Estimation of Relationship between Frequency-Duration and Return Period of Extreme Climatic Events in Khorasan Razavi Province

Nowadays there is more attention to extreme climatic events because of its consequent financial, social and economic damages. It is proved that changes in frequency and intensity of extreme events have more damaging effects on human life, social and natural systems than the average climate changes. Therefore, more studies are required to assess these events for better risk management. The objective of this study is to assess the relation between occurrence probability, duration and frequency of extreme events in Khorasan Razavi province. Daily temperature and rainfall data of 22 stations between the years of 1982 to 2012 were used. For more accuracy, these stations were first clustered with Ward method and were fitted by some statistical distribution. The best distribution was chosen and equations of frequency-duration-return period were derived from each cluster. One can know the frequency of extreme event with an arbitrary duration and return period based on the abovementioned relations, so these equations could help to manage risk and crisis regarding agricultural crops and also for more efficient insurance.