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1

Influence of sea ice on the atmosphere: A study with an Arctic atmospheric regional climate model  

Microsoft Academic Search

The impact of the lower-boundary forcing over ocean grid points, namely of sea surface temperature (SST), sea ice fraction, and sea ice thickness, on the mean atmospheric simulation is investigated with an Arctic atmospheric regional climate model. The assessment shows that the sea ice\\/SST forcing has an impact on the atmospheric simulations. The near-surface air temperature response shows a strong,

Annette Rinke; Wieslaw Maslowski; Klaus Dethloff; Jaclyn Clement

2006-01-01

2

Utility of soil linear alkylbenzenes to assess regional anthropogenic influences with special reference to atmospheric transport.  

PubMed

Tracing regional anthropogenic influences is important for assessing the magnitude of human interferences with the environment. In the present study, the utility of soil linear alkylbenzenes (LABs) as indicators of anthropogenic influences was examined, with the emphasis on the role of atmospheric transport in dissipating LABs from input sources to remote areas. The Pearl River Delta, South China, which has experienced rapid economic growth and urbanization, was selected as the study region. The concentrations of LABs (mean: 8.6ng/g and median: 5.7ng/g, with an outlier of 2020ng/g excluded) suggested that sewage contamination throughout the entire study region was generally light. The spatial variation of sewage pollution was significantly positively correlated with population density and per capita gross domestic product, with hot spots concentrated in the central PRD. Atmospheric deposition was hypothesized as an important input route for soil LABs in forestry and drinking water source areas with little impact of irrigation or direct wastewater discharge. This proposition could explain the opposite spatial patterns of LAB concentrations and values of a biodegradation index (5-C12+5-C13)/(5-C11+5-C10), where i-Cn defines a specific LAB congener with i and n indicating the position of the phenyl group and the number of carbon atoms on the alkyl chain, respectively. These findings somewhat validated LABs as tracers of regional anthropogenically derived contamination, with atmospheric transport of LABs as a viable dissipating mechanism. PMID:24813768

Wei, Gao-Ling; Bao, Lian-Jun; Guo, Ling-Chuan; He, Zai-Cheng; Wu, Feng-Chang; Zeng, Eddy Y

2014-07-15

3

Influence of the interplanetary electric field on atmospheric processes in the southern polar region  

NASA Astrophysics Data System (ADS)

Fluxes of galactic cosmic rays altered by solar wind and spikes of solar cosmic rays are usually examined as one possible mechanism of solar activity influencing the Earth's atmosphere. To study effects of the solar wind variability on atmospheric processes the hourly data from meteorological station "MILOS-500" at the Antarctic base Vostok along with data from the automatic weather meteorological stations (WMS) located at the Antarctic ice dome have been examined. The detail analysis of the meteorological data (atmospheric temperature, pressure, and winds) for 1999-2001 made it possible to conclude that dramatic changes of the troposphere temperature, observed in the Southern near-pole region in relation to the interplanetary shocks, accompanying Forbush decreases (FD), are caused, in actuality, by sharp changes of the Interplanetary Magnetic Field and, correspondingly, by fluctuations in the interplanetary electric field (Esw). The warming is observed when changes in the IMF Bz component are negative and ESW increases. The typical time delay between changes in the interplanetary electric ield and appropriate response in the ground temperature is estimated. The spatial extent of the influence is derived from comparison of ffects observed at automatic WM stations surrounding the region of geomagnetic pole.

Janzhura, A. S.; Troshichev, O. A.

2003-04-01

4

Influence of the solar wind variability on atmospheric processes in the southern polar region  

NASA Astrophysics Data System (ADS)

Fluxes of galactic cosmic rays altered by solar wind and spikes of solar cosmic rays are usually examined as one possible mechanism of solar activity influencing the Earth's atmosphere. To study effects of the solar wind variability the daily data of aerological sounding carried out at the Antarctic station Vostok ( = 78°27S,= 106°52E) have been examined in the analysis. Vostok station is located at the ice flat homogeneous plain at height of 3.5 km, inland 1500 km from the coast, and is not subjected to local atmospheric vortices. The catabatic type of atmospheric circulation (i.e. vertical type of circulation) is typical of the central part of Antarctic, where the stratosphere cold air masses go down to ice dome and then flow along the dome surface toward the cost. All of these circumstances allow the Vostok station location act like a window into the nature of the nighttime middle atmosphere where solar influences are stronger than in the lower atmosphere. The detail analysis of the Vostok data for 1978-1992 made it possible to conclude that dramatic changes of the troposphere temperature, observed in the Southern near-pole region in relation to the interplanetary shocks, accompanying Forbush decreases (FD) and solar protons events (SPE), are caused, in actuality, by sharp changes of the IMF Bz component typical of interplanetary shocks, and by the corresponding fluctuations of the interplanetary electric field (ESW ). The warming is observed at altitudes h<5 km and cooling at h>10 km when changes in the IMF B Z component are negative and ESW increases. The regularity is especially supported by the fact that opposite temperature deviations are observed in relation with the northward BZ leaps. There is a linear relationship between the value ofE SW and ground temperature at Vostok station: the larger leap in the E W the stronger is temperature deviation. The effect reachesS maximum within one day and is damped equally quickly. It is suggested that electric field E W influences the catabatic system of atmospheric circulation, typical of theS winter Antarctic, through formation of screen for the cold stratospheric air masses going down to the Antarctic ice dome.

Troshichev, O.; Egorova, L.; Vovk, V.

5

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

6

Influence of Sea-Land Breezes on the Tempospatial Distribution of Atmospheric Aerosols over Coastal Region  

Microsoft Academic Search

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 PM2.5–10 (PM with aerodynamic

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

2011-01-01

7

The influence of the radiative non-symmetric ion-atom collisions on the stellar atmospheres in VUV region  

NASA Astrophysics Data System (ADS)

The aim of this work is to draw attention to the processes of radiative charge exchange in non-symmetric ion-atom collisions as a factor of influence on the opacity of stellar atmospheres in VUV region. For that purpose calculations of the spectral absorption coefficients for several ion-atom systems, namely He + H^{+} and H + X^{+}, where X = Na and Li, have been performed. On chosen examples it has been established that the examined processes generate rather wide molecular absorption bands in the VUV region, which should be taken into account for the interpretation of data obtained from laboratory measurements or astrophysical observations. This paper discusses the potential significance of the considered radiative processes for DB white dwarfs and solar atmospheres, as well as for the atmospheres of the so-called lithium stars.

Sre?kovi?, V. A.; Mihajlov, A. A.; Ignjatovi?, Lj. M.; Dimitrijevi?, M. S.

2013-05-01

8

Processes for identifying regional influences of and responses to increasing atmospheric CO(sub 2) and climate change: The MINK project. An overview.  

National Technical Information Service (NTIS)

This overview report explains the rationale for and the methodology used in conduct of the study ''Processes for Identifying Regional Influences of and Responses to Increasing Atmospheric CO(sub 2) and Climate Change -- The MINK Project'' commissioned by ...

N. J. Rosenberg P. R. Crosson

1991-01-01

9

Influence of coupling on atmosphere, sea ice and ocean regional models in the Ross Sea sector, Antarctica  

NASA Astrophysics Data System (ADS)

Air-sea ice-ocean interactions in the Ross Sea sector form dense waters that feed the global thermohaline circulation. In this paper, we develop the new limited-area ocean-sea ice-atmosphere coupled model TANGO to simulate the Ross Sea sector. TANGO is built up by coupling the atmospheric limited-area model MAR to a regional configuration of the ocean-sea ice model NEMO. A method is then developed to identify the mechanisms by which local coupling affects the simulations. TANGO is shown to simulate realistic sea ice properties and atmospheric surface temperatures. These skills are mostly related to the skills of the stand alone atmospheric and oceanic models used to build TANGO. Nonetheless, air temperatures over ocean and winter sea ice thickness are found to be slightly improved in coupled simulations as compared to standard stand alone ones. Local atmosphere ocean feedbacks over the open ocean are found to significantly influence ocean temperature and salinity. In a stand alone ocean configuration, the dry and cold air produces an ocean cooling through sensible and latent heat loss. In a coupled configuration, the atmosphere is in turn moistened and warmed by the ocean; sensible and latent heat loss is therefore reduced as compared to the stand alone simulations. The atmosphere is found to be less sensitive to local feedbacks than the ocean. Effects of local feedbacks are increased in the coastal area because of the presence of sea ice. It is suggested that slow heat conduction within sea ice could amplify the feedbacks. These local feedbacks result in less sea ice production in polynyas in coupled mode, with a subsequent reduction in deep water formation.

Jourdain, Nicolas C.; Mathiot, Pierre; Gallée, Hubert; Barnier, Bernard

2011-04-01

10

Processes for identifying regional influences of and responses to increasing atmospheric CO sub 2 and climate change: The MINK project  

SciTech Connect

This overview report explains the rationale for and the methodology used in conduct of the study Processes for Identifying Regional Influences of and Responses to Increasing Atmospheric CO{sub 2} and Climate Change -- The MINK Project'' commissioned by the US Department of Energy. The MINK project includes four states -- Missouri, Iowa, Nebraska and Kansas. The major findings of the study are also presented in this overview, which accompanies a series of reports in which the requisite technical details on methodology, sectoral analyses and integrated analysis of climate change impacts and responses are provided in detail. The report topics in this analysis series of potential greenhouse effects are: (1) background and baseline; (2) agricultural production and resource use in the MINK region without and with climate change; (3) a farm-level simulation of the effects of climate change on crop productivity in the MINK region; (4) forest resources; (5) water resources; (6) energy; (7) consequences of climate change for the MINK economy: impacts and responses.

Rosenberg, N.J.; Crosson, P.R.

1991-08-01

11

Influence of air mass downward transport on the variability of surface ozone at Xianggelila Regional Atmosphere Background Station, southwest China  

NASA Astrophysics Data System (ADS)

In situ measurements of ozone (O3), carbon monoxide (CO) and meteorological parameters were made from December 2007 to November 2009 at the Xianggelila Regional Atmosphere Background Station (28.006° N, 99.726° E; 3580 m a.s.l.), southwest China. It was found that both O3 and CO peaked in spring while the minima of O3 and CO occurred in summer and winter, respectively. A normalized indicator (marked as "Y") on the basis of the monthly normalized O3, CO and water vapor, is proposed to evaluate the occurrence of O3 downward transport from the upper, O3-rich atmosphere. This composite indicator has the advantage of being less influenced by the seasonal or occasional variations of individual factors. It is shown that the most frequent and effective transport occurred in winter (accounting for 39% of the cases on the basis of a threshold of the Y value larger than 4) and they can make a significant contribution to surface O3 at Xianggelila. A 9.6 ppb increase (21.0%) of surface ozone is estimated based on the impact of deep downward transport events in winter. A case of strong O3 downward transport event under the synoptic condition of a deep westerly trough is studied by the combination of the Y indicator, potential vorticity, total column ozone and trajectory analysis. Asian monsoon plays an important role in suppressing O3 accumulation in summer and fall. The seasonal variation of O3 downward transport, as suggested by the Y indicator at Xianggelila, is consistent with the seasonality of stratosphere-to-troposphere transport and the subtropical jet stream over the Tibetan Plateau.

Ma, J.; Lin, W. L.; Zheng, X. D.; Xu, X. B.; Li, Z.; Yang, L. L.

2014-06-01

12

How the Atmosphere Influences Aridity  

NSDL National Science Digital Library

This site, produced by the U.S. Geological Survey, describes the circulation pattern of Earth's atmosphere, which is influenced by differential heating and the Coriolis Effect. This circulation causes the formation of warm, dry areas on the Earth's surface which are where deserts are likely to exist. The site features text, a photograph, and a scientific illustration showing the atmospheric circulation pattern.

13

Atmospheric composition - Influence of biology  

NASA Technical Reports Server (NTRS)

The variability of atmospheric constituents influenced by biological organisms over various time scales is examined, together with the human contribution to atmospheric sulfur. The biogeochemistry of nitrogen is discussed, with an emphasis on N2O, NO, and microbially mediated reactions in soil and water. Carbon species are bound up mainly in sediments and the deep ocean, but human activities involving combustion may cause a doubling of the atmospheric levels of CO2 in the near future, which could produce a general low-level atmospheric warming. Longer term measurements are required to assess the effects of CH4 augmentation in the atmosphere through fuel combustion. Coal burning effectively doubles the amount of SO2 produced by natural sources, and reduces the pH of rainwater, thus posing hazards to fish, plankton, and mollusc life.

Mcelroy, M. B.

1983-01-01

14

Ionosphere F2-region under the influence of the evolutional atmospheric gravity waves in horizontal shear flow  

NASA Astrophysics Data System (ADS)

The ambipolar diffusion equation for the height distribution of electron density in the ionospheric F2-layer is solved in the presence of neutral horizontal shear flow. By using this nonstationary solution the reaction of the F2-region electron density on the evolution of atmospheric acoustic-gravity waves (AGW) is investigated. The evolution of the AGW and the corresponding behaviour of the height distribution of the F2-region electron density are described by the characteristic time, ta, of transient development of shear waves in the horizontal shear flow. For long times t > ta, the gravity wave frequency tends to the isothermal Brunt-Väisälä frequency, which appears in the F2-layer as wavelike behaviour of hmF2 and NmF2 with periods close to 16-20 min, when the scale height of the neutral gas is H = 60 km. The shear wave, which is due to the presence of horizontal shear flow, gives sufficient changes of the height profile of electron density for times of t <= ta.

Didebulidze, G. G.; Pataraya, A. d.

1999-04-01

15

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

16

Influence of Atmospheric Absorption on Visibility of Galaxies  

NASA Astrophysics Data System (ADS)

We discuss the influence of atmospheric extinction to visibility of galaxies in the visual region of the spectrum. For this purpose the plates covering the same, small region of the sky taken with 2-m telescope, at different zenith distances were obtained. We investigated the relation between galaxy counts and the zenith distance. We show that the influence of the atmospheric mass to the visibility of galaxies is the same as for stars. JENAM-2007 Special Session #6: Archaeoastronomy

Panko, Elena A.

2007-08-01

17

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 SMB and 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.

2013-08-01

18

Influence of aerosol source regions and transport pathway on ?D of terrestrial biomarkers in atmospheric aerosols from the East China Sea  

NASA Astrophysics Data System (ADS)

We measured stable hydrogen isotope ratios (?D) of terrestrial biomarkers (n-alkanes and n-fatty acids) in atmospheric total suspended particles collected at Jeju Island in the East China Sea, from April 2001 to March 2002, to better understand the influence of long-range atmospheric transport on their seasonal variations. The ?D values of the C27, C29 and C31n-alkanes (?DALK) show a significant negative correlation with the CPI values of n-alkanes (r2 = 0.26, p < 0.01), suggesting that the ?DALK variations are partly attributed to a superimposed contribution from fossil fuel hydrocarbons. Seasonal variations in the concentrations of the C22-C28 even-carbon numbered n-fatty acids revealed relatively high concentrations in spring, autumn and winter seasons, in which the air masses are transported from northeast Asia. In contrast, the concentrations are low in summer when the air masses are transported from Southeast Asia and the Pacific. Relatively high C26/FA and low C24/FA ratios in spring, autumn and winter samples suggest that the C26n-fatty acids are more abundantly transported from the Asian continent during these seasons. Seasonal variations in the ?D of the C22-C26 even-carbon numbered n-fatty acids exhibit significant enrichment with D (by ˜40‰) in May and June to August samples, whereas the ?D of the C28n-fatty acids gradually decrease during summer. The magnitude of the ?D offsets (˜45‰) between the C28n-fatty acid and the other homologues are much larger than those observed in East Asia spanning 18°N-50°N latitude (ca. 30‰), suggesting that the decoupling is likely attributed to the mixing of distinct source vegetation with different ?D ratios. Comparison of the weighted-mean ?D values of n-fatty acids (?DFA) between air mass source categories revealed relatively low values (˜-170‰) in samples with trajectories from the northeastern part of the Asian continent, supporting that the ?D analyses may be a powerful tool in deciphering the source regions of terrestrial biomarkers in atmospheric aerosols from the Asian continent. The results of this study provides important implications for paleoclimate studies that the ?D variations of long-range transported terrestrial biomarkers in remote ocean sediments may have recorded past changes in source strengths of the biomarkers and therefore have a potential to reconstruct paleo-wind patterns and transport of terrestrial carbon over the Pacific.

Yamamoto, Shinya; Kawamura, Kimitaka; Seki, Osamu; Kariya, Tadashi; Lee, Meehye

2013-04-01

19

Regional signals in the atmospheric excitation function of polar motion  

NASA Astrophysics Data System (ADS)

The influence of the atmosphere on variations of polar motion in the spectral range from 10 days to a few years is now generally accepted. Nevertheless, a better understanding of atmospheric forcing of polar motion would be gained by careful study of interactions between regional atmospheric variations and polar motion excitations. Regional patterns of variations of atmospheric excitation function are shown at different time scales. The data used here are regional Effective Atmospheric Angular Momentum (EAAM) computed both globally and in 108 geographic regions from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, for the period 1948-1999. The wind term and two surface pressure terms [pressure with an without the inverted barometer (IB) approximation, which adjusts the atmosphere model to account for an isostatic equilibrium response of the ocean to overlying atmospheric pressure] are considered. Fractional covariance amplitudes between regional and global atmospheric excitation functions are computed to identify the sectors of the globe over which changes contribute most importantly. Correlation coefficients between atmospheric and geodetic excitation function of observed polar motion are computed from the global series and in sectors for the period 1963-2000 to understand the relative role of the atmosphere versus polar motion. The covariance and correlation coefficients are computed from series that are separated to include annual, semiannual, 120 days (terannual), and short period (90-10 days) oscillations. The geographic distribution of fractional covariance and correlation maxima depends on the chosen spectral band. Some regions appear to be important in exciting polar motion in all these spectral bands: Eurasia, North Pacific, Greenland and North Atlantic, and Southern Ocean near South America. Applying the IB correction results in the dominance of Eurasia and North America, with disappearing contributions in almost all the ocean-dominated southern hemisphere regions, but the influence of the IB also depends on spectral band.

Nastula, Jolanta

20

The regional atmospheric chemistry mechanism, version 2  

NASA Astrophysics Data System (ADS)

The Regional Atmospheric Chemistry Mechanism (RACM) is a gas-phase chemical mechanism that is widely used for the modeling of regional atmospheric chemistry. Much new data has been published since the original RACM was completed (Stockwell et al., 1997). The RACM mechanism was updated to create the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2). Like the RACM1 mechanism, the RACM2 mechanism is designed to simulate remote to polluted conditions from the Earth's surface through the upper troposphere. The RACM2 mechanism includes updated reaction schemes, rate constants and product yields. It has been tested against environmental chamber data and compared with previous RACM scenario simulations. The aromatic chemistry was expanded to include a greater number of species with highly revised reaction schemes. The reaction mechanism for isoprene was expanded to include a more explicit treatment of methyl vinyl ketone. Alcohols were speciated to more accurately reflect peroxy-peroxy reactions in the remote atmosphere. Acetone was speciated due to its importance in the upper troposphere.

Goliff, Wendy S.; Stockwell, William R.; Lawson, Charlene V.

2013-04-01

21

Processes for identifying regional influences of and responses to increasing atmospheric CO{sub 2} and climate change - the MINK project: An overview  

SciTech Connect

Scientists believe that a serious change in the climate of the earth could occur in the course of the next two to five decades as a result of warming caused by the rapid accumulation of radiatively active trace gases in the atmosphere. There is concern that not only the amount of warming but the rate at which it occurs could be unprecedented, at least since the current interglacial period began. Scientific uncertainties remain in our understanding of the climatic changes that may follow from greenhouse warming. Nevertheless, large and rapid changes in regional climate are conceivable. General circulation models (GCMs) predict changes for the central U.S. as large as an 8{degrees}C increase in mean summertime temperature accompanied by a 1 mm/day decrease in mean precipitation. Most predictions are less extreme but, so long as the direction of change is credible, efforts are warranted to identify just what kinds of impacts to expect if society chooses to allow climate to change or cannot stop it from changing, and just what might be done to adjust to those impacts.

Rosenberg, N.J.; Crosson, P.R. [Resources for the Future, Washington, DC (United States)

1991-08-01

22

Moon influence on equatorial atmospheric angular momentum  

NASA Astrophysics Data System (ADS)

The variation of the equatorial atmospheric angular momentum function, coordinated with respect to a star-fixed system, is investigated in relation with the lunar tide. We isolate the rapid fluctuations, below 30 days, where Moon motion has a possible influence. First we notice that pressure term and wind term are almost proportional, by contrast to celestial seasonal band (S1). This would mean that, in this frequency band, the torque of the atmosphere on the solid Earth mostly results from the equatorial bulge. Spectrum reveals sharp lunar tidal peaks at 13.66 days (O1 diurnal tide in the terrestrial frame) and 13.63 days, reflecting the Moon influence on meridional circulation. We also observe powerful episodic fluctuations between 5 and 8 days (up to 10 mas), possibly resulting from non linear effect of the O1 tide, or tidal waves 2Q1 (6.86 days) and ?1 (7.095 days).

Bizouard, Christian; Zotov, Leonid; Sidorenkov, Nikolay

2014-05-01

23

Solar wind influence on atmosphere processes in winter Antarctica  

NASA Astrophysics Data System (ADS)

. Galactic cosmic rays altered by the solar wind are traditionally regarded as the most plausible agent of the solar activity influence on the Earth's atmosphere. Meanwhile, it is well known that severe reductions in the galactic cosmic rays flux, known as Forbush decrease (FD), are caused by the solar wind of high speed and density, which sweeps the galactic cosmic rays on its way. Since the FD beginnings are registered at the Earth's orbit simultaneously with dramatic disturbances in the solar wind, the atmospheric effects, assigned to Forbush decreases, can be, in reality, result of the solar wind influence on the atmospheric processes. The paper presents the summary of the experimental results demonstrating the strong influence of the interplanetary electric field on atmospheric processes in the central Antarctica, where the large-scale system of vertical circulation is formed during the winter seasons. The influence is realized through acceleration of the air masses, descending into the lower atmosphere from troposphere, and formation of cloudiness above the Antarctic Ridge, where the descending air masses income into the surface layer. The acceleration is followed by sharp increase of the atmospheric pressure in the near-pole region, which gives rise to the katabatic wind strengthening above the entire Antarctica. The cloudiness formation is resulted in the sudden warmings in the surface atmosphere, since the cloud layer efficiently backscatters the long wavelength radiation going from the ice sheet, but does not affect the adiabatic warming process of the descending tropospheric air masses. When drainage flow strong strengthening the circumpolar vortex about the periphery of the Antarctic continent decays, the surface easterlies typical of the coast stations during the winter season are replaced by southerlies and the cold Antarctic air masses rush in the Southern ocean.

Troshichev, Oleg

24

Solar wind influence on atmospheric processes in winter Antarctica  

NASA Astrophysics Data System (ADS)

Galactic cosmic rays (GCRs) altered by solar wind are traditionally regarded as the most plausible agent of solar activity influence on the Earth's atmosphere. However, it is well known that severe reductions in the GCRs flux, known as Forbush decreases (FDs), are caused by solar wind of high speed and density, which sweeps away the GCRs on its way. Since the FD beginnings are registered at the Earth's orbit simultaneously with dramatic disturbances in the solar wind, the atmospheric effects, assigned to FDs, can be, in reality, the results of the solar wind influence on the atmospheric processes. This paper presents a summary of the experimental results demonstrating the strong influence of the interplanetary electric field on atmospheric processes in central Antarctica, where the large-scale system of vertical circulation is formed during winter seasons. The influence is realized through acceleration of the air masses, descending into the lower atmosphere from the troposphere, and the formation of cloudiness above the Antarctic Ridge, where the descending air masses enter the surface layer. The acceleration is followed by a sharp increase of the atmospheric pressure near-pole region, which gives rise to the katabatic wind strengthening above the entire Antarctica. The cloudiness formation results in the sudden warmings in the surface atmosphere, since the cloud layer efficiently backscatters the long wavelength radiation from the ice sheet, but does not affect the adiabatic warming process of the descending tropospheric air masses. When the drainage flow strengthening the circumpolar vortex around the periphery of the Antarctic continent decays, the surface easterlies typical of the coast stations during the winter season are replaced by southerlies and the cold Antarctic air masses flow out to the Southern ocean.

Troshichev, O.

2008-12-01

25

Atlantic Coast Unique Regional Atmospheric Tracer Experiment (ACURATE).  

National Technical Information Service (NTIS)

The Atlantic Coast Unique Regional Atmospheric Tracer Experiment (ACURATE) is a program designed to obtain data necessary to evaluate atmospheric transport and diffusion models used to calculate regional population doses caused by nuclear facility emissio...

J. F. Schubert J. L. Heffter G. A. Mead

1983-01-01

26

Influence of CO on Titan atmospheric reactivity  

NASA Astrophysics Data System (ADS)

The atmosphere of Titan is mainly composed of N2 and CH4, and photochemical volatiles products CxHyNz. Most of the laboratory studies simulating Titan's atmospheric reactivity focus on the highly complex carbon and nitrogen organic chemistry leading to a production of laboratory analogues of Titan's aerosols, called Tholins [Alcouffe et al., 2010]. However, the atmosphere of Titan also contains traces of oxygen compounds. The most abudant one detected is carbon monoxyde CO with a 47 ppmv concentration measured in high stratosphere [de Kok et al., 2007]. In this work we investigate the influence of CO on the N2-CH4 reactivity. We simulate the whole reaction chains with a laboratory Radio Frequency Capacitively Coupled plasma discharge (RF CCP) gas mixture of nitrogen, methane and carbon monoxyde. In order to detect unambiguously the possible effects, CO is introduced with amounts of 0 - 1 - 2.25 - 4.5 %, larger than in Titan's atmosphere. The kinetics of the methane is monitored by mass spectrometry and the compositions of the gas phase and tholins are monitored by GC-MS and elemental analysis respectively. We find that CO modifies the composition of the gas phase with the detection of oxygenated compounds. CO decreases drastically the production efficiency of tholins, involving also a perturbation on the methane kinetics. The oxygen incorporation in tholins is found to be efficient . As a conclusion, we show that carbon monoxyde is effectively coupled with N2-CH4 chemistry and that it impacts even the solid organic aerosols. References: Alcouffe, G., et al (2010), Capacitively coupled plasma used to simulate Titan's atmospheric chemistry, Plasma Sources Science and Technology, 19(1), 015008. de Kok, R., et al. (2007), Oxygen compounds in Titan's stratosphere as observed by Cassini CIRS, Icarus, 186(2), 354-363.

Fleury, B.; Carrasco, N.; Gautier, T.; Mahjoub, A.; He, J.; Szopa, C.; Buch, A.; Cernogora, G.

2013-12-01

27

Solar wind influence on atmospheric processes in winter Antarctica  

NASA Astrophysics Data System (ADS)

The experimental results demonstrate influence of the great southward interplanetary magnetic field (IMF) and the corresponding geoeffective interplanetary electric field on atmospheric pro-cesses in the central Antarctica, where the large-scale system of vertical circulation takes place during the winter seasons. The interplanetary electric field influence is realized through ac-celeration of the air masses, descending into the lower atmosphere from the troposphere, and formation of cloudiness above the Antarctic Ridge, where the descending air masses enter the surface layer. The cloudiness results in the sudden warmings in the surface atmosphere, because the cloud layer efficiently backscatters the long wavelength radiation going from ice sheet, but does not affect the process of adiabatic warming of the descending air masses. Influence of the interplanetary electric field on cloudiness has been revealed for epochs of the solar activity minimum, when Forbush decreases effect is absent. The altitudinal profiles of temperature, varying in the opposite manner under influence of the southward and northward IMF, indicate that the cloud layer formation occurs at h = 8 -10 km. The acceleration of the descending air masses is followed by a sharp increase of the atmospheric pressure in the near-pole region, which gives rise to the katabatic wind strengthening above the entire Antarctica. As a result, the circumpolar vortex around the periphery of the Antarctic continent decays and the surface easterlies, typical of the coast stations during the winter season, are replaced by southerlies. It is suggested that the resulting invasion of the cold air masses into the Southern ocean leads to destruction the regular relationships between the sea level pressure fluctuations in the South-east Pacific high and the North Australian-Indonesian low, since development the El-Niño event n strongly follows anomalous atmospheric processes in the winter Antarctica.

Troshichev, Oleg; Egorova, Larisa; Vovk, Valery; Janzhura, Alexander

28

Influence of CO on Titan atmospheric reactivity  

NASA Astrophysics Data System (ADS)

The atmosphere of Titan is mainly composed of N2 and CH4 which are the source of various CxHyNz photochemical volatiles products. Laboratory simulations of the Titan’s atmospheric reactivity were mainly interested in the study of the complex organic chemistry which leads to the formation of analogues of Titan’s aerosols, called tholins. These studies were mainly interested in the reactivity of the N2/CH4 gaseous mixture and with the primary products of reactions without oxygen. However, the atmosphere of Titan also contains oxygenated volatile species. The most abundant one to have been detected is CO with a concentration about 50 ppmv. The work presented here is an experimental simulation devoted to estimate the influence of CO on the Titan’s atmospheric reactivity. With this aim, CO is introduced in a standard N2/CH4 mixture at different mixing ratio up to 4.5%. The kinetics of the methane consumption is monitored with in situ mass spectrometry and the compositions of the gaseous phase and tholins produced in the reactor are characterized ex situ with GC-MS and elemental analysis. This work shows that CO modifies the composition of the gas phase with the detection of oxygenated compounds: CO2 and N2O. The presence of CO also drastically decreases the production rate of tholins, involving also a perturbation on the methane kinetics. Tholins are produced in lower global amounts, but their sizes are found to be significantly larger than without CO. The oxygen incorporation in tholins is found to be efficient, with an oxygen content of the same order of magnitude as the amount of CO in the initial gas mixture.

Fleury, B.; Carrasco, N.; Gautier, T.; Mahjoub, A.; He, J.; Szopa, C.; Hadamcik, E.; Buch, A.; Cernogora, G.

2014-08-01

29

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

30

Regional Atmospheric Modeling of Caribbean Climate  

NASA Astrophysics Data System (ADS)

We use the Regional Atmospheric Modeling System (RAMS) to simulate climatic pattern on the island of Puerto Rico. We hope our analyses will be used to determine the effects of climate change on other Caribbean and tropical islands. Our first experiments were to simulate the precipitation patterns on the island and the urban heat island effect. The main model configuration consists of two grids. Grid 1 covers the entire Caribbean area and has a horizontal resolution of 20 km; it was used mainly for downscaling the large-scale observational data and for boundary nudging. Grid 2 has a horizontal resolution of 5 km and covers the island of Puerto Rico and surrounding waters with the full microphysical parameterization. RAMS was configured to use a vegetation index based on AVHRR data from NOAA 12 and NOAA 14 satellites. From these images we show that the vegetation for the month of January is more abundant than in March. Mean diameters for cloud droplets and raindrops where specified as 35 micrometers and 100 micrometers, respectively. We minimized errors due to clouds by combining data into a monthly composites. We found that experimentation with the microphysical parameterization had a significant impact in the total precipitation amount over the island. RAMS robustly simulated the total accumulated precipitation for the month of April 1998 as well the dependence of the precipitation pattern on the local topography over the island of Puerto Rico. To test the urban heat island effect RAMS was configured using only infrared emission and absorption of water vapor and carbon dioxide without treating clouds or condensate. A soil model was used with ten layers 5 cm thick. The model clearly shows that because of the urban heat island effect San Juan is 5° warmer than the surrounding area. The model results were validated using an extensive network of environmental monitoring instruments from various agencies covering the island of Puerto Rico. The data was converted to a common format using the Java application and made available over the internet using Java Server Pages. Statistical analysis and neural network techniques were employed to improve resolution of sparse lower atmospheric data.

Winter, A.; Gonzalez, J.; Ramirez, N.; Vásquez, R.

2002-12-01

31

Topographic Influence and Atmospheric Dynamics in the Indian Wells Valley  

NASA Astrophysics Data System (ADS)

Indian Wells Valley (IWV) is home to the China Lake Naval Air Weapons Station (NAWS) whose operations necessitate regional forecasting and weather analysis relevant to aviation and plume release scenarios. In order to better understand the terrain influenced mesoscale circulations in the varied complex terrain of Indian Wells Valley surrounding Ridgecrest, four seasonal WRF simulations were analyzed using linear shallow water theory and nonlinear theory for flows over two-dimensional mountains. The goal is to better understand the relationships between atmospheric dynamical processes and the wind/thermal structure of the mesoscale at Indian Wells Valley. This will involve exploring relationships linking theoretical meteorology in complex terrain and advanced high resolution atmospheric modeling in this region. The WRF simulation results show several distinct circulations which rely on the interaction between complex terrain and the background weather conditions: 1) In calm synoptic conditions, diurnal processes guide the evolution of boundary layer stability and slope flows. 2) In periods of greatest seasonal surface heating (i.e. summer), the pressure gradient across the Sierra Nevada drives near surface westerlies across IWV. 3) In conditions with strong synoptic scale increase in stability and meridional winds across the Sierra Nevada, a downslope windstorm can develop in IWV. The downslope winds and compensatory gravity wave activity over IWV will conclude once there is a significant change in conditions aloft, or an increase in convective instability at the surface of IWV which prevents air aloft from sinking towards the surface. These results provide a better understanding of the mesoscale meteorology in this region and improve forecast and analysis for plume transport and aviation needs while also laying the groundwork for future projects managing environmental concerns in this region.

Uher, Erich J.

32

A Climate Version of the Regional Atmospheric Modeling System  

Microsoft Academic Search

Summary   The Regional Atmospheric Modeling System (RAMS) has been widely used to simulate relatively short-term atmospheric processes.\\u000a To perform full-year to multi-year model integrations, a climate version of RAMS (ClimRAMS) has been developed, and is used\\u000a to simulate diurnal, seasonal, and annual cycles of atmospheric and hydrologic variables and interactions within the central\\u000a United States during 1989. The model simulation

G. E. Liston; R. A. Pielke

2000-01-01

33

Regional forecasting with global atmospheric models  

NASA Astrophysics Data System (ADS)

The scope of the report is to present the results of the fourth year's work on the atmospheric modeling part of the global climate studies task. The development testing of computer models and initial results are discussed. The appendices contain studies that provide supporting information and guidance to the modeling work and further details on computer model development. Complete documentation of the models, including user information, will be prepared under separate reports and manuals.

Crowley, T. J.; North, G. R.; Smith, N. R.

1994-05-01

34

Data on atmospheric transmission in the IR spectral region  

NASA Technical Reports Server (NTRS)

The weakening of radiation by the atmosphere in the infrared region of the spectrum was studied. The instrument used for the measurements was the IKAU-1 infrared atmospheric unit, and measurements were carried out both on an inclined path and a near-earth horizontal path.

Paramonova, N. N.; Kazakova, K. V.; Brounshteyn, A. M.

1979-01-01

35

Generation of Regional Climate Ensembles Using Atmospheric Forcing Shifting  

NASA Astrophysics Data System (ADS)

One of the main challenges in climate change research is improving knowledge about how regional climates may change in the next decades. Reliable information about changes of the mean climate state and extreme events such as heavy precipitation and dry spells are required for the water and risk management as well as for the development of adaptation and mitigation strategies. High-resolution ensembles are used to perform studies on the variability and change of regional climate and to assess the uncertainty of regional climate model (RCM) projections. In this study, we present Atmospheric Forcing Shifting (AFS) as an innovative ensemble generation technique and address the question how AFS affects the results of the regional climate simulations. Furthermore, the influence of synoptic conditions on the effect of AFS and the benefit of AFS for the generation of RCM ensembles are discussed. AFS is realised by introducing small shifts to the atmospheric fields derived from global data (here: ERA40 reanalyses) to each direction by 25 and 50 km, respectively. The shifted fields drive COSMO-CLM simulations for Europe with a horizontal resolution of 50 km. Besides the reference simulation, eight shifting scenarios are included into the RCM ensemble. The effect of AFS on 2m temperature and precipitation is studied for Central Europe and the period from 1980 to 1984. This includes the quantification and validation of the ensemble spread in comparison to the E-OBS dataset and COSMO-CLM simulations driven by different global climate models (GCMs). The investigation of the mean annual cycle and spatial distribution indicates that the effect of AFS on precipitation is larger and more heterogeneous than on 2m temperature. In summer, the ensemble variability is larger than in winter which is likely to be related to the frequency of synoptic conditions. Furthermore, AFS affects the probability distribution of 2m temperature and precipitation, including their extremes. Consequently, AFS may provide a suitable method to improve the statistics of extreme events. The next step is to generate an RCM ensemble with a resolution of 7 km for past (1971-2000) and future (2011-2040) decades using AFS and different GCMs. Based on the results, change signals of the mean climate state as well as of the likelihood and variability of extreme events will be determined.

Sasse, R.; Schädler, G.; Feldmann, H.; Kottmeier, Ch.

2012-04-01

36

Biogenic influence on cloud microphysics in the 'clean' oceanic atmosphere  

NASA Astrophysics Data System (ADS)

A 20 years old hypothesis postulates a feedback relationship between marine biota and climate through the emission of dimethylsulfide (DMS) as the principal natural source of Sulfate Secondary Aerosols (S-DMS) that are very efficient as cloud condensation nuclei (CCN). In recent years, the biological influence on cloud microphysics have been expanded to other potential biogenic cloud precursors: (i) volatile organic compounds produced by plankton and emitted to the atmosphere to form Secondary Organic Aerosols (SOA); (ii) biological particles and biogenic polymers, lifted with the seaspray by wind friction and bubble-bursting processes, that act as Primary Organic Aerosols (POA). Besides these biogenic aerosols, also seaspray-associated Sea Salt (SS) emissions, which are the dominant contribution to aerosol mass in the remote mixed boundary layer, also contribute to cloud condensation. All these aerosols affect cloud microphysics by providing new CCN, reducing the size of cloud droplets, and increasing cloud albedo. We have compared the seasonalities of the parameterized source functions of these natural cloud precursors with that of the satellite-derived cloud droplet effective radius (CLEFRA) over large regions of the ocean. Regions where big loads of continental aerosols (including anthropogenic -industrial, urban, and biomass burning) dominate during a significant part of the year were identified by use of remote sensing aerosol optical properties and excluded from our analysis. Our results show that the seasonality of cloud droplet effective radius matches those of S-DMS and SOA in the clean marine atmosphere, whereas SS and chlorophyll-associated POA on their own do not seem to play a major role in driving cloud droplet size.

Lana, A.; Simó, R.; Vallina, S. M.; Jurado, E.; Dachs, J.

2009-12-01

37

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

38

Regional climatic effects of atmospheric SO2 on Mars  

NASA Astrophysics Data System (ADS)

The conditions under which the valley networks on Mars may have formed remains controversial. The magnitude of an atmospheric greenhouse effect by an early massive CO2 atmosphere has recently been questioned by Kasting. Recent calculations indicate that if solar luminosity were less than about 86 percent of its current value, formation of CO2 clouds in the Martian atmosphere would depress the atmospheric lapse rate and reduce the magnitude of surface warming. In light of recent revisions of magma generation on Mars during each Martian epoch, and the suggestions by Wanke et al. that the role of liquid SO2 should be more carefully explored, we have recalculated the potential greenhouse warming by atmospheric SO2 on Mars, with an emphasis on more localized effects. In the vicinity of an active eruption, the concentration of atmospheric SO2 will be higher than if it is assumed that the erupted SO2 is instantaneously globally distributed. The local steady-state concentration of SO2 is a function of the rate at which it is released, its atmospheric lifetime, and the rate at which local winds act to disperse the SO2. We have made estimates of eruption rates, length of eruption, and dispersion rates of volcanically released SO2, for a variety of atmospheric conditions and atmospheric lifetimes of SO2 to explore the maximum regional climatic effect of SO2.

Postawko, S. E.; Fanale, F. P.

39

Influences of Atmospheric Stability State on Wind Turbine Aerodynamic Loadings  

NASA Astrophysics Data System (ADS)

Wind turbine power and loadings are influenced by the structure of atmospheric turbulence and thus on the stability state of the atmosphere. Statistical differences in loadings with atmospheric stability could impact controls, blade design, etc. Large-eddy simulation (LES) of the neutral and moderately convective atmospheric boundary layer (NBL, MCBL) are used as inflow to the NREL FAST advanced blade-element momentum theory code to predict wind turbine rotor power, sectional lift and drag, blade bending moments and shaft torque. Using horizontal homogeneity, we combine time and ensemble averages to obtain converged statistics equivalent to ``infinite'' time averages over a single turbine. The MCBL required longer effective time periods to obtain converged statistics than the NBL. Variances and correlation coefficients among wind velocities, turbine power and blade loadings were higher in the MCBL than the NBL. We conclude that the stability state of the ABL strongly influences wind turbine performance. Supported by NSF and DOE.

Vijayakumar, Ganesh; Lavely, Adam; Brasseur, James; Paterson, Eric; Kinzel, Michael

2011-11-01

40

Influence of atmospheric aerosols and desert reflectance properties on satellite radiance measurements  

NASA Technical Reports Server (NTRS)

The influence of surface bidirectional reflectance factors, including shadowing, and of atmospheric aerosol variability are modeled for their effects on the remote sensing of desert targets from space in the 0.7-micron region at high spatial resolution. The white sand reflectance data of Salomonson (1968) are used as the basis for the simulation. The effects of the surface bi-directional reflectance and atmospheric aerosol on the nadir-normalized reflectance measured at the satellite are discussed individually and jointly. The net influence of these two factors is shown to depend on the magnitude of other parameters, such as the surface reflectance and solar zenith angle.

Bowker, D. E.; Davis, R. E.

1992-01-01

41

Regional climate model of the Arctic atmosphere  

NASA Astrophysics Data System (ADS)

A regional climate model of the whole Arctic using the dynamical package of the High-Resolution Limited Area Model (HIRLAM) and the physical parameterizations of the Hamburg General Circulation Model (ECHAM3) has been applied to simulate the climate of the Arctic north of 65°N at a 50-km horizontal resolution. The model has been forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses at the lateral boundaries and with climatological or actual observed sea surface temperatures and sea ice cover at the lower boundary. The results of simulating the Arctic climate of the troposphere and lower stratosphere for January 1991 and July 1990 have been described. In both months the model rather closely reproduces the observed monthly mean circulation. While the general spatial patterns of surface air temperature, mean sea level pressure, and geopotential are consistent with the ECMWF analyses, the model shows biases when the results are examined in detail. The largest biases appear during winter in the planetary boundary layer and at the surface. The underestimated vertical heat and humidity transport in the model indicates the necessity of improvements in the parameterizations of vertical transfer due to boundary layer processes. The tropospheric differences between model simulations and analyses decrease with increasing height. The temperature bias in the planetary boundary layer can be reduced by increasing the model sea ice thickness. The use of actual observed sea surface temperatures and sea ice cover leads only to small improvements of the model bias in comparison with climatological sea surface temperatures and sea ice cover. The validation of model computed geopotential, radiative fluxes, surface sensible and latent heat fluxes and clouds against selected station data shows deviations between model simulations and observations due to shortcomings of the model. This first validation indicates that improvements in the physical parameterization packages of radiation and in the description of sea ice thickness and sea ice fraction are necessary to reduce the model bias.

Dethloff, Klaus; Rinke, Annette; Lehmann, Ralph; Christensen, Jens H.; Botzet, Michael; Machenhauer, Bennert

1996-10-01

42

Radiosonde observational evidence of the influence of extreme SST gradient upon atmospheric meso-scale circulation  

NASA Astrophysics Data System (ADS)

Although the influence of the anomalous midlatitude SST upon atmospheric local circulation has been getting common in particular over the Kuroshio and the Gulf Stream regions, observational studies on the influence of the Okhotsk Sea, which is to the north of the Kuroshio, upon the atmospheric local circulation is much less than those of the Kuroshio. The climate of the Okhotsk SST is very peculiar. Extremely cold SST spots, whose summertime SST is lower than 5 Celsius degrees, are formed around Kuril Islands. Because SSTs are generally determined by local air-sea interaction as well as temperature advection, it is very difficult to isolate only the oceanic influence upon the atmosphere. The SST in this cold spot is, however, dominated by the tidal mixing, which is independent of the atmospheric processes. This unique condition may ease the account for the oceanic influence only. Although the SST environment of the Okhotsk Sea is good for understanding the oceanic influence upon the atmosphere, only a few studies has been executed in this region because of the difficulty of observations by research vessels in this region, where territory problems between Japan and Russia is unsolved. Because of the scant of direct observation, the Okhotsk Sea was still mysterious. In 2006 August, GPS radiosonde observation was carried out by Russian research vessel Khromov in the Sea of Okhotsk by the cooperation between Japan and Russia, and strong SST gradient of about 7 Celsius degrees/10km was observed around the Kuril Islands. The purpose of this study is to demonstrate observational finding of meso-scale atmospheric anticyclonic circulation influenced by the cold oceanic spot around the Kuril Island. The summaries of the observation are as follows. Meso-scale atmospheric ageostrophic anticyclonic circulation in the atmospheric marine-boundary layer is observed in and around the cold spot. A high air pressure area as compared with other surrounding areas is also located at the area of the ageostrophic anticyclonic circulation. In addition, the location of the cold dome in the atmospheric marine-boundary layer is in accordance with that of the large SST gradient. The cold dome with denser air than the surroundings probably strengthened the high pressure associated with subsidence over the cold dome. The downward direction of the sensible heat flux estimated by surface meteorological observation suggests that the cold dome was formed by the cooling by the cold sea. During the observation period around this area, the synoptic-scale sea level pressure field hardly changed. No reanalysis data sets resolve this anticyclonic circulation in this area. Therefore, we can conclude that the meso-scale anticyclone was formed by the influence of this cold SST and its large gradient.

Nishikawa, H.; Tachibana, Y.; Udagawa, Y.

2012-12-01

43

Geomagnetic Activity Influence on Thermobaric Characteristics of the Atmosphere.  

NASA Astrophysics Data System (ADS)

The main points of the model of the solar activity effect on the Earth climatic system are presented. The model is based on the physical mechanism of heliogeophysical factors influence on climatic characteristics and atmospheric circulation in the high-latitude troposphere through the atmospheric electricity. In accordance with this mechanism, the atmospheric electricity parameters in the high latitudes depend on the solar activity; at the same time, they influence the altitude distribution of charged condensation nuclei in the troposphere, as well as the cloudiness formation and radiation balance. The mechanism is proved to operate more efficiently in the high latitudes resulting in additional cloudiness formation in areas with adequate vapour concentration. We present complex analysis results of response of temperature and tropospheric pressure fields to different heliogeophysical disturbances. It is detected that regular changes of the temperature and pressure field dynamic accompany these disturbances.

Rubtsova, O. A.; Zherebtsov, G. A.; Kovalenko, V. A.; Molodykh, S. I.

2009-10-01

44

Investigating causes of regional variations in atmospheric carbon dioxide concentrations  

NASA Astrophysics Data System (ADS)

Atmospheric CO2 concentrations are rapidly increasing due to anthropogenic activities; however, only about half of the emissions have accumulated in the atmosphere, and the fate of the remaining half remains uncertain. Since atmospheric CO2 concentrations contain information regarding carbon sources and sinks, it is important to understand CO 2 variability. This study investigated causes of atmospheric CO 2 variability, focusing on the relationship between CO2 concentrations and clouds, the impact of heterogeneous land cover and agricultural production, and the effect of redistributing fossil fuel emissions. Due to global coverage and sheer data volume, satellite CO2 concentrations will be used in inverse models to improve carbon source and sink estimates. Satellite concentrations will only retrieve CO2 measurements in clear conditions, and it is important to understand how CO 2 concentrations vary with cloud cover in order to optimally utilize these data. This study evaluated differences between clear-sky and mean concentrations on local, regional, and global scales. Analyses of in situ data, regional model simulations, and global model output all revealed clear-sky differences that were regionally coherent on sub-continental scales and that varied both with time and location. In the mid-latitudes, clear-sky CO2 concentrations were systematically lower than on average, and these differences were not due to biology, but rather to frontal convergence of large-scale gradients that were covered by clouds. Instead of using satellite data to represent temporal averages, inverse models and data assimilation systems that use satellite data to calculate carbon sources and sinks must be sampled consistently with the observations, including precise modeling of winds, clouds, fronts, and frontal timing. Just as CO2 concentrations vary with cloud cover, variability in atmospheric CO2 concentrations is also caused by heterogeneity in land cover and surface fluxes. This study focused on the impacts of land-cover heterogeneity and the effects of agricultural production on regional variations of atmospheric CO2 concentrations. Including sub-grid scale land cover heterogeneity improved simulated atmospheric CO2 concentrations by ˜ 1 ppm. Implementing a crop-phenology model that explicitly simulated corn and soybeans into a coupled ecosystem-atmosphere model dramatically improved CO2 fluxes and concentrations over the mid-continent, with reductions in CO2 concentration root mean square errors of nearly 50% (over 10 ppm at some locations). Both the model and observations showed concentrations as low as 340 ppm over central Iowa, and a regional gradient of over 30 ppm in ˜ 200 km occurred due to a combination of fluxes and meteorology. Since corn and soybeans have such a significant impact on both carbon fluxes and atmospheric concentrations, it is essential to model these crops accurately. In addition to biological surface fluxes, surface emissions due to fossil fuel combustion also cause variability in regional atmospheric CO2 concentrations. Using high-resolution fossil fuel emissions caused differences of over 10 ppm near the surface; and including temporal variability in the emissions impacted regional CO2 concentrations on monthly timescales, causing seasonal differences of more than 20 ppm in some locations. Using coarse spatial distributions and unaccounting for temporal variability in fossil fuel emissions created biases in the atmospheric CO2 concentrations and thus may cause significant errors in source and sink estimates from atmospheric inversions.

Corbin, Katherine D.

45

Atmospheric energy cycle: a regional indicator of the climate vulnerability  

NASA Astrophysics Data System (ADS)

The assessment of the vulnerability of densely populated regions to major natural disasters, including climatic variations, is a topic of intense investigation. Indices of vulnerability have been developed based on social, economic and climatic factors. However, the relative importance of the processes involved is still subject of debate. Here, we investigate the possibility to employ the Lorentz energy cycle as an indicator of the climatic conditions. We compute the energy and energy conversion for a period of 30 years for regions that are already defined as vulnerable to climate variations. The atmospheric energetics of São Paulo is calculated climatically and highlighted the periods occurrence of floods. From detailed studies of energy during periods posted some regional indicators of the climate vulnerabilities are suggested for cities studied, showing the importance of atmospheric dynamics in defining these indicators. This work is supported by FAPESP under the grant agreement no. 2008/58161-1 (PFPMCG - Projeto Temático) and no. 2011/13976-0.

Da Silva, L. A.; Marengo, J. A.; Vieira, L. A.; Chan, C. S.; Lyra, A.

2013-05-01

46

Introducing surface waves in a coupled wave-atmosphere regional climate model: Impact on atmospheric mixing length  

NASA Astrophysics Data System (ADS)

The marine atmospheric boundary layer is strongly influenced by the moving surface in the presence of surface waves; the impact depends on the wave conditions and the interaction with the atmosphere. Previous studies using measurements as well as numerical simulations with large-eddy simulations have shown that surface waves propagating faster than the wind (swell) alter the surface exchange as well as turbulence properties in the atmosphere. This impact is here introduced in a coupled wave-atmosphere regional climate model with a so-called E - l turbulence scheme (where E is the turbulent kinetic energy and l is a mixing length). A wave age dependent coefficient (here called Wmix) is added to the mixing length in the turbulence parameterization. This acts similarly to inducing additional convection, with larger mixing length and increased eddy diffusivity, when we have near neutral stratification and strong swell. For shallow boundary layers the regional coupled climate model shows a larger response to the introduced wave coupling with increased near surface wind speed and smaller wind gradient between the surface and middle part of the boundary layer. The impact for the studied areas is relatively minor for parameters averaged over 1 year, but for limited periods and specific situations the impact is larger. One could expect a larger impact in areas with stronger swell dominance. We thus conclude that the impact of swell waves on the mixing in the boundary layer is not insignificant and should be taken into account when developing wave-atmosphere coupled regional climate models or global climate models.

Rutgersson, A.; Nilsson, E. O.; Kumar, R.

2012-11-01

47

Regional Carbon Fluxes and Atmospheric Carbon Dynamics in the Southern Great Plains during the 2007 CLASIC intensive  

Microsoft Academic Search

In June 2007, a regional campaign took place in the Southern Great Plains (SGP) to estimate land-atmosphere exchanges of CO2, water, and energy at 1 to 100 km scales. The primary goals of this campaign were to evaluate top-down and bottom-up estimates of regional fluxes and to understand the influence of moisture gradients, surface heterogeneity, and atmospheric transport patterns on

S. C. Biraud; M. S. Torn; W. J. Riley; M. L. Fischer; D. P. Billesbach; R. Avissar; J. A. Berry; A. Hirsch; M. Loewenstein; J. Lopez

2007-01-01

48

Influence of dust loading on atmospheric ionizing radiation on Mars  

NASA Astrophysics Data System (ADS)

Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

2014-01-01

49

Influence of Dust Loading on Atmospheric Ionizing Radiation on Mars  

NASA Technical Reports Server (NTRS)

Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

2014-01-01

50

Middle atmosphere temperature and dynamics as revealed from D-region observations  

NASA Technical Reports Server (NTRS)

The concept of so-called meteorological control of the ionospheric D-region is presently undergoing development. According to this concept the electron concentration in this region is governed not only by solar and geomagnetic parameters but strongly depends on the temperature and dynamical regime of the mesosphere and stratosphere. How this connection between D-region and meteorological parameters can be used to obtain some information about middle atmosphere temperature and dynamics is examined. The essential points of the meteorological control concept are reviewed and the influence of turbulence on nitric oxide distribution and thus the ion production rate is discussed.

Danilov, A. D.

1984-01-01

51

Precipitation, sublimation, and snow drift in the Antarctic Peninsula region from a regional atmospheric model  

Microsoft Academic Search

A regional atmospheric model, with a horizontal grid spacing (?x) of 14 km, is used to study the surface mass balance components (precipitation, sublimation, and snow drift) in the region of the Antarctic Peninsula (AP). An integration is performed for the 7-year period 1987–1993, using a realistic forcing at the lateral model boundaries and at the sea surface. Output from

N. P. M. van Lipzig; J. C. King; T. A. Lachlan-Cope; M. R. van den Broeke

2004-01-01

52

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

53

Relative Influence of Initial Surface and Atmospheric Conditions on Seasonal Water and Energy Balances  

NASA Technical Reports Server (NTRS)

We constructed and analyzed wet and dry soil moisture composites for the mid-latitude GCIP region of the central US using long climate model simulations made with the NCAR CCM3 and reanalysis products from NCEP. Using the diagnostic composites as a guide, we have completed a series of predictability experiments in which we imposed soil water initial conditions in CCM3 for the GCIP region for June 1 from anomalously wet and dry years, with atmospheric initial conditions taken from June 1 of a year with 'near-normal' soil water, and initial soil water from the near-normal year and atmospheric initial conditions from the wet and dry years. Preliminary results indicate that the initial state of the atmosphere is more important than the initial state of soil water determining the subsequent late spring and summer evolution of sod water over the GCIP region. Surprisingly, neither the composites or the predictability experiments yielded a strong influence of soil moisture on the atmosphere. To explore this further, we have made runs with extreme dry soil moisture initial anomalies imposed over the GCIP region (the soil close to being completely dry). These runs did yield a very strong effect on the atmosphere that persisted for at least three months. We conclude that the magnitude of the initial soil moisture anomaly is crucial, at least in CCM3, and are currently investigating whether a threshold exists, below which little impact is seen. In a complementary study, we compared the impact of the initial condition of snow cover versus the initial atmospheric state over the western US (corresponding to the westward extension of the GAPP program follow-on to GCIP). In this case, the initial prescription of snow cover is far more important than the initial atmospheric state in determining the subsequent evolution of snow cover. We are currently working to understand the very different soil water and snow cover results.

Oglesby, Robert J.; Marshall, Susan; Roads, John O.; Robertson, Franklin R.; Goodman, H. Michael (Technical Monitor)

2001-01-01

54

Atmosphere Dynamics of the Active Region NOAA 11024  

NASA Astrophysics Data System (ADS)

We present results of the study of chromospheric and photospheric line-of-sight velocity fields in the young active region NOAA 11024. Multi-layer, multi-wavelength observational data were used for the analysis of the emerging flux in this active region. Spectropolarimetric observations were carried out with the telescope THEMIS on Tenerife (Canary Islands) on 4 July 2009. In addition, space-borne data from SOHO/MDI, STEREO and GOES were also considered. The combination of data from ground- and space-based telescopes allowed us to study the dynamics of the lower atmosphere of the active region with high spatial, spectral, and temporal resolutions. THEMIS spectra show strong temporal variations of the velocity in the chromosphere and photosphere for various activity features: two pores, active and quiet plage regions, and two surges. The range of variations of the chromospheric line-of-sight velocity at the heights of the formation of the H? core was extremely large. Both upward and downward motions were observed in these layers. In particular, a surge with upward velocities up to -73 km s-1 was detected. In the photosphere, predominantly upward motions were found, varying from -3.1 km s-1 upflows to 1.4 km s-1 downflows in different structures. The velocity variations at different levels in the lower atmosphere are compatible with the emergence of magnetic flux.

Kondrashova, N. N.; Pasechnik, M. N.; Chornogor, S. N.; Khomenko, E. V.

2013-06-01

55

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

56

Atmospheric Pollution and Emission Sources in South Asian Urban Region  

NASA Astrophysics Data System (ADS)

Rapid urbanization, and lack of efficient monitoring and control of pollution, along with phenomena like Asian Brown Haze or prolonged episodes of winter fog, makes the South Asian atmospheric chemistry a very complex one. The anthropogenic aerosols released from this region are projected to become the dominant component of anthropogenic aerosols worldwide in the next 25 years (Nakicenovic and Swart, 2000). The region is one of the most densely populated in the world, with present population densities of 100-500 persons km-2. There are six big cities, namely, Delhi, Dhaka, Karachi, Kolkata, Lahore, and Mumbai, each housing a population around or above 10 million. There is now a real concern about the sustainability of the region's ability to support the population due to air pollution, loss of biodiversity and soil degradation. Therefore, we conducted several extensive campaigns over last 10 years in Lahore, Karachi, and Islamabad in Pakistan to (1) chemically characterize the aerosols (PM2.5 mass, concentrations of trace elements, ions, black and organic carbon), and gaseous pollutants (concentrations of NH3, SO2, HONO, HNO3, HCl and (COOH)2, and (2) identify the major emission sources in this region. Exceedingly high concentrations of all species, relative to major urban areas of US and Europe, were observed. Concentrations of PM2.5, BC, Pb, SO42-, NH4+, HONO, NH3 respectively, up to 476, 110, 12, 66, 60, 19.6 and 50 ?gm-3 were observed in these cities, which were far in excess of WHO and US EPA air quality standard (Biswas et al., 2008). We use air parcel back trajectories, intercomponent relationships and meteorological observations to explain chemistry and emission sources of aerosol constituents. Carbonaceous aerosols contributed up to 69% of the PM2.5 mass (Husain et al., 2007). Source apportionment was conducted using positive matrix factorization. The analysis has classified six emission sources of aerosol components, namely, industrial activities, wood burning, secondary aerosols, metal processing, vehicular emissions, and crustal and road dust. Findings of our study will play a vital role in adopting a strategy to regulate emissions, and to mitigate the long-term climate change in the region. References: Nakicenovic, N. and Swart, R., 2000. In: N. Nakicenovic and R. Swart, Eds, Emissions Scenarios 2000. Special Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge. Biswas, K.F., Ghauri, B.M., Husain, L., 2008. Gaseous and aerosol pollutants during fog and clear episodes in South Asian urban atmosphere. Atmospheric Environment, 42, 7775-7785. Husain, L., Dutkiewicz, V.A., Khan, A.J., Ghauri, B.M., 2007. Characterization of carbonaceous aerosols in urban air. Atmospheric Environment, 41, 6872-6883.

Biswas, K. F.; Husain, Liaquat

2009-04-01

57

Influence of the Indian Ocean Dipole on Atmospheric Subseasonal Variability.  

NASA Astrophysics Data System (ADS)

The relationship between atmospheric subseasonal variability and interannual variation of SST over the tropical Indian Ocean is examined using winds and humidity from the NCEP-NCAR reanalysis, outgoing longwave radiation (OLR), and the monthly SST analysis. The primary focus is on whether and how the subseasonal variability is related to the zonal dipole structure of SST, which peaks during boreal fall. The level of subseasonal wind activity is measured by standard deviation of bandpass-filtered zonal wind fields on the 6-30- and 30-90-day time scales.During boreal fall (September-November), the interannual variation of 6-30-day (submonthly) near-surface zonal wind activity in the central and eastern equatorial Indian Ocean is highly correlated with the large-scale zonal SST gradient. The intensity of submonthly variability is largely reduced during positive dipole years. A significant reduction of intraseasonal (30-90-day) wind activity is also evident during large dipole events. However, the correlation with the zonal SST gradient is much weaker than that of submonthly variability.The mechanism by which the Indian Ocean dipole influences equatorial submonthly winds is investigated based on a cross-correlation analysis of OLR and winds. During negative dipole years, submonthly convection is active in the southeast Indian Ocean where the anomalous convergence of surface moisture associated with dipole events is at its maximum. The submonthly convection in this region is often associated with a cyclonic circulation, and these disturbances propagate westward. Consequently, equatorial westerlies and northwesterly winds near the coast of Sumatra are generated. During positive dipole years, submonthly convective activity is highly reduced in the southeast Indian Ocean, and thus no equatorial westerly is generated.Ocean response to submonthly disturbances is examined using OGCM experiments forced with winds from the NCEP-NCAR reanalysis. Results suggest that submonthly winds can generate significant upper-ocean response, including strong eastward surface currents near the equator and sea surface height anomalies along the coast of Sumatra where the large SST anomalies associated with dipole events are observed.

Shinoda, Toshiaki; Han, Weiqing

2005-09-01

58

Modulation mechanisms of marine atmospheric boundary layer at the Brazil-Malvinas Confluence region  

NASA Astrophysics Data System (ADS)

The influence of the Brazil-Malvinas Confluence (BMC) region on the marine atmospheric boundary layer (MABL) is investigated through in situ data analysis of five different cruises (2004 to 2008) and numerical experiments with a regional atmospheric model. Two different groups of numerical experiments were performed in order to evaluate the relevance of static stability and hydrostatic balance physical mechanisms for the MABL instability. The first group used monthly climatological sea surface temperature (SST) as bottom boundary condition while the second used daily updated Advanced Microwave Scanning Radiometer-EOS SST data together with radiosondes and surface data assimilation. A reasonable agreement between numerical results and QuikSCAT wind data was observed through correlation coefficients and mean square error values. In terms of the horizontal structure of the MABL, stronger winds were found over the warm side of the BMC region as well as over the thermal front itself, which supports the coexistence of both modulation mechanisms. The analyzed patterns of surface atmospheric thermal advection showed a clear interaction between the synoptic and regional scales. The signature of the oceanic thermal front (almost meridionally oriented) on the air temperature at 2 m makes the temperature advection strongly determined by the zonal component of the wind. The analysis of momentum budget terms did not show a clear and reasonable explanation of the existence or predominance of the modulation mechanisms, and it also suggested the relevance of other effects, such as the idea based on unbalanced Coriolis force and turbulence/friction effects.

Camargo, Ricardo; Todesco, Enzo; Pezzi, Luciano Ponzi; Souza, Ronald Buss

2013-06-01

59

Middle Atmosphere Program. Handbook for MAP. Volume 16: Atmospheric structure and its variation in the region 20 to 120 km. Draft of a new reference middle atmosphere  

NASA Technical Reports Server (NTRS)

A draft of a new reference atmosphere for the region between 20 and 80 km which depends largely on recent satellite experiments covering the globe from 80 deg S to 80 deg N is given. A separate international tropical reference atmosphere is given, as well as reference ozone models for the middle atmosphere.

Labitzke, K. (editor); Barnett, J. J. (editor); Edwards, B. (editor)

1985-01-01

60

Assessing the contribution of natural sources to regional atmospheric mercury budgets  

SciTech Connect

Contributions to the global atmospheric mercury budget originate from natural and anthropogenic sources. Constraining inputs from anthropogenic point sources has been the emphasis of past research leaving the contribution from diffuse natural and anthropogenic mercury enriched landscapes poorly constrained and underestimated. From September 1--4, 1997 mercury researchers convened in Reno, NV, US to intercompare methods used to determine in situ mercury flux from a naturally enriched landscape. Data collected indicate that naturally mercury-enriched areas constitute a significant atmospheric Hg source term. Mercury fluxes of 30 to 2,000 ng/m{sup 2} h were measured at the Steamboat springs Geothermal Area. These values are one to three orders of magnitude greater than that applied for natural sources in global mercury budgets. Air concentrations measured in the area indicate that natural sources can increase ambient levels above background concentrations. Assessment of these and other data indicate that natural sources constitute a significant source of atmospheric mercury that is available to the global mercury budget, and that the strength of the source is influenced significantly by environmental factors. Determining the contribution of mercury to the atmosphere from diffuse terrestrial sources is necessary to develop local and regional baselines for environmental regulations and risk assessments, and valid emission inventories. A scaling up mercury fluxes measured for diffuse terrestrial surfaces suggests that the natural atmospheric mercury source term in the US is comparable to the anthropogenic source term.

Gustin, M.S. [Univ. of Nevada, Reno, NV (United States). Dept. of Environmental and Resource Sciences; Lindberg, S.E. [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.

1997-12-31

61

Lichens as indicators of the atmosphere state in the oil exploration district of Tomsk Region  

NASA Astrophysics Data System (ADS)

Lichens are widespread in the vegetative cover of West Siberia, particularly in the north. They play an important role in the migration and transformation of chemical pollutants. Lichens lack waxy cuticles and are largely dependent on the atmosphere for their water and nutrient uptake. Lichens are not only studied and used as indicators, but also as accumulators, e.g. for trace and heavy metals. In fact, lichens are known for their ability to accumulate airborne substances to concentrations far greater those in the atmosphere, and the element contents of lichen thalli proved to be directly correlated with environmental levels. Monitoring of the atmosphere pollution using lichens is more efficient than that using snow cover. Because of the long lichen life it is possible to obtain persistent mean characteristics of the ecosystems state. Epiphytic lichens, growing on tree stems are more appropriate to use than that which grow on soil. Epiphytic lichens are more sensitive to changes of the chemical composition of the atmosphere. Pollutants penetrate in the lichen thalli from the atmosphere together with precipitations and dust. Moreover the precipitations are saturated with pollutants when going through crowns of trees and trickling down the steams and branches. Lichen studies are especially important in territories subjected to excessive human activity. Because a great part of Tomsk region (West Siberia, Russia) is the territory of the oil-field exploration, there the atmosphere monitoring is a necessary part of the whole environmental monitoring. The aim of this investigation is the estimation of the influence of oil exploration industry in Tomsk region on the atmosphere by means of the study of epiphytic lichens. Lichen samples were collected in August and September 2010-2011. Sampling net included seven areas distributed inside the oil-exploration districts of Tomsk region. In total 27 samples were collected. In these samples 53 chemical elements were detected by ICP-MS. Comparing the obtained results with the data of other Siberian regions (Yamal and Irkutsk regions) and also, Austria (Zemmering), Finland, Netherlands the authors have revealed excesses for Cr, Co, Zn, As, Rb, ? etc. three and more times.

Bolshunova, Tatiana; Ivan, Podkozlin

2013-04-01

62

Interactive coupling of regional atmosphere with biosphere in the new generation regional climate system model REMO-iMOVE  

NASA Astrophysics Data System (ADS)

The main objective of this study is the coupling of the regional climate model REMO with a new land surface scheme including dynamic vegetation phenology, and the evaluation of the new model version called REMO with interactive MOsaic-based VEgetation: REMO-iMOVE. First, we focus on the documentation of the technical aspects of the new model constituents and the coupling mechanism. The representation of vegetation in iMOVE is based on plant functional types (PFTs). Their geographical distribution is prescribed to the model which can be derived from different land surface data sets. Here, the PFT distribution is derived from the GLOBCOVER 2000 data set which is available on 1 km × 1 km horizontal resolution. Plant physiological processes like photosynthesis, respiration and transpiration are incorporated into the model. The vegetation modules are fully coupled to atmosphere and soil. In this way, plant physiological activity is directly driven by atmospheric and soil conditions at the model time step (two minutes to some seconds). In turn, the vegetation processes and properties influence the exchange of substances, energy and momentum between land and atmosphere. With the new coupled regional model system, dynamic feedbacks between vegetation, soil and atmosphere are represented at regional to local scale. In the evaluation part, we compare simulation results of REMO-iMOVE and of the reference version REMO2009 to multiple observation data sets of temperature, precipitation, latent heat flux, leaf area index and net primary production, in order to investigate the sensitivity of the regional model to the new land surface scheme and to evaluate the performance of both model versions. Simulations for the regional model domain Europe on a horizontal resolution of 0.44° had been carried out for the time period 1995-2005, forced with ECMWF ERA-Interim reanalyses data as lateral boundary conditions. REMO-iMOVE is able to simulate the European climate with the same quality as the parent model REMO2009. Differences in near-surface climate parameters can be restricted to some regions and are mainly related to the new representation of vegetation phenology. The seasonal and interannual variations in growth and senescence of vegetation are captured by the model. The net primary productivity lies in the range of observed values for most European regions. This study reveals the need for implementing vertical soil water dynamics in order to differentiate the access of plants to water due to different rooting depths. This gets especially important if the model will be used in dynamic vegetation studies.

Wilhelm, C.; Rechid, D.; Jacob, D.

2014-06-01

63

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

64

The Influence of Large Solar Proton Events on the Atmosphere  

NASA Technical Reports Server (NTRS)

Solar proton events (SPEs) can cause changes in constituents in the Earth s polar middle atmosphere. A number of large SPEs have occurred over the past 50 years and tend to happen most frequently near solar maximum. The highly energetic protons cause ionizations, excitations, dissociations, and dissociative ionizations of the background constituents. Complicated ion chemistry leads to HOx (H, OH, HO2) production and dissociation of N2 leads to NOy (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2) production. Both the HOx and NOy increases can result in changes to ozone in the stratosphere and mesosphere. The HOx increases lead to short-lived (days) ozone decreases in the mesosphere and upper stratosphere. The NOy increases lead to long-lived (several months) stratospheric ozone changes because of the long lifetime of NOy constituents in this region. UARS HALogen Occultation Experiment (HALOE) instrument observations showed SPE-caused polar stratospheric NOx (NO+NO2) increases over 10 ppbv in September 2000 due to the very large SPE of July 2000, which are reasonably well simulated with the Whole Atmosphere Community Climate Model (WACCM). WACCM-computed SPE-caused polar stratospheric ozone decreases >10% continued for up to 5 months past the largest events in the past 50 years, however, SPE-caused total ozone changes were not found to be statistically significant. Small polar middle atmospheric temperature changes of <4 K have also been predicted to occur as a result of the larger SPEs. The polar atmospheric effects of large SPEs during solar cycle 23 and 24 will be emphasized in this presentation.

Jackman, Charles H.

2012-01-01

65

Influence of the Laurentian Great Lakes on Regional Climate  

NASA Astrophysics Data System (ADS)

The influence of the Laurentian Great Lakes on climate is assessed by comparing two decade-long simulations, with the lakes either included or excluded, using the Abdus Salam International Centre for Theoretical Physics Regional Climate Model Version 4. The Great Lakes dampen the variability in near-surface air temperature across the surrounding region, while reducing the amplitude of the diurnal cycle and annual cycle of air temperature. The impacts of the Great Lakes on the regional surface energy budget include an increase (decrease) in turbulent fluxes during the cold (warm) season and an increase in surface downward shortwave radiation flux during summer due to diminished atmospheric moisture and convective cloud amount. Changes in the hydrologic budget due to the presence of the Great Lakes include increases in evaporation and precipitation during October-March and decreases during May-August, along with springtime reductions in snowmelt-related runoff. Circulation responses consist of a regionwide decrease in sea-level pressure in autumn-winter and an increase in summer, with enhanced ascent and descent in the two seasons, respectively. The most pronounced simulated impact of the Great Lakes on synoptic systems traversing the basin is a weakening of cold-season anticyclones.

Notaro, M.; Holman, K.; Zarrin, A.; Fluck, E.; Vavrus, S. J.; Bennington, V.

2012-12-01

66

Atmospheric Impact of Large Methane Emission in the Arctic Region  

NASA Astrophysics Data System (ADS)

A highly potent greenhouse gas, methane, is locked in the solid phase as ice-like deposits containing a mixture of water and gas (mostly methane) called clathrates, in ocean sediments and underneath permafrost regions. Clathrates are stable under high pressure and low temperatures. Recent estimates suggest that about 1600 - 2000GtC of clathrates are present in oceans and 400GtC in Arctic permafrost (Archer et al.2009) which is about 4000 times that of current annual emissions. In a warming climate, increase in ocean temperatures could alter the geothermal gradient, which in turn could lead to dissociation of the clathrates and release of methane into the ocean and subsequently into the atmosphere as well. This could be of particular importance in the shallow part of the Arctic Ocean where the clathrates are found in depths of only 300m. In this presentation, we shall show results from our ongoing simulation of a scenario of large scale methane outgassing from clathrate dissociation due to warming ocean temperatures in the Arctic based on ocean sediment modeling. To that end we use the CESM (Community Earth System Model) version 1 with fully active coupled atmosphere-ocean-land model together with fast atmospheric chemistry module to simulate the response to increasing methane emissions in the Barents Sea, Canadian Archipelago and the Sea of Okhotsk. The simulation shows the effect these methane emissions could have on global surface methane, surface ozone, surface air temperature and other related indices. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-491764

Bhattacharyya, S.; Cameron-Smith, P. J.; Bergmann, D.; Reagan, M. T.; Collins, W.; Elliott, S. M.; Maltrud, M. E.

2011-12-01

67

Atmospheric rivers induced heavy precipitation and flooding in the western U.S. simulated by the WRF regional climate model  

NASA Astrophysics Data System (ADS)

A 20-year regional climate simulated by the Weather Research and Forecasting model has been analyzed to study the influence of the atmospheric rivers and land surface conditions on heavy precipitation and flooding in the western U.S. The simulation realistically captured the mean and extreme precipitation, and the precipitation/temperature anomalies of all the atmospheric river events between 1980-1999. Contrasting the 1986 President Day and 1997 New Year Day events, differences in atmospheric stability have an influence on the spatial distribution of precipitation. Although both cases yielded similar precipitation, the 1997 case produced more runoff. Antecedent soil moisture, rainfall versus snowfall, and existing snowpack all seem to play a role, leading to a higher runoff to precipitation ratio for the 1997 case. This study underscores the importance of the atmospheric rivers and land surface conditions for predicting heavy precipitation and floods in the current and future climate of the western U.S.

Leung, L. Ruby; Qian, Yun

2009-02-01

68

Influence of seasonal cycles in Martian atmosphere on entry, descent and landing sequence  

NASA Astrophysics Data System (ADS)

The phenomena like high eccentricity of Martian orbit, obliquity of the orbital plane and close alignment of the winter solstice and the orbital perihelion, separately or together can significantly alter not only the level of some Martian atmospheric parameters but also the characteristics of its diurnal and seasonal cycle. Considering that entry, descent and landing (EDL) sequence is mainly driven by the density profile of the atmosphere and aerodynamic characteristic of the entry vehicle. We have performed the analysis of the influence of the seasonal cycles of the atmospheric parameters on EDL profiles by using Mars Global Reference Atmospheric Model (Mars-GRAM). Since the height of the deployment of the parachute and the time passed from the deployment to propulsion firing (descent time) are of crucial importance for safe landing and the achievable landing site elevation we paid special attention to the influence of the areocentric longitude of the Sun (Ls) on these variables. We have found that these variables have periodic variability with respect to Ls and can be very well approximated with a sine wave function whose mean value depends only on the landing site elevation while the amplitudes and phases depend only on the landing site latitude. The amplitudes exhibit behavior which is symmetric with respect to the latitude but the symmetry is shifted from the equator to the northern mid-tropics. We have also noticed that the strong temperature inversions which are usual for middle and higher northern latitudes while Mars is around its orbital perihelion significantly alter the descent time without influencing the height of the parachute deployment. At last, we applied our model to determine the dependence of the accessible landing region on Ls and found that this region reaches maximum when Mars is around the orbital perihelion and can vary 50° in latitude throughout the Martian year.

Mar?eta, Dušan; Šegan, Stevo; Rašuo, Boško

2014-05-01

69

Atmospheric energetics in regions of intense convective activity  

NASA Technical Reports Server (NTRS)

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 that enclose regions of intense convection are shown to have systematic changes that relate to the life cycles of the convection. Some of the synoptic-scale energy processes associated with the convection are found to be larger than those observed in the vicinity of mature cyclones. Volumes enclosing intense convection are found to have large values of cross-contour conversion of potential to kinetic energy and large horizontal export of kinetic energy. Although small net vertical transport of kinetic energy is observed, values at individual layers indicate large upward transport. Transfer of kinetic energy from grid to subgrid scales of motion occurs in the volumes. Latent heat release is large in the middle and upper troposphere and is thought to be the cause of the observed cyclic changes in the budget terms. Total potential energy is found to be imported horizontally in the lower half of the atmosphere, transported aloft, and then exported horizontally. Although local changes of kinetic energy and total potential energy are small, interaction between volumes enclosing convection with surrounding larger volumes is quite large.

Fuelberg, H. E.

1977-01-01

70

Atmospheric aerosol layers over Bangkok Metropolitan Region from CALIPSO observations  

NASA Astrophysics Data System (ADS)

Previous studies suggested that aerosol optical depth (AOD) from the Earth Observing System satellite retrievals could be used for inference of ground-level air quality in various locations. This application may be appropriate if pollution in elevated atmospheric layers is insignificant. This study investigated the significance of elevated air pollution layers over the Bangkok Metropolitan Region (BMR) from all available aerosol layer scenes taken from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) for years 2007 to 2011. The results show that biomass burning smoke layers alone were the most frequently observed. The smoke layers accounted for high AOD variations and increased AOD levels. In the dry seasons, the smoke layers alone with high AOD levels were likely brought to the BMR via northeasterly to easterly prevailing winds and found at altitudes above the typical BMR mixing heights of approximately 0.7 to 1.5 km. The smoke should be attributed to biomass burning emissions outside the BMR.

Bridhikitti, Arika

2013-06-01

71

Regional forecasting with global atmospheric models; Final report  

SciTech Connect

The purpose of the project was to conduct model simulations for past and future climate change with respect to the proposed Yucca Mtn. repository. The authors report on three main topics, one of which is boundary conditions for paleo-hindcast studies. These conditions are necessary for the conduction of three to four model simulations. The boundary conditions have been prepared for future runs. The second topic is (a) comparing the atmospheric general circulation model (GCM) with observations and other GCMs; and (b) development of a better precipitation data base for the Yucca Mtn. region for comparisons with models. These tasks have been completed. The third topic is preliminary assessments of future climate change. Energy balance model (EBM) simulations suggest that the greenhouse effect will likely dominate climate change at Yucca Mtn. for the next 10,000 years. The EBM study should improve rational choice of GCM CO{sub 2} scenarios for future climate change.

Crowley, T.J.; Smith, N.R. [Applied Research Corp., College Station, TX (United States)

1994-05-01

72

Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models  

Microsoft Academic Search

Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates

Kevin Robert Gurney; Rachel M. Law; A. Scott Denning; Peter J. Rayner; David Baker; Philippe Bousquet; Lori Bruhwiler; Yu-Han Chen; Philippe Ciais; Songmiao Fan; Inez Y. Fung; Manuel Gloor; Martin Heimann; Kaz Higuchi; Jasmin John; Takashi Maki; Shamil Maksyutov; Ken Masarie; Philippe Peylin; Michael Prather; Bernard C. Pak; James Randerson; Jorge Sarmiento; Shoichi Taguchi; Taro Takahashi; Chiu-Wai Yuen

2002-01-01

73

Influence of atmospheric stability on wind-turbine wakes: A large-eddy simulation study  

NASA Astrophysics Data System (ADS)

In this study, large-eddy simulation is combined with a turbine model to investigate the influence of atmospheric stability on wind-turbine wakes. In the simulations, subgrid-scale turbulent fluxes are parameterized using tuning-free Lagrangian scale-dependent dynamic models. These models optimize the local value of the model coefficients based on the dynamics of the resolved scales. The turbine-induced forces are parameterized with an actuator-disk model with rotation. In this technique, blade-element theory is used to calculate the lift and drag forces acting on the blades. Emphasis is placed on the structure and characteristics of wind-turbine wakes in the cases where the incident flows to the turbine have the same mean velocity at the hub height but different stability conditions. The simulation results show that atmospheric stability has a significant effect on the spatial distribution of the mean velocity deficit and turbulent fluxes in the wake region. In particular, the magnitude of the velocity deficit increases with increasing stability in the atmosphere. In addition, the locations of the maximum turbulence intensity and turbulent stresses are closer to the turbine in convective boundary layer compared with neutral and stable ones. Detailed analysis of the resolved turbulent kinetic energy (TKE) budget inside the wake reveals also that the thermal stratification of the incoming wind considerably affects the magnitude and spatial distribution of the turbulent production, transport term and dissipation rate (transfer of energy to the subgrid scales). It is also shown that the near-wake region can be extended to a farther distance downstream in stable condition compared with neutral and unstable counterparts. In order to isolate the effect of atmospheric stability, additional simulations of neutrally-stratified atmospheric boundary layers are performed with the same turbulence intensity at hub height as convective and stable ones. The results show that the turbulence intensity alone is not sufficient to describe the impact of atmospheric stability on the wind-turbine wakes.

Abkar, Mahdi; Porté-Agel, Fernando

2014-05-01

74

Influence of cathode temperature on the parameters of an atmospheric pressure dc glow discharge  

NASA Astrophysics Data System (ADS)

It is shown that the cathode temperature has a significant influence on the properties of the cathode fall in a self-sustained, normal, dc, atmospheric pressure glow discharge in helium and, in particular, on the electric field distribution, the thickness of the cathode fall layer, the current density and the gas temperature. An increase in the cathode temperature leads to an increase in the gas temperature and cathode fall thickness, a decrease in the current density and a modification in the radial distribution of the electric field close to the cathode surface. A discussion based on a one-dimensional model of the cathode fall region including gas heating is presented.

Arkhipenko, V. I.; Kirillov, A. A.; Safronau, Ya A.; Simonchik, L. V.; Zgirouski, S. M.

2008-11-01

75

CHIMERE 2013: a model for regional atmospheric composition modelling  

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, kinetics and efficiency of the chemistry and the deposition. All these processes are highly variable in time and space, and their relative contribution to the pollutants budgets can be quantified with chemistry-transport models. The CHIMERE chemistry-transport model is dedicated to regional atmospheric pollution event studies. Since it has now reached a certain level a maturity, the new stable version, CHIMERE 2013, is described to provide a reference model paper. The successive developments of the model are reviewed on the basis of published investigations that are referenced in order to discuss the scientific choices and to provide an overview of the main results.

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

2013-07-01

76

Natural sources of atmospheric aerosols influencing air quality across Europe.  

PubMed

Atmospheric aerosols are emitted by natural and anthropogenic sources. Contributions from natural sources to ambient aerosols vary widely with time (inter-annual and seasonal variability) and as a function of the distance to source regions. This work aims to identify the main natural sources of atmospheric aerosols affecting air quality across Europe. The origin, frequency, magnitude, and spatial and temporal variability of natural events were assessed for the years 2008 and 2009. The main natural sources of atmospheric aerosols identified were African dust, sea spray and wildfires. Primary biological particles were not included in the present work. Volcanic eruptions did not affect air quality significantly in Europe during the study period. The impact of natural episodes on air quality was significant in Southern and Western Europe (Cyprus, Spain, France, UK, Greece, Malta, Italy and Portugal), where they contributed to surpass the PM10 daily and annual limit values. In Central and Northern Europe (Germany, Austria and Latvia) the impact of these events was lower, as it resulted in the exceedance of PM daily but not annual limit values. Contributions from natural sources to mean annual PM10 levels in 2008 and 2009 ranged between 1 and 2 ?g/m(3) in Italy, France and Portugal, between 1 and 4 ?g/m(3) in Spain (10 ?g/m(3) when including the Canary Islands), 5 ?g/m(3) in UK, between 3 and 8 ?g/m(3) in Greece, and reached up to 13 ?g/m(3) in Cyprus. The evaluation of the number of monitoring stations per country reporting natural exceedances of the daily limit value (DLV) is suggested as a potential tool for air quality monitoring networks to detect outliers in the assessment of natural contributions. It is strongly suggested that a reference methodology for the identification and quantification of African dust contributions should be adopted across Europe. PMID:24342088

Viana, M; Pey, J; Querol, X; Alastuey, A; de Leeuw, F; Lükewille, Anke

2014-02-15

77

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

NASA Astrophysics Data System (ADS)

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, and 18O in CO2) in the biological and chemical processes which produce and consume CO2. This work applies known methods of CO2 isolation and mass spectrometric analysis to address questions regarding the mechanisms of isotopic fractionation during land-atmosphere exchange where global, regional, local, and point-spot studies are researched. Atmospheric CO2 exchange with land masses influences about 80% of the delta18O signature yielding exchange fluxes on the order of 200 GtC yr-1. Land biosphere controls the seasonal cycle of CO2 and the offsets observed in the seasonal swing of the isotopic ratios, 13C/12C and 18O/16O (4--6 month shifts). When we looked closer at magnitudes of land-atmosphere exchanges, we saw that the respiratory flux was 100 times greater than the photosynthetic flux during the summer on the day of measurement in a coniferous forest system (3612 mumol m-2 s-1). Therefore, this regional isotopic signature was thought to be dominated by the delta 18O of soil respired CO2. Further inspection of the controlling mechanisms of soil respired CO 2 was then addressed where offsets (20‰) from soil water were observed in moisture limited ridge-top soils. Also, kinetic fractionation due to molecular diffusion through the soil column (thought to be 8.8‰) was not observed within the moisture limited, unsaturated, or saturated conditions within a grassland or forest ecosystem. On a localized scale, we conducted experiments on isotopically tracing water movement in a rooting zone. The results showed increased production of trace gases leading to increased emission rates (shown in CO2). In conclusion, plant ecosystems have a strong influence on isotopic compositions of atmospheric CO2, where fluxes can be monitored with delta 18O.

Fessenden, Julianna Eileen

78

Soil occupation and atmospheric variations over Sobradinho Lake area. Part two: a regional modeling study  

NASA Astrophysics Data System (ADS)

The impact of the changes on soil cover and land use brought about by the construction of the Sobradinho Dam in the semi-arid region of the São Francisco River Hydrographic Basin is analyzed by means of a numerical model RAMS. Disregarding the influence of a large scale flow, a set of factors were responsible for the creation of a rather complex circulation system that includes mountain-valley winds, lake breeze (LB) and non-conventional circulation all induced by the surface non-homogeneous aspect. Results have demonstrated that the implementation of works of such magnitude brings about environmental changes in an area that stretches far beyond the surroundings of the reservoir. The soil cover alterations due to the ever increasing development of the area with the presence of irrigated crops in a sparsely vegetated region ( caatinga) does affect land surface characteristics, occasioning for that matter the splitting of the available energy into latent and sensible heat fluxes. LB behavior varies in accordance with atmospheric conditions and also in view of the type of vegetation found in the lake surrounding areas. Hydro availability in root zones, even under adverse atmospheric conditions (high temperature and low air humidity) brings up the high rates of evaporation and plant transpiration that contribute towards the increase of humidity and the fall of temperature in lower atmospheric layers.

Correia, M. F.; da Silva Dias, M. A. F.; da Silva Aragão, M. R.

2006-11-01

79

Atmospheric effects on NOAA AVHRR data over Sahelian regions  

Microsoft Academic Search

Variable atmospheric conditions have a significant impact on satellite monitoring of vegetation in the Sahelian zone of Africa. The effects of atmospheric O3, H2O and aerosols on spectral, directional reflectances and derived measures, such as the normalized difference vegetation index, are discussed using a sensitivity study. An atmospheric correction scheme is presented based on measurements of optical thicknesses from the

V. Soufflet; D. Tanré; A. Begue; A. Podaire; P. Y. Deschamps

1991-01-01

80

Evidence for tropical SST influence on Antarctic polar atmospheric dynamics  

NASA Astrophysics Data System (ADS)

A Singular Value Decomposition analysis is applied to climatological data to determine the modes of variability of monthly mean Sea Surface Temperature (SST) in the tropics coupled with the southern hemisphere stratospheric polar vortex intensity for the 1958 to 2006 period and to identify the tropical region strongly influencing the high latitude stratospheric dynamics. Two subsets of data have been considered by explicitly taking into account the phase of the Pacific Decadal Oscillation (PDO). The study evidences a shift of the tropical region affecting the polar vortex from the Western Pacific to the Indo-Pacific Ocean, driven by the modulation of the SST pattern, due to the phase of the PDO. The analysis shows in both cases (years with positive/negative PDO phases) a high degree of correlation between an SST related index, calculated from NOAA/ERSST and HadISST datasets, and an index of the polar vortex intensity based on ECMWF data.

Grassi, Barbara; Redaelli, Gianluca; Visconti, Guido

2009-05-01

81

Global and Regional Constraints on Exchanges of CO2 Between the Atmosphere and Terrestrial Biosphere  

NASA Astrophysics Data System (ADS)

The vigorous atmospheric circulation rapidly mixes CO2 that is exchanged with the terrestrial biosphere and oceans. Therefore, at time scales greater than 1 year, the approximate interhemispheric exchange time of the atmosphere, an average of CO2 measurements from a network of surface stations can be used to accurately determine the global net change in atmospheric CO2. By subtracting CO2 produced by fossil fuel combustion, which is well characterized by national statistics, the global the sum of terrestrial biospheric and oceanic net fluxes, here termed the "nonfossil" CO2 flux, can also be accurately determined. The nonfossil CO2 flux averaged -2.1+/-0.3 PgC/yr and -3.2+/-0.4 PgC/yr in the 1980s and 1990s respectively (negative denotes out of the atmosphere), and varied in annual average from about 0 to -4 PgC/yr over these two decades. Two primary methods have been used to further partition the nonfossil CO2 flux between land and oceans: the O2 and 13C/12C methods, which rely, respectively, on measurements of atmospheric O2 (actually O2/N2 for technical reasons) and of the 13C/12C ratio of CO2. Burning of fossil fuel consumes atmospheric O2 and releases CO2 with a 13C/12C ratio lower than that of atmospheric CO2 whereas uptake of CO2 by terrestrial plants releases O2, and increases the atmospheric 13C/12C ratio owing to the preferential assimilation of 12CO2 relative to 13CO2. In contrast, the uptake of CO2 by the oceans has little effect on either the atmospheric O2 or 13C/12C ratio. Therefore, the net CO2 uptake or release from the terrestrial biosphere can be calculated in either method by subtracting the change owing to fossil fuel emissions from the measured change in the atmosphere, utilizing known stoichiometric ratios of O2 and CO2 in the O2 method, and isotopic fractionation factors in the 13C/12C method. Currently, the O2 method gives a net global terrestrial biospheric CO2 flux of -0.2+/-0.7 PgC/yr and -1.4+/-0.7 PgC/yr for the 1980s and the 1990s, respectively. Both the O2 and 13C/12C methods have complications and limitations that will be discussed. To partition the global biospheric flux further to zonal or regional detail or to shorter time steps, atmospheric models are required to simulate the transport of tracer from source regions to individual stations where air is sampled. An ongoing collaborative project to compare atmospheric models has highlighted significant differences in transport characteristics, mainly owing to differences in how the boundary layer is modeled. Accordingly, a recent compilation of model calculations showed a wide range of estimates for the tropical biosphere, from a significant release of CO2 to an uptake over recent decades; however, the calculations showed reasonable agreement on a significant northern biospheric sink. Fluxes of biospheric CO2 can be determined accurately at the global scale as well as at individual sites. An ingenious blend of observations and models will be required to bridge the gap between these two extreme spatial scales, and thereby gain an understanding sufficient to predict the influence of the terrestrial biosphere on variations in atmospheric CO2.

Piper, S. C.

2001-12-01

82

The influence of a semi-infinite atmosphere on solar oscillations  

NASA Astrophysics Data System (ADS)

The influence of a semi-infinitive atmosphere on solar investigations is investigated using a model in which the corona is represented by a gravitationally stratified fluid. The solar corona can be modeled as a semi-infinitive region of plasma that occupies the space above the xy- plane in Cartesian coordinates with the z-axis taken along the gravitational acceleration vec g = gvec uz. This assumption is reasonable, as the plasma density of the atmosphere is much lower than the density of the photosphere. So, we consider the phostosphere as a solid and immobile boundary for the atmosphere. The standard mathematical procedures in Helioseismology field are based on normal mode approach for various solar models. The region is assumed quasi-isothermal and without magnetic fields. In this work, in order to show how the modes appear in the response to an initial perturbation, we consider the initial value problem (IPV). The p-modes and g-modes possess only continuous spectra -as opposed to discrete spectrum like that previous investigators found for this problem- and the solution to the initial value problem is obtained through an appropiate Green's function.

González, Ángel De Andrea

2014-06-01

83

Modern and historic atmospheric mercury fluxes in both hemispheres: Global and regional mercury cycling implications  

NASA Astrophysics Data System (ADS)

Using two different natural archiving media from remote locations, we have reconstructed the atmospheric deposition of mercury (Hg) over the last 800-1000 years in both hemispheres. This effort was designed (1) to quantify the historical variation and distributional patterns of atmospheric Hg fluxes in the midlatitudes of North America at Nova Scotia (N.S.) and at a comparable midlatitude region in the Southern Hemisphere at New Zealand (N.S.), (2) to identify and quantify the influence of anthropogenic and natural Hg contributions to atmospheric Hg fluxes, (3) to further investigate the suitability and comparability of our two selected media (lake sediments and ombrotrophic peat) for Hg depositional reconstructions, and (4) to assess the relative importance of wet and dry deposition to the study areas. Significant findings from the study include the following: (1) The lake sediments examined appear to faithfully record the contemporary flux of Hg from the atmosphere (e.g., 1997: N.S. Lakes: approximately 8 ± 3 ?g m-2 yr-1; N.S. Rain: 8 ?g m-2 yr-1). The upper 10 cm (approximately 10 yr) of ombrotrophic peat cores from Nova Scotia were dated using a biological chronometer (Polytrichum) and were also consistent with the flux data provided by current direct sampling of precipitation. These observations place limits on the contribution of dry deposition (40 ± 50% of wet flux). Unfortunately, the peat samples could not be dated below 10 cm. This was due to the apparent diagenetic mobility of the geochronological tracer (210Pb). (2) There is no evidence of a significant enhancement in the atmospheric Hg flux as a result of preindustrial (<1900 c.e. (Common Era)) activities such as the extensive Au and Ag mining in the Americas. (3) A factor of 3 and 5x increase in the deposition of Hg to the lake sediment archives was observed since the advent of the industrial revolution in New Zealand and Nova Scotia respectively, suggesting a worldwide increase in the atmospheric deposition of Hg. Furthermore, this increase is synchronous with increases in the release of CO2 from combustion of fossil fuels on a global scale. The magnitude of increase since industrialization appears larger in Nova Scotia than in New Zealand. This may be due to enhanced deposition of Hg as a result of either regional emission of Hg or enhanced regional oxidation of Hg°.

Lamborg, C. H.; Fitzgerald, W. F.; Damman, A. W. H.; Benoit, J. M.; Balcom, P. H.; Engstrom, D. R.

2002-12-01

84

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

85

Regional scale evaporation and the atmospheric boundary layer  

NASA Technical Reports Server (NTRS)

In this review we briefly summarize some current models of evaporation and the atmospheric boundary layer (ABL) and discuss new experimental and computational oppurtunities that may aid our understanding of evaporation at these larger scales. In particular, consideration is given to remote sensing of the atmosphere, computational fluid dynamics and the role numerical models can play in understanding land-atmosphere interactions. These powerful modeling and measurement tools are allowing us to visualize and study spatial and temporal scales previously untouched, thereby increasing the oppurtunities to improve our understanding of land-atmosphere interaction.

Parlange, Marc B.; Eichinger, William E.; Albertson, John D.

1995-01-01

86

Mesoscale circulations and atmospheric CO2 variations in the Tapajós Region, Pará, Brazil  

Microsoft Academic Search

We have investigated mesoscale circulations and atmospheric CO2 variations over a heterogeneous landscape of forests, pastures, and large rivers during the Santarém Mesoscale Campaign (SMC) of August 2001. The atmospheric CO2 concentration variations were simulated using the Colorado State University Regional Atmospheric Modeling System with four nested grids that included a 1-km finest grid centered on the Tapajós National Forest.

Lixin Lu; A. Scott Denning; Maria Assuncao da Silva-Dias; Pedro da Silva-Dias; Marcos Longo; Saulo R. Freitas; Sassan Saatchi

2005-01-01

87

Rare earth element components in atmospheric particulates in the Bayan Obo mine region.  

PubMed

The Bayan Obo mine, located in Inner Mongolia, China, is the largest light rare earth body ever found in the world. The research for rare earth elements (REEs) enrichment in atmospheric particulates caused by mining and ore processing is fairly limited so far. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 ?m (PM10) were collected around the Bayan Obo mine region, in August 2012 and March 2013, to analyze the levels and distributions of REEs in particles. The total concentrations of REEs for TSP were 149.8 and 239.6 ng/m(3), and those for PM10 were 42.8 and 68.9 ng/m(3), in August 2012 and March 2013, respectively. Enrichment factor was calculated for all 14 REEs in the TSP and PM10 and the results indicated that REEs enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in springtime. The spatial distribution of REEs in TSP showed a strong gradient concentration in the prevailing wind direction. REE chondrite normalized patterns of TSP and PM10 were similar and the normalized curves inclined to the right side, showing the conspicuous fractionation between the light REEs and heavy REE, which supported by the chondrite normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N), Gd(N)/Yb(N)). PMID:24657942

Wang, Lingqing; Liang, Tao; Zhang, Qian; Li, Kexin

2014-05-01

88

Solar Activity Influences on Atmospheric Electricity and on Some Structures in the Middle Atmosphere.  

National Technical Information Service (NTIS)

Only processes in the troposphere and the lower stratosphere are reviewed. General aspects of global atmospheric electricity are summarized in Chapter 3 of NCR (1986); Volland (1984) has outlined the overall problems of atmospheric electrodynamics; and Ro...

R. Reiter

1989-01-01

89

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

90

Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR)  

NSF Publications Database

... of the upper atmosphere research community. A primary objective of CEDAR research is to understand ... its scientific payload supported by NASA. Its primary purpose is to forecast the presence of ...

91

Regional Carbon Fluxes and Atmospheric Carbon Dynamics in the Southern Great Plains during the 2007 CLASIC intensive  

NASA Astrophysics Data System (ADS)

In June 2007, a regional campaign took place in the Southern Great Plains (SGP) to estimate land-atmosphere exchanges of CO2, water, and energy at 1 to 100 km scales. The primary goals of this campaign were to evaluate top-down and bottom-up estimates of regional fluxes and to understand the influence of moisture gradients, surface heterogeneity, and atmospheric transport patterns on these fluxes (and their estimation). The work was integrated with the Cloud and Land Surface Interaction Campaign (CLASIC), centered on the US DOE Atmospheric Radiation Measurement (ARM) Program SGP region. CO2 concentration data were collected from tower and airborne platforms. Eddy flux towers were deployed in the four major land cover types, distributed over the region's SE to NW precipitation gradient. In addition, CO2, water, and energy fluxes were observed with the Duke Helicopter Observation Platform (HOP) at various heights in the boundary layer, including in the surface layer (the few meters near the surface). One aircraft carried precise CO2, CO, and CH4 continuous measurement systems, and 14C, radon, and NOAA 12-flask (carbon cycle gases and isotopes) packages. Continuous CO2, CO, and radon concentrations, NOAA 2-flask package, and isotope diel flasks (14C, 13C, and 18O) were also collected from a centrally located 60 m tower. Flights were planned to constrain simple boundary layer budget models and to conduct Lagrangian air mass following experiments. We present these data in the context of characterizing surface carbon exchanges via bottom-up and top-down approaches. We also describe results from forward (using MM5-LSM) and inverse (using STILT) modeling to estimate regional surface carbon and energy fluxes. In addition to characterizing the influence of the land surface on the atmosphere, the aircraft data (in combination with observations of atmospheric dynamics) provides a very well characterized southern boundary condition to the NACP Mid-Continent Intensive.

Biraud, S. C.; Torn, M. S.; Riley, W. J.; Fischer, M. L.; Billesbach, D. P.; Avissar, R.; Berry, J. A.; Hirsch, A.; Loewenstein, M.; Lopez, J.

2007-12-01

92

Influence of different propagation paths on the propagation of laser in atmospheric turbulence  

NASA Astrophysics Data System (ADS)

The analytical expressions for the average intensity, root mean square (RMS) beam width and angular spread of Gaussian Schell-model (GSM) beams propagating under slant atmospheric turbulence are derived, and they are used to study the influence of different propagation paths on the propagation of laser beams in atmospheric turbulence. It is shown that under the same condition, the influence of atmospheric turbulence along a downlink path on the GSM beam propagation is the smallest among the three paths. Therefore, the downlink propagation is more beneficial to the beam propagation through atmospheric turbulence compared with the uplink propagation and horizontal propagation.

Duan, Mei-ling; Li, Jin-hong; Wei, Ji-lin

2013-11-01

93

Evaluation of wind fields for storm events in the black sea region using a numerical regional atmospheric circulation model  

Microsoft Academic Search

A method of the NCEP\\/NCAR reanalysis wind data recalculation using a regional atmospheric circulation model is described.\\u000a A comparison of model results and satellite measurements is performed. The results of wind wave computation using the reanalysis\\u000a and model winds are presented and their comparison is made. It is shown that the NCEP\\/NCAR reanalysis wind recalculation using\\u000a a regional atmospheric circulation

O. I. Komarovskaya; V. V. Efimov; V. S. Barabanov

2007-01-01

94

Can we distinguish fluxes from transport in regional-scale atmospheric inversions?  

NASA Astrophysics Data System (ADS)

Atmospheric inversions to determine land-atmosphere exchange of CO2 or other trace gases rely heavily upon accurate representation of atmospheric transport. Limited knowledge of land-atmosphere fluxes and atmospheric transport make it difficult to use existing atmospheric observations to determine land-atmosphere fluxes with accuracy. Restated, it is very difficult to determine whether model-data differences in atmospheric CO2 are due to flaws in modeled transport or fluxes. For regional models, limited information about CO2 lateral boundary conditions further complicate this situation. Flux, boundary conditions and transport errors, however, may have characteristic signatures in atmospheric properties, including CO2 mole fractions, associated trace gases and atmospheric state variables that enable these errors to be distinguished unambiguously. This paper presents a preliminary comparative investigation of the nature of flux vs. transport vs. boundary errors, focusing on the continental scale. We attempt to identify observational approaches that could capitalize on these characteristic differences to provide independent constraints of flux, boundary and transport errors, thus potentially improving substantially the accuracy of atmospheric inverse estimates of land-atmosphere fluxes. Potential observations that will be considered include column CO2 from satellites, trace gases such as CO, atmospheric properties including winds and potential temperature, aircraft profile and ground-based column CO2 measurements, and spatially extensive airborne observations. Our results will be translated into recommendations for future atmospheric observational efforts.

Davis, K. J.; Normile, C. P.; Diaz Isaac, L. I.; Lauvaux, T.; Berry, J. A.; Browell, E. V.; Denning, S.

2013-12-01

95

Examining the Arctic Energy Fluxes and Atmospheric Circulation in a Regional Perspective  

NASA Astrophysics Data System (ADS)

Surface energy fluxes are directly affected by Arctic sea ice cover due to ice albedo feedbacks and the great heat capacity of the Arctic Ocean. Changes in surface heat flux may initialize a redistribution of the Arctic heat budget, including poleward heat transport associated with atmospheric circulation. Consequently, sea ice anomalies may ultimately have an impact on atmospheric circulation in middle and high latitudes. In addition, temporal variations in Arctic energy fluxes are shown to exhibit distinct regionality. For this reason, the goal of this study is to investigate the changes in energy fluxes, surface heat flux, radiation at the top of the atmosphere, and poleward atmospheric energy transport on a regional basis using the climate forecast system reanalysis (CFSR), and to conceptualize the linkages between Arctic sea ice and the atmospheric circulation. Initial results suggest a logical pathway between declines in Arctic sea-ice cover, variations in regional Arctic energy fluxes and indices of atmospheric circulation.

Chan, W.

2012-12-01

96

Seasonal oscillations in regional and global atmospheric excitation of polar motion  

NASA Astrophysics Data System (ADS)

Time variable spectra of seasonal oscillations of global and regional atmospheric excitation functions of polar motion for the period 1948-1999 are computed from the NCEP/NCAR (National Centres for Environmental Prediction/ National Centre for Atmospheric Research) reanalysis Atmospheric Angular Momentum (AAM) data, namely from the pressure and the pressure with the inverted barometric (IB) correction. Amplitudes of the time variable spectra of seasonal oscillations of the global and regional atmospheric excitation functions of polar motion are variable. Contributions of atmospheric excitation function of polar motion from lands and especially from the Eurasia are the most important in the seasonal spectrum range of polar motion excitation function. The maps of the mean amplitudes of seasonal oscillations of atmospheric excitation functions of polar motion are computed for the fifty years period in 108 equal-weight sectors. They show the regions in which these oscillations are the most energetic. Correlations between the global and regional atmospheric excitation functions of polar motion and the geodetic excitation functions are investigated. The correlation coefficients computed between the global/regional atmospheric and geodetic excitation functions of polar motion became more stable and achieved the highest values of about 0.8 after 1970, 1975 and 1985 for annual, semi-annual and 120 days oscillations, respectively. The correlation coefficients in the Asia region are the closest to those of the global data.

Nastula, J.; Kolaczek, B.

2002-07-01

97

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

98

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

99

Solar influence on a major mode of atmospheric variability  

Microsoft Academic Search

We find that the North Annular Mode (NAM) of the wintertime geopotential height anomalies between 10 and 1000 hPa is influenced by solar changes and that the effect is statistically significant. This evidence suggests that a mechanism of solar influence on climate operates through the excitation of this mode. The influence depends on the phase of the quasi-biennial oscillation (QBO).

Alexander Ruzmaikin; Joan Feynman

2002-01-01

100

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

101

REGIONAL MODELING OF THE ATMOSPHERIC TRANSPORT AND DEPOSITION OF ATRAZINE  

EPA Science Inventory

A version of the Community Multiscale Air Quality (CMAQ) model has been developed by the U.S. EPA that is capable of addressing the atmospheric fate, transport and deposition of some common trace toxics. An initial, 36-km rectangular grid-cell application for atrazine has been...

102

Elemental concentrations and regional signatures in atmospheric aerosols over Hungary  

Microsoft Academic Search

Samples of atmospheric particles collected during one year at rural sites were analysed up to 20 elements by PIXE. The average concentrations, enrichment factors and size distribution curves are presented and discussed. Concentration ratios for selected trace elements sometimes used as tracers in following long distance transport of air masses were deduced and compared with the data of Rahn. Conclusions

I. Borbély-Kiss; L. Haszpra; E. Koltay; S. László; A. Mészáros; E. Mészáros; Gy Szabó

1988-01-01

103

On validation of regional atmosphere and wave models for the Black Sea region  

NASA Astrophysics Data System (ADS)

Mesoscale atmospheric models MM5 and WRF adapted to the Black Sea region in Marine Hydrophysical Institute (MHI, National Academy of Sciences of Ukraine) together with wave model WAM are widely using in the last decade. Black Sea meteorological and wave climate assessing, 3-5 days operational forecast, researches of various physical phenomena typical for the Black Sea coastal zone are examples of application of such regional model calculations. Therefore we made some inspection of their quality. Results of operational regional forecast of catastrophic weather events in the Black Sea region are considered. Flooding of 6-7 July 2012 in the Krasnodar Region, Russia caused a loss of more than 170 lives and huge economic damage. Hazardous storm of 11 November 2007 near the Crimean coast caused accidents and sinks of many vessels including ones carrying fuel oil and sulfur, more than 20 members of the crews were missing and severe ecological damage was suffered. However, the forecast of rainfall intensity had appeared five days before the flood at free access on the Internet website http://vao.hydrophys.org and the forecast of the wave height appeared on the same website three days before the storm. Quality of the regional forecast and its advantages over the global forecast are discussed. In situ wave data including 2D wave spectra obtained at the MHI Black Sea Research Platform in 2012-2013 over all seasons were compared with model calculations. The distance of the Platform to the shore is 0.5 km where the sea depth is 28 m. Only part of wave spectrum belonging to wave frequencies lower than 0.4 Hz was considered to filter out waves developing from the coastal line. It is concluded that scatter indexes for modeled significant wave height and mean frequency are about of 50% and 15%. Some systematic defects of model calculations are revealed but the use of the model-based forecasts could lead to significant reduction in human losses and economic damage from catastrophic weather events. The core support of this work was provided by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant Agreement 287844 for the project 'Towards COast to COast NETworks of marine protected areas (from the shore to the high and deep sea), coupled with sea-based wind energy potential (CoCoNet)'. The research leading to these results has also received funding from Ukrainian State Agency of Science, Innovations and Information under contracts F53/117-2013 and M/281-2013. Authors gratefully acknowledge continuing support of these foundations.

Dulov, Vladimir; Shokurov, Mikhail; Chechina, Katerina; Soukissian, Takvor; Malinovsky, Vladimir

2014-05-01

104

Spatial and temporal characteristics of urban atmospheric methane in Nagoya City, Japan:. an assessment of the contribution from regional landfills  

NASA Astrophysics Data System (ADS)

The spatial and temporal behavior of atmospheric methane (CH 4) in the Nagoya metropolitan area was investigated in relation to the regional meteorological and topographical characteristics. It was found that the daily maximum CH 4 concentrations in the central city area were observed when the northeast wind blew from the foothill of the northeastern mountainous area down into the central city areas, under stable atmospheric conditions. The large and active landfills are the major anthropogenic CH 4 sources and are located at the hill sites in the northeast. Therefore, it was considered that the air mass with the high concentration of CH 4 flowed from the landfill sites into the urban area, and exerted substantial influences on the spatial and temporal variations of atmospheric CH 4 concentrations in the central city area.

Ito, A.; Takahashi, I.; Nagata, Y.; Chiba, K.; Haraguchi, H.

105

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

106

Solar activity influences on atmospheric electricity and on some structures in the middle atmosphere  

NASA Astrophysics Data System (ADS)

Only processes in the troposphere and the lower stratosphere are reviewed. General aspects of global atmospheric electricity are summarized in Chapter 3 of NCR (1986); Volland (1984) has outlined the overall problems of atmospheric electrodynamics; and Roble and Hays (1982) published a summary of solar effects on the global circuit. The solar variability and its atmospheric effects (overview by Donelly et al, 1987) and the solar-planetary relationships (survey by James et al. 1983) are so extremely complex that only particular results and selected papers of direct relevance or historical importance are compiled herein.

Reiter, Reinhold

1989-09-01

107

Regional forecasting with global atmospheric models; Fourth year report  

SciTech Connect

The scope of the report is to present the results of the fourth year`s work on the atmospheric modeling part of the global climate studies task. The development testing of computer models and initial results are discussed. The appendices contain studies that provide supporting information and guidance to the modeling work and further details on computer model development. Complete documentation of the models, including user information, will be prepared under separate reports and manuals.

Crowley, T.J.; North, G.R.; Smith, N.R. [Applied Research Corp., College Station, TX (United States)

1994-05-01

108

External interannual ENSO forcing : which regions outside equatorial Pacific may influence the evolution of ENSO ?  

NASA Astrophysics Data System (ADS)

Low-frequency coupled ocean-atmosphere dynamics intrinsic to the Pacific Ocean are essential to El Niño development. Some recent studies (e.g Annamalai 2005, Izumo and al. 2010, Rodriguez-Fonseca 2009, Terray 2010, Vimont and al. 2003) however suggest that external interannual forcing may influence the evolution of El Niño. In the present study, we aim at identifying regions outside the Pacific Ocean, which can affect the evolution of ENSO. Our assumption is that zonal wind anomalies within the Pacific equatorial waveguide are a necessary condition to influence ENSO evolution. We thus aim at identifying teleconnections between SST anomalies outside of the equatorial Pacific, and Pacific equatorial zonal wind anomalies that are independent of ENSO. To that end, we first remove the ENSO signal from interannual wind and SST anomalies in several re-analyses by regression to all the principal components of an EOF analysis of Tropical Pacific Sea Surface Temperature which display significant correlations with Niño3.4 within 12 months of the ENSO peak. Results show that non-negligible (25% of interannual variance) ENSO-independent zonal winds anomalies remain in the western/central equatorial Pacific. We further show that SST anomalies in six regions (equatorial, northern and southern central Pacific; Tropical and southern Atlantic and southern Indian Ocean) display significant 0-3 months lead correlations to those ENSO-independent wind variations. These regions may hence influence ENSO evolution through remote influence on equatorial Pacific winds, as previously suggested by, e.g, Rodriguez-Fonseca (2009), Terray (2010), Vimont and al. (2003). While our statistical methodology did allow to isolate those regions, we still have to confirm from forced atmospheric and coupled simulations that: - SST anomalies in those regions can indeed influence zonal winds over the tropical Pacific, - the response of the Tropical Pacific coupled system to this external forcing can lead to an El Niño.

Dayan, H.; Vialard, J.; Izumo, T.; Lengaigne, M.; Terray, P.

2012-04-01

109

Regional Assimilation of NASA Atmospheric Infrared Sounder (AIRS) Data  

NASA Technical Reports Server (NTRS)

The NASA Short-term Prediction Research and Transition (SPORT) Center seeks to accelerate the infusion of NASA Earth Science Enterprise (ESE) observations, data assimilation and modeling research into NW S forecast operations and decision-making. The Atmospheric Infrared Sounder (AIRS), is expected to advance climate research and weather prediction into the 21 st century. It is one of six instruments onboard Aqua, a satellite that is part of NASA s Earth Observing System. AIRS, along with two partner microwave sounding instruments, represents the most advanced atmospheric sounding system ever deployed in space. The system is capable of measuring the atmospheric temperature in the troposphere with radiosonde accuracies of 1 K over 1 km-thick layers under both clear and cloudy conditions, while the accuracy of the derived moisture profiles will exceed that obtained by radiosondes. It is imperative that the scientific community is prepared to take full advantage of next-generation satellite data that will become available within the next decade. The purpose of this paper is to describe a procedure designed to optimally assimilate AIRS data at high spatial resolution over both land and ocean. The assimilation system used in this study is the Local Analysis and Prediction System (LAPS) developed at the Forecast System Laboratory used extensively around the globe. Results will focus on quality control issues associated with AIRS, optimal assimilation strategies, and the impact of the AIRS data on subsequent numerical forecasts at 12 km produced by the next generation Weather Research and Forecast (WRF) model.

Chou, Shih-Hung; Lapenta, William; Jediovec, Gary J.; McCarty, William; Mecikalski, John R.

2004-01-01

110

Regional hydrologic consequences of increases in atmospheric CO2 and other trace gases  

Microsoft Academic Search

Concern over changes in global climate caused by growing atmospheric concentrations of carbon dioxide and other trace gases has increased in recent years as our understanding of atmospheric dynamics and global climate systems has improved. Yet despite a growing understanding of climatic processes, many of the effects of human-induced climatic changes are still poorly understood. Major alterations in regional hydrologic

Peter H. Gleick

1987-01-01

111

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

Microsoft Academic Search

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

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

2004-01-01

112

Space-based sensing of atmospheric conditions over data-void regions  

Microsoft Academic Search

Multispectral satellite data from frequencies in the visible, infrared, and microwave regions have been applied to the analysis of atmospheric conditions where no in situ data were available on the earth's surface or aloft. Atmospheric quantities diagnosed were surface temperature, surface and upper air wind, visibility, solar insolation and precipitation, and cloud cover descriptors such as percent coverage, cloud-free locations,

Jan L. Behunek; Thomas H. Vonder Haar

1991-01-01

113

Estimation of Regional Methane Emission from Rice Fields Using Simple Atmospheric Diffusion Models  

Microsoft Academic Search

Two atmospheric diffusion models, the box model ad the ATDL (Atmospheric Turbulent and Diffusion Laboratory) model, were used to calculate regional methane (CH4) emissions of rice fields in the Beijing area. Compared with conventional closed chamber measurements, the box model overestimated CH4 emission because of meteorological conditions--the ground inverse layer was not favorable for the application of the model during

J. G. Liu; Y. H. Zhang; K. S. Shao; M. Shao; L. M. Zeng; S. H. Lu; S. Slanina; H. A. C. Denier van der Gon

2000-01-01

114

Atmospheric correction analysis on LANDSAT data over the Amazon region. [Manaus, Brazil  

NASA Technical Reports Server (NTRS)

The Amazon Region natural resources were studied in two ways and compared. A LANDSAT scene and its attributes were selected, and a maximum likelihood classification was made. The scene was atmospherically corrected, taking into account Amazonic peculiarities revealed by (ground truth) of the same area, and the subsequent classification. Comparison shows that the classification improves with the atmospherically corrected images.

Parada, N. D. J. (principal investigator); Dias, L. A. V.; Dossantos, J. R.; Formaggio, A. R.

1983-01-01

115

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

116

The influence of life on the evolution of the atmosphere.  

PubMed

The early history of life on earth may have been characterized by coevolution of microbial metabolism and atmospheric composition. Metabolic developments affected the composition of the atmosphere, and the resulting changes in the atmosphere stimulated the evolution of new metabolic capabilities. The first organisms eked out an existence by deriving energy from the fermentation of organic compounds abiotically synthesized. The abiotic source was meager, however, and when autotrophy arose, life was freed from its dependence on abiotic synthesis. The expanded level of biological activity made possible by autotrophy resulted in an increased rate of burial of reduced organic matter in sea floor sediments. The resultant drain on the concentration of electron donors in the biosphere caused a decline in the hydrogen content of the atmosphere. Biological productivity was limited by the supply of reduced compounds. This paper explores the biogeochemical circulation of electron donors in the primitive anaerobic ocean, concluding that their shortage was so critical as to provide strong selective pressure for the evolution of algal photosynthesis. PMID:11968213

Walker, J C

1980-01-01

117

Influence of atmospheric structure and topography on infrasonic wave propagation  

NASA Astrophysics Data System (ADS)

The effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling. This paper presents the first long-term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source (Sakurajima Volcano, Japan). The data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media. Moreover, waveforms also change significantly in both time and space. Numerical simulations were performed using a two-dimensional finite difference time domain (2-D FDTD) method. Effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction. The simulation successfully reproduced the variations of amplitudes and waveforms. Results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers. Our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible. To evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data, atmospheric data with a time resolution higher than is currently available are required. If the data are available, the present results suggest that the propagation effects could be evaluated using 2-D FDTD modeling at realistic calculation times.

Lacanna, G.; Ichihara, M.; Iwakuni, M.; Takeo, M.; Iguchi, M.; Ripepe, M.

2014-04-01

118

Possible physical mechanism of solar activity influence on atmosphere  

NASA Astrophysics Data System (ADS)

Studies of different indexes of solar activity (sunspot numbers W, radiation flux F10.7, X-ray flux) showed that all these indexes have variations with a period close to period of QBO. We show, using a method of mathematical filtration (analogue of wave-let analysis), that variations with the period of QBO in these indexes are in phase. It is usually considered that atmospheric QBO are caused by terrestrial processes and not connected with the solar QBO. It is natural because even more intensive 11-year cyclicity is developed weakly in atmospheric processes and only in some of them. However, it is known that variations of solar activity with long periods (hundreds and thousands of years) are seen in climate variability of atmosphere. Recent spaced measurements detected that ozone concentration on stratospheric heights varies with period of QBO. We show that such variations of ozone concentration lead to formation of west-east streams in the equatorial atmosphere. QBO of these streams, as and QBO of ozone concentration are in phase with QBO of solar activity. This result allows to do conclusion concerning solar nature of their origin.

Ivanov-Kholodny, G.

2003-04-01

119

Influence of atmospheric pollutants on the biodeterioration of stone  

Microsoft Academic Search

Studies have been carried out on specimens of Saltrio stone, Carrara and Candoglia marbles, exposed for some years to the polluted atmosphere of Milan. The test specimens, which were directly exposed to the washing away, showed alterations in the form of grey-black stains which were different in dimensions and quantity according to the stone material, while those sheltered showed only

E. Zanardini; P. Abbruscato; N. Ghedini; M. Realini; C. Sorlini

2000-01-01

120

Atmospheric winter conditions 2007/08 over the Arctic Ocean based on NP-35 data and regional model simulations  

NASA Astrophysics Data System (ADS)

Atmospheric measurements on the drifting Arctic sea ice station "North Pole-35" crossing the Eastern part of the Arctic Ocean during winter 2007/2008 have been compared with regional atmospheric HIRHAM model simulations. The observed near-surface temperature, mean sea level pressure and the vertical temperature, wind and humidity profiles are satisfactorily reproduced by the model. The strongest temperature differences between observations and the simulations occur near the surface due to an overestimated vertical mixing of heat in the stable Arctic boundary layer (ABL). The observations show very strong temperature inversions near the surface, whereas the simulated inversions occur frequently between the surface and 415 m at too high levels. The simulations are not able to reproduce the observed inversion strength. The regional model underestimates the wind speeds and the sharp vertical wind gradients. The strength of internal atmospheric dynamics on the temporal development of atmospheric surface variables and vertical profiles of temperature, wind and relative humidity has been examined. Although the HIRHAM model systematically overestimates relative humidity and produces too high long-wave downward radiation during winter, two different atmospheric circulation states, which are connected to higher or lower pressure systems over the Eastern part of the Arctic Ocean, are simulated in agreement with the NP-35 observations. Sensitivity studies with reduced vertical mixing of heat in the stable ABL have been carried out. A slower increase in the stability functions with decreasing Richardson number under stable stratification has an impact on the horizontal and vertical atmospheric structure. Changes in synoptical cyclones on time scales from 1-3 days over the North Atlantic cyclone path are generated, which influences the atmospheric baroclinic and planetary waves on time scales up to 20 days over the Arctic Ocean basin. The use of increased vertical stability in the model simulation leads to diminished planetary-scale variability over the Arctic Ocean.

Mielke, M.; Zinoviev, N. S.; Dethloff, K.; Rinke, A.; Kustov, V. J.; Makshtas, A. P.; Sokolov, V. T.; Neuber, R.; Maturilli, M.; Klaus, D.; Handorf, D.; Graeser, J.

2014-05-01

121

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

122

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

123

The influence of atmospheric pressure on landfill methane emissions.  

PubMed

Landfills are the largest source of anthropogenic methane (CH4) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH4 emissions have been reported. Here, we present the results of a multi-season study of whole landfill CH4 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 m3 CH4 min(-1). A simple regression model of our results was used to calculate an annual emission rate of 8.4 x 10(6) m3 CH4 year(-1). These data, along with CH4 oxidation estimates based on emitted landfill gas isotopic characteristics and gas collection data, were used to estimate annual CH4 generation at this landfill. A reported gas collection rate of 7.1 x 10(6) m3 CH4 year(-1) and an estimated annual rate of CH4 oxidation by cover soils of 1.2 x 10(6) m3 CH4 year(-1) resulted in a calculated annual CH4 generation rate of 16.7 x 10(6) m3 CH4 year(-1). These results underscore the necessity of understanding a landfill's dynamic environment before assessing long-term emissions potential. PMID:12957154

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

2003-01-01

124

Influence of the El Niño-Southern Oscillation on the middle atmosphere temperature and ozone  

NASA Astrophysics Data System (ADS)

Using the middle atmosphere temperature dataset observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite experiment between 2002 and 2012, and temperatures simulated by the Whole Atmospheric Community Climate Model version 3.5 (WACCM3.5) between 1953 and 2005, we studied the influence of the El Niño-Southern Oscillation (ENSO) on middle atmosphere temperature and ozone during the Northern Hemisphere (NH) wintertime. Both temperature and ozone responses to ENSO observed by SABER show similar patterns to those simulated by the WACCM3.5 model. For the first time, a significant winter temperature response to ENSO in the middle mesosphere has been observed, with an anomalous warming of ~1.0 K/MEI (Multivariate ENSO Index) in the tropics and an anomalous cooling of ~-2.0 K/MEI in the NH middle latitudes. The observed temperature responses to ENSO in the mesosphere are opposite to those in the stratosphere, in agreement with previous modeling studies. In the lower stratosphere (below 30 km), the ozone response to ENSO is positively correlated with the temperature response, suggesting that the ENSO modulation of the residual mean meridional circulation primarily contributes to the lower stratosphere ozone response. While in the upper stratosphere (40-50 km), the ozone response to ENSO is anti-correlated with temperature in the tropics and middle latitudes, suggesting that the photochemical effects of adiabatic temperature changes play important roles in this region. But in the polar upper stratosphere, the ozone response simulated by the WACCM is again positively correlated with temperature, suggesting that the dynamical effect is dominant. Figure 1. Meridional cross section of the zonal mean temperature response to ENSO in winter derived from the WACCM3.5 simulation (left) and the SABER observational dataset (right). The contour interval is 0.2 K/MEI, the blue dash contour lines denote the negative values and the red solid contour lines denote positive values. The white regions indicate that the results are significant above 95% (1.96?) confidence level. Figure 2. As in Figure 1, but for the zonal mean ozone response to ENSO in winter between 20 and 60 km derived from the WACCM3 simulation (left) and the SABER observations (right). The ozone results are percentage variations with contour interval of 0.5%/MEI.

Li, T.; Calvo, N.; Yue, J.; Russell, J. M.; Smith, A. K.; Mlynczak, M. G.; She, C. Y.

2013-12-01

125

The Influence of High Aerosol Concentration on Atmospheric Boundary Layer Temperature Stratification  

SciTech Connect

Investigations of the changing in the atmospheric boundary layer (ABL) radiation balance as cased by natural and anthropogenic reasons is an important topic of the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program. The influence of aerosol on temperature stratification of ABL while its concentration was extremely high within a long period of time was studied experimentally. The case was observed in Moscow region (Russia) with the transport of combustion products from peat-bog and forest fires in July-September, 2002. At this time the visibility was some times at about 100-300 m. Aerosol concentration measured by Moscow University Observatory and A.M. Obukhov Institute of Atmospheric Physics field station in Zvenigorod (55.7 N; 36.6 E) for several days was in 50-100 times more than background one (Gorchakov at al 2003). The high aerosol concentration can change the radiation balance at ABL, and so to change thermal stratification in ABL above the mega lopolis. For the analysis the data were used of synchronous measurements by MTP-5 (Microwave Temperature Profiler operating at wavelength 5 mm) in two locations, namely: downtown Moscow and country-side which is 50 km apart to the West (Zvenigorod station). (Kadygrov and Pick 1998; Westwater at al 1999; Kadygrov at al 2002). Zvenigorod station is located in strongly continental climate zone which is in between of the climates of ARM sites (NSANorth Slope of Alaska and SGP-Southern Great Plains). The town of Zvenigorod has little industry, small traffic volume and topography conductive to a good air ventilation of the town. For these reasons Zvenigorod can be considered as an undisturbed rural site. For the analysis some days were chosen with close meteorological parameters (average temperature, humidity, wind, pressure and cloud form) but strongly differing in aerosol concentration level.

Khaykin, M.N.; Kadygrove, E.N.; Golitsyn, G.S.

2005-03-18

126

Regional forecasting with global atmospheric models; Third year report  

SciTech Connect

This report was prepared by the Applied Research Corporation (ARC), College Station, Texas, under subcontract to Pacific Northwest Laboratory (PNL) as part of a global climate studies task. The task supports site characterization work required for the selection of a potential high-level nuclear waste repository and is part of the Performance Assessment Scientific Support (PASS) Program at PNL. The work is under the overall direction of the Office of Civilian Radioactive Waste Management (OCRWM), US Department of Energy Headquarters, Washington, DC. The scope of the report is to present the results of the third year`s work on the atmospheric modeling part of the global climate studies task. The development testing of computer models and initial results are discussed. The appendices contain several studies that provide supporting information and guidance to the modeling work and further details on computer model development. Complete documentation of the models, including user information, will be prepared under separate reports and manuals.

Crowley, T.J.; North, G.R.; Smith, N.R. [Applied Research Corp., College Station, TX (United States)

1994-05-01

127

Aerosol variability and atmospheric transport in the Himalayan region from CALIOP 2007-2010 observations  

NASA Astrophysics Data System (ADS)

Himalayan Plateau is surrounded by regions with high natural and anthropogenic aerosol emissions that have a strong impact on regional climate. This is particularly critical for the Himalayan glaciers whose equilibrium is also largely influenced by radiative direct and indirect effects induced by aerosol burden. This work focuses on the spatial and vertical distribution of different aerosol types, their seasonal variability and sources. The analysis of the 2007-2010 yr of CALIPSO vertically resolved satellite data allows the identification of spatial patterns of desert dust and carbonaceous particles in different atmospheric layers. Clusters of Lagrangian back-trajectories highlight the transport pathways from source regions during the dusty spring season. The analysis shows a prevalence of dust; at low heights they are distributed mainly north (with a main contribution from the Gobi and Taklamakan deserts) and west of the Tibetan Plateau (originating from the deserts of South-West Asia and advected by the westerlies). Above the Himalayas the dust amount is minor but still not negligible (detectable in around 20% of the measurements), and transport from more distant deserts (Sahara and Arabian Peninsula) is important. Smoke aerosol, produced mainly in North India and East China, is subject to shorter range transport and is indeed observed closer to the sources while there is a limited amount reaching the top of the plateau. Data analysis reveals a clear seasonal variability in the frequencies of occurrence for the main aerosol types; dust is regulated principally by the monsoon dynamics, with maxima of occurrence in spring. The study also highlights relevant interannual differences, showing a larger presence of aerosol in the region during 2007 and 2008 yr.

Bucci, S.; Cagnazzo, C.; Cairo, F.; Di Liberto, L.; Fierli, F.

2013-06-01

128

The solar atmosphere and the structure of active regions  

NASA Technical Reports Server (NTRS)

The existence of 'holes' in the corona is reported characterized by abnormally low densities and temperatures. It was found that such coronal holes appear to be the source of high-velocity, enhanced-density streams in the solar wind as observed at the earth's orbit. It was further noted that coronal holes appear to be associated with regions of diverging magnetic fields in the corona. Models were developed to accomplish the objective for the principal energy flows in the transition region and corona.

Sturrock, P. A.

1974-01-01

129

Analysis of regional albedo characteristics and its influence in the regional climate model REMO  

NASA Astrophysics Data System (ADS)

The effects of land-use changes on climate have a high priority in climate impact researches. Nevertheless it is not trivial to integrate land-use changes in the Regional atmospherical climate Model REMO (Jacob 2001) so that characteristics of a typical land-use type can be created and therewith systematical effects can be analyzed. As in many regional dynamical climate models, REMO is calculating in the target resolution with parameters which are independent of land-use classes. Considering only one of these parameters, e.g. the albedo, the processing chain (Rechid et al. 2008) to construct the underlying model-albedo uses a number of assumptions which levels phase and amplitude of the albedo-cycle of a regional typical land cover. The albedo data product ALBEDOMAP (Fischer et al. 2006) of the Medium Resolution Imaging Spectrometer (MERIS) on the ESA platform ENVISAT is used as comparative data set. The annual cycle of the ALBEDOMAP data exceeds the modeled variability of the annual albedo cycle permanently in some cases by a factor of ten. Results of REMO-sensitivity studies show, that even small changes in the albedo about one percent is influencing the simulation. Within this study the relevance of characteristically surface information concerning land-use change for fine resolutions in REMO were shown. Fischer, J. ; Preusker, R.; Muller, J.-P. & M. Zühlke (2007): ALBEDOMAP -Validation Report - ESA AO/1-4559/04/I-LG, Online-Publikation: http://www.brockmann-consult.de/albedomap/pdf/MERIS-AlbedoMap-Validation-1.0.pdf. Jacob, D. (2001): A note to the simulation of the annual and inter-annual variability of the water budget over the Baltic Sea drainage basin; Meteorol. Amtos. Phys., 77, 61-73, 2001. Rechid, D.; Raddatz, T. & D. Jacob (2008): Parameterization of snow-free land surface albedo as a function of vegetation phenology based on MODIS data and applied in climate modelling.; Theor. Appl. Climatol., DOI 10.1007/s00704-008-0003-y.

Preuschmann, S.; Jacob, D.

2010-09-01

130

The influence of atmospheric loss processes to the evolution of the Martian atmosphere and water inventory  

NASA Astrophysics Data System (ADS)

We apply a diffusive-gravitational equilibrium and thermal balance model for high X-ray and EUV flux values which can be expected after the Sun arrived at the Zero- Age-Main-Sequence for the study of the radiation impact on the CO2-rich Martian thermosphere due to photodissociation and ionization processes, exothermic chemical reactions and cooling by CO2 IR emission in the 15 micro-m band. Our results show, that during the Noachian epoch high XUV fluxes between 10 to 100 times that of the present Sun were responsible for much higher temperatures of the early Martian thermosphere-exosphere environment. We found that the exobase level could expand to an altitude which was about 10 times that of the present one of about 200 km (4.5 Gyr ago). In order to study the effect of high XUV fluxes and the part of the upper atmosphere which could have been lost to space over the planet's history, we apply a global 3-D magnetohydrodynamic (MHD) simulation model of the solar wind interaction with the extended upper atmosphere. Furthermore we study the possible protection of the early Martian atmosphere and its water inventory by an intrinsic magnetic field against ion pick up by the solar wind plasma of the young active Sun. If one assumes that impact erosion was nearly in balance with impact atmospheric delivery, our results would favour a weak early dynamo with a magnetic moment less than 0.1 that of the present Earth combined with a higher heating efficiency in the thermosphere, or a late onset of the Martian dynamo at least after about the first 150 to 200 Myr after the planet's origin. In such cases the XUV heated and expanded upper atmosphere could have lost, depending from the solar wind mass flux of the young Sun from several bar up to several tens of bar.

Lammer, H.; Terada, N.; Kulikov, Yu. N.; Lichtenegger, H. I. M.

2007-08-01

131

Solar influence on a major mode of atmospheric variability  

NASA Astrophysics Data System (ADS)

We find that the North Annular Mode (NAM) of the wintertime geopotential height anomalies between 10 and 1000 hPa is influenced by solar changes and that the effect is statistically significant. This evidence suggests that a mechanism of solar influence on climate operates through the excitation of this mode. The influence depends on the phase of the quasi-biennial oscillation (QBO). In early winter for the west QBO and late winter for the east QBO the solar changes affect the NAM in both the stratosphere and the troposphere almost equally. The results are compared with earlier studies of the role of the QBO and solar UV changes on near-polar temperatures and geopotential heights. Thus the late winter effect for the west QBO found by Labitzke and van Loon [1988] is clearly evident in the NAM in the stratosphere but does not appear in the troposphere.

Ruzmaikin, Alexander; Feynman, Joan

2002-07-01

132

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

133

Estimating regional carbon exchange in New England and Quebec by combining atmospheric, ground-based and satellite data  

NASA Astrophysics Data System (ADS)

We derive regional-scale (~104 km2) CO2 flux estimates for summer 2004 in the northeast United States and southern Quebec by assimilating extensive data into a receptor-oriented model-data fusion framework. Surface fluxes are specified using the Vegetation Photosynthesis and Respiration Model (VPRM), a simple, readily optimized biosphere model driven by satellite data, AmeriFlux eddy covariance measurements and meteorological fields. The surface flux model is coupled to a Lagrangian atmospheric adjoint model, the Stochastic Time-Inverted Lagrangian Transport Model (STILT) that links point observations to upwind sources with high spatiotemporal resolution. Analysis of CO2 concentration data from the NOAA-ESRL tall tower at Argyle, ME and from extensive aircraft surveys, shows that the STILT-VPRM framework successfully links model flux fields to regionally representative atmospheric CO2 data, providing a bridge between `bottom-up' and `top-down' methods for estimating regional CO2 budgets on timescales from hourly to monthly. The surface flux model, with initial calibration to eddy covariance data, produces an excellent a priori condition for inversion studies constrained by atmospheric concentration data. Exploratory optimization studies show that data from several sites in a region are needed to constrain model parameters for all major vegetation types, because the atmosphere commingles the influence of regional vegetation types, and even high-resolution meteorological analysis cannot disentangle the associated contributions. Airborne data are critical to help define uncertainty within the optimization framework, showing for example, that in summertime CO2 concentration at Argyle (107 m) is ~0.6 ppm lower than the mean in the planetary boundary layer.

Matross, Daniel M.; Andrews, Arlyn; Pathmathevan, Mahadevan; Gerbig, Christoph; Lin, John C.; Wofsy, Steven C.; Daube, Bruce C.; Gottlieb, Elaine W.; Chow, Victoria Y.; Lee, John T.; Zhao, Conglong; Bakwin, Peter S.; Munger, J. William; Hollinger, David Y.

2006-11-01

134

Integrated atmospheric water vapor estimates from a regional GPS network  

NASA Astrophysics Data System (ADS)

Integrated atmospheric water vapor (IWV) estimates from a 15-station-wide network of Global Positioning System (GPS) receivers have been collected continuously since November 1997. The core of this network consists of five stations of the active GPS reference system in the Netherlands. A network with sufficient long baselines was chosen to secure the absolute accuracy of the GPS IWV data. Rapid satellite orbits available 12 to 24 hours after data acquisition are used in the processing of the GPS data, and IWV estimates are available with a typical delay of 1 day. Comparison of the GPS IWV data with data retrieved from a water vapor radiometer and radiosondes shows a good agreement. Different network configurations and processing strategies have been investigated to optimize the network and processing for future near-real-time use. In near-real-time applications, only predicted orbits are available; however, the accuracy of the predicted orbits is, in general, not sufficient for accurate IWV retrieval. We tested whether orbit relaxation, i.e., the simultaneous adjustment of orbit parameters during the processing of the GPS data, could increase the accuracy of the IWV estimates. During an experiment with orbit relaxation applied to predicted orbits a significant improvement of the accuracy of the GPS IWV data was found. The accuracy was comparable to GPS IWV data retrieved with final orbits, the most accurate orbit data available. Results of the experiments and the analysis of operational acquired data are presented.

Baltink, Henk Klein; van der Marel, Hans; van der Hoeven, André G. A.

2002-02-01

135

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

136

The Sun's Influence on the Earh's Atmosphere and Interplanetary Space.  

PubMed

The bulk of the sun's radiation is in the visible and infrared. Solar radiation at these wavelengths controls the weather in the lowest levels of the earth's atmosphere. The rate at which this energy is emitted (the so-called solar constant) varies by a few tenths of 1 percent over a time scale of days. Longer period variations may exist, but have yet to be detected. Far more variable are the amounts of energy emitted as ultraviolet, extreme ultraviolet, and x-rays, and in the continuous outflow of ionized solar particles. The latter controls the properties of the space between the earth and the sun as well as those of the earth's magnetosphere. The ultraviolet and particle emissions control the properties of the earth's upper atmosphere, including the global wind circulation and changes therein associated with intense auroral storms. While considerable progress has been made in exploring the solar-terrestrial system since the advent of space research, many problems remain. These include the question of how magnetic energy is converted into ionized particle energy in the sun and in the earth's magnetosphere, the way in which solar and terrestrial magnetic fields join or merge, and how large electric fields are generated and sustained a few thousand kilometers above the earth's poles. Perhaps the most intriguing question concerns the possible relation between solar variability and the earth's weather and climate. PMID:17735724

Evans, J V

1982-04-30

137

Characteristics of auroral electron acceleration regions observed by Atmosphere Explorer C  

Microsoft Academic Search

Measurements of electron precipitation and ion drift velocities on the spacecraft Atmosphere Explorer C have revealed that electron acceleration regions (or inverted 'V's') in the 1200--1800 MLT quadrant exhibit the following systematic behavior: (1) Electron distribution functions in the acceleration regions are in all cases well described by Maxwellian primary electron beams which have been accelerated through an electrostatic potential

J. L. Burch; S. A. Fields; W.B. Hanson; R.A. Heelis; R. A. Hoffman; R. W. Janetzke

1976-01-01

138

Atmospheric pollution in a coal mine region of Romania and solutions to assure sustainable development  

Microsoft Academic Search

The present paper examines the atmospheric pollution in the Jiu-Valley coal mining region of Romania. It identifies: polluting sources, pointing out the pollution favourizing conditions; the pollution impacts; and measures for short-, middle-, and long-term which could be taken in order to obtain a sustainable future development of this region. The importance of the problems presented in this paper is

I. I. Irimie; I. Tulbure

1996-01-01

139

Analysis of regional characteristics of the atmospheric heat balance in the Tokyo metropolitan area in summer  

Microsoft Academic Search

The heat island phenomenon in the Tokyo metropolitan area has spread ever more widely, and it is now too wide to treat as a single regional phenomenon. In this paper, the authors have analyzed the climate on an urban scale in summer, and compared the regional characteristics of the atmospheric heat balance at the center of Tokyo, an inland satellite

Taiki Sato; Shuzo Murakami; Ryozo Ooka; Shinji Yoshida

2008-01-01

140

Regional Carbon Fluxes and Atmospheric Carbon Dynamics in the Southern Great Plains during the 2007 Mid Continent Intensive of NACP  

NASA Astrophysics Data System (ADS)

In June 2007, an intensive regional campaign will take place in the Southern Great Plains (SGP) to estimate land-atmosphere exchanges of CO2, water, and energy at 1 to 100 km scales. The primary goals of this North American Carbon Program (NACP) campaign are to evaluate top-down and bottom-up estimates of regional fluxes and to understand the influence of moisture gradients, surface heterogeneity, and atmospheric transport patterns on these fluxes (and their estimation). The work will be integrated with the Cloud and Land Surface Interaction Campaign (CLASIC), centered on the US DOE Atmospheric Radiation Measurement Program SGP region. CLASIC will focus on interactions among the land surface, convective boundary layer, and cumulus clouds, and will utilize an array of atmospheric measurements. Carbon and meteorological data streams and logistical resources will be available to other NACP researchers. Carbon flux and concentration data will be collected from tower and airborne platforms. Eddy flux towers will be deployed in the four major land cover types, distributed over the region's SE to NW precipitation gradient. In addition, CO2, water, and energy fluxes will be observed with the Duke Helicopter Observation Platform (HOP) at various heights in the boundary layer, including in the surface layer (the few meters near the surface). Two aircraft will carry precise CO2 measurement systems and NOAA12-flask packages for carbon cycle gases and isotopes. Continuous CO2 and CO concentrations, NOAA flasks, and isotope diel flasks (14C, 13C, and 18O) will also be collected from a centrally located 60 m tower. Flights are planned to constrain simple boundary layer budget models and to conduct Lagrangian air mass following experiments. A distributed model of land surface fluxes will be run off line and coupled to MM5 with tracer capability. In addition to characterizing the influence of the land surface on the atmosphere, the aircraft data (in combination with observations of atmospheric dynamics) will provide a very well characterized southern boundary condition to the Mid-Continent Intensive.

Torn, M. S.; Fischer, M. L.; Riley, W. J.; Jackson, T. J.; Avissar, R.; Biraud, S. C.; Billesbach, D. P.; Sweeney, C.; Tans, P. P.; Berry, J. A.

2006-12-01

141

Influence of local waste burning on atmospheric aerosol properties in urban environment  

NASA Astrophysics Data System (ADS)

Aerosols affect the radiative energy budget on both the regional and global scales. The wavelength-dependent aerosol optical depth (AOD) is a fundamental determinant of the amount by which extra-terrestrial incoming sunlight and outgoing terrestrial radiation are being attenuated in the atmosphere. The present study addresses the influence of local waste burning on aerosol characteristics, black carbon (BC) aerosol mass concentration and spectral solar irradiance using ground-based measurements over the tropical urban environment of Hyderabad, India. AOD has been observed to be maximum during burning days compared to normal days. Aerosol size spectra suggest bimodal distributions during pre-and post-burning periods and trimodal distributions during burning periods. Angstrom wavelength exponent estimated from spectral variation of AOD suggested dominance of accumulation mode particle loading during burning days compared to normal days. Diurnal variation of BC on normal days showed a broad nocturnal peak during ˜20:00 to ˜24:00 h with a maximum value of BC aerosol concentration of ˜14,000 ng m-3 whereas on local waste burning days enormous increases in BC concentrations have been observed with a peak at ˜60,000 ng m-3. Relative attenuation of global solar irradiance during burning days has been found to be of the order of 30% in the visible and 28% in the near-infrared regions. The results are discussed in detail in this paper.

Madhavi Latha, K.; Badarinath, K. V. S.

2006-03-01

142

Precipitating electron interaction with the atmosphere. II - The dayside cusp region  

NASA Technical Reports Server (NTRS)

Interaction of precipitating low-energy magnetosheath electrons with the atmosphere in the dayside cusp region has been studied. Both pitch angle and energy distributions of the fluxes as well as excitation functions for selected N2 and O UV emissions were obtained by numerically solving the multiangle equations of electron transport. There is some possibility that atmospheric emissions may be used for remote measurements of incident soft energy flux, because the ratios of molecular to atomic emission line intensities in the low-energy region are quite different from those in the high-energy region.

Prasad, S. S.; Strickland, D. J.; Chiu, Y. T.

1985-01-01

143

Longitudinal variations in the Saturnian atmosphere. I - Equatorial region  

NASA Astrophysics Data System (ADS)

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.

Killen, R. M.

1988-02-01

144

Atmospheric general circulation and its low frequency variance - Radiative influences  

NASA Technical Reports Server (NTRS)

The possible effects of radiation on the evolution of the atmosphere on time scales ranging from about a week to about 90 days are examined with reference to the available observational and modeling studies. The clear-sky and cloud radiative processes are shown to exert significant vertical, latitudinal, and longitudinal gradients in the diabatic heating within the troposphere and the stratosphere. The meridional heating gradient, which drives the general circulation, is altered significantly by clouds. The major conclusion of the study is that the observed negative anomalies in the outgoing IR radiation following intense warm episodes of tropicl sea-surface temperature (El Nino) are indeed anomalies in the cloud-radiative forcing.

Ramanathan, V.

1987-01-01

145

The Influence of Tropospheric Processes in Modeling the Middle Atmosphere with Gravity Waves  

NASA Technical Reports Server (NTRS)

Our Numerical Spectral Model (NSM) extends from the ground up into the thermosphere and has a vertical grid point resolution of about 0.5 km to resolve the interactions of gravity waves (GWs) described with Hines' Doppler Spread Parameterization (DSP). This model produces in the stratosphere and mesosphere the major features of QBO, SAO, tides, and planetary waves. The purpose of this paper is to discuss results from an initial study with our 3D model that shows how certain tropospheric processes can affect the dynamics of the middle atmosphere. Under the influence of tropospheric heating, and augmented by GW interactions, two distinct but related processes can be identified. (1) A meridional circulation develops in the stratosphere, with rising motions at low latitudes that are in magnitude comparable to the downward propagation of the QBO. As Dunkerton pointed out, a larger GW source is then required to reproduce the observed QBO, which tends to move us closer to the values recommended for the DSP. This has significant consequences for our model results that describe the upper mesosphere, considering the general importance of GWs for this region and in influencing planetary waves (e.g., 2-day wave) and tides in particular. (2) Tropospheric heating produces zonal jets near the tropopause that are related to latitudinal variations in pressure and reversing temperature variations (resembling the dynamical conditions near the mesopause), which in turn is conducive to generate baroclinic instability. Modeling results show that our ability to generate the QBO critically depends on the magnitude of the temperature reversal that is a measure of this instability. Planetary waves are generated in this process, which can apparently interfere with or augment the GW interactions. As originally demonstrated by Lindzen and Holton, the eastward propagating Kelvin waves and westward propagating Rossby gravity waves (generated by tropospheric convection) can in principle provide the acceleration to influence the QBO, and we were able to confirm this with our 3D model.

Mayr, H. G.; Mengel, J. G.; Drob, D. P.; Porter, H. S.

2002-01-01

146

The influence of trace constituents of the atmosphere on radiative and thermal conditions  

NASA Astrophysics Data System (ADS)

The effect of trace constituents on the radiative and heat balance of the atmosphere is examined with regard to such topics as the formation of the radiative heat influx, and the dependence of variations of the vertical profile of radiative changes of temperature on meteorological conditions. A method for calculating the greenhouse effect is presented, and the evolution of the atmosphere with regard to the greenhouse effect is considered. Anthropogenic factors influencing the radiative heat transfer and the greenhouse effect are discussed, and consideration is given to the numerical modeling of the effects of atmospheric gas-composition variations on climate.

Kondratev, K. Ia.; Moskalenko, N. I.

147

Influence of Land Use Change on the 18O in Atmospheric CO2: Comparison of Preindustrial, Modern and Future Scenarios  

NASA Astrophysics Data System (ADS)

Understanding the governing influences on the concentration of CO2 continues to be of importance for climate change investigations. Attribution of atmospheric CO2 signals to various source components is also crucial for fully understanding the carbon cycle. As the isotopic composition of atmospheric CO2 is dependent upon the processes active at the source region there is the possibility of estimating the importance of various conditions at the source region by examining the isotopic signature. In particular, the stable isotope CO18O ratio of atmospheric CO2 reflects the isotopic state of the soil water of the terrestrial biosphere and the equilibrium and kinetic fractionation processes during both soil respiration and leaf photosynthesis. To better understand the impact of changes in the biosphere on the global CO18O signal, physically based modeling of the hydrologic and physiological processes is employed. To this end, an atmospheric general circulation model (GCM) is adapted to predict the concentration of 18O in meteoric water vapor and the precipitation resulting from condensation. This is coupled to a land surface model adapted to trace isotopic ratios of precipitation entering the soil, uptake by the roots and exchange of the heavy 18O with plant and soil CO2 fluxes. As such, the isotopic ratio of the photosynthetic uptake and respirational loss of CO2 from various ecosystem types can be mechanistically simulated. The resulting fluxes are fed back to the atmospheric component at each model time step as a passive tracer. In this manner, the isotopic concentration of the atmospheric CO2 is eventually found prognostically from the time integration of the model. The importance of variations in land use on the 18O of CO2 is explored with this isotopic GCM. With this approach, simulations reflecting pre-industrial, modern, and future land use conditions are compared to provide a physical basis for interpretation the potential impacts of biosphere changes on the 18O signal in the observational record.

Noone, D. C.; Still, C. J.; Riley, W. J.

2001-12-01

148

Critical Hydrologic and Atmospheric Measurements in Complex Alpine Regions  

NASA Astrophysics Data System (ADS)

The Alps are often referred to as the « Water Towers of Europe » and as such play an essential role in European water resources. The impact of climatic change is expected to be particularly pronounced in the Alps and the lack of detailed hydrologic field observations is problematic for predictions of hydrologic and hazard assessment. Advances in information technology and communications provide important possibilities to improve the situation with relatively few measurements. We will present sensorscope technology (arrays of wireless weather stations including soil moisture, pressure, and temperature) that has now been deployed at the Le Genepi and Grand St. Bernard pass. In addition, a Distributed Temperature Sensor array on the stream beds has been deployed and stream discharge monitored. The high spatial resolution data collected in these previously "ungaged" regions are used in conjunction with new generation hydrologic models. The framework as to what is possible today with sensor arrays and modeling in extreme mountain environments is discussed.

Parlange, M. B.; Bou-Zeid, E.; Barrenetxea, G.; Krichane, M.; Ingelrest, F.; Couach, O.; Luyet, V.; Vetterli, M.; Lehning, M.; Duffy, C.; Tobin, C.; Selker, J.; Kumar, M.

2007-12-01

149

Sensitivity of Boreal-Summer Circulation and Precipitation to Atmospheric Aerosols in Selected Regions. Part 2; The Americas  

NASA Technical Reports Server (NTRS)

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 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.

2009-01-01

150

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

151

On empirical models of the upper atmosphere in the polar regions.  

NASA Technical Reports Server (NTRS)

The expression for the exospheric temperature in Jacchia's static diffusion models of the upper atmosphere has a discontinuous gradient at the poles. Therefore it cannot describe the true state of the upper atmosphere in the polar regions. Furthermore, it cannot be used to calculate quantities that depend on the derivative of the exospheric temperature, or the density, like pressure gradients, horizontal forces or horizontal heat fluxes. A modified expression for the exospheric temperature is suggested. This modification yields variables of state of the upper atmosphere that deviate little from Jacchia's values, but it has continuous gradient at the poles and is therefore more suitable for treating dynamical problems like the global wind pattern.

Blum, P. W.; Harris, I.

1973-01-01

152

Influence of solar magnetic sector structure on terrestrial atmosphere vorticity  

NASA Technical Reports Server (NTRS)

The solar magnetic sector structure has a sizable and reproducible influence on tropospheric and lower stratospheric vorticity. The average vorticity during winter in the Northhern Hemisphere north of 20 deg N latitude reaches a minimum approximately one day after the passing of a sector boundary, and then increases during the following two or three days. The effect is found at all heights within the troposphere, but is not prominent in the stratosphere, except at the lower levels. No single longitudinal interval appears to dominate the effect.

Wilcox, J. M.; Scherrer, P. H.; Svalgaard, L.; Roberts, W. O.; Olson, R. H.; Jenne, R. L.

1973-01-01

153

Atmospheric Mercury Transport Across Southern Lake Michigan: Influence from the Chicago\\/Gary Urban Area  

Microsoft Academic Search

The local and regional impacts of mercury emissions from major urban and industrial areas are critical to quantify in order to further understand mercury cycling in the environment. The Chicago\\/Gary urban area is one such location in which mercury emissions from industrial sources are significant and regional mercury transport needs to be further examined. Speciated atmospheric mercury was measured in

L. E. Gratz; G. J. Keeler; J. T. Dvonch

2008-01-01

154

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

155

High altitude plume emissions in atmospheric-window region  

SciTech Connect

Quantum-Mechanical Spectator model (Impulse Approximation) is used to calculate the cross section for rotation-vibration excitation of CO during collision with atomic oxygen at relative velocity (energy) of 5 (1.3), 8 (3.3), 11 (5.3), and 14 km/s (10.2 eV). The calculation is carried out for initial CO vibrational level v=o and rotational levels J=O and J=10 and final vibrational levels v'=o - 6 and final rotational levels up to J'=100. It is shown that the final results are almost independent of the initial rotational level. The rotational distribution in the final vibrational levels is rather flat and cannot be described by a Maxwell-Boltzmann distribution. The final rotation-vibration distributions are translated into relative emission in the 4.7-micron region. The emitted radiation from each level shows an R-branch bandhead around 4.4 microns with P-branch extending beyond 6 microns. It is expected that carbon dioxide and water generated by the plumes at high altitudes, upon collision with atomic oxygen, would also emit band infrared radiation around 6, 4.3, and 2.7 microns.

Sharma, R.D.; Bakshi, P.; Sindoni, J.

1989-02-01

156

EVIDENCE OF A SOLAR INFLUENCE ON THE ATMOSPHERIC ELECTRIC ELEMENTS AT MAUNA LOA OBSERVATORY  

Microsoft Academic Search

The monitored atmospheric electric elements at Mauna Loa Observatory, Hawaii, have provided good evidence of a direct solar influence on some of the electric elements recorded at the mountain observatory. An analysis of the data has shown that following a solar flare eruption, both the air-earth conduction current and the electric field, meas- ured during fair weather at Mauna Loa,

WILLIAM E. COBB

1967-01-01

157

The influence of processing atmosphere on twin-roll melt-spinning of aluminum alloys  

SciTech Connect

Melt-spun samples of Al-2%Fe have been produced in two different processing atmospheres, ambient pressure argon and a high vacuum. High speed video photography and microstructural analysis of the ribbons indicate that the processing pressure influences the interaction of the melt with the copper rolls and thus the thermal history. This results in significant differences in ribbon microstructure.

Sellers, C.H.; Aldrich, K.S.; Cortez, M.M.; Wright, R.N.

1992-01-01

158

The influence of processing atmosphere on twin-roll melt-spinning of aluminum alloys  

SciTech Connect

Melt-spun samples of Al-2%Fe have been produced in two different processing atmospheres, ambient pressure argon and a high vacuum. High speed video photography and microstructural analysis of the ribbons indicate that the processing pressure influences the interaction of the melt with the copper rolls and thus the thermal history. This results in significant differences in ribbon microstructure.

Sellers, C.H.; Aldrich, K.S.; Cortez, M.M.; Wright, R.N.

1992-09-01

159

Influences of gas flow on atmospheric pressure glow discharge in helium  

Microsoft Academic Search

Atmospheric pressure glow discharge (APGD) was produced in a 5-mm helium gap between two plane-parallel electrodes of 50 mm in diameter, each covered by a 1-mm thick quartz plate. The influence of the helium gas flowing in parallel through the helium gap on APGD was studied. The helium flow rate varies up to 12 liter per minute, corresponding to helium

H. Luo; Z. Liang; B. Lv; X. Wang; Z. Guan; L. Wang

2008-01-01

160

Influence of Elevated Atmospheric Carbon Dioxide on Transcriptional Responses of Bradyrhizobium japonicum in the Soybean Rhizoplane  

PubMed Central

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.

Sugawara, Masayuki; Sadowsky, Michael J.

2013-01-01

161

Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models  

NASA Astrophysics Data System (ADS)

Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants. We find an uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO2 observation network within the tropics.

Gurney, Kevin Robert; Law, Rachel M.; Denning, A. Scott; Rayner, Peter J.; Baker, David; Bousquet, Philippe; Bruhwiler, Lori; Chen, Yu-Han; Ciais, Philippe; Fan, Songmiao; Fung, Inez Y.; Gloor, Manuel; Heimann, Martin; Higuchi, Kaz; John, Jasmin; Maki, Takashi; Maksyutov, Shamil; Masarie, Ken; Peylin, Philippe; Prather, Michael; Pak, Bernard C.; Randerson, James; Sarmiento, Jorge; Taguchi, Shoichi; Takahashi, Taro; Yuen, Chiu-Wai

2002-02-01

162

Influence of volcanic eruptions on the climate of the Asian monsoon region  

NASA Astrophysics Data System (ADS)

Several state-of-the-art general circulation models (GCMs) predict that large volcanic eruptions should result in anomalous dry conditions throughout much of monsoon Asia. Here, we use long and well-validated proxy reconstructions of Asian droughts and pluvials to detect the influence of volcanic radiative forcing on the hydroclimate of the region since the late Medieval period. Superposed epoch analysis reveals significantly wetter conditions over mainland southeast Asia in the year of an eruption, with drier conditions in central Asia. Our proxy and model comparison suggests that GCMs may not yet capture all of the important ocean-atmosphere dynamics responsible for the influence of explosive volcanism on the climate of Asia.

Anchukaitis, K. J.; Buckley, B. M.; Cook, E. R.; Cook, B. I.; D'Arrigo, R. D.; Ammann, C. M.

2010-11-01

163

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

164

An atmosphere–ocean regional climate model for the Mediterranean area: assessment of a present climate simulation  

Microsoft Academic Search

We present an atmosphere–ocean regional climate model for the Mediterranean basin, called the PROTHEUS system, composed by\\u000a the regional climate model RegCM3 as the atmospheric component and by a regional configuration of the MITgcm model as the\\u000a oceanic component. The model is applied to an area encompassing the Mediterranean Sea and compared to a stand-alone version\\u000a of its atmospheric component.

Vincenzo Artale; Sandro Calmanti; Adriana Carillo; Alessandro Dell’Aquila; Marine Herrmann; Giovanna Pisacane; Paolo M. Ruti; Gianmaria Sannino; Maria Vittoria Struglia; Filippo Giorgi; Xunqiang Bi; Jeremy S. Pal; Sara Rauscher

2010-01-01

165

Toward the influence of clouds on the shortwave radiation budget of the earth-atmosphere system estimated from satellite data  

Microsoft Academic Search

The purpose of this paper is to investigate the influence of cloudiness on the shortwave radiation budget at the top of the atmosphere, at the surface, and, as a residual, for the atmosphere itself. The data used for this study are derived exclusively from satellite measurements. Calculations for the top of the atmosphere are based entirely on measurements of the

M. Rieland; R. Stuhlmann

1993-01-01

166

The Influence of Regional-Scale Circulation on Precipitation Variability in the Southern United States  

NASA Astrophysics Data System (ADS)

The proximity of the southern United States to large water bodies, mountain systems, and the arid climate of the desert southwest makes extended precipitation forecasts exceedingly difficult. In order to better understand the complex precipitation mechanisms, this analysis addresses the relationships between the regional-scale circulation and long-term precipitation variability and change in the southern US for each season through a 42 year study period. Five unique precipitation regions were created for each season, and seasonal anomalies were calculated and examined by region for changes in variability and slope through time. Long -term climate change was detected in the precipitation regions only during the autumn season. During autumn, the western regions showed a significant increase in precipitation through the study period while the eastern region recorded a significant decrease. To explain the significant variations and trends, relationships with the mean hemispheric flow regimes were analyzed. Atmospheric teleconnection indices and a formulated regional-scale flow index were correlated to the regional precipitation anomalies. Results indicated that the regional -scale flow index was the best estimator of regional precipitation variability during every season. To investigate the influence of the regional-scale circulation further, isolation of the primary circulation anomalies associated with the Atlantic Subtropical High (STH) was necessary. Results indicated the importance of five dominant circulation regimes which transcend the seasonal analysis. Three of the patterns related to variations in the STH while two related to variations in the generalized hemispheric longwave flow. Of these, the most important patterns with respect to changes in precipitation related to variations in the STH, especially during the autumn season. It was found that strengthening of the STH over the eastern US causes persistent drought while advecting moisture into the continental interior. Position of the STH anomaly is critical to the corresponding precipitation regime as an eastward displaced STH causes negative precipitation anomalies in the western regions and positive precipitation anomalies in the east. This analysis proves the importance of regional-scale circulation variation on the precipitation variability of the US south. Given current global warming predictions, studies which fully integrate regional-scale atmospheric circulation variability are crucial to future impact scenarios.

Vega, Anthony Jude

167

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

168

Energetic particles and their influence on the atmosphere of the Earth: 3D model simulations and comparison with MIPAS data  

NASA Astrophysics Data System (ADS)

Solar high energetic particles (protons mostly), which reach polar regions of the Earth after Solar Proton Events (SPEs) initiate inonization of the atmosphere below 100 km. Such kind of forcing leads to strong enhancement of electron density (and other ions) in D-region of the ionoshere, ?nd also, via ion-neutral chemical reactions, to the disturbances in chemical composition (first of all, to additional NOx and HOx production). Theoretical analysis (Porter et al., 1976; Solomon et al., 1981) showed, that each pair of ions, which are created by solar protons in the atmosphere gives one molecular of NOx and two molecular of HOx. Than this additional molecular amount leads to the intensification of chemical catalitical cycles of ozone destruction. Global 3D numerical models haven been used to investigate the influence of SPEs on chemical composition, temperature and circulation of the atmosphere. In order to calculate the ionization rates produced by solar protons satellite data (GOES) of corresponding proton fluxes in different canals of energy were used. It was shown by simulations, that ozone was strongly destroyed by SPEs in the polar stratosphere and mesosphere, and it leads to the changes in temperature and circulation. It was found also, that these changes penetrate to the lower latitudes and may has a long-term consequences. The comparison between photochemical simulation for SPE of October-November 2003 and satellite observations (MIPAS instrument on board of ENVISAT) showed rather good agreement including ozone depletion, increased NOy and HOx compounds in the mesosphere and higher stratosphere.

Krivolutsky, Alexei; Vyuskova, Tat'yana

2010-05-01

169

Influence of stochastic sea ice parametrization on climate and the role of atmosphere-sea ice-ocean interaction.  

PubMed

The influence of a stochastic sea ice strength parametrization on the mean climate is investigated in a coupled atmosphere-sea ice-ocean model. The results are compared with an uncoupled simulation with a prescribed atmosphere. It is found that the stochastic sea ice parametrization causes an effective weakening of the sea ice. In the uncoupled model this leads to an Arctic sea ice volume increase of about 10-20% after an accumulation period of approximately 20-30 years. In the coupled model, no such increase is found. Rather, the stochastic perturbations lead to a spatial redistribution of the Arctic sea ice thickness field. A mechanism involving a slightly negative atmospheric feedback is proposed that can explain the different responses in the coupled and uncoupled system. Changes in integrated Antarctic sea ice quantities caused by the stochastic parametrization are generally small, as memory is lost during the melting season because of an almost complete loss of sea ice. However, stochastic sea ice perturbations affect regional sea ice characteristics in the Southern Hemisphere, both in the uncoupled and coupled model. Remote impacts of the stochastic sea ice parametrization on the mean climate of non-polar regions were found to be small. PMID:24842027

Juricke, Stephan; Jung, Thomas

2014-06-28

170

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...

171

Evaluation of a method to reduce uncertainty in wind hindcasts performed with regional atmosphere models  

Microsoft Academic Search

For more and more applications in coastal and offshore engineering, numerical simulations of waves and surges are required. An important input parameter for such simulations are wind fields. They represent one of the major sources for uncertainties in wave and surge simulations. Wind fields for such simulations are frequently obtained from numerical hindcasts with regional atmospheric models (RAMs). The skill

R. Weisse; F. Feser

2003-01-01

172

Urban–rural solar radiation loss in the atmosphere of Greater Cairo region, Egypt  

Microsoft Academic Search

A comparative study for measured global solar radiation, G, during the period (1969–2006) and the corresponding global radiation loss in the atmosphere, RL%, over urban and rural districts in Greater Cairo region have been performed. The climatic variabilities of G radiation at the urban and rural sites are also investigated and discussed. Monthly, seasonal and annual mean values of extraterrestrial

S. M. Robaa

2009-01-01

173

The influence of atmospheric turbulence on 3D flash lidar range imagery  

NASA Astrophysics Data System (ADS)

Three dimensional flash imaging lidar technology is widely used in the field of military and national economic construction. The preliminary simulation research is an indispensable aspect in the design of the new lidar. In order to establish a simulation model most close to the real scene, the spatial effect of the simulation system during the laser roundtrip transmission process must be considered. This paper describes the physical mechanism of the formation of atmospheric turbulence, the power spectral density function of the distribution of atmospheric refractive index and the phase distortion due to atmospheric disturbances during light propagation in space. Then the phase-screen distribution of atmospheric turbulence is derived using power spectrum retrieval and time-dependent wavefront tilt parameter. In addition, numerical simulation is conducted using statistical methods. A three dimensional target range imaging simulation model containing laser characteristics, target characteristics, receiver characteristics and laser speckle is established. And the phase screen is introduced into the calculation model to simulate the results in turbulent atmosphere. The major contribution of this paper is transforming the influence of beam spreading and drifting caused by laser propagation in turbulent flow to the influence of target range imaging, which better reveals the diffusion and position drift of imaging on detection surface caused by turbulence. Results show that larger values of refractive index structure parameters and lidar target distance produce blurry and drifting imagery.

Zhao, Yan; Han, Shaokun; Zhao, Wen; Wang, Ping; Xia, Wenze

2013-12-01

174

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

175

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

176

Source identification of aerosols influencing atmospheric extinction: Integrating PMF and PSCF with emission inventories and satellite observations  

NASA Astrophysics Data System (ADS)

The relative influence of source categories of aerosols that affect atmospheric extinction is analyzed by evaluating the potential source contribution function (PSCF) based source regions of the positive matrix factorization (PMF) estimated factors against satellite retrievals of aerosol index and active fires and combining with emission inventory information. This approach has been applied to aerosol chemical data obtained from the integrated campaign undertaken during March-May 2006: Integrated Campaign for Aerosols, Gases and Radiation Budget (ICARB). Four source categories were identified: dust, nitrate-and-dust, biomass-and-fossil combustion, and secondary species. The relative influence of dust and nitrate-and-dust was higher during north-south transport from west Asia over the Arabian Sea during the period of campaign, coincident with highs in the spatial distribution of Ultraviolet Aerosol Index (UVAI) from the Ozone Monitoring Instrument (OMI), implying dust-nitrate association in the outflow from west Asia. The relative influence of anthropogenic sources (biomass-and-fossil combustion and secondary species) was higher over Bay of Bengal during March-April 2006. High fire frequency from the Moderate Resolution Imaging Spectroradiometer (MODIS), coincident with the probable source regions identified in the central Indo-Gangetic plain and central India (south of 27°N), indicates influence of biomass burning source. The biomass-and-fossil combustion factor arising from biofuel, crop residue, and forest fires is evident by their large emission flux rather than from industrial sources in the probable source regions associated with this factor. In contrast, thermal power plant and industries largely influenced the secondary species factor. This approach provides verification of source categories identified through PMF against active sources from satellite remote sensing and provides an estimate of their relative strength based on emission inventory information.

Cherian, R.; Venkataraman, C.; Kumar, A.; Sarin, M. M.; Sudheer, A. K.; Ramachandran, S.

2010-11-01

177

Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model  

NASA Astrophysics Data System (ADS)

A large scale mismatch exists between our understanding and quantification of ecosystem atmosphere exchange of carbon dioxide at local scale and continental scales. This paper will focus on the carbon exchange on the regional scale to address the following question: What are the main controlling factors determining atmospheric carbon dioxide content at a regional scale? We use the Regional Atmospheric Modelling System (RAMS), coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C), and including also sub models for urban and marine fluxes, which in principle include the main controlling mechanisms and capture the relevant dynamics of the system. To validate the model, observations are used which were taken during an intensive observational campaign in the central Netherlands in summer 2002. These included flux-site observations, vertical profiles at tall towers and spatial fluxes of various variables taken by aircraft. The coupled regional model (RAMS-SWAPS-C) generally does a good job in simulating results close to reality. The validation of the model demonstrates that surface fluxes of heat, water and CO2 are reasonably well simulated. The comparison against aircraft data shows that the regional meteorology is captured by the model. Comparing spatially explicit simulated and observed fluxes we conclude that in general simulated latent heat fluxes are underestimated by the model to the observations which exhibit large standard deviation for all flights. Sensitivity experiments demonstrated the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same test also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

Ter Maat, H. W.; Hutjes, R. W. A.

2008-10-01

178

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

179

Local and regional factors influence the structure of treehole metacommunities  

PubMed Central

Background Abiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are also influenced by regional factors such as immigration and colonization. We used three years of monthly treehole census data to evaluate the relative influence of local and regional factors on our study system. Results Every species responded to at least one of three local environmental factors measured: water volume, leaf litter mass, and presence of a top predator. Several species were affected by water volume, and a non-exclusive group of species were influenced by leaf litter mass. Relative abundance of Aedes triseriatus was higher in treeholes with higher volumes of water, and relative abundances of three out of six other species were lower in treeholes with higher volumes of water. Leaf litter mass positively affected densities of Aedes triseriatus and relative abundance of several dipteran species. The density of the top predator, Toxorhynchites rutilus, affected the relative abundance of the two most common species, A. triseriatus and Culicoides guttipennis. Treeholes with T. rutilus had an average of two more species than treeholes without T. rutilus. We found little evidence of synchrony between pairs of treeholes, either spatially or temporally. There were high levels of spatial and temporal turnover, and spatial turnover increased with distance between patches. Conclusion The strong effects of water volume, leaf litter mass, and presence of a top predator, along with the high temporal turnover strongly suggest that species presence and density are determined by local factors and changes in those factors over time. Both low water volume and high predator densities can eliminate populations in local patches, and those populations can recolonize patches when rain refills or predators exit treeholes. Population densities of the same species were not matched between pairs of treeholes, suggesting variation in local factors and limited dispersal. Distance effects on spatial turnover also support limitations to dispersal in the metacommunity, and we conclude that the weight of evidence favors a strong influence of local factors relative to regional factors.

Paradise, Christopher J; Blue, Jarrod D; Burkhart, John Q; Goldberg, Justin; Harshaw, Lauren; Hawkins, Katherine D; Kegan, Benjamin; Krentz, Tyler; Smith, Leslie; Villalpando, Shawn

2008-01-01

180

The influence of several changes in atmospheric states over semi-arid areas on the incidence of mental health disorders  

NASA Astrophysics Data System (ADS)

The incidence of suicide attempts [Deliberate Self Harm (DSH); ICD-10: X60-X84] and psychotic attacks (PsA; ICD-10, F20-F29) in association with atmospheric states, typical for areas close to big deserts, was analyzed. A retrospective study is based on the 4,325 cases of DSH and PsA registered in the Mental Health Center (MHC) of Ben-Gurion University (Be'er-Sheva, Israel) during 2001-2003. Pearson and Spearman test correlations were used; the statistical significance was tested at p < 0.1. The influence of temperature and humidity on suicide attempts ( N SU ) and psychotic attacks ( N PS ) was weakly pronounced ( p > 0.1). Correlation coefficients between N SU and N PS and speed WS of westerly wind reaches 0.3 ( p < 0.05), while their dependence on easterly WS was weaker ( p > 0.09). Variations in easterly wind direction WD influence N SU and N PS values ( p < 0.04), but no corresponding correlation with westerly winds was found ( p > 0.3). Obviously ,in transition areas located between different regions ,the main role of air streams in meteorological-biological impact can scarcely be exaggerated. An unstable balance in the internal state of a weather-sensitive person is disturbed when the atmospheric state is changed by specific desert winds, which can provoke significant perturbations in meteorological parameters. Results indicate the importance of wind direction, defining mainly the atmospheric situation in semi-arid areas: changes in direction of the easterly wind influence N SU and N PS , while changes in WS are important for mental health under westerly air streams. Obviously, N SU and N PS are more affected by the disturbance of weather from its normal state, for a given season, to which the local population is accustomed, than by absolute values of meteorological parameters.

Yackerson, Naomy S.; Zilberman, Arkadi; Todder, Doron; Kaplan, Zeev

2011-05-01

181

Regional scale variations of atmospheric CO2 and CH4 from satellite observation  

NASA Astrophysics Data System (ADS)

To identify the sources, sinks and changes of atmospheric CO2 and CH4, this study investigates the spatio-temporal changes of atmospheric CO2 and CH4 concentration on the regional scale by the satellite observations. In this paper, choosing the land region of China as the study area, we investigate the spatio-temporal changes of atmospheric CO2 and CH4 concentrations using the data of the CO2 dry air mixing ratio (XCO2), and the CH4 dry air mixing ratio (XCH4), retrieved by the Greenhouse Gases Observing Satellite (GOSAT) from Jan. 2010 to Dec. 2012. The results show that (1) both XCO2 and XCH4 show higher concentrations in southeastern regions than that in the northwestern, and tend to yearly increasing from 2010 to 2013; (2) XCO2 shows obvious seasonal change with higher values in the spring than that in summer. The seasonal peak-to-peak amplitude is 8 ppm and the annual growth is about 2 ppm. XCH4, however, does not show a seasonal change; (3) With regard to different land-use backgrounds, XCO2 shows larger concentrations over the areas of urban agglomeration than that over the grasslands and deserts, and XCH4 shows lower concentrations over deserts than that over the Yangtze River Delta region and Sichuan Basin.

Ru, F.; Lei, L.; Bu, R.; Guan, X.; Qi, J.

2014-03-01

182

LRO Lyman-Alpha Mapping Project (LAMP): Exploration of Permanently Shadowed Regions and the Lunar Atmosphere  

NASA Astrophysics Data System (ADS)

LRO/LAMP is a UV spectrograph designed to address how water is formed on the moon, transported through the lunar atmosphere, and deposited in permanently shadowed regions (PSRs). Its main objectives are to 1) identify exposed water frost in PSRs, 2) characterize landforms and albedos in PSRs, 3) demonstrate the feasibility of using natural starlight and sky-glow illumination for future lunar surface mission applications, and 4) to assay the lunar atmosphere and its variability. The LAMP spectrograph will accomplish the first three objectives by measuring interplanetary HI Ly? sky-glow and FUV starlight reflected from the PSRs. Both of these light sources provide fairly uniform, but faint, illumination (e.g., the reflected Ly? signal is expected to be ~10~R). Thanks to LAMP's sensitivity, however, by the end of the nominal 1-year mission the SNR for a Ly? albedo map will be >100/km2 in the polar regions, allowing the characterization of subtle compositional and structural features. Dayside and nightside lunar surface reflectance measurements of other regions are also planned to measure variations in the illumination sources for improved accuracy. The production and transport of Lunar atmosphere constituents H and Ar will be investigated by observation of their resonantly scattered FUV emissions. The detection and discovery of other constituent emissions is also expected. LAMP albedo maps of PSR landforms and potential surface water ice will be used to identify landing sites for future scientific exploration of these regions and investigation of the intriguing processes that occur within them.

Retherford, K. D.; Stern, S. A.; Black, R. K.; Slater, D. C.; Gladstone, G. R.; Feldman, P. D.; Crider, D. H.; Parker, J. W.; Dirks, G. J.; Versteeg, M. H.; Persson, K. B.; Sykes, H. A.; Davis, M. W.; Stack, J. A.; Case, T. R.; McCullough, L. D.; de Los Santos, A.; Kaufmann, D. E.; Andrews, P. M.

2006-12-01

183

Influence of Ocean Surface Conditions on Atmospheric Vertical Thermodynamic Structure and Deep Convection.  

NASA Astrophysics Data System (ADS)

The authors analyze the influence of sea surface temperature (SST) and surface wind divergence on atmospheric thermodynamic structure and the resulting effects on the occurrence of deep convection using National Meteorological 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 an 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. Specifically, when SST28°C, CAPE is always positive, and surface wind divergence does not qualitatively change the buoyancy profile above the PBL. Strong surface wind divergence, however, stabilizes the PBL so as to suppress the initiation of deep convection. In warm SST regions, CAPE>0 regardless of assumptions about condensate loading, although the pseudoadiabatic limit is more consistent with the observed deep convection than the reversible moist-adiabatic limit under these circumstances. When SST<27°C, CAPE is usually negative and inhibits convection, but strong surface wind convergence can destabilize the inversion 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 SST28°C in the absence of strong surface wind divergence or when strong surface wind convergence occurs even if SST<27°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.

Fu, Rong; del Genio, Anthony D.; Rossow, William B.

1994-07-01

184

The atmospheric influence, size and possible asteroidal nature of the July 2009 Jupiter impactor  

NASA Astrophysics Data System (ADS)

Near-infrared and mid-infrared observations of the site of the 2009 July 19 impact of an unknown object with Jupiter were obtained within days of the event. The observations were used to assess the properties of a particulate debris field, elevated temperatures, and the extent of ammonia gas redistributed from the troposphere into Jupiter's stratosphere. The impact strongly influenced the atmosphere in a central region, as well as having weaker effects in a separate field to its west, similar to the Comet Shoemaker-Levy 9 (SL9) impact sites in 1994. Temperatures were elevated by as much as 6 K at pressures of about 50-70 mbar in Jupiter's lower stratosphere near the center of the impact site, but no changes above the noise level (1 K) were observed in the upper stratosphere at atmospheric pressures less than ˜1 mbar. The impact transported at least ˜2 × 10 15 g of gas from the troposphere to the stratosphere, an amount less than derived for the SL9 C fragment impact. From thermal heating and mass-transport considerations, the diameter of the impactor was roughly in the range of 200-500 m, assuming a mean density of 2.5 g/cm 3. Models with temperature perturbations and ammonia redistribution alone are unable to fit the observed thermal emission; non-gray emission from particulate emission is needed. Mid-infrared spectroscopy of material delivered by the impacting body implies that, in addition to a silicate component, it contains a strong signature that is consistent with silica, distinguishing it from SL9, which contained no evidence for silica. Because no comet has a significant abundance of silica, this result is more consistent with a "rocky" or "asteroidal" origin for the impactor than an "icy" or "cometary" one. This is surprising because the only objects generally considered likely to collide with Jupiter and its satellites are Jupiter-Family Comets, whose populations appear to be orders of magnitude larger than the Jupiter-encountering asteroids. Nonetheless, our conclusion that there is good evidence for at least a major asteroidal component of the impactor composition is also consistent both with constraints on the geometry of the impactor and with results of contemporaneous Hubble Space Telescope observations. If the impact was not simply a statistical fluke, then our conclusion that the impactor contained more rocky material than was the case for the desiccated Comet SL9 implies a larger population of Jupiter-crossing asteroidal bodies than previously estimated, an asteroidal component within the Jupiter-Family Comet population, or compositional differentiation within these bodies.

Orton, G. S.; Fletcher, L. N.; Lisse, C. M.; Chodas, P. W.; Cheng, A.; Yanamandra-Fisher, P. A.; Baines, K. H.; Fisher, B. M.; Wesley, A.; Perez-Hoyos, S.; de Pater, I.; Hammel, H. B.; Edwards, M. L.; Ingersoll, A. P.; Mousis, O.; Marchis, F.; Golisch, W.; Sanchez-Lavega, A.; Simon-Miller, A. A.; Hueso, R.; Momary, T. W.; Greene, Z.; Reshetnikov, N.; Otto, E.; Villar, G.; Lai, S.; Wong, M. H.

2011-01-01

185

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

NASA Technical Reports Server (NTRS)

The authors analyze the influence of Sea Surface Temperature (SST) and surface wind divergence on atmospheric thermodynamic structure and the resulting effects on the occurrence of deep convection using National Meteorological 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 an 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. Specifically, when SST is greater than or equal to 28 C, CAPE is always positive, and surface wind divergence does not qualitatively change the buoyancy profile above the PBL. Strong surface wind divergence, however, stabilizes the PBL so as to suppress the initiation of deep convection. In warm SST regions, CAPE is greater than 0 regardless of assumptions about condensate loading, although the pseudoadiabatic limit is more consistent with the observed deep convection than the reversible moist-adiabatic limit under these circumstances. When SST is less than 27 C, CAPE is usually negative and inhibits convection, but strong surface wind convergence can destabilize the inversion 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 is greater than or equal to 28 C in the absence of strong surface wind divergence or when strong surface wind convergence occurs even if SST is less than 27 C. The anomalous suppression of deep convection in the warm area of the equatorial west Pacific lying between the intertropical convergence zone (ITCZ) and south Pacific convergence zone (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.

Fu, Rong; Del Genio, Anthony D.; Rossow, William B.

1994-01-01

186

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

187

Micrometeorological Influences on Mass Transfer of BVOC?s at the Canopy Atmosphere Interface  

NASA Astrophysics Data System (ADS)

The interactions between micrometeorological, plant physiological, hydrobiological and chemical processes on the net gas fluxes of BVOC's into the atmosphere on the stand scale from different field experiments (ECHO 2002, 2003; BEMA 1993-1997) are analyzed. Terms of the balance equations for micrometeorological and scalar quantities up to the third moment are determined from measurements. The influences of advection, convection and turbulence and the role of hydrological conditions on mass budgets will be discussed. In addition, the influence of the water status on mixing time scales and chemical reaction time scales will be analyzed.

Dlugi, R.

2003-12-01

188

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

189

Atmospheric Components and Dopant Carry-Over Influence During Laser Ablation  

Microsoft Academic Search

In order to improve the efficiency of multi-crystalline (mc)-silicon solar cells, laser ablation as a non-contact tool is highly suitable for various processes. Apart from the laser and scanning parameters frequently reported in the liter-ature, other factors exist upon which the observable results of laser ablation depend. In addition to laser and scanning parameters, the influence of various atmospheres on

Viktor Schütz; Oliver Haupt; Uwe Stutea

2011-01-01

190

Influences of the hydrological cycle on observed interannual variations in atmospheric CO18O  

NASA Astrophysics Data System (ADS)

The global increase in atmospheric CO2 since the preindustrial era has not been accompanied by a long-term trend in the CO18O/CO2 ratio (denoted as ?Ca), though many monitoring stations around the world observed a downward excursion in ?Ca (of about 0.1‰ y-1) after 1992/1993 that lasted for 5-6 years. A number of studies have suggested that the interannual variation, seasonal cycle, and spatial structure of ?Ca depend on terrestrial ecosystem fluxes. The ?Ca budget is evaluated to identify meteorological variables that could potentially influence the observed interannual ?Ca variations. Using global data sets, time series of relative humidity, 18O composition of precipitation (?WP), air temperature, precipitation, and solar radiation were correlated with Mauna Loa ?Ca variations. Observed ?Ca negatively correlated with relative humidity in tropical and middle- and high-latitude regions, and we estimated that observed relative humidity variations drove a 0.14‰ decrease in ?Ca during the mid-1990s. Similar variations in precipitation rates were also found within the tropics that suggest positive correlations between ?WP and ?Ca consistent with an amount effect (?WP decreases as precipitation increases). The decrease in ?WP during the 1990s was estimated to decrease ?Ca by as much as 0.48‰. In contrast to previous work, little evidence was found that would suggest carbon flux anomalies as the primary driver of interannual ?Ca variations. We conclude that interannual ?Ca variations were driven primarily by isotope hydrology and relative humidity, and that ?Ca can be exploited as a new constraint on hydrological cycle variations at a variety of scales.

Buenning, Nikolaus H.; Noone, David C.; Riley, William J.; Still, Christopher J.; White, James W. C.

2011-12-01

191

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

192

Regional US carbon sinks from three-dimensional atmospheric CO2 sampling  

PubMed Central

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 CO2 from the troposphere. We base our study on the unique sampling strategy of atmospheric CO2 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 CO2 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.

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

2010-01-01

193

Vertical and horizontal structure of atmospheric waves observed with the Indonesian regional CPEA radar network  

NASA Astrophysics Data System (ADS)

Although the global structure of tides and planetary waves in the middle atmosphere including MLT Mesosphere Lower Thermosphere has extensively been studied with ground-based and satellite observations structures of atmospheric waves within thousands of km are rarely reported by observations Such structures of a regional scale should reflect locality and are expected to include information of wave sources as well as interactions with smaller scale waves We have carried out meteor MF radar observations in the MLT region at three locations Kototabang 100E 0S West Sumatra Pontianak 109E 0N West Kalimantan and Pameungpeuk 107 5E 7 5S West Jawa in Indonesia as an activity of CPEA Coupling Processes of Equatorial Atmosphere project The diurnal variaiton of wind velocities over the equator at Pontianak and Kototabang with an average amplitude of 10 - 20 m s at 86 - 90 km showed significant difference indicating strong effect of non-migrating diurnal tides The significant phase difference between the two site 9 deg distance suggesting existence of high zonal wave number 4 waves Enhancement of diurnal variation of MLT wind seems to correlate with the enhancement of diurnal oscillation in the OLR outgoing longwave radiation of the Asia-Pacific area Vertical propagation of tides and other atmospheric waves are also addressed by comparing OLR data radiosonde observations during CPEA campaigns and other observational data

Nakamura, T.; Sridharan, S.; Tsuda, T.; Vincent, R.; Kozu, T.

194

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

195

Regional frequency analysis of precipitation using large-scale atmospheric variables  

NASA Astrophysics Data System (ADS)

Effective estimates of the magnitude and frequency of precipitation are necessary for hydrological designs. However, often the available data at target site are inadequate to arrive at reliable estimates. Practicing hydrometeorologists overcome this impediment by pooling information at target site with that from other locations depicting similar characteristics of precipitation. To facilitate pooling of information, hydrometeorologists use regionalization approaches for partitioning sites in the study region into groups having similar precipitation characteristics. The conventional approaches to regionalization are based on statistics computed from observed precipitation, rather than attributes affecting hydrometeorology in a region. Therefore independent validation of the delineated regions for homogeneity in precipitation was not possible. To address this issue, a new approach is proposed. Large-scale atmospheric variables affecting the precipitation in study region and location attributes are suggested as features for regionalization by K-means cluster analysis. This allows independent validation of the identified regions for homogeneity using statistics computed from the observed precipitation. The summer monsoon rainfall (SMR) regions that are currently in use by India Meteorological Department (IMD) are shown to be heterogeneous. Subsequently the effectiveness of the proposed approach to regionalization is illustrated through application to India for delineating new SMR regions. Frequency distributions are identified to fit rainfall in the regions using L-moment-based goodness-of-fit test. Error in rainfall quantile estimates for the new regions is found to be significantly less than that estimated for the IMD SMR regions. The results show that the proposed approach to regional frequency analysis of precipitation is promising.

Satyanarayana, P.; Srinivas, V. V.

2008-12-01

196

Effects of land-conversion in a biosphere-atmosphere model of Northern South America - Part 1: Regional differences in hydrometeorology  

NASA Astrophysics Data System (ADS)

This work investigates how landuse changes over northern South America, driven by human interventions, have affected the regional patterns of hydrology. Comparisons are made to scenarios where no human disturbance of the regional vegetation is assumed. A numerical model of the terrestrial biosphere (Ecosystem Demography Model 2 - ED2) is combined with an atmospheric model (Brazilian Regional Atmospheric Modeling System - BRAMS) to investigate how land conversion in the Amazon and Northern South America have changed the hydrology of the region. Two numerical realizations of the structure and composition of terrestrial vegetation are used as boundary conditions in a simulation of the regional land surface and atmosphere. One realization seeks to capture the present day vegetation condition that includes deforestation and land-conversion, the other is an estimate of the potential structure and composition of the region without human influence. Model output is assessed for consistent and significant pattern differences in hydrometeorology. Results show that South American land conversion has a consistent impact on the regional patterning of precipitation. Land-conversion was not associated with a significant bias in continental mean precipitation, but was associated with a negative bias in mean continental evaporation and a positive bias in continental runoff. A companion paper continues this analysis, with case studies that focus on specific areas that show significant differential hydrologic response.

Knox, R. G.; Longo, M.; Swann, A. L. S.; Zhang, K.; Levine, N. M.; Moorcroft, P. R.; Bras, R. L.

2013-12-01

197

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

2013-10-22

198

Evaluation of Amazonian Rainfall Using the Regional Atmospheric Modeling System-RAMS  

NASA Astrophysics Data System (ADS)

Land surface interaction with atmospheric processes has been a primary focus of recent scientific investigation. A key objective of the WETAMC/LBA campaign, launched during the Amazonian wet season, is to assess the impact of deforestation on the regional meteorology. Data was obtained at various temporal and spatial scales from an integrated instrumentation network centered in Rondonia, Brazil, at the boundary between pasture and forest. The Regional Atmospheric Modeling System (RAMS), developed at Colorado State University, was used to examine case studies of varying precipitation regimes. RAMS's interactive grid nesting capability allows features to be resolved and analyzed at different spatial scales. Data from two ground radars, a vertical profiler, micrometeorological flux tower, tethersonde and SODAR flux tower, TRMM satellite, NASA disdrometers and rain gauge, lightning and radiosonde networks was used to validate RAMS. Emphasis is placed on the performance of RAMS to accurately predict the timing, location, intensity and diurnal variation of rainfall over a 2,048 square kilometer domain.

Thompson, L. A.; Avissar, R.

2001-05-01

199

The influence of thermal stratification in the free atmosphere on the power extracted by a very large wind farm  

NASA Astrophysics Data System (ADS)

In the present study, the influence of thermally-stratified free atmosphere on the power extracted by a very large wind farm is investigated. A suit of large-eddy simulations of atmospheric boundary layer (ABL) flow inside and above an infinite wind farm is performed including the effect of earth's rotation and free-atmosphere stability. In the simulations, tuning-free Lagrangian scale-dependent dynamic models are used to model the subgrid-scale turbulent fluxes, while the turbine-induced forces are parameterized taking advantage of an actuator disk model. It is shown that for a given surface cover (with and without turbines) the thermal stratification in the free atmosphere limits the turbulent transport away from the surface compared with the unstratified case, leading to lower entrainment and boundary-layer depth. Due to the fact that in an infinite wind farm, vertical energy transport associated with turbulence is the only source of kinetic energy, lower entrainment leads to lower power production by the wind turbines. In particular, for the wind-turbine arrangement considered in this study, the power output from the wind farm is reduced by 40 percent when the potential temperature lapse rate in the free atmosphere increases from 1 to 10 K/km. Moreover, it is shown that the presence of the turbines has significant effect on the growth of the boundary-layer height. The output of LES is also employed to analyze the turbulent kinetic energy (TKE) budgets in a very large wind farm. It is shown that the shear production, which is the main source of TKE, has a peak at the top of the wind-turbine region where the strong wind shear occurs. This is consistent with the fact that the peak shear stress also occurs at the edge of the wind-turbine wake and has higher value compared with the surface shear stress in the absence of turbines. It is also shown that in a very large wind farm the energy transfer from the resolved-scale TKE to the SGS also has a peak at the top of the wind-turbine region. The LES data is further used to study the other terms in the TKE budget equation such as turbulent transport and diffusion by pressure effects and subgrid modes for different values of potential temperature lapse rate in the free atmosphere.

Abkar, Mahdi; Porté-Agel, Fernando

2013-04-01

200

What do instruments in NASA's A-Train reveal about regional trends in atmospheric water vapor?  

Microsoft Academic Search

Several instruments in NASA's A-Train satellite constellation are providing a 5+ year record of atmospheric water vapor and related quantities. Detecting climate-related changes in water vapor using these observations is challenging because trends may be caused by instrumental or other factors. We describe regional long-term variability in water vapor inferred from A-Train instruments, and relate those changes to known and

E. J. Fetzer; W. G. Read; S. L. Granger; M. de La Torre Juarez; F. W. Irion; B. H. Lambrigtsen; B. H. Kahn; V. T. Dang; D. E. Waliser

2008-01-01

201

Present-day climate of Antarctica : A study with a regional atmospheric climate model  

Microsoft Academic Search

The present-day climate of Antarctica is studied with a regional climate model. In this research, foci are the surface mass balance, i.e. the accumulation of snow on the ice cap, and the heat budget of the atmosphere above Antarctica. Insight in the surface mass balance of the Antarctic ice cap is gained by explanation, evaluation and subsequently calibration of model-simulated

W. J. van de Berg

2008-01-01

202

Atmospheric and Laser Spectral Influences on the Column CO2 Measurements at 1.57 ?m  

NASA Astrophysics Data System (ADS)

The 2007 National Research Council Decadal Survey recommended implementation of the Active Sensing of CO2 Emission over Nights, Days, and Seasons (ASCENDS) mission to address uncertainties in the knowledge of the sources and sinks of atmospheric carbon dioxide. Consequently, ASCENDS has become a part of NASA plans to monitor atmospheric carbon dioxide form space using active remote sensing. One such technique under evaluation by NASA Langley Research Center is the integrated path differential absorption (IPDA) lidar operating near 1571 nm. High precision and accuracy, of about 0.1% each, are required for the carbon dioxide mixing ratio measurements in order to improve our understanding of the gas sources and sinks. Therefore, applying the IPDA technique requires an evaluation of the influence of systematic errors and biases resulting from uncertainties in various atmospheric conditions. These conditions include atmospheric temperature, pressure and relative humidity. Furthermore, the impacts of these conditions on the spectral characteristics of the carbon dioxide absorption, transmitted laser source and other interfering atmospheric species, such as absorbing molecules and scattering aerosols have to be investigated. In this paper systematic error sources are evaluated for measurements of atmospheric carbon dioxide using the IPDA technique. The study is focused on the carbon dioxide R24 line at 1571.111903 nm wavelength. This line has been selected for operation by the airborne Multi-functional Fiber Laser Lidar (MFLL) system that is a precursor to a space-based IPDA system. For modeling the systematic effects, 2008 HITRAN database was used, as well as most recent updates, to obtain the spectral lines parameters. The Voigt profile was applied to model the absorption spectra of carbon dioxide, as well as those of the interfering species consisting of water vapor, carbon monoxide, nitrous oxide, oxygen, ozone, acetylene and methane. For all species, absorption lines within the spectral range of 1570.95 nm to 1571.30 nm were included in the calculation. The 1986 AFGL mid-latitude summer atmospheric model parameters were applied covering 0 to 80 km altitude. The calculations were performed at the carbon dioxide line-center (on-line), +3 pm and +10 pm side-lines, and +50 pm and -50 pm off-lines. Influences of pressure (and pressure shift) and temperature sensitivities of the absorption cross-section on column carbon dioxide measurements are presented. Influences of laser line-width, spectral purity and spectral stability for operation at the on-line and side-line positions are also discussed.

Refaat, T. F.; Ismail, S.; Kooi, S. A.; Lin, B.; Harrison, F. W.; Browell, E. V.

2012-12-01

203

Effects of Agricultural Production on Regional Variations of Atmospheric CO2 Concentrations  

NASA Astrophysics Data System (ADS)

The North American Carbon Program (NACP) Mid-Continent Intensive Campaign (MCI) sponsored measurements of atmospheric concentrations at five towers centered over Iowa during the summer of 2007. The towers have shown dramatic spatial gradients in CO2 over this relatively small region during 2007 and 2008. This work attempted to evaluate the cause of these gradients, and to test our coupled model's ability to reproduce these gradients. We simulated both CO2 fluxes and concentrations for June through August 2007 using the coupled ecosystem-atmosphere model SiB3-RAMS, focusing on the concentrations over the MCI region. To improve CO2 fluxes in this region, we coupled a crop phenology model to SiB3- RAMS, which calculates the leaf area index (LAI), fraction of photosynthetically active radiation absorbed by the plants (FPAR), and net ecosystem exchange (NEE) for corn, soybeans, and wheat. Including the crop model dramatically improved the concentrations at all the towers, reducing the root mean square errors by nearly half. Concentrations as low as 340 ppm were seen both in the model and in the observations. The CO2 gradient between the towers increased throughout the summer until mid-August and had considerable day-to-day variability. The model simulation suggested that large changes in the CO2 differences between the towers were due to a large-scale gradient between high concentrations to the south of the MCI region and low concentrations to the north. During the 2007 summer, the southeast United States experienced record temperatures and a severe drought. SiB3 thus simulated a large source of CO2 from the region, leading to high atmospheric CO2 concentrations in the southeast. Depending on the synoptic conditions, the large-scale gradient shifted across the MCI region, creating the large day-to-day variability seen in the differences among the towers.

Corbin, K. D.; Denning, A. S.; Lokupitiya, E. Y.; Davis, K. J.; Miles, N.; Richardson, S.; Baker, I. T.; Paustian, K. H.

2008-12-01

204

Recent sediment dynamics in the region of Mekong water influence  

NASA Astrophysics Data System (ADS)

The recent fine sediment dynamics in the region of fresh water influence (ROFI) off the Mekong River are subject of this study. Each year about 160 t of sediment discharges from the river and disperses over the shelf. The typical tropical monsoon regime induces the pronounced seasonal cycle of the discharge of water and sediment. This cycle is reflected in rates of erosion and deposition on the shelf. The modern hypothesis says that this cycle of sediment results in deposition of sediment on the shelf during the high flow season and the transport back into the river mouth during the low flow season. A coupled hydrodynamic-wind-wave and sediment model, which simulates the seasonal cycle of the system, is used to prove this hypothesis.

Hein, Hartmut; Hein, Birte; Pohlmann, Thomas

2013-11-01

205

Procedures for the estimation of regional scale atmospheric emissions—An example from the North West Region of England  

NASA Astrophysics Data System (ADS)

This paper considers the value of applying an alternative pro rata methodology to the estimation of atmospheric emissions from a given regional or local area. Such investigations into less time and resource intensive means of providing estimates in comparison to traditional methods are important due to the potential role of new methods in the development of air quality management plans. A pro rata approach is used here to estimate emissions of SO 2, NO x, CO, CO 2, VOCs and black smoke from all sources and Pb from transportation for the North West region of England. This method has the advantage of using readily available data as well as being an easily repeatable procedure which provides a good indication of emissions to be expected from a particular geographical region. This can then provide the impetus for further emission studies and ultimately a regional/local air quality management plan. Results suggest that between 1987 and 1991 trends in the emissions of the pollutants considered have been less favourable in the North West region than in the nation as a whole.

Lindley, S. J.; Longhurst, J. W. S.; Watson, A. F. R.; Conlan, D. E.

206

Using regional-scale atmospheric ?13C of CO2 as an indicator of ecosystem health and function  

NASA Astrophysics Data System (ADS)

Year to year terrestrial CO2 uptake and release is highly variable and is a result of, among other factors, weather and climate variability. One of the key ecosystem parameters that links surface-atmosphere fluxes of energy, water and carbon is stomatal conductance. By measuring and analyzing atmospheric patterns of CO2 and its 13C content over North America, we can begin to identify regional scale changes in stomatal conductance, because conductance is closely related to plant isotopic discrimination. Furthermore, 13C is a useful tracer of the differential responses of C3 and C4 plants to climate and weather anomalies, because C3 and C4 plants have very different isotopic discrimination. Both aspects of the terrestrial carbon cycle are of great interest to those seeking to understand the potential effects of global climate change on cropland and forest productivity, natural CO2 sinks, continental runoff, and continental water and energy exchange with the atmosphere. Our findings may be particularly important for parameterization of process-based models, in light of recent results suggesting that stomatal conductance models driven by vapor pressure deficit (Leuning Model) better predict atmospheric ?13C than do models driven by relative humidity (Ball-Berry Model). For the first time, spatial and temporal density of ?13C of CO2 atmospheric observations may be high enough to allow for regional inversions of ?13CO2 to optimize prior estimates of plant discrimination (and disequilibrium flux -- an isoflux resulting from the combination of a finite residence time of carbon in terrestrial biosphere pools and a changing atmospheric signature due to human burning of fossil fuels with a plant-derived ?13C signature). We perform a Bayesian synthesis inversion for 1) CO2 fluxes and 2) ?13CO2 isofluxes, over the North American region: 145-25°W longitude and 10-80°N latitude. Inversion resolution, in order to avoid aggregation errors, is 1°x1° and 3-hourly, but optimized fluxes are interpreted at monthly and regional (~106 km2) scales. Influence functions (footprints) are generated with FLEXPART, driven by National Centers for Environmental Prediction Global Forecast System meteorology. Prior information is from CarbonTracker 2011 and SiB, and background CO2 and ?13C values are from NOAA/ESRL marine boundary layer and aircraft data. Quasi-daily atmospheric observations are from NOAA/ESRL Global Monitoring Division tall towers in Park Falls, Wisconsin; Argyle, Maine; Moody, Texas; West Branch, Iowa; and Beech Island, South Carolina. Weekly observations are from Environment Canada tall towers in Estevan Point, British Columbia; Sable Island, Nova Scotia; Fraserdale, Ontario; Churchill, Manitoba; and East Trout Lake, Saskatchewan. We will present optimized, monthly spatial fields of 13C plant discrimination for North America. By comparing these posterior results to the SiB prior, we will begin to evaluate potential shortcomings in SiB with regard to both C3/C4 distribution and conductance.

Alden, C. B.; Miller, J. B.; White, J. W.; Yadav, V.; Michalak, A. M.

2012-12-01

207

Atmospheric constraints on Plant Water Use Efficiency - drivers and regional patterns of change since 1900  

NASA Astrophysics Data System (ADS)

Water Use Efficiency (WUE) defines the relationship between land-atmosphere water and carbon fluxes. With this simple mechanism, hydrological and carbon-cycle responses of vegetation to climate change can be more easily quantified. WUE increases with atmospheric carbon dioxide (CO2) concentration but also depends on changes in humidity and temperature. A positive CO2 fertilization effect can be locally constrained by humidity and temperature. By combining observed trends of these three climate variables over the 20th century regional trends in WUE can be calculated. The ecosystem WUEe is defined as a ratio of gross primary production and transpiration fluxes. On the leaf scale this is equal to the atmospheric WUEa, which is a function of the ambient and internal CO2 concentration, the saturated specific humidity (a function of temperature) and relative humidity. Using Fluxnet and CRU TS3.2 observations, and the JULES and HadCM3 models we explore the temporal and spatial variation of WUEe and WUEa, and how they respond to climate change. Leaf level definitions are valid at site level, where WUEe and WUEa simulated with JULES are equal and linearly increasing with atmospheric CO2 concentration for a range of sites. For drier sites lower values of both were simulated. The simulated values are within the same range as values derived from eddy covariance observations. Having shown the near equivalence between WUEe and WUEa for specific sites, we can use the formula for WUEa to estimate the change in global plant WUE over the 20th century, using observed climatological data and CO2 concentrations. The global average WUE increased by 25% since 1900, closely following the atmospheric CO2 concentration. But we identify large regional variation, with regions where WUE increased, but some significant regions where WUE has actually decreased during the last century. Here the CO2 fertilization effect is overtaken by an increasing offsetting temperature and related saturated specific humidity effect. In the future these drier regions will not only have to cope with a decreasing water availability but also with the related decrease in WUE, amplifying a decreasing plant carbon uptake, and if occurring in areas of agriculture, then reducing crop yield.

Groenendijk, M.; Cox, P.; Lambert, F. H.; Booth, B.; Huntingford, C.

2013-12-01

208

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

209

Near-surface air temperature retrieval from satellite images and influence by wetlands in urban region  

NASA Astrophysics Data System (ADS)

Near-surface air temperature (NSAT) directly reflects the thermal conditions above the ground and has been considered as a relevant indicator of resident health in urban regions. The rapid retrieval of NSAT data is necessary to assess urban environments. In this paper, a method of NSAT retrieval is developed that employs Landsat Thematic Mapper images using an Energy Balance Bowen Ratio model. This model is established based on the energy balance over land and the Bowen ratio. The degree of retrieval error obtained when using this model is determined on the basis of a comparison with the observed values obtained from weather stations; the mean error is approximately 2.21 °C. Moreover, the spatial relationship between NSAT and urban wetlands is analyzed using Geographical Information System technology. The results show that wetlands have an obvious influence on atmospheric temperature and that this influence decreases as the distance from the wetland increases. When that distance is less than 300 m, its influence on the NSAT is significant.

Hou, Peng; Chen, Yunhao; Qiao, Wang; Cao, Guangzhen; Jiang, Weiguo; Li, Jing

2013-01-01

210

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

NASA Astrophysics Data System (ADS)

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 few studies have addressed the importance of studying the air-sea coupling at the BMC region. Lateral temperature gradients at the study region were as high as 0.3°C km-1 at the surface and subsurface. In the oceanic boundary layer, the vertical temperature gradient reached 0.08°C m-1 at 500 m depth. Our results show that the marine atmospheric boundary layer (MABL) at the BMC region is modulated by the strong sea surface temperature (SST) gradients present at the sea surface. The mean MABL structure is thicker over the warmside of the BMC where Brazil Current (BC) waters predominate. The opposite occurs over the coldside of the confluence where waters from the Malvinas (Falkland) Current (MC) are found. The warmside of the confluence presented systematically higher MABL top height compared to the coldside. This type of modulation at the synoptic scale is consistent to what happens in other frontal regions of the world ocean, where the MABL adjusts itself to modifications along the SST gradients. Over warm waters at the BMC region, the MABL static instability and turbulence were increased while winds at the lower portion of the MABL were strong. Over the coldside of the BC/MC front an opposite behavior is found: the MABL is thinner and more stable. Our results suggest that the sea-level pressure (SLP) was also modulated locally, together with static stability vertical mixing mechanism, by the surface condition during all cruises. SST gradients at the BMC region modulate the synoptic atmospheric pressure gradient. Postfrontal and prefrontal conditions produce opposite thermal advections in the MABL that lead to different pressure intensification patterns across the confluence.

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

2009-10-01

211

Land-atmosphere coupling over north America in Canadian regional climate model (CRCM5)  

NASA Astrophysics Data System (ADS)

Land-atmosphere coupling over North America as simulated by the fifth generation of the Canadian Regional Climate model (CRCM5) is studied in this paper. To this effect, two simulations - with and without land-atmosphere coupling - have been performed with CRCM5. In the coupled simulation, the soil moisture interacts freely with the atmosphere at each time step, while in the uncoupled simulation, soil moisture is replaced with its climatological value, thus suppressing the soil moisture-atmosphere interactions. CRCM5 is able to reproduce the amount and the spatial distribution of mean and standard deviation of the seasonal mean precipitation and daily maximum temperature over North America, suggesting the utility of the model for sensitivity study. Analysis of simulations shows strong soil moisture-temperature coupling over Great Plains, consistent with GLACE results, whereas the soil moisture-precipitation coupling strength is found to be generally weaker than the soil moisture-temperature coupling, and is also slightly shifted westwards. The experiments also indicate that the soil moisture-temperature coupling increases the variability, contributing more than three-fourth of the total inter annual variability of the seasonal mean daily maximum temperature. Soil moisture - temperature coupling is also found to have significant effects on temperature extremes such as the percentage of hot days, the frequency and maximum duration of heat waves in summer.

Diro, G.; Sushama, L.; Martynov, A.; Jeong, D. I.

2013-12-01

212

Regional and seasonal variations in the flux of oceanic carbon monoxide to the atmosphere  

NASA Astrophysics Data System (ADS)

Carbon monoxide (CO) is produced photochemically in the surface ocean and emitted to the atmosphere. To assess the magnitude of this ocean-atmosphere flux, seawater and atmospheric CO mole fractions were measured on six cruises throughout the Pacific Ocean from 1987 to 1994. The results showed consistent regional and seasonal variations in surface seawater CO concentrations with daily averaged concentrations ranging from 0.1 to 4.7 nM. Based on the concentration fields, the data were divided into four seasons and 10 latitude zones from 75°S to 75°N. Using monthly Comprehensive Ocean-Atmosphere Data Set wind and surface seawater temperature data and the Wanninkhof [1992] wind speed/transfer velocity relationship, the calculated zonal average fluxes ranged from 0.25 to 13 ?mol/m2/d. The combined seasonal and zonal fluxes result in a total global flux of 0.46 Tmol CO/y with 2/3 of this flux in the southern hemisphere. The estimated uncertainty in this number is approximately a factor of 2.

Bates, Timothy S.; Kelly, Kimberly C.; Johnson, James E.; Gammon, Richard H.

1995-11-01

213

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

214

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

215

NO Detection by Pulsed Polarization of Lambda Probes-Influence of the Reference Atmosphere  

PubMed Central

The pulsed polarization measurement technique using conventional thimble type lambda probes is suitable for low ppm NOx detection in exhaust gas applications. To evaluate the underlying sensor mechanism, the unknown influence of the reference atmosphere on the NO sensing behavior is investigated in this study. Besides answering questions with respect to the underlying principle, this investigation can resolve the main question of whether a simplified sensor element without reference may be also suitable for NO sensing using the pulsed polarization measurement technique. With an adequate sensor setup, the reference atmosphere of the thimble type lambda probe is changed completely after a certain diffusion time. Thus, the sensor response regarding NO is compared with and without different gas atmospheres on both electrodes. It is shown that there is still a very good NO sensitivity even without reference air, although the NO response is reduced due to non-existing overlying mixed potential type voltage, which is otherwise caused by different atmospheres on both electrodes. Considering these results, we see an opportunity to simplify the standard NOx sensor design by omitting the reference electrode.

Fischer, Sabine; Schonauer-Kamin, Daniela; Pohle, Roland; Fleischer, Maximilian; Moos, Ralf

2013-01-01

216

THE INFLUENCE OF ATMOSPHERIC SCATTERING AND ABSORPTION ON OHMIC DISSIPATION IN HOT JUPITERS  

SciTech Connect

Using semi-analytical, one-dimensional models, we elucidate the influence of scattering and absorption on the degree of Ohmic dissipation in hot Jovian atmospheres. With the assumption of Saha equilibrium, the variation in temperature is the main driver of the variations in the electrical conductivity, induced current, and Ohmic power dissipated. Atmospheres possessing temperature inversions tend to dissipate most of the Ohmic power superficially, at high altitudes, whereas those without temperature inversions are capable of greater dissipation deeper down. Scattering in the optical range of wavelengths tends to cool the lower atmosphere, thus reducing the degree of dissipation at depth. Purely absorbing cloud decks (in the infrared), of a finite extent in height, allow for localized reductions in dissipation and may reverse a temperature inversion if they are dense and thick enough, thus greatly enhancing the dissipation at depth. If Ohmic dissipation is the mechanism for inflating hot Jupiters, then variations in the atmospheric opacity (which may be interpreted as arising from variations in metallicity and cloud/haze properties) and magnetic field strength naturally produce a scatter in the measured radii at a given strength of irradiation. Future work will determine if these effects are dominant over evolutionary effects, which also contribute a scatter to the measured radii.

Heng, Kevin [ETH Zuerich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland)

2012-03-20

217

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

218

The importance of atmospheric ammonia in the Rocky Mountain region of the western U.S  

NASA Astrophysics Data System (ADS)

Although it is not a regulated pollutant, ammonia is an important contributor to several air quality problems. Included among these are the formation of fine particles that contribute to visibility degradation and adverse health effects as well as contributions to excess nitrogen deposition to sensitive ecosystems. Because it is not regulated, gaseous ammonia and fine particle ammonium have traditionally not been routinely measured in many air quality monitoring networks. Measurements of ammonium wet deposition by the National Atmospheric Deposition Program, however, clearly indicate an increasing contribution to reactive nitrogen deposition. Here we report observations of several recent research efforts to characterize atmospheric ammonia and ammonium in the Rocky Mountain region of the western United States. These include measurements made as part of the Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS) deposition study (2006-10), the Grand Teton Reactive Nitrogen Deposition Study (GrandTReNDS) (2011), and through pilot-scale operation of an NHx (NHx = gaseous NH3 plus fine particle NH4+) monitoring effort at 9 sites within the Interagency Monitoring of PROtected Visual Environments (IMPROVE) program (2011-12). Measurements during RoMANS clearly reveal the importance of agricultural source emission contributions to both dry and wet reactive nitrogen deposition in Rocky Mountain National Park. The importance of ammonia and ammonium deposition is even greater at Grand Teton National Park, which often sits downwind of extensive agricultural operations in central Idaho and northern Utah. Over a year of measurements in the IMPROVE NHx pilot network reveals strong spatial gradients in reduced nitrogen concentrations across the Rocky Mountain region, with higher concentrations in regions closer to agricultural sources and at locations and times strongly impacted by wildfires. These observations, along with additional observations from other related studies in the region, will be discussed.

Collett, J. L.; Benedict, K. B.; Chen, D.; Day, D.; Prenni, A. J.; Li, Y.; Kreidenweis, S. M.; Schichtel, B. A.; McDade, C.; Malm, W. C.

2013-12-01

219

Premixed Atmosphere and Convection Influences on Flame Inhibition and Combustion (PACIFIC)  

NASA Technical Reports Server (NTRS)

Under NASA-Lewis Grant NAG3-1611, starting date 6/1/94, a three-year experimental and theoretical study of the effects of ambient atmosphere on the properties of flame spread over thin and thick solid fuel beds has been initiated. In particular the effect of the type of inert gas, which affects the Lewis numbers of fuel and oxidant, and the effect of the addition of sub-flammability-limit concentrations of gaseous fuels to the oxidizing atmosphere will be studied. The effect of convection will be studied through one-g and mu g experiments with and without a forced flow. Moreover, the influence of thermal radiation, whose effect is known to be markedly different depending on the convection level, will be addressed.

Ronney, Paul D.

1995-01-01

220

Earth-atmosphere system and surface reflectivities in arid regions from LANDSAT multispectral scanner measurements  

NASA Technical Reports Server (NTRS)

Programs for computing atmospheric transmission and scattering solar radiation were used to compute the ratios of the Earth-atmosphere system (space) directional reflectivities in the vertical direction to the surface reflectivity, for the four bands of the LANDSAT multispectral scanner (MSS). These ratios are presented as graphs for two water vapor levels, as a function of the surface reflectivity, for various sun elevation angles. Space directional reflectivities in the vertical direction are reported for selected arid regions in Asia, Africa and Central America from the spectral radiance levels measured by the LANDSAT MSS. From these space reflectivities, surface vertical reflectivities were computed applying the pertinent graphs. These surface reflectivities were used to estimate the surface albedo for the entire solar spectrum. The estimated albedos are in the range 0.34-0.52, higher than the values reported by most previous researchers from space measurements, but are consistent with laboratory measurements.

Otterman, J.; Fraser, R. S.

1976-01-01

221

Influence of atmospheric turbulence on the energy focusability of Gaussian beams with spherical aberration  

NASA Astrophysics Data System (ADS)

By using the four-dimensional (4D) computer code of the time-dependent propagation of laser beams through atmospheric turbulence, the influence of atmospheric turbulence on the energy focusability of Gaussian beams with spherical aberration is studied in detail, where the mean-squared beam width, the power in the bucket (PIB), the ? parameter and the energy Strehl ratio are taken as the characteristic parameters. It is shown that turbulence results in beam spreading, and the effect of spherical aberration on the beam spreading decreases due to turbulence. Gaussian beams with negative spherical aberration are more affected by turbulence than those with positive spherical aberration. For the negative spherical aberration case, the focus position moves to the source plane due to turbulence. It is mentioned that the influence of turbulence on the energy focusability defined by a certain energy (i.e. PIB = 63%) is very heavy when the negative spherical aberration is very heavy. On the other hand, the influence of turbulence on the energy focusability defined by the energy within a given bucket radius (i.e. mean-squared beam width) is heaviest when a certain negative spherical aberration coefficient is adopted.

Deng, Jinping; Ji, Xiaoling

2014-05-01

222

Simulation of iron/dust in the atmosphere by a regional model  

NASA Astrophysics Data System (ADS)

During sporadic desert dust storms mineral aerosol is raised from the ground, diffused to higher elevations and transported away from sources. Through sedimentation, dry deposition and wet scavenging, dust deposited to the ocean brings at the same time iron and phosphorus embedded in dust particles. Iron exposed to the atmospheric (photo-) chemical processing converts from almost non-soluble to relative high soluble state. Only as soluble, iron can be consumed as a nutrient by microorganisms in a primary marine bio-production phase. In ocean regions distant from coastlines where upwelling and river inputs are missing, iron (and phosphorus) is the major potential marine nutrient. Current knowledge on the atmospheric iron cycle is rather unsatisfactory. First, distribution of iron minerals in desert soils is not yet well known. Second, there are uncertainties on how the iron minerals are chemically processed in the atmosphere since there is no agreement on the roles of solar radiation, clouds and pollution and their relative importance. Finally, current iron models are of global domain and cannot sufficiently resolve the dust (and associated iron) life cycle which is highly variable in time and space. Therefore, more accurate information on deposition of iron to the ocean and its soluble state are generally missing today. This paper presents developments of an atmospheric iron model performed by adding the iron component to the regional dust model DREAM. To specify the iron sources in deserts, relatively high resolution data on soil types (4 km) and land cover (1 km) are used in combination with recent field mineralogy studies. Iron minerals are assumed to be embedded in dust and therefore driven by dust; a corresponding governing set of equations specific for the dynamics of embedded iron, as well as pseudo-first order chemical reaction converting from non-soluble to soluble is then developed. Finally, experiments were performed using the model horizontal resolution of about 40 km to simulate an extensive marine bacterial bloom associated with a major dust deposition in the Canary Islands region. Results show that the model is able to reproduce the observed increase of iron solubility along the downwind distance. The model shows that the iron solubility behaves in the same way with respect to the vertical distribution as well - i.e. increases with height. Such findings are consistent with recent studies that showing that the link between atmospheric iron processing and solubility is primarily physical rather than chemical in nature.

Nickovic, S.; Perez, C.

2008-12-01

223

Regional and Local Carbon Flux Information from a Continuous Atmospheric CO2 Network in the Rocky Mountains  

Microsoft Academic Search

We have established a Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON) to improve our understanding of regional carbon fluxes and to fill key gaps in the North American Carbon Program (NACP). There are strong scientific and societal motivations for determining CO2 exchanges on regional scales. Mountain forests in particular represent a significant potential net CO2 sink

S. Heck; B. Stephens; A. Watt; D. Schimel; S. Aulenbach

2006-01-01

224

Advanced Modeling Techniques to Study Anthropogenic Influences on Atmospheric Chemical Budgets  

NASA Technical Reports Server (NTRS)

This research work is a collaborative effort between research groups at MCNC and the University of North Carolina at Chapel Hill. The overall objective of this research is to improve the level of understanding of the processes that determine the budgets of chemically and radiatively active compounds in the atmosphere through development and application of advanced methods for calculating the chemical change in atmospheric models. The research performed during the second year of this project focused on four major aspects: (1) The continued development and refinement of multiscale modeling techniques to address the issue of the disparate scales of the physico-chemical processes that govern the fate of atmospheric pollutants; (2) Development and application of analysis methods utilizing process and mass balance techniques to increase the interpretive powers of atmospheric models and to aid in complementary analysis of model predictions and observations; (3) Development of meteorological and emission inputs for initial application of the chemistry/transport model over the north Atlantic region; and, (4) The continued development and implementation of a totally new adaptive chemistry representation that changes the details of what is represented as the underlying conditions change.

Mathur, Rohit

1997-01-01

225

Influence of Surface Seawater and Atmospheric Conditions on the Ccn Activity of Ocean-Derived Aerosol  

NASA Astrophysics Data System (ADS)

Ocean-derived aerosols are produced from direct injection into the atmosphere (primary production) and gas-to-particle conversion in the atmosphere (secondary production). These different production mechanisms result in a broad range of particle sizes that has implications for the impact of ocean-derived aerosol on climate. The chemical composition of ocean-derived aerosols is a result of a complex mixture of inorganic sea salt and organic matter including polysaccharides, proteins, amino acids, microorganisms and their fragments, and secondary oxidation products. Both production mechanisms and biological processes in the surface ocean impact the ability of ocean-derived aerosol to act as cloud condensation nuclei (CCN). In addition, CCN activity can be impacted by atmospheric processing that modifies particle size and composition after the aerosol is emitted from the ocean. To understand relationships between production mechanism, surface ocean biology, and atmospheric processing, measurements were made of surface ocean chlorophyll and dissolved organic matter; nascent sea spray aerosol freshly emitted from the ocean surface; and ambient marine aerosol. These measurements were made along the coast of California and in the North Atlantic between the northeast US and Bermuda. These regions include both eutrophic and oligotraphic waters and, thus, provide for observations over a wide range of ocean conditions.

Quinn, P.; Bates, T. S.; Russell, L. M.; Frossard, A. A.; Keene, W. C.; Kieber, D. J.; Hakala, J. P.

2012-12-01

226

Statistical analysis of the MODIS atmosphere products for the Tomsk region  

NASA Astrophysics Data System (ADS)

The paper presents the results of using the MODIS Atmosphere Products satellite information to study the atmospheric characteristics (the aerosol and water vapor) in the Tomsk Region (56-61°N, 75-90°E) in 2001-2004. The satellite data were received from the NASA Goddard Distributed Active Archive Center (DAAC) through the INTERNET.To use satellite data for a solution of scientific and applied problems, it is very important to know their accuracy. Despite the results of validation of the MODIS data have already been available in the literature, we decided to carry out additional investigations for the Tomsk Region. The paper presents the results of validation of the aerosol optical thickness (AOT) and total column precipitable water (TCPW), which are in good agreement with the test data. The statistical analysis revealed some interesting facts. Thus, for example, analyzing the data on the spatial distribution of the average seasonal values of AOT or TCPW for 2001-2003 in the Tomsk Region, we established that instead of the expected spatial homogeneity of these distributions, they have similar spatial structures.

Afonin, Sergey V.; Belov, Vladimir V.; Engel, Marina V.

2005-10-01

227

The influence of land-atmosphere interactions on variability of the North American Monsoon  

NASA Technical Reports Server (NTRS)

Our project focused on the influence of land-atmosphere interactions on variability of North American Monsoon System (NAMS) precipitation is summarized in seven published manuscripts (listed below). Three of these manuscripts (Matsui et al. 2003; Matsui et al. 2005; Small and Kurc 2003) were completed solely with support from this NASA project. The remaining four were completed with additional support from NOAA. Our primary results are summarized: 1) Test of Rocky Mountains snowcover-NAMS rainfall hypothesis. Testing radiation and convective precipitation parameterization in MM5. Analysis of soil moisture-radiation feedbacks in semiarid environments from field observations and modeling.

Small, Eric; Lakshmi, Venkat

2005-01-01

228

The Influence of Arctic Amplification on Mid-Latitude Atmospheric Circulation and Extreme Weather Events  

NASA Astrophysics Data System (ADS)

We expand on our recent work that provided evidence for a mechanism linking Arctic Amplification to changes in mid-latitude circulation patterns that favor extreme weather events (Francis and Vavrus, 2012). Here we analyze greenhouse-forced projections from the Community Climate System Model (CCSM4) to assess the future evolution of Arctic change on Northern Hemisphere weather patterns. We hypothesize that remote impacts of changes in the energy budget of the Arctic surface will influence the atmospheric circulation in middle latitudes through changes in large-scale, deep-tropospheric, meridional thickness gradients that induce generally weaker zonal flow and higher amplitude large-scale waves aloft. Because such features are slow-moving and associated with persistent weather conditions, they favor more frequent and severe extreme weather episodes resulting from prolonged cold-air outbreaks, heat waves, droughts, and heavy precipitation. The primary physical mechanism driving this change is an enhanced and seasonally varying Arctic heating: in fall/winter it is ocean-based due to substantial sea ice loss, while in warmer months it is land-based due to earlier snow melt and reduced soil moisture. Simulations by CCSM4 support our hypothesized linkages, as the projected climate changes depict a seasonally varying circulation response hinging on the enhanced warming and resulting geopotential height increases aloft in the Arctic. During boreal autumn and winter, sea ice loss leads to upper-air height increases mainly over the Arctic Ocean with compensating decreases over mid-latitudes, which reduces the poleward gradient. During spring and summer, however, the band of maximum ridging shifts southward over high-latitude land. This behavior resembles the upper-air circulation changes induced by prescribed reductions in sea ice and snow cover in previous versions of the model. The associated seasonal changes in mid-tropospheric zonal winds exhibit a nearly symmetrical reduction in mid-latitude westerlies in all seasons, suggesting a combination of weaker winds and perhaps a poleward shift in the flow. Weaker zonal winds slow the eastward progression of planetary waves, favoring more persistent weather conditions, thermal isolation of mid-latitude continents, and thus greater seasonality superimposed on an overall warming world. During summer, changes in upper-air geopotential heights are expected to act synergistically with projected reductions in soil moisture in middle latitudes to foster more frequent and intense heat waves and droughts. During winter a slowing and meridional elongation of planetary waves caused by Arctic Amplification favors cold-air outbreaks over the continents, thereby tempering the greenhouse-forced decline in extreme cold events and favoring regionally alternating snowy patterns and abnormal winter warmth that vary year to year.

Vavrus, S. J.; Francis, J. A.

2012-12-01

229

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

230

Revisiting regional flood frequency analysis in Slovakia: the region-of-influence method vs. traditional regional approaches  

NASA Astrophysics Data System (ADS)

During the last 10-15 years, the Slovak hydrologists and water resources managers have been devoting considerable efforts to develop statistical tools for modelling probabilities of flood occurrence in a regional context. Initially, these models followed concepts to regional flood frequency analysis that were based on fixed regions, later the Hosking and Wallis's (HW; 1997) theory was adopted and modified. Nevertheless, it turned out to be that delineating homogeneous regions using these approaches is not a straightforward task, mostly due to the complex orography of the country. In this poster we aim at revisiting flood frequency analyses so far accomplished for Slovakia by adopting one of the pooling approaches, i.e. the region-of-influence (ROI) approach (Burn, 1990). In the ROI approach, unique pooling groups of similar sites are defined for each site under study. The similarity of sites is defined through Euclidean distance in the space of site attributes that had also proved applicability in former cluster analyses: catchment area, afforested area, hydrogeological catchment index and the mean annual precipitation. The homogeneity of the proposed pooling groups is evaluated by the built-in homogeneity test by Lu and Stedinger (1992). Two alternatives of the ROI approach are examined: in the first one the target size of the pooling groups is adjusted to the target return period T of the estimated flood quantiles, while in the other one, the target size is fixed, regardless of the target T. The statistical models of the ROI approach are inter-compared by the conventional regionalization approach based on the HW methodology where the parameters of flood frequency distributions were derived by means of L-moment statistics and a regional formula for the estimation of the index flood was derived by multiple regression methods using physiographic and climatic catchment characteristics. The inter-comparison of different frequency models is evaluated by means of the root mean square error of data from Monte Carlo simulations. The analysis is based on the annual peak discharges from 168 small and mid-sized catchments from Slovakia. The study is supported by the Grant Agency of AS CR under project B300420801; the Slovak Research and Development Agency under the contract No. APVV-0443-07 and the Slovak VEGA Grant Agency under the project No. 1/0103/10. Burn, D.H., 1990: Evaluation of regional flood frequency analysis with a region of influence approach. Water Resources Research, 26(10), 2257-2265. Hosking, J.R.M., Wallis, J.R., 1997: Regional frequency analysis: an approach based on L-moments. Cambridge University Press, Cambridge. Lu, L.-H., Stedinger, J.R., 1992: Sampling variance of normalized GEV/PWM quantile estimators and a regional homogeneity test. Journal of Hydrology, 138(1-2), 223-245.

Gaál, Ladislav; Kohnová, Silvia; Szolgay, Ján.

2010-05-01

231

Influence of monsoons on atmospheric CO2 spatial variability and ground-based monitoring over India.  

PubMed

This study examines the role of Asian monsoons on transport and spatial variability of atmospheric CO2 over the Indian subcontinent, using transport modeling tools and available surface observations from two atmospheric CO2 monitoring sites Sinhagad (SNG) and Cape Rama (CRI) in the western part of peninsular India. The regional source contributions to these sites arise from the horizontal flow in conduits within the planetary boundary layer. Greater CO2 variability, greater than 15ppm, is observed during winter, while it is reduced nearly by half during summer. The SNG air sampling site is more susceptible to narrow regional terrestrial fluxes transported from the Indo-Gangetic Plains in January, and to wider upwind marine source regions from the Arabian Sea in July. The Western Ghats mountains appear to play a role in the seasonal variability at SNG by trapping polluted air masses associated with weak monsoonal winds. A Lagrangian back-trajectory analysis further suggests that the horizontal extent of regional sensitivity increases from north to south over the Indian subcontinent in January (Boreal winter). PMID:24880546

Tiwari, Yogesh K; Vellore, Ramesh K; Ravi Kumar, K; van der Schoot, Marcel; Cho, Chun-Ho

2014-08-15

232

Medium term modelling of coupled hydrodynamics, turbulence and sediment pathways in a region of freshwater influence.  

NASA Astrophysics Data System (ADS)

Liverpool Bay, in the northwest of the UK, is a shallow, hypertidal region of freshwater influence. In this region, baroclinic processes significantly affect the residual circulation, which in turn influences the long term transport of sediment. A nested modelling system is implemented to simulate the coupled hydro and sediment dynamics in the bay. We use the Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS), which is based on a three-dimensional baroclinic numerical model formulated in spherical polar terrain-following coordinates. The hydrodynamic model solves the three-dimensional, hydrostatic, Boussinesq equations of motion separated into depth-varying and depth-independent parts to allow time splitting between barotropic and baroclinic components. This model is coupled to the General Ocean Turbulence Model (GOTM), to the WAve Model (WAM), and includes state-of-the-art Eulerian and Lagrangian sediment transport models. We implement POLCOMS to Liverpool Bay at a horizontal resolution of approximately 180 m. The bathymetry consists of digitized hydrographic charts combined with LIDAR and multibeam data. Three-dimensional baroclinic effects, river inputs, surface heating and offshore density structure are all considered. Liverpool Bay is subjected to a spring tidal range in excess of 10 m and thus intertidal areas are significant. Wetting and drying algorithms are therefore also implemented. A nesting approach is employed to prescribe offshore boundary conditions for elevations, currents, temperature and salinity. Boundary values are obtained from numerical simulations for the entire Irish and are then used to force the three-dimensional hydrodynamics in the Liverpool Bay domain. Atmospheric forcing consists of hourly wind velocity and atmospheric pressure, and three-hourly cloud cover, humidity and air temperature. We focus here on numerical simulations for a full year, 2008, which is considered to be a typical year for atmospheric, riverine and coastal conditions. We will assess the model's capabilities for currents, water column vertical structure and sediment dynamics via comparisons of numerical results with coastal observations. The observational data were collected at several locations in Liverpool Bay from two moorings, which were part of the National Oceanographic Centre's Coastal Observatory, and from month-long deployments of two bottom-instrumented tripods near the mouth of the Dee Estuary. In turn, the validated numerical results will be interrogated for spatial information on sediment dynamics and pathways in Liverpool Bay, which are difficult to obtain solely from few point measurements.

Amoudry, Laurent; Brown, Jenny; Souza, Alex; Norman, Danielle; Olsen, Karine

2014-05-01

233

Mesoscale circulations and atmospheric CO2 variations in the Tapajós Region, Pará, Brazil  

NASA Astrophysics Data System (ADS)

We have investigated mesoscale circulations and atmospheric CO2 variations over a heterogeneous landscape of forests, pastures, and large rivers during the Santarém Mesoscale Campaign (SMC) of August 2001. The atmospheric CO2 concentration variations were simulated using the Colorado State University Regional Atmospheric Modeling System with four nested grids that included a 1-km finest grid centered on the Tapajós National Forest. Surface CO2 fluxes were prescribed using idealized diurnal cycles over forest and pasture that derived from flux tower observations; while surface water CO2 efflux was prescribed using a value suggested by in situ measurements in the Amazon region. Our simulation ran from 1 August through 15 August 2001, which was concurrent with the SMC. Evaluation against flux tower observations and Belterra meteorological tower measurements showed that the model captured the observed 2-m temperatures and 10-m winds reasonably well. At 57 m the model reproduced the daytime CO2 concentration better than the nighttime concentration but missed the observed early morning CO2 maxima, in part because of the difficulties of simulating stable nocturnal boundary conditions and subgrid-scale intracanopy processes. The results also suggested that the topography, the differences in roughness length between water and land, the "T" shape juxtaposition of Amazon and Tapajós Rivers, and the resulting horizontal and vertical wind shears all facilitated the generation of local mesoscale circulations. Possible mechanisms producing a low-level convergence (LLC) line near the east bank of the Tapajós River were explored. Under strong trade wind conditions, mechanical forcing is more important than thermal forcing in LLC formation. Persistent clouds near the east side of the Tapajós River may have a significant impact on observed ecosystem carbon flux and should be taken into account if tower fluxes are to be generalized to a larger region.

Lu, Lixin; Denning, A. Scott; da Silva-Dias, Maria Assuncao; da Silva-Dias, Pedro; Longo, Marcos; Freitas, Saulo R.; Saatchi, Sassan

2005-11-01

234

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

235

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

236

Coupling of a regional atmospheric model (RegCM3) and a regional oceanic model (FVCOM) over the maritime continent  

NASA Astrophysics Data System (ADS)

Climatological high resolution coupled climate model simulations for the maritime continent have been carried out using the regional climate model (RegCM) version 3 and the finite volume coastal ocean model (FVCOM) specifically designed to resolve regions characterized by complex geometry and bathymetry. The RegCM3 boundary forcing is provided by the EMCWF-ERA40 re-analysis. FVCOM is embedded in the Global MITgcm which provides boundary forcing. The domain of the coupled regional model covers the entire South China Sea with its through-flow, the entire Indonesian archipelago with the Indonesian through-flow (ITF) and includes a large region in the western Pacific and eastern Indian oceans. The coupled model is able to provide stable and realistic climatological simulations for a specific decade of atmospheric-oceanic variables without flux correction. The major focus of this work is on oceanic properties. First, the coupled simulation is assessed against ocean-only simulations carried out under two different sets of air-sea heat fluxes. The first set, provided by the MITgcm, is proved to be grossly deficient as the heat fluxes are evaluated by a two-dimensional, zonally averaged atmosphere and the simulated SST have anomalous cold biases. Hence the MITgcm fluxes are discarded. The second set, the NCEP re-analysis heat fluxes, produces a climatological evolution of the SST with an average cold bias of ~-0.8 °C. The coupling eliminates the cold bias and the coupled SST evolution is in excellent agreement with the analogous evolution in the SODA re-analysis data. The detailed comparison of oceanic circulation properties with the International Nusantara Stratification and Transport observations shows that the coupled simulation produces the best estimate of the total ITF transport through the Makassar strait while the transports of three ocean-only simulations are all underestimated. The annual cycle of the transport is also very well reproduced. The coupling also considerably improves the vertical thermal structure of the Makassar cross section in the upper layer affected by the heat fluxes. On the other hand, the coupling is relatively ineffective in improving the precipitation fields even though the coupled simulation captures reasonably well the precipitation annual cycle at three land stations in different latitudes.

Wei, Jun; Malanotte-Rizzoli, Paola; Eltahir, Elfatih A. B.; Xue, Pengfei; Xu, Danya

2013-11-01

237

Influence of the atmospheric surface layer on the penetration of the electric field from the earth's surface into the ionosphere  

NASA Astrophysics Data System (ADS)

In the used model, the quasistationary electric field in the atmosphere of the Earth is obtained by solving the conductivity equation. The penetration characteristics of the electric field from the Earth's surface into the ionosphere depend on both atmospheric and ionosphere conductivity. The ionosphere is taken into account by setting a special condition on the upper boundary of the atmosphere. The influence of the atmospheric surface layer with a reduced conductivity on the penetration of the electric field from the surface of the Earth into the ionosphere is analyzed.

Pomozov, E. V.

2014-01-01

238

Large-scale atmospheric influence on the physical and biogeochemical properties of the Benguela upwelling system  

NASA Astrophysics Data System (ADS)

The Namibian upwelling region is one of the four Eastern Boundary Upwelling Ecosystems and among the most productive areas in the World Ocean. Here, upwelling indices have been defined in three ways. First, by performing EOF analyses of Sea Surface Temperature (SST) observations HadlSST1 and high resolution ocean model simulations (MPI-OM (STORM) and MOM4), driven by meteorological reanalysis. Second, water vertical velocity of STORM and MOM4. Third, the area between the 13°C isotherm and the coastline was used to indicate the intensity of the upwelling. Correlations with observed atmospheric variables (NCEP reanalysis) over the whole southern Atlantic show which conditions favour upwelling: higher than normal South Atlantic anticyclone, strong and southerly wind/wind stress and pressure and air temperature contrast between ocean and land. Separating the coastal area off southern Africa at Lüderitz (28°S) depicts the differences between the northern and southern Benguela upwelling region. Northern Benguela is characterised by a negative trend in upwelling over the last 60 year, Southern Benguela by a positive one. Furthermore, Northern Benguela upwelling seems to be influenced strongly by the conditions described above while the wind field correlated with the upwelling south of 28°S do not show stronger southerly winds. Additionally, the southern upwelling index of MOM4 is not reflected properly in the corresponding SST field. A reason for this could be an overlaying signal, possibly the advection of warm air from the Indian or the central Atlantic Ocean. The sea level pressure (SLP) gradient between land and ocean of NCEP reanalysis provide a opposite trend to the one postulated by Bakun (¹). We did not find an indication for a stronger pressure contrast between land and ocean. Correlations with indices of El Niño Southern Oscillation (ENSO), the Antarctic Oscillation (AAO) and an index of the tropical Atlantic SST variability. None of these correlations is strong enough to claim a detection of a main driver of upwelling. However, a significant relationship between the summer upwelling and ENSO can be found. The SST-based index is also significantly correlated with the tropical Atlantic. In contrast, the upwelling indices of the vertical velocities show significant correlations with the AAO. Spectral analysis of the vertical velocity index (STORM) shows especially in summer a clear peak at timescales of 5 years. The longer series of HadlSST1 additionally displays decadal variability. The oxygen minimum zone in the Benguela region has an important impact on the ecosystem and local fisheries. The content of South Atlantic Central Water (SACW) on the shelf drives the intensity and extension of the oxygen minimum zone. Therefore, the water masses with the STORM and MOM4 simulations have been analysed. The STORM simulation does not contain biogeochemistry and the MOM4 simulation is too short. Thus, the analysis of the water masses, their origin and pathways through the South Atlantic will be analysed with a longer MOM simulation and the MPI run of the Climate Model Intercomparison project 5. (¹) Bakun, A. (1990). Global climate change and intensification of coastal ocean upwelling. Science, 247:198-201.

Tim, Nele; Zorita, Eduardo; Hünicke, Birgit

2014-05-01

239

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

240

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

241

The Influence of the Several Very Large Solar Proton Events in Years 2000-2003 on the Neutral Middle Atmosphere  

NASA Technical Reports Server (NTRS)

Solar proton events (SPEs) are known to have caused changes in constituents in the Earth's 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 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, Charles H.; Sinnhuber, Miriam; Anderson, John; McPeters, Richard D.; FLeming, Eric L.; Russell, James M.

2004-01-01

242

The Influence of North American Carbon Flux Spatial Distribution on the Temporal Variability of Atmospheric Carbon Dioxide  

Microsoft Academic Search

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

D. N. Huntzinger; S. Gourdji; A. M. Michalak

2009-01-01

243

Surface pretreatment of plastics with an atmospheric pressure plasma jet - Influence of generator power and kinematics  

NASA Astrophysics Data System (ADS)

The industrial use of atmospheric pressure plasmas in the plastics processing industry has increased significantly in recent years. Users of this treatment process have the possibility to influence the target values (e.g. bond strength or surface energy) with the help of kinematic and electrical parameters. Until now, systematic procedures have been used with which the parameters can be adapted to the process or product requirements but only by very time-consuming methods. For this reason, the relationship between influencing values and target values will be examined based on the example of a pretreatment in the bonding process with the help of statistical experimental design. Because of the large number of parameters involved, the analysis is restricted to the kinematic and electrical parameters. In the experimental tests, the following factors are taken as parameters: gap between nozzle and substrate, treatment velocity (kinematic data), voltage and duty cycle (electrical data). The statistical evaluation shows significant relationships between the parameters and surface energy in the case of polypropylene. An increase in the voltage and duty cycle increases the polar proportion of the surface energy, while a larger gap and higher velocity leads to lower energy levels. The bond strength of the overlapping bond is also significantly influenced by the voltage, velocity and gap. The direction of their effects is identical with those of the surface energy. In addition to the kinematic influences of the motion of an atmospheric pressure plasma jet, it is therefore especially important that the parameters for the plasma production are taken into account when designing the pretreatment processes.

Moritzer, E.; Leister, C.

2014-05-01

244

A new approach to the convective parameterization of the regional atmospheric model BRAMS  

NASA Astrophysics Data System (ADS)

The summer characteristics of January 2010 was performed using the atmospheric model Brazilian developments on the Regional Atmospheric Modeling System (BRAMS). The convective parameterization scheme of Grell and Dévényi was used to represent clouds and their interaction with the large scale environment. As a result, the precipitation forecasts can be combined in several ways, generating a numerical representation of precipitation and atmospheric heating and moistening rates. The purpose of this study was to generate a set of weights to compute a best combination of the hypothesis of the convective scheme. It is an inverse problem of parameter estimation and the problem is solved as an optimization problem. To minimize the difference between observed data and forecasted precipitation, the objective function was computed with the quadratic difference between five simulated precipitation fields and observation. The precipitation field estimated by the Tropical Rainfall Measuring Mission satellite was used as observed data. Weights were obtained using the firefly algorithm and the mass fluxes of each closure of the convective scheme were weighted generating a new set of mass fluxes. The results indicated the better skill of the model with the new methodology compared with the old ensemble mean calculation.

Dos Santos, A. F.; Freitas, S. R.; de Campos Velho, H. F.; Luz, E. F.; Gan, M. A.; de Mattos, J. Z.; Grell, G. A.

2013-05-01

245

The influence of volcanic eruptions on the climate of the Asian monsoon region during the Common Era  

NASA Astrophysics Data System (ADS)

Most state-of-the-art general circulation models (GCMs) predict that large volcanic eruptions should result in anomalous dry conditions throughout much of monsoon Asia. Here, we use long and well-validated proxy reconstructions of Asian droughts and pluvials to detect the influence of volcanic radiative forcing on the hydroclimate of the region since the late Medieval period. Superposed epoch analysis reveals significantly wetter conditions over mainland southeast Asia in the year of an eruption, with drier conditions in Pakistan, China, and Tibet. The forced GCM simulations examined here predict the opposite response. Our proxy and model comparison suggests that GCMs may not yet capture all of the important ocean-atmosphere dynamics responsible for the influence of explosive volcanism on the Asia monsoon region.

Anchukaitis, K. J.; Buckley, B.; Cook, E.; Cook, B. I.; D'Arrigo, R.; Ammann, C. M.

2010-12-01

246

Influence of atmospheric pressure plasma treatment on surface properties of PBO fiber  

NASA Astrophysics Data System (ADS)

In order to improve the interfacial adhesion property between PBO fiber and epoxy, the surface modification effects of PBO fiber treated by atmospheric pressure plasma jet (APPJ) in different time, atmosphere and moisture regain (MR) were investigated. The fiber surface morphology, functional groups, surface wettability for control and plasma treated samples were analyzed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. Meanwhile, the fiber interfacial shear strength (IFSS), representing adhesion property in epoxy, was tested using micro-bond pull-out test, and single fiber tensile strength was also tested to evaluate the mechanical performance loss of fibers caused by plasma treatment. The results indicated that the fiber surface was etched during the plasma treatments, the fiber surface wettability and the IFSS between fiber and epoxy had much improvement due to the increasing of surface energy after plasma treatment, the contact angle decreased with the treatment time increasing, and the IFSS was improved by about 130%. The processing atmosphere could influence IFSS significantly, and moisture regains (MR) of fibers also played a positive role on improving IFSS but not so markedly. XPS analysis showed that the oxygen content on fiber surface increased after treatment, and Cdbnd O, Osbnd Cdbnd O groups were introduced on fiber surface. On the other hand, the observed loss of fiber tensile strength caused by plasma treatment was not so remarkable to affect the overall performance of composite materials.

Zhang, Ruiyun; Pan, Xianlin; Jiang, Muwen; Peng, Shujing; Qiu, Yiping

2012-11-01

247

Tracing industrial ammonium in atmospheric deposition in the Athabasca Oil Sands Region, Alberta, Canada  

NASA Astrophysics Data System (ADS)

The expanding industrial development in the Athabasca oil sands region (AOSR) in northeastern Alberta, Canada, has raised concerns about increasing nitrogen (N) emissions from oil sands operations and their potential effects on the surrounding terrestrial and aquatic ecosystems. Stable isotope techniques may help to trace industrial emissions provided that they are isotopically distinct from background isotope ratios of atmospheric N compounds. Ammonium deposition rates (NH4-N) typically exceed nitrate deposition rates (NO3-N) in the AOSR (Proemse et al., 2013), suggesting that emissions of reduced nitrogen compounds play a significant role for the atmospheric nitrogen budget in the AOSR. We collected atmospheric ammonium in open field bulk deposition and throughfall using ion exchange resins over ~6 months time periods from summer 2007 to summer 2011 located at distances between 3 to 113 km to one of the major oil sands developments in the AOSR. Ammonium deposition rates and ?15N-NH4 values were determined using ion chromatography and the ammonium diffusion method (Sebilo et al., 2004) on resin extracts. Atmospheric ammonium deposition rates in open field bulk collectors and throughfall collectors ranged from 1.0 to 4.7 kg ha-1 yr-1 NH4-N, and from 1.0 to 18.3 kg ha-1 yr-1 NH4-N, respectively. ?15N-NH4 values varied from -6.3 to +14.8‰ with the highest ?15N values typically associated with elevated NH4-N deposition rates. ?15N-NH4 values of up to +20.1‰ were observed for industrially emitted NH4 in particulate matter (PM2.5) emissions (Proemse et al., 2012) suggesting that industrial NH3 and NH4 emissions are associated with elevated ?15N values providing a potential tracer. Applying a two-end-member mixing analysis using a background ?15N-NH4 value of -3.6‰ for summer and -3.2‰ for winter periods revealed that particularly sites within ~30 km radius from the main oil sands developments are significantly affected by industrial contributions to atmospheric NH4 deposition. References: Sebilo et al., 2004: Environmental Chemistry, Vol. 1, 99-103. Proemse et al., 2012: Atmospheric Environment, Vol. 60, 555-563. Proemse et al., 2013: Environmental Pollution, Vol. 182, 80-91.

Mayer, B.; Proemse, B. C.; Fenn, M. E.

2013-12-01

248

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

249

Structure of the disturbed region of the atmosphere after the nuclear explosion in Hiroshima  

NASA Astrophysics Data System (ADS)

An attempt is undertaken to describe the development of the disturbed region of the atmosphere caused by the nuclear explosion over Hiroshima on August 6, 1945. Numerical simulation of the phenomenon is performed using the dynamic equations for a nonconducting inviscid gas taking into account the combustion of urban buildings, phase changes of water, electrification of ice particles, and removal of soot particles. The results of the numerical calculation of the development of the disturbed region indicate heavy rainfall, the formation of a storm cloud with lightning discharges, removal of soot particles, and the formation of vertical vortices. The temporal sequence of these meteorological phenomena is consistent with the data of observations. Because of the assumptions and approximations used in solving the problem, the results are of qualitative nature. Refinement of the results can be obtained by a more detailed study of the approximate initial and boundary conditions of the problem.

Shcherbin, M. D.; Pavlyukov, K. V.; Salo, A. A.; Pertsev, S. F.; Rikunov, A. V.

2013-09-01

250

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

251

An atmospheric bridge mechanism for sea ice influence on the position of the marine ITCZ  

NASA Astrophysics Data System (ADS)

We identify a mechanism for high latitude sea ice influence on the meridional position of the marine ITCZ in the Community Climate model version 3 coupled to a simple slab ocean model. The marine ITCZ in all three ocean basins shift meridionally away from the hemisphere with imposed additional sea ice. The impact on the ITCZ does not appear to depend on the longitudinal position, nor the hemisphere, of the additional sea ice. Examination of the zonal mean transient response shows the apparent propagation of cooler atmospheric temperature and humidity anomalies, and cooler surface temperature anomalies, from the high latitudes of the additional sea ice to the equator. When the anomalies reach ITCZ latitudes, the resulting meridional gradient in SST formed across that latitude shifts the ITCZ away from the hemisphere with increased sea ice. The resulting change to the Hadley circulation transports moisture away from the drier hemisphere into the moister hemisphere, creating a positive feedback that amplifies the hemispheric asymmetry in atmospheric moisture. We discuss the potential relevance of this mechanism to the 'real' climate, in particular as a candidate for communicating high latitude climate changes to the tropics in the paleoclimate, and also as an influence to present day interannual-decadal variability.

Chiang, J. C.; Bitz, C. M.

2003-12-01

252

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

253

Predicting wetland contamination from atmospheric deposition measurements of pesticides in the Canadian Prairie Pothole region  

NASA Astrophysics Data System (ADS)

Although it has been suggested that atmospheric deposition alone can result in detectable levels of pesticides in wetlands of the Pairie Pothole Region of Canada, this is the first field study to compare the masses of pesticides entering wetlands by atmospheric deposition with those concentrations of pesticides detected in the water-column of prairie wetlands. Weekly air and bulk deposition samples were collected from May 26th to Sept. 15th, 2008 at the Manitoba Zero Tillage Research Association (MZTRA) Farm, Brandon, Manitoba, with four on-site wetlands (approximate sizes 0.15-0.45 ha) monitored every second week. Twelve pesticides were detected in the air, with MCPA (one of the three pesticides applied on the farm in 2008 in addition to clopyralid and glyphosate), triallate, and ?-HCH being detected every week. Calculations were performed to predict wetland pesticide concentrations based on bulk deposits alone for those pesticides that had detectable concentrations in the bulk deposition samples (in order of the highest total seasonal deposition mass to the lowest): MCPA, glyphosate, 2,4-D, clopyralid, bromoxynil, atrazine, dicamba, metolachlor, and mecoprop. The estimated concentrations were closest to actual concentrations for MCPA (Pearson correlation coefficient's = 0.91 to 0.98; p-values < 0.001) and predictions were also reasonable for a range of other herbicides, but a source other than atmospheric deposition was clearly relevant to detections of clopyralid in the wetland water-column. Although the types and levels of pesticides detected in the wetlands of the current study suggest that regional pesticide applications can contribute to pesticide surface water contamination following atmospheric transport and deposition, the greater frequency and concentrations of clopyralid, MCPA, and glyphosate detections in wetlands confirm that on-farm pesticide applications have a greater impact on on-site water quality. Beneficial management practices that reduce application drift, as well as rainfall or snowmelt runoff, will be important measures in reducing pesticide loading into wetlands situated in agricultural fields of the Prairie Pothole Region of North America.

Messing, Paul G.; Farenhorst, Annemieke; Waite, Don T.; McQueen, D. A. Ross; Sproull, James F.; Humphries, David A.; Thompson, Laura L.

2011-12-01

254

A Unified Data Assimilation Strategy for Regional Coupled Atmosphere-Ocean Prediction Systems  

NASA Astrophysics Data System (ADS)

Improving tropical cyclone (TC) forecasts is a top priority in weather forecasting. Assimilating various observational data to produce better initial conditions for numerical models using advanced data assimilation techniques has been shown to benefit TC intensity forecasts, whereas assimilating large-scale environmental circulation into regional models by spectral nudging or Scale-Selective Data Assimilation (SSDA) has been demonstrated to improve TC track forecasts. Meanwhile, taking into account various air-sea interaction processes by high-resolution coupled air-sea modelling systems has also been shown to improve TC intensity forecasts. Despite the advances in data assimilation and air-sea coupled models, large errors in TC intensity and track forecasting remain. For example, Hurricane Nate (2011) has brought considerable challenge for the TC operational forecasting community, with very large intensity forecast errors (27, 25, and 40 kts for 48, 72, and 96 h, respectively) for the official forecasts. Considering the slow-moving nature of Hurricane Nate, it is reasonable to hypothesize that air-sea interaction processes played a critical role in the intensity change of the storm, and accurate representation of the upper ocean dynamics and thermodynamics is necessary to quantitatively describe the air-sea interaction processes. Currently, data assimilation techniques are generally only applied to hurricane forecasting in stand-alone atmospheric or oceanic model. In fact, most of the regional hurricane forecasting models only included data assimilation techniques for improving the initial condition of the atmospheric model. In such a situation, the benefit of adjustments in one model (atmospheric or oceanic) by assimilating observational data can be compromised by errors from the other model. Thus, unified data assimilation techniques for coupled air-sea modelling systems, which not only simultaneously assimilate atmospheric and oceanic observations into the coupled air-sea modelling system, but also nudging the large-scale environmental flow in the regional model towards global model forecasts are of increasing necessity. In this presentation, we will outline a strategy for an integrated approach in air-sea coupled data assimilation and discuss its benefits and feasibility from incremental results for select historical hurricane cases.

Xie, Lian; Liu, Bin; Zhang, Fuqing; Weng, Yonghui

2014-05-01

255

Atmospheric mercury observations from Antarctica: seasonal variation and source and sink region calculations  

NASA Astrophysics Data System (ADS)

Long term atmospheric mercury measurements in the Southern Hemisphere are scarce and in Antarctica completely absent. Recent studies have shown that the Antarctic continent plays an important role in the global mercury cycle. Therefore, long term measurements of gaseous elemental mercury (GEM) were initiated at the Norwegian Antarctic Research Station, Troll (TRS) in order to improve our understanding of atmospheric transport, transformation and removal processes of GEM. GEM measurements started in February 2007 and are still ongoing, and this paper presents results from the first four years. The mean annual GEM concentration of 0.93 ± 0.19 ng m-3 is in good agreement with other recent southern-hemispheric measurements. Measurements of GEM were combined with the output of the Lagrangian particle dispersion model FLEXPART, for a statistical analysis of GEM source and sink regions. It was found that the ocean is a source of GEM to TRS year round, especially in summer and fall. On time scales of up to 20 days, there is little direct transport of GEM to TRS from Southern Hemisphere continents, but sources there are important for determining the overall GEM load in the Southern Hemisphere and for the mean GEM concentration at TRS. Further, the sea ice and marginal ice zones are GEM sinks in spring as also seen in the Arctic, but the Antarctic oceanic sink seems weaker. Contrary to the Arctic, a strong summer time GEM sink was found, when air originates from the Antarctic plateau, which shows that the summertime removal mechanism of GEM is completely different and is caused by other chemical processes than the springtime atmospheric mercury depletion events. The results were corroborated by an analysis of ozone source and sink regions.

Pfaffhuber, K. A.; Berg, T.; Hirdman, D.; Stohl, A.

2012-04-01

256

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

257

Elevated atmospheric carbon dioxide and leaf litter chemistry: Influences on microbial respiration and net nitrogen mineralization  

SciTech Connect

Elevated atmospheric CO{sub 2} has the potential to influence rates of C and N cycling in terrestrial ecosystems by altering plant litter chemistry and slowing rates of organic matter decomposition. We tested the hypothesis that the chemistry of leaf litter produced at elevated CO{sub 2} would slow C and N transformations in soil. Soils were amended with Populus leaf produced under two levels of atmospheric CO{sub 2} (ambient and twice-ambient) and soil N availability (low and high). Kinetic parameters for microbial respiration and net N mineralization were determined on soil with and without litter during a 32-wk lab incubation. Product accumulation curves for CO{sub 2}-C and inorganic N were fit to a first order rate equation [y=A(1-e{sup -kt})] using nonlinear regression analyses. Although CO{sub 2} treatment affected soluble sugar concentration in leaf litter (ambient =120 g kg{sup -1}, elevated =130 g kg{sup -1}), it did not affect starch concentration or C/N ratio. Microbial respiration, microbial biomass, and leaf litter C/N ratio were affected by soil N availability but not by atmospheric CO{sub 2}. Net N mineralization was a linear function of time and was not significantly different for leaves grown at ambient (50 mg N kg{sup -1}) and elevated CO{sub 2} (35 mg N kg{sup -1}). Consequently, we found no evidence for the hypothesis that leaf litter produced at elevated atmospheric CO{sub 2} will dampen the rates of C and N cycling in soil. 35 refs., 1 fig., 4 tabs.

Randlett, D.L.; Zak, D.R. [Univ. of Michigan, Ann Arbor, MI (United States); Pregitzer, K.S. [Michigan Technical Univ., Houghton, MI (United States); Curtis, P.S. [Ohio State Univ., Columbus, OH (United States)

1996-09-01

258

REGIONAL APPLICATION OF A BIOGEOCHEMICAL MODEL (PNET-BGC) TO THE ADIRONDACK REGION OF NEW YORK: RESPONES TO CURRENT AND FUTURE CHANGES IN ATMOSPHERIC DEPOSITION  

EPA Science Inventory

Understanding the response of soil and surface waters to changes in atmospheric deposition is critical for guiding future legislation on air pollutants. In this study, the regional response of soil and surface waters in 37 lake watersheds in the Adirondack region of New York to c...

259

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

260

Estimating the Influence of Biological Ice Nuclei on Clouds with Regional Scale Simulations  

NASA Astrophysics Data System (ADS)

Cloud properties are largely influenced by the atmospheric formation of ice particles. Some primary biological aerosol particles (PBAP), e.g. certain bacteria, fungal spores or pollen, have been identified as effective ice nuclei (IN). The work presented here quantifies the IN concentrations originating from PBAP in order to estimate their influences on clouds with the regional scale atmospheric model COSMO-ART in a six day case study for Western Europe. The atmospheric particle distribution is calculated for three different PBAP (bacteria, fungal spores and birch pollen). The parameterizations for heterogeneous ice nucleation of PBAP are derived from AIDA cloud chamber experiments with Pseudomonas syringae bacteria and birch pollen (Schaupp, 2013) and from published data on Cladosporium spores (Iannone et al., 2011). A constant fraction of ice-active bacteria and fungal spores relative to the total bacteria and spore concentration had to be assumed. At cloud altitude, average simulated PBAP number concentrations are ~17 L-1 for bacteria and fungal spores and ~0.03 L-1 for birch pollen, including large temporal and spatial variations of more than one order of magnitude. Thus, the average, 'diagnostic' in-cloud PBAP IN concentrations, which only depend on the PBAP concentrations and temperature, without applying dynamics and cloud microphysics, lie at the lower end of the range of typically observed atmospheric IN concentrations . Average PBAP IN concentrations are between 10-6 L-1 and 10-4 L-1. Locally but not very frequently, PBAP IN concentrations can be as high as 0.2 L-1 at -10° C. Two simulations are compared to estimate the cloud impact of PBAP IN, both including mineral dust as an additional background IN with a constant concentration of 100 L-1. One of the simulations includes additional PBAP IN which can alter the cloud properties compared to the reference simulation without PBAP IN. The difference in ice particle and cloud droplet concentration between both simulations is a result of the heterogeneous ice nucleation of PBAP. In the chosen case setup, two effects can be identified which are occurring at different altitudes. Additional PBAP IN directly enhance the ice crystal concentration at lower parts of a mixed-phase cloud. This increase comes with a decrease in liquid droplet concentration in this part of a cloud. Therefore, a second effect takes place, where less ice crystals are formed by dust-driven heterogeneous as well as homogeneous ice nucleation in upper parts of a cloud, probably due to a lack of liquid water reaching these altitudes. Overall, diagnostic PBAP IN concentrations are very low compared to typical IN concentration, but reach maxima at temperatures where typical IN are not very ice-active. PBAP IN can therefore influence clouds to some extent. Iannone, R., Chernoff, D. I., Pringle, A., Martin, S. T., and Bertram, A. K.: The ice nucleation ability of one of the most abundant types of fungal spores found in the atmosphere, Atmos. Chem. Phys., 11, 1191-1201, 10.5194/acp-11-1191-2011, 2011. Schaupp, C.: Untersuchungen zur Rolle von Bakterien und Pollen als Wolkenkondensations- und Eiskeime in troposphärischen Wolken, Ph.D. thesis, Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany, 2013.

Hummel, Matthias; Hoose, Corinna; Schaupp, Caroline; Möhler, Ottmar

2014-05-01

261

Local Atmospheric Wind Hazards to Entry, Descent and Landing Operations of the Mars Exploration Rover Mission as Predicted by the Mars Regional Atmospheric Modeling System  

Microsoft Academic Search

The entry, descent and landing (EDL) phases of the Mars Exploration Rover are sensitive to the wind, particularly below one scale height. The Mars Regional Atmospheric Modeling System is used to predict the local meteorology of high priority landing sites at horizontal scales of O(1 km) and vertical scales of O(10-100 m). The results show that sites located in highly

S. C. Rafkin

2002-01-01

262

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

263

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

264

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

265

Morphology and Chemical composition of Atmospheric Particles over Semi-Arid region (Jaipur, Rajasthan) of India  

NASA Astrophysics Data System (ADS)

Uncertainties associated with the radiative forcing of atmospheric dust particles is highest, owing to lack of region-specific dust morphology (particle shape, size) and mineralogy (chemical composition) database, needed for modeling their optical properties (Mishra and Tripathi, 2008). To fill this gap for the Indian region, we collected atmospheric particles (with aerodynamic size <5um, PM5 and a few bulk particles; TSP) from seven sites of Jaipur and nearby locales (semi-arid region, in the vicinity of Thar Desert of Rajasthan) at varying altitude, during late winters of ca. 2012. PM5 particles were collected on Teflon filters (for bulk chemical analyses), while pure Tin substrates (~1×1 mm2) were used for investigating individual particle morphology. Using Scanning Electron Microscope equipped with Energy Dispersive X ray (SEM-EDX) facility at NPL, images of individual particles were recorded and the morphological parameters (e.g. Aspect ratio; AR, Circulatory parameter; CIR.) were retrieved following Okada et al. (2001), whereas chemical compositions of individual particles were determined by EDX and bulk samples by X ray fluorescence (XRF). The geometrical size distributions of atmospheric particles were generated for each site. Based on NIST (National Institute of Standard and Technology, USA) morphology database, the site-specific individual particle shapes reveal predominance of "Layered" (calcite and quartz rich), "Angular" structures (quartz rich) and "Flattened" particles over all the sites. Particles were found to be highly non-spherical with irregular shapes (CIR varying from 1 to 0.22 with median value ~0.76; AR varying from 1 to 5.4 with median value ~1.64). Noteworthy to mention, that unit values of AR and CIR represent spherical particles. Chemical analyses of PM5 particles revealed dominance of crustal elements e.g. Si, Al, Fe, Ca, Mg, in general. Particles over Kukas Hill (27.027° N, 75.919° E; ~800 MAGL) showed highest Fe mass fractions (~43%), i.e. a key element (in form of hematite; Fe2O3) for solar (visible) energy absorption and thus heating the atmosphere. The retrieved morphological parameters help to construct particle shape and number size distribution that are highly useful to reduce the uncertainty in radiative forcing of dust particles appreciably when combined with particle chemical composition as suggested by Kalashnikova and Sokolik (2004). References : Mishra, S. K., and S. N. Tripathi (2008), Modeling optical properties of mineral dust over the Indian Desert, J. Geophys. Res., 113, D23201, 19 PP., doi:10.1029/2008JD010048. Okada, K., J. Heintzenberg, K. Kai, and Y. Qin (2001), Shape of atmospheric mineral particles collected in three Chinese arid-regions, Geophys. Res. Lett., 28, 3123-3126 Kalashnikova OV, Sokolik IN. (2004) Modeling the radiative properties of nonspherical soil-derived mineral aerosols, J Quant Spectrosc Radiat Transfer, 87, 137-66.

Mishra, S. K.; Agnihotri, R.; Yadav, P.; Singh, S.; Tawale, J. S.; Rashmi, R.; Prasad, M.; Arya, B. C.; Mishra, N.

2012-12-01

266

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

267

The Influence of Anthropogenic Aerosol on Multi-Decadal Variations of Historical Global and Regional Climate  

NASA Astrophysics Data System (ADS)

Aerosol presents a large source of uncertainty in climate simulations. The representation of aerosol, and their interaction with clouds, in climate models is changing rapidly. It is important to gauge model performance in simulating these processes, and which aspects of aerosol-climate interaction contribute to uncertainty, to enable effort to be prioritized. Future changes in aerosol entwine air-quality and climate change mitigation options. With rapid reductions in aerosol emissions anticipated in the near-term, it is important to constrain uncertainty to facilitate sound decisions on future policy. We show that climate models that include a representation of the indirect effect of aerosol better reproduce inter-decadal variability in historical global-mean near-surface temperatures, particularly the cooling in the 1950s and 1960s, compared to models with representation of the aerosol direct effect only. Using an adaptive decomposition technique to identify nonlinear trends, analysis of single forcing runs from CMIP5 simulations shows that the mid-twentieth century temperature hiatus is likely to have been influenced strongly by anthropogenic aerosol forcing. In addition to global impacts, aerosol can have a pronounced influence on local climate. Using case studies from regions with large responses to aerosol forcing, we investigate inter-model differences in aerosol burden, and in the sensitivity of atmospheric metrics to aerosol changes. We find a large range of sensitivities to aerosol perturbations, as well as considerable differences in the mass loading of some species on regional scales. This inter-model diversity in aerosol burden and representation of aerosol-cloud interaction can produce substantial variation in simulations of climate variability on multi-decadal timescales.

Wilcox, L.; Highwood, E.

2013-12-01

268

Atmosphere  

NASA Astrophysics Data System (ADS)

This paper investigates the high-temperature corrosion behavior of microstructurally different regions of the weldment of 9 Cr-1 Mo steel used in thermal power plant boiler in SO2 + O2 environment. The weldment is produced by tungsten inert gas welding method, and the different regions of the weldment (weld metal, heat-affected zone, and base metal) are exposed in SO2 + O2 (ratio 2:1) environment at 973 K for 120 h. The reaction kinetics and corrosion growth rate of different regions of weldment in isothermal condition are evaluated. The post corroded scales of the different specimens are studied in SEM, EDS, and XRD. The results indicate that the weld metal shows higher corrosion rate followed by HAZ and base metal. The higher rate of corrosion of weldmetal is mainly attributed to the least protective inner scale of Cr2O3 with minimum Cr Content. This is due to the formation of delta ferrite, which leads to the precipitation of the Cr-based secondary phases and depletes the free Cr from the matrix. The thermal cycles during welding at high temperature are favorable for the formation of delta ferrite. On the other hand, in absence of delta ferrite, the base metal and HAZ regions of the weldment show lower corrosion rate than weld metal. The difference in corrosion rate in the three regions of the weldment is supplemented by post-corroded scale characterizations.

Ghosh, D.; Mitra, S. K.

2014-05-01

269

Himalayan Wintertime Climate Variability: Large-Scale Atmospheric Circulation and Regional Precipitation  

NASA Astrophysics Data System (ADS)

The future state of High Mountain Asia's (HMA) glaciers is of critical importance to water security throughout densely populated regions of Asia. Without understanding regional climatic influences, the prediction of terrestrial water fluxes is not possible. Glacier records in the eastern and central Himalaya (CH) yield some of the world's most rapid retreat rates. However, there are a number of steady state or positive mass-balance glaciers in the Karakoram and western Himalaya (KH) regions. The goal of this research is to investigate multi-annual variations in synoptic wintertime weather as a contributing factor to regional mass-balance trends. Winter Westerly Disturbances (WWD) are the primary climatic influence within HMA during the boreal winter. This research investigates variations and changes in WWD over the period 1979--2010 and relationships with extreme precipitation in the KH and CH using multiple datasets. It is demonstrated that extreme precipitation events occurring in the KH and CH are often spatiotemporally independent, suggesting differing behavior of WWD affecting each region. The wavelet power spectrum of 200hPa geopotential height anomalies is used to characterize the frequency and magnitude of individual disturbances and to distinguish synoptic scale variability through time. This analysis exhibits an enhancement in the strength and frequency of WWD in the KH and indicates an increase in local extreme precipitation events. In contrast, the CH is observed to experience weakening influence of these disturbances and consequently, a decrease in extreme precipitation. Additionally, peak melt season temperatures are observed to decrease (increase) in the KH (CH) during the study period. This study also investigates multi-annual variability of WWD and teleconnections with some known modes of climate variability affecting central Asia, including the Arctic Oscillation, the El Nino Southern Oscillation, and the Siberian High. Although there is clear evidence that these modes affect circulation and precipitation in HMA, their competing influences on WWD are complex and non-linear. These results suggest that a thorough understanding of WWD and their spatiotemporal variations are crucial to improve our knowledge of the hydrologic cycle within HMA as well as our ability to project the future status of Asia's water resources.

Cannon, Forest Glen

270

Regional and Seasonal Variations of the Clear Sky Atmospheric Longwave Cooling over Tropical Oceans.  

NASA Astrophysics Data System (ADS)

The vertical distribution of the clear sky longwave cooling of the atmosphere over tropical oceans is inferred from three different datasets. Two of the datasets refer to the TIROS-N Operational Vertical Sounder (TOVS) NOAA/NASA Pathfinder project, PathA and PathB, and the last one refers to the ECMWF reanalysis (ERA-15). Differences are identified originating from the temperature and water vapor fields. They affect the geographical distribution of the longwave fields to various degrees. However, the three datasets lead to similar conclusions concerning the sensitivity of the clear sky total longwave cooling to SST variations. For the highest values of the SST (greater than 27°C), positively correlated to the increased efficiency of the longwave trapping (super-greenhouse effect), the atmosphere shows a lesser efficiency to cool radiatively. The atmosphere does reradiate the longwave radiation toward the surface as efficiently as it traps it. This is verified on regional as well as on seasonal scales. Such longwave cooling behavior is due to an increased mid- and upper-tropospheric humidity resulting from convective transports. The three datasets agree with the vertical distribution of the radiative cooling variations from normal to favorable to super-greenhouse effect conditions, except in the boundary layer, where the coarse resolution of the TOVS-retrieved data makes them not reliable in it. In `normal' conditions the cooling uniformly increases over the vertical with the SST. Over 27°C, the cooling is intensified above 400 hPa and reduced between 900 and 400 hPa.

Chéruy, F.; Chevallier, F.

2000-08-01

271

Lessons learned from the Bay Region Atmospheric Chemistry Experiment (BRACE) and implications for nitrogen management of Tampa Bay  

NASA Astrophysics Data System (ADS)

Results from air quality modeling and field measurements made as part of the Bay Region Atmospheric Chemistry Experiment (BRACE) along with related scientific literature were reviewed to provide an improved estimate of atmospheric reactive nitrogen (N) deposition to Tampa Bay, to apportion atmospheric N between local and remote sources, and to assess the impact of regulatory drivers on N deposition to Tampa Bay. Simulations using the Community Multiscale Air Quality model v4.4 modified with the University of California Davis aerosol module (CMAQ-UCD) provided a framework for this review. For 2002, CMAQ-UCD modeled atmospheric loading rates were 6910 metric tons N to the land surface of the watershed and 548 metric tons N to bay surface of the watershed, respectively. If an 18% transfer rate of atmospherically-deposited N from watershed to bay is assumed, then the corresponding atmospheric loading to Tampa Bay was 1790 metric tons N or 57% of the total N loading to the bay. From CMAQ-UCD modeling, oxidized N sources both within and outside Tampa Bay's watershed were important contributors to atmospheric N loading to the bay. Within the watershed, oxidized N emissions from mobile sources had a disproportionately larger impact than did power plant sources on atmospheric N loading. Predicted decreases in atmospheric N deposition to Tampa Bay by 2010 due to regulatory drivers were significant, and plausibly evident in recent declines in ambient air NOx concentrations in urban Tampa and St. Petersburg.

Poor, Noreen D.; Cross, Lindsay M.; Dennis, Robin L.

2013-05-01

272

The Influences of Fresh Water co2 Effluxes and Mesoscale Circulations on Regional Carbon Balance in the Tapajos Region, Para, Brazil  

Microsoft Academic Search

We have investigated mesoscale variations of atmospheric co2 over a heterogeneous landscape of forests, pastures, and large rivers during Santarem Mesoscale Campaign (SMC) during August 2001. We simulated the variations of surface fluxes and atmospheric concentration of co2 using the CSU Regional Atmospheric Modeling System (RAMS) on 4-level nested grids which including a 1-km finest grid centered on the Flona

L. Lu; S. A. Denning; P. D. Silva-Diaz; M. A. Silva-Diaz; E. Inazawa

2003-01-01

273

Impact of Atmospheric Infrared Sounder (AIRS) Thermodynamic Profiles on Regional Precipitation Forecasting  

NASA Technical Reports Server (NTRS)

In data sparse regions, remotely-sensed observations can be used to improve analyses and lead to better forecasts. One such source comes from the Atmospheric Infrared Sounder (AIRS), which together with the Advanced Microwave Sounding Unit (AMSU), provides temperature and moisture profiles in clear and cloudy regions with accuracy which approaches that of radiosondes. The purpose of this paper is to describe an approach to assimilate AIRS thermodynamic profile data into a regional configuration of the Advanced Research WRF (ARW) model using WRF-Var. Quality indicators are used to select only the highest quality temperature and moisture profiles for assimilation in clear and partly cloudy regions, and uncontaminated portions of retrievals above clouds in overcast regions. Separate error characteristics for land and water profiles are also used in the assimilation process. Assimilation results indicate that AIRS profiles produce an analysis closer to in situ observations than the background field. Forecasts from a 37-day case study period in the winter of 2007 show that AIRS profile data can lead to improvements in 6-h cumulative precipitation forecasts resulting from improved thermodynamic fields. Additionally, in a convective heavy rainfall event from February 2007, assimilation of AIRS profiles produces a more unstable boundary layer resulting in enhanced updrafts in the model. These updrafts produce a squall line and precipitation totals that more closely reflect ground-based observations than a no AIRS control forecast. The location of available high-quality AIRS profiles ahead of approaching storm systems is found to be of paramount importance to the amount of impact the observations will have on the resulting forecasts.

Chou, S.-H.; Zavodsky, B. T.; Jedloved, G. J.

2010-01-01

274

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

SciTech Connect

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 temporal resolutions. A menu-driven shell was developed to facilitate use of models at different temporal scales and to facilitate exchange information between models at different temporal scales. A detailed ecosystem model predicted that C{sub 3} temperate grasslands wig respond more strongly to elevated CO{sub 2} than temperate C{sub 4} grasslands in the short-term while a large positive N-PP response was predicted for a C{sub 4} Kenyan grassland. Long-term climate change scenarios produced either decreases or increases in Colorado plant productivity (NPP) depending on rainfall, but uniform increases in N-PP were predicted in Kenya. Elevated CO{sub 2} is likely to have little effect on ecosystem carbon storage in Colorado while it will increase carbon storage in Kenya. A synoptic climate classification processor (SCP) was developed to evaluate results of GCM climate sensitivity experiments. Roughly 80% agreement was achieved with manual classifications. Comparison of lx and 2xCO{sub 2} GCM Simulations revealed relatively small differences.

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

1993-10-01

275

Water Vapor Tacers as Diagnostics of the Regional Atmospheric Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

Understanding of the local and remote sources of water vapor can be a valuable diagnostic in understanding the regional atmospheric hydrologic cycle, especially in North America where moisture transport and local evaporation are important sources of water for precipitation. In the present study, we have implemented passive tracers as prognostic variables to follow water vapor evaporated in predetermined regions until the water tracer precipitates. All evaporative sources of water are accounted for by tracers, and the water vapor variable provides the validation of the tracer water and the formulation of the sources and sinks. The Geostationary Operational Environmental Satellites General Circulation Model (GEOS GCM) is used to simulate several summer periods to determine the source regions of precipitation for the United States and India. Using this methodology, a detailed analysis of the recycling of water, interannual variability of the sources of water and links to the Great Plains low-level jet and North American monsoon will be presented. Potential uses in GCM sensitivity studies, predictability studies and data assimilation especially regarding the North American monsoon and GEWEX America Prediction Project (GAPP) will be discussed.

Bosilovich, Michael G.; Schubert, Siegfried D.; Einaudi, Franco (Technical Monitor)

2000-01-01

276

The influence of Tropical Pacific on hydrological pattern at the South America central region during two El Niño events  

NASA Astrophysics Data System (ADS)

The aim of this study was to see how wet and dry periods occurred over the central region of South America, could be associated to ENSO events with same sign. In this study we considered El Niño events occurred on 1972-1973 and on 1982-1983. South America central region during 1972-1973 was characterized by a drier climatic pattern in comparison to that occurred during 1982-1983. Precipitation, river outflow at South America region and sea surface temperature (SST) over Pacific and Indian oceans were used to identify linear correlation between ocean and continental regions. After verifying the linear relationship between these areas, filtered stream function at high tropospheric levels was used to identify the presence of possible wave trains patterns crossing the Pacific Ocean and influencing South America climatic pattern. During the 1972-1973 EN event, the SST positive anomaly observed to the west portion of Equatorial Pacific probably forced atmospheric fields and have extended its influence to the east portion of Pacific, reaching the data line. Actually, the SST anomaly area was placed very closed to the Nino3.4 region in this period. This surface pattern had been related to positive anomaly of stream function at tropospheric high level. From the positive anomalies of stream function over the central area of equatorial Pacific, a wave train pattern was observed crossing the south Pacific from west to east, and providing the appearance of negative stream function anomalies over the central area of South America. Negative stream function anomalies should be related to the strengthening of convergence or to divergence weakness at high levels. Them, we assume the strengthening of divergent movements at low atmospheric levels that could better explain drier pattern in the period of 1972-1973. On the other hand, the SST positive anomaly area observed on the 1982-1983 EN event was placed more to the east of the Pacific equatorial basin, closer to the Nino1.2 region. This displacement considered together to the SST negative anomalies observed on extratropical latitudes on both hemisphere over the second analyzed period probably lead to a wave train showing positive stream function anomalies at high atmospheric levels over the central part of South America. In relation to positive stream function anomalies at high atmospheric levels we could expect negative anomalies at low levels. This pattern can be related to wetter periods over the central part of South America during the period of 1982-1983. From these results, we assume that the positioning of forcing oceanic areas, even considering two El Niño events, is fundamental to analyze the repercussions of ENSO events around the globe, in particular over South America.

Batista Silva, Carlos; Siqueira Silva, Maria Elisa

2013-04-01

277

Five-year monitoring study of chemical characteristics of Wet atmospheric precipitation in the southern region of Jordan.  

PubMed

Wet atmospheric samples were collected from different locations in the southern region of Jordan during a 5-year period (October 2006 to May 2011). All samples were analyzed for pH, EC, major ions (Ca(2+), Mg(2+), Na(+), K(+), HCO3(-), Cl(-), NO3(-), and SO4(2-)), and trace metals (Fe(2+), Al(3+), Cu(2+), Pb(2+), and Zn(2+)). The highest ion concentrations were observed during the beginning of the rainfall events because large amounts of dust accumulated in the atmosphere during dry periods and were scavenged by rain. The rainwater in the study area is characterized by low salinity and neutral pH. The major ions found in rainwater followed the order of HCO3? > ?Cl(-)?> ?SO4(2-) and Ca(2+)?>? Na(+) > Mg(2+) > NH4(+) > K(+). Trace metals were identified to be of anthropogenic origin resulting from cement and phosphate mining activities located within the investigated area and from heating activities during the cold period of the year (January to April). The wet precipitation chemistry was analyzed using factor component analysis for possible sources of the measured species. Factor analysis (principal component analysis) was used to assess the relationships between the concentrations of the studied ions and their sources. Factor 1 represents the contribution of ions from local anthropogenic activities, factor 2 represents the contribution of ions from natural sources, and factor 3 suggests biomass burning and anthropogenic source. Overall, the results revealed that rainwater chemistry is strongly influenced by local anthropogenic sources rather than natural and marine sources, which is in a good agreement with the results obtained by other studies conducted in similar sites around the world. PMID:23138417

Al-Khashman, Omar Ali; Jaradat, Aiman Qasem; Salameh, Elias

2013-07-01

278

On the Influence of the Dielectric Barriers on the Atmospheric Pressure Glows in Helium  

NASA Astrophysics Data System (ADS)

Based on a two-dimensional fluid model with a local field approximation, the atmospheric pressure glow discharges (APGs) with two dielectric barriers in helium with nitrogen impurities are studied. The model self-consistently solves the Poisson equation for the electric field and the continuity equations for the densities of all species. The momentum equations are simplified by the drift-diffusion flux. The electrons, helium atomic and molecular ions, helium metastables, and nitrogen molecular ions are included in the simulation. The model successfully predicts the formation of self-organized filaments in the discharge gap. The results showed that smaller number of filaments forms for dielectric material with lower permittivity. And a uniform Townsend-like discharge can be obtained by using of a material with lower permittivity. Based on the simulation model, the APG initiation process in the reactor with a single dielectric barrier is studied. And the influence of the thickness of the dielectric is also investigated.

Zhang, Peng; Zhou, Ning; Kortshagen, Uwe

2006-10-01

279

Influence of scattering, atmospheric refraction, and ground effect on sound propagation through a pine forest.  

PubMed

Sound propagation through a forest is affected by the microclimate in the canopy, scattering by trunks and stems, and ground reflection. Each of these effects is such a strong contributor to the attenuation of sound that mutual interactions between the phenomena could become important. A sound propagation model for use in a forest has been developed that incorporates scattering from trunks and branches and atmospheric refraction by modifying the effective wave number in the Green's function parabolic equation model. The ground effect for a hard-backed pine straw layer is approximated as a local reaction impedance condition. Comparisons to experimental data are made for frequencies up to 4,200 Hz. Cumulative influences of the separate phenomena are examined. The method developed in this paper is compared to previously published methods. The overall comparison with spectral transmission data is good, suggesting that the model captures the necessary details. PMID:17614470

Swearingen, Michelle E; White, Michael J

2007-07-01

280

Albedo of the ocean-atmosphere system - Influence of sea foam  

NASA Technical Reports Server (NTRS)

The influence of the ocean's optical properties and wind induced sea surface foam (white caps) on the short-wave albedo of the ocean-atmosphere system is studied by solving the radiative transfer equation using a Monte Carlo method. It is found that for a foam free ocean, the planetary albedo of a very clear ocean is at most 10 percent greater than that for a totally absorbing ocean. However, the introduction of a relatively small amount of sea foam on the surface can produce a considerable increase in the albedo, especially if the foam is highly reflecting. For example, it is shown that for foam which is totally reflecting (the foam albedo is 1), an increase in the wind speed from 6 to 14 m/sec would double the planetary albedo for small solar zenith angles.

Gordon, H. R.; Jacobs, M. M.

1977-01-01

281

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

2013-09-01

282

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

283

Magnetic resonance investigation of Zn1-xFexO properties influenced by annealing atmosphere  

NASA Astrophysics Data System (ADS)

ZnO is an attractive system for a wide variety of practical applications, being a chemically stable oxide semiconductor. It has been shown that Fe doping produces ferromagnetic semiconductor at room temperature. This material, therefore, has the potential for use in spintronic devices such as spin transistors, spin light emitting diodes, very high density nonvolatile semiconductor memory and optical emitters. It is believed that oxygen vacancies and substitutional incorporation are important to produce ferromagnetism in semiconductor oxide doped with transition metal ions. The present paper reports detailed electron paramagnetic resonance investigations (EPR) of the samples in order to investigate how annealing atmosphere (Air and Argon) influenced the magnetic behavior of the samples. X-band electron paramagnetic resonance (EPR) studies of Fe ions in ZnFeO powders with x = 1%, 3% is reported. These samples are interesting to investigate as Fe doping produce ferromagnetism in ZnO, making a promising ferromagnetic semiconductor at room temperature.

Raita, O.; Popa, A.; Toloman, D.; Stan, M.; Giurgiu, L. M.

2013-11-01

284

Influence of oxygen traces on an atmospheric-pressure radio-frequency capacitive argon plasma discharge  

NASA Astrophysics Data System (ADS)

An atmospheric-pressure capacitive discharge source driven by radio-frequency power supply at 13.56 MHz has been developed experimentally that is capable of producing a homogeneous and cold glow discharge in O2/Ar. With respect to the influence of oxygen component when diluted into argon plasma discharge on the discharge characteristics, the measurements of the electrical parameters (impedance, phase angle, resistance, and reactance) are made systematically and the densities of the metastable and resonant state of argon are determined by means of optical emission spectroscopy (OES). It is shown that the admixture of oxygen into argon plasma not only changes the electric characteristics but also alters the optical emission spectra greatly due to strong interaction between the oxygen content and the argon in the plasma environment.

Li, Shou-Zhe; Wu, Qi; Yan, Wen; Wang, Dezhen; Uhm, Han S.

2011-10-01

285

Interplanetary magnetic field and atmospheric electric circuit influences on ground-level pressure at Vostok  

NASA Astrophysics Data System (ADS)

The Mansurov effect, which for the Southern Hemisphere consists of a positive association between the By component (east-west) of the interplanetary magnetic field (IMF) and the ground-level pressure for stations poleward of ~80° magnetic latitude, is confirmed for Vostok (78.5°S, 106.9°E magnetic latitude 83.6°S) using modern data. The magnitude of the association is small (0.19 hP per nT; 1.2% common covariance) but statistically significant (at the 96.1% level). A more substantial association exists, with a slight delay (2-3 days) and a cumulative influence, between the Vostok station pressure and the local vertical electric field, a proxy for the air-Earth current Jz. A composite series constructed as a weighted sum of vertical electric field values at lags between 1 and 4 days yields a linear regression gradient with respect to Vostok station-level pressure of 0.10 hP per Vm-1, 10.0% common covariance and is statistically significant at the 99.9% level. We confirm a previously reported Sun-weather linkage (the Mansurov effect), provide evidence that the mechanism operates via the atmospheric electric circuit and present data supporting an inferred and more substantial surface pressure response to changes in the global atmospheric circuit.

Burns, G. B.; Tinsley, B. A.; Frank-Kamenetsky, A. V.; Bering, E. A.

2007-02-01

286

Climate-induced variability of sea level in Stockholm: Influence of air temperature and atmospheric circulation  

NASA Astrophysics Data System (ADS)

This study is focused on climate-induced variation of sea level in Stockholm during 1873 1995. After the effect of the land uplift is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months (June and August) that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables (zonal winds, vorticity and mean air temperature during the previous two months) and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

Chen, Deliang; Omstedt, Anders

2005-09-01

287

Influence of solar UV irradiance on quasi-biennial oscillations in the Earth's atmosphere  

NASA Astrophysics Data System (ADS)

A study of relationships between variations in the solar ultraviolet irradiance and quasi-biennial oscillations (QBO) in the Earth's atmosphere has been carried out by using the composite MgII index as a proxy of the solar UV irradiance. Detail analysis of changes in the stratospheric wind directions at layers from 10 mB to 70 mB for 1978-2001 showed that the wind changes start at higher altitudes and go down to lower ones, the wind intensity being the greatest in layer of the maximum ozone content (about 20 mB). The definite relationship between periodicity of changes in the solar UV irradiance and QBO is found: the averaged UV irradiance is obviously larger for the east QBO phase than for the west QBO phase. The reversal of stratospheric winds proceeds from the top to down with the certain ciclicity, and efficiency of the UV irradiation influence on stratosphere seems to be different at various stages of this ciclicity. As a result, the character and duration of the mean zonal wind direction in the equatorial stratosphere is determined by proper combination of the UV variation and seasonal changes in atmospheric circulation.

Gabis, I.; Troshichev, O.

2003-04-01

288

Influence of the solar activity on the green atmospheric airglow emission  

NASA Astrophysics Data System (ADS)

Middle latitude airglow emissions are sensitive to thermal and helio-geophysical conditions including atmospheric gravity waves vertical perturbations and conductivity seismic activity etc The investigation of their variability presents an effective method of studying physical and physico-chemical properties of the middle and upper Earth s atmosphere The nighttime airglow emissions from the upper mesosphere and lower thermosphere are dominantly produced through reactions driven by the recombination of atomic oxygen to its molecular form Intensities of the O 1 S 5577 AA emission has been observed at Stara Zagora Bulgaria by zenith tilting photometer during the period of July 2001 -- May 2002 23 rd Solar Cycle maximum Measurements from 143 nights have been used to analyse the nocturnal day to day and seasonal variations of the oxygen green emission line In order to avoid the dynamical influence of tides on the daily variations monthly mean values have been derived from averaged night intensities taken in 2 hour time interval 21-23UT The same analysis has been conducted using data measured at Irkutsk Russia at 50 r latitude and 70 r difference in geographic longitude in the same time period Semiannual oscillations have been well outlined in the two emissions showing equinoctial maxima The large green line intensity observed at Irkutsk in December and partly in January is associated with the stratospheric warming Correlation between green line intensities relative sunspot number and F10 7 radio emission

Stoeva, P.; Mikhalev, A.; Benev, B.; Medvedeva, I.; Mishin, V.

289

Regional assessment of atmospheric organic and black carbon in South Africa  

NASA Astrophysics Data System (ADS)

At present limited data exists for atmospheric black carbon (BC) and organic carbon (OC) in South Africa. In this paper BC and OC concentrations were explored in terms of spatial and temporal patterns, mass fractions of BC and OC of the overall aerosol mass, as well as linked to possible sources. PM10 and PM2.5 samples were collected at five sampling sites in South Africa operated within the DEBITS IDAF network, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano, with MiniVol samplers. Samples were analysed with a Thermal/Optical Carbon analyser. OC were higher than BC concentrations at all sites in both size fractions. Most OC and BC were present in the PM2.5 fraction. OC/BC ratios reflected the location of the different DEBITS sites, with sites in or close to anthropogenic source regions having the lowest OC/BC ratios, while background sites had the highest OC/BC ratios. The OC mass fraction percentage varied between 1% and 24%, while the BC mass fraction ranged between 1 and 12 %. The highest OC mass fraction was found at Skukuza in the Kruger National Park, which was attributed to both natural sources and anthropogenic impacts from a dominant path of air mass movement from the anthropogenic industrial hub of South Africa. The highest mass fraction of BC was found at the Vaal Triangle situated within an region highly impacted by industry and household combustion for space heating and cooking. A relatively distinct seasonal pattern was observed, with higher OC and BC concentrations determined between May and October, which coincide with the dry season in the interior of South Africa. Positive correlations between OC and BC concentrations with the distance from back trajectories passing over veld fires were observed, indicating that veld fires contribute significantly to atmospheric OC and BC during the burning months.

Gideon van Zyl, Pieter; Maritz, Petra; Beukes, Johan Paul; Liousse, Cathy; Galy-Lacaux, Corinne; Castéra, Pierre; Venter, Andrew; Pienaar, Kobus

2014-05-01

290

Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants - examples of DDT and ?-HCH  

NASA Astrophysics Data System (ADS)

A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and ?-hexachlorocyclohexane (?-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of ?-HCH are studied over a decade.

The global environment is predicted to be contaminated by the substances within ca. 2a (years). DDT reaches quasi-steady state within 3-4a in the atmosphere and vegetation compartments, ca. 6a in the sea surface mixed layer and near to or slightly more than 10a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2a, in soils within 8 years and near to or slightly more than 10a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, ?overall. ?overall?0.8a for ?-HCH's and ?1.0-1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5-12° for DDT and 6.7° for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models.

Semeena, V. S.; Feichter, J.; Lammel, G.

2006-04-01

291

Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants examples of DDT and ?-HCH  

NASA Astrophysics Data System (ADS)

A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and ?-hexachlorocyclohexane (?-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of ?-HCH are studied over a decade. The global environment is predicted to be contaminated by the substances within ca. 2 a (years). DDT reaches quasi-steady state within 3-4 a in the atmosphere and vegetation compartments, ca. 6 a in the sea surface mixed layer and near to or slightly more than 10 a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2 a, in soils within 8 years and near to or slightly more than 10 a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, ?overall. ?overall?0.8 a for ?-HCH's and ?1.0-1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5-12° for DDT and 6.7° for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models.

Semeena, V. S.; Feichter, J.; Lammel, G.

2005-12-01

292

A Wintertime Investigation of Atmospheric Pollutants Deposition in the Alberta Oil Sands Region, Canada  

NASA Astrophysics Data System (ADS)

Atmospheric deposition is a potentially important pathway of trace metals and polycyclic aromatic hydrocarbons (PAH) input to the landscape in the oil sands region of Alberta. With planned expansion of oil sands facilities, there is interest in being able to characterize the magnitude and extent of trace metal and PAH deposition in the oil sands region. A pilot study was undertaken to assess the feasibility of a bulk collection system to characterize atmospheric deposition of selected organic and inorganic contaminants in the Athabasca Oil Sands Region. The study was carried out in four sampling sites near and distant to oil sands facilities from late December 2011 to the end of March 2012 (3-month period). To check the precision of the bulk deposition method, triplicate bulk samplers were used, which were placed next to each other and as close as possible considering similar microenvironment. Monthly deposition samples were analyzed for 36 trace metals (including 13 U.S. EPA priority pollutants), ultra-low mercury, and 25 PAH (including alkylated-, parent-, and carcinogenic-PAH). At two sampling sites located within 20 km of major oil sands facilities, 3-month integrated deposition rates for some priority metals were up to 20-fold higher compared to two background sites located >45 km away from the oil sands facilities. Winter deposition rates of alkylated-PAH and parent-PAH were up to 70-fold lower at the background sampling sites than at sites near oil sands facilities. Deposition fluxes of total carcinogenic PAH were found to be 6- to 75-fold higher at the two sampling sites near oil sands development facilities compared to the north and south background sites. Another notable finding is the apparent precision of the sampling method. Median coefficient of variation for 13 priority metals were ±21% and within ±15% for both alkylated- and parent-PAH. The Athabasca oil sands region is considered a large area of current interest with respect to potential deposition of trace metals and PAH. However, access to power for any type of air pollution monitoring is, for the most part, lacking in locations at distances excess of 30 km from oil sands facilities. The bulk collection systems investigated here offer the ability to obtain direct measures of trace metal and PAH deposition in these remote areas.

Bari, M.; Kindzierski, W.

2012-12-01

293

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

NASA Astrophysics Data System (ADS)

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.

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

1980-10-01

294

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

295

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

Microsoft Academic Search

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

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

2003-01-01

296

Influence of the Aerosol-Size Spread on Dissipative Instability of Aerosol Flows in the Planetary Atmospheres. II. Atmospheres of Mars and Titan  

NASA Astrophysics Data System (ADS)

The results on the aerosol-size spread influence on dissipative instability of aerosol flow in a cold weakly ionized collisional plasma, which were obtained in the first part of this paper [1], are used for the Mars (altitudes 70-100 km) and Titan (altitudes 900-1200 km) atmospheric conditions. The threshold charges and characteristic space-time instability scales are quantitatively estimated.

Grach, V. S.

2013-12-01

297

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

298

Atmospheric deposition of mercury and methylmercury to landscapes and waterbodies of the athabasca oil sands region.  

PubMed

Atmospheric deposition of metals originating from a variety of sources, including bitumen upgrading facilities and blowing dusts from landscape disturbances, is of concern in the Athabasca oil sands region of northern Alberta, Canada. Mercury (Hg) is of particular interest as methylmercury (MeHg), a neurotoxin which bioaccumulates through foodwebs, can reach levels in fish and wildlife that may pose health risks to human consumers. We used spring-time sampling of the accumulated snowpack at sites located varying distances from the major developments to estimate winter 2012 Hg loadings to a ?20 000 km(2) area of the Athabasca oil sands region. Total Hg (THg; all forms of Hg in a sample) loads were predominantly particulate-bound (79 ± 12%) and increased with proximity to major developments, reaching up to 1000 ng m(-2). MeHg loads increased in a similar fashion, reaching up to 19 ng m(-2) and suggesting that oil sands developments are a direct source of MeHg to local landscapes and water bodies. Deposition maps, created by interpolation of measured Hg loads using geostatistical software, demonstrated that deposition resembled a bullseye pattern on the landscape, with areas of maximum THg and MeHg loadings located primarily between the Muskeg and Steepbank rivers. Snowpack concentrations of THg and MeHg were significantly correlated (r = 0.45-0.88, p < 0.01) with numerous parameters, including total suspended solids (TSS), metals known to be emitted in high quantities from the upgraders (vanadium, nickel, and zinc), and crustal elements (aluminum, iron, and lanthanum), which were also elevated in this region. Our results suggest that at snowmelt, a complex mixture of chemicals enters aquatic ecosystems that could impact biological communities of the oil sands region. PMID:24873895

Kirk, Jane L; Muir, Derek C G; Gleason, Amber; Wang, Xiaowa; Lawson, Greg; Frank, Richard A; Lehnherr, Igor; Wrona, Fred

2014-07-01

299

Ice-ocean-atmosphere coupling in the Regional Arctic System Model  

NASA Astrophysics Data System (ADS)

This work demonstrates the sea ice model performance in the latest version of the Regional Arctic System Model (RASM), which is a fully coupled regional climate model developed by a group of U.S. institutions as a regional counterpart to the Community Earth System Model (CESM). RASM is comprised of the Parallel Ocean Program (POP), Los Alamos Sea Ice Model (CICE), Variable Infiltration Capacity (VIC) hydrology model and the Weather Research and Forecasting (WRF) Model. It uses the same coupling infrastructure as CESM, with important physics differences that we have found to be important in our high-resolution model. Model evaluations using SSM/I sea ice extent and concentration, ICESat sea ice thickness measurements, ice-ocean buoys, and satellite retrievals of sea ice drift and deformation, lead us to adjust the standard CESM Monin-Obukhov ice-ocean-atmospheric coupling and ice-ocean stress term used for coupling with POP-CICE at eddy-permitting resolution of 1/12 degree with the 50km resolution WRF and VIC models. Evaluation metrics based on scaling laws and wavelet techniques illustrate that 20-minute coupling produces deformation and drift statistics commensurate with high temporal and spatial resolution measurements. However, dynamical interactions are compromised when typical radiative settings are used as in stand-alone POP-CICE and WRF. This highlights the limitations of surface polar boundary conditions in stand-alone models relative to fully coupled interactions. Our results suggest that use of uncoupled models as testbeds for improved polar components of next-generation global Earth System Models may introduce biases into fully coupled systems, and these can be reduced using a regional coupled climate system model, such as RASM, as a testbed instead.

Roberts, A.; Brunke, M.; Cassano, J. J.; Craig, A.; Duvivier, A.; Hughes, M.; Maslowski, W.; Nijssen, B.; Osinski, R.

2013-12-01

300

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

301

Influence of different land surfaces on atmospheric conditions measured by a wireless sensor network  

NASA Astrophysics Data System (ADS)

Atmospheric conditions close to the surface, like temperature, wind speed and humidity, vary on small scales because of surface heterogeneities. Therefore, the traditional measuring approach of using a single, highly accurate station is of limited representativeness for a larger domain, because it is not able to determine these small scale variabilities. However, both the variability and the domain averages are important information for the development and validation of atmospheric models and soil-vegetation-atmosphere-transfer (SVAT) schemes. Due to progress in microelectronics it is possible to construct networks of comparably cheap meteorological stations with moderate accuracy. Such a network provides data in high spatial and temporal resolution. The EPFL Lausanne developed such a network called SensorScope, consisting of low cost autonomous stations. Each station observes air and surface temperature, humidity, wind direction and speed, incoming solar radiation, precipitations, soil moisture and soil temperature and sends the data via radio communication to a base station. This base station forwards the collected data via GSM/GPRS to a central server. Within the FLUXPAT project in August 2009 we deployed 15 stations as a twin transect near Jülich, Germany. One aim of this first experiment was to test the quality of the low cost sensors by comparing them to more accurate reference measurements. It turned out, that although the network is not highly accurate, the measurements are consistent. Consequently an analysis of the pattern of atmospheric conditions is feasible. For example, we detect a variability of ± 0.5K in the mean temperature at a distance of only 2.3 km. The transect covers different types of vegetation and a small river. Therefore, we analyzed the influence of different land surfaces and the distance to the river on meteorological conditions. On the one hand, some results meet our expectations, e.g. the relative humidity decreases with increasing distance to the river. But on the other hand we found unexpected anomalies in the air temperature, which will be discussed in detail by selected case studies.

Lengfeld, Katharina; Ament, Felix

2010-05-01

302

Statistical characteristics of atmospheric gravity wave in the mesopause region observed with a sodium lidar at Beijing, China  

NASA Astrophysics Data System (ADS)

The nightly and seasonal variations in atmospheric gravity wave (AGW) activity in the sodium layer are investigated by analyzing 253 nights of sodium lidar observations obtained from April 2010 to September 2011 at Yanqing, Beijing (40.3°N,116.2°E). There are 147 quasi-monochromatic AGWs have been distinguished, and the parameter values for each AGW have been extracted from the sodium density profile sequences. And an average parameter relationship of ? z = 0.247 Tob0.509 is found. The nightly and monthly varied wave event rates (WER) of AGWs have been analyzed, respectively. It is found that the activity of AGW usually has two maxima in one night and they occur respectively during 22-24 LST and 03-04 LST. The monthly distributions of WER show that the AGW activity has maximum in summer and minimum in winter. To provide some explanations for the seasonal variation characteristic of AGW activity, the most probable sources and the influences from the background winds have been analyzed. It is found that the convection and topography over Qinghai-Tibet Plateau are the main sources of most AGWs observed in the mesopause region above Beijing. And the seasonal variation characteristic of AGW activity is mainly ascribed to the seasonally varied temperature and background wind.

Gong, Shaohua

2012-07-01

303

Influence of daily versus monthly fire emissions on atmospheric model applications in the tropics  

NASA Astrophysics Data System (ADS)

Fires are widely used throughout the tropics to create and maintain areas for agriculture, but are also significant contributors to atmospheric trace gas and aerosol concentrations. However, the timing and magnitude of fire activity can vary strongly by year and ecosystem type. For example, frequent, low intensity fires dominate in African savannas whereas Southeast Asian peatland forests are susceptible to huge pulses of emissions during regional El Niño droughts. Despite the potential implications for modeling interactions with atmospheric chemistry and transport, fire emissions have commonly been input into global models at a monthly resolution. Recognizing the uncertainty that this can introduce, several datasets have parsed fire emissions to daily and sub-daily scales with satellite active fire detections. In this study, we explore differences between utilizing the monthly and daily Global Fire Emissions Database version 3 (GFED3) products as inputs into the NASA GISS-E2 composition climate model. We aim to understand how the choice of the temporal resolution of fire emissions affects uncertainty with respect to several common applications of global models: atmospheric chemistry, air quality, and climate. Focusing our analysis on tropical ozone, carbon monoxide, and aerosols, we compare modeled concentrations with available ground and satellite observations. We find that increasing the temporal frequency of fire emissions from monthly to daily can improve correlations with observations, predominately in areas or during seasons more heavily affected by fires. Differences between the two datasets are more evident with public health applications: daily resolution fire emissions increases the number of days exceeding World Health Organization air quality targets.

Marlier, M. E.; Voulgarakis, A.; Faluvegi, G.; Shindell, D. T.; DeFries, R. S.

2012-12-01

304

Ocean-atmosphere exchange and atmospheric speciation of ammonia and methylamines in the region of the NW Arabian Sea  

Microsoft Academic Search

Concentrations of ammonia \\/ ammonium (NH3 \\/NH4+) and its methyl-derivatives the methylamines (MAs) were determined in seawater, atmospheric, and rainwater samples during the U.K. Joint Global Ocean Flux Study ARABESQUE program in the Arabian Sea (August - December 1994). In seawater, concentrations Of NH3\\/NH4+ were shown to be 10–100 times greater than those of MAs, of which monomethylamine was the

Stuart W. Gibb; R. Fauzi C. Mantoura; Peter S. Liss

1999-01-01

305

Ocean-atmosphere exchange and atmospheric speciation of ammonia and methylamines in the region of the NW Arabian Sea  

Microsoft Academic Search

Concentrations of ammonia\\/ammonium (NH3\\/NH4+) and its methyl-derivatives the methylamines (MAs) were determined in seawater, atmospheric, and rainwater samples during the U.K. Joint Global Ocean Flux Study ARABESQUE program in the Arabian Sea (August-December 1994). In seawater, concentrations of NH3\\/NH4+ were shown to be 10-100 times greater than those of MAs, of which monomethylamine was the most abundant. Concentrations of all

Stuart W. Gibb; R. Fauzi C. Mantoura; Peter S. Liss

1999-01-01

306

Influence of helium mole fraction distribution on the properties of cold atmospheric pressure helium plasma jets  

NASA Astrophysics Data System (ADS)

The influence of helium mole fraction distribution in air on the cold atmospheric plasma jets excited by 1.5 kHz rectangular high voltage pulse is studied in this work. Computational fluid dynamics (CFD) with incorporation of large eddy simulation (LES) model is used to simulate the helium mole fraction distribution in air under the helium flow from laminar to turbulent regime with increasing helium outlet velocity. Numerical simulation results are combined with experimental results in order to determine the influence of helium distribution on the cold plasma jets. It reveals that the structure of the helium distribution caused by diffusion or by turbulent mixing in turbulent regime determines the characteristics of the cold plasma jets. On the other hand, the curves of plasma jet length (L) versus helium outlet velocity (V) at different jet diameters (D) are unified in a map of jet Reynolds number (Re = ?He.V.D/?He, where ?He is the helium viscosity constant) versus dimensionless plasma jet length (l = L/D). The map is allowed to predict the flow pattern of helium jet in order to estimate and control the plasma jet length at different jet diameters.

Xiong, Ranhua; Xiong, Qing; Nikiforov, Anton Yu.; Vanraes, Patrick; Leys, Christophe

2012-08-01

307

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

308

Effects of Variable Atmospheric Dust on the Surface and Atmospheric Absorption in the Polar Cap Regions on Mars  

NASA Astrophysics Data System (ADS)

We report our first results on the effects of dust on the CO2 sublimation in the Martian polar cups. The Spherical Discrete Ordinate Method for 3D atmospheric radiative transfer (Evans, K. F. 1998, Journ. Atm. Sci, 55, 429) has been used in order to examine the dust effect on the surface and atmospheric absorption as a function of the dust extinction, surface albedo, and solar zenith angle. A constant mixing ratio is assumed for the vertical distribution of the dust, with the scattering phase function adopted from Clancy & Lee (1991, Icarus, 93, 135). The albedo of single scattering of the dust for 600 nm is adopted from Wolff et al. (1997, JGR, 102, 1679). The effect of the atmospheric dust is fairly complex, depending on the solar zenith angle, dust opacity, and surface albedo. The presented results will be ultimately used to study the interannual variability in the polar cap recession that can be produced by variable dust. This research was supported by a Mars Data Analysis Grant NAG5-8183.

James, P. B.; Bonev, B.; Wolff, M. J.

2000-10-01

309

Influence of the Atmosphere on the Thermoluminescence of a Crystalline Powder (Influence de l'Atmosphere sur la Thermoluminescence d'une poudre Cristalline).  

National Technical Information Service (NTIS)

The note presents results relative to the effects of gaseous atmosphere and pressure on the natural thermoluminescence of a powdered crystalline sample. The authors demonstrate, in particular, that the peaks do not disappear at pressures below 0.01 torr, ...

D. Lapraz P. Iacconi P. Keller

1972-01-01

310

About the Influence of the initial Atmosphere on the Earth's Temperature Distribution during it's Accumulation  

NASA Astrophysics Data System (ADS)

We suggested a new model for accumulation of planets of the Earth's group [1], which is based on the contemporary results of geochemical analyses, which allow to obtain the concentrations of short living radioactive isotopes of 26Al in the matter of the pre planet cloud [2]. With use of that data new estimations of temperature distribution into the growing planetary pre planetary bodies into the Earth's nebular zone had been obtained. For the further Earth's temperature evolution, as it had been showed by the results of numerical modeling, the main role belongs to the temperature distribution in the forming Earth's core and the existence of a dense and transparent atmosphere. The shadow influence of the initial atmosphere had been researched in the paper [3]. We shall give the main consideration to these problems in that paper. It had been shown in [1], that on the earliest accumulation stage the heat release by the decay of 26Al it is sufficient for forming a central melted area and solid relatively thin mainly silicate upper envelope in the pre planetary body, with dimensions, larger than (50-100) km. The impact velocities on that stage are yet not large, therefore by the bodies impact with these or near dimensions liquid and mainly iron their parts merge, but the masses of the pre planetary bodies are not sufficient to gravitational keeping of silicate parts of the cold solid envelope. On that stage they remain into the nebular zone of the proto planet and the mechanism of matter differentiation for the future core and mantle reservoirs realizes. The process takes place yet in small bodies and is in time to finish during less than 10 million years. The next forming of the core and mantle structure continues according to all known estimations about 100 million years. Because of the merging of inner liquid parts of impacting bodies occur due to inelastic impact, the main part of potential energy transforms into heat. That continues up to that time when the iron core mass increases to the main part of the contemporary mass. The silicate particles of different dimensions remain in the proto planet cloud and in the initial atmosphere, reducing it's transparency and release of the heat radiation. On the finishing stage of the core growing the mass of the pre planetary body is sufficient for keeping of the rising part of the silicate envelope of falling bodies. The matter of the growing planet enriches more and more with a touch of silicates. The impact process of accumulated bodies gradually converts to the mechanism of elastic impact, by which only a small part of kinetic energy transforms into the merging by the pre planet body heat. The atmosphere losses the silicate particles and it's transparency exceeds. It is forming either a non melted mantle, or a mantle with a rising melted layer. That results show that the existence of a dense, nontransparent atmosphere leads to temperature growing in the inner areas of the planet during it's accumulation process. 1.Anfilogov V.N., Khachay Yu.V. A possible variant of matter differentiation on the initial stage of Earth's forming. // DAN. 2005, V. 403, N. 6, 803-806. 2.Merk R.,Breuer D., Spohn T., 2002. Numerical modeling of 26Al - Induced radioactive melting of asteroids concerning accretion, Icarus, 159, 183-191. 3.Hayashi C., Nakazawa K., Mizuno H. Earth's melting due to the blanketing effect of primordial dense atmosphere. // Earth and Plenetary Science Letters. (1979). v. 43, 22-28

Khachay, Y.; Anfilogov, V.; Antipin, A.

2012-04-01

311

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

312

Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling  

NASA Astrophysics Data System (ADS)

We present an oxidation mechanism of intermediate size for isoprene (2-methyl-1,3-butadiene) suitable for simulations in regional and global atmospheric chemistry models, which we call MIM2. It is a reduction of the corresponding detailed mechanism in the Master Chemical Mechanism (MCM v3.1) and intended as the second version of the well-established Mainz Isoprene Mechanism (MIM). Our aim is to improve the representation of tropospheric chemistry in regional and global models under all NOx regimes. We evaluate MIM2 and re-evaluate MIM through comparisons with MCM v3.1. We find that MIM and MIM2 compute similar O3, OH and isoprene mixing ratios. Unlike MIM, MIM2 produces small relative biases for NOx and organic nitrogen-containing species due to a good representation of the alkyl and peroxy acyl nitrates (RONO2 and RC(O)OONO2). Moreover, MIM2 computes only small relative biases with respect to hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), methanol (CH3OH), formaldehyde (HCHO), peroxy acetyl nitrate (PAN), and formic and acetic acids (HCOOH and CH3C(O)OH), being always below ?6% in all NOx scenarios studied. Most of the isoprene oxidation products are represented explicitly, including methyl vinyl ketone (MVK), methacrolein (MACR), hydroxyacetone and methyl glyoxal. MIM2 is mass-conserving with respect to carbon, including CO2 as well. Therefore, it is suitable for studies assessing carbon monoxide (CO) from biogenic sources, as well as for studies focused on the carbon cycle. Compared to MIM, MIM2 considers new species like acetaldehyde (CH3CHO), propene (CH2=CHCH3) and glyoxal (CHOCHO) with global chemical production rates for the year 2005 of 7.3, 9.5 and 33.8 Tg/yr, respectively. Our new mechanism is expected to substantially improve the results of atmospheric chemistry models by representing many more intermediates, that are transported and deposited, which allows us to test model results with many more new measurements. MIM2 allows regional and global models to easily incorporate new experimental results on the chemistry of organic species.

Taraborrelli, D.; Lawrence, M. G.; Butler, T. M.; Sander, R.; Lelieveld, J.

2009-04-01

313

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

314

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

315

The influence of atmospheric circulation on the climate over Western Siberia  

NASA Astrophysics Data System (ADS)

The correlations between variabilities of large- and mesoscale circulation processes and surface temperatures in West-Siberian region were analysed. The surface temperature trends over this region were also obtained. The coordinate positions of the region were bounded at 50-70°N and 60-110°E. We used the daily observational data (ftp://ftp.cdc.noaa) at 169 stations for 1976-2006, the SCAND and POL indices (http://www.cpc.ncep.noaa.gov) describing the global circulation and the synoptic data (a surface pressure in the centers and a lifetime of cyclons and anticyclons in West-Siberian region) describing the regional circulation. The method of multiple linear regression was applied for analysis of correlations between variabilities of surface temperature fields and atmospheric circulation characteristics. Main results are the following: - for 1976-2006 the positive trend of annual average surface temperature was observed at most stations of West-Siberian region. The mean trend assessment was 0.36°C/decade. While there was the negative trend of annual average surface pressure by -0.18 hPa/decade. The maximal values of warming were observed in February, March, May and October; - the variability of surface temperatures in West-Siberian region is well correlated with the variability of large- and mesoscale circulation processes. For all months the multiple regression coefficients are variated from 0.57 to 0.84 on significance level at 0.05; - the essential correlations (from 25 to 100 %) between variabilities of surface temperatures and large-scale circulation processes in West-Siberian region are observated within a year except January for SCAND indices; - for POL indices, the essential correlations (from 25 to 29 %) are only observated in January, September and October; - the variability of surface pressure in the centers of cyclons from January until April is well correlated with the variability of surface temperatures (C. of C. are 36-42 %), the variability of lifetime of anticyclons in autumn and spring times has essential correlation (15-22 %) with the variability of surface temperatures

Ippolitov, Ivan; Gorbatenko, Valentina; Loginov, Sergey; Podnebesnych, Natalie; Kharyutkina, Elena

2010-05-01

316

LIDAR first results from the Oil Sands Region: A complex vertical atmosphere  

NASA Astrophysics Data System (ADS)

Environment Canada is using LIDAR technology to probe the complex vertical structure of the atmosphere over the oil sands region. This provided the critical vertical context for the interpretation of ground-based chemistry measurements and model verification and validation. In recent years, Environment Canada has designed an autonomous aerosol LIDAR system that can be deployed to remote areas such as the oil sands. The trailer that contains the LIDAR system includes a roof hatch assembly, basic meteorological tower, radar interlock system, climate control system and leveling stabilizers. A precipitation sensor is used to operate the roof hatch and three pan/tilt webcams capture sky conditions and monitor the Lidar system's health. A remote control interface is used to monitor all vital components of the system, including the ability to provide hard resets to the various electronic devices onboard. Every 10 seconds the system provides vertical aerosol profiles from near ground to 20 km. The LIDAR transmitter emits two wavelengths (1064nm and 532nm) and the detector assembly collects three channels (1064nm backscatter, 532nm backscatter and 532nm depolarization). The depolarization channel provided key information in identifying and discriminating the various aerosol layers aloft such as dust, forest fire plumes, industrial plume sources or ice crystals. It operates 24 hours a day, seven days a week except during precipitation events and when aircraft fly over the site. The system is operated remotely and the data are updated every hour to a website to allow near real-time capability. First results from an intensive field campaign will be presented. LIDAR false color plot showing the bottom 7 km of the atmosphere during a forest fire event. Note the forest fire plume is between 1.5 and 5 km.

Strawbridge, K. B.

2012-12-01

317

Impact of Atmospheric Infrared Sounder (AIRS) Thermodynamic Profiles on Regional Weather Forecasting  

NASA Technical Reports Server (NTRS)

In data sparse regions, remotely-sensed observations can be used to improve analyses and lead to better forecasts. One such source comes from the Atmospheric Infrared Sounder (AIRS), which together with the Advanced Microwave Sounding Unit (AMSU), provides temperature and moisture profiles with accuracy comparable to that of radiosondes. The purpose of this paper is to describe a procedure to assimilate AIRS thermodynamic profile data into a regional configuration of the Advanced Research Weather Research and Forecasting (WRF-ARW) model using its three-dimension variational (3DVAR) analysis component (WRF-Var). Quality indicators are used to select only the highest quality temperature and moisture profiles for assimilation in both clear and partly cloudy regions. Separate error characteristics for land and water profiles are also used in the assimilation process. Assimilation results indicate that AIRS profiles produce an analysis closer to in situ observations than the background field. Forecasts from a 37-day case study period in the winter of 2007 show that AIRS profile data can lead to improvements in 6-h cumulative precipitation forecasts due to instability added in the forecast soundings by the AIRS profiles. Additionally, in a convective heavy rainfall event from February 2007, assimilation of AIRS profiles produces a more unstable boundary layer resulting in enhanced updrafts in the model. These updrafts produce a squall line and precipitation totals that more closely reflect ground-based observations than a no AIRS control forecast. The location of available high-quality AIRS profiles ahead of approaching storm systems is found to be of paramount importance to the amount of impact the observations will have on the resulting forecasts.

Chou, Shih-Hung; Zavodsky, Bradley T.; Jedlovee, Gary J.

2010-01-01

318

Modelling soil-plant-atmosphere interactions by coupling the regional weather model WRF to mechanistic plant models  

NASA Astrophysics Data System (ADS)

Climate change causes altering distributions of meteorological factors influencing plant growth and its interactions between the land surface and the atmosphere. Recent studies show, that uncertainties in regional and global climate simulations are also caused by lacking descriptions of the soil-plant-atmosphere system. Therefore, we couple a mechanistic soil-plant model to a regional climate and forecast model. The detailed simulation of the water and energy exchanges, especially the transpiration of grassland and forests stands, are the key features of the modelling framework. The Weather Research and Forecasting model (WRF) (Skamarock 2008) is an open source mesoscale numerical weather prediction model. The WRF model was modified in a way, to either choose its native, static land surface model NOAH or the mechanistic eco-system model Expert-N 5.0 individually for every single grid point within the simulation domain. The Expert-N 5.0 modelling framework provides a highly modular structure, enabling the development and use of a large variety of different plant and soil models, including heat transfer, nitrogen uptake/turnover/transport as well as water uptake/transport and crop management. To represent the key landuse types grassland and forest, we selected two mechanistic plant models: The Hurley Pasture model (Thornley 1998) and a modified TREEDYN3 forest simulation model (Bossel 1996). The models simulate plant growth, water, nitrogen and carbon flows for grassland and forest stands. A mosaic approach enables Expert-N to use high resolution land use data e.g. CORINE Land Cover data (CLC, 2006) for the simulation, making it possible to simulate different land use distributions within a single grid cell. The coupling results are analyzed for plausibility and compared with the results of the default land surface model NOAH (Fei Chen and Jimy Dudhia 2010). We show differences between the mechanistic and the static model coupling, with focus on the feedback effects of evapotranspiration, heat flow and radiation of thermodynamic values. Bossel, H. 1996. "TREEDYN3 forest simulation model." Ecological modelling 90 (3): 187-227. CLC, 2006. CORINE Land Cover 2006. http://www.eea.europa.eu/themes/landuse/interactive/clc-download. Accessed 16.12.2012. Fei Chen, and Jimy Dudhia. 2010. Coupling an Advanced Land Surface-Hydrology Model with the Penn State-NCAR MM5 Modeling System. Part II: Preliminary Model Validation. Research-article. February 25. Skamarock, W. C. 2008. "Coauthors 2008: A description of the Advanced Research WRF version 3." NCAR Tech. Note NCAR/TN-475+ STR. http://www.wrf-model.org/. Thornley, John. 1998. Grassland dynamics: an ecosystem simulation model. Wallingford,New York: CAB international.

Klein, C.; Hoffmann, P.; Priesack, E.

2012-04-01

319

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

320

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

321

Influence of the vertical structure of the atmosphere on the seasonal variation of precipitable water and greenhouse effect  

Microsoft Academic Search

By using satellite observations and European Centre for Medium Range Weather Forecasts analyses, we study the seasonal variations of the precipitable water and the greenhouse effect, defined as the normalized difference between the longwave flux emitted at the surface and that emergent at the top of the atmosphere. Results show a strong systematic influence of the vertical structure of the

Sandrine Bony; Jean-Philippe Duvel

1994-01-01

322

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

323

Tillage and N-source influence soil-emitted nitrous oxide in the Alberta Parkland region  

SciTech Connect

Zero tillage systems are receiving attention as possible strategies for sequestering atmospheric carbon. This benefit may be offset by increased N2O emissions, which have been reported for soils under zero tillage (ZT) compared to those under more intensive tillage (IT). Comparisons of N2O emissions from the two systems have been restricted to the growing season, but substantial losses of N2O have been reported during spring thaw events in many regions. Inorganic and organic additions of nitrogen and fallowing have also been shown to increase levels of soil-emitted N2O. The objectives for this study were: (i) to confirm that losses of N2O are higher under ZT than under IT in Alberta Parkland agroecosystems; (ii) to compare the relative influence of urea fertilizer (56 or 100 kg N h--1), field pea residue (dry matter at 5 Mg h--1), sheep manure (dry matter at 40 Mg h--1) additions, and fallow on total N2O losses; and (iii) to investigate possible interactions between fertility and tillage treatments. Gas samples were collected using vented soil covers at three sites near Edmonton, Alberta during 1993, 1994, and 1995. Gas samples were analyzed using a gas chromatograph equipped with a 63Ni electron capture detector. Estimated annual N2O loss ranged from 0.1 to 4.0 kg N ha-1. Emissions during summer were slightly higher, similar, or lower on ZT compared to those under IT, but were consistently lower on ZT plots during spring thaw. Combined estimates (spring plus summer) of N2O loss under ZT were equal to or lower than those under IT. Highest overall losses were observed on fallow plots, followed by fertilizer, pea residue, and then either manure or control plots. We conclude that ZT management systems have potential for reducing agricultural greenhouse gas emissions in the Alberta Parkland region.

Lemke , R L.; Izaurralde, R Cesar C.; Nyborg, M.; Solberg, E D.

1999-01-01

324

Influence of the Cardiac Myosin Hinge Region on Contractile Activity  

Microsoft Academic Search

The participation of cardiac myosin hinge in contractility was investigated by in vitro motility and ATPase assays and by measurements of sarcomere shortening. The effect on contractile activity was analyzed using an antibody directed against a 20-amino acid peptide within the hinge region of myosin. This antibody bound specifically at the hinge at a distance of 55 nm from the

Sarkis S. Margossian; John W. Krueger; James R. Sellers; Giovanni Cuda; James B. Caulfield; Paul Norton; Henry S. Slayter

1991-01-01

325

Influence of increased isoprene emissions on regional ozone modeling  

Microsoft Academic Search

The role of biogenic hydrocarbons on ozone modeling has been a controversial issue since the 1970s. In recent years, changes in biogenic emission algorithms have resulted in large increases in estimated isoprene emissions. This paper describes a recent algorithm, the second generation of the Biogenic Emissions Inventory System (BEIS2). A sensitivity analysis is performed with the Regional Acid Deposition Model

Thomas Pierce; Christopher Geron; Lucille Bender; Robin Dennis; Gail Tonnesen; Alex Guenther

1998-01-01

326

Changes in Atmospheric CO2 Influence the Allergenicity of Aspergillus fumigatus fungal spore  

NASA Astrophysics Data System (ADS)

Increased allergic susceptibility has been documented without a comprehensive understanding for its causes. Therefore understanding trends and mechanisms of allergy inducing agents is essential. In this study we investigated whether elevated atmospheric CO2 levels can affect the allergenicity of Aspergillus fumigatus, a common allergenic fungal species. Both direct exposure to changing CO2 levels during fungal growth, and indirect exposure through changes in the C:N ratios in the growth media were inspected. We determined the allergenicity of the spores through two types of immunoassays, accompanied with genes expression analysis, and proteins relative quantification. We show that fungi grown under present day CO2 levels (392 ppm) exhibit 8.5 and 3.5 fold higher allergenicity compared to fungi grown at preindustrial (280 ppm) and double (560 ppm) CO2 levels, respectively. A corresponding trend is observed in the expression of genes encoding for known allergenic proteins and in the major allergen Asp f1 concentrations, possibly due to physiological changes such as respiration rates and the nitrogen content of the fungus, influenced by the CO2 concentrations. Increased carbon and nitrogen levels in the growth medium also lead to a significant increase in the allergenicity, for which we propose two different biological mechanisms. We suggest that climatic changes such as increasing atmospheric CO2 levels and changes in the fungal growth medium may impact the ability of allergenic fungi such as Aspergillus fumigatus to induce allergies. The effect of changing CO2 concentrations on the total allergenicity per 10^7 spores of A. fumigatus (A), the major allergen Asp f1 concentration in ng per 10^7 spores (B), and the gene expression by RT-PCR (C). The error bars represent the standard error of the mean.

Lang-Yona, N.; Levin, Y.; Dannemoller, K. C.; Yarden, O.; Peccia, J.; Rudich, Y.

2013-12-01

327

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

328

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

329

Autofluorescence of atmospheric bioaerosols - Biological standard particles and the influence of environmental conditions  

NASA Astrophysics Data System (ADS)

Primary biological aerosol particles (PBAP) such as pollen, fungal spores, bacteria, biogenic polymers and debris from larger organisms are known to influence atmospheric chemistry and physics, the biosphere and public health. PBAP can account for up to ~30% of fine and up to ~70% of coarse particulate matter in urban, rural and pristine environment and are released with estimated emission rates of up to ~1000 Tg/a [1]. Continuous measurements of the abundance, variability and diversity of PBAP have been difficult until recently, however. The application of on-line instruments able to detect autofluorescence from biological particles in real-time has been a promising development for the measurement of PBAP concentrations and fluxes in different environments [2,3]. The detected fluorescent biological aerosol particles (FBAP) can be regarded as a subset of PBAP, although the exact relationship between PBAP and FBAP is still being investigated. Autofluorescence of FBAP is usually a superposition of fluorescence from a mixture of individual fluorescent molecules (fluorophores). Numerous biogenic fluorophores such as amino acids (e.g., tryptophan, tyrosine), coenzymes (e.g., NAD(P)H, riboflavin) and biopolymers (e.g., cellulose) emit fluorescent light due to heterocyclic aromatic rings or conjugated double bonds within their molecular structures. The tryptophan emission peak is a common feature of most bioparticles because the amino acid is a constituent of many proteins and peptides. The influence of the coenzymes NAD(P)H and riboflavin on the autofluorescence of bacteria can be regarded as an indicator for bacterial metabolism and has been utilized to discriminate between viable and non-viable organisms [4]. However, very little information is available about other essential biofluorophores in fungal spores and pollen. In order to better understand the autofluorescence behavior of FBAP, we have used fluorescence spectroscopy and fluorescence microscopy to analyze standard bioparticles (pollen, fungal spores, and bacteria) as well as atmospherically relevant chemical substances. We addressed the sensitivity and selectivity of autofluorescence based online techniques. Moreover, we investigated the influence of environmental conditions, such as relative humidity and oxidizing agents in the atmosphere, on the autofluorescence signature of standard bioparticles. Our results will support the molecular understanding and quantitative interpretation of data obtained by real-time FBAP instrumentation [5,6]. [1] Elbert, W., Taylor, P. E., Andreae, M. O., & Pöschl, U. (2007). Atmos. Chem. Phys., 7, 4569-4588. [2] Huffman, J. A., Treutlein, B., & Pöschl, U. (2010). Atmos. Chem. Phys., 10, 3215-3233. [3] Pöschl, U., et al. (2010). Science, 329, 1513-1516. [4] Lakowicz, J., Principles of fluorescence spectroscopy, Plenum publishers, New York, 1999. [5] Pöhlker, C., Huffman, J. A., & Pöschl, U., (2012). Atmos. Meas. Tech., 5, 37-71. [6] Pöhlker, C., Huffman, J. A., Förster J.-D., & Pöschl, U., (2012) in preparation.

Pöhlker, Christopher; Huffman, J. Alex; Förster, Jan-David; Pöschl, Ulrich

2013-04-01

330

The influence of low energy hadron interaction models in CORSIKA code on atmospheric ionization due to heavy nuclei  

NASA Astrophysics Data System (ADS)

The largest uncertainties in a numerical simulation of cosmic ray induced atmospheric cascade are due to hadron interaction models. The influence of low energy hadron interaction models in CORSIKA code on longitudinal cascade development is important. It results longitudinal cascade development, respectively energy deposit and atmospheric ionization by secondary particles. In this work are presented simulations with CORSIKA 6.990 code using GHEISHA 2000, FLUKA 2011 and QGSJET II hadron generators. The energy deposit in the atmosphere by various nuclei, namely Helium, Oxygen and Iron is calculated. The ion pair production in the atmosphere and the impact of the different shower components, precisely the electromagnetic, muon and hadron is estimated according the used hadron generators. The yield function Y for total ionization is compared for various cases. The observed differences and applications are discussed.

Mishev, A.; Y Velinov, P. I.

2013-02-01

331

Retrieval ot snow grain size and pollution amount in Polar regions from MODIS data with atmospheric correction  

NASA Astrophysics Data System (ADS)

This paper presents a new analytical algorithm to retrieve Snow Grain Size and Pollution concentration (SGSP) from satellite spectral data along with a new method of atmospheric correction in the coupled system snow-atmosphere developed in the framework of the DAMOCLES Integrated Project. The algorithm is based on a new approach to snow optics. The underlying model considers snow pack as a medium with close-packed, irregularly shaped particles. Traditionally, more idealistic models of snow as a medium with independent spherical particles have been used. The main advantage of the new algorithm is that it does not need any a priori assumptions about the snow particle shapes. Beside, the SGPS analytical retrieval provides an extremely fast satellite data processing. The original atmospheric correction procedure uses fast code for radiative transfer computation developed by authors earlier that includes bi-directionality of the snow reflection and coupluing in snow-atmosphere system. The accuracy of the SGSP with newly developed atmocpheric correction technique for the specific conditions of Polar Regions (first of all, for large sun zenith angles) was checked and has been shown to be satisfactory. The comparison with results of retrieval by known techniques demonstrates some advantages of the developed approach specifically for the Polar regions with oblique Sun illumination. The satellite data processing includes cloud masking and atmospheric correction. The data processing with regular retrieval snow grain sizes and soot pollution amount for Polar Regions from MODIS satellite data is arranged and results will be demonstrated.

Zege, E.; Katsev, I.; Prikhach, A.; Malinka, A.; Heygster, G.; Wiebe, H.

2009-04-01

332

Surfactants in the sea-surface microlayer and atmospheric aerosol around the southern region of Peninsular Malaysia.  

PubMed

This study was conducted to determine the composition of surfactants in the sea-surface microlayer (SML) and atmospheric aerosol around the southern region of the Peninsular Malaysia. Surfactants in samples taken from the SML and atmospheric aerosol were determined using a colorimetric method, as either methylene blue active substances (MBAS) or disulphine blue active substances (DBAS). Principal component analysis with multiple linear regressions (PCA-MLR), using the anion and major element composition of the aerosol samples, was used to determine possible sources of surfactants in atmospheric aerosol. The results showed that the concentrations of surfactants in the SML and atmospheric aerosol were dominated by anionic surfactants and that surfactants in aerosol were not directly correlated (p>0.05) with surfactants in the SML. Further PCA-MLR from anion and major element concentrations showed that combustion of fossil fuel and sea spray were the major contributors to surfactants in aerosol in the study area. PMID:24930738

Jaafar, Shoffian Amin; Latif, Mohd Talib; Chian, Chong Woan; Han, Wong Sook; Wahid, Nurul Bahiyah Abd; Razak, Intan Suraya; Khan, Md Firoz; Tahir, Norhayati Mohd

2014-07-15

333

Local and regional effects of large scale atmospheric circulation patterns on winter wind power output in Western Europe  

NASA Astrophysics Data System (ADS)

Recent studies (Brayshaw, 2009, Garcia-Bustamante, 2010, Garcia-Bustamante, 2013) have drawn attention to the sensitivity of wind speed distributions and likely wind energy power output in Western Europe to changes in low-frequency, large scale atmospheric circulation patterns such as the North Atlantic Oscillation (NAO). Wind speed variations and directional shifts as a function of the NAO state can be larger or smaller depending on the North Atlantic region that is considered. Wind speeds in Ireland and the UK for example are approximately 20 % higher during NAO + phases, and up to 30 % lower during NAO - phases relative to the long-term (30 year) climatological means. By contrast, in southern Europe, wind speeds are 15 % lower than average during NAO + phases and 15 % higher than average during NAO - phases. Crucially however, some regions such as Brittany in N.W. France have been identified in which there is negligible variability in wind speeds as a function of the NAO phase, as observed in the ERA-Interim 0.5 degree gridded reanalysis database. However, the magnitude of these effects on wind conditions is temporally and spatially non-stationary. As described by Comas-Bru and McDermott (2013) for temperature and precipitation, such non-stationarity is caused by the influence of two other patterns, the East Atlantic pattern, (EA), and the Scandinavian pattern, (SCA), which modulate the position of the NAO dipole. This phenomenon has also implications for wind speeds and directions, which has been assessed using the ERA-Interim reanalysis dataset and the indices obtained from the PC analysis of sea level pressure over the Atlantic region. In order to study the implications for power production, the interaction of the NAO and the other teleconnection patterns with local topography was also analysed, as well as how these interactions ultimately translate into wind power output. The objective is to have a better defined relationship between wind speed and power output at a local level and a tool that wind farm developers could use to inform site selection. A particular priority was to assess how the potential wind power outputs over a 25-30 year windfarm lifetime in less windy, but resource-stable regions, compare with those from windier but more variable sites.

Zubiate, Laura; McDermott, Frank; Sweeney, Conor; O'Malley, Mark

2014-05-01

334

Toward the Influence of Clouds on the Shortwave Radiation Budget of the Earth Atmosphere System Estimated from Satellite Data  

Microsoft Academic Search

The purpose of this paper is to investigate the influence of cloudiness on the shortwave radiation budget at the top of the atmosphere, at the surface, and, as a residual, for the atmosphere itself. The data used for this study are derived exclusively from satellite measurements. Calculations for the top of the atmosphere are based entirely on measurements of the

M. Rieland; R. Stuhlmann

1993-01-01

335

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

336

The Atmospheric Radiation Measurement Program May 2003 Intensive Operations Period Examining Aerosol Properties and Radiative Influences: Preface to Special Section  

NASA Technical Reports Server (NTRS)

Atmospheric aerosols influence climate by scattering and absorbing radiation in clear air (direct effects) and by serving as cloud condensation nuclei, modifying the microphysical properties of clouds, influencing radiation and precipitation development (indirect effects). Much of present uncertainty in forcing of climate change is due to uncertainty in the relations between aerosol microphysical and optical properties and their radiative influences (direct effects) and between microphysical properties and their ability to serve as cloud condensation nuclei at given supersaturations (indirect effects). This paper introduces a special section that reports on a field campaign conducted at the Department of Energy Atmospheric Radiation Measurement site in North Central Oklahoma in May, 2003, examining these relations using in situ airborne measurements and surface-, airborne-, and space-based remote sensing.

Ferrare, Richard; Feingold, Graham; Ghan, Steven; Ogren, John; Schmid, Beat; Schwartz, Stephen E.; Sheridan, Pat

2006-01-01

337

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

338

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

Microsoft Academic Search

(1) 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

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

2003-01-01

339

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

340

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

341

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

342

Aerosol variability and atmospheric transport in the Himalayan region from CALIOP 2007-2010 observations  

NASA Astrophysics Data System (ADS)

This work quantifies the spatial distribution of different aerosol types, their seasonal variability and sources.The analysis of four years of CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) vertically resolved aerosol data allows the identification of spatial patterns of desert dust and carbonaceous particles in different atmospheric layers. Clusters of Lagrangian back trajectories highlight the transport pathways from source regions during the dusty spring season. The analysis shows a prevalence of dust; at low heights it occurs frequently (up to 70% of available observations) and is distributed north of the Tibetan Plateau with a main contribution from the Gobi and Taklamakan deserts, and west of the Tibetan Plateau, originating from the deserts of southwest Asia and advected by the Westerlies. Above the Himalayas the dust amount is minor but still not negligible (occurrence around 20%) and mainly affected by the transport from more distant deserts sources (Sahara and Arabian Peninsula). Carbonaceous aerosol, produced mainly in northern India and eastern China, is subject to shorter-range transport and is indeed observed closer to the sources, while there is a limited amount reaching the top of the plateau. Data analysis reveals a clear seasonal variability in the frequencies of occurrence for the main aerosol types; dust is regulated principally by the monsoon dynamics, with maximal occurrence in spring. We also highlight relevant interannual differences, showing a larger presence of aerosol in the region during 2007 and 2008. The characterization of the aerosol spatial and temporal distribution in terms of observational frequency is a key piece of information that can be directly used for the evaluation of global aerosol models.

Bucci, S.; Cagnazzo, C.; Cairo, F.; Di Liberto, L.; Fierli, F.

2014-05-01

343

New Developments in the Regional Atmospheric Modeling System Suitable for Simulations of Snowpack Augmentation over Complex Terrain  

Microsoft Academic Search

The Colorado State University Regional Atmospheric Modeling System (RAMS) has been used to emulate cloud seeding operations in the Colorado Rocky Mountains for the winter of 2003-2004 in a previous study (Cotton et al. 2006). This paper documents new developments in RAMS since that study using a winter storm simulation that occurred in Colorado from 3-4 November 2003 as an

Stephen M. Saleeby; William Y. Y. Cheng; William R. Cotton

2007-01-01

344

Application of aerosol speciation data as an in situ dust proxy for validation of the Dust Regional Atmospheric Model (DREAM)  

Microsoft Academic Search

The Dust REgional Atmospheric Model (DREAM) predicts concentrations of mineral dust aerosols in time and space, but validation is challenging with current in situ particulate matter (PM) concentration measurements. Measured levels of ambient PM often contain anthropogenic components as well as windblown mineral dust. In this study, two approaches to model validation were performed with data from preexisting air quality

Patrick Shaw

2008-01-01

345

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

346

Investigating the sources of synoptic variability in atmospheric CO2 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. Geels; S. C. Doney; R. Dargaville; J. Brandt; J. H. Christensen

2004-01-01

347

The effect of large anthropogenic particulate emissions on atmospheric aerosols, deposition and bioindicators in the eastern Gulf of Finland region  

Microsoft Academic Search

The effect of the emissions from large oil shale fuelled power plants and a cement factory in Estonia on the elemental concentration of atmospheric aerosols, deposition, elemental composition of mosses and ecological effects on mosses, lichens and pine trees in the eastern Gulf of Finland region has been studied. In addition to chemical analysis, fly ash, moss and aerosol samples

Liisa Jalkanen; Ahti Mäkinen; Erkki Häsänen; Jyrki Juhanoja

2000-01-01

348

Spatial and seasonal variations of atmospheric organic carbon and elemental carbon in Pearl River Delta Region, China  

Microsoft Academic Search

The concentrations of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were investigated at eight sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of the Pearl River Delta Region (PRDR), China, during winter and summer 2002. The comparison of summer and winter results was made in order to investigate spatial and seasonal variations. PM2.5 and PM10

J. j. Cao; S. c. Lee; K. f. Ho; S. c. Zou; Kochy Fung; Y. Li; John G. Watson; Judith C. Chow

2004-01-01

349

Diurnal changes in middle atmospheric H2O and O3: Observations in the Alpine region and climate models  

Microsoft Academic Search

In this paper we investigate daily variations in middle atmospheric water vapor and ozone based on data from two ground-based microwave radiometers located in the Alpine region of Europe. Temperature data are obtained from a lidar located near the two stations and from the SABER experiment on the TIMED satellite. This unique set of observations is complemented by three different

A. Haefele; K. Hocke; N. Kämpfer; P. Keckhut; M. Marchand; S. Bekki; B. Morel; T. Egorova; E. Rozanov

2008-01-01

350

Assessing Predictability of Cotton Yields in the Southeastern United States Based on Regional Atmospheric Circulation and Surface Temperatures  

Microsoft Academic Search

The potential to predict cotton yields up to one month before planting in the southeastern United States is assessed in this research. To do this, regional atmospheric variables that are related to historic summer rainfall and cotton yields were identified. The use of simulations of those variables from a global circulation model (GCM) for estimating cotton yields was evaluated. The

Guillermo A. Baigorria; James W. Hansen; Neil Ward; James W. Jones; James J. O’Brien

2008-01-01

351

The Evaluation of the Regional Atmospheric Modeling System in the Eastern Range Dispersion Assessment System  

NASA Technical Reports Server (NTRS)

The Applied Meteorology Unit (AMU) evaluated the Regional Atmospheric Modeling System (RAMS) contained within the Eastern Range Dispersion Assessment System (ERDAS). ERDAS provides emergency response guidance for Cape Canaveral Air Force Station and Kennedy Space Center operations in the event of an accidental hazardous material release or aborted vehicle launch. The RAMS prognostic data are available to ERDAS for display and are used to initialize the 45th Space Wing/Range Safety dispersion model. Thus, the accuracy of the dispersion predictions is dependent upon the accuracy of RAMS forecasts. The RAMS evaluation consisted of an objective and subjective component for the 1999 and 2000 Florida warm seasons, and the 1999-2000 cool season. In the objective evaluation, the AMU generated model error statistics at surface and upper-level observational sites, compared RAMS errors to a coarser RAMS grid configuration, and benchmarked RAMS against the nationally-used Eta model. In the subjective evaluation, the AMU compared forecast cold fronts, low-level temperature inversions, and precipitation to observations during the 1999-2000 cool season, verified the development of the RAMS forecast east coast sea breeze during both warm seasons, and examined the RAMS daily thunderstorm initiation and precipitation patterns during the 2000 warm season. This report summarizes the objective and subjective verification for all three seasons.

Case, Jonathan

2001-01-01

352

Evaluation of the Regional Atmospheric Modeling System in the Eastern Range Dispersion Assessment System  

NASA Technical Reports Server (NTRS)

The Applied Meteorology Unit is conducting an evaluation of the Regional Atmospheric Modeling System (RAMS) contained within the Eastern Range Dispersion Assessment System (ERDAS). ERDAS provides emergency response guidance for operations at the Cape Canaveral Air Force Station and the Kennedy Space Center in the event of an accidental hazardous material release or aborted vehicle launch. The prognostic data from RAMS is available to ERDAS for display and is used to initialize the 45th Range Safety (45 SW/SE) dispersion model. Thus, the accuracy of the 45 SW/SE dispersion model is dependent upon the accuracy of RAMS forecasts. The RAMS evaluation task consists of an objective and subjective component for the Florida warm and cool seasons of 1999-2000. The objective evaluation includes gridded and point error statistics at surface and upper-level observational sites, a comparison of the model errors to a coarser grid configuration of RAMS, and a benchmark of RAMS against the widely accepted Eta model. The warm-season subjective evaluation involves a verification of the onset and movement of the Florida east coast sea breeze and RAMS forecast precipitation. This interim report provides a summary of the RAMS objective and subjective evaluation for the 1999 Florida warm season only.

Case, Jonathan

2000-01-01

353

Impact of swell on simulations using a regional atmospheric climate model  

NASA Astrophysics Data System (ADS)

When long, fast swell waves travel in approximately the same direction as the wind, the surface stress is reduced compared with under wind-sea conditions. Using measurements from the Östergarnsholm site in the Baltic Sea, new expressions of the roughness length were developed for wind sea and swell. These new expressions were implemented in the RCA3 regional climate model covering Europe. A 3-year simulation and two case studies using the wavefield from the ECMWF reanalysis (ERA-40) were analysed using the improved formulations. Wind-following swell led to a significant reduction of mean wind stress and heat fluxes. The mean surface layer wind speed was redistributed horizontally and the marine boundary layer cooled and dried slightly. This cooling was most pronounced over North Sea and the Norwegian Sea (almost 0.2 °C annually on average) whereas the drying was most pronounced over the Mediterranean Sea (almost 0.4 g kg-1). Somewhat less convective precipitation and low-level cloudiness over the sea areas were also indicated, in particular over the Mediterranean Sea. The impact on the atmosphere, however, is significantly locally greater in time and space.

Carlsson, Björn; Rutgersson, Anna; Smedman, Ann-Sofi

2009-08-01

354

Regional Sea Level Changes Projected by the NASA/GISS Atmosphere-Ocean Model  

NASA Technical Reports Server (NTRS)

Sea level has been rising for the past century, and inhabitants of the Earth's coastal regions will want to understand and predict future sea level changes. In this study we present results from new simulations of the Goddard Institute for Space Studies (GISS) global atmosphere-ocean model from 1950 to 2099. Model results are compared with observed sea level changes during the past 40 years at 17 coastal stations around the world. Using observed levels of greenhouse gases between 1950 and 1990 and a compounded 0.5% annual increase in Co2 after 1990, model projections show that global sea level measured from 1950 will rise by 61 mm in the year 2000, by 212 mm in 2050, and by 408 mm in 2089. By 2089, two thirds of the global sea level rise will be due to thermal expansion and one third will be due to ocean mass changes. The spatial distribution of sea level rise is different than that projected by rigid lid ocean models.

Russell, Gary L.; Gornitz, Vivien; Miller, James R.

1999-01-01

355

Neutral Atmospheric Influences of the Solar Proton Events in October-November 2003  

NASA Technical Reports Server (NTRS)

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 (HO(sub x)) and odd nitrogen (NO(sub y)). NO(sub x) (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 HO(sub x) 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 NO(sub y) 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 NO(sub y) constituents is the same in both hemispheres, the NO(sub y) 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.

2005-01-01

356

Ionospheric Joule Heating under the influence of Corotating Interaction Regions  

NASA Astrophysics Data System (ADS)

During the declining phase of the solar cycle, the dominant solar phenomenon affecting geomagnetic activity is coronal holes. High-speed solar winds emanate from those and when high-speed streams overtake slow-speed streams, plasma and magnetic field compressions take place. The intense compressed magnetic field regions are called corotating interaction regions, CIRs. When CIRs impinge upon the Earth's magnetosphere, they can cause geomagnetic disturbances. It has been claimed that though the average energy input rate into the magnetosphere and ionosphere during CIR intervals is not great, their long duration might cause the total energy input in the magnetosphere-ionosphere system to become even greater than during sunspot maximum conditions. The main energy input mechanism to the ionosphere is Joule heating. We have used the unique EISCAT-radar one-month measurements in March 2006 to derive the local ionospheric electric fields and Pedersen conductances. From those, the ionospheric Joule heating rates have been calculated (the possible effect of neutral winds was neglected). During the studied period, at least six several days long CIR regions were identified from the ACE-satellite data. We show that the Joule heating rate was most of the time very small and the result doesn't support the idea of large total energy input rate to the ionosphere. We also study the relationship between the Joule heating rate and the AE index as well as the local magnetic X-component. The results show that the generally used proxies are not well valid in individual events.

Aikio, Anita; Kauristie, Kirsti; Selkälä, Anne

357

Study on the Microsecond Pulse Homogeneous Dielectric Barrier Discharges in Atmospheric Air and Its Influencing Factors  

NASA Astrophysics Data System (ADS)

The homogeneous dielectric barrier discharge (DBD) in atmospheric air between two symmetric-columnar copper electrodes with epoxy plates as the dielectric barriers is generated using a ?s pulse high voltage power supply. The discharge characteristics are studied by measurement of its electrical discharge parameters and observation of its light emission phenomena, and the main discharge parameters of the homogenous DBD, such as discharge current and average discharge power, are calculated. Results show that the discharge generated is a homogeneous one with one larger single current pulse of about 2 ?s duration appearing in each voltage pulse, and its light emission is radially homogeneous and covers the entire surface of the two electrodes. The influences of applied voltage amplitude, air gap distance and barrier thickness on the transition of discharge modes are studied. With the increase of air gap distance, the discharge will transit from homogeneous mode to filamentary mode. The higher the thickness of dielectric barriers, the larger the air gap distance for generating the homogeneous discharge mode. The average discharge power increases non-linearly with increasing applied voltage amplitude, and decreases non-linearly with the increase of air gap distance and barrier thickness. In order to generate stable and homogeneous DBD with high discharge power, thin barriers distance should be used, and higher applied voltage amplitude should be applied to small air gap.

Fang, Zhi; Lei, Xiao; Cai, Lingling; Qiu, Yuchang; Edmund, Kuffel

2011-12-01

358

The influence of plants on atmospheric methane in an agriculture-dominated landscape.  

PubMed

The primary objective of this study was to clarify the influence of crop plants on atmospheric methane (CH4) in an agriculture-dominated landscape in the Upper Midwest of the United States. Measurements were carried out at two contrasting scales. At the plant scale, CH4 fluxes from soybean and corn plants were measured with a laser-based plant chamber system. At the landscape scale, the land surface flux was estimated with a modified Bowen ratio technique using measurements made on a tall tower. The chamber data revealed a diurnal pattern for the plant CH4 flux: it was positive (an emission rate of 0.4?±?0.1 nmol m(-2) s(-1), average of soybean and corn, in reference to the unit ground area) during the day, and negative (an uptake rate of -0.8?±?0.8 nmol m(-2) s(-1)) during the night. At the landscape scale, the flux was estimated to be 14.8 nmol m(-2) s(-1) at night and highly uncertain during the day, but the available references and the flux estimates from the equilibrium methods suggested that the CH4 flux during the entire observation period was similar to the estimated nighttime flux. Thus, soybean and corn plants have a negligible role in the landscape-scale CH4 budget. PMID:23612798

Zhang, Xin; Lee, Xuhui; Griffis, Timothy J; Baker, John M; Erickson, Matt D; Hu, Ning; Xiao, Wei

2014-07-01

359

The influence of plants on atmospheric methane in an agriculture-dominated landscape  

NASA Astrophysics Data System (ADS)

The primary objective of this study was to clarify the influence of crop plants on atmospheric methane (CH4) in an agriculture-dominated landscape in the Upper Midwest of the United States. Measurements were carried out at two contrasting scales. At the plant scale, CH4 fluxes from soybean and corn plants were measured with a laser-based plant chamber system. At the landscape scale, the land surface flux was estimated with a modified Bowen ratio technique using measurements made on a tall tower. The chamber data revealed a diurnal pattern for the plant CH4 flux: it was positive (an emission rate of 0.4 ± 0.1 n