Spatio-Temporal Trends and Variability of Temperature Over Bale Zone, Ethiopia

Abstract

Understanding of temperature trends and their spatiotemporal variability has great significances on making deep insight for planners, managers, professionals and decision makers of water resources and agriculture. Therefore, this research was set with aim to analyze spatiotemporal variability of temperature and their time series trends over Bale Zone. Statistical analysis: Parametric test with regression analysis on the anomalies like deviation from mean and Non-parametric test with Mann-Kendall test together with Sen’s Slope Estimator & Zs statistics has been used for estimation of trends of a historical data series of monthly, seasonal and annually maximum and minimum temperature of selected meteorological stations in Bale Zone. Both tests relatively shows same results for monthly, seasonal and yearly temperature series. The coefficient of variation (CV) was used for variability analysis. Arc GIS 9.3 software was also used to investigate the spatial variability temperature (minimum and maximum) for the period under review. These methodology has shown a significant increasing and decreasing trends at 95% confidence level for certain time scale temperature series: temperature trends (i.e the mean maximum temperature series) showed a significant increasing trend in Robe (Annual, Spring, February, March, April, May, July, and October), Ginir (February, July, September, and December).Mean minimum temperature series showed a substantial increasing trend in Robe (May, July, September, and November) and Hunte (September). It is also observed that Mean seasonal and annually minimum temperature of the stations have shown higher variability than those mean seasonal and annual maximum temperature of the stations.