Average Seasonal Precipitation

The daily GPM\_3IMERGDF product from 2001 to 2015 is aggregated into the average seasonal precipitation @ 0.1◦ spatial resolution as shown in Figure 2b–e. The equation deriving the average seasonal precipitation is as follows in Equation (1):

$$P\_{GPM\\_S} = \frac{\sum\_{j=1}^{m} \sum\_{i=1}^{n} P\_{GPM\_{ij}}}{N} \tag{1}$$

where *PGPM*\_*<sup>S</sup>* is the average seasonal precipitation which individually corresponds to DJF (December, January and February), MAM (March, April and May), JJA (June, July and August), and SON (September, October and November), respectively. *PGPMij* is the daily GPM\_3IMERGDF precipitation for *i*-th day, i.e., DJF (*n* = 90), MAM (*n* = 92), JJA (*n* = 92), SON (*n* = 91) and *j*-th year (*m* = 15), and *N* is the total number of observations. Hence, hereafter, the average winter precipitation for DJF, the average spring precipitation for MAM, the average summer precipitation for JJA, and the average autumn precipitation for SON will be used.

Average Monthly, and Average Annual Precipitation

The daily GPM\_3IMERGDF product from 2001 to 2015 is aggregated into the average monthly and the average annual precipitation @ 0.1◦ spatial resolution as shown in Figure 2f,g, respectively. The equation deriving the average monthly, and the average annual precipitation is as follows in Equation (2):

$$P\_{\text{GPM\\_Avy}} = \frac{\sum\_{j=1}^{m} \sum\_{i=1}^{n} P\_{\text{GPM}ij}}{N} \tag{2}$$

where *PGPM*\_*Avg* is the average monthly and the average annual precipitation for the study area, *PGPMij* is the daily GPM\_3IMERGDF precipitation for *i*-th day (*n* = 365) and *j*-th year (*m* = 15), and *N* is the total number of observations (e.g., for the average monthly precipitation *N* = 180, and for the average annual precipitation *N* = 15).
