Sudden Stratospheric Warmings And Planetary Waves Influence On Middle And High Latitude Atmosphere

The environmental problems caused by climate change have become more and more serious,and have been a hot topic in recent years.Climate change is closely related to atmospheric processes,and has a profound impact on the environment and human life.The frequent occurrence of extreme weather has endangered the survival of human homes and the overall development of society.Today,with the rapid development of heavy industry,the problem of air pollution is related to the people’s livelihood and economic development.The change of the atmosphere cannot be ignored.Therefore,it needs in enhanced study of atmospheric processes.In winter polar regions,stratospheric dynamics vary with height.Planetary waves propagating upward from the troposphere can cause the westerly circulation in the stratosphere to slow down or even reverse.This decrease in wind speed can lead to a dramatic increase in stratospheric temperatures,a phenomenon known as sudden stratospheric warming events(SSW events).SSW events can significantly affect the whole middle atmosphere,leading to changes in the thermal and dynamic structure of the stratosphere,mesosphere and low thermosphere,which has a crucial role and influence on the dynamics of the middle atmosphere.It has been shown that the downward propagation of SSW events can affect the tropospheric weather system.Therefore,the study of this event is helpful for weather and climate prediction in short and long–time scales.In addition,many observational studies on SSW events have confirmed that planetary wave propagation dominated by zonal wave number 1 and 2from the troposphere is an essential driving factor for stratospheric warming process and the occurrence of SSW events.With the development of science and technology,scientists have more advanced instruments to investigate the atmospheric composition and dynamics,such as satellites,space stations,rockets,balloons,aircraft,and ground–based equipment.Each observation method has its own corresponding altitude,and the observation method is usually selected according to demand.Among them,microwave remote sensing has become one of the main instruments of modern atmospheric remote sensing because of its relatively low observation cost,small atmospheric transmission attenuation,day–and–night operation and almost no weather dependent.In microwave radiometry,emission spectra from rotational transitions within the observed atmospheric molecular species are measured providing information about the atmosphere.The microwave radiometer introduced in this paper is ground–based passive microwave instrument for atmospheric remote sensing.Through the reception and analysis of signals,the information of ozone and carbon monoxide molecules in the atmosphere can be obtained.This work deals with the study of the sudden stratospheric warmings and planetary waves influence on polar and midlatitude atmosphere based on the data and data processing methods from two ground-based microwave radiometers(MWR)installed one in Kharkiv(Ukraine)and second one – new microwave radiometer recently installed in Jilin University in Changchun,and microwave remote sensing satellite data from Microwave Limb Sounder(Aura MLS).Based on the molecular emission spectra information of ozone and carbon monoxide measured by microwave radiometer,together with the joint analysis of the Aura MLS satellite data,ERA–Interim and ERA–5 reanalyzes data,Modern–Era Retrospective Analysis for Research and Applications(MERRA–2)reanalysis data and other databases,the changes of zonal wind,temperature,geopotential height,atmospheric ozone and CO concentration and other parameters,the planetary waves in the stratosphere and mesosphere,and the sudden stratospheric warming(SSW)events are analyzed.In order to promote the application of microwave based remote sensing in atmospheric dynamics and to receive better understanding of processes during SSWs,my work during my postgraduate period is as follows:1.Development and application of the methods for corrections of microwave emission of ozone and CO molecules observation data,and determine the central channel of molecular spectral line,to improve the measurements of the new microwave radiometer recently installed in Jilin University.The central frequency channel is 3996 when observing ozone molecule with radiometer,and 4015 when observing carbon monoxide molecule.It is found that the baseline of microwave radiometer is unstable and needs to be updated intermittently.Re-evaluate the old baseline of the equipment and replace the new baseline.When processing the recent observation data,the standard deviation of the difference between the high-frequency and low-frequency channels is0.56 K when the old baseline is selected,and 0.17 K when the new baseline is selected,reducing to one third of the original.Study the inversion method in the Qpack software package,analyze and compare the confidence interval of the vertical distribution of ozone molecules and carbon monoxide molecules when selecting different types of core matrix when retrieving the molecular content of ozone and carbon monoxide.Comparing the measured results with Aura MLS satellite data,the maximum difference of the measured ozone volume mixing ratio is about 25%,and the average difference is about 15%.The maximum difference of measured carbon monoxide volume mixing ratio is about 20%,and the average difference is about 15%.2.Based on the microwave radiometer observation and satellite data,analyze and retrieve the differences between the sudden stratospheric warming events in the winter of 2017–2018(SSW1)and 2018–2019(SSW2).The variations and differences in zonal wind,temperature,geopotential height and carbon monoxide concentration in the stratosphere and mesosphere during the two consecutive years of SSW are analyzed in detail.The research shows that the temperature rises during SSW1 and SSW2 is accompanied by the zonal wind reversal,which is defined as the major SSW event.After the SSW event,the vortex recovery time of SSW2 is earlier and stronger than that of SSW1.At the main stage of the SSW2 event,the maximum value of carbon monoxide in the polar vortex appeared over midlatitudes(Kharkov)and moved away during the post-warming period.The vortex strengthening after SSW2 was accompanied by the amplification of planetary wave 1 – 3 in March 2019.This phenomenon did not occur after SSW1.These results show that planetary waves play a major role in the changes of zonal wind,temperature and trace gases observed locally in the SSW event.3.Analyze the difference and correlation of planetary wave components wave–1and wave–2 in the sudden stratospheric warming event in the winter of 2020–2021.The research shows that the change of planetary wave–2 is ahead of planetary wave–1 in the mesosphere layer,and correlation coefficient between amplitudes of wave–1 and wave–2 is r=0.4–0.6.Although the correlation coefficient is not very high,it is statistically significant at the 95% confidence level with the lag time of 1–5 days,which indicates that there is a causal relationship between waves.In the stratosphere,there is a negative correlation between the wave–1 and the wave–2 of the planetary wave,and a positive correlation at 75–91 km in the mesosphere.4.Analyze the evolution process of planetary wave component wave–1 and –2when there is no SSW event in winter to retrieve.the evolution of the stratopause with a particular focus on its zonally asymmetric wave 1 pattern.It was found that the vertical amplification of planetary wave–1 between 50 and 60 kilometers coincides in time with the rapid descent event of the stratopause in the anticyclone region.The amplitude of wave–2 was much lower,but due to the negative correlation coupling with wave–1,it may also partially participate in these processes.During the events from mid–December 2019 to mid–January 2020,the maximum temperature of the anticyclone was located in the range of 30 km to 50 km.In contrast,the maximum temperature inside the polar vortex dropped from about 60 km to about 50 km.This means that the stratopause is inclined,falling from the mesosphere above the polar vortex to the stratosphere above the anticyclone region.The innovation of this thesis:(1)the methods developed for correction and inversion to retrieve the data from the new ground–based microwave radiometer,designed and recently installed in Jilin University;(2)new results on behavior of local mesospheric zonal wind speed variations indicated the development of the sudden stratospheric warming event using microwave radiometer data;(3)the new results for better understanding of atmospheric processes based on analysis and comparison of sudden stratospheric warming events in different years using microwave radiometer observations and satellite data;by analyzing the difference and correlation between planetary wave components,the asymmetry of the stratopause is studied for the first time.This result allows finding out the mechanism responsible for coupling between the vertical wave–1 amplification and zonally asymmetric stratopause descent in the conditions of strong polar vortex and absence of the SSW event.