The results indicate that a mechanically-driven Foehn occurred in Alborz Mountains during 7-9 January 2016. On the synoptic scale, the Foehn event occurred due to existence of a high pressure over the interior regions of Iran and lee cyclone over the southern Caspian Sea, with a strong pressure gradient in south-north direction across the Alborz Mountains, which was followed by a rapid increase in the intensity of the southerly wind in leeward side of the Alborz Mountains. Alborz Mountains are the primary source of the localized southerly wind maximum around the lee side of Alborz. The Foehn event persisted over the area until a mid-tropospheric trough destroyed the permanent southerly wind and changed it to northerly wind. The WRF simulation reveals that strong meridional surface pressure differences along with a southerly flow is blocked upstream of the Alborz Mountains, resulting in higher nonlinearity and creating large amplitude vertically-propagating mountain waves over the Alborz Mountains. The large long-lived mountain waves, in turn, create a down-slope windstorm (Foehn wind) in the lee of the Alborz Mountains. To quantify these effects the Froude number is calculated. A value of 1.2 is found at 1500 UTC 08 January 2016, indicating a supercritical flow on the lee side of Western Alborz. The study also indicates that the wave-breaking region on the lee side is responsible for reflecting the mountain wave energy back to the ground and for creation of severe down-slope wind in leeward side of Alborz Mountains.
Supplementary URL: Dear Madam or Sir, I would like to attend and present our paper entitled “Simulation of the Structure of Foehn Wind over the Al