Seasonal variability of land water storage in South América using GRACE data

TOCHO CLAUDIA; GUARRACINO LUIS; MONACHESI LEONARDO; CESANELLI ANDRÉS; ANTICO PABLO

Buenos Aires

Congreso; International Association of Geodesy (IAG) 2009 Scientific Assembly "Geodesy for Planet Earth"; 2009

International Association of Geodesy (IAG)

Variations of water storage at regional and continental scales are not known with sufficient accuracy due to the lack of appropriated direct observations and limitations in global hydrological  models. An alternative method to quantify variations of water storage is based on satellite observations of Earth?s time variable gravity field from the Gravity Recovery and Climate Experiment (GRACE). GRACE is the first satellite remote-sensing mission which is directly applicable to the assessment of land water storage under all types of terrestrial conditions, and represents a promising contribution to global hydrology. Since the GRACE satellite mission was launched in 2002, time variable components of the Earth´s gravity field have been provided. Each gravity field solution is derived in term of Stokes´ coefficients of a spherical harmonic expansion. The gravity field varies with time due to mass redistribution on both solid Earth and fluid envelopes (atmosphere, oceans, ice caps and water reservoirs). Satellite measurements of the time-variable gravity can be used to study a wide variety of geophysical problems that involve mass redistribution like continental water storage, global sea level, polar ice sheet mass balances, etc. The objective of the present study is to analyze seasonal variability of water land storage in South America from GRACE data. High precision estimations of temporal variations in the Earth´s gravity are obtained using monthly Release-04 (RL04) gravity field coefficients provided by the Center for Space Research (CSR). Water mass anomalies, as equivalent height of water, are calculated based on the direct relationship between gravity and mass. To remove the effects of the noise observed in the equivalent-water thickness solutions at high harmonic degrees an optimized smoothing technique is applied. Finally, temporal distributions of water land storage are compared to monthly mean precipitation data extracted from global climate models in order to identify, correlate, and understand patterns of water movement at continental scale in South America.