Synoptic characteristics of extreme heatwaves over the Korean Peninsula based on ERA Interim reanalysis data

The characteristics of heatwaves (HWs) in South Korea are studied using data from the European Centre for Medium‐Range Weather Forecasts Reanalysis Interim (ERA Interim) dataset and from automatic surface weather stations. The synoptic conditions of three specific years (1994, 2013, and 2016) during which serious HWs affected South Korea are examined. HWs in South Korea are related to the northwestwardly extension of the western North Pacific subtropical high (WNPSH) toward the Korean Peninsula. Examination of the blocking indices revealed widespread blocking over the northern Pacific Ocean and Asia during South Korean HWs, and blocking is related to stationary weather patterns. The severe temperatures associated with HWs in this region are due to prolonged subsidence. Analysis of the moist static energy (MSE) budget indicated that the energy source of subsidence is derived from both MSE advection and the net heat flux. When compared to the synoptic situation during an HW in South Korea, the relative southward movement of the WNPSH is found before and after the HW. The blocking indices also revealed weak signals and changes in vertical motion due to MSE advection. Composites of spatial distributions during the peak of heatwaves (HWs) over South Korea in 1994, 2013, and 2016: (a) P−E, (b) OLR (W m−2), (c) −〈q∇ ∙ ν〉, (d) 500 hPa ω (pa s−1), (e) −〈ν ∙ ∇q〉, (f) 〈ω∂ph〉, (g) Fnet, and (h) −〈ν ∙ ∇T〉. The unit for the other terms is W⋅m−2 shown at the bottom colour bar.