## 3 Results
### Spatiotemporal Variability
#### 3.1.2 Seasonal Pattern of Precipitation in Nepal  
The annual cycles of precipitation in the gauge observed data, and all four SBP estimates in the western, central, and eastern regions of Nepal from 2015 to 2016 (only a two-year was chosen due to incomplete annual SBP datasets in 2014) are shown in Figure 4. High precipitation occurs from June-September in all three regions (Figure 4). The mean precipitation in the winter (December to February) was heavier over the western (0.74 mm/day) region than in the central (0.54 mm/day), and eastern regions (0.28 mm/day). In contrast, western Nepal was drier (4.90 mm/day) than the central (7.02 mm/day) and eastern regions (6.85 mm/day) during the other seasons (March to November) due to the influence of  
Figure 4: Monthly variation in precipitation (mm/day) over the (**a**) western (80–82°E), (**b**) central (83–85°E), and (**c**) eastern (86–88°E) regions, derived from the gauge observed data and four SBP products averaged over 2015 to 2016. Figure 3: Spatial distribution of mean precipitation (mm/day) estimated by (**a**) observations, (**b**) IMERG-UC, (**c**) GSMaP-MVK, (**d**) IMERG-C and (**e**) GSMaP-Gauge averaged over March 2014 to December 2016. The magenta and black dotted lines represent the national boundary of the country and the three subregions, respectively. summer monsoon. The precipitation in winter is primarily influenced by the westerlies system and is more pronounced in the western part of the country, while, moisture transfer from Bay of Bengal (monsoon) produces the widespread precipitation during the monsoon season (JJAS) over the country. All four SBP datasets show higher precipitation during the summer monsoon and lower precipitation in winter, with the maximum in July except for GSMaP-MVK in the eastern region (Figure 4c). The satellite-only datasets overestimated the precipitation during winter and pre-monsoon season; however, after the gauge calibration, the positive bias was reduced and is more consistent with observed datasets. Figure 4 indicates that among all four SBP datasets, the gauge calibrated datasets (i.e., IMERG-C and GSMaP-Gauge) represent well the seasonal precipitation variation across all three regions of Nepal, although they all yield underestimations. However, all four SBP datasets well captured the seasonal precipitation dynamics across the country. For a detailed analysis, the statistical metrics of the four SBP datasets from 2015 to 2016 were calculated against the station observations (Table 3). In the western region, IMERG-UC and GSMaP-MVK showed smaller MBs than their gauge-calibrated datasets, i.e., IMERG-C and GSMaP-Gauge, respectively. Nevertheless, both gauge-calibrated datasets showed better overall performance as indicated by lower RRMSE and higher R-value (Table 3). For the central region, IMERG-UC showed the smaller MBs of \(-0.93\) mm/day than that of \(-1.48\) mm/day in IMERG-C; however, both have proximal RRMSE. Meanwhile, among all SBP, GSMaP-Gauge outperformed GSMaP-MVK and both IMERG datasets as indicated by the lowest MBs and RRMSE (Table 3). Both gauge-calibrated datasets showed very similar MBs with their corresponding satellite-only in the eastern region, although gauge calibrated IMERG-C performed more consistently, with a smaller RRMSE of 0.18, followed by GSMaP-Gauge. In the whole country, among all products, IMERG-UC showed the smallest MB of \(-0.47\) mm/day and IMERG-C showed the lowest RRMSE of 0.28. It is worth noting that the positive bias in IMERG-UC and GSMaP-MVK between January and June later reduces the negative bias during July to October and shows smaller MBs among the datasets (Figures 4a-c and A1). The seasonal performances of all four SBP datasets were calculated to check the consistency in different seasons and presented in Table A1. The seasonal performance also showed that gauge calibrated datasets well represent the seasonal dynamics than satellite-only as indicated by lower MBs, RRMSE and higher R-value in Table A1.