Satellite Rainfall Estimation: The Role of Integrated (Hydrologic) Validation

Abstract:

As satellites enable high space-time resolution global mapping of precipitation in near real time, the demand for space-based products is ever increasing. So is the range of applications that include warnings against rainfall-induced hazards as well as resources monitoring. All these activities require some level of validation. In many places, where there is no alternative to satellite products, a simple naïve validation is sufficient. The users decide if the product helps them fulfill their responsibility. A more rigorous validation (evaluation) of the products is possible where an independent reference exists. If the focus is on flood prediction, the reference may include streamflow observations and hydrologic rainfall-runoff models. A key evaluation issue is satellite product uncertainty and performance characterization across scales and within a hydrologic context. The author demonstrates that simple examination of hydrograph at the outlet of a basin can be misleading. Using data collected during the Iowa Flood Studies Ground Validation field campaign, he presents a spatio-dynamic framework as a more comprehensive tool for product evaluation. He also demonstrates how hydrologic validation can help in specifying scale-dependent accuracy requirements for space-based products. Different applications may lead to different requirements.