HR: 16:00h
AN: H34A-03    [Abstracts]
TI: Time-Evolution Statistics of GPS Surface Reflectivity Following Precipitation in Desert and Cultivated Environments
AU: * Grant, M S
EM: Michael.S.Grant@nasa.gov
AF: NASA Langley Research Center, Mail Stop 472, Hampton, VA 23681 United States
AU: Katzberg, S J
EM: Stephen.J.Katzberg@nasa.gov
AF: South Carolina State University, SCSU, Orangeburg, SC 29116 United States
AB: Use of the L-band Global Positioning System (GPS) forward-reflected signal for remote sensing of surface moisture shows promise as a new and complimentary method to more developed backscattering and emission techniques. The ratio of reflected-to-direct GPS signals provides a measurement of surface reflectivity. At present, due to the relatively high incident angles, embedded range code, and forward reflection of the signal, the reflected GPS signal statistical characteristics as a function of soil type, vegetation, precipitation amount, and drying time are not well known. The objective of this analysis is to examine the effect of precipitation amount and surface characteristics on the distribution of GPS surface reflectivity as a function of time following rain events over both a desert environment in New Mexico and cultivated areas near Ames, Iowa (Soil Moisture Experiments 2002). Reflectivity data from New Mexico and Iowa were collected using an airborne GPS Remote Sensor (GPSRS)/reflectometer. Iowa data sets include measurements over both sparsely and heavily vegetated areas. Reflectivity measurements from Iowa are examined with respect to precipitation amount, vegetation coverage (i.e. leaf-area-index), and measured surface soil moisture. A fuller understanding of variations in GPS reflectivity distribution and parametric form due to precipitation and drying time, over various soil/terrain types, is necessary for the development of GPS-based soil moisture retrieval algorithms that are specific to the surface type and environmental conditions.
UR: http://centauri.larc.nasa.gov/gps/home.htm
DE: 1866 Soil moisture
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2005 Joint Assembly