The purpose of this study is to characterize the synoptic climatic patterns of extreme humansensible temperature (HST) events in Jeju Island, Korea under a subtropical climate condition as well as to examine their teleconnections with the large-scale climate systems. According to the extreme case analysis of the recent 30 years (1988-2017) data sets, the maximum daily average HST in the coastal areas of Jeju Island can rise up to about 40°C in mid-summer and even up to about 48°C during mid-daytime. These extreme HST events occur when the expansion of subtropical Pacific high pressure toward East Asia as well as the poleward shift of the Changma front provides hot and humid conditions over Jeju Island surrounded by seas, particularly in La Niña years with a positive (+) Arctic Oscillation mode. In contrast, the intensified western high and eastern low dipole pressure pattern in mid-winter, which accompanies the downward shear of upper tropospheric cold air toward the southern region of the Korean Peninsula under a negative (-) Arctic Oscillation mode, provides favorable conditions for frequent low HST extreme events. These conditions can lower daily average HST as much as -10°C in the coastal region of Jeju Island, and lower nighttime HST by -25°C on the peak areas of Mt. Halla due to wind chill effects. These findings will be used as a base for establishing prediction and warming systems of extreme HST events on Jeju Island, which is needed to mitigate the damage to the lives of Jeju residents and tourists under climate change.

The purpose of this study is to uncover the characteristics of spatio-temporal patterns and synoptic climatic patterns of thermodynamic föhn phenomenon accompanying orographic precipitation across Mt. Halla for the recent several decades. Analyses of surface observational data reveal that thermodynamic föhn days occur mainly between mid-spring and early summer (April-June) particularly in the form of North warm-South wet type across Mt. Halla due to the accelerated moisture advection around a migratory low pressure. In extreme cases of thermodynamic föhn across Mt. Halla, more than 6.0°C of daily mean temperature difference between windward and leeward sides is observed though its spatial patterns vary seasonally. Composite maps of upper synoptic climatic variables for multiple strong föhn days show that the relative position and intensity of a migratory low or high pressure anomaly cores as well as of semi-stationary fronts and air masses affect the seasonal spatial patterns and severity magnitudes of thermodynamic föhn around Mt. Halla. These results provide a scientific basis for developing a proactive föhn prediction system to reduce potential damages of föhn phenomenon to local economic activities in Jeju Island.