## 4 Discussion  
Several studies [8; 9; 10; 11] have been performed to evaluate satellite precipitation products over the TP. However, none of these studies were concerned with sub-daily scale examination in this region. It should also be emphasized that the performance of the GPM-era Day-1 IMERG product was examined over regions of high elevation and complex terrain for the first time. The differences between two satellite products (i.e., IMERG and 3B42V7) and gauge data showed clearly whether the IMERG datasets perform better. Note that the resampling and interpolation methods are used to make the different satellite (i.e., IMERG and 3B42V7) and gauge data comparable. More studies will be carried out to evaluate the possible errors introduced by the above two methods. Satellite precipitation products can provide alternatives for estimating rainfall data and create new opportunities for hydrologists in understanding and applying remotely-sensed information. The work in [38] forced the Coupled Routing and Excess STorage (CREST) hydrological model with 3B42V7 products and yielded comparable skill scores with in situ gauges even without recalibration of the hydrological model by the satellite precipitation. TRMM-era research products also showed a satisfactory capability as the forcing of the Variable Infiltration Capacity (VIC) model to simulate streamflow in basins [11; 39; 40]. GPM is regarded as the successor of TRMM for satellite precipitation estimates. Although no significant advantages were observed for the GPR-era IMERG product at the sub-daily scale over the TP, it seems to be acceptable for regional hydrological studies. Given the sparse distribution of rain gauges over the TP, especially in the west and central part, the IMERG datasets are extremely valuable in deriving temporal and spatial patterns of precipitation with high resolution. It can also be a substitute for the TRMM-era rainfall product, such as 3B42V7. The results of IMERG and 3B42V7 data assessment in river basins, especially over the upper reaches of the Yellow and Yangtze Rivers, showed a new opportunity for basin-scale hydrological applications. However, a few extreme high positive or negative relative biases (i.e., \(>\)100% and \(<\)-50%) were detected in the Brahmaputra basin. The work in [41] indicated that regions characterized by complex terrain and a rigid climate would still be problematic for the Day-1 IMERG and 3B42V7 products under current observing skills. We found that the complex terrain and local strong convectional weather significantly influence the satellite rainfall retrieval and result in unexpected errors between satellite estimates and gauge observations in the Brahmaputra basin. For satellite rainfall products over land, the passive microwave algorithms depend primarily on scattering by ice, but the orographic rains might not produce much ice aloft [42]. Thus, the noticeable IMERG and 3B42V7 rainfall errors in the Brahmaputra basin might be due to complex orography and associated warm-rain process [43; 44]. Furthermore, it is noted that discrepancies between satellite products and gauge measurements might be due to the shortcomings in the automatic gauge network. Although the gauge data have gone through three levels of quality control, systematic biases induced by wind and blown snow undercatch, wetting and evaporation errors may contribute to potential sources of uncertainty in mountainous regions over the TP [2]. Moreover, nearly no rain gauges are installed over the western and central TP. More efforts are therefore urgently needed to build a denser rain gauge observation network in these regions. The influence of the Indian monsoon is critical for the advection of heat and moisture and climate patterns in the TP region [17; 45]. The continuous domains of IMERG and 3B42V7 precipitation estimates help characterize rainfall space-time structures under the domination of the Indian monsoon in the warm season over the TP. The onset, maturation and dissipation of the