Jaeyoung Hwang

Seoul National University | SNU · Department of Earth and Environmental Sciences

Atmospheric blocking has been identified as one of the key elements of the extratropical atmospheric variabilities, controlling extreme weather events in mid-latitudes. Future projections indicate that Northern Hemisphere winter blocking frequency may decrease as CO 2 concentrations increase. Here, we show that such changes may not be reversed when...

On 8–11 August 2022, South Korea experienced a catastrophic heavy rainfall event (HRE) with 14 fatalities. To elucidate its driving mechanisms, the present study performs a multiscale analysis by hierarchically delineating the synoptic and large-scale characteristics of the HRE. Its synoptic condition was featured by the confrontation of the wester...

In a warming climate, storm tracks are projected to intensify on their poleward side. Here we use large-ensemble CO2 ramp-up and ramp-down simulations to show that these changes are not reversed when CO2 concentrations are reduced. If CO2 is removed from the atmosphere following CO2 increase, the North Atlantic storm track keeps strengthening until...

Future changes of extratropical cyclones (ETCs) over East Asia are investigated using the models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). To quantify ETC frequency, intensity, and genesis changes in a warming climate, the objective tracking algorithm is applied to nine CMIP5 models. These models provide...

This study investigates the growth mechanisms of the North Pacific Oscillation (NPO), one of the primary causes of winter temperature extremes at midlatitudes. We find that the NPO has two distinct origins. One is the Rossby wave propagating across Eurasia that strengthens during cold or warm surges over East Asia. The corresponding vorticity and t...

Atmospheric blockings and their impacts on wintertime surface air temperature in East Asia are investigated by using three blocking indices. Blockings in two specific regions that indirectly or directly modulate East Asian climate variability are analyzed: Ural (UR) blocking over East Asia’s northwest and Okhotsk (OK) blocking over East Asia’s nort...

In recent winters, there have been repeated observations of extreme warm and cold spells in the mid-latitude countries. This has evoked questions regarding how winter temperature extremes are induced. In this study, we demonstrate that abnormally warm winter weather in East Asia can drive the onset of extremely cold weather in North America approxi...

The subseasonal relationship between Arctic and Eurasian surface air temperature (SAT) is re-examined using reanalysis data. Consistent with previous studies, a significant negative correlation is observed in cold season from November to February, but with a local minimum in late December. This relationship is dominated not only by the warm Arctic-...

The mechanism of North Pacific (NP) blocking formation is investigated by conducting a reanalysis-based budget analysis of the quasi-geostrophic geopotential tendency equation. It is confirmed that the amplification of NP blocking anomalies primarily results from vorticity fluxes with a minor contribution of heat fluxes. In winter, the cross-freque...