Geo-Spatial Analysis of Rainfall Amounts and Rainy Days Using Satellites and Ground-Based Data in Nigeria

Abstract

Nigerian rainfall is critical for domestic use through the surface and sub-surface recharge and agricultural production, mostly rain-fed. Analysing three (3) long-term precipitation data (Rain Gauges, CHIRPSv2.0, and TAMSATv3) is vital to account for hydrological extremes in other design and operations of water systems and agricultural monitoring. This study analysed (i) the spatiotemporal variability of rainfall amounts focusing on inter-annual and seasonal variability, and (ii) average monthly rainy days for the period of 39 years (1981-2019). Temporal distribution was analysed using descriptive statistics. The kriging interpolation method in ArcGIS 10.4 was used to map the spatial distribution of rainfall amounts and wet-dry days. Findings revealed that the Southern part contributes 65.3 per cent to the total annual rainfall, and June - November rain contributes 76.6 per cent. 39 years climatological average of the total number of 14,244 days showed the least (57) and highest (235) monthly rainy days observed in the north and south. During June, July and August months, most parts of the country received rain with varying intensities, while the decline begins in September from the north-east and reaches the south in November. Rainfall amounts and rainy days increased from the north to the south and vice versa, except July, August, and September. Accurate and detailed rainfall observations are required and essential for many applications. Therefore, satellite precipitation estimates can be used as alternative sources of input data in many meteorological and hydrological applications, especially in Nigeria, characterised by a low density of rain gauge stations.