The 14th Conference on Hydrology

2B.7
SGP97 HYDROLOGY EXPERIMENT REMOTE SENSING (INVITED)

Thomas J. Jackson, Beltsville, MD

Remote sensing was a critical component in the Southern Great Plains 1997 Hydrology Experiment. Primary investigations utilizing remote sensing involved soil moisture mapping, vegetation mapping, water vapor profiling, and estimating evapotranspiration. Soil moisture estimation will utilize both passive and active microwave instruments. Passive microwave remote sensing included; a truck mounted sensor system consisting of radiometers operating at 1.4, 2.65, and 4-7 GHz, a tower system that simulates the SSM/I satellites (19, 37 and 85 GHz), aircraft mappers operating at 1.4 GHz, an aircraft line profiler at 5 GHz, the SSM/I satellites, and a suite of sensors on the MIR space station (Priroda). All of the active microwave sensors were on satellite platforms; Radarsat, ERS, and JERS. The most extensive of these radar data sets was collected by Radarsat. The 1.4 GHz passive microwave mapper (Electronically scanned thinned array radiometer, ESTAR) was the critical instrument for this experiment. Data from ESTAR have been fully processed and used to produce a series of surface soil moisture maps. Quantitative evaluation of these results has shown that the soil moisture estimates are accurate within 3% volumetric soil moisture. Patterns and processes associated with precipitation and evapotranspiration are clearly evident in the images. SSM/I and MIR/Priroda data collected at shorter wavelengths and coarser resolutions have been geometrically resampled and atmospherically corrected. These data show clear correlations with the ESTAR results and surface sol moisture. It is possible to have up to 6 overpasses at different times of the day with the SSM/I satellites and diurnal patterns are clearly evident in these data sets despite their coarse resolution. Radar analyses have progressed slowly due to problems in the quality of the data provided. Vegetation mapping utilized several Landsat TM and NOAA AVHRR images. Extensive ground data collection was conducted for both land cover mapping and specific vegetation parameters, i.e. biomass. Land cover mapping at 30 m was based on a multiscene analysis of 3 Landsat TM images. All of the acceptable AVHRR images (cloud free) and the Landsat TM from July 25, 1997 were atmospherically corrected. These data sets were used to derive a high resolution NDVI (TM) and a multitemporal NDVI data set (AVHRR). Higher resolution aircraft data were collected using visible, near infrared and thermal infrared sensor systems and some processing has been completed. A focus of SGP97 is the interaction of surface soil moisture in atmospheric processes. One investigation was to collect data using the ESTAR soil moisture mapper simultaneous with the Lidar Atmospheric Sounding Experiment Instrument (LASE). Due to experiment constraints, only a limited number of these simultaneous data sets were obtained. Results from LASE demonstrated its capability to provided a two dimensional profile of atmospheric parameters. Remote sensing investigations to date in SGP97 have focused on the complete processing of the data sets that were the primary focus and serve as input to further multisensor and modeling studies. There is still much work to be done especially in the processing and analysis of higher spatial resolution data sets

The 14th Conference on Hydrology