Surface Water Hydrology
The objective of this study is to evaluate two satellite rainfall products (GPM IMERG and TRMM 3B42V7) in southern Tibet Plateau region, with special focuses on the dependence of products' performance on topography and rainfall intensities. Over 500 in-situ rain gauges constitute an unprecedentedly dense rain-gauge network over this region, and provide an exceptional resource for ground validation of satellite rainfall estimates. Our evaluation centers on the rainy season from May to October in 2014. Results indicate that: (1) GPM product outperforms TRMM at all spatial scales and elevation ranges in detecting daily rainfall; (2) Rainfall accumulation over the entire rainy season is negatively correlated with mean elevation for rain gauges and the two products, while evaluation metrics of TRMM also significantly correlate with topographic variations; (3) In terms of the ability of rainfall detection, false alarming ratio of TRMM (21%) is larger than that of GPM (14%), while missing ratio of GPM (13%) is larger than that of TRMM (9%). GPM tends to underestimate the amount of light rain events (0-1 mm/day), where the opposite (overestimation) is true for TRMM. GPM shows better detecting ability for light rainfall events but there is no detection skill for both GPM and TRMM at high elevation (>4500m) regions, which needs to be further improved. Our results highlight the superiority of GPM to TRMM in southern Tibet Plateau region, but also recommend further improvement on the rainfall retrieval algorithm is needed by considering topographical factors for both GPM and TRMM satellite rainfall products.
Hydrology Bureau, Ministry of Water Resources