## 4 Results
### Evaluation of Satellite Precipitation Products
#### 4.1.2 Daily Precipitation  
To evaluate the quality of 3B42V7 and IMERG products, the daily precipitation estimates of these two satellite products at the locations of the five rain gauges were derived and compared with the gauge-based precipitation. Figure 4 shows that both 3B42V7 and IMERG can capture the temporal variation patterns of daily precipitation at the five rain gauges. However, Table 2 indicates that these two products still contain considerable errors. The values of CC for both products were considerably low, ranging from 0.247 to 0.356 between the 3B42V7 estimates and the observations, and from 0.224 to 0.316 between the IMERG estimates and the gauge-based precipitation. 3B42V7 had a much higher  
Figure 3: Spatial distribution of precipitation estimates from: (**a**) 3B42V7; and (**b**) IMERG satellite precipitation products from 1 January to 31 December 2015; and (**c**) 3B42V7 and IMERG precipitation estimates at the locations of main weather stations in comparison with gauge-based daily precipitation data during the periods of 1 April–31 December 2014 and 1 January–31 December 2015. CC than IMERG at the Hkamti, Homalin and Mawlaik stations, and IMERG had a slightly higher CC than 3B42V7 at the Kalewa and Monywa stations. IMERG underestimated precipitation at all the five rain gages, particularly at the Hkamti and Homalin stations, displaying a large negative BIAS of \(-37.1\%\) and \(-41.2\%\). 3B42V7 presented significant underestimation at Hkamti (14.9% BIAS), a slight underestimation of daily precipitation at Homalin and Monywa (by 5.2% and 2.7%), and a moderate overestimation at Mawlaik and Kalewa (BIAS of 6.4% and 5.4%). In terms of RMSE, both products contained similar magnitudes of errors. Regarding the contingency of satellite precipitation estimates, the POD values were low at all the rain gauges, ranging from 0.092 to 0.299 for 3B42V7 and from 0.117 to 0.207 for IMERG, implying that 3B42V7 and IMERG correctly identified real rainfall events by 29.9% and 20.7% at most. Moreover, Table 2 indicates that both products had comparatively large FAR and small CSI values, implying considerable errors in the two satellite products. Comparison of all statistical indices in Table 2 reveals that 3B42V7 is more accurate than IMERG at the Hkamti, Homalin, Mawlaik, and Kalewa stations but is slightly less accurate at the Monywa station. To assess the performance of IMERG and 3B42V7 products in detecting historical heavy precipitation events, we defined the gauge-based daily precipitation exceeding 25 mm as a real \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Weather Stations** & **Satellite Precipitation** & **CC** & **BIAS (\%)** & **RMSE (mm)** & **POD** & **FAR** & **CSI** \\ \hline \multirow{2}{*}{Hkamti} & 3B42V7 & 0.335 & \(-14.9\) & 22.8 & 0.299 & 0.417 & 0.246 \\  & IMERG & 0.232 & \(-37.1\) & 24.7 & 0.207 & 0.404 & 0.181 \\ \hline \multirow{2}{*}{Homalin} & 3B42V7 & 0.320 & \(-5.2\) & 19.3 & 0.253 & 0.440 & 0.211 \\  & IMERG & 0.301 & \(-41.2\) & 18.6 & 0.180 & 0.432 & 0.158 \\ \hline \multirow{2}{*}{Mawlaik} & 3B42V7 & 0.356 & 6.4 & 14.6 & 0.158 & 0.480 & 0.138 \\  & IMERG & 0.224 & \(-12.3\) & 16.3 & 0.176 & 0.445 & 0.154 \\ \hline \multirow{2}{*}{Kalewa} & 3B42V7 & 0.247 & 5.4 & 16.7 & 0.145 & 0.494 & 0.127 \\  & IMERG & 0.294 & \(-23.7\) & 15.0 & 0.145 & 0.457 & 0.129 \\ \hline \multirow{2}{*}{Monywa} & 3B42V7 & 0.281 & \(-2.7\) & 9.0 & 0.092 & 0.626 & 0.080 \\  & IMERG & 0.316 & \(-6.3\) & 9.1 & 0.117 & 0.608 & 0.099 \\ \hline \end{tabular}
\end{table} 
Table 2: Statistical indices of daily precipitation estimates at the five weather stations in the Chindwin River basin (1 April 2014–31 December 2015). Figure 4: Comparison of daily precipitation estimates from 3B42V7 and IMERG satellite precipitation products at the main weather stations against the gauge-based daily precipitation time series from 1 April 2014 to 31 December 2015.  
heavy precipitation event.