How Does Climate Change Affect Changma Precipitation
Thermodynamic Component
: latent heat of vaporization
: gas constant for water vapor
: absolute temperature
The Clausius-Clapeyron (CC) equation governs the maximum amount of water vapor that the atmosphere can hold. The CC equation dictates that the saturation vapor pressure increases exponentially with absolute temperature. The saturation vapor pressure has high temperature sensitivity. Plugging in standard atmospheric values shows that saturation vapor pressure increases by approximately 7% for every 1K in temperature. Thus, as global temperatures rise due to climate change, the atmosphere's capacity to hold moisture increases significantly, leading to a higher specific humidity. The higher specific humidity results in an increase in the moisture flux moving through the atmosphere.
Difference in sea level pressure(SLP) and Moisture Flux at 850hPa
(Moon et al. 2023)
Dynamic Component
The atmospheric dynamics during the summer season are driven by a deepened continental heating, which leads to a large land-sea thermal contrast. The resulting low pressure over the warmed continent and high pressure over the North Pacific Ocean generates strong winds toward East Asia.
As global temperatures rise, the sea surface temperatures in the Western North Pacific ensures that these air masses moving toward the Korean Peninsula substantially transport more moisture. Recalling the moisture budget equation from climatological dynamics, this increased moisture flux convergence is the direct physical mechanism that will lead to an increase in regional precipitation.
Changes in Changma
Unlike our prediction, the processes contributing to increased precipitation over the Korean Peninsula are complex, primarily due to the inconclusive response of the Western North Pacific Subtropical High (WNPSH) to climate change. Based on multiple climate models, some studies project a reinforced WNPSH, while others suggest it will weaken and retreat eastward due to the weakened meridional temperature gradient. Consequently, the only consensus regarding the WNPSH under global warming is an increase in variability and unpredictability.
Despite this dynamic uncertainty, two facts remain certain. The WNPSH is undeniably a major transport pathway for water vapor and the warming of the atmosphere remains the main driver for having more water vapor available in the air masses. This ensures the overall rise in precipitation amount over the Korean Peninsula due to enhanced moisture flux convergence.