*3.2. IMERG Data*

Global Precipitation Measurement (GPM) mission was launched on 27 February 2014, as a successor of the Tropical Rainfall Measuring Mission (TRMM). GPM constellation incorporates passive microwave (PMW) and infrared (IR) satellites, providing global precipitation measurements within the range 60◦ N–60◦ S and better temporal and spatial analysis (see [25,35,36]).

GPM consists of one Core Observatory and approximately 10 constellation satellites. The Core Observatory carries a Ku/Ka-band dual-frequency precipitation radar and a multi-channel GPM microwave imager, extending the measurement range of TRMM instruments. GPM provides three levels of precipitation-related products. The level-3 products are produced with the IMERG (Integrated Multi-satellitE Retrievals for GPM) algorithm, which intercalibrates and merges precipitation estimates from all constellation microwave sensors, microwave-calibrated infrared satellite estimates, and monthly gauge precipitation data [37,38]. It is important here to comment on the PMW sensitivity of retrieved rainfall, since the launch of GPM, the overland rainfall retrieval algorithm, is transitioning from an inversion technique based on rainfall–brightness temperature scattering relationships to a Bayesian framework consistent with the over-ocean algorithm [39]. GPM IMERG precipitation estimates are available from 12 March 2014 to present. The GPM IMERG products offer a relatively fine spatial resolution of 0.1◦ × 0.1◦ and high temporal resolution of 30 min, with a spatial coverage from 60◦ S to 60◦ N. The IMERG Final product [18] was chosen for our study and so, especially, was the IMERG (v05B) data for the period from April 2014 to June 2018.
