Hydrologic Evaluation of NWP-adjusted Satellite Rainfall over Mountainous Areas

Abstract:

This study investigates improvements in the use of Numerical Weather Prediction based error corrected satellite precipitation estimates (Zhang et al. 2013*1, Zhang et al. 2015*2) in flood modeling over mountainous regions. Overall, satellite rainfall estimates tend to underestimate the magnitude and spatial variability of heavy precipitation in complex topography. Gauge adjustment to these estimates are considered as a more reliable data source but it requires relatively dense surface networks, which is not typically available in mountainous regions. This study will evaluate the performance of the NWP-based error correction procedure applied on NOAA Climate Prediction Center morphing technique (CMORPH) product over three mountainous regions (Mid-Atlantic, South America and East Africa) and selected heavy precipitation events. The performance evaluation compares the NWP-adjusted CMORPH precipitation fields to the original (unadjusted) CMORPH and the gauge-adjusted CMORPH products in terms of: (i) precipitation error properties across the study domains and at different basin scales; and (ii) flood simulations driven by the different precipitation products. The results demonstrate significant improvements resulting from the NWP-adjusted CMORPH precipitation estimates in terms of both the precipitation error characteristics and associated flood simulations. These improvements are shown to be comparable to those from the post-processed gauge-adjusted CMORPH precipitation product, which is promising for advancing hydrologic uses of satellite rainfall in mountainous areas lacking ground observations.

*¹ Zhang, X. et al. 2013: Using NWP Simulations in Satellite Rainfall Estimation of Heavy Precipitation Events over Mountainous Areas. J. Hydrometeorology, 14, 1844-1858.

*² Zhang, X. et al. 2015 (accepted): Hydrologic Evaluation of NWP-adjusted CMORPH Estimates of Hurricane-induced Precipitation in Southern Appalachians. J. Hydrometeorology