SOIL-MOISTURE ESTIMATION UNDER A VEGETATION COVER - COMBINED ACTIVE-PASSIVE MICROWAVE REMOTE-SENSING APPROACH

Authors
Citation
Ns. Chauhan, SOIL-MOISTURE ESTIMATION UNDER A VEGETATION COVER - COMBINED ACTIVE-PASSIVE MICROWAVE REMOTE-SENSING APPROACH, International journal of remote sensing, 18(5), 1997, pp. 1079-1097
Citations number
29
Categorie Soggetti
Photographic Tecnology","Remote Sensing
ISSN journal
01431161
Volume
18
Issue
5
Year of publication
1997
Pages
1079 - 1097
Database
ISI
SICI code
0143-1161(1997)18:5<1079:SEUAVC>2.0.ZU;2-E
Abstract
Data gathered during the NASA sponsored Multisensor Aircraft Campaign Hydrology (MACHYDRO) experiment in central Pennsylvania (U.S.A.) in Ju ly, 1990 have been analysed to study the combined use of active and pa ssive microwave sensors for estimating soil moisture from vegetated ar eas. These data sets were obtained during an eleven-day period with NA SA's Airborne Synthetic Aperture Radar (AIRSAR), and Push-Broom Microw ave Radiometer (PBMR) over an instrumented watershed, which included a gricultural fields with a number of different crop covers. Simultaneou s ground truth measurements were also made in order to characterize th e state of vegetation and soil moisture under a variety of meteorologi cal conditions. Various multi-sensor techniques are currently under in vestigation to improve the accuracy of remote sensing estimates of the soil moisture in the presence of vegetation and surface roughness con ditions using these data sets. One such algorithm involving combinatio n of active and passive microwave sensors is presented here, and is ap plied to representative corn fields in the Mahantango watershed that w as the focus of study during the MACHYDRO experiment. In this algorith m, a simple emission model is inverted to obtain Fresnel reflectivity in terms of ground and vegetation parameters. Since Fresnel reflectivi ty depends on soil dielectric constant, soil moisture is determined fr om reflectivity using dielectric-soil moisture relations. The algorith m requires brightness temperature, vegetation and ground parameters as the input parameters. The former is measured by a passive microwave t echnique and the later two are estimated by using active microwave tec hniques. The soil moisture estimates obtained by this combined use of active and passive microwave remote sensing techniques, show an excell ent agreement with the in situ soil moisture measurements made during the MACHYDRO experiment.