Northwest of Iran's Classification by Precipitation's Characteristics

Ever-increasing in climatic observations, appearing advanced computers and changing of outlook towards natural phenomenon have caused that multivariate statistical methods to be accepted by climatic experts. The importance of the subject is clarified by utilizing classification in identifying climatic homogenous regions. In order to classify the precipitation's characteristics based on 260 stations over observation period of 1966 - 2005, cluster analysis technique has been used. Cluster analysis is a multivariate statistical method that classifies a group of cases according to difference or similarity scales. This method has been used much in climatology and indicates more exact classification in comparison with traditional methods. Precipitation annual mean in northwest of country is 360.9 mm that it has a range equal to 587.3 mm and it's spatial coefficient of variation is 24 percent. To achieve results of research, softwares SPSS / win, surfer / win and Matlab was used. By using cluster analysis in 5374 pixels, finally 4 precipitation regions were identified in northwest part of Iran. These regions with different dimension and different distribution contain:- Low concentrated precipitation region with moderate snowfall- Moderate precipitation region with tendency to low distributed precipitation and much snowfall- Moderate precipitation region with tendency to much distributed precipitation and moderate snowfall- Much concentrated precipitation region with moderate snowfall