## 4 Results
### Comparison on an Interannual Scale for Different Seasons
In the monsoon season, with peak precipitation, the differences were also higher for all GPPs. MSWEP, CHIRPS and PERSIANN-CDR produced higher differences (\(>\)28 mm) in the upper parts, with a decrease toward the southern plain regions. TMPA produced low RMSD values for stations located in both northern (\(<\)32 mm) and southern (\(<\)16 mm) regions. In autumn, the performance of GPPs improved, MSWEP still had higher RMSD values (\(>\)24 mm) for stations located in northern parts of the country. From Figure 9 it can be seen that the RMSD was higher during peak precipitation seasons, as indicated in the winter, pre--monsoon season and especially the monsoon season. Stations located in different climate regions and at different elevations reported dissimilar results. The higher RMSD values in the north and lower values in central and southwestern regions could be possibly due to differences in land cover, precipitation magnitude, station geography towards precipitation bearing winds and altitude that influence the rain rates [35; 37]. Figure 10 shows the linear relationship of westerlies (Figure 10a,b) and the monsoonal (Figure 10c,d) precipitation system, which together are the key drivers of the local hydrological cycle in the country. In the northern region (Figure 10a), MSWEP and PERSIANN-CDR substantially overestimated in-situ precipitation. In the southwest (Figure 10b), gridded products tended to produce a positive linear relationship with respect to in-situ precipitation. MSWEP slightly underestimated precipitation events, while, except for TMPA, the other products overestimated precipitation events. Figure 10c shows that during the monsoon season, MSWEP underestimated in-situ precipitation, CHIRPS produced a very similar pattern to in-situ, while PERSIANN-CDR overestimated in-situ records. TMPA produced the best results among all GPPs, with a very close linear relationship and thus exhibited similar dynamics as of in-situ. In terms of a close positive relationship with in-situ data, the performance of all GPPs was best in the southern parts of the study region (Figure 10d). MSWEP was closely related to in-situ precipitation and thus produced a similar pattern, whereas PERSIANN-CDR overestimated precipitation. The descriptive statistics (Table 4) further demonstrate the performance of GPPs in both the westerly and monsoon seasons in the study region. For westerlies (regions 1 and 3), variations among the GPPs in depicting the in-situ precipitation pattern are obvious, however, in region 3 the correlation between GPPs and in-situ was improved. The regression coefficients for TMPA in both regions (0.92 and 1.13 in regions 1 and 4 respectively) indicated a close linear relationship with in-situ. Compared to MSWEP, CHIRPS and PERSIANN-CDR, TMPA had lower RMSD values for mean precipitation, a higher temporal agreement, relative amplitude agreement and a lower bias for monsoonal precipitation. Figure 9: Root mean-square difference (mm) of interannual precipitation for in-situ and GPPs in different seasons. Figure 10 shows that for westerlies and monsoonal precipitation at interannual scale, TMPA produced better results than the other GPPs for both westerlies and monsoonal precipitation, followed by CHIRPS and MSWEP. These findings concur with those of [36; 37; 38; 52] for TMPA, [47; 53] for