**6. Conclusions**

In this study, the gridded precipitation products (GB and SB products) were evaluated against the reference data during 1979–2017 and 2003–2017 periods on annual, winter, and summer monsoon scale by using multiple statistical methods in order to gain an understanding for the potential of Gauge and satellite based precipitation products over the Punjab province, Pakistan. The major outcomes of the study can be summarized as follows.

The result indicated that the temporal magnitude in all of the precipitation products was different and deviated up to 100–200 mm with overall spatial pattern of underestimation (GB products) and overestimation (SB products) from north to south gradient as compared with in-situ measurements. Though, the GPCC and TRMM products outperformed the relative GPPs and showed the best agreement against the reference data in terms of higher R2 values of <sup>≥</sup> 0.90 and lower values of estimated RME ≤ 25% at annual and summer monsoon seasons. However, CRU performed better during winter monsoon season with the estimated ME of −25.08 (−20.49%) and R-squared value of 0.91 as compared with the reference data during the period 1979–2017. All of the GB products performed better in terms of lower values of estimated ME during winter following by annual and summer monsoon season. However, SB products showed better performance during annual scale following by summer and winter monsoon period. Overall, the degree of accuracy of GB products with observed precipitation decreases with the increase in the magnitude of precipitation and vice versa for SB precipitation products

The Mann–Kendall results indicated that, the annual observed precipitation revealed the insignificant positive trend during the periods 1979–2017 and 2003–2017 with the rate of 1.12 and 5.5 mm/decade, respectively. However, the abrupt transition analysis indicates the multiple turning points in the reference data series during the period 1980–2005 with major abrupt changes were detected during the period of 1984–1985 (negative), 1988–1989 (positive), 1998–1999 (negative), and 2005–2006 (positive). The large inter-annual variability in the reference data series were well captured by GPCC and TRMM products during the period 1979–2017 and 2003–2017, respectively. In view of significant extent of biases in the GPPs, the estimated correction factor during annual, winter and summer monsoon seasons for each GPP can be useful for future hydro-climate projects over the Punjab region. The range of discrepancies in precipitation products pointed out the further improvement of GPPs for the enhancement of its accuracy over the arid and semi-arid regions, like Punjab Province. Moreover, the degree of accuracy in precipitation products varies with time and resolution; therefore, products should be assessed at different spatio-temporal scale.

**Author Contributions:** X.L. and Y.C. designed and supervised this study. Z.N. carried out the research and wrote the manuscript. N.N. and R.G. assisted in formatting and editing the manuscript. A.E. helped in data processing and analysis. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study is supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, Grant No. XDA20100104, and the National Natural Science Foundation of China through Grant No. 41871280.

**Acknowledgments:** The authors acknowledge the climate agencies efforts for providing the GPPs datasets. We also used in-situ data from the Pakistan Meteorological Department (PMD). The authors cordially appreciate the PMD, whose efforts made it possible for us to access the data. We also recognize the support of the CAS-TWAS president fellowship program for PhD.

**Conflicts of Interest:** The authors declare no conflict of interest.
