**3. Results**

### *3.1. Daily Evaluation*

Figure 2 shows the distribution of continuous statistical quantities compared between rain gauge measurements and the three IMERGs. In summary, the mean CC values in relation to the rain gauge for IMERG-E, IMERG-L and IMERG-F were 0.33, 0.32 and 0.35, respectively. Although low values of CC could be seen, IMERG-F appears to be more consistent with rain gauge observations at the LTB (Figure 2a–c). The mean RMSE value (Figure 2d–f) is between a range of 3.96 mm/day and 7.96 mm/day (mean 5.19 mm/day) for the three IMERGs evaluated. The spatial distribution of PBIAS (Figure 2g–i) showed an underestimation (overestimation) of precipitation at 77% (23%) (mean) of the stations, with overestimates of precipitation in the eastern and northeastern part of the LTB for all the three IMERGs. The mean PBIAS values were −13.52% (IMERG-E), −20.54% (IMERG-L) and 2.68% (IMERG-F).

**Figure 2.** Spatial distribution of CC (**<sup>a</sup>**–**<sup>c</sup>**), RMSE (**d**–**f**) and PBIAS (**g**–**i**) of daily rain gauge data in relation to IMERG.

### *3.2. Monthly Evaluation*

The results indicate that IMERG-F was relatively better. The highest correlation (Figure 3a–c) of the monthly evaluation was observed in IMERG-F data in relation to the rain gauges with a mean CC value of 0.90 (the lowest correlation was observed in IMERG-E with a mean CC value of 0.85). IMERG-F showed a correlation greater than 0.79, with a maximum value of 0.94, followed by IMERG-E with a correlation greater than 0.70 and a maximum value of 0.92, while the CC of IMERG-L was between a range of 0.68 and 0.92. The monthly RMSE results (Figure 3d–f) were between a mean range of 32.01 mm/month (IMERG-F) and 42.22 mm/month (IMERG-L) compared to the rain gauge data. IMERG-F compared to IMERG-L and E obtained lower errors at most stations (Figure 3f).

**Figure 3.** Spatial distribution of CC (**<sup>a</sup>**–**<sup>c</sup>**) and RMSE (**d**–**f**) of monthly rain gauge data in relation to IMERG.

### *3.3. Annual Evaluation*

In the annual IMERG products, the error increases and the correlation decreases with respect to the monthly evaluation, becoming worse in some stations. Figure 4 shows the spatial distribution of the continuous statistical quantities compared between annual rain gauge measurements and the three IMERGs. The highest correlation (Figure 4a–c) of the annual assessment was observed in the IMERG-F data relative to the rain gauge data with a mean CC value of 0.50 (the lowest correlation was observed in the IMERG-L with a mean CC value of 0.43). IMERG-F showed a CC between −0.55 and 0.85, followed by IMERG-E with a CC between −0.58 and 0.91, while the CC of IMERG-L ranged from −0.65 to 0.92. For IMERG-E, -L and -F, negative correlations were found at 5%, 5% and 3%, while a 3% resulted with a CC < 0.15 (0.11, 0.09 and 0.06) of the total of stations, respectively. Consequently, the CC was greater than 0.15 in 92% of the stations evaluated, with a mean of 0.51 for the three IMERGs. On the other hand, the annual RMSE results (Figure 4d–f) were between a mean range of 175.28 mm/year (IMERG-F) and 262.84 mm/year (IMERG-L) compared to the rain gauge data.

**Figure 4.** Spatial distribution of CC (**<sup>a</sup>**–**<sup>c</sup>**) and RMSE (**d**–**f**) of annual rain gauge data in relation to IMERG.
