Abstract:
o investigate the potential of passive microwave techniques for observing the atmosphere over land, it is important
to understand the nature of emissions from the land surface.
The heterogeneity of large-scale land surface emissions has been
cited as a major impediment in conducting observations of the atmosphere
over land. Many models, both theoretical and empirical,
have been developed to explain the surface emission with varying
degrees of success. In the past, most field-supported research in
soil observations using microwave techniques has concentrated
on lower frequencies (L-band). This paper reports on a study,
supported by field data, that seeks to improve our understanding
of surface emission at various frequencies using passive microwave
radiometers. This provides a crucial link between remote sensing
of the land surface and the atmosphere. We show that it is important
to consider shadowing associated with rough wet surfaces. By
incorporating shadowing effects, the advanced integral equation
model (AIEM) shows remarkable agreement with observations at
all frequencies and polarizations. Although the roughness parameters
obtained during our experiment correspond to very rough
conditions, by including shadowing effects the AIEM model is able
to transition from the not so rough natural condition as observed
from space to the very rough as obtained during field experiments.
