## 5 Conclusions and Recommendations  
After four years of operation of the GPM, it was proven to be a good successor to the TRMM, offering new opportunities for meteorological studies and hydrological applications, especially in mountainous areas. In this study, we investigated the performance of the latest GPM IMERG V5 and GSMaP V7 satellite precipitation products over the TP. Firstly, the statistical assessment of the accuracy of the satellite products was performed against gridded gauge-based data. Then, their hydrological simulation utilities were evaluated using the VIC model in the upper Yellow River basin. Our study shows that IMERG and GSMaP products can appropriately capture spatial patterns of precipitation across the TP. IMERG-UC significantly underestimated the reference precipitation (\(-39.32\%\)), while obvious overestimation was found in GSMaP-MVK (\(26.11\%\)). After bias adjustment, the under- and overestimations were clearly reduced, with slight underestimation for IMERG-C \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Time** & **Precipitation** & \multicolumn{3}{c}{**Benchmarking Calibration**} & \multicolumn{3}{c}{**Product-Specific Calibration**} \\
**Scales** & **Products** & **NSE** & **RB (\%)** & **RMSE (m3/s)** & **NSE** & **RB (\%)** & **RMSE (m3/s)** \\ \hline Daily & GCDPA & 0.41 & 26.39 & 274.05 & 0.63 & 0.55 & 217.11 \\  & IMERG-UC & \(-0.12\) & \(-46.00\) & 377.46 & \(-0.08\) & \(-18.96\) & 370.33 \\  & IMERG-C & 0.18 & 17.97 & 323.77 & 0.62 & \(-7.26\) & 220.87 \\  & GSMaP-MVK & \(-9.85\) & 151.97 & 1175.70 & \(-2.93\) & 66.73 & 707.77 \\  & GSMaP-Gauge & 0.53 & 11.64 & 243.91 & 0.67 & 0.13 & 205.56 \\ Monthly & GCDPA & 0.53 & 26.48 & 214.93 & 0.70 & 0.62 & 168.61 \\  & IMERG-UC & \(-0.17\) & \(-45.96\) & 333.21 & 0.15 & \(-18.90\) & 286.48 \\  & IMERG-C & 0.63 & 18.05 & 191.45 & 0.76 & \(-7.19\) & 150.74 \\  & GSMaP-MVK & \(-6.88\) & 152.16 & 876.17 & \(-1.85\) & 66.85 & 518.21 \\  & GSMaP-Gauge & 0.74 & 11.73 & 160.89 & 0.79 & 0.21 & 140.43 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of daily and monthly observed and simulated streamflow when the Variable Infiltration Capacity (VIC) model was forced by the gauge- and satellite-based precipitation datasets in 2015. Figure 11: Comparison of VIC simulated streamflow with recalibrated parameters using product-specific inputs. (\(-8.32\%\)) and GSMaP-Gauge (\(-6.99\%\)). Among the four studied satellite estimates, GSMaP-Gauge had the best performance in nearly all statistical indices with higher correlation, lower bias, and better detection, while GSMaP-MVK had worst performance. This results suggest that the calibration procedure in GSMaP-gauge performs better than that in IMERG-C. Considering that IMERG-C ingests monthly GPCC gauge analyses and that GSMaP-Gauge is calibrated by CPC daily gauge analyses, it seems important to use daily gauge data for IMERG in the future. In fact, the GPCC started computing daily adjustments based on station meteorological data, and it will be used in a future version of IMERG [47]. The GPM sensors were designed to extend the capability for detecting light-intensity precipitation and falling snow, making IMERG perform better than TMPA, which was confirmed by previous studies [29; 32; 82]. However, in the present study, we found that all satellite precipitation products had a relatively lower accuracy in winter, and missed bias was the main problem during the winter season. On the other hand, higher error values were found at low rain rates compared to at moderate-high rain rates. Such results indicate that the current GPM-era satellite precipitation products still have significant room for improving the estimation of light rainfall and falling snow events. The hydrological simulations presented here show that the gauge-adjusted products are more promising than their unadjusted counterparts. The satellite-only products have unsatisfactory performance with large runoff errors.