to confirmation with other models, these findings imply that LCLUC is an important contributor to climate change even in remote areas such as the Southern Ocean, and that attribution studies should include interactive oceans and need to consider LCLUC, including irrigation, as a truly global forcing that affects climate and the water cycle over ocean as well as land areas.

  2. Modelling the response of 7 Alpine glaciers using a coupled mass-balance geometric model forced with gridded observed climate data and GCM and RCM results.

    NASA Astrophysics Data System (ADS)

    Candela, Romain; Raper, Sarah; Braithwaite, Roger

    2010-05-01

    Seven Alpine glaciers are investigated using an updated version of the coupled Temperature-Index Mass-Balance - Geometric Ice Volume model developed by Dr. Raper and Dr. Braithwaite [Raper and Braithwaite, 2000]. The set of 7 glaciers have continuous relatively long-term mass-balance and area observation series and belong to the 30 Reference glaciers of the World Monitoring Service. The final purpose of our project is to produce a new estimation of the contribution of the Alpine glaciers to the sea-level rise. For each glacier the model was calibrated for the years between 1958-1967 to 1995 according to the availability of glacier observations. Monthly mean temperature data (0.5 degree Climate Research Unit TS 3.0) and precipitation data (10 minute Alpine Climate Data) were used as forcing. A major uncertainty is the altitudinal precipitation profile at the glacier. To address this problem and capture a range of uncertainty, as part of the calibration process we estimate time-average high, medium and low precipitation profiles for the calibration periods. The model is forced with temperature and precipitation anomalies interpolated from four adjacent grid points. The calibration process involves the estimation of two temperature downscaling parameters that adjust the mean and standard deviation of the temperature data at the glacier surface. The model is tested by comparing model output with post-1995 observed mass-balance data. Reconstructions of the glacier areas and volumes are made for the period 1901 to 2006 using the gridded climate data detailed above as forcing. For projections of future glacier volume, we force our model with temperature and precipitation climate model results from the Ensembles Project (RT3) for emission scenario A1B up to the year 2100. Hadley Centre model results for three GCM and three RCM runs are used. These climate models have three sensitivities (low, medium and high) and a resolution up to 25 km2 for the RCM. The volume response

  3. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model

    NASA Astrophysics Data System (ADS)

    Zeebe, R. E.

    2011-06-01

    The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  4. The role of ocean-atmosphere reorganizations in glacial cycles

    NASA Astrophysics Data System (ADS)

    Broecker, Wallace S.; Denton, George H.

    A case is made that glacial-to-interglacial transitions involve major reorganizations of the ocean-atmosphere system. Such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere. Only in this way can the rapidity of glacial terminations, the hemispheric synchroneity and symmetry of mountain glaciation, and the large polar air temperature and dustiness variations be accounted for. If these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes, then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean's salinity distribution.

  5. The role of ocean-atmosphere reorganizations is glacial cycles

    NASA Astrophysics Data System (ADS)

    Broecker, Wallace S.; Denton, George H.

    1989-10-01

    A case is made that glacial-to-interglacial transitions involve major reorganizations of the ocean-atmosphere system. Such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere. Only in this way can the rapidity of glacial terminations, the hemispheric synchroneity and symmetry of mountain glaciation, and the large polar air temperature and dustiness variations be accounted for. If these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes, then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean's salinity distribution.

  6. Ocean Atmosphere Flux Variability in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Virmani, J. I.; Weisberg, R. H.

    2001-12-01

    Sea surface temperature within the Gulf of Mexico shows considerable spatial and temporal variability. Understanding causes of this variability is important because this region is a major source of moisture flux to the U.S. Heartlands. Some of this variability is due to ocean dynamics associated with coastal upwelling and the Loop Current, but an equally important amount is associated with local ocean-atmosphere fluxes. Many commonly available data sets such as COADS and NCEP reananlysis are unable to reproduce observed temporal and spatial variability due to coarse spatial resolution. This is a particular problem along the continental shelves and prevents the study of ocean-atmosphere interactions in these regions. In-situ measurements of oceanic and atmospheric parameters on the West Florida Shelf (WFS) allow us to describe the annual cycle of fluxes and how they interact with the underlying ocean circulation and mixed layer. Comparisons have also been made with NCEP reananlysis fields. Driving ocean models with the reanalysis fields, without flux corrections, fails to produce observed seasonally varying features on the WFS. Reconciling these differences and their impacts on the climate variability of this region provides challenges to models and their supporting observing systems.

  7. Negative ocean--atmosphere feedback in the South Atlantic Convergence Zone

    NASA Astrophysics Data System (ADS)

    de Almeida, R. F.; Nobre, P.; Haarsma, R. J.; Campos, E. J.

    2007-05-01

    The temporal evolution of the coupled variability between the South Atlantic Convergence Zone (SACZ) and the underlying sea surface temperature (SST) during austral summer is investigated using monthly data from the NCEP/NCAR reanalysis. A maximum covariance analysis shows that the SACZ is intensified [weakened] by warm [cold] SST anomalies in the beginning of summer, drifting northward. This migration is accompanied by the cooling [warming] of the underlying oceanic anomalies. The results confirm earlier analyses using numerical models, and suggest the existence of a negative feedback between the SACZ and the underlying South Atlantic SST field. A linear regression of daily anomalies of SST and omega at 500 hPa to the equations of a stochastic oscillator reveals a negative ocean--atmosphere feedback in the western South Atlantic, stronger during January and February and directly underneath the oceanic band of the SACZ.

  8. Negative ocean-atmosphere feedback in the South Atlantic Convergence Zone

    NASA Astrophysics Data System (ADS)

    De Almeida, R. A. F.; Nobre, P.; Haarsma, R. J.; Campos, E. J. D.

    2007-09-01

    The temporal evolution of the coupled variability between the South Atlantic Convergence Zone (SACZ) and the underlying sea surface temperature (SST) during austral summer is investigated using monthly data from the NCEP/NCAR reanalysis. A maximum covariance analysis shows that the SACZ is intensified [weakened] by warm [cold] SST anomalies in the beginning of summer, drifting northward. This migration is accompanied by the cooling [warming] of the original oceanic anomalies. The results confirm earlier analyses using numerical models that suggest the existence of a negative feedback between the SACZ and the underlying South Atlantic SST field. A linear regression of daily anomalies of SST and omega at 500 hPa to the equations of a stochastic oscillator reveals a negative ocean-atmosphere feedback in the western South Atlantic, stronger during January and February directly underneath the oceanic band of the SACZ.

  9. Comparison of GCM subgrid fluxes calculated using BATS and SiB schemes with a coupled land-atmosphere high-resolution model

    SciTech Connect

    Shen, Jinmei; Arritt, R.W.

    1996-12-31

    The importance of land-atmosphere interactions and biosphere in climate change studies has long been recognized, and several land-atmosphere interaction schemes have been developed. Among these, the Simple Biosphere scheme (SiB) of Sellers et al. and the Biosphere Atmosphere Transfer Scheme (BATS) of Dickinson et al. are two of the most widely known. The effects of GCM subgrid-scale inhomogeneities of surface properties in general circulation models also has received increasing attention in recent years. However, due to the complexity of land surface processes and the difficulty to prescribe the large number of parameters that determine atmospheric and soil interactions with vegetation, many previous studies and results seem to be contradictory. A GCM grid element typically represents an area of 10{sup 4}-10{sup 6} km{sup 2}. Within such an area, there exist variations of soil type, soil wetness, vegetation type, vegetation density and topography, as well as urban areas and water bodies. In this paper, we incorporate both BATS and SiB2 land surface process schemes into a nonhydrostatic, compressible version of AMBLE model (Atmospheric Model -- Boundary-Layer Emphasis), and compare the surface heat fluxes and mesoscale circulations calculated using the two schemes. 8 refs., 5 figs.

  10. Using oceanic-atmospheric oscillations for long lead time streamflow forecasting

    NASA Astrophysics Data System (ADS)

    Kalra, Ajay; Ahmad, Sajjad

    2009-03-01

    We present a data-driven model, Support Vector Machine (SVM), for long lead time streamflow forecasting using oceanic-atmospheric oscillations. The SVM is based on statistical learning theory that uses a hypothesis space of linear functions based on Kernel approach and has been used to predict a quantity forward in time on the basis of training from past data. The strength of SVM lies in minimizing the empirical classification error and maximizing the geometric margin by solving inverse problem. The SVM model is applied to three gages, i.e., Cisco, Green River, and Lees Ferry in the Upper Colorado River Basin in the western United States. Annual oceanic-atmospheric indices, comprising Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and El Nino-Southern Oscillations (ENSO) for a period of 1906-2001 are used to generate annual streamflow volumes with 3 years lead time. The SVM model is trained with 86 years of data (1906-1991) and tested with 10 years of data (1992-2001). On the basis of correlation coefficient, root means square error, and Nash Sutcliffe Efficiency Coefficient the model shows satisfactory results, and the predictions are in good agreement with measured streamflow volumes. Sensitivity analysis, performed to evaluate the effect of individual and coupled oscillations, reveals a strong signal for ENSO and NAO indices as compared to PDO and AMO indices for the long lead time streamflow forecast. Streamflow predictions from the SVM model are found to be better when compared with the predictions obtained from feedforward back propagation artificial neural network model and linear regression.

  11. Ocean-atmosphere-wave characterisation of a wind jet (Ebro shelf, NW Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Grifoll, Manel; Navarro, Jorge; Pallares, Elena; Ràfols, Laura; Espino, Manuel; Palomares, Ana

    2016-06-01

    In this contribution the wind jet dynamics in the northern margin of the Ebro River shelf (NW Mediterranean Sea) are investigated using coupled numerical models. The study area is characterised by persistent and energetic offshore winds during autumn and winter. During these seasons, a seaward wind jet usually develops in a ˜ 50 km wide band offshore. The COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modelling system was implemented in the region with a set of downscaling meshes to obtain high-resolution meteo-oceanographic outputs. Wind, waves and water currents were compared with in situ observations and remote-sensing-derived products with an acceptable level of agreement. Focused on an intense offshore wind event, the modelled wind jet appears in a limited area offshore with strong spatial variability. The wave pattern during the wind jet is characterised by the development of bimodal directional spectra, and the ocean circulation tends to present well-defined two-layer flow in the shallower region (i.e. inner shelf). The outer shelf tends to be dominated by mesoscale dynamics such as the slope current. Due to the limited fetch length, ocean surface roughness considering sea state (wave-atmosphere coupling) modifies to a small extent the wind and significant wave height under severe cross-shelf wind events. However, the coupling effect in the wind resource assessment may be relevant due to the cubic relation between the wind intensity and power.

  12. Ocean-atmosphere processes driving Indian summer monsoon biases in CFSv2 hindcasts

    NASA Astrophysics Data System (ADS)

    Narapusetty, Balachandrudu; Murtugudde, Raghu; Wang, Hui; Kumar, Arun

    2016-09-01

    This paper analyzes the role of the Indian Ocean (IO) and the atmosphere biases in generating and sustaining large-scale precipitation biases over Central India (CI) during the Indian summer monsoon (ISM) in the climate forecast system version 2 (CFSv2) hindcasts that are produced by initializing the system each month from January 1982 to March 2011. The CFSv2 hindcasts are characterized by a systematic dry monsoon bias over CI that deteriorate with forecast lead-times and coexist with a wet bias in the tropical IO suggesting a large-scale interplay between coupled ocean-atmosphere and land biases. The biases evolving from spring-initialized forecasts are analyzed in detail to understand the evolution of summer biases. The northward migration of the Inter Tropical Convergence Zone (ITCZ) that typically crosses the equator in the IO sector during April in nature is delayed in the hindcasts when the forecast system is initialized in early spring. Our analyses show that the delay in the ITCZ coexists with wind and SST biases and the associated processes project onto the seasonal evolution of the coupled ocean-atmosphere features. This delay in conjunction with the SST and the wind biases during late spring and early summer contributes to excessive precipitation over the ocean and leading to a deficit in rainfall over CI throughout the summer. Attribution of bias to a specific component in a coupled forecast system is particularly challenging as seemingly independent biases from one component affect the other components or are affected by their feedbacks. In the spring-initialized forecasts, the buildup of deeper thermocline in association with warmer SSTs due to the enhanced Ekman pumping in the southwest IO inhibits the otherwise typical northward propagation of ITCZ in the month of April. Beyond this deficiency in the forecasts, two key ocean-atmosphere coupled mechanisms are identified; one in the Arabian Sea, where a positive windstress curl bias in conjunction

  13. Group Combustion Module (GCM) Installation

    NASA Image and Video Library

    2016-09-27

    ISS049e011638 (09/27/2016) --- Expedition 49 crewmember Takuya Onishi of JAXA works on the setup of the Group Combustion Module (GCM) inside the Japanese Experiment Module. The GCM will be used to house the Group Combustion experiment from the Japan Aerospace Exploration Agency (JAXA) to test a theory that fuel sprays change from partial to group combustion as flames spread across a cloud of droplets.

  14. The polarization properties of reflectance from coastal waters and the ocean-atmosphere system

    NASA Astrophysics Data System (ADS)

    Ahmed, S.; Gilerson, A.; Oo, M.; Zhou, J.; Chowdhary, J.; Gross, B.; Moshary, F.

    2006-09-01

    The polarization characteristics of the water leaving radiance can provide information on bio-optical properties and composition of coastal water and can be used as well as a tool for the separation of chlorophyll fluorescence from elastic reflectance spectra. We report the results of simulations using a coupled ocean-atmosphere vector radiative transfer code (NASA GISS) to obtain the polarized reflectance for various water compositions typical for coastal zones, as function of wavelength and sun/sensor geometry. Results show that even for sensor orientations outside of the principal scattering plane, the polarization can nearly approach the maximum values observable in the principal scattering plane thereby minimizing undesirable sun glint effects. Simulations are complemented by laboratory and field measurements in Chesapeake Bay and near Sapelo Island, GA. We also report the results of the fluorescence retrieval from reflectance spectra using polarization discrimination as well as fluorescence line height (FLH) algorithms. Performance of these algorithms is analyzed in conjunction with the relationship between fluorescence magnitude and chlorophyll concentrations in the conditions typical for coastal waters.

  15. Predicting land cover changes in the Amazon rainforest: An ocean-atmosphere-biosphere problem

    NASA Astrophysics Data System (ADS)

    Pereira, Marcos Paulo Santos; Malhado, Ana Cláudia Mendes; Costa, Marcos Heil

    2012-05-01

    Accurate studies of the impacts of climate change on the distribution of major vegetation types are essential for developing effective conservation and land use policy. Such studies require the development of models that accurately represent the complex and interacting biophysical factors that influence regional patterns of vegetation. Here we investigate the impacts of Sea Surface Temperature (SST) on the vegetation of the Amazon, testing the hypothesis that changes in Amazonian vegetation structure are a consequence of an ocean-atmosphere-biosphere interaction. We design a numerical experiment in which we force a coupled climate-biosphere model by 10 SST patterns produced by different IPCC AR4 models, for the A2 scenario for the period 2000-2050. Simulations for 2011-2050 show that certain patterns of SST are likely to decrease the ensemble for tropical evergreen rainforest and savanna, and that these areas will be occupied mainly by tropical deciduous rainforest, emitting an average of 0.53 Pg-C.yr-1 during the transition.

  16. Ocean-atmosphere dynamics changes associated with prominent ocean surface turbulent heat fluxes trends during 1958-2013

    NASA Astrophysics Data System (ADS)

    Yang, Hu; Liu, Jiping; Lohmann, Gerrit; Shi, Xiaoxu; Hu, Yongyun; Chen, Xueen

    2016-03-01

    Three prominent features of ocean surface turbulent heat fluxes (THF) trends during 1958-2013 are identified based on the Objectively Analyzed air-sea Fluxes (OAFlux) data set. The associated ocean-atmosphere dynamics changes are further investigated based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. First, the THF are enhanced over the mid-latitude expansions of the subtropical western boundary currents (WBCs). An intensified oceanic heat transport, forced by stronger near-surface zonal wind, is likely to be the cause of such THF tendency. Second, the THF are reduced over the tropical eastern Pacific Ocean, which is primarily caused by the decreasing near-surface wind speed and sea surface temperature (SST), associated with a local coupled ocean-atmosphere cooling mode. Finally, the THF are reduced over the northern tropical Atlantic Ocean, which is attributed to the decreasing air-sea humidity and temperature differences as a result of the convergence of near-surface air and the divergence of ocean currents (upwelling).

  17. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4

    NASA Astrophysics Data System (ADS)

    Zeebe, R. E.

    2012-01-01

    The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  18. DMS cycle in the marine ocean-atmosphere system a global model study

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Feichter, J.; Maier-Reimer, E.; Six, K. D.; Stier, P.; Wetzel, P.

    2005-08-01

    A global coupled ocean-atmosphere modeling system is established to study the production of Dimethylsulfide (DMS) in the ocean, the DMS flux to the atmosphere, and the resulting sulfur concentrations in the atmosphere. The DMS production and consumption processes in the ocean are simulated in the marine biogeochemistry model HAMOCC5, embedded in a ocean general circulation model (MPI-OM). The atmospheric model ECHAM5 is extended by the microphysical aerosol model HAM, treating the sulfur chemistry in the atmosphere and the evolution of the microphysically interacting internally- and externally mixed aerosol populations.

    We simulate a global annual mean DMS sea surface concentration of 1.8 nmol/l, a DMS emission of 28 Tg(S)/yr, a DMS burden in the atmosphere of 0.077 Tg(S), and a DMS lifetime of 1.0 days. To quantify the role of DMS in the atmospheric sulfur cycle we simulate the relative contribution of DMS-derived SO2 and SO4-2 to the total atmospheric sulfur concentrations. DMS contributes 25% to the global annually averaged SO2 column burden. For SO4-2 the contribution is 27%.

    The coupled model setup allows the evaluation of the simulated DMS quantities with measurements taken in the ocean and in the atmosphere. The simulated global distribution of DMS sea surface concentrations compares reasonably well with measurements. The comparison to SO4-2 surface concentration measurements in regions with a high DMS contribution to SO4-2 shows an overestimation by the model. This overestimation is most pronounced in the biologically active season with high DMS emissions and most likely caused by a too high simulated SO4-2 yield from DMS oxidation.

  19. Dynamics and predictability of a low-order wind-driven ocean - atmosphere model

    NASA Astrophysics Data System (ADS)

    Vannitsem, Stéphane

    2013-04-01

    The dynamics of a low order coupled wind-driven Ocean-Atmosphere (OA) system is investigated with emphasis on its predictability properties. The low-order coupled deterministic system is composed of a baroclinic atmosphere for which 12 dominant dynamical modes are only retained (Charney and Straus, 1980) and a wind-driven, quasi-geostrophic and reduced-gravity shallow ocean whose field is truncated to four dominant modes able to reproduce the large scale oceanic gyres (Pierini, 2011). The two models are coupled through mechanical forcings only. The analysis of its dynamics reveals first that under aperiodic atmospheric forcings only dominant single gyres (clockwise or counterclockwise) appear. This feature is expected to be related with the specific domain choice over which the coupled system is defined. Second the dynamical quantities characterizing the short-term predictability (Lyapunov exponents, Lyapunov dimension, Kolmogorov-Sinaï (KS) entropy) displays a complex dependence as a function of the key parameters of the system, namely the coupling strength and the external thermal forcing. In particular, the KS-entropy is increasing as a function of the coupling in most of the experiments, implying an increase of the rate of loss of information about the localization of the system on his attractor. Finally the dynamics of the error is explored and indicates, in particular, a rich variety of short term behaviors of the error in the atmosphere depending on the (relative) amplitude of the initial error affecting the ocean, from polynomial (at2 + bt3 + ct4) up to purely exponential evolutions. These features are explained and analyzed in the light of the recent findings on error growth (Nicolis et al, 2009). References Charney J G, Straus DM (1980) Form-Drag Instability, Multiple Equilibria and Propagating Planetary Waves in Baroclinic, Orographically Forced, Planetary Wave Systems. J Atmos Sci 37: 1157-1176. Nicolis C, Perdigao RAP, Vannitsem S (2009) Dynamics of

  20. Rapid ocean-atmosphere response to Southern Ocean freshening during the last glacial period

    NASA Astrophysics Data System (ADS)

    Turney, Christian; Jones, Richard; Phipps, Steven; Thomas, Zoë; Hogg, Alan; Kershaw, Peter; Fogwill, Christopher; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad; Staff, Richard; Grosvenor, Mark; Golledge, Nicholas; Rasmussen, Sune; Hutchinson, David; Haberle, Simon; Lorrey, Andrew; Boswijk, Gretel

    2017-04-01

    Contrasting Greenland and Antarctic temperature trends during the late last glacial period (60,000 to 11,703 years ago) are thought to be driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'), with cooling in the north leading the onset of warming in the south. Some events, however, appear to have occurred independently of changes in deep water formation but still have a southern expression, implying that an alternative mechanism may have driven some global climatic changes during the glacial. Testing these competing hypotheses is challenging given the relatively large uncertainties associated with correlating terrestrial, marine and ice core records of abrupt change. Here we exploit a bidecadally-resolved 14C calibration dataset obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate datasets spanning 28,400 to 30,400 years ago. We observe no divergence between terrestrial and marine 14C datasets implying limited impact of freshwater hosing on the Atlantic Meridional Overturning Circulation (AMOC). However, an ice-rafted debris event (SA2) in Southern Ocean waters appears to be associated with dramatic synchronous warming over the North Atlantic and contrasting precipitation patterns across the low latitudes. Using a fully coupled climate system model we undertook an ensemble of transient meltwater simulations and find that a southern salinity anomaly can trigger low-latitude temperature changes through barotropic and baroclinic oceanic waves that are atmospherically propagated globally via a Rossby wave train, consistent with contemporary modelling studies. Our results suggest the Antarctic ice sheets and Southern Ocean dynamics may have contributed to some global climatic changes through rapid ocean-atmospheric teleconnections, with implications for past (and future) change.

  1. The Flexible Global Ocean-Atmosphere-Land system model, Spectral Version 2: FGOALS-s2

    NASA Astrophysics Data System (ADS)

    Bao, Qing; Lin, Pengfei; Zhou, Tianjun; Liu, Yimin; Yu, Yongqiang; Wu, Guoxiong; He, Bian; He, Jie; Li, Lijuan; Li, Jiandong; Li, Yangchun; Liu, Hailong; Qiao, Fangli; Song, Zhenya; Wang, Bin; Wang, Jun; Wang, Pengfei; Wang, Xiaocong; Wang, Zaizhi; Wu, Bo; Wu, Tongwen; Xu, Yongfu; Yu, Haiyang; Zhao, Wei; Zheng, Weipeng; Zhou, Linjiong

    2013-05-01

    The Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 (FGOALS-s2) was used to simulate realistic climates and to study anthropogenic influences on climate change. Specifically, the FGOALS-s2 was integrated with Coupled Model Intercomparison Project Phase 5 (CMIP5) to conduct coordinated experiments that will provide valuable scientific information to climate research communities. The performances of FGOALS-s2 were assessed in simulating major climate phenomena, and documented both the strengths and weaknesses of the model. The results indicate that FGOALS-s2 successfully overcomes climate drift, and realistically models global and regional climate characteristics, including SST, precipitation, and atmospheric circulation. In particular, the model accurately captures annual and semi-annual SST cycles in the equatorial Pacific Ocean, and the main characteristic features of the Asian summer monsoon, which include a low-level southwestern jet and five monsoon rainfall centers. The simulated climate variability was further examined in terms of teleconnections, leading modes of global SST (namely, ENSO), Pacific Decadal Oscillations (PDO), and changes in 19th-20th century climate. The analysis demonstrates that FGOALS-s2 realistically simulates extra-tropical teleconnection patterns of large-scale climate, and irregular ENSO periods. The model gives fairly reasonable reconstructions of spatial patterns of PDO and global monsoon changes in the 20th century. However, because the indirect effects of aerosols are not included in the model, the simulated global temperature change during the period 1850-2005 is greater than the observed warming, by 0.6°C. Some other shortcomings of the model are also noted.

  2. Impact of the SH sea-ice cover and ocean surface on the Southern Ocean atmospheric variability

    NASA Astrophysics Data System (ADS)

    Merz, N.; Sedlacek, J.; Raible, C. C.

    2012-04-01

    Satellite observations of the last 30 years have shown a slight increase in the Antarctic sea-ice area (SIA). This increase seems to be counterintuitive regarding global warming and the strong decrease observed in Arctic SIA. Thus, dynamical processes rather than thermodynamical processes would be a more plausible cause for the Southern Hemisphere (SH) sea-ice increase. This raises interest in understanding the dynamics of the Southern Ocean climate system and its recent changes. Based on ERA-40 reanalysis data and satellite-borne HadISST1 observations for 1979-2008 we detect synchronous variability in the Southern Ocean mean sea-level pressure (SLP), sea surface temperatures (SST) and sea-ice concentration (SIC) fields. The strength of the Amundsen-Sea low (ASL) is strongly connected with the phase of a dipole-pattern in SICs and SSTs identified across the Western longitudes. With the aid of a comprehensive climate model, we further investigate the one-way impact of the lower boundaries on the Southern Ocean atmosphere. Therefore, a set of sensitivity atmosphere-land-only simulations is performed forced either with inter-annually variable (the HadISST1 observations) or climatological input data of SICs and SSTs. The sensitivity experiments exhibit a clear impact of both, the SSTs and the sea-ice cover on the Southern Ocean atmospheric inter-annual variability. For example, the variability of the ASL is drastically reduced in the experiment with climatological lower boundaries. The strongest decrease is due to the missing SST variability in the mid-latitudinal Pacific suppressing the generation of the so-called Pacific South America teleconnection, an ENSO-related wave pattern significantly influencing the state of the ASL. The wave generation is inhibited due to reduced variability of the latent heat flux. Further, variable sea ice impacts the SLP variability but to a lower degree. In summary, there is clear evidence that the Southern Ocean atmospheric variability

  3. The role of ocean-atmosphere interaction in shaping climate change in the North Atlantic sector

    NASA Astrophysics Data System (ADS)

    Hand, Ralf; Nour-Eddine, Omrani; Keenlyside Noel, S.; Richard, Greatbatch

    2015-04-01

    Here, we present an analysis of North Atlantic ocean-atmosphere interaction in a warming climate, based on a long-term coupled general circulation model experiment forced by the RCP 8.5 (Representative Concentration Pathways 8.5) scenario. In addition to globally strongly increased SSTs as a direct response to the radiative forcing, the model run shows a distinct change of the local sea surface temperature (SST hereafter) pattern in the Gulf Stream region. This includes changes of the SST gradients in the region of the Gulf Stream SST front, likely as a response of the wind-driven part of the oceanic surface circulation. As a consequence of a massive slow-down of the Atlantic Meridional Overturning Circulation the northern North Atlantic furthermore shows a much weaker warming than the other oceans. The feedback of these changes on the atmosphere was studied in a set of sensitivity experiments based on the SST climatology of the coupled runs. The set consists of four runs: a control experiment based on the historical run, a run using the full SST from coupled RCP 8.5 run and two runs, where where we deconstructed the SST signal into a homogenous mean warming part and a local SST pattern change. In the region of the precipitation maximum in the historical run the future scenario shows an increase of absolute SSTs, but a a significant decrease in local precipitation. We show evidence that the local response in that region is connected to the (with respect to the historical run) weakened SST gradients rather than to the absolute SST. Consistently, the model shows enhanced precipitation north of this region, where the SST gradients are enhanced. The warming causes a decreased low-level convergence and upward motion in the region with reduced SST gradient. However, the signal restricts to the low and mid-troposphere and does not reach the higher model levels. There is little evidence for a large-scale response to the SST pattern changes in the Gulf Stream region

  4. Global flood risk response to large-scale land-ocean-atmospheric interactions

    NASA Astrophysics Data System (ADS)

    Ward, P. J.; Dettinger, M. D.; Jongman, B.; Sperna Weiland, F.; Winsemius, H.

    2012-12-01

    The economic consequences of flooding are huge, as exemplified by recent major floods in Thailand, Pakistan, and the Mississippi Basin. Moreover, research shows that economic flood risks are increasing around the world. Whilst much research is being carried out to assess how this may be related to socioeconomic development (increased exposure to floods) or climate change (increased hazard), the role of interannual climate variability caused by land-ocean-atmospheric interactions, is poorly understood at the global scale. To address these issues, we recently initiated a 4-year project to assess and map the impacts of large scale interannual climate variability on both flood risk (in terms of expected annual economic damages) and flood hazard at the global scale. In this contribution, we assess El Niño Southern Oscillation's (ENSO) impact on global flood risk, and discuss implications for key stakeholders. The research involves a model chain coupling the results of a hydrological model, inundation model, and flood damage model. In terms of risk, we simulate clear and significant differences in annual expected economic damage between El Niño (EN) years and non-EN years, and between La Niña (LN) and non-LN years. These are related to large-scale land-ocean atmospheric interactions, which force significant changes in flood hazard magnitudes. However, our analyses reveal asymmetrical results between ENSO modes. For example, whilst several basins in southern Africa have much higher annual floods in LN years than in neutral years, the opposite signal is less clear. We present seasonal composites of climatic and atmospheric variables to explain these differences. Moreover, we find strong correlations between ENSO indices and (simulated and observed) peak annual floods in rivers all around the world. In many regions, the strength of these relationships is greater than those between the ENSO indices and mean annual discharge. The application of these results to short and

  5. Structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean-atmosphere system

    NASA Astrophysics Data System (ADS)

    Fang, Jiabei; Yang, Xiu-Qun

    2016-09-01

    The structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean-atmosphere system are examined in this study, using the NCEP/NCAR atmospheric reanalysis, HadISST SST and Simple Ocean Data Assimilation data for 1960-2010. The midlatitude decadal anomalies associated with the Pacific Decadal Oscillation are identified, being characterized by an equivalent barotropic atmospheric low (high) pressure over a cold (warm) oceanic surface. Such a unique configuration of decadal anomalies can be maintained by an unstable ocean-atmosphere interaction mechanism in the midlatitudes, which is hypothesized as follows. Associated with a warm PDO phase, an initial midlatitude surface westerly anomaly accompanied with intensified Aleutian low tends to force a negative SST anomaly by increasing upward surface heat fluxes and driving southward Ekman current anomaly. The SST cooling tends to increase the meridional SST gradient, thus enhancing the subtropical oceanic front. As an adjustment of the atmospheric boundary layer to the enhanced oceanic front, the low-level atmospheric meridional temperature gradient and thus the low-level atmospheric baroclinicity tend to be strengthened, inducing more active transient eddy activities that increase transient eddy vorticity forcing. The vorticity forcing that dominates the total atmospheric forcing tends to produce an equivalent barotropic atmospheric low pressure north of the initial westerly anomaly, intensifying the initial anomalies of the midlatitude surface westerly and Aleutian low. Therefore, it is suggested that the midlatitude ocean-atmosphere interaction can provide a positive feedback mechanism for the development of initial anomaly, in which the oceanic front and the atmospheric transient eddy are the indispensable ingredients. Such a positive ocean-atmosphere feedback mechanism is fundamentally responsible for the observed decadal anomalies in the midlatitude North Pacific ocean-atmosphere

  6. Structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean-atmosphere system

    NASA Astrophysics Data System (ADS)

    Fang, Jiabei; Yang, Xiu-qun

    2017-04-01

    The structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean-atmosphere system are examined in this study, using the NCEP/NCAR atmospheric reanalysis, HadISST SST and Simple Ocean Data Assimilation data for 1960-2010. The midlatitude decadal anomalies associated with the Pacific Decadal Oscillation are identified, being characterized by an equivalent barotropic atmospheric low (high) pressure over a cold (warm) oceanic surface. Such a unique configuration of decadal anomalies can be maintained by an unstable ocean-atmosphere interaction mechanism in the midlatitudes, which is hypothesized as follows. Associated with a warm PDO phase, an initial midlatitude surface westerly anomaly accompanied with intensified Aleutian low tends to force a negative SST anomaly by increasing upward surface heat fluxes and driving southward Ekman current anomaly. The SST cooling tends to increase the meridional SST gradient, thus enhancing the subtropical oceanic front. As an adjustment of the atmospheric boundary layer to the enhanced oceanic front, the low-level atmospheric meridional temperature gradient and thus the low-level atmospheric baroclinicity tend to be strengthened, inducing more active transient eddy activities that increase transient eddy vorticity forcing. The vorticity forcing that dominates the total atmospheric forcing tends to produce an equivalent barotropic atmospheric low pressure north of the initial westerly anomaly, intensifying the initial anomalies of the midlatitude surface westerly and Aleutian low. Therefore, it is suggested that the midlatitude ocean-atmosphere interaction can provide a positive feedback mechanism for the development of initial anomaly, in which the oceanic front and the atmospheric transient eddy are the indispensable ingredients. Such a positive ocean-atmosphere feedback mechanism is fundamentally responsible for the observed decadal anomalies in the midlatitude North Pacific ocean-atmosphere

  7. Thermosphere-Ionosphere-Mesosphere Modeling Using the TIME-GCM

    DTIC Science & Technology

    2014-09-30

    Systems Modeling effort in examining the couplings between the upper and lower atmospheres and in an attempt to understand the effects of the variable...Thermosphere-Ionosphere-Mesosphere Modeling Using the TIME-GCM Raymond G. Roble High Altitude Observatory National Center for Atmospheric ...http://www.hao.ucar.edu/ LONG-TERM GOALS A major goal of the research is to understand how elements in the coupled upper atmosphere

  8. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    NASA Astrophysics Data System (ADS)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2016-09-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  9. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    NASA Astrophysics Data System (ADS)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2017-07-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  10. The role of hydrological processes in ocean-atmosphere interactions

    SciTech Connect

    Webster, P.J.

    1994-11-01

    Earth is unique among the planets of the solar system in possessing a full hydrological cycle. The role of water in the evolution of planetary atmospheres is discussed. As the atmospheres of the planets developed and modified the early climates of the planets, only the climate trajectory of Earth intercepted the water phase transitions near the triplet point of water, thus allowing the full gamut of water forms to coexist. As a result, transitions between the water phases pervade the entire system and probably are responsible for the creation of a unique climate state. The interactions between the components of the climate system are enriched by the nonlinearity of the water phase transitions. The nonlinear character of the phase transitions of water suggests that the climate should be particularly sensitive to hydrological processes, especially in the tropics. Signatures of the nonlinearity are found in both the structures of the oceans and the atmosphere. Models of the ocean and atmospheric and oceanic data and models of the coupled system are used to perform systematic analyses of hydrological processes and their role in system interaction. The analysis is extended to consider the role of hydrological processes in the basic dynamics and thermodynamics of oceanic and atmospheric systems. The role hydrological processes play in determining the scale of the major atmospheric circulation patterns is investigated. Explanations are offered as to why large-scale convection in the tropical atmosphere is constrained to lie within the 28{degrees}C sea surface temperature contour and how hydrological processes are involved in interannual climate variability. The relative roles of thermal and haline forcing of the oceanic thermohaline circulation are discussed. Hydrological processes are considered in a global context by the development of a conceptual model of a simple planetary system. 94 refs., 38 figs., 5 tabs.

  11. Coupled ocean-atmosphere loss of marine refractory dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Kieber, David J.; Keene, William C.; Frossard, Amanda A.; Long, Michael S.; Maben, John R.; Russell, Lynn M.; Kinsey, Joanna D.; Tyssebotn, Inger Marie B.; Quinn, Patricia K.; Bates, Timothy S.

    2016-03-01

    The oceans hold a massive quantity of organic carbon, nearly all of which is dissolved and more than 95% is refractory, cycling through the oceans several times before complete removal. The vast reservoir of refractory dissolved organic carbon (RDOC) is a critical component of the global carbon cycle that is relevant to our understanding of fundamental marine biogeochemical processes and the role of the oceans in climate change with respect to long-term storage and sequestration of atmospheric carbon dioxide. Here we show that RDOC includes surface-active organic matter that can be incorporated into primary marine aerosol produced by bursting bubbles at the sea surface. We propose that this process will deliver RDOC from the sea surface to the atmosphere wherein its photochemical oxidation corresponds to a potentially important and hitherto unknown removal mechanism for marine RDOC.

  12. Understanding the Nature of Marine Aerosols and Their Effects in the Coupled Ocean-Atmosphere System

    DTIC Science & Technology

    2013-09-30

    into aqueous- phase mechanistic relationships leading up to oxalate production. Monocarboxylic and dicarboxylic acids exhibited contrasting spatial...ocean surface. Three case flights show that oxalate (and no other organic acid ) concentrations drop by nearly an order of magnitude relative to...aerosol- cloud interactions. REFERENCES Crahan, K. K., D. Hegg, D. S. Covert, and H. Jonsson (2004), An exploration of aqueous oxalic acid

  13. Coupled Ocean-Atmospheric Modeling for 3-15 Day Numerical Prediction: A Workshop Report

    DTIC Science & Technology

    1983-06-01

    averaging tends to smooth temporal variability, the spatially averaged MLD still shallows fairly abruptly, indicating that the transition occurs almost...least two polar orbiting satellites to give adequate temporal as well as spatial resolution. Horizontal resolution of the SST fields needs only be...atmospheric model a long term simulation should be run to define the model’s clima - tology. Climatological SST values should be used in these tests

  14. Coupled Ocean-Atmosphere Models, International Liege Colloguium on Ocean Hydrodynamics (21st)

    DTIC Science & Technology

    1990-01-02

    Albuquerque, New Mexico J , Na’ 0 N plementary Notes. 1w O ;ributionlAvailability Statement. 12b. Distribution Code. CV oved for public release...ir At times nan. K . Clittae and asma viocwu niip herto fUCIs using the PE approach likein that the temporal und spatial scale mis- one memher of the

  15. Coupled Ocean-Atmosphere Dynamics and Predictability of MJO’s

    DTIC Science & Technology

    2011-09-30

    2005 to 2009) wavenumber-frequency spectral density of the symmetric component (2.5N-10N) of (a) NOAA OLR (W2/m4) and (b) NCEP U10 (m2/s2). (c...166 days) NOAA OLR (shading) and NCEP U10 (contours). (b) As in (a) but from the model. The negative wind anomalies are show in dashed contours (CI...and 200 hPa and OLR from (left) NCEP and OLR from the NOAA satellite for 1980 – 1999 and (right) the 20 yr CCSM4 run. The total variance accounted

  16. Coupled Ocean-Atmosphere Dynamics and Predictability of MJO’s

    DTIC Science & Technology

    2011-09-30

    NOAA OLR (W2/m4) and (b) NCEP U10 (m2/s2). (c) Coherence squared between OLR and U10. (Right) As in (left) except from the WRF simulation. 6...Figure 3. (a) Filtered (k=0~8, w=0.006~0.055 cpd, 18-166 days) NOAA OLR (shading) and NCEP U10 (contours). (b) As in (a) but from the model. The...modes of 20-100 day 15S-15N-averaged zonal wind at 850 hPa and 200 hPa and OLR from (left) NCEP and OLR from the NOAA satellite for 1980 – 1999 and

  17. Evolution of Titan's coupled ocean-atmosphere system and interaction of ocean with bedrock

    NASA Technical Reports Server (NTRS)

    Lunine, J. I.; Stevenson, D. J.

    1985-01-01

    A recent model for the surface state of Titan proposes a liquid ethane-methane-molecular nitrogen layer of order one kilometer thick which because of stratospheric methane photolysis has become increasingly ethane-rich with time. The interaction of such an ocean with the underlying 'bedrock' of Titan (assumed to be water-ice or ammonia hydrate) and with the primarily nitrogen atmosphere is explored. It is concluded that although modest exchange of oceanic hydrocarbons with enclathrated methane in the bedrock can in principle occur, it is unlikely for reasonable regolith depths. The surprisingly high solubility of water-ice in liquid methane implies that topographic features on Titan of order 100 meters in height can be eroded away on a time scale of one-billion years. The large solubility difference of N2 in methane versus ethane implies that the ocean composition is a strong determinant of atmospheric pressure; a simple radiative model of the Titan atmosphere is employed to demonstrate that significant surface pressure and temperature changes can occur as the oceanic composition evolves with time.

  18. Upper-bound general circulation of coupled ocean-atmosphere: Part 1. Atmosphere

    NASA Astrophysics Data System (ADS)

    Ou, Hsien-Wang

    2013-11-01

    We consider the general atmospheric circulation within the deductive framework of our climate theory. The preceding three parts of this theory have reduced the troposphere to the tropical and polar air masses and determined their temperature and the surface latitude of their dividing boundary, which provide the prior thermal constraint for the present dynamical derivation. Drawing upon its similar material conservation as the thermal property, the (columnar) potential vorticity (PV) is assumed homogenized as well in air masses, which moreover has a zero tropical value owing to the hemispheric symmetry. Inverting this PV field produces an upper-bound zonal wind that resembles the prevailing wind, suggesting that the latter may be explained as the maximum macroscopic motion extractable by random eddies - within the confine of the thermal differentiation.

  19. Understanding the Nature of Marine Aerosols and Their Effects in the Coupled Ocean-Atmosphere System

    DTIC Science & Technology

    2012-09-30

    instruments (DASH-SP and CVI). Dr. Graham Feingold (National Oceanic and Atmospheric Administration) collaborated with the PI on using cloud models...E-PEACE). An on-going collaboration with Dr. Daniel Partridge (University of Oxford) has involved conducting inverse modelling of aerosol-cloud

  20. Coupled Ocean-Atmosphere Dynamics and Predictability of MJO’s

    DTIC Science & Technology

    2012-09-30

    to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data...needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection...equator to a double ITCZ structure and the separation of the weather and intraseasonal time-scales. The addition of a heat source representing land

  1. Coupled Ocean-Atmosphere Dynamics and Predictability of MJO’s

    DTIC Science & Technology

    2012-09-30

    information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and...maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of...reach one Rossby radius of deformation, there is a switch from a single convergence on the equator to a double ITCZ structure and the separation of

  2. Coupled Ocean-Atmosphere Dynamics and Predictability of MJO’s

    DTIC Science & Technology

    2012-09-30

    estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the...data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this...maximum SSTs reach one Rossby radius of deformation, there is a switch from a single convergence on the equator to a double ITCZ structure and the

  3. Development and Testing of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS)

    DTIC Science & Technology

    1993-11-01

    1970’s that numerical models based on the nonhydrostatic equations were devel- oped. Several of these models were used to study convective processes...Miller and Pearce, 1974; Schlesinger, 1975; Clark, 1977; Klemp and Wilhelmson, 1978; Clark, 1979; Tripoli and Cotton, 1982) while others studied ...operational use (Tapp and White, 1976; Carpenter, 1979) and Tripoli (1992a) has recently developed a nonhydrostatic 1 model to study scale interaction

  4. Coupled Ocean-Atmosphere Nested Modeling of the Adriatic Sea During Winter and Spring 2001

    DTIC Science & Technology

    2003-10-15

    offshore of Zadar . The 36-km COAMPS mean wind stress fails to resolve the bora fingers situated over the Gulf of Trieste and off Zadar . Where the bora blows...Adriatic. However, in the Gulf of Trieste and offshore of Zadar , fluctuating and mean wind stress values are stronger in the 4-km-resolution model. Also...the northern portion of the Gulf of Trieste, off the southern tip of the Istrian peninsula, and north of the Croatian town of Zadar . By contrast, the

  5. Numerical simulation of large-scale ocean-atmosphere coupling and the ocean's role in climate

    NASA Technical Reports Server (NTRS)

    Gates, W. L.

    1983-01-01

    The problem of reducing model generated sigma coordinate data to pressure levels is considered. A mass consistent scheme for performing budget analyses is proposed, wherein variables interpolated to a given pressure level are weighted according to the mass between a nominal pressure level above and either a nominal pressure level below or the Earth's surface, whichever is closer. The method is applied to the atmospheric energy cycle as simulated by the OSU two level atmospheric general circulation model. The results are more realistic than sigma coordinate analyses with respect to eddy decomposition, and are in agreement with the sigma coordinate evaluation of the numerical energy sink. Comparison with less sophisticated budget schemes indicates superiority locally, but not globally.

  6. A Water Mass Tracer Detected in Aerosols Demonstrates Ocean-Atmosphere Mass Transfer and Links Sea Spray Aerosol to Source Waters

    NASA Astrophysics Data System (ADS)

    Pendergraft, M.; Grimes, D. J.; Giddings, S. N.; Feddersen, F.; Prather, K. A.; Santander, M.; Lee, C.; Beall, C.

    2016-12-01

    During September and October of 2015 the Cross Surfzone/Inner-shelf Dye Exchange (CSIDE) project released rhodamine WT dye to study nearshore water movement and exchange offshore along a Southern California sandy beach. We utilized this opportunity to investigate ocean-atmosphere mass transfer via sea spray aerosol and linkage to source waters. Aerosol-concentrating sampling equipment was deployed at beachside and inland locations during three dye releases. Concentrated aerosol samples were analyzed for dye content using fluorescence spectroscopy. Here we present the ocean and atmosphere conditions associated with the presence and absence of dye in aerosol samples. Dye was identified in aerosol samples collected 0.1-0.3 km from the shoreline for 6 hs during the first and third dye releases of the CSIDE project. During these releases the dye persisted in the waters upwind of the sampling equipment. Dye was not detected in aerosol samples collected during the second release during which dye was moved away from waters upwind of the sampling equipment. Recovery of a chemical tracer in sea spray aerosol allows direct linkage to a known source area in the ocean that is independent of, but supported by, wind data. Our observations demonstrate: a tight ocean-atmosphere spatial coupling; a short residence time of coastal marine constituents before transfer to the atmosphere; that the ocean is both a sink for and a source of atmospheric and terrestrial material; and that human inputs to the ocean can return to us in sea spray aerosol.

  7. Decadal prediction of Colorado River streamflow anomalies using ocean-atmosphere teleconnections

    NASA Astrophysics Data System (ADS)

    Switanek, Matthew B.; Troch, Peter A.

    2011-12-01

    The Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) time series are used to forecast a decade ahead streamflow anomalies in the upper Colorado River at Lee's Ferry. In the instrumental record, we obtain unusually high decadal forecast skill that is statistically significant at the 95% confidence level, suggesting strong ocean-atmosphere-land teleconnection. In order to test whether such teleconnection existed in the past, we compare the retrospective forecast skill to the skills obtained using the available ocean-atmosphere teleconnection and streamflow reconstructions derived from tree rings. We find much lower skill in the reconstructed record. Using frequency analysis, we show that the streamflow and sea surface temperature oscillations in the instrumental records all have dominant low frequency periodicities (>35 years) that explain much of the total variance. However, such dominant periodicities do not appear in the power spectra of the reconstructed records of AMO, PDO and streamflow. Given that these dominant low periodicities are likely responsible for the high prediction skill in the instrumental record, it remains uncertain whether reliable decadal streamflow predictions in the upper Colorado River basin will be possible in the years ahead.

  8. The Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data - HOAPS-3

    NASA Astrophysics Data System (ADS)

    Andersson, A.; Fennig, K.; Klepp, C.; Bakan, S.; Graßl, H.; Schulz, J.

    2010-09-01

    The availability of microwave instruments on satellite platforms allows the retrieval of essential water cycle components at high quality for improved understanding and evaluation of water processes in climate modelling. HOAPS-3, the latest version of the satellite climatology "Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data" provides fields of turbulent heat fluxes, evaporation, precipitation, freshwater flux and related atmospheric variables over the global ice-free ocean. This paper describes the content, methodology and retrievals of the HOAPS climatology. A sophisticated processing chain, including all available Special Sensor Microwave Imager (SSM/I) instruments aboard the satellites of the Defense Meteorological Satellites Program (DMSP) and careful inter-sensor calibration, ensures a homogeneous time-series with dense data sampling and hence detailed information of the underlying weather situations. The completely reprocessed data set with a continuous time series from 1987 to 2005 contains neural network based algorithms for precipitation and wind speed and Advanced Very High Resolution Radiometer (AVHRR) based SST fields. Additionally, a new 85 GHz synthesis procedure for the defective SSM/I channels on DMSP F08 from 1988 on has been implemented. Freely available monthly and pentad means, twice daily composites and scan-based data make HOAPS-3 a versatile data set for studying ocean-atmosphere interaction on different temporal and spatial scales. HOAPS-3 data products are available via http://www.hoaps.org.

  9. The Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data - HOAPS-3

    NASA Astrophysics Data System (ADS)

    Andersson, A.; Fennig, K.; Klepp, C.; Bakan, S.; Graßl, H.; Schulz, J.

    2010-05-01

    The availability of microwave instruments on satellite platforms allows the retrieval of essential water cycle components at high quality for improved understanding and evaluation of water processes in climate modelling. HOAPS-3, the latest version of the satellite climatology "Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data" provides fields of turbulent heat fluxes, evaporation, precipitation, freshwater flux and related atmospheric variables over the global ice-free ocean. This paper describes the content, methodology and retrievals of the HOAPS climatology. A sophisticated processing chain, including all available Special Sensor Microwave Imager (SSM/I) instruments aboard the satellites of the Defense Meteorological Satellites Program (DMSP) and careful inter-sensor calibration, ensures a homogeneous time-series with dense data sampling and hence detailed information of the underlying weather situations. The completely reprocessed data set with a continuous time series from 1987 to 2005 contains neural network based algorithms for precipitation and wind speed and Advanced Very High Resolution Radiometer (AVHRR) based SST fields. Additionally, a new 85 GHz synthesis procedure for the defective SSM/I channels on DMSP F08 from 1989 on has been implemented. Freely available monthly and pentad means, twice daily composites and scan-based data make HOAPS-3 a versatile data set for studying ocean-atmosphere interaction on different temporal and spatial scales. HOAPS-3 data products are available via http://www.hoaps.org.

  10. Studies of oceanic, atmospheric, cryospheric, and fluvial processes through spectral analysis of seismic noise

    NASA Astrophysics Data System (ADS)

    Anthony, Robert Ernest

    During the past decade, there has been rapidly growing interest in using the naturally occurring seismic noise field to study oceanic, atmospheric, and surface processes. As many seismic noise sources, are non-impulsive and vary over a broad range of time scales (e.g., minutes to decades), they are commonly analyzed using spectral analysis or other hybrid time-frequency domain methods. The PQLX community data analysis program, and the recently released Noise Tool Kit that I co-developed with Incorporated Research Institutions for Seismology's Data Management Center are used here to characterize seismic noise for a variety of environmental targets across a broad range of frequencies. The first two chapters of the dissertation place a strong emphasis on analysis of environmental microseism signals, which occur between 1-25 s period and are dominated by seismic surface waves excited by multiple ocean-solid Earth energy transfer processes. I move away from microseisms in Chapter 3 to investigate the generally higher frequency seismic signals (> 0.33 Hz) generated by fluvial systems. In Chapter 1, I analyze recently collected, broadband data from temporary and permanent Antarctic stations to quantitatively assess background seismic noise levels across the continent between 2007-2012, including substantial previously unsampled sections of the Antarctic continental interior. I characterize three-component noise levels between 0.15-150 s using moving window probability density function-derived metrics and analyze seismic noise levels in multiple frequency bands to examine different noise sources. These metrics reveal and quantify patterns of significant seasonal and geographic noise variations across the continent, including the strong effects of seasonal sea ice variation on the microseism, at a new level of resolution. Thorough analysis of the seismic noise environment and its relation to instrumentation and siting techniques in the Polar Regions facilitates new science

  11. The Influence of Indian Ocean Atmospheric Circulation on Warm Pool Hydroclimate During the Holocene Epoch

    NASA Technical Reports Server (NTRS)

    Tierney, J.E.; Oppo, D. W.; LeGrande, A. N.; Huang, Y.; Rosenthal, Y.; Linsley, B. K.

    2012-01-01

    Existing paleoclimate data suggest a complex evolution of hydroclimate within the Indo-Pacific Warm Pool (IPWP) during the Holocene epoch. Here we introduce a new leaf wax isotope record from Sulawesi, Indonesia and compare proxy water isotope data with ocean-atmosphere general circulation model (OAGCM) simulations to identify mechanisms influencing Holocene IPWP hydroclimate. Modeling simulations suggest that orbital forcing causes heterogenous changes in precipitation across the IPWP on a seasonal basis that may account for the differences in time-evolution of the proxy data at respective sites. Both the proxies and simulations suggest that precipitation variability during the September-November (SON) season is important for hydroclimate in Borneo. The preeminence of the SON season suggests that a seasonally lagged relationship between the Indian monsoon and Indian Ocean Walker circulation influences IPWP hydroclimatic variability during the Holocene.

  12. Decadal variability of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model

    NASA Technical Reports Server (NTRS)

    Mehta, Vikram M.; Delworth, Thomas

    1995-01-01

    processes may be responsible for the choice of the decadal and multidecadal timescales. Finally, it must be emphasized that the GFDL coupled ocean-atmosphere model generates the decadal and multidecadal timescale variability without any externally applied force, solar or lunar, at those timescales.

  13. Decadal variability of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model

    NASA Technical Reports Server (NTRS)

    Mehta, Vikram M.; Delworth, Thomas

    1995-01-01

    processes may be responsible for the choice of the decadal and multidecadal timescales. Finally, it must be emphasized that the GFDL coupled ocean-atmosphere model generates the decadal and multidecadal timescale variability without any externally applied force, solar or lunar, at those timescales.

  14. Forecasting of rainfall using ocean-atmospheric indices with a fuzzy neural technique

    NASA Astrophysics Data System (ADS)

    Srivastava, Gaurav; Panda, Sudhindra N.; Mondal, Pratap; Liu, Junguo

    2010-12-01

    SummaryForecasting of rainfall is imperative for rainfed agriculture of arid and semi-arid regions of the world where agriculture consumes nearly 80% of the total water demand. Fuzzy-Ranking Algorithm (FRA) is used to identify the significant input variables for rainfall forecast. A case study is carried out to forecast monthly rainfall in India with several ocean-atmospheric predictor variables. Three different scenarios of ocean-atmospheric predictor variables are used as a set of possible input variables for rainfall forecasting model: (1) two climate indices, i.e. Southern Oscillation Index (SOI) and Pacific Decadal Oscillation Index (PDOI); (2) Sea Surface Temperature anomalies (SSTa) in the 5° × 5° grid points in Indian Ocean; and (3) both the climate indices and SSTa. To generate a set of possible input variables for these scenarios, we use climatic indices and the SSTa data with different lags between 1 and 12 months. Nonlinear relationship between identified inputs and rainfall is captured with an Artificial Neural Network (ANN) technique. A new approach based on fuzzy c-mean clustering is proposed for dividing data into representative subsets for training, testing, and validation. The results show that this proposed approach overcomes the difficulty in determining optimal numbers of clusters associated with the data division technique of self-organized map. The ANN model developed with both the climate indices and SSTa shows the best performance for the forecast of the monthly August rainfall in India. Similar approach can be applied to forecast rainfall of any period at selected climatic regions of the world where significant relationship exists between the rainfall and climate indices.

  15. Late Holocene Water Mass Change in the Norwegian Sea Caused by Different Ocean- Atmosphere Circulation Patterns

    NASA Astrophysics Data System (ADS)

    Bauch, H. A.; Kandiano, E. S.

    2008-12-01

    There is common consensus that the Holocene climate history of the polar North was strongly tied to the insolation change on one the hand and the specific post-deglacial water mass evolution on the other. Using deep-sea sediment records we have investigated two crucial areas of the Norwegian Sea (Arctic Front; Voring Plateau) in order to understand the natural variability of oceanic-atmospheric change in this area since the middle Holocene. The information available from this longer time scale allows better insight for predictive purposes, since these records would then provide a longer time frame within which to evaluate any natural variability. We analyzed different foraminiferal species for O-isotope analyses and interpreted the planktic foraminiferal assemblage variations in combination with records of ice-rafted detritus (IRD) >150μm. It is shown that surface temperatures started to decrease at the Arctic Front after 6 ka, concomitant with the occurrence of IRD. This cooling trend continued into the Little Ice Age (LIA) when highest IRD input is noted. At the Voring Plateau, relatively stable and warm conditions are still recognized between 2.5 and 1 ka, in both planktic and benthic O-isotopes. Although variability among certain foraminiferal species would indicate some surface changes, the abundance of the polar species N. pachyderma (s) increased from 30% before 1 ka to 70% during the LIA. This increase is associated with highly variable isotope values through the entire water column (up to 1‰) and the sudden occurrence of basaltic IRD, presumably from Iceland. We interpret the records of the last 2.5 ka, and in particular the time of the LIA, to be the result of a major change in overall ocean-atmosphere circulation (from NAO+ to NAO-) which forced colder water masses and sea ice far into the eastern Norwegian Sea.

  16. Amplification of European Little Ice Age by sea ice-ocean-atmosphere feedbacks

    NASA Astrophysics Data System (ADS)

    Lehner, Flavio; Born, Andreas; Raible, Christoph C.; Stocker, Thomas F.

    2013-04-01

    The transition from the Medieval Climate Anomaly (~950-1250 AD) to the Little Ice Age (~1400-1700 AD) is believed to have been driven by an interplay of external forcing and climate system-internal variability. While the hemispheric signal seems to have been dominated by solar irradiance and volcanic eruptions, the understanding of mechanisms shaping the climate on continental scale is less robust. Examining an ensemble of transient model simulations as well as a new type of sensitivity experiments with artificial sea ice growth, we identify a sea ice-ocean-atmosphere feedback mechanism that amplifies the Little Ice Age cooling in the North Atlantic-European region and produces the temperature pattern expected from reconstructions. Initiated by increasing negative forcing, the Arctic sea ice substantially expands at the beginning of the Little Ice Age. The excess of sea ice is exported to the subpolar North Atlantic, where it melts, thereby weakening convection of the ocean. As a consequence, northward ocean heat transport is reduced, reinforcing the expansion of the sea ice and the cooling of the Northern Hemisphere. In the Nordic Seas, sea surface height anomalies cause the oceanic recirculation to strengthen at the expense of the warm Barents Sea inflow, thereby further reinforcing sea ice growth in the Barents Sea. The absent ocean-atmosphere heat flux in the Barents Sea results in an amplified cooling over Northern Europe. The positive nature of this feedback mechanism enables sea ice to remain in an expanded state for decades to centuries and explain sustained cold periods over Europe such as the Little Ice Age. Support for the feedback mechanism comes from recent proxy reconstructions around the Nordic Seas.

  17. The relative role of ocean-atmosphere interaction and African easterly waves in the generation and development of Tropical cyclones in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Cabos, William; Sein, Dmitry; Hodges, Kevin; Jacob, Daniela

    2016-04-01

    We use the regionally coupled ocean - atmosphere model ROM and its atmospheric component REMO in standalone configuration in order to assess the relative role of ocean feedbacks and the African easterly waves in the simulation of tropical cyclonic activity in the Atlantic ocean. To this end, a number of coupled and uncoupled simulations forced by ERA-Interim boundary conditions have been carried out. In one set of simulations, the atmospheric domain includes the Northern Africa land masses, where the easterly waves are formed. In a second set of simulations, the easterly waves are taken from the ERA Interim reanalysis, as atmospheric domain excludes explicitly the African land masses. We study the statistics of modeled tracks of the tropical cyclones in the simulations. We found that the coupling has a strong impact on the number of tropical cyclones generated in the Northern Tropical Atlantic. In the coupled run it was close to the observations, while in the uncoupled runs the number of tropical cyclones was strongly overestimated. The coupling also influences the simulated position of the ITCZ.

  18. Simulation of the Caribbean Climate during the early and mid-Holocene with GCM

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Lohmann, Gerrit

    2010-05-01

    Although a set of coupled ocean-atmosphere simulations using state-of-the-art climate models is available for the mid-Holocene since PMIP2 (Paleoclimate Modeling Intercomparison Project Phase II), little research has been directed towards climate variability in the early Holocene when the Laurentide ice sheet presented. The Holocene thermal maximum between 11,000 and 5,000 years ago is mostly recorded in the middle and high latitudes; however, the subtropical and tropical regions play a quite important role in modulating the global climate, and more debates exist concerning the consistence of simulation and proxy reconstructions in these regions. Long-term Simulations with a coupled atmosphere-ocean-vegetation general circulation model (ECHAM5/JSBACH/MPI-OM ) configured for the present, mid-Holocene (6 ka B.P.) and early Holocene (9 ka B.P. with/without Laurentide ice sheet) are performed in this study by specifying the appropriate change of forcing, i.e., orbital parameter, greenhouse gases and topography. Prescribed changes in insolation due to orbital variations are considered to be the major external forcing, which leads to increased seasonality in the Caribbean as indicated by the surface temperature, with a cooling in the winter and a warming in the summer. The magnitude of the seasonality variation is approximately 1-2°C, comparably much smaller than that in the extratropics, whereas, it is consistent with coral-based δ18O and Sr/Ca seasonality analysis. Compared to the mid-Holocene, the early Holocene seasonality increase is more dramatic due to more incoming radiation in summer and less in winter. The sea surface temperature (SST) is similar, showing the expansion of the Atlantic warm pool in summer during the Holocene. Weakening of the thermohaline circulation during the Holocene results in less northwards heat transport at 30°N and thus partly contributes to the warming in the summer. Comparison of the two simulations for the early Holocene shows that

  19. Observations of Recent Arctic Sea Ice Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and Ice Production

    NASA Technical Reports Server (NTRS)

    Kurtz, N. T.; Markus, T.; Farrell, S. L.; Worthen, D. L.; Boisvert, L. N.

    2011-01-01

    Using recently developed techniques we estimate snow and sea ice thickness distributions for the Arctic basin through the combination of freeboard data from the Ice, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic sea ice model to calculate ocean-atmosphere heat exchange and ice volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and ice growth rates are in agreement with previous observations over multiyear ice. In this study, we calculate heat fluxes and ice growth rates for the full distribution of ice thicknesses covering the Arctic basin and determine the impact of ice thickness change on the calculated values. Thinning of the sea ice is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in sea ice thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in ice thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of sea ice. The anomalously low sea ice coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that sea ice losses are now playing a role in increasing surface air temperatures in the Arctic.

  20. The Lithosphere-Ocean-Atmosphere Seismo-Electromagnetic Transformer and Applications for the Seaquake Monitoring

    NASA Astrophysics Data System (ADS)

    Novik, O.; Ershov, S.; Mikhaylovskaya, I.; Ruzhin, Y.

    2004-12-01

    To clear the physical nature of seismic electromagnetic (EM) signals observed in near sea regions a mathematical model of seismo-hydro-EM interaction in a lithosphere-ocean-atmosphere domain is formulated on the basis of principles of electrodynamics of moving continuous media. Generation and propagation of seismic, EM, temperature, and hydrodynamic waves caused by elastic displacements (main frequencies 0.1 to 1 Hz and amplitude and duration of the order of a few cm and sec respectively) in the upper mantle under the seafloor are traced numerically up to the low boundary of the ionosphere. The first measurable (50 pT) signal of the described seismic excitation (SE) of the ocean lithosphere arises in the form of ULF oscillations, in the frequency range of the SE, of the horizontal component of the magnetic field at the sea bottom's surface 3.5 sec after the beginning (t = 0) of the seaquake (the axes of polarization of the SE is approximately vertical). The seismic P wave caused by the SE arrives at the bottom a few sec later (depends on the focal depth). Let us note that the computed diffusive EM signal arises (t = 7 sec) at the sea surface together with the hydro-acoustic wave propagating upward from the sea bottom deformed by the seismic P wave. By runs with different reasonable geophysical characteristics of the medium and weak precursory SEs (see above), the magnetic signal amplitude is of the order of a few hundreds of pT at the sea surface and a of the order of a few tens of pT near the lower boundary of ionosphere, t=10 sec. The signal amplitude increases in proportion to the amplitude of a SE. So, the lithosphere-ocean-atmosphere system may be regarded as a seismo-EM transformer. The computed long (150 km) tsunami wave's amplitude far from a shore is about 15 cm only and EM signals (propagating in the atmosphere above the ocean with the light velocity) must be recorded. Basing on these and other numerical results (computed amplitudes, frequencies and

  1. Ocean-atmosphere state dependence of the atmospheric response to Arctic sea ice loss

    NASA Astrophysics Data System (ADS)

    Osborne, Joe; Screen, James; Collins, Mat

    2017-04-01

    The Arctic is warming faster than the global average. This disproportionate warming - known as Arctic amplification - has caused significant local changes to the Arctic system and more uncertain remote changes across the Northern Hemisphere midlatitudes. Here, an atmospheric general circulation model (AGCM) is used to test the sensitivity of the atmospheric and surface response to Arctic sea ice loss to the phase of the Atlantic Multidecadal Oscillation (AMO), which varies on (multi-) decadal time scales. Four experiments are performed, combining low and high sea ice states with global sea surface temperature (SST) anomalies associated with opposite phases of the AMO. A trough-ridge-trough response to wintertime sea ice loss is seen in the Pacific-North American sector in the negative phase of the AMO. We propose that this is a consequence of an increased meridional temperature gradient in response to sea ice loss, just south of the climatological maximum, in the midlatitudes of the central North Pacific. This causes a southward shift in the North Pacific storm track, which strengthens the Aleutian low with circulation anomalies propagating into North America. While the climate response to sea ice loss is sensitive to AMO-related SST anomalies in the North Pacific, there is little sensitivity to larger-magnitude SST anomalies in the North Atlantic. With background ocean-atmosphere states persisting for a number of years, there is the potential to improve predictions of the impacts of Arctic sea ice loss on decadal time scales.

  2. Assessing the capability of EOS sensors in measuring ocean-atmosphere moisture exchange

    NASA Technical Reports Server (NTRS)

    Liu, W. T.

    1985-01-01

    As part of the Science Synergism Studies to identify interdisciplinary Scientific studies, which could be addressed by the Environmental Observing System (EOS), the techniques being developed to measure ocean-atmosphere moisture exchanges using satellite sensors were evaluated. Studies required to use sensors proposed for EOS were examined. A method has been developed to compute the moisture flux using the wind speed, sea surface temperature, and preciptable water measured by satellite sensors. It relies on a statistical model which predicts surface-level humidity from precipitable water. The Scanning Multichannel Microwave Radiometer (SMMR) measures all 3 parameters and was found to be sensitive to the annual cycle and large interannual variations such as the 1982 to 1983 El Nino. There are systematic differences between geophysical parameters measured by Nimbus/SMMR and in situ measurements. After quadratic trends and crosstalks were removed from the parameters through multivariate regressions, the latent heat fluxes computed from SMMR agree with those computed from ship reports to within 30 W/sq m. The poor quality of ship reports may be the cause of a portion of this scatter. Similar results are found using SEASAT/SMMR data. When the scatterometer winds were used instead of the SMMR winds, the difference between the satellite fluxes and the ship fluxes was reduced.

  3. AMS Observations over Coastal California from the Biological and Oceanic Atmospheric Study (BOAS)

    NASA Astrophysics Data System (ADS)

    Bates, K. H.; Coggon, M. M.; Hodas, N.; Negron, A.; Ortega, A. M.; Crosbie, E.; Sorooshian, A.; Nenes, A.; Flagan, R. C.; Seinfeld, J.

    2015-12-01

    In July 2015, fifteen research flights were conducted on a US Navy Twin Otter aircraft as part of the Biological and Oceanic Atmospheric Study (BOAS) campaign. The flights took place near the California coast at Monterey, to investigate the effects of sea surface temperature and algal blooms on oceanic particulate emissions, the diurnal mixing of urban pollution with other airmasses, and the impacts of biological aerosols on the California atmosphere. The aircraft's payload included an aerosol mass spectrometer (AMS), a differential mobility analyzer, a cloud condensation nuclei counter, a counterflow virtual impactor, a cloudwater collector, and two instruments designed to detect biological aerosols - a wideband integrated biological spectrometer and a SpinCon II - as well as a number of meteorology and aerosol probes, two condensation particle counters, and instruments to measure gas-phase CO, CO2, O3, and NOx. Here, we describe in depth the objectives and outcomes of BOAS and report preliminary results, primarily from the AMS. We detail the spatial characteristics and meteorological variability of speciated aerosol components over a strong and persistent bloom of Pseudo-Nitzschia, the harmful algae that cause 'red tide', and report newly identified AMS markers for biological particles. Finally, we compare these results with data collected during BOAS over urban, forested, and agricultural environments, and describe the mixing observed between oceanic and terrestrial airmasses.

  4. Ocean-atmosphere forcing of centennial hydroclimatic variability in the Pacific Northwest

    USGS Publications Warehouse

    Steinman, Byron A.; Abbott, Mark B.; Mann, Michael E.; Ortiz, Joseph D.; Feng, Song; Pompeani, David P.; Stansell, Nathan D.; Anderson, Lesleigh; Finney, Bruce P.; Bird, Broxton W.

    2014-01-01

    Reconstructing centennial timescale hydroclimate variability during the late Holocene is critically important for understanding large-scale patterns of drought and their relationship with climate dynamics. We present sediment oxygen isotope records spanning the last two millennia from 10 lakes, as well as climate model simulations, indicating that the Little Ice Age was dry relative to the Medieval Climate Anomaly in much of the Pacific Northwest of North America. This pattern is consistent with observed associations between the El Niño Southern Oscillation (ENSO), the Northern Annular Mode and drought as well as with proxy-based reconstructions of Pacific ocean-atmosphere variations over the past 1000 years. The large amplitude of centennial variability indicated by the lake data suggests that regional hydroclimate is characterized by longer-term shifts in ENSO-like dynamics, and that an improved understanding of the centennial timescale relationship between external forcing and drought conditions is necessary for projecting future hydroclimatic conditions in western North America.

  5. Decadal Variations in Eastern Canada's Taiga Wood Biomass Production Forced by Ocean-Atmosphere Interactions.

    PubMed

    Boucher, Etienne; Nicault, Antoine; Arseneault, Dominique; Bégin, Yves; Karami, Mehdi Pasha

    2017-05-26

    Across Eastern Canada (EC), taiga forests represent an important carbon reservoir, but the extent to which climate variability affects this ecosystem over decades remains uncertain. Here, we analyze an extensive network of black spruce (Picea mariana Mill.) ring width and wood density measurements and provide new evidence that wood biomass production is influenced by large-scale, internal ocean-atmosphere processes. We show that while black spruce wood biomass production is primarily governed by growing season temperatures, the Atlantic ocean conveys heat from the subtropics and influences the decadal persistence in taiga forests productivity. Indeed, we argue that 20-30 years periodicities in Sea Surface Temperatures (SSTs) as part of the the Atlantic Multi-decadal Oscillation (AMO) directly influence heat transfers to adjacent lands. Winter atmospheric conditions associated with the North Atlantic Oscillation (NAO) might also impact EC's taiga forests, albeit indirectly, through its effect on SSTs and sea ice conditions in surrounding seas. Our work emphasizes that taiga forests would benefit from the combined effects of a warmer atmosphere and stronger ocean-to-land heat transfers, whereas a weakening of these transfers could cancel out, for decades or longer, the positive effects of climate change on Eastern Canada's largest ecosystem.

  6. Frigatebird behaviour at the ocean-atmosphere interface: integrating animal behaviour with multi-satellite data.

    PubMed

    De Monte, Silvia; Cotté, Cedric; d'Ovidio, Francesco; Lévy, Marina; Le Corre, Matthieu; Weimerskirch, Henri

    2012-12-07

    Marine top predators such as seabirds are useful indicators of the integrated response of the marine ecosystem to environmental variability at different scales. Large-scale physical gradients constrain seabird habitat. Birds however respond behaviourally to physical heterogeneity at much smaller scales. Here, we use, for the first time, three-dimensional GPS tracking of a seabird, the great frigatebird (Fregata minor), in the Mozambique Channel. These data, which provide at the same time high-resolution vertical and horizontal positions, allow us to relate the behaviour of frigatebirds to the physical environment at the (sub-)mesoscale (10-100 km, days-weeks). Behavioural patterns are classified based on the birds' vertical displacement (e.g. fast/slow ascents and descents), and are overlaid on maps of physical properties of the ocean-atmosphere interface, obtained by a nonlinear analysis of multi-satellite data. We find that frigatebirds modify their behaviours concurrently to transport and thermal fronts. Our results suggest that the birds' co-occurrence with these structures is a consequence of their search not only for food (preferentially searched over thermal fronts) but also for upward vertical wind. This is also supported by their relationship with mesoscale patterns of wind divergence. Our multi-disciplinary method can be applied to forthcoming high-resolution animal tracking data, and aims to provide a mechanistic understanding of animals' habitat choice and of marine ecosystem responses to environmental change.

  7. Behavior of the Brightness Temperature of the Ocean-Atmosphere System Under Conditions of Midlatitude and Tropical Cyclone Activity

    NASA Astrophysics Data System (ADS)

    Grankov, A. G.; Milshin, A. A.; Novichikhin, E. P.

    2014-03-01

    We analyze the behavior of the ocean-atmosphere system characteristics based on direct (contact) and satellite microwave radiometric measurements. Some common and distinctive features of their dynamics in the mid-latitudes of the North Atlantic (in its Norwegian, Newfoundland, and Gulf Stream energy-active zones), which significanty affect the weather conditions in Europe, and in the tropical latitudes of the Atlantic (the Gulf of Mexico and the Bahamas area), which are the sources of tropical cyclogenesis, are considered.

  8. Titration of the Earth: Ocean-Atmosphere Evolution Recorded in Marine Carbonates

    NASA Astrophysics Data System (ADS)

    Kah, L. C.

    2012-12-01

    feedback for understanding the temporal evolution of the ocean-atmosphere system.

  9. Long-lead probabilistic forecasting of streamflow using ocean-atmospheric and hydrological predictors

    NASA Astrophysics Data System (ADS)

    Araghinejad, Shahab; Burn, Donald H.; Karamouz, Mohammad

    2006-03-01

    A geostatistically based approach with a local regression method is used to predict the magnitude of seasonal streamflow using ocean-atmospheric signals and the hydrological condition of a basin as predictors. The model characterizes the stochastic behavior of a forecast variable by generating a conditional distribution of the predicted value for different hydroclimatic conditions. The correlation structure between dependent and independent variables is represented by the variography of the predicted values in which the distance variable in the variogram is determined by measuring the distance between the predictors. This variogram in a virtual field constructed from the predictors makes it possible to predict variables as unmeasured points while considering historic information as measurement points of the field. Different types of kriging, as well as a generalized linear model regression, are used to predict data in interpolation and extrapolation modes. The forecast skill is evaluated using a linear error in probability space score for different combinations of predictors and different kriging methods. The method is applied to a case study of the Zayandeh-rud River in Isfahan, Iran. The utility of the method is demonstrated for forecasting autumn-winter and spring streamflow using the Southern Oscillation Index, the North Atlantic Oscillation, serial correlation between seasonal streamflow series, and the snow budget. The study analyzes the application of the proposed method in comparison with a K-nearest neighbor regression method. The results of this study show that the proposed method can significantly improve the long-lead probabilistic forecast skill for a nonlinear relationship between hydroclimatic predictors and streamflow in a region.

  10. Multisegment statistical bias correction of daily GCM precipitation output

    NASA Astrophysics Data System (ADS)

    Grillakis, Manolis G.; Koutroulis, Aristeidis G.; Tsanis, Ioannis K.

    2013-04-01

    improved bias correction method for daily general circulation model (GCM) precipitation is presented. The method belongs to the widely used family of quantile mapping correction methods. The method uses different instances of gamma function that are fitted on multiple discrete segments on the precipitation cumulative density function (CDF), instead of the common quantile-quantile approach that uses one theoretical distribution to fit the entire CDF. This imposes to the method the ability to better transfer the observed precipitation statistics to the raw GCM data. The selection of the segment number is performed by an information criterion to poise between complexity and efficiency of the transfer function. The global precipitation output of Institut Pierre Simon Laplace Coupled Model for the period 1960-2000 is bias corrected using the precipitation observations of WATCH Forcing Data. The 1960-1980 period of observations was used to calibrate the bias correction method, while 1981-2000 was used for validation. The proposed method performs well on the validation period, according to two performance estimators.

  11. Atmosphere-only GCM (ACCESS1.0) simulations with prescribed land surface temperatures

    NASA Astrophysics Data System (ADS)

    Ackerley, Duncan; Dommenget, Dietmar

    2016-06-01

    General circulation models (GCMs) are valuable tools for understanding how the global ocean-atmosphere-land surface system interacts and are routinely evaluated relative to observational data sets. Conversely, observational data sets can also be used to constrain GCMs in order to identify systematic errors in their simulated climates. One such example is to prescribe sea surface temperatures (SSTs) such that 70 % of the Earth's surface temperature field is observationally constrained (known as an Atmospheric Model Intercomparison Project, AMIP, simulation). Nevertheless, in such simulations, land surface temperatures are typically allowed to vary freely, and therefore any errors that develop over the land may affect the global circulation. In this study therefore, a method for prescribing the land surface temperatures within a GCM (the Australian Community Climate and Earth System Simulator, ACCESS) is presented. Simulations with this prescribed land surface temperature model produce a mean climate state that is comparable to a simulation with freely varying land temperatures; for example, the diurnal cycle of tropical convection is maintained. The model is then developed further to incorporate a selection of "proof of concept" sensitivity experiments where the land surface temperatures are changed globally and regionally. The resulting changes to the global circulation in these sensitivity experiments are found to be consistent with other idealized model experiments described in the wider scientific literature. Finally, a list of other potential applications is described at the end of the study to highlight the usefulness of such a model to the scientific community.

  12. Evaluating the relationship between oceanic-atmospheric indices and variability in the streamflow: A continental U.S. study

    NASA Astrophysics Data System (ADS)

    Sagarika, S.; Kalra, A.; Ahmad, S.

    2013-12-01

    Oceanic-atmospheric indices and variability has been found to influence the hydrological process. This study evaluates the possible influences of two indicators of oceanic-atmospheric variability i.e., sea surface temperatures (SSTs) and 500 mbar geopotential height (Z500) index on 864 unimpaired streamflows stations categorized according to hydrologic unit codes for a 60 year period from 1950 to 2010 in the continental United States. Singular Value Decomposition (SVD) is used to evaluate the spatio-temporal association between oceanic-atmospheric indices and streamflow. A lead-time approach of six months i.e., seasonal average of monthly SSTs and Z500 for April to September of previous year was used to obtain the temporal expansion series between the oceanic-atmospheric indicators and water year streamflow values. This was followed by an interdecadal-temporal evaluation of the Pacific and Atlantic Ocean based warm and cold phases of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). This resulted in the identification of new regions of highly correlated SSTs and Z500 that may not be represented by conservative index regions of El Niño Southern Oscillation (ENSO), PDO, and AMO. Results showed the Pacific SSTs had strong correlations with the Midwest, southern South-Atlantic-Gulf and Pacific Northwest regions, where as the Atlantic SSTs showed strong correlations with New England, South-Atlantic-Gulf and Upper and Lower Colorado regions. The Pacific and Atlantic Z500 showed strong correlations with the Midwest, New England, Souris-Red-Rainy, Arkansas-White-Red, and Texas-Gulf regions. The PDO warm phase showed strong correlations with most of California, Upper and Lower Colorado, and South-Atlantic-Gulf regions; the PDO cold phases showed correlations with Pacific Northwest, eastern Ohio, and South-Atlantic-Gulf regions. The warm phase of AMO showed correlations with Midwest, Souris-Red-Rainy, Upper Mississippi, Arkansas

  13. Regional Ocean-Atmosphere Prediction System (ROAPS) and its application to land-air-sea interaction processes in the southeastern United States

    NASA Astrophysics Data System (ADS)

    Jin, Hao

    In this study, a three-dimensional Regional Ocean- Atmosphere Prediction System (ROAPS) using a terrain- following vertical coordinate is developed by coupling the Advanced Regional Prediction System (ARPS) with the Princeton Ocean Model (POM) to provide ocean-atmosphere prediction. The three models: ARPS, POM, and ROAPS are used to study coastal land-air-sea interaction in the southeastern U.S. during the second Intensive Observation Period (IOP 2) of the Genesis of Atlantic Lows Experiment (GALE). Both coupled and uncoupled simulations are conducted and compared with each other to investigate the importance of the coupled air-sea interaction processes. Coastal fronts are simulated using ARPS with fixed SST in the control run of atmospheric simulations. Results show that coastal fronts can be simulated within the half-a- day simulation, and the existence of the SST gradients in coastal water is a primary factor for the frontogenesis along the Carolina coast. A simulation with hourly SST data generated from POM is used to compare with the control run. The simulated coastal front is sensitive to the SST distribution in the coastal waters and fixed SST cannot capture the detailed mesoscale features with a time scale of one to two days. Results from a series of sensitivity experiments indicate that low level easterly ambient winds are most favorable for the Carolina coastal frontogenesis and cold-air damming east of the Appalachian Mountains helps maintain the coastal front. Short-term shelf oceanic responses to surface turbulent fluxes across air-sea interface are simulated using POM with realistic ocean bottom topography under different atmospheric forcings. The initial state of the SST and ocean currents is generated by a 30-day dynamic adjustment toward the observed characteristics and a feature model of the Gulf Stream. Results indicate that surface atmospheric cooling can decrease the SST in the shelf water within 24 hours and increase the vertical mixing to

  14. The Oceanic, Atmospheric and Vegetation Response to Pliocene Closing of the Indonesian Passages

    NASA Astrophysics Data System (ADS)

    Krebs-Kanzow, U.; Park, W.; Schneider, B.

    2010-12-01

    Tectonic changes of the Early- to Mid-Pliocene largely modified the Indonesian Passages by constricting and shallowing southerly passages between todays New Guinea and Sulawesi. While nowadays the Indonesian throughflow (ITF) of upper ocean waters from the tropical Pacific to the Indian Ocean primarily occurs through the Makassar Strait, these deepened and widened southerly passages might have been an important alternative pathway which might have influenced the ITF and its water masses and eventually climate of the Indo-Pacific. We study the climate response to changes in the geometry of the Indonesian Passages by using a global climate model (GCM). We compare control experiments using the present day topography (constricted set-up) with experiments using a topography resembling the early Pliocene situation (widened set-up). We find that circulation through the Indonesian Archipelago is considerably changed down to a depth of 1000 meters. In the constricted setting the ITF is weakened while the strength of the Pacific western boundary currents increases. Consistent with recent proxy evidence this results in cooling subsurface waters in the Indian Ocean while surface waters of the Pacific warm pool area exhibit a slight local increase in temperature. We observe strong changes in precipitation of the Indo-Pacific which is related to Sea surface temperature anomalies that do not exceed 1 °C. In particular the Australian continent experiences a pronounced aridification. Using an uncouple vegetation model we demonstrate that the simulated climate change might explain the observed Miocene to Pleistocene desertification of Australia

  15. Latest results of the LMD Venus GCM

    NASA Astrophysics Data System (ADS)

    Lebonnois, S.; Marcq, E.; Lott, F.

    2012-12-01

    The LMD Venus General Circulation Model (GCM), under development since 2005, models the circulation in Venus atmosphere (from the surface up to roughly 100 km), in particular the superrotation feature. The temperature structure is computed using a specific radiative transfer module based on net-exchange matrix formulation. Since the publication of the GCM details (Lebonnois et al, JGR 115, 2010, doi:10.1029/2009JE003458), some improvements were done, especially for the boundary layer scheme that affects the exchange of angular momentum between atmosphere and surface. Surprising impact of initial conditions on the steady-state zonal winds is also discussed. Passive tracers, tuned to mimic CO and OCS distributions, have also been added to the model to simulate the latitudinal distributions induced by transport. In this presentation, comparisons between our latest simulations and available observations from Venus Express (winds, temperature fields, CO and OCS distributions) are detailed: zonal and meridional wind distributions in the cloud region and above, thermal tide features in winds and temperature near the cloud-top, CO and OCS latitudinal profiles below the clouds. These comparisons help constrain the meridional circulation and its impact on trace species distributions, the chemical relaxation timescale of the same trace species as well as the thermal tides and their role in the angular momentum budget and in the superrotation mechanism. The impact on the zonal wind field of gravity waves that may be generated near the surface is currently investigated with a new parametrisation. These gravity waves have been suggested as a significant contributor in the angular momentum budget and superrotation mechanism (Hou and Farrell, J. Atmos. Sci. 44, pp.1049-1061, 1987, doi:10.1175/1520-0469(1987)044<1049:SIBCLA>2.0.CO;2). This parametrisation and its first results are presented here.

  16. Should we use quantile mapping to post-process seasonal GCM precipitation forecasts?

    NASA Astrophysics Data System (ADS)

    Zhao, Tongtiegang; Schepen, Andrew; Bennett, James; Wang, Qj; Wood, Andy; Robertson, David; Ramos, Maria-Helena

    2017-04-01

    Quantile mapping (QM) - the correction of cumulative distribution functions - has been widely used to correct biases in seasonal ensemble precipitation forecasts from coupled global climate models (GCMs). The literature commonly demonstrates QM's efficacy for bias-correction, particularly in climate change studies. A crucial difference between climate change projections and seasonal GCM forecasts is that seasonal forecasts are synchronous with observations. This opens the possibility for more sophisticated post-processing methods that 1) correct biases but also 2) correct ensemble spread and, crucially, 3) ensure forecasts are at least as skilful as climatology - a property termed 'coherence'. Coherence is a necessary precursor for forecasts to have economic value. Through a case study of precipitation predictions from the Australian POAMA GCM, we show that QM does not guarantee reliable ensemble forecasts, nor can it ensure 'coherent' forecasts. Further, we show that a formal statistical calibration using the Bayesian Joint Probability (BJP) modelling approach ensures unbiased, reliable and coherent forecasts. In choosing a post-processing method for GCM precipitation forecasts, the technical benefits of formal calibration methods over QM have to be weighed against their added complexity. In general, however, we caution against the use of quantile mapping to post-process GCM forecasts and recommend the use of more rigorous methods.

  17. Lagged effects of the Mistral wind on heavy precipitation through ocean-atmosphere coupling in the region of Valencia (Spain)

    NASA Astrophysics Data System (ADS)

    Berthou, Ségolène; Mailler, Sylvain; Drobinski, Philippe; Arsouze, Thomas; Bastin, Sophie; Béranger, Karine; Lebeaupin Brossier, Cindy

    2016-05-01

    The region of Valencia in Spain has historically been affected by heavy precipitation events (HPEs). These HPEs are known to be modulated by the sea surface temperature (SST) of the Balearic Sea. Using an atmosphere-ocean regional climate model, we show that more than 70 % of the HPEs in the region of Valencia present a SST cooling larger than the monthly trend in the Northwestern Mediterranean before the HPEs. This is linked to the breaking of a Rossby wave preceding the HPEs: a ridge-trough pattern at mid-levels centered over western France associated with a low-level depression in the Gulf of Genoa precedes the generation of a cut-off low over southern Spain with a surface depression over the Alboran Sea in the lee of the Atlas. This latter situation is favourable to the advection of warm and moist air towards the Mediterranean Spanish coast, possibly leading to HPEs. The depression in the Gulf of Genoa generates intense northerly (Mistral) to northwesterly (Tramontane/Cierzo) winds. In most cases, these intense winds trigger entrainment at the bottom of the oceanic mixed layer which is a mechanism explaining part of the SST cooling in most cases. Our study suggests that the SST cooling due to this strong wind regime then persists until the HPEs and reduces the precipitation intensity.

  18. Improvement of the Cloud Physics Formulation in the U.S. Navy Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS)

    DTIC Science & Technology

    2006-09-30

    processing of CCN in COAMPS Results from our investigation of aerosol-cloud-precipitation interactions in COAMPS using the CIMMS bulk drizzle...parameterization, giant CCN parameterization) developed at CIMMS /OU will be made available to NRL and registered COAMPS users at large. Our results have

  19. Improvement of the Cloud Physics Formulation in the U.S. Navy Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS)

    DTIC Science & Technology

    2007-09-30

    3. Dynamics and microphysics of continental stratus have been simulated by the CIMMS LES and found to be in good agreement with radar-derived...large eddy simulation framework using the new CIMMS GCCN parameterization. Adding GCCN to a clean CCN background has little effect on cloud parameters...responsible for most of the transport. High resolution cloud radar observations (95 GHz W-band ARM Cloud Radar -- WACR) and the new CIMMS large eddy

  20. Validation Test Report for the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) Version 5.0

    DTIC Science & Technology

    2010-09-27

    FOR EIGHT ADRIATIC SEA MOORINGS (VR1, VR2, VR4, VR5, VR6, CP2 , CP3, AND KB1). GREEN INDICATES THE BEST RESULTS. ............................ 27... CP2 , CP3, AND KB1). GREEN INDICATES BETTER RESULTS. ............................... 29 TABLE 1-11: UNCOUPLED MEAN DIRECTIONAL ERROR FOR EIGHT...ADRIATIC SEA MOORINGS (VR1, VR2, VR4, VR5, VR6, CP2 , CP3, AND KB1). GREEN INDICATES IMPROVED RESULTS. ............................................. 29

  1. Influence of coupled ocean-atmosphere phenomena on the Greater Horn of Africa droughts and their implications.

    PubMed

    Mpelasoka, Freddie; Awange, Joseph L; Zerihun, Ayalsew

    2017-08-17

    Drought-like humanitarian crises in the Greater Horn of Africa (GHA) are increasing despite recent progress in drought monitoring and prediction efforts. Notwithstanding these efforts, there remain challenges stemming from uncertainty in drought prediction, and the inflexibility and limited buffering capacity of the recurrent impacted systems. The complexity of the interactions of ENSO, IOD, IPO and NAO, arguably remains the main source of uncertainty in drought prediction. To develop practical drought risk parameters that potentially can guide investment strategies and risk-informed planning, this study quantifies, drought characteristics that underpin drought impacts management. Drought characteristics that include probability of drought-year occurrences, durations, areal-extent and their trends over 11 decades (1903-2012) were derived from the Standardized Precipitation Index (SPI).Transient probability of drought-year occurrences, modelled on Beta distribution, across the region ranges from 10 to 40%, although most fall within 20-30%. For more than half of the drought events, durations of up to 4, 7, 14 and 24months for the 3-, 6-, 12- and 24-month timescales were evident, while 1 out of 10 events persisted for up to 18months for the short timescales, and up to 36months or more for the long timescales. Apparently, only drought areal-extent showed statistically significant trends of up to 3%, 1%, 3.7%, 2.4%, 0.7%, -0.3% and -0.6% per decade over Sudan, Eritrea, Ethiopia, Somalia, Kenya, Uganda and Tanzania, respectively. Since there is no evidence of significant changes in drought characteristics, the peculiarity of drought-like crises in the GHA can be attributed (at least in part) to unaccounted for systematic rainfall reduction. This highlights the importance of distinguishing drought impacts from those associated with new levels of aridity. In principle drought is a temporary phenomenon while aridity is permanent, a difference that managers and decision-makers should be more aware. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Particulate polycyclic aromatic hydrocarbons in the Atlantic and Indian Ocean atmospheres during the Indian Ocean Experiment and Aerosols99: Continental sources to the marine atmosphere

    NASA Astrophysics Data System (ADS)

    Crimmins, Bernard S.; Dickerson, Russell R.; Doddridge, Bruce G.; Baker, Joel E.

    2004-03-01

    Polycyclic aromatic hydrocarbons (PAHs), mutagenic compounds predominantly derived from combustion, have been used as markers of combustion sources to the atmosphere. Marine aerosol collected aboard the NOAA R/V Ronald Brown during the Aerosols99 and the Indian Ocean Experiment (INDOEX) projects was analyzed for PAHs to assess the continental impact of combustion-derived particulate matter on the Atlantic and Indian Ocean atmospheres. PAH concentrations in the Atlantic and southern Indian Ocean atmospheres were consistent and low, ranging from <0.45 pg/m3 for coronene to 30 pg/m3 for 9, 10-dimethylanthracene. PAH concentrations increased ten fold as the ship crossed the Intertropical Convergence Zone (ITCZ) into the northern Indian Ocean, indicating an increased anthropogenic influence. PAH concentrations over the northern Indian Ocean atmosphere were approximately an order of magnitude greater than those in the northern Atlantic Ocean atmosphere. PAH composition profiles over the northern Indian Ocean were specific to wind regimes and influenced by a combination of biomass and fossil fuel combustion. This was supported by significant correlations between select PAHs and organic carbon (OC), elemental carbon (EC), SO4-2 and K+ for particular wind regimes. Indeno[1,2,3-cd]pyrene/EC ratios used as a combustion source marker suggest that fossil fuel combustion, rather than biomass burning, is the predominant source of PAHs to the Northern Hemisphere Indian Ocean atmosphere. Interestingly, fossil fuel consumption in the Indian sub-continent is a fraction of that in Europe and the United States but the soot and PAH levels in the adjacent Northern Indian Ocean atmosphere are significantly greater than those in the Northern Atlantic atmosphere.

  3. Sensitivity of the Tropical Ocean-Atmosphere to Seasonal and Long-Term Climate Forcing

    NASA Technical Reports Server (NTRS)

    Kim, K.-M.; Lau, K.-M.

    1999-01-01

    Since the pioneer works of Bjerknes (1966,1969) many studies have been conducted to understand the El Nino and Southern Oscillation (ENSO) phenomenon. These studies have led to a basic understanding of the dynamics of El Nino. Central to the couple dynamics of ENSO is the delayed action oscillator theory (Suarez and Schopf 1988), which successfully describes the cyclic feature of El Nino. While the oscillatory feature of El Nino is reasonably well understood, the irregularity of El Nino, the effect of monsoon on ENSO, and the response of coupled system to the global warming are still under debate. In the present study, we attempt to provide some theoretical understanding of possible impacts of seasonal cycle, monsoon, and climate changes on ENSO using intermediate coupled model.

  4. Tropical ocean-atmospheric forcing of Late Glacial and Holocene glacier fluctuations in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Stansell, Nathan D.; Licciardi, Joseph M.; Rodbell, Donald T.; Mark, Bryan G.

    2017-05-01

    Evaluating the timing and style of past glacier fluctuations in the tropical Andes is important for our scientific understanding of global environmental change. Terrestrial cosmogenic nuclide ages on moraine boulders combined with 14C-dated clastic sediment records from alpine lakes document glacial variability in the Cordillera Blanca of Peru during the last 16 ka. Late Glacial ice extents culminated at the start of the Antarctic Cold Reversal and began retracting prior to the Younger Dryas. Multiple moraine crests dating to the early Holocene mark brief readvances or stillstands that punctuated overall retreat of the Queshque Valley glacier terminus during this interval. Glaciers were less extensive during the middle Holocene before readvancing during the latest Holocene. These records suggest that tropical Atlantic and Pacific ocean-atmospheric processes exerted temporally variable forcing of Late Glacial and Holocene glacial changes in the Peruvian Andes.

  5. Rapid ocean wave teleconnections linking Antarctic salinity anomalies to the equatorial ocean-atmosphere system

    NASA Astrophysics Data System (ADS)

    Atkinson, C. P.; Wells, N. C.; Blaker, A. T.; Sinha, B.; Ivchenko, V. O.

    2009-04-01

    The coupled climate model FORTE is used to investigate rapid ocean teleconnections between the Southern Ocean and equatorial Pacific Ocean. Salinity anomalies located throughout the Southern Ocean generate barotropic signals that propagate along submerged topographic features and result in the growth of baroclinic energy anomalies around Indonesia and the tropical Pacific. Anomalies in the Ross, Bellingshausen and Amundsen Seas exchange the most barotropic kinetic energy between high and low latitudes. In the equatorial Pacific, baroclinic Kelvin waves are excited which propagate eastwards along the thermocline, resulting in SST anomalies in the central and eastern Pacific. SST anomalies are subsequently amplified to magnitudes of 1.25°C by air-sea interaction, which could potentially influence other coupled Pacific phenomena.

  6. Information content of downscaled GCM precipitation variables for crop simulations

    NASA Astrophysics Data System (ADS)

    Ines, A. V. M.; Mishra, A. K.

    2015-12-01

    A simple statistical downscaling procedure for transforming daily global climate model (GCM) rainfall was applied at the local scale in Katumani, Kenya. We corrected the rainfall frequency bias of the GCM by truncating its daily rainfall cumulative distribution into the station's distribution using a wet-day threshold. Then, we corrected the GCM's rainfall intensity bias by mapping its truncated rainfall distribution into the station's truncated distribution. Additional tailoring was made to the bias corrected GCM rainfall by linking it with a stochastic disaggregation scheme based on a conditional stochastic weather generator to correct the temporal structure inherent with daily GCM rainfall. Results of the simple and hybridized GCM downscaled precipitation variables (total, probability of occurrence, intensity and dry spell length) were linked with a crop model. An objective evaluation of the tailored GCM data was done using entropy. This study is useful for the identification of the most suitable downscaling technique, as well as the most effective precipitation variables for forecasting crop yields.

  7. Maps of clouds modeled with the IPSL Titan 3D-GCM

    NASA Astrophysics Data System (ADS)

    Burgalat, J.; Rannou, P.; Lebonnois, S.

    2011-10-01

    A new climate model for Titan's atmosphere has been developed at the IPSL. This model uses the current version of the LMDZ General Circulation Model (GCM) dynamical core with the physics part of the 2D Titan's IPSL-GCM. First simulations made at the LMD (Laboratoire de Météorologie Dynamique) used a version of the model with coupled haze microphysics only. We update the model with the implementation of the clouds microphysics scheme inherited frome the previous 2D version. The model is now fully coupled with clouds processes and is a full 3D extension of the Titan IPSL-GCM ([2], [3]). Currently the model is not optimized and is demanding in term of computational time (approximatively 17 days of execution for one Titan's year simulation) and the model can not be used with its full capacities. Therefore all the microphysics is still computed as zonal averages. Nevertheless, new simulations performed including clouds, shows some encouraging results. The lack of asymmetry of the clouds coverage in the results of the 2D simulations. seems to vanish using the new model which tends to show that dissipation process in the 2D model was too strong. With this new model, we intented to get a better tool to understand Titan's climate and to interpret the large amount of data collected by the probes.

  8. Maps of clouds modeled with the IPSL Titan 3D-GCM

    NASA Astrophysics Data System (ADS)

    Burgalat, J.; Rannou, P.; Lebonnois, S.

    2012-09-01

    A new climate model for Titan's atmosphere has been developed at the IPSL. This model uses the current version of the LMDZ General Circulation Model (GCM) dynamical core with the physics part of the 2D Titan's IPSL-GCM. First simulations made at the LMD (Laboratoire de Météorologie Dynamique) used a version of the model with coupled haze microphysics only. We update the model with the implementation of the clouds microphysics scheme inherited from the previous 2D version. The model is now fully coupled with clouds processes and is a full 3D extension of the Titan IPSL-GCM ([2], [3]). Currently the model is not optimized and is demanding in term of computational time (approximatively 17 days of execution for one Titan's year simulation) and the model can not be used with its full capacities. Therefore all the microphysics is still computed as zonal averages. Nevertheless, new simulations performed including clouds, shows some encouraging results. The lack of asymmetry of the clouds coverage in the results of the 2D simulations seems to vanish using the new model which tends to show that dissipation process in the 2D model was too strong. With this new model, we intented to get a better tool to understand Titan's climate and to interpret the large amount of data collected by the probes.

  9. Collaborative project. Ocean-atmosphere interaction from meso- to planetary-scale. Mechanics, parameterization, and variability

    SciTech Connect

    Saravanan, Ramalingam; Small, Justin

    2015-12-01

    Most climate models are currently run with grid spacings of around 100km, which, with today’s computing power, allows for long (up to 1000 year) simulations, or ensembles of simulations to explore climate change and variability. However this grid spacing does not resolve important components of the weather/climate system such as atmospheric fronts and mesoscale systems, and ocean boundary currents and eddies. The overall aim of this project has been to look at the effect of these small-scale features on the weather/climate system using a suite of high and low resolution climate models, idealized models and observations. High-resolution global coupled integrations using CAM/CESM were carried out at NCAR by the lead PI. At TAMU, we have complemented the work at NCAR by analyzing datasets from the high-resolution (28km) CESM integrations (Small et al., 2014) as well as very high resolution (9km, 3km) runs using a coupled regional climate (CRCM) carried out locally. The main tasks carried out were: 1. Analysis of surface wind in observations and high-resolution CAM/CCSM simulations 2. Development of a feature-tracking algorithm for studying midlatitude air-sea interaction by following oceanic mesoscale eddies and creating composites of the atmospheric response overlying the eddies. 3. Applying the Lagrangian analysis technique in the Gulf Stream region to compare data from observational reanalyses, global CESM coupled simulations, 9km regional coupled simulations and 3km convection-resolving regional coupled simulations. Our main findings are that oceanic mesoscale eddies influence not just the atmospheric boundary layer above them, but also the lower portions of the free troposphere above the boundary layer. Such a vertical response could have implications for a remote influence of Gulf Stream oceanic eddies on North Atlantic weather patterns through modulation of the storm track, similar to what has been noted in the North Pacific. The coarse resolution

  10. Flying the TRMM Satellite in a GCM

    NASA Technical Reports Server (NTRS)

    Lin, Xin; Fowler, Laura D.; Randall, David A.

    2001-01-01

    By incorporating the Tropical Rainfall Measurement Mission (TRMM) satellite orbital information into the Colorado State University General Circulation Model (CSU GCM), we are able to 'fly' a satellite in the GCM, and sample the simulated atmosphere in the same way as the TRMM sensors sample the real atmosphere. The TRMM-sampled statistics for precipitation and radiative fluxes at annual, intraseasonal, monthly-mean and seasonal-mean diurnal time scales are evaluated by comparing the satellite-sampled against fully-sampled simulated atmospheres. The sampling rates of the TRMM sensors are significantly affected by the sensors' swath widths. The TRMM Microwave Imager (TMI) and the Visible Infrared Scanner (VIRS) sample each 2.25 x 2.25 degree grid box in the Tropics and subtropics about once per day, but at a different local time every day, while the Precipitation Radar (PR) and the Clouds and the Earth's Radiant Energy System (CERES) sensor visit each grid box about once every three days and twice per day, respectively. Besides inadequate samplings resulting from sensors' swath widths, there is a large, systematic diurnal undersampling associated with TRMM's orbital geometry for grid boxes away from the Equator. When only one month of TRMM data are used, this diurnal undersampling can lead to more daytime samples relative to nighttime samples in one hemisphere, and more nighttime samples relative to daytime samples in the other hemisphere. The resulting sampling biases (3-6 W m(exp-2)) are very pronounced in outgoing longwave radiation (OLR) over the subtropical land masses. The sampling errors in OLR monthly- and seasonal-means are less than 8 W m(exp-2) (5%) for each 2.25 x 2.25 degree grid box. The OLR monthly- and seasonal-means are not sensitive to diurnal undersamplings associated with the TRMM orbits and sensors' swath widths. However, this is not the case for total precipitation. Diurnal undersampling could produce errors as large as 20% in the Tropics and 40

  11. Tropical ocean-atmosphere interaction, the Pacific cold tongue, and the El Nino-Southern Oscillation

    SciTech Connect

    Jin, F.F.

    1996-10-04

    The tropical Pacific basin allows strong feedbacks among the trade winds, equatorial zonal sea surface temperature contrast, and upper ocean heat content. Coupled atmosphere-ocean dynamics produce both the strong Pacific cold tongue climate state and the El Nino-Southern Oscillation phenomenon. A simple paradigm of the tropical climate system is presented, capturing the basic physics of these two important aspects of the tropic Pacific and basic features of the climate states of the Atlantic and Indian ocean basins. 21 refs., 3 figs.

  12. A review of the Southern Oscillation - Oceanic-atmospheric circulation changes and related rainfall anomalies

    NASA Technical Reports Server (NTRS)

    Kousky, V. E.; Kagano, M. T.; Cavalcanti, I. F. A.

    1984-01-01

    The region of South America is emphasized in the present consideration of the Southern Oscillation (SO) oceanic and atmospheric circulation changes. The persistence of climate anomalies associated with El Nino-SO events is due to strong atmosphere-ocean coupling. Once initiated, the SO follows a certain sequence of events with clearly defined effects on tropical and subtropical rainfall. Excessive rainfall related to the SO in the central and eastern Pacific, Peru, Ecuador, and southern Brazil, are complemented by drought in Australia, Indonesia, India, West Africa, and northeast Brazil. El Nino-SO events are also associated with dramatic changes in the tropospheric flow pattern over a broad area of both hemispheres.

  13. A review of the Southern Oscillation - Oceanic-atmospheric circulation changes and related rainfall anomalies

    NASA Technical Reports Server (NTRS)

    Kousky, V. E.; Kagano, M. T.; Cavalcanti, I. F. A.

    1984-01-01

    The region of South America is emphasized in the present consideration of the Southern Oscillation (SO) oceanic and atmospheric circulation changes. The persistence of climate anomalies associated with El Nino-SO events is due to strong atmosphere-ocean coupling. Once initiated, the SO follows a certain sequence of events with clearly defined effects on tropical and subtropical rainfall. Excessive rainfall related to the SO in the central and eastern Pacific, Peru, Ecuador, and southern Brazil, are complemented by drought in Australia, Indonesia, India, West Africa, and northeast Brazil. El Nino-SO events are also associated with dramatic changes in the tropospheric flow pattern over a broad area of both hemispheres.

  14. Sea ice simulations based on fields generated by the GLAS GCM. [Goddard Laboratory for Atmospheric Sciences General Circulation Model

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.; Herman, G. F.

    1980-01-01

    The GLAS General Circulation Model (GCM) was applied to the four-month simulation of the thermodynamic part of the Parkinson-Washington sea ice model using atmospheric boundary conditions. The sea ice thickness and distribution were predicted for the Jan. 1-Apr. 30 period using the GCM-fields of solar and infrared radiation, specific humidity and air temperature at the surface, and snow accumulation; the sensible heat and evaporative surface fluxes were consistent with the ground temperatures produced by the ice model and the air temperatures determined by the atmospheric concept. It was concluded that the Parkinson-Washington sea ice model results in acceptable ice concentrations and thicknesses when used with GLAS GCM for the Jan.-Apr. period suggesting the feasibility of fully coupled ice-atmosphere simulations with these two approaches.

  15. Response of the GISS GCM to prescribed forcings

    SciTech Connect

    Borenstein, S.R. |

    1996-12-31

    The Global Circulation Model or GCM is a computer simulation of the Earth`s climate, used to predict future weather and climate from present conditions and known forcings. The GCM is a Cartesian grid-point model, run at a resolution of 4{degree}x5{degree} in the horizontal (latitude x longitude) and nine-layers in the vertical. The crucial question is: How accurately and reliably can this be done, given the extreme complication and non-linearity of the system being modelled as well as the intrinsically chaotic nature of the climate. One of the long term goals of the GCM is to predict the effect of anthropogenic greenhouse gases on the future climate. Comparative images representing the model simulations and observations of surface temperatures and precipitation are shown. By comparing the model data to real world observations, the GCM can be evaluated, criticized and ultimately modified to produce more realistic results.

  16. Usefulness of AIRS-Derived OLR, Temperature, Water Vapor and Cloudiness Anomaly Trends for GCM Validation

    NASA Technical Reports Server (NTRS)

    Molnar, Gyula I.; Susskind, Joel; Iredell, Lena F.

    2010-01-01

    Mainly due to their global nature, satellite observations can provide a very useful basis for GCM validations. In particular, satellite sounders such as AIRS provide 3-D spatial information (most useful for GCMs), so the question arises: can we use AIRS datasets for climate variability assessments? We show that the recent (September 2002 February 2010) CERES-observed negative trend in OLR of approx.-0.1 W/sq m/yr averaged over the globe is found in the AIRS OLR data as well. Most importantly, even minute details (down to 1 x 1 degree GCM-scale resolution) of spatial and temporal anomalies and trends of OLR as observed by CERES and computed based on AIRS-retrieved surface and atmospheric geophysical parameters over this time period are essentially the same. The correspondence can be seen even in the very large spatial variations of these trends with local values ranging from -2.6 W/sq m/yr to +3.0 W/sq m/yr in the tropics, for example. This essentially perfect agreement of OLR anomalies and trends derived from observations by two different instruments, in totally independent and different manners, implies that both sets of results must be highly accurate, and indirectly validates the anomalies and trends of other AIRS derived products as well. These products show that global and regional anomalies and trends of OLR, water vapor and cloud cover over the last 7+ years are strongly influenced by EI-Nino-La Nina cycles . We have created climate parameter anomaly datasets using AIRS retrievals which can be compared directly with coupled GCM climate variability assessments. Moreover, interrelationships of these anomalies and trends should also be similar between the observed and GCM-generated datasets, and, in cases of discrepancies, GCM parameterizations could be improved based on the relationships observed in the data. First, we assess spatial "trends" of variability of climatic parameter anomalies [since anomalies relative to the seasonal cycle are good proxies of

  17. Usefulness of AIRS-Derived OLR, Temperature, Water Vapor and Cloudiness Anomaly Trends for GCM Validation

    NASA Technical Reports Server (NTRS)

    Molnar, Gyula I.; Susskind, Joel; Iredell, Lena F.

    2010-01-01

    Mainly due to their global nature, satellite observations can provide a very useful basis for GCM validations. In particular, satellite sounders such as AIRS provide 3-D spatial information (most useful for GCMs), so the question arises: can we use AIRS datasets for climate variability assessments? We show that the recent (September 2002 February 2010) CERES-observed negative trend in OLR of approx.-0.1 W/sq m/yr averaged over the globe is found in the AIRS OLR data as well. Most importantly, even minute details (down to 1 x 1 degree GCM-scale resolution) of spatial and temporal anomalies and trends of OLR as observed by CERES and computed based on AIRS-retrieved surface and atmospheric geophysical parameters over this time period are essentially the same. The correspondence can be seen even in the very large spatial variations of these trends with local values ranging from -2.6 W/sq m/yr to +3.0 W/sq m/yr in the tropics, for example. This essentially perfect agreement of OLR anomalies and trends derived from observations by two different instruments, in totally independent and different manners, implies that both sets of results must be highly accurate, and indirectly validates the anomalies and trends of other AIRS derived products as well. These products show that global and regional anomalies and trends of OLR, water vapor and cloud cover over the last 7+ years are strongly influenced by EI-Nino-La Nina cycles . We have created climate parameter anomaly datasets using AIRS retrievals which can be compared directly with coupled GCM climate variability assessments. Moreover, interrelationships of these anomalies and trends should also be similar between the observed and GCM-generated datasets, and, in cases of discrepancies, GCM parameterizations could be improved based on the relationships observed in the data. First, we assess spatial "trends" of variability of climatic parameter anomalies [since anomalies relative to the seasonal cycle are good proxies of

  18. Tropical North Atlantic ocean-atmosphere interactions synchronize forest carbon losses from hurricanes and Amazon fires

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Randerson, James T.; Morton, Douglas C.

    2015-08-01

    We describe a climate mode synchronizing forest carbon losses from North and South America by analyzing time series of tropical North Atlantic sea surface temperatures (SSTs), landfall hurricanes and tropical storms, and Amazon fires during 1995-2013. Years with anomalously high tropical North Atlantic SSTs during March-June were often followed by a more active hurricane season and a larger number of satellite-detected fires in the southern Amazon during June-November. The relationship between North Atlantic tropical cyclones and southern Amazon fires (r = 0.61, p < 0.003) was stronger than links between SSTs and either cyclones or fires alone, suggesting that fires and tropical cyclones were directly coupled to the same underlying atmospheric dynamics governing tropical moisture redistribution. These relationships help explain why seasonal outlook forecasts for hurricanes and Amazon fires both failed in 2013 and may enable the design of improved early warning systems for drought and fire in Amazon forests.

  19. Role of ocean-atmosphere interactions in tropical cooling during the last glacial maximum

    SciTech Connect

    Bush, A.B.G.; Philander, S.G.H.

    1998-02-27

    A simulation with a coupled atmosphere-ocean general circulation model configured for the Last Glacial Maximum delivered a tropical climate that is much cooler than that produced by atmosphere-only models. The main reason is a decrease in tropical sea surface temperatures, up to 6{degree}C in the western tropical Pacific, which occurs because of two processes. The trade winds induce equatorial upwelling and zonal advection of cold water that further intensify the trade winds, and an exchange of water occurs between the tropical and extratropical Pacific in which the poleward surface flow is balanced by equatorward flow of cold water in the thermocline. Simulated tropical temperature depressions are of the same magnitude as those that have been proposed from recent proxy data. 25 refs., 4 figs.

  20. From GCM grid cell to agricultural plot: scale issues affecting modelling of climate impact

    PubMed Central

    Baron, Christian; Sultan, Benjamin; Balme, Maud; Sarr, Benoit; Traore, Seydou; Lebel, Thierry; Janicot, Serge; Dingkuhn, Michael

    2005-01-01

    General circulation models (GCM) are increasingly capable of making relevant predictions of seasonal and long-term climate variability, thus improving prospects of predicting impact on crop yields. This is particularly important for semi-arid West Africa where climate variability and drought threaten food security. Translating GCM outputs into attainable crop yields is difficult because GCM grid boxes are of larger scale than the processes governing yield, involving partitioning of rain among runoff, evaporation, transpiration, drainage and storage at plot scale. This study analyses the bias introduced to crop simulation when climatic data is aggregated spatially or in time, resulting in loss of relevant variation. A detailed case study was conducted using historical weather data for Senegal, applied to the crop model SARRA-H (version for millet). The study was then extended to a 10°N–17° N climatic gradient and a 31 year climate sequence to evaluate yield sensitivity to the variability of solar radiation and rainfall. Finally, a down-scaling model called LGO (Lebel–Guillot–Onibon), generating local rain patterns from grid cell means, was used to restore the variability lost by aggregation. Results indicate that forcing the crop model with spatially aggregated rainfall causes yield overestimations of 10–50% in dry latitudes, but nearly none in humid zones, due to a biased fraction of rainfall available for crop transpiration. Aggregation of solar radiation data caused significant bias in wetter zones where radiation was limiting yield. Where climatic gradients are steep, these two situations can occur within the same GCM grid cell. Disaggregation of grid cell means into a pattern of virtual synoptic stations having high-resolution rainfall distribution removed much of the bias caused by aggregation and gave realistic simulations of yield. It is concluded that coupling of GCM outputs with plot level crop models can cause large systematic errors due to

  1. Internal ocean-atmosphere variability drives megadroughts in Western North America

    NASA Astrophysics Data System (ADS)

    Coats, S.; Smerdon, J. E.; Cook, B. I.; Seager, R.; Cook, E. R.; Anchukaitis, K. J.

    2016-09-01

    Multidecadal droughts that occurred during the Medieval Climate Anomaly represent an important target for validating the ability of climate models to adequately characterize drought risk over the near-term future. A prominent hypothesis is that these megadroughts were driven by a centuries-long radiatively forced shift in the mean state of the tropical Pacific Ocean. Here we use a novel combination of spatiotemporal tree ring reconstructions of Northern Hemisphere hydroclimate to infer the atmosphere-ocean dynamics that coincide with megadroughts over the American West and find that these features are consistently associated with 10-30 year periods of frequent cold El Niño-Southern Oscillation conditions and not a centuries-long shift in the mean of the tropical Pacific Ocean. These results suggest an important role for internal variability in driving past megadroughts. State-of-the-art climate models from the Coupled Model Intercomparison Project Phase 5, however, do not simulate a consistent association between megadroughts and internal variability of the tropical Pacific Ocean, with implications for our confidence in megadrought risk projections.

  2. Simulations of aerosol constituents and their sources of origin over Indo-Gangetic plain (IGP) to Himalayan foothills: a new perspective of GCM estimates

    NASA Astrophysics Data System (ADS)

    Kumar, B. D.; Verma, S.; Wang, R.; Boucher, O.

    2016-12-01

    In the present study, we evaluated aerosol constituents of the model using the measurements during premonsoon over Indo-Gangetic plain (IGP) to Himalayan foothills. Aerosol transport simulations were carried out in general circulation model (GCM) of Laboratoire de M ´et ´eorologie Dynamique (LMD-GCM) with three set of emissions including Indian emissions in GCM-Indemiss, global emissions in GCM coupled with aerosol interactive chemistry (GCM-INCA-I), and the global emissions with updated BC emission inventory over Asia in GCM-INCA-II. Among three models, GCM-indemiss reproduced measured single scattering albedo (SSA) at 670 nm with a relative bias of 5%. However, the estimated 30-50% of the measured aerosol optical depth (AOD) at 550 nm and 20-60% of the measured surface concentration of aerosol constituents (e.g. black carbon (BC), organic carbon (OC), and sulfate) at most of the times over the study period. Inability of model to reproduce observed AOD changes was attributed to the paucity of emissions represented in the model. Design of retrieval simulations using existing GCM-indemiss estimates was further carried out. Retrieval simulations have produced better results, which showed constituent surface concentration in the vicinity of the measurements with normalized mean bias (NMB) of <30%. Scatter analysis between surface and elevated contribution of region's emissions showed anthropogenic emissions from the IGP on anthropogenic days and the north west India (NWI) on anthropogenic with dust days influence aerosols over northern India (NI). Our analysis showed BC emissions from base inventory for the corresponding grids of source region influencing NI were lower by 200% compared to that of modified scenario. These emissions will further be implemented in an atmospheric GCM to evaluate their performance validating with measurements data.

  3. Relative roles of land- and ocean-atmosphere interactions in Asian-Pacific thermal contrast variability at the precessional band.

    PubMed

    Wang, Yue; Jian, ZhiMin; Zhao, Ping; Xiao, Dong; Chen, JunMing

    2016-07-06

    In a 250-kyr transient simulation of the Community Earth System Model (CESM), we identified a precessional forced seesaw of the summer middle-upper tropospheric eddy temperature between Asia and the North Pacific as the paleo-APO (Asian-Pacific oscillation). The paleo-APO variability is out of phase with the precession parameter. Corresponding to a positive paleo-APO phase, both the subtropical anticyclonic circulation over the North Pacific and the East Asian summer monsoon (EASM) strengthen. Summer anomalous sea surface temperature shows a western cold-eastern warm pattern over the extratropical North Pacific and a zonal positive-negative-positive pattern over the tropical Pacific. The variations in the simulated paleo-APO and East Asian southerly wind at the precessional band agree well with the geological proxies at the Dongge, Sanbao, Linzhu, and Hulu caves in China, which also implies that these proxies may well reflect the variability in the southerly wind over East Asia. Sensitivity experiments further reveal that the reduced precession parameter may enhance the positive paleo-APO phase and the associated EASM because of the response of the land-atmosphere interactions to the precessional insolation changes. The effect of the ocean-atmosphere interactions on the paleo-APO is secondary.

  4. Carbon-isotope composition of Lower Cretaceous fossil wood: Ocean-atmosphere chemistry and relation to sea-level change

    SciTech Connect

    Groecke, D.R.; Hesselbo, S.P.; Jenkyns, H.C.

    1999-02-01

    The carbon-isotope composition of fossil wood fragments, collected through a biostratigraphically well-constructed Aptian (Lower Cretaceous) shallow-marine siliciclastic succession on the Isle of Wight, southern Britain, shows distinct variations with time. The results indicate that the stratigraphic signature of {delta}{sup 13}C{sub wood} through the Aptian was influenced primarily by fluctuations in the isotopic composition of CO{sub 2} in the global ocean-atmosphere system, as registered in marine carbonates elsewhere, and was not governed by local paleoenvironmental and/or paleoecological factors. Negative and positive excursions in {delta}{sup 13}C{sub wood} through the lower Aptian occur in phase with inferred transgressions and regressions, respectively -- a pattern that contrasts with that observed in many previous studies for different time intervals. The relationship between {delta}{sup 13}C variations and relative sea-level change is tentatively interpreted as a response to various climatic and eustatic factors, relating to rapid sea-floor spreading, thermal uplift of ocean floor, emplacement of plateaus, volcanic CO{sub 2} emissions, weathering, and sedimentary rate.

  5. Relative roles of land- and ocean-atmosphere interactions in Asian-Pacific thermal contrast variability at the precessional band

    PubMed Central

    Wang, Yue; Jian, ZhiMin; Zhao, Ping; Xiao, Dong; Chen, JunMing

    2016-01-01

    In a 250-kyr transient simulation of the Community Earth System Model (CESM), we identified a precessional forced seesaw of the summer middle-upper tropospheric eddy temperature between Asia and the North Pacific as the paleo-APO (Asian-Pacific oscillation). The paleo-APO variability is out of phase with the precession parameter. Corresponding to a positive paleo-APO phase, both the subtropical anticyclonic circulation over the North Pacific and the East Asian summer monsoon (EASM) strengthen. Summer anomalous sea surface temperature shows a western cold-eastern warm pattern over the extratropical North Pacific and a zonal positive-negative-positive pattern over the tropical Pacific. The variations in the simulated paleo-APO and East Asian southerly wind at the precessional band agree well with the geological proxies at the Dongge, Sanbao, Linzhu, and Hulu caves in China, which also implies that these proxies may well reflect the variability in the southerly wind over East Asia. Sensitivity experiments further reveal that the reduced precession parameter may enhance the positive paleo-APO phase and the associated EASM because of the response of the land-atmosphere interactions to the precessional insolation changes. The effect of the ocean-atmosphere interactions on the paleo-APO is secondary. PMID:27381940

  6. Comparison of the hydrological impact driven by RCM-, GCM- and NCEP- simulated and bias corrected precipitation

    NASA Astrophysics Data System (ADS)

    Hou, Yukun; Chen, Hua; Xu, Chongyu; Hu, Kang

    2016-04-01

    Statistical downscaling methods are a common tool to compensate for the gaps between large-scale climate model simulations and station-scale observations. This study evaluates the performance of the raw precipitation from National Centers for Environmental Prediction (NCEP), outputs of Global Climate Model (GCM)-NorESM and corresponding Regional Climate Model (RCM)-the East Asian regional climate model driven by WRF model driven with NorESM. Meanwhile, their bias-corrected series by four different bias correction methods are simultaneously evaluated in order to find whether NCEP with observation coupled or RCM with modified spatial distribution of surface climate can have a better performance than GCM on analyzing hydrological impact. The Xin'anjiang lumped hydrological model is used to assess the hydrological impacts by simulating the streamflows in Xiangjiang basin with the corresponding observed, model-simulated and bias-corrected precipitation as input. The results show that hydrological simulations using the RCM and NCEP historical precipitation do not have a better agreement with observed runoff than using raw GCM data as input in this case study. However, when the raw precipitation of climate models is bias-corrected, an obvious improvement is obtained from all the climate models, and the bias-corrected RCM precipitation gives the best fitness in the runoff simulations. Comparing different bias correction methods with the same climate model, the method with occurrence and intensity adjustment outperforms other methods in the runoff simulation. It can be inferred that without bias correction, it can be hardly concluded that NCEP or RCM brings an improvement of precipitation simulation from GCM for driving hydrological models. However, the RCM precipitation corrected by a proper bias correction method provides better runoff simulation results over other climate datasets.

  7. Statistical and dynamical assessment of land-ocean-atmosphere interactions across North Africa

    NASA Astrophysics Data System (ADS)

    Yu, Yan

    impacts is evaluated through ensembles of fully coupled CESM dynamical experiments, with modified leaf area index (LAI) and soil moisture across the Sahel or West African Monsoon (WAM) region. The atmospheric responses to oceanic and terrestrial forcings are generally consistent between the dynamical experiments and statistical GEFA, confirming GEFA's capability of isolating the individual impacts of oceanic and terrestrial forcings on North African climate. Furthermore, with the incorporation of stepwise selection, GEFA can now provide reliable estimates of the oceanic and terrestrial impacts on the North African climate with the typical length of observational datasets, thereby enhancing the method's applicability. After the successful validation of GEFA, the key observed oceanic and terrestrial drivers of North African climate are identified through the application of GEFA to gridded observations, remote sensing products, and reanalyses. According to GEFA, oceanic drivers dominate over terrestrial drivers in terms of their observed impacts on North African climate in most seasons. Terrestrial impacts are comparable to, or more important than, oceanic impacts on rainfall during the post-monsoon across the Sahel and WAM region, and after the short rain across the Horn of Africa (HOA). The key ocean basins that regulate North African rainfall are typically located in the tropics. While the observed impacts of SST variability across the tropical Pacific and tropical Atlantic Oceans on the Sahel rainfall are largely consistent with previous model-based findings, minimal impacts from tropical Indian Ocean variability on Sahel rainfall are identified in observations, in contrast to previous modeling studies. The current observational analysis verifies model-hypothesized positive vegetation-rainfall feedback across the Sahel and HOA, which is confined to the post-monsoon and post-short rains season, respectively. However, the observed positive vegetation feedback to rainfall

  8. Multi-model GCM ensemble simulations of idealized tropical cyclones

    NASA Astrophysics Data System (ADS)

    Reed, K. A.; Jablonowski, C.; Ullrich, P. A.; Kent, J.; Lauritzen, P. H.; Taylor, M.; Nair, R.

    2013-12-01

    As General Circulation Models (GCMs) are now capable of running operationally at higher horizontal resolutions than ever before, such models have become a tool of choice for the evaluation of tropical cyclones in current and future climate conditions. GCM horizontal resolutions in the range between 10-50 km are now computationally achievable for seasonal or multi-year simulations and there is growing confidence that high-resolution global models provide reliable representations of many characteristics of tropical storms. However, model design choices are an important source of uncertainty. This is widely documented for physical parameterization suites, but it is less recognized for the dynamical component of models and the physics-dynamics coupling. The study offers a first look into these structural uncertainties. This study focuses on dynamical core model intercomparisons. In particular, it looks at the results of the Dynamical Core Model Intercomparison Project (DCMIP) that took place at the National Center for Atmospheric Research (NCAR) in August 2012. The analysis is focused on the evaluation of an idealized tropical storm and uncertainties triggered by the choice of model dynamical core formulation in various global models. These models include the four dynamical cores available in NCAR's Community Atmosphere Model (Finite-Volume (FV), Spectral-Element (SE) and the Eulerian and semi-Lagrangian spectral transform dynamical cores), the NOAA model FIM, the model ICON (Max-Planck Institute and German Weather Service), GFDL's FV3 model on the cubed-sphere grid, ECMWF's Integrated Forecasting System (IFS) and the model PUMA from the University of Hamburg.

  9. MAD-VenLA: a microphysical modal representation of clouds for the IPSL Venus GCM

    NASA Astrophysics Data System (ADS)

    Guilbon, Sabrina; Määttänen, Anni; Burgalat, Jérémie; Montmessin, Franck; Stolzenbach, Aurélien; Bekki, Slimane

    2016-10-01

    Venus is enshrouded by 20km-thick clouds, which are composed of sulfuric acid-water solution droplets. Clouds play a crucial role on the climate of the planet. Our goal is to study the formation and evolution of Venusian clouds with microphysical models. The goal of this work is to develop the first full 3D microphysical model of Venus coupled with the IPSL Venus GCM and the photochemical model included (Lebonnois et al. 2010, Stolzenbach et al. 2016).Two particle size distribution representations are generally used in cloud modeling: sectional and modal. The term 'sectional' means that the continuous particle size distribution is divided into a discrete set of size intervals called bins. In the modal approach, the particle size distribution is approximated by a continuous parametric function, typically a log-normal, and prognostic variables are distribution or distribution-integrated parameters (Seigneur et al. 1986, Burgalat et al. 2014). These two representations need to be compared to choose the optimal trade-off between precision and computational efficiency. At high radius resolution, sectional models are computationally too demanding to be integrated in GCMs. That is why, in other GCMs, such as the IPSL Titan GCM, the modal scheme is used (Burgalat et al. 2014).The Venus Liquid Aerosol cloud model (VenLA) and the Modal Dynamics of Venusian Liquid Aerosol cloud model (MAD-VenLA) are respectively the sectional and the modal model discussed here and used for defining the microphysical cloud module to be integrated in the IPSL Venus GCM. We will compare the two models with the key microphysical processes in 0D setting: homogeneous and heterogeneous nucleation, condensation/evaporation and coagulation. Then, MAD-VenLA will be coupled with the IPSL VGCM. The first results of the complete VGCM with microphysics coupled with chemistry will be presented.

  10. Collecting TIME-GCM Output Along TIMED Satellite Tracks

    NASA Astrophysics Data System (ADS)

    Hartsough, C. S.; Hagan, M. E.; Roble, R. G.

    2001-12-01

    The CEDAR/TIMED research effort focuses on increasing our understanding of the physical processes which affect and control the energetics and dynamics of the mesosphere and low er thermosphere. Use of upper-atmosphere models such as NCAR TIME-GCM can aid scientists in the interpretation of both satellite and ground-based observations. Our goals are (1) to make TIME-GCM model output readily available for researchers to use in their studies, and (2) to use the CEDAR/TIMED data to improve and upgrade the TIME-GCM model. We are preparing samples of TIME-GCM output to make available to the community via the Web. The data will be in netCDF format and accessible from the CEDAR database. Data will be sampled along the instrument observing tracks to facilitate direct comparisons with the TIMED instrument data. The data made available will approximately cover a 60-day period. The altitude range and fields to be made available will vary with each instrument, but will include neutral temperatures and winds, ion temperatures and drifts, and basic constituents, over approximately 50-300 km. Similar products will be made available for the CEDAR ground-based component of TIMED, including the NSF CEDAR Class 1 Facilities. We will present some sample data files and describe the Web site layout which researchers can use to access the TIME-GCM output as it becomes available.

  11. Impact of cloud microphysics on the CSU GCM atmospheric moisture budget

    SciTech Connect

    Fowler, L.D.; Randall, D.A.

    1993-12-31

    In this article, we present the first maps of the global distribution of the cloud liquid and ice water contents of the atmosphere. It is shown that the cloud microphysics package produces realistic distributions of both moisture variables. We axe presently adapting the present model so that long-term simulations with the CSU GCM may be made. In the near future, we plan to couple the cloud liquid and ice water contents prognosed by the cloud microphysics package with the cloud fraction and cloud optical properties.

  12. The Bisa GEM-Mars GCM

    NASA Astrophysics Data System (ADS)

    Neary, Lori; Daerden, Frank

    2013-04-01

    GEM-Mars is a three-dimensional general circulation model of the Mars atmosphere extending from the surface to approximately 170 km based on the latest version of the GEM (Global Environmental Mesoscale) model, the operational data assimilation and weather forecasting system for Canada [Côté et al., 1998]. The dynamical core is an implicit two-time-level semi-Lagrangian scheme on an Arakawa C-grid with a terrain-following, log-hydrostatic-pressure vertical coordinate discretized on a Charney-Phillips grid. The model has both a hydrostatic and non-hydrostatic formulation, providing a single platform for simulations on a variety of horizontal scales. The model code is fully parallelized using OMP and MPI. The GCM includes the relevant physical processes such as CO2 condensation, planetary boundary layer mixing, gravity wave drag and surface parameterizations. A simple water cycle, basic gas-phase chemistry and passive tracers are also included in the model. Because of the vertical extent of the model, UV heating, non-LTE effects and molecular diffusion are also included. Dust is prescribed using the MGS scenario for total opacities and a Conrath profile shape. In the dust radiative transfer code, dust optical properties are based on the Wolff et al [2006, 2009] data. Temperatures in the lower and middle atmosphere have been evaluated using TES [Smith, 2004] and MCS [Kleinbohl et al. 2009] data. Winds and atmospheric circulation (mass stream functions) have been compared with the literature and show a good correspondence to other Mars GCMs. In parallel, active lifting and settling of size-distributed dust has also been implemented. The soil model has been improved to better match surface and near-surface temperatures from the Viking Landers, Phoenix [Davy et al. 2010], and TES. Near-surface winds and friction velocities have been compared with the literature and show reasonable performance. Condensation of CO2 in surface ice has been validated using CO2 ice mass

  13. An Intense Ocean-Atmosphere Interaction during the Holocene Optimum: Evidence from Sub-alpine Lake Sediments in Taiwan

    NASA Astrophysics Data System (ADS)

    Kandasamy, S.; Chen, C. A.; Lou, J. Y.; Kao, S.

    2009-12-01

    The Holocene climate reconstructions indicate an optimum climate in terms of either temperature or precipitation or both between ca. 10.5 and 4.5 calendar thousand years before the Present (ka BP). This so called Holocene optimum (HO) exhibits a time lagged phenomenon across the East Asia where the interaction of summer and winter modes of East Asian monsoon (EAM) has produced diverse climatic and environmental finger prints for the entire Holocene (the past ~11.5 ka). Yet, we lack evidence for the role of ocean and atmosphere during the HO given the fact that quantification of such input in the continental archives has not been done earlier, especially on the land-ocean-atmosphere interface. To fulfill this gap, a sediment core (~1.7 m) raised from Retreat Lake in northeastern Taiwan was studied for Relative Grey Index (RGI), bulk density, water content, total organic carbon (TOC), total nitrogen, and selected major and trace elements, including indicator elements for sea salt input (Br, Cl and Na). Time series of RGI shows high values (>80) ~170-155 cm and top ~45 cm of the core due to the presence of white, dense, minerogenic sediments with low water and TOC contents. Such an association of parameters indicates cool-wet and warm-dry climates and respectively corresponds to early Holocene (~10.3-8.6 ka BP) and late Holocene (since 4.5 ka BP). By contrast, sediments ~155-45 cm of the core show low RGI values (mostly <50) due to the presence of dark, less dense, peaty sediments with high water and TOC contents, indicating the warmest perhaps the wettest climate (HO) ~8.6-4.5 ka BP. Interestingly, the peaty sediments of HO show very high Br concentrations of up to 230 μg g-1, almost all values are >150 μg g-1. These values are ~7-12 times higher than Br values found in early and late Holocene sediments (0-20 μg g-1) as well as source rock Br values. Depth profiles of Br, Cl, and Na mimic each other and Br shows a linear relationship with Cl and Na in sediments of

  14. Ocean-atmosphere exchange of ammonia in the 21st century and the competing effects of temperature and ocean acidification

    NASA Astrophysics Data System (ADS)

    Steadman, Claudia; Stevenson, David; Heal, Mathew; Sutton, Mark; Buitenhuis, Erik; Fowler, David

    2017-04-01

    Ammonia is the principal alkaline gas in the atmosphere. It therefore plays an important role in atmospheric chemistry, reacting with sulphuric and nitric acids to form ammonium aerosols, which serve as cloud condensation nuclei and negatively impact human health. Anthropogenic ammonia emissions are increasing rapidly in many areas of the world, and are expected to increase dramatically in the future due to the strong effect of temperature on the emission of ammonia. It is therefore of interest to understand the impact of increasing temperatures, atmospheric CO2, and anthropogenic ammonia emissions on the ocean-atmosphere exchange of ammonia. Global scale estimates of this exchange are difficult to constrain due to the variability of fluxes and the difficulties in measuring them. A modelling approach is therefore required. An interactive scheme for the global exchange of ammonia between the atmosphere and the ocean was developed, and implemented in both an offline physico-chemical model, and the global atmospheric chemistry and aerosol model UKCA-CLASSIC. The scheme takes into account future projections of changes in temperature, terrestrial ammonia emissions, and ocean pH. Results show that ocean acidification has the largest effect, leading to a decrease in global ocean ammonia emissions from a range of 2.8 to 6.6 Tg-N/yr for the present day to a range of -1.1 to 2.3 Tg-N/yr for 2100 (RCP 8.5), suggesting this is one of several routes through which the flux of nitrogen to the oceans will increase in the future.

  15. Ocean-atmospheric linkages

    NASA Technical Reports Server (NTRS)

    Rintoul, Stephen R.

    1992-01-01

    This chapter focuses on the role of the ocean in the global carbon cycle on the time scale of decades to centuries. The input rate of CO2 to the atmosphere due to fossil fuel burning and deforestation has continued to increase over the last century. To balance the global carbon budget, a sink is required whose magnitude is changing on similar time scales. We have sought to identify aspects of the ocean system that are capable of responding on decadal time scales, to examine our present ability to model such changes, and to pinpoint ways in which this ability could be improved. Many other important aspects of the ocean's role in global change are not addressed, including the importance of oceanic heat transport and thermal inertia to the climate system, biogeochemical cycling of elements other than carbon, and the importance of the ocean as a source or sink of trace gases.

  16. Optimization studies on GCM for iodine waste forms

    SciTech Connect

    Nenoff, Tina Maria

    2014-09-01

    We are purusing an understand of the durability and materials processability of the low temperature sintering Bi-Si oxide Glass Composite Material (GCM)1 Waste Form for iodine capture materials. The chemical and physical controls over iodine release from candidate 129I waste forms must be quantified to predict long-term waste form effectiveness.

  17. Develop Plan for Analysis of the Effluent from GCM Production.

    SciTech Connect

    Nenoff, Tina M.; Mowry, Curtis D.

    2015-08-24

    This milestone is focused on developing a plan for the analysis of the effluent from the Sandia low temperature sintering Bi-Si-Zn oxide glass composite material (GCM) waste form for the long term storage of iodine and its capture materials.

  18. A stochastic precipitation disaggregation scheme for GCM applications

    NASA Technical Reports Server (NTRS)

    Gao, Xiaogang; Sorooshian, Soroosh

    1994-01-01

    In the surface hydrologic parameterization of general circulation models (GCMs), it is commonly assumed that the precipitation processes are homogeneous over a GCM grid square and that the precipitation intensity is uniformly distributed. Based on evidence that the spatial distribution of precipitation within a GCM grid square is crucial for the land surface hydrology parameterization, a few researchers have explored the impacts of assuming that the precipitation is exponentially distributed. This paper explores the suitability of the aforementioned assumptions. First, a statistical analysis is conducted of historical precipitation data for three GCM grids in different regions of the United States. The analysis suggests that neither the uniform nor the exponential distribution assumption may be suitable at the GCM grid scale and, that instead, the spatial variability in precipitation is characterized by statistical patterns that are inhomogeneous. These patterns vary from grid to grid and are induced by the interaction between atmospheric conditions and various land surface characteristics, such as topographical features, surface properties, etc. Within the same grid square, however, the statistical patterns are generally constant from year to year. Based on this analysis, a computationally viable (i.e., usable with GCMs) stochastic precipitation disaggregation scheme that utilizes these stable statistical patterns is proposed. The method was used to generate spatially distributed hourly rainfall for a summer season in the southwestern region of the continental United States. Analysis of the results shows that the methodology preserves the seasonal characteristics of spatial variability in precipitation that is observed in the long-term historical data.

  19. Snow complexity representation and GCM climate

    NASA Astrophysics Data System (ADS)

    Dutra, Emanuel; Viterbo, Pedro; Miranda, Pedro M. A.; Balsamo, Gianpaolo

    2010-05-01

    Accurate simulations of the snow cover strongly impact on the quality of weather and climate predictions as the solar radiation absorption at land-atmosphere interface is modified by a factor up to 4 in response to snow presence (albedo effect). In Northern latitudes and Mountainous regions snow acts also as an important energy and water reservoir and a correct representation of snow mass and snow density is crucial for temperature predictions at all time-scales, with direct consequences for soil hydrology (thermal insulation effect). Three different complexity snow schemes implemented in the ECMWF land surface scheme HTESSEL are tested within the EC-EARTH framework. The snow schemes are: 1) OLD, the original HTESSEL single bulk layer snow scheme (same as in the ERA-40 and ERA-Interim reanalysis); 2) OPER, a new snow scheme in operations since September 2009, with a liquid water reservoir and revised formulations of snow density, fractional cover and snow albedo; and 3) ML3, a multi-layer version of OPER. All three snow schemes in HTESSEL are energy- and mass- balance models. The multi-layer snow scheme, ML3, was validated in offline mode covering several spatial and temporal scales: (i) site simulations for several observation locations from the Snow Models intercomparison project-2 (SnowMip2) and (ii) global simulations driven by the meteorological forcing from the Global Soil Wetness Project-2 (GSWP2) and the ECMWF ERA-Interim re-analysis. On point locations ML3 improve snow mass simulations, while on a global scale the impacts are residual pointing to the need of coupled atmosphere simulations. The 3 schemes are compared in the framework of the atmospheric model of EC-EARTH, based on the current seasonal forecast system of ECMWF. The standard configuration runs at T159 horizontal spectral resolution with 62 vertical levels. Three member ensembles of 30 years (1979-2008) simulations, with prescribed SSTs and sea ice, were performed for each of the snow schemes

  20. Trace element content of sedimentary pyrite as a new proxy for deep-time ocean-atmosphere evolution

    NASA Astrophysics Data System (ADS)

    Large, Ross R.; Halpin, Jacqueline A.; Danyushevsky, Leonid V.; Maslennikov, Valeriy V.; Bull, Stuart W.; Long, John A.; Gregory, Daniel D.; Lounejeva, Elena; Lyons, Timothy W.; Sack, Patrick J.; McGoldrick, Peter J.; Calver, Clive R.

    2014-03-01

    Sedimentary pyrite formed in the water column, or during diagenesis in organic muds, provides an accessible proxy for seawater chemistry in the marine rock record. Except for Mo, U, Ni and Cr, surprisingly little is known about trace element trends in the deep time oceans, even though they are critical to developing better models for the evolution of the Earth's atmosphere and evolutionary pathways of life. Here we introduce a novel approach to simultaneously quantify a suite of trace elements in sedimentary pyrite from marine black shales. These trace element concentrations, at least in a first-order sense, track the primary elemental abundances in coeval seawater. In general, the trace element patterns show significant variation of several orders of magnitude in the Archaean and Phanerozoic, but less variation on longer wavelengths in the Proterozoic. Certain trace elements (e.g., Ni, Co, As, Cr) have generally decreased in the oceans through the Precambrian, other elements (e.g., Mo, Zn, Mn) have generally increased, and a further group initially increased and then decreased (e.g., Se and U). These changes appear to be controlled by many factors, in particular: 1) oxygenation cycles of the Earth's ocean-atmosphere system, 2) the composition of exposed crustal rocks, 3) long term rates of continental erosion, and 4) cycles of ocean anoxia. We show that Ni and Co content of seawater is affected by global Large Igneous Province events, whereas redox sensitive trace elements such as Se and Mo are affected by atmosphere oxygenation. Positive jumps in Mo and Se concentrations prior to the Great Oxidation Event (GOE1, c. 2500 Ma) suggest pulses of oxygenation may have occurred as early as 2950 Ma. A flat to declining pattern of many biologically important nutrient elements through the mid to late Proterozoic may relate to declining atmosphere O2, and supports previous models of nutrient deficiency inhibiting marine evolution during this period. These trace elements (Mo

  1. New Planetary Energy Balance, Ocean-Atmosphere Interaction and their Effects on Extreme Events in North Atlantic

    NASA Astrophysics Data System (ADS)

    Karrouk, Mohammed-Said

    2016-04-01

    Global warming has now reached the energetic phase of H2O's return to the ground after the saturation of the atmosphere in evaporation since the 80s and 90s of the last century, which were characterized by severe droughts, mainly in Africa. This phase is the result of the accumulation of thermal energy exchanges in the Earth-Ocean-Atmosphere system that resulted in the thrust reversal of the energy balance toward the poles. This situation is characterized by a new thermal distribution: above the ocean, the situation is more in surplus compared to the mainland, or even opposite when the balance is negative on the land, and in the atmosphere, warm thermal advection easily reach the North Pole (planetary crests), as well as cold advection push deep into North Africa and the Gulf of Mexico (planetary valleys). This "New Ground Energy Balance" establishes a "New Meridian Atmospheric Circulation (MAC)" with an undulating character throughout the year, including the winter characterized by intense latitudinal very active energy exchanges between the surplus areas (tropical) and the deficit (polar) on the one hand, and the atmosphere, the ocean and the continent on the other. The excess radiation balance increases the potential evaporation of the atmosphere and provides a new geographical distribution of H2O worldwide: the excess water vapor is easily converted by cold advection (polar vortex) to heavy rains that cause floods or snow storms that paralyze the normal functioning of human activities, which creates many difficulties for users and leaves damage and casualties, but ensures water availability missing since a long time in many parts of the world, in Africa, Europe and America. The new thermal distribution reorganizes the geography of atmospheric pressure: the ocean energy concentration is transmitted directly to the atmosphere, and the excess torque is pushed northward. The Azores anticyclone is strengthened and is a global lock by the Atlantic ridge at Greenland

  2. Evidence for a Progressive Change of Interglacial Climate Conditions Forced by Different Ocean-Atmosphere Circulation Regimes

    NASA Astrophysics Data System (ADS)

    Bauch, H. A.; Kandiano, E. S.; Helmke, J. P.

    2005-12-01

    quite comparable to the two younger periods, the weakest penetration of warm surface water into the northern high latitudes. In summary, a stepwise, northward expansion of polar-directed heat transfer from one interglaciation to the next youngest is proposed, marking the Holocene a time with the strongest impact on north-polar warming. A fundamental difference in ocean-atmosphere circulation with consequences on high-latitude precipitation-runoff rates and seas-ice drift patterns seems to be the likely forcing behind the unprecedented situation found for the Holocene.

  3. Large Scale Water Mass Redistributions between Oceans, Atmosphere and Land and their Signature in the Gravity Field

    NASA Astrophysics Data System (ADS)

    Meyssignac, B.; Cazenave, A. A.; Lemoine, J. M.; Maisongrande, P.

    2012-12-01

    Llovel et al. 2011 have shown that interannual Global Mean Sea Level (GMSL) and total land water storage variations are inversely correlated in particular during ENSO events. Total water storage is lower/higher than average on land when GMSL is higher/lower than average during El Nino/La Nina. This result is in agreement with the observed rainfall deficit/excess over land/oceans during El Nino and vice versa during La Nina. It suggests that the GMSL anomalies observed during ENSO events are likely due to an ocean mass rather than thermal expansion increase. In a recent study (Cazenave et al., in revision, 2012) that focuses on the large positive GMSL anomaly observed during the 1997/1998 El Nino, we showed that this anomaly is almost exclusively due to an ocean mass excess located in a small region of the north tropical Pacific (0°-20°N latitude and 120°E -160°W longitude). At the same time we observe a total land mass deficit that is equivalent in amplitude and phasing to the ocean mass excess observed in the north tropical Pacific. These results suggest that the main modes of interannual climate variability (in particular ENSO) generate large mass redistributions (essentially water) over the globe between remote places. In this study, we investigate further these large scale water mass redistributions and their signature in the gravity field. We analyse variations of the low degree spherical harmonics (C2,0- the Earth's oblateness-, C2,1, S2,1, C2,2 and S2,2) measured by LAGEOS1/2 during a 18-year period (1993-2009), and GRACE since 2002. The considered 1993-2009 time span encompasses the intense 1997/1998 El Nino. By accounting for ocean thermal expansion and water mass distribution changes in the ocean, atmosphere and land hydrology with independent observations (including GRACE) and models, we are able to explain the interannual variability in large scale mass redistribution observed since 1993 in the C2,0, C2,2 and S2,2 low degree spherical harmonics

  4. Arctic Ocean Atmosphere Sea Ice Snowpack (OASIS) Interactions Affecting Atmospheric Biogeochemistry, Climate and Ecosystems in the Arctic

    NASA Astrophysics Data System (ADS)

    Beine, H.

    2006-12-01

    The Arctic Ocean is central to the understanding of climate and global environmental change. As a critical component of the Earth system, the Arctic region both influences and responds rapidly to natural variations and to human-induced perturbations, such as warming, contaminant accumulation, and associated impacts. While it is clear that there are dramatic changes occurring in the Arctic, the interactions between the air and surfaces are still not understood. The international, multidisciplinary Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) program addresses the knowledge gaps and coordinates studies of Arctic atmosphere-surface interactions and associated feedbacks to the climate system. OASIS is planned as a long term science program for the next decade. OASIS is linked to a number of international organizations and activities, including AMAP, the IGBP programs IGAC under the AICI (Air Ice Chemical Interactions) activity, and SOLAS (Surface Ocean Lower Atmosphere Study), and the WCRP project CliC (Climate and Cryosphere). The abundant snowpack in the Arctic is not just a white cover: an array of intriguing reactions has been observed within and on snowpacks and sea-ice during springtime Arctic sunrise that dramatically influences the composition of the atmosphere. Building on these discoveries, the OASIS research approach is aimed at a better understanding of air-surface chemical exchange in the context of a changing climate. Fundamental physical, chemical, and biologically-mediated chemical exchange processes will be studied to answer questions such as: Will climate change increase or decrease the amount of mercury deposited in the Arctic? How will warming affect regional and global climate? How are sea ice and snow chemistry and physics changing? What is the role of biological processes in producing reactive atmospheric gases? What is the role of sea-salt in ozone depletion? What are ecological and human health impacts of toxic materials such as mercury and

  5. COUPLING

    DOEpatents

    Frisch, E.; Johnson, C.G.

    1962-05-15

    A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)

  6. Aircraft Measurements for Understanding Air-Sea Coupling and Improving Coupled Model Predictions

    DTIC Science & Technology

    2013-09-30

    measured solar /IR irradiance profiles as input to, and validation of, the Navy’s coupled ocean/atmosphere model , COAMPS. FY13 effort focused on...coupling in different stages of the MJO. The objectives of the NRL project are to obtain vertical profiles of the solar and IR irradiance ...of the NRL solar and IR broadband radiometer irradiance data from the NOAA P-3 aircraft was completed. QC’ed datasets, with documentation, of the

  7. Comparison of CHAMP and TIME-GCM nonmigrating tidal signals in the thermospheric zonal wind

    NASA Astrophysics Data System (ADS)

    Häusler, K.; Lühr, H.; Hagan, M. E.; Maute, A.; Roble, R. G.

    2010-02-01

    Four years (2002-2005) of continuous accelerometer measurements taken onboard the CHAMP satellite (orbit altitude ˜400 km) offer a unique opportunity to investigate the thermospheric zonal wind on a global scale. Recently, we were able to relate the longitudinal wave-4 structure in the zonal wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with zonal wave number 3 (DE3). The DE3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds. In order to investigate the mechanisms that couple the tidal signals to the upper thermosphere, we undertook a comparison with the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) developed at the National Center for Atmospheric Research (NCAR). We ran the model for a day in March, June, September, and December and applied the same processing steps to the model output as was done for the CHAMP tidal analysis. The main results of the comparison can be summarized as follows: (1) TIME-GCM simulations do not correctly reproduce the observed intra-annual variations of DE3 and the eastward propagating diurnal tide with zonal wave number 2 (DE2). (2) Simulations of DE3 for June are more successful. Both TIME-GCM and CHAMP show an increase in DE3 amplitudes with decreasing solar flux level. (3) The amplitudes of the simulated westward propagating diurnal tide with zonal wave number 2 (DW2) and the standing diurnal tide (D0) increase with increasing solar flux in June. The predicted dependence of DW2 and DO on solar flux is also observed by CHAMP.

  8. Assessment of CMIP5 GCM daily predictor variables for statistical downscaling

    NASA Astrophysics Data System (ADS)

    Mpelasoka, F. S.; Charles, S.; Chiew, F. H.; Fu, G.; Beecham, S.

    2012-04-01

    Assessment of CMIP5 GCM daily predictor variables for statistical downscaling To support adaptation to climate change in the water resource sector in South Australia, downscaled climate projections are being constructed within the Goyder Institute for Water Research - a 5-year multi-million dollar collaborative research partnership between the Government of South Australia, CSIRO and the university sector. Statistical downscaling is a robust approach providing a link between observed (re-analysis) large-scale atmospheric variables (predictors) and local or regional surface climate variables such as daily station rainfall. When applied to outputs of Global Climate Models (GCMs), the credibility of statistically downscaled future projections is dependent on the ability of GCMs to reproduce the re-analysis data statistics for the current climate. The main objective of this study is thus to assess daily predictor variables simulated by phase Five of Coupled Model Inter-comparison Project (CMIP5) GCMs, while acknowledging that an optimal measure of overall GCM performance does not exist and the usefulness of any assessment approach varies with the intended application. Here we assess GCMs by comparing cumulative probability density functions of predictor variables against the re-analysis data using the Kolmogorov test metric. Historical daily data simulations from 12 GCMs (BCC-csm1, CanESM2, CSIRO-Mk3.6.0, GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, IPSL-CM5A-MR, MIROC4h, MIROC-ESM-CHEM, MPI-ESM-LR, MRI-CGCM3, and NorESM1-M) for the period 1961-2005 are used. The variables assessed include specific/relative humidity, winds, geopotential heights at different atmospheric levels and sea-level pressure over the Australian region (7-45oS, 100-160oE). We present a summary of results for the South Australia region quantifying the ability of these GCMs in reproducing the mean state and the relative frequency of extremes for these predictors. The complexity and challenges in GCM

  9. Coral Evidence for Abrupt Changes in Ocean-Atmosphere Dynamics in the SW Pacific since 1565 AD

    NASA Astrophysics Data System (ADS)

    Hendy, E. J.; Gagan, M. K.; McCulloch, M. T.; Lough, J. M.

    2004-12-01

    A coral-based multi-tracer approach can give an overview of the whole tropical ocean-atmosphere system. Key indicators are sea surface temperature (SST), which sets climate boundary conditions, sea surface salinity (SSS), which provides a measure of energy transfer through the evaporation-precipitation balance, and river runoff, which can establish the strength and variability of precipitation. We present palaeoenvironmental records from eight massive { \\it Porites} coral colonies, spanning 120 to 420 years of continuous growth, collected from the central Great Barrier Reef, Australia. Stable isotopes (\\delta18O and \\delta13C), Sr/Ca, U/Ca, and Ba/Ca ratios were measured in 5-year increments and a record of annual UV luminescence was developed. By replicating the measurements between colonies we demonstrate how faithfully corals record changes in their environment over decadal-to-centennial timescales, constructing composite records in a manner analogous to dendroclimatology and confidence intervals for each proxy. The competing environmental influences affecting a number of tracers can be distinguished by comparison between the SST-tracers (Sr/Ca, U/Ca, \\delta18O), the freshwater flux tracers (\\Delta\\delta18O, Ba/Ca and luminescence) and tracers of water mass characteristics (\\delta18O, \\delta13C, and \\Delta14C). The coral palaeothermometers Sr/Ca and U/Ca ratios, measured in tandem with \\delta18O, allow the separation of SST changes from changes in seawater \\delta18O, thereby resolving SSS. The composite Sr/Ca and U/Ca are in excellent agreement back to 1565, and capture the 20th century warming trend, up to the 1980s when the cores were collected. The most remarkable feature of the 420-year record is that SSTs were consistently as warm as the second half of the 20th century from the early 18th and through most of the 19th centuries. Changes in the evaporation-precipitation balance dominate the \\delta18O record. A striking 0.2\\permil\\ shift from the

  10. Investigating TIME-GCM Atmospheric Tides for Different Lower Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Haeusler, K.; Hagan, M. E.; Lu, G.; Forbes, J. M.; Zhang, X.; Doornbos, E.

    2013-12-01

    It has been recently established that atmospheric tides generated in the lower atmosphere significantly influence the geospace environment. In order to extend our knowledge of the various coupling mechanisms between the different atmospheric layers, we rely on model simulations. Currently there exist two versions of the Global Scale Wave Model (GSWM), i.e. GSWM02 and GSWM09, which are used as a lower boundary (ca. 30 km) condition for the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) and account for the upward propagating atmospheric tides that are generated in the troposphere and lower stratosphere. In this paper we explore the various TIME-GCM upper atmospheric tidal responses for different lower boundary conditions and compare the model diagnostics with tidal results from satellite missions such as TIMED, CHAMP, and GOCE. We also quantify the differences between results associated with GSWM02 and GSWM09 forcing and results of TIMEGCM simulations using Modern-Era Retrospective Analysis for Research and Application (MERRA) data as a lower boundary condition.

  11. Studies of African wave disturbances with the GISS GCM

    NASA Technical Reports Server (NTRS)

    Druyan, Leonard M.; Hall, Timothy M.

    1994-01-01

    Simulations made with the general circulation model of the NASA/Goddard Institute for Space Studies (GISS GCM) run at 4 deg latitude by 5 deg longitude horizontal resolution are analyzed to determine the model's representation of African wave disturbances. Waves detected in the model's lower troposphere over northern Africa during the summer monsoon season exhibit realistic wavelengths of about 2200 km. However, power spectra of the meridional wind show that the waves propagate westward too slowly, with periods of 5-10 days, about twice the observed values. This sluggishness is most pronounced during August, consistent with simulated 600-mb zonal winds that are only about half the observed speeds of the midtropospheric jet. The modeled wave amplitudes are strongest over West Africa during the first half of the summer but decrease dramatically by September, contrary to observational evidence. Maximum amplitudes occur at realistic latitudes, 12 deg - 20 deg N, but not as observed near the Atlantic coast. Spectral analyses suggest some wave modulation of precipitation in the 5-8 day band, and compositing shows that precipitation is slightly enhanced east of the wave trough, coincident with southerly winds. Extrema of low-level convergence west of the wave troughs, coinciding with northerly winds, were not preferred areas for simulated precipitation, probably because of the drying effect of this advection, as waves were generally north of the humid zone. The documentation of African wave disturbances in the GISS GCM is a first step toward considering wave influences in future GCM studies of Sahel drought.

  12. Chemistry-Climate Interactions in the GISS GCM. Part 1; Tropospheric Chemistry Model Description and Evaluation

    NASA Technical Reports Server (NTRS)

    Shindell, Drew T.; Grenfell, J. Lee; Rind, David; Price, Colin; Grewe, Volker; Hansen, James E. (Technical Monitor)

    2001-01-01

    A tropospheric chemistry module has been developed for use within the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to study interactions between chemistry and climate change. The model uses a simplified chemistry scheme based on CO-NOx-CH4 chemistry, and also includes a parameterization for emissions of isoprene, the most important non-methane hydrocarbon. The model reproduces present day annual cycles and mean distributions of key trace gases fairly well, based on extensive comparisons with available observations. Examining the simulated change between present day and pre-industrial conditions, we find that the model has a similar response to that seen in other simulations. It shows a 45% increase in the global tropospheric ozone burden, within the 25% - 57% range seen in other studies. Annual average zonal mean ozone increases by more than 125% at Northern Hemisphere middle latitudes near the surface. Comparison of model runs that allow the calculated ozone to interact with the GCM's radiation and meteorology with those that do not shows only minor differences for ozone. The common usage of ozone fields that are not calculated interactively seems to be adequate to simulate both the present day and the pre-industrial ozone distributions. However, use of coupled chemistry does alter the change in tropospheric oxidation capacity, enlarging the overall decrease in OH concentrations from the pre-industrial to the present by about 10% (-5.3% global annual average in uncoupled mode, -5.9% in coupled mode). This indicates that there may be systematic biases in the simulation of the pre-industrial to present day decrease in the oxidation capacity of the troposphere (though a 10% difference is well within the total uncertainty). Global annual average radiative forcing from pre-industrial to present day ozone change is 0.32 W/sq m. The forcing seems to be increased by about 10% when the chemistry is coupled to the GCM. Forcing values greater

  13. Ocean Data Assimilation for Coupled Models

    DTIC Science & Technology

    2016-06-07

    ability to analyze and predict the upper ocean/lower atmosphere environment, using sophisticated techniques that can exploit data from all available...sources. This ability is fundamental to meeting DOD’s needs for real-time analysis and improved air/sea simulation and prediction on a variety of scales...is developing the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS), and has already transitioned the atmospheric prediction system and

  14. A review of recent research on improvement of physical parameterizations in the GLA GCM

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Walker, G. K.

    1990-01-01

    A systematic assessment of the effect of a series of improvements in physical parameterizations of the Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) are summarized. The implementation of the Simple Biosphere Model (SiB) in the GCM is followed by a comparison of SiB GCM simulations with that of the earlier slab soil hydrology GCM (SSH-GCM) simulations. In the Sahelian context, the biogeophysical component of desertification was analyzed for SiB-GCM simulations. Cumulus parameterization is found to be the primary determinant of the organization of the simulated tropical rainfall of the GLA GCM using Arakawa-Schubert cumulus parameterization. A comparison of model simulations with station data revealed excessive shortwave radiation accompanied by excessive drying and heating to the land. The perpetual July simulations with and without interactive soil moisture shows that 30 to 40 day oscillations may be a natural mode of the simulated earth atmosphere system.

  15. GCM Simulations of the Tropical Hydrogen Distribution Observed by Mars Odyssey

    NASA Technical Reports Server (NTRS)

    Mischna, M. A.; Richardson, M. I.

    2005-01-01

    The age and nature of the tropical hydrogen deposits on Mars remain uncertain. Competing theories suggest that the deposits are composed of either ancient, hydrated minerals or recently emplaced water ice. We use the GFDL Mars GCM with a fully coupled atmosphere-regolith water cycle to explore which of these hypotheses is best supported by model results. Such a conclusion can be drawn from the resultant trends in subsurface ice evolution during various obliquity and polar cap conditions. Our results suggest that the tropical hydrogen distribution is best explained by recent emplacement of ice through either exposure of the south polar ice cap or by burial of tropical surface ice from the most recent high obliquity excursions.

  16. The MJO in a Coarse-Resolution GCM with a Stochastic Multicloud Parameterization

    NASA Astrophysics Data System (ADS)

    Khouider, B.; Deng, Q.; Majda, A.

    2014-12-01

    The representation of the Madden-Julian oscillation (MJO) is still a challenge for numerical weather prediction and general circulation models (GCMs) due to the inadequate treatment of convection and the associated interactions across scales by the underlying cumulus parameterizations. One new promising direction is the use of the stochastic multicloud model (SMCM) that has been designed specifically to capture the missing variability due to unresolved processes of convection and their impact on the large scale flow. The SMCM specifically models the area fractions of the three cloud types (congestus, deep and stratiform) that characterize organized convective systems on all scales. The SMCM captures the stochastic behavior of these three cloud types via a judiciously constructed Markov birth-death process using a particle interacting lattice model. The SMCM has been successfully applied for convectively coupled waves in a simplified primitive equation model and validated against radar data of tropical precipitation. In this work, we use for the first time the SMCM in a GCM. We build on previous work of coupling the High-Order Methods Modeling Environment (HOMME) NCAR-GCM to a simple multicloud model. We tested the new SMCM-HOMME model in the parameter regime considered previously and found that the stochastic model drastically improves the results of the deterministic model. Clear MJO-like structures with many realistic features from nature are reproduced by SMCM-HOMME in the physically relevant parameter regime including wave trains of MJO's that organize intermittently in time. Also one of the caveats of the deterministic simulation of requiring a doubling of the moisture background is not required anymore.

  17. Equatorial waves in a stratospheric GCM - Effects of vertical resolution

    NASA Technical Reports Server (NTRS)

    Boville, Byron A.; Randel, William J.

    1992-01-01

    It is noted that equatorially trapped wave modes, e.g., Kelvin and Rossby-gravity waves, are thought to play a critical role in forcing the quasi-biennial oscillation of the lower tropical stratosphere. The ability of a GCM to simulate these waves is examined and the changes in the wave properties as a function of the vertical resolution of the model are investigated. The dependence of the equatorial wave simulation of vertical resolution is examined utilizing three experiments with vertical grid spacings of about 2.8, 1.4, and 0.7 km. At high vertical resolution, the simulated waves are shown to agree with the available observations.

  18. GCM Simulations of Cirrus Clouds and Cloud Feedbacks

    NASA Technical Reports Server (NTRS)

    DelGenio, Anthony D.

    1998-01-01

    Cirrus clouds are a particularly uncertain component of general circulation model (GCM simulations of long-term climate change for a variety of reasons: (1) They encompass a wide range of optical thicknesses and altitudes, from thin tropopause cirrus to thick anvil cirrus that descend to the freezing level, and thus can exert both positive and negative forcing and feedback on the climate; (2) The dynamical processes that create them are poorly resolved in climate GCMs and different in the tropics and midlatitudes; (3) Predictions of their formation and microphysical properties depend on the accuracy of dynamical transports of small concentrations of water vapor to and within the upper troposphere; (4) The relative humidity conditions at which they form depends on the nature and concentration of nucleating particles and is poorly understood; (5) They are more difficult to observe than other cloud types, and hence their parameterization is more loosely constrained by available data. We will illustrate the potential sensitivity of the perturbed climate to uncertainties in cirrus cloud formulation. We will also examine the processes that form cirrus in climate models and discuss the accuracy with which climate GCMs represent these processes. We will also discuss ways in which GCM grid-scale parameterizations might be derived from cloud-scale observations. Finally, we will emphasize the types of global observations needed to constrain parameterizations of cirrus in climate GCMs.

  19. Long Lead-Time Forecasting of Snowpack and Precipitation in the Upper Snake River Basin using Pacific Oceanic-Atmospheric Variability

    NASA Astrophysics Data System (ADS)

    Anderson, S.; Tootle, G.; Parkinson, S.; Holbrook, P.; Blestrud, D.

    2012-12-01

    Water managers and planners in the western United States are challenged with managing resources for various uses, including hydropower. Hydropower is especially important throughout the Upper Snake River Basin, where a series of hydropower projects provide a low cost renewable energy source to the region. These hydropower projects include several dams that are managed by Idaho Power Company (IPC). Planners and managers rely heavily on forecasts of snowpack and precipitation to plan for hydropower availability and the need for other generation sources. There is a pressing need for improved snowpack and precipitation forecast models in the Upper Snake River Basin. This research investigates the ability of Pacific oceanic-atmospheric data and climatic variables to provide skillful long lead-time (three to nine months) forecasts of snowpack and precipitation, and examines the benefits of segregating the warm and cold phases of the Pacific Decadal Oscillation (PDO) to reduce the temperature variability within the target dataset. Singular value decomposition (SVD) was used to identify regions of Pacific Ocean sea surface temperatures (SST) and 500mbar geopotential heights (Z500) for various lead times (three, six, and nine months) that were teleconnected with snowpack and precipitation stations in Upper Snake River Basin headwaters. The identified Pacific Ocean SST and Z500 regions were used to create indices that became predictors in a non-parametric forecasting model. The majority of forecasts resulted in positive statistical skill, which indicated an improvement of the forecast over the climatology forecast (no-skill forecast). The results from the forecasts models indicated that derived indices from the SVD analysis resulted in improved forecast skill when compared to forecasts using established climate indices. Segregation of the cold phase PDO years resulted in the identification of different regions in the Pacific Ocean and vastly improved skill for the nine month

  20. Modelling snow accumulation on Greenland in Eemian, glacial inception and modern climates in a GCM

    NASA Astrophysics Data System (ADS)

    Punge, H. J.; Gallée, H.; Kageyama, M.; Krinner, G.

    2012-04-01

    Changing climate conditions on Greenland influence the snow accumulation rate and surface mass balance (SMB) on the ice sheet and, ultimately, its shape. This can in turn affect local climate via orography and albedo variations and, potentially, remote areas via changes in ocean circulation triggered by melt water or calving from the ice sheet. Examining these issues in the IPSL global model requires improving the representation of snow at the ice sheet surface. In this paper, we present the new snow scheme implemented in LMDZ, the atmospheric component of the IPSL coupled model. We analyze surface climate and SMB on the Greenland ice sheet under insolation and oceanic boundary conditions for modern, but also for two different past climates, the last glacial inception (115 kyr BP) and the Eemian (126 kyr BP). While being limited by the low resolution of the GCM, present-day SMB is on the same order of magnitude as recent regional model findings. It is affected by a moist bias of the GCM in Western Greenland and a dry bias in the north-east. Under Eemian conditions, the SMB diminishes largely, and melting affects areas with today high surface altitude including recent ice core drilling sites as NEEM. In contrast, glacial inception conditions lead to a higher mass balance overall due to the reduced melting in the colder summer climate. Compared to the widely applied positive degree day (PDD) parameterization of SMB, our direct modelling results suggest a weaker sensitivity of SMB to changing climatic forcing. In addition, significant differences in surface climate and SMB are found between simulations using monthly climatological mean and actual interannually varying monthly mean forcings for the ocean surface temperature and sea ice cover, in particular for the Eemian.

  1. Modelling snow accumulation on Greenland in Eemian, glacial inception, and modern climates in a GCM

    NASA Astrophysics Data System (ADS)

    Punge, H. J.; Gallée, H.; Kageyama, M.; Krinner, G.

    2012-11-01

    Changing climate conditions on Greenland influence the snow accumulation rate and surface mass balance (SMB) on the ice sheet and, ultimately, its shape. This can in turn affect local climate via orography and albedo variations and, potentially, remote areas via changes in ocean circulation triggered by melt water or calving from the ice sheet. Examining these interactions in the IPSL global model requires improving the representation of snow at the ice sheet surface. In this paper, we present a new snow scheme implemented in LMDZ, the atmospheric component of the IPSL coupled model. We analyse surface climate and SMB on the Greenland ice sheet under insolation and oceanic boundary conditions for modern, but also for two different past climates, the last glacial inception (115 kyr BP) and the Eemian (126 kyr BP). While being limited by the low resolution of the general circulation model (GCM), present-day SMB is on the same order of magnitude as recent regional model findings. It is affected by a moist bias of the GCM in Western Greenland and a dry bias in the north-east. Under Eemian conditions, the SMB decreases largely, and melting affects areas in which the ice sheet surface is today at high altitude, including recent ice core drilling sites as NEEM. In contrast, glacial inception conditions lead to a higher mass balance overall due to the reduced melting in the colder summer climate. Compared to the widely applied positive degree-day (PDD) parameterization of SMB, our direct modelling results suggest a weaker sensitivity of SMB to changing climatic forcing. For the Eemian climate, our model simulations using interannually varying monthly mean forcings for the ocean surface temperature and sea ice cover lead to significantly higher SMB in southern Greenland compared to simulations forced with climatological monthly means.

  2. A cloud modal representation for the IPSL Venus GCM: validation and first results

    NASA Astrophysics Data System (ADS)

    Guilbon, Sabrina; Määttänen, Anni; Montmessin, Franck; Burgalat, Jérémie; Lebonnois, Sébastien; Stolzenbach, Aurélien; Rannou, Pascal; Beth, Arnaud; Laakso, Anton; Kokkola, Harri; McGouldrick, Kevin; Lefèvre, Maxence; Lefèvre, Franck

    2017-04-01

    Venus is a terrestrial planet enshrouded by 20 km-thick clouds, which are composed of sulphuric acid-water solution droplets. To understand the Venus atmosphere, LMD and LATMOS laboratories have developed a 3D IPSL Venus Global Climate Model (Lebonnois et al. 2010). In this GCM, the cloud description is simplified. As clouds play a crucial role in radiative transfer, dynamics and generally the climate of Venus, it is necessary to improve the VGCM with a microphysical representation. To this end, we develop a Modal Aerosol Dynamics of Venusian Liquid Aerosol cloud model (MAD-VenLA). This model uses an implicit moment scheme to describe the particle size distribution and the microphysical processes in 0D. The particle size distribution is described by its first moments: total particle number (zeroth moment) and total particle volume (third moment) of the size distribution (Seigneur et al. 1986, Burgalat et al. 2014). Moreover, with this representation, the form of the size distribution is assumed to be a log-normal function. To represent a source of aerosol particles and the sedimentation of our cloud droplets, we have developed a 1D extension to our model. We are currently coupling MAD-VenLA with the 1D version of the IPSL Venus GCM. First, we will describe MAD-VenLA. Then, for validation, we will compare it with the sectional model SALSA in 0D (Kokkola et al. 2008), and with the CARMA Venus model (McGouldrick et al. 2007) and the Pioneer Venus LCPS observations (Knollenberg and Hunten, 1980) in 1D. In case of successful validation in 1D, we will be able to conduct 3D simulations with full microphysics in the future.

  3. The hypoparathyroidism-associated mutation in Drosophila Gcm compromises protein stability and glial cell formation

    PubMed Central

    Xi, Xiao; Lu, Lu; Zhuge, Chun-Chun; Chen, Xuebing; Zhai, Yuanfen; Cheng, Jingjing; Mao, Haian; Yang, Chang-Ching; Tan, Bertrand Chin-Ming; Lee, Yi-Nan; Chien, Cheng-Ting; Ho, Margaret S.

    2017-01-01

    Differentiated neurons and glia are acquired from immature precursors via transcriptional controls exerted by factors such as proteins in the family of Glial Cells Missing (Gcm). Mammalian Gcm proteins mediate neural stem cell induction, placenta and parathyroid development, whereas Drosophila Gcm proteins act as a key switch to determine neuronal and glial cell fates and regulate hemocyte development. The present study reports a hypoparathyroidism-associated mutation R59L that alters Drosophila Gcm (Gcm) protein stability, rendering it unstable, and hyperubiquitinated via the ubiquitin-proteasome system (UPS). GcmR59L interacts with the Slimb-based SCF complex and Protein Kinase C (PKC), which possibly plays a role in its phosphorylation, hence altering ubiquitination. Additionally, R59L causes reduced Gcm protein levels in a manner independent of the PEST domain signaling protein turnover. GcmR59L proteins bind DNA, functionally activate transcription, and induce glial cells, yet at a less efficient level. Finally, overexpression of either wild-type human Gcmb (hGcmb) or hGcmb carrying the conserved hypoparathyroidism mutation only slightly affects gliogenesis, indicating differential regulatory mechanisms in human and flies. Taken together, these findings demonstrate the significance of this disease-associated mutation in controlling Gcm protein stability via UPS, hence advance our understanding on how glial formation is regulated. PMID:28051179

  4. A comparison of GCM-simulated and observed mean January and July surface air temperature

    NASA Technical Reports Server (NTRS)

    Willmott, Cort J.; Legates, David R.

    1993-01-01

    Results are presented of a comparison of four present-day GCM simulations (GFDL, OSU, GISS, and UKMO) of high-resolution surface air temperature climatology, with both January and July scenarios being evaluated for each GCM. Results indicate that the surface air temperature simulations are significantly affected by model representations of the topography, sea level pressure, and precipitation, with the other factors being the inclusion of the diurnal cycle and the type of ocean model. The GISS and UKMO GCMs were found to simulate well the mean January and July surface air temperatures, whereas the OSU GCM overestimated and the GFDL GCM underestimated the temperatures.

  5. Air-Sea Interaction in the Ligurian Sea: Assessment of a Coupled Ocean-Atmosphere Model Using In Situ Data from LASIE07

    DTIC Science & Technology

    2011-06-01

    coordinates. Includes a free surface (the sigma coordinates move up and down with the surface elevation) Martin (2000); Barron et al. (2006) In deep...the NCOM, 1/8 degree model Barron et al. (2006) Boundary conditions are 6-hourly. Orlanski (1976) radiation boundary conditions [except Flather and...SST data, processed onto a 4-km grid (May et al. 1998), and corrected to show a subsurface or ‘‘bulk’’ SST ( Barron and Kara 2006), as well as in situ

  6. The Impact of Coastal Phytoplankton Blooms on Ocean-Atmosphere Thermal Energy Exchange: Evidence from a Two-Way Coupled Numerical Modeling System

    DTIC Science & Technology

    2012-12-25

    distribu- tion of nutrients in the coastal transition zone off Northern California: Effects on primary production , phytoplankton biomass and species com...chlorophyll-a product ; the inner nest ocean model domain is indicated by the red box. (c) Bathymetry map for Monterey Bay, California with reference...pixel in the composite product averages all clear observations ofthat pixel over the 4-month period. The two-dimensional surface chlo- rophyll

  7. Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

    USGS Publications Warehouse

    Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

    2012-01-01

    Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from and . Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

  8. Sensitivity of a GCM climate to enhanced shortwave cloud absorption

    SciTech Connect

    Kiehl, J.T.; Hack, J.J.; Cess, R.D.

    1995-09-01

    Recent studies find that clouds absorb significantly more shortwave radiation than currently modeled by general circulation models. Initial calculations for the global annuals shortwave energy budget imply that including the additional shortwave cloud absorption leads to an additional 22 W m{sup {minus}2} absorption in the atmosphere, with an equivalent reduction of shortwave flux at the surface. The present study investigates the climate implications of enhanced cloud absorption with use of the National Center for Atmospheric Research Community Climate Model. The GCM response to this forcing is to warm the upper troposphere by as much as 4 K. The additional shortwave heating in the upper troposphere reduces the strength of the Hadley circulation by 12% and leads to lower surface wind speeds in the Tropics. In turn, these lower wind speeds lead to a 25 W m{sup {minus}2} reduction in surface latent heat flux. 16 refs., 16 figs., 3 tabs.

  9. Maintenance of Northern Summer Stationary Waves in a GCM.

    NASA Astrophysics Data System (ADS)

    Ting, Mingfang

    1994-11-01

    The maintenance of northern summer stationary waves is studied with data from a 15-year integration of the general circulation model (GCM) experiment performed at the Geophysical Fluid Dynamics Laboratory. The model has relatively high resolution (rhomboidal 30 wavenumbers, 9 vertical levels) and simulates the summertime stationary waves reasonably well.A steady, linear, baroclinic model is used to understand the various forcing mechanisms for the northern summer stationary waves. The linear model response to global diabatic heating is found to play a dominant role in maintaining the summertime stationary waves in the GCM, especially in the subtropics. This response to diabatic heating shows a baroclinic structure in the vertical with a node at about = 0.5. On the other hand, stationary nonlinear interaction terms are found to be largely responsible for the extratropical, equivalent barotropic stationary wave features. It is hypothesized that this nonlinear interaction is a result of the thermally induced stationary waves interacting with the local orography. The direct linear response to orography is found to be rather insignificant, however. Transient vorticity and heat fluxes also tend to play a negligible role in explaining the summer stationary wave patterns.Further decomposition of the linear model response to global diabatic heating indicates that the response to the Indian monsoon and the western Pacific heat source is of primary importance in determining the global stationary wave pattern. This large heat source not only determines the stationary flow features locally, but also remotely controls the flow structure over the whole Pacific, North America, and the Atlantic region. Thus, variabilities in the Indian monsoon and the western Pacific heating may exert a strong influence on the global climate variability.

  10. Investigating vegetation-climate interactions during glacial times using the IPSL GCM

    NASA Astrophysics Data System (ADS)

    Woillez, Marie-Noelle; Kageyama, Masa; Krinner, Gerhard

    2010-05-01

    Vegetation plays an important role in the climate system, through its impact on albedo, rugosity and water fluxes. Only few GCM studies have investigated the climatic impact of vegetation changes in glacial times, some using a fixed glacial vegetation based on pollinic reconstructions (e.g. Crowley & Baum 1997; Wyputta & McAvaney 2001) and some others using vegetation models ( Kubatzki & Claussen 1998; Levis & Foley 1999; Crucifix & Hewitt 2005), but seldom with a full atmosphere-vegetation coupling. Moreover, most of these simulations have been run with fixed sea surface temperatures, thus inhibiting potential oceanic retroactions. Here we force two different vegetation models, ORCHIDEE and BIOME4, with outputs from the IPSL_CM4 Atmosphere-Ocean General Circulation Model (AOGCM). Two different glacial climates are used: with and without collapsed Atlantic Meridional Overturning Circulation (AMOC).The state with a collapsed AMOC results from an imposed additional freshwater flux in the North Atlantic ocean. Then, the different resulting vegetations are used to force the AOGCM. The new climatic states are compared with data and with results from other simulations performed in the PMIP2 project. If time allows we will also show the results from a fully coupled glacial simulation IPSL_CM4-ORCHIDEE and compare the results to those obtained in forced mode.

  11. Modeling Studies of the Effects of Tropical Rainfall on Ocean-Atmosphere Interactions and Oceanic Hydrological Cycle

    NASA Technical Reports Server (NTRS)

    Chen, Dake

    2000-01-01

    This research project is a joint effort of UMD/JCESS, NASA/GSFC, NOAA/PMEL and LDEO, with UMD/JCESS being the leader and LDEO being responsible for coupled modeling. Although the project as a whole is for three years, the LDEO part was terminated at the end of the second year because of a shift of focus. The detailed description of the whole project and the effort made at LDEO have been given in the two joint annual reports and the two annual reports from LDEO. Here we only provide a brief summary of what we have done here at LDEO and a list of publications that resulted partly from this project.

  12. The Gcm/Glide molecular and cellular pathway: new actors and new lineages.

    PubMed

    Laneve, Pietro; Delaporte, Claude; Trebuchet, Guillaume; Komonyi, Orban; Flici, Hakima; Popkova, Anna; D'Agostino, Giuseppe; Taglini, Francesca; Kerekes, Irene; Giangrande, Angela

    2013-03-01

    In Drosophila, the transcription factor Gcm/Glide plays a key role in cell fate determination and cellular differentiation. In light of its crucial biological impact, major efforts have been put for analyzing its properties as master regulator, from both structural and functional points of view. However, the lack of efficient antibodies specific to the Gcm/Glide protein precluded thorough analyses of its regulation and activity in vivo. In order to relieve such restraints, we designed an epitope-tagging approach to "FLAG"-recognize and analyze the functional protein both in vitro (exogenous Gcm/Glide) and in vivo (endogenous protein). We here (i) reveal a tight interconnection between the small RNA and the Gcm/Glide pathways. AGO1 and miR-1 are Gcm/Glide targets whereas miR-279 negatively controls Gcm/Glide expression (ii) identify a novel cell population, peritracheal cells, expressing and requiring Gcm/Glide. Peritracheal cells are non-neuronal neurosecretory cells that are essential in ecdysis. In addition to emphasizing the importance of following the distribution and the activity of endogenous proteins in vivo, this study provides new insights and a novel frame to understand the Gcm/Glide biology. Copyright © 2012 Elsevier Inc. All rights reserved.

  13. A novel mutation in the GCM2 gene causing severe congenital isolated hypoparathyroidism

    PubMed Central

    Doyle, Daniel; Kirwin, Susan M.; Sol-Church, Katia; Levine, Michael A.

    2013-01-01

    Objective To investigate the GCM2 gene in three siblings with congenital hypoparathyroidism and perform functional analysis. Materials and methods We sequenced the GCM2 gene by PCR and analyzed the functional consequence of the mutation by transient transfection studies. Haplotype analysis was performed. Results We identified a nucleotide change, c.408C>A, in exon 3 that is predicted to truncate the Gcm2 protein (p.Tyr136Ter). All three affected siblings were homozygous and both parents were heterozygous for the mutation. Transfection studies revealed the mutant mRNA but not expression of the Gcm2 protein. Haplotype analysis revealed that the two mutant GCM2 alleles shared genotypes on chromosome 6p24.2. Conclusions We describe the first GCM2 mutation in exon 3 in patients with severe congenital hypoparathyroidism. Informative genetic markers could not exclude identity by descent for the mutant alleles. Gcm2 protein was not detected after transfection, suggesting that complete lack of Gcm2 action accounts for severe hypoparathyroidism. PMID:23155703

  14. DREAM mediated regulation of GCM1 in the human placental trophoblast.

    PubMed

    Baczyk, Dora; Kibschull, Mark; Mellstrom, Britt; Levytska, Khrystyna; Rivas, Marcos; Drewlo, Sascha; Lye, Stephen J; Naranjo, Jose R; Kingdom, John C P

    2013-01-01

    The trophoblast transcription factor glial cell missing-1 (GCM1) regulates differentiation of placental cytotrophoblasts into the syncytiotrophoblast layer in contact with maternal blood. Reduced placental expression of GCM1 and abnormal syncytiotrophoblast structure are features of hypertensive disorder of pregnancy--preeclampsia. In-silico techniques identified the calcium-regulated transcriptional repressor--DREAM (Downstream Regulatory Element Antagonist Modulator)--as a candidate for GCM1 gene expression. Our objective was to determine if DREAM represses GCM1 regulated syncytiotrophoblast formation. EMSA and ChIP assays revealed a direct interaction between DREAM and the GCM1 promoter. siRNA-mediated DREAM silencing in cell culture and placental explant models significantly up-regulated GCM1 expression and reduced cytotrophoblast proliferation. DREAM calcium dependency was verified using ionomycin. Furthermore, the increased DREAM protein expression in preeclamptic placental villi was predominantly nuclear, coinciding with an overall increase in sumolylated DREAM and correlating inversely with GCM1 levels. In conclusion, our data reveal a calcium-regulated pathway whereby GCM1-directed villous trophoblast differentiation is repressed by DREAM. This pathway may be relevant to disease prevention via calcium-supplementation.

  15. DREAM Mediated Regulation of GCM1 in the Human Placental Trophoblast

    PubMed Central

    Baczyk, Dora; Kibschull, Mark; Mellstrom, Britt; Levytska, Khrystyna; Rivas, Marcos; Drewlo, Sascha; Lye, Stephen J.; Naranjo, Jose R.; Kingdom, John C. P.

    2013-01-01

    The trophoblast transcription factor glial cell missing-1 (GCM1) regulates differentiation of placental cytotrophoblasts into the syncytiotrophoblast layer in contact with maternal blood. Reduced placental expression of GCM1 and abnormal syncytiotrophoblast structure are features of hypertensive disorder of pregnancy – preeclampsia. In-silico techniques identified the calcium-regulated transcriptional repressor – DREAM (Downstream Regulatory Element Antagonist Modulator) - as a candidate for GCM1 gene expression. Our objective was to determine if DREAM represses GCM1 regulated syncytiotrophoblast formation. EMSA and ChIP assays revealed a direct interaction between DREAM and the GCM1 promoter. siRNA-mediated DREAM silencing in cell culture and placental explant models significantly up-regulated GCM1 expression and reduced cytotrophoblast proliferation. DREAM calcium dependency was verified using ionomycin. Furthermore, the increased DREAM protein expression in preeclamptic placental villi was predominantly nuclear, coinciding with an overall increase in sumolylated DREAM and correlating inversely with GCM1 levels. In conclusion, our data reveal a calcium-regulated pathway whereby GCM1-directed villous trophoblast differentiation is repressed by DREAM. This pathway may be relevant to disease prevention via calcium-supplementation. PMID:23300953

  16. Ocean-Atmosphere interaction observed from comparison of the ENSO signatures in the time series of J2 and the Earth's spin rate

    NASA Astrophysics Data System (ADS)

    Fernandez, L.; Fang, M.; Zang, X.; Zheng, D.; Hager, B. H.; Wunsch, C.; Ding, X.

    2003-12-01

    Significant interannual variations have been observed from the multi-satillite SLR solutions of the Earth's oblateness, known as the J2 time series, by the Texas CSR group (Cheng & Tapley, submitted) with a time span from 1975 to the present, as well as by our independent analysis of the Godard series (courtesy of Ben Chao for the data) with a time span from 1979 to the present. These variations are closely related to the ENSO events as evidenced by their apparent correlation, not perfect though, with the Southern Oscillation Index. Our preliminary analysis shows that the ENSO signature in the atmospheric circulation is not adequate to account for up to 50% of the interannuals in the J2 series. In contrast, the atmosphere contributes better than 80% of the observed time variation of the Earth's rotation rate i.e. the length of day (LOD) at the ENSO time scale, mostly from the thermally driven eastward wind fields (e.g. Zheng et al, 2003). We normalize the LOD and J2 series by making the maxima in both data sets units, and make a comparison. A strong correlation is found between the LOD and J2. It is apparently due to a common cause from the ENSO. At the same time, noticeable differences are observed, especially with the phases. These differences are ultimately attributed to the ocean-atmosphere interaction during the ENSO events. As a preliminary study, we calculate the oceanic contribution to the interannuals of LOD and J2 by running a high-resolution state-of-art self-consistent and volume conserving ocean numerical model with realistic atmospheric forcing. A simple model for the ocean-atmospheric interaction will be employed to calculate the changes in the wind and pressure fields. Solid Earth deformation induced by the bottom pressure change is also considered in the modeling. Correlation analysis are conducted between the "fully model" ENSO driven LOD and J2. Comparisons between the observed and modeled correltions will be presented.

  17. Collaborative project. Ocean-atmosphere interaction from meso-to planetary-scale. Mechanisms, parameterization, and variability

    SciTech Connect

    Small, Richard; Bryan, Frank; Tribbia, Joseph; Park, Sungsu; Dennis, John; Saravanan, R.; Schneider, Niklas; Kwon, Young-Oh

    2015-06-11

    This project aims to improve long term global climate simulations by resolving ocean mesoscale activity and the corresponding response in the atmosphere. The main computational objectives are; i) to perform and assess Community Earth System Model (CESM) simulations with the new Community Atmospheric Model (CAM) spectral element dynamical core; ii) use static mesh refinement to focus on oceanic fronts; iii) develop a new Earth System Modeling tool to investigate the atmospheric response to fronts by selectively filtering surface flux fields in the CESM coupler. The climate research objectives are 1) to improve the coupling of ocean fronts and the atmospheric boundary layer via investigations of dependency on model resolution and stability functions: 2) to understand and simulate the ensuing tropospheric response that has recently been documented in observations: and 3) to investigate the relationship of ocean frontal variability to low frequency climate variability and the accompanying storm tracks and extremes in high resolution simulations. This is a collaborative multi-institution project consisting of computational scientists, climate scientists and climate model developers. It specifically aims at DOE objectives of advancing simulation and predictive capability of climate models through improvements in resolution and physical process representation.

  18. THOR: an open-source exo-GCM

    NASA Astrophysics Data System (ADS)

    Grosheintz, Luc; Mendonça, João; Käppeli, Roger; Lukas Grimm, Simon; Mishra, Siddhartha; Heng, Kevin

    2015-12-01

    In this talk, I will present THOR, the first fully conservative, GPU-accelerated exo-GCM (general circulation model) on a nearly uniform, global grid that treats shocks and is non-hydrostatic. THOR will be freely available to the community as a standard tool.Unlike most GCMs THOR solves the full, non-hydrostatic Euler equations instead of the primitive equations. The equations are solved on a global three-dimensional icosahedral grid by a second order Finite Volume Method (FVM). Icosahedral grids are nearly uniform refinements of an icosahedron. We've implemented three different versions of this grid. FVM conserves the prognostic variables (density, momentum and energy) exactly and doesn't require a diffusion term (artificial viscosity) in the Euler equations to stabilize our solver. Historically FVM was designed to treat discontinuities correctly. Hence it excels at resolving shocks, including those present in hot exoplanetary atmospheres.Atmospheres are generally in near hydrostatic equilibrium. We therefore implement a well-balancing technique recently developed at the ETH Zurich. This well-balancing ensures that our FVM maintains hydrostatic equilibrium to machine precision. Better yet, it is able to resolve pressure perturbations from this equilibrium as small as one part in 100'000. It is important to realize that these perturbations are significantly smaller than the truncation error of the same scheme without well-balancing. If during the course of the simulation (due to forcing) the atmosphere becomes non-hydrostatic, our solver continues to function correctly.THOR just passed an important mile stone. We've implemented the explicit part of the solver. The explicit solver is useful to study instabilities or local problems on relatively short time scales. I'll show some nice properties of the explicit THOR. An explicit solver is not appropriate for climate study because the time step is limited by the sound speed. Therefore, we are working on the first fully

  19. Mars Ozone Absorption Line Shapes from Infrared Heterodyne Spectra Applied to GCM-Predicted Ozone Profiles and to MEX/SPICAM Column Retrievals

    NASA Technical Reports Server (NTRS)

    Fast, Kelly E.; Kostiuk, T.; Annen, J.; Hewagama, T.; Delgado, J.; Livengood, T. A.; Lefevre, F.

    2008-01-01

    We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry Mars' atmosphere, serving as an observable with which to test predictions of photochemistry-coupled GCMs. Infrared heterodyne spectroscopy at 9.5 microns with spectral resolving power >1,000,000 is the only technique that can directly measure fully-resolved line shapes of Martian ozone features from the surface of the Earth. Measurements were made with Goddard Space Flight Center's Heterodyne instrument for Planetary Wind And Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii on February 21-24 2008 UT at Ls=35deg on or near the MEX orbital path. The HIPWAC observations were used to test GCM predictions. For example, a GCM-generated ozone profile for 60degN 112degW was scaled so that a radiative transfer calculation of its absorption line shape matched an observed HIPWAC absorption feature at the same areographic position, local time, and season. The RMS deviation of the model from the data was slightly smaller for the GCM-generated profile than for a line shape produced by a constant-with-height profile, even though the total column abundances were the same, showing potential for testing and constraining GCM ozone-profiles. The resulting ozone column abundance from matching the model to the HIPWAC line shape was 60% higher than that observed by SPICAM at the same areographic position one day earlier and 2.5 hours earlier in local time. This could be due to day-to-day, diurnal, or north polar region variability, or to measurement sensitivity to the ozone column and its distribution, and these possibilities will be explored. This work was supported by NASA's Planetary Astronomy Program.

  20. Mars Ozone Absorption Line Shapes from Infrared Heterodyne Spectra Applied to GCM-Predicted Ozone Profiles and to MEX/SPICAM Column Retrievals

    NASA Technical Reports Server (NTRS)

    Fast, Kelly E.; Kostiuk, T.; Annen, J.; Hewagama, T.; Delgado, J.; Livengood, T. A.; Lefevre, F.

    2008-01-01

    We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry Mars' atmosphere, serving as an observable with which to test predictions of photochemistry-coupled GCMs. Infrared heterodyne spectroscopy at 9.5 microns with spectral resolving power >1,000,000 is the only technique that can directly measure fully-resolved line shapes of Martian ozone features from the surface of the Earth. Measurements were made with Goddard Space Flight Center's Heterodyne instrument for Planetary Wind And Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii on February 21-24 2008 UT at Ls=35deg on or near the MEX orbital path. The HIPWAC observations were used to test GCM predictions. For example, a GCM-generated ozone profile for 60degN 112degW was scaled so that a radiative transfer calculation of its absorption line shape matched an observed HIPWAC absorption feature at the same areographic position, local time, and season. The RMS deviation of the model from the data was slightly smaller for the GCM-generated profile than for a line shape produced by a constant-with-height profile, even though the total column abundances were the same, showing potential for testing and constraining GCM ozone-profiles. The resulting ozone column abundance from matching the model to the HIPWAC line shape was 60% higher than that observed by SPICAM at the same areographic position one day earlier and 2.5 hours earlier in local time. This could be due to day-to-day, diurnal, or north polar region variability, or to measurement sensitivity to the ozone column and its distribution, and these possibilities will be explored. This work was supported by NASA's Planetary Astronomy Program.

  1. An evaluation of ENSO and climate change using the GCM/ZC model

    NASA Astrophysics Data System (ADS)

    Eichler, Timothy Paul

    2000-06-01

    Since ENSO has well-established effects on global climate, it is logical to ask how ENSO's intensity and frequency may change due to climate change. To address this question, a model has been developed at the Goddard Institute for Space Studies (GISS) which couples the GISS gcm with the El Nino-generating model developed by Dr. Stephen Zebiak and Dr. Mark Cane (ZC) of the Lamont Doherty Earth Observatory (LDEO). The first chapter of the thesis details the coupling technique used for the model, while chapter 2 describes the model's ENSO response. In particular, the GCM/ZC model is found to generate a realistic ENSO response, though at a higher frequency than observed. In addition, the ENSO response is found to weaken the Walker Circulation and strengthen the Hadley Circulation when the model is in the El Nino phase. The model's ENSO response is due to the dynamical heating term inputted from the ZC model, with latent heat and shortwave fluxes from the ocean's surface acting to modify the warm anomalies. The global response of the model to ENSO shows the GCM/ZC model produces jet-stream configurations much like the observed ENSOs. Chapter 3 analyzes the possible effect of volcanoes on climate. 10 3-year control runs are compared with 10 3-year runs with a volcanic eruption in month 1 of the runs. The results suggest an amplification of the ENSO cycle due to volcanic aerosol in six of the 10 simulations while four of the runs show a deamplification. The trigger mechanism for the two solutions appears to be the wind stress anomaly field. Chapter 4 tests the effects of increased CO2 on ENSO variability. The 4XCO2 equilibrium solution shows a 50 percent decrease in magnitude of ENSO variability relative to control, due to increasingly warm upwelled water being incorporated into the mixed-layer of the ZC model. Decadal standard deviation of NINO3 shows increased variability of ENSO from decade 2 to decade 7 of the simulation as the Hadley Circulation strengthens due to

  2. GCM simulated geopotential heights compared to GPS RO data

    NASA Astrophysics Data System (ADS)

    Molodtsov, S.; Kirilenko, A.; Olsen, D.

    2012-12-01

    Accurate, high-quality, global coverage data is required for global climate monitoring. It also provides possibility of additional validation of the general circulation models (GCMs). GPS Radio occultation (GPS RO) measurements have potential of becoming a new benchmark in data acquisition, providing new high-quality profiles of the parameters of the atmosphere, such as the temperature, water vapor pressure, and geopotential heights. In our study we use GPS RO data with a purpose to test global circulation models (GCMs). We study how climate change signal emerges in the GPS RO data and how these signals are reflected in GCM simulations. We use temperature and geopotential height profiles from 2001-2006 CHAMP and 2006-2011 COMIC acquisitions to validate the output from twelve IPCC AR4 GCMs run under A1B SRES scenario. We found that the 2001-2011 trends of the temperature and geopotential height derived from the IPCC AR4 GCMs show the same pattern with trends derived from GPS RO data - warming of the upper troposphere (UT) and cooling of the lower stratosphere (LS). There is some discrepancy between trends in lower troposphere (LT) between models and GPS RO data: some GCMs show decreasing temperature and geopotential height trends while the GPS RO trends are positive. The statistical analysis of these trends will be reported.

  3. A GCM simulation of the climate 6000 years ago

    SciTech Connect

    Hall, N.M.J.; Valdes, P.J.

    1997-01-01

    Two 10-yr integrations of the UGAMP GCM are presented. Each has a full seasonal cycle, T42 resolution, interactive land and sea ice, and prescribed sea surface temperatures. They differ in that one integration represents present day climate (PD) and the other has a perturbed orbit and reduced atmospheric concentrations of CO{sub 2} appropriate to the climate of 6000 years ago (6 kyr, hereafter 6K). the 6K integration produces enhanced continental warmth during summer and cold during winter. Changes in atmospheric temperature gradients brought about by the surface response lead to altered jet stream structures and transient eddy activity, which in turn affect precipitation patterns. Tropical {open_quotes}monsoon{close_quotes}-type circulation patterns are also affected, also leading to altered precipitation. Many of the changes in hydrology mimic the geological record remarkably well: the Sahel is much wetter, as are the midwestern United States and the Mediterranean regions; California and northern Europe are drier. Processes leading to the model`s surface responses in both temperature and hydrology are described in detail. Finally, the sensitivity of the results to an alternative, objective definition of the 6k calendar is investigated. The sensitivity is found to be smaller than the overall signal to the extent that the principal conclusions are no altered. 35 refs., 9 figs., 1 tab.

  4. Equatorial Mountain Torques and Cold Surges in a GCM

    NASA Astrophysics Data System (ADS)

    Lott, Francois; Mailler, Sylvain

    2014-05-01

    The dynamical relations between the equatorial atmospheric angular momentum, the equatorial mountain torque and the cold surges are analysed in a General Circultaion Model (GCM). First we show that the global equatorial atmospheric momentum budget is very well closed in the model which is a clear benefit when we compare with results from the NCEP reanalysis. We then confirm that the equatorial torques due to the Tibetan plateau, the Rockies and the Andes are well related to the cold surges developping over South Eastern China, North America, and the Southern South America respectively. For all these mountains, a peack in the Equatorial mountain torque component that points locally toward the pole preceeds by few days the development of the cold surges, yielding a predictive interest to our results. We also analyse the contributions to the torques of the parameterized mountain stresses and find that they contribute substantially. In experiments without the parameterized stresses, we also find that the explicit terms partly compensate the parameterized contributions to the torque, and the cold surges are not much affected. This shows that the cold surges can be well captured by models, providing that the synoptic conditions prior to their onset are well represented. The compensation between torques is nevertheless not complete and some weekening of the cold surges is found when the mountain forcings are reduced. This illustrates how the exact torques are needed at a given time to produce the correct synoptic scale dynamics at a later stage.

  5. GCM studies of intermediate and deep waters in the Mediterranean

    NASA Astrophysics Data System (ADS)

    Haines, Keith; Wu, Peili

    1998-12-01

    Results from GCM simulations of the Mediterranean thermohaline circulation are presented under repeating year wind and surface buoyancy forcings and the reproduction of important physical processes is discussed. It is shown that baroclinic eddies are critical to the effective dispersal of Levantine intermediate water (LIW) throughout the eastern Mediterranean basin. These develop rapidly even in a 1/4 degree model which does not resolve the deformation radius, provided horizontal friction is small enough. It is shown that LIW enters the Adriatic basin and pre-conditions deep water formation which would not otherwise occur due to low surface salinity in winter. The dispersal of Adriatic deep waters is modelled, and it is shown that the introduction of the Gent and McWilliams advective scheme greatly improves the distribution of deep waters in the eastern basin by permitting the formation of dense overflow waters from the Otranto straits. This is achieved with very small parametrised advection that still permits the formation of baroclinic eddies unlike most applications which use the scheme to replace eddies. Results from a 100-year climate simulation are then presented in which the thermohaline circulation has reached equilibrium conditions. Dense water formation in both eastern and western basin still occur after 100 years. While the eastern basin water masses are reasonably realistic, the western basin is a little too cold and fresh, suggesting that insufficient LIW is reaching the deep water formation site in the northwest basin. Further work is needed in this area.

  6. GCM studies of the influence of vegetation on the general circulation: The role of albedo in modulating climate change. [GCM (general circulation model)

    SciTech Connect

    Dirmeyer, P.A.

    1992-01-01

    An atmospheric general circulation model (GCM) coupled to a simple biosphere model is used to examine the role of vegetation change on climate. Various biomes are substituted to simulate degradation of vegetation. It is found that albedo change plays a distinct role in the local decrease of rainfall. Changes in vegetation morphology and physiology do not cause catastrophic decreases in precipitation. Simulations of Amazon deforestation show that the climate response is very dependent on the amount of change in albedo between rainforest and degraded grass. Precipitation drops as albedo increases. The change in plant physiology decreases evapotranspiration, but moisture convergence increases to offset the drying. This compensation is a result of cloud feedback in this model, and does not occur when cloudiness is prescribed. Experiments with idealized boundary conditions show a similar dependence of rainfall on albedo in cases of tropical deforestation, subtropical desertification, and mid-latitude deforestation. In the topics, rainfall decreases over land only when reflectivity is increased, even when the rainforest is left intact. The monsoon precipitation of the subtropical experiment fails when savannah is replaced by high-albedo desert. When low-albedo desert is used, the decrease in summer rainfall is small. When mid-latitude forest is replaced by grassland, precipitation patterns shift, but net rainfall remains unchanged. Additional simulations of mid-latitude drought show that low soil moisture leads to moderate spring and summer droughts, but dry soil combined with dormant vegetation produces extremely severe droughts. Soil moisture deficits were more persistent when vegetation did not go dormant.

  7. Revisiting the role of the Gcm transcription factor, from master regulator to Swiss army knife.

    PubMed

    Cattenoz, Pierre B; Giangrande, Angela

    2016-10-01

    Master genes are known to induce the differentiation of a multipotent cell into a specific cell type. These molecules are often transcription factors that switch on the regulatory cascade that triggers cell specification. Gcm was first described as the master gene of the glial fate in Drosophila as it induces the differentiation of neuroblasts into glia in the developing nervous system. Later on, Gcm was also shown to regulate the differentiation of blood, tendon and peritracheal cells as well as that of neuronal subsets. Thus, the glial master gene is used in at least 4 additional systems to promote differentiation. To understand the numerous roles of Gcm, we recently reported a genome-wide screen of Gcm direct targets in the Drosophila embryo. This screen provided new insight into the role and mode of action of this powerful transcription factor, notably on the interactions between Gcm and major differentiation pathways such as the Hedgehog, Notch and JAK/STAT. Here, we discuss the mode of action of Gcm in the different systems, we present new tissues that require Gcm and we revise the concept of 'master gene'.

  8. A statistical study of the regional impact of deforestation on climate in the LMD GCM

    SciTech Connect

    Polcher, J.; Laval, K.

    1994-09-01

    The present study uses the general circulation model of the Laboratoire de Meteorologie Dynamique (LMD-GCM) coupled to the land-surface, vegetation model SECHIBA. The impact of deforestation on climate is discussed. Replacing tropical forests by degraded pastures changes albedo, the roughness length and the hydrological properties of the surface. The experiment was carried out over eleven years using the observed sea surface temperature from 1978 to 1988, which includes two major El Nino events. The discussion of the results in this study is limited to the regional impact of deforestation. The changes found for the surface fluxes in Amazonia, Africa, and Indonesia are examined in detail and compared in order to understand the impact on temperature. Special attention is paid to feedback mechanisms which compensate for the surface changes and to the statistical significant of these results within athe tropical variability of climate. It is shown that the relatively small regional impact of deforestation in this study is statistically significant and largely independent of the El Nino-Southern Oscillation phenomenon. 27 refs., 7 figs., 11 tabs.

  9. GCM simulations of Titan's middle and lower atmosphere and comparison to observations

    NASA Astrophysics Data System (ADS)

    Lora, Juan M.; Lunine, Jonathan I.; Russell, Joellen L.

    2015-04-01

    Simulation results are presented from a new general circulation model (GCM) of Titan, the Titan Atmospheric Model (TAM), which couples the Flexible Modeling System (FMS) spectral dynamical core to a suite of external/sub-grid-scale physics. These include a new non-gray radiative transfer module that takes advantage of recent data from Cassini-Huygens, large-scale condensation and quasi-equilibrium moist convection schemes, a surface model with "bucket" hydrology, and boundary layer turbulent diffusion. The model produces a realistic temperature structure from the surface to the lower mesosphere, including a stratopause, as well as satisfactory superrotation. The latter is shown to depend on the dynamical core's ability to build up angular momentum from surface torques. Simulated latitudinal temperature contrasts are adequate, compared to observations, and polar temperature anomalies agree with observations. In the lower atmosphere, the insolation distribution is shown to strongly impact turbulent fluxes, and surface heating is maximum at mid-latitudes. Surface liquids are unstable at mid- and low-latitudes, and quickly migrate poleward. The simulated humidity profile and distribution of surface temperatures, compared to observations, corroborate the prevalence of dry conditions at low latitudes. Polar cloud activity is well represented, though the observed mid-latitude clouds remain somewhat puzzling, and some formation alternatives are suggested.

  10. A GCM simulation of global climate interannual variability: 1950-1988

    SciTech Connect

    Smith, I.N.

    1995-04-01

    Three long-term climate simulations have been performed with an atmospheric general circulation model using monthly global SSTs for the period 1950-1988. EOF analysis is used to study the ensemble-mean results for seasonal-mean fields as a means of evaluating the capability to simulate interannual variability. The analysis reveals a strong ENSO-related signal in the major fields of mean sea level pressure, rainfall, cloud cover, and zonal winds. The leading EOFs are compared, where possible, with observed ENSO-related patterns. The EOF for surface pressure closely resembles the Southern Oscillation pattern but, although significantly correlated with the Southern Oscillation index, cannot explain a large proportion of the observed variance. This is evident in the simulation of the 1982/83 warm event, which appears far less distinguished than observed. EOFs for both rainfall and low-level zonal winds also resemble, and are significantly correlated with, ENSO-related patterns deduced from observations. However, there are a number of important differences between the model rainfall pattern and known ENSO-related rainfall anomaly patterns that may limit any potential predictability given accurate SST forecasts. Similarly, differences between model zonal winds and observed zonal-wind stresses in the tropical Pacific would be expected to limit the performance of any coupled model comprising this particular low-resolution atmospheric GCM. 36 refs., 9 figs., 3 tabs.

  11. Simulation of monsoon intraseasonal oscillations in a coarse-resolution aquaplanet GCM

    NASA Astrophysics Data System (ADS)

    Ajayamohan, R. S.; Khouider, Boualem; Majda, Andrew J.

    2014-08-01

    The skill of the global climate models (GCMs) to realistically simulate the monsoon intraseasonal oscillations (MISOs) is related to the sensitivity of their convective parameterization schemes. Here we show that by coupling a simple multicloud parameterization to a coarse-resolution aquaplanet GCM, realistic MISOs can be simulated. We conduct three different simulations with a fixed nonhomogeneous sea surface temperature mimicking the Indian Ocean/western Pacific warm pool (WP) centered at the three latitudes 5°N, 10°N, and 15°N, respectively, to replicate the seasonal migration of the Tropical Convergence Zone (TCZ). This results in the generation of mean circulation resembling the monsoonal flow pattern in boreal summer. Succession of eastward propagating Madden-Julian Oscillation (MJO) disturbances with phase speed, amplitude, and structure similar to summer MJOs are simulated when the WP is at 5°N. When the WP is located over 10°N, northward and eastward propagating MISOs are simulated. This case captures the meridional seesaw of convection between continental and oceanic TCZ observed during boreal summer over South Asia. Westward propagating Rossby wave-like disturbances are simulated when the WP is over 15°N congruous with the synoptic disturbances seen over the monsoon trough. The initiation of intraseasonal oscillations in the model can occur internally through organization of convective events above the WP associated with internal dynamics.

  12. Do GCM's predict the climate.... Or the low frequency weather?

    NASA Astrophysics Data System (ADS)

    Lovejoy, S.; Schertzer, D.; Varon, D.

    2012-04-01

    control runs (i.e. without climate forcing) of GCM based climate forecasting systems including those of the Institut Pierre Simon Laplace (Paris) and the Earth Forecasting System (Hamburg). In order for these systems to go beyond simply predicting low frequency weather i.e. in order for them to predict the climate, they need appropriate climate forcings and/ or new internal mechanisms of variability. Using statistical scaling techniques we examine the scale dependence of fluctuations from forced and unforced GCM outputs, including from the ECHO-G and EFS simulations in the Millenium climate reconstruction project and compare this with data, multiproxies and paleo data. Our general conclusion is that the models systematically underestimate the multidecadal, multicentennial scale variability.

  13. Smagorinsky-type diffusion in a high-resolution GCM

    NASA Astrophysics Data System (ADS)

    Schaefer-Rolffs, Urs; Becker, Erich

    2013-04-01

    The parametrization of the (horizontal) momentum diffusion is a paramount component of a Global Circulation Model (GCM). Aside from friction in the boundary layer, a relevant fraction of kinetic energy is dissipated in the free atmosphere, and it is known that a linear harmonic turbulence model is not sufficient to obtain a reasonable simulation of the kinetic energy spectrum. Therefore, often empirical hyper-diffusion schemes are employed, regardless of disadvantages like the violation of energy conservation and the second law of thermodynamics. At IAP we have developed an improved parametrization of the horizontal diffusion that is based on Smagorinsky's nonlinear and energy conservation formulation. This approach is extended by the dynamic Smagorinsky model (DSM) of M. Germano. In this new scheme, the mixing length is no longer a prescribed parameter but calculated dynamically from the resolved flow such as to preserve scale invariance for the horizontal energy cascade. The so-called Germano identity is solved by a tensor norm ansatz which yields a positive definite frictional heating. We present results from an investigation using the DSM as a parametrization of horizontal diffusion in a high-resolution version of the Kühlungborn Mechanistic general Circulation Model (KMCM) with spectral truncation at horizontal wavenumber 330. The DSM calculates the Smagorinsky parameter cS independent from the resolution scale. We find that this method yields an energy spectrum that exhibits a pronounced transition from a synoptic -3 to a mesoscale -5-3 slope at wavenumbers around 50. At the highest wavenumber end, a behaviour similar to that often obtained by tuning the hyper-diffusion is achieved self-consistently. This result is very sensitive to the explicit choice of the test filter in the DSM.

  14. The Effect of Saharan Dust on North Atlantic Hydroclimate and Tropical Cyclones in a High-Resolution GCM

    NASA Astrophysics Data System (ADS)

    Strong, J. D.; Vecchi, G. A.

    2015-12-01

    Climate of the tropical North Atlantic and West Africa is sensitive to dust optical properties as shown by our previous work (Strong et al., 2015) using a fully coupled global climate model (GCM). However, that study was limited by the relatively coarse resolution of the GCM which could not resolve explicitly sub-scale processes important to the simulation of tropical cyclones (TCs).Using simulations with the higher resolution, fully coupled GFDL Climate Model 2.5, Forecast-oriented Low Ocean Resolution version (CM2.5-FLOR), for several realistic sets of optical properties, we investigate the climatic response across the tropical Atlantic basin to an idealized aerosol radiative forcing from Saharan-born mineral dust, comparable to the observed changes between the 1960s and 1990s, with a focus on the hydrological cycle and TCs. CM2.5-FLOR has a higher resolution atmosphere which is able to resolve TCs and has been shown to accurately reproduce the observed tropical cyclone climatology.In the first part, we will show that the sign of the radiative response at the top of the atmosphere (ToA) changes between the more absorbing dust and more scattering dust simulations, in agreement with previous studies. Conversely, the radiative response at the surface is generally comparable between sets of optical properties. These differences result in opposing regional hydrologic and thermodynamic effects of dust both in the atmosphere and in the upper ocean. In the second part, the effect of Saharan-born mineral dust on TCs will be analyzed. In all simulations, dust causes a decrease in tropical cyclone activity in the North Atlantic with the largest response occurring in the most absorbing and scattering optical regimes. We also note significant changes in the West Pacific in these simulations. The changes in tropical cyclone activity are found to not be explained by common genesis potential indexes, but a relationship between accumulated cyclone energy and ToA radiative flux

  15. Using the Model Coupling Toolkit to couple earth system models

    USGS Publications Warehouse

    Warner, J.C.; Perlin, N.; Skyllingstad, E.D.

    2008-01-01

    Continued advances in computational resources are providing the opportunity to operate more sophisticated numerical models. Additionally, there is an increasing demand for multidisciplinary studies that include interactions between different physical processes. Therefore there is a strong desire to develop coupled modeling systems that utilize existing models and allow efficient data exchange and model control. The basic system would entail model "1" running on "M" processors and model "2" running on "N" processors, with efficient exchange of model fields at predetermined synchronization intervals. Here we demonstrate two coupled systems: the coupling of the ocean circulation model Regional Ocean Modeling System (ROMS) to the surface wave model Simulating WAves Nearshore (SWAN), and the coupling of ROMS to the atmospheric model Coupled Ocean Atmosphere Prediction System (COAMPS). Both coupled systems use the Model Coupling Toolkit (MCT) as a mechanism for operation control and inter-model distributed memory transfer of model variables. In this paper we describe requirements and other options for model coupling, explain the MCT library, ROMS, SWAN and COAMPS models, methods for grid decomposition and sparse matrix interpolation, and provide an example from each coupled system. Methods presented in this paper are clearly applicable for coupling of other types of models. ?? 2008 Elsevier Ltd. All rights reserved.

  16. Climatic Forcings of the Last Major Glacial Inception: A GCM Simulation of 115.5 Ka

    NASA Astrophysics Data System (ADS)

    Essig, M.; Oglesby, R.; Otieno, F.; Bromwich, D.

    2007-12-01

    The onset of Northern Hemisphere glaciation at around 115.5 Ka is thought to have been caused by a number of factors. Two of the most important of these are a reduction in atmospheric CO2 from approximately 380 ppm to 180 ppm, and changes in the earth's eccentricity, precession, and obliquity due to Milankovitch orbital cycles. We used the NCAR CCSM3 GCM in fully coupled mode to simulate the climate at 115.5 ka B.P. The fully-coupled mode includes dynamical atmospheric and oceanic components, as well as sophisticated land surface and sea ice schemes. Sea level and the distribution of the continents were held at present-day values, since they changed little between 0 Ka and 115.5 Ka. Thus, our model simulation can also be thought of as examining the roles of lowered CO2 and orbital configuration in driving glacial inception. In particular, we hypothesize that these climatic forcings will lead to a succession of cool summers and warm wet winters in key regions of the high latitude Northern Hemisphere. In turn, we expect this will be conducive to building the perennial snow pack that is an essential precursor to the Laurentide and Fenno-Scandinavian ice sheets. Though the simulation is still underway at this writing, preliminary results from the first 100 years of the run suggest that this does indeed take place. Key results from the completed run will be presented at the meeting, along with an assessment of how they differ from a present-day CCSM3 control run. Furthermore, in glacial inception regions the performance of both the control run and an existing CCSM3 preindustrial simulation are being compared to ERA40 reanalyses as an additional test of model fidelity. The model simulation is also being verified using all available data from geologic record for the time around 115.5 Ka.

  17. The Nonlinear Response of the Equatorial Pacific Ocean-Atmosphere System to Periodic Variations in Insolation and its Association with the Abrupt Climate Transitions during the Quaternary.

    NASA Astrophysics Data System (ADS)

    Lopes, P. G.

    2015-12-01

    The evidences of climate changes during the Quaternary are abundant but the physical mechanisms behind the climate transitions are controversial. The theory of Milankovitch takes into account the periodic orbital variations and the solar radiation received by the Earth as the main explanation for the glacial-interglacial cycles. However, some gaps in the theory still remain. In this study, we propose elucidating some of these gaps by approaching the Equatorial Pacific Ocean as a large oscillator, capable of triggering climate changes in different temporal scales. A mathematical model representing El Ninõ-like phenomena, based on Duffing equation and modulated by the astronomical cycle of 100 ka, was used to simulate the variability of the equatorial Pacific climate system over the last 2 Ma. The physical configuration of the Pacific Ocean, expressed in the equation, explains the temporal limit of the glacial-interglacial cycles. According to the simulation results, consistent with paleoclimate records, the amplification of the effects of the gradual variation of the Earth's orbit eccentricity - another unclear question - is due to the feedback mechanism of the Pacific ocean-atmosphere system, which responds non-linearly to small variations in insolation forcing and determines the ENSO-like phase (warm or cold) at different time scales and different intensities. The approach proposed here takes into account that the abrupt transitions between the ENSO-like phases, and the consequent changes in the sea surface temperature (SST) along the Equatorial Pacific Ocean, produce reactions that act as secondary causes of the temperature fluctuations that result in a glaciation (or deglaciation) - as the drastic change on the rate of evaporation/precipitation around the globe, and the increase (or decrease) of the atmospheric CO2 absorption by the phytoplankton. The transitional behavior between the warm and the cold phases, according to the presented model, is enhanced as

  18. Analysis of cloud radiative forcing and feedback in a climate GCM. Final report

    SciTech Connect

    Lacis, A.

    1996-12-31

    The principal objectives of the research supported at the Goddard Institute for Space Studies (GISS) by the Atmospheric Radiation Measurement (ARM) Program for a three year period commencing September 1990, were: (1) to improve and validate the radiation parameterizations in the GISS GCM through model intercomparisons with line-by-line calculations and through comparisons with ARM observations; (2) to improve the GISS GCM diagnostic output to enable more effective comparisons to global cloud/radiation data sets; and (3) to use ARM data to develop improved parameterization of clouds in the GCM and to study the interaction of dynamics and radiation. The ARM Program support has made it possible to establish and support an active and productive research group at GISS specializing in radiative transfer and cloud process modeling in support of improving the performance of a climate GCM.

  19. Comparison of paleoclimate data with GCM`s results and modern climate changes

    SciTech Connect

    Selyakov, K.I.

    1996-12-31

    Three types of data: paleoclimate reconstructions, GCM results, and observations on modern climate change are compared. The paleoanolag hypothesis (PH), which implies that regional patterns of climate change depends mostly on the mean global temperature change, is the basis for this study. Paleoclimate reconstructions for the Mid-Holocene, Eemeian, Mid-Pliocene are used to test the PH. Besides, the results of the GCM models, data on modern climate changes are scaled on the basis of PH. It was shown that the disagreement between paleo- and GCM data is in the difference in describing the equator-pole temperature changes. Precipitation anomalies in GCM data are not in agreement with paleoclimates. Temperature anomalies of the modern warming (1980-s) agree to some extent with paleodata.

  20. Internal variability in a coupled general circulation model in radiative-convective equilibrium

    NASA Astrophysics Data System (ADS)

    Coppin, David; Bony, Sandrine

    2017-05-01

    Numerical models run in non-rotating radiative-convective equilibrium (RCE) using prescribed sea surface temperatures (SSTs) show that convection can spontaneously aggregate into dry and moist areas, and that convective aggregation tends to increase with temperature. Using a general circulation model coupled to an ocean mixed layer, we show that in RCE the coupled ocean-atmosphere system exhibits some internal variability. This variability arises from the interplay between mean surface temperature, SST gradients and convective aggregation, and its timescale is proportional to the depth of the ocean mixed layer. For an ocean layer deeper than 10 m, the variability occurs at the interannual timescale, and variations of convective aggregation are almost out of phase with those of surface temperature. The coupled RCE framework might be relevant to understand some internal modes of variability of the tropical ocean-atmosphere system such as El Niño Southern Oscillation.

  1. The quasi 2 day wave response in TIME-GCM nudged with NOGAPS-ALPHA

    NASA Astrophysics Data System (ADS)

    Wang, Jack C.; Chang, Loren C.; Yue, Jia; Wang, Wenbin; Siskind, D. E.

    2017-05-01

    The quasi 2 day wave (QTDW) is a traveling planetary wave that can be enhanced rapidly to large amplitudes in the mesosphere and lower thermosphere (MLT) region during the northern winter postsolstice period. In this study, we present five case studies of QTDW events during January and February 2005, 2006 and 2008-2010 by using the Thermosphere-Ionosphere-Mesosphere Electrodynamics-General Circulation Model (TIME-GCM) nudged with the Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) Weather Forecast Model. With NOGAPS-ALPHA introducing more realistic lower atmospheric forcing in TIME-GCM, the QTDW events have successfully been reproduced in the TIME-GCM. The nudged TIME-GCM simulations show good agreement in zonal mean state with the NOGAPS-ALPHA 6 h reanalysis data and the horizontal wind model below the mesopause; however, it has large discrepancies in the tropics above the mesopause. The zonal mean zonal wind in the mesosphere has sharp vertical gradients in the nudged TIME-GCM. The results suggest that the parameterized gravity wave forcing may need to be retuned in the assimilative TIME-GCM.

  2. A Performance Comparison of Coupled and Uncoupled Versions of the Met Office Seasonal Prediction GCM

    NASA Astrophysics Data System (ADS)

    Graham, R. J.; Gordon, M.; McLean, P. J.; Ineson, S.; Huddleston, M. R.; Davey, M. K.; Brookshaw, A.; Barnes, R. T.

    2005-05-01

    The launch of COSMIC/Formosat-3 constellation represents a tremendous step forward in the remote sensing of the atmosphere with the GPS radio occultation technique. Not only does it dramatically increase the spatiotemporal coverage over the existing pseudo-constellation of CHAMP, SAC-C, and GRACE, but it is also designed to acquire the occulting GPS signal through the open-loop (OL) tracking mode from the very start. Previous studies have shown that over moist regions, the presence of fine vertical-scale water vapor structures could lead to strong signal dynamics and periods of low signal-to-noise ratio. Data acquired using the traditional closed-loop (CL) tracking mode are therefore prone to introduce errors in the lower troposphere. This has a profound consequence on the water vapor retrievals, especially in the tropics. In this study, we will present results from the analysis of recent OL data from COSMIC and SAC-C. We will discuss the improvement of water vapor retrievals from OL data over CL data from CHAMP and GRACE. An assessment of accuracy in the lower troposphere and the planetary boundary layer will be given, taking into account the possible dry bias due to ducting.

  3. Effects of Cloud-Microphysics on Tropical Atmospheric Hydrologic Processes in the GEOS GCM

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Wu, H. T.; Sud, Y. C.; Walker, G. K.

    2004-01-01

    The sensitivity of tropical atmospheric hydrologic processes to cloud-microphysics is investigated using the NASA GEOS GCM. Results show that a faster autoconversion - rate produces more warm rain and less clouds at all levels. Fewer clouds enhances longwave cooling and reduces shortwave heating in the upper troposphere, while more warm rain produces increased condensation heating in the lower troposphere. This vertical heating differential destablizes the tropical atmosphere, producing a positive feedback resulting in more rain over the tropics. The feedback is maintained via a two-cell secondary circulation. The lower cell is capped by horizontal divergence and maximum cloud detrainment near the melting/freezing, with rising motion in the warm rain region connected to descending motion in the cold rain region. The upper cell is found above the freezing/melting level, with longwave-induced subsidence in the warm rain and dry regions, coupled to forced ascent in the deep convection region. The tropical large scale circulation is found to be very sensitive to the radiative-dynamic effects induced by changes in autoconversion rate. Reduced cloud-radiation processes feedback due to a faster autoconversion rate results in intermittent but more energetic eastward propagating Madden and Julian Oscillations (MJO). Conversely,-a slower autconversion rate, with increased cloud radiation produces MJO's with more realistic westward propagating transients, resembling a supercloud cluster structure. Results suggests that warm rain and associated low and mid level clouds, i.e., cumulus congestus, may play a critical role in regulating the time-intervals of deep convections and hence the fundamental time scales of the MJO.

  4. GCM Simulations of the Aerosol Indirect Effect: Sensitivity to Cloud Parameterization and Aerosol Burden

    NASA Technical Reports Server (NTRS)

    Menon, Surabi; DelGenio, Anthony D.; Koch, Dorothy; Tselioudis, George; Hansen, James E. (Technical Monitor)

    2001-01-01

    We describe the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea-salt that is used to estimate the aerosol indirect effect. The cloud droplet number concentration is diagnosed empirically from field experiment datasets over land and ocean that observe droplet number and all three aerosol types simultaneously; corrections are made for implied variations in cloud turbulence levels. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows us to predict aerosol effects on cloud optical thickness and microphysical process rates. We calculate the aerosol indirect effect by differencing the top-of-the-atmosphere net cloud radiative forcing for simulations with present-day vs. pre-industrial emissions. Both the first (radiative) and second (microphysical) indirect effects are explored. We test the sensitivity of our results to cloud parameterization assumptions that control the vertical distribution of cloud occurrence, the autoconversion rate, and the aerosol scavenging rate, each of which feeds back significantly on the model aerosol burden. The global mean aerosol indirect effect for all three aerosol types ranges from -1.55 to -4.36 W/sq m in our simulations. The results are quite sensitive to the pre-industrial background aerosol burden, with low pre-industrial burdens giving strong indirect effects, and to a lesser extent to the anthropogenic aerosol burden, with large burdens giving somewhat larger indirect effects. Because of this dependence on the background aerosol, model diagnostics such as albedo-particle size correlations and column cloud susceptibility, for which satellite validation products are available, are not good predictors of the resulting indirect effect.

  5. GCM Simulations of the Aerosol Indirect Effect: Sensitivity to Cloud Parameterization and Aerosol Burden

    NASA Technical Reports Server (NTRS)

    Menon, Surabi; DelGenio, Anthony D.; Koch, Dorothy; Tselioudis, George; Hansen, James E. (Technical Monitor)

    2001-01-01

    We describe the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea-salt that is used to estimate the aerosol indirect effect. The cloud droplet number concentration is diagnosed empirically from field experiment datasets over land and ocean that observe droplet number and all three aerosol types simultaneously; corrections are made for implied variations in cloud turbulence levels. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows us to predict aerosol effects on cloud optical thickness and microphysical process rates. We calculate the aerosol indirect effect by differencing the top-of-the-atmosphere net cloud radiative forcing for simulations with present-day vs. pre-industrial emissions. Both the first (radiative) and second (microphysical) indirect effects are explored. We test the sensitivity of our results to cloud parameterization assumptions that control the vertical distribution of cloud occurrence, the autoconversion rate, and the aerosol scavenging rate, each of which feeds back significantly on the model aerosol burden. The global mean aerosol indirect effect for all three aerosol types ranges from -1.55 to -4.36 W m(exp -2) in our simulations. The results are quite sensitive to the pre-industrial background aerosol burden, with low pre-industrial burdens giving strong indirect effects, and to a lesser extent to the anthropogenic aerosol burden, with large burdens giving somewhat larger indirect effects. Because of this dependence on the background aerosol, model diagnostics such as albedo-particle size correlations and column cloud susceptibility, for which satellite validation products are available, are not good predictors of the resulting indirect effect.

  6. The seasonal cycle of energetics from the GLAS/UMD climate GCM

    NASA Technical Reports Server (NTRS)

    Straus, David M.; Shukla, J.

    1988-01-01

    The annual cycle of atmospheric energetics from a 2-year integration of the GLAS/UMD Climate GCM is computed and compared to results from the European Centre analyses of the GWE year, and to previously published results on a global basis. All calculations are done in the mixed space-time domain. The main conclusions are: (1) the seasonal cycle of today's eddy kinetic energy (in both hemispheres), and of the transient eddy available potential energy and the potential-to-kinetic energy conversions (mean and eddy) in the Northern Hemisphere are well simulated by the GCM; (2) the GCM's tendency to have anomalously large mean u-winds at upper levels in high latitudes leads to excessive wintertime values of mean kinetic and available potential energies, and causes distortions in the GCM latitude-height distribution of kinetic energy and of many of the conversions; (3) the eddy conversion of available potential-to-kinetic energy obtained from the ageostrophic wind in these analyses; and (4) the conversions in the Southern Hemisphere are not well simulated by the GCM, although the observations are somewhat questionable.

  7. An improved standardization procedure to remove systematic low frequency variability biases in GCM simulations

    NASA Astrophysics Data System (ADS)

    Mehrotra, Rajeshwar; Sharma, Ashish

    2012-12-01

    The quality of the absolute estimates of general circulation models (GCMs) calls into question the direct use of GCM outputs for climate change impact assessment studies, particularly at regional scales. Statistical correction of GCM output is often necessary when significant systematic biasesoccur between the modeled output and observations. A common procedure is to correct the GCM output by removing the systematic biases in low-order moments relative to observations or to reanalysis data at daily, monthly, or seasonal timescales. In this paper, we present an extension of a recently published nested bias correction (NBC) technique to correct for the low- as well as higher-order moments biases in the GCM-derived variables across selected multiple time-scales. The proposed recursive nested bias correction (RNBC) approach offers an improved basis for applying bias correction at multiple timescales over the original NBC procedure. The method ensures that the bias-corrected series exhibits improvements that are consistently spread over all of the timescales considered. Different variations of the approach starting from the standard NBC to the more complex recursive alternatives are tested to assess their impacts on a range of GCM-simulated atmospheric variables of interest in downscaling applications related to hydrology and water resources. Results of the study suggest that three to five iteration RNBCs are the most effective in removing distributional and persistence related biases across the timescales considered.

  8. Simulation of heavy rainfall events over Indian region: a benchmark skill with a GCM

    NASA Astrophysics Data System (ADS)

    Goswami, Prashant; Kantha Rao, B.

    2015-10-01

    Extreme rainfall events (ERE) contribute a significant component of the Indian summer monsoon rainfall. Thus an important requirement for regional climate simulations is to attain desirable quality and reliability in simulating the extreme rainfall events. While the global circulation model (GCM) with coarse resolution are not preferred for simulation of extreme events, it is expected that the global domain in a GCM would allow better representation of scale interactions, resulting in adequate skill in simulating localized events in spite of lower resolution. At the same time, a GCM with skill in simulation of extreme events will provide a more reliable tool for seamless prediction. The present work provides an assessment of a GCM for simulating 40 ERE that occurred over India during 1998-2013. It is found that, expectedly, the GCM forecasts underestimate the observed (TRMM) rainfall in most cases, but not always. Somewhat surprisingly, the forecasts of location are quite accurate in spite of low resolution (~50 km). An interesting result is that the highest skill of the forecasts is realized at 48 h lead rather than at 24 or 96 h lead. Diagnostics of dynamical fields like convergence shows that the forecasts can capture contrasting features on pre-event, event and post-event days. The forecast configuration used is similar to one that has been used for long-range monsoon forecasting and tropical cyclones in earlier studies; the present results on ERE forecasting, therefore, provide an indication for the potential application of the model for seamless prediction.

  9. The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM

    NASA Technical Reports Server (NTRS)

    Pawson, S.; Takacs, L.; Molod, A.; Nebuda, S.; Chen, M.; Rood, R.; Read, W. L.; Fiorino, M.

    1999-01-01

    The structure of the tropical upper troposphere and lower stratosphere in the GEOS-2 General Circulation Model (GCM) is discussed. The emphasis of this study is on the reality of monthly-mean temperature and water vapor distributions in the model, compared to reasonable observational estimates. It is shown that although the zonal-mean temperature is in good agreement with observations, the GCM supports an excessive zonal asymmetry near the tropopause compared to the ECMWF Reanalyses. In reality there is a QBO-related variability in the zonally averaged lower stratospheric temperature which is not captured by the model. The observed upper tropospheric temperature and humidity fields show variations related to those in the sea surface temperature, which are not incorporated in the GCM; nevertheless, there is some interannual variability in the GCM, indicating a component arising from internal processes. The model is too moist in the middle troposphere (500 hPa) but too dry in the upper troposphere, suggesting that there is too little vertical transport or too much drying in the GCM. Transport into the stratosphere shows a pronounced annual cycle, with drier air entering the tropical stratosphere when the tropopause is coldest in northern winter; while the alternating dry and moist air masses can be traced ascending through the tropical lower stratosphere, the progression of the anomalies is too rapid.

  10. STOIC: An Assessment of Coupled Model Climatology and Variability in Tropical Ocean Regions

    SciTech Connect

    Davey, M.K.; Sperber, K.R.; Huddleston, M

    2000-08-30

    The tropics are regions of strong ocean-atmosphere interaction on seasonal and interannual timescales, so a good representation of observed tropical behavior is a desirable objective for coupled ocean-atmosphere general circulation models (CGCMs). To broaden and update previous assessments (Mechoso et al. 1995, Neelin et al. 1992), two complementary projects were initiated by the CLIVAR Working Group on Seasonal to Interannual Prediction (WGSIP): the El Nino Simulation Intercomparison Project (ENSIP, by Mojib Latif) and STOIC (Study of Tropical Oceans In Coupled models). The aim was to compare models against observations to identify common weaknesses and strengths. Results from ENSIP concentrating on the equatorial Pacific have been described by Latif et al. (2000), hereafter ENSIP2000. A detailed report on STOIC is available via anonymous ftp at email.meto.gov.uk/pub/cr/ ''stoic'' and is summarized in Davey et al. (2000). The STOIC analyses extend beyond the equatorial Pacific, to examine behavior in all three tropical ocean regions.

  11. Ensemble Predictions of Future Snowfall Scenarios in the Karakorum and Hindu-Kush Mountains Using Downscaled GCM Data

    NASA Astrophysics Data System (ADS)

    Mosier, T. M.; Hill, D. F.; Sharp, K. V.

    2014-12-01

    Climate change is affecting the seasonality and mass of snow, and impacting the water resources of hundreds of millions of people who depend on streamflow originating in High Asia. Global climate model (GCM) outputs are the primary forcing data used to investigate future projections of changes in snow and glacier processes; however, these processes occur at a much finer spatial scale than the resolution of current GCMs. To facilitate studying the cryosphere in High Asia, we developed a software package to downscale monthly GCM data to 30-arcseconds for any global land area. Using this downscaling package, we produce an ensemble of downscaled GCM data from 2020-2100, corresponding to representative concentration pathways (RCPs) 4.5 and 8.5. We then use these data to model changes to snowfall in the Karakorum and Hindu Kush (KHK) region, which is located in High Asia. The ensemble mean of these data predict that total annual snowfall in 2095 will decrease by 22% under RCP 4.5 and 46% under RCP 8.5, relative to 1950-2000 climatological values. For both scenarios, the changes in snowfall are dependent on elevation, with the maximum decreases in snowfall occurring at approximately 2,300 m. While total snowfall decreases, an interesting feature of snowfall change for the RCP 8.5 scenario is that the ensemble mean projection shows an increase in snowfall for elevations between 3,000- 5,000 m relative to historic values. These fine-scale spatial, temporal, and elevation-dependent patterns of changes in projected snowfall significantly affect the energy balance of the snowpack, in turn affecting timing of melt and discharge. Therefore, our work can be coupled with a glacio-hydrological model to assess effects of these snowfall patterns on other processes or compared to existing model results to assess treatment of snow processes in the existing model. Our method is designed to downscale climate data for any global land area, allowing for the production of these fine

  12. The Annual Cycle of SST in the Eastern Tropical Pacific, Diagnosed in an Ocean GCM*.

    NASA Astrophysics Data System (ADS)

    Kessler, William S.; Rothstein, Lewis M.; Chen, Dake

    1998-05-01

    The annual onset of the east Pacific cold tongue is diagnosed in an ocean GCM simulation of the tropical Pacific. The model uses a mixed-layer scheme that explicitly simulates the processes of vertical exchange of heat and momentum with the deeper layers of the ocean; comparison with observations of temperature and currents shows that many important aspects of the model fields are realistic. As previous studies have found, the heat balance in the eastern tropical Pacific is notoriously complicated, and virtually every term in the balance plays a significant role at one time or another. However, despite many complications, the three-dimensional ocean advection terms in the cold tongue region tend to cancel each other in the annual cycle and, to first order, the variation of SST can be described as simply following the variation of net solar radiation at the sea surface (sun minus clouds). The cancellation is primarily between cooling due to equatorial upwelling and warming due to tropical instability waves, both of which are strongest in the second half of the year (when the winds are stronger). Even near the equator, where the ocean advection is relatively intense, the terms associated with cloudiness variations are among the largest contributions to the SST balance. The annual cycle of cloudiness transforms the semiannual solar cycle at the top of the atmosphere into a largely 1 cycle yr1 variation of insolation at the sea surface. However, the annual cycle of cloudiness appears closely tied to SST in coupled feedbacks (positive for low stratus decks and negative for deep cumulus convection), so the annual cycle of SST cannot be fully diagnosed in an ocean-only modeling context as in the present study. Zonal advection was found to be a relatively small influence on annual equatorial cold tongue variations; in particular, there was little direct (oceanic) connection between the Peru coastal upwelling and equatorial annual cycles. Meridional advection driven by

  13. Use of Ocean Remote Sensing Data to Enhance Predictions with a Coupled General Circulation Model

    NASA Technical Reports Server (NTRS)

    Rienecker, Michele M.

    1999-01-01

    Surface height, sea surface temperature and surface wind observations from satellites have given a detailed time sequence of the initiation and evolution of the 1997/98 El Nino. The data have beet complementary to the subsurface TAO moored data in their spatial resolution and extent. The impact of satellite observations on seasonal prediction in the tropical Pacific using a coupled ocean-atmosphere general circulation model will be presented.

  14. Use of Ocean Remote Sensing Data to Enhance Predictions with a Coupled General Circulation Model

    NASA Technical Reports Server (NTRS)

    Rienecker, Michele M.

    1999-01-01

    Surface height, sea surface temperature and surface wind observations from satellites have given a detailed time sequence of the initiation and evolution of the 1997/98 El Nino. The data have beet complementary to the subsurface TAO moored data in their spatial resolution and extent. The impact of satellite observations on seasonal prediction in the tropical Pacific using a coupled ocean-atmosphere general circulation model will be presented.

  15. Global Climate Simulation in a Multi-scale Modeling Framework: Sensitivity to GCM- Resolution

    NASA Astrophysics Data System (ADS)

    Duffy, P. B.; Bala, G.; Gleckler, P. J.; Taylor, K. E.; Mirin, A. A.; Wickett, M. E.

    2006-12-01

    We investigate sensitivity of the simulated climate in the NCAR CAM3 atmospheric climate model to increases in horizontal spatial resolution, and to use an alternative representation of unresolved motions. In the Multi-scale Modeling Framework (MMF), cloud parameterizations in are replaced by a two-dimensional Cloud System Resolving Model (CSRM) that is embedded in each column of the general circulation model (GCM. Here we investigate both the resolution-sensitivity of the baseline version (that employing parameterizations) of the CAM3 atmospheric model as well as the sensitivity to decreasing the horizontal grid size of the GCM in an MMF version of the same model. Generally speaking, climate quantities related to clouds, precipitation, and radiative fluxes are more sensitive to treatment of subgrid scale processes than to GCM grid size. Simulated top-of-atmosphere cloud radiative forcings and related radiative fluxes are substantially improved in the MMF simulations; aspects of simulated precipitation and the simulated MJO are also substantially improved. In both the MMF and parameterized simulations, the large-scale climate shows less sensitivity to GCM resolution than has been seen in some other models, particularly the NCAR CCM3, a predecessor to CAM3. However, comparison to published simulations using CAM3 with Eulerian spectral dynamics indicates that that CAM3 configuration has very similar sensitivities to horizontal resolution as the Finite Volume dynamics version used here; comparison to MMF simulations with different GCM grid sizes confirms that parameterized physics influences resolution-sensitivity more than dynamical formulation does. Because the MMF is based more closely on first-principles physics than parameterizations are, one need not retune model parameters when the horizontal resolution of the GCM is changed in the MMF.

  16. a Dynamically Interactive Column Physics Model Suitable for Diagnosing Regional Climate Variability and GCM Errors

    NASA Astrophysics Data System (ADS)

    Sardeshmukh, P.

    2002-12-01

    formula are obtained empirically from a separate dry linear Primitive Equation (PE) model forced by steady idealized diabatic heating. The ability of this dynamical coupling formula to determine local vertical velocities from the history of local diabatic heating rates is tested in a linear PE model forced by oscillating 3-dimensional heating fields. The formula works surprisingly well over a wide range of spatial and temporal heating scales, even passing the hard test of correctly reproducing the phase shift and amplication of the response for near-resonant heating. This success suggests that to obtain the correct advective tendencies, detailed knowledge of the vertical and temporal structure of the diabatic forcing is necessary, but that of its horizontal structure is not. The single column model with vertical velocities coupled to the local temperature and humidity in this manner effectively eliminates the spurious SCM instabilities alluded to above. Such a dynamically interactive SCM would be useful in increasing the realism of simple "Box"-type models of regional climate variability. It is also argued that future SCM diagnoses of GCM physics would benefit from such a coupling.

  17. Regional Climate Simulation with a Variable Resolution Stretched Grid GCM: The Regional Down-Scaling Effects

    NASA Technical Reports Server (NTRS)

    Fox-Rabinovitz, Michael S.; Takacs, Lawrence L.; Suarez, Max; Sawyer, William; Govindaraju, Ravi C.

    1999-01-01

    The results obtained with the variable resolution stretched grid (SG) GEOS GCM (Goddard Earth Observing System General Circulation Models) are discussed, with the emphasis on the regional down-scaling effects and their dependence on the stretched grid design and parameters. A variable resolution SG-GCM and SG-DAS using a global stretched grid with fine resolution over an area of interest, is a viable new approach to REGIONAL and subregional CLIMATE studies and applications. The stretched grid approach is an ideal tool for representing regional to global scale interactions. It is an alternative to the widely used nested grid approach introduced a decade ago as a pioneering step in regional climate modeling. The GEOS SG-GCM is used for simulations of the anomalous U.S. climate events of 1988 drought and 1993 flood, with enhanced regional resolution. The height low level jet, precipitation and other diagnostic patterns are successfully simulated and show the efficient down-scaling over the area of interest the U.S. An imitation of the nested grid approach is performed using the developed SG-DAS (Data Assimilation System) that incorporates the SG-GCM. The SG-DAS is run with withholding data over the area of interest. The design immitates the nested grid framework with boundary conditions provided from analyses. No boundary condition buffer is needed for the case due to the global domain of integration used for the SG-GCM and SG-DAS. The experiments based on the newly developed versions of the GEOS SG-GCM and SG-DAS, with finer 0.5 degree (and higher) regional resolution, are briefly discussed. The major aspects of parallelization of the SG-GCM code are outlined. The KEY OBJECTIVES of the study are: 1) obtaining an efficient DOWN-SCALING over the area of interest with fine and very fine resolution; 2) providing CONSISTENT interactions between regional and global scales including the consistent representation of regional ENERGY and WATER BALANCES; 3) providing a high

  18. Ocean and atmosphere feedbacks affecting AMOC hysteresis in a GCM

    NASA Astrophysics Data System (ADS)

    Jackson, L. C.; Smith, R. S.; Wood, R. A.

    2016-10-01

    Theories suggest that the Atlantic Meridional Overturning Circulation (AMOC) can exhibit a hysteresis where, for a given input of fresh water into the north Atlantic, there are two possible states: one with a strong overturning in the north Atlantic (on) and the other with a reverse Atlantic cell (off). A previous study showed hysteresis of the AMOC for the first time in a coupled general circulation model (Hawkins et al. in Geophys Res Lett. doi: 10.1029/2011GL047208, 2011). In this study we show that the hysteresis found by Hawkins et al. (2011) is sensitive to the method with which the fresh water input is compensated. If this compensation is applied throughout the volume of the global ocean, rather than at the surface, the region of hysteresis is narrower and the off states are very different: when the compensation is applied at the surface, a strong Pacific overturning cell and a strong Atlantic reverse cell develops; when the compensation is applied throughout the volume there is little change in the Pacific and only a weak Atlantic reverse cell develops. We investigate the mechanisms behind the transitions between the on and off states in the two experiments, and find that the difference in hysteresis is due to the different off states. We find that the development of the Pacific overturning cell results in greater atmospheric moisture transport into the North Atlantic, and also is likely responsible for a stronger Atlantic reverse cell. These both act to stabilize the off state of the Atlantic overturning.

  19. Ocean and atmosphere feedbacks affecting AMOC hysteresis in a GCM

    NASA Astrophysics Data System (ADS)

    Jackson, L. C.; Smith, R. S.; Wood, R. A.

    2017-07-01

    Theories suggest that the Atlantic Meridional Overturning Circulation (AMOC) can exhibit a hysteresis where, for a given input of fresh water into the north Atlantic, there are two possible states: one with a strong overturning in the north Atlantic (on) and the other with a reverse Atlantic cell (off). A previous study showed hysteresis of the AMOC for the first time in a coupled general circulation model (Hawkins et al. in Geophys Res Lett. doi: 10.1029/2011GL047208, 2011). In this study we show that the hysteresis found by Hawkins et al. (2011) is sensitive to the method with which the fresh water input is compensated. If this compensation is applied throughout the volume of the global ocean, rather than at the surface, the region of hysteresis is narrower and the off states are very different: when the compensation is applied at the surface, a strong Pacific overturning cell and a strong Atlantic reverse cell develops; when the compensation is applied throughout the volume there is little change in the Pacific and only a weak Atlantic reverse cell develops. We investigate the mechanisms behind the transitions between the on and off states in the two experiments, and find that the difference in hysteresis is due to the different off states. We find that the development of the Pacific overturning cell results in greater atmospheric moisture transport into the North Atlantic, and also is likely responsible for a stronger Atlantic reverse cell. These both act to stabilize the off state of the Atlantic overturning.

  20. Development of useful climate scenarios at regional scales using GCM outputs

    SciTech Connect

    Werner, P.C.

    1997-12-31

    If climate changes are expected, their regional impacts are of special interest. Up to now (and in the near future) global climate models have been unable to deliver applicable results to describe the climate situation within a selected region (IPCC, 1995). That is why the description of the climate development in such an area must be realised by another possibility of creating meteorological data. Of importance besides is that the consistency in space and time and also between all meteorological parameters is not infracted. The used method proceeds on the assumption that the large scale changes of several meteorological parameters for a defined region calculated by a GCM can be regarded as correct as regards their tendencies. Based on such an assumption, long-term observed time series are prepared by statistical methods in such a way that they reflect the GCM-calculated changes by a scenario. The advantage of this method lies in the reduction of the defects of the GCM to a minimum. Simultaneously the consistency between the meteorological parameters can be ensured. A disadvantage is the missing physical connection between the GCM results and the given scenario. This method was applied successfully to develop several climate scenarios for a limited area (state Brandenburg) in Germany.

  1. 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.

  2. Determine Minimum Silver Flake Addition to GCM for Iodine Loaded AgZ

    SciTech Connect

    Garino, Terry J.; Nenoff, Tina M.; Rodriguez, Mark A.

    2014-04-01

    The minimum amount of silver flake required to prevent loss of I{sub 2} during sintering in air for a SNL Glass Composite Material (GCM) Waste Form containing AgI-MOR (ORNL, 8.7 wt%) was determined to be 1.1 wt% Ag. The final GCM composition prior to sintering was 20 wt% AgI-MOR, 1.1 wt% Ag, and 80 wt% Bi-Si oxide glass. The amount of silver flake needed to suppress iodine loss was determined using thermo gravimetric analysis with mass spectroscopic off-gas analysis. These studies found that the ratio of silver to AgI-MOR required is lower in the presence of the glass than without it. Therefore an additional benefit of the GCM is that it serves to inhibit some iodine loss during processing. Alternatively, heating the AgI-MOR in inert atmosphere instead of air allowed for densified GCM formation without I{sub 2} loss, and no necessity for the addition of Ag. The cause of this behavior is found to be related to the oxidation of the metallic Ag to Ag{sup +} when heated to above ~300{degrees}C in air. Heating rate, iodine loading levels and atmosphere are the important variables that determine AgI migration and results suggest that AgI may be completely incorporated into the mordenite structure by the 550{degrees}C sintering temperature.

  3. Sensitivity of CO2 Simulation in a GCM to the Convective Transport Algorithms

    NASA Technical Reports Server (NTRS)

    Zhu, Z.; Pawson, S.; Collatz, G. J.; Gregg, W. W.; Kawa, S. R.; Baker, D.; Ott, L.

    2014-01-01

    Convection plays an important role in the transport of heat, moisture and trace gases. In this study, we simulated CO2 concentrations with an atmospheric general circulation model (GCM). Three different convective transport algorithms were used. One is a modified Arakawa-Shubert scheme that was native to the GCM; two others used in two off-line chemical transport models (CTMs) were added to the GCM here for comparison purposes. Advanced CO2 surfaced fluxes were used for the simulations. The results were compared to a large quantity of CO2 observation data. We find that the simulation results are sensitive to the convective transport algorithms. Overall, the three simulations are quite realistic and similar to each other in the remote marine regions, but are significantly different in some land regions with strong fluxes such as Amazon and Siberia during the convection seasons. Large biases against CO2 measurements are found in these regions in the control run, which uses the original GCM. The simulation with the simple diffusive algorithm is better. The difference of the two simulations is related to the very different convective transport speed.

  4. Pluto's Atmosphere and Surface Ices as Simulated by the PlutoWRF GCM

    NASA Astrophysics Data System (ADS)

    Toigo, A. D.; French, R. G.; Gierasch, P. J.; Richardson, M. I.; Guzewich, S.

    2013-12-01

    The PlutoWRF general circulation model (GCM) was built to examine the large-scale structure and dynamics of the atmosphere, the nature and propagation of waves within the atmosphere, and the exchanges of volatiles between the atmosphere and the surface. We seek to provide an comprehensive framework for the study of the increasingly rich observational data sets (including stellar occultations of the atmosphere) and to provide context and analysis of observations from the New Horizons mission. The PlutoWRF GCM is based on the planetary adaptation of the NCAR Weather Research and Forecasting (WRF) model. It is a compressible, nonhydrostatic model where we have added physics to treat radiative transfer following Zhu et al. (2013), a bulk nitrogen cycle including condensation of surface ice, and cycles of additional trace volatile species. Existing subsurface heat diffusion, surface layer exchange and boundary layer mixing schemes have been adapted to Pluto. Boundary conditions for initial ice distribution and surface pressure are taken from energy balance and non-GCM volatile transport models constrained by observations. In this work we focus on the performance of the PlutoWRF GCM compared with our linear tidal model (Toigo et al., 2010), and will examine the generation and propagation of large-scale gravity waves associated with diurnal sublimation and condensation.

  5. Combined assimilation of hydrography and TOPEX data into an Indian Ocean GCM using the adjoint method

    NASA Technical Reports Server (NTRS)

    Marotzke, T. L. J.

    1997-01-01

    To study seasonal circulation and meridional heat transport of the Indian Ocean by synthesizing dynamics with data, climatological monthly temperatures and salinities, surface heat and freshewater fluxes, and wind stresses, together with monthly ensembles of three years (93-95) of TOPEX-derived surface geostrophic velocity anomalies, are assimilated into an Indian Ocean GCM.

  6. Understanding and Improving CRM and GCM Simulations of Cloud Systems with ARM Observations

    SciTech Connect

    Wu, Xiaoqing

    2014-02-25

    The works supported by this ASR project lay the solid foundation for improving the parameterization of convection and clouds in the NCAR CCSM and the climate simulations. We have made a significant use of CRM simulations and ARM observations to produce thermodynamically and dynamically consistent multi-year cloud and radiative properties; improve the GCM simulations of convection, clouds and radiative heating rate and fluxes using the ARM observations and CRM simulations; and understand the seasonal and annual variation of cloud systems and their impacts on climate mean state and variability. We conducted multi-year simulations over the ARM SGP site using the CRM with multi-year ARM forcing data. The statistics of cloud and radiative properties from the long-term CRM simulations were compared and validated with the ARM measurements and value added products (VAP). We evaluated the multi-year climate simulations produced by the GCM with the modified convection scheme. We used multi-year ARM observations and CRM simulations to validate and further improve the trigger condition and revised closure assumption in NCAR GCM simulations that demonstrate the improvement of climate mean state and variability. We combined the improved convection scheme with the mosaic treatment of subgrid cloud distributions in the radiation scheme of the GCM. The mosaic treatment of cloud distributions has been implemented in the GCM with the original convection scheme and enables the use of more realistic cloud amounts as well as cloud water contents in producing net radiative fluxes closer to observations. A physics-based latent heat (LH) retrieval algorithm was developed by parameterizing the physical linkages of observed hydrometeor profiles of cloud and precipitation to the major processes related to the phase change of atmospheric water.

  7. On Simulating the Mid-western-us Drought of 1988 with a GCM

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Mocko, D. M.; Lau, William K.-M.; Atlas, R.

    2002-01-01

    The primary cause of the midwestern North American drought in the summer of 1988 has been identified to be the La Nina SST anomalies. Yet with the SST anomalies prescribed, this drought has not been simulated satisfactorily by any general circulation model. Seven simulation-experiments, each containing an ensemble of 4-sets of simulations, were conducted with the GEOS GCM for both 1987 and 1988. All simulations started from January 1 and continued through the end of August. In the first baseline case, Case 1, only the SST anomalies and some vegetation parameters were prescribed, while everything else (such as soil moisture, snow-cover, and clouds) was interactive. The GCM did produce some of the circulation features of a drought over North America, but they could only be identified on the planetary scales. The 1988 minus 1987 precipitation differences show that the GCM was successful in simulating reduced precipitation in the mid-west, but the accompanying circulation anomalies were not well simulated, leading one to infer that the GCM has simulated the drought for the wrong reason. To isolate the causes for this unremarkable circulation, analyzed winds and soil moisture were prescribed in Case 2 and Case 3 as continuous updates by direct replacement of the GCM-predicted fields. These cases show that a large number of simulation biases emanate from wind biases that are carried into the North American region from surroundings regions. Inclusion of soil moisture also helps to ameliorate the strong feedback, perhaps even stronger than that of the real atmosphere, between soil moisture and precipitation. Case 2 simulated one type of surface temperature anomaly pattern, whereas Case 3 with the prescribed soil moisture produced another.

  8. AgI-MOR Loading Effect on the Durability of the Sandia Low Temperature Sintering GCM Waste Form

    SciTech Connect

    Nenoff, Tina Maria; Brady, Patrick Vane.; Mowry, Curtis D.; Garino, Terry J.

    2014-09-01

    Herein, we study the durability of the Sandia Bi-Si oxide Glass Composite Material (GCM) waste form when formulated with different weight percent levels of AgI-MOR. The post-iodine exposure AgI-MOR material was provided to SNL by ORNL. Durability results for the GCM fabricated with 22 and 25% AgI-MOR indicate releases of Ag and I at the same low rates as 15% AgI-MOR GCM, and by the same mechanism. Iodine and Ag release is controlled by the low solubility of an amorphous, hydrated silver iodide, not by the surface-controlled dissolution of I2- loaded Ag-Mordenite. Based on this data, we postulate that much higher loading levels of AgIMOR are probable in this GCM waste form, and limits will govern by retention of mechanical integrity of the GCM versus the solubility of silver iodide.

  9. Towards a coupled ocean-wave-atmosphere four dimensional data assimilation system

    NASA Astrophysics Data System (ADS)

    Ngodock, Hans; Carrier, Matthew; Amerault, Clark; Campbell, Timothy; Holt, Teddy; Xu, Liang; Rowley, Clark

    2015-04-01

    Individual 4dvar systems have been developed at the Naval Research Laboratory (NRL) for the ocean model (Navy coastal ocean model, NCOM), the wave model (simulating waves in the nearshore, SWAN) and the atmospheric component of the coupled ocean-atmosphere mesoscale prediction system (COAMPS). Although the three models within COAPMS are coupled in the forward integration, the initialization of each model is done separately. The coupled system forecast is hindered, however, by the lack of a fully coupled and dynamically balanced ocean-atmosphere analysis. A recent work by Ngodock and Carrier (2013) has highlighted this shortcoming with the NCOM-4DVAR, showing that while the NCOM-4DVAR is able to adjust the ocean state properly, the resulting ocean forecast degrades quickly due to the fact that the atmospheric state has not also been adjusted relative to the ocean observations. Likewise, . Currently, the coupled model is initialized using separate analyses for the ocean and atmosphere that do not account for observations in the adjacent fluid. The lack of a coupled analysis produces shocks in the coupled model in the form of gravity waves that degrade the information gained through DA and increase the error in the coupled forecast. The goal of this presentation is to describe ongoing developments at NRL in building a fully coupled ocean-wave-atmosphere four-dimensional variational (4dvar) data assimilation system using the Earth System Modeling Framework (ESMF).

  10. Nonmigrating Diurnal Tidal Variability in Mesopause Region Winds: TIDI, TIME-GCM and GSWM Comparisons

    NASA Astrophysics Data System (ADS)

    Oberheide, J.; Hagan, M. E.; Wu, Q.; Ortland, D. A.; Killeen, T. L.; Roble, R. G.; Niciejewski, R.; Skinner, W.

    2004-12-01

    We compare nonmigrating diurnal wind estimates determined from measurements made by the TIMED Doppler Inteferometer (TIDI) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite with predictions from the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) and the Global-Scale Wave Model (GSWM). The models account for two different nonmigrating tidal sources. The GSWM includes tropospheric latent heat release associate with deep tropical convection, while the TIME-GCM includes nonlinear interactions between quasi-stationary planetary waves and migrating tides. The model and measurement comparisons suggest that both sources are important to the interpretation of the TIDI tidal winds. We contrast the true model tidal results with estimates that we determine from the subsets of model wind predictions that represent what TIDI would observe if it flew through the model atmospheres. These contrasts allow us to quantify the sampling issues associated determining tidal signatures from the slowly precessing TIMED TIDI satellite data.

  11. A study of the effect of synoptic scale processes in GCM modelling

    NASA Technical Reports Server (NTRS)

    Herman, Gerald F.

    1989-01-01

    Research was conducted to help modeling groups at NASA to develop better weather forecasting and general circulation models (GCM) for activities relating to the meteorological uses of satellite data. The focus was on the physical processes that were being simulated by models: radiative effects and latent heat release associated with clouds; orographic influences; and heat transfer at the ocean and ice surfaces. An attempt was made to deduce the role of diabatic heating in North Atlantic cyclogenesis and in the global heat budget. Inferences were made in four studies: heat budget statistics from GCM assimilations; dynamics of north Atlantic cyclones; Cage-type energy budget calculations; and grid scale cloud formation. Mechanisms that were responsible for the variability and structure of the atmospheric on a hemispheric scale were studied by a hybrid of statistical analysis and theoretical modeling. Variability and structure are both related to synoptic scale processes through baroclinic and barotropic energy transformations.

  12. Realistic Solar and Infra-Red Radiative Forcing within a Venus GCM

    NASA Astrophysics Data System (ADS)

    Lee, C.; Richardson, M. I.

    2011-12-01

    Recent updates to the VenusFMS General Circulation Model have included a realistic Radiative Transfer Model (RTM) based upon on the Hadley Centre two-stream flux solver and constrained by a Discrete Ordinate model (Lee and Richardson, 2011). This RTM is capable of simulating the radiative fluxes in a Venus atmosphere modeled using 4 scattering cloud modes and 9 gases. In the current configuration the RTM is fast enough to compete with the Newtonian Relaxation approach used in earlier Venus GCMs (e.g. Lee et al. (2007), while providing much more accurate heating rates within the atmosphere and allowing interactive radiative forcing in the GCM. We show that the new RTM compares well with a DISORT/TWOSTR based solver using fewer spectral bands in the calculation (47 in the GCM versus 350 bands with DISORT/TWOSTR). We show that the RTM is capable of calculating solar and Infra-Red (IR) fluxes and therefore provides a consistent radiative heating for use in Venus GCMs. Previous heating parameterizations for Venus GCMs have used Newtonian Relaxation with prescribed heating rates or have calculated only some components of the radiative forcing, for example by calculating IR cooling rates and prescribing solar heating rates. The updated Venus GCM is then used to generate a super-rotating atmospheric circulation maintained by momentum transporting eddies. The underlying mechanism driving these eddies is described and the sensitivity of the circulation to the radiative forcing is discussed. Finally, we compare the atmospheric circulation and momentum transport to prior work conducted with this GCM using a simpler Newtonian Relaxation method (Lee and Richardson, 2010).

  13. Modeling GCM and scenario uncertainty using a possibilistic approach: Application to the Mahanadi River, India

    NASA Astrophysics Data System (ADS)

    Mujumdar, P. P.; Ghosh, Subimal

    2008-06-01

    Climate change impact assessment on water resources with downscaled General Circulation Model (GCM) simulation output is characterized by uncertainty due to incomplete knowledge about the underlying geophysical processes of global change (GCM uncertainties) and due to uncertain future scenarios (scenario uncertainties). Disagreement between different GCMs and scenarios in regional climate change impact studies indicates that overreliance on a single GCM with a scenario could lead to inappropriate planning and adaptation responses. This paper focuses on modeling GCM and scenario uncertainty using possibility theory in projecting streamflow of Mahanadi river, at Hirakud, India. A downscaling method based on fuzzy clustering and Relevance Vector Machine (RVM) is applied to project monsoon streamflow from three GCMs with two green house emission scenarios. Possibilities are assigned to all the GCMs with scenarios based on their performance in modeling the streamflow of the recent past (1991-2005), when there are signals of climate forcing. The possibilities associated with different GCMs and scenarios are used as weights in computing the possibilistic mean of the CDFs projected for three standard time slices 2020s, 2050s, and 2080s. The result shows that the value of streamflow at which the CDF reaches 1 reduces with time, which shows the reduction in probability of occurrence of extreme high flow events in future. Historic record of monsoon streamflow of Mahanadi river also shows similar decreasing trend, which may be due to the effect of high surface warming. Reduction in Mahandai streamflow is likely to pose a major challenge for water resources engineers in meeting water demands in future.

  14. Climatology of terdiurnal tide in the mesosphere and lower thermosphere from TIMED SABER/TIDI, ground-based sodium lidar and NCAR TIME-GCM model

    NASA Astrophysics Data System (ADS)

    Yue, J.; Wu, Q.; Xu, J.; Liu, H.; Hagan, M. E.; Maute, A. I.; Yuan, T.; She, C.; Russell, J. M.

    2011-12-01

    In this paper, we investigate the nature of the terdiurnal tide (8 hour period) in the mesosphere and lower thermosphere (MLT), using the Colorado State University (CSU) temperature/wind sodium lidar data set (41N, 105W) (5 years, 2002 to 2006), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature and Doppler interferometer (TIDI) wind measurement for 7 years (2003 to 2009) both onboard of Thermosphere-ionosphere-Mesosphere-Energetics and Dynamics (TIMED) satellite, and the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model runs (TIME-GCM). The seasonal variability and global structure of the terdiurnal tide will be provided. The amplitude of the terdiurnal tide depends heavily on season, latitude and altitude. For example, at northern mid-latitude, the maximum amplitudes in horizontal wind (20 m/s) and temperature (8 K) appear at 100 km in late winter from the lidar measurement, while it is the weakest in summer. SABER measurement reveals that the maximum of the terdiurnal tide temperature above 100 km occurs near equinox at mid-latitude. TIDI wind finds that the maximum amplitude in meridional wind at mid-latitude is before and after the solstice. The vertical wavelength of the terdiurnal tide will be estimated. The comparison between the TIME-GCM and the observations will enhance our understandings of the excitation, propagation and dissipation of the terdiurnal tide in the atmosphere. This will benefit our future study of the terdiurnal tidal impact in the thermosphere/ionosphere coupling.

  15. Assessment of the NASA GISS CMIP5 ModelE GCM Simulated Clouds and TOA Radiation Budgets Using CERES-MODIS, CALIPSO/CloudSat, and ISCCP Observations

    NASA Astrophysics Data System (ADS)

    Stanfield, R. E.; Dong, X.; Xi, B.; Kennedy, A. D.; Del Genio, A. D.; Minnis, P.; Loeb, N. G.; Doelling, D.

    2012-12-01

    To evaluate the GISS ModelE simulated global clouds and TOA radiation budgets, we have collected and processed NASA CERES and MODIS observations during the period 2000-2005. In detail, the 1x1 degree resolution monthly averaged SYN1 cloud product has been used with combined observations from both Terra and Aqua satellites, and degraded to a 2x2.5 degree grid box to match the GCM spatial resolution. The monthly means of the CERES EBAF radiation dataset have been used in this study, where the EBAF data are temporally interpolated using geostationary observations to infer the diurnal signal between CERES measurements. The GISS ModelE products were downloaded from the CMIP5 (Coupled Model Intercomparison Project Phase 5) being prepared for the IPCC-AR5. The model shows a high degree of accuracy in cloud fractions and radiation budgets when compared globally, however large differences are observed between the observations and the model when examined regionally. In particular, cloud fraction can be greatly underestimated or overestimated while Ice water path and liquid water path values are largely overestimated by the model in the southern mid-latitudes. This study examines these differences and the impact they have on the radiation budget. To determine whether these biases are caused by the microphysics or dynamics within the GCM, results will be partitioned by atmospheric states determined by Self Organizing Maps trained by reanalysis data.

  16. Uncertainty analysis of impacts of climate change on snow processes: Case study of interactions of GCM uncertainty and an impact model

    NASA Astrophysics Data System (ADS)

    Kudo, Ryoji; Yoshida, Takeo; Masumoto, Takao

    2017-05-01

    The impact of climate change on snow water equivalent (SWE) and its uncertainty were investigated in snowy areas of subarctic and temperate climate zones in Japan by using a snow process model and climate projections derived from general circulation models (GCMs). In particular, we examined how the uncertainty due to GCMs propagated through the snow model, which contained nonlinear processes defined by thresholds, as an example of the uncertainty caused by interactions among multiple sources of uncertainty. An assessment based on the climate projections in Coupled Model Intercomparison Project Phase 5 indicated that heavy-snowfall areas in the temperate zone (especially in low-elevation areas) were markedly vulnerable to temperature change, showing a large SWE reduction even under slight changes in winter temperature. The uncertainty analysis demonstrated that the uncertainty associated with snow processes (1) can be accounted for mainly by the interactions between GCM uncertainty (in particular, the differences of projected temperature changes between GCMs) and the nonlinear responses of the snow model and (2) depends on the balance between the magnitude of projected temperature changes and present climates dominated largely by climate zones and elevation. Specifically, when the peaks of the distributions of daily mean temperature projected by GCMs cross the key thresholds set in the model, the GCM uncertainty, even if tiny, can be amplified by the nonlinear propagation through the snow process model. This amplification results in large uncertainty in projections of CC impact on snow processes.

  17. GCM simulations of intraseasonal variability in the Pacific/North American region

    NASA Technical Reports Server (NTRS)

    Schubert, Siegfried; Suarez, Max; Park, Chung-Kyu; Moorthi, Shrinivas

    1993-01-01

    General circulation model (GCM) simulations of low-frequency variability with time scales of 20 to 70 days are analyzed for the Pacific sector during boreal winter. The GCM's leading mode in the upper-tropospheric zonal wind is associated with fluctuations of the East Asian jet; this mode resembles, in both structure and amplitude, the Pacific/North American (PNA) pattern found in the observations on these time scales. In both the model and observations, the PNA anomaly is characterized by: (1) a linear balance in the upper-tropospheric vorticity budget with no significant Rossby wave source in the tropics, (2) a barotropic conversion of kinetic energy from the time mean Pacific jet, and (3) a north/south displacement of the Pacific storm track. In the GCM, the latter is associated with synoptic eddy heat flux and latent heat anomalies that appear to contribute to a strong lower-tropospheric source of wave activity over the North Pacific. This is in contrast to the observations, which show only a weak source of wave activity in this region.

  18. The impact of vertical resolution upon GCM simulations of marine stratocumulus

    NASA Astrophysics Data System (ADS)

    Bushell, A. C.; Martin, G. M.

    The impact of increased vertical resolution in the Hadley Centre Climate Model upon the simulation of stratocumulus is investigated in experiments using single column (SCM) and general circulation (GCM) model configurations. A threefold enhancement of vertical resolution in the boundary layer leads to improvements in the vertical structure of the cloud-topped boundary layer produced by the SCM and GCM in both well-mixed and decoupled situations. However, single and decoupled mixed layers in the marine stratocumulus subsidence regions are still too shallow and, despite increasing, layer cloud amounts remain generally too low. Moreover, closer examination of GCM data and SCM timeseries reveals an underlying sensitivity to vertical resolution in model interactions between boundary layer and convection processes which appears unrealistic. Stratocumulus simulation is thus unlikely to improve significantly as a result of enhanced resolution alone and further work is being undertaken to improve the Hadley Centre model's boundary layer scheme and, in particular, its interaction with the convection scheme. Nevertheless, this study shows that the full benefit of an improved boundary layer scheme will not be realized if the boundary layer structure is constrained by the rather poor lower troposphere resolution of the standard 19-level climate model. Future Hadley Centre model versions will seek to combine the added flexibility of a better resolved structure with improvements to the subgrid boundary layer parametrizations.

  19. Post-processing GCM daily rainfall and temperature forecasts for applications in water management and agriculture

    NASA Astrophysics Data System (ADS)

    Schepen, Andrew; Wang, Qj; Everingham, Yvette; Zhao, Tongtiegang

    2017-04-01

    Ensemble time series forecasts of rainfall and temperature up to six months ahead are sought for applications in water management and agricultural production. Raw GCM forecasts are generally not suitable for direct use in hydrological models or agricultural production simulators and must be post-processed first, to ensure they are reliable, as skilful as possible, and have realistic temporal patterns. In this study, we test two post-processing approaches to produce daily forecasts for cropping regions and water supply catchments in Australia. In the first approach, we apply the calibration, bridging and merging (CBaM) method to produce statistically reliable monthly forecasts based on GCM outputs of rainfall, temperature and sea surface temperatures. We then disaggregate the monthly forecasts to obtain realistic daily time series forecasts that can be used as inputs to crop and hydrological models. In the second approach, we develop a method for directly post-processing daily GCM forecasts using a Bayesian joint probability (BJP) model. We demonstrate and evaluate the two approaches through a case study for the Tully sugar region in north-eastern Australia. The daily post-processed forecasts will benefit applications in streamflow forecasting and crop yield forecasting.

  20. Regional Climate Simulation with a Variable Resolution Stretch Grid GCM: The 1998 Summer Drought

    NASA Technical Reports Server (NTRS)

    Fox-Rabinovitz, Michael; Stein, Uri; Takacs, Lawrence; Govindaraju, Ravi; Suarez, Max

    1999-01-01

    The variable resolution stretched grid(SG) GCM based on the Goddard Earth Observing System (GEOS) GCM, has been developed and tested in a regional climate simulation mode. The GEOS SG-GCM is used for simulation of the 1988 summer drought over the U.S. Midwest. Within the stretched grid, the region of interest with a uniform about 60 km resolution is a rectangle over the U.S. Outside the region, the grid intervals increase or stretch with a constant stretching factor (as a geometric progression). The results of two-month simulation for the anomalous climate event of the U.S. drought of 1988, are validated against data analysis fields and diagnostics. The event has been chosen by the Project to Inter-compare Regional Climate Simulations(PIRCS). The efficient regional down-scaling as well as the positive impact of fine regional resolution, are obtained. More specifically, the precipitation, 500 hPa, and low-level jet patterns and characteristics are well represented in the simulation. The SG-concept appeared to be a promising candidate for regional and subregional climate studies and applications.

  1. Comparison of stochastic MOS corrections for GCM and RCM simulated precipitation

    NASA Astrophysics Data System (ADS)

    Widmann, Martin; Eden, Jonathan; Maraun, Douglas; Vrac, Mathieu

    2014-05-01

    In order to assess to what extent regional climate models (RCMs) yield better representations of climatic states than general circulation models (GCMs) the output of the two model types is usually directly compared with observations and the value added through RCMs has been clearly demonstrated. RCM output is often bias-corrected and in some cases bias correction methods can also be applied to GCMs. The question thus arises what the added value of RCMs in this setup is, i.e. whether bias-corrected RCMs perform better than bias-corrected GCMs. Here we present some first results from such a comparison. We used a stochastic Model Output Statistics (MOS) method, which can be seen as a general version of bias correction, to estimate daily precipitation at 465 UK stations between 1961-2000 using simulated precipitation from the RACMO2 and CCLM RCMs and from the ECHAM5 GCM as predictors. The MOS method uses logistic regression to model rainfall occurrence and a Gamma distribution for the wet-day distribution. All model parameters are made linearly dependent on the predictors, i.e. the simulated precipitation. The fitting and validation of the statistical model requires the daily, large-scale weather states in the RCM and GCM to represent the actual, historic weather situation. For the RCMs this is achieved by using simulations driven by reanalysis data; RACMO2 is just driven at the boundaries, whereas in CCLM the circulation within the model domain is additionally kept close to the reanalysis through spectral nudging. For the GCM we have used a simulation nudged towards ERA40. The model validation is done in a cross-validation setup and is based on Brier scores for occurrence and quantile scores for the estimated probability distributions. The comparison of the validation skills for the two RCM cases shows some improved skill if spectral nudging is used, indicating that on daily timescales RCMs can generate internal variability that needs to be kept in mind when designing

  2. Dealing with multi-GCM ensemble in developing the climate change scenarios the probabilistic impact assessments

    NASA Astrophysics Data System (ADS)

    Dubrovsky, M.

    2010-09-01

    The volume of GCM simulations available for climate change impact studies continually increases. On the one hand, this allows for a better representation of uncertainties (between GCMs, between emission scenarios, between parameterizations, etc.). On the other hand, the volume of available GCM output data has become so large such that it poses a strong requirement for more effective organization of climate change impact analyses: it is not always possible to involve scenarios from all available GCMs. To account for the uncertainties in this case, two approaches are at hand: (i) Applying scenarios from a subset of all available GCMs. (ii) Applying scenario emulator/generator, which may produce a large set of climate change scenarios representing the multivariate probability density function of the scenarios. The present contribution addresses both of these two approaches: (A) Choice of the "representative" subset of GCMs. In defining the subset, two circumstances are taken into account: (i) performance of GCMs to reproduce the present climate, (ii) ability of the subset to represent the variability of scenarios across the whole set of GCMs. The gridded maps will show the chosen subsets for the whole Europe. (B) Use of the stochastic climate change scenario generator. The generator used here is based on a multivariate parametric model whose parameters are derived from a set of GCM based scenarios (no limit on the size of the calibration set, the model may also be calibrated with a very large perturbed-physics ensemble). Once calibrated, the generator may produce an arbitrarily large set of climate change scenarios. The results of the validation of the scenario generator will be presented. The validation consists in comparing distribution functions of changes in temperature, precipitation and drought conditions (in terms of Palmer drought indices) in several sites in Europe and U.S.A. based on (i) a set of individual GCM simulations (taken from IPCC AR4 database) vs

  3. Impact of atmospheric convectively coupled equatorial Kelvin waves on upper ocean variability

    NASA Astrophysics Data System (ADS)

    Baranowski, Dariusz B.; Flatau, Maria K.; Flatau, Piotr J.; Matthews, Adrian J.

    2016-03-01

    Convectively coupled Kelvin waves (CCKWs) are atmospheric weather systems that propagate eastward along the equatorial wave guide with phase speeds between 11 and 14 m s-1. They are an important constituent of the convective envelope of the Madden-Julian oscillation (MJO), for which ocean-atmosphere interactions play a vital role. Hence, ocean-atmosphere interactions within CCKWs may be important for MJO development and prediction and for tropical climate, in general. Although the atmospheric structure of CCKWs has been well studied, their impact on the underlying ocean is unknown. In this paper, the ocean-atmosphere interactions in CCKWs are investigated by a case study from November 2011 during the CINDY/DYNAMO field experiment, using in situ oceanographic measurements from an ocean glider. The analysis is then extended to a 15 year period using precipitation data from the Tropical Rainfall Measuring Mission and surface fluxes from the TropFlux analysis. A methodology is developed to calculate trajectories of CCKWs. CCKW events are strongly controlled by the MJO, with twice as many CCKWs observed during the convectively active phase of the MJO compared to the suppressed phase. Coherent ocean-atmosphere interaction is observed during the passage of a CCKW, which lasts approximately 4 days at any given longitude. Surface wind speed and latent heat flux are enhanced, leading to a transient suppression of the diurnal cycle of sea surface temperature (SST) and a sustained decrease in bulk SST of 0.1°C. Given that a typical composite mean MJO SST anomaly is of the order of 0.3°C, and more than one CCKW can occur during the active phase of a single MJO event, the oceanographic impact of CCKWs is of major importance to the MJO cycle.

  4. El Nino-southern oscillation: A coupled response to the greenhouse effect?

    SciTech Connect

    Sun, De-Zheng

    1997-11-01

    The purpose of this article to elucidate the link between the El Nino-Southern Oscillation (ENSO) and radiative forcing (of which the greenhouse effect is a major part). A unified theory for the tropical Pacific climate is developed by considering the response of the coupled ocean-atmosphere to a changing radiative forcing. The hypothesis is that both the zonal surface sea temperature (SST) gradients and ENSO are a coupled response to the strong radiative heating or the tropical warmth. Owing to ocean-atmosphere interaction, the stronger the radiative heating, the larger the zonal SST gradients. When the SST gradients exceed a critical value, however, the ocean-atmosphere interaction in the cold-tongue region is too strong for the coupled system to hold steady. Consequently, the coupled system enters an oscillatory state. These coupled dynamics are examined in a simple mathematical model whose behavior is consistent with the hypothesis. With a linear temperature profile throughout the depth of subsurface ocean, the model predicts that both the magnitude and period of the oscillation increase with increases in radiative forcing or the greenhouse effect. The increase in the magnitude of the oscillation largely comes from an enhancement of the magnitude of the cold anomalies, while the increase in the period mostly comes from a prolonged duration of the warm events. With a profile in which the lapse rate decreases with depth, the sensitivity is more moderate. The simplicity of the model prevents a quantitative simulation of the sensitivity of ENSO to increases in the greenhouse effect, but qualitatively the model results support the empirical interpretation of the prolonged duration of the 1990-1995 ENSO event. 5 refs., 7 figs.

  5. Comparison of GCM- and RCM-simulated precipitation following stochastic postprocessing

    NASA Astrophysics Data System (ADS)

    Eden, Jonathan M.; Widmann, Martin; Maraun, Douglas; Vrac, Mathieu

    2014-10-01

    In order to assess to what extent regional climate models (RCMs) yield better representations of climatic states than general circulation models (GCMs), the output of each is usually directly compared with observations. RCM output is often bias corrected, and in some cases correction methods can also be applied to GCMs. This leads to the question of whether bias-corrected RCMs perform better than bias-corrected GCMs. Here the first results from such a comparison are presented, followed by discussion of the value added by RCMs in this setup. Stochastic postprocessing, based on Model Output Statistics (MOS), is used to estimate daily precipitation at 465 stations across the United Kingdom between 1961 and 2000 using simulated precipitation from two RCMs (RACMO2 and CCLM) and, for the first time, a GCM (ECHAM5) as predictors. The large-scale weather states in each simulation are forced toward observations. The MOS method uses logistic regression to model precipitation occurrence and a Gamma distribution for the wet day distribution, and is cross validated based on Brier and quantile skill scores. A major outcome of the study is that the corrected GCM-simulated precipitation yields consistently higher validation scores than the corrected RCM-simulated precipitation. This seems to suggest that, in a setup with postprocessing, there is no clear added value by RCMs with respect to downscaling individual weather states. However, due to the different ways of controlling the atmospheric circulation in the RCM and the GCM simulations, such a strong conclusion cannot be drawn. Yet the study demonstrates how challenging it is to demonstrate the value added by RCMs in this setup.

  6. 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.

  7. Interannual Atmospheric Variability Simulated by a Mars GCM: Impacts on the Polar Regions

    NASA Technical Reports Server (NTRS)

    Bridger, Alison F. C.; Haberle, R. M.; Hollingsworth, J. L.

    2003-01-01

    It is often assumed that in the absence of year-to-year dust variations, Mars weather and climate are very repeatable, at least on decadal scales. Recent multi-annual simulations of a Mars GCM reveal however that significant interannual variations may occur with constant dust conditions. In particular, interannual variability (IAV) appears to be associated with the spectrum of atmospheric disturbances that arise due to baroclinic instability. One quantity that shows significant IAV is the poleward heat flux associated with these waves. These variations and their impacts on the polar heat balance will be examined here.

  8. Polar predictability: exploring the influence of GCM and regional model uncertainty on future ice sheet climates

    NASA Astrophysics Data System (ADS)

    Reusch, D. B.

    2015-12-01

    Evaluating uncertainty in GCMs and regional-scale forecast models is an essential step in the development of climate change predictions. Polar-region skill is particularly important due to the potential for changes affecting both local (ice sheet) and global (sea level) environments through more frequent/intense surface melting and changes in precipitation type/amount. High-resolution, regional-scale models also use GCMs as a source of boundary/initial conditions in future scenarios, thus inheriting a measure of GCM-derived externally-driven uncertainty. We examine inter- and intramodel uncertainty through statistics from decadal climatologies and analyses of variability based on self-organizing maps (SOMs), a nonlinear data analysis tool. We evaluate a 19-member CMIP5 subset and the 30-member CESM1.0-CAM5-BGC Large Ensemble (CESMLE) during polar melt seasons (boreal/austral summer) for recent (1981-2000) and future (2081-2100, RCP 8.5) decades. Regional-model uncertainty is examined with a subset of these GCMs driving Polar WRF simulations. Decadal climatologies relative to a reference (recent: the ERA-Interim reanalysis; future: a skillful modern GCM) identify model uncertainty in bulk, e.g., BNU-ESM is too warm, CMCC-CM too cold. While quite useful for model screening, diagnostic benefit is often indirect. SOMs extend our diagnostics by providing a concise, objective summary of model variability as a set of generalized patterns. Joint analysis of reference and test models summarizes the variability of multiple realizations of climate (all the models), benchmarks each model versus the reference (frequency analysis helps identify the patterns behind GCM bias), and places each GCM in a common context. Joint SOM analysis of CESMLE members shows how initial conditions contribute to differences in modeled climates, providing useful information about internal variability, such as contributions from each member to overall uncertainty using pattern frequencies. In the

  9. Sensitivity of the equilibrium surface temperature of a GCM to systematic changes in atmospheric carbon dioxide

    NASA Technical Reports Server (NTRS)

    Oglesby, Robert J.; Saltzman, Barry

    1990-01-01

    The equilibrium response of surface temperature to atmospheric CO2 concentration, for six values between 100 and 1000 ppm, is calculated from a series of GCM experiments. This response is nonlinear, showing greater sensitivity for lower values of CO2 than for the higher values. It is suggested that changes in CO2 concentration of a given magnitude (e.g., 100 ppm) played a larger role in the Pleistocene ice-age-type temperature variations than in causing global temperature changes due to anthropogenic increases.

  10. Coupled atmosphere-ocean-wave simulations of a storm event over the Gulf of Lion and Balearic Sea

    NASA Astrophysics Data System (ADS)

    Renault, Lionel; Chiggiato, Jacopo; Warner, John C.; Gomez, Marta; Vizoso, Guillermo; Tintoré, Joaquin

    2012-09-01

    The coastal areas of the North-Western Mediterranean Sea are one of the most challenging places for ocean forecasting. This region is exposed to severe storms events that are of short duration. During these events, significant air-sea interactions, strong winds and large sea-state can have catastrophic consequences in the coastal areas. To investigate these air-sea interactions and the oceanic response to such events, we implemented the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System simulating a severe storm in the Mediterranean Sea that occurred in May 2010. During this event, wind speed reached up to 25 m.s-1 inducing significant sea surface cooling (up to 2°C) over the Gulf of Lion (GoL) and along the storm track, and generating surface waves with a significant height of 6 m. It is shown that the event, associated with a cyclogenesis between the Balearic Islands and the GoL, is relatively well reproduced by the coupled system. A surface heat budget analysis showed that ocean vertical mixing was a major contributor to the cooling tendency along the storm track and in the GoL where turbulent heat fluxes also played an important role. Sensitivity experiments on the ocean-atmosphere coupling suggested that the coupled system is sensitive to the momentum flux parameterization as well as air-sea and air-wave coupling. Comparisons with available atmospheric and oceanic observations showed that the use of the fully coupled system provides the most skillful simulation, illustrating the benefit of using a fully coupled ocean-atmosphere-wave model for the assessment of these storm events.

  11. Coupled atmosphere-ocean-wave simulations of a storm event over the Gulf of Lion and Balearic Sea

    USGS Publications Warehouse

    Renault, Lionel; Chiggiato, Jacopo; Warner, John C.; Gomez, Marta; Vizoso, Guillermo; Tintore, Joaquin

    2012-01-01

    The coastal areas of the North-Western Mediterranean Sea are one of the most challenging places for ocean forecasting. This region is exposed to severe storms events that are of short duration. During these events, significant air-sea interactions, strong winds and large sea-state can have catastrophic consequences in the coastal areas. To investigate these air-sea interactions and the oceanic response to such events, we implemented the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System simulating a severe storm in the Mediterranean Sea that occurred in May 2010. During this event, wind speed reached up to 25 m.s-1 inducing significant sea surface cooling (up to 2°C) over the Gulf of Lion (GoL) and along the storm track, and generating surface waves with a significant height of 6 m. It is shown that the event, associated with a cyclogenesis between the Balearic Islands and the GoL, is relatively well reproduced by the coupled system. A surface heat budget analysis showed that ocean vertical mixing was a major contributor to the cooling tendency along the storm track and in the GoL where turbulent heat fluxes also played an important role. Sensitivity experiments on the ocean-atmosphere coupling suggested that the coupled system is sensitive to the momentum flux parameterization as well as air-sea and air-wave coupling. Comparisons with available atmospheric and oceanic observations showed that the use of the fully coupled system provides the most skillful simulation, illustrating the benefit of using a fully coupled ocean-atmosphere-wave model for the assessment of these storm events.

  12. Impacts of Ocean-Atmosphere Interaction in the Pacific Asian Marginal Seas on the Variability of the North Pacific Oscillation/Victoria Mode

    NASA Astrophysics Data System (ADS)

    Tseng, Y. H.; Jin, X. L.; Chow, C. H.; Ding, R.; Di Lorenzo, E.; Small, J.; Huang, X.

    2016-02-01

    The interannual variability of North Pacific Oscillation (NPO)/Victoria Mode (VM) is found to be closely linked with the surface winds and temperature in the Pacific Asian Marginal Sea (PAMS). The coupled oceanic and atmospheric processes in the PAMS are analyzed. Composite analysis indicates an enhanced surface latent heat flux anomalies develop in response to Sea Surface Temperature (SST) in the strong NPO/VM phase. The winter SST and meridional wind anomalies in the PAMS acts as a pivotal driver to modulate the NPO/VM pattern through atmospheric teleconnection. The upper-level eastward propagation strengthens the south lobe of the NPO from the subtropical pressure low anomaly. Dynamical processes are validated using the observation and the Linear Baroclinic Model. Further analysis shows that the East Asian Winter Monsoon (EAWM) may play an important role in controlling low-level meridional wind variability in the PAMS but does not explain its completed variability. Finally, the impacts of storm-track are also evaluated.

  13. Functional Conservation of the Glide/Gcm Regulatory Network Controlling Glia, Hemocyte, and Tendon Cell Differentiation in Drosophila

    PubMed Central

    Cattenoz, Pierre B.; Popkova, Anna; Southall, Tony D.; Aiello, Giuseppe; Brand, Andrea H.; Giangrande, Angela

    2016-01-01

    High-throughput screens allow us to understand how transcription factors trigger developmental processes, including cell specification. A major challenge is identification of their binding sites because feedback loops and homeostatic interactions may mask the direct impact of those factors in transcriptome analyses. Moreover, this approach dissects the downstream signaling cascades and facilitates identification of conserved transcriptional programs. Here we show the results and the validation of a DNA adenine methyltransferase identification (DamID) genome-wide screen that identifies the direct targets of Glide/Gcm, a potent transcription factor that controls glia, hemocyte, and tendon cell differentiation in Drosophila. The screen identifies many genes that had not been previously associated with Glide/Gcm and highlights three major signaling pathways interacting with Glide/Gcm: Notch, Hedgehog, and JAK/STAT, which all involve feedback loops. Furthermore, the screen identifies effector molecules that are necessary for cell-cell interactions during late developmental processes and/or in ontogeny. Typically, immunoglobulin (Ig) domain–containing proteins control cell adhesion and axonal navigation. This shows that early and transiently expressed fate determinants not only control other transcription factors that, in turn, implement a specific developmental program but also directly affect late developmental events and cell function. Finally, while the mammalian genome contains two orthologous Gcm genes, their function has been demonstrated in vertebrate-specific tissues, placenta, and parathyroid glands, begging questions on the evolutionary conservation of the Gcm cascade in higher organisms. Here we provide the first evidence for the conservation of Gcm direct targets in humans. In sum, this work uncovers novel aspects of cell specification and sets the basis for further understanding of the role of conserved Gcm gene regulatory cascades. PMID:26567182

  14. Functional Conservation of the Glide/Gcm Regulatory Network Controlling Glia, Hemocyte, and Tendon Cell Differentiation in Drosophila.

    PubMed

    Cattenoz, Pierre B; Popkova, Anna; Southall, Tony D; Aiello, Giuseppe; Brand, Andrea H; Giangrande, Angela

    2016-01-01

    High-throughput screens allow us to understand how transcription factors trigger developmental processes, including cell specification. A major challenge is identification of their binding sites because feedback loops and homeostatic interactions may mask the direct impact of those factors in transcriptome analyses. Moreover, this approach dissects the downstream signaling cascades and facilitates identification of conserved transcriptional programs. Here we show the results and the validation of a DNA adenine methyltransferase identification (DamID) genome-wide screen that identifies the direct targets of Glide/Gcm, a potent transcription factor that controls glia, hemocyte, and tendon cell differentiation in Drosophila. The screen identifies many genes that had not been previously associated with Glide/Gcm and highlights three major signaling pathways interacting with Glide/Gcm: Notch, Hedgehog, and JAK/STAT, which all involve feedback loops. Furthermore, the screen identifies effector molecules that are necessary for cell-cell interactions during late developmental processes and/or in ontogeny. Typically, immunoglobulin (Ig) domain-containing proteins control cell adhesion and axonal navigation. This shows that early and transiently expressed fate determinants not only control other transcription factors that, in turn, implement a specific developmental program but also directly affect late developmental events and cell function. Finally, while the mammalian genome contains two orthologous Gcm genes, their function has been demonstrated in vertebrate-specific tissues, placenta, and parathyroid glands, begging questions on the evolutionary conservation of the Gcm cascade in higher organisms. Here we provide the first evidence for the conservation of Gcm direct targets in humans. In sum, this work uncovers novel aspects of cell specification and sets the basis for further understanding of the role of conserved Gcm gene regulatory cascades.

  15. A GCM investigation of impact of aerosols on the precipitation in Amazon during the dry to wet transition

    NASA Astrophysics Data System (ADS)

    Gu, Yu; Liou, K. N.; Jiang, J. H.; Fu, R.; Lu, Sarah; Xue, Y.

    2016-06-01

    The climatic effects of aerosols on the precipitation over the Amazon during the dry to wet transition period have been investigated using an atmospheric general circulation model, NCEP/AGCM, and the aerosol climatology data. We found increased instability during the dry season and delayed wet season onset with aerosols included in the model simulation, leading to the delay of the maximum precipitation over the Amazon by about half a month. In particular, our GCM simulations show that surface solar flux is reduced in the Amazon due to the absorption and scattering of the solar radiation by aerosols, leading to decreased surface temperature. Reduced surface solar flux is balanced by decreases in both surface sensible heat and latent heat fluxes. During the wet season, the subtropical system over the Amazon has a shallower convection. With the inclusion of aerosols in the simulation, precipitation in the rainy season over the Amazon decreases in the major rainfall band, which partially corrects the overestimate of the simulated precipitation in that region. The reduced surface temperature by aerosols is also coupled with a warming in the middle troposphere, leading to increased atmosphere stability and moisture divergence over the Amazon. However, during the dry season when the convective system is stronger over the Amazon, rainfall increases in that region due to the warming of the air over the upper troposphere produced by biomass burning aerosols, which produces an anomalous upward motion and a convergence of moisture flux over the Amazon and draws the moisture and precipitation further inland. Therefore, aerosol effects on precipitation depend on the large-scale atmospheric stability, resulting in their different roles over the Amazon during the dry and wet seasons.

  16. Modeling biophysical/biogeochemical/ecological/ocean/atmosphere two-way interactions using NCEP CFS/SSiB5/TRIFFID/DAYCENT: challenge and promising

    NASA Astrophysics Data System (ADS)

    Xue, Y.; Liu, Y.; Cox, P. M.; De Sales, F.; Lee, J.; Marx, L.; Hartman, M. D.; Yang, R.; Parton, W. J.; Qiu, B.; Ek, M. B.

    2016-12-01

    Evaluations of several dynamic vegetation models' (DVM) performances in the offline experiments and in the CMIP5 simulations suggest that most of the DVMs substantially overestimate leaf area index (LAI) and length of the growing season, which contribute to overestimation in their coupled models' precipitation. These results suggest important deficiencies in today's DVMs but also show the importance of proper ecological processes in the Earth System Modeling. We have developed a water-carbon-energy balance-based ecosystem model (SSiB4/TRIFFID) and verified it with field and satellite measurement at seasonal to decadal and longer scales. In the global offline tests, the model was integrated from 1950 to 2010 driven by observed meteorological forcing. The simulated trend and decadal variabilities in surface ecosystem conditions (e.g., Plant functional types, LAI, GPP), and surface water and energy balances are analyzed; further experiments and analyses are carried to isolate the contribution due to elevated atmospheric carbon concentration, global warming, soil moisture, and climate variability. How nitrogen processes simulated by the DayCent model Climate Forecast System (CFS) model, which has consistently shown improvements in simulated atmospheric & ocean conditions compared with those runs with specified vegetation conditions. In an experiment, two parametrizations that calculate the mean water potential in soil layers, which affect transpiration and plants' mortality, are tested. It shows that these two methods have substantial impact on global decadal variability of precipitation and surface temperature, with even opposite signs over some regions in the worlds. These results show the uncertainty in DVM modeling with significant implication for the future prediction. It is imperative to evaluate DVMs with comprehensive observational data.

  17. Ocean-Atmosphere Environments of Antarctic-Region Cold-Air Mesocyclones: Evaluation of Reanalyses for Contrasting Adjacent 10-Day Periods ("Macro-Weather") in Winter.

    NASA Astrophysics Data System (ADS)

    Carleton, A. M.; Auger, J.; Birkel, S. D.; Maasch, K. A.; Mayewski, P. A.; Claud, C.

    2015-12-01

    Mesoscale cyclones in cold-air outbreaks (mesocyclones) feature in the weather and climate of the Antarctic (e.g., Ross Sea) and sub-antarctic (Drake Passage). They adversely impact field operations, and influence snowfall, the ice-sheet mass balance, and sea-air energy fluxes. Although individual mesocyclones are poorly represented on reanalyses, these datasets robustly depict the upper-ocean and troposphere environments in which multiple mesocyclones typically form. A spatial metric of mesocyclone activity—the Meso-Cyclogenesis Potential (MCP)—used ERA-40 anomaly fields of: sea surface temperature (SST) minus marine air temperature (MAT), near-surface winds, 500 hPa air temperature, and the sea-ice edge location. MCP maps composited by teleconnection phases for 1979-2001, broadly correspond to short-period satellite "climatologies" of mesocyclones. Here, we assess 3 reanalysis datasets (CFSR, ERA-I and MERRA) for their reliably to depict MCP patterns on weekly to sub-monthly periods marked by strong regional shifts in mesocyclone activity (frequencies, track densities) occurring during a La Niña winter: June 21-30, 1999 (SE Indian Ocean) and September 1-10, 1999 (Ross Sea sector). All reanalyses depict the marked variations in upper ocean and atmosphere variables between adjacent 10-day periods. Slight differences may owe to model resolution or internal components (land surface, coupled ocean models), and/or how the observations are assimilated. For June 21-30, positive SST-MAT, southerly winds, proximity to the ice edge, and negative T500, accompany increased meso-cyclogenesis. However, for September 1-10, surface forcing does not explain frequent comma cloud "polar lows" north-east of the Ross Sea. Inclusion of the upper-level diffluence (e.g., from Z300 field) in the MCP metric, better depicts the observed mesocyclone activity. MCP patterns on these "macro-weather" time scales appear relatively insensitive to the choice of reanalysis.

  18. A Two-Habit Ice Cloud Optical Property Parameterization for GCM Application

    NASA Technical Reports Server (NTRS)

    Yi, Bingqi; Yang, Ping; Minnis, Patrick; Loeb, Norman; Kato, Seiji

    2014-01-01

    We present a novel ice cloud optical property parameterization based on a two-habit ice cloud model that has been proved to be optimal for remote sensing applications. The two-habit ice model is developed with state-of-the-art numerical methods for light scattering property calculations involving individual columns and column aggregates with the habit fractions constrained by in-situ measurements from various field campaigns. Band-averaged bulk ice cloud optical properties including the single-scattering albedo, the mass extinction/absorption coefficients, and the asymmetry factor are parameterized as functions of the effective particle diameter for the spectral bands involved in the broadband radiative transfer models. Compared with other parameterization schemes, the two-habit scheme generally has lower asymmetry factor values (around 0.75 at the visible wavelengths). The two-habit parameterization scheme was widely tested with the broadband radiative transfer models (i.e. Rapid Radiative Transfer Model, GCM version) and global circulation models (GCMs, i.e. Community Atmosphere Model, version 5). Global ice cloud radiative effects at the top of the atmosphere are also analyzed from the GCM simulation using the two-habit parameterization scheme in comparison with CERES satellite observations.

  19. GCM (general circulation model)-data intercomparison: The good news and the bad

    SciTech Connect

    Grotch, S.L.

    1990-09-01

    General circulation models (GCMs) are being actively used to assess possible climate change due to increasing greenhouse gas concentrations. Because such simulations provide detailed climatic predictions at a wide range of scales, they are of particular interest to those making regional assessments of climatic change. It is especially important that workers using the results of such simulations be aware of some of the limitations of these results. In this study some of the positive results from these model simulations will be shown and some of the deficiencies will also be highlighted. Following an introductory section describing the nature of GCM climate simulations the issue of the spatial scales of such simulations is examined. A comparison of the results of seven GCM simulations of the current climate and the predictions of these models for the changes due to a doubling of CO{sub 2} will be discussed. In these intercomparisons, the spatial scale over which the results are compared varies from global to zonal (longitudinally averaged at a given latitude) to individual slices through the data along specified latitudes or longitudes. Finally, the dangers and pitfalls of relying on simple averages will be highlighted. 19 refs., 9 figs., 1 tab.

  20. Improved Upper Ocean/Sea Ice Modeling in the GISS GCM for Investigating Climate Change

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This project built on our previous results in which we highlighted the importance of sea ice in overall climate sensitivity by determining that for both warming and cooling climates, when sea ice was not allowed to change, climate sensitivity was reduced by 35-40%. We also modified the Goddard Institute for Space Studies (GISS) 8 deg x lO deg atmospheric General Circulation Model (GCM) to include an upper-ocean/sea-ice model involving the Semtner three-layer ice/snow thermodynamic model, the Price et al. (1986) ocean mixed layer model and a general upper ocean vertical advection/diffusion scheme for maintaining and fluxing properties across the pycnocline. This effort, in addition to improving the sea ice representation in the AGCM, revealed a number of sensitive components of the sea ice/ocean system. For example, the ability to flux heat through the ice/snow properly is critical in order to resolve the surface temperature properly, since small errors in this lead to unrestrained climate drift. The present project, summarized in this report, had as its objectives: (1) introducing a series of sea ice and ocean improvements aimed at overcoming remaining weaknesses in the GCM sea ice/ocean representation, and (2) performing a series of sensitivity experiments designed to evaluate the climate sensitivity of the revised model to both Antarctic and Arctic sea ice, determine the sensitivity of the climate response to initial ice distribution, and investigate the transient response to doubling CO2.

  1. Improved Upper Ocean/Sea Ice Modeling in the GISS GCM for Investigating Climate Change

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This project built on our previous results in which we highlighted the importance of sea ice in overall climate sensitivity by determining that for both warming and cooling climates, when sea ice was not allowed to change, climate sensitivity was reduced by 35-40%. We also modified the GISS 8 deg x lO deg atmospheric GCM to include an upper-ocean/sea-ice model involving the Semtner three-layer ice/snow thermodynamic model, the Price et al. (1986) ocean mixed layer model and a general upper ocean vertical advection/diffusion scheme for maintaining and fluxing properties across the pycnocline. This effort, in addition to improving the sea ice representation in the AGCM, revealed a number of sensitive components of the sea ice/ocean system. For example, the ability to flux heat through the ice/snow properly is critical in order to resolve the surface temperature properly, since small errors in this lead to unrestrained climate drift. The present project, summarized in this report, had as its objectives: (1) introducing a series of sea ice and ocean improvements aimed at overcoming remaining weaknesses in the GCM sea ice/ocean representation, and (2) performing a series of sensitivity experiments designed to evaluate the climate sensitivity of the revised model to both Antarctic and Arctic sea ice, determine the sensitivity of the climate response to initial ice distribution, and investigate the transient response to doubling CO2.

  2. Quantifying Precipitation Variability on Titan Using a GCM and Implications for Observed Geomorphology

    NASA Astrophysics Data System (ADS)

    Faulk, Sean P.; Mitchell, Jonathan L.; Moon, Seulgi; Lora, Juan Manuel

    2016-10-01

    Titan's zonal-mean precipitation behavior has been widely investigated using general circulation models (GCMs), but the spatial and temporal variability of rainfall in Titan's active hydrologic cycle is less well understood. We conduct statistical analyses of rainfall, diagnosed from GCM simulations of Titan's atmosphere, to determine storm intensity and frequency. Intense storms of methane have been proposed to be critical for enabling mechanical erosion of Titan's surface, as indicated by observations of dendritic valley networks. Using precipitation outputs from the Titan Atmospheric Model (TAM), a GCM shown to realistically simulate many features of Titan's atmosphere, we quantify the precipitation variability within eight separate latitude bins for a variety of initial surface liquid distributions. We find that while the overall wettest regions are indeed the poles, the most intense rainfall generally occurs in the high mid-latitudes, between 45-67.5 degrees, consistent with recent geomorphological observations of alluvial fans concentrated at those latitudes. We also find that precipitation rates necessary for surface erosion, as estimated by Perron et al. (2006) J. Geophys. Res. 111, E11001, frequently occur at all latitudes, with recurrence intervals of less than one Titan year. Such analysis is crucial towards understanding the complex interaction between Titan's atmosphere and surface and defining the influence of precipitation on observed geomorphology.

  3. Wavy structures of temperature and density in the polar thermosphere simulated by a whole atmosphere GCM

    NASA Astrophysics Data System (ADS)

    Fujiwara, Hitoshi; Miyoshi, Yasunobu

    Using a whole atmosphere general circulation model (GCM), which includes all the atmospheric regions from the ground to the exobase, we have performed numerical simulations to investigate generation mechanisms of wavy structures in the polar thermosphere during low solar and geomagnetically quiescent periods. Some observations showed existence of disturbances and waves in the upper thermosphere not only during geomagnetically active periods but also the quiescent conditions. Our previous simulations (Fujiwara and Miyoshi, 2006) also indicated that longitudinally-extent wavy structures were generated in the polar upper thermosphere, while wavy structures were found in the vicinity of the solar terminator in the mid-and low-latitude regions even when geomagnetically quiescent periods. In the present study, we discuss effects of the offset between the geographic and geomagnetic coordinates on producing the wavy structures in the vicinity of the auroral oval and the polar cap region. In addition, variations with periods of 2-3 hours due to atmospheric gravity waves, which would be originated in the lower atmosphere, were found in the polar upper thermosphere from the GCM simulations (Miyoshi and Fujiwara, 2008; Fujiwara and Miyoshi, 2010). The interactions between these wavy structures and disturbances due to the lower atmospheric effects are also discussed here.

  4. A GCM parameterization for the shortwave radiative properties of water clouds

    NASA Technical Reports Server (NTRS)

    Slingo, A.

    1990-01-01

    A new parameterization was developed for predicting the shortwave radiative properties of water clouds, suitable for inclusion in general circulation models (GCMs). The parameterization makes use of the simple relationships found by Slingo and Schrecker, giving the three input parameters required to calculate the cloud radiative properties (the optical depth, single scatter albedo and asymmetry parameter) in terms of the liquid water path and equivalent radius of the drop size distribution. The input parameters are then used to derive the cloud radiative properties, using standard two-stream equations for a single layer. The relationships were originally derived for fairly narrow spectral bands but it was found that it is possible to average the coefficients so as to use a much smaller number of bands, without sacrificing accuracy in calculating the cloud radiative properties. This makes the parameterization fast enough to be included in GCMs. The parameterization was programmed into the radiation scheme used in the U.K. Meteorological Office GCM. This scheme and the 24 band Slingo/Schrecker scheme were compared with each other and with observations, using a variety of published datasets. There is good agreement between the two schemes for both cloud albedo and absorption, even when only four spectral bands are employed in the GCM.

  5. Regional climate change predictions from the Goddard Institute for Space Studies high resolution GCM

    NASA Technical Reports Server (NTRS)

    Crane, Robert G.; Hewitson, Bruce

    1990-01-01

    Model simulations of global climate change are seen as an essential component of any program aimed at understanding human impact on the global environment. A major weakness of current general circulation models (GCMs), however, is their 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. This research is directed toward the development of a methodology for the validation of the synoptic scale climatology of GCMs. This is developed with regard to the Goddard Institute for Space Studies (GISS) GCM Model 2, with the specific objective of using the synoptic circulation form a doubles CO2 simulation to estimate regional climate change over North America, south of Hudson Bay. This progress report is specifically concerned with validating the synoptic climatology of the GISS GCM, and developing the transfer function to derive grid-point temperatures from the synoptic circulation. Principal Components Analysis is used to characterize the primary modes of the spatial and temporal variability in the observed and simulated climate, and the model validation is based on correlations between component loadings, and power spectral analysis of the component scores. The results show that the high resolution GISS model does an excellent job of simulating the synoptic circulation over the U.S., and that grid-point temperatures can be predicted with reasonable accuracy from the circulation patterns.

  6. Effect of altered boundary conditions on GCM studies of the climate of the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Hyde, William T.; Peltier, W. Richard

    1993-05-01

    Since publication of the paper by Bard et al. (1990) it has been known that GCM studies of the climate of the last glacial maximum (LGM), employed lower boundary conditions appropriate to this time but astronomical parameters of an era 3000 years later. The LGM boundary conditions from CLIMAP were for 18 kyr BP on the 14C timescale. The GCM simulations employed the insolation regime appropriate to 18 kyr BP on the sidereal timescale whereas the appropriate LGM insolation regime is that of 21 kyr BP. These studies also used the CLIMAP ice sheet reconstruction. However, on the basis of most recent analyses the reconstruction by Tushingham and Peltier (1991) is to be preferred. Hyde et al. (1989) showed that a simple EBM compared favourably with the NCAR CCM, when both were used to simulate the temperature distribution of the LGM. Here we shall employ the same EBM to study the effect on LGM climate of the timing mismatch, and of the different horizontal extents of the different ice sheet reconstructions. In each case the climatic effect is found to be significant. Thus we cannot claim an accurate LGM simulation unless the orbital and terrestrial inputs match to within 1,000 years and unless we employ the best possible ice sheet reconstruction in the analysis.

  7. Conductivities consistent with Birkeland currents in the AMPERE-driven TIE-GCM

    NASA Astrophysics Data System (ADS)

    Marsal, S.

    2015-09-01

    The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite mission has offered for the first time global snapshots of the geomagnetic field-aligned currents with unprecedented space and time resolution, thus providing an opportunity to feed an acknowledged first-principles model of the Earth's upper atmosphere such as the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR TIE-GCM). In the first step, Marsal et al. (2012) used AMPERE data in the current continuity equation between the magnetosphere and the ionosphere to drive the TIE-GCM electrodynamics. In the present work, ionospheric conductivities have been made consistent with enhanced upward field-aligned currents, which are assumed to correspond to electrons plunging as a result of downward acceleration by electric fields built up along the geomagnetic field lines. The resulting conductance distribution is reasonably commensurate with an independent model that has tried to quantify the ionizing effect of precipitating particles onto the auroral ionosphere. On the other hand, comparison of geomagnetic observatory data with the ground magnetic variations output by the model only shows a modest improvement with respect to our previous approach.

  8. An evaluation of the effects of cloud parameterization in the R42L9 GCM

    NASA Astrophysics Data System (ADS)

    Wu, Tongwen; Wang, Zaizhi; Liu, Yimin; Yu, Rucong; Wu, Guoxiong

    2004-04-01

    Cloud is one of the uncertainty factors influencing the performance of a general circulation model (GCM). Recently, the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP) has developed a new version of a GCM (R42L9). In this work, roles of cloud parameterization in the R42L9 are evaluated through a comparison between two 20-year simulations using different cloud schemes. One scheme is that the cloud in the model is diagnosed from relative humidity and vertical velocity, and the other one is that diagnostic cloud is replaced by retrieved cloud amount from the International Satellite Cloud Climatology Project (ISCCP), combined with the amounts of high-, middle-, and low-cloud and heights of the cloud base and top from the NCEP. The boreal winter and summer seasonal means, as well as the annual mean, of the simulated top-of-atmosphere shortwave radiative flux, surface energy fluxes, and precipitation are analyzed in comparison with the observational estimates and NCEP reanalysis data. The results show that the scheme of diagnostic cloud parameterization greatly contributes to model biases of radiative budget and precipitation. When our derived cloud fractions are used to replace the diagnostic cloud amount, the top-of-atmosphere and surface radiation fields are better estimated as well as the spatial pattern of precipitation. The simulations of the regional precipitation, especially over the equatorial Indian Ocean in winter and the Asia-western Pacific region in summer, are obviously improved.

  9. A New CO2 Transmittance Parameterization and Its Impact on the GLA GCM

    NASA Technical Reports Server (NTRS)

    Wobus, R.; Wui, M. L. C.; Susskind, J.

    1985-01-01

    The Wu-Kaplan radiation parameterization (Krishnamurthy, 1982) used in the GLA Global Circulation Model (GCM) was improved by replacing its fixed tables of CO2 transmittance in the 15 micron band with models developed by regression on line-by-line transmittances. The transmittances between layers are modeled as products of effective sublayer transmittances. The GLA GCM was integrated for 20 days starting at OZ, January 21, 1979, using the transmittance model. In the control run the fixed table of 15 micron CO2 transmittances is used. The effect of the change of initial cooling rate is illustrated by a map of the difference of 50 mb temperature after 6 hours. The cooling is reduced over high topography, where the fixed table underestimates the transmittance, and is reduced slightly throughout the tropics and the north polar area where the stratosphere is relatively cold. Over elevated topography the surface cooling increases, also as expected. The stratospheric temperature increases over a degree in the arctic and smaller amounts over Antarctica and elsewhere. Tropospheric equilibrium temperature response is obscured by time dependent differences in synoptic disturbances.

  10. Stationary eddies in the Mars general circulation as simulated by the NASA-Ames GCM

    NASA Technical Reports Server (NTRS)

    Barnes, J. R.; Pollack, J. B.; Haberle, Robert M.

    1993-01-01

    Quasistationary eddies are prominent in a large set of simulations of the Mars general circulation performed with the NASA-Ames GCM. Various spacecraft observations have at least hinted at the existence of such eddies in the Mars atmosphere. The GCM stationary eddies appear to be forced primarily by the large Mars topography, and (to a much lesser degree) by spatial variations in the surface albedo and thermal inertia. The stationary eddy circulations exhibit largest amplitudes at high altitudes (above 30-40 km) in the winter extratropical regions. In these regions they are of planetary scale, characterized largely by zonal wavenumbers 1 and 2. Southern Hemisphere winter appears to be dominated by a very strong wave 1 pattern, with both waves 1 and 2 being prominent in the Northern Hemisphere winter regime. This difference seems to be basically understandable in terms of differences in the topography in the two hemispheres. The stationary eddies in the northern winter extratropics are found to increase in amplitude with dust loading. This behavior appears to be at least partly associat