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ABSTRACT: This study documents monthly temperature and precipitation anomalies over Korea during the different phases of El Niño‐Southern Oscillation (ENSO) for the two types of ENSO evolution. The evolution process of ENSO can be classified into two groups based on whether El Niño turns into La Niña in the subsequent year. The first group involves the transition process from El Niño to La Niña, while the second group shows the prolonged El Niño or neutral conditions after the mature phase of El Niño. Because the mid‐latitude atmospheric responses as well as the equatorial heating anomalies for the two groups of ENSO are different each other, the ENSO‐related climate variation over Korea are investigated separately for the two ENSO evolution groups. In particular, this study focuses on the entire monthly evolution of the temperature and precipitation over Korea during the different phases of ENSO. The statistically robust signals can be found in several particular months, which provides statistical basis for predicting monthly climate over Korea. In addition to the observational data analyses, we further investigate the forecast skill of the Asia‐Pacific Economic Cooperation Climate Center (APCC) Multi‐Model Ensemble (MME) in simulating two groups of ENSO evolution and their impacts on Korean climate. The result shows that the MME reasonably predicts the two different evolution of ENSO as in observation but their prediction skills for the ENSO‐related Korean climate are diverse, which largely depends on the phase of ENSO. [ABSTRACT FROM AUTHOR]

Two distinct modes of snow cover variability over Eurasia are investigated using cyclostationary empirical orthogonal function (CSEOF) analysis. The first mode of Eurasian snow cover extent (SCE) represents a seasonally asymmetric trend between spring and fall. The spring SCE shows a decreasing trend, while the fall SCE particularly in October exhibits a clear increasing trend. This seasonally asymmetric trend of SCE is closely linked to Arctic sea ice decline accompanied by warming in the northern Eurasia. The decreased SCE during spring is primarily attributed to the warm air temperature anomalies, while the increased SCE in October results from the loss of sea ice and the ensuing moisture transport to the atmosphere, which is realized as increased snow in October. The second mode of Eurasian SCE, on the other hand, is closely related to Arctic Oscillation (AO), which is a dominant mode of Northern Hemisphere atmospheric variability. The snow cover variability over Europe during winter is largely affected by AO variability, rather than the warming signal represented by the first CSEOF mode. Detailed descriptions of the two distinct modes of Eurasian SCE and their interactions with oceanic and atmospheric variables are presented along with possible implications for future climate. [ABSTRACT FROM AUTHOR]

This study investigates heat wave variability over Korea during 1979-2017. It is found that the heat waves in Korea can be classified into two distinct types based on the spatial patterns of atmospheric circulation anomalies: the zonal wave (Z-wave) type and the meridional wave (M-wave) type. The Z-wave type is accompanied by large-scale atmospheric waves across the Eurasian continent while the M-wave type is associated with convective activities over the subtropical western North Pacific. The Z-wave type occurs when the high pressure node of eastward propagating wave located around Korea and it seems that the associated wave energy could originate from North Atlantic Ocean. The M-wave type, on the other hand, is driven by northward propagating wave train from subtropical western North Pacific to East Asia which is triggered by anomalous convective activity over the subtropical western North Pacific. It is also found that the downward net radiation flux and reduced latent cooling are main factors for driving severe high temperature over Korea for both types of heat wave. By analyzing radiative as well as dynamical and thermodynamical variables, detailed descriptions on the physical characteristics of two types of heat wave are presented in this study along with the possible implications for summer climate variability over Korea [ABSTRACT FROM AUTHOR]