*2.2. Ground-Based Precipitation Data*

Rain gauges (RGs) are considered as standard sources of precipitation estimates that are used for satellite precipitation calibration and validation processes. The Pakistan Meteorology Department (PMD) and the Snow and Ice Hydrology Project (SIHP) of Water And Power Development Authority (WAPDA) own the climate and hydrological data in Pakistan. SIHP operates the meteorological stations at high elevation mostly located in glacial and humid regions. For the current study, daily precipitation records from 102 meteorological stations for the period 2000–2015 were collected from both organizations, where precipitation records of 79 RGs were collected from PMD and 23 from WAPDA. The location of meteorological stations across Pakistan is shown in Figure 1b. RGs in the current studies are named with respect to each climate region, i.e., RGs in glacial, humid, arid and hyper-arid regions are represented as GRG, HRG, ARG, and HARG, respectively. Main features and number of RGs in selected climate regions are presented in Table 1.


**Table 1.** Main features of the selected four climate regions.

The data obtained from PMD and WAPDA were manually collected, and consequently might be subjected to personal and instrumental errors. Besides, the stations located at high elevation may also be subjected to splashing and wind errors. These associated errors affect the quality of the data. Therefore, PMD and WAPDA correct the RGs precipitation following the World Meteorology Organization's standard code (WMO-N). Moreover, the quality of the data was tested using skewness and kurtosis methods, and missing data was filled using the zero-order method [47].
