Validating the Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage dataset using Terra MODIS NDVI anomaly.

Sachin Malhari Bhere; Shweta Panaskar; Raju Narwade; Karthik Nagarajan

Abstract

The Gravity Recovery and Climate Experiment (GRACE) is the advance tool for mapping the changes in the gravitation field of the earth. The satellite launches in 2002 and the follow off mission is in 2016. The gravitational changes of the earth are downscaled into the changes in the mass with the different algorithm by three institutions. Further the mass anomaly is converted into the equivalent water thickness of the terrestrial water storage which comprises of different water component which can be used and modelled for different application. The objective of this paper is to validate the GRACE data for soil moisture and land use analysis using MODIS NDVI anomaly. For calculating NDVI index Moderate resolution imaging spectroradiometer (MODIS) vegetation index product is used. NDVI is used to determine the condition of healthy vegetation. It ranges from -1 to 1. These values represent the health of vegetation. Values near one represent the healthy vegetation. It is calculated by taking ratios of spectral reflectance of NIR and Red spectrum of electromagnetic wave. The study shows the GRACE includes all aspects of water storage deficit including groundwater and soil moisture which important for region like Western Ghat as many farmers depends on ground water resources like well and borewells. NDVI sometimes fails to show the monsoon drought condition but it can be used to for characterization of post monsoon condition as it shows the vegetation health index. The study significant correlation with GRACE and NDVI, one should adopt these indices for characterization of Vegetation, soil moisture and canopy cover.