Combined effect of urbanization and aerosol on the light precipitation in the mid-Korean peninsula

 

Authors

Byung-Gon Kim — Gangneung-Wonju National University
Seung-Hee Eun — Gangneung-Wonju National University


Category

Aerosol-Cloud-Radiation Interactions

Description

Many observational and numerical studies have indicated that urbanization and aerosols can change or modify local and nearby meteorological phenomenon. Our previous study presented the analysis of long-term (1972~2007) precipitation trends in the mid-Korean peninsula around Seoul for the westerly condition, along with the WRF model simulations with the change of anthropogenic heat and surface roughness length. From 1972 to 2007, the precipitation amount (PA) and frequency (PF) together in the downwind region of Seoul significantly increased for the westerly and light precipitation (PA≤1 mm d-1) cases, while PA and PF in the mountainous area decreased. Especially the enhancement ratio of PA and PF for the downwind area versus urban area remarkably increased, implying the possible urbanization effect on the downwind precipitation.

The WRF simulation applied for a golden case (2009/2/11) also demonstrated enhanced updraft and its associated convergence in the downwind area, leading to an increase in the cloud mixing ratio. Sensitivity simulation with an increase in anthropogenic heat shows that updraft is enhanced in the near-downstream region together with the low-level convergence, but creates an insignificant change in cloud water mixing ratio. On the other hand, additional simulations with the WDM6 (WRF Double-moment Six class) microphysics scheme varying CCN concentrations demonstrate a decrease in cloud water mixing ratio in the near-downstream region (up to 60 kilometers from the urban region) and an increase in far-downstream region. In spite of limitations in the observation-based analysis and simulation, the preliminary result could represent combined response such as cancellation and enhancement of urbanization and aerosol effects, especially on the light precipitation in the mid-Korean peninsula.