Numerical Modeling of Cold Air Intrusion in the Crimean Region on January 22–24, 2010

V. V. Efimov✉, D. A. Iarovaia

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: vefim38@mail.ru

Abstract

Purpose. The purpose of the work is to numerically investigate the response of near-surface marine and atmospheric fields in the Crimean region to the cold air intrusion in January 22−24, 2010.

Methods and Results. A coupled mesoscale sea–atmosphere model NOW (NEMO-OASIS-WRF) with a 1 km resolution was used. The interaction of incoming airflow with the Crimean Mountains during the cold intrusion was reproduced, as well as the main changes in near-surface atmospheric and marine fields that occurred in the region of the Southern coast of Crimea during the cold air intrusion were analyzed. It is shown that the cold intrusion was characterized by a northeasterly wind throughout the region with maximum speeds up to 10 m/s over the land and up to 20 m/s over the sea. The sea surface temperature in the region decreased mainly by ~ 0.5 °C. To the south of peninsula, in the Rim Current area, a local decrease in sea surface temperature constituted ~ −1.5 … −1 °C. A distinctive feature of the considered case was a small thickness (less than 1 km) of the cold airflow incoming to the Crimean Mountains. On the over-land atmospheric profiles corresponding to the foothill region, a relatively thin cold surface layer with the increased wind speed and high values of stability frequency at its upper boundary is clearly pronounced.

Conclusions. Despite their short duration, winter intrusions of cold air across the northern boundary of the Black Sea region induce significant regional disturbances in the atmospheric and marine fields. The sea responds to cold air intrusions with a decrease in sea surface temperature, which can be explained by strong fluxes of sensible and latent heat from the sea surface, as well as by the entrainment processes at the lower boundary of the upper mixed layer. To the south of the Crimean Peninsula, there is an additional factor contributing to temperature decrease, namely the transport of colder water from the open sea towards the coast, which develops in response to the strengthening of along-coastal northeasterly winds over the sea. In the atmosphere, at its lower levels, the incoming cold flow is blocked by the coastal Crimean Mountains. As a result, the descending compensatory flows arise over the leeward slope of the mountains that leads to an increase in near-surface air temperature at the Southern coast of Crimea. Another consequence of the blocking is the absence of a cold gravity flow on the leeward slope of the Crimean Mountains, unlike other cases of cold air intrusions, such as the Yalta bora event in December 2013.

Keywords

mesoscale coupled modeling, cold air intrusion, Crimea region, near-surface current velocity fields in the sea, near-surface temperature fields in the sea, Black Sea

Acknowledgements

The study was conducted as part of the state assignment (No. FNNN-2024-0014).

Original russian text

Original Russian Text © V. V. Efimov, D. A. Iarovaia, 2025, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 41, Iss. 4, pp. 501–514 (2025)

For citation

Efimov, V.V. and Iarovaia, D.A., 2025. Numerical Modeling of Cold Air Intrusion in the Crimean Region on January 22–24, 2010. Physical Oceanography, 32(4), pp. 524-536.

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