Search

The geopotential height observations from the Aura Microwave Limb Sounder show that the quasi‐6‐day wave (Q6DW) events with westward zonal wavenumber 1 (W1) in the Northern Hemisphere (NH) mesosphere and lower thermosphere (MLT) during September 2013 and 2014 had a prolonged lifetime of ∼45–50 days and reached their maximum amplitudes after the September equinox, while the climatological Q6DW‐W1 is completely dissipated in the background atmosphere before the equinoxes. The Eliassen‐Palm flux diagnostic results indicate that Q6DW‐W1 during September 2013 and 2014 obtained an additional source at ∼60°‐80°S and ∼40–50 km as the September equinox approached, which is related to the baroclinic/barotropic instability in this region. Further investigation on the background atmosphere reveals that several stratospheric minor warming (SMW) events occurred in the Antarctic region during September 2013 and 2014 due to the enhancement of wavenumber 1 activities, accompanied by the increase in the stratospheric temperature, changes in the shape of the polar vortex and the reversal in the zonal mean circulation. The strong planetary wave breaking during the September 2013 and 2014 Antarctic SMW events significantly weakened the strength of the polar night jet (PNJ) and made its peak height descend below ∼35 km, which generated the baroclinic/barotropic instability at the new upper boundary of the PNJ (∼60°‐80°S and ∼40–50 km) by an anomalous double‐jet configuration in the background winds. This unusual instability provided additional wave source and energy for the trans‐equatorial propagation of Q6DW‐W1, which finally led to prolonged wave activities in the NH MLT region. Previous studies have suggested that sudden stratosphere warming (SSW) during wintertime can additionally trigger large‐amplitude traveling planetary waves (PWs) in the mesosphere and lower thermosphere (MLT) region. However, due to the lower occurrence rate and intensity, there are few opportunities to study the impact of Southern Hemisphere (SH) stratospheric warming on global PW behaviors, especially for the climatological event of the eigenmode in the Earth's atmosphere. The Aura satellite observations show that the third climatological event of quasi‐6‐day wave (Q6DW) with westward zonal wavenumber 1 (W1) over one year had an exceptionally long duration in the Northern Hemisphere (NH) MLT region in 2013 and 2014, and abnormally peaked after the September equinox, which is not observed in other years since 2004. The reanalysis data confirms that the stratospheric minor warming (SMW) events occurred over the Antarctic region during September 2013 and 2014, which generated instability under an unusual double‐jet structure in the background winds to provide additional energy for the extension of Q6DW‐W1. The current results establish the relationship between the abnormal PW activities in the NH MLT region and the Antarctic SMW events and provide the first observational evidence that the double‐jet structure can influence the westward propagating PW. The duration of the quasi‐6‐day wave (Q6DW) with s= 1 (W1) in the Northern Hemisphere (NH) was greatly extended in September 2013 and 2014The Antarctic stratospheric minor warmings provided additional wave sources to disrupt the typical dissipation pattern of Q6DW‐W1 in the NHThe impact of the double‐jet structure in the Southern Hemisphere on the behavior of westward propagating planetary waves is first observed The duration of the quasi‐6‐day wave (Q6DW) with s= 1 (W1) in the Northern Hemisphere (NH) was greatly extended in September 2013 and 2014 The Antarctic stratospheric minor warmings provided additional wave sources to disrupt the typical dissipation pattern of Q6DW‐W1 in the NH The impact of the double‐jet structure in the Southern Hemisphere on the behavior of westward propagating planetary waves is first observed

During February 2023, the quasi‐4‐day wave (Q4DW) with westward zonal wavenumber 2 (W2) reached its largest amplitude of ∼400 m in the Southern Hemisphere (SH) geopotential height observations since 2004, which occurred simultaneously with an Arctic major sudden stratospheric warming (SSW) with an elevated stratopause (ES). However, the Q4DW‐W2 perturbations in the Northern Hemisphere (NH) were unexpectedly suppressed despite the unstable Arctic stratosphere and mesosphere during the 2023 ES‐SSW. Diagnostic analysis shows that the westward winds at ∼54°N–70°N in the upper stratosphere of ∼‐79 m/s during the 2023 ES‐SSW were the strongest during boreal winters over the past two decades, which benefited from the onset of a preceding minor SSW at the end of January. The strongest westward wind generated a wave geometry configuration of full reflection for Q4DW‐W2 in the NH, while the Q4DW‐W2 enhancement in the SH was induced by the in‐situ amplification of the surviving seeding perturbations. Among the planetary waves with a period of about 4 days, the eastward quasi‐4‐day wave (Q4DW) excited by the double‐jet structure in the Southern Hemisphere is the most famous one, while another Q4DW with westward zonal wavenumber 2 (W2) belonging to the normal modes of the Earth's atmosphere has attracted little attention. During the February 2023 sudden stratospheric warming (SSW) with an elevated stratopause (ES), the exceptional enhancement and suppression of Q4DW‐W2 were captured in the Southern Hemisphere and Northern Hemisphere, respectively. Such global structure is first observed and abnormal among traveling planetary waves during SSW since they usually have a peak region in the unstable winter hemisphere. We found that the rare sequence of stratospheric disturbances in the 44‐year historical record that a minor SSW followed by an ES‐SSW led to the excessively strong westward wind during the 2023 ES‐SSW, which resulted in a wave geometry configuration of full reflection for Q4DW‐W2 in the Northern Hemisphere. Our current results well establish the relationship between a new global structure of traveling planetary waves during SSW and the rare sequence of stratospheric disturbances. This will deepen the understanding of the less studied Q4DW‐W2 and the Earth's whole atmospheric coupling during SSW. The anomalous burst and suppression of quasi‐4‐day wave (Q4DW) with westward zonal wavenumber 2 (W2) were observed in the Southern Hemisphere and Northern Hemisphere (NH) respectively during the February 2023 major sudden stratospheric warming (SSW) with elevated stratopause (ES)The rare sequence of SSWs in January and February 2023 led to the strongest westward wind during boreal winters over the past two decadesThe strongest westward wind during the 2023 ES‐SSW created a wave geometry configuration of full reflection weakening the Q4DW‐W2 in the NH The anomalous burst and suppression of quasi‐4‐day wave (Q4DW) with westward zonal wavenumber 2 (W2) were observed in the Southern Hemisphere and Northern Hemisphere (NH) respectively during the February 2023 major sudden stratospheric warming (SSW) with elevated stratopause (ES) The rare sequence of SSWs in January and February 2023 led to the strongest westward wind during boreal winters over the past two decades The strongest westward wind during the 2023 ES‐SSW created a wave geometry configuration of full reflection weakening the Q4DW‐W2 in the NH

Fabry Perot interferometer (FPI) is an essential ground‐based passive optical observation device to detect middle and upper atmospheric information. Three FPIs are located at Kunming (103.8°E, 25.6°N), Xinglong (117.4°E, 40.2°N), and Mohe (122.3°E, 53.5°N), China. The diurnal and annual variation of night wind at 87, 97, and 250 km are investigated from 2019 to 2021, compared to Horizontal Wind Model 14 (HWM14) to check the prediction accuracy for the local wind field. Our results are as follows: (a) At 87 km, the zonal winds are similar in Kunming and Xinglong, but the meridional winds are generally stronger in Kunming. The zonal and meridional winds in both locations are dominated by semidiurnal variations. (b) At 97 km, the duration of semidiurnal variation of zonal winds and diurnal variation of meridional winds in Kunming is long, which is opposite to that of Xinglong. (c) At 250 km, the wind speed increases with latitude for both zonal and meridional winds, which are both dominated by diurnal variations for all the three sites. Unlike 87 and 97 km, the entire wind field at 250 km is dominated by annual variation, except for a significant semiannual variation at midnight in Mohe. (d) Overall, the HWM14 predictions are stronger than the FPI measurements at peak wind speeds and similar at 87 and 97 km, which surpasses the performance at 250 km. Especially at 250 km, the model results are worse for the zonal winds of Kunming and the meridional winds of Mohe. These results will help to understand the wind field in the middle and upper atmosphere and improve the accuracy of the model. Characteristics of mesospheric and thermospheric winds over the three stations are studied using three FPIs and compared with HWM14The winds over the three observatories showed latitudinal variation characteristicsOverall, HWM14 predicts stronger winds than FPI measurements Characteristics of mesospheric and thermospheric winds over the three stations are studied using three FPIs and compared with HWM14 The winds over the three observatories showed latitudinal variation characteristics Overall, HWM14 predicts stronger winds than FPI measurements