The 2018 Extreme Heat Wave Characteristics over East Asia

In recent years, record-breaking temperatures have been increasing due to global warming and climate variability. Heat waves (HWs) are the most fatal disaster occurring in East Asia, and the necessary science for analyzing and predicting its occurrence have greatly increased with the demand of society. Since the last 100-year of observation history over the Korean Peninsula, the 2018 summer HW and tropical nights was recorded as the most extreme event in terms of its temperature and days of occurrence.

This study investigates the characteristics of 2018 HW in East Asia using European Centre for Medium‐Range Weather Forecasts Re-Analysis (ERA) Interim model data and the surface automatic weather station data. The HW of 2018 summer is compared with three other years (1994, 2013, and 2016) which were also severe HW events. HW conditions in the region are related to the northwestward extension of the western North Pacific subtropical high (WNPSH) toward East Asia. Examination of blocking indices revealed a wide range of blocking over the North Pacific and the Asian continent during periods of HWs, and the occurrence of such blocking was found to be related to stationary weather patterns. The severe temperatures associated with HWs in this region are primarily due to prolonged subsidence. A moist static energy (MSE) budget analysis indicated that the energy source of subsidence is derived not only from advection of MSE but also from net heat flux. In comparison with the synoptic situation during the extreme HW days, relative southward movement of the WNPSH was found before and after the occurrence of the HW. The blocking indices also revealed weak signals and changes in vertical motions due to MSE advection.

Key words: heatwave, tropical night, moist static energy, blocking index