How Well Do Multisatellite Products Capture the Space-Time Dynamics of Precipitation? Part I: Five Products Assessed via a Wavenumber-Frequency Decomposition

As more global satellite-derived precipitation products become available, it is imperative to evaluate them more carefully for providing guidance as to how well precipitation space-time features are captured for use in hydrologic modeling, climate studies, and other applications. Here we propose a space-time Fourier spectral analysis and define a suite of metrics that evaluate the spatial organization of storm systems, the propagation speed and direction of precipitation features, and the space-time scales at which a satellite product reproduces the variability of a reference ground-truth'' product (effective resolution''). Wedemonstrate how the methodology relates to our physical intuition using the case study of a storm system with rich space-time structure. We then evaluate five high-resolution multisatellite products (CMORPH, GSMaP, IMERG-Early, IMERG-Final, and PERSIANN-CCS) over a period of 2 years over the southeastern United States. All five satellite products show generally consistent space-time power spectral density when compared to a reference ground gauge-radar dataset (GV-MRMS), revealing agreement in terms of average morphology and dynamics of precipitation systems. However, a deficit of spectral power at wavelengths shorter than 200 km and periods shorter than 4 h reveals that all satellite products are excessively ``smooth.'' The products also show low levels of spectral coherence with the gauge-radar reference at these fine scales, revealing discrepancies in capturing the location and timing of precipitation features. From the space-time spectral coherence, the IMERG-Final product shows superior ability in resolving the spacetime dynamics of precipitation down to 200-km and 4-h scales compared to the other products.

Automated summary

This study evaluates five high-resolution multisatellite precipitation products using space-time Fourier spectral analysis, revealing that all products show deficiencies in capturing the spatial organization and dynamics of precipitation systems, appearing excessively "smooth." IMERG-Final product demonstrates superior ability in resolving the space-time dynamics of precipitation at scales down to 200 km and 4 hours.