Preliminary Evaluation of GPM-IMERG Rainfall Estimates Over Three Distinct Climate Zones With APHRODITE

Evaluation of Global Precipitation Measurement-Integrated Multi-satellitE Retrieval for GPM (GPM-IMERG) final precipitation product is performed over Japan, Nepal, and Philippines regions against further improved APHRODITE-2 V1801R1 product. The evolution is carried out for nearly two consecutive years 2014-2015. Various qualitative and quantitative statistical indices such as mean bias, root-mean-square error, correlation coefficient, false alarming ratio, and probability of detection are considered to evaluate GPM-IMERG precipitation estimates with APHRODITE-2. Intraseasonal variability of two products is shown to explore the seasonal dependency of GPM-IMERG performance. The performance of GPM-IMERG research product with respect to rainfall intensity is shown by the cumulative probability distribution of target and reference data sets. Percentile-based statistics is implemented for evaluating the advantages of GPM-IMERG over Tropical Rainfall Measuring Mission-3B42 while detecting the light and heavy rainfall events during wet/dry seasons. The overall performance of GPM-IMERG seems to be good over Japan followed by Philippines and Nepal regions. This feature is clearly evidenced in terms of mean bias, root-mean-square error, and correlation magnitudes over three regions. GPM-IMERG shows ability to follow the intraseasonal variability as shown by APHRODITE-2 product with minor differences observed in precipitation maximum values during rainy season. Good agreement is seen between GPM-IMERG and APHRODITE-2 at different rainfall intensities except underestimation during heavy rainfall events. GPM-IMERG seems to be improved in detecting light/heavy rainfall event magnitude than TRM-3B42. However, the performance of both data sets encountered clear dependency on seasons.