| Major environmental issues such as climate change and environmental evolution are closely related to human activities and have been the research hotpots in recent decades.Although the meteorological data about the troposphere can be used as a data source for seasonal or longer-scale weather forecasts,meteorological data about the middle atmosphere has also become more and more important in climate change forecasts.Since the 21 st century,more and more data models have been added atmospheric dynamics studies on the stratosphere and even mesosphere.Compared with the troposphere,the middle atmosphere evolves more slowly,and the downward transmission effects from the middle atmosphere may lead to continuous and predictable changes in the surface of earth.Therefore,the observation and analysis of the characteristics of the middle atmosphere are of great significance to the study of tropospheric weather conditions.Ozone molecules,which mainly exist in the stratosphere,can absorb the high-energy ultraviolet rays emitted by the sun and are an important barrier to protect the earth's organisms.Carbon monoxide mainly exists in mesosphere and the lower layer of the thermosphere.Because of its long chemical life and low chemical activity,it is a good tracer for the middle atmosphere.Because of the different distribution of ozone and carbon monoxide heights,the coordinated observation of these two molecules can provide comprehensive information about chemistry,mutual transport of substances,atmospheric dynamics,and the influence of solar radiation on the atmospheric composition in the middle atmosphere,and can also provide indispensable data support for a more in-depth explanation of phenomena in the middle atmosphere.In the past few decades,there have been many measuring methods for different types of molecules in the atmosphere at different altitudes.Among them,ground-based microwave radiation measurement technology is favored by people in the field of atmospheric research in various countries because it can observe molecular radiation lines day and night without human supervision,its observations are less effected by the weather,and also because of its advantages of small size and relatively low equipment cost.Nowadays,microwave radiation remote sensing technology is very mature,and the established remote sensing technology can be used to measure the vertical distribution of some gases in the stratosphere and the mesosphere.Wind speed information is particularly important for the study of middle atmosphere dynamics.The study of wind speed can not only reveal the nature of atmospheric circulation changes,but also make reasonable explanations for changes in surface and tropospheric weather.At present,other countries have invested a lot of in-depth research on the middle atmosphere,atmospheric circulation fluctuations and numerical models for predicting future changes.Our country has invested little in the process research and numerical simulations on the middle atmosphere,resulting in a lack of observational data,and the development of related scientific research work is relatively slow.In order to promote the research of the middle atmosphere,the following researches were mainly carried out during the postgraduate period:1.Participate in the design process,observation platform construction and operation of the first ground-based microwave radiometer system RSO3CO-120-1 for middle atmosphere in China.This radiometer uses frequency switching technology to realize the day and night observation of the rotational transition spectrum of ozone and carbon monoxide in the middle atmosphere in the 110-116 GHz frequency band.The total noise of the system is about 560 K and 760 K at the observation frequencies of ozone and carbon monoxide respectively.The radiometer is compact in structure,small in size,easy to move,and can be used as an independent observation unit for long-term stable observation.The radiometer can be operated remotely and requires almost little maintenance.(1)An observation cycle suitable for the microwave radiometer was designed to realize the day and night observation of the spectrum;(2)a new baseline calibration method was proposed for the spectrum data received by the radiometer.Using the data of the heavy rain on August 24,2020,the gain changes of the signal channel and the reference channel was studied.The ratio of the baseline of the two channels excluding the contribution from the molecular signal was determined.This method significantly reduces the asymmetry of the ozone signal in the sidebands.The mean square error of the asymmetry of the ozone line has changed from 0.269 to 0.126.(3)The measurement of the tropospheric opacity is achieved by using the tipping curve measurement.After baseline calibration and tropospheric calibration,the spectral lines well show the day and night changes in ozone content and the seasonal changes in carbon monoxide abundance.2.Based on the ARTS software and the Qpack inversion software package,the simulation of the forward transmission and the inversion algorithm of the spectrum suitable for Changchun area are studied,and the method of calculating the wind speed based on the molecular spectrum and the Doppler effect is provided.(1)Through forward simulation,it can be seen that the mean square error of the noise of the O3 spectrum is about 0.0652 K,and the mean square error of the noise of the CO spectrum is about 0.1444 K.(2)Perform inversion simulation on the observed O3 and CO spectrum,and the inversion results can well reflect the secondary peaks of O3 in winter.Compared with the Aura MLS data,it is found that the inversion data of O3 and CO are in good agreement with the satellite observation data.(3)The study of its average kernel matrix found that the confidence interval of ozone under this algorithm is 30km~81km,and the confidence interval of carbon monoxide is55km~89km.Such an inversion algorithm can also be applied to other molecules,such as the inversion of the distribution of O2 and H2 O.This continuous measurement can help us understand the influence of atmospheric phenomena such as the evolution of the ozone layer,the interannual changes of O3 and CO,the polar vortex and the Brewer-Dobson circulation on mid-latitudes in the future.3.Using the raw data of the CO spectrum observed by the microwave radiometer in Kharkov(36°E,50°N),Ukraine,the CO distribution and wind speed information in the mesosphere were obtained by inversion.Combined with Aura MLS data,ERA-interim data,MERRA-2 reanalysis data and NCEP/NCAR reanalysis data,etc.,the impacts of 2017/2018 the stratospheric sudden warming(SSW)phenomenon in the northern hemisphere on midlatitudes were studied.This study found that:(1)during SSW in 2018,the distribution of CO,the zonal wind,and the temperature of the mesosphere and stratosphere all showed vertical oscillations;the microwave radiometer recorded that the wind speed in the mesosphere changed from westerly 10m/s to easterly-10m/s on February 10,and the fluctuation of CO content in the middle atmosphere was also recorded.(2)The CO changes observed by the microwave radiometer and Aura MLS show similar changes.CO changes over the Kharkov area can be explained by the horizontal redistribution of air caused by changes in planetary wave activity and changes in polar vortices.(3)The study on the changes of planetary waves in the mid-latitude middle atmosphere found that the reversal of the zonal wind has a huge impact on the structure of planetary waves.In the mid-latitude middle atmosphere,the phenomenon that the planetary wave 1 changed from eastward to westward before and after the occurrence of SSW was found;(4)Ten days after the occurrence of SSW,abnormal low temperature was found on the surface of Kharkov.Innovations: This article proposes the data calibration method and inversion method of Chinese first ground-based microwave receiver for middle atmosphere observations;using microwave radiometers has recorded the mesospheric wind speed reversal events during the2018 SSW;the first study of planetary waves Spectrum evolution in the mid-latitude middle atmosphere was conducted. |
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