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1

Influence of atmospheric circulation on regional 14CO2 differences  

Microsoft Academic Search

Detailed analyses of published 14C data from tree rings and atmospheric CO2 samples for the northern tropics in Asia (India, Thailand, and Vietnam) and Africa (Ethiopia) have been performed for the heavily bomb-influenced period 1963–1967 A.D. The results show that the Asian summer monsoon and Intertropical Convergence Zone (ITCZ) position influenced atmospheric 14CO2 over the study area. Similar analyses of

Quan Hua; Mike Barbetti

2007-01-01

2

Influence of Uncertainty in Atmospheric Transport Modeling on Regional and Continental Scale Inversions  

NASA Astrophysics Data System (ADS)

Atmospheric transport modeling and its uncertainty play a crucial role in inversion studies with a goal to estimate fluxes of trace gases like carbon dioxide from available concentration measurements. Lagrangian particle models (e.g., CSU LPDM, STILT, FLEXPART) driven by regional meteorological models (e.g., WRF, RAMS) are state of the art tools in regional CO2 research including not only inversion studies, but also designing of tower network, or testing and supporting flight scenarios. They are typically used backward in time as an adjoint transport model providing, for each data point, influence functions (footprints) for surface fluxes and inflow fluxes across a domain perimeter. Modeling system used at CSU is based on SiB-RAMS (Regional Atmospheric Modeling System with Simple Biosphere model) providing meteorological fields for the LPDM (Lagrangian Particle Dispersion Model). Our LPDM can be run both in a forward and backward in time mode. Therefore, we recommend to use the comparison of forward and backward in time simulations as a method to evaluate internal model uncertainty. In addition the LPDM concentration fields can be compared to tracer concentrations simulated directly by RAMS, i.e. Eulerian grid model. We will discuss how simulated concentration fields, and in turn, the results of atmospheric inversions are affected by (1) model simplifications and optimizations, (2) time and space resolution of meteorological fields, and (3) selection of a domain for inversion study. The simulations are performed for the North America and smaller regional domains for a passive tracer and a tracers resulting from different CO2 fluxes (assimilation and respiration). Finally, we would like to propose a framework for inter comparison of different LPDMs coupled to regional meteorological models. This framework includes a sparse matrix format for influence functions to facilitate exchange and further applications of this product by different research groups.

Uliasz, M.; Schuh, A. E.

2011-12-01

3

Influence of sea-land breezes on the tempospatial distribution of atmospheric aerosols over coastal region.  

PubMed

The influence of sea-land breezes (SLBs) on the spatial distribution and temporal variation of particulate matter (PM) in the atmosphere was investigated over coastal Taiwan. PM was simultaneously sampled at inland and offshore locations during three intensive sampling periods. The intensive PM sampling protocol was continuously conducted over a 48-hr period. During this time, PM2.5 and PM(2.5-10) (PM with aerodynamic diameters < 2.5 microm and between 2.5 and 10 microm, respectively) were simultaneously measured with dichotomous samplers at four sites (two inland and two offshore sites) and PM10 (PM with aerodynamic diameters < or =10 microm) was measured with beta-ray monitors at these same 4 sites and at 10 sites of the Taiwan Air Quality Monitoring Network. PM sampling on a mobile air quality monitoring boat was further conducted along the coastline to collect offshore PM using a beta-ray monitor and a dichotomous sampler. Data obtained from the inland sites (n=12) and offshore sites (n=2) were applied to plot the PM10 concentration contour using Surfer software. This study also used a three-dimensional meteorological model (Pennsylvania State University/National Center for Atmospheric Research Meteorological Model 5) and the Comprehensive Air Quality Model with Extensions to simulate surface wind fields and spatial distribution of PM10 over the coastal region during the intensive sampling periods. Spatial distribution of PM10 concentration was further used in investigating the influence of SLBs on the transport of PM10 over the coastal region. Field measurement and model simulation results showed that PM10 was transported back and forth across the coastline. In particular, a high PM10 concentration was observed at the inland sites during the day because of sea breezes, whereas a high PM10 concentration was detected offshore at night because of land breezes. This study revealed that the accumulation of PM in the near-ocean region because of SLBs influenced the tempospatial distribution of PM10 over the coastal region. PMID:21516932

Tsai, Hsieh-Hung; Yuan, Chung-Shin; Hung, Chung-Hsuang; Lin, Chitsan; Lin, Yuan-Chung

2011-04-01

4

Local and Regional Influences on Atmospheric Nutrient Deposition in Southeast Brazil  

NASA Astrophysics Data System (ADS)

The objective of this work was to quantify sources of atmospheric nutrients, which are subsequently deposited to agricultural soils and natural ecosystems of São Paulo State (Brazil). The atmospheric concentrations of soluble ions (NO3-, NH4+, PO43-, SO42-, Cl-, K+, Na+, Mg2+ and Ca2+) in aerosol were evaluated, together with the gases NO2, NH3, HNO3 and SO2. Identification of nutrient sources was achieved using principal component analysis (PCA) followed by multiple linear regression analysis (MLRA). Dry deposition fluxes were estimated using the measured atmospheric concentrations together with dry deposition velocities of gases and aerosols to different surface types. Results showed that the main sources of nutrients to the regions atmosphere were fossil and biofuel combustion (N and S species), agricultural biomass burning (N, S, K and P), re-suspension of soils and dusts (Ca and Mg), and to a lesser extent long-range transport (S). NO2 concentrations were more influenced by local emissions and subsequent chemical transformations occurring on a scale of up to 200-300 km. HNO3 was much less spatially variable, with consistently higher concentrations during warmer, drier periods, indicating an agreement with gas phase/aerosol phase thermodynamic equilibrium theory. Scavenging of gaseous HNO3 was a source of nitrate, for which deposition fluxes were higher during the dry season, when significant relationships were obtained between nitrate concentrations and biomass burning intensity. Additional sources were indicated for particulate nitrate and sulphate, such as road transport and secondary reactions. During winter, the main source of gaseous ammonia was biomass burning, while emissions from soils and wastes predominated during summer. Modeled deposition fluxes were highest to tropical forest and lowest to water and pasture surfaces. In agricultural areas, the deposition fluxes of aerosol components N, P and K (0.37, 0.029 and 0.59 kg ha-1 yr-1, respectively) were equivalent to < 0.5 % of the amounts in fertilizer applied annually to plantations. Inclusion of gaseous dry deposition of nitrogen-containing compounds increased the total nitrogen flux by around 5 to 10-fold, depending on surface type.

Allen, A. G.; Machado, C. M.; Cardoso, A. A.

2009-05-01

5

Atmospheric circulation in regional climate models over Central Europe: links to surface air temperature and the influence of driving data  

NASA Astrophysics Data System (ADS)

We examine simulation of atmospheric circulation and links between circulation and daily surface air temperatures in current climate models over Central Europe. Large-scale atmospheric circulation is represented by circulation indices (flow direction, strength and vorticity) derived from mean sea level pressure. We explore control simulations of five 25-km resolution RCMs from the ENSEMBLES project, driven by the ERA-40 re-analysis and the ECHAM5 GCM, and runs of one RCM (RCA) driven by different GCMs. The driving GCMs are investigated as well. The models' performance is compared against the dataset gridded from a high-density stations network (temperature) and the ERA-40 re-analysis (pressure). The aims of the study are (i) to identify errors in simulated distributions of circulation indices in individual seasons, (ii) to identify errors in simulated temperatures under particular circulation indices in winter and summer, and (iii) to compare performance of individual RCMs with respect to the driving data. We find that most of the RCMs qualitatively reflect observed distributions of the airflow indices; however, each produces distributions significantly different from the observations. General biases include overestimation of the frequency of strong cyclonic vorticity and of strong flow days. HIRHAM driven by ECHAM5 and RCA driven by BCM are the RCMs with the most distorted atmospheric circulation. Our results show that some circulation biases obviously propagate from the driving data. For example, ECHAM5 and all simulations driven by ECHAM5 underestimate frequency of easterly flow. However, except for HIRHAM, all RCMs driven by ECHAM5 improve on the driving GCM in simulating atmospheric circulation. A set of RCA simulations with different driving data demonstrates that the influence on circulation characteristics in the nested RCM differs between GCMs. We find relatively strong relationships between circulation indices and surface air temperatures in the observed data for Central Europe. The RCMs qualitatively reproduce these relationships, which differ by season and are usually stronger for daily maxima than minima. Our results suggest that the RCM formulation appears to be more important than the driving data in representing the links to surface temperature. Differences of the circulation-to-temperature links among the RCA simulations are smaller and the links tend to be more realistic compared to the driving GCMs. Plavcová E., Kyselý J., 2012: Atmospheric circulation in regional climate models over Central Europe: links to surface air temperature and the influence of driving data. Climate Dynamics [10.1007/s00382-011-1278-8.

Plavcová, E.; Kyselý, J.

2012-04-01

6

Atmospheric circulation in regional climate models over Central Europe: links to surface air temperature and the influence of driving data  

NASA Astrophysics Data System (ADS)

The study examines simulation of atmospheric circulation, represented by circulation indices (flow direction, strength and vorticity), and links between circulation and daily surface air temperatures in regional climate models (RCMs) over Central Europe. We explore control simulations of five high-resolution RCMs from the ENSEMBLES project driven by re-analysis (ERA-40) and the same global climate model (ECHAM5 GCM) plus of one RCM (RCA) driven by different GCMs. The aims are to (1) identify errors in RCM-simulated distributions of circulation indices in individual seasons, (2) identify errors in simulated temperatures under particular circulation indices, and (3) compare performance of individual RCMs with respect to the driving data. Although most of the RCMs qualitatively reflect observed distributions of the airflow indices, each produces distributions significantly different from the observations. General biases include overestimation of the frequency of strong flow days and of strong cyclonic vorticity. Some circulation biases obviously propagate from the driving data. ECHAM5 and all simulations driven by ECHAM5 underestimate frequency of easterly flow, mainly in summer. Except for HIRHAM, however, all RCMs driven by ECHAM5 improve on the driving GCM in simulating atmospheric circulation. The influence on circulation characteristics in the nested RCM differs between GCMs, as demonstrated in a set of RCA simulations with different driving data. The driving data control on circulation in RCA is particularly weak for the BCM GCM, in which case RCA substantially modifies (but does not improve) the circulation from the driving data in both winter and summer. Those RCMs with the most distorted atmospheric circulation are HIRHAM driven by ECHAM5 and RCA driven by BCM. Relatively strong relationships between circulation indices and surface air temperatures were found in the observed data for Central Europe. The links differ by season and are usually stronger for daily maxima than minima. RCMs qualitatively reproduce these relationships. Effects of the driving model biases were found on RCMs' performance in reproducing not only atmospheric circulation but also the links to surface temperature. However, the RCM formulation appears to be more important than the driving data in representing the latter. Differences of the circulation-to-temperature links among the RCA simulations are smaller and the links tend to be more realistic compared to the driving GCMs.

Plavcová, Eva; Kyselý, Jan

2012-10-01

7

Indonesian peat and vegetation fire emissions: Study on factors influencing large-scale smoke haze pollution using a regional atmospheric chemistry model  

Microsoft Academic Search

Numerical modelling of fire-related smoke haze episodes in Southeast Asia is important for both prediction and assessment\\u000a of atmospheric impacts, especially when observational data are fragmentary, as is the case in Indonesia. This work describes\\u000a the atmospheric fate of smoke particles emitted during the 1997 Indonesian fires modelled with a regional atmospheric chemistry\\u000a model. We established a new fire emission

A. Heil; B. Langmann; E. Aldrian

2007-01-01

8

Regional Ecosystem-Atmosphere CO2 Exchange Via Atmospheric Budgets  

SciTech Connect

Inversions of atmospheric CO2 mixing ratio measurements to determine CO2 sources and sinks are typically limited to coarse spatial and temporal resolution. This limits our ability to evaluate efforts to upscale chamber- and stand-level CO2 flux measurements to regional scales, where coherent climate and ecosystem mechanisms govern the carbon cycle. As a step towards the goal of implementing atmospheric budget or inversion methodology on a regional scale, a network of five relatively inexpensive CO2 mixing ratio measurement systems was deployed on towers in northern Wisconsin. Four systems were distributed on a circle of roughly 150-km radius, surrounding one centrally located system at the WLEF tower near Park Falls, WI. All measurements were taken at a height of 76 m AGL. The systems used single-cell infrared CO2 analyzers (Licor, model LI-820) rather than the siginificantly more costly two-cell models, and were calibrated every two hours using four samples known to within ± 0.2 ppm CO2. Tests prior to deployment in which the systems sampled the same air indicate the precision of the systems to be better than ± 0.3 ppm and the accuracy, based on the difference between the daily mean of one system and a co-located NOAA-ESRL system, is consistently better than ± 0.3 ppm. We demonstrate the utility of the network in two ways. We interpret regional CO2 differences using a Lagrangian parcel approach. The difference in the CO2 mixing ratios across the network is at least 2?3 ppm, which is large compared to the accuracy and precision of the systems. Fluxes estimated assuming Lagrangian parcel transport are of the same sign and magnitude as eddy-covariance flux measurements at the centrally-located WLEF tower. These results indicate that the network will be useful in a full inversion model. Second, we present a case study involving a frontal passage through the region. The progression of a front across the network is evident; changes as large as four ppm in one minute are captured. Influence functions, derived using a Lagrangian Particle Dispersion model driven by the CSU Regional Atmospheric Modeling System and nudged to NCEP reanalysis meteorological fields, are used to determine source regions for the towers. The influence functions are combined with satellite vegetation observations to interpret the observed trends in CO2 concentration. Full inversions will combine these elements in a more formal analytic framework.

Davis, K.J.; Richardson, S.J.; Miles, N.L.

2007-03-07

9

Influence of the Antarctic ozone hole on the polar mesopause region as simulated by the Canadian Middle Atmosphere Model  

NASA Astrophysics Data System (ADS)

It is well established that variations in polar stratospheric winds can affect mesospheric temperatures through changes in the filtering of gravity wave fluxes, which drive a residual circulation in the mesosphere. The Canadian Middle Atmosphere Model (CMAM) is used to examine this vertical coupling mechanism in the context of the mesospheric response to the Antarctic ozone hole. It is found that the response differs significantly between late spring and early summer, because of a changing balance between the competing effects of parametrised gravity wave drag (GWD) and changes in resolved wave drag local to the mesosphere. In late spring, the strengthened stratospheric westerlies arising from the ozone hole lead to reduced eastward GWD in the mesosphere and a warming of the polar mesosphere, just as in the well known mesospheric response to sudden stratospheric warmings, but with an opposite sign. In early summer, with easterly flow prevailing over most of the polar stratosphere, the strengthened easterly wind shear within the mesosphere arising from the westward GWD anomaly induces a positive resolved wave drag anomaly through baroclinic instability. The polar cooling induced by this process completely dominates the upper mesospheric response to the ozone hole in early summer. Consequences for the past and future evolution of noctilucent clouds are discussed.

Lossow, Stefan; McLandress, Charles; Jonsson, Andreas I.; Shepherd, Theodore G.

2012-01-01

10

Influence of the orographic roughness of glacier valleys across the Transantarctic Mountains in an atmospheric regional model  

Microsoft Academic Search

Glacier valleys across the Transantarctic Mountains are not properly taken into account in climate models, because of their\\u000a coarse resolution. Nonetheless, glacier valleys control katabatic winds in this region, and the latter are thought to affect\\u000a the climate of the Ross Sea sector, frsater formation to snow mass balance. The purpose of this paper is to investigate the\\u000a role of

Nicolas C. Jourdain; Hubert Gallée

2011-01-01

11

Future surface mass balance of the Antarctic ice sheet and its influence on sea level change, simulated by a regional atmospheric climate model  

NASA Astrophysics Data System (ADS)

A regional atmospheric climate model with multi-layer snow module (RACMO2) is forced at the lateral boundaries by global climate model (GCM) data to assess the future climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS). Two different GCMs (ECHAM5 until 2100 and HadCM3 until 2200) and two different emission scenarios (A1B and E1) are used as forcing to capture a realistic range in future climate states. Simulated ice sheet averaged 2 m air temperature (T2m) increases (1.8-3.0 K in 2100 and 2.4-5.3 K in 2200), simultaneously and with the same magnitude as GCM simulated T2m. The SMB and its components increase in magnitude, as they are directly influenced by the temperature increase. Changes in atmospheric circulation around Antarctica play a minor role in future SMB changes. During the next two centuries, the projected increase in liquid water flux from rainfall and snowmelt, together 60-200 Gt year-1, will mostly refreeze in the snow pack, so runoff remains small (10-40 Gt year-1). Sublimation increases by 25-50 %, but remains an order of magnitude smaller than snowfall. The increase in snowfall mainly determines future changes in SMB on the AIS: 6-16 % in 2100 and 8-25 % in 2200. Without any ice dynamical response, this would result in an eustatic sea level drop of 20-43 mm in 2100 and 73-163 mm in 2200, compared to the twentieth century. Averaged over the AIS, a strong relation between UpdeltaSMB and Updelta{T}_{2m} of 98 ± 5 Gt w.e. year-1 K-1 is found.

Ligtenberg, S. R. M.; van de Berg, W. J.; van den Broeke, M. R.; Rae, J. G. L.; van Meijgaard, E.

2013-04-01

12

Metal contamination and health risk from consumption of organically grown vegetables influenced by atmospheric deposition in a seasonally dry tropical region of India.  

PubMed

Pot-culture experiments showed that organically grown Vicia faba, influenced by atmospheric deposition, accumulated (?g g(-1)) 0.088-3.246 Cadmium, 0.19-42.48 Chromium, 0.0124-30.43 Copper, 0.075-4.28 Lead and 0.63-67.68 Zinc. Similar trends appeared for Abelmoschus esculentus. At high deposition sites, Cadmium, Lead and Zinc exceeded the safe limits of Prevention of Food Adulteration standards. Health risk index for Cadmium, Copper and Lead exceeded the safe limits of United States Environmental Protection Agency. The study suggests that atmospheric deposition could substantially elevate metal levels in organically grown vegetables in 2011. PMID:22653308

Singh, Ashima; Pandey, Jitendra

2012-06-01

13

Influence of temperature, moisture, and organic carbon on the flux of H2 and CO between soil and atmosphere: Field studies in subtropical regions  

Microsoft Academic Search

Production and deposition rates of atmospheric hydrogen and carbon monoxide were studied during field measurements in subtropical regions, i.e., Transvaal (South Africa), Andalusia (Spain), and the Karoo (South Africa). Measurements were carried out by applying static and equilibrium box techniques. The equilibrium technique has been introduced as a novel method to measure production and destruction rates simultaneously even when soil

Ralf Conrad; Wolfgang Seiler

1985-01-01

14

A Regional Modeling Study of the Influence of Urban Land Cover Change on the Lower Atmosphere in Baltimore-Washington DC  

NASA Astrophysics Data System (ADS)

The land-use and land cover (LULC) history of the Baltimore-Washington region has been intensively studied through a variety of environmental research collaborations and regional partnerships. One such partnership, the Baltimore-Washington Regional Collaboratory, involved multiple Federal and local agencies cooperating on a 200-year urban growth study in the Chesapeake region. Information from this study on pre-1900 and current LULC conditions for the Baltimore-Washington DC area was integrated with data from other sources to construct different lower boundary conditions for a series of simulations using the Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS). We use the RAMS simulations to diagnose the extent and nature of the effect of urban anomalies in surface heat, moisture, and momentum on mid-summer local and regional climate. The experimental design adopted for this study takes advantage of the grid-nesting capability of RAMS. A fine grid with 1km horizontal resolution was nested into a coarser 5 km grid, which extends from southern Pennsylvania, Maryland, to parts of Virginia, and West Virginia. Two sets of month-long simulations for July 2000 were conducted with RAMS running in parallel on a 26-processor cluster of computers at the Cooperative Institute for Research in the Atmosphere (CIRA), CSU. In the first set of simulations, we initially used satellite-derived current land cover data as the lower boundary condition in a 31-day RAMS run. We then replaced this data with the pre-1900 land cover data for the same region and ran a similar RAMS simulation. Identical observed meteorology was retained for the lateral boundary conditions in both cases. The model results for the initial run were validated with July 2000 surface climate data and flux measurements of sensible and latent heat from sites located within the fine grid model domain. Additional simulations were conducted to compare RAMS model performance using prescribed land surface conditions with results from a physically based scheme for urban energy budget coupled to RAMS. The urban surface scheme used here is the Town Energy Budget (TEB) model recently developed at the Center for Meteorological Research (CNRM), France. The TEB model allows for a refinement of model computed radiative budgets, heat and momentum based on a generalization of the classic canyon approach. Results from both sets of simulations, and the implications, for surface climate, of the driving human-induced land cover transformations are discussed.

Adegoke, J.; Gallo, K.; Pielke, R.; Rozoff, C.; Steyaert, L.

2001-12-01

15

Distribution of atmospheric methane concentration over different tectonic regions  

NASA Astrophysics Data System (ADS)

Measurements of atmospheric methane concentrations were made over the territories of Donetsk and Rostov Oblasts, Krasnodarsk Kray, the Uzbek, Kazakh, Turkmen, Azerbaijan, Georgian and Armenian republics. About 400 measurements were made at altitudes of 50 to 5,000 m. With transition from geosynclinal regions to ancient platforms there is a distinct decrease in methane concentration in the lower layers, attributable to different geological and tectonic conditions for the migration of methane into the atmosphere. Ancient platforms are tectonically quiet and subvertical migration processes are difficult. In geosynclinal regions there are favorable conditions for the subvertical migration of lithospheric gases due to the revival of existing and appearance of new fractures, dislocations and faults. The data demonstrated a definite influence of geotectonic conditions on formation of the atmospheric methane field. There is a distinct relationship between atmospheric methane concentration and the presence of petroleum- and gas-bearing structures beneath the Earth's surface. The geotectonic factor exerts an influence on methane concentration to the level 2,000 to 2,500 m. The presence of petroleum and gas in the underlying geological formations is reflected only in the lower layers of the atmosphere (up to 50 to 150 m).

Stadnik, Ye. V.; Sklyarenko, I. Ya.; Guliyev, I. S.; Feyzullayev, A. A.

1987-03-01

16

Global and regional environmental atmospheric chemistry  

SciTech Connect

More than two hundred fifty scientists from eighteen different countries attended the first International Conference on Global and Regional Environmental Atmospheric Chemistry in the Science Hall of Friendship Hotel at Beijing, May 3--10, 1989. This volume documents the proceedings of this historical event. Following the meeting, some 173 papers were submitted for this publication. When follow up papers were not submitted the original abstract is presented. Also included are abstracts of the posters presented by the Chinese participants who could not be accommodated during the more formal sessions. We might add that this more informal session was particularly useful for the exchange of ideas and information between east and west. Indeed, the conference overall certainly provided an enthusiastic platform for interactions among scientists from around the world. It is our hope that these proceedings will serve as a vehicle to further enhance collaboration for joint studies of the changes in the global environment.

Newman, L. (Brookhaven National Lab., Upton, NY (USA)); Wang, Wenxing (Chinese Research Academy of Environmental Science, Beijing (China)); Kiang, C.S. (Georgia Inst. of Tech., Atlanta, GA (USA). Div. of Atmospheric Science)

1990-08-01

17

Variability Of Atmospheric Water Vapor In The Martian Polar Regions  

NASA Astrophysics Data System (ADS)

We present analysis of spatial and temporal variability of water vapor in the Mars Northern Polar Region (NPR) during spring and summer seasons using data from Vikings and MGS missions. This study provides a new level of detail on the Martian water vapor cycle relative to the previous longitudinally averaged studies. We also present new water vapor retrievals extending MGS dataset over the North polar cap. Water vapor spatial distribution in the NPR evolves on short temporal (several sols) and small spatial (100 km) scales indicating complex interactions between surface/subsurface water ice and atmosphere. Similar average NPR abundances correspond to very different spatial patterns. Water vapor abundances observed by Vikings exceed MGS abundances by a factor of 2 during early summer, suggesting long term interannual variability of Martian polar water cycle. On the other hand, the difference between Viking and MGS observations may potentially be reconciled if water vapor is distributed non-uniformly with height, concentrating near surface. A reanalysis of Viking water vapor retrievals may be warranted. Much of the water vapor observed by Vikings during summer comes from the permanent polar cap, contrary to the earliest conclusion of the regolith being the main source. High degree of correlation between water vapor distribution and surface topography is probably due to interaction between mesoscale circulation and surface topography. Outbursts of water vapor are observed in late spring and summer, suggesting that water ice sublimation rates could be highly variable across the water ice cap, and strongly influenced by atmospheric circulation. Correlation between MGS water vapor and dust spatial distributions in NPR suggests sublimation winds as the source of both water vapor and dust in the atmosphere in late spring and summer. A historic record of the atmospheric water vapor at the Phoenix landing site is provided for comparison with ongoing observations.

Pankine, Alexey A.; Tamppari, L. K.

2008-09-01

18

REGIONAL-SCALE ATMOSPHERIC MERCURY MODELING  

EPA Science Inventory

This PowerPoint presentation gives a short synopsis of the state of the science of atmospheric mercury modeling, including a description of recent publications of model codes by EPA, a description of a recent mercury model intercomparison study, and a description of a synthesis p...

19

Atmospheric Chemistry: Response to Human Influence  

Microsoft Academic Search

Present understanding of global atmospheric chemistry is reviewed. Models are presented and compared with a wide range of atmospheric observations, with emphasis on the stratosphere. In general, excellent agreement is found between the calculated and observed distributions of long lived trace gases. The abundances of many shorter lived species are also satisfactorily reproduced, including NO2, HNO3, O, O3, OH and

Jennifer A. Logan; M. J. Prather; S. C. Wofsy; M. B. McElroy

1978-01-01

20

Volcanic influences on the atmospheric methane budget  

Microsoft Academic Search

It is well known that volcanic gases can pollute the atmosphere. Certain volcanic gases can produce biogeochemical effects that lead to an indirect volcanic effect on the atmosphere. Microbially mediated emission of CH4 from wetlands can be reduced as a result of SO4-- deposition by stimulating competitive exclusion of methanogens by sulfate reducing microorganisms. Hence, a large emission of volcanic

V. Gauci; S. Blake; D. Stevenson

2003-01-01

21

Atmospheric moisture's influence on fire behavior: surface moisture ...  

Treesearch

Title: Atmospheric moisture's influence on fire behavior: surface moisture and ... dew point temperature, dew point depression, wet bulb temperature and wet bulb ... a modified version of the same quantity) are also tested for the same fire data.

22

Research on atmospheric turbulence's influence on active laser reconnaissance  

NASA Astrophysics Data System (ADS)

In order to study the atmospheric turbulence's influence on active laser reconnaissance, a theoretical model of cat-eye system illuminated by Gaussian-beam which propagates through atmospheric turbulence over a long distance was constructed. The mean irradiance and the scintillation index were calculated under the Rytov approximation. The theoretical analysis and numerical simulation results indicate that the mean irradiance and scintillation index of the active laser reconnaissance echo influenced by atmospheric turbulence are both increased near the optical axis. Experiment was carried out to validate the theoretical analysis results and the experimental results are shown to be in good agreement with the theoretical predictions.

Dou, Xian-An; Zhang, Chuang-Xin; Sun, Xiao-Quan; Shao, Li; Tong, Zhong-Cheng

2009-07-01

23

Ocean-atmosphere coupling over monsoon regions  

Microsoft Academic Search

In monsoon regions, the seasonal migration of the intertropical convergence zone (ITCZ) is manifested as a seasonal reversal of winds. Most of the summer monsoon rainfall over India occurs owing to synoptic and large-scale convection associated with the continental ITCZ (Fig. 1). We have investigated the interaction between these large-scale convective systems and the ocean over which they are generated1-3,

Sulochana Gadgil; P. V. Joseph; N. V. Joshi

1984-01-01

24

Pesticides in the Atmosphere: Current Understanding of Distribution and Major Influences  

USGS Publications Warehouse

This report summarizes a comprehensive analysis of existing information on national and regional patterns of pesticides in the atmosphere and major influences on their sources and transport. It is one of a four-part series that synthesizes current knowledge and understanding of pesticides in water resources of the nation as part of the National Water-Quality Assessment.

Geological Survey (U.S.)

1995-01-01

25

Influence of solar activity on the lower atmosphere state  

NASA Astrophysics Data System (ADS)

This paper briefly reviews modern ideas about plausible mechanisms of influence of solar activity on the lower atmosphere state and weather. The possible reasons for the disturbances in the lower atmosphere are as follows: (1) variations in solar irradiance, (2) changes in the global electric circuit parameters caused by variations in cosmic ray fluxes, (3) variations in the conditions of propagation and dissipation energy of planetary waves in the atmosphere, and (4) changes in the atmospheric transparency and cloudiness are considered. Specific features of development of individual (with duration of several days) disturbances in the lower atmosphere observed during Forbush decreases of galactic cosmic rays and solar proton events are discussed. It is concluded that at latitudes of 55o-70o the disturbances considered are mainly due to variations in atmospheric transparency and cloudiness. Data on cyclic variations of the lower atmosphere state and their connection with variations in solar activity, atmospheric transparency, volcano eruptions, and other geophysical phenomena are analyzed. In conclusion, some unresolved problems of morphology of atmospheric disturbances are formulated.

Pudovkin, M. I.

2004-12-01

26

Regional atmospheric composition modeling with CHIMERE  

NASA Astrophysics Data System (ADS)

Tropospheric trace gas and aerosol pollutants have adverse effects on health, environment and climate. In order to quantify and mitigate such effects, a wide range of processes leading to the formation and transport of pollutants must be considered, understood and represented in numerical models. Regional scale pollution episodes result from the combination of several factors: high emissions (from anthropogenic or natural sources), stagnant meteorological conditions, velocity and efficiency of the chemistry and the deposition. All these processes are highly variable in time and space, and their relative importance to the pollutants budgets can be quantified within a chemistry-transport models (CTM). The offline CTM CHIMERE model uses meteorological model fields and emissions fluxes and calculates deterministically their behavior in the troposphere. The calculated three-dimensional fields of chemical concentrations can be compared to measurements to analyze past periods or used to make air quality forecasts and CHIMERE has enabled a fine understanding of pollutants transport during numerous measurements campaigns. It is a part of the PREVAIR french national forecast platform, delivering pollutant concentrations up to three days in advance. The model also allows scenario studies and long term simulations for pollution trends. The modelling of photochemical air pollution has reached a good level of maturity, and the latest projects involving CHIMERE now aim at increasing our understanding of pollution impact on health at the urban scale or at the other end of the spectrum for long term air quality and climate change interlinkage studies, quantifying the emissions and transport of pollen, but also, at a larger scale, analyzing the transport of pollutants plumes emitted by volcanic eruptions and forest fires.

Menut, L.; Bessagnet, B.; Khvorostyanov, D.; Beekmann, M.; Colette, A.; Coll, I.; Curci, G.; Foret, G.; Hodzic, A.; Mailler, S.; Meleux, F.; Monge, J.-L.; Pison, I.; Turquety, S.; Valari, M.; Vautard, R.; Vivanco, M. G.

2013-01-01

27

The interplanetary magnetic field influences mid-latitude surface atmospheric pressure  

NASA Astrophysics Data System (ADS)

The existence of a meteorological response in the polar regions to fluctuations in the interplanetary magnetic field (IMF) component By is well established. More controversially, there is evidence to suggest that this Sun-weather coupling occurs via the global atmospheric electric circuit. Consequently, it has been assumed that the effect is maximized at high latitudes and is negligible at low and mid-latitudes, because the perturbation by the IMF is concentrated in the polar regions. We demonstrate a previously unrecognized influence of the IMF By on mid-latitude surface pressure. The difference between the mean surface pressures during times of high positive and high negative IMF By possesses a statistically significant mid-latitude wave structure similar to atmospheric Rossby waves. Our results show that a mechanism that is known to produce atmospheric responses to the IMF in the polar regions is also able to modulate pre-existing weather patterns at mid-latitudes. We suggest the mechanism for this from conventional meteorology. The amplitude of the effect is comparable to typical initial analysis uncertainties in ensemble numerical weather prediction. Thus, a relatively localized small-amplitude solar influence on the upper atmosphere could have an important effect, via the nonlinear evolution of atmospheric dynamics, on critical atmospheric processes.

Lam, M. M.; Chisham, G.; Freeman, M. P.

2013-12-01

28

Preface: Subsurface, surface and atmospheric processes in cold regions hydrology  

Technology Transfer Automated Retrieval System (TEKTRAN)

This special section presents papers from three sessions at the 24th General Assembly of the International Union of Geodesy and Geophysics (IUGG), held in Perugia, Italy, in July 2007: ‘Interactions between snow, vegetation and the atmosphere’, ‘Hydrology in mountain regions’ and ‘Climate-permafrost...

29

Atmospheric measurements of water vapor in the 442-nm region  

Microsoft Academic Search

In recent years much interest has been generated in the atmospheric community concerning low resolution water vapor cross sections in the blue spectral region. Proper removal of water absorption from long path tropospheric and zenith sky stratospheric measurements has posed a significant problem for recovery of absorption spectra of low concentration molecular species which overlap the water vapor spectrum. The

J. W. Harder; J. W. Brault

1997-01-01

30

The Influence of Atmospheric Stability on Potential Evaporation  

Microsoft Academic Search

The Penman relationship for potential evaporation is modified to simply include the influence of atmospheric stability on turbulent transport of water vapor. Explicit expressions for the stability-dependent, surface exchange coefficient developed by Louis are used. The diurnal variation of potential evaporation is computed for the stability-dependent and original Penman relationships using Wangara data.The influence of afternoon instability increases the aerodynamic

L. Mahrt; Michael Ek

1984-01-01

31

Identifying human influences on atmospheric temperature  

PubMed Central

We perform a multimodel detection and attribution study with climate model simulation output and satellite-based measurements of tropospheric and stratospheric temperature change. We use simulation output from 20 climate models participating in phase 5 of the Coupled Model Intercomparison Project. This multimodel archive provides estimates of the signal pattern in response to combined anthropogenic and natural external forcing (the fingerprint) and the noise of internally generated variability. Using these estimates, we calculate signal-to-noise (S/N) ratios to quantify the strength of the fingerprint in the observations relative to fingerprint strength in natural climate noise. For changes in lower stratospheric temperature between 1979 and 2011, S/N ratios vary from 26 to 36, depending on the choice of observational dataset. In the lower troposphere, the fingerprint strength in observations is smaller, but S/N ratios are still significant at the 1% level or better, and range from three to eight. We find no evidence that these ratios are spuriously inflated by model variability errors. After removing all global mean signals, model fingerprints remain identifiable in 70% of the tests involving tropospheric temperature changes. Despite such agreement in the large-scale features of model and observed geographical patterns of atmospheric temperature change, most models do not replicate the size of the observed changes. On average, the models analyzed underestimate the observed cooling of the lower stratosphere and overestimate the warming of the troposphere. Although the precise causes of such differences are unclear, model biases in lower stratospheric temperature trends are likely to be reduced by more realistic treatment of stratospheric ozone depletion and volcanic aerosol forcing.

Santer, Benjamin D.; Painter, Jeffrey F.; Mears, Carl A.; Doutriaux, Charles; Caldwell, Peter; Arblaster, Julie M.; Cameron-Smith, Philip J.; Gillett, Nathan P.; Gleckler, Peter J.; Lanzante, John; Perlwitz, Judith; Solomon, Susan; Stott, Peter A.; Taylor, Karl E.; Terray, Laurent; Thorne, Peter W.; Wehner, Michael F.; Wentz, Frank J.; Wigley, Tom M. L.; Wilcox, Laura J.; Zou, Cheng-Zhi

2013-01-01

32

Influence of atmospheric circulation variations on the ozone layer  

Microsoft Academic Search

This paper reviews results related to the influence of long?term changes of the atmospheric wave activity and circulation on the ozone layer, in particular on the Antarctic ozone hole in 2002. These results provide evidence that an important role is played by natural factors in the ozone layer changes, together with the known anthropogenic impacts. Specifically, these factors are connected

E. A. Jadin; K. Y. A. Kondratyev; V. I. Bekoryukov; P. N. Vargin

2005-01-01

33

Regional-scale atmospheric inversions of greenhouse gas fluxes in Europe  

Microsoft Academic Search

Estimating regional-scale surface fluxes of long-lived trace gases from atmospheric concentration measurements requires the use of a high-resolution inversion system capable of accounting for small-scale variability in fluxes and transport within the domain as well as large-scale influences penetrating the domain through the lateral boundaries. High-resolution inversions on global scale are, however, not feasible with present-day computing capabilities. Therefore a

U. Karstens; C. Roedenbeck; K. Trusilova; C. Gerbig; M. Heimann

2010-01-01

34

Regional differences in worldwide emissions of mercury to the atmosphere  

Microsoft Academic Search

Annual emissions of anthropogenic Hg to the atmosphere in different regions of the world during the last decade show an interesting dichotomy: the emissions in the developed countries increased at the rate of about 4.5–5.5% yr?1 up to 1989 and have since remained nearly constant, while in developing countries the emissions continue to rise steadily at the rate of 2.7–4.5%

Nicola Pirrone; Gerald J. Keeler; Jerome O. Nriagu

1996-01-01

35

The influence of variations of vegetation and soil moisture on surface weather and atmospheric circulation  

SciTech Connect

The influence of variations of vegetation and soil moisture on surface weather and atmospheric circulation is studied through the use of the Simple Biosphere Model (SiB) and the Center for Ocean-Land-Atmosphere interactions (COLA) GCM. Tests for the SiB sensitivity to the conversion of the forest to other short vegetation or bare soil were performed at Amazonian and Great Plains sites, and a North Wales spruce forest site respectively. The results show that deforestation has a significant influence on the local surface energy budget and surface weather. The influence is especially prominent at the Amazon and Great Plains sites, and larger in summer than in other seasons. The influence on the partitioning of surface incoming radiative energy is generally constrained by the local atmospheric boundary condition. The sensitivity of the COLA GCM to changes in initial soil wetness (ISW) is determined by repeating three 10-day model integrations with the same initial and boundary conditions as the control runs except the values of ISW, which are revised at 69 model grid points covering much of the continental U.S. It is found that the relations between the changes in the 5-day mean forecast surface air temperature/surface specific humidity and the changes in ISW depend upon vegetation type and the values of ISW, and can be approximated by regression equations. These relations are also confirmed with independent data. With the ISW revised based on these regression equations the surface forecasts of the revised runs are consistently improved. The spatial scale of the ISW anomaly determines the degree and range of the influence. The influence of a small regional ISW change is mainly confined to the local region and to low atmospheric levels. The influence on surface fluxes is strong and persists for more than one month, but the effects on precipitation are relatively weak, changeable, and complex, particularly when an interactive cloud scheme is used.

Yang, R.

1992-01-01

36

The interplanetary magnetic field influences middle-latitude surface atmospheric pressure  

NASA Astrophysics Data System (ADS)

Results have been published over several decades that indicate a meteorological response in the polar regions to fluctuations in the east-west component of the interplanetary magnetic field (IMF), By. There is evidence that this Sun-weather coupling occurs via the global atmospheric electric field. It has been assumed that the effect maximises at high latitudes and is negligible at low and mid latitudes because the IMF-induced convection electric field is concentrated in the polar ionospheres. However, the spatial variation of the IMF-weather coupling has not previously been investigated in detail, neither have the global consequences of such forcing on the atmosphere. Here we demonstrate a previously unrecognised influence of IMF By on mid-latitude surface pressure. The difference between the mean surface pressure for high positive and high negative values of IMF By possesses a statistically-significant mid-latitude wave structure, similar in location and form to the cyclones and anti-cyclones produced by the action of atmospheric Rossby waves on the jet stream. Thus our results indicate that a mechanism that is known to produce atmospheric responses to the IMF in the polar regions is also able to modulate pre-existing weather patterns at mid-latitudes. A relatively localised and small amplitude solar influence on the upper atmosphere could therefore have an important effect, via the nonlinear evolution of storm tracks, on critical processes such as European climate and the breakup of Arctic sea ice.

Lam, Mai Mai; Chisham, Gareth; Freeman, Mervyn

2013-04-01

37

Studying the hydrological cycle in the Iberian Peninsula using the LEAFHYDRO LSM: Influence of groundwater dynamics on soil moisture and land-atmosphere coupling. Impacts of artificial water extraction in the regional water cycle, including land-surface f  

NASA Astrophysics Data System (ADS)

We perform long-term (10 year) simulations over the Iberian Peninsula at 2.5 km resolution with the LEAFHYDRO LSM, which includes groundwater dynamics and river routing. Atmospheric forcing comes from ERA-interim and a regional high-resolution analysis of precipitation over Spain and Portugal. The model simulates the coupled evolution of the groundwater, land surface (soil moisture and vegetation) and river reservoirs and we validate the simulation with all available observations of river flow and water table depth. In an experiment, we impose an artificial water extraction rate from the groundwater reservoir based on observations and estimations of irrigation withdrawals and we investigate the impact on the regional water cycle. The extraction rates induce a depression of the water table that over the years becomes quite significant and that matches observed decreasing rates of water table levels. The depressed water table discontinues groundwater input into rivers and the stream flow is diminished notably, in particular during the dry summer. Moreover, in areas with semiarid climate where the water table was naturally relatively shallow and connected to soil moisture and vegetation, which include most of the agricultural areas inland Spain, the depression of the water table has a significant impact on soil moisture and land-surface fluxes, with a decrease of root zone soil water availability and evapotranspiration and increasing water stress for the vegetation. The land hydrology alteration is more pronounced in the summer when there is an absence of precipitation, and as the model shows, through the induced changes in land-surface fluxes can potentially have a noticeably impact on the regional climate.

Martinez, A.; Miguez-Macho, G.

2012-04-01

38

Critical review of studies on atmospheric dispersion in coastal regions  

SciTech Connect

This study effort was required as a preliminary step prior to initiation of field measurements of atmospheric dispersion in coastal regions. The Nuclear Regulatory Commission (NRC) is in the process of planning an extensive field measurement program to generate data which will serve as improved data bases for licensing decisions, confirmation of regulations, standards, and guides, and for site characterizations. The study being reported here is an effort directed to obtaining as much information as is possible from existing studies that is relevant toward NRC's objectives. For this study, reports covering research and meteorological measurements conducted for industrial purposes, utility needs, military objectives, and academic studies were obtained and critically reviewed in light of NRC's current data needs. This report provides an interpretation of the extent of existing usable information, an indication of the potential for tailoring existing research toward current NRC information needs, and recommendations for several follow-on studies which could provide valuable additional information through reanalysis of the data. Recommendations are also offered regarding new measurement programs. Emphasis is placed on the identification and acquisition of data from atmospheric tracer studies conducted in coastal regions. A total of 225 references were identified which deal with the coastal atmosphere, including meteorological and tracer measurement programs, theoretical descriptions of the relevant processes, and dispersion models.

Shearer, D.L.; Kaleel, R.J.

1982-09-01

39

Spatial variability in large-scale and regional atmospheric drivers of Pinus halepensis growth in eastern Spain  

Microsoft Academic Search

In this study we analyzed the influence of general atmospheric circulation patterns and the frequency of weather types on the spatio-temporal variability of tree-ring growth in Pinus halepensis forests in eastern Spain. Three atmospheric circulation patterns affecting the western Mediterranean region were included in the study: the North Atlantic Oscillation (NAO), the Western Mediterranean Oscillation (WeMO) and the Mediterranean Oscillation

Edmond Pasho; J. Julio Camarero; Martín de Luis; Sergio M. Vicente-Serrano

2011-01-01

40

A new mechanism for regional atmospheric chemistry modeling  

NASA Astrophysics Data System (ADS)

A new gas-phase chemical mechanism for the modeling of regional atmospheric chemistry, the "Regional Atmospheric Chemistry Mechanism" (RACM) is presented. The mechanism is intended to be valid for remote to polluted conditions and from the Earth's surface through the upper troposphere. The RACM mechanism is based upon the earlier Regional Acid Deposition Model, version 2 (RADM2) mechanism [Stockwell et al., 1990] and the more detailed Euro-RADM mechanism [Stockwell and Kley, 1994]. The RACM mechanism includes rate constants and product yields from the most recent laboratory measurements, and it has been tested against environmental chamber data. A new condensed reaction mechanism is included for biogenic compounds: isoprene, ?-pinene, and d-limonene. The branching ratios for alkane decay were reevaluated, and in the revised mechanism the aldehyde to ketone ratios were significantly reduced. The relatively large amounts of nitrates resulting from the reactions of unbranched alkenes with NO3 are now included, and the production of HO from the ozonolysis of alkenes has a much greater yield. The aromatic chemistry has been revised through the use of new laboratory data. The yield of cresol production from aromatics was reduced, while the reactions of HO, NO3, and O3 with unsaturated dicarbonyl species and unsaturated peroxynitrate are now included in the RACM mechanism. The peroxyacetyl nitrate chemistry and the organic peroxy radical-peroxy radical reactions were revised, and organic peroxy radical +NO3 reactions were added.

Stockwell, William R.; Kirchner, Frank; Kuhn, Michael; Seefeld, Stephan

1997-11-01

41

Ocean-atmosphere interface: its influence on radiation.  

PubMed

The influence of the ocean-atmosphere interface on the radiance distribution in both the ocean and atmosphere is investigated. At visible wavelengths in the real ocean just below the surface, the downwelling radiance is a maximum within the critical angle and drops off by 1 or 2 orders of magnitude toward the horizon. The usual explanation that this is due to the sky radiation concentrated within the critical angle and the total internal reflection of the weak upward radiance at the ocean surface at angles outside the critical angle is too simplistic. There are two other important factors: (1) the atmosphere must have sufficient optical thickness so that appreciable sky (multiple scattered) radiation develops at all angles in the downward direction; (2) the water must have appreciable absorption so that the upwelling radiance just below the ocean surface is only a small fraction of the downwelling radiance entering the ocean. Examples show that, if either one of these conditions is not satisfied, an entirely different radiance distribution develops. The variation of the following quantities with depth is studied: radiance; vector and scalar irradiance; distribution function; reflectance; and heating rate. The radiance distribution in a homogeneous medium is compared with that in the same medium with an atmosphere-ocean interface at various depths within the medium. Most of the calculations are done for Rayleigh scattering centers, but some results are given for Mie-type scattering. PMID:20309232

Plass, G N; Humphreys, T J; Kattawar, G W

1981-03-15

42

Solar Influence on Global and Regional Climates  

NASA Astrophysics Data System (ADS)

The literature relevant to how solar variability influences climate is vast—but much has been based on inadequate statistics and non-robust procedures. The common pitfalls are outlined in this review. The best estimates of the solar influence on the global mean air surface temperature show relatively small effects, compared with the response to anthropogenic changes (and broadly in line with their respective radiative forcings). However, the situation is more interesting when one looks at regional and season variations around the global means. In particular, recent research indicates that winters in Eurasia may have some dependence on the Sun, with more cold winters occurring when the solar activity is low. Advances in modelling "top-down" mechanisms, whereby stratospheric changes influence the underlying troposphere, offer promising explanations of the observed phenomena. In contrast, the suggested modulation of low-altitude clouds by galactic cosmic rays provides an increasingly inadequate explanation of observations.

Lockwood, Mike

2012-07-01

43

Large-scale atmospheric response to eastern Mediterranean summer-autumn SST anomalies and the associated regional impact  

NASA Astrophysics Data System (ADS)

Since the Mediterranean Sea is halfway between subtropical and middle latitudes, and it represents a marginal oceanic region, research has tended to focus on how large-scale modes of atmospheric variability modulate its surface temperature. Conversely, the present study examines the potential influence of the Mediterranean Sea surface temperature (SST) anomalies on the Northern Hemisphere atmospheric circulation. In particular, this work explores the large-scale changes in the global circulation forced/influenced by the eastern Mediterranean summer-autumn SST pattern. To isolate the atmospheric response, AGCM sensitivity experiments with prescribed SST over the Mediterranean Sea and climatology elsewhere are analysed. Observational diagnostics upon the period used to define the boundary conditions (1979-2002) are also interpreted. Our results support the hypothesis of an atmospheric pattern initiated in the Mediterranean basin, pointing out both a local baroclinic response and a barotropic circumglobal anomaly. This atmospheric teleconnection pattern projects onto a hemispheric wave-like structure, reflecting the waveguide effect of the westerly jets. Results suggest, thereby, that the recurrent summer-autumn circumglobal teleconnection pattern can be excited locally by changes in the atmosphere over the Mediterranean region. A linear behaviour is found upon a regional impact over northeastern Africa. The remote impacts present however a nonlinear signature: anomalous warm conditions influencing on northern Europe and Euro-Asia, whereas anomalous cold conditions impacting more on the North Pacific basin. Limitations in our model setup are also discussed.

García-Serrano, J.; Polo, I.; Rodríguez-Fonseca, B.; Losada, T.

2013-09-01

44

Influence of two atmospheric transport models on inferring sources and sinks of atmospheric CO2  

NASA Astrophysics Data System (ADS)

Atmospheric transport models are a source of uncertainty in the diagnostics of the CO2 sources and sinks. We propose here a protocol to compare two transport models: a 2-dimensional (2D) and a 3-dimensional (3D) model, based on 3 different experiments that reveal the ability of each model to account for the different components of the atmospheric carbon cycle. The 2D model we use is the one described by Tans etal. and the 3D model is the TM2 model, developed by Heimann etal. First, we conduct the same fossil fuel experiment in both models and show that the 2D model has a stronger interhemispheric mixing than the 3D model (~ 25%), even though the 2D model presents a weaker intra-hemispheric mixing above source regions (experiment A). The influence of year-to-year variability of transport on the latitudinal profile in fossil-fuel CO2 appears to be weak for the 1990s. We then use a set of "all but fossil fuel" fluxes, originally inferred from the 2D model, as an input to the 3D model (experiment B). Even if the main discrepancy on the resulting latitudinal CO2 concentrations occurs between the 2D and 3D models in the tropics and at the mid-northern latitudes, the differences implied by three longitudinal distributions tested in the 3D model are important and can be explained by a few global transport mechanisms. Finally, we quantify the differences in latitudinal CO2 concentrations observed in experiment B in terms of net carbon fluxes at the surface. To do so, an inverse calculation of the CO2 fluxes in latitude and time is performed with the 3D model, using as an input a smoothed latitudinal profile of atmospheric measurements for the period 1990 1993 (experiment C=A+B). We find with the 3D model that, averaged on the period 1990 1993, the equatorial release is reduced by 40 Tmol yr-1 (roughly 25% of the original source) compared with the initial 2D budget and is shifted southward by roughly 10°. The mid northern latitude sink is also reduced by 80 Tmol yr-1 (roughly 25% of the original sink). In summary, this study shows that the changes in the carbon budget required when moving from the 2D model to this 3D model are important, but they are not radical changes.

Bousquet, P.; Ciais, P.; Monfray, P.; Balkansk1, Y.; Ramonet, M.; Tans, P.

1996-09-01

45

TES Regional and Global Atmospheric Chemistry Data Available From the NASA Langley Atmospheric Science Data Center  

NASA Astrophysics Data System (ADS)

TES Regional and Global Atmospheric Chemistry Data Available from the NASA Langley Atmospheric Science Data Center The Tropospheric Emission Spectrometer (TES) was launched into a sun-synchronous orbit aboard Aura, the third of NASA's Earth Observing System spacecraft, on July 15, 2004. The primary objective of TES is to make global, three-dimensional measurements of ozone and other chemical species involved in its formation and destruction. The NASA Langley Atmospheric Science Data Center (ASDC) is the archive and distribution center for data from the TES instrument. The TES instrument is a high-resolution imaging infrared Fourier-transform spectrometer that operates in both nadir and limb-sounding modes. TES standard Level 2 data products include global-scale vertical profile and total column measurements of ozone, water vapor, HDO, carbon monoxide, methane, and nitric acid for 16 orbits every other day. Additional products include atmospheric temperature profiles, surface temperatures, and land surface emissivity A recent reprocessing effort has produced a new version of the data which includes additional limb species and a new summary product. In the past year, Level 3 TES products have been released which provide daily or monthly global survey chemical species data interpolated onto a global latitude/longitude grid at selected pressure levels. Browse images for the Level 3 and associated Level 2 data are available with these new Level 3 products. Between global surveys, TES can make special observations using its ability to point at a specific location for a few minutes on any given orbit. This capability is used for targets such as gas-emitting volcanoes, for regional air quality studies, and in conjunction with field campaigns. The ASDC provides data access, services and tools for over 40 projects in the discipline areas of Earth's radiation budget, clouds, aerosols and tropospheric chemistry. Additional information is available from our web site, http://eosweb.larc.nasa.gov

Hunt, L. A.

2007-12-01

46

Perturbations of the upper atmosphere in the cleft region  

NASA Astrophysics Data System (ADS)

In the dayside polar region--loosely referred to as the cleft region--particle precipitation and Joule heating cause significant perturbations of the upper atmosphere. Here Dynamics Explorer-2 satellite data are used to present a synopsis of these disturbance effects. Documented are an increase in electron temperature and a decrease in electron density; increases in ion drift speed and ion temperature; an increase in the upward-directed ion velocity; increases in zonal wind speed and neutral gas temperature; and changes in the neutral gas composition and mass density. It is suggested that the increase in electron temperature is partly controlled by the decrease in electron density; that the ion upflow velocity mainly depends on the electron temperature, less frequently on the ion temperature; and that the observed decrease in thermospheric mass density is due to a decrease in the atomic oxygen density, which in turn is caused by diverging wind flows.

Prölss, Gerd W.

2008-12-01

47

Dynamo region and the equatorial electrojet in the Jovian atmosphere  

NASA Astrophysics Data System (ADS)

The existence of the dynamo region is identified in the atmosphere of Jupiter. It is found that the dynamo region extends from an altitude of 130 km (0.153 mbar) to 330 km (0.027 microbar) reckoned from zero altitude corresponding to 43.8 mbar pressure level. Physical features of the equatorial electrojet in the ionosphere of Jupiter are modelled in detail. The Jovian equatorial electrojet has a maximum eastward current density of about 1.5 A/sq km at an altitude of 270 km (0.33 microbar) with a latitudinal half width of about + or - 11 degrees. The thickness of the equatorial half width is 100 km in altitude range. The type I instability in the electrojet can exist only if the electron streaming velocity exceeds the value of about 250 m/s.

Raghavarao, R.; Dagar, R.

1983-06-01

48

Reactive nitrogen oxides in remote regions: Atmospheric concentrations and atmosphere/biosphere exchange  

SciTech Connect

Atmospheric concentrations and elements of the atmospheres/biosphere exchange of reactive nitrogen oxides (NO{sub y}) were measured in two disparate, remote ecosystems: the Amazon rain forest in central Brazil (wet season, 1987) and the moist tundra of southwestern Alaska (summer, 1988). Concentrations of total NO{sub y} and the NO{sub y} species NO and NO{sub 2} in both locations were found to be generally low compared to the few other remote continental regions where measurements have been made. In Alaska the concentrations of NO + NO{sub 2} (=NO{sub x}) were in the range (10-20 pptv) thought to be more typical of marine air masses. Occasional observations of higher concentrations, especially in Brazil, indicated that polluted air reached even these remote sites. The soils in both locations were modest sources of NO{sub x} to the atmosphere. In Brazil this source was approximately balanced, during unpolluted periods, by dry deposition of other NO{sub y} species to the forest canopy, while in Alaska the net flux of NO{sub y} was strongly downward. Diurnal variations in the NO{sub y} concentrations and fluxes at both sites suggest that dry deposition rates are controlled by the supply of reactive components such as HNO{sub 3} and that a significant portion of the observed NO{sub y} may consist of compounds with relatively long tropospheric lifetimes which are resistant to dry deposition.

Bakwin, P.S.

1989-01-01

49

Atmospheric absorption strips' influence on optical pyrometers' work in the infrared spectral range  

Microsoft Academic Search

There is a great interest in investigating the constant decrease of infrared radiation, which influences essentially general reduction in the atmospheric absorption strips. The atmospheric absorption strips are of great importance when solving important problems concerning ecology, defence and especially, space research. The subject of the paper is detection of atmospheric strips' absorption, their influence on the operation conditions in

Jivko Zhekov; Garo Mardirossian; Angel Manev; Kunyo Palazov; Ivan Hristov

2005-01-01

50

Climate Variability of Free Atmosphere in the Polar Regions  

NASA Astrophysics Data System (ADS)

Preliminary investigations of free atmosphere above the Arctic Ocean fulfilled with sounding data of the drifting stations "North Pole" show that in 70% of the soundings the inversion base was on the surface; boundary layer height did not exceed 200 m; mean air temperature gradient in the inversion layer was 0.5-1.0 C/100 m. Low-level jets were found in 30% of the soundings. During the investigated period (1955-1991) the boundary layer height and surface inversion depth tended to decrease, and the temperature change through the inversion tended to increase. Longest time series of soundings, executed at the polar station Dickson, shows the maximal inversion height in late 1940s - early 1950s, minimal - in 1980s- early 1990s, and graduate increase in the last years of 20th century. Long-term variations of the monthly mean air temperature and humidity in the free atmosphere above the North Polar Region (60-90 N) were investigated with the original database, created in the Arctic and Antarctic Institute, Russia by V. Maistrova. This database combines the results of soundings executed on 116 aerological stations, ship observations and observations on the drifting stations "North Pole". The analysis of temperature trends for 1959-2003 shows that the annual mean air temperature in the North Polar Region increased in the low and middle troposphere (850-400 hPa) and decreased in the upper troposphere and in the low stratosphere. The total energy of the Arctic atmosphere attributed to the so-called "mean energetic level" shows weak positive trend with strong long-term variations. Preliminary estimates of temporal variability of mean specific humidity at 850, 700, 500, 400 and 300 hPa show pronounced increase from surface to 850 hPa and decrease above 850 hPa. The spatial distributions of air temperature and humidity trends demonstrate strong inhomogenity of relevant meteorological fields. Comparison the trends of the annual mean air temperature and humidity for 1959-2003 in the North and South Polar Regions shows strong differences, especially in the low stratosphere, where negative trends in the Arctic much more pronounced. In total the data demonstrate the increase of local instability in the polar upper troposphere and low stratosphere, which could be explain as due to direct greenhouse effect, as well as due to changes in global circulation, originated by the increase of global or tropical ocean temperature.

Maistrova, V. V.; Makshtas, A. P.; Alexeev, V. A.

2004-05-01

51

Baltic Sea Ice Regional Indices and their relationship with atmospheric circulation patterns and maritime navigation  

NASA Astrophysics Data System (ADS)

The Baltic navigation and urban activities of the coastal communities around the Baltic Sea depended always very much on the ice conditions in the sea. The sea ice occurs different in form and amount, depending on the sea area and the winter season. The aim of the work was the investigation of influence of atmospheric circulation patterns on sea ice condition of Baltic Sea (by the sea ice regional indices). The atmospheric circulation patterns were represented by the German Weather Service's - Grosswetterlagen. The relationship between the ice severity indices and icebreakers activities (number of cases, in which the Swedish and Finnish icebreakers assisted the ships) were investigated. The work was done under the Seaman project (Norwegian Financial Mechanism)

Sztobryn, M.; Kowalska, B.

2009-04-01

52

Grassland/atmosphere response to changing climate: Coupling regional and local scales. Final report.  

National Technical Information Service (NTIS)

The objectives of the study were: to evaluate the response of grassland ecosystems to atmospheric change at regional and site scales, and to develop multiscaled modeling systems to relate ecological and atmospheric models with different spatial and tempor...

M. B. Coughenour T. G. F. Kittel R. A. Pielke J. Eastman

1993-01-01

53

Use of Corrosion Probes to Assess the Influence of Relative Humidity on Atmospheric Corrosion.  

National Technical Information Service (NTIS)

Atmospheric corrosion is known to be influenced by prevailing relative humidity and the composition of surface contamination. The memorandum shows how atmospheric corrosion probes can be used to compare the corrosivity of various sites. It also shows how ...

W. B. R. Moore

1988-01-01

54

Midlatitude daytime D region ionosphere variations measured from radio atmospherics  

NASA Astrophysics Data System (ADS)

We measured the midlatitude daytime ionospheric D region electron density profile height variations in July and August 2005 near Duke University by using radio atmospherics (or sferics for short), which are the high-power, broadband very low frequency (VLF) signals launched by lightning discharges. As expected, the measured daytime D region electron density profile heights showed temporal variations quantitatively correlated with solar zenith angle changes. In the midlatitude geographical regions near Duke University, the observed quiet time heights decreased from ˜80 km near sunrise to ˜71 km near noon when the solar zenith angle was minimum. The measured height quantitative dependence on the solar zenith angle was slightly different from the low-latitude measurement given in a previous work. We also observed unexpected spatial variations not linked to the solar zenith angle on some days, with 15% of days exhibiting regional differences larger than 0.5 km. In these 2 months, 14 days had sudden height drops caused by solar flare X-rays, with a minimum height of 63.4 km observed. The induced height change during a solar flare event was approximately proportional to the logarithm of the X-ray flux. In the long waveband (wavelength, 1-8 Å), an increase in flux by a factor of 10 resulted in 6.3 km decrease of the height at the flux peak time, nearly a perfect agreement with the previous measurement. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short, rather than the long, wavelength X-ray flux changes.

Han, Feng; Cummer, Steven A.

2010-10-01

55

Influence of wind direction on pollen concentration in the atmosphere  

NASA Astrophysics Data System (ADS)

The daily pollen concentration in the atmosphere of Badajoz (SW Spain) was analysed over a 6-year period (1993-1998) using a volumetric aerobiological trap. The results for the main pollination period are compared with the number of hours of wind each day in the four quadrants: 1 (NE), 2 (SE), 3 (SW) and 4 (NW). The pollen source distribution allowed 16 pollen types to be analysed as a function of their distribution in the four quadrants with respect to the location of the trap. Four of them correspond to species growing in an irrigated farmland environment (Amaranthaceae-Chenopodiaceae, Plantago, Scirpus, and Typha), five to riparian and woodland species (Salix, Fraxinus, Alnus, Populus, and Eucalyptus), four to urban ornamentals (Ulmus, Arecaceae, Cupressaceae, and Casuarina), and three which include the most frequent pollen grains of widely distributed species (Poaceae, Quercus, and Olea). The results show that the distribution of the sources and the wind direction play a very major role in determining the pollen concentration in the atmosphere when these sources are located in certain quadrants, and that the widely distributed pollen sources show no relationship with wind direction. In some years the values of the correlations were not maintained, which leads one to presume that, in order to draw significant conclusions and establish clear patterns of the influence of wind direction, a continuous and more prolonged study will be required.

Silva Palacios, I.; Tormo Molina, R.; Muñoz Rodríguez, A. F.

56

Relative influences of atmospheric chemistry and transport on Arctic ozone trends  

NASA Astrophysics Data System (ADS)

The reduction in the amount of ozone in the atmospheric column over the Arctic region, observed during the 1990s,, resembles the onset of the Antarctic ozone `hole' in the mid-1980s, but the two polar regions differ significantly with respect to the relative contributions of chemistry and atmospheric dynamics to the ozone abundance. In the strong, cold Antarctic vortex, rapid springtime chemical ozone loss occurs throughout a large region of the lower stratosphere, whereas in the Arctic, although chemical ozone depletion has been observed,,,,,,,,, the vortex is generally much smaller, weaker and more variable. Here we report a model-based analysis of the relative importance of dynamics and chemistry in causing the Arctic ozone trend in the 1990s, using a state-of-the-art three-dimensional stratospheric chemistry-transport model. North of 63°N we find that, on average, dynamical variations dominate the interannual variability, with little evidence for a trend towards more wintertime chemical depletion. However, increases in the burden of atmospheric halogens since the early 1970s are responsible for a large (14%) reduction in the average March column ozone, but this effect is mostly caused by increased destruction throughout the year rather than by halogen chemistry associated with wintertime polar statospheric clouds. Any influence of climate change on future average Arctic ozone amounts may thus be dominated by possible circulation changes, rather than by changes in chemical loss.

Chipperfield, M. P.; Jones, R. L.

1999-08-01

57

Midlatitude D region variations measured from broadband radio atmospherics  

NASA Astrophysics Data System (ADS)

The high power, broadband very low frequency (VLF, 3--30 kHz) and extremely low frequency (ELF, 3--3000 Hz) electromagnetic waves generated by lightning discharges and propagating in the Earth-ionosphere waveguide can be used to measure the average electron density profile of the lower ionosphere (D region) across the wave propagation path due to several reflections by the upper boundary (lower ionosphere) of the waveguide. This capability makes it possible to frequently and even continuously monitor the D region electron density profile variations over geographically large regions, which are measurements that are essentially impossible by other means. These guided waves, usually called atmospherics (or sferics for short), are recorded by our sensors located near Duke University. The purpose of this work is to develop and implement algorithms to derive the variations of D region electron density profile which is modeled by two parameters (one is height and another is sharpness), by comparing the recorded sferic spectra to a series of model simulated sferic spectra from using a finite difference time domain (FDTD) code. In order to understand the time scales, magnitudes and sources for the midlatitude nighttime D region variations, we analyzed the sferic data of July and August 2005, and extracted both the height and sharpness of the D region electron density profile. The heights show large temporal variations of several kilometers on some nights and the relatively stable behavior on others. Statistical calculations indicate that the hourly average heights during the two months range between 82.0 km and 87.2 km with a mean value of 84.9 km and a standard deviation of 1.1 km. We also observed spatial variations of height as large as 2.0 km over 5 degrees latitudes on some nights, and no spatial variation on others. In addition, the measured height variations exhibited close correlations with local lightning occurrence rate on some nights but no correlation with local lightning or displaced lightning on others. The nighttime profile sharpness during 2.5 hours in two different nights was calculated, and the results were compared to the equivalent sharpness derived from International Reference Ionosphere (IRI) models. Both the absolute values and variation trends in IRI models are different from those in broadband measurements. Based on sferic data similar to those for nighttime, we also measured the day-time D region electron density profile variations in July and August 2005 near Duke University. As expected, the solar radiation is the dominant but not the only determinant source for the daytime D region profile height temporal variations. The observed quiet time heights showed close correlations with solar zenith angle changes but unexpected spatial variations not linked to the solar zenith angle were also observed on some days, with 15% of days exhibiting regional differences larger than 0.5 km. During the solar flare, the induced height change was approximately proportional to the logarithm of the X-ray fluxes. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short (wavelength 0.5--4 A), rather than the long (wavelength 1--8 A) X-ray flux changes. The daytime profile sharpness during morning, noontime and afternoon periods in three different days and for the solar zenith angle range 20 to 75 degrees was calculated. These broadband measured results were compared to narrowband VLF measurements, IRI models and Faraday rotation base IRI models (called FIRI). The estimated sharpness from all these sources was more consistent when the solar zenith angle was small than when it was large. By applying the nighttime and daytime measurement techniques, we also derived the D region variations during sunrise and sunset periods. The measurements showed that both the electron density profile height and sharpness decrease during the sunrise period while increase during the sunset period.

Han, Feng

58

An investigation of aerosol optical properties: Atmospheric implications and influences  

NASA Astrophysics Data System (ADS)

An experimental, observational, and theoretical investigation of aerosol optical properties has been made in this work to study their implications and influences on the atmosphere. In the laboratory the scientific and instrumental methodology consisted of three parts, namely, aerosol generation, optical and mass concentration measurements, and computational calculations. In particular the optical properties of ammonium sulfate and caffeine aerosol were derived from measurements made with a transmissometer cell-reciprocal- integrating nephelometer (TCRIN), equipped with a laser beam at 632.8 nm, and by applying a Mie theory computer code The aerosol generators, optical equipment and calibration procedures were reviewed. The aerosol shape and size distribution were studied by means of scanning electron microscopy and the Gumprecht- Sliepcevich/Lipofsky-Green extinction-sedimentation method. In particular the spherical and cylindrical shape were considered. During this investigation, an alternative method for obtaining the optical properties of monodisperse spherical non-absorbing aerosol using a cell-transmissometer, which is based on a linearisation of the Lambert-Beer law, was found. In addition, adapting the TCRIN to electrooptical aerosol studies, the optical properties of a circular-cylindrical aerosol of caffeine were undertaken under the condition of random orientation in relation with the laser beam, and perpendicular orientation to it. A theoretical study was conducted to assess the sensitivity of aerosol to a change of shape under different polarisation modes. The aerosol optical properties, obtained previously in the laboratory, were then used to simulate the direct radiative forcing. The calculations and results were obtained by applying a one- dimensional energy-balance box model. The influence of atmospheric aerosol on the sky brightness due to a total solar eclipse was studied using the photometric and meteorological observations made during the eclipse of 26 February 1998 which occurred in Venezuela. With additional data, a comparison could be made between this eclipse and the other one which took place in the same country on 3 February 1916.

Penaloza-Murillo, Marcos A.

59

The Deuterium Excess in Precipitation and Atmospheric Moisture in the Southern Great Plains Region of USA  

NASA Astrophysics Data System (ADS)

Systematic study of variations in the isotopic ratios of oxygen and hydrogen in various components of the water cycle is helpful for understanding local and regional hydro-climatology. The relationship between the isotopic ratios of oxygen and hydrogen in precipitation, defined as the Meteoric Water Line (MWL) yields valuable information about the climatic factors and secondary moisture sources which influence the precipitation process, when compared with global MWL(?D = 8*?18O + 10). It is estimated that a significant portion of precipitation on land is a result of evapo-transpired moisture that is recycled in the atmosphere. In order to understand the response of regional water cycles to climatic variations, it is important to quantify the influence of locally derived moisture on precipitation. The Deuterium Excess (defined as: d = ?D - 8*?18O) in precipitation is a valuable tool for estimating the contribution of such secondary moisture sources to precipitation. As part of the DOE Water Cycle Pilot Study to improve predictability in part by integrating stable isotope variations in to climatological models, atmospheric vapor samples were collected in the southern Great Plains region. Vapor samples were collected at the surface and between 900 and 5000 meters(msl) and were analyzed for their ?D and ?18O values. The ?D and ?18O of the vapor samples showed a progressive depletion with increasing altitude. The samples collected below the Atmospheric Boundary Layer (ABL) showed a remarkable increase in the d-excess (19‰ ) compared to the sample above the ABL (4‰ ). Precipitation samples collected in 1999 from the National Atmospheric Deposition Program (NADP) stations in Texas and Oklahoma were also analyzed for their stable isotope values. The precipitation in the inland station of Oklahoma is characterized by higher d-excess than that of the coastal Texas station. Such higher d-excess is shown to result from an admixture of locally evapo-transpired moisture with the moisture from the Gulf of Mexico, the predominant source of precipitation in the Great Plains region.

Machavaram, M. V.; Conrad, M. E.; Miller, N. L.

2002-12-01

60

Influences of Forest Tree Species and Early Spring Temperature on Surface-Atmosphere Transfers of Water and Carbon in the Northeastern U.S  

Microsoft Academic Search

Influences of Forest Tree Species and Early Spring Temperature on Surface-Atmosphere Transfers of Water and Carbon in the Northeastern U.S. Julian Hadley, Paul Kuzeja, Safina Singh and Thomas Mulcahy Transfers of water vapor from terrestrial ecosystems to the atmosphere affect regional hydrology, weather and climate over short time scales, and forest-atmosphere CO2 exchange affects global climate over long timescales. To

J. L. Hadley; P. Kuzeja; T. Mulcahy; S. Singh

2008-01-01

61

The influence of atmospheric circulation on plant phenological phases in central and eastern Europe  

NASA Astrophysics Data System (ADS)

The objective of this study is to analyse relationships between the start dates of spring phenological phases and large-scale atmospheric circulation patterns. The timing of phenological phases in temperate zones is driven by temperature, and temperature regime is generally determined by atmospheric circulation. The database analysed consists of the first dates of flowering of coltsfoot (Tussilago farfara L.), of birch (Betula pendula Roth.) leaf unfolding and of flowering of lilac (Syringa vulgaris L.); the North Atlantic oscillation (NAO) and the Arctic oscillation (AO) indices, frequencies of the circulation forms classified by Vangengeim and Girs, and of the groups of Grosswetterlagen presented by Hess and Brezowsky. The study area covers central and eastern Europe, and the period considered is 1951-98.The results show that the influence of the westerly airflow is more pronounced in the winter half-year, and weakens and even disappears as spring advances. Phases have the highest correlation with NAO and AO indices during winter (December-March) and the first three months of the year (January-March), which have correlations stronger than -0.5 in the Baltic Sea region. Among the phenological phases, flowering of coltsfoot is the most strongly correlated with the NAO and AO indices, followed by leafing of birch and flowering of lilac. Airflow from the north and from the east has a greater influence in springtime, particularly in the northernmost and southernmost regions of the study area.

Aasa, Anto; Jaagus, Jaak; Ahas, Rein; Sepp, Mait

2004-10-01

62

Investigation of Boundary Layer Fine Structure in Arid Regions: Injection of Fine Dust into the Atmosphere  

Microsoft Academic Search

Fine structure of the atmospheric boundary layerin desert regions of Kalmykia and on dried bottom of theAral Sea and its relation to soil particle emission in theatmosphere are discussed. It was found that in a hot seasonin the absence of dust storms convective processes lift updust particles into the atmospheric boundary layer fromsandy landscapes of Kalmykia and Sub-Aral regions. Thisaerosol

G. S. Golitsyn; I. G. Granberg; A. V. Andronova; V. M. Ponomarev; S. S. Zilitinkevich; V. V. Smirnov; M. Yu. Yablokov

2003-01-01

63

A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms  

NASA Astrophysics Data System (ADS)

We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyacetyl nitrate by 40%, and organic nitrate by 41%. RACM2 enhances ozone compared to CB05TU at all ambient levels. Although it exhibited greater overestimates at lower observed concentrations, it displayed an improved performance at higher observed concentrations. The RACM2 ozone predictions are also supported by increased ozone production efficiency that agrees better with observations. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean sulfate by 10%, nitrate by 6%, ammonium by 10%, anthropogenic secondary organic aerosols by 42%, biogenic secondary organic aerosols by 5%, and in-cloud secondary organic aerosols by 7%. Increased inorganic and organic aerosols with RACM2 agree better with observed data. Any air pollution control strategies developed using the two mechanisms do not differ appreciably.

Sarwar, G.; Godowitch, J.; Henderson, B. H.; Fahey, K.; Pouliot, G.; Hutzell, W. T.; Mathur, R.; Kang, D.; Goliff, W. S.; Stockwell, W. R.

2013-10-01

64

A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms  

NASA Astrophysics Data System (ADS)

We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyacetyl nitrate by 40%, and organic nitrate by 41%. RACM2 predictions generally agree better with the observed data than the CB05TU predictions. RACM2 enhances ozone for all ambient levels leading to higher bias at low (< 60 ppbv) concentrations but improved performance at high (>70 ppbv) concentrations. The RACM2 ozone predictions are also supported by increased ozone production efficiency that agrees better with observations. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean sulfate by 10%, nitrate by 6%, ammonium by 10%, anthropogenic secondary organic aerosols by 42%, biogenic secondary organic aerosols by 5%, and in-cloud secondary organic aerosols by 7%. Increased inorganic and organic aerosols with RACM2 agree better with observed data. While RACM2 enhances ozone and secondary aerosols by relatively large margins, control strategies developed for ozone or fine particles using the two mechanisms do not differ appreciably.

Sarwar, G.; Godowitch, J.; Henderson, B.; Fahey, K.; Pouliot, G.; Hutzell, W. T.; Mathur, R.; Kang, D.; Goliff, W. S.; Stockwell, W. R.

2013-03-01

65

The role of regional bioproductivity in atmospheric carbon dioxide changes  

NASA Astrophysics Data System (ADS)

This study attempts to further understanding of the glacial-interglacial cycles of atmospheric CO2 observed in ice core records. To accomplish this, a global coupled ocean-mixed-layer-atmosphere energy-salt- carbon-phosphorus-alkalinity conservation box model is developed. The model, with parameterizations for variable seaice and land-snow cover incorporates the temperature- albedo feedback as well as the CO2- temperature-water vapor-radiation feedback. The chief result is the discovery of the importance of low-latitude ocean bioproductivity in determining atmospheric CO2 levels. Low-latitude bioproductivity is as much as an order of magnitude more important than high-latitude bioproductivity at affecting modeled atmospheric CO2 levels. This in turn is a consequence of latitudinal differences in water stratification. To the extent that changes in surface bioproductivity are possible-itself a function of the stratification-controlled rate of return to the surface of nutrients-more highly stratified areas will have more impact on atmospheric CO2 than less stratified areas. The objective of this study is to draw attention to the role of changes in the strength of low-latitude ocean bioproductivity in glacial- interglacial atmospheric CO2 changes and to challenge the prevailing assumption that atmospheric CO2 levels are determined primarily by high- latitude processes.

Rich, Jonathan J.

66

Isolating mesoscale coupled ocean-atmosphere interactions in the Kuroshio Extension region  

NASA Astrophysics Data System (ADS)

The Kuroshio Extension region is characterized by energetic oceanic mesoscale and frontal variability that alters the air-sea fluxes that can influence large-scale climate variability in the North Pacific. We investigate this mesoscale air-sea coupling using a regional eddy-resolving coupled ocean-atmosphere (OA) model that downscales the observed large-scale climate variability from 2001 to 2007. The model simulates many aspects of the observed seasonal cycle of OA coupling strength for both momentum and turbulent heat fluxes. We introduce a new modeling approach to study the scale-dependence of two well-known mechanisms for the surface wind response to mesoscale sea surface temperatures (SSTs), namely, the 'vertical mixing mechanism' (VMM) and the 'pressure adjustment mechanism' (PAM). We compare the fully coupled model to the same model with an online, 2-D spatial smoother applied to remove the mesoscale SST field felt by the atmosphere. Both VMM and PAM are found to be active during the strong wintertime peak seen in the coupling strength in both the model and observations. For VMM, large-scale SST gradients surprisingly generate coupling between downwind SST gradient and wind stress divergence that is often stronger than the coupling on the mesoscale, indicating their joint importance in OA interaction in this region. In contrast, VMM coupling between crosswind SST gradient and wind stress curl occurs only on the mesoscale, and not over large-scale SST gradients, indicating the essential role of the ocean mesocale. For PAM, the model results indicate that coupling between the Laplacian of sea level pressure and surface wind convergence occurs for both mesoscale and large-scale processes, but inclusion of the mesoscale roughly doubles the coupling strength. Coupling between latent heat flux and SST is found to be significant throughout the entire seasonal cycle in both fully coupled mode and large-scale coupled mode, with peak coupling during winter months. The atmospheric response to the oceanic mesoscale SST is also studied by comparing the fully coupled run to an uncoupled atmospheric model forced with smoothed SST prescribed from the coupled run. Precipitation anomalies are found to be forced by surface wind convergence patterns that are driven by mesoscale SST gradients, indicating the importance of the ocean forcing the atmosphere at this scale.

Putrasahan, Dian A.; Miller, Arthur J.; Seo, Hyodae

67

The role of regional bioproductivity in atmospheric carbon dioxide changes  

Microsoft Academic Search

This study attempts to further understanding of the glacial-interglacial cycles of atmospheric CO2 observed in ice core records. To accomplish this, a global coupled ocean-mixed-layer-atmosphere energy-salt- carbon-phosphorus-alkalinity conservation box model is developed. The model, with parameterizations for variable seaice and land-snow cover incorporates the temperature- albedo feedback as well as the CO2- temperature-water vapor-radiation feedback. The chief result is the

Jonathan J. Rich

1998-01-01

68

Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics: revised  

NASA Astrophysics Data System (ADS)

This study investigates the influence of a major solar proton event (SPE) similar to the Carrington event of 1–2 September 1859 by means of the 3D chemistry climate model (CCM) SOCOL v2.0. Ionization rates were parameterized according to CRAC:CRII (Cosmic Ray-induced Atmospheric Cascade: Application for Cosmic Ray Induced Ionization), a detailed state-of-the-art model describing the effects of SPEs in the entire altitude range of the CCM from 0 to 80 km. This is the first study of the atmospheric effect of such an extreme event that considers all the effects of energetic particles, including the variability of galactic cosmic rays, in the entire atmosphere. We assumed two scenarios for the event, namely with a hard (as for the SPE of February 1956) and soft (as for the SPE of August 1972) spectrum of solar particles. We have placed such an event in the year 2020 in order to analyze the impact on a near future atmosphere. We find statistically significant effects on NOx, HOx, ozone, temperature and zonal wind. The results show an increase of NOx of up to 80 ppb in the northern polar region and an increase of up to 70 ppb in the southern polar region. HOx shows an increase of up to 4000%. Due to the NOx and HOx enhancements, ozone reduces by up to 60% in the mesosphere and by up to 20% in the stratosphere for several weeks after the event started. Total ozone shows a decrease of more than 20 DU in the northern hemisphere and up to 20 DU in the southern hemisphere. The model also identifies SPE induced statistically significant changes in the surface air temperature, with warming in the eastern part of Europe and Russia of up to 7 K for January.

Calisto, M.; Usoskin, I.; Rozanov, E.

2013-12-01

69

Aerosol radiative impact on the Mediterranean climate in coupled atmosphere-ocean-land-river regional climate simulations  

NASA Astrophysics Data System (ADS)

Various natural and anthropogenic aerosols observed over the Mediterranean region show a strong spatio-temporal variability and a large variety in aerosol physical-chemical and optical properties. Through their interactions with solar and thermal radiations, they have significant effects on the regional climate in one of the most climatically sensitive areas. In order to better understand the influence of aerosols on the Mediterranean climate, we consider in the present work a regional climate system modelling (RCSM) approach, using the ALADIN-climate model. This regional climate model can be coupled to the regional ocean model NEMOMED8, the land surface model ISBA and the river routine scheme TRIP. This RCSM approach enables to take into account the high-frequency feedback of the sea surface temperature (SST) on the atmosphere, as well as the river-ocean-atmosphere feedback. Aerosols are included in ALADIN through monthly interannual climatologies, coming from a combination of satellite-derived and model-simulated products, and considered as the most possible relevant estimation of the atmospheric aerosol content for the five most relevant species (sea salt, desert dust, sulfates, black and organic carbon aerosols). Ensemble simulations have been carried out over the period 2003-2009 both in a forced mode (only the atmospheric model ALADIN) and in a coupled mode (ALADIN with NEMOMED8), with and without aerosols. The first results of these simulations confirm the strong impact of aerosols due to absorption and scattering of the incident radiation, and also show contrasts between different regions. Regional climate response to aerosols is all the more complex in a region where local winds, complex coastlines and orography interact with the atmospheric flow. We will present the aerosol direct effect in both modes (forced and coupled) on shortwave and longwave radiation, and the resulting effects on atmospheric parameters such as temperature, dynamics and precipitation. For coupled atmosphere-ocean simulations, the decrease of SST due to aerosol forcing is observed, as well as changes in ocean-atmosphere fluxes and deep water formation.

Nabat, Pierre; Somot, Samuel; Mallet, Marc

2013-04-01

70

Numerical simulations of the influence of solar proton events on the atmosphere of the Earth  

NASA Astrophysics Data System (ADS)

The Whole Atmosphere Community Climate Model (WACCM) has been used to simulate the influence of solar proton events (SPEs) on the Earth's middle atmosphere (stratosphere and mesosphere). The latest solar maximum was especially active with SPEs (e.g., July and November 2000, November 2001, and October/November 2003), which impacted the middle atmospheric polar cap regions. The SPE-caused ionization, as well as dissociation processes, led to the production of HOx (H, OH, HO2 ) and NOy (N, NO, NO2 , NO3 , HNO3 , HO2 NO2 , N2 O5 , ClONO2 , BrONO2 ). Large (>40%) short-lived mesospheric ozone decreases followed these enhancements of HOx and NOy and significant (>10%) stratospheric ozone changes continued for months beyond the very largest SPEs due to the long-lived NOy . These model simulation results will be compared with satellite instrument (e.g., UARS HALOE and Envisat MIPAS) measurements of SPE-caused effects. Both shortand longer-term simulated changes due to SPEs will be shown in this talk.

Jackman, Charles; Marsh, Daniel; Vitt, Francis; Garcia, Rolando; Fleming, Eric

71

Atmospheric Rivers Induced Heavy Precipitation and Flooding in the Western U.S. Simulated by the WRF Regional Climate Model  

SciTech Connect

Twenty years of regional climate simulated by the Weather Research and Forecasting model for North America has been analyzed to study the influence of the atmospheric rivers and the role of the land surface on heavy precipitation and flooding in the western U.S. Compared to observations, the simulation realistically captured the 95th percentile extreme precipitation, mean precipitation intensity, as well as the mean precipitation and temperature anomalies of all the atmospheric river events between 1980-1999. Contrasting the 1986 President Day and 1997 New Year Day atmospheric river events, differences in atmospheric stability are found to have an influence on the spatial distribution of precipitation in the Coastal Range of northern California. Although both cases yield similar amounts of heavy precipitation, the 1997 case was found to produce more runoff compared to the 1986 case. Antecedent soil moisture, the ratio of snowfall to total precipitation (which depends on temperature), and existing snowpack all seem to play a role, leading to a higher runoff to precipitation ratio simulated for the 1997 case. This study underscores the importance of characterizing or simulating atmospheric rivers and the land surface conditions for predicting floods, and for assessing the potential impacts of climate change on heavy precipitation and flooding in the western U.S.

Leung, Lai R.; Qian, Yun

2009-02-12

72

A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry MechanismsChemistry Mechanisms  

EPA Science Inventory

We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RAC...

73

Regionality of Soil Moisture-Atmosphere Feedback in the Central United States  

NASA Astrophysics Data System (ADS)

Soil moisture has been found to greatly impact the partitioning of energy fluxes at the surface-atmosphere interface and thus precipitation systems. Using the NCAR/Penn State mesoscale model MM5 with the NOAH land surface scheme, this study carried out four experiments to examine this impact along with soil moisture- precipitation feedbacks over different regions of varying climate regimes. The first and second experiments were performed by multiplying the initial soil moisture values by 0.5 and 1.5 (SMinitX0.5 and SMinitX1.5) for the 1-month simulation. The third and forth experiments were carried out by forcing the soil moisture to the saturation and wilting-point values (SatSM and WiltSM) throughout the month-long simulation. The SMinitX0.5 and SMinitX1.5 mimic circumstances with pre-existing abnormally dry or wet soil conditions, while SatSM and WiltSM represent situations where the soil surface was kept at extreme levels and not allowed to dry out or recharge for the month. The results show that on a sub-seasonal scale (a month) during summer, in the dry Great Plains region, soil moisture can have a significant effect on both local atmospheric processes, and downstream remote atmospheric structure and stability. In contrast in the relatively wet Midwest, soil moisture was found to have a much weaker influence. The differences in soil moisture effects are associated with varying responses of boundary-layer heights, convective stability, and the low-level jets. In the Great Plains where the boundary layer is deeper and convection is more surfaced-based, soil moisture tends to play a larger role, whereas in the Midwest where the boundary layer is generally shallower and convection is more elevated, soil moisture plays a smaller role. Among all four experiments, the SatSM simulation produced shallowest boundary layer and weakest low-level jets, and thus resulted in the least amount of rainfall for both regions, suggesting that soil moisture has a negative feedback on precipitation in this case. The results also show that the resultant rainfall sensitivity to soil moisture changes were larger than evapotranspiration, reflecting the nonlinear interactions among rainfall and evapotranspiration. In the Great Plains the rainfall change was five times that of evapotranspiration, meaning that the nonlinear atmospheric processes such as horizontal convergence can significantly augment resultant rainfall increase from increased evaporation.

Tentinger, B.; Pan, Z.

2006-12-01

74

Influence of modelled soil biogenic NO emissions on related trace gases and the atmospheric oxidizing efficiency  

NASA Astrophysics Data System (ADS)

The emission of nitric oxide (NO) by soils (SNOx) is an important source of oxides of nitrogen (NOx=NO+NO2) in the troposphere, with estimates ranging from 4 to 21 Tg of nitrogen per year. Previous studies have examined the influence of SNOx on ozone (O3) chemistry. We employ the ECHAM5/MESSy atmospheric chemistry model (EMAC) to go further in the reaction chain and investigate the influence of SNOx on lower tropospheric NOx, O3, peroxyacetyl nitrate (PAN), nitric acid (HNO3), the hydroxyl radical (OH) and the lifetime of methane (?CH4). We show that SNOx is responsible for a significant contribution to the NOx mixing ratio in many regions, especially in the tropics. Furthermore, the concentration of OH is substantially increased due to SNOx, resulting in an enhanced oxidizing efficiency of the global troposphere, reflected in a ~10% decrease in ?CH4 due to soil NO emissions. On the other hand, in some regions SNOx has a negative feedback on the lifetime of NOx through O3 and OH, which results in regional increases in the mixing ratio of NOx despite lower total emissions in a simulation without SNOx. In a sensitivity simulation in which we reduce the other surface NOx emissions by the same amount as SNOx, we find that they have a much weaker impact on OH and ?CH4 and do not result in an increase in the NOx mixing ratio anywhere.

Steinkamp, J.; Ganzeveld, L. N.; Wilcke, W.; Lawrence, M. G.

2009-04-01

75

Influences of land-ocean-atmosphere dynamics and emissions sectors on atmospheric chemical transport during VOCALS REx  

NASA Astrophysics Data System (ADS)

Measurements and modeling from the VOCALS REx campaign have identified a range of transport regimes based on synoptic meteorology, and suggested roles for the marine boundary layer inversion, downslope katabatic winds from the Andean cordillera, and Hadley cell subsidence as primary causes for observed aerosol and trace gas concentration gradients over the Southeast Pacific. This study employs atmospheric chemical transport modeling and airmass trajectory analyses to more directly address the influence of orographic winds, boundary layer dynamics, coastal circulations, and large-scale circulation by the subtropical high on the diurnal and episodic variability of pollution transport in the region. Using hourly simulations with the Weather Research and Forecasting model and the STEM chemical transport model at 12 km x 12 km resolution, we introduce tracer emissions within and above the boundary layer at representative locations--including the western slopes of the Andes, on-shore and off-shore coastal areas, metropolitan Santiago, the Chilean altiplano, and the free troposphere over the open ocean--and follow their transport and fate throughout the REx experiment of October-November 2008. Comparison between trajectories and tracer concentrations illustrate long range airmass history and allow for an understanding of the representativeness of instantaneous trajectories on transport phenomena. We further assess the contributions of emissions from power generation, copper smelters, natural sources, and anthropogenic area sources to aerosol concentrations over the Southeast Pacific, identifying their role in each transport regime.

Spak, S.; Mena, M.; Carmichael, G. R.

2009-12-01

76

Real time GPS data processing for regional atmospheric delay derivation  

Microsoft Academic Search

We have developed a GPS data processing software and demonstrate that by using receivers in an area of approximately 800 × 400 km we can produce estimates of the atmospheric zenith total delay (ZTD) with a latency of a few seconds. It is based on a Kalman filter which simultaneously estimates clock offsets and satellite coordinates. The ZTD quality is

Per O. J. Jarlemark; Jan M. Johansson; Borys Stoew; Gunnar Elgered

2002-01-01

77

Atmospheric Energetics in Regions of Intense Convective Activity.  

National Technical Information Service (NTIS)

Synoptic-scale budgets of kinetic and total potential energy are computed using 3- and 6-h data at nine times from NASA's fourth Atmospheric Variability Experiment (AVE IV). Two intense squall lines occurred during the period. Energy budgets for areas tha...

H. E. Fuelberg

1977-01-01

78

The influence of atmospheric scattering on imaging of Titan's surface  

NASA Astrophysics Data System (ADS)

In the visible and near-infrared wavelength range (500--1000 nm), the optical thickness of Titan's atmosphere generally varies between about 0.5 and 4, although it can be much higher in methane absorption bands. This has two effects on the radiance as measured from outside the atmosphere. First, the illumination of the surface is strongly wavelength dependent because of methane absorption bands. Second, the direct radiance coming upward from the surface is attenuated due to atmospheric extinction, and a diffuse component due to scattering by the atmosphere is added. We assess both effects by radiative transfer computations based on a microphysical model for aerosol formation. Taking into account scattering by aerosol particles, Rayleigh scattering by nitrogen, and methane absorption, we simulate spectra as observed from outside the atmosphere. The modeled radiances can be used to subtract the atmospheric component from observed images or spectra and to correct for the wavelength dependent illumination. The Descent Imager/Spectral Radiometer (DISR) aboard the Huygens probe will provide in situ measurements of the optical properties during its descent through Titan's atmosphere. Radiative transfer computations based on DISR measurements will make the correction procedure independent of a priori assumptions.

Grieger, B.; Schröder, S.; Rodin, A. V.

79

Regional spatial and temporal interpolation of atmospheric PCBs: Interpretation of Lake Michigan mass balance data  

SciTech Connect

During the Lake Michigan Mass Balance (LMMB) Project, over 600 atmospheric samples were collected at eight shoreline sites and during seven cruises. These samples were analyzed for persistent organic pollutants, including PCB congeners, atrazine, and trans-nonachlor. The authors have developed a method for interpreting the gas-phase data that includes fractionating the observed PCB concentration into land- and water-based sources. This approach accounts for differences in gas-phase atmospheric PCB concentration over water and over land. Using this fractionation approach, they have interpolated the measured data over time and space to predict PCB air concentrations over the lake during the LMMB field period. The results predict gas-phase {Sigma}PCB (sum of {approximately}98 congener groups) concentrations for each of 2,319 grid cells over the lake, on a monthly basis. The authors estimate that lake-wide monthly average {sigma}PCB gas-phase concentrations range from 0.136 to 1.158 ng/m{sup 3}, with an annual average PCB concentration of 0.457 ng/m{sup 3}. As expected, the highest concentrations of PCBs over the lake when the winds are from the southwest (out of the Chicago-Gary region) and when land surface temperatures are elevated. The predicted influence of Chicago is described on a monthly basis as a zone of elevated PCB concentrations for approximately 40 km into Lake Michigan.

Green, M.L.; Depinto, J.V.; Sweet, C.; Hornbuckle, K.C.

2000-05-01

80

Atmospheric glow at a wavelength of 630 nm in a region of subauroral red arcs  

Microsoft Academic Search

The characteristics of atmospheric glow at 630 nm in a subauroral red arc region is investigated, assuming the glow energy source to be electromagnetic ion-cyclotron waves generated in the topside plasmasphere. Profiles of the volume emission rate of the atmosphere in the 140-1000 km height range are calculated. It is shown that, in contrast to nighttime conditions, two peaks can

Iu. V. Konikov; A. V. Pavlov

1990-01-01

81

Roles of atmospheric and land surface data in dynamic regional downscaling  

Microsoft Academic Search

In studies dealing with the impact of land use changes on atmospheric processes, a key methodological step is the validation of simulated current conditions. However, regions lacking detailed atmospheric and land use data provide limited information with which to accurately generate control simulations. In this situation, the difference between baseline control simulations and different land use change simulations can be

Deepak K. Ray; Roger A. Pielke Sr; Udaysankar S. Nair; Dev Niyogi

2010-01-01

82

Influence of Ocean-Atmosphere Interaction on the Arctic Oscillation in Two General Circulation Models  

Microsoft Academic Search

The influence of ocean-atmosphere interaction on the wintertime Arctic oscillation (AO) is investigated using a hierarchy of experiments made with two general circulation models (GCMs), ranging from climatologically forced atmospheric to fully coupled ocean-atmosphere GCMs with increasing greenhouse gas concentrations.Both GCMs reproduce well the AO spatial pattern, defined by the leading hemispheric mode of monthly sea level pressure or daily

Andrew W. Robertson

2001-01-01

83

Simulation of the influence of atmospheric parameters on infrared target signature  

NASA Astrophysics Data System (ADS)

The radiation temperature of targets is studied as a function of horizontal range for different target temperatures and atmospheric conditions. The atmospheric infrared window regions 3 to 5 and 8 to 14 microns are investigated simulating AGA 680 cameras as sensors. Atmospheric parameters are summer/winter atmospheres, rural/maritime aerosols, humidity, and meteorological range. Target/background contrast of radiation temperature is given as a function of the chosen atmospheric and range parameters. Target detection probabilities for simple homogeneous backgrounds can be calculated from the results.

Richter, R.

1985-12-01

84

Influence of atmospheric pollution on nutrient limitation in the ocean  

Microsoft Academic Search

IN the midst of the debate over the ocean being phosphorus- or nitrogen-limited1,2, the 'acid rain' controversy prompted studies related to the atmospheric transport and delivery of pollutant nitrogen compounds over the ocean3-9. Some of those investigations concluded that atmospheric nitrogen had only minimal effects on euphotic-zone productivity7,8 or on nitrate at the Atlantic thermocline9, thus suggesting a negligible oceanic

Kent A. Fanning

1989-01-01

85

Multiyear measurements of the oceanic and atmospheric boundary layers at the Brazil-Malvinas confluence region  

Microsoft Academic Search

This study analyzes and discusses data taken from oceanic and atmospheric measurements performed simultaneously at the Brazil-Malvinas Confluence (BMC) region in the southwestern Atlantic Ocean. This area is one of the most dynamical frontal regions of the world ocean. Data were collected during four research cruises in the region once a year in consecutive years between 2004 and 2007. Very

Luciano Ponzi Pezzi; Ronald Buss de Souza; Otávio Acevedo; Ilana Wainer; Mauricio M. Mata; Carlos A. E. Garcia; Ricardo de Camargo

2009-01-01

86

Ionospheric D region remote sensing using VLF radio atmospherics  

Microsoft Academic Search

Lightning discharges radiate the bulk of their electromagnetic energy in the very lowfrequency (VLF, 3-30 kHz) and extremely lowfrequency (ELF, 3-3000 Hz) bands. This energy, contained in impulse-like signals called radio atmospherics or sferics, is guided for long distances by multiple reflections from the ground and lower ionosphere. This suggests that observed sferic waveforms radiated from lightning and received at

S. A. Cummer; T. F. Bell

1998-01-01

87

Measurements of Atmospheric X and gamma Rays-Balloon Experiments at Subantarctic Region.  

National Technical Information Service (NTIS)

The results of two stratospheric balloon experiments conducted to measure the atmospheric X-and gamma rays are presented. These experiments, conducted at Comandante Ferraz base in subantarctic region, have provided the spectrum of ground radioactivity in ...

U. B. Jayanthi R. V. Correa F. G. Blanco

1986-01-01

88

Terrestrial influence on atmospheric carbon dioxide, a mechanistic study using oxygen-18  

Microsoft Academic Search

The present carbon budget is unbalanced due to anthropogenic influences. Atmospheric warming might have resulted from rising atmospheric carbon dioxide levels. Sequestration of this CO2 is observed in oceans and land vegetation, though questions arise regarding the magnitude of the terrestrial biosphere sink. These questions can be addressed by measuring the abundance of the light stable isotopes of oxygen (16O,

Julianna Eileen Fessenden

1999-01-01

89

Pollution of atmospheric air in certain regions of Georgia and radiation background of open areas  

Microsoft Academic Search

Has been studied pollution of atmospheric air and radiation background of open area in certain regions of Georgia - Kutaisi, districts of Imereti and Samtskhe-Javakheti. Investigations have shown that in 1996-2001 years indices of atmospheric pollution were decreased (in Imereti region from 0,813 thousand t\\/sec to 0,399 thousand t\\/sec; in Kutaisi - from 0,455 thousand t\\/sec to 0,066 thousand t\\/sec;

Irma Tskhovrebadze

90

Regional Ecosystem-Atmosphere CO2 Exchanged Via Atmospheric Budgets (September 2002-August 2005).  

National Technical Information Service (NTIS)

Inversions of atmospheric CO2 mixing ratio measurements to determine CO2 sources and sinks are typically limited to coarse spatial and temporal resolution. This limits our ability to evaluate efforts to upscale chamber- and stand-level CO2 flux measuremen...

K. J. Davis S. J. Richardson

2005-01-01

91

Potential for atmospheric deposition of bacteria to influence bacterioplankton communities.  

PubMed

Biogeographic patterns in microbial communities are an exciting but controversial topic in microbial ecology. Advances in theory pertaining to assembly of microbial communities have made strong assumptions about dispersal of bacteria without exploration. For this reason, we investigated rates of atmospheric bacterial deposition and compared the taxonomic composition of bacteria in rain with that of common freshwater bacterial communities. Our findings suggest that it is not appropriate to take for granted that atmospheric deposition of bacteria is a significant vector of immigration to freshwater ecosystems. PMID:18393990

Jones, Stuart E; Newton, Ryan J; McMahon, Katherine D

2008-04-02

92

East African food security as influenced by future climate change and land use change at local to regional scales  

Microsoft Academic Search

Climate change impacts food production systems, particularly in locations with large, vulnerable populations. Elevated greenhouse\\u000a gases (GHG), as well as land cover\\/land use change (LCLUC), can influence regional climate dynamics. Biophysical factors such\\u000a as topography, soil type, and seasonal rainfall can strongly affect crop yields. We used a regional climate model derived\\u000a from the Regional Atmospheric Modeling System (RAMS) to

Nathan Moore; Gopal Alagarswamy; Bryan Pijanowski; Philip Thornton; Brent Lofgren; Jennifer Olson; Jeffrey Andresen; Pius Yanda; Jiaguo Qi

2012-01-01

93

Influence of the North Atlantic SST on the atmospheric circulation  

Microsoft Academic Search

Using the monthly COADS dataset and NMC-NCAR archives we show that significant anomalies of the atmospheric circulation are related to previous SST anomalies in the North Atlantic. A signal over the northwest Labrador Sea in late spring is associated with the dominant mode of SST variability during the preceeding winter. It is more clearly seen in the mid-troposhere than at

Arnaud Czaja; Claude Frankignoul

1999-01-01

94

INFLUENCE OF THE TURBULENCE OF ATMOSPHERE DURIG OPTIC MEASUREMENTS  

Microsoft Academic Search

Turbulent phenomena in the atmosphere, which lead to fluctuation of the intensity of the optical signal, are the cause for additional errors in optical and electronic goniometric devices. A quantitative evaluation of these errors is presented in this paper. Different goniometric devices are used in optical and electronic devices for targeting, chasing and control. These goniometric devices consist mainly of

Stiliyan Stoyanov; Valya Dimitrova; Angel Manev; Kunyu Palazov

2007-01-01

95

Time-history influence of global dust storms on the upper atmosphere at Mars  

NASA Astrophysics Data System (ADS)

A recent survey of the Mars Global Surveyor (MGS) electron data for dayside photoelectron observations over regions of strong crustal fields revealed an unusual bimodal solar flux dependence. The elevated-flux population was associated with the timing of a large global dust storm in late 2001. The results of a systematic study parameterizing the photoelectron flux intensities against a solar flux proxy and MGS-observed atmospheric dust opacity are presented here. Instantaneous dust opacities were used as well as time-history averages and maximal values. The result is a functional form for the photoelectron fluxes against these parameters. The inclusion of instantaneous dust opacity values in the function do not improve the correlation, but a time-history window significantly enhances the correlation and explains the bimodal distribution in the electron fluxes. The best relationship was obtained with 7-Earth-month time-history dust opacity variables included in the function. The most likely explanation for this long-lived influence of dust storms is a composition and/or density change in the upper atmosphere.

Liemohn, Michael W.; Dupre, Ava; Bougher, Stephen W.; Trantham, Matthew; Mitchell, David L.; Smith, Michael D.

2012-06-01

96

Sensitivity of stationary wave amplitude to regional changes in Laurentide ice sheet topography in single-layer models of the atmosphere  

Microsoft Academic Search

Climate variability on millennial timescales has been observed in many geologic records covering the last glacial cycle. A potential source of this variability is the Laurentide ice sheet (LIS) in its periodic discharge of large quantities of icebergs to the North Atlantic. The present analysis considers whether regional variations in LIS topography could exert a significant influence on the atmosphere's

Charles Jackson

2000-01-01

97

Variability Of Atmospheric Water Vapor In The Martian Polar Regions  

Microsoft Academic Search

We present analysis of spatial and temporal variability of water vapor in the Mars Northern Polar Region (NPR) during spring and summer seasons using data from Vikings and MGS missions. This study provides a new level of detail on the Martian water vapor cycle relative to the previous longitudinally averaged studies. We also present new water vapor retrievals extending MGS

Alexey A. Pankine; L. K. Tamppari

2008-01-01

98

MODELING REGIONAL-SCALE ATMOSPHERIC MERCURY USING RELMAP  

EPA Science Inventory

The Regional Lagrangian Model of Air Pollution (RELMAP) is used to simulate the emission, transport and diffusion, chemical transformation, and wet and dry deposition of elemental mercury gas, divalent mercury gas and particulate mercury. ased on recent modeling advances in Europ...

99

Impact of Ingesting Satellite-Derived Cloud Cover into the Regional Atmospheric Modeling System  

Microsoft Academic Search

This study investigates the extent to which assimilating high-resolution remotely sensed cloud cover into the Regional Atmospheric Modeling System (RAMS) provides an improved regional diagnosis of downward short- and longwave surface radiation fluxes and precipitation. An automatic procedure was developed to derive high- resolution (4 km 3 4 km) fields of fractional cloud cover from visible band Geostationary Operational Envi-

Ismail Yucel; W. James Shuttleworth; R. T. Pinker; L. Lu; S. Sorooshian

2002-01-01

100

The chemical composition of atmospheric admixtures in the region of Abastumani  

NASA Astrophysics Data System (ADS)

Measurements of the concentrations of NO, NO2, SO2, H2S, SO4(2-), NO3(-), NH4(+), CH2O, and O3, of the cosmogenic radioisotopes Be-7, P-32, and P-33, and of short-lived decay products of radon made in the atmospheric surface layer in the region of Abastumani (the Caucasus) in July and August 1975 and August 1978 are presented. It is shown that this region is relatively free of anthropogenic atmospheric pollution. The measured levels of the admixtures derive from transport from distant regions and local natural sources. The principal components of aerosols are compounds of ammonium and sulfates.

Shopauskas, K. K.; Gedraitis, B. I.; Girgzhdis, A. I.; Girgzhdene, R. V.; Linkaitite, E. Iu.; Shopauskene, D. A.

1982-08-01

101

Influence of Atmospheric Pressure Torch Plasma Irradiation on Plant Growth  

NASA Astrophysics Data System (ADS)

Growth stimulation characteristics of plants seeds are investigated by an atmospheric discharge irradiation into plasma seeds. Atmospheric pressure plasma torch is consisted of alumina ceramics tube and the steel mesh electrodes wind inside and outside of the tube. When AC high voltage (8 kHz) is applied to the electrode gap, the barrier discharge plasma is produced inside the alumina ceramics tube. The barrier discharge plasma is blown outside with the gas flow in ceramics tube. Radish sprouts seeds locate at 1 cm from the torch edge. The growth stimulation was observed in the length of a stem and a root after the plasma irradiation. The stem length increases approximately 2.8 times at the cultivation time of 24 h. And the growth stimulation effect is found to be maintained for 40 h, after sowing seeds. The mechanism of the growth stimulation would be the redox reaction inside plant cells induced by oxygen radicals.

Akiyoshi, Yusuke; Hayashi, Nobuya; Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu

2011-11-01

102

The electric Earth: Cosmic influences on the atmosphere  

NASA Astrophysics Data System (ADS)

A new generation of tools for examining the global atmosphere is transforming our understanding of the role of electricity in the Earth's climate. Neil Arnold and Torsten Neubert review this developing field. The universe is full of exotic particles and waves. Some, such as neutrinos, pass through our neighbourhood unnoticed; others, such as extreme uv radiation, are absorbed by the upper atmosphere before they are able to do too much damage. For a long time, any systematic attempt to understand how our weather can be affected by extra-terrestrial sources other than solar visible and infrared radiation has been a lively and often controversial diversion from mainstream research. But recent scientific and technological breakthroughs and concern over long-term climate change have brought this subject into the spotlight.

Arnold, Neil; Neubert, Torsten

2002-12-01

103

Influence of combustion atmospheres on the phase transformation of zirconia  

Microsoft Academic Search

This letter is concerned with the phase changes and changes in chemical composition in different combustion atmospheres at 700 to 900°C of a commercial partially stabilized ZrO2 material (designated ZN40, manufactured by Feldmfihle AG, Germany), with approximately 12 mol % MgO (Mg ZrO2). Observed low-temperature degradation of a commercial tetragonal stabilized ZrO2 material (manufactured by NTK, Japan) (Y ZrO2), with

A. K. Tjernlund; L. Hermansson; R. Carlsson; K. O. Axelsson

1986-01-01

104

Coordinated radar observations of atmospheric diurnal tides in equatorial regions  

NASA Astrophysics Data System (ADS)

The long-term behavior of atmospheric tides in the mesosphere and lower thermosphere has been observed with the meteor wind radar (MWR) in Jakarta, Indonesia (6°S, 107°E) from November 1992 to August 1997. The amplitudes and phases of the diurnal tides show systematic seasonal variations, particularly distinct in the meridional component. In addition, substantial interannual variability is evident, characterized by a biennial periodicity of tidal parameters, and considerably small tidal amplitudes exclusively seen in 1996. The MWR results are compared with the Global Scale Wave Model (GSWM) as well as MF radar data collected in two equatorial sites in Pontianak (0.03°N, 109°E) and Christmas Island (2°N, 158°W) for November 1995-July 1997 and January 1996-October 1997, respectively. Comparison studies of these radar data have revealed the detailed latitudinal structure of the diurnal tide near the equator. The GSWM has successfully described the general characteristics of the radar results, although some discrepancies are recognized. In 1996 when radar data are available at all the three sites, the monthly mean values of tidal amplitudes at 90 km agreed very well between Jakarta and Pontianak, while significant discrepancy was found for Christmas Island, suggesting the existence of geographical effects such as non-migrating tides.

Tsuda, T.; Ohnishi, K.; Isoda, F.; Nakamura, T.; Vincent, R. A.; Reid, I. M.; Harijono, S. W. B.; Sribimawati, T.; Nuryanto, A.; Wiryosumarto, H.

1999-07-01

105

Atmospheric Extreme Events in the North Atlantic Region  

NASA Astrophysics Data System (ADS)

An important part of European weather and climate are storms. European winter storms cause economic damage and insurance losses on the order of billions of Euro per year. European winter storms rank as the second highest cause of global natural catastrophe insurance loss. Many of these hazard events are not independent; for instance, severe storms can occur in trains of storms. Recent examples of such subsequently occurring storms include January 2008 (Paula and Resi) and March 2008 (Emma, Johanna and Kirsten). Each of these trains of storms caused damages on the order of ~€1bn. Extreme value statistics are based on the premise that extreme events are iid but this is rarely the case in natural systems where extreme events tend to cluster. Thus, no account is taken of memory and correlation that characterise many natural time series; this fundamentally limits our ability to forecast and to estimate return periods of extreme events. In my presentation I will discuss two possible causes of this clustering: (i) The propensity of extreme events to depend on large-scale circulation regimes and (ii) the long-range correlation properties of surface windspeeds enhances the likelihood of extreme events to cluster. These two characteristics affect the return periods of atmospheric extreme events and thus insurance pricing.

Franzke, C.

2012-04-01

106

Investigating Regional Scale Processes Using Remotely Sensed Atmospheric CO 2 Column Concentrations from SCIAMACHY  

Microsoft Academic Search

\\u000a Satellite observations of atmospheric CO2 are a rapidly emerging area of scientific research which have the potential to reduce the uncertainties in global carbon\\u000a cycle fluxes and provide insight into surface sources and sinks. In this chapter, the potential of atmospheric CO2 measurements, retrieved by the SCIAMACHY instrument on-board the ENVISAT satellite, to investigate regional carbon cycle\\u000a processes is explored.

M. P. Barkley; A. J. Hewitt; P. S. Monks

107

Dry and wet atmospheric deposition of nitrogen, phosphorus and silicon in an agricultural region  

Microsoft Academic Search

We measured atmospheric nutrient deposition as wet deposition and dry deposition to dry and wet surfaces. Our analyses offer estimates of atmospheric transport of nitrogen (N), phosphorus (P) and silicon (Si) in an agricultural region. Annual dry and wet deposition (ha?1 year?1) was 0.3 kg of P, 7.7 kg of N, and 6.1 kg of Si; lower than or similar

Kelsy A. Anderson; John A. Downing

2006-01-01

108

Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions &ndash Part 2: The Americas  

NASA Astrophysics Data System (ADS)

Aerosol perturbations over selected land regions are imposed in Version-4 of the Goddard Earth Observing System (GEOS-4) general circulation model (GCM) to assess the influence of increasing aerosol concentrations on regional circulation patterns and precipitation in four selected regions: India, Africa, and North and South America. Part 1 of this paper addresses the responses to aerosol perturbations in India and Africa. This paper presents the same for aerosol perturbations over the Americas. GEOS-4 is forced with prescribed aerosols based on climatological data, which interact with clouds using a prognostic scheme for cloud microphysics including aerosol nucleation of water and ice cloud hydrometeors. In clear-sky conditions the aerosols interact with radiation. Thus the model includes comprehensive physics describing the aerosol direct and indirect effects on climate (hereafter ADE and AIE respectively). Each simulation is started from analyzed initial conditions for 1 May and was integrated through June-July-August of each of the six years: 1982-1987 to provide a 6-ensemble set. Results are presented for the difference between simulations with double the climatological aerosol concentration and one-half the climatological aerosol concentration for three experiments: two where the ADE and AIE are applied separately and one in which both the ADE and AIE are applied. The ADE and AIE both yield reductions in net radiation at the top of the atmosphere and surface while the direct absorption of shortwave radiation contributes a net radiative heating in the atmosphere. A large net heating of the atmosphere is also apparent over the subtropical North Atlantic Ocean that is attributable to the large aerosol perturbation imposed over Africa. This atmospheric warming and the depression of the surface pressure over North America contribute to a northward shift of the inter-Tropical Convergence Zone over northern South America, an increase in precipitation over Central America and the Caribbean, and an enhancement of convergence in the North American monsoon region.

Wilcox, E. M.; Sud, Y. C.; Walker, G.

2009-10-01

109

Longitudinal variations in the Saturnian atmosphere. I. Equatorial region  

SciTech Connect

Longitudinal variations in the equatorial regions of Saturn are sought in both Voyager orange and methane-filter and ground-based 6000-6600 A observations. The spectral variations found are inconsistent with reflecting layer height variation; they are alternatively modeled by changes in the single-scattering albedo of the haze, as well as in the specific abundance of haze gas. The 500-km spatial resolution data furnished by Voyager are found to be consistent with a specific abundance of haze gas between 10 and 24 km-am. Ammonia and methane mixing ratios are derived. 44 references.

Killen, R.M.

1988-02-01

110

The influence of atmospheric pressure on landfill methane emissions  

SciTech Connect

Landfills are the largest source of anthropogenic methane (CH{sub 4}) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH{sub 4} emissions have been reported. Here, we present the results of a multi-season study of whole landfill CH{sub 4} emissions using atmospheric tracer methods at the Nashua, New Hampshire Municipal landfill in the northeastern United States. The measurement data include 12 individual emission tests, each test consisting of 5-8 plume measurements. Measured emissions were negatively correlated with surface atmospheric pressure and ranged from 7.3 to 26.5 m{sup 3} CH{sub 4} min{sup -1}. A simple regression model of our results was used to calculate an annual emission rate of 8.4x10{sup 6} m{sup 3} CH{sub 4} year{sup -1}. These data, along with CH{sub 4} oxidation estimates based on emitted landfill gas isotopic characteristics and gas collection data, were used to estimate annual CH{sub 4} generation at this landfill. A reported gas collection rate of 7.1x10{sup 6} m{sup 3} CH{sub 4} year{sup -1} and an estimated annual rate of CH{sub 4} oxidation by cover soils of 1.2x10{sup 6} m{sup 3} CH{sub 4} year{sup -1} resulted in a calculated annual CH{sub 4} generation rate of 16.7x10{sup 6} m{sup 3} CH{sub 4} year{sup -1}. These results underscore the necessity of understanding a landfill's dynamic environment before assessing long-term emissions potential.

Czepiel, P.M.; Shorter, J.H.; Mosher, B.; Allwine, E.; McManus, J.B.; Harriss, R.C.; Kolb, C.E.; Lamb, B.K

2003-07-01

111

Influence of interplanetary trajectory selection on Mars atmospheric entry velocity  

NASA Astrophysics Data System (ADS)

Many current manned Mars mission studies are using low lift-to-drag ratio (L/D) vehicles to aerobrake at both Mars and Earth. The use of these low L/D vehicles could limit the allowable velocity at the atmospheric interface. This paper will demonstrate that if entry velocity constraints are incorporated into the interplanetary analysis of aerobraking Mars missions, many opportunities can be achieved for a small increase in initial mass in low-Earth orbit (IMLEO). These opportunities result from varying the initial launch date and the encounter dates and possibly using a powered Venus swingby on either the inbound or outbound transfer. This paper demonstrates this technique by using three atmospheric entry velocity ranges at Mars arrival (6.0-8.5, 6.4-8.1, and 7.2-7.3 km/s), unconstrained Mars entry velocities, and an Earth return entry velocity below 14 km/s. The results indicate that, by carefully selecting the interplanetary trajectory, an optimum IMLEO mission can be found for even highly restrictive entry velocity missions in practically all of the 15 yr studied.

Striepe, Scott A.; Braun, Robert D.; Powell, Richard W.; Fowler, Wallace T.

1993-08-01

112

Atmospheric modes influence on the inter- annual variability of the Iberian Poleward Current from 1985 to 2006  

NASA Astrophysics Data System (ADS)

The inter-annual variability of the Iberian poleward current (IPC) along the northwestern coast of the Iberian Peninsula (IP) (40- 43N) and its intrusion in the Cantabrian Sea (Navidad, 6- 8W) were analyzed. The January Sea Surface Temperature (J SST) was obtained from the advanced very high resolution radiometer (AVHRR) NOAA satellite from 1985 to 2006. In addition, the dependence of IPC SST on the most representative regional patterns with some influence upon the eastern North Atlantic region was analyzed by means of correlations between November- December atmospheric modes and J SST. The considered modes were: North Atlantic Oscillation pattern (NAO), Eastern Atlantic pattern (EA), Eastern Atlantic Western Russia pattern (EA/WR), Polar/Eurasia pattern (POL) and Scandinavia pattern (SCA). In the present study it has been highlighted that: (1) there are several years (1986, 1987, 1992, 1995, 1997, 1999, 2004 and 2005) during which water in the IPC region is colder than the oceanic one remarking a weak or inexistent IPC during these Januaries and (2) three atmospheric patterns (N-D NAO, N-D EA/WR and N-D POL) are responsible of the main variability of the J SST in the IPC region of the western IP and only two indices (N-D EA/WR, N-D NAO) have shown to be significant to explain the variability of the J SST in the IPC region of the northern IP region.

Decastro, M.; Gómez-Gesteira, M.; Álvarez, I.; Crespo, A. J. C.; Ramos, A. M.

2009-04-01

113

On mechanisms for the formation of atmospheric irregularities in the solar terminator region  

NASA Astrophysics Data System (ADS)

The mechanisms of formation of atmospheric irregularities (AI) by the solar terminator (ST) have been considered. All of these mechanisms are divided into two classes, linear or nonlinear, according to the mechanism of AI generation. All mechanisms determined by a moving step of some atmospheric parameter (pressure, temperature, and so on) belong to linear mechanisms for wave excitation. Mechanisms determined by instabilities in the atmosphere inside the ST region are nonlinear mechanisms. Examples are the gradient-radiative instability (GRI), which arises from the vertically inhomogeneous absorption of solar radiation, turbulence arising in the ST region, and the plasma instability in the evening hours caused by the increase of the electron pressure gradient inside the ST region.

Somsikov, V. M.

1995-01-01

114

Proximate humid and dry regions in Jupiter's atmosphere indicate complex local meteorology.  

PubMed

Models of Jupiter's formation and structure predict that its atmosphere is enriched in oxygen, relative to the Sun, and that consequently water clouds should be present globally near the 5-bar pressure level. Past attempts to confirm these predictions have led to contradictory results; in particular, the Galileo probe revealed a very dry atmosphere at the entry site, with no significant clouds at depths exceeding the 2-bar level. Although the entry site was known to be relatively cloud-free, the contrast between the observed local dryness and the expected global wetness was surprising. Here we analyse near-infrared (around 5 microm) observations of Jupiter, a spectral region that can reveal the water vapour abundance and vertical cloud structure in the troposphere. We find that humid and extremely dry regions exist in close proximity, and that some humid regions are spatially correlated with bright convective clouds extending from the deep water clouds to the visible atmosphere. PMID:10821265

Roos-Serote, M; Vasavada, A R; Kamp, L; Drossart, P; Irwin, P; Nixon, C; Carlson, R W

2000-05-11

115

The ORCA West Coast Regional Project - Atmospheric Top-Down Modeling to constrain Regional Carbon Budgets at high Temporal and Spatial Resolution  

NASA Astrophysics Data System (ADS)

The ORCA project aims at determining the regional carbon balance of Oregon, California and Washington, with a special focus on the effect of disturbance history and climate variability on carbon sources and sinks. ORCA provides a regional test of the overall NACP strategy by demonstrating bottom-up and top-down modeling approaches to derive carbon balances at subregional to regional scales. The ORCA top-down modeling component has been set up to capture flux variability on the regional scale at high temporal and spatial resolution. Atmospheric transport is simulated coupling the mesoscale model WRF (Weather Research and Forecast) with the STILT (Stochastic Time Inverted Lagrangian Transport) footprint model. This setup allows identifying sources and sinks that influence atmospheric observations with highly resolved mass transport fields and realistic turbulent mixing. High-precision atmospheric CO2 concentrations are monitored as continuous time series in hourly timesteps at 5 locations within the model domain, west to east from the Pacific Coast to the Great Basin, and include two flux sites for evaluation of computed fluxes. Terrestrial biosphere carbon fluxes are simulated at an effective spatial resolution of smaller than 1km and subdaily timesteps, considering effects of ecoregion, land cover type and disturbance regime on the carbon budgets. Flux computation assimilates high-resolution remote sensing products (e.g. LandSat, MODIS) and interpolated surface meteorology (DayMet, SOGS, PRISM). We present results on regional carbon budgets for the ORCA modeling domain that have been optimized using Bayesian inversion and the information provided by the network of high-precision CO2 observations. We address the influence of spatial and temporal resolution in the general modeling setup on the findings, and test the level of detail that can be resolved by top-down modeling on the regional scale, given the uncertainties introduced by various sources for model-data mismatch. Application of the approach highlights the strong regional variability in CO2 exchange rates on the regional scale. For Oregon, we found that this type of model must account for water availability and drought stress to avoid overestimating terrestrial sinks for CO2.

Goeckede, M.; Michalak, A. M.; Vickers, D.; Turner, D.; Law, B.

2008-12-01

116

California reanalysis downscaling at 10 km using an ocean-atmosphere coupled regional model system  

NASA Astrophysics Data System (ADS)

A fully coupled regional downscaling system based on the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and NCEP/DOE (R-2) atmospheric reanalysis in order to study the impact of coupling on the regional scale atmospheric analysis. The results were subsequently compared with the uncoupled downscaling forced by the prescribed observed sea surface temperature (SST). The coupled experiment yielded the SST and ocean current with realistic small-scale oceanic features that are almost absent in the oceanic reanalysis. Upwelling over the California coast is well resolved and comparable to findings obtained from high-resolution observations. The coupling impact on the atmospheric circulation mainly modulates the near surface atmospheric variables when compared to the simulation conducted without coupling. The duration of the Catalina Eddy detected in the coupled experiment increased by about 6.5% when compared to that in the uncoupled experiment. The offshore land breeze is enhanced by about 10%, whereas the change in the onshore sea breeze is very small during the summer.

Li, Haiqin; Kanamitsu, Masao; Hong, Song-You

2012-06-01

117

Atmospheric Particulate Metals and Metalloids in Lake Ontario Region 2005- 2007  

NASA Astrophysics Data System (ADS)

Particles in rural and urban air were collected at two ground sites along the north-east shorelines of Lake Ontario, Canada. CEPA (Canadian Environmental Protection Act) metals and metalloids As, Cd, Cu, Hg, Ni, Pb, Se, Zn were captured on quartz fibre filters (PM10). Particulate metal concentrations per cubic meter of air was As˜0.1-2.9, Cd˜0.02-2.6, Cu˜2.5-19.5, Fe˜110-4400, Hg˜0.07-0.94, Mn˜30- 140, Ni˜1.0-46.0, Pb˜1.5-10.5, Se˜0.1-0.9 and Zn˜12-53 ng which can generally represent mixed ambient and urban contributions during that time period. Elevated particulate metals and metalloids concentrations were found in the industrial areas of the Lake Ontario region with Fe and Mn reaching 100 times ambient levels. Calculated (2005) dry and wet atmospheric metal deposition (Zhang model 2001) showed a slight gradual decrease from recent years for Pb, Cd, As but remain unchanged for Se. Meteorological conditions were found to have major influences in the characteristics of metal particulates collected and their size fractions. Results of particle size distribution (AGU 2006, 2007) and particulate metal content can provide better estimates of metal loading by dry and wet deposition.

Wong, H. K.; Blanchard, P.; Muir, D.

2009-05-01

118

A new coupled Atmosphere-Ocean Regional Climate Model: study of the Eastern Mediterranean Transient  

NASA Astrophysics Data System (ADS)

The Mediterranean sea is an active semi-enclosed marginal sea which communicates with the Atlantic ocean through the Strait of Gibraltar. Its ideal configuration provides an opportunity to investigate hydrological mechanisms and heat and freshwater budgets over its basin. These surface fluxes and their variability at various temporal and spatial scale influence the formation of the Mediterranean water masses. Modeling the mean behavior, the decadal variability and the trends of the Mediterranean sea water is a challenging task and important for future climate change scenarios. A new coupled Atmosphere-Ocean Regional Climate Model (AORCM) forced by ERA40 as boundary conditions simulates the recent climate from 1959 to 2001. A validation of the modeled heat or freshwater budget of the Mediterranean basin is done in comparison with a large panel of observation datasets. The Eastern Mediterranean Transient (EMT) which occurred in the early 1990's formed over those winter large amount of dense Cretan Deep water. This dense water then cascaded and spread into the Eastern basin. For the first time the EMT event is studied in a realistic frame using a high-resolution coupled model with no constraint on the spatio-temporal variability of the air-sea fluxes. Preconditioning step, air-sea fluxes over the Aegean Sea, water mass formation in the Cretan basin, cascading and spreading of the newly formed water in the Eastern Mediterranean is analysed

Dubois, Clotilde; Calmanti, Sandro; Sevault, Florence; Somot, Samuel

2010-05-01

119

Influence of transport uncertainty on annual mean and seasonal inversions of atmospheric CO2 data  

NASA Astrophysics Data System (ADS)

Inversion methods are often used to estimate surface CO2 fluxes from atmospheric CO2 concentration measurements, given an atmospheric transport model to relate the two. The published estimates disagree strongly on the location of the main sources and sinks, however. Are these differences due to the different time spans considered, or are they artifacts of the method and data used? Here we assess the uncertainty in such estimates due to the choice of time discretization of the measurements and fluxes, the spatial resolution of the fluxes, and the transport model. A suite of 27 Bayesian least squares inversions has been run, given by varying the number of flux regions solved for (7, 12, and 17), the time discretization (annual/annual, annual/monthly, and monthly/monthly for the fluxes/data), and the transport model (TM2, TM3, and GCTM), while holding all other inversion details constant. The estimated fluxes from this ensemble of inversions for the land + ocean sum are stable over large zonal bands, but the spread in the results increases when considering the longitudinal flux distribution inside these bands. On average for 1990-1994 the inversions place a large CO2 uptake north of 30°N (3.2 ± 0.3 GtC yr-1), mostly over the land regions, with more in Eurasia than North America. The ocean fluxes are generally smaller than given by [1999], especially south of 15°S and in the global total, where they are less than half as large. A small uptake is found for the tropical land regions, suggesting that growth more than compensates for deforestation there. The results for the different transport models are consistent with their known mixing properties; the longitudinal pattern of their land biosphere rectifier, in particular, strongly influences the regional partitioning of the flux in the north. While differences between the transport models contribute significantly to the spread of the results, an equivalent or even larger spread is due to the time discretization method used: Solving for annual mean fluxes with monthly mean measurements tended to give spurious land/ocean flux partition in the north. We suggest then that this time discretization method be avoided. Overall, the uncertainty quoted for the estimated fluxes should include not only the random error calculated by the inversion equations but also all the systematic errors in the problem, such as those addressed in this study.

Peylin, Philippe; Baker, David; Sarmiento, Jorge; Ciais, Philippe; Bousquet, Philippe

2002-10-01

120

Numerical simulation of the marine atmospheric boundary layer flow over Cape Canaveral region and Gulf Stream using AVHRR SST: an atmospheric sea breeze model  

NASA Astrophysics Data System (ADS)

An atmospheric mesoscale numerical model has been developed and applied to the marine atmospheric boundary layer in the vicinity of sharp sea-surface temperature (SST) gradients. The Gulf Stream offshore of Each Central Florida near Cape Canaveral is the region of interest. The model equations which govern atmospheric behavior are based on the basic conservation laws of mass, momentum, and energy. A 'primitive' equation formulation is used to produce preliminary predictions of horizontal velocity, potential temperature, and water vapor. The hydrostatic approximation is applied to the vertical momentum conservation equation and the anelastic form of the continuity equation is used to approximate mass conservation. Surface fluxes of momentum, heat, and moisture are estimated using high-resolution SST data obtained in near-real time from the AVHRR IR instrument. Interaction of the boundary layer flow with the nearby Central Florida peninsula is simulated by inducing a diurnal sea breeze circulation across the coastline. It is found through a series of simulations that the distribution of sea-surface temperatures influences the boundary layer flow field - especially over the region of the Gulf Stream front and the low level convergence field, which may be an important factor for initiating convective precipitation over the land-water margin and Gulf Stream. The importance of the air-sea or air-land interfaces are thus fully recognized as being crucial to parameterize via remote sensing data in order to proceed with further model developments of the newly developed sea-breeze model. Further examination of methods for estimating surface temperatures of the water and land as well as inclusion of surface gravity wave forcing due to the diurnal sea breeze over the complex land-water margin in the Indian River Lagoon will need to be included in order to utilize the model for future application.

Bostater, Charles R.; Gimond, Manuel; Uhlhorn, Erik; McNally, Ted

2000-12-01

121

Atmospheric and oceanic influences on the winter and spring Miño river flow  

NASA Astrophysics Data System (ADS)

We examine the climatic mechanisms associated to Miño streamflow anomalies during winter and spring, exploring the relationships between the streamflow and several atmospheric teleconnections patterns and seasonal sea level pressure and sea surface temperature (SST) for the previous and simultaneous seasons. The Miño river basin is located in the Northwestern Iberian Peninsula. It covers a limited territory, bordered by the Atlantic Ocean and Cantabric Sea. The data base of streamflows comprises montlhy data form 19 stations, covering the period from October 1956 to September 2007. We have performed a Principal Component Analysis of these monthly data, finding only one significant PC with a associated variance of 86%. Following the approach adopted by other authors, in a first step we try to identify teleconnections patterns and sectors of oceanic SST and SLP anomalies that can be related with Miño's river flow. In order to do that we have evaluated the point linear correlation between the winter and spring streamflow PC series and the teleconnections indices, the Northern Hemisphere SLP and the global SST anomalies from simultaneous previous seasons. Teleconnections and regions showing significant correlations are identified as potential explanatory mechanisms, or even predictors. The second step is to identify, among these selected teleconnections and regions, those that can be considered as stable. This is achieved through the analysis of the variability of the correlation between winter and spring Miño flow anomalies and potential explanatory variables using a moving window of 20 years. The correlation is considered to be stable for those regions where spring streamflow and explanatory variables are significantly correlated at 90% level (r = 0.36) for more than 80% of the 20-year windows covering the period 1956-2007 and, furthermore, that the sign of the correlation does not change with time. Teleconnections and regions verifying this criterion are considered as robust explanatory variables and predictors, which could be used in a multiple linear regression model for the Miño streamflow. The preliminary results show that winter Miño streamflow are more dominated by contemporary NAO, EA, and SCA teleconnections and also by the SLP anomalies over Iberian and Scandinavian Peninsula and Northeastern Canada. On the other hand, for the spring stream flow, there is also a remarkable influence of the contemporary SCA, but also an influence on previous winter SLP anomalies on the Northeastern Canada and with previous winter SST anomalies of the region El Niño3. These variables will be used as explanatory variables for the spring Miño river flow in a model based on linear regression. Acknowledgments: The Spanish Ministry of Science and Innovation, with additional support from the European Community Funds (FEDER), project CGL2007-61151/CLI, has financed this study.

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

2010-09-01

122

Use of a regional atmospheric model to simulate lake-atmosphere feedbacks associated with Pleistocene Lakes Lahontan and Bonneville  

USGS Publications Warehouse

A regional model of the atmosphere (version 4 of the NCAR mesoscale model, MM4) was used to assess whether lake-effect precipitation was a significant component of the late-Pleistocene hydrologic budgets of Lakes Lahontan and Bonneville. Control simulations for January and July of 1979 were made using MM4, and the Pleistocene highstand surface areas of the lakes were added to the model and the simulations repeated. In the January simulations, 18% of the moisture added to the modeled atmosphere by Lake Lahontan returned to the Lahontan basin as precipitation, while 32% of the water evaporated from Lake Bonneville fell as precipitation over the Bonneville basin. In the July simulations, 7% of the moisture added to the modeled atmosphere by Lake Lahontan returned to the Lahontan basin as precipitation, and 4% of the water evaporated from Lake Bonneville fell as precipitation over the Bonneville basin. An additonal January simulation was made with the lake surface areas set at onehalf their highstand extents (the average surface area 20 to 15 ka BP). Results from this simulation were similar to the simulation with the highstand lakes, indicating lake-effect precipitation could have been a significant component of the hyrologic budgets of the lakes before and during the highstand period. ?? 1992 Springer-Verlag.

Hostetler, S. W.; Giorgi, F.

1992-01-01

123

Atmosphere  

NSDL National Science Digital Library

What is this atmosphere that surrounds the Earth? This instructional tutorial, part of an interactive laboratory series for grades 8-12, introduces students to the structure, effects, and components of the atmosphere. Here students investigate the composition of the atmosphere; effects of temperature, pressure, and ozone; the greenhouse effect; and how Earth compares with other planets. Interactive activities present students with opportunities to explore ideas and answer questions about the atmosphere, including its structure, the making of ozone, rocket launching, and measuring the atmosphere. Pop-up boxes provide additional information on topics such as dust, rain, and atmospheric composition. Students complete a final written review of six questions about the atmosphere. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

124

Atmospheric trace elements over source regions for Chinese dust: concentrations, sources and atmospheric deposition on the Loess plateau  

NASA Astrophysics Data System (ADS)

The mass-particle size distributions of up to 17 trace elements in aerosol particle samples from dust storm and non-dust storm periods were determined for three sites in or near the source regions of Chinese dust. The mass of particulate material in the atmosphere at the sites is dominated by mineral aerosol particles. An absolute principal component analysis of the non-dust storm elemental data for the loess region allows the estimation of the mass contributions from two coarse-particle classes (soil dust and dust associated with pollutants), and two fine-particle classes (soil dust and anomalously enriched). For most elements (Al, Si, Ca, Fe, Ti, K, S and As), the mass-particle size distributions (MSDs) were approximately log-normal. The mass-median diameters (MMDs) of the soil-derived elements tended to decrease with distance from the desert region and when the dust storms subsided. Total dry deposition velocities were calculated by fitting a log-normal distribution to the aerosol data and calculating deposition rates for 100 particle-size intervals using a two-layer deposition model. The mean dry-deposition rates and fluxes were highest during dust storms over desert regions. In thloess region, the calculated dry deposition velocities of soil derived elements (Al, Si, Ca, Fe and Ti) during non-dust storm periods were from 3.1 to 3.7 cm s -1. From the estimated mass-particles size distributions, the coarser and finer mineral particles were found to benriched with Ca, Fe, Ti and K relative to Al or Si. On a yearly basis, the dry atmospheric input to the Loess Plateau was mainly attributable to normal transport processes, i.e. non-dust storm conditions. Wet deposition fluxes estimated from scavenging ratios indicate that dry deposition dominated the total atmospheric deposition of mineral aerosol. The deposition of aerosol particles associated with coal burning or other anthropogenic sources also was considerable on the Loess Plateau.

Zhang, Xiaoye; Arimoto, Richard; An, Zhisheng; Chen, Tuo; Zhang, Guangyu; Zhu, Guanghua; Wang, Xinfu

125

Organochlorine pesticides in the atmosphere of Guangzhou and Hong Kong: Regional sources and long-range atmospheric transport  

NASA Astrophysics Data System (ADS)

Organochlorine pesticides (OCPs) were measured in the atmosphere over the period of December 2003-December 2004 at four sampling sites in Guangzhou and Hong Kong. Gas phase and particle phase concentrations of 8 OCP species, including trans-chlordane ( t-CHL), cis-chlordane ( c-CHL), p, p'-DDT, p, p'-DDE, o, p'-DDT, ?-endosulfan, ?- and ?-hexachlorocyclohexane (HCH), were studied. OCPs were found predominantly in the gas phase in all seasons. t-CHL, c-CHL, o, p'-DDT, p, p'-DDT and ?-endosulfan had significantly ( p<0.001) higher concentrations than other OCPs, with mean values (gas+particle) typically ranging from 103 to 1440 pg m -3. In general, the concentrations of OCPs in summer were higher than that in winter, except for ?-HCH which showed no clear seasonal pattern. Higher levels of ?-HCH and o, p'-DDT found in Guangzhou could be attributed to the present usage of lindane and dicofol in the Pearl River Delta (PRD) region. The very high concentrations of p, p'-DDT and ?-endosulfan were observed at all sampling sites. The results of 7 days air back trajectory analysis indicated that the unusual high p, p'-DDT levels in summer in both cities could be related to the seasonal usage of DDT containing antifouling paints for fishing ships in the upwind seaports of the region. The high concentrations of ?-endosulfan in winter in the study area suggested an atmospheric transport by the winter monsoon from the East China, where endosulfan is being used as insecticide in cotton fields. The consistency of the seasonal variation of concentrations and isomeric ratios of DDTs and ?-endosulfan with the alternation of winter monsoon and summer monsoon suggested that the Asian monsoon plays an important role in the long-range atmospheric transport of OCPs.

Li, Jun; Zhang, Gan; Guo, Lingli; Xu, Weihai; Li, Xiangdong; Lee, Celine S. L.; Ding, Aijun; Wang, Tao

126

Modeling evaporation from porous media influenced by atmospheric processes  

NASA Astrophysics Data System (ADS)

Modeling evaporation processes from partially saturated soils into the ambient air is a challenging task. It involves usually a variety of interacting processes and depends on the multitude of properties of the fluids and of the porous medium. Often, the ambient free-flow and the porous-medium compartments are modeled separately with a specification of the evaporation rate as boundary condition. We have developed a coupling concept, which allows the combined modeling of a free-flow and a porous-medium system under non-isothermal conditions with the evaporative fluxes across the soil-atmosphere interface as model output. It is based on flux continuity and local thermodynamic equilibrium at the interface. Darcy's law for multiple phases is used in the porous medium, whereas the ambient air flow is modeled as a compositional single-phase Stokes system. The concept has been implemented in the numerical simulator DuMux. A comparison of simulated and measured data from wind tunnel experiments performed in the group of D. Or (ETH Zürich) will be shown. Furthermore, the impact of several parameters, such as a varying wind velocity, temperature or different soil properties on the evaporation process has been analyzed in a numerical parameter study. The results will be presented and discussed.

Mosthaf, K.; Baber, K.; Flemisch, B.; Helmig, R.

2012-04-01

127

Influence of ocean surface conditions on atmospheric vertical thermodynamic structure and deep convection  

SciTech Connect

The influence of sea surface temperature (SST) and surface wind divergence on atmospheric thermodynamic structure is analysed along with the resulting effects on the occurrence of deep convection using National Meterological Center radiosonde data and International Satellite Cloud Climatology Program data for July 1983-July 1985. The onset of deep convection requires not only the existence of positive convective available potential energy (CAPE), but also unstable planetary boundary layer (PBL). A stable PBL is observed to suppress deep convection even when CAPE is positive. Variations of SSt have a major effect on CAPE, but surface wind divergence can also affect deep convection by changing the lapse rate in the lower troposphere and humidity in the PBL. In warm SST regions, CAPE > 0 regardless of assumptions about condensate loading. When SST <27[degrees]C, CAPE layer and moisten the PBL enough to make the atmosphere neutrally stable in the mean. As a result, deep convection is generally enhanced either when SST [>=] 28[degrees]C in the absence of strong surface wind divergence or when strong surface wind convergence occurs even if SST < 27[degrees]. The anomalous suppression wind divergence or when strong surface wind convergence occurs even if SST < 27[degrees]C. The anomalous suppression of deep convection in the warm area of the equatorial west Pacific lying between the ITCZ and SPCZ is probably caused by dryness in the PBL and an inversion in that area. The seasonal cycles of deep convection and surface wind divergence are in phase with the maximum solar radiation and lead SST for one to three months in the central Pacific. The change of PBL relative humidity plays a critical role in the changeover to convective instability in this case. The seasonal change of deep convection and associated clouds seems not to have important effects on the seasonal change of local SST in the central Pacific. 37 refs., 11 figs., 1 tab.

Fu, Rong (California Institute of Technology, Pasadena, CA (United States)); Del Genio, A.D.; Rossow, W.B. (NASA/Goddard Space Flight Center, New York, NY (United States))

1994-07-01

128

Atmosphere-ocean exchanges between the Canadian Regional Climate Model (CRCM) and the Gulf of Saint-Lawrence Ocean Model (GOM)  

NASA Astrophysics Data System (ADS)

Atmosphere-ocean exchanges over the Gulf of Saint-Lawrence (Canada) are investigated using an atmosphere-ocean climate simulation system developed with the Canadian Regional Climate Model (CRCM) and the Gulf of Saint-Lawrence Ocean Model (GOM). Within the ocean (atmosphere) model, the atmospheric (oceanic) fields are not calculated but are required to compute the turbulent vertical surface fluxes. Therefore, the models interact through the exchange of atmospheric and oceanic fields in an iterative process. The experience consists in the execution of three iterations by the two models over the same period of one year. Results show the ability of the CRCM-GOM system to reproduce realistic exchanges between the atmosphere and the ocean over the Gulf of Saint-Lawrence. We find that the solution of each model converges after several iterations. These results confirm the influence of turbulent fluxes during winter and of radiatives fluxes during summer on the net surface heat flux and consequently on the sea surface temperature. This study is a part of the development of a coupled ocean-ice-atmosphere modeling system for coastal waters of Eastern Canada, including the Gulf of Saint-Lawrence and the Hudson Bay, with the aim of furthering our understanding of regional-scale coastal climate processes and improving their simulations in current as well as in perturbed climate.

Charpentier, D.; Caya, D.; Saucier, F.; Laprise, R.

2003-04-01

129

Mercury emissions to the atmosphere from natural and anthropogenic sources in the Mediterranean region  

Microsoft Academic Search

This report discusses past, current and projected mercury emissions to the atmosphere from major industrial sources, and presents a first assessment of the contribution to the regional mercury budget from selected natural sources. Emissions (1995 estimates) from fossil fuels combustion (29.8tyr?1), cement production (28.8tyr?1) and incineration of solid wastes (27.6tyr?1), all together account for about 82% of the regional anthropogenic

N. Pirrone; P. Costa; J. M. Pacyna; R. Ferrara

2001-01-01

130

Atmospheric brown clouds: Hemispherical and regional variations in long-range transport, absorption, and radiative forcing  

Microsoft Academic Search

The study uses satellite observations, global assimilated aerosol data sets, Atmospheric Brown Clouds (ABC) observatories, a Monte Carlo aerosol-cloud-radiation model and a regional chemical transport model (STEM-2K) to characterize the spatial extent of brown clouds, regional and megacity ABC hot spots, chemical composition and the direct radiative forcing. It presents the first annual cycle of aerosol observations and forcing from

V. Ramanathan; F. Li; M. V. Ramana; P. S. Praveen; D. Kim; C. E. Corrigan; H. Nguyen; Elizabeth A. Stone; James J. Schauer; G. R. Carmichael; Bhupesh Adhikary; S. C. Yoon

2007-01-01

131

The association between regional and global atmospheric patterns and winter precipitation in Iran  

Microsoft Academic Search

This paper attempts to find the associations between the atmospheric circulation patterns ranging from regional to global scales and winter precipitation patterns over Iran. This study utilizes Principal Component Analysis (PCA), running correlations and composite maps for extremely dry and wet conditions. A PCA of winter precipitation reveals five components that account for 63% of the total variance. Analyses of

Ahmad Reza Ghasemi; Davar Khalili

2008-01-01

132

A Regional Ocean Atmosphere Model for Eastern Pacific Climate: Toward Reducing Tropical Biases  

Microsoft Academic Search

The tropical Pacific Ocean is a climatically important region, home to El Niño and the Southern Oscil- lation. The simulation of its climate remains a challenge for global coupled ocean-atmosphere models, which suffer large biases especially in reproducing the observed meridional asymmetry across the equator in sea surface temperature (SST) and rainfall. A basin ocean general circulation model is coupled

Shang-Ping Xie; Toru Miyama; Yuqing Wang; Haiming Xu; Simon P. de Szoeke; R. Justin O. Small; Kelvin J. Richards; Takashi Mochizuki; Toshiyuki Awaji

2007-01-01

133

REPRESENTATION OF ATMOSPHERIC MOTION IN MODELS OF REGIONAL-SCALE AIR POLLUTION  

EPA Science Inventory

A method is developed for generating ensembles of wind fields for use in regional scale (1000 km) models of transport and diffusion. The underlying objective is a methodology for representing atmospheric motion in applied air pollution models that permits explicit treatment of th...

134

The Equivalent Heights of the Atmospheric Ionised Regions in England and America  

Microsoft Academic Search

IT was recorded in NATURE of Sept. 3, 1927, that, in experiments carried out for the Radio Research Board of the Department of Scientific and Industrial Research, evidence had been obtained of the existence of at least two ionised regions in the upper atmosphere. This evidence was derived, in the first instance, from observations made at night using wireless waves

E. V. Appleton

1929-01-01

135

Laser methods for ecological atmospheric monitoring in regions with large factories  

NASA Astrophysics Data System (ADS)

Results of lidar investigating atmospheric aerosol parameters at regions of large industrial centers have been presented. Technical characteristics and design of lidar stations are described. Optical parameter spectra of industrial aerosol are different from background ones. Investigating processes of aerosol pollution spread from large factories have been carried out.

Chaikovsky, Anatoly P.; Hutko, I. S.; Ivanov, A. P.; Osipenko, F. P.; Shcherbakov, V. N.; Tauroginskaya, S. B.; Kovalev, A. A.; Kostyukevich, S. B.; Samusenko, A. M.; Rybaltchenko, E. V.; Slesar, A. S.

1995-01-01

136

Australian region tropical cyclones: Influence of environment at different scales  

Microsoft Academic Search

This dissertation explores the influence of environmental factors on a variety of spatial and temporal scales on tropical cyclones (TCs) in the Australian region. Chapter 1 provides the motivation for the work presented, and leads into a discussion on the current state of knowledge of large-scale factors affecting the interannual variability of TCs in each of the seven global TC

Hamish Andrew Ramsay

2008-01-01

137

Transboundary Atmospheric Pollution of Oil-Gas Industry Emissions from North Caspian region of Kazakhstan  

NASA Astrophysics Data System (ADS)

The Atyraus region (Republic of Kazahstan) is occupied with more than 60 oil-gas fields which are actively developing. Moreover, a new world largest field so-called Kashagan has been discovered on the Caspian Sea shelf and its exploitation is planned by the end of 2012. In our study, this region has been selected as a source region of sulphates emissions accounting about 15 tons (2009 estimates). Three locations have been chosen in the region covering adjacent Caspian Sea aquatoria, and emissions were equally distributed among these locations (with an emission rate of 4.72*10-4 kg/sec). From original sulphates emissions between 46-82% are subjected to atmospheric transport away from the sources. Releases were considered to be continuous. The long-term modelling of atmospheric transport, dispersion and deposition of sulphates was done employing the Lagrangian type model called DERMA, run at the NEC SX6 supercomputing facilities. After each day of release the atmospheric transport has been tracked for the next 2 week period. Input meteorological 3D fields were obtained from the ECMWF data archives. The generated output included air concentration (at model levels), time integrated air concentration, dry and wet deposition (at the surface). The results of dispersion modelling had been post-processed and integrated into GIS environment (using ArcGIS). These have been further used to calculate annual averaged and summary concentration and deposition fields for administrative regions, counties and cities of Kazakhstan, as well as territories of the neighboring countries. It has been found that on an annual scale, the dominating atmospheric transport of pollution from the Atyraus region is toward east and north-east, mostly due to prevailing westerlies. Although on a hemispheric scale, the wet deposition dominates over dry (63 vs. 37%), for Kazakhstan the wet deposition contribution is slightly larger (65%). For Turkmenistan, dry deposition is almost twice higher compared with wet (65 vs. 35%) which is due to significantly smaller precipitation in this country. Considering total deposition during transboundary atmospheric transport, it should be noted that 80.3% of transported sulphates will be deposited over territories of Kazakhstan, 13.8% - Russia, about 2% each - Turkmenistan and Uzbekistan, and less than 1% over other countries. Among considered 14 Regions of Kazakhstan and 8 Federal District of Russia, the highest concentrations and depositions were identified in the Atyraus and Magistaus regions of Kazakhstan as well as in the South Federal District of Russia. For Kazakhstan, the lowest values were identified in the Almaty, East-Kazakhstan, Dzhambul and Pavlodar regions. Among most populated cities the city of Atyrau (Kazakhstan), Astrakhan (Russia) and Baku (Azerbaijan) showed the largest concentrations during transboundary atmospheric transport.

Zakarin, E.; Balakay, L.; Mirkarimova, B.; Mahura, A.; Baklanov, A.; Sorensen, J. H.

2012-04-01

138

Atmospheric dispersion of radon gas and its decay products under stable conditions in arid regions of Australia  

Microsoft Academic Search

The radon and radon daughter concentration-in-air from natural background are assessed along with the micrometeorology and synoptic weather systems in an arid region of Australia. The radon daughter contribution to population dose is biased towards the frequency of nocturnal inversions. Classical atmospheric models are not applicable during stable atmospheric conditions in inland Australia. An atmospheric Box Model is used along

V. A. Leach; W. P. Chandler

1992-01-01

139

Long-range atmospheric transport of heavy metals from industrial regions of Ural and Norilsk to siberian environment  

NASA Astrophysics Data System (ADS)

The main idea of the work is to analyze atmospheric transport of heavy metals (Ni, Cu, Pb) from the industries of the region of Norilsk, and the Ural over the territory of Siberia. The basic data were 5-days air mass trajectories from the sources calculated for every day of January, April, July, and October during 28 years from 1981 to 2008. NCEP/NCAR Reanalysis Data Files and HYSPLIT 4 model were used. Spatial, seasonal and long-term variations in heavy metal (HM) concentrations in surface air and precipitations, as well as in fluxes of these elements onto the surface were studied. The obtained results (presented as maps) may be used as assessment of anthropogenic influence of the sources under investigation on the environment of remote and hard-to-reach areas. The HM air concentrations and fluxes onto the surface depend on surface properties and precipitation regime, and experience great seasonal and spatial variations. The maximal air concentrations are in cold seasons, whereas the maximal fluxes onto the surface occur in warm period. In comparison anthropogenic loadings at different places the cleanest air does not guarantees the minimal vertical fluxes. The pollution trends (modulo) caused only by the transformation of air circulation processes are quite comparable with the contributions of source-emissions' changes. The main result is the decreasing of Siberian environment pollution through the atmosphere from regarded sources during the last years. At a distance about 2000 km from a large source under investigation its atmospheric emissions form only the background levels of HM in the surface environment, and the real pollution levels are determined by local anthropogenic sources (with less emissions) if they exist. So, for the Lake Baikal the HM inputs from our distant sources through atmosphere to the water surface are insignificant in comparison with the flowing rivers' ones, and lake water pollution occurs mainly due to rivers' pollution. However, annual HM fluxes from Ural and Norilsk regions through atmosphere on the territories of basins of large Siberian Rivers - Ob, Yenisei or Lena - are quite comparable with HM's fluxes carrying away in river's water to the Arctic Ocean. Thus, the long-range atmospheric transport of heavy metals from Ural and Norilsk regions must be taken into account as one of the processes forming compositions of surface water objects and soils, as well as of food chains in different ecosystems of Siberia.

Vinogradova, Anna; Maksimenkov, Leonid; Pogarskii, Fedor

2010-05-01

140

Fruit Maturity and Storage Temperature Influence Response of Strawberries to Controlled Atmospheres  

Microsoft Academic Search

Chandler' strawberries (Fragaria ×ananassa Duch.) harvested three-quarter colored or fully red were stored in air or a controlled atmosphere (CA) of 5% O2 + 15% CO2 at 4 or 10 °C to evaluate the influence of fruit maturity and storage temperature on the response to CA. Quality evaluations were made after 1 and 2 weeks in air or CA, and

M. C. N. Nunes; A. M. M. B. Morais; J. K. Brecht; S. A. Sargent

2002-01-01

141

Influence of elevated atmospheric carbon dioxide on transcriptional responses of Bradyrhizobium japonicum in the soybean rhizoplane.  

PubMed

Elevated atmospheric CO2 can influence the structure and function of rhizoplane and rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizoplane and rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizoplane of soybean plants exposed to elevated atmospheric CO2. The results of microarray analyses indicated that elevated atmospheric CO2 concentration indirectly influenced the expression of a large number of genes in Bradyrhizobium attached to soybean roots. In addition, relative to plants and bacteria grown under ambient CO2 growth conditions, genes involved in C1 metabolism, denitrification and FixK2-associated genes, including those involved in nitrogen fixation, microaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2 in the rhizosphere. The expression profile of genes involved in lipochitooligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, the results of these studies indicate that the growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizoplane, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency. PMID:23666536

Sugawara, Masayuki; Sadowsky, Michael J

2013-05-11

142

Atmospheric conditions influencing the spillover of rainfall to lee of the Southern Alps, New Zealand  

Microsoft Academic Search

Atmospheric conditions influencing precipitation distribution over a large lee-side catchment in the Southern Alps of New Zealand are investigated. A significant proportion of rainfall received in the upper Waimakariri catchment is generated by its spillover from the windward side of the alps during conditions of westerly flow. A transect of rain gauges was installed to examine the distribution of rainfall

Amanda M. Chater; Andrew P. Sturman

1998-01-01

143

Dietary intake of pollutant aerosols via vegetables influenced by atmospheric deposition and wastewater irrigation  

Microsoft Academic Search

Pot culture experiments were conducted to study dietary intake of heavy metals via vegetables, spinach (Spinacia oleracea L.), radish (Raphanus sativus L.) and tomato (Lycopersicon esculentum Mill) grown under the influence of atmospheric deposition and wastewater irrigation. The results indicated substantial accumulation of heavy metals in vegetables, which contribute significantly to dietary intake of total heavy metals ranging from 1.34

Richa Pandey; Kumar Shubhashish; Jitendra Pandey

144

Quantification of source region influences on the ozone burden  

NASA Astrophysics Data System (ADS)

A project was performed to quantify different influences on the ozone burden. It could be shown that large-scale meteorological influences determine a very large percentage of the ozone concentration. Local measures intended to reduce peak ozone concentrations in summer turn out to be not very effective as a result. The aim of this paper is to quantify regional emission influences on the ozone burden. The investigation of these influences is possible by comparison of the ozone (O 3) and oxidant (O x=O 3+NO 2) concentrations at high-elevation sites downwind and upwind of a source region by using back trajectories. It has been shown that a separation between large-scale influenced meteorological and regional ozone burdens at these sites is possible. This method is applied for an important emission area in Germany—the Ruhrgebiet. On average, no significant ozone contribution of this area to the regional ozone concentration could be found. A large part of the ozone concentration is highly correlated with synoptic weather systems, which exhibit a dominant influence on the local ozone concentrations. Significant contributions of related photochemical ozone formation of the source area of 13-15% have been found only during favourable meteorological situations, identified by the hourly maximum day temperature being above 25°C. This is important with respect to the EU daughter directive to EU 96/62/EC (Official Journal L296 (1996) 55) because Member States should explore the possibilities of local measures to avoid the exceedance of threshold values and, if effective local measures exist, to implement them.

Treffeisen, Renate; Grunow, Katja; Möller, Detlev; Hainsch, Andreas

145

Investigation of the ocean-atmosphere-continent coupling in the Gulf of Guinea and West Africa at intraseasonal timescales in boreal spring and summer with a regional atmospheric model (WRF)  

NASA Astrophysics Data System (ADS)

Using 2000-2009 satellite data (Reynolds for SST and QuikSCAT for surface winds), a strong ocean-atmosphere coupling was put in evidence in the equatorial region (northern front) of the Tropical Atlantic cold tongue, implying surface winds and sea surface temperature (SST): a cold (respectively warm) SST anomaly strengthens (weakens) southerlies between the Equator and the Guinean coast during a few days. Similar investigations with ERA-Interim and NCEP-CFSR reanalyses emphasized the significant contribution of these wind fluctuations to the triggering of the Guinean coastal rainfall in spring. In this study, mechanisms at stake behind the statistical results are investigated by using a regional atmospheric model, WRF (Weather Research and Forecasting) with horizontal resolution of 50 km for the period April-July 2006. First, the influence of the SST on the spring and summer precipitation is quantified through the analysis of the moisture flux convergence over the continent. Then, some hints of a potential feedback from the changing continental surface (under rainy conditions) over the regional atmospheric circulation are shown , likely involving the southward low-level atmospheric circulation (or Shallow Meridional Circulation), subsidence over the Gulf of Guinea and then surface southerlies again, closing an active loop of ocean-atmosphere-continent interaction.

Meynadier, R.; De Coëtlogon, G.; Leduc-Leballeur, M.; Bastin, S.; Peter, A.-C.; Janicot, S.; Bock, O.; Flamant, C.

2012-04-01

146

Intra-annual variation of atmospheric static stability in the Mediterranean region: a 60-year climatology  

NASA Astrophysics Data System (ADS)

The seasonal characteristics of atmospheric static stability in the Mediterranean region are examined, for the 60-year period 1948-2007 and for the four 15-year sub-periods 1948-1962, 1963-1977, 1978-1992 and 1993-2007. S-Mode and T-Mode Factor Analysis are applied to the mean 5-day values of K static stability index over the Mediterranean region. Three dominant modes are revealed for both, the intra-annual variation and the spatial distribution of K-index. It is found that these modes are connected to the seasonal characteristics of the main atmospheric circulation systems affecting the region and the thermal properties of the Earth's surface (land or sea). The differences among the results of the four sub-periods partially reflect the inter-decadal variations of the strength of the above factors.

Lolis, C. J.; Bartzokas, A.; Lagouvardos, K.; Metaxas, D. A.

2012-10-01

147

Methane emissions from a wetland region within the Hudson Bay Lowland: An atmospheric approach  

NASA Astrophysics Data System (ADS)

Continuous observations of methane (CH4) mixing ratios in combination with the atmospheric 222Rn activity and stable isotope ratios of carbon and hydrogen in atmospheric CH4 at a remote midcontinental monitoring station at Fraserdale, Ontario (49°53'N, 81°34'W) are used to characterize and quantify the regional CH4 emissions from the Hudson Bay Lowland (HBL). Large diurnal variations are observed in both trace substances during the summer which are due to emissions from ground level sources accumulating during strong nocturnal inversions. Diurnal changes of the stable isotopic composition of atmospheric CH4 at Fraserdale were used to determine the isotopic signature of the regional wetland CH4 source to be ?13CVPDB = (-60.0±3.2)‰ and ?DVSMOW = (-442±142)‰. These integrated values are regarded as representative of several hundred square kilometers. The atmospheric 222Rn daughter observations made during the months of September and October 1994-1996 were used to estimate total CH4 emission rates in the region of Fraserdale. The fluxes of CH4 for September and October were (11.5±1.2) mg CH4 m-2 d-1 and (4.7±2.7) mg CH4 m-2 d-1, respectively, with an estimated absolute uncertainty of ±30%. These values are well comparable with summer flux measurements performed during the 1990 NOWES campaign using static chambers [Roulet et al., 1994] as well as using eddy correlation measurements performed on a tall tower [Edwards et al., 1994].

Kuhlmann, A. J.; Worthy, D. E. J.; Trivett, N. B. A.; Levin, I.

1998-01-01

148

Evaluation of Atmospheric Electric Field as Increasing Seismic Activity Indicator on the example of Caucasus Region  

NASA Astrophysics Data System (ADS)

The present paper deals with reliability of a gradient of atmospheric electric field potential as an indicator of seismic activity increase. With this in view, records of atmospheric electric field potential gradients of Caucasus region for 1953-1992 with respect to periods before average and large earthquakes, which took place in the same time interval, were considered. It is worth to pay attention to the fact that the avalanche-like unstable model of fault formation based on theoretical model of self-generated seismo-electromagnetic oscillations of LAI system explains convincingly spectral succession of electromagnetic emission frequency of the periods preceding earthquakes.

Kachakhidze, M. K.; Kereselidze, Z. A.; Kachakhidze, N. K.

2013-01-01

149

Protein patterning utilizing region-specific control of wettability by surface modification under atmospheric pressure  

NASA Astrophysics Data System (ADS)

Wettability control can be crucial in improving the uniformity of selective protein immobilization in high-density microarrays. In this study, we propose an atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD)-based method in conjunction with photolithography to implement region-specific control of wettability on Si substrate. The proposed PECVD method under atmospheric pressure condition would be a useful alternative of conventional reactive plasma-based treatments methods requiring vacuum condition for uniform protein patterning. Layers with dissimilar wettability and roughness prepared by AP-PECVD process using tetraethoxysilane (TEOS) or TEOS-O2 as precursors could realize uniform protein patterning in a micrometer-scale.

Lee, Donghee; Kwon, Min-Sung; Hyun, Ji-Chul; Jun, Chang-Duk; Chung, Euiheon; Yang, Sung

2013-09-01

150

Atmospheric stability of surface boundary layer in coastal region of the Wol-Ryong site  

NASA Astrophysics Data System (ADS)

In order to provide statistically reliable information of a wind energy site, accurate analysis on the atmospheric stability and climate characteristics in a certain area is a prerequisite. Two 2-D ultrasonic anemometers and one cup anemometer, located perpendicular to the prevailing wind direction, were used to measure the atmospheric wind environment at a height of 4.5 m in coastal region of the Wol-Ryong, Jeju, South Korea. The study is aiming to understand the atmospheric stability about a coastal region, and the effect of roughness length. We calculate the Monin-Obukhov length for division of atmospheric stability about unstable regime, neutral regime and stable regime. The distribution of diurnal Monin-Obukhov length is highly sporadic in the coastal region due to the effect of radiant heat from the surface or other environmental effects. In order to calculate the roughness length in coastal region, three different methods are applied in terms of the surface roughness, flow fluctuation and gust wind, which are called logarithmic profile, standard deviation and gust factor methods. In the study, the atmospheric stability was insignificant when applying these three methods. In the results, three different roughness length scales sufficiently showed the effect of obstacle and surface conditions around the measurement position. On the basis of an overall analysis of the short-term data measured in the Wol-Ryong area, Jeju Island, it is concluded that for the development of future wind energy resources, the Wol-Ryong site could be a good candidate for a future wind energy site.

Lim, Hee-Chang

2012-08-01

151

Influence of Increased CO2 on Regional Climate Simulations  

NASA Astrophysics Data System (ADS)

Several PCM (Parallel Climate Model) coupled (atmosphere-ocean) simulations have been developed starting from a period back in the 1800s through 2095, using historical CO2 concentrations for the past and "business-as-usual" CO2 concentrations for the future. What differences occur if these global low-resolution (T42L18) simulations are down-scaled with a regional climate model? Toward this goal, three basic numerical simulations with the regional spectral model (RSM) at a spatial resolution of about 50 km are being conducted to investigate regional US responses. Both the NCEP Reanalysis II (T62L28) and the PCM simulation (T42L18) data are used as initial and boundary conditions for present-day conditions (1986-present). The observed sea surface temperature (SST) is used in the RSM-reanalysis run while in the RSM-PCM run, the SST is given by the global simulation. The other surface fields in both runs are given by the climatological data. Initial comparisons indicate that the RSM simulations preserve the larger scale features of the reanalysis and PCM simulation, while providing more realistic smaller scale features not present in the driving large-scale fields. The years of 2040-2060 with the increased CO2 found in the PCM simulations are chosen for the period of increased CO2. Several additional ensemble PCM members will be used as boundary conditions in order to assess uncertainty at regional scales from both the global PCM and regional RSM.

Han, J.; Roads, J. O.

2001-12-01

152

Influence of solar-probe inherent atmosphere on in-situ observations  

SciTech Connect

The solar corona is the source of the solar wind, which is responsible for the heliosphere and plays a crucial role in solar/terrestrial phenomena. A comprehensive understanding of these phenomena can be established only by directly measuring ion and electron velocity distributions, plasma waves, and fluxes of energetic particles near the sun. The problem resulting from the inherent atmosphere of a spacecraft moving in the vicinity of the sun and the influence of this atmosphere on in-situ measurements of the solar corona plasma is key to the realization and success of any solar probe mission. To evaluate the influence of the probe-inherent atmosphere on in-situ observations, the authors have developed comprehensive radiation hydrodynamic models. The physics of plasma/probe/vapor interaction are also being developed in a self-consistent model to predict the effect of probe inherent atmosphere on in-situ measurements of corona parameters during solar flares. Interaction of the ionized atmosphere with the ambient natural plasma will create a turbulent shock wave that can affect in-situ measurements and must be taken into account in designing the spacecraft and its scientific components.

Hassanein, A. [Argonne National Lab., IL (United States); Konkashbaev, A.I.; Konkashbaev, I.K.; Nikandrov, L.B. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation)

1998-08-01

153

Constraining regional scale carbon budgets at the US West Coast using a high-resolution atmospheric inverse modeling approach  

NASA Astrophysics Data System (ADS)

The study presented is embedded within the NACP (North American Carbon Program) West Coast project ORCA2, which aims at determining the regional carbon balance of the US states Oregon, California and Washington. Our work specifically focuses on the effect of disturbance history and climate variability, aiming at improving our understanding of e.g. drought stress and stand age on carbon sources and sinks in complex terrain with fine-scale variability in land cover types. The ORCA2 atmospheric inverse modeling approach has been set up to capture flux variability on the regional scale at high temporal and spatial resolution. Atmospheric transport is simulated coupling the mesoscale model WRF (Weather Research and Forecast) with the STILT (Stochastic Time Inverted Lagrangian Transport) footprint model. This setup allows identifying sources and sinks that influence atmospheric observations with highly resolved mass transport fields and realistic turbulent mixing. Terrestrial biosphere carbon fluxes are simulated at spatial resolutions of up to 1km and subdaily timesteps, considering effects of ecoregion, land cover type and disturbance regime on the carbon budgets. Our approach assimilates high-precision atmospheric CO2 concentration measurements and eddy-covariance data from several sites throughout the model domain, as well as high-resolution remote sensing products (e.g. LandSat, MODIS) and interpolated surface meteorology (DayMet, SOGS, PRISM). We present top-down modeling results that have been optimized using Bayesian inversion, reflecting the information on regional scale carbon processes provided by the network of high-precision CO2 observations. We address the level of detail (e.g. spatial and temporal resolution) that can be resolved by top-down modeling on the regional scale, given the uncertainties introduced by various sources for model-data mismatch. Our results demonstrate the importance of accurate modeling of carbon-water coupling, with the representation of water availability and drought stress playing a dominant role to capture spatially variable CO2 exchange rates in a region characterized by strong climatic gradients.

Goeckede, M.; Michalak, A. M.; Vickers, D.; Turner, D.; Law, B.

2009-04-01

154

Aerosol effect on atmospheric heating rates in the Mediterranean region using vertically resolved satellite aerosol data  

NASA Astrophysics Data System (ADS)

It is well known that the main direct effect of aerosols is the cooling of the surface and warming of the atmosphere, which impact atmospheric dynamics via the weakening of convection and the inhibition of cloud forming. In order to be able to fully understand and parameterize this throughout the atmosphere, a detailed vertical profile of the aerosol induced surface cooling and atmospheric heating is required. To get a vertical profile like this, detailed vertically resolved data on aerosol optical properties are required. Such data have now become available from CALIOP lidar onboard CALIPSO satellite. Its near-nadir viewing geometry allows for viewing curtains of the atmosphere, thereby defining with sufficient accuracy the vertical position of aerosols and clouds. In this study, CALIOP Level 2-Version 3 Layer and Profile data for the Mediterranean region from January 2007 to December 2011 have been used. The Mediterranean region was chosen, as it is an area with a mixture of aerosol types, both natural and anthropogenic, where aerosol radiative effects take large values. Furthermore, it is in the proximity of Sahara desert dust, making the area one with large aerosol load. The original CALIOP data have been regridded at a 1°x1° latitude-longitude resolution and at 160 vertical layers. The use of both Layer and Profile data has enabled the derivation of useful 'climatological' products, like spatial properties of aerosol layers, as well as optical properties of them. A comparison with the recently distributed (December 2011) CALIOP Level 3 data, as well as with other satellite data, is presented. Initial results, in agreement with previous studies, reveal that CALIOP aerosol optical depth (AOD) is biased low by around 20%, when compared to other satellite products, such as MODIS. The regridded data are subsequently used in a spectral radiative transfer model and the vertical profile of direct radiative effect is computed. From that, a vertical heating rate profile due to aerosols is derived for each model grid. The geographical and seasonal variability of these rates are investigated, in relation with the corresponding variability of aerosol optical properties. According to preliminary results, the determination of the cooling/heating rate above the surface and within the atmosphere is not affected by the aforementioned bias of CALIOP AOD. The findings of this study are expected to be particularly useful to future studies that deal with the modelling of the aerosol direct, indirect and semi-direct effects (e.g.. Monitoring Atmospheric Composition and Climate II) while the aerosol induced modification of atmospheric lapse rates will be the basis for further studies of aerosol effects on atmospheric dynamics.

Pappas, Vasileios; Hatzianastassiou, Nikos; Matsoukas, Christos; Vardavas, Ilias

2013-04-01

155

Study of The Interannual Variability In The Arctic Ocean Using Regional Coupled Ocean-atmosphere Model  

NASA Astrophysics Data System (ADS)

The interannual variability in the Nordic Seas and Arctic ocean is studied using a regional high resolution coupled ocean - sea ice - atmosphere model. The ocean com- ponent consists of the formally global C-HOPE model, which contains the option of conformal mapping and thus allows to increase the resolution substantially. The atmo- spheric component is the REgional atmospheric MOdel REMO. It runs with a resolu- tion of approx. 110 km for a region covering the North Atlantic, Europe and the entire Arctic. Inside this domain the resolution of the C-HOPE model varies between 30 to 50 km. Both models are coupled using the OASIS coupler developed at CERFACS. The regional coupled model has been run for the years 1979-1993 using ERA15 re- analysis data as boundary values and atmospheric forcing outside the coupled domain. The model simulates pronounced climate variability both in sea ice and in ocean cli- mate. One mode of the simulated climate variability is charcterized by fluctuations in sea ice export from the Arctic and the subsequent propagation of salinity anomalies in the ocean.

Sein, D. V.; Mikolajewicz, U.; Jacob, D.; Semmler, T.; Podzun, R.

156

Sensitivity of a regional ocean-atmosphere coupled model to convection parameterization over western North Pacific  

NASA Astrophysics Data System (ADS)

With the motivation to improve the simulation of western North Pacific (WNP) summer monsoon, the regional climate model RegCM3 is coupled with the Princeton ocean model (POM2000) through the coupler OASIS3.0 (Ocean Atmosphere Sea Ice Soil 3.0). The performance of the regional ocean-atmosphere coupled model (hereafter ROAM) is assessed by doing case simulation of the 1998 summer monsoon. The cold bias of simulated sea surface temperature (SST) is evident as previous ROAM simulations over the Asian-Australian summer monsoon region. Five sets of sensitivity experiments with convection suppression criterion based on the averaged relative humidity from cloud base to cloud top are designed to improve the performance of ROAM. The results show that the column-averaged cloud fraction is reduced in convection suppression experiments. A reduction of column-averaged cloud cover, which is dominated by the decrease of convective cloud cover, increases the solar shortwave radiation reaching in sea surface, then warms the SST. A reduction of convective rainfall is followed by an increase of large-scale rainfall which results from increasing cloud water. When the critical value is set to 0.70, the rainfall is partly improved in terms of the spatial distribution and root-mean-square error. The percentage of convective rainfall over WNP is also improved. The authors show evidence that the SST cold biases, which are evident in many regional ocean-atmosphere coupled models in the Asian-Australian summer monsoon region, may partly stem from the overestimation of convection frequency by the atmospheric model.

Zou, Liwei; Zhou, Tianjun

2011-09-01

157

Atmospheric water balance over oceanic regions as estimated from satellite, merged, and reanalysis data  

NASA Astrophysics Data System (ADS)

The column integrated atmospheric water balance over the ocean was examined using satellite-based and merged data sets for the period from 2000 to 2005. The data sets for the components of the atmospheric water balance include evaporation from the HOAPS, GSSTF, and OAFlux and precipitation from the HOAPS, CMAP, and GPCP. The water vapor tendency was derived from water vapor data of HOAPS. The product for water vapor flux convergence estimated using satellite observation data was used. The atmospheric balance components from the MERRA reanalysis data were also examined. Residuals of the atmospheric water balance equation were estimated using nine possible combinations of the data sets over the ocean between 60°N and 60°S. The results showed that there was considerable disagreement in the residual intensities and distributions from the different combinations of the data sets. In particular, the residuals in the estimations of the satellite-based atmospheric budget appear to be large over the oceanic areas with heavy precipitation such as the intertropical convergence zone, South Pacific convergence zone, and monsoon regions. The lack of closure of the atmospheric water cycle may be attributed to the uncertainties in the data sets and approximations in the atmospheric water balance equation. Meanwhile, the anomalies of the residuals from the nine combinations of the data sets are in good agreement with their variability patterns. These results suggest that significant consideration is needed when applying the data sets of water budget components to quantitative water budget studies, while climate variability analysis based on the residuals may produce similar results.

Park, Hyo-Jin; Shin, Dong-Bin; Yoo, Jung-Moon

2013-05-01

158

Regional US carbon sinks from three-dimensional atmospheric CO2 sampling.  

PubMed

Studies diverge substantially on the actual magnitude of the North American carbon budget. This is due to the lack of appropriate data and also stems from the difficulty to properly model all the details of the flux distribution and transport inside the region of interest. To sidestep these difficulties, we use here a simple budgeting approach to estimate land-atmosphere fluxes across North America by balancing the inflow and outflow of CO(2) from the troposphere. We base our study on the unique sampling strategy of atmospheric CO(2) vertical profiles over North America from the National Oceanic and Atmospheric Administration/Earth System Research Laboratory aircraft network, from which we infer the three-dimensional CO(2) distribution over the continent. We find a moderate sink of 0.5 ± 0.4 PgC y(-1) for the period 2004-2006 for the coterminous United States, in good agreement with the forest-inventory-based estimate of the first North American State of the Carbon Cycle Report, and averaged climate conditions. We find that the highest uptake occurs in the Midwest and in the Southeast. This partitioning agrees with independent estimates of crop uptake in the Midwest, which proves to be a significant part of the US atmospheric sink, and of secondary forest regrowth in the Southeast. Provided that vertical profile measurements are continued, our study offers an independent means to link regional carbon uptake to climate drivers. PMID:20937899

Crevoisier, Cyril; Sweeney, Colm; Gloor, Manuel; Sarmiento, Jorge L; Tans, Pieter P

2010-10-11

159

High-resolution ocean and atmospheric modeling of the Florida Big Bend region  

NASA Astrophysics Data System (ADS)

An ocean and atmospheric modeling system is developed for the Florida Big Bend Region (BBR) in the northeastern Gulf of Mexico for interdisciplinary studies and support of a coastal observing system. The ocean modeling component consists of ROMS configured at 30 arcsec resolution nested within a 1/25° HYCOM Gulf of Mexico - Western Atlantic nowcast/forecast system. This methodology is employed to accurately simulate the impacts of offshore mesoscale circulation features and propagating signals along the shelf on the fine scale processes in the BBR. The atmospheric modeling component is a 1.33km WRF triply nested within a 4 km Gulf of Mexico -Western Atlantic domain and the 12 km WRF North American Mesoscale atmospheric prediction system run at NCEP. Real-time oceanic and atmospheric measurements from an array of instruments within the domain are used for validation of the modeling system. The observations and modeling system are applied to studies of air-sea interaction associated with cold air outbreak events over the shelf and sea breeze circulation over the coastal region. The system also supports marine ecosystem and fisheries research programs in the northeastern Gulf.

Morey, S. L.; Dukhovskoy, D. S.; van Dyke, D.; Todd, A. C.; Chassignet, E. P.

2008-12-01

160

Three-dimensional multifluid modeling of atmospheric electrodynamics in Mars' dynamo region  

NASA Astrophysics Data System (ADS)

The interactions between Mars' unique crustal magnetic fields and upper atmospheric particles lead to the formation of currents in the ionospheric dynamo region. This work is specifically focused on the collisions between ions, electrons, and neutrals in the atmospheric column of Mars. The remanent fields embedded in the Martian crust generate a very rich magnetic topology with important variations in terms of geometry and amplitude. Here we present mesoscale, self-consistent, three-dimensional, multifluid simulations of Mars' ionospheric electrodynamics in the dynamo region (˜100-400 km altitude), where differential motions of ions and electrons occur. In particular, we develop and validate a new method through the study of simple, uniform magnetic geometries. Our results demonstrate the existence of a dynamo current in the Martian atmosphere, which depends on the magnitude of the applied magnetic field and the neutral wind speeds. The simulation outputs are analyzed from mathematical and physical perspectives to identify the dominant processes at work in the formation of this current. Both case studies presented in this paper are qualitatively and quantitatively consistent with theoretical estimates and confirm the validity of the model, hence laying the groundwork for future studies of Mars' atmosphere using this new approach.

Riousset, Jeremy A.; Paty, Carol S.; Lillis, Robert J.; Fillingim, Matthew O.; England, Scott L.; Withers, Paul G.; Hale, John P. M.

2013-06-01

161

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

Microsoft Academic Search

This study examines time evolution and statistical relationships involving the two leading ocean-atmosphere coupled modes\\u000a of variability in the tropical Atlantic and some climate anomalies over the tropical 120?°W–60?°W region using selected historical\\u000a files (75-y near global SSTs and precipitation over land), more recent observed data (30-y SST and pseudo wind stress in the\\u000a tropical Atlantic) and reanalyses from the

B. Fontaine; Serge Janicot; P. Roucou

1999-01-01

162

Harvard Forest regional-scale air mass composition by Patterns in Atmospheric Transport History (PATH)  

Microsoft Academic Search

We calculated 4 years (1990-1993) of back trajectories arriving at Harvard Forest and used them to define patterns in atmospheric transport history. This information was used to assess the degree to which regional-scale transport modulates the chemical composition of air masses sampled at Harvard Forest. Different seasonal signals in trace-gas concentration are derived for different flow patterns. Throughout the year,

J. L. Moody; J. W. Munger; A. H. Goldstein; D. J. Jacob; S. C. Wofsy

1998-01-01

163

Regional and microclimatic pollution effects on atmospheric corrosion in Prague and Europe  

SciTech Connect

Atmospheric corrosion test results for structural metals in open air and under shelter from multilateral European programs (1968 to 1992) are presented and the effects of SO{sub 2} pollution analyzed. Regional and microclimatic pollution effects are documented by test results from Czech permanent test sites, test sites throughout Prague, and test sites on the St. Vitus Cathedral. The effects of variations in pollution activity, time of wetness, and type of metal are considered.

Knotkova, D.; Vlckova, J.; Kreislova, K. [SVUOM Praha a.s., Prague (Czech Republic)

1995-06-01

164

Carbonaceous particles in the atmosphere and precipitation of the Nam Co region, central Tibet.  

PubMed

A continuous air and precipitation sampling for carbonaceous particles was conducted in a field observatory beside Nam Co, Central Tibetan Plateau during July of 2006 through January of 2007. Organic carbon (OC) was the dominant composition of the carbonaceous particles both in the atmosphere (1660 ng/m3) and precipitation (476 ng/g) in this area, while the average elemental carbon (BC) concentrations in the atmosphere and precipitation were only 82 ng/m3 and 8 ng/g, respectively. Very high OC/BC ratio suggested local secondary organic carbon could be a dominant contribution to OC over the Nam Co region, while BC could be mainly originated from Southern Asia, as indicated by trajectory analysis and aerosol optical depth. Comparison between the BC concentrations measured in Lhasa, those at "Nepal Climate Observatory at Pyramid (NCO-P)" site on the southern slope of the Himalayas, and Nam Co suggested BC in the Nam Co region reflected a background with weak anthropogenic disturbances and the emissions from Lhasa might have little impact on the atmospheric environment here, while the pollutants from the Indo-Gangetic Basin of Southern Asia could be transported to the Nam Co region by both the summer monsoon and the westerly. PMID:21235163

Ming, Jing; Xiao, Cunde; Sun, Junying; Kang, Shichang; Bonasoni, Paolo

2010-01-01

165

Genetic Influences on Cortical Regionalization in the Human Brain  

PubMed Central

Summary Animal data demonstrate that the development of distinct cortical areas is influenced by genes that exhibit highly regionalized expression patterns. In this paper, we show genetic patterning of cortical surface area derived from MRI data from 406 adult human twins. We mapped genetic correlations of areal expansion between selected seed regions and all other cortical locations, with the selection of seed points based on results from animal studies. “Marching seeds” and a data-driven, hypothesis-free, fuzzy clustering approach provided convergent validation. The results reveal strong anterior-to-posterior graded, bilaterally symmetric patterns of regionalization, largely consistent with patterns previously reported in non-human mammalian models. Broad similarities in genetic patterning between rodents and humans may suggest a conservation of cortical patterning mechanisms while dissimilarities might reflect the functionalities most essential to each species.

Chen, Chi-Hua; Panizzon, Matthew S.; Eyler, Lisa T.; Jernigan, Terry L.; Thompson, Wes; Fennema-Notestine, Christine; Jak, Amy J.; Neale, Michael C.; Franz, Carol E.; Hamza, Samar; Lyons, Michael J.; Grant, Michael D.; Fischl, Bruce; Seidman, Larry J.; Tsuang, Ming T.; Kremen, William S.; Dale, Anders M.

2011-01-01

166

Influence of 21st century atmospheric and sea surface temperature forcing on West African climate  

SciTech Connect

he persistence of extended drought events throughout West Africa during the 20th century has motivated a substantial effort to understand the mechanisms driving African climate variability, as well as the possible response to elevated greenhouse gas (GHG) forcing. We use an ensemble of global climate model experiments to examine the relative roles of future direct atmospheric radiative forcing and SST forcing in shaping potential future changes in boreal summer precipitation over West Africa. We find that projected increases in precipitation throughout the Western Sahel result primarily from direct atmospheric radiative forcing. The changes in atmospheric forcing generate a slight northward displacement and weakening of the African easterly jet (AEJ), a strengthening of westward monsoon flow onto West Africa and an intensification of the tropical easterly jet (TEJ). Alternatively, we find that the projected decreases in precipitation over much of the Guinea Coast region are caused by SST changes that are induced by the atmospheric radiative forcing. The changes in SSTs generate a weakening of the monsoon westerlies and the TEJ, as well as a decrease in low-level convergence and resultant rising air throughout the mid levels of the troposphere. Our experiments suggest a potential shift in the regional moisture balance of West Africa should global radiative forcing continue to increase, highlighting the importance of climate system feedbacks in shaping the response of regional-scale climate to global-scale changes in radiative forcing.

Skinner, Chris B [Stanford University; Ashfaq, Moetasim [ORNL; Diffenbaugh, Noah [Stanford University

2011-01-01

167

Flood regionalization: A hybrid geographic and predictor-variable region-of-influence regression method  

USGS Publications Warehouse

To facilitate estimation of streamflow characteristics at an ungauged site, hydrologists often define a region of influence containing gauged sites hydrologically similar to the estimation site. This region can be defined either in geographic space or in the space of the variables that are used to predict streamflow (predictor variables). These approaches are complementary, and a combination of the two may be superior to either. Here we propose a hybrid region-of-influence (HRoI) regression method that combines the two approaches. The new method was applied with streamflow records from 1,091 gauges in the southeastern United States to estimate the 50-year peak flow (Q50). The HRoI approach yielded lower root-mean-square estimation errors and produced fewer extreme errors than either the predictor-variable or geographic region-of-influence approaches. It is concluded, for Q50 in the study region, that similarity with respect to the basin characteristics considered (area, slope, and annual precipitation) is important, but incomplete, and that the consideration of geographic proximity of stations provides a useful surrogate for characteristics that are not included in the analysis. ?? 2007 ASCE.

Eng, K.; Milly, P. C. D.; Tasker, G. D.

2007-01-01

168

On the simulation of allergenic pollen exposition and its atmospheric transport on regional scale  

NASA Astrophysics Data System (ADS)

In Germany approximately 30% of the population is vulnerable to pollinosis (hay fever). Exposure to allergenic pollen affects vulnerable persons recurring seasonally, but depending on the individual susceptibility to individual pollen species. To prevent the suffering the patients usually use preventive drugs and rely on the current pollen forecast. However, recently used pollen forecast models mainly consider temperature sums to predict pollen exposition by different plant species. The models often fail to describe the impact of regionally variable environmental conditions on plant growth which depends on the soil characteristics that affect the water and nutrient availability. Furthermore, water and nutrient availability may significantly affect the pollen yield and its allergenic potential. Thus, the improvement of the simulations of the exposition of allergenic pollen by plants and atmospheric pollen loads on the regional scale could improve the preventive medication of vulnerable persons. We propose a new soil-plant-atmosphere model system that allows a dynamic ressource aquisition for the plant biomass growth to account for the allergenic potential of exposed pollen and the subsequent pollen transport in the atmosphere. Therefore, to simulate pollen exposure the land surface model Expert-N (soil-plant-system model) was coupled to the Weather Research and Forecast model (WRF). Expert-N uses site specific physical soil properties to simulate the nutrient and water transport, and the carbon and nitrogen turnover, as well as the interactions between plant and soil. The allergenic potential of pollen yield is simulated using a new C- and N-allocation model which accounts for the production of carbon-based secondary compounds (CBSCs). These CBSCs are involved in the determination of the allergenic potential of pollen. The WRF model is used to predict the weather conditions for plant growth. Depending on the weather conditions pollen exposed by the plants is then released into the atmosphere and transported using the WRF-Chem model, an upgrade of the WRF model, to simulate matter transport in the atmosphere.

Biernath, Christian; Klein, Christian; Hoffmann, Peter; Gayler, Sebastian; Priesack, Eckart

2013-04-01

169

Probabilistic indicators of atmospheric transport for regional monitoring and emergency preparedness systems.  

PubMed

In this paper, following a methodology developed within the "Arctic Risk" Project of the Nordic Arctic Research Programme, several probabilistic indicators to evaluate the risk site possible impact on the geographical regions, territories, countries, counties, cities, etc., due to atmospheric transport from the risk site region were suggested. These indicators-maximum possible impact zone, maximum reaching distance, and typical transport time-were constructed by applying statistical methods and using a dataset of isentropic trajectories originated over the selected nuclear risk site (Ignalina nuclear power plant, Lithuania) during 1991-1996. For this site, the areas enclosed by isolines of the maximum possible impact zone and maximum reaching distance indicators are equal to 42 x 10(4) and 703 x 10(4) km(2), respectively. The maximum possible impact zone's boundaries are more extended in the southeast sector from the site and include, in particular, Latvia, Lithuania, Belarus, and several western regions of Russia. The maximum reaching distance's boundaries are twice more extended in the eastern direction from the site (reaching the Caspian Sea) compared with the western direction. The typical transport time to reach the southern territories of Sweden and Finland, northern regions of Ukraine, and northeast of Poland is 1 day. During this time, the atmospheric transport could typically occur over the Baltic States, Belarus, and western border regions of Russia, and central aquatoria of the Baltic Sea. Detailed analysis of temporal patterns for these indicators showed importance of the seasonal variability. PMID:14680889

Mahura, Alexander; Baklanov, Alexander

2004-02-01

170

Atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model  

Microsoft Academic Search

The mechanisms controlling the decadal to multidecadal variability of the Atlantic Meridional Overturning Circulation (MOC)\\u000a and its influence on the atmosphere are investigated using a control simulation with the IPSL-CM4 climate model. The multidecadal\\u000a fluctuations of the MOC are mostly driven by deep convection in the subpolar gyre, which occurs south of Iceland in the model.\\u000a The latter is primarily

Rym Msadek; Claude Frankignoul

2009-01-01

171

Photoacoustic measurement of ammonia in the atmosphere: influence of water vapor and carbon dioxide  

Microsoft Academic Search

The photoacoustic determination of the ammonia concentration in atmospheric air by absorption of COâ laser radiation at 9.22 μm is influenced by the presence of HâO and COâ. Kinetic cooling due to the coupling of excited COâ and Nâ levels causes important changes in phase and amplitude of the photoacoustic signal. Theoretical background is presented to deduce the correct NHâ

R. A. Rooth; A. J. L. Verhage; L. W. Wouters

1990-01-01

172

Atmospheric Aerosol and Cloud Condensation Nuclei Formation: A Possible Influence of Cosmic Rays?  

Microsoft Academic Search

A physical mechanism which may have a potential to connect climate with cosmic rays (CR) involves aerosol particle formation\\u000a by CR generated atmospheric ions followed by new particle growth. Only grown particles can scatter sunlight efficiently and\\u000a can eventually act as cloud condensation nuclei (CCN) and thereby may influence climate. Moreover grown particles live longer\\u000a as they are less rapidly

F. Arnold; Max Planck

2006-01-01

173

Statistical Analysis of Atmospheric Turbidity over Japan: The Influence of Three Volcanic Eruptions  

Microsoft Academic Search

Direct solar radiation data observed since 1933 at the Japan Meteorological Agency (JMA) observing stations have been analyzed. The transformed turbidity factor ln(?0--1), where ?0 is the Feussner-Dubois' turbidity coefficient, is introduced in order to normalize the frequency distribution. This allows for a better statistical analysis of atmospheric turbidity. The turbidity factor clearly shows the influence of three large volcanic

Toyotaro Yamauchi

1995-01-01

174

Human and natural influences on the changing thermal structure of the atmosphere.  

PubMed

Since the late 1970s, satellite-based instruments have monitored global changes in atmospheric temperature. These measurements reveal multidecadal tropospheric warming and stratospheric cooling, punctuated by short-term volcanic signals of reverse sign. Similar long- and short-term temperature signals occur in model simulations driven by human-caused changes in atmospheric composition and natural variations in volcanic aerosols. Most previous comparisons of modeled and observed atmospheric temperature changes have used results from individual models and individual observational records. In contrast, we rely on a large multimodel archive and multiple observational datasets. We show that a human-caused latitude/altitude pattern of atmospheric temperature change can be identified with high statistical confidence in satellite data. Results are robust to current uncertainties in models and observations. Virtually all previous research in this area has attempted to discriminate an anthropogenic signal from internal variability. Here, we present evidence that a human-caused signal can also be identified relative to the larger "total" natural variability arising from sources internal to the climate system, solar irradiance changes, and volcanic forcing. Consistent signal identification occurs because both internal and total natural variability (as simulated by state-of-the-art models) cannot produce sustained global-scale tropospheric warming and stratospheric cooling. Our results provide clear evidence for a discernible human influence on the thermal structure of the atmosphere. PMID:24043789

Santer, Benjamin D; Painter, Jeffrey F; Bonfils, Céline; Mears, Carl A; Solomon, Susan; Wigley, Tom M L; Gleckler, Peter J; Schmidt, Gavin A; Doutriaux, Charles; Gillett, Nathan P; Taylor, Karl E; Thorne, Peter W; Wentz, Frank J

2013-09-16

175

The influence of timing error on performance of optical pulse PPM system in atmospheric turbulence  

NASA Astrophysics Data System (ADS)

With the avalanche photodiode (APD) as the receiver, we have studied the timing error influence on performance of the optical pulse PPM system after analyzing the channel model of the atmospheric laser communication, and respectively obtained the relationship between the normalized timing error and PWE in the strong and weak turbulent environment. In addition, we obtained the influences of parameters such as the scintillation index, APD average gain and the levels of PPM modulation on performance of the optical pulse PPM system by simulation when there are timing errors in the system.

Fan, Wei; Yang, Xiao-Li; E., Yu

2011-06-01

176

Influence of impurities on the uniform atmospheric-pressure discharge in helium  

SciTech Connect

The influence of small nitrogen impurities on the uniform barrier discharge at atmospheric pressure in helium is investigated by numerical simulation with a one-dimensional fluid model. The simulation results show that in different discharge modes the influence of impurities is completely different. For glow discharge, small impurities result in the breakdown voltage dropping and thus cause the decrease in charged particle densities and discharge current density. In the case of Townsend discharge, nitrogen impurities can lead to the increase of charged particle densities and discharge current density, and even the change of discharge mode, but do not have a distinct impact on the breakdown voltage.

Wang Yanhui; Wang Dezhen [State Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams, Department of Physics, Dalian University of Technology, Dalian 116024 (China)

2005-02-01

177

Atmospheric chemistry in the Arctic and subarctic: Influence of natural fires, industrial emissions, and stratospheric inputs  

NASA Astrophysics Data System (ADS)

Haze layers with perturbed concentrations of trace gases, believed to originate from tundra and forest wild fires, were observed over extensive areas of Alaska and Canada in 1988. Enhancements of CH4, C2H2, C2H6, C3H8, and C4H10 were linearly correlated with CO in haze layers, with mean ratios (mole hydrocarbon/mole CO) of 0.18 (± 0.04 (1 ?)), 0.0019 (± 0.0001), 0.0055 (± 0.0002), 0.0008 (± 0.0001), and 1.2 × 10-4 (±0.2× 10-4), respectively. Enhancements of NOy, were variable, averaging 0.0056 (± 0.0030) mole NOy/mole CO, while perturbations of NOx were very small, usually undetectable. At least 1/3 of the NOy in the haze layers had been converted to peroxyacetyl nitrate (PAN), representing a potential source of NOx to the global atmosphere; much of the balance was oxidized to nitrate (HNO3 and paniculate). The composition of sub-Arctic haze layers was consistent with aged emissions from smoldering combustion, except for CH4, which appears to be partly biogenic. Inputs from the stratosphere and from biomass fires contributed major fractions of the NOy in the remote sub-Arctic troposphere. Analysis of aircraft and ground data indicates relatively little influence from mid-latitude industrial NOy in this region during summer, possibly excepting transport of PAN. Production of O3 was inefficient in sub-Arctic haze layers, less than 0.1 O3 molecules per molecule of CO, reflecting the low NOx/CO emission ratios from smoldering combustion. Mid-latitude pollution produced much more O3, 0.3 - 0.5 O3 molecules per molecule of CO, a consequence of higher NOx/CO emission ratios.

Wofsy, S. C.; Sachse, G. W.; Gregory, G. L.; Blake, D. R.; Bradshaw, J. D.; Sandholm, S. T.; Singh, H. B.; Barrick, J. A.; Harriss, R. C.; Talbot, R. W.; Shipham, M. A.; Browell, E. V.; Jacob, D. J.; Logan, J. A.

1992-10-01

178

Steep declines in atmospheric base cations in regions of Europe and North America  

NASA Astrophysics Data System (ADS)

HUMAN activities have caused marked changes in atmospheric chemistry over large regions of Europe and North America. Although considerable attention has been paid to the effects of changes in the deposition of acid anions (such as sulphate and nitrate) on terrestrial and aquatic ecosystems1-7, little is known about whether the concentrations of basic components of the atmosphere have changed over time8,9 and what the biogeochemical consequences of such potential changes might be. In particular, there has been some controversy8-12 as to whether declines in base-cation deposition have countered effects of recent reductions in SO2emission. Here we report evidence for steep declines in the atmospheric concentrations of base cations (sum of non-sea-salt Ca2+, Mg2+, K+ and Na+) over the past 10 to 26 years from high-quality precipitation chemistry records in Europe and North America. To varying but generally significant degrees, these base-cation trends have offset recent reductions in sulphate deposition in the regions examined. The observed trends seem to be ecologically important on decadal timescales, and support earlier contentions8-10 that declines in the deposition of base cations may have contributed to increased sensitivity of poorly buffered ecosystems.

Hedin, Lars O.; Granat, Lennart; Likens, Gene E.; Adri Buishand, T.; Galloway, James N.; Butler, Thomas J.; Rodhe, Henning

1994-01-01

179

A new SNR model for space-borne hyperspectral imagers including atmospheric scattering influence  

NASA Astrophysics Data System (ADS)

Space-borne hyperspectral imagery is widely used in the fields of earth science and mineral detection. High signal-to-noise ratio (SNR) of imaging spectrometers is required to guarantee the image data validity. To describe the system sensitivity, previous SNR models mainly focused on the optical parameters and the detector characteristics. However, the sensitivity of space-borne hyperspectral imagers is also limited by the atmospheric scattering effect to a large extent. A quantified and complete SNR model including atmospheric scattering influence is valuable for the development of imaging spectrometers. In this paper, scattering influence on hyperspectral imaging quality was analyzed in the spectral range of 0.4?m-2.5?m. Atmospheric simulation was presented and system performance reduction caused by the scattering effect was also quantified. The results show that the scattered light will occupy a large proportion of the system dynamic range and bring additional shot noise, which causes evident SNR attenuation. Based on the analysis a new SNR model including atmospheric parameters was provided. Hyperspectral imaging quality was calculated with both the new SNR model and the classical SNR model respectively, and comparative study of the two models was given in this paper. In order to validate the new SNR model, a hyperspectral imaging system and a multiband camera were built, and the imaging experiments were conducted. The results show that the atmospheric scattering effect could lead to significant SNR reduction and contrast attenuation of spectral images, especially at visible bands. Using the new SNR model could allow designers to estimate the system performance more precisely. Corresponding instrument design measures were also proposed based on the analysis and experiments.

Lang, Junwei; Wang, Yueming; Wang, Jianyu

2013-08-01

180

Identification of atmospheric mercury sources and transport pathways on local and regional sales  

NASA Astrophysics Data System (ADS)

Mercury (Hg) is a hazardous air pollutant and bioaccumulative neurotoxin whose intricate atmospheric chemistry complicates our ability to define Hg source-receptor relationships on all scales. Our detailed measurements of Hg in its different forms together with atmospheric tracers have improved our understanding of Hg chemistry and transport. Daily-event precipitation samples collected from 1995 to 2006 in Underhill, VT were examined to identify Hg wet deposition trends and source influences. Analysis revealed that annual Hg deposition at this fairly remote location did not vary significantly over the 12-year period. While a decreasing trend in volume-weighted mean Hg concentration was observed, Hg wet deposition did not decline as transport of emissions from the Midwest and along the Atlantic Coast consistently contributed to the largest observed Hg wet deposition events. Receptor modeling of Hg and trace elements in precipitation indicated that ---60% of Hg wet deposition at Underhill could be attributed to emissions from coal-fired utility boilers (CFUBs), and their contribution to Hg wet deposition did not change significantly over time. Hybrid-receptor modeling further defined these CFUBs to be located predominantly in the Midwestern U.S. Atmospheric Hg chemistry and transport from the Chicago urban/industrial area was the focus of speciated Hg measurements performed in the southern Lake Michigan basin during summer 2007. Transport from Chicago, IL to Holland, MI occurred during 27% of the study period, resulting in a five-fold increase in divalent reactive gaseous Hg (RGM) at the downwind Holland site. Dispersion modeling of case study periods demonstrated that under southwesterly flow approximately half of the RGM in Holland could be attributed to primary RGM emissions from Chicago after transport and dispersion, with the remainder due to Hg0 oxidation in the atmosphere en route. Precipitation and ambient vapor phase samples were also collected in Chicago, Holland, and Dexter, MI and analyzed for Hg isotopes. The Hg isotopic fractionation observed in atmospheric samples was in contrast to a recently published report which predicted that aqueous photoreduction may be a dominant source of atmospheric Hg. Our results suggest that other redox reactions and source related processes likely contribute to isotopic fractionation of atmospheric Hg.

Gratz, Lynne E.

181

Multi-decadal variations of atmospheric aerosols from 1980 to 2009: sources and regional trends  

NASA Astrophysics Data System (ADS)

Aerosol variations and trends over different land and ocean regions during 1980-2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and observations from multiple satellite sensors and ground-based networks. Excluding time periods with large volcanic influences, the tendency of aerosol optical depth (AOD) and surface concentration over polluted land regions is consistent with the anthropogenic emission changes. The largest reduction occurs over Europe, and regions in North America and Russia also exhibit reductions. On the other hand, East Asia and South Asia show AOD increases, although relatively large amount of natural aerosols in Asia makes the total changes less directly connected to the pollutant emission trends. Over major dust source regions, model analysis indicates that the dust emissions over the Sahara and Sahel respond mainly to the near-surface wind speed, but over Central Asia they are largely influenced by ground wetness. The decreasing dust trend in the tropical North Atlantic is most closely associated with the decrease of Sahel dust emission and increase of precipitation over the tropical North Atlantic, likely driven by the sea surface temperature increase. Despite significant regional trends, the model-calculated global annual average AOD shows little changes over land and ocean in the past three decades, because opposite trends in different regions cancel each other in the global average. This highlights the need for regional-scale aerosol assessment, as the global average value conceals regional changes, and thus is not sufficient for assessing changes in aerosol loading.

Chin, Mian; Diehl, T.; Tan, Q.; Prospero, J. M.; Kahn, R. A.; Remer, L. A.; Yu, H.; Sayer, A. M.; Bian, H.; Geogdzhayev, I. V.; Holben, B. N.; Howell, S. G.; Huebert, B. J.; Hsu, N. C.; Kim, D.; Kucsera, T. L.; Levy, R. C.; Mishchenko, M. I.; Pan, X.; Quinn, P. K.; Schuster, G. L.; Streets, D. G.; Strode, S. A.; Torres, O.; Zhao, X.-P.

2013-07-01

182

Influence of Gas Atmosphere Dew Point on the Galvannealing of CMnSi TRIP Steel  

NASA Astrophysics Data System (ADS)

The Fe-Zn reaction occurring during the galvannealing of a Si-bearing transformation-induced plasticity (TRIP) steel was investigated by field-emission electron probe microanalysis and field-emission transmission electron microscopy. The galvannealing was simulated after hot dipping in a Zn bath containing 0.13 mass pct Al at 733 K (460 °C). The galvannealing temperature was in the range of 813 K to 843 K (540 °C to 570 °C). The kinetics and mechanism of the galvannealing reaction were strongly influenced by the gas atmosphere dew point (DP). After the galvannealing of a panel annealed in a N2+10 pct H2 gas atmosphere with low DPs [213 K and 243 K (-60 °C and -30 °C)], the coating layer consisted of ? (FeZn10) and ? (Zn) phase crystals. The Mn-Si compound oxides formed during intercritical annealing were present mostly at the steel/coating interface after the galvannealing. Galvannealing of a panel annealed in higher DP [263 K and 273 K, and 278 K (-10 °C, 0 °C, and +5 °C)] gas atmospheres resulted in a coating layer consisting of ? and ? (Fe3Zn10) phase crystals, and a thin layer of ? 1 (Fe11Zn40) phase crystals at the steel/coating interface. The Mn-Si oxides were distributed homogeneously throughout the galvannealed (GA) coating layer. When the surface oxide layer thickness on panels annealed in a high DP gas atmosphere was reduced, the Fe content at the GA coating surface increased. Annealing in a higher DP gas atmosphere improved the coating quality of the GA panels because a thinner layer of oxides was formed. A high DP atmosphere can therefore significantly contribute to the suppression of Zn-alloy coating defects on CMnSi TRIP steel processed in hot dip galvanizing lines.

Cho, Lawrence; Kim, Myung Soo; Kim, Young Ha; De Cooman, Bruno C.

2013-11-01

183

Atmospheric deposition of trace elements recorded in snow from the Mt. Nyainqêntanglha region, southern Tibetan Plateau.  

PubMed

In May 2009, snowpit samples were collected from a high-elevation glacier in the Mt. Nyainqêntanglha region on the southern Tibetan Plateau. A set of elements (Al, V, Cr, Mn, Co, Ni, Cu, Zn, Cd, Hg and Pb) was analyzed to investigate the concentrations, deposition fluxes of trace elements, and the relative contributions from anthropogenic and natural sources deposited on the southern Tibetan Plateau. Concentrations of most of the trace elements in snowpit samples from the Zhadang glacier are significantly lower than those examined from central Asia (e.g., eastern Tien Shan), with higher concentrations during the non-monsoon season than during the monsoon season. The elements of Al, V, Cr, Mn, Co, and Ni display low crustal enrichment factors (EFs), while Cu, Zn, Cd, Hg, and Pb show high EF values in the snow samples, suggesting anthropogenic inputs are potentially important for these elements in the remote, high-elevation atmosphere on the southern Tibetan Plateau. Together with the fact that the concentration levels of such elements in the Mt. Nyainqêntanglha region are significantly higher than those observed on the south edge of the Tibetan Plateau, our results suggest that the high-elevation atmosphere on the southern Tibetan Plateau may be more sensitive to variations in the anthropogenic emissions of atmospheric trace elements than that in the central Himalayas. Moreover, the major difference between deposition fluxes estimated in our snow samples and those recently measured at Nam Co Station for elements such as Cr and Cu may suggest that atmospheric deposition of some of trace elements reconstructed from snowpits and ice cores could be grossly underestimated on the Tibetan Plateau. PMID:23535470

Huang, Jie; Kang, Shichang; Zhang, Qianggong; Guo, Junming; Chen, Pengfei; Zhang, Guoshuai; Tripathee, Lekhendra

2013-03-25

184

Numerical study of local\\/regional atmospheric changes caused by a large solar central receiver power plant  

Microsoft Academic Search

A two-dimensional numerical atmospheric mesoscale model with a vertical cross section is applied to study the potential local\\/regional atmospheric effects of the installation of a 100 MWe solar thermal central receiver power plant in California. The plant comprises heliostats (mirrors) covering a portion of ground surface and reflecting sunlight onto a central receiving tower. The model is able to simulate

C. M. Bhumralkar; A. J. Slemmons; K. C. Nitz

1981-01-01

185

Effects of atmospheric pollution on lichen biodiversity (LB) in a Mediterranean region (Liguria, northwest Italy)  

Microsoft Academic Search

The effects of air pollution on lichen biodiversity (LB) were monitored in Liguria (northwest Italy). A systematic sampling strategy was adopted in order to avoid the influence of spatial autocorrelation on the results. An eight LB class scale permitted to point out the levels of naturality\\/alteration in the region. The comparison of these results with the ones obtained by mean

Paolo Giordani; Giorgio Brunialti; Dario Alleteo

2002-01-01

186

Influence of equilibrium flows and the atmospheric magnetic field on solar oscillation modes  

NASA Astrophysics Data System (ADS)

The competing effects of an atmospheric magnetic field and an equilibrium flow in the internal regions of the Sun are studied on the helioseismic f- and p-modes. The Sun is modeled as a multi-layered plasma, where the upper parts, representing the chromosphere and corona, are embedded in a unidirectional though inhomogeneous magnetic field, meanwhile the lower part, representing the sub-photospheric polytropic region, is in a steady equilibrium state. The steady state sub-surface region can be considered as a first approximation of dynamic motions (e.g., convective motion, differential rotation, sub-surface flows, meridional flows, etc.). The obtained frequency shifts of the different eigenmodes are associated with flow and magnetic effects. We also found damping of the eigenfrequencies which apparently can be associated with the universal mechanism of resonant absorption. Resonant absorption (already known as a viable heating mechanism in the solar corona) is present due to inhomogeneities in the atmosphere which give rise to Alfvén and slow continua. Damping of helioseismic modes occurs when the modes are coupled into these continua. When both atmospheric magnetic field and sub-surface flows are present, a complex picture of competition of these two effects is found. The theoretically predicted frequency shifts in a steady state are in excellent agreement with the observed values. For related works see also the papers by Erdélyi & Taroyan and Varga & Erdélyi in the present Volume.

Pintér, B.; Erdélyi, R.; New, R.; Goossens, M.

2001-01-01

187

The Atmospheric Bridge: The Influence of ENSO Teleconnections on Air-Sea Interaction over the Global Oceans  

Microsoft Academic Search

During El Niño-Southern Oscillation (ENSO) events, the atmospheric response to sea surface temperature (SST) anomalies in the equatorial Pacific influences ocean conditions over the remainder of the globe. This connection between ocean basins via the `atmospheric bridge' is reviewed through an examination of previous work augmented by analyses of 50 years of data from the National Centers for Environmental Prediction-National

Michael A. Alexander; Ileana Bladé; Matthew Newman; John R. Lanzante; Ngar-Cheung Lau; James D. Scott

2002-01-01

188

Atmospheric conditions influencing the spillover of rainfall to lee of the Southern Alps, New Zealand  

NASA Astrophysics Data System (ADS)

Atmospheric conditions influencing precipitation distribution over a large lee-side catchment in the Southern Alps of New Zealand are investigated. A significant proportion of rainfall received in the upper Waimakariri catchment is generated by its spillover from the windward side of the alps during conditions of westerly flow. A transect of rain gauges was installed to examine the distribution of rainfall across the mountains during northwesterly events, and an index was devised to quantify the magnitude of each spillover event, allowing comparison with other events that occurred within the study period. The spillover index combines a measure of the total quantity of rainfall reaching the ground with its distance east of the main divide.Correlation and regression techniques were used to assess the role of various processes in determining the observed spillover distributions during 42 events. Several atmospheric parameters were considered, including measures of air-mass temperature, humidity, instability, windspeed and direction, and frontal intensity. It was found that spillover of rainfall into the upper Waimakariri catchment is largely determined by lower level wind speeds, latent instability and frontal intensity. Existing knowledge of atmospheric processes is used to explain how these factors influence spillover activity.

Chater, Amanda M.; Sturman, Andrew P.

1998-01-01

189

On the influence of Stark broadening on Cr I lines in stellar atmospheres  

NASA Astrophysics Data System (ADS)

Using the semiclassical perturbation method, electron-, proton-, and ionized helium-impact line widths and shifts for the nine Cr i spectral lines from the 4p^7P^0{-}4d^7D multiplet were calculated for a perturber density of 1014 cm-3 and for temperatures T = 2500 {-} 50 000 K. The results were used to investigate the influence of Stark broadening effect in the Cr-rich Ap star ? CrB atmosphere on line shapes of these lines. It was found that the contribution of proton and He ii collisions to the line width and shift is significant and comparable, and is sometimes even larger than electron-impact contribution depending of the electron temperature. Moreover, not only the Stark line width, but also the Stark shift may contribute to the blue as well as to the red asymmetry of the same line depending on the electron-, proton-, and He ii density in stellar atmosphere. The results were used to investigate the influence of Stark broadening effect on Cr i line shapes in the atmosphere of the Cr-rich Ap star ? CrB.

Dimitrijevi?, M. S.; Ryabchikova, T.; Popovi?, L. ?.; Shulyak, D.; Khan, S.

2005-06-01

190

Influence of water vapour and permanent gases on the atmospheric optical depths and transmittance  

NASA Astrophysics Data System (ADS)

The influence of the atmospheric state on the extinction of direct solar radiation has been studied by using a four layer atmospheric model. Simple analytical formulae are established for the spectral optical depths of permanent gases and water vapour. These formulae use the ground level values of air pressure, temperature and relative huniidity. An additional parameter, related to the vertical distribution of the hunmidity content, is used for a better estimation of the water vapour optical depth. Good agreement between theory and measurements is found. The paper shows the dependence of the atmospheric spectral transmittance on the above mentioned parameters. L'influence de l'état atmosphérique sur l'extinction de la radiation solaire directe a été étudiée à l'aide d'un modèle atmosphérique développé antérieurement par l'auteur. Des formules simples ont été établies pour l'épaisseur optique spectrale des gaz et de la vapeur d'eau. Ces formules utilisent les valeurs de la pression atmosphérique, de la température et de l'humidité relative, mesurées au niveau du sol. Un paramètre supplémentaire, lié à la distribution verticale du contenu d'humidité, est utilisé pour calculer l'épaisseur optique due à la vapeur d'eau. La théorie est en bon accord avec les résultats des mesures. Le travail montre la dépendance de la transmittance atmosphérique spectrale en fonction des paramètres spécifiés ci-dessus.

Badescu, V.

1991-05-01

191

Atmospheric influence on a laser beam observed on the OICETS - ARTEMIS communication demonstration link  

NASA Astrophysics Data System (ADS)

In 2006 bi-directional optical inter-satellite communication experiments have been conducted between the Japan Aerospace Exploration Agency (JAXA) Optical Inter-orbit Communications Engineering Test Satellite (OICETS) and the European Space Agency (ESA) multi purpose telecommunications and technology demonstration satellite (Advanced Relay and Technology MISsion) ARTEMIS. On 5 April 2006 an experiment was successfully carried out maintaining the inter-satellite link during OICETS's setting behind the Earth limb until the signal was lost. This setup resembles an occultation observation where the influence of Earth's atmosphere is evident in the power fluctuations recorded at ARTEMIS's (and OICETS's) receiver. These fluctuations are not existing or at a low level at a link path above the atmosphere and steadily increase as OICETS sets behind the horizon until the tracking of the signal is lost. This specific experiment was performed only once since atmospheric science was not the goal of this demonstration. Nevertheless this kind of data, if available more frequently in future, can help to study atmospheric turbulence and validate respective models. The data presented here had been recorded at ARTEMIS.

Löscher, A.

2010-05-01

192

Atmospheric influence on a laser beam observed on the OICETS - ARTEMIS communication demonstration link  

NASA Astrophysics Data System (ADS)

In 2006 bi-directional optical inter-satellite communication experiments were conducted between the Japan Aerospace Exploration Agency (JAXA) Optical Inter-orbit Communications Engineering Test Satellite (OICETS) and the European Space Agency (ESA) multi-purpose telecommunications and technology demonstration satellite (Advanced Relay and Technology MISsion) ARTEMIS. On 5 April 2006, an experiment was successfully carried out by maintaining the inter-satellite link during OICETS's setting behind the Earth limb until the signal was lost. This setup resembles an occultation observation where the influence of Earth's atmosphere is evident in the power fluctuations recorded at ARTEMIS's (and OICETS's) receiver. These fluctuations do not exist or are at a low level at a link path above the atmosphere and steadily increase as OICETS sets behind the horizon until the tracking of the signal is lost. This specific experiment was performed only once since atmospheric science was not the goal of this demonstration. Nevertheless, this kind of data, if available more frequently in future, can help to study atmospheric turbulence and validate models. The data present here were recorded at ARTEMIS.

Löscher, A.

2010-09-01

193

Analysis of influence of atmosphere extinction to Raman lidar monitoring CO2 concentration profile  

NASA Astrophysics Data System (ADS)

Lidar (Light detection and ranging) system monitoring of the atmosphere is a novel and powerful technique tool. The Raman lidar is well established today as a leading research tool in the study of numerous important areas in the atmospheric sciences. In this paper, the principle of Raman lidar technique measurement CO2 concentration profile is presented and the errors caused by molecular and aerosol extinction for CO2 concentration profile measurement with Raman lidar are also presented. The standard atmosphere extinction profile and 'real-time' Hefei area extinction profile are used to conduct correction and the corresponding results are yielded. Simulation results with standard atmosphere mode correction indicate that the errors caused by molecule and aerosol extinction should be counted for the reason that they could reach about 8 ppm and 5 ppm respectively. The relative error caused by Hefei area extinction correction could reach about 6%. The errors caused by the two components extinction influence could produce significant changes for CO2 concentration profile and need to be counted in data processing which could improve the measurement accuracies.

Zhao, Pei-Tao; Zhang, Yin-Chao; Wang, Lian; Zhao, Yue-Feng; Su, Jia; Fang, Xin; Cao, Kai-Fa; Xie, Jun; Du, Xiao-Yong

2007-08-01

194

Coupling of regional atmospheric-ocean models for climate applications in the Mediterranean basin by using CORDEX-compliant simulations  

NASA Astrophysics Data System (ADS)

Nowadays, most regional climate models (RCMs) are essentially composed of an atmospheric component coupled to a land surface scheme and driven over ocean areas by prescribed sea surface temperature (SST). Although such a RCM can be sufficient for many applications, there are cases (like in the Mediterranean basin) in which fine scale feedbacks associated with air-sea interactions can substantially influence the spatial and temporal structure of regional climates. Therefore, in this work we present the first testing phase of the application of a coupled atmospheric-ocean regional climate model (AORCM) for the Mediterranean basin under the framework of the CORWES project. CORWES is a Spanish consortium of research groups using the Weather Research and Forecasting (WRF) model to contribute to the Coordinated Regional Climate Downscaling Experiment (CORDEX). We use WRF and ROMS models as the atmospheric and oceanic component, respectively. Coupling between WRF and ROMS is achieved in the following way: on a prescribed interval of 2 h, WRF sends wind stress, surface heat and water fluxes to ROMS time-averaged over the previous two hours. One hour later, and also with a prescribed interval of 2 h, ROMS sends time-averaged SST to WRF. Here, we mainly focus on the performance of the coupled system in reproducing the ocean surface temperatures. To separate effects of the coupling on SST, additional uncoupled atmospheric simulations are also done in parallel. The case study covers the years 2001-2005 and is described below. The resolution of the domain used is 12 km. The number of vertical levels is 30 for WRF. The ROMS domain, with 32 vertical levels, is slightly smaller than WRF innermost nest and has a higher resolution of 4 km. The lateral atmospheric boundary conditions for WRF are taken from ERA-Interim reanalysis. The lateral oceanic boundary conditions for ROMS come from the downscaling of the Simple Ocean Data Assimilation analysis (SODA) by an uncoupled nested ROMS simulation covering the Mediterranean. The atmospheric forcing for this simulation is also provided by ERA-Interim. To isolate effects of coupling on the atmosphere solutions, an atmosphere-only WRF simulation forced by ERA-Interim has been run. The results indicate that there is an overall good agreement between WRF-ROMS simulations and the E-OBS gridded dataset. During winter, the land temperature fields over most subregions in both WRF-ROMS and WRF achieve a closer agreement with E-OBS than ERAIN reanalyses, as a consequence of the dynamical downscaling. During JJA, the regional simulations exhibit a cold bias with respect to E-OBS, which is somewhat corrected by the coupled simulation. WRF-ROMS and WRF have similar average temperatures during all seasons. During summer, WRF-ROMS provides higher temperatures in the southern Mediterranean (Alboran, Benghazi, Mersa Matrouh) and lower temperatures in the Adriatic and the north-eastern Levantine basin than the atmosphere-only WRF simulations. This pattern corresponds to the prevailing anti-cyclonic oceanic structures along the southern coasts and to the cyclonic structures along the northern Mediterranean coasts, the two being separated by the Mid-Mediterranean jet. Also, 2-m summer temperatures for coupled vs. uncoupled simulations are marked by the differences in SST. WRF-ROMS and WRF-alone have similar temperature averages. Main differences are found over coastal areas (but are lower than 0.2 °C for all the Mediterranean basin). Therefore, the atmosphere-ocean coupling over this region does not significantly change the simulations of present climate 2-m temperature. Moreover, the precipitation in the WRF-ROMS and WRF simulations do not present substantial differences for total precipitation, suggesting a weak effect of air-sea feedbacks on seasonal mean precipitation over land in our modelling system. This result is somewhat expected from the well established notion that the Mediterranean area is mainly subject to large scale orographic precipitation associated to synoptic systems travelling eastward from t

Jimenez-Guerrero, Pedro; Montávez, Juan P.; Lorente-Plazas, Raquel

2013-04-01

195

Modulation of the midlatitude ionospheric E region by atmospheric gravity waves through polarization electric field  

NASA Astrophysics Data System (ADS)

We have studied coupling between the neutral atmosphere and the ionospheric E region in the midlatitude by combining two numerical simulation models. Atmospheric gravity waves generated in the troposphere propagate through the stratosphere and the mesosphere and can reach the lower thermosphere. When a zonal wind shear that can accumulate a sporadic-E (Es) layer (eastward below and westward above) is applied, the accumulated Es layer is strongly modulated by the gravity waves, and polarization electric field due to the modulated Es layer produces wave-like patterns of plasma density in the upper E region. Since the eastward wind below the shear node filters out gravity waves with eastward phase velocity, those with westward phase velocity are dominant where the Es layer is accumulated. Because of the angle between phase front of gravity waves and the geomagnetic field line, gravity waves with southward phase velocity is more effective to generate polarization electric field than those with northward phase velocity. Since gravity waves with southwestward phase velocity have phase fronts aligned from northwest to southeast, polarization electric field also has the similar structure. This mechanism can explain the spatial structure of quasi-periodic (QP) echoes associated with plasma irregularities in the midlatitude E region which often shows northwest-southeast alignment.

Yokoyama, T.; Horinouchi, T.; Yamamoto, M.; Fukao, S.

2004-12-01

196

Pre-Eruption Magnetic Configurations in the Low Atmosphere of Solar Active Regions  

NASA Astrophysics Data System (ADS)

Major solar eruptions, namely flares and coronal mass ejections, rely on significant local accumulations of non-potential (free; stored in electric currents) magnetic energy and, quite likely, magnetic helicity in the solar atmosphere. Without [both of] them, eruptions cannot be powered. Simple tests can show that most free energy and helicity reside close to the lower atmospheric boundary in solar active regions, i.e. their photospheric or low chromospheric interface. Therefore, the pre-eruption configuration in this boundary should reflect these high free-energy and helicity conditions that jointly determine the degree of non-potentiality in active regions. We review the two main active-region photospheric/low-chromospheric configurations leading to major eruptions: instances of intense magnetic flux emergence in the absence of intense magnetic polarity inversion lines (PILs), and instances of strong PILs. In these configurations we discuss multiple measures that can be thought of as proxies of free magnetic energy and helicity and we outline a method to actually calculate these budgets. Combining information from different, but concerted, analyses and approaches, a new picture of eruption initiation emerges. We highlight this new insight and project on its physical plausibility and the advances that it may bring.

Georgoulis, Manolis K.

2012-07-01

197

Complex topography influences atmospheric nitrate deposition in a neotropical mountain rainforest  

NASA Astrophysics Data System (ADS)

Future increase of atmospheric nitrogen deposition in tropical regions is expected to have negative impacts on forests ecosystems and related biogeochemical processes. In tropical mountain forests topography causes complex streamflow and rainfall patterns, governing the atmospheric transport of pollutants and the intensity and spatial variability of deposition. The main goal of the current study is to link spatio-temporal patterns of upwind nitrogen emissions and nitrate deposition in the San Francisco Valley (eastern Andes of southern Ecuador) at different altitudinal levels. The work is based on Scanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) retrieved-NO2 concentrations, NOx biomass burning emissions from the Global Fire Emissions Database (GFEDv3), and regional vehicle emissions inventory (SA-INV) for urban emissions in South America. The emission data is used as input for lagrangian atmospheric backward trajectory modeling (FLEXTRA) to model the transport to the study area. The results show that NO concentrations in occult precipitation samples are significantly correlated to long-range atmospheric secondary nitrogen transport at the highest meteorological stations (MSs) only, whereas for NO concentrations in rain samples this correlation is more pronounced at the lower MSs. We conclude that ion concentrations in occult precipitation at the uppermost MSs are mainly linked to distant emission sources via the synoptic circulation impinging the more exposed higher sites. Lower correlations close to the valley bottom are due to a lower occult precipitation frequency and point to a contamination of the samples by local pollution sources not captured by the used emission data sources.

Makowski Giannoni, Sandro; Rollenbeck, Rütger; Fabian, Peter; Bendix, Jörg

2013-11-01

198

Local oceanic response to atmospheric forcing in the Gulf Stream region  

NASA Astrophysics Data System (ADS)

The dominance of shifts in the location of the Gulf Stream (GS) in the local heat balance was observed in an hourly 15-month record of unprecedented surface mooring measurements at a site in the western North Atlantic occupied from November 2005 to January 2007. Instrumentation on the buoy provided a high quality record of air-sea exchanges of momentum, heat, and freshwater flux; and oceanographic sensors recorded ocean variability in the upper 640 m. The mooring was at times in the GS and at other times north of the GS. Our intent was to isolate the local oceanic response to the atmosphere from the influence of the GS shifts. A one-dimensional heat budget analysis indicated that the advective contribution from the GS shifts dwarfed the heat contribution by atmospheric forcing and therefore played the dominant role for upper oceanic thermal variability during the whole time record. A GS case study (i.e., when the surface mooring was in the GS), isolated the upper oceanic response to the atmospheric forcing in the GS and supported the critical role of GS shifts in total oceanic heat content. Through both an Empirical Orthogonal Function (EOF) analysis and by referencing temperatures to that observed at 200 m, the impact of GS shifts and atmospheric forcing were decomposed, allowing the local oceanic thermal response to be isolated. This local oceanic response was particularly prominent during the period of sustained heating during summer. A case study of summer conditions revealed a near surface flow consistent with Ekman dynamics within a shallow, warm ocean mixed layer.

Davis, Xujing Jia; Weller, Robert A.; Bigorre, Sebastien; Plueddemann, Albert J.

2013-07-01

199

The ionospheric wind dynamo: Effects of its coupling with different atmospheric regions  

NASA Astrophysics Data System (ADS)

Effects of the ionospheric wind dynamo related to its coupling with different atmospheric regions are reviewed. Early studies showed that height-averaged tidal-like winds of order 30 m/s must be present in the dynamo region (90-200 km height) to produce the observed geomagnetic daily variations. They also indicated that diurnal solar tides drive more current than semidiurnal tides, although the latter are important in explaining the observed electric fields and asymmetries of the currents about the equator. Lunar tidal winds of order 10 m/s in the dynamo region, roughly opposite in phase to the tides at ground level, are required to explain the observed lunar geomagnetic variations. There is strong seasonal and longitudinal variability in lunar geomagnetic variations that indicates similar variability in the lunar tidal winds. Day-to-day variability in ionospheric dynamo effects points to short-term variability in the global winds, probably due to variability in tidal propagation conditions through the middle atmosphere and/or to penetration of planetary waves into the dynamo region. However, attempts to correlate observed upper-mesospheric winds with geomagnetic variations have had only limited success. Searches for two-day variations in geomagnetic data associated with the two-day wave in megospheric winds have not consistently found a significant signal. Suggestions of a 16-day variation in geomagnetic and ionospheric data associated with 16-day planetary waves remain to be verified, as do suggestions of possible associations between the stratospheric quasi-biennial oscillation and geomagnetic variations. Coupling among dynamo electric fields and currents, ionospheric plasma variations, and thermospheric dynamics have been shown to be important in a number of situations. Recently, global simulation models that take these mutual-coupling effects into account have been developed. Coupling between the ionospheric and magnetospheric dynamos is also significant, though the quantitative importance and full implications of the "flywheel" effect, "fossil-wind" effect, and "disturbance-dynamo" effect remain to be determined. Fruitful areas of future research will be the further exploitation of observed geomagnetic and ionospheric phenomena to study tidal and planetary-wave propagation conditions in the middle atmosphere, including possible long-term changes associated with a changing atmospheric state; exploitation of simulation models of coupled thermosphere/ionosphere dynamics and electrodynamics; and further investigation of effects associated with coupling between the ionospheric and magnetospheric dynamos.

Richmond, A. D.

200

Titan's atmosphere from Voyager infrared observations. I - The gas composition of Titan's equatorial region  

Microsoft Academic Search

After inferring minor atmospheric-constituent abundances in Titan's equatorial region from Voyager 1 IR spectra, a stratospheric temperature profile is derived. An analysis of three different sections has yielded stratospheric mole fractions for C2H2, C2H4, C2H6, C3H4, C3H8, C4H2, HCN, and CO2; an altitude-dependent CO2 profile has been tested against observations, but no conclusive data on vertical distribution could be extracted.

A. Coustenis; B. Bezard; D. Gautier

1989-01-01

201

RSL: A parallel Runtime System Library for regional atmospheric models with nesting  

SciTech Connect

RSL is a parallel runtime system library developed at Argonne National Laboratory that is tailored to regular-grid atmospheric models with mesh refinement in the form of two-way interacting nested grids. RSL provides high-level stencil and interdomain communication, irregular domain decomposition, automatic local/global index translation, distributed I/O, and dynamic load balancing. RSL was used with Fortran90 to parallelize a well-known and widely used regional weather model, the Penn State/NCAR Mesoscale model.

Michalakes, J.G.

1997-08-01

202

Influence of Atmospheric Intraseasonal Oscillations on Seasonal and Interannual Variability in the Upper Indian Ocean  

NASA Astrophysics Data System (ADS)

An ocean general circulation model (the Hybrid Coordinate Ocean Model, HYCOM) is used to examine the rectification of atmospheric intraseasonal oscillations (ISOs) on lower-frequency seasonal to interannual sea surface temperature (SST), mixed layer thickness (hm) and upper ocean heat content in the Indian Ocean (IO). Existing studies have shown that ISOs rectify on low-frequency equatorial surface currents and on cross-equatorial transport, suggesting that they may also have important impacts on low-frequency upper ocean variability. To evaluate these impacts, a hierarchy of experiments is run with HYCOM that isolates the ocean response to atmospheric forcing by 10-90 day (atmospheric ISO) events. Other experiments isolate the ocean response to a range of intraseasonal forcing fields including shortwave radiation, precipitation, and winds. Results indicate that rectification of ISOs onto seasonal and interannual upper ocean variability does occur, and that it is important in some regions. The regions displaying maximum rectification vary between SST, hm, and upper ocean heat content, and between seasonal and interannual timescales. Strong seasonal SST rectification occurs in the Arabian Sea and in the Bay of Bengal. Because SSTs in the Arabian Sea are already warm (28°C), the ISO-forced seasonal cycle peak of 0.6°C in May can affect convection there. Intraseasonal wind speed and wind stress have a much larger impact on seasonal and interannual SST, hm, and upper ocean heat content than either intraseasonal shortwave radiation or precipitation. The relative importance of entrainment and turbulent heat flux due to intraseasonal wind speed, and of upwelling and horizontal advection due to intraseasonal wind stress, varies with region. Atmospheric ISOs appear to have a larger impact on the Indian Ocean Dipole Mode Index during non-dipole years than during strong dipole years.

Duncan, B.; Han, W.

2011-12-01

203

Radiative transfer in the earth's atmosphere and ocean: influence of ocean waves.  

PubMed

The radiance in the earth's atmosphere and ocean is calculated for a realistic model including an ocean surface with waves. Individual photons are followed in a Monte Carlo calculation. In the atmosphere, both Rayleigh scattering by the molecules and Mie scattering by the aerosols as well as molecular and aerosol absorption are taken into account. Similarly, in the ocean, both Rayleigh scattering by the water molecules and Mie scattering by the hydrosols as well as absorption by the water molecules and hydrosols are considered. Separate single-scattering functions are used which are calculated separately for the aerosols and the hydrosols from the Mie theory with appropriate and different size distributions in each case. The scattering angles are determined from the appropriate scattering function including the strong forwardscattering peak when there is aerosol or hydrosol scattering. Both the reflected and refracted rays, as well as the rays that undergo total internal reflection, are followed at the oceanc surface. The wave slope is chosen from the Cox-Munk distribution. Graphs show the influence of the waves on the upward radiance at the top of the atmosphere and just above the ocean surface and on the downward radiance just below the ocean surface as well as deeper within the ocean. The radiance changes are sufficient at the top of the atmosphere to determine the sea state from satellite measurements. Within the ocean the waves smooth out the abrupt transition that occurs at the edge of the allowed cone for radiation entering a calm ocean. The influence of the waves on the contrast between the sky and sea at the horizon is discussed. It is shown that the downward flux just below the surface increases with wind speed at all solar angles. PMID:20154940

Plass, G N; Kattawar, G W; Guinn, J A

1975-08-01

204

The influence of atmospheric variability on ice formation in the mesosphere  

NASA Astrophysics Data System (ADS)

LIMA Leibniz Institute Middle Atmosphere Model is a new model which nicely reproduces the mean conditions of the summer mesopause region at middle and polar latitudes It includes all relevant atmospheric processes such as dynamics radiation and chemistry from the ground to the lower thermosphere In the lower atmosphere LIMA assimilates ECMWF ERA-40 data and thereby introduces natural variability We have run an ice particle model in the mesosphere using the background conditions from LIMA which vary with season and height The ice model is interactively coupled to water vapor and thereby includes the redistribution of H 2 O by the so called freeze drying effect In this paper we discuss the importance of natural variability on the geographical and seasonal distribution of ice layers known as noctilucent clouds NLC and polar mesosphere summer echoes PMSE We will present a detailed comparison of the LIMA ice model results with lidar and radar measurements at our three stations namely K u hlungsborn 54° N ALOMAR 69° N and Longyearbyen 78° N The average layer characteristics in the model such as mean NLC altitude and brightness agree nicely with observations There is a close correlation between the occurrence of ice layers and cold and wet periods in the upper mesosphere We will also compare LIMA ice results with satellite borne observations of ice clouds known as polar mesospheric clouds PMC Despite mixing by atmospheric waves and mean circulation we find a substantial modification of the background

Luebken, F.-J.; Berger, U.; Herbort, F.; Baumgarten, G.; Fiedler, J.; Gerding, M.

205

Retrieving the atmospheric aerosol properties over Beijing region by combining rotational Raman - Mie lidar and CALIPSO  

NASA Astrophysics Data System (ADS)

Typically, we use Klett-Fernald method for retrieving aerosol optical properties. However, the results from these methods critically depend on the lidar ratio, thus affecting the accuracy of the inversion results. In this paper, we adopted a new method to retrieve the vertical distribution profiles of aerosol backscatter coefficient, aerosol extinction coefficient and lidar ratio over Beijing region by combining rotational Raman - Mie lidar and CALIPSO(Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations). The results were compared with the results determined by the conventional method, which shows a good agreement. Compared with the conventional method, the results from this new method are more reliable and less noisy, which provide richer information for researching the atmospheric aerosol properties over Beijing region.

Zhang, Yinchao; Li, Dan; Chen, Binglong; Chen, Siying; Chen, He; Guo, Pan

2013-05-01

206

Empirical and modeling evidence of regional atmospheric transport of current-use pesticides.  

PubMed

Water samples from 30 lakes in Canada and the northeastern United States were analyzed for the occurrence of 27 current-use pesticides (CUPs). Eleven CUPs were frequently detected in lakes receiving agricultural inputs as well as in remote lakes hundreds of kilometers from known application areas. These included the triazine herbicide atrazine and its desethylated degradation product; the herbicides alachlor, metolachlor, and dacthal; the organophosphate insecticides chlorpyrifos, diazinon, and disulfoton; the organochlorine insecticides alpha-endosulfan and lindane; and the fungicides chlorothalonil and flutriafol. For six of the pesticides, empirical half-distances on the order of 560 to 1,820 km were estimated from the water-concentration gradient with latitude. For most of the pesticides, a suite of assessment models failed to predict such atmospheric long-range transport behavior, unless the effect of periods of lower hydroxyl radical concentrations and dry weather were taken into account. Observations and model results suggest that under the conditions prevailing in south-central Canada (relatively high latitude, low precipitation rates), many CUPs will be able to undergo regional-scale atmospheric transport and reach lakes outside areas of agricultural application. When assessing the potential of fairly reactive and water-soluble substances to undergo long-range transport, it is imperative to account for periods of no precipitation, to assure that degradation rate constants are correct, and to apply oxidant concentrations that are valid for the region and time period of interest. PMID:15511103

Muir, Derek C G; Teixeira, Camilla; Wania, Frank

2004-10-01

207

Coherence between atmospheric teleconnections, Great Lakes water levels, and regional climate  

NASA Astrophysics Data System (ADS)

We investigated the frequency domain relationships between four atmospheric teleconnections (Trans-Niño Index TNI, Pacific Decadal Oscillation PDO, Northern Annular Mode/Arctic Oscillation Index NAM/AO, and Pacific/North American PNA pattern) and water levels in the Great Lakes from 1948 to 2002 by quantifying the coherence between these time series. The levels in all Great Lakes are significantly correlated with the TNI in the frequency range (3-7) -1 cycles year -1, and with the PDO in interdecadal frequencies. The levels in Lakes Superior, Michigan, and Erie are significantly correlated with the PNA pattern in interdecadal frequencies, and the levels in all Great Lakes are significantly correlated with the NAM/AO in interannual frequencies. We investigated also the coherence, or "climate link", between atmospheric teleconnections and the Great Lakes regional climate, namely precipitation, evaporation, air temperature, and connecting channel flows, and the coherence, or "hydrologic link" between regional climate and lake levels. The effect of the teleconnections on lake levels is mostly transmitted through the "climate links" and the "hydrologic links", particularly through the channel inflows to Lakes Michigan, Erie, and Ontario. Connecting channel flows depend on the cumulative effect of upstream lakes and their watersheds and transmit interannual and interdecadal signals better than precipitation, evaporation, and air temperature.

Ghanbari, Reza Namdar; Bravo, Hector R.

208

The influence of the several very large solar proton events in years 2000-2003 on the neutral middle atmosphere  

NASA Astrophysics Data System (ADS)

Solar proton events (SPEs) are known to have caused changes in constituents in the Earth's polar neutral middle atmosphere. The highly energetic protons produce ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which lead to the production of HOx (H, OH, HO2) and NOy (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The HOx increases lead to short-lived ozone decreases in the polar mesosphere and upper stratosphere due to the short lifetimes of the HOx constituents. The NOy increases lead to long-lived stratospheric ozone changes because of the long lifetime of the NOy family in this region. The past four years, 2000-2003, have been replete with SPEs and huge fluxes of high energy protons occurred in July and November 2000, September and November 2001, April 2002, and October 2003. Smaller, but still substantial, proton fluxes impacted the Earth during other months from year 2000 to 2003. The Goddard Space Flight Center (GSFC) Two-dimensional (2D) Model was used in computing the influence of the SPEs. The impact of these extremely large SPEs was calculated to be especially large in the upper stratosphere and mesosphere. The results of the GSFC 2D Model will be shown along with comparisons to the Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) and Solar Backscatter Ultraviolet 2 (SBUV/2) instruments.

Jackman, C.; Sinnhuber, M.; Anderson, J.; McPeters, R.; Fleming, E.; Russell, J.

209

Influence of Equatorial Diatom Processes on Si Deposition and Atmospheric CO(2) Cycles at Glacial\\/Interglacial Timescales  

Microsoft Academic Search

The causes of the glacial cycle remain unknown, although the primary driver is changes in atmospheric CO(2), likely controlled by the biological pump and biogeochemical cycles. The two most important regions of the ocean for exchange of CO(2) with the atmosphere are the equatorial Pacific and the Southern Ocean ( SO), the former a net source and the latter a

R. C. Dugdale; M. Lyle; F. P. Wilkerson; Fei Chai; R. T. Barber; T.-H. Peng

2004-01-01

210

Influence of equatorial diatom processes on Si deposition and atmospheric CO2 cycles at glacial\\/interglacial timescales  

Microsoft Academic Search

The causes of the glacial cycle remain unknown, although the primary driver is changes in atmospheric CO2, likely controlled by the biological pump and biogeochemical cycles. The two most important regions of the ocean for exchange of CO2 with the atmosphere are the equatorial Pacific and the Southern Ocean (SO), the former a net source and the latter a net

R. C. Dugdale; M. Lyle; F. P. Wilkerson; F. Chai; R. T. Barber; T.-H. Peng

2004-01-01

211

Atmospheric correction using near-infrared bands for satellite ocean color data processing in the turbid western Pacific region.  

PubMed

A regional near-infrared (NIR) ocean normalized water-leaving radiance (nL(w)(?)) model is proposed for atmospheric correction for ocean color data processing in the western Pacific region, including the Bohai Sea, Yellow Sea, and East China Sea. Our motivation for this work is to derive ocean color products in the highly turbid western Pacific region using the Geostationary Ocean Color Imager (GOCI) onboard South Korean Communication, Ocean, and Meteorological Satellite (COMS). GOCI has eight spectral bands from 412 to 865 nm but does not have shortwave infrared (SWIR) bands that are needed for satellite ocean color remote sensing in the turbid ocean region. Based on a regional empirical relationship between the NIR nL(w)(?) and diffuse attenuation coefficient at 490 nm (K(d)(490)), which is derived from the long-term measurements with the Moderate-resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, an iterative scheme with the NIR-based atmospheric correction algorithm has been developed. Results from MODIS-Aqua measurements show that ocean color products in the region derived from the new proposed NIR-corrected atmospheric correction algorithm match well with those from the SWIR atmospheric correction algorithm. Thus, the proposed new atmospheric correction method provides an alternative for ocean color data processing for GOCI (and other ocean color satellite sensors without SWIR bands) in the turbid ocean regions of the Bohai Sea, Yellow Sea, and East China Sea, although the SWIR-based atmospheric correction approach is still much preferred. The proposed atmospheric correction methodology can also be applied to other turbid coastal regions. PMID:22274419

Wang, Menghua; Shi, Wei; Jiang, Lide

2012-01-16

212

A New Mass Spectrometer for Upper Atmospheric Measurements in the Auroral Region  

NASA Astrophysics Data System (ADS)

We have previously presented a new rocket-borne time-of-flight mass spectrometer (TOF-MS) for measurements in the mesosphere / lower thermosphere (MLT). Traditionally, mass spectrometry in the MLT has been difficult, mainly due to the elevated ambient pressures of the MLT and high speeds of a sounding rocket flight, which affect the direct sampling of the ambient atmosphere and spatial resolution. The TOF-MS is a versatile, inherently adaptable, axial-sampling instrument, capable of operating in a traditional TOF mode or in a multiplexing Hadamard-transform mode where high spatial resolution is desired. To minimize bow shock effects at low altitudes (~70-110km), the ram surface of the TOF-MS can be cryogenically cooled using liquid He to adsorb impinging gas particles. The vacuum pumping system for the TOF-MS is tailored to the specific mission and instrument configuration. Depending on the instrument gas load and operating altitude, cryo, miniature turbo pump or getter-based pumping systems may be employed. Terrestrial TOF-MS instruments often employ a reflectron, essentially an ion-mirror, to improve mass resolving power and compensate for the thermal velocity distribution of particles being measured. The TOF-MS can be arranged in either a simple linear or reflectron configuration. Simulations and modeling are used to compare instrument mass resolution for linear and reflectron configurations for several variable conditions including vehicle velocity and ambient temperature, ultimately demonstrating the potential to make rocket-borne mass spectrometry measurements with unit-mass resolution up to at least 48 amu. Preliminary analyses suggest that many species of interest (including He, CO2, O2, O2+ , N2, N2+, and NO+) can be measured with an uncertainty below 10% relative standard deviation on a sounding rocket flight. We also present experimental data for a laboratory prototype linear TOF-MS. Experimental data is compared to simulation and modeling efforts to validate and confirm instrument performance and capability. Two proposed rocket campaigns for investigations of the auroral region include the TOF-MS. By making accurate composition measurements of the neutral atmosphere from 70 to 120km, Mass Spectrometry of the Turbopause Region (MSTR) aims to improve the accuracy of temperature measurements in the turbopause region, improve the MSIS model atmosphere and examine the transition from the turbulently mixed lower atmosphere to the diffusive equilibrium of the upper atmosphere. The ROCKet-borne STorm Energetics of Auroral Dosing in the E-region (ROCK-STEADE) mission will study energy transfer in the E-region during an aurora by examining auroral emissions and measuring concentrations of neutrals and ions. The instrument suite for ROCK-STEADE includes two mass spectrometers, one each to measure neutrals and ions in the altitude range of 70 - 170km. The ability of the TOF-MS instrument to make accurate measurements will greatly aid in better understanding the MLT.

Everett, E. A.; Dyer, J. S.; Watson, M.; Sanderson, W.; Schicker, S.; Work, D.; Mertens, C. J.; Bailey, S. M.; Syrstad, E. A.

2011-12-01

213

Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics  

NASA Astrophysics Data System (ADS)

We have modeled the atmospheric impact of a major solar energetic particle event similar in intensity to what is thought of the Carrington Event of 1-2 September 1859. Ionization rates for the August 1972 solar proton event, which had an energy spectrum comparable to the Carrington Event, were scaled up in proportion to the fluence estimated for both events. We have assumed such an event to take place in the year 2020 in order to investigate the impact on the modern, near future atmosphere. Effects on atmospheric chemistry, temperature and dynamics were investigated using the 3-D Chemistry Climate Model SOCOL v2.0. We find significant responses of NOx, HOx, ozone, temperature and zonal wind. Ozone and NOx have in common an unusually strong and long-lived response to this solar proton event. The model suggests a 3-fold increase of NOx generated in the upper stratosphere lasting until the end of November, and an up to 10-fold increase in upper mesospheric HOx. Due to the NOx and HOx enhancements, ozone reduces by up to 60-80% in the mesosphere during the days after the event, and by up to 20-40% in the middle stratosphere lasting for several months after the event. Total ozone is reduced by up to 20 DU in the Northern Hemisphere and up to 10 DU in the Southern Hemisphere. Free tropospheric and surface air temperatures show a significant cooling of more than 3 K and zonal winds change significantly by 3-5 m s-1 in the UTLS region. In conclusion, a solar proton event, if it took place in the near future with an intensity similar to that ascribed to of the Carrington Event of 1859, must be expected to have a major impact on atmospheric composition throughout the middle atmosphere, resulting in significant and persistent decrease in total ozone.

Calisto, M.; Verronen, P. T.; Rozanov, E.; Peter, T.

2012-09-01

214

Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics  

NASA Astrophysics Data System (ADS)

We have modeled the atmospheric impact of a major solar energetic particle event similar in intensity to what is thought of the Carrington Event of 1-2 September 1859. Ionization rates for the August 1972 solar proton event, which had an energy spectrum comparable to the Carrington Event, were scaled up in proportion to the fluence estimated for both events. We have assumed such an event to take place in the year 2020 in order to investigate the impact on the modern, near future atmosphere. Effects on atmospheric chemistry, temperature and dynamics were investigated using the 3-D Chemistry Climate Model SOCOL v2.0. We find significant responses of NOx, HOx, ozone, temperature and zonal wind. Ozone and NOx have in common an unusually strong and long-lived response to this solar proton event. The model suggests a 3-fold increase of NOx generated in the upper stratosphere lasting until the end of November, and an up to 10-fold increase in upper mesospheric HOx. Due to the NOx and HOx enhancements, ozone reduces by up to 60-80% in the mesosphere during the days after the event, and by up to 20-40% in the middle stratosphere lasting for several months after the event. Total ozone is reduced by up to 20 DU in the Northern Hemisphere and up to 10 DU in the Southern Hemisphere. Free tropospheric and surface air temperatures show a significant cooling of more than 3 K and zonal winds change significantly by 3-5 m s-1 in the UTLS region. In conclusion, a solar proton event, if it took place in the near future with an intensity similar to that ascribed to of the Carrington Event of 1859, must be expected to have a major impact on atmospheric composition throughout the middle atmosphere, resulting in significant and persistent decrease in total ozone.

Calisto, M.; Verronen, P. T.; Rozanov, E.; Peter, T.

2012-06-01

215

Influence of the Spray Angle on the Characteristics of Atmospheric Plasma Sprayed Hard Material Based Coatings  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90 and 20° by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. Every spray bead was characterized by a Gaussian fit. This opens the opportunity to analyze the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, porosity, hardness, and morphology were carried out and the deposition efficiency as well as the tensile strength was measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, width, and form of the spray beads. The coatings become rougher and their quality decreases.

Tillmann, Wolfgang; Vogli, Evelina; Krebs, Benjamin

2008-12-01

216

Influence of atmospheric pressure supplied on permittivity of air-film of aerostatic bearing  

NASA Astrophysics Data System (ADS)

Influence of atmospheric pressure supplied on permittivity of the air-film is researched based on the capacitive testing method of the air film thickness of aerostatic bearing. An experiment platform is designed. The experimental results illustrate that permittivity has significant negative correlation with atmospheric pressure which varies from 0.1MPa to 0.48MPa when other environmental conditions remain unchanged. The curves conform to the fourth-order polynomial approximately. All of the values of R2 are beyond 0.944 which means that trend lines fit the data curves well. Relative permittivity of the air film is between 0.996 and 1.324. This interval shows that weak current exists between restrictor and flat of the experiment which are not absolutely insulating and atmosphere of the air film is not pure. This result provides a basis both for establishing accurate mathematical model of air film thickness and capacitance value of the aerostatic bearing and for other exploratory experiments later.

Li, Min; Zhang, Yubing; Li, Dong-sheng

2013-01-01

217

Core region of Arctic Oscillation and the main atmospheric events impact on the Arctic  

NASA Astrophysics Data System (ADS)

Arctic Oscillation (AO) is a seesaw pattern in which sea level pressure (SLP) at the polar and middle latitudes in North Hemisphere fluctuates between positive and negative phases. It has been used as a representative atmospheric circulation index to express climate change. The purpose of this paper is to reveal the regional difference of SLP variation. By calculating the correlation coefficients of AO Index with all the gridded SLPs, we have uncovered a special region named as Arctic Oscillation Core Region (AOCR), where the running correlation coefficients (RCC) between gridded SLP and AO index are all negative. The averaged SLP of this region correlates significantly with the AO index. The correlations between local SLPs and AO index outside of AOCR are weaker than those inside. RCC analysis reveals several strong discrepant events different from AO. These events occurred in the years of 1954, 1955, 1962, 1971, 1982/83, 1995, 1996/97, 1998, and 1999. A comparison of these events and the ENSO or PDO indices suggests that the events in 1982/83 and 1998 are probably associated with the ENSO processes. Events centered in other years are likely connected with PDO, which reached their minima in the years of 1950, 1955, 1962 and 1971. The result in this study provides an alternative insight to look at the mechanism of the variation of Arctic Oscillation.

Zhao, Jinping; Cao, Yong; Shi, Jiuxin

2006-11-01

218

Atmosphere aerosol transfer and sources localisation in the East European region by AERONET data  

NASA Astrophysics Data System (ADS)

The typical transfer paths of atmospheric aerosol particles registered at five AERONET network stations equipped by sunphotometers in Belsk, Kyiv, Kishinev, Minsk, Sevastopol, were investigated by the cluster analysis and back trajectory methods. The transfer of fine- and coarse mode particles is considered in warm and cold times of year. The territories, where the air masses bringing to the monitoring stations the aerosol with the total volume column content exceeded mean values in 1.5 times, were revealed. For the same stations the cases of enhanced fine and coarse aerosol faction concentrations and correspondent source regions have been revealed by the method of trajectory statistics. The enhanced aerosol concentration areas were identified with potential sources. In the average for all stations the air masses with the large concentration values of coarse mode aerosol particles were brought from the Donetsk, Rostov, and Kharkiv regions. The fine mode aerosol fraction comes mostly from Tambov, Voronezh and Kharkov areas. The localized aerosol source regions are partially correspond to the European Monitoring and Evaluation Programme (EMEP) data for East Europe. The cause of difference between calculated regions of enhanced aerosol content releases and sources of particle emission by EMEP data are discussed. This publication is based on work supported by US CRDF Award No. UKG2-2969-KV-09, by the projects F41/106-2012 Derzhinformnauky of Ukraine and the project F11?-88 of Belarusian Republican Foundation for Fundamental Research.

Milinevsky, Gennadi; Kabashnikov, Vitaly; Aculinin, Aleksandr; Danylevsky, Vassyl; Kalinskaya, Dariya; Korchemkina, Elena; Miatselskaya, Nataliya; Bovchaliuk, Andrii; Pietruczuk, Alexander; Sobolewsky, Piotr; Chaikovsky, Anatoly

2013-04-01

219

Determination of regional evapotranspiration from measurements of the atmospheric boundary layer. Final report  

SciTech Connect

Many surface flux experiments have been conducted at local scales over irrigated and nonirrigated agricultural fields, and over forests. These experiments have collected a vast amount of information on the microclimate, hydrological cycle, and energy balance for these areas. The information is used to make groundwater recharge estimates from which irrigation schedules and general water management practices are developed. The focus of the research is to study the local and regional values of sensible and latent heat flux in a closed desert basin typical of the Great Basin. The local scale fluxes were found by several eddy correlation stations located throughout the study site. Net radiation and soil heat flux were also measured at one site. Temporal and spatial variability in the local scale sensible and latent heat fluxes were examined. The surface fluxes were averaged to give regional flux estimates. The regional surface flux estimate was then used as the ground truth for the regional scale estimates made by the Atmospheric Boundary Layer (ABL) approaches.

Hipps, L.E.; Swiatek, E.

1993-01-01

220

Atmospheric Transport of Arid Aerosol from Desert Regions of Central Asia  

NASA Astrophysics Data System (ADS)

Investigation of atmospheric transport of arid aerosol from Central Asia was held within the ISTC project 3715. Particular attention was paid to the removal of aerosol from the Aral Sea region and its further transport, because aerosol and pollutants emission from Central Asia affect the airspace of the entire Asian continent. At the same time measurements of aerosols in the atmosphere of Central Asia are holding in a small number of stations, and currently available data are insufficient to define the initial conditions and/or verification of models of long-range transport. To identify sources of pollution transported from Central Asia, in Kyrgyzstan measurement and sampling of air were organized: at the station on the northern slope of the Kirgiz Range, 30 km south of Bishkek, at an altitude of 1700 m above sea level (Bishkek Site, 42,683N; 74,694E ), and on permanent alpine Teploklyuchenka lidar station in the Central Tien Shan at an altitude of 2000 m above sea level (Lidar Site, 42,467N; 78,533E). The chemical analysis of collected aerosol and soils samples was carried out. Measurements of aerosol at these stations have been merged with the simulation of the trajectories of air masses in the study region and with the satellite (the Terra and Aqua satellites) observations of aerosol optical thickness in this region. Satellite data for the region 43-47 N, and 58-62 E (Aral Sea) from April 2008 to September 2009 were analyzed. The moments were selected, when the value of aerosol optical thickness (AOT) was greatest (more than 0.5), and the transport from the Aral Sea region to the observation sites took place. For each of these days, the forward trajectories, which started at 6 points within the region, were calculated using the HYSPLIT model. The days, on which the trajectories reached the BISHKEK and LIDAR sites, were determined from the data obtained. Calculations on the basis of the RAMS model were performed for these days. These calculations were performed using a grid of 160*120*30 points. The obtained meteorological fields were used in the HYPACT model; the source of Lagrangian particles was located over the Aral Sea region. As the result for 2008 11 days were detected when aerosol from the Aral Sea was actively transported to the observation sites. Comparative chemical analysis of aerosol samples at the stations of observation and soil samples from the Aral Sea region would confirm the presence of emissions and regional transport. It should be noted that the main source of aerosol in Central Asia is Taklamakan desert. Average value and AOT variability over it several times higher than corresponding AOT values over the rest of the region. The greatest variability aerosol over Taklamakan observed from late March to mid-May. For example, on April 22, 2008 average of the AOT in cell 5° x 5° over the western part of Taklamakan - value reached 3,171. AOT virtually throughout the region positively correlated with AOT over Taklamakan desert. The most noticeable effect makes an aerosol of Taklamakan found in the south-east Kyrgyzstan, Tajikistan in the east and north of the Tibetan highlands. The impact of the Aral Sea area is restricted significantly less. In doing so, AOT in the central part of the region reveals a weak negative correlation with the AOT over the Aral Sea.

Chen, Boris; Solomon, Paul; Sitnov, Sergei; Grechko, Evgeny; Maximenkov, Leonid; Artamonova, Maria; Pogarski, Fedor

2010-05-01

221

Bog Plant Tissue Chemistry as Indicators of Regionally Elevated Atmospheric N and S Deposition in the Alberta Oil Sands Region  

NASA Astrophysics Data System (ADS)

Nitrogen oxide and sulfur oxide emission from ongoing development of oil sands in northern Alberta results in regionally elevated atmospheric deposition of N and S in an area where background deposition of both N and S is exceptionally low (less than 1 kg/ha/yr). Because bogs, which represent major landforms in the Alberta oil sands region, are believed to be N-limited and potentially sensitive to S inputs, we have been investigating the effects of elevated N deposition on C, N, and S cycling in bogs, as well as the potential of bogs to serve as monitors of N and S deposition. Toward this latter end, we have measured seasonal variation (5 sampling dates between June and October 2009) concentrations of N and S, as well as ?15N value, in leaf tissues (Picea mariana (ectomycorrhizal); Ledum groenlandicum, Oxycoccos microcarpon, Vaccinium vitis-idaea (ericoid mycorrhizal); Rubus chamaemorus, and Smilacina trifolia (nonmycorrhizal), Sphagnum (S. fuscum, S. capillifolium, S. magellanicum, S. angustifolium) moss capitula (top 1-cm of plant) and lichens (Cladina mitis and Evernia mesomorpha) at 5 bogs at distances ranging from 14 to 300 km from the heart of the oil sands mining area. Averaged across all sites and sampling dates, N concentrations in ectomycorrhizal, ericoid mycorrhizal, nonmycorrhizal, Sphagnum, and lichens was 8.6 + 0.2, 11.9 + 0.2, 26.3 + 0.6, 10.2 + 0.1, 7.2 + 0.2 mg/g, respectively; ?15N values were -10.3 + 0.1, -6.0 + 0.1, 1.7 + 0.2, -5.3 + 0.1, -4.7 + 0.1 mg/g, respectively, and S concentrations were 1.07 + 0.2, 1.31 + 0.2, 1.94 + 0.6, 1.46 + 0.2, 1.11 + 0.3 mg/g, respectively. Plant functional groups and individual species behaved differently with respect to both seasonal variation and site differences, often with significant interactions when analyzed using two-way analyses of variance. Some species exhibited seasonal variation in some aspects of plant tissue chemistry, while others did not; when a species did exhibit seasonal variation, the variation was rather consistent between sites. More importantly, however, canonical discriminant analysis (with potential variables of C, N, or S concentrations, C:N, C:S, or N:S ratios, and ?15N values) indicated that the five sites can be differentiated based on plant tissue chemistry, most clearly separating the site closest and the site farthest from the oil sands mining area. The first canonical axis explained between 66 and 91 percent of the overall variation, but the variables that were significantly correlated with the first canonical axis differed between species. We conclude that plant tissue chemistry exhibited a significant variation between plant functional groups, between species, between sites, and seasonally. Some of this variation appears to be related to distance from the heart of oil sands mining activity in northern Alberta, possibly reflecting regionally elevated atmospheric deposition of N and S. Bog plants, through analysis of tissue chemistry, have the potential to serve as biomonitors of the anticipated spread of elevated atmospheric N and S deposition as oil sands development continues to grow in northern Alberta.

Wieder, R.; Vile, M. A.; Scott, K. D.; Vitt, D. H.; Quinn, J.

2011-12-01

222

Influence of ethylene glycol pretreatment on effectiveness of atmospheric pressure plasma treatment of polyethylene fibers  

NASA Astrophysics Data System (ADS)

For atmospheric pressure plasma treatments, the results of plasma treatments may be influenced by liquids adsorbed into the substrate. This paper studies the influence of ethylene glycol (EG) pretreatment on the effectiveness of atmospheric plasma jet (APPJ) treatment of ultrahigh molecular weight polyethylene (UHMWPE) fibers with 0.31% and 0.42% weight gain after soaked in EG/water solution with concentration of 0.15 and 0.3 mol/l for 24 h, respectively. Scanning electron microscopy (SEM) shows that the surface of fibers pretreated with EG/water solution does not have observable difference from that of the control group. The X-ray photoelectron spectroscopy (XPS) results show that the oxygen concentration on the surface of EG-pretreated fibers is increased less than the plasma directly treated fibers. The interfacial shear strength (IFSS) of plasma directly treated fibers to epoxy is increased almost 3 times compared with the control group while that of EG-pretreated fibers to epoxy does not change except for the fibers pretreated with lower EG concentration and longer plasma treatment time. EG pretreatment reduces the water contact angle of UHMWPE fibers. In conclusion, EG pretreatment can hamper the effect of plasma treatment of UHMWPE fibers and therefore longer plasma treatment duration is required for fibers pretreated with EG.

Wen, Ying; Li, Ranxing; Cai, Fang; Fu, Kun; Peng, Shujing; Jiang, Qiuran; Yao, Lan; Qiu, Yiping

2010-03-01

223

Investigating the Influence of Atmospheric Changes on the Variability of the North Pacific Using a Fully Coupled GCM  

NASA Astrophysics Data System (ADS)

In this study we attempt to investigate whether changes in atmospheric concentrations in ozone and greenhouse gases (GHGs), including CO2, N2O, and methane, have an influence on decadal-scaled oceanic and atmospheric dynamics in the Northeast Pacific. Using a coupled ocean-atmosphere GCM (FOAM1.5) we simulate climatic conditions for the pre-industry and the present day while focusing on the North Pacific. We explore how the ozone hole over the Southern Hemisphere and increased concentrations in GHGs observed in the present day influence the Pacific (Inter)Decadal Oscillation (PDO) and the North Pacific High (NPH), two dominant modes of variability in the North Pacific. In each model we examine the spatial and temporal patterns of the NPH, sea-surface temperatures and salinities (SSTs, SSSs) as well as wind and ocean currents on the order of interannual to interdecadal time scales. We find that within these simulations the influence of the prescribed atmospheric perturbations is small. We observe that the present-day SST and SSS fields of the Northeast Pacific are similar in both model runs as well as sea level pressure. In both simulations the PDO dominates the patterns of variability in the North Pacific and does not appear to change either in character or expression as a result of the atmospheric perturbations. The atmospheric change caused by the rise in GHG concentrations and the decline in ozone is not prominent as a primary influence on the decadal scale variability within the Northeast Pacific.

Gomez, P.; Poulsen, C. J.; Stott, L. D.

2004-12-01

224

Atmospheric discharge and dispersion of radionuclides during the Fukushima Dai-ichi Nuclear Power Plant accident. Part II: verification of the source term and analysis of regional-scale atmospheric dispersion.  

PubMed

Regional-scale atmospheric dispersion simulations were carried out to verify the source term of (131)I and (137)Cs estimated in our previous studies, and to analyze the atmospheric dispersion and surface deposition during the Fukushima Dai-ichi Nuclear Power Plant accident. The accuracy of the source term was evaluated by comparing the simulation results with measurements of daily and monthly surface depositions (fallout) over land in eastern Japan from March 12 to April 30, 2011. The source term was refined using observed air concentrations of radionuclides for periods when there were significant discrepancies between the calculated and measured daily surface deposition, and when environmental monitoring data, which had not been used in our previous studies, were now available. The daily surface deposition using the refined source term was predicted mostly to within a factor of 10, and without any apparent bias. Considering the errors in the model prediction, the estimated source term is reasonably accurate during the period when the plume flowed over land in Japan. The analysis of regional-scale atmospheric dispersion and deposition suggests that the present distribution of a large amount of (137)Cs deposition in eastern Japan was produced primarily by four events that occurred on March 12, 15-16, 20, and 21-23. The ratio of wet deposition to the total varied widely depending on the influence by the particular event. PMID:22721917

Terada, Hiroaki; Katata, Genki; Chino, Masamichi; Nagai, Haruyasu

2012-06-19

225

Boreal and California forest fire emissions and influences on atmospheric composition & chemistry during ARCTAS  

NASA Astrophysics Data System (ADS)

The 2008 NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) mission was conducted in three phases from bases in Alaska (April), California (June) and western Canada (June-July). ARCTAS involved three aircraft: a DC-8 with detailed gas/aerosol payload, a P-3 with aerosol/radiation payload, and a B-200 with remote aerosol instrumentation. High frequency (1-10s) measurements of important greenhouse gases (CO2, CH4, CO2, N2O), O3 and key precursors (NOy, HOx, HCHO), aerosol composition (SO4--, NO3-, OA, BC) and key tracers (CH3CN, HCN, CO, acetone, methanol, SO2) were available from the DC-8 payload. Complementing these were an array of lower frequency measurements of NMHC, halocarbons, alkyl nitrates, and bulk aerosol. The DC-8 with its extensive chemical composition payload sampled forest fire plumes as well as anthropogenic pollution plumes of varying ages in all three phases of ARCTAS. Tracers measured on the DC-8 together with meteorological analysis permitted identification of pollution influences and their stratification by source types. In the arctic/subarctic most low altitude (<4 km) fire plumes originated from extensive local (boreal) fires while at higher altitudes these were generally transported from Eurasia and North America. High altitude plumes originating from Asia often contained traces of anthropogenic pollution as well as stratospheric influences. California fire emissions were generally capped below 3 km and many cases appear to be impacted by accumulated deposition from anthropogenic sources. While fire emissions perturbed the atmospheric composition greatly their influence on ozone was small. In this study we analyze ARCTAS data, using observations and models, to compare the characteristics of a variety of plumes originating from Boreal and California fires and evaluate the impact of these emissions on the composition of the atmosphere especially as it relates to ozone formation.

Singh, H. B.; Apel, E. C.; Blake, D. R.; Carmichael, G. R.; Cohen, R. C.; Czech, E.; Jacob, D.; Jimenez, J. L.; Olson, J. R.; Sachse, G. W.; Vay, S. A.; Weinheimer, A. J.; Wennberg, P. O.; Wisthaler, A.; Arctas, S. T.

2009-12-01

226

The Use of Atmospheric Science to Determine Optimal Air Quality Management Regions.  

NASA Astrophysics Data System (ADS)

The Clean Air Act (CAA) has required that states meet the National Ambient Air Quality Standards (NAAQS) through the development of State Implementation Plans (SIPs). In the case of relatively long-lived pollutants such as tropospheric ozone and fine particulate matter it is often not possible for an individual state to attain compliance with the NAAQS simply by controlling its own emissions because of long-range transport of these pollutants and their precursors from outside the state. Recognizing this problem, the 1990 CAA amendments provided for the establishment of multi-state air quality management regions. One such region is the eleven northeastern states which form the Northeast Ozone Transport Region (OTR). These states have cooperated in the creation of a NOx emissions trading program among large stationary sources. However, cooperation has been problematic and numerous lawsuits have resulted. If federal authority existed to define non-attainment areas such that they included all sources which contributed to the violation, regardless of whether they were in different states, attainment of environmental goals would be facilitated. The use of atmospheric chemical tracer models in conjunction with measurements of ambient concentrations of pollutants could be used to determine the distribution of the sources that significantly contribute to the violation of the NAAQS in a given region and the spatial and temporal dependences of the air quality violations on the emission sources. With federal authority, a non-attainment region could then be defined and addressed in a scientifically coherent fashion rather than in a way determined by political jurisdictions. In this talk I will discuss how a national policy goal of determining appropriate scales for air quality control could catalyze additional scientific research including analysis of measurements of ambient pollutant concentrations, improvements in air quality models, and the development of chemical weather forecasting capabilities. I will also discuss how recent scientific advances make such a policy objective possible.

Mauzerall, D. L.

2002-05-01

227

Influences of impedance matching network on pulse-modulated radio frequency atmospheric pressure glow discharges  

SciTech Connect

Pulse-modulated RF atmospheric pressure glow discharges (APDGs) were investigated in recent years to reduce the thermal accumulation and extend the operation region of the stable alpha glow mode. Different pulse-modulated voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue and associated phenomenon via positive and negative feedback effects derived from varying the series capacitor in the inversely L-shaped matching network used in our pulse-modulated RF APGD source. The evolutions of pulse-modulated RF waveforms were found to be associated with the feedback region and the pulsed plasma absorbed RF power. In the positive feedback region, pulse-modulated RF APGDs are relatively stable. In the negative feedback region, wide spikes as well as undershoots occur in RF voltage and current waveforms and the plasma absorbed RF power. In case of a high RF power discharge with a low modulation frequency, the pulse-modulated RF APGD is extinguished and re-ignited due to the enhanced undershoot during the initial pulse phase. The pulse-modulated RF APGD can transit from positive to negative feedback region in a range of series capacitance. Experimental results are discussed by the aid of equivalent circuit, negative and positive feedback effects.

Huo, W. G. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029 (China); Xu, K.; Sun, B.; Ding, Z. F. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China)

2012-08-15

228

Influences of impedance matching network on pulse-modulated radio frequency atmospheric pressure glow discharges  

NASA Astrophysics Data System (ADS)

Pulse-modulated RF atmospheric pressure glow discharges (APDGs) were investigated in recent years to reduce the thermal accumulation and extend the operation region of the stable alpha glow mode. Different pulse-modulated voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue and associated phenomenon via positive and negative feedback effects derived from varying the series capacitor in the inversely L-shaped matching network used in our pulse-modulated RF APGD source. The evolutions of pulse-modulated RF waveforms were found to be associated with the feedback region and the pulsed plasma absorbed RF power. In the positive feedback region, pulse-modulated RF APGDs are relatively stable. In the negative feedback region, wide spikes as well as undershoots occur in RF voltage and current waveforms and the plasma absorbed RF power. In case of a high RF power discharge with a low modulation frequency, the pulse-modulated RF APGD is extinguished and re-ignited due to the enhanced undershoot during the initial pulse phase. The pulse-modulated RF APGD can transit from positive to negative feedback region in a range of series capacitance. Experimental results are discussed by the aid of equivalent circuit, negative and positive feedback effects.

Huo, W. G.; Xu, K.; Sun, B.; Ding, Z. F.

2012-08-01

229

XAFS Measurements under Atmospheric Pressure in the Soft X-ray Region  

SciTech Connect

We have developed a compact experimental set-up for X-ray absorption fine structure (XAFS) measurements in He at atmospheric pressure (AP) in the soft X-ray region and used it for Mg and Cl K-edge XAFS measurements of MgCl{sub 2} and MgCl{sub 2{center_dot}}6H{sub 2}O. The spectra of MgCl{sub 2{center_dot}}6H{sub 2}O measured in He at AP were significantly different from those measured in vacuum. This suggests the importance of performing soft X-ray XAFS experiments under AP to obtain reliable spectra from hydrated compounds.

Nakanishi, Koji; Ohta, Toshiaki [SR center, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga, 525-8577 (Japan); Yagi, Shinya [School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)

2010-06-23

230

Signatures of atmospheric wave propagation from troposphere to ionosphere seeding plasma bubbles in the equatorial region  

NASA Astrophysics Data System (ADS)

From the South American equatorial and low latitude regions we investigate atmospheric wave generation and propagations, mainly planetary and gravity waves. Ultra Fast Kelvin wave (3-4 day period) was monitored by Meteor radar and airglow photometer in the mesosphere and by ionosonde in the ionosphere. Large scale gravity waves (horizontal wavelength of ¿ 100 km and the period longer than 30 minutes) were observed by mesospheric airglow imager. Ionospheric irregularities and seeding of plasma bubbles were investigated by ionosonde, VHF coherent radar and OI 6300 all sky imagers. Further, forward and backward Ray -tracing of the gravity waves made it possible to understand how these waves came from and reach the F-layer bottom side and to initiate Rayleigh-Taylor Instability.

Takahashi, Hisao; Medeiros, Amauri; Buriti, Ricardo; Wrasse, Cristiano Max; Vadas, Sharon; Abdu, Mangalathayil Ali

231

Numerical study of local\\/regional atmospheric changes caused by a large solar central receiver power plant  

Microsoft Academic Search

A two-dimensional, vertical cross section, numerical atmospheric mososcale model has been applied to study the potential local\\/regional atmospheric effects of the installation of a 100 MW\\/sub e\\/ solar thermal central receiver power plant at Barstow, California. Such a plant consists of heliostats (mirrors) which cover a portion of ground surface and reflect sunlight onto a central receiving tower. The model

Chandrakant M. Bhumralkar; Arthur J. Slemmons; Kenneth C. Nitz

1981-01-01

232

Atmospheric solar absorption measurements in the 9 to 11 mu m region using a diode laser heterodyne spectrometer  

Microsoft Academic Search

A tunable diode laser heterodyne radiometer was developed for ground-based measurements of atmospheric solar absorption spectra in the 8 to 12 microns spectral range. The performance and operating characteristics of this Tunable Infrared Heterodyne Radiometer (TIHR) are discussed along with atmospheric solar absorption spectra of HNO3, O3, CO2, and H2O in the 9 to 11 microns spectral region.

C. N. Harward; J. M. Hoell Jr.

1980-01-01

233

Regional inversion of CO2 ecosystem fluxes from atmospheric measurements: reliability of the uncertainty estimates  

NASA Astrophysics Data System (ADS)

The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5° resolution are applied for the western European domain where ~ 50 eddy covariance sites are operated. These inversions are conducted for the period 2002-2007. They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. Averaged over monthly periods and over the whole domain, the misfits are in good agreement with the theoretical uncertainties for prior and inverted NEE, and pass the chi-square test for the variance at the 30% and 5% significance levels respectively, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion decreases the standard deviation of the misfits by 38%. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modelling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that this study does not engender confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than represented by the prior ecosystem model.

Broquet, G.; Chevallier, F.; Bréon, F.-M.; Kadygrov, N.; Alemanno, M.; Apadula, F.; Hammer, S.; Haszpra, L.; Meinhardt, F.; Morguí, J. A.; Necki, J.; Piacentino, S.; Ramonet, M.; Schmidt, M.; Thompson, R. L.; Vermeulen, A. T.; Yver, C.; Ciais, P.

2013-09-01

234

Ambient concentrations of atmospheric ammonia, nitrogen dioxide and nitric acid in an intensive agricultural region  

NASA Astrophysics Data System (ADS)

The spatial and temporal distribution of ambient atmospheric gaseous reactive nitrogen (Nr) species concentrations (ammonia [NH3], nitrogen dioxide [NO2] and nitric acid [HNO3]) were measured at the field scale in an intensive agricultural region in southern Ontario, Canada. Atmospheric concentrations were measured with the Willems badge diffusive passive sampler (18 sites for NH3, 9 sites for NO2 and HNO3) for one year (April 2010-March 2011; under a two week measurement frequency) within a 15 km × 15 km area. Dry deposition was calculated using the inferential method and estimated across the entire study area. The spatial distribution of emission sources associated with agricultural activity resulted in high spatial variability in annual average ambient NH3 concentrations (<3->8 ?g m-3 within a 2 km distance, coefficient of variation ˜50%) and estimated dry deposition (4-13 kg N ha-1 yr-1) between sample sites. In contrast, ambient concentrations and deposition of both NO2 (˜5.2->6.5 ?g m-3; 1.0-1.5 kg N ha-1 yr-1) and HNO3 (0.6-0.7 ?g m-3; 0.5-1 kg N ha-1 yr-1) had low variability (coefficient of variation <10%). The observed NH3 concentrations accounted for ˜70% of gaseous Nr dry deposition. High NH3 concentrations suggest that reduced nitrogen species (NHx) will continue to make up an increasing fraction of Nr deposition within intensive agricultural regions in southern Ontario under legislated nitrogen oxide emission reductions. Further, estimated total inorganic Nr deposition (15-28 kg N ha-1 yr-1) may lead to potential changes in soil processes, nutrient imbalance and altered composition of mycorrhiza and ground vegetation within adjacent semi-natural ecosystems (estimated at ˜10% of the study area).

Zbieranowski, Antoni L.; Aherne, Julian

2013-05-01

235

A fully coupled regional atmospheric numerical model for integrated air quality and weather forecasting.  

NASA Astrophysics Data System (ADS)

A new numerical modelling tool devoted to local and regional studies of atmospheric chemistry from surface to the lower stratosphere designed for both operational and research purposes will be presented. This model is based on the limited-area model CATT-BRAMS (Coupled Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System, Freitas et al. 2009, Longo et al. 2010) which is a meteorological model (BRAMS) including transport processes of gaseous and aerosols (CATT model). BRAMS is a version of the RAMS model (Walko et al. 2000) adapted to better represent tropical and subtropical processes and several new features. CATT-BRAMS has been used operationally at CPTEC (Brazilian Center for Weather Prediction and Climate Studies) since 2003 providing coupled weather and air quality forecast. In the Chemistry-CATT-BRAMS (called hereafter CCATT-BRAMS) a chemical module is fully coupled to the meteorological/tracer transport model CATT-BRAMS. This module includes gaseous chemistry, photochemistry, scavenging and dry deposition. The CCATT-BRAMS model takes advantages of the BRAMS specific development for the tropics/subtropics and of the recent availability of preprocessing tools for chemical mechanisms and of fast codes for photolysis rates. Similarly to BRAMS this model is conceived to run for horizontal resolutions ranging from a few meters to more than a hundred kilometres depending on the chosen scientific objective. In the last decade CCATT-BRAMS has being broadly (or extensively) used for applications mainly over South America, with strong emphasis over the Amazonia area and the main South American megacities. An overview of the model development and main applications will be presented.

Freitas, S. R.; Longo, K. M.; Marecal, V.; Pirre, M.; Gmai, T.

2012-04-01

236

Atmospheric brown clouds: Hemispherical and regional variations in long-range transport, absorption, and radiative forcing  

NASA Astrophysics Data System (ADS)

The study uses satellite observations, global assimilated aerosol data sets, Atmospheric Brown Clouds (ABC) observatories, a Monte Carlo aerosol-cloud-radiation model and a regional chemical transport model (STEM-2K) to characterize the spatial extent of brown clouds, regional and megacity ABC hot spots, chemical composition and the direct radiative forcing. It presents the first annual cycle of aerosol observations and forcing from the ABC observatories in the Indo-Asia-Pacific regions. East Asia, Indo-Gangetic Plains, Indonesian region, southern Africa and the Amazon basin are the regional hot spots defined by the criteria that anthropogenic aerosol optical depths (AODs) should exceed 0.3 and absorbing AOD > 0.03. Over these hot spots, as well as in other polluted oceanic regions, the EC mass exceeds 0.5 ?g m-3, the OC mass exceeds 2 ?g m-3 and sulfate mass exceeds 10 ?g m-3 from the surface to 3 km. The brown clouds also have strong seasonal dependence. In the tropics the seasonal dependence is driven by pollution accumulating during the dry seasons, December to February in Northern Hemisphere tropics and June to August in Southern Hemisphere tropics. In the extratropics the pollution peaks during the summer. The brown cloud problem is not restricted to the tropical regions. Over the eastern half of US and western Europe the AODs exceeds 0.2 and absorption AODs exceed 0.02. Brown clouds also extend well into the western Pacific Ocean, the Indian Ocean reaching as far south as 60°S and the eastern Atlantic Ocean. The largest total SO2 emission occurs over China and US, while SO2 emission per unit surface area is maximum over Germany and England. The largest total EC and OC emissions occur over China, but the largest OC emission per unit surface area occur over India. As a result, the maximum negative annual mean TOA direct forcing is over India and Germany. The surface annual-diurnal mean dimming over the regional hot spots is of the order of -10 W m-2 and -20 W m-2 over megacity hotpots.

Ramanathan, V.; Li, F.; Ramana, M. V.; Praveen, P. S.; Kim, D.; Corrigan, C. E.; Nguyen, H.; Stone, Elizabeth A.; Schauer, James J.; Carmichael, G. R.; Adhikary, Bhupesh; Yoon, S. C.

2007-11-01

237

On transient events in the upper atmosphere generated away of thunderstorm regions  

NASA Astrophysics Data System (ADS)

Experimental data on transient events in UV and Red-IR ranges obtained in the MSU missions "Unversitetsky-Tatiana" (wavelengths 300-400 nm) and "Unversitetsky-Tatiana-2" (wavelengths 300-400 nm and 600-800 nm), published by Garipov et al, in 2010 at COSPAR session http://www.cospar2010.org, at TEPA conference http://www.aragats.am/Conferences/tepa2010 and in 2011 by Sadovnichy et al, Solar System Research, 45, #1, 3-29 (2011); Vedenkin et al, JETP, v. 140, issue 3(9), 1-11 (2011) demonstrated existence of transients at large distances (up to thousands km) away of cloud thunderstorm regions. Those "remote" transients are short (1-5 msec) and are less luminous than the transients above thunderstorm regions. The ratio of Red-IR to UV photon numbers in those transients indicates high altitude of their origin (~70 km). Important observation facts are also: 1. a change of the exponent in transient distribution on luminosity Q ("-1" for photon numbers Q=1020 -1023 to "-2" for Q>1023), 2. a change of global distribution of transient with their luminosity (transients with Q>1023 are concentrated in equatorial range above continents, while transients with low luminosity are distributed more uniformly), 3. a phenomenon of transient sequences in one satellite orbit which is close to geomagnetic meridian. In the present paper phenomenological features of transients are explained in assumption that the observed transients have to be divided in two classes: 1. transients related to local, lower in the atmosphere, lightning at distance not more than hundreds km from satellite detector field of view in the atmosphere and 2. transients generated by far away lightning. Local transients are luminous and presumably are events called "transient luminous events" (TLE). In distribution on luminosity those events have some threshold Q~1023 and their differential luminosity distribution is approximated by power law exponent "-2". Remote transients have to be considered separately. Their origin may be related to electromagnetic pulses (EMP) or waves (whistler, EMW) generated by lightning. The EMP-EMW is transmitted in the ionosphere- ground channel to large distances R with low absorption. The part of EMP-EMW "visible" in the detector aperture diminishes with distance as R-1 due to observation geometry. The EMP-EMW triggers the electric discharge in the upper atmosphere (lower ionosphere, ~70 km). Estimates of resulting transients luminosity and their correlation with geomagnetic field are in progress.

Morozenko, V.; Garipov, G.; Khrenov, B.; Klimov, P.; Panasyuk, M.; Sharakin, S.; Zotov, M.

2011-12-01

238

OASIS: Ocean-Atmosphere-Sea-Ice-Snowpack Interactions in Polar Regions  

NASA Astrophysics Data System (ADS)

While Polar regions encompass a large part of the globe, little attention has been paid to the interactions between the atmosphere and its extensive snow-covered surfaces. Recent discoveries in the Arctic and Antarctic show that the top ten centimeters of snow is not simply a white blanket but in fact is a surprisingly reactive medium for chemical reactions in the troposphere. It has been concluded that interlinked physical, chemical, and biological mechanisms, fueled by the sun and occurring in the snow, are responsible for depletion of tropospheric ozone and gaseous mercury. At the same time production of highly reactive compounds (e.g. formaldehyde, nitrogen dioxide) has been observed at the snow surface. Air-snow interactions also have an impact on the chemical composition of the snow and hence the nature and amounts of material released in terrestrial/marine ecosystems during the melting of seasonal snow-packs. Many details of these possibly naturally occurring processes are yet to be discovered. For decades humans have added waste products including acidic particles (sulphates) and toxic contaminants such as gaseous mercury and POPs (persistent organic pollutants) to the otherwise pristine snow surface. Virtually nothing is known about transformations of these contaminants in the snowpack, making it impossible to assess the risk to the polar environment, including humans. This is especially disconcerting when considering that climate change will undoubtedly alter the nature of these transformations involving snow, ice, atmosphere, ocean, and, ultimately, biota. To address these topics an interdisciplinary group of scientists from North America, Europe and Japan is developing a set of coordinated research activities under the banner of the IGBP programs IGAC and SOLAS. The program of Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) interactions has been established with a mission statement aimed at determining the impact of OASIS chemical exchange on tropospheric chemistry and climate, as well as on the surface/biosphere and their feedbacks in the Polar regions of the globe. It is proposed that this program will culminate in a concerted field project during the IPY. In this contribution we will present the details of the emerging OASIS science plan and progress towards its implementation.

Bottenheim, J. W.; Abbatt, J.; Beine, H.; Berg, T.; Bigg, K.; Domine, F.; Leck, C.; Lindberg, S.; Matrai, P.; MacDonald, R.; McConnell, J.; Platt, U.; Raspopov, O.; Shepson, P.; Shumilov, O.; Stutz, J.; Wolff, E.

2004-05-01

239

Influence of mountain ranges on the mid-latitude atmospheric response to El Niño events  

Microsoft Academic Search

TROPICAL heating associated with El Niño events influences weather patterns around the globe1-4, in part by generating wave-like disturbances of vorticity (a measure of local fluid circulation about the vertical) in the upper troposphere which extend into the mid-latitude regions. But these waves do not account well for the observed mid-latitude consequences of E1 Niño5-8 events. Here we show that

Eric Deweaver; Sumant Nigam

1995-01-01

240

Characteristics and Numerical Simulations of Extremely Large Atmospheric Boundary-layer Heights over an Arid Region in North-west China  

NASA Astrophysics Data System (ADS)

Over arid regions in north-west China, the atmospheric boundary layer can be extremely high during daytime in late spring and summer. For instance, the depth of the observed convective boundary layer can exceed 3,000 m or even be up to 4,000 m at some stations. In order to characterize the atmospheric boundary-layer (ABL) conditions and to understand the mechanisms that produce such an extreme boundary-layer height, an advanced research version of the community weather research and forecasting numerical model (WRF) is employed to simulate observed extreme boundary-layer heights in May 2000. The ability of the WRF model in simulating the atmospheric boundary layer over arid areas is evaluated. Several key parameters that contribute to the extremely deep boundary layer are identified through sensitivity experiments, and it is found that the WRF model is able to capture characteristics of the observed deep atmospheric boundary layer. Results demonstrate the influence of soil moisture and surface albedo on the simulation of the extremely deep boundary layer. In addition, the choice of land-surface model and forecast lead times also plays a role in the accurate numerical simulation of the ABL height.

Ma, Minjin; Pu, Zhaoxia; Wang, Shigong; Zhang, Qiang

2011-07-01

241

Variations of the atmospheric electric field in the near-pole region related to the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Variations in the atmospheric, near-surface vertical electric field component Ez measured at the Russian Antarctic station Vostok in 1998 are analyzed in conjunction with changes of the interplanetary magnetic field (IMF). A total of 134 days were selected which satisfied the ``fair weather'' conditions, that is, days with absence of high winds, falling or drifting snow, clouds, and electric field ``pollution'' from the station's power plant. It is shown that the average diurnal variation of Ez for these days follows the global geoelectric field ``fair-weather'' diurnal variation: the ``Carnegie'' curve, which describes the global electric circuit formed by the thunderstorm activity occurring mostly over equatorial regions. The Ez diurnal variation shows strong seasonal dependence: it is maximal (~40% of the average daily magnitude) in summer but gradually reduces through the equinoctial months and is almost negligible during the austral winter. Ez at Vostok is strongly affected by variations in both the IMF By and Bz components. The influence of By is dominant during geomagnetic daytime hours (1100-1400 UT at Vostok): Ez increases with By in the range from -10 to +10 nT. The IMF Bz effect is mainly seen at dawn (Ez decreases with Bz) and dusk (Ez increases with Bz).

Frank-Kamenetsky, A. V.; Troshichev, O. A.; Burns, G. B.; Papitashvili, V. O.

2001-01-01

242

The influence of atmospheric turbulence on IM/DD space optical communication system  

NASA Astrophysics Data System (ADS)

Lots of researches have simulated performance of optical system based on plane wave or spherical wave model, but optical field is Gauss distribution in real optical communication system. So we derive the relationships between the signal-to-noise ratio (SNR), bit error rate (BER), channel capacity (C) and the transmission distance of the space laser communication system, which is obtained by the Gaussian beam propagation model for on-off keying (OOK) modulated signal under horizontal link. We numerically study the influence of atmospheric turbulence on system performance. we get the conclusions: Under weak turbulence intensity, as the turbulence intensity increases, the C and SNR for OOK modulated space laser communication system decrease while the BER increase; In the case of strong turbulence intensity, the intensity scintillation and the BER dramatically increase with the increase of transmission distance, and then become saturated; In the condition of turbulence intensity and transmission distance are both constant, the longer the wavelength results in greater C, higher SNR and lower BER. Selecting longer communication wavelength can mitigate the impact of the atmosphere turbulence on the communication system in some extent.

Wei, Anhai; Han, Biao; Zhao, Wei; Xie, Xiaoping; Hu, Hui; Su, Yulong; Zhang, Kewei

2013-08-01

243

Understanding the Influences of Radiation and Advection in Hot Jupiter Atmospheric Flows  

NASA Astrophysics Data System (ADS)

Radiative timescales at the photospheres of hot Jupiters are expected to be much shorter than those of solar system giants, a first-order difference that directly affects the nature of circulation on these planets. To test its influence on atmospheric flow, we ran tests with the Reading Intermediate General Circulation Model of a shallow 3-D model, using a simple Newtonian relaxation scheme for the radiative forcing. The amount of heat advection from the permanent day to night side depends on the relation between radiative and advective timescales, which is non-linear since shorter radiative timescales lead to faster winds. We find that winds remain subsonic (even for very short radiative times) and that models with shorter radiative timescales show less effective heat advection. We present other trends, including flow pattern and variability. These results illustrate the level of uncertainty present in interpreting data from systems with poorly known radiative timescales.

Rauscher, Emily; Menou, K.

2008-09-01

244

Natural hazards for the Earth's civilization from space, 1. Cosmic ray influence on atmospheric processes  

NASA Astrophysics Data System (ADS)

In this paper we give a short description of global natural disasters for the Earth's civilization from space: 1) Galactic and solar cosmic ray (CR) influence on the atmospheric processes; 2) Impacts of great space magnetic storms during big Forbush-effects in CR, 3) Impacts of great radiation hazards from solar CR during flare energetic particle events, 4) Great impacts on planetary climate during periods of the Solar system capturing by molecular-dust clouds, 5) Catastrophic disasters from nearby Supernova explosions, and 6) Catastrophic disasters from asteroid impacts on the Earth. Some of these problems have been already studied (see e.g. Dorman, 1957, 1963a, b; Dorman and Miroshnichenko, 1968; Dorman, 1972, 1974, 1975a, b, 1978; Velinov et al., 1974; Miroshnichenko, 2001, 2003; Dorman, 2004, 2006, 2008). We present here a detailed treatment of the first disaster only, leaving to future papers the analysis of the other aspects.

Dorman, L. I.

2008-04-01

245

Atmospheric pressure plasma pretreatment of sugarcane bagasse: the influence of moisture in the ozonation process.  

PubMed

Sugarcane bagasse samples were pretreated with ozone via atmospheric O2 pressure plasma. A delignification efficiency of approximately 80 % was observed within 6 h of treatment. Some hemicelluloses were removed, and the cellulose was not affected by ozonolysis. The quantity of moisture in the bagasse had a large influence on delignification and saccharification after ozonation pretreatment of the bagasse, where 50 % moisture content was found to be best for delignification (65 % of the cellulose was converted into glucose). Optical absorption spectroscopy was applied to determine ozone concentrations in real time. The ozone consumption as a function of the delignification process revealed two main reaction phases, as the ozone molecules cleave the strong carbon-carbon bonds of aromatic rings more slowly than the weak carbon-carbon bonds of aliphatic chains. PMID:23817790

Souza-Corrêa, J A; Oliveira, C; Wolf, L D; Nascimento, V M; Rocha, G J M; Amorim, J

2013-07-02

246

The influences of atmospheric half-yearly cycle on the sea ice extent in the Antarctic  

NASA Astrophysics Data System (ADS)

The relationship between sea ice and weather, one of the least known components of the climatic system, could be an important factor for the climate of high latitudes. The annual cycle of the sea ice extent is characterized by a asymmetric development, with the sea ice area slowly advancing toward the equator in the winter and rapidly retreating in summer. In this study the seasonal asymmetric behavior of ice extent and the changes in sea ice concentration are shown to be linked to the atmospheric convergence line (ACL) around Antarctica. It is found that the relative positions of the ACL characterized by the half-year cycle exert a strong influence upon the mean movement of the sea ice. It is also observed from the investigations of the areal concentration of the sea ice that a decrease in ice concentration prior to the sea ice retreat is needed for a rapid retreat.

Enomoto, Hiroyuki; Ohmura, Atsumu

1990-06-01

247

Influence of atmospheric intraseasonal oscillations on seasonal and interannual variability in the upper Indian Ocean  

NASA Astrophysics Data System (ADS)

An ocean general circulation model, the Hybrid Coordinate Ocean Model (HYCOM), is used to examine the rectification of atmospheric intraseasonal oscillations (ISOs) on the mean and seasonal-to-interannual sea surface temperature (SST), mixed layer thickness (hm) and upper ocean heat content in the Indian Ocean. Existing studies have shown that ISOs rectify on seasonal and interannual equatorial surface currents and on cross-equatorial transport, suggesting that they may also have important impacts on upper ocean variability. To evaluate these impacts, a hierarchy of HYCOM experiments isolates the ocean response to forcing by atmospheric ISO events. Other experiments isolate the ocean response to a range of intraseasonal forcing fields including shortwave radiation, precipitation, and winds. Results indicate that rectification of ISOs onto seasonal and interannual upper ocean variability does occur, and that it is important in some regions. The regions displaying maximum rectification vary between SST, hm, and upper ocean heat content, and from seasonal to interannual timescales. Strong seasonal SST rectification occurs in the Arabian Sea and in the Bay of Bengal. Because SSTs in the Arabian Sea are already warm (28°C), the ISO-forced seasonal cycle peak of 0.6°C in May can affect convection there. Intraseasonal wind speed and stress have a much larger impact on seasonal and interannual SST, hm, and upper ocean heat content than either intraseasonal shortwave radiation or precipitation. The relative importance of entrainment and turbulent heat flux due to intraseasonal wind speed, and of upwelling, horizontal advection, and vertical mixing due to intraseasonal wind stress, varies with region.

Duncan, BenéT.; Han, Weiqing

2012-11-01

248

Water resources of the South Asian region in a warmer atmosphere  

NASA Astrophysics Data System (ADS)

The global mean surface temperature may rise by about 0.3° C per decade during the next few decades as a result of anthropogenic greenhouse gas emissions in the earth's atmosphere. The data generated in the greenhouse warming simulations (Business-as-Usual scenario of IPCC) with the climate models developed at Max Planck Institute for Meteorology, Hamburg have been used to assess future plausible hydrological scenario for the South Asian region. The model results indicate enhanced surface warming (2.7°C for summer and 3.6°C for winter) over the land reginos of South Asia during the next hundred years. While there is no significant change in the precipitation over most of the land regions during winter, substantial increase in precipitation is likely to occur during summer. As a result, an increase in soil moisture is likely over central India, Bangladesh and South China during summer but a statistically significant decline in soil moisture is expected over central China in winter. A moderate decrease in surface runoff may occur over large areas of central China during winter while the flood prone areas of NE-India, Bangladesh and South China are likely to have an increase in surface runoff during summer by the end of next century.

Lal, M.

1994-06-01

249

Development and validation of a regional coupled atmosphere lake model for the Caspian Sea Basin  

NASA Astrophysics Data System (ADS)

We present a validation analysis of a regional climate model coupled to a distributed one dimensional (1D) lake model for the Caspian Sea Basin. Two model grid spacings are tested, 50 and 20 km, the simulation period is 1989-2008 and the lateral boundary conditions are from the ERA-Interim reanalysis of observations. The model is validated against atmospheric as well as lake variables. The model performance in reproducing precipitation and temperature mean seasonal climatology, seasonal cycles and interannual variability is generally good, with the model results being mostly within the observational uncertainty range. The model appears to overestimate cloudiness and underestimate surface radiation, although a large observational uncertainty is found in these variables. The 1D distributed lake model (run at each grid point of the lake area) reproduces the observed lake-average sea surface temperature (SST), although differences compared to observations are found in the spatial structure of the SST, most likely as a result of the absence of 3 dimensional lake water circulations. The evolution of lake ice cover and near surface wind over the lake area is also reproduced by the model reasonably well. Improvements resulting from the increase of resolution from 50 to 20 km are most significant in the lake model. Overall the performance of the coupled regional climate—1D lake model system appears to be of sufficient quality for application to climate change scenario simulations over the Caspian Sea Basin.

Turuncoglu, Ufuk Utku; Elguindi, Nellie; Giorgi, Filippo; Fournier, Nicolas; Giuliani, Graziano

2013-10-01

250

Nitrate Aerosol Partitioning in the 2003 Bay Regional Atmospheric Chemistry Experiment (BRACE) : Aloft and Surface Comparisons  

NASA Astrophysics Data System (ADS)

The Bay Regional Atmospheric Chemistry Experiment (BRACE) field intensive in May 2003 was designed to help understand nitrogen chemistry and cycling in the airshed of Tampa, FL and included gas-phase and aerosol measurements at two downwind urban locations (Sydney and Tower Dairy) and a bay shoreline location (Gandy) as well as aboard the NOAA Twin Otter aircraft. The Twin Otter made 21 flights in the greater Tampa region over urban, suburban, and rural areas, Tampa Bay, and the Gulf of Mexico. Among these flights were several vertical profiles extending from 60 to 3000 m MSL over the Bay, the Gulf, and the ground sites. Aerosol samples on the Twin Otter were made with high flow rate filter packs followed by IC analysis; surface measurements for aerosols were made with a combination of filter packs, MOUDI samplers, annular denuders, and near-real time wet denuder collection followed by IC analysis. The degree of nitrate partitioning observed with the Twin Otter filter pack samples onto fine (2.5u and smaller) and large aerosols is examined separately for the three flow regimes that predominated during the intensive: strong synoptic, when local effects were overwhelmed; synoptic shift, with wind shifts due to changing synoptic features; and sea/bay breeze, when local effects of the sea and bay breeze forced wind shifts. Analysis of these aloft results are then compared with nitrate aerosol values on the ground.

Arnold, J. R.; Luke, W. T.; Watson, T. B.

2003-12-01

251

Mercury Deposition to the Gulf Coast Region from Deep Convection and Long-range Atmospheric Transport  

NASA Astrophysics Data System (ADS)

Wet scavenging is a large source of mercury deposition in the Gulf Coast of the United States. Following concern about mercury's impact on ecosystems and humans, the US EPA Mercury Deposition Network (MDN) makes ongoing weekly wet deposition measurements at 10 sites in the Gulf region. Deposition in this area peaks in the summer months when rain is its most frequent and intense. Previous studies have variously argued that mercury in rainwater derives primarily from nearby sources or from long-range transport at high altitude. As a new test for high-altitude wet scavenging contributing to mercury deposition, we use lightning counts from the National Lightning Detection Network (NLDN) and cloud top temperatures from the International Satellite Cloud Climatology Project (ISCCP-B1) as proxies for deep convection. We find a significant correlation between lightning and mercury deposition, after accounting for precipitation depth. This implies that scavenging of mercury from the global mercury pool in the upper troposphere is a significant source of mercury deposition in the Gulf region. We compare the MDN observations against wet deposition estimates from a global atmospheric chemical transport model (GEOS-Chem) with Hg(0) oxidation primarily by atomic Br. The comparison constrains the wet scavenging efficiency of Hg(II) and the origin of the high- altitude mercury pool.

Holmes, C. D.; Sturges, E. D.; Jacob, D. J.; Murray, L. T.

2008-12-01

252

Development and validation of a regional coupled atmosphere lake model for the Caspian Sea Basin  

NASA Astrophysics Data System (ADS)

We present a validation analysis of a regional climate model coupled to a distributed one dimensional (1D) lake model for the Caspian Sea Basin. Two model grid spacings are tested, 50 and 20 km, the simulation period is 1989-2008 and the lateral boundary conditions are from the ERA-Interim reanalysis of observations. The model is validated against atmospheric as well as lake variables. The model performance in reproducing precipitation and temperature mean seasonal climatology, seasonal cycles and interannual variability is generally good, with the model results being mostly within the observational uncertainty range. The model appears to overestimate cloudiness and underestimate surface radiation, although a large observational uncertainty is found in these variables. The 1D distributed lake model (run at each grid point of the lake area) reproduces the observed lake-average sea surface temperature (SST), although differences compared to observations are found in the spatial structure of the SST, most likely as a result of the absence of 3 dimensional lake water circulations. The evolution of lake ice cover and near surface wind over the lake area is also reproduced by the model reasonably well. Improvements resulting from the increase of resolution from 50 to 20 km are most significant in the lake model. Overall the performance of the coupled regional climate—1D lake model system appears to be of sufficient quality for application to climate change scenario simulations over the Caspian Sea Basin.

Turuncoglu, Ufuk Utku; Elguindi, Nellie; Giorgi, Filippo; Fournier, Nicolas; Giuliani, Graziano

2012-12-01

253

Future surface mass balance of the Antarctic ice sheet using a regional atmospheric climate model  

NASA Astrophysics Data System (ADS)

It has been proposed that the surface mass balance of the Antarctic ice sheet is likely to change significantly in next centuries, thereby impacting global sea level. Because of insufficient resolution, General Circulation Models (GCM) are not yet able to accurately simulate regional changes in the Antarctic climate and surface mass balance. Therefore, a regional atmospheric climate model with sophisticated snow module (RACMO2/ANT) is forced at the lateral boundaries with GCM data to represent the Antarctic climate in more detail. As part of Ice2Sea, a EU FW7 project to determine the contribution of land ice to future sea level rise, we use two different GCMs (ECHAM5 and HadCM3) and two different emission scenarios (A1B and E1) to simulate changes in Antarctic climate and surface mass balance over the period 2000-2200. Temperature increases by 2-5 °C, thereby enhancing snowmelt and sublimation in the next two centuries. However, a more significant increase in precipitation leads to a positive trend in surface mass balance and therefore a negative contribution to future sea level rise.

Ligtenberg, S.; van den Broeke, M. R.; Van De Berg, W.; van Meijgaard, E.

2011-12-01

254

Enhanced atmospheric oxygen outflow on Earth and Mars driven by a corotating interaction region  

NASA Astrophysics Data System (ADS)

Solar wind controls nonthermal escape of planetary atmospheric volatiles, regardless of the strength of planetary magnetic fields. For both Earth with a strong dipole and Mars with weak remnant fields, the oxygen ion (O+) outflow has been separately found to be enhanced during corotating interaction region (CIR) passage. Here we compared the enhancements of O+ outflow on Earth and Mars driven by a CIR in January 2008, when Sun, Earth, and Mars were approximately aligned. The CIR propagation was recorded by STEREO, ACE, Cluster, and Mars Express (MEX). During the CIR passage, Cluster observed enhanced flux of upwelling oxygen ions above the Earth's polar region, while MEX detected an increased escape flux of oxygen ions in the Martian magnetosphere. We found that (1) under a solar wind dynamic pressure increase of 2-3 nPa, the rate of increase in Martian O+ outflow flux was 1 order higher than those on Earth; and (2) as a response to the same part of the CIR body, the rate of increase in Martian O+ outflow flux was on the same order as for Earth. The comparison results imply that the dipole effectively prevents coupling of solar wind kinetic energy to planetary ions, and the distance to the Sun is also crucially important for planetary volatile loss in our inner solar system.

Wei, Y.; Fraenz, M.; Dubinin, E.; Woch, J.; Lühr, H.; Wan, W.; Zong, Q.-G.; Zhang, T. L.; Pu, Z. Y.; Fu, S. Y.; Barabash, S.; Lundin, R.; Dandouras, I.

2012-03-01

255

Atmospheric effects and societal consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism  

NASA Astrophysics Data System (ADS)

We assess the potential damage and smoke production associated with the detonation of small nuclear weapons in modern megacities. While the number of nuclear warheads in the world has fallen by about a factor of three since its peak in 1986, the number of nuclear weapons states is increasing and the potential exists for numerous regional nuclear arms races. Eight countries are known to have nuclear weapons, 2 are constructing them, and an additional 32 nations already have the fissile material needed to build substantial arsenals of low-yield (Hiroshima-sized) explosives. Population and economic activity worldwide are congregated to an increasing extent in megacities, which might be targeted in a nuclear conflict. Our analysis shows that, per kiloton of yield, low yield weapons can produce 100 times as many fatalities and 100 times as much smoke from fires as high-yield weapons, if they are targeted at city centers. A single "small'' nuclear detonation in an urban center could lead to more fatalities, in some cases by orders of magnitude, than have occurred in the major historical conflicts of many countries. We analyze the likely outcome of a regional nuclear exchange involving 100 15-kt explosions (less than 0.1% of the explosive yield of the current global nuclear arsenal). We find that such an exchange could produce direct fatalities comparable to all of those worldwide in World War II, or to those once estimated for a "counterforce'' nuclear war between the superpowers. Megacities exposed to atmospheric fallout of long-lived radionuclides would likely be abandoned indefinitely, with severe national and international implications. Our analysis shows that smoke from urban firestorms in a regional war would rise into the upper troposphere due to pyro-convection. Robock et al. (2006) show that the smoke would subsequently rise deep into the stratosphere due to atmospheric heating, and then might induce significant climatic anomalies on global scales.We also anticipate substantial perturbations of global ozone. While there are many uncertainties in the predictions we make here, the principal unknowns are the type and scale of conflict that might occur. The scope and severity of the hazards identified pose a significant threat to the global community. They deserve careful analysis by governments worldwide advised by a broad section of the world scientific community, as well as widespread public debate.

Toon, O. B.; Turco, R. P.; Robock, A.; Bardeen, C.; Oman, L.; Stenchikov, G. L.

2006-11-01

256

Atmospheric effects and societal consequences of regional scale nuclear conflicts and acts of individual nuclear terrorism  

NASA Astrophysics Data System (ADS)

We assess the potential damage and smoke production associated with the detonation of small nuclear weapons in modern megacities. While the number of nuclear warheads in the world has fallen by about a factor of three since its peak in 1986, the number of nuclear weapons states is increasing and the potential exists for numerous regional nuclear arms races. Eight countries are known to have nuclear weapons, 2 are constructing them, and an additional 32 nations already have the fissile material needed to build substantial arsenals of low-yield (Hiroshima-sized) explosives. Population and economic activity worldwide are congregated to an increasing extent in megacities, which might be targeted in a nuclear conflict. We find that low yield weapons, which new nuclear powers are likely to construct, can produce 100 times as many fatalities and 100 times as much smoke from fires per kt yield as previously estimated in analyses for full scale nuclear wars using high-yield weapons, if the small weapons are targeted at city centers. A single "small" nuclear detonation in an urban center could lead to more fatalities, in some cases by orders of magnitude, than have occurred in the major historical conflicts of many countries. We analyze the likely outcome of a regional nuclear exchange involving 100 15-kt explosions (less than 0.1% of the explosive yield of the current global nuclear arsenal). We find that such an exchange could produce direct fatalities comparable to all of those worldwide in World War II, or to those once estimated for a "counterforce" nuclear war between the superpowers. Megacities exposed to atmospheric fallout of long-lived radionuclides would likely be abandoned indefinitely, with severe national and international implications. Our analysis shows that smoke from urban firestorms in a regional war would rise into the upper troposphere due to pyro-convection. Robock et al. (2007) show that the smoke would subsequently rise deep into the stratosphere due to atmospheric heating, and then might induce significant climatic anomalies on global scales. We also anticipate substantial perturbations of global ozone. While there are many uncertainties in the predictions we make here, the principal unknowns are the type and scale of conflict that might occur. The scope and severity of the hazards identified pose a significant threat to the global community. They deserve careful analysis by governments worldwide advised by a broad section of the world scientific community, as well as widespread public debate.

Toon, O. B.; Turco, R. P.; Robock, A.; Bardeen, C.; Oman, L.; Stenchikov, G. L.

2007-04-01

257

Complex Patterns in Climate and Atmospheric Nitrogen Deposition Influence Rocky Mountain Ecosystems  

NASA Astrophysics Data System (ADS)

Long-term monitoring of physical and biogeochemical characteristics in Loch Vale watershed, Rocky Mountain National Park, has revealed complicated patterns in temperature, precipitation, and atmospheric nitrogen deposition. July mean and maximum temperatures have increased since 1985 by 0.1-0.2 ° C, while March mean and maximum temperatures became 0.1-0.3 ° C colder. There is no long-term trend in annual or monthly precipitation; annual totals range 75-140 cm yr-1. Atmospheric N deposition has increased approximately 2% yr-1 since 1985, and there are strong upward trends in July and September deposition. A combination of observations, ecosystem modeling (DayCent-Chem model), and structural equation modeling (SEM) suggests this alpine/subalpine catchment is responding physically, biologically, and chemically. Observed stream discharge was greater than measured precipitation in several recent years, indicating melt from glacier ice contributes to flow. Model results suggest a strong increase in alpine microbial activity and plant N uptake, and a moderate increase in forest microbial activity driven by increased temperatures and increased N deposition. Alpine lichen activity appears to also have been significantly stimulated. There has been a significant increase in observed stream nitrogen concentrations and flux. Annual mean stream N concentrations in alpine/subalpine Loch Vale watershed of Rocky Mountain National Park have increased from approximately 1.0 to 1.5 mg NO3 L-1 between 1991 and 2005; the annual amplitude has also increased. Mean annual N efflux from the catchment doubled between 1991 and 2005. SEM suggests N loss from Loch Vale appears to result most strongly from the combined influence of temperature and precipitation on stream flow, and secondarily from the influence of terrestrial nitrogen cycling.

Baron, J. S.; Schmidt, T.; Hartman, M. D.; Enders, S. K.; Pagani, M.; Wolfe, A. P.; Krcmarik, A.

2007-12-01

258

Influence of Regional Climate Model spatial resolution on wind climates  

NASA Astrophysics Data System (ADS)

Global and regional climate models are being run at increasingly fine horizontal and vertical resolution with the goal of increased skill. However, relatively few studies have quantified the change in modeled wind climates that derives from applying a Regional Climate Model (RCM) at varying resolutions, and the response to varying resolution may be highly non-linear since most models run in climate mode are hydrostatic. Thus, herein we examine the influence of grid-resolution on modelled wind speeds and gusts and derived extremes thereof over southern Scandinavia using output from the Rossby Centre (RCA3) RCM run at four different resolutions from 50 x 50 km to 6 x 6 km, and with two different vertical grid-spacings. Domain averaged fifty-year return period wind speeds and wind gusts derived using the method of moments approach to compute the Gumbel parameters, increase with resolution (Table 1), though the change is strongly mediated by the model grid-cell surface characteristics. Power spectra of the 3-hourly model time-step ‘instantaneous’ wind speeds and daily wind gusts at all four resolutions show clear peaks in the variance associated with bi-annual, annual, seasonal and synoptic frequencies. The variance associated with these peaks is enhanced with increased resolution, though not in a monotonic fashion, and is more marked in wind gusts than wind speeds. Relative to in situ observations, the model generally underestimates the variance, particularly associated with the synoptic time scale, even for the highest resolution simulations. There is some evidence to suggest that the change in the power spectra with horizontal resolution is less marked in the transition from 12.5 km to 6.25 km, than from 50 to 25 km, or 25 km to 12.5 km.Table 1. Domain averaged mean annual wind speed (U), 50-year return period extreme wind speed (U50yr) and wind gust (Gust50yr) (m/s) from the four RCA3 simulations at different resolution based on output from 1987-2008. The domain extends from approximately 51-60°N, 4-16°E, and thus covers northern Germany, Denmark and southern portions of Norway and Sweden.

Pryor, S. C.; Barthelmie, R. J.; Nikulin, G.; Jones, C.

2010-12-01

259

An Investigation on the role of Planetary Boundary Layer Parameterization scheme on the performance of a hydrostatic atmospheric model over a Coastal Region  

NASA Astrophysics Data System (ADS)

As part of the ocean/land-atmosphere interaction, more than half of the total kinetic energy is lost within the lowest part of atmosphere, often referred to as the planetary boundary layer (PBL). A comprehensive understanding of the energetics of this layer and turbulent processes responsible for dissipation of kinetic energy within the PBL require accurate estimation of sensible and latent heat flux and momentum flux. In numerical weather prediction (NWP) models, these quantities are estimated through different surface-layer and PBL parameterization schemes. This research article investigates different factors influencing the accuracy of a surface-layer parameterization scheme used in a hydrostatic high-resolution regional model (HRM) in the estimation of surface-layer turbulent fluxes of heat, moisture and momentum over the coastal regions of the Indian sub-continent. Results obtained from this sensitivity study of a parameterization scheme in HRM revealed the role of surface roughness length (z_{0}) in conjunction with the temperature difference between the underlying ground surface and atmosphere above (?T = T_{G} - T_{A}) in the estimated values of fluxes. For grid points over the land surface where z_{0} is treated as a constant throughout the model integration time, ?T showed relative dominance in the estimation of sensible heat flux. In contrast to this, estimation of sensible and latent heat flux over ocean were found to be equally sensitive on the method adopted for assigning the values of z_{0} and also on the magnitudes of ?T.

Anurose, J. T.; Subrahamanyam, Bala D.

2012-07-01

260

Effects of the Andes on Eastern Pacific Climate: A Regional Atmospheric Model Study(.  

NASA Astrophysics Data System (ADS)

A regional atmospheric model is used to study the effects of the narrow and steep Andes on the eastern Pacific climate. In the Southern Hemisphere cold season (i.e., August October 1999), the model reproduces key climatic features, including the intertropical convergence zone (ITCZ) north of the equator and an extensive low-level cloud deck capped by a temperature inversion to the south. Blocking the warm easterly winds from South America, the Andes help maintain the divergence and temperature inversion and, hence, the stratocumulus cloud deck over the southeast Pacific off South America. In an experiment where the Andean mountains are removed, the warm advection from the South American continent lowers the inversion height and reduces the low-level divergence offshore, leading to a significant reduction in cloud amount and an increase in solar radiation that reaches the sea surface.In March and early April 1999, the model simulates a double ITCZ in response to the seasonal warming on and south of the equator, in agreement with satellite observations. Under the same sea surface temperature forcing, the removal of the Andes prolongs the existence of the southern ITCZ for 3 weeks. Without the mountains, the intrusion of the easterlies from South America enhances the convergence in the lower atmosphere, and the transient disturbances travel freely westward from the continent. Both effects of the Andes removal favor deep convection south of the equator.The same sensitivity experiments are repeated with orography used in T42 global models, and the results confirm that an underrepresentation of the Andes reduces the stratus clouds in the cold season and prolongs the southern ITCZ in the warm season, with both acting to weaken the latitudinal asymmetry of eastern Pacific climate. The implications of these results for coupled modeling of climatic asymmetry are discussed.

Xu, Haiming; Wang, Yuqing; Xie, Shang-Ping

2004-02-01

261

Systematics of radon daughters ([sup 210]Pb - [sup 210]Po) atmospheric fallout to coastal regions  

SciTech Connect

The radon daughters [sup 210]Pb and [sup 210]Po were analyzed in coastal bulk precipitation from Camargue (Mediterranean, France) and Lewes (mid-Atlantic, Delaware, USA) as part of the ECOMARGE and SEEP programs and over periods of 12 and 15 months in 1988 and 1989 respectively. The [sup 210]Po/[sup 210]Pb activity ratio in the Camargue fallout is on the order of 0.4, and less than 0.2 in Lewes fallout. Such low [sup 210]Po/[sup 210]Pb activity ratio in precipitation at the American east coast, may partially explain similar deficit values observed in the surface sea waters along the New England shelf (Bacon et al., 1988). The annual fluxes of [sup 210]Pb in these two regions (Camargue and Lewes) have seen determined to be 0.4 and 0.6 dpm cm[sup -2] respectively, somewhat lower than previous records. The [sup 210]Pb fallout at Camargue shows strong correlation with the rainfall, while that at Lewes showed no such correlation. Efficiency in convective fallout characteristic of the mistral conditions in the Camargue may be one explanation. A the coast in Lewes there is characteristic mixing of continental (dry, radon rich) and marine (wet, radon poor) air masses, and a greater proportion of dry fallout. The atmospheric deposition data for [sup 210]Pb-[sup 210]Po radon daughters will be compared to that sampled simultaneously in coastal oceanic sediment traps to document the potential coupling between coastal atmospheric fallout and ocean fluxes.

Hussain, N.; Church, T. (Univ. of Delaware, Newark (United States)); Heyraud, M.; Fowler, S. (International Lab. Mar. Radioactivity, Monaco (France)); Heussner, S.; Monaco, A. (Univ. of Perpignan (France)); Biscaye, P.; Anderson, R. (Bothat Geochemical, Palisades, NY (United States))

1990-01-09

262

Influence of geomagnetic disturbances on atmospheric electric field (Ez) variations at high and middle latitudes  

NASA Astrophysics Data System (ADS)

The variations of the vertical atmospheric electric field (Ez) represent the state of the global atmospheric electric circuit, which is controlled by the world thunderstorm activity and by magnetosphere-ionosphere disturbances as well. Here we present a synthesis of our main results of the effects of the geomagnetic disturbances on the Ez variations, measured at the Earth?s surface at high and middle latitudes, which were previously published by Kleimenova et al. (2008, 2010). We studied the high latitude geomagnetic substorm effects on the Ez variations on the base of the continue Ez registrations at the polar station Hornsund (Spitsbergen). This station can map into the polar cap, auroral oval or near the border between these structures in dependence on the local time and the level of the geomagnetic activity. The high-latitude Ez variations associated with the substorm activity have been established. It was found that the Ez deviations were positive (Ez values increase) in the local morning and negative ones (Ez values decrease) in the local evening. We speculate that the direction of the Ez excursion depends on the station location relative to the positive or negative vortex of the polar ionospheric plasma convection.The Ez variations at the mid-latitude station ?wider (near Warsaw) have been studied during 14 magnetic storms. To avoid the meteorological influences on the Ez measurements we used only the Ez data, obtained under the “fair weather” conditions. For the first time the main phase effect of all mentioned above magnetic storms was established in the mid-latitude atmospheric electricity variations. The strong daytime Ez negative excursions (Ez value decreases) were found in association with the simultaneous night-side magnetospheric substorm developing during the studied magnetic storms. The considered Ez deviations could be results an interplanetary electric field penetration into the magnetosphere. Another plausible reason could be related to the common ionosphere conductivity increasing due to substorm energetic electron precipitation, modifying the high-latitude ionospheric part of the global atmospheric electric circuit.

Kleimenova, N.; Kozyreva, O.; Michnowski, S.; Kubicki, M.

2013-07-01

263

Influence of HITRAN database updates on retrievals of atmospheric CO2 from near-infrared spectra  

NASA Astrophysics Data System (ADS)

The line-transition parameters of the High Resolution Transmission (HITRAN) 2008 database have been updated relative to previous editions. The transmission spectra and sensitivity to changes in CO2 concentrations using line parameters from the HITRAN 2004 and HITRAN 2008 databases are compared to evaluate the effect of the database updates on retrievals of carbon dioxide vertical columns from near-infrared reflected sunlight. This comparison is done in three spectral regions covering the 2.06-, 1.61-, and 1.58-µm CO2 bands used by the Greenhouse Gases Observatory Satellite (GOSAT) instrument and the planned successor to the Orbiting Carbon Observatory (OCO). The updates to the HITRAN database have the largest effects on the transmittance and the off-line to on-line transmittance ratio in the 2.06-µm region and the smallest effects on these parameters in the 1.58-µm region. The influence of the updates to the HITRAN database on the off-line to on-line ratio calculation in the narrow spectral region 4855-4880 cm-1 could be equivalent to a change in CO2 of more than 50 ppmv. Use of the HITRAN 2004 database will lead to an underestimate of the column CO2 abundance in the 2.06- and 1.61-µm spectral regions, whereas it will lead to an overestimate of the column CO2 abundance in the 1.58-µm spectral region.

Dai, Tie; Shi, Guangyu; Zhang, Xingying; Xu, Na

2012-10-01

264

Using a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to simulate the interaction between land surface processes and atmospheric boundary layer in semi-arid regions  

NASA Astrophysics Data System (ADS)

This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts: atmospheric boundary layer processes and land surface processes. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feasibility of the model is well proved in this paper. The numerical simulation results from MSPAS show good agreement with reality. The scheme is used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature of boundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity, turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS is used to simulate the interaction between desert and oasis at night, and again it obtains reasonable results. This indicates that MSPAS can be used to study the interaction between land surface processes and the atmospheric boundary layer over various underlying surfaces and can be extended for regional climate and numerical weather prediction study.

Liu, Shuhua; Yue, Xu; Hu, Fei; Liu, Huizhi

2004-04-01

265

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

NASA Astrophysics Data System (ADS)

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still unclear. This study, investigated the influence of feedstock particle size in RPS of aluminum nitride (AlN) coatings, through plasma nitriding of aluminum (Al) feedstock powders. It was possible to fabricate AlN-based coatings through plasma nitriding of all kinds of Al powders in atmospheric plasma spray (APS) process. The nitriding ratio was improved with decreasing the particle size of feedstock powder, due to improving the nitriding reaction during flight. However, decreasing the particle size of feedstock powder suppressed the coatings thickness. Due to the loss of the powder during the injection, the excessive vaporization of fine Al particles and the completing nitriding reaction of some fine Al particles during flight. The feedstock particle size directly affects on the nitriding, melting, flowability, and the vaporization behaviors of Al powders during spraying. It concluded that using smaller particle size powders is useful for improving the nitriding ratio and not suitable for fabrication thick AlN coatings in reactive plasma spray process. To fabricate thick AlN coatings through RPS, enhancing the nitriding reaction of Al powders with large particle size during spraying is required.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2011-03-01

266

Factors influencing the soil-air partitioning and the strength of soils as a secondary source of polychlorinated biphenyls to the atmosphere.  

PubMed

Soils are a major reservoir of persistent organic pollutants, and soil-air partitioning and exchange are key processes controlling the atmospheric concentrations and regional fate of pollutants. Here, we report and discuss the concentrations of polychlorinated biphenyls (PCBs) in soils, their measured fugacities in soil, the soil-air partition coefficients (K(SA)) and soil-air fugacity gradients in rural background areas of N-NE Spain and N-NW England. Four sampling campaigns were carried out to assess seasonal and daily variability and differences between sampling sites. K(SA) values were significantly dependent on soil temperature and soil organic matter quantity, and to a minor extent organic matter type. All the PCB congeners in the soil are close to equilibrium with the atmosphere at rural Ebro sites, but soil fugacities tend to be higher than ambient air fugacities in early and late summer, consistent with the influence of temperature on soil-air partitioning. Therefore, during warm periods, soils increment their strength as secondary sources to the atmosphere. The mixture of PCBs found in the atmosphere is clearly strongly influenced by the mixture of PCBs which escape from soil, with significant correlations between them (R(2) ranging between 0.35 and 0.74 and p-level <0.001 for the Ebro sampling sites). Conversely, the close-to-equilibrium to net sink status of rural UK sites, suggest a close coupling of air and soil concentrations, but it is not possible to elucidate the importance of these soils as secondary sources yet, and presumably there are still significant primary sources to the regional/global environment. PMID:21534636

Cabrerizo, Ana; Dachs, Jordi; Moeckel, Claudia; Ojeda, María-José; Caballero, Gemma; Barceló, Damià; Jones, Kevin C

2011-05-03

267

The influence of atmospheric circulation on the mid-Holocene climate of Europe: a data-model comparison  

NASA Astrophysics Data System (ADS)

The atmospheric circulation is a key area of uncertainty in climate model simulations of future climate change, especially in mid-latitude regions such as Europe where atmospheric dynamics have a significant role in climate variability. It has been proposed that the mid-Holocene was characterized in Europe by a stronger westerly circulation in winter comparable with a more positive AO/NAO, and a weaker westerly circulation in summer caused by anti-cyclonic blocking near Scandinavia. Model simulations indicate at best only a weakly positive AO/NAO, whilst changes in summer atmospheric circulation have not been widely investigated. Here we use a new pollen-based reconstruction of European mid-Holocene climate to investigate the role of atmospheric circulation in explaining the spatial pattern of seasonal temperature and precipitation anomalies. We find that the footprint of the anomalies is entirely consistent with those from modern analogue atmospheric circulation patterns associated with a strong westerly circulation in winter (positive AO/NAO) and a weak westerly circulation in summer (positive SCAND). We find little agreement between the reconstructed anomalies and those from a climate model simulation, which as with most model simulations shows a much greater sensitivity to local radiative forcing from top-of-the-atmosphere changes in solar insolation. Our findings are consistent with data-model comparisons on contemporary timescales that indicate that models underestimate the role of atmospheric circulation in climate change, whilst also highlighting the importance of atmospheric dynamics in explaining interglacial warming.

Mauri, A.; Davis, B. A. S.; Collins, P. M.; Kaplan, J. O.

2013-10-01

268

Northern Hemisphere atmospheric influence of the solar proton events and ground level enhancement in January 2005  

NASA Astrophysics Data System (ADS)

Solar eruptions in early 2005 led to a substantial barrage of charged particles on the Earth's atmosphere during the 16-21 January period. Proton fluxes were greatly increased during these several days and led to the production of HOx (H, OH, HO2) and NOx (N, NO, NO2), which then caused the destruction of ozone. We focus on the Northern polar region, where satellite measurements and simulations with the Whole Atmosphere Community Climate Model (WACCM3) showed large enhancements in mesospheric HOx and NOx constituents, and associated ozone reductions, due to these solar proton events (SPEs). The WACCM3 simulations show enhanced short-lived OH throughout the mesosphere in the 60-82.5° N latitude band due to the SPEs for most days in the 16-21 January 2005 period, in reasonable agreement with the Aura Microwave Limb Sounder (MLS) measurements. Mesospheric HO2 is also predicted to be increased by the SPEs, however, the modeled HO2 results are somewhat larger than the MLS measurements. These HOx enhancements led to huge predicted and MLS-measured ozone decreases of greater than 40% throughout most of the northern polar mesosphere during the SPE period. Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurements of hydrogen peroxide (H2O2) show increases throughout the stratosphere with highest enhancements of about 60 pptv in the lowermost mesosphere over the 16-18 January 2005 period due to the solar protons. WACCM3 predictions indicate H2O2 enhancements over the same time period of more than twice that amount. Measurements of nitric acid (HNO3) by both MLS and MIPAS show an increase of about 1 ppbv above background levels in the upper stratosphere during 16-29 January 2005. WACCM3 simulations show only minuscule HNO3 changes in the upper stratosphere during this time period. Polar mesospheric enhancements of NOx are computed to be greater than 50 ppbv during the SPE period due to the small loss rates during winter. Computed NOx increases, which were statistically significant at the 95% level, lasted about a month past the SPEs. The SCISAT-1 Atmospheric Chemistry Experiment Fourier Transform Spectrometer NOx measurements and MIPAS NO2 measurements for the polar Northern Hemisphere are in reasonable agreement with these predictions. An extremely large ground level enhancement (GLE) occurred during the SPE period on 20 January 2005. We find that protons of energies 300 to 20 000 MeV, not normally included in our computations, led to enhanced lower stratospheric odd nitrogen concentrations of less than 0.1% as a result of this GLE.

Jackman, C. H.; Marsh, D. R.; Vitt, F. M.; Roble, R. G.; Randall, C. E.; Bernath, P. F.; Funke, B.; López-Puertas, M.; Versick, S.; Stiller, G. P.; Tylka, A. J.; Fleming, E. L.

2011-03-01

269

Northern Hemisphere atmospheric influence of the solar proton events and ground level enhancement in January 2005  

NASA Astrophysics Data System (ADS)

Solar eruptions in early 2005 led to a substantial barrage of charged particles on the Earth's atmosphere during the 16-21 January period. Proton fluxes were greatly increased during these several days and led to the production of HOx (H, OH, HO2) and NOx (N, NO, NO2), which then caused the destruction of ozone. We focus on the Northern polar region, where satellite measurements and simulations with the Whole Atmosphere Community Climate Model (WACCM3) showed large enhancements in mesospheric HOx and NOx constituents, and associated ozone reductions, due to these solar proton events (SPEs). The WACCM3 simulations show enhanced short-lived OH and HO2 concentrations throughout the mesosphere in the 60-82.5° N latitude band due to the SPEs for most days in the 16-21 January 2005 period, somewhat higher in abundance than those observed by the Aura Microwave Limb Sounder (MLS). These HOx enhancements led to huge predicted and MLS-measured ozone decreases of greater than 40 % throughout most of the northern polar mesosphere during the SPE period. Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurements of hydrogen peroxide (H2O2) show increases throughout the stratosphere with highest enhancements of about 60 pptv in the lowermost mesosphere over the 16-18 January 2005 period due to the solar protons. WACCM3 predictions indicate H2O2 enhancements over the same time period of about three times that amount. Measurements of nitric acid (HNO3) by both MLS and MIPAS show an increase of about 1 ppbv above background levels in the upper stratosphere during 16-29 January 2005. WACCM3 simulations show only minuscule HNO3 increases (<0.05 ppbv) in the upper stratosphere during this time period. Polar mesospheric enhancements of NOx are computed to be greater than 50 ppbv during the SPE period due to the small loss rates during winter. Computed NOx increases, which were statistically significant at the 95 % level, lasted about a month past the SPEs. The SCISAT-1 Atmospheric Chemistry Experiment Fourier Transform Spectrometer NOx measurements and MIPAS NO2 measurements for the polar Northern Hemisphere are in reasonable agreement with these predictions. An extremely large ground level enhancement (GLE) occurred during the SPE period on 20 January 2005. We find that protons of energies 300 to 20 000 MeV, associated with this GLE, led to very small enhanced lower stratospheric odd nitrogen concentrations of less than 0.1 % and ozone decreases of less than 0.01 %.

Jackman, C. H.; Marsh, D. R.; Vitt, F. M.; Roble, R. G.; Randall, C. E.; Bernath, P. F.; Funke, B.; López-Puertas, M.; Versick, S.; Stiller, G. P.; Tylka, A. J.; Fleming, E. L.

2011-07-01

270

Evidence that local land use practices influence regional climate, vegetation, and stream flow patterns in adjacent natural areas  

USGS Publications Warehouse

We present evidence that land use practices in the plains of Colorado influence regional climate and vegetation in adjacent natural areas in the Rocky Mountains in predictable ways. Mesoscale climate model simulations using the Colorado State University Regional Atmospheric Modelling System (RAMS) projected that modifications to natural vegetation in the plains, primarily due to agriculture and urbanization, could produce lower summer temperatures in the mountains. We corroborate the RAMS simulations with three independent sets of data: (i) climate records from 16 weather stations, which showed significant trends of decreasing July temperatures in recent decades; (ii) the distribution of seedlings of five dominant conifer species in Rocky Mountain National Park, Colorado, which suggested that cooler, wetter conditions occurred over roughly the same time period; and (iii) increased stream flow, normalized for changes in precipitation, during the summer months in four river basins, which also indicates cooler summer temperatures and lower transpiration at landscape scales. Combined, the mesoscale atmospheric/land-surface model, short-term in regional temperatures, forest distribution changes, and hydrology data indicate that the effects of land use practices on regional climate may overshadow larger-scale temperature changes commonly associated with observed increases in CO2 and other greenhouse gases.

Stohlgren, T. J.; Chase, T. N.; Pielke, Sr. , R. A.; Kittel, T. G. F.; Baron, J. S.

1998-01-01

271

The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations  

Microsoft Academic Search

The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was an international field program designed to make observations of poorly understood but critical components of the coupled climate system of the southeast Pacific. This region is characterized by strong coastal upwelling, the coolest SSTs in the tropical belt, and is home to the largest subtropical stratocumulus deck on Earth. The field intensive

R. Wood; C. S. Bretherton; C. R. Mechoso; R. A. Weller; B. Huebert; F. Straneo; B. A. Albrecht; H. Coe; G. Allen; G. Vaughan; P. Daum; C. Fairall; D. Chand; L. Gallardo Klenner; R. Garreaud; C. Grados Quispe; T. S. Bates; R. Krejci; L. M. Russell; S. de Szoeke; A. Brewer; S. E. Yuter; S. R. Springston; A. Chaigneau; T. Toniazzo; P. Minnis; R. Palikonda; S. J. Abel; W. O. J. Brown; S. Williams; J. Fochesatto; J. Brioude

2010-01-01

272

The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations  

Microsoft Academic Search

The VAMOS1 Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was an international field program designed to make observations of poorly understood but critical components of the coupled climate system of the southeast Pacific. This region is characterized by strong coastal upwelling, the coolest SSTs in the tropical belt, and is home to the largest subtropical stratocumulus deck on Earth. The field intensive

R. Wood; C. R. Mechoso; C. S. Bretherton; R. A. Weller; B. Huebert; F. Straneo; B. A. Albrecht; H. Coe; G. Allen; G. Vaughan; P. Daum; C. Fairall; D. Chand; L. Gallardo Klenner; R. Garreaud; C. Grados; T. S. Bates; R. Krejci; L. M. Russell; S. de Szoeke; A. Brewer; S. E. Yuter; S. R. Springston; A. Chaigneau; T. Toniazzo; P. Minnis; R. Palikonda; S. J. Abel; W. O. J. Brown; S. Williams; J. Fochesatto; J. Brioude; K. N. Bower

2011-01-01

273

Regional analysis of soil-atmosphere nitrous oxide emissions in the Northern Atlantic Zone of Costa Rica  

Microsoft Academic Search

Regional analysis of greenhouse gas emissions is becoming increasingly important in answering questions related to environmental change, and typically employs a Geographic Information System (GIS) linked with a process-based simulation model. For the Northern Atlantic Zone (NAZ) in Costa Rica (281 649 ha), a regional analysis of soil-atmosphere nitrous oxide fluxes from the dominant land-use types forest, cattle pastures, and

Roel A. J. Plant

2000-01-01

274

Pollution characterization and diurnal variation of PBDEs in the atmosphere of an E-waste dismantling region  

Microsoft Academic Search

Diurnal air samples were collected from the E-waste dismantling region Guiyu and the underwear industry region Chendian. This was the first report to present the diurnal variation of PBDEs in the atmosphere. The average concentrations of 11 PBDE congeners were 11,742pgm?3 in the daytime, and 4830pgm?3 at night in Guiyu, while the concentrations were lower in Chendian with 376pgm?3 in

Duohong Chen; Xinhui Bi; Jinping Zhao; Laiguo Chen; Jihua Tan; Bixian Mai; Guoying Sheng; Jiamo Fu; Minghung Wong

2009-01-01

275

Solar migrating atmospheric tides in the winds of the polar region of Venus  

NASA Astrophysics Data System (ADS)

We study the effects of migrating solar tides on the winds at the cloud tops of the polar region of Venus. The winds were measured using cloud tracking on images obtained at wavelengths of 3.9 and 5.0 ?m by the instrument VIRTIS-M onboard Venus Express. These wavelengths probe about the same altitude close to the cloud tops, allowing for the first time to retrieve winds simultaneously in the day and nightside of the planet. We use a dataset with observations from 16 orbits, covering a time span of 289 days and a latitude range between 70°S and 85°S, the region where the so called cold collar resides. Diurnal and quarter-diurnal tides (wavenumbers 1 and 4) were detected in the wind field, with a decoupled influence on the zonal and meridional directions. The diurnal tide is the dominant harmonic with amplitudes of about 4.7 m/s exclusively affecting the meridional component of the wind and forcing a solar-to-antisolar circulation at the polar region. The quarter-diurnal mode is only apparent in the zonal wind in a restricted latitude range with amplitudes ˜2.2 m/s. The spatial structure of the diurnal tide has also been investigated, obtaining a vertical wavelength of about 8 km, in accordance with predictions by models. Finally, a theoretical relation between the amplitudes of tidal temperature and tidal wind has been derived and its validity tested with models and results from previous missions.

Peralta, J.; Luz, D.; Berry, D. L.; Tsang, C. C. C.; Sánchez-Lavega, A.; Hueso, R.; Piccioni, G.; Drossart, P.

2012-08-01

276

Investigating the sources of synoptic variability in atmospheric CO 2 measurements over the Northern Hemisphere continents: a regional model study  

Microsoft Academic Search

Continuous measurements of atmospheric CO2 over the continents are potentially powerful tools for understanding regional carbon budgets, but our limited understanding of the processes driving the high-frequency variability in these measurements makes interpretation difficult. In this paper we examine the synoptic variability (?days) of surface CO2 concentrations in four continental records from Europe and North America. Three source functions corresponding

C. G EELS; S. C. D ONEY; R. DARGA V ILLE; J. B RANDT; J. H. C HRISTENSEN

277

Atmospheric inverse modeling to constrain regional-scale CO2 budgets at high spatial and temporal resolution  

Microsoft Academic Search

We present an inverse modeling framework designed to constrain CO2 budgets at regional scales. The approach captures atmospheric transport processes in high spatiotemporal resolution by coupling a mesoscale model with Lagrangian Stochastic backward trajectories. Terrestrial biosphere CO2 emissions are generated through a simple diagnostic flux model that splits the net ecosystem exchange into its major components of gross primary productivity

Mathias Göckede; Anna M. Michalak; Dean Vickers; David P. Turner; Beverly E. Law

2010-01-01

278

Spatial Decision Support for Assessing Impacts of Atmospheric Sulfur Deposition on Aquatic Ecosystems in the Southern Appalachian Region  

Microsoft Academic Search

We present foundational work on the use of niche modeling to predict continuous surfaces of acid neutralizing capacity (ANC) and base cation weathering (BCw) within the southern Appalachian Mountain Region of the United States. Predicted ANC and BCw surfaces are subsequently used to estimate steady-state critical loads (CLs) of atmospheric sulfur deposition. We then present a logic-based model for assessing

Keith M. Reynolds; Paul F. Hessburg; Timothy Sullivan; Nicholas Povak; Todd McDonnell; Bernard Cosby; William Jackson

2012-01-01

279

Atmospheric three-dimensional inverse modeling of regional industrial emissions and global oceanic uptake of carbon tetrachloride  

NASA Astrophysics Data System (ADS)

Carbon tetrachloride (CCl4) has substantial stratospheric ozone depletion potential and its consumption is controlled under the Montreal Protocol and its amendments. We implement a Kalman filter using atmospheric CCl4 measurements and a 3-dimensional chemical transport model to estimate the interannual regional industrial emissions and seasonal global oceanic uptake of CCl4 for the period of 1996-2004. The Model of Atmospheric Transport and Chemistry (MATCH), driven by offline National Center for Environmental Prediction (NCEP) reanalysis meteorological fields, is used to simulate CCl4 mole fractions and calculate their sensitivities to regional sources and sinks using a finite difference approach. High frequency observations from the Advanced Global Atmospheric Gases Experiment (AGAGE) and the Earth System Research Laboratory (ESRL) of the National Oceanic and Atmospheric Administration (NOAA) and low frequency flask observations are together used to constrain the source and sink magnitudes, estimated as factors that multiply the a priori fluxes. Although industry data imply that the global industrial emissions were substantially declining with large interannual variations, the optimized results show only small interannual variations and a small decreasing trend. The global surface CCl4 mole fractions were declining in this period because the CCl4 oceanic and stratospheric sinks exceeded the industrial emissions. Compared to the a priori values, the inversion results indicate substantial increases in industrial emissions originating from the South Asian/Indian and Southeast Asian regions, and significant decreases in emissions from the European and North American regions.

Xiao, X.; Prinn, R. G.; Fraser, P. J.; Weiss, R. F.; Simmonds, P. G.; O'Doherty, S.; Miller, B. R.; Salameh, P. K.; Harth, C. M.; Krummel, P. B.; Golombek, A.; Porter, L. W.; Butler, J. H.; Elkins, J. W.; Dutton, G. S.; Hall, B. D.; Steele, L. P.; Wang, R. H. J.; Cunnold, D. M.

2010-11-01

280

Influence of the Flow Rate of Oxidising Atmosphere on the Flame Spread Rate on the Surface of Organic Setlled Dust  

NASA Astrophysics Data System (ADS)

The presented paper deals with determining the influence of the flow rate of oxidising atmosphere on the flame spread along the surface of the organic settled dust layer. We determined the rate of the flame spread on the surface of the organic settled dust layer (whole grain rye and spelt flour) with absolute moisture of 10 % wt., for the flow rates of oxidising atmosphere 1, 3, 5 and 10 cm/s. Pure oxygen was used as an oxidising atmosphere. The obtained results suggest that there exists a power relationship of the flame spread rate along the surface of organic settled dust layer to the flow rate of the oxidising mixture. The method described is suitable for the relative comparison of the organic settled dust layer from the point of its ability to spread the flame and the influence of the air flow rate on this process.

Martinka, Jozef; Balog, Karol; Hrušovský, Ivan; Valentová, Veronika

2013-01-01

281

Photodegradation of Chromophoric Dissolved Organic Matter (CDOM) in Atmospheric Waters and its Influence on the Redox Chemistry of the Troposhere  

Microsoft Academic Search

The abundance and spectral characteristics of chromophoric dissolved organic matter (CDOM) was determined in atmospheric waters in Wilmington, North Carolina USA over an 18 month sampling period. Fluorescence excitation - emission spectra (EEMs) of condensed phase samples showed four major peaks which were indicative of both terrestrial and marine influences. The absorbance spectra of samples generally decreased exponentially with wavelength

R. J. Kieber; J. D. Willey; R. F. Whitehead; G. B. Avery; P. J. Seaton

2007-01-01

282

Influence of modified atmosphere packaging on quality, vitamin C and phenolic content of artichokes ( Cynara scolymus L.)  

Microsoft Academic Search

The influence of modified atmosphere packaging (MAP) on the visual quality and the content of phenolics and vitamin C in artichokes cv. Blanca de Tudela stored at 5 °C was studied in order to prolong shelf life. Six different films were used: perforated polypropylene (Control), polyvinylchloride (PVC), low density polyethylene (LDPE) and three microperforated polypropylene films (PP1, PP2 and PP3).

Angel Gil-Izquierdo; Maria Angeles Conesa; Federico Ferreres; Maria Isabel Gil

2002-01-01

283

Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics  

NASA Astrophysics Data System (ADS)

Phase transitions of atmospheric water play a ubiquitous role in the Earth's climate system, but their direct impact on atmospheric dynamics has escaped wide attention. Here we examine and advance a theory as to how condensation influences atmospheric pressure through the mass removal of water from the gas phase with a simultaneous account of the latent heat release. Building from fundamental physical principles we show that condensation is associated with a decline in air pressure in the lower atmosphere. This decline occurs up to a certain height, which ranges from 3 to 4 km for surface temperatures from 10 to 30 °C. We then estimate the horizontal pressure differences associated with water vapor condensation and find that these are comparable in magnitude with the pressure differences driving observed circulation patterns. The water vapor delivered to the atmosphere via evaporation represents a store of potential energy available to accelerate air and thus drive winds. Our estimates suggest that the global mean power at which this potential energy is released by condensation is around one per cent of the global solar power - this is similar to the known stationary dissipative power of general atmospheric circulation. We conclude that condensation and evaporation merit attention as major, if previously overlooked, factors in driving atmospheric dynamics.

Makarieva, A. M.; Gorshkov, V. G.; Sheil, D.; Nobre, A. D.; Li, B.-L.

2013-01-01

284

Primary and secondary sources of formaldehyde in urban atmospheres: Houston Texas region  

NASA Astrophysics Data System (ADS)

We evaluate the rates of secondary production and primary emission of formaldehyde (CH2O) from petrochemical industrial facilities and on-road vehicles in the Houston Texas region. This evaluation is based upon ambient measurements collected during field studies in 2000, 2006 and 2009. The predominant CH2O source (92 ± 4% of total) is secondary production formed during the atmospheric oxidation of highly reactive volatile organic compounds (HRVOCs) emitted from the petrochemical facilities. Smaller contributions are primary emissions from these facilities (4 ± 2%), and secondary production (~3%) and primary emissions (~1%) from vehicles. The primary emissions from both sectors are well quantified by current emission inventories. Since secondary production dominates, control efforts directed at primary CH2O emissions cannot address the large majority of CH2O sources in the Houston area, although there may still be a role for such efforts. Ongoing efforts to control alkene emissions from the petrochemical facilities, as well as volatile organic compound emissions from the motor vehicle fleet, will effectively reduce the CH2O concentrations in the Houston region. We have not addressed other emission sectors, such as off-road mobile sources or secondary formation from biogenic hydrocarbons. Previous analyses based on correlations between ambient concentrations of CH2O and various marker species have suggested much larger primary emissions of CH2O, but those results neglect confounding effects of dilution and loss processes, and do not demonstrate the causes of the observed correlations. Similar problems must be suspected in any source apportionment analysis of secondary species based upon correlations of ambient concentrations of pollutants.

Parrish, D. D.; Ryerson, T. B.; Mellqvist, J.; Johansson, J.; Fried, A.; Richter, D.; Walega, J. G.; Washenfelder, R. A.; de Gouw, J. A.; Peischl, J.; Aikin, K. C.; McKeen, S. A.; Frost, G. J.; Fehsenfeld, F. C.; Herndon, S. C.

2011-12-01

285

Primary and secondary sources of formaldehyde in urban atmospheres: Houston Texas region  

NASA Astrophysics Data System (ADS)

We evaluate the rates of secondary production and primary emission of formaldehyde (CH2O) from petrochemical industrial facilities and on-road vehicles in the Houston Texas region. This evaluation is based upon ambient measurements collected during field studies in 2000, 2006 and 2009. The predominant CH2O source (92 ± 4% of total) is secondary production formed during the atmospheric oxidation of highly reactive volatile organic compounds (HRVOCs) emitted from the petrochemical facilities. Smaller contributions are primary emissions from these facilities (4 ± 2%), and secondary production (~3%) and primary emissions (~1%) from vehicles. The primary emissions from both sectors are well quantified by current emission inventories. Since secondary production dominates, control efforts directed at primary CH2O emissions cannot address the large majority of CH2O sources in the Houston area, although there may still be a role for such efforts. Ongoing efforts to control alkene emissions from the petrochemical facilities, as well as volatile organic compound emissions from the motor vehicle fleet, will effectively reduce the CH2O concentrations in the Houston region. We do not address other emission sectors, such as off-road mobile sources or secondary formation from biogenic hydrocarbons. Previous analyses based on correlations between ambient concentrations of CH2O and various marker species have suggested much larger primary emissions of CH2O, but those results neglect confounding effects of dilution and loss processes, and do not demonstrate the causes of the observed correlations. Similar problems must be suspected in any source apportionment analysis of secondary species based upon correlations of ambient concentrations of pollutants.

Parrish, D. D.; Ryerson, T. B.; Mellqvist, J.; Johansson, J.; Fried, A.; Richter, D.; Walega, J. G.; Washenfelder, R. A.; de Gouw, J. A.; Peischl, J.; Aikin, K. C.; McKeen, S. A.; Frost, G. J.; Fehsenfeld, F. C.; Herndon, S. C.

2012-04-01

286

On testing two major cumulus parameterization schemes using the CSU Regional Atmospheric Modeling System  

SciTech Connect

One of the objectives of the DOE ARM Program is to improve the parameterization of clouds in general circulation models (GCMs). The approach taken in this research is two fold. We first examine the behavior of cumulus parameterization schemes by comparing their performance against the results from explicit cloud simulations with state-of-the-art microphysics. This is conducted in a two-dimensional (2-D) configuration of an idealized convective system. We then apply the cumulus parameterization schemes to realistic three-dimensional (3-D) simulations over the western US for a case with an enormous amount of convection in an extended period of five days. In the 2-D idealized tests, cloud effects are parameterized in the ``parameterization cases`` with a coarse resolution, whereas each cloud is explicitly resolved by the ``microphysics cases`` with a much finer resolution. Thus, the capability of the parameterization schemes in reproducing the growth and life cycle of a convective system can then be evaluated. These 2-D tests will form the basis for further 3-D realistic simulations which have the model resolution equivalent to that of the next generation of GCMs. Two cumulus parameterizations are used in this research: the Arakawa-Schubert (A-S) scheme (Arakawa and Schubert, 1974) used in Kao and Ogura (1987) and the Kuo scheme (Kuo, 1974) used in Tremback (1990). The numerical model used in this research is the Regional Atmospheric Modeling System (RAMS) developed at Colorado State University (CSU).

Kao, C.Y.J.; Bossert, J.E.; Winterkamp, J.; Lai, C.C.

1993-10-01

287

Volcanic emissions of mercury to the atmosphere: global and regional inventories.  

PubMed

A comprehensive, time-averaged inventory of subaerial emissions of mercury from volcanoes that were active between 1980 and 2000 is derived based on the Hg/SO(2) ratios of the exhalations. Worldwide flux of mercury from volcanic eruptions is estimated to be 57 t/year while the flux from degassing activities is 37.6 t/year. After correcting for 'unmeasured' SO(2) emissions, the total global flux of Hg to the atmosphere is estimated to be 112 t/year. There are regional differences in average emissions during the 20-year period, with the estimated fluxes being 29 t/year in South and Central America, 27 t/year in Southeast Asia; 24 t/year in North America (including Hawaii), 4.1 t/year in Australia, 3.4 t/year in Japan and northern Asia, 3.1 t/year in Europe and western Asia and 2.3 t/year in Africa. PMID:12663167

Nriagu, Jerome; Becker, Christian

2003-03-20

288

The Rossby Centre Regional Atmospheric Climate Model part II: application to the Arctic climate.  

PubMed

The Rossby Centre regional climate model (RCA2) has been integrated over the Arctic Ocean as part of the international ARCMIP project. Results have been compared to observations derived from the SHEBA data set. The standard RCA2 model overpredicts cloud cover and downwelling longwave radiation, during the Arctic winter. This error was improved by introducing a new cloud parameterization, which significantly improves the annual cycle of cloud cover. Compensating biases between clear sky downwelling longwave radiation and longwave radiation emitted from cloud base were identified. Modifications have been introduced to the model radiation scheme that more accurately treat solar radiation interaction with ice crystals. This leads to a more realistic representation of cloud-solar radiation interaction. The clear sky portion of the model radiation code transmits too much solar radiation through the atmosphere, producing a positive bias at the top of the frequent boundary layer clouds. A realistic treatment of the temporally evolving albedo, of both sea-ice and snow, appears crucial for an accurate simulation of the net surface energy budget. Likewise, inclusion of a prognostic snow-surface temperature seems necessary, to accurately simulate near-surface thermodynamic processes in the Arctic. PMID:15264599

Jones, Colin G; Wyser, Klaus; Ullerstig, Anders; Willén, Ulrika

2004-06-01

289

Influences of fireworks on chemical characteristics of atmospheric fine and coarse particles during Taiwan's Lantern Festival  

NASA Astrophysics Data System (ADS)

In recent years, the celebration activities of various folk-custom festivals have been getting more and more attention from the citizens in Taiwan. Festivities throughout the whole island are traditionally accompanied by loud and brightly colored firework displays. Among these activities, the firework displays during Taiwan's Lantern Festival in Kaohsiung harbor is one of the largest festivals in Taiwan each year. Therefore, it is of importance to investigate the influence of fireworks displays on the ambient air quality during the Taiwan's Lantern Festival. Field measurements of atmospheric particulate matter (PM) were conducted on February 9th-11th, 2009 during Taiwan's Lantern Festival in Kaohsiung City. Moreover, three kinds of fireworks powders obtained from the same manufacturing factory producing Kaohsiung Lantern Festival fireworks were burned in a self-designed combustion chamber to determine the physicochemical properties of the fireworks' particles and to establish the source profile of firework burning. Several metallic elements of PM during the firework display periods were notably higher than those during the non-firework periods. The concentrations of Mg, K, Pb, and Sr in PM2.5 during the firework periods were 10 times higher than those during the non-firework periods. Additionally, the Cl-/Na+ ratio was approximately 3 during the firework display periods as Cl- came from the chlorine content of the firework powder. Moreover, the OC/EC ratio increased up to 2.8. Results obtained from PCA and CMB receptor modeling showed that major sources of atmospheric particles during the firework display periods in Kaohsiung harbor were fireworks, vehicular exhausts, soil dusts and marine sprays. Particularly, on February 10th, the firework displays contributed approximately 25.2% and 16.6% of PM10 at two downwind sampling sites, respectively.

Tsai, Hsieh-Hung; Chien, Li-Hsing; Yuan, Chung-Shin; Lin, Yuan-Chung; Jen, Yi-Hsiu; Ie, Iau-Ren

2012-12-01

290

Ice-atmosphere interactions during sea-ice advance and retreat in the western Antarctic Peninsula region  

NASA Astrophysics Data System (ADS)

The seasonal evolution of sea-ice extent, concentration, and drift in the western Antarctic Peninsula (WAP) region, along with regional atmospheric synoptic variability, are described for a winter period (1992) when sea-ice advance and retreat were both anomalously early. Daily time series of winds, opening and closing of the sea-ice cover, and volume fluxes in and out of the WAP region indicate that synoptic variability in meridional winds determines whether the ice-edge advances or retreats on daily to weekly timescales. The importance of this finding is that the dynamics, as opposed to the thermodynamics, initiate, and thereby dominate, in the production of ice-edge anomalies. Further, the abrupt mid-winter shift from persistently positive to negative ice-edge anomalies indicates that there was a distinct change in the regional atmospheric circulation. The ice-atmosphere interactions in the winter of 1992 are then compared to those in the winter of 1990, when sea-ice advance and retreat were both late instead of early, but again the mid-winter shift was abrupt. The comparison highlights possible circumpolar and tropical-polar atmospheric linkages in the South Pacific that involve changes in the amplitude/phase of the semi-annual oscillation (SAO), which in turn appear to be related to El Niño-Southern Oscillation (ENSO) changes in the tropical Pacific. The implication of a dynamically driven ice-atmosphere system, together with an intraseasonal ENSO linkage, further supports the idea that the WAP region is particularly sensitive to changes in the tropical Pacific.

Stammerjohn, S. E.; Drinkwater, M. R.; Smith, R. C.; Liu, X.

2003-10-01

291

The impact of different glacial boundary conditions on atmospheric dynamics and precipitation in the North Atlantic region  

NASA Astrophysics Data System (ADS)

Using a highly resolved atmospheric general circulation model the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Seven 30-yr time slice experiments of the Last Glacial Maximum (21 ka ago) and of a less pronounced glacial state - the Middle Weichselian (65 ka ago) - are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing, and in the prescribed time-varying lower boundary conditions, which are taken from a lower-resolved but fully-coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A large altitude of this ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying lower boundary conditions - evaluated using two simulations of the Last Glacial Maximum with a global mean temperature difference of 1.1 °C - are of second order compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner as the topographic changes.

Hofer, D.; Raible, C. C.; Dehnert, A.; Kuhlemann, J.

2012-01-01

292

The impact of different glacial boundary conditions on atmospheric dynamics and precipitation in the North Atlantic region  

NASA Astrophysics Data System (ADS)

Using a highly resolved atmospheric general circulation model, the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Six 30-yr time slice experiments of the Last Glacial Maximum at 21 thousand years before the present (ka BP) and of a less pronounced glacial state - the Middle Weichselian (65 ka BP) - are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing and in the prescribed time-varying sea surface temperature and sea ice, which are taken from a lower-resolved, but fully coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A high surface elevation of the Laurentide ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying sea surface temperatures and sea ice are of second order importance compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner compared with the topographic changes.

Hofer, D.; Raible, C. C.; Dehnert, A.; Kuhlemann, J.

2012-05-01

293

The impact of Eurasian dust storms and anthropogenic emissions on atmospheric nutrient deposition rates in forested Japanese catchments and adjacent regional seas  

NASA Astrophysics Data System (ADS)

Bulk precipitation and stream water chemistry data from 1993 to 2005 are used to analyze the relationship between Eurasian dust storms and nutrient deposition rates in the Kutsuki experimental forest (near Lake Biwa). From 2000 to 2005, atmospheric deposition, total nitrogen (TN), total phosphorus (TP) and dissolved silica (DSi) deposition rates increased by 26%, 132%, and 38%, respectively in the Kutsuki experimental forest. These TN and TP increases are associated with three seasonal factors: the increasing frequency and intensity of Eurasian spring dust events (March/April); the annual typhoon period (late August/September); and autumn/early winter (October to December) monsoons. The annual typhoon and monsoon winter periods are drivers for atmospheric TP and DSi deposition due to the correlation between the deposition and precipitation. In addition, increased spring dust deposition is a primarily driver for TN deposition changes. Increased emissions from urbanized areas in China (and likely Korea) affect the chemical properties of aerosols reaching downwind Japanese regions. Aerosol processes are responsible for increasing TN in aerosols, which are affected primarily by anthropogenic emissions. From 2000 to 2005, coal burning emissions from East Asia have contributed to an increase in TP (and possibly DSi) deposition rates. The observed increase in nutrient deposition did not noticeably impact short-term (5 year) stream water fluxes in the Kutsuki experimental forest. Due to plant uptake, the forest ecosystem retained atmospherically deposited N and P. Finally, the observed increases in nutrient deposition rates over the East China Sea and the Sea of Japan may significantly influence intra-annual net primary production. It is recommended that earth system modeling incorporate changes in atmospheric nutrient deposition rates and their impacts on the regional carbon cycle as well as aquatic and terrestrial ecosystems.

Hartmann, Jens; Kunimatsu, Takao; Levy, Jason K.

2010-05-01

294

The Effect of Atmosphere-Ocean-Wave Interactions and Model Resolution on Hurricane Katrina in a Coupled Regional Climate Model  

NASA Astrophysics Data System (ADS)

The sensitivity of simulated strength, track, and structure of Hurricane Katrina to atmospheric model resolution, cumulus parameterization, and initialization time, as well as mesoscale ocean-atmosphere interactions with and without small-scale ocean-wave effect, are investigated with a fully coupled regional climate model. The atmosphere, ocean, and wave components are represented by the Weather Research and Forecasting Model (WRF), Regional Ocean Modeling System (ROMS), and Simulating WAves Nearshore (SWAN) model. Uncoupled atmosphere-only simulations with horizontal resolutions of 1, 3, 9, and 27 km show that while the simulated cyclone track is highly sensitive to initialization time, its dependence on model resolution is relatively weak. Using NCEP/CFSR reanalysis as initial and boundary conditions, WRF, even at low resolution, is able to track Katrina accurately for 3 days before it made landfall on August 29, 2005. Katrina's strength, however, is much more difficult to reproduce and exhibits a strong dependence on model resolution. At its lowest resolution (27 km), WRF is only capable of simulating a maximum strength of Category 2 storm. Even at 1 km resolution, the simulated Katrina only reaches Category 4 storm intensity. Further WRF experiments with and without cumulus parameterization reveal minor changes in strength. None of the WRF-only simulations capture the observed rapid intensification of Katrina to Category 5 when it passed over a warm Loop-Current eddy (LCE) in the Gulf of Mexico, suggesting that mesoscale ocean-atmosphere interactions involving LCEs may play a crucial role in Katrina's rapid intensification. Coupled atmosphere-ocean simulations are designed and carried out to investigate hurricane Katrina-LCE interactions with and without considering small-scale ocean wave processes in order to fully understand the dynamical ocean-atmosphere processes in the observed rapid cyclone intensification.

Patricola, C. M.; Chang, P.; Saravanan, R.; Montuoro, R.

2012-04-01

295

The Influence of Ocean Waves on Radiative Transfer in the Earth's Atmosphere and Ocean.  

National Technical Information Service (NTIS)

The radiance in the earth's atmosphere and ocean is calculated for a realistic model including an ocean surface with waves. Individual photons are followed in a Monte Carlo calculation. In the atmosphere, both Rayleigh scattering by the molecules and Mie ...

G. N. Plass G. W. Kattawar J. A. Guinn

1975-01-01

296

Atmospheric pollution in a semi-urban, coastal region in India following festival seasons  

NASA Astrophysics Data System (ADS)

The traditional Vishu festival in the state of Kerala in South India is celebrated in April with extensive coordinated fireworks display. The influence of these celebrations on the immediate and long-term air quality and impact on the health and well being of the public needs research. The combustion clouds contain harmful fumes (sulfur dioxide, oxides of nitrogen) and particulate matter released at the surface. This study is focused on the influence of fireworks on the air quality at Kannur, India, during Vishu in April 2010 and 2011. Elevated concentrations of various air pollutants such as O3, NO2, NO and PM10 were measured during the intense usage of fireworks. Surprisingly, the organic analysis of the Particulate Matter (PM) samples collected on Vishu day revealed the emission of a variety of hazardous organic compounds during the fireworks display. One of the unique observations in this work is the nighttime production of O3 by the photodissociation of NO2 from the flash of firecrackers. The concentration of O3 was observed to increase two fold over the control days of observation during the same month. Moreover, the concentrations of NO2, and PM10 increased by 100%. The concentration of NO was reduced by four fold during the event. A scheme based on the organic combustion from fireworks and peroxyl radical mediation is proposed for the nighttime production of ozone. The diurnal profile of all pollutants except NO showed higher concentrations starting from the Vishu eve on April 14 to Vishu day on April 15 and this pattern repeated for years 2010 and 2011. The fireworks activities have been increasing every year and generation of pollutants at their increased levels for short duration can potentially cause adverse health impacts on a regional scale in a highly populated region.

Nishanth, T.; Praseed, K. M.; Rathnakaran, K.; Satheesh Kumar, M. K.; Ravi Krishna, R.; Valsaraj, K. T.

2012-02-01

297

Wildfire and the atmosphere: Modelling the chemical and dynamic interactions at the regional scale  

NASA Astrophysics Data System (ADS)

Forest fires release significant amounts of trace gases and aerosols into the atmosphere. Depending on meteorological conditions, fire emissions can efficiently reduce air quality and visibility, even far away from emission sources. In 2005, an arson forest fire burned nearly 700 ha near Lançon-de-Provence, southeast France. This paper explores the impact of this Mediterranean fire on the atmospheric dynamics and chemistry downwind of the burning region. The fire smoke plume was observed by the MODIS-AQUA instrument several kilometres downwind of the burning area out of the Mediterranean coast. Signatures of the fire plume on air pollutants were measured at surface stations in southeastern France by the air quality network AtmoPACA. Ground-based measurements revealed unusually high concentrations of aerosols and a well marked depletion of ozone concentrations on the day of the fire. The Lançon-de-Provence fire propagation was successfully simulated by the semi-physical fire spread model ForeFire. ForeFire provided the burnt area at high temporal and spatial resolutions. The burnt areas were scaled to compute the fire heat and water vapour fluxes in the three-dimensional meso-scale non-hydrostatic meteorological model MesoNH. The simulated fire plume kept confined in the boundary layer with high values of turbulent kinetic energy. The plume was advected several kilometres downwind of the ignition area by the Mistral winds in accordance with the MODIS and AtmoPACA observations. The vertical plume development was found to be more sensitive to the sensible heat flux than to the fire released moisture. The burnt area information is also used to compute emissions of a fire aerosol-like tracer and gaseous pollutants, using emission factors for Mediterranean vegetation. The coupled model simulated high concentrations of the fire aerosol-like tracer downwind of the burning zone at the right timing compared to ground-based measurements. A chemical reaction mechanism was coupled on-line to the MesoNH model to account for gaseous chemistry evolution in the fire plume. High levels of ozone precursors (NOx, CO) were simulated in the smoke plume which led to the depletion of ozone levels above and downwind of the burning zone. This depletion of ozone was indeed observed at ground-based stations but with a higher impact than simulated. The difference may be explained by the simplified design of the model with no anthropogenic sources and no interaction of the smoke aerosols with the photolysis rates. Ozone production was modelled tens of kilometres downwind of the ignition zone out of the coast.

Strada, S.; Mari, C.; Filippi, J.-B.; Bosseur, F.

2012-05-01

298

Anthropogenic Aerosol Radiative Forcing in Asia Derived From Regional Models With Atmospheric and Aerosol Data Assimilation  

SciTech Connect

A high-resolution estimate of monthly 3D aerosol solar heating rates and surface solar fluxes in Asia from 2001 to 2004 is described here. This product stems from an Asian aerosol assimilation project, in which a) the PNNL regional model bounded by the NCEP reanalyses was used to provide meteorology, b) MODIS and AERONET data were integrated for aerosol observations, c) the Iowa aerosol/chemistry model STEM-2K1 used the PNNL meteorology and assimilated aerosol observations, and d) 3D (X-Y-Z) aerosol simulations from the STEM-2K1 were used in the Scripps Monte-Carlo Aerosol Cloud Radiation (MACR) model to produce total and anthropogenic aerosol direct solar forcing for average cloudy skies. The MACR model and STEM both used the PNNL model resolution of 0.45º×0.4º in the horizontal and of 23 layers in the troposphere. The 2001–2004 averaged anthropogenic all-sky aerosol forcing is ?1.3 Wm-2 (TOA), +7.3 Wm-2 (atmosphere) and ?8.6 Wm-2 (surface) averaged in Asia (60?138°E & Eq. ?45°N). In the absence of AERONET SSA assimilation, absorbing aerosol concentration (especially BC aerosol) is much smaller, giving ?2.3 Wm-2 (TOA), +4.5 Wm-2 (atmosphere) and ?6.8 Wm-2 (surface), averaged in Asia. In the vertical, monthly forcing is mainly concentrated below 600hPa with maxima around 800hPa. Seasonally, low-level forcing is far larger in dry season than in wet season in South Asia, whereas the wet season forcing exceeds the dry season forcing in East Asia. The anthropogenic forcing in the present study is similar to that in Chung et al.’s [2005] in overall magnitude but the former offers fine-scale features and simulated vertical profiles. The interannual variability of the computed anthropogenic forcing is significant and extremely large over major emission outflow areas. In view of this, the present study’s estimate is within the implicated range of the 1999 INDOEX result. However, NCAR/CCSM3’s anthropogenic aerosol forcing is much smaller than the present study’s estimate at the surface, and is outside of what the INDOEX findings can support.

Chung, Chul Eddy; Ramanathan, V.; Carmichael, Gregory; Kulkarni, S.; Tang, Youhua; Adhikary, Bhupesh; Leung, Lai-Yung R.; Qian, Yun

2010-07-05

299

Anthropogenic aerosol radiative forcing in Asia derived from regional models with atmospheric and aerosol data assimilation  

NASA Astrophysics Data System (ADS)

An estimate of monthly 3-D aerosol solar heating rates and surface solar fluxes in Asia from 2001 to 2004 is described here. This product stems from an Asian aerosol assimilation project, in which a) the PNNL regional model bounded by the NCEP reanalyses was used to provide meteorology, b) MODIS and AERONET data were integrated for aerosol observations, c) the Iowa aerosol/chemistry model STEM-2K1 used the PNNL meteorology and assimilated aerosol observations, and d) 3-D (X-Y-Z) aerosol simulations from the STEM-2K1 were used in the Scripps Monte-Carlo Aerosol Cloud Radiation (MACR) model to produce total and anthropogenic aerosol direct solar forcing for average cloudy skies. The MACR model and STEM-2K1 both used the PNNL model resolution of 0.45°×0.4° in the horizontal and of 23 layers in the troposphere. The 2001-2004 averaged anthropogenic all-sky aerosol forcing is -1.3 Wm-2 (TOA), +7.3 Wm-2 (atmosphere) and -8.6 Wm-2 (surface) averaged in Asia (60-138° E and Equator-45° N). In the absence of AERONET SSA assimilation, absorbing aerosol concentration (especially BC aerosol) is much smaller, giving -2.3 Wm-2 (TOA), +4.5 Wm-2 (atmosphere) and -6.8 Wm-2 (surface), averaged in Asia. In the vertical, monthly forcing is mainly concentrated below 600 hPa with maximum around 800 hPa. Seasonally, low-level forcing is far larger in dry season than in wet season in South Asia, whereas the wet season forcing exceeds the dry season forcing in East Asia. The anthropogenic forcing in the present study is similar to that in Chung et al. (2005) in overall magnitude but the former offers fine-scale features and simulated vertical profiles. The interannual variability of the computed anthropogenic forcing is significant and extremely large over major emission outflow areas. Given the interannual variability, the present study's estimate is within the implicated range of the 1999 INDOEX result.

Chung, C. E.; Ramanathan, V.; Carmichael, G.; Kulkarni, S.; Tang, Y.; Adhikary, B.; Leung, L. R.; Qian, Y.

2010-07-01

300

Anthropogenic aerosol radiative forcing in Asia derived from regional models with atmospheric and aerosol data assimilation  

NASA Astrophysics Data System (ADS)

A high-resolution estimate of monthly 3-D aerosol solar heating rates and surface solar fluxes in Asia from 2001 to 2004 is described here. This product stems from an Asian aerosol assimilation project, in which a) the PNNL regional model bounded by the NCEP reanalyses was used to provide meteorology, b) MODIS and AERONET data were integrated for aerosol observations, c) the Iowa aerosol/chemistry model STEM-2K1 used the PNNL meteorology and assimilated aerosol observations, and d) 3-D (X-Y-Z) aerosol simulations from the STEM-2K1 were used in the Scripps Monte-Carlo Aerosol Cloud Radiation (MACR) model to produce total and anthropogenic aerosol direct solar forcing for average cloudy skies. The MACR model and STEM both used the PNNL model resolution of 0.45°×0.4° in the horizontal and of 23 layers in the troposphere. The 2001-2004 averaged anthropogenic all-sky aerosol forcing is -1.3 W m-2 (TOA), +7.3 W m-2 (atmosphere) and -8.6 W m-2 (surface) averaged in Asia (60-138° E and Eq. -45° N). In the absence of AERONET SSA assimilation, absorbing aerosol concentration (especially BC aerosol) is much smaller, giving -2.3 W m-2 (TOA), +4.5 W m-2 (atmosphere) and -6.8 W mm-2 (surface), averaged in Asia. In the vertical, monthly forcing is mainly concentrated below 600 hPa with maxima around 800 hPa. Seasonally, low-level forcing is far larger in dry season than in wet season in South Asia, whereas the wet season forcing exceeds the dry season forcing in East Asia. The anthropogenic forcing in the present study is similar to that in Chung et al. (2005) in overall magnitude but the former offers fine-scale features and simulated vertical profiles. The interannual variability of the computed anthropogenic forcing is significant and extremely large over major emission outflow areas. Given the interannual variability, the present study's estimate is within the implicated range of the 1999 INDOEX result. However, NCAR/CCSM3's anthropogenic aerosol forcing is much smaller than the present study's estimate at the surface, and is outside of what the INDOEX findings can support.

Chung, C. E.; Ramanathan, V.; Carmichael, G.; Kulkarni, S.; Tang, Y.; Adhikary, B.; Leung, L. R.; Qian, Y.

2010-01-01

301

Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions  

NASA Astrophysics Data System (ADS)

This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer-Aerodynamic Particle Sizer (H-DMA-APS). Similar to former studies, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-?m range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The average hygroscopic particle growth factors at 90 % RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 ?m. The data recorded between 12 August and 20 October 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp?150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in continentally influenced air masses. Particle size distributions and hygroscopic growth factors were used to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its summer daytime values around 70-80 %, up to 50-70 % of the calculated visibility reduction was due to the hygroscopic growth of the particles by water compared to the effect of the dry particles alone. The estimated aerosol direct radiative forcings for both, marine and continentally influenced air masses were negative indicating a net cooling of the atmosphere due to the aerosol. The radiative forcing ?Fr was nevertheless governed by the total aerosol concentration most of the time: ?Fr was typically more negative for continentally influenced aerosols (ca. -4 W m-2) compared to rather clean marine aerosols (ca. -1.5 W m-2). When RH occasionally reached 90 % in marine air masses, ?Fr even reached values down to -7 W m-2. Our results emphasize, on the basis of explicit particle hygroscopicity measurements, the relevance of ambient RH for the radiative forcing of regional atmospheres.

Stock, M.; Cheng, Y. F.; Birmili, W.; Massling, A.; Wehner, B.; Müller, T.; Leinert, S.; Kalivitis, N.; Mihalopoulos, N.; Wiedensohler, A.

2011-05-01

302

Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions  

NASA Astrophysics Data System (ADS)

This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer - Aerodynamic Particle Sizer (H-DMA-APS). Like in several studies before, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-?m range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The hygroscopic particle growth factors at 90% RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 ?m. All data recorded between 12 August and 20 October, 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp ? 150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in more continentally influenced air masses. Particle size distributions and hygroscopic growth factors were employed to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its daytime values around 70-80% in summer, up to 50-70% of the calculated visibility reduction was due to the hygroscopic growth of the particles by water compared to the effect of the dry particles alone. The estimated aerosol direct radiative forcings for both, marine and continentally influenced air masses were negative indicating a net cooling of the atmosphere due to the aerosol. The radiative forcing ?Fr was, nevertheless, dominated by the total aerosol concentration most of the time: ?Fr was typically more negative for continentally influenced aerosols (ca. -4 W m-2) compared to rather clean marine aerosols (ca. -1.5 W m-2). When RH occasionally reached 90% in marine air, ?Fr even reached values down to -7 W m-2. Our results emphasize, on the basis of explicit particle hygroscopicity measurements, the relevance of ambient relative humidity for the radiative forcing of regional atmospheres.

Stock, M.; Cheng, Y. F.; Birmili, W.; Massling, A.; Wehner, B.; Müller, T.; Leinert, S.; Kalivitis, N.; Mihalopoulos, N.; Wiedensohler, A.

2010-11-01

303

Observations and simulations of synoptic, regional, and local variations in atmospheric CO2  

NASA Astrophysics Data System (ADS)

Synoptic events may play an important role in determining the CO2 spatial distribution and temporal variations on a regional scale. In this study, we chose a front that passed the WLEF tower site on 16 August 2001, which had the most significant CO2 concentration variation in our case pool. The CO2 concentration, or [CO2], at the WLEF site had a strong dip and an increasing trend before the front arrived and a decreasing trend afterward. The concentration at 396 m above the ground varied by more than 40 ppm within 36 hours. We investigated the CO2 variations associated with this frontal case using a fully coupled model of land surface physics and carbon exchange (SiB 2.5) and the atmosphere (RAMS 5.04), in which CO2 was treated as a free variable and used to determine photosynthesis rate. Our simulation showed that high-[CO2] air mass was built up in the southern Great Plains on 14 and15 August 2001 because of the slow photosynthesis rate caused by hot and dry air over Oklahoma and Texas and the relatively strong nighttime respiration in the southeast United States. The low-[CO2] air to the southwest of Wisconsin and the high-[CO2] air over Kansas and Oklahoma traveled north and was responsible for part of the [CO2] variations at the WLEF site from 15 to 16 August 2001. Surface weather station confirmed the hot and dry weather in Oklahoma and Texas in this event, and the tower observations corroborated the existence of southwest-northeast concentration gradient. Weak daytime photosynthesis on 15 August 2001 and stronger nighttime respiration on 16 August 2001 under overcast sky condition were also partially responsible for the quick CO2 accumulation at the lower levels at the WLEF site before the front's arrival. This case study confirmed the existence of mixing signals from at least two different scales: large-scale horizontal advection and local ecosystem response to the changing weather. SiB-RAMS showed its strength in simulating the coherent anomalies in biospheric CO2 flux and in the regional weather pattern. Further refinement of the model is needed to better capture the timing and location of synoptic events and CO2 signals that travel across North America. Exploitation of continuous tower data in data assimilation and inverse modeling to determine regional sources and sinks will require careful error attribution to either transport or surface flux estimates.

Wang, Jih-Wang; Denning, A. Scott; Lu, Lixin; Baker, Ian T.; Corbin, Katherine D.; Davis, Kenneth J.

2007-02-01

304

Influence of Fuel Combustion Gases on the Oxygen Levels in City Atmosphere  

Microsoft Academic Search

Air, which is the material that composes the atmosphere, is a mixture of invisible gases. The atmospheric air consists of approximately 78% nitrogen and 21% oxygen. The remainder is made up of argon, carbon dioxide, several other gases, and water vapor. The combustion of fossil fuels is the greatest source of atmospheric pollution. A convenient way to develop quantitative theory

A. Demirbas

2008-01-01

305

Factors Influencing Regional Municipal Solid Waste Management Strategies  

Microsoft Academic Search

Although regionalization policies have been proven as good strategies for municipal solid waste (MSW) management in previous studies, the optimal allocation of the waste stream is significantly affected by several influential factors, thus further investigation of the impacts of these factors on regional MSW management strategies is necessary. This study demonstrated the impacts of waste-to-electricity transformation coefficient (WETC) of incinerators

Chungching Wang; Min-Der Lin; Chenfang Lin; Kevin Tory; Dale Hess; Sunhee Lee; Manuela Burgers; Bill Lilley; Richard Baldauf; Eben Thoma; Michael Hays; Richard Shores; John Kinsey; Brian Gullett; Sue Kimbrough; Vlad Isakov; Thomas Long; Richard Snow; Andrey Khlystov; Jason Weinstein; Fu-Lin Chen; Robert Seila; David Olson; Ian Gilmour; Seung-Hyun Cho; Nealson Watkins; Patricia Rowley; Gary Whitten; Greg Yarwood; Marc Carreras-Sospedra; Donald Dabdub; Jacob Brouwer; Eladio Knipping; Naresh Kumar; Ken Darrow; Anne Hampson; Bruce Hedman; James Droppo; Bruce Napier; Cynthia Howard-Reed; Victor Henzel; Steven Nabinger; Andrew Persily; B. deCastro; Lu Wang; Jana Mihalic; Patrick Breysse; Alison Geyh; Timothy Buckley; M. Garci´a; M. Sa´nchez; Isidro rez; Beatriz Torre; Gui Li; Alex Visscher; Seoung Kim; Chivalai Temiyasathit; Victoria Chen; Sun-Kyoung Park; Melanie Sattler; Armistead Russell

2008-01-01

306

Neutral atmospheric influences of the solar proton events in October-November 2003  

NASA Astrophysics Data System (ADS)

The large solar storms in October-November 2003 caused solar proton events (SPEs) at the Earth and impacted the middle atmospheric polar cap regions. Although occurring near the end of the maximum of solar cycle 23, the fourth largest period of SPEs measured in the past 40 years happened 28-31 October 2003. The highly energetic protons associated with the SPEs produced ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which led to the production of odd hydrogen (HOx) and odd nitrogen (NOy). NOx (NO + NO2) was observed by the UARS HALOE instrument to increase over 20 ppbv throughout the Southern Hemisphere polar lower mesosphere. The NOAA 16 SBUV/2 instrument measured a short-term ozone depletion of 40% in the Southern Hemisphere polar lower mesosphere, probably a result of the HOx increases. SBUV/2 observations showed ozone depletions of 5-8% in the southern polar upper stratosphere lasting days beyond the events, most likely a result of the NOy enhancements. Longer-term Northern Hemisphere polar total ozone decreases of >0.5% were predicted to last for over 8 months past the events with the Goddard Space Flight Center two-dimensional model. Although the production of NOy constituents is the same in both hemispheres, the NOy constituents have a much larger impact in the northern than the southern polar latitudes because of the seasonal differences between the two hemispheres. These observations and model computations illustrate the substantial impact of solar protons on the polar neutral middle atmosphere.

Jackman, Charles H.; Deland, Matthew T.; Labow, Gordon J.; Fleming, Eric L.; Weisenstein, Debra K.; Ko, Malcolm K. W.; Sinnhuber, Miriam; Russell, James M.

2005-09-01

307

Identification of atmospheric mercury sources and transport pathways on local and regional sales  

Microsoft Academic Search

Mercury (Hg) is a hazardous air pollutant and bioaccumulative neurotoxin whose intricate atmospheric chemistry complicates our ability to define Hg source-receptor relationships on all scales. Our detailed measurements of Hg in its different forms together with atmospheric tracers have improved our understanding of Hg chemistry and transport. Daily-event precipitation samples collected from 1995 to 2006 in Underhill, VT were examined

Lynne E. Gratz

2010-01-01

308

Titan's atmospheric and surface properties of the Ontario Lacus region from Cassini\\/VIMS remote sensing  

Microsoft Academic Search

The existence of oceans or lakes of liquid hydrocarbons on Titan's surface was predicted more than 20 years ago. These would serve as a source of atmospheric methane and would also contain the end products of the photochemical reactions occurring high in the atmosphere. Although no oceans were ever found, lake-like features poleward of 70°N were first detected by the

A. Negrão; A. Adriani; M. Moriconi; A. Coradini; E. D'Aversa; G. Filacchione; J. Lunine

2009-01-01

309

The effect of stabilizing atmospheric carbon dioxide concentrations on global and regional climate change  

Microsoft Academic Search

The effect on climate of stabilising atmospheric carbon dioxide concentrations at 550 ppm and 750 ppm is investigated using a coupled ocean-atmosphere model and compared with the response to a baseline case (1% per year increase in carbon dioxide concentrations beyond 1990). Changes in other well-mixed greenhouse gases are not considered (although these are expected to increase in the future),

J. F. B. Mitchell; T. C. Johns; W. J. Ingram; J. A. Lowe

2000-01-01

310

Influence of atmospheric vapour pressure deficit on ozone responses of snap bean (Phaseolus vulgaris L.) genotypes  

PubMed Central

Environmental conditions influence plant responses to ozone (O3), but few studies have evaluated individual factors directly. In this study, the effect of O3 at high and low atmospheric vapour pressure deficit (VPD) was evaluated in two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156) used as O3 bioindicator plants. Plants were grown in outdoor controlled-environment chambers in charcoal-filtered air containing 0 or 60 nl l?1 O3 (12 h average) at two VPDs (1.26 and 1.96 kPa) and sampled for biomass, leaf area, daily water loss, and seed yield. VPD clearly influenced O3 effects. At low VPD, O3 reduced biomass, leaf area, and seed yield substantially in both genotypes, while at high VPD, O3 had no significant effect on these components. In clean air, high VPD reduced biomass and yield by similar fractions in both genotypes compared with low VPD. Data suggest that a stomatal response to VPD per se may be lacking in both genotypes and it is hypothesized that the high VPD resulted in unsustainable transpiration and water deficits that resulted in reduced growth and yield. High VPD- and water-stress-induced stomatal responses may have reduced the O3 flux into the leaves, which contributed to a higher yield compared to the low VPD treatment in both genotypes. At low VPD, transpiration increased in the O3 treatment relative to the clean air treatment, suggesting that whole-plant conductance was increased by O3 exposure. Ozone-related biomass reductions at low VPD were proportionally higher in S156 than in R123, indicating that differential O3 sensitivity of these bioindicator plants remained evident when environmental conditions were conducive for O3 effects. Assessments of potential O3 impacts on vegetation should incorporate interacting factors such as VPD.

Fiscus, Edwin L.; Booker, Fitzgerald L.; Sadok, Walid; Burkey, Kent O.

2012-01-01

311

Influence of plant diversity and elevated atmospheric carbon dioxide levels on belowground bacterial diversity  

PubMed Central

Background Changes in aboveground plant species diversity as well as variations of environmental conditions such as exposure of ecosystems to elevated concentrations of atmospheric carbon dioxide may lead to changes in metabolic activity, composition and diversity of belowground microbial communities, both bacterial and fungal. Results We examined soil samples taken from a biodiversity × CO2 grassland experiment where replicate plots harboring 5, 12, or 31 different plant species had been exposed to ambient or elevated (600 ppm) levels of carbon dioxide for 5 years. Analysis of soil bacterial communities in these plots by temporal temperature gradient gel electrophoresis (TTGE) showed that dominant soil bacterial populations varied only very little between different experimental treatments. These populations seem to be ubiquitous. Likewise, screening of samples on a high-resolution level by terminal restriction fragment length polymorphism (T-RFLP) showed that increased levels of carbon dioxide had no significant influence on both soil bacterial community composition (appearance and frequency of operational taxonomic units, OTUs) and on bacterial richness (total number of different OTUs). In contrast, differences in plant diversity levels had a significant effect on bacterial composition but no influence on bacterial richness. Regarding species level, several bacterial species were found only in specific plots and were related to elevated carbon dioxide or varying plant diversity levels. For example, analysis of T-RFLP showed that the occurrence of Salmonella typhimurium was significantly increased in plots exposed to elevated CO2 (P < 0.05). Conclusion Plant diversity levels are affecting bacterial composition (bacterial types and their frequency of occurrence). Elevated carbon dioxide does not lead to quantitative alteration (bacterial richness), whereas plant diversity is responsible for qualitative changes (bacterial diversity).

Gruter, Dominique; Schmid, Bernhard; Brandl, Helmut

2006-01-01

312

Atmospheric inverse modeling to constrain regional-scale CO2 budgets at high spatial and temporal resolution  

NASA Astrophysics Data System (ADS)

We present an inverse modeling framework designed to constrain CO2 budgets at regional scales. The approach captures atmospheric transport processes in high spatiotemporal resolution by coupling a mesoscale model with Lagrangian Stochastic backward trajectories. Terrestrial biosphere CO2 emissions are generated through a simple diagnostic flux model that splits the net ecosystem exchange into its major components of gross primary productivity and autotrophic and heterotrophic respirations. The modeling framework assimilates state-of-the-art data sets for advected background CO2 and anthropogenic fossil fuel emissions as well as highly resolved remote sensing products. We introduce a Bayesian inversion setup, optimizing a posteriori flux base rates for surface types that are defined through remote sensing information. This strategy significantly reduces the number of parameters to be optimized compared with solving fluxes for each individual grid cell, thus permitting description of the surface in a very high resolution. The model is tested using CO2 concentrations measured in the fall and winter of 2006 at two AmeriFlux sites in Oregon. Because this database does not cover a full seasonal cycle, we focus on conducting model sensitivity tests rather than producing quantitative CO2 flux estimates. Sensitivity tests on the influence of spatial and temporal resolution indicate that optimum results can be obtained using 4 h time steps and grid sizes of 6 km or less. Further tests demonstrate the importance of dividing biome types by ecoregions to capture their different biogeochemical responses to external forcings across climatic gradients. Detailed stand age information was shown to have a positive effect on model performance.

GöCkede, Mathias; Michalak, Anna M.; Vickers, Dean; Turner, David P.; Law, Beverly E.

2010-08-01

313

Influence of atmospheric turbulence on imaging quality of electro-optical sensors in different climates  

NASA Astrophysics Data System (ADS)

During long-term experiments FGAN-FOM measured Cn2 values over land with identical scintillometers in two different climates, in moderate climate in mid-Europe and in arid climate. Since Cn2 usually changes as a function of time-of-day and of season its influence on electro-optical systems can only be expressed in a statistical way. The cumulative frequencies of occurrence were calculated for a time period of one month for different times of the day. The statistical analysis was applied to calculate the effects of atmospheric turbulence on sensor performance like turbulence MTF, the resolution limit due to turbulence and intensity fluctuation. The calculations were performed for a SWIR sensor (active imaging system) and for typical MWIR and LWIR warning sensors. Turbulence MTF were calculated for a slant path of 5 km from the ground to a height of 100 m for upward and downward looking cases. For horizontal paths at a height of 2 m and 30 m the resolution limits due to turbulence were compared with the corresponding diffraction-limited ones. Calculations of the normalized intensity fluctuations were carried out for two slant propagation paths (zenith angle ? = 30° and 80°).

Weiss-Wrana, Karin R.

2004-02-01

314

Influence of atmospheric parameters on downward longwave radiation and features of its regime in Moscow  

NASA Astrophysics Data System (ADS)

Measurement results of downward longwave radiation (DLR) in a wavelength range of 3.5-50 ?m are considered which have been obtained with the use of a precision IR radiometer (Eppley pyrgeometer) of the PIR model at the Meteorological Observatory of Moscow State University in 2008-2010. The influence of air temperature and atmospheric moisture content on the DLR values has been analyzed; correlations between DLR and the above parameters have been found. The effect of clouds on DLR has been estimated: DLR increases by about 30% in daytime and by 25% in nighttime under overcast low clouds. The annual average DLR in Moscow is 305 W/m2, with a minimum in December-March and a maximum in July-August. Variations in DLR throughout a year can exceed 250 W/m2. The daily average amplitude is 18-33 W/m2 in summer and 6-13 W/m2 in winter. An increase in DLR by about 40 W/m2 is noted under conditions of haze from forest and peat-bog fires and an aerosol optical depth of about 4 at a wavelength of 500 nm.

Nezval, E. I.; Chubarova, N. E.; Gröbner, J.; Omura, A.

2012-11-01

315

Variation trends and influencing factors of total gaseous mercury in the Pearl River Delta—A highly industrialised region in South China influenced by seasonal monsoons  

NASA Astrophysics Data System (ADS)

Studies on atmospheric mercury in the Pearl River Delta (PRD) region are important because of the economic relevance of this region to China, because of its economic developmental pattern and because it is a highly industrialised area influenced by the strong seasonal monsoons. Total gaseous mercury (TGM), meteorological parameters and criteria pollutant concentrations were measured at Mt. Dinghu (DH, a regional monitoring site) and Guangzhou (GZ, an urban monitoring site) in the PRD region from October 2009 to April 2010 and from November 2010 to November 2011, respectively. The ranges of daily average TGM concentrations at the DH and GZ sites were 1.87–29.9 ng m?3 (5.07 ± 2.89 ng m?3) and 2.66–11.1 ng m?3 (4.60 ± 1.36 ng m?3), respectively, which were far more significant than the background values in the Northern Hemisphere (1.5–1.7 ng m?3), suggesting that the atmosphere in the PRD has suffered from mercury pollution. Similar TGM seasonal distributions at the two sites were observed, with a descending order of spring, winter, autumn and summer. The different seasonal monsoons were the dominant factor controlling the seasonal variability of the TGM, with variations in the boundary layer and oxidation also possibly partially contributing. Different diurnal patterns of the TGM at two sites were observed. TGM levels during the daytime were higher than those during the nighttime and were predominantly influenced by mountain and valley winds at the DH site, whereas the opposite trend was evident at the GZ site, which was primarily influenced by the boundary-layer height and O3 concentration. During the monitoring period, the correlations between the daily TGM levels and the SO2 and NO2 levels at the DH site were significant (r = 0.36, p < 0.001; r = 0.29, p < 0.001), suggesting that coal-fired emission is an important source of mercury for this regional monitoring site. At the GZ site, the correlations between the daily TGM level and the NO, NO2, CO levels were significant (r = 0.501, p < 0.001; r = 0.579, p < 0.001; r = 0.358, p < 0.001). However, TGM was partially correlated with SO2, suggesting that the combined vehicle emissions and coal combustion were the dominant mercury sources for this urban monitoring site. The TGM distribution figure, which related to the wind-rose pattern and the distribution figure of emission sources, indicated significant contributions from anthropogenic emission sources.

Chen, Laiguo; Liu, Ming; Xu, Zhencheng; Fan, Ruifang; Tao, Jun; Chen, Duohong; Zhang, Deqiang; Xie, Donghai; Sun, Jiaren

2013-10-01

316

EVIDENCE FOR WIDESPREAD COOLING IN AN ACTIVE REGION OBSERVED WITH THE SDO ATMOSPHERIC IMAGING ASSEMBLY  

SciTech Connect

A well-known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times than hotter channels. This time lag is understood to be the result of hot coronal loop plasma cooling through these lower respective temperatures. However, loops typically comprise only a minority of the total emission in active regions (ARs). Is this cooling pattern a common property of AR coronal plasma, or does it only occur in unique circumstances, locations, and times? The new Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) data provide a wonderful opportunity to answer this question systematically for an entire AR. We measure the time lag between pairs of SDO/AIA EUV channels using 24 hr of images of AR 11082 observed on 2010 June 19. We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the AR including the diffuse emission between loops for the entire 24 hr duration. The pattern persists consistently for all channel pairs and choice of window length within the 24 hr time period, giving us confidence that the plasma is cooling from temperatures of greater than 3 MK, and sometimes exceeding 7 MK, down to temperatures lower than {approx}0.8 MK. This suggests that the bulk of the emitting coronal plasma in this AR is not steady; rather, it is dynamic and constantly evolving. These measurements provide crucial constraints on any model which seeks to describe coronal heating.

Viall, Nicholeen M.; Klimchuk, James A. [NASA Goddard Space Flight Center, Solar Physics Laboratory, Greenbelt, MD 20706 (United States)

2012-07-01

317

Process Model for Studying Regional 13C Stable Isotope Exchange between Vegetation and Atmosphere  

NASA Astrophysics Data System (ADS)

The variation of the stable isotope 13CO2 in the air in exchange with land ecosystems results from fractionation processes in both plants and soil during photosynthesis and respiration. Its diurnal and seasonal variations therefore contain information on the carbon cycle. We developed a model (BEPS-iso) to simulate its exchange between vegetation and the atmosphere. To be useful for regional carbon cycle studies, the model has the following characteristics: (i) it considers the turbulent mixing in the vertical profile from the soil surface to the top of the planetary boundary layer (PBL); (ii) it scales individual leaf photosynthetic discrimination to the whole canopy through the separation of sunlit and shaded leaf groups; (iii) through simulating leaf-level photosynthetic processes, it has the capacity to mechanistically examine isotope discrimination resulting from meteorological forcings, such as radiation, precipitation and humidity; and (iv) through complete modeling of radiation, energy and water fluxes, it also simulates soil moisture and temperature needed for estimating ecosystem respiration and the 13C signal from the soil. After validation using flask data acquired at 20 m level on a tower near Fraserdale, Ontario, Canada, during intensive campaigns (1998-2000), the model has been used for several purposes: (i) to investigate the diurnal and seasonal variations in the disequilibrium in 13C fractionation between ecosystem respiration and photosynthesis, which is an important step in using 13C measurements to separate these carbon cycle components; (ii) to quantify the 13C rectification in the PBL, which differs significantly from CO2 rectification because of the diurnal and seasonal disequilibriums; and (iii) to model the 13C spatial and temporal variations over the global land surface for the purpose of CO2 inversion using 13C as an additional constraint.

Chen, J. M.; Chen, B.; Huang, L.; Tans, P.; Worthy, D.; Ishizawa, M.; Chan, D.

2007-12-01

318

Atmospheric three-dimensional inverse modeling of regional industrial emissions and global oceanic uptake of carbon tetrachloride  

NASA Astrophysics Data System (ADS)

Carbon tetrachloride (CCl4) has substantial stratospheric ozone depletion potential and its consumption is controlled under the Montreal Protocol and its amendments. We implement a Kalman filter using atmospheric CC14 measurements and a 3-dimensional chemical transport model to estimate the interannual regional industrial emissions and seasonal global oceanic uptake of CCl4 for the period of 1996-2004. The Model of Atmospheric Transport and Chemistry (MATCH), driven by offline National Center for Environmental Prediction (NCEP) reanalysis meteorological fields, is used to simulate CCl4 mole fractions and calculate their sensitivities to regional sources and sinks using a finite difference approach. High frequency observations from the Advanced Global Atmospheric Gases Experiment (AGAGE) and NOAA Earth System Research Laboratory (ESRL) and low frequency flask observations are together used to constrain the source and sink magnitudes, estimated as factors that multiply the a priori fluxes. Although industry data imply that the global industrial emissions were substantially declining with large interannual variations, the optimized results show only small interannual variations and a small decreasing trend. The global surface CCl4 mole fractions were declining in this period because the CCl4 oceanic and stratospheric sinks exceeded the industrial emissions. Compared to the a priori values, the inversion results indicate substantial increases in industrial emissions originating from the South Asian/Indian and Southeast Asian regions, and significant decreases in emissions from the European and North American regions.

Xiao, X.; Prinn, R. G.; Fraser, P. J.; Weiss, R. F.; Simmonds, P. G.; O'Doherty, S.; Miller, B. R.; Salameh, P. K.; Harth, C. M.; Krummel, P. B.; Golombek, A.; Porter, L. W.; Elkins, J. W.; Dutton, G. S.; Hall, B. D.; Steele, L. P.; Wang, R. H. J.; Cunnold, D. M.

2010-05-01

319

Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora  

SciTech Connect

The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the postmidnight sector. A combination of chemical release rocket wind measurements, intrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of {approximately}100 m s{sup -1} developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of {approximately}150 m s{sup -1} developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nomially unstable with a Richardson number of {approximately}0.08. 17 refs., 12 figs.

Larsen, M.F.; Marshall, T.R. [Clemson Univ., Clemson, SC (United States); Mikkelsen, I.S. [Meteorological Institute, Copenhagen (Denmark)] [and others

1995-09-01

320

Atmospheric iodine levels influenced by sea surface emissions of inorganic iodine  

NASA Astrophysics Data System (ADS)

Naturally occurring bromine- and iodine-containing compounds substantially reduce regional, and possibly even global, tropospheric ozone levels. As such, these halogen gases reduce the global warming effects of ozone in the troposphere, and its capacity to initiate the chemical removal of hydrocarbons such as methane. The majority of halogen-related surface ozone destruction is attributable to iodine chemistry. So far, organic iodine compounds have been assumed to serve as the main source of oceanic iodine emissions. However, known organic sources of atmospheric iodine cannot account for gas-phase iodine oxide concentrations in the lower troposphere over the tropical oceans. Here, we quantify gaseous emissions of inorganic iodine following the reaction of iodide with ozone in a series of laboratory experiments. We show that the reaction of iodide with ozone leads to the formation of both molecular iodine and hypoiodous acid. Using a kinetic box model of the sea surface layer and a one-dimensional model of the marine boundary layer, we show that the reaction of ozone with iodide on the sea surface could account for around 75% of observed iodine oxide levels over the tropical Atlantic Ocean. According to the sea surface model, hypoiodous acid--not previously considered as an oceanic source of iodine--is emitted at a rate ten-fold higher than that of molecular iodine under ambient conditions.

Carpenter, Lucy J.; MacDonald, Samantha M.; Shaw, Marvin D.; Kumar, Ravi; Saunders, Russell W.; Parthipan, Rajendran; Wilson, Julie; Plane, John M. C.

2013-02-01

321

Generation of VHF radio emissions by electric discharges in the lower atmosphere over a seismic region  

NASA Astrophysics Data System (ADS)

Observational data of the seismic related VHF radio emissions at 41 and 53 MHz obtained at the four stations of Create Island are presented. The epicenter of EQs is located at the distance more than 300 km behind the horizon. It was shown that VHF radiation is generated at the altitudes 1-10 km in the atmosphere over the epicenter of EQs. The theory of generation of electromagnetic radiation by random electric discharges was developed. These discharges are excited by DC electric field enhanced up to the breakdown value in the atmosphere. The field is connected with the electric current flowing in the atmosphere-ionosphere circuit, whose source is generated by convective transport of charged aerosols, which are injected in the atmosphere by soil gases during the enhancement of seismicity. Calculations of the spectrum of electromagnetic radiation are derived, and the theoretical results are confirmed by observation data.

Sorokin, V. M.; Ruzhin, Yu. Ya.; Yaschenko, A. K.; Hayakawa, M.

2011-04-01

322

Atmospheric CO2 as a Global Change Driver Influencing Plant-Animal Interactions  

Microsoft Academic Search

SYNOPSIS. Plants respond to changes in atmospheric carbon dioxide. To herbivores, the decreased leaf protein contents and increased C\\/N ratios common to all leaves under elevated atmospheric carbon dioxide imply a reduction in food quality. In addition to these fine-scale adjustments, the abundance of C3 and C4 plants (particularly grasses) are affected by atmospheric carbon dioxide. C 4 grasses currently

JAMES R. EHLERINGER; THURE E. CERLING; M. DENISE DEARING

2002-01-01

323

Influence of Asteroid and Comet Impacts on Atmospheric Abundances at Venus, Earth, and Mars  

NASA Astrophysics Data System (ADS)

Asteroid and comet impacts have undoubtedly altered the atmospheres of the terrestrial planets over billions of years. Impacts are capable of either delivering or removing atmospheric particles from a planet depending upon the characteristics of the impact. With many thousands of impacts large enough to alter the atmospheres of each terrestrial planet, all with varying compositions, velocities, impact angles, and sizes, it is not entirely clear how impacts have contributed to changes in atmospheric abundance over time. Some theoretical and numerical work has been undertaken in the past for generic individual impacts, and several studies have considered the net effect of impacts on the atmospheres of Mars and Earth over time. However, the full parameter space of atmospheric impact calculations remains unexplored, particularly in regards to Venus and the effect of oblique impacts on atmospheres. This work uses Monte Carlo simulations to model atmospheric erosion and delivery from impacts at Venus, Earth, and Mars. Flexibility in the code allows us to examine the effects of changing impactor populations (i.e. size and composition), velocity distributions, and angles of impact on the resultant atmospheric pressure, as well as the different sensitivities to these factors between the planets. The work we present relies on published analytic expressions for the effects of individual impacts. However, the results of detailed simulations of individual impacts (e.g. using the RAGE hydrocode) can be incorporated into our future modeling efforts to help validate these expressions.

Heath, Caitlin; Brain, D. A.

2013-10-01

324

Tracheal dead space influences regional ventilation measurement in dogs  

SciTech Connect

The lung volume at which airway closure begins during expiration (closing volume, CV) can be measured (1) with a radioactive bolus inspired at residual volume (RV) and (2) with the single-breath N2 elimination test. In previous studies in dogs, we observed that N2 CV was systematically larger than 133Xe bolus CV (Xe CV) (N2 CV %vital capacity (VC) = 35 +/- 2.3 (SE) vs. Xe CV %VC = 24 +/- 2.2, P less than 0.01). Because the regional RV in the dog is evenly distributed throughout the lung and all airways closed at RV, N2 CV is related to the regional distribution of the tracheal N2; differences between N2 and Xe CV could then be related to the size of the inhaled dead space. Simultaneous measurements of Xe and N2 CV were performed at various sites of Xe bolus injection while the regional distribution of the bolus was measured. Injections at the level of the carina increased Xe CV to a value (30 +/- 1.4%VC) near simultaneous N2 CV (32 +/- 1.5%VC) and increased the unevenness of regional distribution of the Xe bolus. The difference between N2 and Xe CV is then the result of the size of the inspired tracheal dead space. Moreover, comparisons between different values of Xe CV require injections of the boluses at the same distance from the carina.

Delaunois, L.; Boileau, R.; Martin, R.R. (McGill Univ., Royal Victoria Hospital, Montreal, Quebec (Canada))

1990-02-01

325

Socioeconomic Influences on Benzodiazepine Consumption in an Irish Region  

Microsoft Academic Search

Misuse of prescription sedatives is a significant problem for addiction treatment services. The aim of this study was to examine the prescribing of diazepam in disadvantaged Irish communities, and to identify factors which may predict diazepam consumption in that population. We examined prescribing trends for those aged 16–69 years in 2002 in a region of the state-funded General Medical Services

P. Quigley; C. Usher; K. Bennett; J. Feely

2006-01-01

326

Local and regional contributions to photochemical atmospheric pollution in southern France  

Microsoft Academic Search

In France, an important air quality surveillance network is organized by region. Each region has a number of measurement sites available. In southern France for each region studied, measurement sites show highly correlated variations of daily ozone maxima during the summer periods (from April to September). Thus, we can calculate a mean regional distribution representative of each region considered. We

Véronique Pont; Jacques Fontan

2000-01-01

327

Atmospheric background trace elements deposition in Tierra del Fuego region (Patagonia, Argentina), using transplanted Usnea barbata lichens  

Microsoft Academic Search

Lichen, Usnea barbata, transplants taken from Tierra del Fuego (south Patagonia, Argentina) were tested as potential biomonitors of atmospheric\\u000a airborne deposition in an apparently pristine environment. In 2005, lichens were sampled in a reference site (n?=?31) and transplanted in the northern Region of Tierra del Fuego. After, respectively, 1 month and 1 year of exposure, we\\u000a collected them. The aim of the

Marcelo Enrique Conti; Maria Grazia Finoia; Beatrice Bocca; Giustino Mele; Alessandro Alimonti; Anna Pino

328

Improved simulation of feedbacks between atmosphere and sea ice over the Arctic Ocean in a coupled regional climate model  

Microsoft Academic Search

Modeling sea ice in a realistic manner is still a great challenge, in particular with respect to the minimum ice extent at the end of the summer. Modified descriptions of ice growth, snow and ice albedo, and snow cover on ice have been incorporated into the coupled regional atmosphere–ocean–ice model HIRHAM–NAOSIM, and a series of sensitivity experiments has been performed

W. Dorn; K. Dethloff; A. Rinke

2009-01-01

329

Background concentrations of reactive gases and the impacts of long-range transport at the Jinsha regional atmospheric background station  

Microsoft Academic Search

Lorentz curve fittings are applied to frequency distributions of the concentrations of O3, CO, NO\\u000a x\\u000a and SO2 recorded at the Jinsha regional atmospheric background station (JSH) from June 2006 to July 2007, and the peak concentrations\\u000a of these species for the different seasons are obtained. The peak concentrations are considered to be representative of different\\u000a background levels for certain

WeiLi Lin; XiaoBin Xu; JunYing Sun; XiWen Liu; Ying Wang

330

High-resolution atmospheric absorption by water vapor in the 830-985 nm region: Evaluation of spectroscopic databases  

Microsoft Academic Search

We present high spectral resolution (0.05 cm-1) ground-based measurements of direct solar absorption in the clear-sky atmosphere by water vapor over the 830 to 985 nm (10,150-12,050 cm-1) region. Observations were made from the Rutherford Appleton Laboratory on several days in different seasons during 1999. Using these observations water vapor line data in HITRAN and the ESA-WVR database, derived from

K. M. Smith; D. A. Newnham

2001-01-01

331

High-resolution atmospheric absorption by water vapor in the 830–985 nm region: Evaluation of spectroscopic databases  

Microsoft Academic Search

We present high spectral resolution (0.05 cm?1) ground-based measurements of direct solar absorption in the clear-sky atmosphere by water vapor over the 830 to 985 nm (10,150–12,050 cm?1) region. Observations were made from the Rutherford Appleton Laboratory on several days in different seasons during 1999. Using these observations water vapor line data in HITRAN and the ESA-WVR database, derived from

K. M. Smith; D. A. Newnham

2001-01-01

332

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

NASA Astrophysics Data System (ADS)

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 processes at the ocean/atmosphere interface that create anomaly gradients in the meridional plane in a way which tends to alter the north-south movement of the seasonal cycle. This appears to be consistent with the intrinsic non-dipole character of the tropical Atlantic surface variability at the interannual time step and over the recent period, but produces abnormal amplitude and/or delayed excursions of the intertropical convergence zone (ITCZ). Connections with continental rainfall are approached through three (NCEP/NCAR and observed) rainfall indexes over the Nordeste region in Brazil, and the Guinea and Sahel zones in West Africa. These indices appear to be significantly linked to the SST component of the coupled modes only when the two Atlantic modes+the ENSO-like Nino3 index are taken into account in the regressions. This suggests that thermal forcing of continental rainfall is particularly sensitive to the linear combinations of some basic SST patterns, in particular to those that create meridional thermal gradients. The first mode in the Atlantic is associated with transequatorial pressure, moist static energy and precipitable water anomaly patterns which can explain abnormal location of the ITCZ particularly in northern winter, and hence rainfall variations in Nordeste. The second mode is more associated with in-phase variations of the same variables near the southern edge of the ITCZ, particularly in the Gulf of Guinea during the northern spring and winter. It is primarily linked to the amplitude and annual phase of the ITCZ excursions and thus to rainfall variations in Guinea. Connections with Sahel rainfall are less clear due to the difficulty for the model to correctly capture interannual variability over that region but the second Atlantic mode and the ENSO-like Pacific variability are clearly involved in the Sahel climate interannual fluctuations: anomalous dry (wet) situations tend to occur when warmer (cooler) waters are present in the eastern Pacific and the gulf of Guinea in northern summer which contribute to create a northward (southward) transequ

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

333

Assessment of ground-based atmospheric observations for verification of greenhouse gas emissions from an urban region  

PubMed Central

International agreements to limit greenhouse gas emissions require verification to ensure that they are effective and fair. Verification based on direct observation of atmospheric greenhouse gas concentrations will be necessary to demonstrate that estimated emission reductions have been actualized in the atmosphere. Here we assess the capability of ground-based observations and a high-resolution (1.3 km) mesoscale atmospheric transport model to determine a change in greenhouse gas emissions over time from a metropolitan region. We test the method with observations from a network of CO2 surface monitors in Salt Lake City. Many features of the CO2 data were simulated with excellent fidelity, although data-model mismatches occurred on hourly timescales due to inadequate simulation of shallow circulations and the precise timing of boundary-layer stratification and destratification. Using two optimization procedures, monthly regional fluxes were constrained to sufficient precision to detect an increase or decrease in emissions of approximately 15% at the 95% confidence level. We argue that integrated column measurements of the urban dome of CO2 from the ground and/or space are less sensitive than surface point measurements to the redistribution of emitted CO2 by small-scale processes and thus may allow for more precise trend detection of emissions from urban regions.

McKain, Kathryn; Wofsy, Steven C.; Nehrkorn, Thomas; Eluszkiewicz, Janusz; Ehleringer, James R.; Stephens, Britton B.

2012-01-01

334

Influence of microphysical schemes on atmospheric water in the Weather Research and Forecasting model  

NASA Astrophysics Data System (ADS)

This study examines how different microphysical parameterization schemes influence orographically-induced precipitation and the distributions of hydrometeors and water vapour for mid-latitude summer conditions in the Weather Research and Forecasting (WRF) model. A high-resolution two-dimensional idealized simulation is used to assess the differences between the schemes in which a moist air flow is interacting with a bell-shaped 2 km high mountain. Periodic lateral boundary conditions are chosen to recirculate atmospheric water in the domain. It is found that the 13 selected microphysical schemes conserve the water in the model domain. The gain or loss of water is less than 0.81% over a simulation time interval of 61 days. The differences of the microphysical schemes in terms of the distributions of water vapour, hydrometeors and accumulated precipitation are presented and discussed. The Kessler scheme, the only scheme without ice-phase processes, shows final values of cloud liquid water 14 times greater than the other schemes. The differences among the other schemes are not as extreme, but still they differ up to 79% in water vapour, up to 10 times in hydrometeors and up to 64% in accumulated precipitation at the end of the simulation. The microphysical schemes also differ in the surface evaporation rate. The WRF single-moment 3-class scheme has the highest surface evaporation rate compensated by the highest precipitation rate. The different distributions of hydrometeors and water vapour of the microphysical schemes induce differences up to 49 W m-2 in the downwelling shortwave radiation and up to 33 W m-2 in the downwelling longwave radiation.

Cossu, F.; Hocke, K.

2013-09-01

335

Conversion of Atmospheric Aerosol by Bacteria and Their Influence on Ice-Nucleation Activity  

NASA Astrophysics Data System (ADS)

The presence of microorganisms such as bacteria and fungi in the boundary layer of the atmosphere has been established for some time. These species can also convert organic aerosol species (e.g. dicarboxylic acids), a transformation that was so far assumed to occur only via physico-chemical pathways. As a result, the ice nucleation activity of certain aerosol species can be altered by biochemical transformations including metabolite production and bacterial growth and these new species as well as the microorganisms themselves can act as ice nuclei. In this study we have used dicarboxylic acids (DCA) as model nutrients, which are commonly observed in the aerosol population of the boundary layer. Pseudomonas syringae and Erwinia herbicolae are two types of bacteria that have been found to possess ice nucleation ability, caused by lipoglycoprotein, which consists of a sequence of amino acids that favor the formation of ice. The main objective was to look into the conversion of DCA by bacterial species, their ice nucleating ability and the identification of metabolites from bacterial activity. Furthermore, the influence of different parameters on the ice nucleation of bacteria was investigated. A Freezing Nuclei apparatus was used in order to assess the freezing temperature of a population of small drops to study both homogenous and heterogeneous nucleation of different concentrations of malonic acid containing bacterial species. An acid concentration in the lower Fg/l-range was chosen, matching earlier observations in an urban environment. Other varied parameters include the pH and bacterial membrane shearing. All labware was sterilized prior to use and airtight containers minimized external contamination. Malonic acid concentration was determined by gas chromatography with mass spectrometric detection (GC-MS) after esterification with a mixture of borontrifluoride and 1-propanol, modified from Kawamura, 1991. Malonic acid and its metabolites were identified by characteristic mass spectra.

Kos, G.; Shawi, M.; Ariya, P. A.

2004-05-01

336

First observations of an F-region turbulent upwelling coincident with severe E-region plasma and neutral atmosphere perturbations  

Microsoft Academic Search

Highly structured electron densities in the E and F regions over Puerto Rico during the night of February 20\\/21, 1999 were accompanied by intense coherent VHF radar backscatter from the E region and perturbations in neutral sodium in the mesosphere. Simultaneous observations of the event were made with the VHF Cornell University Portable Radar Interferometer (CUPRI) located near Isabela, PR,

Wesley E. Swartz; Stephen C. Collins; Michael C. Kelley; Jonathan J. Makela; Erhan Kudeki; Steve Franke; Julio Urbina; Nestor Aponte; Sixto González; Michael P. Sulzer; Jonathan S. Friedman

2002-01-01

337

Influence of the voltage polarity on the properties of a nanosecond surface barrier discharge in atmospheric-pressure air  

SciTech Connect

The properties of a surface barrier discharge in atmospheric-pressure air at different polarities of applied voltage were studied experimentally. The influence of the voltage polarity on the spatial structure of the discharge and the electric field in the discharge plasma was determined by means of spectroscopic measurements. It is found that the energy deposited in the discharge does not depend on the voltage polarity and that discharges of positive polarity are more homogenous and the electric fields in them are higher.

Nudnova, M. M.; Aleksandrov, N. L. [Moscow Institute of Physics and Technology (Russian Federation); Starikovskii, A. Yu. [Drexel University (United States)

2010-01-15

338

Study of the Influence of the Atmosphere on the Performance of an Imaging Microwave Radiometer.  

National Technical Information Service (NTIS)

Errors induced by the intervening atmosphere on the determination of ground parameters from a set of radiometers operating in two polarization states and in the frequency range from 5 to 90 GHz were analyzed. The precision with which the atmospheric param...

A. Guissard

1980-01-01

339

Influence of Wave Propagation on the Doppler Spreading of Atmospheric Gravity Waves  

Microsoft Academic Search

The ''Doppler spread'' theory of atmospheric gravity waves has developed rapidly in recent years, from an initial theory of wave spectra into a general parameterization of gravity wave effects for use in global models of the middle atmosphere. Yet the theory currently employs certain key approximations that have still to be tested. The author focuses on the omission of the

Stephen D. Eckermann

1997-01-01

340

Influence of barrier material and surface roughness on atmospheric pressure uniform dielectric barrier discharge in air  

Microsoft Academic Search

Summary form only given. An atmospheric pressure uniform discharge has a great potential for improving surface treatment, efficiency of ozone generation, de-NOx and so on. So far, we have studied a stable generation of atmospheric pressure uniform discharge using dielectric barrier discharge device, and we already reported that by elevating barrier temperature or by using acrylic barrier material, the discharge

N. Osawa; Y. Mochizuki; Y. Yoshioka

2009-01-01

341

The influence of convection on the atmospheric structures and observable properties of red giant stars.  

NASA Astrophysics Data System (ADS)

During the recent years significant progress has been made in the modeling of red giant atmospheres with the aid of 3D hydrodynamical model atmosphere codes. In this contribution we provide an overview of selected results obtained in this context by utilizing 3D hydrodynamical CO5BOLD stellar model atmospheres. Hydrodynamical simulations show that convective motions lead to significant differences in the atmospheric structures of red giants with respect to those predicted by the classical 1D model atmospheres. Results of these simulations also show that in certain cases 1D models fail to reproduce even the average properties of the 3D hydrodynamical models, such as P-T profiles. Large horizontal temperature fluctuations in the 3D model atmospheres, as well as differences between the temperature profiles of the average xtmean {3D} and 1D models, lead to large discrepancies in the strengths of spectral lines predicted by the 3D and 1D model atmospheres. This is especially important in models at lowest metallicities ([M/H]<-2.0) where the 3D-1D abundance differences may reach (or even exceed) -0.6 dex for lines of neutral atoms and molecules. We also discuss several simplifications and numerical aspects involved in the present 3D hydrodynamical modeling of red giant atmospheres, and briefly address several issues where urgent progress may be needed.

Ku?inskas, A.; Ludwig, H.-G.; Steffen, M.; Dobrovolskas, V.; Klevas, J.; Prakapavi?ius, D.; Caffau, E.; Bonifacio, P.

342

The influence of atmospheric zonal wave three on Antarctic sea ice variability  

Microsoft Academic Search

The study examines the relationship between atmospheric zonal wave three and Antarctic sea ice variability using an index of zonal wave three and sea ice concentration. The net sensible heat flux and the surface air temperature are used to explain the apparent atmosphere-sea ice interaction. The results show that zonal wave three forces an alternating pattern of equatorward (colder) and

M. N. Raphael

2007-01-01

343

The influence of atmospheric circulation on plant phenological phases in central and eastern Europe  

Microsoft Academic Search

The objective of this study is to analyse relationships between the start dates of spring phenological phases and large-scale atmospheric circulation patterns. The timing of phenological phases in temperate zones is driven by temperature, and temperature regime is generally determined by atmospheric circulation. The database analysed consists of the first dates of flowering of coltsfoot (Tussilago farfara L.), of birch

Anto Aasa; Jaak Jaagus; Rein Ahas; Mait Sepp

2004-01-01

344

The influence of ocean waves on radiative transfer in the earth's atmosphere and ocean  

Microsoft Academic Search

The radiance in the earth's atmosphere and ocean is calculated for a realistic model including an ocean surface with waves. Individual photons are followed in a Monte Carlo calculation. In the atmosphere, both Rayleigh scattering by the molecules and Mie scattering by the aerosols as well as molecular and aerosol absorption are taken into account. Similarly, in the ocean, both

G. N. Plass; G. W. Kattawar; J. A. Guinn Jr.

1975-01-01

345

The influence of forward-scattered light in transmission measurements of (exo)planetary atmospheres  

NASA Astrophysics Data System (ADS)

The transmission of light through a planetary atmosphere can be studied as a function of altitude and wavelength using stellar or solar occultations, giving often unique constraints on the atmospheric composition. For exoplanets, a transit yields a limb-integrated, wavelength-dependent transmission spectrum of an atmosphere. When scattering haze and/or cloud particles are present in the planetary atmosphere, the amount of transmitted flux not only depends on the total optical thickness of the slant light path that is probed, but also on the amount of forward-scattering by the scattering particles. Here, we present results of calculations with a three-dimensional Monte Carlo code that simulates the transmitted flux during occultations or transits. For isotropically scattering particles, like gas molecules, the transmitted flux appears to be well-described by the total atmospheric optical thickness. Strongly forward-scattering particles, however, such as commonly found in atmospheres of Solar System planets, can increase the transmitted flux significantly. For exoplanets, such added flux can decrease the apparent radius of the planet by several scale heights, which is comparable to predicted and measured features in exoplanet transit spectra. We performed detailed calculations for Titan's atmosphere between 2.0 and 2.8 ?m and show that haze and gas abundances will be underestimated by about 8% if forward-scattering is ignored in the retrievals. At shorter wavelengths, errors in the gas and haze abundances and in the spectral slope of the haze particles can be several tens of percent, also for other Solar System planetary atmospheres. We also find that the contribution of forward-scattering can be fairly well described by modelling the atmosphere as a plane-parallel slab. This potentially reduces the need for a full three-dimensional Monte Carlo code for calculating transmission spectra of atmospheres that contain forward-scattering particles.

de Kok, R. J.; Stam, D. M.

2012-11-01

346

Influences of Atlantic multidecadal oscillation phases on spatial and temporal variability of regional precipitation extremes  

NASA Astrophysics Data System (ADS)

Precipitation extremes in Florida are influenced by warm and cool phases of AMO.Increase in extreme precipitation events in warm phase of AMO is evident.Influences of AMO warm phase on precipitation extremes are varied across the region.Temporal occurrences of extremes vary in warm to cool phases of AMO in the region.Extremes from one phase of AMO are higher than those from two phases.

Teegavarapu, Ramesh S. V.; Goly, Aneesh; Obeysekera, Jayantha

2013-07-01

347

The Influence of North American Carbon Flux Spatial Distribution on the Temporal Variability of Atmospheric Carbon Dioxide  

NASA Astrophysics Data System (ADS)

A small subset of biospheric model estimates of net ecosystem exchange (NEE) are used to assess the ability of the North American CO2 sampling network to detect regional spatial variability (i.e., 1° x 1°) in land-atmospheric carbon flux. The atmospheric signal at continuous observation locations operating in 2004 resulting from biospheric model derived NEE is quantified using the WRF-STILT atmospheric transport model. The resulting CO2 concentration time series are then compared to determine if changes in the spatial distribution and degree of grid-scale variability in surface fluxes translate into detectable differences in their corresponding atmospheric CO2 signal. If no significant differences are observed, then inverse modeling approaches may be unable to infer a unique grid-scale (i.e., 1° x 1°) surface flux distribution (given the current sampling network). Tower-specific model-data mismatch error derived from real data and estimated using Restricted Maximum Likelihood (RML) is used to assess the significance of observed differences among transported CO2 signals. In general, distinct atmospheric CO2 signals of transported fluxes resulting from the different biospheric models are seen more frequently during the growing versus the dormant season and at towers located in areas of greater flux magnitude (e.g., forested regions). In addition, the greatest difference in CO2 time series is observed at towers with larger measurement footprints, such as Park Falls, Wisconsin (WLEF). Although the magnitude of carbon flux variability varies significantly among the biospheric models examined here, in many cases, these differences do not necessarily translate into significant differences in atmospheric CO2 signal at measurement locations. Thus, while inversions using atmospheric measurements may be able to detect ecoregion-scale or coarse resolution differences among surface flux distributions, they may be unable to detect unique distributions of grid-scale flux variability. Overall, this work provides information about the uniqueness of NEE estimations from inversions, or rather the information content of the atmospheric data with regards to the estimated fluxes. Such information will help inform inverse modeling, and improve our understanding of land-atmosphere carbon exchange.

Huntzinger, D. N.; Gourdji, S.; Michalak, A. M.

2009-12-01

348

Identification of potential regional sources of atmospheric total gaseous mercury in Windsor, Ontario, Canada using hybrid receptor modeling  

NASA Astrophysics Data System (ADS)

Windsor (Ontario) - the automotive capital of Canada does not have any significant mercury (Hg) sources. However, Windsor experiences trans-boundary air pollution as it is located immediately downwind of industrialized regions of the United States of America. A study was conducted in 2007 aimed to identify the potential regional sources of total gaseous mercury (TGM) and investigate the effects of regional sources and other factors on seasonal variability of TGM concentrations in Windsor. TGM concentration was measured at the University of Windsor campus using a Tekran® 2537A Hg vapour analyzer. An annual mean of 2.02±1.63 ng/m3 was observed in 2007. The average TGM concentration was high in the summer (2.48 ng/m3) and winter (2.17 ng/m3), compared to spring (1.88 ng/m3) and fall (1.76 ng/m3). Hybrid receptor modeling potential source contribution function (PSCF) was used by incorporating 72-h backward trajectories and measurements of TGM in Windsor. The results of PSCF were analyzed in conjunction with the Hg emissions inventory of North America (by state/province) to identify regions affecting Windsor. In addition to annual modeling, seasonal PSCF modeling was also conducted. The potential source region was identified between 24-61° N and 51-143° W. Annual PSCF modeling identified major sources southwest of Windsor, stretching from Ohio to Texas. The emissions inventory also supported the findings, as Hg emissions were high in those regions. Results of seasonal PSCF modeling were analyzed to find the combined effects of regional sources, meteorological conditions, and surface reemissions, on intra-annual variability of Hg concentrations. It was found that the summer and winter highs of atmospheric Hg can be attributed to areas where large numbers of coal fired power plants are located in the USA. Weak atmospheric dispersion due to low winds and high reemission from surfaces due to higher temperatures contributed to high concentrations in the summer. In the winter, the atmospheric removal of Hg was slow, but strong winds led to more dispersion, resulting in lower concentrations than the summer. Future studies could use smaller grid sizes and refined emission inventories, for more accurate analysis of source-receptor relationship of atmospheric Hg. Abbreviations of states/provinces: Alabama (AL), Arkansas (AR), British Columbia (BC), Georgia (GA), Iowa (IA), Illinois (IL), Indiana (IN), Kentucky (KY), Louisiana (LA), Manitoba (MB), Michigan (MI), Minnesota (MN), Mississippi (MS), Missouri (MO), Newfoundland and Labrador (NL), Ohio (OH), Ontario (ON), Oregon (OR), Pennsylvania (PA), Tennessee (TN), Texas (TX), West Virginia (WV), Wisconsin (WI).

Xu, X.; Akhtar, U. S.

2009-11-01

349

Influence of ketamine on regional brain glucose use  

SciTech Connect

The purpose of this study was to determine the effect of different doses of ketamine on cerebral function at the level of individual brain structures as reflected by glucose use. Rats received either 5 or 30 mg/kg ketamine intravenously as a loading dose, followed by an infusion to maintain a steady-state level of the drug. An additional group received 30 mg/kg as a single injection only, and was studied 20 min later, by which time they were recovering consciousness (withdrawal group). Regional brain energy metabolism was evaluated with (6-/sup 14/C)glucose and quantitative autoradiography during a 5-min experimental period. A subhypnotic, steady-state dose (5 mg/kg) of ketamine caused a stimulation of glucose use in most brain areas, with an average increase of 20%. At the larger steady-state dose (30 mg/kg, which is sufficient to cause anesthesia), there was no significant effect on most brain regions; some sensory nuclei were depressed (inferior colliculus, -29%; cerebellar dentate nucleus, -18%; vestibular nucleus, -16%), but glucose use in the ventral posterior hippocampus was increased by 33%. In contrast, during withdrawal from a 30-mg/kg bolus, there was a stimulation of glucose use throughout the brain (21-78%), at a time when plasma ketamine levels were similar to the levels in the 5 mg/kg group. At each steady-state dose, as well as during withdrawal, ketamine caused a notable stimulation of glucose use by the hippocampus.

Davis, D.W.; Mans, A.M.; Biebuyck, J.F.; Hawkins, R.A.

1988-08-01

350

The influence of oxygen fugacity on melt evolution: 1 atmosphere experiments on Aleutian basaltic andesites  

NASA Astrophysics Data System (ADS)

Magmatic differentiation trends can be approximated geochemically by liquid lines of descent, which can be modeled using high pressure and temperature experiments. Prior experimental studies indicate that oxygen fugacity (fO2) influences the compositional evolution of the melt phase during equilibrium crystallization, with more oxidized systems producing melts along a calc-alkaline differentiation trend, while more reduced systems produced tholeiitic melts. This study focuses on the influence of oxygen fugacity on equilibrium crystallization in natural basaltic andesites from Westdahl and Okmok volcanoes, Aleutians, Alaska. We conducted a series of experiments at 1 atmosphere with fO2 approximating the Ni-NiO (NNO) and Quartz-Fayalite-Magnetite (QFM) buffers, using H2-CO2 gas mixtures, at temperatures between 1053 and 1262 °C. We employed Fe-plated Pt wire loops as sample containers to minimize experiment Fe-loss. Melting experiments run above 1150 °C were texturally glassy with generally sparse, well-formed phenocrysts. Experiments that were aimed at crystallization at much lower temperatures (1100 °C or lower), required a controlled cooling-rate approach, and the experiments were first equilibrated for 24 hours at 1180 °C, and then temperature was ramped down at a rate of 0.8 °C per hour, resulting in well-crystallized run products. Basaltic andesite (52.4 wt. % SiO2) from the 1997 Okmok eruption run at fO2 ~NNO crystallized plagioclase, clinopyroxene, and Fe-Ti oxides at relatively high temperatures between 1200 and 1250 °C, with olivine forming at temperatures below 1200 °C. At NNO, the 1992 Westdahl basaltic andesite (54.2 wt. % SiO2) starting material produced plagioclase and Fe-Ti oxides between 1200 and 1250 °C, with clinopyroxene forming below about 1180 °C. Olivine did not form in the Westdahl starting composition in the NNO experiments. In both starting compositions run at fO2 ~ QFM, the experiments remained more melt-rich to lower temperatures. At QFM, the Okmok composition produced plagioclase on the liquidus at temperatures above 1200 °C, but Fe-bearing phases did not form until olivine appeared at 1150 °C, followed by clinopyroxene at ~1125 °C. At QFM, the Westdahl basaltic andesite produced only glass and plagioclase to temperatures as low as 1113 °C, with olivine, clinopyroxene, and Fe-Ti oxides crystallizing between 1053 and 1113 °C. Our preliminary results agree with those of prior experimental studies, which predict that higher oxygen fugacities enhance the early crystallization of Fe-Ti oxides, pyroxenes, and olivine, thus influencing the liquid line of descent towards early Fe-depletion and a higher degree of melt compositional evolution. Our experiments demonstrate that at NNO, both Westdahl and Okmok starting materials produced early crystallization of all Fe-bearing phases, while at QFM, the system remained more melt-rich, with plagioclase dominating at higher temperatures, and mafic phases crystallizing only at temperatures below about 1150 to 1100 °C.

Larsen, J. F.; Rader, E. L.

2010-12-01

351

The impact of the October-November 2003 intense solar storm events on the atmospheric circulation in the Pacific Southern Hemisphere Magnetic Anomaly region  

NASA Astrophysics Data System (ADS)

Evidences of the solar activity modulation of the Earth's climate have been observed on different time scales. The main solar activity mechanisms to control climate proposed to explain these observations are: (1) the variability of the total solar irradiance causing a change in the total energy input to the earth's atmosphere and consequent warming/cooling; (2) the variability of the solar ultraviolet emission and its effects on the stratospheric ozone and thermal structure; (3) the cosmic rays effects on the cloud coverage; and (4) high energy particle precipitation effects on mesospheric and stratospheric ozone in the auroral and/or southern hemisphere magnetic anomaly regions during solar storm events. It is conceivable that these mechanisms contribute to varying extends on different regions. However, the precise roles of each process during extreme solar events have not yet been investigated. Here we show that the unusual atmospheric circulation conditions over the southern Pacific and Atlantic oceans, and South America on late October and early November 2003 could be related to the large solar storm events, the Halloween events. We observed the development of anti-cyclones in the South Pacific after the onset of the main proton events. We observed also changes in the position and intensity of the Intertropical Convergence Zone and in the South Pacific Convergence zone. This result reveals that effects on the atmospheric conditions, including cloud coverage and radiative flux in the atmosphere, in the southern hemisphere magnetic anomaly region could be observed during extreme solar conditions. Previous studies suggested that the influence of solar activity on climate could be observed on decadal to millennia time scales. Our results demonstrate that the variability of the solar activity could have impact on southern hemisphere weather and climatic conditions. We anticipate our analysis to be a starting point for more sophisticated weather and climatic models. For example, the predictability of El Niño events could be tested, including its worldwide effects, based on space weather processes. Furthermore, the increase of the southern hemisphere temperature could be investigated based on changes of the Earth's magnetic field configuration.

Vieira, L. A.; da Silva, L. A.; Guarnieri, F.; Echer, E.; Prestes, A.; Dal Lago, A.; da Silva, M. R.; Schuch, N.; Wrasse, C. M.

2007-05-01

352

Influence of soils on oxygen isotope ratio of atmospheric CO2  

NASA Astrophysics Data System (ADS)

The soil component of atmospheric CO2 oxygen isotope budget is evaluated in light of the recent recognition of abiotic oxygen isotope exchange of atmospheric CO2 and soil water in excess of soil respiratory CO2 flux. By using variations of published analytical models, we estimate that the amount of atmospheric CO2 that undergoes oxygen isotope exchange with soil water, exclusive of soil-respired CO2, to be approximately 0.2-0.7 ?mol m-2 s-1 for representative unsaturated soils from a range of biomes. Globally, the amount of atmospheric CO2 that undergoes oxygen isotope exchange with soil water through purely nonbiological processes is probably significantly larger than the current annual fossil fuel combustion, yet this process has been neglected in all recent global 18O-CO2 budgets. Furthermore, abiotic oxygen isotope exchange with soils will occur roughly equally in soils with low and high respiration rates, suggesting that soils with low respiration rates are currently under-represented disproportionately in the existing global CO2 oxygen isotope budgets. Because soils with low respiration rates tend to have the most extreme soil water ? 18O values, their underrepresentation may have a large and heretofore unsuspected impact on the global atmospheric C18 O16O budget. Finally, soil carbon is no longer in steady state due to land use practices, and this additional source of CO2 to the atmosphere may contribute to the decreasing trend in atmospheric CO2-?18O values through time.

Stern, Libby A.; Amundson, Ronald; Baisden, W. Troy

2001-09-01

353

Anthropogenic Influence on Secondary Aerosol Formation and Total Water-Soluble Carbon on Atmospheric Particles  

NASA Astrophysics Data System (ADS)

On a global scale, the atmosphere is an important source of nutrients, as well as pollutants, because of its interfaces with soil and water. Important compounds in the gaseous phase are in both organic and inorganic forms, such as organic acids, nitrogen, sulfur and chloride. In spite of the species in gas form, a huge number of process, anthropogenic and natural, are able to form aerosols, which may be transported over long distances. Sulfates e nitrates are responsible for rain acidity; they may also increase the solubility of organic compounds and metals making them more bioavailable, and also can act as cloud condensation nuclei (CCN). Aerosol samples (PM2.5) were collected in a rural and industrial area in Rio de Janeiro, Brazil, in order to quantify chemical species and evaluate anthropogenic influences in secondary aerosol formation and organic compounds. Samples were collected during 24 h every six days using a high-volume sampler from August 2010 to July 2011. The aerosol mass was determined by Gravimetry. The water-soluble ionic composition (WSIC) was obtained by Ion Chromatography in order to determine the major anions (NO3-, SO4= and Cl-); total water-soluble carbon (TWSC) was determined by a TOC analyzer. The average aerosol (PM2.5) concentrations ranged from 1 to 43 ug/m3 in the industrial site and from 4 to 35 ug/m3 in the rural area. Regarding anions, the highest concentrations were measured for SO42- (10.6 ?g/m3-12.6 ?g/m3); where the lowest value was found in the rural site and the highest in the industrial. The concentrations for NO3- and Cl- ranged from 4.2 ?g/m3 to 9.3 ?g/m3 and 3.1 ?g/m3 to 6.4 ?g /m3, respectively. Sulfate was the major species and, like nitrate, it is related to photooxidation in the atmosphere. Interestingly sulfate concentrations were higher during the dry period and could be related to photochemistry activity. The correlations between nitrate and non-sea-salt sulfate were weak, suggesting different sources for these species. The secondary aerosol represented an important fraction of total compounds in PM2.5 ranged from 16 to 18% for (NH4)2SO4 and 6 to 8% for NH4NO3. The values for TWSC ranged from 0.28 to 6.35 ?g/m3 in the industrial area and 0.12 to 7.49 ?g/m3 for rural area. The similarity between the areas regarding secondary aerosols formation and water-soluble carbon compounds is probably due to the particle size.

Gioda, Adriana; Mateus, Vinicius; Monteiro, Isabela; Taira, Fabio; Esteves, Veronica; Saint'Pierre, Tatiana

2013-04-01

354

Bioclimatic regions influence genetic structure of four Jordanian Stipa species.  

PubMed

Strong environmental gradients can affect the genetic structure of plant populations, but little is known as to whether closely related species respond similarly or idiosyncratically to ecogeographic variation. We analysed the extent to which gradients in temperature and rainfall shape the genetic structure of four Stipa species in four bioclimatic regions in Jordan. Genetic diversity, differentiation and structure of Stipa species were investigated using amplified fragment length polymorphism (AFLP) molecular markers. For each of the four study species, we sampled 120 individuals from ten populations situated in distinct bioclimatic regions and assessed the degree of genetic diversity and genetic differentiation within and among populations. The widespread ruderals Stipa capensis and S. parviflora had higher genetic diversity than the geographically restricted semi-desert species S. arabica and S. lagascae. In three of the four species, genetic diversity strongly decreased with precipitation, while genetic diversity increased with temperature in S. capensis. Most genetic diversity resided among populations in the semi-desert species (?(ST) = 0.572/0.595 in S. arabica/lagascae) but within populations in the ruderal species (?(ST) = 0.355/0.387 S. capensis/parviflora). Principal coordinate analysis (PCoA) and STRUCTURE analysis showed that Stipa populations of all species clustered ecogeographically. A genome scan revealed that divergent selection at particular AFLP loci contributed to genetic differentiation. Irrespective of their different life histories, Stipa species responded similarly to the bioclimatic gradient in Jordan. We conclude that, in addition to predominant random processes, steep climatic gradients might shape the genetic structure of plant populations. PMID:23369254

Hamasha, H R; Schmidt-Lebuhn, A N; Durka, W; Schleuning, M; Hensen, I

2012-12-17

355

PROBING THE TERMINATOR REGION ATMOSPHERE OF THE HOT-JUPITER XO-1b WITH TRANSMISSION SPECTROSCOPY  

SciTech Connect

We report here the first infrared spectrum of the hot-Jupiter XO-1b. The observations were obtained with the NICMOS instrument on board the Hubble Space Telescope during a primary eclipse of the XO-1 system. Near photon-noise-limited spectroscopy between 1.2 and 1.8 {mu}m allows us to determine the main composition of this hot-Jupiter's planetary atmosphere with good precision. This is the third hot-Jupiter's atmosphere for which spectroscopic data are available in the near-IR. The spectrum shows the presence of water vapor (H{sub 2}O), methane (CH{sub 4}), and carbon dioxide (CO{sub 2}), and suggests the possible presence of carbon monoxide (CO). We show that the published IRAC secondary transit emission photometric data are compatible with the atmospheric composition at the terminator determined from the NICMOS spectrum, with a range of possible mixing ratios and thermal profiles; additional emission spectroscopy data are needed to reduce the degeneracy of the possible solutions. Finally, we note the similarity between the 1.2-1.8 {mu}m transmission spectra of XO-1b and HD 209458b, suggesting that in addition to having similar stellar/orbital and planetary parameters the two systems may also have a similar exoplanetary atmospheric composition.

Tinetti, G. [University College London, Department of Physics and Astronomy, Gower Street, London WC1E 6BT (United Kingdom); Deroo, P.; Swain, M. R.; Vasisht, G.; Brown, L. R. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Griffith, C. A. [University of Arizona, Lunar and Planetary Laboratory, 1629 E. University Boulevard, Tucson, AZ 85721 (United States); Burke, C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-65, Cambridge, MA 02138 (United States); McCullough, P. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)], E-mail: g.tinetti@ucl.ac.uk

2010-04-01

356

Study the effect of ozone layer depletion on aircraft design at atmospheric region of Pakistan  

Microsoft Academic Search

Ozone is of considerable importance to mankind because of its role as a shield for the biosphere against the Ultraviolet (UV) radiation from the outer space, in particular from the sun. Due to a serious reduction of O3 content in the atmosphere, life-forms on the earth are exposed to a new hazard in the form of an increase of harmful

M. A. K. Y. Zai; M. R. K. Ansari

2008-01-01

357

Polychlorinated biphenyl emissions to the atmosphere in the Great Lakes region. Municipal landfills and incinerators  

SciTech Connect

In an effort to identify sources of polychlorinated biphenyls (PCBs) to the atmosphere, the concentration of PCBs in emissions from several municipal sanitary landfills and refuse and sewage sludge incinerators in the Midwest was determined. Sanitary landfills continuously emit the gaseous products of anaerobic fermentation along with other volatile materials to the atmosphere. Thus, they can be continuing sources of vapor-phase contaminants to the atmosphere. A projection, based on the amount of methane generated annually from landfills and a PCB to methane ratio of 0.3 ..mu..g of PCBs/m/sup 3/ of CH/sub 4/ found from the landfills sampled, indicates that the annual PCB emissions from sanitary landfills in the US is on the order of 10-100 kg/year. The concentrations of PCBs from the incinerator stacks sampled ranged from 0.3 to 3 ..mu..g/m/sub 3/, and the annual emissions per stack sampled were 0.25 kg/year. The emission rates found here are small compared to the 900,000 kg/year of PCBs estimated to cycle through the atmosphere over the US annually.

Murphy, T.J.; Formanski, L.J.; Brownawell, B.; Meyer, J.A.

1985-10-01

358

Future Changes in Biogenic Isoprene Emissions: How Might They Affect Regional and Global Atmospheric Chemistry?  

Microsoft Academic Search

Isoprene is emitted from vegetation to the atmosphere in sig- nificant quantities, and it plays an important role in the reactions that control tropospheric oxidant concentrations. As future climatic and land-cover changes occur, the spatial and temporal variations, as well as the magnitude of these biogenic isoprene emissions, are expected to change. This paper presents a study of the change

Christine Wiedinmyer; Xuexi Tie; Alex Guenther; Ron Neilson; Claire Granier

2006-01-01

359

Africa as a regional and global source of atmospheric gases and particulates  

Microsoft Academic Search

The role of the continent of Africa as a source of gaseous and particulate emissions to the atmosphere is investigated in this study. Sources of gases and particulates from Africa include fossil fuel combustion, biomass burning, and biogenic soil emissions of nitric oxide. This study represents the first comprehensive database of gaseous and particulate emissions developed for the continent of

Lawrence Mtetwa

1998-01-01

360

A mesoscale model study of summertime atmospheric circulations in the north polar region of Mars  

Microsoft Academic Search

The Oregon State University Mars MM5 was used in a comprehensive high-resolution study of northern polar summertime circulations. Three simulations (Ls = 120, Ls = 135, and Ls = 150) characterize the changing circulation. The atmosphere is dry, and model dynamics are hydrostatic. A modified TES thermal inertia map provides a realistic simulation of the polar thermal environment. The highest-resolution

Daniel Tyler Jr.; Jeffrey R. Barnes

2005-01-01

361

The effect of mercury speciation and meteorological processing on concentrations, transport and deposition of atmospheric mercury  

Microsoft Academic Search

The toxic trace element mercury can be transported locally, regionally or globally within the atmosphere before deposition to a watershed. The fate of atmospheric mercury is dependent on its chemical and physical form, which determine its deposition rate under different environmental conditions. The importance of these influences on atmospheric mercury was investigated in dew, clouds and the coastal atmosphere. Measurements

Elizabeth Glover Malcolm

2002-01-01

362

ADPIC--A Three-Dimensional Particle-in-Cell Model for the Dispersal of Atmospheric Pollutants and its Comparison to Regional Tracer Studies  

Microsoft Academic Search

A hybrid Lagrangian-Eulerian atmospheric transport-diffusion model was developed to calculate the three-dimensional distribution of atmospheric pollutants in transient-region flow fields. This atmospheric diffusion particle-in-cell (ADPIC) code was validated against several existing closed-form analytical solutions including a puff release in steady, unidirectional shear flow, and a puff release with scale-dependent horizontal and vertical eddy diffusion coefficients. These tests showed that the

Rolf Lange

1978-01-01

363

Regional Differences in the Influence of Role Models: Comparing the Entrepreneurial Process of Rural Catalonia  

Microsoft Academic Search

Lafuente E., Vaillant Y. and Rialp J. (2007) Regional differences in the influence of role models: comparing the entrepreneurial process of rural Catalonia, Regional Studies41, 779–795. The paper examines the impact of entrepreneurial role models on the entrepreneurial process in rural areas with a strong entrepreneurial history versus those not necessarily characterized by such a tradition. To attain this objective,

Esteban Lafuente; Yancy Vaillant; Josep Rialp

2007-01-01

364

Experimental and Theoretical Investigations Concerning the Influence of Stagnation Region on Karman Vortex Shedding  

Microsoft Academic Search

The paper contains an attempted explanation of the stagnation region's role in vortex shedding. The stagnation region appears in the closest neighborhood downstream of the bluff body, and is a factor which considerably influences vortex shedding. Former investigations of these phenomena in the vortex meter entitle the author to summarize yielded results and to formulate the overall conclusions concerning the

Grzegorz L. Pankanin

2007-01-01

365

Influence of plumes from biomass burning on atmospheric chemistry over the equatorial and tropical South Atlantic during CITE 3  

NASA Astrophysics Data System (ADS)

During all eight flights conducted over the equatorial and tropical South Atlantic (27°-35°W, 2°N-11°S; September 9-22, 1989) in the course of the Chemical Instrumentation Test and Evaluation (CITE 3) experiment, we observed haze layers with elevated concentrations of aerosols, O3, CO, and other trace gases related to biomass burning emissions. They occurred at altitudes between 1000 and 5200 m and were usually only some 100-300 m thick. These layers extended horizontally over several 100 km and were marked by the presence of visible brownish haze. These layers strongly influenced the chemical characteristics of the atmosphere over this remote oceanic region. Air mass trajectories indicate that these layers originate in the biomass burning regions of Africa and South America and typically have aged at least 10 days since the time of emission. In the haze layers, O3 and CO concentrations up to 90 and 210 ppb were observed, respectively. The two species were highly correlated. The ratio ?O3/?CO (?, concentrations in plume minus background concentrations) is typically in the range 0.2-0.7, much higher than the ratios in the less aged plumes investigated previously in Amazonia. In most cases, aerosol (0.12-3 ?m diameter) number concentrations were also elevated by up to 400 cm-3 in the layers; aerosol enrichments were also strongly correlated with elevated CO levels. Clear correlations between CO and NOx enrichments were not apparent due to the age of the plumes, in which most NOx would have already reacted away within 1-2 days. Only in some of the plumes could clear correlations between NOy and CO be identified; the absence of a general correlation between NOy and CO may be due to instrumental limitations and to variable sinks for NOy. The average enrichment of ?NOy/?CO was quite high, consistent with the efficient production of ozone observed in the plumes. The chemical characteristics of the haze layers, together with remote sensing information and trajectory calculations, suggest that fire emissions (in Africa and/or South America) are the primary source of the haze layer components.

Andreae, M. O.; Anderson, B. E.; Blake, D. R.; Bradshaw, J. D.; Collins, J. E.; Gregory, G. L.; Sachse, G. W.; Shipham, M. C.

1994-06-01

366

Cooling Tower Recirculation as Influenced by the Local Atmospheric Flow Field, a Numerical Study.  

National Technical Information Service (NTIS)

A survey of the literature shows that existing methods of numerically modeling cooling tower plume recirculation ignore the aerodynamic effects of the atmospheric flow over the cooling tower. This investigation describes a method of numerically modeling c...

B. R. Becker

1979-01-01

367

Culture influences on emotional responses to on-line store atmospheric cues  

Microsoft Academic Search

On-line retailing created a global marketplace with an innumerable array of competitors. Essential to on-line store's ability to attract and retain customers globally is its store atmospherics, which are design elements used to garner attention and create a positive buying environment [Kotler Phillip. Atmospherics as a marketing tool. Journal of Retailing 1974; 49: 48–64.]. The research presented here assesses how

Lenita Davis; Sijun Wang; Andrew Lindridge

2008-01-01

368

Influence of environmental moisture on atmospheric pressure plasma jet treatment of ultrahigh-modulus polyethylene fibers  

Microsoft Academic Search

One of the main differences between low-pressure and atmospheric-pressure plasma treatments is that there is little moisture involved in the low-pressure plasma treatment, although moisture could exist at the wall of the vacuum chamber or react with the substrate after plasma treatment, while in the atmospheric-pressure plasma treatment moisture exists not only in the environment but also in any hygroscopic

Y. Liu; H. Xu; L. Ge; C. Wang; L. Han; H. Yu; Y. Qiu

2007-01-01

369

High-resolution atmospheric absorption by water vapor in the 830-985 nm region: Evaluation of spectroscopic databases  

NASA Astrophysics Data System (ADS)

We present high spectral resolution (0.05 cm-1) ground-based measurements of direct solar absorption in the clear-sky atmosphere by water vapor over the 830 to 985 nm (10,150-12,050 cm-1) region. Observations were made from the Rutherford Appleton Laboratory on several days in different seasons during 1999. Using these observations water vapor line data in HITRAN and the ESA-WVR database, derived from new laboratory measurements and theoretical calculations, are evaluated. Examples of inter-comparisons between these databases and high-resolution atmospheric transmittance spectra are given. The ESA-WVR and HITRAN 2000 databases were found to give consistently better representations of clear-sky absorption by water vapor in our measurements than previous editions of HITRAN, confirming that spectroscopic errors in databases account in part for discrepancies between modeled and observed short-wave absorption.

Smith, K. M.; Newnham, D. A.

370

On the influence of stratification and tidal forcing upon mixing in sill regions  

Microsoft Academic Search

A cross-sectional non-hydrostatic model with idealized topography was used to examine the processes influencing tidal mixing\\u000a in the region of sills. Initial calculations with appropriate parameters for the sill at the entrance to Loch Etive showed\\u000a that the model could reproduce the main features of the observed mixing in the region. In particular, the hydraulic jump in\\u000a the sill region

Alan M. Davies; Jiuxing Xing

2007-01-01

371

Pollution characterization and diurnal variation of PBDEs in the atmosphere of an E-waste dismantling region.  

PubMed

Diurnal air samples were collected from the E-waste dismantling region Guiyu and the underwear industry region Chendian. This was the first report to present the diurnal variation of PBDEs in the atmosphere. The average concentrations of 11 PBDE congeners were 11,742 pgm(-3) in the daytime, and 4830 pgm(-3) at night in Guiyu, while the concentrations were lower in Chendian with 376 pgm(-3) in the daytime, and 237 pgm(-3) at night. BDE-209 accounted for 22% and 31.3% of the total PBDEs in Guiyu and Chendian, respectively. The diurnal variation trends of BDE-47, -99, -153, -183, and -209 were also analyzed in detail in the two regions. PMID:19062146

Chen, Duohong; Bi, Xinhui; Zhao, Jinping; Chen, Laiguo; Tan, Jihua; Mai, Bixian; Sheng, Guoying; Fu, Jiamo; Wong, Minghung

2008-12-04

372

A method to study the atmospheric influence on the isotopic composition of primary cosmic rays applied to the elements carbon and oxygen  

Microsoft Academic Search

A method to study experimentally the atmospheric influence on the isotopic composition of primary cosmic radiation is described. The method uses isotopic abundances as found in experiments with emulsions exposed in balloon flights. The amount of atmospheric matter passed by a cosmic ray nucleus depends on the zenith angle. The experimental mass spectra at the level of detection obtained within

C. Bjarle; N.-Y. Herrström; G. Jönsson

1980-01-01

373

Numerical Study of Local/Regional Atmospheric Changes Caused by a Large Solar Central Receiver Power Plant. Final Report, 29 September 1978-31 May 1980.  

National Technical Information Service (NTIS)

A two-dimensional, vertical cross-section, numerical atmospheric mesoscale model has been applied to study the potential local/regional atmospheric effects of the installation of a 100 MW/sub e/ solar thermal central receiver power plant at Barstow, Calif...

C. M. Bhumralkar A. J. Slemmons K. C. Nitz

1980-01-01

374

Non-linear Ice Sheet influence during deglaciation and its impact on the evolution of atmospheric teleconnection patterns  

NASA Astrophysics Data System (ADS)

During present conditions atmospheric teleconnections such as the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) have a major impact on Northern Hemispheric climate. However, the Early Holocene is characterized by the presence and melting of the Laurentide Ice Sheet (LIS) leading to a different background climate in comparison to today. Here we investigate the climate evolution during the early (9 ka BP, including LIS and melt water), mid (6 ka BP) and late Holocene (pre-industrial conditions) focussing on the mechanisms and feedbacks during deglaciation by applying the state-of-the-art earth system model COSMOS. A special interest is set on the evolution of atmospheric teleconnection patterns such as the AO/NAO and the Atlantic Multidecadal Oscillation (AMO) that have a major influence on North Atlantic/European climate. The evolution and relative importance of these oscillations throughout the Holocene, however, is still largely unknown. We demonstrate that North Atlantic/European climate is affected by a shift from a more ocean-ice-dominated climate during approx. 9 ka towards a more atmosphere-dominated one during the mid to late Holocene. To isolate the contributions of the presence of the LIS and the melt water we run four different model simulations for the early Holocene sensitivity study (a standard configuration only forced with green house gases and orbital parameters, one with the additional LIS topography, one with a melt water flux of 0.09 Sv, and a fourth that combines all the external forcings). The model results show that the influence of the LIS and its melt water contribution lead to a strong non-linear cooling of surface air temperatures during deglaciation. This synergetic influence of the Laurentide Ice Sheet strengthens the effect of melting on ocean circulation during the early Holocene. The severe colder background climate during deglaciation leads to a more vulnerable ocean circulation in terms of the Atlantic Meridional Overturning Circulation. Changes of this circulation are known to affect the atmosphere as well via mechanisms like the AMO. The corresponding sea level pressure pattern is an atmospheric response to oceanic thermal forcing, which results from variations of the thermohaline circulation. The AMO has a potential to influence the shape of the subtropical high and to shift AO/NAO pressure centres towards easterly and north-easterly directions during the early Holocene. This non-stationary behaviour of the AO/NAO due to deglaciation processes is also demonstrated by a novel set of North Atlantic/European speleothem records that show an active AO/NAO all over the Holocene.

Dietrich, Stephan; Wassenburg, Jasper; Wei, Wei; Lohmann, Gerrit; Jens, Fohlmeister; Adrian, Immenhauser

2013-04-01

375

The Martian surface radiation environment - Influence of higher atmospheric pressure and surface or sub-surface water  

NASA Astrophysics Data System (ADS)

The Noachian epoch (~4.5 - 3.5 billion years ago) is a promising era for a possible emergence of life on Mars. The presence of runoff channels in areas formed during the Noachian suggests that liquid water existed at least sporadically during that time, with liquid water being regarded as a prerequisite for life. To have sustained liquid water, the atmospheric pressure on Noachian Mars must have been significantly higher than in the present. When considering the possibility of life on Noachian Mars, one conceivable restriction is given by the ionizing radiation environment. Using PLANETOCOSMICS- and GEANT4-simulation codes, we calculate the radiation environment on the Martian surface and the resulting radiation exposure for different atmospheric conditions. Here, we present absorbed dose rates resulting from galactic-cosmic-proton and alpha-particle-induced radiation environments, as well as changes of these rates caused by an increase of atmospheric pressure. Furthermore, we analyze which influence the presence of liquid surface water or sub-surface water-ice would have on the radiation environment under these different atmospheric conditions.

Ehresmann, B.; Böhm, E.; Kohler, J.; Martin, C.; Wimmer-Schweingruber, R. F.; Reitz, G.; Hassler, D. M.; Zeitlin, C. J.

2011-12-01

376