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How does the Asian monsoon create the winter-dry Cwa humid subtropical climate?

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Köppen climate classification map — Köppen climate classification The major climatic types are based on patterns of average precipitation, average temperature, and natural vegetation. This map depicts the world distribution of climate types based on the classification originally invented by Wladimir Köppen in 1900.

In the Köppen climate classification, the Cwa subtype is a modified humid subtropical climate defined by a distinct dry winter season, which is primarily driven by the Asian monsoon system.1

During the winter, the intense cooling of the Asian landmass leads to the development of the Siberian anticyclone, a high-pressure system that causes air to diverge outward from the continent. This divergence creates dry, sunny, and cool conditions in regions affected by the Cwa climate. Furthermore, the monsoon circulation influences regional weather patterns by deflecting the paths of the polar front and associated cyclones away from these areas, effectively suppressing winter precipitation.12

In contrast, during the summer, these regions experience moist, maritime airflow that brings higher temperatures and increased rainfall, distinguishing the Cwa climate from the more evenly distributed precipitation found in the Cfa subtype.1