Researches On The Propagation Characteristics Of Tropospheric-sourced Gravity Waves Based On Ground-onboard Joint Detection

The middle and upper atmosphere range from the stratosphere to the thermosphere and the exosphere.It is the transitional area between the troposphere and outer space.It is also the flight environment of aircrafts such as artificial satellites,which are of great significance for scientific research,national defense,and economic construction.Energy exchange and mass transport occur between different layers of the middle and upper atmosphere,including dynamic processes and chemical processes.In the dominant dynamic process part,the propagation,breaking and dissipation of gravity waves are important in energy and momentum coupling,which plays a leading role in driving the circulation of the mesosphere.The gravity waves are mainly caused by the deep convective events in the troposphere and the wind field fluctuation caused by terrain force.This paper introduces the author's research in acquiring master's degree,mainly focus on the study of upward propagation of gravity waves generated by a hurricane event and the propagation of secondary gravity waves in the middle and upper atmosphere generated by mountain waves.In Chapter 3 of this paper,we report the hurricane-generated gravity waves observed simultaneously in the stratosphere,thermosphere and ionosphere respectively,via remote sensing satellites and GPS ground receivers.From 30 Sept.to 9 Oct.2016,Hurricane Matthew westward crossed the Caribbean Sea and then turned north to the east coast of the United States.During its strongest period in midst of the Caribbean Sea,Matthew excited a large number of concentric gravity waves(GWs,CGWs).We find CGWs with horizontal wavelength of 200-300 km in the stratosphere(30-40 km high)and mesosphere(85-90 km high).Concentric traveling ionospheric disturbances(TID or CTID)with horizontal wavelength of about 250-350 km was found in ionosphere(approximately 100-400 km in height).Besides,TIDs lasted for several hours on each day of 1,2,and 7 Oct.2016.We also briefly discussed the vertical and horizontal propagation of GW and TID caused by Hurricane Matthew.These studies show that Hurricane Matthew caused significant dynamic coupling between the troposphere and the middle and upper atmosphere via gravity wave.Moreover,in Chapter 4 of this paper,we analyzed the quiet-time data of the GOCE satellite,and analyzed a string section of local data collected by the satellite at 23 UTC on 5 July 2010,when it overpassed South Andes at a height of 275 km.By extracting 20 largest traveling atmospheric disturbances(TAD)from density and cross-track wind perturbation by FFT,and by using gravity wave dissipation theory that includes realistic molecular viscosity,we search the gravity wave parameter space to determine which thermospheric hotspot TAD is gravity wave.Finally,17 wave components are considered as gravity waves,and the intrinsic parameters of these waves are determined.We determined the propagation direction of 11 gravity waves components and found that most of the gravity waves have large meridional components in the direction of propagation.Using reverse ray-tracing method,we found that 10 of these components must be produced in the mesosphere or thermosphere.Earlier at the observation time,mountain waves were observed in stratosphere by satellites,and these mountain waves were unstable due to convective instability at a height of 70-75 km.We conclude that these gravity wave components may be secondary(or tertiary,or even higher-order)gravity waves excited by the energy deposited from mountain wave breaking.This part of study proves that the thermosphere gravity wave hotspots over Southern Andes in winter quite-time cannot be modeled by the traditional global circulation model,in which only parameterized tropospheric-launched gravity waves are considered.