تحليل آماري احتمال وقوع و دوره هاي برگشت يخبندان هاي زودرس و ديررس زاهدان در دوره آماري (1386-1360)

Statistical Analysis of the Occurrence of Return Periods of Freezing in Zahedan during (1360-1386)

From climatic viewpoint, freezing is the reduction of temperature into 0°C and lower than it. The goal of this research is statistical analysis and prediction of Zahedanʹs precocious freezing (autumn time) and late freezing (springtime). For this purpose, we examined the minimum daily temperature for a 27-year period. In every cold period of year, the first day in which daily minimum temperature reduced to freezing point level was selected as beginning of freezing and last day was as the end of freezing. By choosing the first day of Mehr as starting month, Julius days were calculated. This data were evaluated with various distributions whereby Pearson type distribution was selected. Autumn time precocious freezing and spring time late freezing were calculated in return periods. The results showed that precocious and late freezings are retreating from both sides toward the winter season. It means that the freezing period shorter .