# Mapping Areal Precipitation with Fusion Data by ANN Machine Learning in Sparse Gauged Region
## 3 Results and Discussion
### Assessment of Rainwater Resources of the Qaidam Basin
#### 3.3.2 The Precipitation Variation Trend  
The annual precipitation time series and its variation trend of the gauged precipitation, original and corrected 3B42 RT and 3B43 products at the 20 gauge stations are shown in Figure 8 and Table 4. From Figure 8 we can know that the original 3B42 RT and 3B43 precipitation at the GEM, LH, NMH, XZH. HX, NCT and GEM4 stations, where the precipitation is low, is obviously higher than the gauged precipitation. On the contrary, the original 3B42 RT and 3B43 precipitation at the CHH and SGB stations, where the precipitation is high, is obviously less than the gauged precipitation. This again indicates that the original 3B42 RT and 3B43 are significantly overestimated in the LGPA and underestimated in the HGPA. What is nice is that the 3B42 RT and 3B43 decreases or increases significantly and tends to the gauged precipitation values after the  
Figure 8: _Cont._ \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Station Name** & **Gauged** & **Original 3B42 RT** & **Corrected 3B42 RT** & **Original 3B43** & **Corrected 3B43** \\ \hline GH & \(-2.21\) & \(-0.23\) & \(-0.18\) & \(-0.27\) & \(-0.85\) \\ XRD & \(-1.32\) & \(0.01\) & \(-0.02\) & \(-0.06\) & \(-0.07\) \\ DCD & \(-0.63\) & \(-1.55\) & \(-0.75\) & \(-1.07\) & \(-0.77\) \\ KE & \(-0.62\) & \(-0.37\) & \(-0.40\) & \(-0.47\) & \(-0.59\) \\ DLH & \(-0.32\) & \(-0.94\) & \(-0.91\) & \(-0.27\) & \(-0.33\) \\ HTTL & \(-0.15\) & \(-1.05\) & \(-0.63\) & \(0.13\) & \(-0.10\) \\ CHWS & \(0.09\) & \(2.78\) & \(2.87\) & \(0.58\) & \(0.67\) \\ LH & \(0.13\) & \(0.91\) & \(0.05\) & \(1.10\) & \(0.26\) \\ XZH & \(0.14\) & \(1.44\) & \(0.39\) & \(1.94\) & \(0.57\) \\ DL & \(0.23\) & \(0.01\) & \(0.02\) & \(0.94\) & \(1.05\) \\ GEM4 & \(0.58\) & \(1.87\) & \(0.88\) & \(1.29\) & \(0.58\) \\ NMH & \(0.63\) & \(1.91\) & \(0.95\) & \(2.33\) & \(1.29\) \\ HX & \(0.89\) & \(2.08\) & \(0.69\) & \(2.23\) & \(0.85\) \\ GEM & \(0.93\) & \(1.87\) & \(0.84\) & \(1.29\) & \(0.54\) \\ NCT & \(1.31\) & \(0.63\) & \(0.32\) & \(0.86\) & \(0.35\) \\ MY & \(1.45\) & \(0.17\) & \(0.06\) & \(0.41\) & \(0.13\) \\ SGB & \(2.43\) & \(4.25\) & \(3.95\) & \(3.22\) & \(3.03\) \\ WL & \(4.71\) & \(3.14\) & \(2.77\) & \(2.28\) & \(2.69\) \\ XRH & \(3.21\) & \(2.21\) & \(2.29\) & \(2.94\) & \(3.06\) \\ CHH & \(10.45\) & \(0.19\) & \(0.18\) & \(1.16\) & \(1.78\) \\ \hline Average & \(1.10\) & \(0.97\) & \(0.67\) & \(1.03\) & \(0.71\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of the annual precipitation variation trend (2001–2016) between gauged and TRMM products on the grids with the gauge station. LH: LengHu; XZH: XiaoZaHuo; GEM: GeErMu; HK: HeXi; MY: MangYa; NMH: NuoMuHong; GEM4: GeErMu4; DCD: DaChaDan; HTL: HuaiTouTaiL; GH: GaHai; NCT: NaChiTai; WL: WuLan; DLH: DeLingHa; DL: DuLan; CHWS: ChaHanWuSu; XRH: XiaRiHa; XRD: XiangRiDe; KE: KeEr; SGB: ShangGaBa; CHH: ChaHAnHe; MAP: Mean Annual Precipitation. Figure 8: The annual precipitation time series of the gauged precipitation, original and corrected of 3B42 RT and 3B43 products at the 20 gauge stations. (**a**) DCD: DaChaDan; (**b**) DLH: DeLingHa; (**c**) DL: DuLan; (**d**) GEM: GeErMu; (**e**) LH: LengHu; (**f**) MY: MangYa; (**g**) NMH: NuoMuHong; (**h**) WL: WuLan; (**i**) XZH: XiaoZaHuo; (**j**) CHH: ChaHanHe (**k**) CHWS: ChaHanWuSu (**l**) KE: KeEr; (**m**) HX: HeXi; (**n**) HTL: HuaiTouTaiL; (**o**) GH: GaHai; (**p**) SGB: ShangGaBa; (**q**) XRH: XiaRiHa; (**r**) XRD: XiangRiDe; (**s**) NCT: NaChiTai; (**t**) GEM(4): GeErMu4. From the average change trends of precipitation at the 20 gauge stations in the three data sources, the annual precipitation of the Qaidam Basin shows an increasing trend. The gauged precipitation at GH, XRD DCD, KE, DLH and HTTL stations showed a decreasing trend, and the others showed an increasing trend in different degrees at the other 14 gauge stations. The change trend direction is basically the same.