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Behavior of multitemporal and multisensor passive microwave indices in Southern Hemisphere ecosystems
Author(s) -
Barraza Veronica,
Grings Francisco,
Ferrazzoli Paolo,
Huete Alfredo,
RestrepoCoupe Natalia,
Beringer Jason,
Van Gorsel Eva,
Karszenbaum Haydee
Publication year - 2014
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2014jg002626
Subject(s) - environmental science , eddy covariance , evapotranspiration , moderate resolution imaging spectroradiometer , vegetation (pathology) , grassland , atmospheric sciences , ecosystem , water content , deciduous , enhanced vegetation index , leaf area index , normalized difference vegetation index , satellite , ecology , geology , medicine , geotechnical engineering , pathology , engineering , biology , aerospace engineering , vegetation index
This study focused on the time series analysis of passive microwave and optical satellite data collected from six Southern Hemisphere ecosystems in Australia and Argentina. The selected ecosystems represent a wide range of land cover types, including deciduous open forest, temperate forest, tropical and semiarid savannas, and grasslands. We used two microwave indices, the frequency index (FI) and polarization index (PI), to assess the relative contributions of soil and vegetation properties (moisture and structure) to the observations. Optical‐based satellite vegetation products from the Moderate Resolution Imaging Spectroradiometer were also included to aid in the analysis. We studied the X and Ka bands of the Advanced Microwave Scanning Radiometer‐EOS and Wind Satellite, resulting in up to four observations per day (1:30, 6:00, 13:30, and 18:00 h). Both the seasonal and hourly variations of each of the indices were examined. Environmental drivers (precipitation and temperature) and eddy covariance measurements (gross ecosystem productivity and latent energy) were also analyzed. It was found that in moderately dense forests, FI was dependent on canopy properties (leaf area index and vegetation moisture). In tropical woody savannas, a significant regression ( R 2 ) was found between FI and PI with precipitation ( R 2 > 0.5) and soil moisture ( R 2 > 0.6). In the areas of semiarid savanna and grassland ecosystems, FI variations found to be significantly related to soil moisture ( R 2 > 0.7) and evapotranspiration ( R 2 > 0.5), while PI varied with vegetation phenology. Significant differences ( p < 0.01) were found among FI values calculated at the four local times.