The effect of changing environmental conditions on microwave signatures of forest ecosystems: Preliminary results of the March 1988 Alaskan aircraft SAR experiment

In preparation for the first European Space Agency (ESA) Remote Sensing (ERS-1) mission, a series of multitemporal, multifrequency, multipolariz-ation aircraft synthetic aperture radar (SAR) data sets were acquired over the Bonanza Creek Experimental Forest near Fairbanks, Alaska in March, 1988. P-, L-and C-band data were acquired with the NASA/JPL Airborne SAR on five different days over a period of two weeks. The airborne data were augmented with intensive ground calibration data as well as detailed, simultaneous in situ measurements of the geometric, dielectric and moisture properties of the snow and forest canopy. During the time period over which the SAR data were collected, the environmental conditions changed significantly; temperatures ranged from unseasonably warm (1 to 9°C) to well below freezing (–8 to–15°C), and the moisture content of the snow and trees changed from a liquid to a frozen state. The SAR data clearly indicate the radar return is sensitive to these changing environmental factors and preliminary analysis of the L-band SAR data shows a 0.4 to 5.8 dB increase (depending on polarization and canopy type) in the radar cross section of the forest stands under the warm conditions relative to the cold. These SAR observations are consistent with predictions from a theoretical scattering model. These preliminary results are presented to illustrate the opportunity afforded by the ERS-1 SAR to monitor temporal changes in forest ecosystems. © 1990 Taylor & Francis Ltd.

Duke Scholars

Author Norman L. Christensen Environmental Sciences and Policy