| The strong convective activities in summer,which were related to the wave characteristics of the excitation,can not only induce intense lightning activity in the troposphere,but also excited the concentric gravity waves(CGWs).After being propagated into the stratosphere and mesosphere,the CGWs reached an altitude of 80—90 km,which could modulate the TLEs occurring at the nearby altitude of middle and upper layer.In this paper,the above-mentioned process was taken into full account,and the‘excitation in the troposphere–propagation in the stratosphere–modulation in the mesosphere'was taken as the basic research ideas.Combined with the observation dataset and model verification,it could not only clarify the interrelation between various phenomena,but also provided a basic data sources for the future statistical observations and parameterization.Besides,by using the WWLLN lightning location data,Atmospheric Infrared Sounder(AIRS)data,and FY-2E meteorological satellites data,this study analyzed the distribution characteristics of convective activities and the wave characteristics of observed stratospheric CGWs in the central and eastern China during 2014–2018,and the conditions of stratospheric CGWs propagating to the mesosphere were discussed by the combination of all-sky airglow data,SABER satellite data,and meteoric radar data.In particular,a complete analysis of CGWs event excited by a tropospheric thunderstorm propagating from the stratosphere to mesosphere was carried out.On the basis of actual observation,considering the influence of tropospheric thunderstorm-induced CGWs on neutral atmospheric disturbances,the modulation effect of CGWs on the middle and upper layer TLEs electric field and light radiation field were simulated by using two-dimensional FDTD electromagnetic pulse(EMP)model.The main contents and conclusions were summarized as follows:(1)Convective systems were the main excitation source of stratospheric CGWs in summer.There are two main factors for the stratopsheric CGWs observed by AIRS.On one hand,convetive energy provided by CAPE and the water vapor transpaotation in lower troposphere could mantain the stength of the veritcal convection.On the other hand,the filtering effect of wind field can reduce the interaction of fluctuations between low frequency parts and the high frequency parts,which can mantin the CGWs waveforms.During the summer from 2014 to 2018,the CGWs observed by AIRS propagated eastward,and most of their excitation sources located in the mid-latitude region from 30°N to 40°N.Besides using the least square method,the dispersion relation is necessary to verify the reliability by combining the horizontal wavelength and propagation distance.(2)The waveform parameters of CGWs were associated with the variation character of the convective systems in the excitation period.The values of temperature disturbance ranging from-0.59 K to 1.32 K and average wavelength of 170.81 km,and the propagation distance of 300?700 km were the most common,with the average horizontal propagation distance of 468.28 km.The lack of convective systems was an important reason for the lower amount of AIRS CGWs during the daytime.Both the low value center for the average cloud-top brightness temperature and the lightning concentration area appeared on the east side of the fitting location.At the moment of excitation,the area of TBB below 220 K had an associated correlation with the lightning frequency,and the correlation coefficient between them was 0.53.Within one hour before and after the excitation time,the variation of lightning intensity was related to the amplitude of CGWs,and relative variation of lightning quantity was concentrated in the range of 0.5–1.5 times,positively correlating with the temperature disturbance as a whole.(3)The complete process of CGWs excited by the convective system propagating through the stratosphere and finally reaching the mesosphere layer was observed,and the emergence of thermal inversion layer was conducive to the propagation of the stratospheric CGWs to the mesosphere.After 2.5 hours from the moment of convective excitation,the CGWs propagated to the OH airglow layer(87 km),and the time of CGWs propagation in the stratosphere is 7 hours with a height of 41 km.There was an obvious inversion layer at the height of 85 km.The vertical profile of m~2 show the thermal duct structure(m~2>0)at the height of 82–88 km,which was conducive to the further propagation distance of CGWs.There were five events could propagate to the mesosphere layer among the ten stratospheric CGWs during 2014 to 2018.Gravity wave disturbance was accompanied by the emergence of inversion layer above the height of 80 km,and the inversion layer and extremums of wind velocity appeared at the same height during observation period.The complete process of CGWs excitation and propagation,as well as the multiple observations of the stratospheric CGWs propagating to the middle layer,would provide actual observation data for the parameterization scheme of subsequent studies.(4)By employing the FDTD method,the two-dimensional EMP model established under the influence of CGWs could accurately simulate the development of elves and halos,and the CGWs perturbation had significant influence on electric field and light radiation field.Moreover,the larger the perturbation amplitude was,the more significant change of light radiation pattern was.Concretely,two kinds of lightning current with different amplitude and steepness were selected as the incentive sources respectively,to simulate the process of the electric field variation and the pattern development of the light radiation field of elves and halos.(5)As the result,there were two light radiation field centers in the simulation.The luminous regions were concentrated at 85–100 km,with an inner weaker light radiation center.The electric fields show obvious wavy shape caused by the CGWs at the height of 90–100 km,which mainly occurred during the decline period of electric field with a small gradient,with a40 km distance between the sparse and dense zones corresponding to the horizontal wavelength of the CGWs.The CGWs induced significant deformation of the inner light radiation filed,and particularly split into multiple luminous regions.Simulations of sprite halos indicated that the horizontal range of electrical field generated by lightning current was within 50 km,and a partial strong electric filed formed in the area directly above the lightning channel due to the breakdown current in small areas.Thus,the increased electron density shielded the upper region and reduced the strength of electrical field.The sprite halos luminous zone with a pancake shape,starting at an altitude of 85 km,had a downward tendency.The perturbation of sprite halos luminescence,caused by CGWs,was mainly at the height of 80–100 km directly above the lightning channel,and the main deformation zone was within the horizontal range of 30 km of the lightning channel,which was also the most conspicuous zones for electric field disturbance. |
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