Climate variability in Iran in response to the diversity of the El Niño‐Southern Oscillation

Through emitting large‐scale planetary waves, the El Niño‐Southern Oscillation (ENSO) contributes to the inter‐annual climate variability in extra‐tropical latitudes, although the impact may be intervened by the chaotic extra‐tropical atmosphere. Using meteorological records of 45 synoptic stations across Iran during the period 1980–2016, impacts of La Niña and the eastern Pacific (EP) and central Pacific (CP) El Niño events on the inter‐annual climate variability of Iran are investigated. The data for four EP El Niño, six CP El Niño and nine La Niña events are averaged to produce a composite view of ENSO. On average, annually Iran is anomalously wet during the EP El Niño and anomalously dry during La Niña, and the anomalies in both phases of ENSO are statistically significant. The impact of ENSO depends not only on the strength of the ENSO event in the tropical Pacific but also on the background climate state of the affected regions such that it is found that the impacts of La Niña and the EP El Niño are generally stronger over the warm and arid regions of Iran. It is also found that the ENSO signal changes with season in many climate zones of Iran, indicating complex interactions between ENSO and other seasonally different features of the climate system. In spite of the seasonal variation of the ENSO signal, most regions of Iran have experienced statistically significant anomalously dry conditions during winter and spring of La Niña events. The most noticeable difference between the two types of El Niño is observed over the Makran coastal plain of Iran where the EP and CP El Niño events have been associated with positive and negative precipitation anomalies, respectively.