## 5 Discussion  
Spatial and temporal precipitation data acquisition is highly important for the regional climate studies as well as for the management of water resources and agriculture of the concerned regions. With the advancement in geo-information and remote sensing technologies, this paves the way to acquire gridded data free of cost on a different time and scale. However, the reliability and accuracy of the data must be quantified against the in-situ records at the regional scale [77]. The current study provides a comprehensive assessment of GB and SB precipitation products against the reference records over the Punjab province during annual, winter, and summer monsoon from the period of 1979-2017 and 2003-2017, respectively. Moreover, the changes in trends and detection of abrupt turning point in temporal data series of products were evaluated and compared with the reference data series. In addition, the correction factor for each product was introduced to minimize the percentage of error in the respective products. The results indicate that the spatial and temporal performance of GPCC and TRMM precipitation product outperformed the other corresponding products in terms of statistical measurements (high value of CC and R\({}^{2}\) with lower value of ME and RMSD) during the annual and summer monsoon season  
Figure 10: Comparison of Abrupt change detection in (**A**) (GB) and (**B**) (SB) precipitation products and reference data by using SQMK test (95% confidence Interval). during 1979-2017 and 2003-2017, respectively. However, CRU performed better during winter estimates when compared with reference data during the whole study period. Moreover, the range of deviation among different precipitation products underestimated with different magnitude as compared with the reference data. We found large uncertainties in the magnitude and temporal variability among different products. The magnitude range of deviation was up 100-200 mm among different products within the same category and with reference data. The results of deviation are associated with the findings of [48], who reviewed the 22 global precipitation products and was reported the magnitude of deviation up to 300 mm. All of the selected products estimated the higher amount of annual precipitation in the northern Punjab and exhibited the similar pattern from north to south gradient with the range of 1500-15 mm. However, the spatial deviation was more pronounced in the northern side as compared with the central and southern part of the study region. Moreover, the pattern of underestimation was more pronounced in the GB products as compared with SB products. One of the possible explanations of underestimation is due to lower pixel resolution of GB products over the study region [28]. Furthermore, the results showed that all of the GB products performed better in terms of lower values of ME during winter following by annual and summer monsoon season. However, the SB products showed better performance during annual scale following by summer and winter monsoon period. Overall, the agreement of GB products with observed precipitation decreases with the increase in the amount of precipitation and vice versa for SB precipitation products. The performance of SB precipitation products is well concomitant with the findings of [28; 78], who reported the better performance of SB products to capture the higher magnitude of precipitation and less accurate for low precipitation events over different regions of Pakistan. In contrast, [79] revealed the better performance of SB products with less rainfall events over northwest Himalaya regions. The extent of deviation in product similarity can possibly be attributed to multiple factors, which include difference in study region, elevation, land use and land cover change [28]. The pattern similarity by using Taylor diagram indicates the better performance of GPCC and TRMM products during annual and summer monsoon seasons in terms of higher CC of around 95% during the whole study period.