Abstract
Abstract
The presentresearch aims to identify the date of the start of the rainfall season (Onset Rainfall) at Tel- Abta area western of the province of Nineveh. The study relied on data for daily rainfall,mean maximum and minimum monthly temperatures, mean monthly relative humidity, and wind speed at 2 mheight for the period (1996 to 2010).The study involved four models; three already available in the literature and one is developed in this study. The developed model depends on the principles of water balance in the top soil layer in the field. The previously proposed models depend on some sort of statistical analysis of the daily rainfall. A computer program using Microsoft Excel code is developed for each model. The results revealed that the proposed (developed) model is the most suitable one for the dry areas suffering rainfall shortage. The performance of the second and third model was very close to that of the proposed model. The fourth model, however, gave results that are very much different and far from the other three models. We recommend not to adapt Model 4 at all. Models 2 and 3 may be used for practical and quick applications. However, the proposed model (Model 1) stays the best and most accurate because it depends on sound scientific and realistic bases.
