Study of the persistence of precipitation days in Iran


1 university of Sistan and Baluchestan, Zahedan

2 Tarbiat Moallem University

3 university of Sistan and Baluchistan

4 Applied Meteorological Research Center, Sistan and Baluchistan


There have always been some special problems with the precipitation as an important climatic factor in Iran. These problems, being caused by geographical conditions of this vast country, have brought about the unequality of spatial and temporal distribution of rain.
The purpose of the research in hand is to determine the continuation of two, three and four-day rain in Iran and to decide on its fitness for the precipitation data in this vast territory.
To achieve this goal, the rain data from 44 Synoptic meteorological stations for a 25-year cycle has been collected from the organization of meteorology. Using the first, second and third order of Markov Chain then, the continuation parameters among two, three and four-day precipitation were figured out.
Conclusions drawn from the study are: in the cold period of a year:
• Persistence of three-day rain in Iran does not have any auto-correlation virtues and, from the probable structure point of view, belongs to the Independent Bynum Series.
• Four-day rain continuation does not have any auto-correlations, except in the North part of Iran. This chain belongs to Bynum Independent Series, too.
• The best statistical method, among these three ones, used for rain persistence study in Iran during the cold period of a year is the two-state first order Markov Chain method.
• But, during the warm period of a year, the persistence parameter for three and four-day precipitation does not show any auto-correlations for other parts of Iran except for south-western parts of Caspian Sea.
• The two-state first order Markov Chain is the best and most suitable method for analyzing the continuation of