Seok‐Woo Son

The impact of stratospheric ozone on the tropospheric general circulation of the Southern Hemisphere (SH) is examined with a set of chemistry‐climate models participating in the Stratospheric Processes and their Role in Climate (SPARC)/Chemistry‐Climate Model Validation project phase 2 (CCMVal‐2). Model integrations of both the past and future climates reveal the crucial role of stratospheric ozone in driving SH circulation change: stronger ozone depletion in late spring generally leads to great

Climate change in the Southern Hemisphere (SH) has been robustly documented in the last several years. It has altered the atmospheric circulation in a surprising number of ways: a rising global tropopause, a poleward intensification of the westerly jet, a poleward shift in storm tracks, a poleward expansion of the Hadley cell, and many others. While these changes have been extensively related with anthropogenic warming resulting from the increase in greenhouse gases, their potential link to stra

Abstract The structure of westerly jets in a statistically steady state is investigated with both dry and moist models on the sphere. The dry model is forced with an idealized radiative equilibrium temperature profile that consists of a global-scale base profile plus both localized tropical heating and high-latitude cooling. The tropical heating controls the intensity of the subtropical jet, while the high-latitude cooling modulates the meridional width of the extratropical baroclinic zone. The

The spatiotemporal structure of the lapse-rate tropopause is examined by using state-of-the-art Global Positioning System radio occultation measurements from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Formosa Satellite Mission 3 mission. The high temporal and spatial resolutions of the data reveal the detailed structure of tropopause properties such as pressure (p<inf>t</inf>), temperature (T<inf>t</inf&amp

Abstract The evolution of the tropopause in the past, present, and future climate is examined by analyzing a set of long-term integrations with stratosphere-resolving chemistry climate models (CCMs). These CCMs have high vertical resolution near the tropopause, a model top located in the mesosphere or above, and, most important, fully interactive stratospheric chemistry. Using such CCM integrations, it is found that the tropopause pressure (height) will continue to decrease (increase) in the fut

Abstract Atmospheric river (AR) and its impact on monsoon rainfall in East Asia are investigated by considering their month‐to‐month variations during the East Asian summer monsoon (EASM). The AR in the EASM, defined as an anomalously enhanced plume‐like water vapor transport, frequently forms over eastern China, Korea and western Japan. However, its characteristics vary from the early (June‐July) to the late (August‐September) period of the EASM. In the early EASM, AR is typically characterized

Southern Hemisphere (SH) climate change has been partly attributed to Antarctic ozone depletion in the literatures. Here we show that the ozone hole has affected not only the long‐term climate change but also the interannual variability of SH surface climate. A significant negative correlation is observed between September ozone concentration and the October southern annular mode index, resulting in systematic variations in precipitation and surface air temperature throughout the SH. This time‐l

The Southern Hemisphere (SH) zonal-mean circulation change in response to Antarctic ozone depletion is re-visited by examining a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models reasonably well reproduce Antarctic ozone depletion in the late 20th century. The related SH-summer circulation changes, such as a poleward intensification of westerly jet and a poleward expansion of the Hadley cell, are also well captured. All experiments

Abstract In the summer of 2020, South Korea experienced record-breaking rainfall due to 15 consecutive heavy rainfall events (HREs) from mid-June to early September. Among them, 11 HREs occurred in late June to mid-August with distinct synoptic characteristics depending on the occurrence period. All HREs from 29 June to 27 July (P1) were triggered by extratropical cyclones, while those from 28 July to 15 August (P2) mainly occurred along monsoon rainband. We argue that their transition is associ

Abstract The deterministic prediction skill of the 10 operational models participating in the subseasonal‐to‐seasonal (S2S) prediction project is assessed for both the extratropical stratosphere and troposphere. Based on the mean squared skill score of 50‐ and 500‐hPa geopotential height forecasts, the overall prediction skill is on average 16 days in the stratosphere and 9 days in the troposphere. The high‐top models with a fully resolved stratosphere typically have a higher prediction skill th

The key factors contributing to the formation and maintenance of the recently discovered extra‐tropical tropopause inversion layer are presently unclear. In this study, it is shown that such a layer can form as a consequence of the turbulent dynamics of synoptic‐scale baroclinic eddies alone, in the absence of explicitly parameterized, small‐scale, radiative‐convective processes. A simple general circulation model, initialized from a state of rest, and driven with idealized forcings, is found to

Abstract The nature of the vertical motion responsible for the summertime heavy rainfall events (HREs) in South Korea is quantitatively examined. By compositing 318 HREs from June to September in 1979–2018, it is found that the synoptic conditions of the HREs are typically characterized by a developing surface cyclone with a southwesterly low-level jet on its southeastern flank and an upper-level trough to the west of the HREs. This baroclinic environment allows for well-organized vertical motio

Abstract The effect of topography on storm-track intensity is examined with a set of primitive equation model integrations. This effect is found to be crucially dependent on the latitudinal structure of the background flow impinging on the topography. If the background flow consists of a weak double jet, higher topography leads to an intensification of the storm track downstream of the topography, consistent with enhanced baroclinicity in that region. However, if the background flow consists of

Abstract The mechanism of North Pacific (NP) blocking formation is investigated by conducting a reanalysis-based budget analysis of the quasigeostrophic 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-frequency vorticity fluxes, resulting from interactions between high-frequency eddies and the slowly varying background flow, dominate the blocking