Features and Trends of Rainfall for Selected Stations in Iraq

In this paper , rainfall data were obtained for four weather stations within a time of (60) years : Baghdad (1941- 2000) , Basrah (1941-2000) , Mousal (1941-2000) and Rutba 1941-2000) . They were used to calculate the mean , amount and the variability of seasonal and annual rainfall at each station. First regression analysis was applied to examine the rainfall trend and the significance of the regression coefficient (RC) was verified by assuming fitting of rainfall data to the tdistribution ( at significance levels of 90% and 95%) just to find out if there any significant change in the rainfall time series. The results show that the rainfall trend was only significant at stations ( Baghdad , Rutba ) in Spring and Autumn seasons respectively , but the positive rainfall trend was identified annually at stations ( Basrah , Rutba ) and seasonally at all stations in Autumn and Winter seasons only , hereas the negative rainfall trend was identified annually at stations ( Baghdad , Mousal ) and seasonally at all stations too and in the three seasons ( Autumn , Winter and Spring ) . The significant trends in the seasonal and annual rainfall were hardly indicated , but the large variability of rainfall was observed in the seasons