نوع مقاله : مقاله پژوهشی
1 عضو هیات علمی /پژوهشکده هواشناسی
2 کارشناس /سازمان هواشناسی کشور
3 عضو هیات علمی/ پژوهشکده هواشناسی
عنوان مقاله [English]
Study of extreme precipitations and related extreme events is of great importance in policy making and planning in variety of sectors including agriculture, water management, urbanization and building, and road and transportation. Hence, much attention has been paid to different methods of analysis of extreme precipitations during recent years.
To study extreme precipitations over Iran, we used extreme precipitation indices like Maximum 1-day precipitation (), Maximum consecutive 5-day precipitation (), Simple precipitation intensity index (), Number of days with precipitation equal to or greater than 10, 20, and 25 mm (,, and ), Maximum number of consecutive dry and wet days ( and ), Total precipitation when daily amounts are greater than 95th and 99th percentile of wet days( and ), and Total precipitation in wet days (). Our used data were limited to daily precipitation data from only 27 of Iranian synoptic stations that have reliable data and covering standard normal period 1961-1990.
We found all three behaviors of stationarity, positive and negative trends over the country. As trends for majority of the indices were positive in regions like Hormozgan, Esfahan, and Tehran, but on the contrary, they were negative for majority of the indices in regions like Azerbaijan and Fars. Former results correspond well with findings of Intergovernmental Panel on Climate Change (IPCC) that expects higher number of occurrences of extreme precipitation events beyond of tropical region. Positive trends for 10 indices in Babolsar and negative trends for 10 indices in Bushehr and Tabriz (7 out of 10 are significant at 0.05 level) indicate complex behaviors of extreme precipitation over the country
Occurrence of very abnormal values like total precipitation of 1 mm in Bandar abbas in 1962 have significantly affected slopes of trends in most of the extreme precipitation indices.