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PubMedDate not supplied

A physiological basis for biosphere-atmosphere interactions in the boreal forest: an overview.

Interdisciplinary field experiments for global change research are large, intensive efforts that study the controls on fluxes of carbon, water, trace gases, and energy between terrestrial ecosystems and the atmosphere at a range of spatial scales. Forest ecophysiology can make significant contributions to such efforts by measuring, interpreting, and modeling these fluxes for the individual components of forest ecosystems and then integrating the results into holistic ecosystem process models. The Boreal Ecosystem-Atmosphere Study (BOREAS) was undertaken because of the importance of the boreal forest biome to various global change issues. The study was conducted from 1993 to 1996 at sites in Saskatchewan and Manitoba, Canada. Results have shown that physiological processes of plants in the boreal forest can have large-scale consequences. For example, the composition of tree species strongly influences flux rates, with deciduous species having much higher carbon and water fluxes than coniferous species. Additionally, physiological limitations to transpiration in boreal conifers, even when soil water is abundant, reduces latent heat flux and increases sensible heat flux over large regions. This physiological control of transpiration can increase the depth of the atmospheric boundary layer on warm spring days to a level similar to that found in desert biomes. This special issue features 10 articles that address various aspects of the physiological basis of biosphere-atmosphere interactions in the boreal forest. The articles emphasize the environmental controls on water flux, carbon flux, and ecosystem productivity.

Journal Article↗
PubMed1983

Background atmospheric 222Rn concentrations outdoors and indoors: a review.

The sources of outdoor and indoor atmospheric radon are examined. The variation of outdoor atmospheric radon with time of day, time of year, altitude and geographic location is quantitatively assessed. Average values of outdoor atmospheric radon concentrations are examined and it is estimated that the mean value for normal areas of the contiguous United States lies in the range of 100-400 pCi/m3 and is probably about 250 pCi/m3. Values for Alaska and Hawaii are an order of magnitude lower. Indoor atmospheric radon concentrations are found to vary with time of day, geographic location and story above ground.

Altitude↗
PubMed1985

Contamination of surface-water bodies after reactor accidents by the erosion of atmospherically deposited radionuclides.

Reactor safety analyses usually do not consider the population risk which might result from the contamination of surface-water bodies after reactor accidents by the erosion of atmospherically deposited radionuclides. This paper is intended to provide perspective on the reasonableness of this omission. Data are presented which are suggestive of the rates at which atmospherically deposited radionuclides might erode into surface-water bodies. These rates are used in the calculation of potential health effects resulting from surface-water contamination due to such erosion. These health effects are compared with predicted health effects due to atmospheric and terrestrial pathways after reactor accidents. The presented results support the belief that the contamination of surface-water bodies after reactor accidents by the erosion of atmospherically deposited radionuclides is not a major contributor to the risk associated with such accidents.

Accidents↗
PubMed1990

Atmospheric deposition, resuspension, and root uptake of Pu in corn and other grain-producing agroecosystems near a nuclear fuel facility.

Plutonium released to the environment may contribute to dose to humans through inhalation or ingestion of contaminated foodstuffs. Plutonium contamination of agricultural plants may result from interception and retention of atmospheric deposition, resuspension of Pu-bearing soil particles to plant surfaces, and root uptake. Plutonium on vegetation surfaces may be transferred to grain surfaces during mechanical harvesting. Data obtained from corn grown near the U.S. Department of Energy's H-Area nuclear fuel chemical separations facility on the Savannah River Site were used to estimate parameters of a simple model of Pu transport in agroecosystems. The parameter estimates for corn were compared to those previously obtained for wheat and soybeans. Despite some differences in parameter estimates among crops, the relative importances of atmospheric deposition, resuspension, and root uptake were similar among crops. For even small deposition rates, the relative importances of processes for Pu contamination of corn grain should be: transfer of atmospheric deposition from vegetation surfaces to grain surfaces during combining greater than resuspension of soil to grain surfaces greater than root uptake. Approximately 3.9 X 10(-5) of a year's atmospheric deposition is transferred to grain. Approximately 6.2 X 10(-9) of the Pu inventory in the soil is resuspended to corn grain, and a further 7.3 X 10(-10) of the soil Pu inventory is absorbed and translocated to grains.

Air Pollution, Radioactive↗
PubMed1991

Relative importance of atmospheric and root uptake pathways for 14CO2 transfer from contaminated soil to plants.

Plants growing on soil contaminated with 14C can receive the radionuclide from both direct uptake through the roots or indirect uptake from the atmosphere. The contribution from the atmosphere depends on the rate of volatilization from the soil, the size of the source area, and the meteorological dispersion conditions. An atmospheric dispersion relationship was used to calculate the air concentration for a given area source term. The air concentration was then used to estimate the flux to foliage, which was compared with direct plant uptake through the roots. The ratio of atmospheric to root uptake pathways depended on plant height and source area, exceeding unity when the fetch was greater than a few meters for bean plants, but much greater for maize. A very large fetch, greater than 1000 m, is required before a uniform specific activity throughout the local biosphere can be assumed for a soil source. This quantitative analysis describes the limitations for calculations and experiments used to define simplified transfer coefficients for 14C from soil to vegetation.

Carbon Dioxide↗
PubMed1996

Development of an atmospheric 222Rn concentration model using a hydrodynamic meteorological model: II. Three-dimensional research-purpose model.

This paper describes a new type of three-dimensional numerical model for 222Rn transport in an atmospheric boundary layer. The model is a combination of a prognostic hydrodynamic meteorological model including a turbulence closure model and an atmospheric diffusion model for 222Rn. The first part provides the second part with the meteorological conditions needed for calculations of the 222Rn transport and diffusion. The model is capable of giving consideration to horizontal source distribution, complex terrain, and non-uniform and non-steady atmosphere. The model's results were compared with 222Rn field measurements in a mountain-valley area and represented qualitatively a typical diurnal variation of the 222Rn concentration in nocturnal drainage flows. The model was also applied to the transport of 222Rn in a seacoast area. These results indicated that the model could be effective as a research tool for numerical analysis of 222Rn behavior under various atmospheric conditions.

Air Pollutants, Radioactive↗
PubMed2002

A re-evaluation of the 131I atmospheric releases from the Hanford site.

The atmospheric release of 131I from the Hanford site for the 1950's and 1960's, focused on the period of releases after the year 1950, has been re-evaluated using processing plant stack monitoring data to address a series of questions and concerns that have arisen related to the source term. Historical stack monitoring data have been used to re-assess the releases by creating either a release factor to use with the calculated plant throughput or using the stack monitoring results as the basic estimate, and the results have been verified using historical atmospheric monitoring data from a location several kilometers distant. Uncertainties in all of the historical data have been addressed in the re-assessment. Compared to the original estimate between 1950 and 1971 of 2.46 +/- 0.71 PBq, the stack monitoring results show a release of 131I to the atmosphere of 1.55 +/- 0.23 PBq. The concurrent atmospheric monitoring results imply a release of 1.75 +/- 0.11 PBq over the same period, but this result is inflated by inclusion of global fallout The total effective dose estimated to a full-time, nearby adult resident from 131I using the Heeb source term from 1950 through 1972 is 0.73 mSv; using the source term based on stack monitoring data in the Hanford Environmental Dose Reconstruction project models, it is 0.51 mSv.

Air Pollutants, Radioactive↗
PubMed2002

Solar variability, coupling between atmospheric layers and climate change.

One of the enduring puzzles of atmospheric physics is the extent to which changes in the Sun can influence the behaviour of the climate system. While solar-flux changes tend to be relatively modest, a number of observations of atmospheric parameters indicates a disproportionately large response. Global-scale models of the coupled middle and upper atmosphere have provided new insights into some of the mechanisms that may be responsible for the amplification of the solar signal. In particular, modification of the transport of heat and chemicals such as ozone by waves during periods of solar activity has been shown to make an important contribution to the climate of the stratosphere and mesosphere. In this paper, a review of some of the recent advances in understanding the coupling between atmospheric layers and how this work relates to Sun-weather relations and climate change in the troposphere will be presented, along with a discussion of some of the challenges that remain.

Journal Article↗
PubMed2006

Nonlinear waves in the solar atmosphere.

In this paper, we give a brief review of the contemporary theory of nonlinear waves in the solar atmosphere. The choice of topics reflects personal interests of the author. Historically the theory of nonlinear waves was first applied to the solar atmosphere to explain the chromospheric and coronal heating. It was assumed that the turbulent motion in the solar convective zone excites sound waves that propagate upwards. Due to nonlinearity these waves steepen and form shocks. The wave energy dissipates in these shocks thus heating the corona. We give a brief description of propagation and damping of nonlinear sound waves in the stratified solar atmosphere, and point out that, at present, the acoustic heating remains the most popular theory of heating the lower chromosphere. Then we extend the analysis to nonlinear slow magnetosonic waves in coronal plumes and loops, and discuss its implications for interpretation of observational results. The next topic of interest is the propagation of nonlinear waves in a magnetically structured atmosphere. Here, we restrict our analysis to slow sausage waves in magnetic tubes and discuss properties of solitary waves described by the Leibovich-Roberts equation. We conclude with the discussion of nonlinear theory of slow resonant layers, and its possible application to helioseismology.

Journal Article↗
PubMed2001

Statistics of atmospheric correlations.

For a large class of quantum systems, the statistical properties of their spectrum show remarkable agreement with random matrix predictions. Recent advances show that the scope of random matrix theory is much wider. In this work, we show that the random matrix approach can be beneficially applied to a completely different classical domain, namely, to the empirical correlation matrices obtained from the analysis of the basic atmospheric parameters that characterize the state of atmosphere. We show that the spectrum of atmospheric correlation matrices satisfy the random matrix prescription. In particular, the eigenmodes of the atmospheric empirical correlation matrices that have physical significance are marked by deviations from the eigenvector distribution.

Journal Article↗
PubMed1992

Effect of atmospheric pressure on maize root growth and ethylene production.

Maize (Zea mays) seedlings were exposed to elevated atmospheric pressures while growing in moist sand in open plastic envelopes to evaluate the effects of directly applied atmospheric pressure on ethylene production and root growth. Effects were evaluated after 24 h. The threshold pressures necessary to promote ethylene production and decrease root elongation were about 600 and 400 kPa, respectively. Direct atmospheric pressure, at levels up to 300 kPa, mimicked the control decrease in root diameter and increased diameter only slightly at 500 to 1200 kPa. In contrast, in previous work it was shown that physical impedance resulting from compression of the growth medium by external application of 100 kPa increased the ethylene production rate 4-fold and the root diameter 7-fold while reducing elongation 75% in 10 h. The relative insensitivity of roots to direct atmospheric pressure suggests that they perceive physical impedance, achieved experimentally by compressing the growth medium, via a surface mechanism rather than via a pressure-sensing mechanism.

Journal Article↗
PubMedDate not supplied

An atmospheric visual analysis and exploration system.

Meteorological research involves the analysis of multi-field, multi-scale, and multi-source data sets. In order to better understand these data sets, models and measurements at different resolutions must be analyzed. Unfortunately, traditional atmospheric visualization systems only provide tools to view a limited number of variables and small segments of the data. These tools are often restricted to two-dimensional contour or vector plots or three-dimensional isosurfaces. The meteorologist must mentally synthesize the data from multiple plots to glean the information needed to produce a coherent picture of the weather phenomenon of interest. In order to provide better tools to meteorologists and reduce system limitations, we have designed an integrated atmospheric visual analysis and exploration system for interactive analysis of weather data sets. Our system allows for the integrated visualization of 1D, 2D, and 3D atmospheric data sets in common meteorological grid structures and utilizes a variety of rendering techniques. These tools provide meteorologists with new abilities to analyze their data and answer questions on regions of interest, ranging from physics-based atmospheric rendering to illustrative rendering containing particles and glyphs. In this paper, we will discuss the use and performance of our visual analysis for two important meteorological applications. The first application is warm rain formation in small cumulus clouds. Here, our three-dimensional, interactive visualization of modeled drop trajectories within spatially correlated fields from a cloud simulation has provided researchers with new insight. Our second application is improving and validating severe storm models, specifically the Weather Research and Forecasting (WRF) model. This is done through correlative visualization of WRF model and experimental Doppler storm data.

Journal Article↗
PubMed1994

The relationship between ward atmosphere and staff attitude to treatment in psychiatric in-patient units.

The relationship between staff ratings of ward atmosphere, their attitude to treatment, and their direction of interest was investigated in four psychiatric in-patient units. Two general admission units, one intensive care unit, and one regional secure unit were studied. Fifty-eight psychiatric nurses rated their units using the Ward Atmosphere Scale-Form R (WAS) and expressed their direction of interest and attitude to treatment on the Direction of Interest Questionnaire and the Attitude to Treatment Questionnaire from the Claybury Selection Battery. An equamax factor analysis of the WAS subscales produced three clear factors. These factors, together with the original WAS subscales, were used to compare staff ratings of their units and to correlate with their attitude to treatment and direction of interest. A multivariate analysis of variance showed that staff ratings of ward atmosphere varied according to their unit and their attitude to treatment, but not with their direction of interest. Significant relationships were also found between staff characteristics, such as age, qualifications and experience, and ratings of ward atmosphere.

Adult↗
PubMed2002

Air-snow interactions and atmospheric chemistry.

The presence of snow greatly perturbs the composition of near-surface polar air, and the higher concentrations of hydroxyl radicals (OH) observed result in a greater oxidative capacity of the lower atmosphere. Emissions of nitrogen oxides, nitrous acid, light aldehydes, acetone, and molecular halogens have also been detected. Photolysis of nitrate ions contained in the snow appears to play an important role in creating these perturbations. OH formed in the snowpack can oxidize organic matter and halide ions in the snow, producing carbonyl compounds and halogens that are released to the atmosphere or incorporated into snow crystals. These reactions modify the composition of the snow, of the interstitial air, and of the overlying atmosphere. Reconstructing the composition of past atmospheres from ice-core analyses may therefore require complex corrections and modeling for reactive species.

Journal Article↗
PubMed1996

Absorption of Solar Energy in the Atmosphere: Discrepancy Between Model and Observations

An atmospheric general circulation model, which assimilates data from daily observations of temperature, humidity, wind, and sea-level air pressure, was compared with a set of observations that combines satellite and ground-based measurements of solar flux. The comparison reveals that the model underestimates by 25 to 30 watts per square meter the amount of solar energy absorbed by Earth's atmosphere. Contrary to some recent reports, clouds have little or no overall effect on atmospheric absorption, a consistent feature of both the observations and the model. Of several variables considered, water vapor appears to be the dominant influence on atmospheric absorption.

Journal Article↗
PubMed1997

Modeling the Exchanges of Energy, Water, and Carbon Between Continents and the Atmosphere

Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited. Some modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.

Journal Article↗
PubMed1997

The atmospheric aerosol-forming potential of whole gasoline vapor.

A series of sunlight-irradiated, smog-chamber experiments confirmed that the atmospheric organic aerosol formation potential of whole gasoline vapor cna be accounted for solely in terms of the aromatic fraction of the fuel. The total amount of secondary organic aerosol produced from the atmospheric oxidation of whole gasoline vapor can be represented as the sum of the contributions of the individual aromatic molecular constituents of the fuel. The urban atmospheric, anthropogenic hydrocarbon profile is approximated well by evaporated whole gasoline, and thus these results suggest that it is possible to model atmospheric secondary organic aerosol formation.

Aerosols↗
PubMed2000

Atmospheric influence of Earth's earliest sulfur cycle

Mass-independent isotopic signatures for delta(33)S, delta(34)S, and delta(36)S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions. These atmospheric reactions also played a role in determining the oxidation state of sulfur, implying that atmospheric oxygen partial pressures were low and that the roles of oxidative weathering and of microbial oxidation and reduction of sulfur were minimal. Atmospheric fractionation processes should be considered in the use of sulfur isotopes to study the onset and consequences of microbial fractionation processes in Earth's early history.

Journal Article↗