Long-term trend analysis of climatic variables and reference evapotranspiration over different urban areas in Tunisia

In this study, the trend analysis of annual climatic variables including Tmax, Tmin, Tmean, RHmean, WS and SR as well as FAO-56 PM ET0 were investigated in three locations in Tunisia during 1984-2007. The Mann-Kendall Test, the Sen's Slope Estimator and linear regression tests were used for the analysis. The obtained results showed a significant increasing trends (a < 0.001) and (a < 0.01) in annual Tmax, Tmin and Tmean at all the considered locations. However, Tmin increase faster than Tmax with a slope of magnitudes ranging between 0.057 to 0.1 oC year-1. For RHmean, a non-significant tendency of decrease was observed in Chott-Mariem station. However, significantly increasing trends were found for Kelibia and Tunis Carthage. Concerning the WS variable, a tendency of decrease is observed during the study period for all the stations. Nevertheless, the statistical analysis of decreasing tendency of wind speed varied from non-significant for Tunis Carthage to highly significant (a <= 0.001) at Chott-Mariem and Kelibia. Despite the highly significant upward trend of temperature, the temporal pattern of mean annual FAO56 PM-ET0, over the different stations, did not exhibit any significant trend except for Kelibia station.