A first approach to global runoff simulation using satellite rainfall estimation

Motivated by the recent increasing availability of global remote sensing data for estimating precipitation and describing land surface characteristics, this note reports an approximate assessment of quasi- global runoff computed by incorporating satellite rainfall data and other remote sensing products in a relatively simple rainfall- runoff simulation approach: the Natural Resources Conservation Service ( NRCS) runoff curve number ( CN) method. Using an antecedent precipitation index ( API) as a proxy of antecedent moisture conditions, this note estimates time- varying NRCS- CN values determined by the 5- day normalized API. Driven by a multiyear ( 1998 - 2006) Tropical Rainfall Measuring Mission Multi- satellite Precipitation Analysis, quasi- global runoff was retrospectively simulated with the NRCS- CN method and compared to Global Runoff Data Centre data at global and catchment scales. Results demonstrated the potential for using this simple method when diagnosing runoff values from satellite rainfall for the globe and for medium to large river basins. This work was done with the simple NRCS- CN method as a first- cut approach to understanding the challenges that lie ahead in advancing the satellite- based inference of global runoff. We expect that the successes and limitations revealed in this study will lay the basis for applying more advanced methods to capture the dynamic variability of the global hydrologic process for global runoff monitoring in real time. The essential ingredient in this work is the use of global satellite- based rainfall estimation.