Terrestrial
ecosystems are major sources and sinks of carbon. Quantifying their role in the
continental carbon budget requires an understanding of both fast (hours to
days) and longer-term fluxes (years to decades). The Intercontinental Chemical
Transport Experiment-North America (INTEX-NA) is a major NASA science campaign
designed to understand the transport and transformation of gases and aerosols
on transcontinental and intercontinental scales and their impact on air quality
and climate. During the INTEX-NA summer 2004 phase, regional-scale in-situ
measurements of atmospheric CO2 were made from the NASA DC-8 over
the conterminous U.S.
affording the opportunity to explore how land surface heterogeneity relates to
the airborne observations utilizing remote-sensing data products and GIS-based
methods. In this presentation, several derived products from the LANDSAT, NOAA
AVHRR, and MODIS sensors are invoked to specify spatiotemporal patterns of land
use cover and vegetation characteristics for linking the aircraft-based CO2
data with terrestrial sources of carbon. In examining the landscape mosaic
utilizing these available tools, preliminary results suggest that the lowest CO2
mixing ratios observed during the mission were over agricultural fields in IL
dominated by corn then secondarily soybean crops. Low CO2
concentrations are attributable to sampling during the peak growing season over
such C4 plants as corn having a higher photosynthetic rate via the
C4-dicarboxylic acid pathway of carbon fixation compared to C3 plants such as
soybeans. In addition to LANDSAT derived biophysical products, results from
comparisons of the CO2 observations with NDVI values derived from
MODIS data will be presented.
Author: Y. Choi, V.K. Prasad, and S.A. Vay (y dot choi at larc dot nasa dot gov)
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