## 3 Results
### Elevation Impact Analyses  
All gauges in the TP were rearranged in Figures 6-8 according to their elevations ranging from 1200 m-5135 m. A comparison of CC, POD and FAR for IMERG and 3B42V7 along elevated sites is presented at the three-hourly scale in Figure 6. All of the metrics showed similar trends for both satellite products as elevations increased from 1200 m-5135 m. No significant CC differences occurred in the two satellite products along the elevated stations. Furthermore, there was no apparent difference for POD and FAR values between IMERG and 3B42V7 products with increasing elevations. 3B42V7, however, showed slightly higher POD for the elevation above 4200 m and obviously higher FAR for the elevation below 3000 m. This implied that regions characterized by higher altitudes (e.g., >4200 m) might still be problematic for the Day-1 multisatellite retrieval in GPM over the TP. Note that potential errors originating from different places under various rainfall regimes might influence the statistical results. Figure 7 shows daily rainfall regimes, i.e., maximum, mean and conditional mean values, with elevations ranging from 1200 m-5135 m in the warm season of 2014 over the TP. The conditional mean rainfall is defined as the average value among the detected rainfall days within the warm season of 2014 at each station. There was a gradually downward trend for the daily rainfall, including maximum, mean and conditional mean values, below the elevation of 3000 m. When the elevation exceeds 3000 m, no clear trend was detected for each daily rainfall regime. Regarding the daily mean rainfall, high consistency was observed among IMERG, 3B42V7 products and gauge measurements for various elevations. However, there were large biases between IMERG and 3B42V7 in terms of daily maximum and conditional mean rain rates at elevations higher than 3000 m. This phenomenon was more significant in the conditional mean value due to the removal of  
Figure 6: Elevation-related analyses of three-hourly rainfall indices in the warm season of 2014: (**a–c**) the Correlation Coefficients (CC), Probability Of Detection (POD) and False Alarm Ratio (FAR) between satellite data and gauge observations as the elevation increases. Note that the grey square stands for 258 gauges recorded according to elevation; the red lines stand for IMERG estimates; the blue lines stand for 3B42V7 products and the comparison was calculated at 3-hourly scale. multiple zero rainfall events. Compared to 3B42V7, IMERG showed higher biases regarding maximum daily rainfall at elevations of approximately 4200 m and slightly higher positive errors in the conditional mean daily estimates at most sites. Rain probability is a description of the likelihood of rainfall within a specified period and location. We define the warm season of 2014 as the specified period and calculate the percentages of rainfall days during this period at each station. Along the elevated stations, there was no noticeable trend for the raining probability (Figure 8a). Significantly positive errors were observed from 3B42V7 estimates for raining probability, indicating that 3B42V7 overestimated rainfall events along the elevated gauges. The classification of raining intensities (i.e., 0-10 mm/d for light rainfall, 10-25 mm/d for moderate rainfall and >25 mm/d for heavy rainfall) is primarily from [9; 36]. Less significant biases were found in IMERG for light rainfall (Figure 8b). Compared to light and heavy rainfall, moderate rainfall derived from the IMERG and 3B42V7 products matched the gauge measurements well along the elevated sites (Figure 8c). In addition, light rainfall events were far more frequent than moderate and heavy rainfall events for both satellite products, where the proportion of heavy rainfall was relatively low, with the mean value lower than 5%. This means that the sample sizes to verify heavy rainfall events from a single warm season are possibly small, which may introduce a potential uncertainty for satellite rainfall estimates.