Influence of Okhotsk Sea Ice Distribution on a Snowstorm Associated with an Explosive Cyclone in Hokkaido, Japan

Abstract

To investigate the influence of the distribution of sea ice in the Sea of Okhotsk on the behavior of a severe snowstorm, which occurred in Hokkaido, Japan, on 2 March 2013 and which was associated with an explosive cyclone, three WRF simulations with realistic, reduced, and enhanced sea ice-cover were carried out. A comparison among these experiments reveals that the extent of the sea ice influenced low-level temperatures and winds to the rear of the cyclone center during the development of the explosive cyclone over the Sea of Okhotsk. Sea ice insulates the ocean from heat exchange with the atmosphere. As a result, when the Okhotsk sea ice extent reaches Hokkaido Island, cold air masses from the north traverse the island without first being heated by the ocean. The consequent temperature reduction produces a low-level higher pressure region to the rear of the cyclone center. As a result, a large geopotential gradient is generated just to the rear of the cyclone center, and low-level winds are intensified within this region. Therefore, the Okhotsk sea ice extent reaching Hokkaido Island plays a significant role in lowering temperatures and intensifying winds in the island.