This study investigates the effect of the QBO on the occurrence of heavy rainfall days in the southern part of Iran during the cold season.
At first, QBO data from the Singapore station at 30 hPa level from the IGRA database and precipitation data for 89 stations in the southern half of Iran are also provided with daily time scale during the cold six-month period (January 1985 to end of April 2018) according to the 80th percentile (heavy rainfall) for each 6 month.
Then, using IDW interpolation method, correlation maps were plotted for each month separately and six cold months
Based on the obtained data, the QBO values were divided into 6 phases (three weak, moderate, and severe positive phases (+1 to +3) and three weak, moderate, and severe negative phases (-1 to -3)) and the number of days with heavy rainfall in each of these six phases calculated. Then, the zoning maps of the effective phases in increasing the number of days with heavy rainfall for each of the 6 months as well as for the cold months, were plotted. Based on the results, from November to January, the weak to moderate negative phases and the next three months, February to April, the weak positive phases were more likely to contribute to increasing the heavy precipitation days. Also, it showed that the highest number of days of heavy rainfall occurred at most stations in the weak positive phase (+1) in cold months