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Dynamics of the Middle Atmosphere: Generation of Planetary Waves by Gravity-Wave Drag
Hye-Yeong Chun 한국기상학회 2021 한국기상학회 학술대회 논문집 Vol.2021 No.4
Large-scale dynamics in the middle atmosphere have been represented mostly by interaction between the mean flow and planetary waves (PWs). As the importance of gravity waves (GWs) has been recognized, with conjunction to GW drag (GWD) parameterization for use in climate and global weather forecasting models that extend to the middle atmosphere has been appreciated more. Now, the large-scale circulations in the middle atmosphere are known to be determined by the interactions among the mean flow, PWs and GWs. Classical wave theory in the middle atmosphere has been represented mostly by the Transformed Eulerian Mean (TEM) equation, which includes the PW and GW forcing separately to the mean flow. Recently, increasing number of modeling studies revealed that stronger GW forcing results in weak PW forcing, implying a compensation between PWs and GWs forcing. There are two ways for GWs to influence on PWs: (i) changing the mean flow that either influences on waveguide of PWs or induces baroclinic/barotropic instabilities to generate in situ PWs, and (ii) generating PWs as a source of potential vorticity equation when asymmetric components of GWD exist. The fist mechanism has been studies extensively associated with stratospheric sudden warmings (SSWs) that are involved large amplitude PWs and GWD. The second mechanism represents more directly the relationship between PWs and GWs, which is essential to understand the dynamics in the middle atmosphere completely (among the mean flow, PWs and GWs). In this talk, a recently reported result of the generation of PWs by GWs associated with the strongest vortex split-type SSW event occurred in January 2009 (Song et al. 2020, JAS) is presented focusing on the second mechanism.
Latitudinal Variations of Convective Source and Propagation Condition of Inertio-Gravity Waves
Hye-Yeong Chun,Jung-Suk Goh 한국기상학회 2004 한국기상학회 학술대회 논문집 Vol.2004 No.-
Latitudinal variations of convective source and vertical propagation condition of IGWs are obtained using GCI and NCEP reanalysis data, and spectral combination of these two factors are analyzed. It was found that convective source that is represented by deep convective heating rate varies significantly in latitude in tropical region between 30°S and 30°N, and the ratio of the maximum to minimum values of DCH is 3.8, which is twice larger than that of potential energy observed in CPS. The vertical propagation condition strongly depends on vertical shear of the zonal-mean zonal wind, and it is not guaranteed that low-frequency IGWs are easy to propagate vertically in the lower latitudes.
Research Collaborations for Better Predictions of Aviation Weather Hazards
Chun, Hye-Yeong,Kim, Jung-Hoon,Lee, Dan-Bi,Kim, Soo-Hyun,Strahan, Matt,Pettegrew, Brian,Gill, Philip,Williams, Paul D.,Schumann, Ulrich,Tenenbaum, Joel,Lee, Young-Gon,Choi, Hee-Wook,Song, In-Sul,Park, American Meteorological Society 2017 Bulletin of the American Meteorological Society Vol.98 No.5