The application of multi-mission satellite data assimilation for studying water storage changes over South America

M Khaki,J Awange

doi:10.1016/j.scitotenv.2018.08.079

Abstract

Constant monitoring of total water storage (TWS; surface, groundwater, and soil moisture) is essential for water management and policy decisions, especially due to the impacts of climate change and anthropogenic factors. Moreover, for most countries in Africa, Asia, and South America that depend on soil moisture and groundwater for agricultural productivity, monitoring of climate change and anthropogenic impacts on TWS becomes crucial. Hydrological models are widely being used to monitor water storage changes in various regions around the world. Such models, however, comes with uncertainties mainly due to data limitations that warrant enhancement from remotely sensed satellite products. In this study over South America, remotely sensed TWS from the Gravity Recovery And Climate Experiment (GRACE) satellite mission is used to constrain the World-Wide Water Resources Assessment (W3RA) model estimates in order to improve their reliabilities. To this end, GRACE-derived TWS and soil moisture observations from the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) and Soil Moisture and Ocean Salinity (SMOS) are assimilated into W3RA using the Ensemble Square-Root Filter (EnSRF) in order to separately analyze groundwater and soil moisture changes for the period 2002–2013. Following the assimilation analysis, Tropical Rainfall Measuring Mission (TRMM)’s rainfall data over 15 major basins of South America and El Niño/Southern Oscillation (ENSO) data are employed to demonstrate the advantages gained by the model from the assimilation of GRACE TWS and satellite soil moisture products in studying climatically induced TWS changes. From the results, it can be seen that assimilating these observations improves the performance of W3RA hydrological model. Significant improvements are also achieved as seen from increased correlations between TWS products and both precipitation and ENSO over a majority of basins. The improved knowledge of sub-surface water storages, especially groundwater and soil moisture variations, can be largely helpful for agricultural productivity over South America.

Highlights

South America, with unique ecosystems and a high biodiversity, has extreme geographic variations and diverse patterns of weather and climate that include tropical, subtropical and extratropical features (Garreaud et al, 2008)
We investigate the impacts of assimilated observations, e.g., Gravity Recovery And Climate Experiment (GRACE) total water storage (TWS) and satellite soil moisture on water storage estimates
Note that the results presented are not used for validation and only show how the assimilation results differ from the open-loop results

Summary

Introduction

South America, with unique ecosystems and a high biodiversity, has extreme geographic variations and diverse patterns of weather and climate that include tropical, subtropical and extratropical features (Garreaud et al, 2008). The. Andes mountain ranges, running along South America’s western side, plays an important role in tropical as well as subtropical latitudes by keeping dry conditions on the west and moist conditions on the east (Garreaud et al, 2008). Andes mountain ranges, running along South America’s western side, plays an important role in tropical as well as subtropical latitudes by keeping dry conditions on the west and moist conditions on the east (Garreaud et al, 2008) These climate variabilities, e.g., due to the different climatic zones across the continent and/or large-scale ocean-atmosphere phenomena, have significant impacts on the continent’s water storages (surface water, groundwater, soil moisture, and vegetation water). The study of South America’s water storage changes in light of the climate change and anthropogenic impacts is necessary for any future water use planning

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