DSpace Collection:

Activities of Small-Scale Gravity Waves in the Upper Mesosphere Observed From Meteor Radar at King Sejong Station, Antarctica (62.22°S, 58.78°W) and Their Potential Sources

2022-03-24T07:15:28Z

Title: Activities of Small-Scale Gravity Waves in the Upper Mesosphere Observed From Meteor Radar at King Sejong Station, Antarctica (62.22°S, 58.78°W) and Their Potential Sources Authors: Song, Byeong-Gwon; Song, I-S; Chun, H-Y; Lee, Changsup; Kam, H.; Kim, Y. H.; Kang, M-J; Hindley, N. P.; Mitchell, N. J. Abstract: Gravity wave (GW) activities in the upper mesosphere (80-100 km) and their potential sources are investigated using meteor radar observations at King Sejong Station, Antarctica (KSS; 62.22°S, 58.78°W) during recent 14 years (2007-2020). GW activities are estimated by horizontal wind variances of small-scale GWs (periods <2 h, horizontal wavelength <400 km, or vertical wavelength <3-5 km). The wind variances show clear semiannual variations with maxima at solstices, and annual variations are also seen above z = 90 km. The deseasonalized wind variances at z = 96.8 km have a statistically significant periodicity of ∼11 years that can be associated with solar cycle variations. Three major potential GW sources in the lower atmosphere are examined. Orography is a potential source of GWs in winter and autumn, when the basic-state wind is westerly from the surface up to the mesosphere. The residual of the nonlinear balance equation (RNBE) at 5 hPa, a diagnostic of the GWs associated with jet stream, is the largest in winter and has a secondary maximum in spring. The correlation between the observed GWs and RNBE is significant in equinoxes, while correlation is low in winter. Deep convection in storm tracks is a potential source in autumn and winter. Secondary GWs generated in the mesosphere can also be observed in the upper mesosphere. Ray-tracing analysis for airglow images observed at KSS indicates that secondary GWs are mostly generated in winter mesosphere, which may be associated with the breaking of orographic GWs.

Temperature teleconnections between the tropical and polar middle atmosphere in the Southern Hemisphere during the 2010 minor sudden stratospheric warming

2022-03-24T07:14:52Z

Title: Temperature teleconnections between the tropical and polar middle atmosphere in the Southern Hemisphere during the 2010 minor sudden stratospheric warming Authors: Eswaraiah, Sunkara; Lee, Changsup; Lee, Wonseok; Kim, Yong Ha; Kumar, Kondapalli Niranjan; Medineni, Venkat Ratnam Abstract: Southern Hemispheric (SH) sudden stratospheric warmings (SSWs) are rela-tively rare compared to their Northern Hemisphere counterparts. No study hasso far investigated the impacts of the SH minor SSWs on the tropical atmo-sphere and connection between the tropical and polar atmospheres. Here, weanalyze the MERRA-2 and ERA-interim datasets, and Microwave LimbSounder satellite temperature measurements to investigate the tropical andpolar atmosphere tele-connections during the SH minor SSW that occurred in2010. Our analysis shows the strong anti-correlation between the polar andtropical temperatures during the 2010 minor SSW in the stratosphere andmesosphere. This is the first observational study over the SH that reveals thetele-connection between the tropical and polar middle atmospheres throughthe temperature during a minor SSW. We verified this tele-connection, usingsimulations of the Ground-to-topside model of Atmosphere and Ionosphere forAeronomy (GAIA) model during the 2010 minor SSW. GAIA model simula-tions show the temperature anti-correlation between the tropical and polarmiddle atmosphere and zonal wind variations. The feature of meridional circu-lation changes was also observed during the SSW period. Hence, the presentstudy strongly suggests that even minor SSW in the SH can affect the meridio-nal circulation in the middle atmosphere via planetary wave activity.

Climatology of polar ionospheric density profile in comparison with mid-latitude ionosphere from long-term observations of incoherent scatter radars: A review

2022-03-24T07:14:17Z

Title: Climatology of polar ionospheric density profile in comparison with mid-latitude ionosphere from long-term observations of incoherent scatter radars: A review Authors: Kim, Eunsol; Jee, Geonhwa; Ji, Eun-Young; Kim, Yong Ha; Lee, Changsup; Kwak, Young-Sil; Shim, Ja-Soon Abstract: Although the horizontal density structures of the polar ionosphere have been extensively studied, there are relatively few studies on the vertical density profiles. In this review, we present the climatology of polar ionospheric density profiles not only in the F-region but also in the E-region and topside ionosphere, in comparison with the mid-latitude ionosphere, using long-term incoherent scatter radar (ISR) observations at Millstone Hill, Tromso, and Svalbard. The observed density profiles during 1995-2015 are analyzed to study on the variations with local time, season, and solar/geomagnetic activity. The diurnal variations of the F-region density are much smaller in the polar region than at mid-latitude, particularly in summer. At Svalbard, there is a characteristic double-peak structure of the polar ionosphere in the diurnal variation in winter and equinox only for high solar activity. The diurnal variation of hmF2 decreases with increasing latitude and eventually disappear at Svalbard for low solar activity. The hmF2 in the polar ionosphere however is greatly enhanced as solar activity increases. The distinctive irregularity in the mid-latitude F1-layer nearly disappears in the polar region, especially at Svalbard. The seasonal variations of the F-region density are less evident in the polar ionosphere especially for low solar activity. The polar E-region density shows characteristic nighttime peaks induced by auroral precipitation but it does not necessarily increase with solar activity. The topside ionospheric density variations are much stronger in the polar region than in the mid-latitude for high solar activity. Finally, it is found that the polar ionospheric density profiles more strongly respond to increasing solar and magnetic activities than the mid-latitude ionosphere.

Unusual Changes in the Antarctic Middle Atmosphere During the 2019 Warming in the Southern Hemisphere

2022-03-24T07:14:40Z

Title: Unusual Changes in the Antarctic Middle Atmosphere During the 2019 Warming in the Southern Hemisphere Authors: Eswaraiah, S.; Kim, Jeong-Han; Lee, Wonseok; Hwang, Junyoung; Kumar, Kondapalli Niranjan; Kim, Yong Ha Abstract: A rare sudden stratosphere warming (SSW) occurred in the southern hemisphere polar region in 2019. The polar stratosphere temperature and planetary wave (PW) enhancements are found to be unusual from the history for 40 years, hence, it is an “Extremely-Rare” SSW. The distinct features of the mesosphere winds were observed during the SSW, in association with the traveling PWs in the stratosphere. The mesosphere zonal winds reversed for about 20 days before the peak SSW. Meteor Radar(MR) and MERRA-2 observations indicate that the zonal wind reversal was descended with time, and the reversal was larger over ~72oS than the MR site (62oS). The MR detected the PWs of 14-22-days before and 8-12-days following the SSW in the mesosphere. We further noticed the enhancement of wavenumber 1 signature in the mesosphere during the peak SSW over the polar region. Thus, the polar middle-atmosphere is greatly affected by the SSW.

DSpace Collection:

Activities of Small-Scale Gravity Waves in the Upper Mesosphere Observed From Meteor Radar at King Sejong Station, Antarctica (62.22°S, 58.78°W) and Their Potential Sources

Temperature tele­connections between the tropical and polar middle atmosphere in the Southern Hemisphere during the 2010 minor sudden stratospheric warming

Climatology of polar ionospheric density profile in comparison with mid-latitude ionosphere from long-term observations of incoherent scatter radars: A review

Unusual Changes in the Antarctic Middle Atmosphere During the 2019 Warming in the Southern Hemisphere

Temperature teleconnections between the tropical and polar middle atmosphere in the Southern Hemisphere during the 2010 minor sudden stratospheric warming