## 1 Introduction  
Humans cannot survive without water. Precipitation replenishes the water resources on Earth via the hydrological cycle, which are essential for agricultural, industrial, domestic, and drinking purposes. An understanding of precipitation patterns is obviously important in water resources management. Apart from this, reliable precipitation information is also vital in monitoring and forecasting water-related hazards such as flood and drought. Therefore, sustainable development of the economic, agricultural, ecological, and social fields requires accurate precipitation data. A precipitation gauge is regarded as one of the most reliable approaches of collecting precipitation information, but it is in point form. Various interpolation techniques such as Kringing, Inverse DistanceWeighting (IDW), multiquadric-biharmonic (MQB), and Spline have been developed to study the spatial pattern of precipitation [1; 2]. In general, a high density of precipitation gauges is essential to produce a good interpolated precipitation pattern. Unfortunately, lack of adequate precipitation gauges is a major issue in many parts of the world, particularly in developing countries, mountains, ocean, and less discovered area (i.e., Amazon rain forest). In recent decades, satellite precipitation products (SPPs) have been increasingly applied in monitoring precipitation patterns. Continuous measurement, extensive coverage, free of charge, and near real-time are among their advantages [3]. The launch of the Global Precipitation Measurement (GPM) mission began a new generation of SPPs [4]. GPM is a satellite constellation with the core observatory satellite (GPM-CO) launched on 14 February 2014 and equipped with a Dual-frequency Precipitation Radar (DPR) and GPM Microwave Imager (GMI) [4]. Spatial (0.1\({}^{\circ}\)\(\times\) 0.1\({}^{\circ}\)) and temporal (30 min) resolutions of GPM are better than the Tropical Rainfall Measurement Mission (TRMM) products (spatial: 0.25\({}^{\circ}\)\(\times\) 0.25\({}^{\circ}\), temporal: three hourly). A prior assessment of GPM products is essential to understand their reliability in a specific region before applying them in any operational system. The findings could also be used for improving the IMERG algorithms and sensors development. For instance, numerous GPM product validation studies have been carried out in China [5], Iran [6], Malaysia [7], Singapore [3], and southern Canada [8]. Most of the studies found that GPM products are applicable to study regional precipitation patterns, but the reliability varies with region, season, elevation, and latitude. Inaccurate precipitation data might lead to false hydrological model outputs and inappropriate decisions [9]. Therefore, assessment of SPPs in hydrological modelling is essential to understand and reduce these errors. However, a hydrological assessment of the Integrated Multi-Satellite Retrievals for GPM (IMERG) product is still limited because these SPPs are only recently available. Also, a more complicated validation scheme is required as compared to the meteorological assessment. [PERSON] et al. [10] compared the IMERG final run (IMERG_F) product with the TRMM 3B42V7 product in streamflow simulations of the Chindwin River Basin, Myanmar. They found that SPPs underestimated the total runoff and high flows of the basin. In Thailand, [PERSON] and [PERSON] [11] studied the capability of six different SPPs in runoff simulations of the 2014 flood event in the Nan River Basin. Similar studies have also been conducted in the Beijing River Basin [12] and Ganjiang River Basin [13; 14] in China, and the Amazon Basin of Peru and Ecuador [15]. These studies reported that the GPM IMERG products have satisfactory performance in hydrology and flood applications. Nevertheless, such evaluation studies should be conducted on different types of basins, such as tropical basins and complex topography basins. The Kelantan River Basin (KRB) is a tropical basin in the north-eastern part of Peninsula Malaysia.