**5. Conclusions**

This study attempted to evaluate the latest four SBP products in the southern slope of central Himalayas, Nepal and compare both satellite-only (IMERG-UC and GSMaP-MVK) and gaugecalibrated (IMERG-C and GSMaP-Gauge) products for their accuracy and discrepancies with 388 gauges measurements from March 2014 to December 2016. Conventional statistical metrics and categorical scores were used to quantify the performances of these SBP products.

Precipitation estimates differ widely between SBP products, depending on the season and location. The GSMaP-Gauge dataset was more consistent at representing the spatial pattern of observed precipitation followed by IMERG-UC, GSMaP-MVK, and IMERG-C. However, all four datasets can capture the seasonal precipitation dynamics across the country. Among them, IMERG-C and GSMaP-Gauge presented more consistent seasonal dynamics range (in terms of RRMSE and R) with the gauge observations than the satellite-only datasets. Even though all four SBP products underestimate the gauge-observed precipitation across Nepal; both gauge-calibrated SBP datasets performed better (lower RRMSE, higher R) than the satellite-only datasets. IMERG-C and GSMaP-Gauge showed similar errors (MB and RRMSE) in Nepal, although both had discrepancies in capturing the precipitation patterns. For instance, GSMaP-Gauge presented a more reasonable spatial distribution, while IMERG-C moderately reproduced the evident elevation-dependent pattern of precipitation as revealed by gauge observations, i.e., increasing precipitation with an increasing elevation below 2000 m and then decreasing above 2000 m.

When selecting 1 mm/day as the threshold defining a daily rainfall event, benefit from merging daily gauge-based NOAA/CPC analysis data, GSMaP-Gauge performed best (with higher POD) for detecting gauge observed precipitation events among four datasets. Gauge observations indicated that more high-intensity precipitation extreme events (95th percentile) occur in regions with an elevation below 2500 m. All four SBP datasets underestimated the total frequency of extreme precipitation events across the country. It is worth noting that IMERG-UC performed much better in presenting the occurrence of extreme events than other products especially in regions below 1500 m, suggesting that sometimes the calibration may skew some important signals contained in the satellite-only product.

The present work addresses the lack of systematic evaluation of the latest two SBP products in the southern slope of central Himalayas, Nepal. This evaluation provides a statistical basis and allows rigorous data selection in meteorological, hydrological, glaciological, and disaster-related studies within the study region. We recommend that further evaluation of SBP products based on the weather characteristics over the complex terrain may provide useful information to algorithm developers and data users.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2072-4292/12/11/1836/s1, Table S1: Location and data availability of selected rain gauge station.

**Author Contributions:** Conceptualization and methodology, Y.C. and S.S.; software and validation, S.S., X.Z., X.H.; formal analysis, S.S. and N.K.; resources, Y.C.; data curation, S.S.; writing—original draft preparation, S.S.; writing—review and editing all authors; supervision and funding acquisition, Y.C., K.Y. All authors have read and agreed to the published version of the manuscript.

**Funding:** National Natural Science Foundation of China (41871280, 41471286), the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (2019QZKK0206), and the 13th five-year Informatization Plan of Chinese Academy of Sciences (XXH13505-06) supported this study.

**Acknowledgments:** The authors are thankful to the scientists at the NASA and JAXA, who were responsible for the development of the IMERG and GSMaP products. The DHM, Evk2-CNR committee (Pyramid station) is also acknowledged for providing the rain-gauge precipitation datasets. The authors would like to thank three anonymous reviewers for their insightful comments and suggestion, which helped to improve the manuscript.

**Conflicts of Interest:** There is no conflict of interest among the authors.
