Retrieval Of Temperature Structure And Identification Of Gravity Wave Events In The Middle Atmosphere From Rayleigh Lidar Observations

Since the first ruby laser was created in 1960,laser detection technologies have been widely used in the fields of environmental monitoring,atmospheric remote sensing,aerospace and national defense because laser beams have good properties in brightness,coherence,directivity,and monochromaticity.Based on different interaction mechanisms between laser beams and atmospheric molecules,various lidar devices have been developed,such as Doppler lidar,resonance fluorescence lidar,Mie scattering lidar,Rayleigh scattering lidar,Raman lidar and so forth.Among them,Rayleigh lidar is a typical facility for remote sensing of atmosphere,and atmospheric density and temperature in the altitude range of 30-70 km can be precisely detected via its observations with high spatial and temporal resolutions.Nowadays,as an active optical detection facility,Rayleigh lidar is meaningful to the monitoring of density and temperature variations in the middle and upper atmosphere.In the last several decades,many studies of atmospheric temperature variations and gravity wave(GW)activities in the middle atmosphere have been reported at different latitudes of the world.However,most of them were carried out at middle and higher latitude regions,and few observations were about the mesospheric temperature structures and gravity wave activities at low latitudes.There are full of complicated physical and chemical dynamics processes in the middle atmosphere,and the monitoring of atmospheric activities is significant to the researches on the energy exchange between the earth and the sun,as well as the development of aircraft technology and communication technology.Gravity wave activity is a typical dynamics phenomenon in the middle atmosphere,and atmospheric parameters usually,such as density and temperature,oscillate with the wave perturbations.Meanwhile,the exchange of energy,momentum,and matter between different atmospheres has been realized while GWs propagate from the low atmosphere into the upper atmosphere,which is important to the variations of circulation and composition of the middle and upper atmosphere.Especially,the observations of temperature variations and GW activities at low latitudes are more significant.Hainan Island is in the China South Sea and close to the equator.GW activities in this low latitude region may have different wave sources from those at inland because of the seasonal varied deep convections and equatorial undercurrents on the ocean.Moreover,since it is tropical oceanic monsoon climate,GW propagations are influenced by the special seasonally varying background atmosphere,and GW activities over Hainan may have different regional characteristics.With the support from the Chinese Meridional project,a key national infrastructure project,Hainan lidar(19.9°N,110.3°E)was built in 2010,and the long-term observation of atmospheric activities in the middle and upper atmosphere were realized at Hainan Island.Based on the observation data from Hainan lidar during the January 2011 to July2013,temperature structure of the middle atmosphere over Haikou is retrieved,and GW activities and their characteristics in the power spectral and parameter distribution are statistically analyzed in present study.The main content of this dissertation is as follows:(1)Chanin-Hounchecone method is introduced for retrieving the temperature structure of the middle atmosphere according to Rayleigh lidar observation data.the retrieved atmospheric temperature profiles are compared with simultaneous satellite measurements,and lidar detection precision is discussed.A data analysis process is well designed by us,mainly including data reading and preprocessing,elimination of invalid data,retrieval of atmospheric density and temperature,and comparison with satellite measurements.(2)A complicated analysis method is introduced for extracting atmospheric gravity wave parameters according to the atmospheric temperature perturbation measured by lidar.By applying wavelet analysis to the lidar-measured temperature perturbations,long period components with low-frequency and high-frequency noise signals are eliminated,and the dominant wave components are extracted for gravity wave events.After the power spectral of atmospheric temperature perturbations are calculated via the Fourier transforming,the characteristic parameters of gravity wave perturbations are extracted,such as the vertical wavelength,observation period,and propagation direction.(3)The designed data analysis process is applied to the identification of atmospheric GW events from Hainan lidar dataset,and the characteristic parameters are obtained for every GW event.Comparison and analysis of the statistical research results of GW events in the middle atmosphere with low latitude regions of Gadanki(13.5 ° N,79.2 ° E)with an altitude range of30-70 km and Arecibo(18 ° N,67 ° W)with an altitude range of 25-105 km.At the same time,the statistical results of atmospheric GW is compared with the mesopause atmosphere(80-105km)of Hainan(19.9 ° N,110.3 ° E).The three-year statistical research results of Hainan lidar observation data show that,Statistic results show that the typical gravity waves observed by lidar in the middle atmosphere over Haikou are 5-9 km in vertical wavelength,and 5-13 hours in observation period.Compared to other low latitude regions,the GW activity of Hainan in the middle atmosphere has obvious regional characteristics.At the same time,it was found that the scale of atmospheric GW in the middle layer of Hainan is larger than that in the mesopause region.