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NASA NTRS1984

Global tropospheric chemistry: A plan for action

Prompted by an increasing awareness of the influence of human activity on the chemistry of the global troposphere, a panel was formed to (1) assess the requirement for a global study of the chemistry of the troposphere; (2) develop a scientific strategy for a comprehensive plan taking into account the existing and projected programs of the government; (3) assess the requirements of a global study in terms of theoretical knowledge, numerical modeling, instrumentation, observing platforms, ground-level observational techniques, and other related needs; and (4) outline the appropriate sequence and coordination required to achieve the most effective utilization of available resources. Part 1 presents a coordinated national blueprint for scientific investigations of biogeochemical cycles in the global troposphere. part 2 presents much of the background information of the present knowledge and gaps in the understanding of tropospheric chemical cycles and processes from which the proposed program was developed.

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NASA NTRS1984

Future remote sensing instruments and systems

Scientific requirements for terrestrial remote-sensing satellites in the 1990's and instrument packages to meet them are discussed, summarizing the results of a preliminary study conducted by the NASA System Z Science and Mission Requirements Working Group. Major questions regarding atmospheric chemistry and circulation, global climate, ocean dynamics, biogeochemical cycles, ice-budget and hydrological cycles, continental geology, biomass dynamics, and land cover and use are listed along with the observational frequency and resolution necessary to answer them, and an instrument use matrix is presented. Large essentially permanent man-tended arrays of instruments serving multiple functions and linked to the users via advanced information-processing networks and (possibly including expert systems) are recommended, and a basic payload and two supplemental packages are outlined.

Broome, D. R., Jr.↗

NASA NTRS1983

Characterization of terrestrial ecosystems for biogeochemical studies using remote sensing

Work is in progress to estimate leaf area index (LAI) of temperate closed canopy coniferous forests using transects in Oregon and California. This variable will be measured using remote sensing techniques including correlations of ground dimensional analysis with linear waveband combinations. LAI will be related to important biological variables such as net primary productivity, biomass, and biogenic gas emission fluxes. The spatial variation in LAI, when coupled with species composition, will be used in part to describe the spatial variation and temporal dynamics of biogeochemical cycling.

Peterson, D. L.↗

NASA NTRS1985

Modeling the controls of forest productivity using canopy variables

A framework is presented by which a generalized, canopy-driven model of biogeochemical cycling in forest ecosystems may be produced. Recent research results demonstrating relationships between canopy characteristics and important ecosystem processes are used to support this approach. Most relationships hold across species groups and suggest that identification of species may not be crucial. Linking this type of model to remote sensing will depend on developing the capability to measure a few key morphological and chemical parameters of whole forest canopies by reflectance characteristics.

Aber, J. D.↗

NASA NTRS1986

Data needs and data bases for climate studies

Two complementary global digital data bases of vegetation and land use, compiled at 1 deg resolution from published sources for use in climate studies, are discussed. The data bases were implemented, in several individually tailored formulations, in a series of climate related applications including: land-surface prescriptions in three-dimensional general circulation models, global biogeochemical cycles (CO2, methane), critical-area mapping for satellite monitoring of land-cover change, and large-scale remote sensing of surface reflectance. The climate applications are discussed with reference to data needs, and data availability from traditional and remote sensing sources.

Matthews, Elaine↗

NASA NTRS1987

N2O fluxes at the soil-atmosphere interface in various ecosystems and the global N2O budget

The overall purpose of this research task is to study the effects of soil properties and ecosystem variables on N2O exchanges at the soil-atmosphere interface, and to assess their effects on the globle N2O budget. Experimental procedures are implemented in various sites to measure the source/sink relations of N2O at the soil-atmosphere interface over prolonged periods of time as part of the research of biogeochemical cycling in terrestrial ecosystems. A data-base for establishing quantitative correlations between N2O fluxes and soil and environmental parameters that are of potential use for remote sensing, is being developed.

Banin, Amos↗

NASA NTRS1988

Ocean alkalinity and the Cretaceous/Tertiary boundary

A biogeochemical cycle model resolving ocean carbon and alkalinity content is applied to the Maestrichtian and Danian. The model computes oceanic concentrations and distributions of Ca(2+), Mg(2+), and Sigma-CO2. From these values an atmospheric pCO2 value is calculated, which is used to estimate rates of terrestrial weathering of calcite, dolomite, and calcium and magnesium silicates. Metamorphism of carbonate rocks and the subsequent outgassing of CO2 to the atmosphere are parameterized in terms of carbonate rock reservoir sizes, total land area, and a measure of overall tectonic activity, the sea-floor generation rate. The ocean carbon reservoir computed by the model is used with Deep Sea Drilling Project (DSDP) C-13 data to estimate organic detrital fluxes under a variety of ocean mixing rate assumptions. Using Redfield ratios, the biogenic detrital flux estimate is used to partition the ocean carbon and alkalinity reservoirs between the mixed layer and deep ocean. The calcite flux estimate and carbonate ion concentrations are used to determine the rate of biologically mediated CaCO3 titration. Oceanic productivity was severely limited for approximately 500 kyr following the K/T boundary resulting in significant increases in total ocean alkalinity. As productivity returned to the ocean, excess carbon and alkalinity was removed from the ocean as CaCO3. Model runs indicate that this resulted in a transient imbalance in the other direction. Ocean chemistry returned to near-equilibrium by about 64 mybp.

Caldeira, K. G.↗

NASA NTRS1988

Oceanographic wide field sensor

The Oceanographic Wide Field Sensor (SeaWiFS) science project will provide measurements of ocean color from space to which will support research into: (1) the character of ocean physical and biological processes; (2) to assess the global oceanic biomass; and (3) to better understand the role of oceanic processes in modulating the Earth's biogeochemical cycles, including the CO2 cycle as it is affected by fossil fuel combustion. The present work extends previous work to study the feasibility of an ocean color mission using the proposed compact Wide-Field Sensor (SeaWiFS) and the EOSAT Corporation's LANDSAT-6 satellite. A Phase A study was conducted which defines a NASA Facility Data System and accompanying Science Program for the EOSAT Company's commercial ocean color instrument called SeaWiFS to be launched on board LANDSAT-6 in 1991.

Kirk, R. G.↗

NASA NTRS1990

Earth observing satellite: Understanding the Earth as a system

There is now a plan for global studies which include two very large efforts. One is the International Geosphere/Biosphere Program (IGBP) sponsored by the International Council of Scientific Unions. The other initiative is Mission to Planet Earth, an unbrella program for doing three kinds of space missions. The major one is the Earth Observation Satellite (EOS). EOS is large polar orbiting satellites with heavy payloads. Two will be placed in orbit by NASA, one by the Japanese and one or two by ESA. The overall mission measurement objectives of EOS are summarized: (1) the global distribution of energy input to and energy output from the Earth; (2) the structure, state variables, composition, and dynamics of the atmosphere from the ground to the mesopause; (3) the physical and biological structure, state, composition, and dynamics of the land surface, including terrestrial and inland water ecosystems; (4) the rates, important sources and sinks, and key components and processes of the Earth's biogeochemical cycles; (5) the circulation, surface temperature, wind stress, sea state, and the biological activity of the oceans; (6) the extent, type, state, elevation, roughness, and dynamics of glaciers, ice sheets, snow and sea ice, and the liquid equivalent of snow in the global cryosphere; (7) the global rates, amounts, and distribution of precipitation; and (8) the dynamic motions of the Earth (geophysics) as a whole, including both rotational dynamics and the kinematic motions of the tectonic plates.

Soffen, Gerald↗

NASA NTRS1990

Field testing of thermal canopy models in a spruce-fir forest

Recent advances in remote sensing technology allow the use of the thermal infrared region to gain information about vegetative surfaces. Extending existing models to account for thermal radiance transfers within rough forest canopies is of paramount importance. This is so since all processes of interest in the physical climate system and biogeochemical cycles are thermally mediated. Model validation experiments were conducted at a well established boreal forest; northern hardwood forest ecotone research site located in central Maine. Data was collected to allow spatial and temporal validation of thermal models. Emphasis was placed primarily upon enhancing submodels of stomatal behavior, and secondarily upon enhancing boundary layer resistance submodels and accounting for thermal storage in soil and vegetation.

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NASA NTRS1991

Biomass burning studies and the International Global Atmospheric Chemistry (IGAC) project

IGAC is an ambitious, decade-long and global research initiative concerned with major research challenges in the field of atmospheric chemistry; its chemists and ecosystem biologists are addressing the problems associated with global biomass burning (BMB). Among IGAC's goals is the achievement of a fundamental understanding of the natural and anthropogenic processes determining changes in atmospheric composition and chemistry, in order to allow century-long predictions. IGAC's studies have been organized into 'foci', encompassing the marine, tropical, polar, boreal, and midlatitude areas, as well as their global composite interactions. Attention is to be given to the effects of BMB on biogeochemical cycles.

Prinn, Ronald G.↗

NASA NTRS1992

Data management for JGOFS: Theory and design

The Joint Global Ocean Flux Study (JGOFS), currently being organized under the auspices of the Scientific Committee for Ocean Research (SCOR), is intended to be a decade long internationally coordinated program. The main goal of JGOFS is to determine and understand on a global scale the processes controlling the time-varying fluxes of carbon and associated biogenic elements in the ocean and to evaluate the related exchanges with the atmosphere, sea floor and continental boundaries. 'A long-term goal of JGOFS will be to establish strategies for observing, on long time scales, changes in ocean biogeochemical cycles in relation to climate change'. Participation from a large number of U.S. and foreign institutions is expected. JGOFS investigators have begun a set of time-series measurements and global surveys of a wide variety of biological, chemical and physical quantities, detailed process-oriented studies, satellite observations of ocean color and wind stress and modeling of the bio-geochemical processes. These experiments will generate data in amounts unprecedented in the biological and chemical communities; rapid and effortless exchange of these data will be important to the success of JGOFS.

Flierl, Glenn R.↗

NASA NTRS1993

Measurements of nitric acid, carboxylic acids, and selected aerosol species for the NASA/GTE Pacific Mission - West (PEM-WEST)

The research investigation funded through this grant to the University of New Hampshire was performed during a major field expedition conducted by the NASA Tropospheric Chemistry Program. The NASA Global Tropospheric Experiment (GTE) executed an airborne science mission (PEM-WEST A) aboard the NASA Ames DC-8 over the Pacific Ocean during Sep./Oct. 1981. The atmosphere over the central Pacific Ocean is the only major region in the Northern Hemisphere that is relatively free from direct anthropogenic influence. Thus, this environment is ideally suited to study the natural biogeochemical cycles of carbon, nitrogen, ozone, sulfur, and aerosols without serious confounding problems related to anthropogenic emissions. Asian sources account for about 17 percent of the global budgets of nitrogen oxides (NO(x)) and sulfur dioxide (SO2). The Pacific Rim region therefore provides the opportunity to study the anthropogenic impact on natural atmospheric chemical cycles. The PEM-WEST A flights were focused on contrasting the chemistry of 'clean' air over the central Pacific with anthropogenically impacted air advected off the Asian continent. The principal objectives of PEM-WEST A were to investigate the atmospheric chemistry of ozone (O3) and its precursors, and to study important aspects of the atmospheric sulfur cycle over the western Pacific Ocean. Measurements conducted by the University of New Hampshire contributed directly to both of these objectives. Subsequent PEM-WEST field missions are planned by GTE in the mid-1990's to contrast atmospheric chemistry documented during PEM-WEST A with other time periods. This report presents preliminary findings from the PEM-WEST A field mission. Data interpretation is currently ongoing with the goal of manuscript submission of scientific results to a special issue of the Journal of Geophysical Research-Atmospheres in Feb. 1994. The reader is strongly encouraged to review this suite of profession articles to appreciate the overall scientific findings and benefits of the PEM-WEST A field mission.

Talbot, Robert W.↗

NASA NTRS1990

Precambrian evolution of the climate system

This paper presents a new examination of the biogeochemical cycles of carbon as they may have changed between an Archean Earth deficient in land, sedimentary rocks, and biological activity, and a Proterozoic Earth much like the modern Earth, but lacking terrestrial life and carbonate-secreting plankton. Results of a numerical simulation of this transition show how increasing biological activity could have drawn down atmospheric carbon dioxide by extracting sedimentary organic carbon from the system. Increasing area of continents could further have drawn down carbon dioxide by encouraging the accumulation of carbonate sediments. An attempt to develop a numerical simulation of the carbon cycles of the Precambrian raises questions about sources and sinks of marine carbon and alkalinity on a world without continents. More information is needed about sea-floor weathering processes.

Walker, James C. G.↗

NASA NTRS1985

Verification of vegetation maps made from remote sensing

Verification of vegetation maps is discussed, including a map of the vegetation of the Mt. Washington area of New Hampshire. This area was chosen to determine the accuracy of mapping by remote sensing at the boundary between two major forest biomass. Verification was carried out by ground observation and through the use of low altitude 70 mm infrared photographs. Two verification sampling schemes were used: a point method and a transect method. Resulting confidence limits gave an area weighted sampling accuracy of 89 pct. Spatial patterns in terrestrial vegetation must be understood in order to choose appropriate spatial resolutions required for remote sensing instruments, and to relate vegetation dynamics to climate dynamics and biogeochemical cycles.

Botkin, Daniel B.↗

NASA NTRS1985

Methyl halide production associated with kelp

Methyl halides (MeX) are important trace constituents of the atmosphere because they, mostly MeCl, have a major impact on the atmospheric ozone layer. Also, MeCl may account for 5 pct. of the total Cl budget and MeI may have a central role in the biogeochemical cycling of iodine. High MeI concentrations were found in seawater from kelp beds and it has been suggested that MeI is produced by kelps and that MeI and MeBr along with numerous other halocarbons were released by non-kelp marine macroalgae. The objective was to determine if kelps (and other seaweeds) are sources of MeX and to assess their contribution to the estimated global source strength (EGSS) of MeX. Although the production of MeX appears to be associated with kelp, microbes involved with kelp degradation also produce MeX. Microbial MeX production may be of global significance. The microbial MeX production potential, assuming annual kelp production equals kelp degradation and 100 pct. conversion of kelp halides to MeX, is approx. 2 x the EGSS. This is not achieved but indicates that microbial production of MeX may be of global significance.

Dastoor, Minoo N.↗

NASA NTRS1985

Seasonal C-13 variations of methane from an anoxic marine sediment

Recent analyses of glacial ice suggest that the atmospheric concentration of methane has doubled in the last several hundred years, presumably due to anthropogenic perturbations of the relevant biogeochemical cycles. In principal, carbon isotopic measurements of atmospheric methane would provide information concerning changes in the sources and sinks of methane. The isotopic composition of methane is dependent on the source of the methane carbon, the mechanism of methane synthesis, and the degree and mode of oxidation which the methane has experienced. Unfortunately, few carbon isotopic measurements of atmospheric variations have been reported, so conclusions about temporal isotopic variations cannot be made. Also, before isotopic measurements of atmospheric methane can be used to identify changes in methane isotopic composition from different sources must be obtained. Methane bubbles from the anoxic sediments of Cape Lookout Bight, NC exhibit seasonal C-13 variations. The C-13 values ranged from -58 in August to -64 in the winter months with the evolution of the C-13 enriched gas occurring during periods of peak methane production. Even though a few intramolecular C-13 measurements of the pore water acetate have been made (methyl group, -26 per mil; carbonyl, -6 per mil), it is not clear how the acetate fermentation pathway affects the methane C-13/C-12 composition.

Blair, Neal↗

NASA NTRS1985

A GIS approach to conducting biogeochemical research in wetlands

A project was initiated to develop an environmental data base to address spatial aspects of both biogeochemical cycling and resource management in wetlands. Specific goals are to make regional methane flux estimates and site specific water level predictions based on man controlled water releases within a wetland study area. The project will contribute to the understanding of the Earth's biosphere through its examination of the spatial variability of methane emissions. Although wetlands are thought to be one of the primary sources for release of methane to the atmosphere, little is known about the spatial variability of methane flux. Only through a spatial analysis of methane flux rates and the environmental factors which influence such rates can reliable regional and global methane emissions be calculated. Data will be correlated and studied from Landsat 4 instruments, from a ground survey of water level recorders, precipitation recorders, evaporation pans, and supplemental gauges, and from flood gate water release; and regional methane flux estimates will be made.

Brannon, David P.↗