Case Study of Foehn Events Over Alborz Mountains in Iran

Warm and dry foehn winds can significantly affect human life in mountainous regions worldwide. Foehn’s features include rising temperature, dropping relative humidity, and a fixed direction high wind commencement. Iran, a mountainous country, is affected by foehn in many places. The northern area of Iran is bordered by the Caspian Sea in the north and the Alborz Mountains in the south. The southwest part of the Caspian Sea coastal area is studied here. Large-amplitude mountain waves have occurred and caused severe wildfires in the Caspian forests.

This study demonstrates that foehn events can occur due to high pressure over the interior regions and a lee cyclone over the southern Caspian Sea, with a strong south-north pressure gradient across the Alborz Mountains. Four typical 2021 wind events will be used to illustrate this foehn situation. Sample simulation results indicate the performance of WRF in predicting the variations of meteorological quantities.