Change Time Study Pricipitain of Hamadan Province Using Statistic's and Neural Network Methods

Climate change is one of the common problems in today’s societies and considerate as threat for earth. Increasing of earth temperature is cased to extensive changes in earth climates and also it laded to same variations of spatial and temporal of precipitation so that these variations cased to a lot of damages especially in last decade. This study to identify of variations and the trend of season and duration of precipitation in different times intervals. Then it is predicted same changes in the future by the method of artificial neural network. In this study we have us of the data from two synoptic stations Hamadan and Nojeh .The statistic’s years in this study; it seems the rainfall season in the central part of Hamadan province in started later and ended later in last decade. In other words the starter of rainfall season in Hamadan which occurred in the fall season, at present tend to ward the winter season and the fall season is more dryer than before ages. This shows that the rainfall season is interchanged in this district. in using of the method of artificial neural network we should consider to two main points in the predicting of precipitation the first one, the low attention of this method in the long –term predicting of precipitation and the second one, the exaggerate in the minimum and maximum amount of precipitation in different seasons of year.