3.2.1. Statistical Scores

Figure 6 illustrates the spatial distributions of the POD, FAR and ACC values in the four SBP datasets at each station across the country. These values were calculated based on daily precipitation data. POD is above 70% at most of the stations in GSMaP-Gauge, followed by 40–80% in IMERG product, and 40–60% in GSMaP-MVK. Therefore, the daily gauge-calibrated GSMaP-Gauge outperformed the other three datasets to detect gauge precipitation events. It is worth noting that POD is higher in GSMaP-Gauge compared to GSMaP-MVK, while similar performances are found in both IMERG datasets. The GSMaP-Gauge datasets were calibrated based on daily scale NOAA/CPC data; therefore, both the amount and the occurrence were corrected, while IMERG-C datasets were corrected based on monthly scale GPCC data, thus only the precipitation amounts were adjusted. This may be the reason for similar POD performance in two IMERG products. All four datasets showed similar FAR distributions, with the best performance in mid-elevation areas and poor performance in high-elevation areas, revealing that the error was lower when the precipitation amount was higher. ACC exceeded 70% in all four SBP datasets at most of the selected stations across the country (Figure 6).

POD, FAR, and ACC were also calculated for the three different elevation intervals (Table 6). The daily gauge-calibrated GSMaP-Gauge performed fair well at detecting the gauge observed precipitation events with PODs of 0.73, 0.71 and 0.66 for elevations below 1500 m, 1500–2500 m, and above 2500 m, respectively. Notably, differences in the ACC and FAR scores were nominal (Table 6). In general, all four datasets performed with acceptable scores (ACC higher than 0.70) in detecting both the precipitation and no-precipitation events across the country.

**Figure 6.** SBP performance at individual station measurements expressed in the form of the panel (**a**) POD, panel (**b**) FAR, and panel (**c**) ACC in % at each station during the study period. The black and blue lines show the national boundary and 3000 m elevation contour, respectively.

**Table 6.** Performances of the four SBP datasets expressed by POD, FAR and ACC at each station, averaged over three elevation intervals (<1500 m, 1500–2500 m and > 2500 m), as well as for the whole study region during the study period. A threshold value of 1 mm/day was selected to separate precipitation and no-precipitation events. Bold font indicates the dataset with the best performance for a given metric.

