Time-variations of equivalent water heights from Grace Mission and in-situ river stages in the Amazon basin [Variações temporais do equivalente à altura d';água obtidas da missão grace e da altura d';água in-situ nos rios da bacia amazônica]

作者：de Almeida F G V; Calmant S; Seyler F; Ramillien G; Blitzkow D; Matos A C C; Silva J S

来源：Acta Amazonica, 2012, 42(1): 125-134.

• Amazon basin
• Grace satellite
• Hydrology
• Spatial geodesy

Gravity Recovery and Climate Experiment (GRACE) mission is dedicated to measuring temporal variations of the Earth';s gravity field. In this study, the Stokes coefficients made available by Groupe de Recherche en Géodésie Spatiale (GRGS) at a 10- day interval were converted into equivalent water height (EWH) for a ~4-year period in the Amazon basin (from July-2002 to May-2006). The seasonal amplitudes of EWH signal are the largest on the surface of Earth and reach ~ 1250mm at that basin';s center. Error budget represents ~130 mm of EWH, including formal errors on Stokes coefficient, leakage errors (12 ~ 21 mm) and spectrum truncation (10 ~ 15 mm). Comparison between in situ river level time series measured at 233 groundbased hydrometric stations (HS) in the Amazon basin and vertically-integrated EWH derived from GRACE is carried out in this paper. Although EWH and HS measure different water bodies, in most of the cases a high correlation (up to ~80%) is detected between the HS series and EWH series at the same site. This correlation allows adjusting linear relationships between in situ and GRACE-based series for the major tributaries of the Amazon river. The regression coefficients decrease from up to down stream along the rivers reaching the theoretical value 1 at the Amazon';s mouth in the Atlantic Ocean. The variation of the regression coefficients versus the distance from estuary is analysed for the largest rivers in the basin. In a second step, a classification of the proportionality between in situ and GRACE time-series is proposed.