Advantages of GSMaP Data for Multi-Timescale Precipitation Estimation in Luzon

The Global Precipitation Measurement Mission (GPM) provides two different sources of post-real-time satellite-based rainfall estimates, including the Integrated Multi-satellitE Retrievals for GPM Final Run (herein IMERG-F) and Global Satellite Mapping of Precipitation-Gauge (herein GSMaP-G). However, relative to IMERG-F, GSMaP-G has been less thoroughly evaluated in the context of studying rainfall variations over Luzon, Philippines. Using rain-gauge observations over Luzon as a reference base, this study aimed to clarify if GSMaP-G v07 is more capable than IMERG-F v06 in regard to representing rainfall variations over Luzon at multiple timescales (including intraseasonal, annual, and interannual). The results revealed that both IMERG-F and GSMaP-G performed better in regard to depicting the temporal phase evolution for the wet season rainfall than they did for the dry season rainfall for Luzon. However, relative to IMERG-F, GSMaP-G exhibited better performance in most examined features, including (a) the detection of temporal variations (both phase and amplitude) of rainfall on the intraseasonal, annual, and interannual timescales; (b) the representation of spatial differences with more rainfall occurring from April to September for western Luzon and from October to March for eastern Luzon; (c) the detection of occurrence of rainfall events at various intensities. The analysis also demonstrates that the difference between the performance of IMERG-F and GSMaP-G in regard to quantitative rainfall estimation is larger during the wet season than it is during the dry season. The possible cause for their performance differences over Luzon is the differences in the gauge-adjustment method and the biases in its pre-non-gauge-adjusted product.