THE PATTERNS, TRENDS AND INTERRELATIONSHIPS AMONG ESSENTIAL CLIMATIC VARIABLES IN OKADA TOWN, EDO STATE, NIGERIA

Abstract

A number of adjustments and changes in many socio-ecological systems globally have directly and indirectly been linked to the variable and changing patterns of climate. All human endeavours including climate-smart agriculture which guarantee sustainable food security to a large extent need in-depth understanding of interactions among essential climate variable (ECV) which are responsible for the changes. The aim of this study was to assess the interrelationships among ECV in Okada Town, Ovia North East Local Government Area of Edo State. Specific objectives were to examine the patterns and trends of ECV in Okada Town, investigate the temporal variations of ECV in the study area, and assess the interrelationships among ECV in the study area. The ECV datasets used include minimum temperature (TMin), maximum temperature (TMax), rainfall, soil moisture (SM) at the depth of 0-40cm, potential evapotranspiration (PET) and normalized difference vegetation index (NDVI). The dataset were on monthly and spanned across 40years starting from January 1980 to December 2019. They were sourced from the University of East Anglia-Climatic Research Unit, the National Aeronautical and Space Administration Goddard Space Flight Center along with the University of Maryland (repository of global climatic data). Data analyses were carried out using descriptive and inferential statistics of simple linear regression, one-way analysis of variance (ANOVA) and Pearson’s Product Moment Correlation (PPMC) in Microsoft Excel and SPSS 22. The results showed that all the investigated ECV exhibited a rising trend: TMin (0.013OC per annum; R2 = 0.169), TMax (0.018OC per annum; R2 = 0.363), rainfall (1.192mm per annum; R2 = 0.007); SM (0.009m3/m3 per annum; R2 = 0.307), PET (0.057mm per annum; R2 = 0.233) and NDVI (0.001 per annum; R2 = 0.293). Also, at 95% level of confidence, it was found that all the studied ECV excluding rainfall varied with time in Okada Town. Regarding the interrelationships, the correlation coefficient (R) between TMin and TMax was 0.594 (p ≤ 0.01), TMin and NDVI (R = 0.356; p ≤ 0.05), TMax and NDVI (R = 0.347; p ≤ 0.01), rainfall and SM (R = 0.485; p ≤ 0.01) as well as SM and NDVI (R = 0.444; p ≤ 0.01). It was concluded that the upward trends in all the studied ECV is a marked indication that Okada Town is gradually getting warmer than before in recent history. The study recommended the establishment of well-equipped synoptic weather station for ECV monitoring and improved weather forecast, early warnings, disaster preparedness and risk reduction in Okada Town.