Multiscale evaluation of satellite precipitation products: Effective resolution of IMERG

Abstract

Satellite precipitation products are essential for global analysis of water cycle dynamics as well as for regional analyses in regions where no ground observations are available. For any climatic or hydrologic application, it is important to know down to which scale a gridded satellite precipitation product can accurately resolve the spatial patterns of precipitation. This scale, which we call “effective resolution”, is a complex combination of the instrument resolution (especially so for multisensor products such as IMERG), the multi-sensor retrieval or merging algorithm, and the type of the precipitating system, and it can differ substantially from the grid size of the satellite product. Here, we use a wavelet-based framework to quantitatively define the effective resolution of the IMERG multi-satellite product by comparison with the MRMS ground radar product at the hourly time scale over the continental United States. Our findings show that the effective resolution varies across geographical areas, seasons and types of precipitation and provide insight for the use of those products in hydrologic applications and for algorithmic improvements.