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Biography:
Research Area:
"Determination of Dynamic Soil-Vegetation-Detritus Interactions with
MODIS Instrument Observations"
My research has mostly focussed on the development of Vegetation Indices
for seasonal and inter-annual vegetation monitoring; climatic - and anthropogenic-
induced change detection; land cover assessment; and the coupling of Vegetation Indices
to vegetation biophysical parameters. There are two important issues to consider in
the extraction of vegetation information from satellite imagery. The first concerns
standardization of all extraneous variables in the remotely sensed signal, namely atmospheric
variability, presence of clouds and sub-pixel clouds, sun angle and sensor view angle
variations, and instrument calibration drift and filter degradation. The MODIS
Vegetation Index products consist of cloud-free and atmospherically corrected, 16 day and
monthly gridded maps, composited to a nadir view angle and standard sun angle at 250m, 1km,
and 0.25° pixel resolutions. We have designed the vegetation index products to
take full advantage of the MODIS atmosphere correction, cloud mask, and BRDF products. The
second issue to consider for quantitative information extraction concerns the
inherent mixing of the vegetation signal with that of the canopy background and
non-photosynthetic components within a canopy such as woody material, senesced vegetation ,
and litter. These influences are considered within the vegetation index equations
themselves, mainly through the application of basic vegetation canopy radiant
transfer theory and empirical observations. As a result, the Vegetation Index products have
been developed for both continuity purposes with the AVHRR-normalized difference
vegetation index (NDVI) as well as for improved, enhanced capabilities with the enhanced
vegetation index (EVI). Examples of the vegetation index products can be found at
http://gaea.fcr.arizona.edu.
Field Work:
We have accumulated extensive ground- and airborne radiometry
observations as well as satellite data over a diverse set of land
cover conditions. Data include SeaWiFS, Landsat TM, AVHRR, ASAS,
AVIRIS, and biophysical sampling of vegetation and soils.
- Monsoon'90 Hydrology experiment at Walnut Gulch, Arizona (TM, AVIRIS,
ASAS, SPOT, AVHRR,...)
- Hydrologic Atmospheric Pilot Experiment in the Sahel (HAPEX-Sahel)
experiment,
1992
- Smoke, Clouds, and Radiation Experiment (SCAR-B) in Brazil, 1995
- Chile transect from hyperarid, arid, semi-arid, subhumid, humid
rainforest (1996).
- U.S. - Mexico Border Region (1992 seasonal TM data set)
- SALSA experiment in Arizona (1995 - 2000)
- Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), 1999 -
2003
- Maricopa Agriculture Center in Arizona (TM, AVIRIS, ATLAS, SPOT,..),
1985-
- La Jornada Experimental Range (1997, 1999)
- Konza Prairie (1999)
- Mongolia field campaign in Mandolgovi (1997 - 2002)
- Railroad Playa, Ivanpah calibration sites (1999)
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