Abstract
Airborne SAR data gathered by the NASA/JPL three-frequency, polarimetric, radar system in winter, spring, and summer over the Bonanza Creek Experimental Forest, near Fairbanks, AK, are compared to estimates of whole-tree aboveground dry biomass from 21 forest stands and two clear-cuts. While C-band radar backscatter shows little sensitivity to biomass, L- and P-band radar backscatter increase by more than 6 dB when biomass increases from 5 to 200 tons/ha. Using second-order polynomial regressions, biomass values are predicted from the radar at L- and P-band and compared to actual biomass values. At P-band HV-polarization, the error in predicted biomass is about 30% of the actual biomass. When HV-, HH-, and VV-polarization are used together in the regression, the error in predicted biomass is about 20%. Errors obtained using L-band data are a few percents larger. These errors are caused by uncertainties in actual stand biomass estimates, significant inner-stand spatial variations in biomass, unusual conditions of forest stands following natural disturbances, along with interactions of the radar signals with a complex three-dimensional structure of the canopy. Multiple incidence angle data reveal that the incidence angle /spl theta//sub i/ of the radar illumination is also a factor influencing the retrieval of biomass, even at HV-polarization, when /spl theta//sub i/>50/spl deg/ or /spl theta//sub i/<25/spl deg/. Finally, the radar response of the forest-and thereby the regression curves for biomass retrieval-are dependent on the seasonal and environmental conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Highlights
Recent experiments using airbome active microwave data indicate forest biomass could be quantified remotely [1]-[3]
The results show that u O is positively correlated with aboveground biomass
This study suggest synthetic-aperture radar (SAR) operating at long radar wavelengths have potential for mapping aboveground biomass of boreal forests in interior Alaska, a variable of prime importance to carbon cycling investigations, ecosystem studies and forest management applications
Summary
Recent experiments using airbome active microwave data indicate forest biomass could be quantified remotely [1]-[3]. The results provide evidence that inversion algorithms could be developed for predicting forest biomass from long wavelength SAR data. This work was camed out at the Jet Propulsion Laboratory, Califomia Institute of Technology, under contract with the National Aeronautics and Space Administration This communication describes algorithms to estimate vertical distribution of stratospheric aerosol extinction based on the solar occultation measurements of the improved limb atmospheric spectrometer (ILAS), which will be installed on the advanced earth observing satellite (ADEOS) in 1996. The vertical structure inversion provides profiles of local atmospheric extinction from ILAS transmittance data. This is followed by a species separation step that decomposes the obtained total extinction into each component of the atmospheric constituents, i.e., air molecules and aerosols. It is shown that the retrieved pressure profiles from ILAS oxygen A-band analysis are available to improve and simplify the aerosol retrieval [6]
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