Investigation of Showery Precipitation and their Change Processes in Guilan Province

Showers are included among natural disasters, and underestanding how they occur and their effects rates are so helpful in decreasing possible damages in various development projects. In this regard, this research is carried out to know, legislate, and predict the showers. The current research is restricted to Guilan Province and statistical period for six years (1380-1386) in ten stations. The results showed that in addition to the change of shower rate in different time-limit, the place of showers have been changed. For this reason, Guilan Province is divided into three western, central and eastern regions according to the rain intensity. The highest range of rain happened in the western region, and the least in the central region. The evaluation of shower data with various statistical distributions for determining basic equations of predicton also shows that in more cases (%84) a logarithm cubic equation can be used, because we can make correct estimation of shower rate in time unit with return period plan by using of these equations.