Abstract
Abstract. The mesosphere and lower thermosphere (MLT) wind structure over Wuhan (30° N, 114° E) in 2000/2001 winter and over Langfang (39.4° N, 116.6° E) in 2009/2010 winter are examined to reveal the effects of stratospheric sudden warming (SSW) in mid-low-latitude MLT region. The result shows that the MLT daily zonal wind over these two sites reversed from eastward wind to westward wind for several days during the SSW events. The reversals were almost coincident with the polar stratospheric temperature reaching its maximum at 10 hPa, 90° N and were about ten days prior to the reversal of high latitude stratospheric zonal wind at 10 hPa, 60° N. The temporal variations of tides, gravity waves and 2-day planetary waves in the mid-latitude MLT showed different behavior during the two SSW events. During the 2001 SSW event, MLT diurnal tide reached its maximum when the MLT zonal wind decreased rapidly and SSW event began in polar stratosphere; the activity of 2-day waves decreased after the onset of the 2001 SSW, while the gravity wave increased when the 2001 SSW developed into a major warming. However, in the 2009/2010 winter, the semidiurnal tide and 2-day wave in MLT over Langfang reached a peak about two days earlier than zonal wind reversal at 10 hPa, 60° N; no significant features were found in diurnal tides, terdiurnal tides and gravity waves related to the 2010 SSW event.
Highlights
The stratospheric sudden warming (SSW) event, first observed by Scherhag in 1952 (Scherhag, 1952), is a spectacular transient phenomenon in the high latitude winter which can influence the whole global atmosphere
The temporal variations of tides, gravity waves and 2-day and diur6n1a8l tideWwuehreanbotdhuirminpgorthanet cpoemripoodneonfts.DTehceemdibure-r 22,pl2a0ne0t0a-ryMwaracvhes1i5n,M2L0T01o.veFroWr utheantinde2s0, 00/2001 winter nal amplitude of zonal wind was sometimes about 15 m s−1 were different from those over Langfang in 2009/2010 winlarger th6a1n9meriddiiuornnaallc,osmempoindeiunrtnaatl9a0nkdmt.eTrdhieudrniuarlntaildaensdare bltuere., WrehdeanntdheblMacLkTrewspinedcstisvtealryte.d to decrease rapidly and semidiurnal tides decayed when the polar stratospheric tem- SSW phenomenon began in Polar Regions around 15 Janperature6r2e0ached its maximum and the mesosphere and lower thermosphere (MLT) zonal winds re- uary 2001, the diurnal tide showed a clear peak while the 2
The observation evidences of this paper prove it is possible the first time, which suggest that the mid-low latitude mesosphere has the same major dynamics with the polar region
Summary
The stratospheric sudden warming (SSW) event, first observed by Scherhag in 1952 (Scherhag, 1952), is a spectacular transient phenomenon in the high latitude winter which can influence the whole global atmosphere It is characterized by a rapid increase of polar stratospheric temperature accompanied with a deceleration or even reversal of the eastward zonal winds. Dowdy et al (2007) investigated the response of the polar MLT atmosphere to seven major SSWs (including the February 2001 event) by using MF radars in the Antarctic and the Arctic They found that on average the zonal winds reversed 4 days earlier in the MLT than in the stratosphere. Observations at Tirunelveli (8.7◦ N, 77.8◦ E) during three major SSW events showed that a reversal of zonal winds occurred several days before the onset of SSWs at high latitude (Sathishkumar et al, 2009). The prevailing winds, tides, gravity waves and planetary waves during the two SSW events were analyzed and compared with the observations in high latitudes
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