Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data

Abstract

Abstract. The coupling processes in the middle atmosphere have been a subject of intense research activity because of their effects on atmospheric circulation, structure, variability, and the distribution of chemical constituents. In this study, the day-to-day variability of Aura-MLS (Microwave Limb Sounder) temperature data are used to reveal the vertical and interhemispheric coupling processes in the stratosphere-mesosphere during four Northern Hemisphere winters (2004/2005-2007/2008). The UKMO (United Kingdom Meteorological Office) assimilated data and mesospheric winds from MF (medium frequency) radars are also applied to help highlight the coupling processes.In this study, a clear vertical link can be seen between the stratosphere and mesosphere during winter months. The coolings and reversals of northward meridional winds in the polar winter mesosphere are often observed in relation to warming events (Sudden Stratospheric Warming, SSW for short) and the associated changes in zonal winds in the polar winter stratosphere. An upper-mesospheric cooling usually precedes the beginning of the warming in the stratosphere by 1-2 days.Inter-hemispheric coupling has been identified initially by a correlation analysis using the year-to-year monthly zonal mean temperature. Then the correlation analyses are performed based upon the daily zonal mean temperature. From the original time sequences, significant positive (negative) correlations are generally found between zonal mean temperatures at the Antarctic summer mesopause and in the ArcCorrespondence to: X. Xu (xix303@mail.usask.ca) tic winter stratosphere (mesosphere) during northern midwinters, although these correlations are dominated by the low frequency variability (i.e. the seasonal trend). Using the short-term oscillations (less than 15 days), the statistical result, by looking for the largest magnitude of correlation within a range of time-lags (0 to 10 days; positive lags mean that the Antarctic summer mesopause is lagging), indicates that the temporal variability of zonal mean temperature at the Antarctic summer mesopause is also positively (negatively) correlated with the polar winter stratosphere (mesosphere) during three (2004/2005, 2005/2006, and 2007/2008) out of the four winters. The highest value of the correlation coefficient is over 0.7 in the winter-stratosphere for the three winters. The remaining winter (2006/2007) has more complex correlations structures; correspondingly the polar vortex was distinguished this winter. The time-lags

Characteristics of Arctic tides at CANDAC-PEARL (80° N, 86° W) and Svalbard (78° N, 16° E) for 2006–2009: radar observations and comparisons with the model CMAM-DAS

“…Xu et al, 2009a, b), as was the case for 2006/2007 (Paper 1). This is consistent with the prevalence of anticyclones to form in the Pacific-Western Canada longitudinal sector, and the cyclone to be resident over Scandinavia (Manson et al, 2008(Manson et al, , 2011Xu et al, 2009b).…”

Coupling in the middle atmosphere related to the 2013 major sudden stratospheric warming

“…2) was used as the reference in the correlations, and the time period, from 1 January-28 February 2013, was chosen to include the main perturbations caused by the SSW. The approach is similar to that of Xu et al (2009), except that in our study the winter mesosphere has been used as a baseline rather than the summer mesosphere.…”

Impact of January 2005 solar proton events on chlorine species

“…The absence of strong temperature increases and associated reversals of the zonal winds indicates that the NH winter of 2004/05 was without major sudden stratospheric warmings (e.g., Chshyolkova et al, 2007;Xu et al, 2009;Damiani et al, 2010b). However, the winter of 2004/05 was particularly cold and dynamically active, especially in the lower stratosphere WMO, 2007;El Amraoui et al, 2008).…”