Geospatial Variability of Vegetation Response to Meteorological Drought in North-East and North-West Nigeria

Abstract This research investigated extreme drought variability and future trends in North-East and North-West Nigeria, addressing essential questions regarding the temporal and spatial variations in rainy and dry seasons. Daily and Monthly observation datasets at (0.50 x 0.50) resolution was obtained from the global gridded climatology of Climate Research covering 1981 to 2019. Simulated daily datasets from the Rossby Centre for Atmospheric Regional Climate Model (RCA4-RCM) under two emission scenarios (RCP4.5 and RCP8.5) for the periods 1976-2005 (historical) and 2020-2100 (projection) were retrieved from CORDEX at a resolution of (0.440 x 0.440) over Africa. The Standardized Precipitation Evaporation Index (SPEI) assessed drought intensities, revealing near normal, moderate, and severe conditions within the range of 1.99 to -1.99. A linear regression model established the relationship between Normalized Difference Vegetation Index (NDVI) and rainfall. Spatial analysis of Consecutive dry days (Drought Index) over three 30-year periods (near, mid, and far future) set a critical/threshold level at -0.4 to 1.2, unveiling distinctive drought severity patterns. Findings highlighted regions with low vulnerability (Bornu, Kano, Katsina) and high risk (Bauchi, Zamfara, Yobe) during the historical period. Projected trends indicated fewer consecutive dry days between 2020 and 2040 under RCP 4.5 and RCP 8.5, with greater emissions and warming in RCP 8.5 leading to increased dry days between 2041 and 2070. The mid-century outlook suggests a rise in dry days, signalling prolonged drought in the region. SPEI analysis revealed potential future aridity in Northern Nigeria due to rising Potential Evaporation (PET) and continuous Climatic Water Balance (CWB) deficits observed over West Africa, leading to increased evaporation losses and higher irrigation demands for drier soils.