Synoptic-dynamic analysis of precipitation anomalies over Iran in different phases of ENSO.

The study of teleconnection patterns is important to define and predict the temperature and precipitation anomalies and climate changes on a regional scale. In this study, the precipitation anomalies and intensities are analyzed in different El Niño–Southern Oscillation (ENSO) phases based on statistic-synoptic and dynamic approaches in Iran's basins. For this purpose, a network of 717 meteorological stations and rain gauges was created during the period 1987–2015 in 6 basins and 30 sub-basins in Iran. The precipitation anomalies and intensities of these basins were statistically analyzed in different ENSO phases and Oceanic Niño Index (ONI), respectively. To analyze the synoptic and dynamic conditions in a medium El Niño, the negative and positive anomalies in the precipitation were examined in winter 2003 and spring 1992 using monthly European Centre for Medium-Range Weather Forecasts (ECMWF) data. Also, moisture flux convergence (MFC) was calculated and plotted for the lower (850–1000), middle (700–750), and upper (500–600) hPa troposphere layers using GrADS. The results of the precipitation anomalies showed positive and negative fluctuations of ± 100 to ± 150 mm in ENSO phases and ± 50 mm in the neutral phase. Consequently, the seasonal and annual precipitation anomalies were escalated in different ENSO intensities and their different phases. Moreover, it was found that the southeastern, eastern, and central plateau basins were slightly affected by the ENSO. Synoptic and dynamic analysis of precipitation anomalies also demonstrated the role of westward displacement (sea to land) and eastward (land to sea) components of Saudi Arabia's high-pressure system. During the positive precipitation anomalies (with a significant eastward displacement to the east and settled on the Arabian Sea), advection of heat and humidity toward Iran and penetration trough in the Middle East caused the increased intensity and extension of precipitations. [ABSTRACT FROM AUTHOR]