IGCP 565 Project Workshops

IGCP 565 Workshop 4: Integration of geodetic observations and products in models of the hydrological cycle Support for water management through hydrological models and data assimilation November 21-22, 2011 Johannesburg, South Africa

New GRACE hydrology products

Laurent Longuevergne
Géosciences Rennes, Université de Rennes, FRANCE

GRACE is a young satellite, the first of its kind. Processing techniques are still evolving and improving towards better products with growing knowledge on satellite behavior, processing techniques and feedbacks from users.

An important difficulty is that GRACE is not a regular remote sensing tool, the support of its measurements are not pixels even if data may be provided on a grid. Gravity is an integrative field, the footprint of GRACE measurement is equivalent to the altitude of its orbit (~400 km, equivalent to areas ~160 000 km²). This integration radius prevents interpretation of GRACE water storage variations for small areas and leads to processing issues when computing basin-scale estimates (bias, amplitude damping of signal inside the area of interest, and leakage, sensitivity to masses outside the area of interest). With the growing interest of applying GRACE on small basins, processing methods should be adjusted and evaluated to verify applicability. A robust estimation of GRACE water storage variations relies on the i) size and shape of the area if interest and ii) the quality of a-priori information when correcting for bias/leakage.A global basin-scale basin product will be presented, with access to database accessible via a google earth interface. Several different GRACE processing techniques and products (gridded, mascon, basin-scale) will be presented and evaluated against ground measurements in the Bengale region.