Assessment of Temperature and Relative Humidity Trends Using Mann-Kendall and CUSUM Methods in Owerri, Nigeria

Abstract

The aim of this study is to analyse the trend and detection of point of change for annual temperature and relative humidity in Owerri, Nigeria. 31-year (1992-2022) meteorological data of daily temperature and relative humidity were obtained from the Nigerian Meteorological Agency. Mann-Kendall trend tests, Sen's slope estimator, CUSUM and Sequential Mann-Kendall change point detection methods were applied to annual maximum and minimum temperatures and annual relative humidity. Results showed weak positive trends in maximum temperature (Kendall's tau = 0.118, p = 0.386) and relative humidity (Kendall's tau = 0.172, p = 0.184), with weak negative trends in minimum temperature (Kendall's tau = -0.095, p = 0.489), all non-significant. Change point analysis identified a significant shift in maximum temperature around 2020-2022 (CUSUM value = 7, exceeding critical threshold of 6.79), while minimum temperature and relative humidity showed no significant change points. Owerri exhibited the most stable temperature regime among South-Eastern Nigerian cities studied, with lower variability reflecting coastal maritime influence. These findings suggest relative climate stability but with potential recent acceleration in maximum temperature requiring continued monitoring. In line with the stable climate of Owerri, agricultural systems will encounter fewer climate-related disruptions, infrastructure design can rely on relatively stable temperature parameters, and reduced public health risks as a result of heat stress.