(3) Variation with Rainfall Thresholds

Figure 11 compares the performance of hourly precipitation detection among the five SPPs by different rainfall magnitude. Each of the three categorical metrics has been sequentially calculated when hourly rainfall exceeds 0.1, 1, 5, 10, and 15 mm. As seem from Figure 11a, the PODs of the five SPPs have all decreased steadily with increasing hourly rainfall thresholds before plunging to nearly 0 at the threshold of 15 mm/hour. In general, the five SPPs do not differ much in their PODs across the entire range of hourly rainfall thresholds. The PODs of the two near-real-time IMERG products are consistently less than those of the TMPA products. The PODs of 3B42RT have actually remained at or nearly the top across the rainfall thresholds.

**Figure 11.** Comparison of the changes in categorical evaluation metrics (April to October) with hourly rainfall thresholds among five SPPs: (**a**) *POD*; (**b**) *FAR*; and (**c**) *CSI*.

As seem from Figure 11b, the FARs of all five SPPs tend to rise with increasing rainfall thresholds. The TMPA products have consistently yielded higher FARs than the IMERG products over the entire range of rainfall thresholds. The more comprehensive CSI values have concluded much similar hourly rainfall detection performance among the SPPs across the rainfall thresholds, with IMERG\_F staying at or near the top most of the time (Figure 11c).
