Assessment of the Variations of some Weather Parameters within the five Regions of The Gambia

The study and forecast of climatic phenomena have progressed over time, but the immense knowledge and information gathered has aided in comprehending and anticipating weather changes and their effects on crop production. The objective was to evaluate weather parameters in the five regions of The Gambia from 2015 to 2024, outline the factors that influence their variations, and assess their impact on crop production. Ten meteorological stations were visited to gather data. For each variable, comprehensive descriptive statistics were calculated, including means, standard deviations, and coefficients of variation. Principal Component Analysis (PCA) and Ward's hierarchical cluster analysis were employed to extract latent structure from the multi-station, multi-parameter dataset and to identify climatically homogeneous sub-regions. The Mann-Kendall trend test with Sen's slope estimator was used to detect monotonic trends. The highest average annual rainfall was observed in the Lower River Region (LRR) with 1,338.0 mm in 2019; the lowest was 522.7 mm in the West Coast Region (WCR) in 2021 (SD = 239.4 mm). Maximum temperature ranged from 32.98°C (WCR, 2019) to 44.78°C (URR, 2021) with an inter-regional SD of 1.59°C. Relative humidity ranged from 31.1% (URR, 2017) to 69% (WCR, 2017). PCA identified two principal components explaining 78.4% of total variance, with PC1 (52.3%) defined by the ocean-to-continent moisture gradient and PC2 (26.1%) capturing inter-annual drought episodes. Cluster analysis delineated three climatically distinct zones: a Maritime-Humid cluster (WCR/NBR), a Sub-humid Transitional cluster (CRR/LRR), and a Semi-arid Continental cluster (URR). Mann-Kendall trend analysis revealed statistically significant declining rainfall trends in URR (τ = −0.47, p < 0.05) and a pan-regional decline in relative humidity, indicating progressive desiccation of the interior.