Monitoring of soil wetness variation using satellite microwave observations from the direct broadcast receiving system at IMD

Abstract

Satellite remote sensing of soil related content for hydrological purposes have been considerably studied and developed over past three decades. This soil estimation by means of remote sensing depends upon the measurements of electromagnetic energy that has either been reflected or emitted from the soil surface and are accessible to remote sensing through measurements at the thermal infrared and microwave wavelengths. Recent advances in remote sensing, in the last few years, have shown that microwave techniques have the ability to measure soil moisture/wetness monitoring under a variety of topographic and vegetation cover conditions quantitatively. This is due to the all-weather and all-time capability of these data, as well as to their high sensitivity to water content in the soil. This study utilize the approach to investigate the soil wetness variation over the Jammu and Kashmir(J&K), which experienced one of the worst floods in the past 60 years, during first week of September 2014, due to unprecedented and intense rains. The Soil Wetness Estimation (SWE) has been computed from the data acquired by real time direct broadcast (DB) receiving system installed at three places of India Meteorological Department (IMD) using microwave radiometer AMSU (Advanced Microwave Sounding Unit), flying aboard NOAA (National Oceanic and Atmospheric Administration) polar satellites. A multi-temporal analysis of AMSU channel 15 (at 89 GHz) and channel 1 (at 23 GHz) have been used to find the variation of SWE. In the present analysis, the proposed SWE indicator has been very well brought out the soil wetness changes specifically for the flood event which could give some indication of early 'signals' of an anomalous value of soil water content. In order to improve the forecast capabilities over the tropics, SWE approach is found to be promising for operational use.