How Does Climate Change Affect Changma Precipitation
Concept of Changma
The etymological meaning of "Changma" (장마) is "a long-lasting rain."
However, the term is currently used in two main contexts.
First, as implied by its origin, it refers to a long-lasting rain, a definition commonly used by the general public. The second definition is the precipitation that falls from the stationary front during the rainy season, which is a common concept among meteorologists.
Recently, precipitation caused by migratory low-pressure systems accompanied by fronts
is also being included in the start of Changma.
Quantitative Definition
Annual cycle of precipitation for the period 1991–2020 (using 56 representative national stations)
(KMA, 2022)
The rainy seasons appear as two distinct periods in summer precipitation, both of which numerically exceed 7mm.
The first period to exceed 7mm begins around June 20, which is called the "Changma season" or the "first rainy season" (1차 우기 - 장마철).
The second period to exceed 7mm occurs from early August to early September and is called the "second rainy season" (2차 우기).
During this second rainy season, the Korean Peninsula moves out of the primary influence of the North Pacific High. This allows phenomena such as extra-tropical cyclones, stationary fronts, and typhoons to bring heavy rainfall. The period from late August to early September, which marks a secondary maximum within the second rainy season, is often referred to as the "autumn Changma".