Cold Air Intrusions Over the Maritime Continent: A Comparative Study of the East Asian Winter Monsoon and the Australian Winter Monsoon Using Isentropic Analysis

Abstract This study presents a climatological analysis of cold air intrusions over the Maritime Continent using atmospheric reanalysis data. We consider the Asian‐Australian monsoon as a cold air intrusion from the winter hemisphere into the Maritime Continent and quantify the amount and flux of cold air by an isentropic analysis method. This approach enables a systematic assessment of the cold air transport along the monsoon routes and a consistent analysis of cold air intrusions associated with seasonally reversing monsoons. During the East Asian winter monsoon, cold air covers the western Maritime Continent and flows from the South China Sea throughout the Java Sea to the north of the Australian continent with high flux of cold air. Cold air enters the Maritime Continent partly from the southeast of the Philippine Islands and from the Timor Sea. During the Australian winter monsoon, cold air inflows from the Coral Sea through the sea between the Australian continent and New Guinea Island and accumulates in the southern Maritime Continent due to the topographic barriers of the islands. Cold air outflowing through the islands to the Java Sea and the Pacific Ocean induces cross‐equatorial flows. Cold air transport over the Coral Sea in August is approximately 1.7 times higher than that over the South China Sea in January. The duration period of cold air inflow associated with the Australian winter monsoon is 1.5 times longer than that associated with the East Asian winter monsoon.