Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)region.In this study,we conduct a comparative analysis of the mesospher...Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)region.In this study,we conduct a comparative analysis of the mesosphere tidal results obtained from two adjacent meteor radars at low latitudes in Kunming,China,from November 2013 to December 2014.These two radars operate at different frequencies of 37.5 MHz and 53.1 MHz,respectively.However,overall good agreement is observed between the two radars in terms of horizontal winds and tide observations.The results show that the dominant tidal waves of the zonal and meridional winds are diurnal and semidiurnal tides.Moreover,we conduct an exhaustive statistical analysis to compare the tidal amplitudes and vertical wavelengths recorded by the dual radar systems,which reveals a high degree of alignment in tidal dynamics.The investigation includes variances and covariances of tidal amplitudes,which demonstrate remarkable consistency across measurements from both radars.This finding highlights clear uniformity in the mesospheric tidal patterns observed at low latitudes by the two neighboring meteor radars.Results of the comparative analysis specifically underscore the significant correlation in vertical wavelength measurements,validating the robustness of radar observations for tidal research.展开更多
From Aug.2013 to Oct.2015,a Rayleigh lidar has been used to study the middle atmosphere at Golmud(36.25°N,94.54°E),Qinghai,located in the northeastern part of the Tibetan Plateau.Mesospheric density profiles...From Aug.2013 to Oct.2015,a Rayleigh lidar has been used to study the middle atmosphere at Golmud(36.25°N,94.54°E),Qinghai,located in the northeastern part of the Tibetan Plateau.Mesospheric density profiles from 50 to 90 km were retrieved based on 205 nights of lidar observation,with a total of 1616hours of operation.We compared our lidar density measurements with SABER observations onboard TIMED satellite and MSIS-00 model data.The results showed that the annual mean density measured by lidar agreed well with SABER data,but both were lower than that of MSIS-00.All datasets exhibited dominant annual oscillation in the mesosphere.From 63 to 85 km,the annual amplitude of lidar density is larger than those of SABER and MSIS-00.PDD(Percentage of Density Difference)was calculated to investigate the mesospheric density climatology.The largest density variations of lidar,MSIS-00,and SABER occurred at around 72 km.Both lidar and SABER PDD reached their maximum in May,about one month earlier than the MSIS-00;while the minimum PDD appeared in late December for all datasets.展开更多
In this paper,an analytical model is used to analyze the modulated polar mesospheric winter echoes(PMWE).The winter parameters were introduced to simulate the effects of different parameters during the artificial elec...In this paper,an analytical model is used to analyze the modulated polar mesospheric winter echoes(PMWE).The winter parameters were introduced to simulate the effects of different parameters during the artificial electron heating of PMWE.The important role of the charged dust particle in the creation of PMWE is confirmed again.It is found that during the heating of PMWE,the increases of the dust size,dust charge,electron temperature,initial electron density,and ion-neutral collision frequency cause the increase of the electron density irregularity,and hence the PMWE strength.However,with increasing the dust density,the electron density irregularity and the PMWE strength decrease.展开更多
In this paper, winds derived from OH Meinel 892.0 nm detection by an FPI （Fabry-Perot Interferometer） are compared with the simultaneous wind measurements from a meteor radar during April-May of 2010. The peak heigh...In this paper, winds derived from OH Meinel 892.0 nm detection by an FPI （Fabry-Perot Interferometer） are compared with the simultaneous wind measurements from a meteor radar during April-May of 2010. The peak height of OH Meinel 892.0 nm is about 87 km. The variations of FPI wind at 87 km mostly have the similar track to meteor radar wind at 87 km, and the data values of FPI wind mainly fall into the range of meteor radar wind. However, there are still quantitative differences between the observations of the two systems. The best cross-correlation occurs in rneridional winds from two systems in April of 2010. An obvious wave signal with 0.2 cycle/d frequency is found in meridional winds observed by both FPI and meteor radar.展开更多
Ground-based remote sensing has been an important technique in the measurement of the mesosphere. This technique involves making high spectral resolution measurement of the predominantly pressure-broadening rotational...Ground-based remote sensing has been an important technique in the measurement of the mesosphere. This technique involves making high spectral resolution measurement of the predominantly pressure-broadening rotational spectra of the mesospheric molecules and then inverting the measured spectra to yield information on the vertical distribution of the molecular mixing ratio. Using this technique, we have measured and studied vertical distribution of the mesospheric ozone in 1989 cooperating with Nagoya University.展开更多
The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado （41°N, 105°W） from 1990 to 2010, are employed to research the temporal and spatial...The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado （41°N, 105°W） from 1990 to 2010, are employed to research the temporal and spatial variations and mesopause. We find that the maximum mean temperature is in summer months above 95 kin, but reverse below 95 kin, and there is a cooler region below 185 K around 97 km in August. The largest seasonal variation is 39.2 K at 81 kin, and the minimum is 6.5 K at 96.5 km. The maximum standard derivation in spring and autumn months are larger than other seasons above 105 kin, but the temperatures in March, June and September are lower than the other months between 82 km and 100 km where winter is the largest season. Moreover, the seasonal variations of the temperature are about 36, 8 and 21 K at 85, 95 and 105 km, respectively, winter is colder and summer is warmer above 97.5 km, but reverse below 92 km. The mesopause height is around 102 km in winter, but 84 km in summer, and the mean speed of decreasing or increasing of the mesopause height is about 5 km/month in spring and autumn months which are about 90 km. The lasting time of the mesopause in winter is near 6 months, longer than other seasons, and the mesopause temperature is about 165 K in cool summer, and 185 K in warm winter.展开更多
Ⅰ. INTRODUCTIONThe recent discovery of ozone-hole in the polar region stimulates people to detect a possible long-term trend of atmospheric ozone. Many experimental techniques have been developed for measuring ozone ...Ⅰ. INTRODUCTIONThe recent discovery of ozone-hole in the polar region stimulates people to detect a possible long-term trend of atmospheric ozone. Many experimental techniques have been developed for measuring ozone to obtain the total ozone content and the vertical profiles.展开更多
An all-sky and a scanning Fabry-Perot interferometers (FPI) have been developed for observations of vertical winds and two-dimensional atmospheric motions in the low-thermosphere and the mesosphere region by the measu...An all-sky and a scanning Fabry-Perot interferometers (FPI) have been developed for observations of vertical winds and two-dimensional atmospheric motions in the low-thermosphere and the mesosphere region by the measurement of Doppler shift and broadening of airglow emission lines. The system of FPI is described and the method of data analysis is proposed, an example of observation is also given.展开更多
Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local summer.Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipi...Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local summer.Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter(EISCAT)heating equipment simultaneously with very high frequency(VHF)radar and ultra high frequency(UHF)radar on 12 July 2007.According to the experimental observations,the PMSEs occurrence rate at VHF was much higher than that at UHF,and the altitude of the PMSEs maximum observed at VHF was higher than that at UHF.Overlapping regions were observed by VHF radar between high energetic particle precipitation and the PMSEs.In addition,highfrequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle precipitation.In addition,an updated qualitative method was used to study the relationship between volume reflectivity and frequency.The volume reflectivity was found to be inversely proportional to the fourth power of radar frequency.The theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.展开更多
Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes （PMSE） is studied using the small-scale structure of electron density caused by charged dust particles. A theoreti...Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes （PMSE） is studied using the small-scale structure of electron density caused by charged dust particles. A theoretical expression for the radar volume reflectivity is derived, which agrees with the statistical result. Both the theoretical and statistical results are confirmed with the data obtained from simultaneous observations at three frequencies. Hence the small-scale structure caused by charged dust particles may be a useful tool for the study on the generation mechanism of PMSE.展开更多
Polar mesosphere summer echoes （PMSE） are very strong radar echoes from alti- tudes close to the polar summer mesopause. The data from sounding rocket campaigns indicate that the radar signal to noise ratio （SNR）,...Polar mesosphere summer echoes （PMSE） are very strong radar echoes from alti- tudes close to the polar summer mesopause. The data from sounding rocket campaigns indicate that the radar signal to noise ratio （SNR）, electron density and dust charge density of polar meso- sphere in summer show obvious layered structure. In this paper the theory of wave propagation in layered media is used to study the reflectance and SNR at each layer in polar mesosphere. The calculated SNR using theory of dusty plasma is found in good agreement with the experimental result, which may imply that the intensity of the radar echoes reflected by the layered structure in polar mesosphere where polar mesosphere summer echoes used to occur can interpret partially the phenomenon of PMSE. In other words, reflection may play an important role in the occurrence of PMSE.展开更多
Using PMSE （polar mesosphere summer echoes） observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite （GOES） a special condit...Using PMSE （polar mesosphere summer echoes） observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite （GOES） a special condition is shown for the occurrence of rare observed UHF PMSE. When electron flux observed from GOES satellites show a decrease, then after being in the presence of precipitation UHF PMSE occurs. The heating effect on PMSE is small when the UHF electron density is enhanced at 90 km due to particle precipitation. We analyzed and compared the frequency dependence of PMSE under the condition of high energy particle precipitation in July of 2004 and 2007 at well separated frequencies （224 and 930 MHz） at the same site, height, and time. The frequency index varies with height and time. At different heights, the maximum as well as the minimum value of volume reflectivity at VHF is greater than that at UHF with 2 to 3 orders of magnitude. A new qualitative method for the analysis of dust distribution is used by analyzing the relationship between volume reflectivity and frequency index. In agreement with the results of the model it is shown that dust particles of smaller size generally did not occur at the edges, instead they occurred in the middle PMSE regions.展开更多
The European Incoherent Scatter Scientific Association(EISCAT) Very High Frequency(224 MHz) Radar has been used to investigate the aspect sensitivity of polar mesosphere summer echoes(PMSE) in the period 13–15 July 2...The European Incoherent Scatter Scientific Association(EISCAT) Very High Frequency(224 MHz) Radar has been used to investigate the aspect sensitivity of polar mesosphere summer echoes(PMSE) in the period 13–15 July 2010. The aspect sensitivity of PMSE using this radar and at such a high frequency has not been previously reported. Data concerning the aspect sensitivity of PMSE were collected by traversing the antenna beam from the zenith direction, and comparing the received power. Surprisingly, as the intensity received by the oblique beam was often larger than that of the vertical beam, suggesting the presence of tilted dusty plasma layers as a potential cause, a theoretical model was developed to confirm the existence of these layers and their formation process. The experimental results and theoretical model presented help elucidate the structural properties of the possible generation mechanism of strong radar echoes in the polar summer mesosphere region.展开更多
A Double Sodium Layer(DSL) structure was observed during the night of August 22, 2011 over Haikou,China(20°N,110°E) by Na lidar.This DSL comprised a typical sodium layer at altitudes of 80～105km and a highe...A Double Sodium Layer(DSL) structure was observed during the night of August 22, 2011 over Haikou,China(20°N,110°E) by Na lidar.This DSL comprised a typical sodium layer at altitudes of 80～105km and a higher sodium layer at altitudes of 105～115km in about 0.5 h.A wavelength of 589 nm dye laser pumped by a Nd:YAG laser was used to make the measurement. The backscattered fluorescence photons from the sodium layer were collected by a telescope with a primary mirror of 1000 mm in diameter.The sodium density of these layers during the nighttime observation in the Mesosphere and Lower-Thermosphere(MLT) was studied.展开更多
Since 2002, we have been observing the mesosphere and lower thermosphere （MLT） region over King Sejong Station （KSS; 62.22°S, 58.78°W）, Antarctica, using various instruments such as the Spectral Airglow ...Since 2002, we have been observing the mesosphere and lower thermosphere （MLT） region over King Sejong Station （KSS; 62.22°S, 58.78°W）, Antarctica, using various instruments such as the Spectral Airglow Temperature Imager （SATI）, All Sky Camera （ASC） and VHF meteor radar. The meteor radar, installed in March 2007, continuously measures neutral winds in the alti- tude region 70-110 km and neutral temperature near the mesopause 24 h.d-1, regardless of weather conditions. In this study, we present results of an analysis of the neutral wind data for gravity wave activity over the tip of the Antarctic Peninsula, where such activity is known to be very high. Also presented is temperature estimation from measurement of the decay times of meteor trails, which is compared with other temperature measurements from SATI and the Sounding of the Atmosphere using Broadband Emis- sion Radiometry （SABER） instrument onboard the Thermosphere Ionosphere Mesosphere Energy and Dynamics （TIMED） satel- lite.展开更多
In this work,for the first time,we have analyzed and compared the responses of polar mesosphere winter echoes(PMWE)and their summer counterpart,polar mesosphere summer echoes(PMSE),to high-frequency(HF)heating in term...In this work,for the first time,we have analyzed and compared the responses of polar mesosphere winter echoes(PMWE)and their summer counterpart,polar mesosphere summer echoes(PMSE),to high-frequency(HF)heating in terms of modulated characteristics(i.e.,backscatter intensity reduction,recovery,and overshoot).Both PMWE and PMSE observations were from the same site(Tromsφ,Norway;69.6°N,19.2°E)and radar(EISCAT[European Incoherent Scatter Scientific Association]very high frequency,224 MHz).The heating patterns of both PMWE and PMSE were found to be similar;however,PMSE was more greatly affected by HF heating.Polar mesosphere summer echoes showed recovery and overshoot more frequently than did PMWE.In addition,the mean recovery and overshoot of PMSE were greater than those of PMWE.The associated electron temperature enhancement was estimated for both PMWE and PMSE and showed that,compared with PMWE,the electron temperature enhancement was more significant in PMSE.The strong heating effects on PMSE may be due to the considerable increase in electron temperature.展开更多
Radar echoes intensity of polar mesosphere summer echoes（PMSE） is greatly affected by the temperature of dusty plasma and the frequency of electromagnetic wave about the radar.In this paper,a new method is developed...Radar echoes intensity of polar mesosphere summer echoes（PMSE） is greatly affected by the temperature of dusty plasma and the frequency of electromagnetic wave about the radar.In this paper,a new method is developed to explain the active experiment results of PMSE.The theory of wave propagation in a layered media is used to study the propagation characteristics of an electromagnetic wave at different electron temperatures.The simulation results show that the variation tendency of the reflected power fraction almost agrees with the results observed by radar in the European Incoherent Scatter Scientific Association（EISCAT）.The radar echoes intensity of PMSE greatly decreases with the increase of the radio frequency and the enhancement of the electron temperature.展开更多
Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mes...Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.展开更多
Polar mesosphere summer echoes(PMSE)are observed simultaneously with Digisonde and EISCAT VHF radar.The phenomenon of irregular Es layers is called PMSE-like or PMSE-Es(Polar Mesosphere Summer Echoes-Es)and has some r...Polar mesosphere summer echoes(PMSE)are observed simultaneously with Digisonde and EISCAT VHF radar.The phenomenon of irregular Es layers is called PMSE-like or PMSE-Es(Polar Mesosphere Summer Echoes-Es)and has some relationship with real PMSE.In this paper,the characteristics of irregular Es layers at 80–100 km were observed by Digisonde at Tromsøduring 2003–2014 are statistically analyzed with ionograms.The diurnal,day-to-day and year-to-year variations and discrepancies of occurrence rate between PMSE and PMSE-Es are compared with the statistical results observed by Esrange MST radar(ESRAD),and the reasons are discussed.The results show that the trends in the occurrence rate of PMSE-Es are similar to the trends in the occurrence rate of PMSE,but there are some notable differences.The occurrence rate of PMSE-Es is much lower than the occurrence rate of PMSE.The minimum value of PMSE-Es appears 1–2 hours earlier than the minimum value of the PMSE occurrence rate,while PMSE-Es appear earlier than PMSE in the year.In addition,there is a significant positive correlation between the annual average occurrence rates of PMSE and PMSE-Es.PMSEEs is a relatively important occurrence in the polar mesopause.Analysis of its characteristics can provide new ideas and methods for studying the formation mechanism of PMSE.展开更多
This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust char...This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 42125402 and 42174183)the National Key Technologies R&D Program of China (Grant No.2022YFF0503703)+2 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences (Grant No. XDB41000000)the foundation of the National Key Laboratory of Electromagnetic Environment and the Fundamental Research Funds for the Central Universitiesthe Chinese Meridian Project
文摘Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)region.In this study,we conduct a comparative analysis of the mesosphere tidal results obtained from two adjacent meteor radars at low latitudes in Kunming,China,from November 2013 to December 2014.These two radars operate at different frequencies of 37.5 MHz and 53.1 MHz,respectively.However,overall good agreement is observed between the two radars in terms of horizontal winds and tide observations.The results show that the dominant tidal waves of the zonal and meridional winds are diurnal and semidiurnal tides.Moreover,we conduct an exhaustive statistical analysis to compare the tidal amplitudes and vertical wavelengths recorded by the dual radar systems,which reveals a high degree of alignment in tidal dynamics.The investigation includes variances and covariances of tidal amplitudes,which demonstrate remarkable consistency across measurements from both radars.This finding highlights clear uniformity in the mesospheric tidal patterns observed at low latitudes by the two neighboring meteor radars.Results of the comparative analysis specifically underscore the significant correlation in vertical wavelength measurements,validating the robustness of radar observations for tidal research.
基金Supported by the National Key R and D Program of China(2018YFC1407301,2016YFC1400301)the National Natural Science Foundation of China(41127901)。
文摘From Aug.2013 to Oct.2015,a Rayleigh lidar has been used to study the middle atmosphere at Golmud(36.25°N,94.54°E),Qinghai,located in the northeastern part of the Tibetan Plateau.Mesospheric density profiles from 50 to 90 km were retrieved based on 205 nights of lidar observation,with a total of 1616hours of operation.We compared our lidar density measurements with SABER observations onboard TIMED satellite and MSIS-00 model data.The results showed that the annual mean density measured by lidar agreed well with SABER data,but both were lower than that of MSIS-00.All datasets exhibited dominant annual oscillation in the mesosphere.From 63 to 85 km,the annual amplitude of lidar density is larger than those of SABER and MSIS-00.PDD(Percentage of Density Difference)was calculated to investigate the mesospheric density climatology.The largest density variations of lidar,MSIS-00,and SABER occurred at around 72 km.Both lidar and SABER PDD reached their maximum in May,about one month earlier than the MSIS-00;while the minimum PDD appeared in late December for all datasets.
基金supported by the National Natural Science Foundation of China under Grants No. 61671116 and No. 11905026Fundamental Research Funds for the Central Universities under Grants No. ZYGX2019Z006 and No. ZYGX2019J012。
文摘In this paper,an analytical model is used to analyze the modulated polar mesospheric winter echoes(PMWE).The winter parameters were introduced to simulate the effects of different parameters during the artificial electron heating of PMWE.The important role of the charged dust particle in the creation of PMWE is confirmed again.It is found that during the heating of PMWE,the increases of the dust size,dust charge,electron temperature,initial electron density,and ion-neutral collision frequency cause the increase of the electron density irregularity,and hence the PMWE strength.However,with increasing the dust density,the electron density irregularity and the PMWE strength decrease.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804037, 40890165, and 40921063)the National Important Basic Research Project of China (Grant No. 2011CB811405)the Chinese Meridian Project and the Specialized Research Fund for State Key Laboratories
文摘In this paper, winds derived from OH Meinel 892.0 nm detection by an FPI （Fabry-Perot Interferometer） are compared with the simultaneous wind measurements from a meteor radar during April-May of 2010. The peak height of OH Meinel 892.0 nm is about 87 km. The variations of FPI wind at 87 km mostly have the similar track to meteor radar wind at 87 km, and the data values of FPI wind mainly fall into the range of meteor radar wind. However, there are still quantitative differences between the observations of the two systems. The best cross-correlation occurs in rneridional winds from two systems in April of 2010. An obvious wave signal with 0.2 cycle/d frequency is found in meridional winds observed by both FPI and meteor radar.
基金the National Natural Science Foundation of China.
文摘Ground-based remote sensing has been an important technique in the measurement of the mesosphere. This technique involves making high spectral resolution measurement of the predominantly pressure-broadening rotational spectra of the mesospheric molecules and then inverting the measured spectra to yield information on the vertical distribution of the molecular mixing ratio. Using this technique, we have measured and studied vertical distribution of the mesospheric ozone in 1989 cooperating with Nagoya University.
基金supported by the National Natural Science Foundation of China(Grant Nos.40505005,41304146)the Specialized Research Fund for State Key Laboratories of China
文摘The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado （41°N, 105°W） from 1990 to 2010, are employed to research the temporal and spatial variations and mesopause. We find that the maximum mean temperature is in summer months above 95 kin, but reverse below 95 kin, and there is a cooler region below 185 K around 97 km in August. The largest seasonal variation is 39.2 K at 81 kin, and the minimum is 6.5 K at 96.5 km. The maximum standard derivation in spring and autumn months are larger than other seasons above 105 kin, but the temperatures in March, June and September are lower than the other months between 82 km and 100 km where winter is the largest season. Moreover, the seasonal variations of the temperature are about 36, 8 and 21 K at 85, 95 and 105 km, respectively, winter is colder and summer is warmer above 97.5 km, but reverse below 92 km. The mesopause height is around 102 km in winter, but 84 km in summer, and the mean speed of decreasing or increasing of the mesopause height is about 5 km/month in spring and autumn months which are about 90 km. The lasting time of the mesopause in winter is near 6 months, longer than other seasons, and the mesopause temperature is about 165 K in cool summer, and 185 K in warm winter.
基金On the Chinese side this project is funded by the National Natural Science Foundation of China.
文摘Ⅰ. INTRODUCTIONThe recent discovery of ozone-hole in the polar region stimulates people to detect a possible long-term trend of atmospheric ozone. Many experimental techniques have been developed for measuring ozone to obtain the total ozone content and the vertical profiles.
文摘An all-sky and a scanning Fabry-Perot interferometers (FPI) have been developed for observations of vertical winds and two-dimensional atmospheric motions in the low-thermosphere and the mesosphere region by the measurement of Doppler shift and broadening of airglow emission lines. The system of FPI is described and the method of data analysis is proposed, an example of observation is also given.
基金This research was funded by the Sichuan Science and Technology Program(no.2019YJ0188)the National Natural Science Foundation of China(nos.61671116,61771096,11905026)+2 种基金the National Key Research and Development Program of China(no.2019YFA0210202)Fundamental Research Funds for the Central Universities(nos.ZYGX2019Z006,ZYGX2019J012)We are grateful to the EISCAT Scientific Association for providing the PMSE experimental data(http://portal.eiscat.se/schedule/schedule.cgi).The EISCAT Scientific Association is supported by China(China Research Institute of Radio Wave Propagation),Finland(Suomen Akatemia of Finland),Japan(the National Institute of Polar Research of Japan and Institute for Space-Earth Environmental Research at Nagoya University),Norway(Norges Forskningsråd of Norway),Sweden(the Swedish Research Council),and the UK(the Natural Environment Research Council).We also acknowledge the China Scholarship Council.
文摘Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local summer.Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter(EISCAT)heating equipment simultaneously with very high frequency(VHF)radar and ultra high frequency(UHF)radar on 12 July 2007.According to the experimental observations,the PMSEs occurrence rate at VHF was much higher than that at UHF,and the altitude of the PMSEs maximum observed at VHF was higher than that at UHF.Overlapping regions were observed by VHF radar between high energetic particle precipitation and the PMSEs.In addition,highfrequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle precipitation.In addition,an updated qualitative method was used to study the relationship between volume reflectivity and frequency.The volume reflectivity was found to be inversely proportional to the fourth power of radar frequency.The theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.
基金supported by National Natural Science Foundation of China (No.40831062)the Foundation of the National Key Laboratory of Electromagnetic Environment of China (No.9140C08060367ZCZJ16)
文摘Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes （PMSE） is studied using the small-scale structure of electron density caused by charged dust particles. A theoretical expression for the radar volume reflectivity is derived, which agrees with the statistical result. Both the theoretical and statistical results are confirmed with the data obtained from simultaneous observations at three frequencies. Hence the small-scale structure caused by charged dust particles may be a useful tool for the study on the generation mechanism of PMSE.
基金supported by National Natural Science Foundation of China (Nos.40831062, 60971034)the Scientific Research Starting Foundation of University of Electronic Science and Technology of China (No.Y02002010401066)
文摘Polar mesosphere summer echoes （PMSE） are very strong radar echoes from alti- tudes close to the polar summer mesopause. The data from sounding rocket campaigns indicate that the radar signal to noise ratio （SNR）, electron density and dust charge density of polar meso- sphere in summer show obvious layered structure. In this paper the theory of wave propagation in layered media is used to study the reflectance and SNR at each layer in polar mesosphere. The calculated SNR using theory of dusty plasma is found in good agreement with the experimental result, which may imply that the intensity of the radar echoes reflected by the layered structure in polar mesosphere where polar mesosphere summer echoes used to occur can interpret partially the phenomenon of PMSE. In other words, reflection may play an important role in the occurrence of PMSE.
基金supported by National Natural Science Foundation of China (Nos. 41104097 and 41304119)the Fundamental Research Funds for the Central Universities (Nos. ZYGX2015J039, ZYGX2015J037, and ZYGX2015J041)
文摘Using PMSE （polar mesosphere summer echoes） observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite （GOES） a special condition is shown for the occurrence of rare observed UHF PMSE. When electron flux observed from GOES satellites show a decrease, then after being in the presence of precipitation UHF PMSE occurs. The heating effect on PMSE is small when the UHF electron density is enhanced at 90 km due to particle precipitation. We analyzed and compared the frequency dependence of PMSE under the condition of high energy particle precipitation in July of 2004 and 2007 at well separated frequencies （224 and 930 MHz） at the same site, height, and time. The frequency index varies with height and time. At different heights, the maximum as well as the minimum value of volume reflectivity at VHF is greater than that at UHF with 2 to 3 orders of magnitude. A new qualitative method for the analysis of dust distribution is used by analyzing the relationship between volume reflectivity and frequency index. In agreement with the results of the model it is shown that dust particles of smaller size generally did not occur at the edges, instead they occurred in the middle PMSE regions.
基金supported by CRIRP (China)NIPR (Japan)+3 种基金NFR (Sweden)PPARC (UK)RCN (Norway)SA (Finland)
文摘The European Incoherent Scatter Scientific Association(EISCAT) Very High Frequency(224 MHz) Radar has been used to investigate the aspect sensitivity of polar mesosphere summer echoes(PMSE) in the period 13–15 July 2010. The aspect sensitivity of PMSE using this radar and at such a high frequency has not been previously reported. Data concerning the aspect sensitivity of PMSE were collected by traversing the antenna beam from the zenith direction, and comparing the received power. Surprisingly, as the intensity received by the oblique beam was often larger than that of the vertical beam, suggesting the presence of tilted dusty plasma layers as a potential cause, a theoretical model was developed to confirm the existence of these layers and their formation process. The experimental results and theoretical model presented help elucidate the structural properties of the possible generation mechanism of strong radar echoes in the polar summer mesosphere region.
基金Supported by High Education Research of the Education Department of Hainan Province(Hjkj2012-21)Specialized Research Fund for State Key Laboratories(Y02211J82S,Y02211A49S)
文摘A Double Sodium Layer(DSL) structure was observed during the night of August 22, 2011 over Haikou,China(20°N,110°E) by Na lidar.This DSL comprised a typical sodium layer at altitudes of 80～105km and a higher sodium layer at altitudes of 105～115km in about 0.5 h.A wavelength of 589 nm dye laser pumped by a Nd:YAG laser was used to make the measurement. The backscattered fluorescence photons from the sodium layer were collected by a telescope with a primary mirror of 1000 mm in diameter.The sodium density of these layers during the nighttime observation in the Mesosphere and Lower-Thermosphere(MLT) was studied.
基金financially supported by research funds(Grant nos.PE13010 and PP12320)from the Korea Polar Research Institute
文摘Since 2002, we have been observing the mesosphere and lower thermosphere （MLT） region over King Sejong Station （KSS; 62.22°S, 58.78°W）, Antarctica, using various instruments such as the Spectral Airglow Temperature Imager （SATI）, All Sky Camera （ASC） and VHF meteor radar. The meteor radar, installed in March 2007, continuously measures neutral winds in the alti- tude region 70-110 km and neutral temperature near the mesopause 24 h.d-1, regardless of weather conditions. In this study, we present results of an analysis of the neutral wind data for gravity wave activity over the tip of the Antarctic Peninsula, where such activity is known to be very high. Also presented is temperature estimation from measurement of the decay times of meteor trails, which is compared with other temperature measurements from SATI and the Sounding of the Atmosphere using Broadband Emis- sion Radiometry （SABER） instrument onboard the Thermosphere Ionosphere Mesosphere Energy and Dynamics （TIMED） satel- lite.
基金supported by the National Natural Science Foundation of China(No.62271113,62201529)the National Key Laboratory of Electromagnetic Environment(No.202102010)the Natural Science Foundation of Sichuan Province(No.2022NSFSC1848).
文摘In this work,for the first time,we have analyzed and compared the responses of polar mesosphere winter echoes(PMWE)and their summer counterpart,polar mesosphere summer echoes(PMSE),to high-frequency(HF)heating in terms of modulated characteristics(i.e.,backscatter intensity reduction,recovery,and overshoot).Both PMWE and PMSE observations were from the same site(Tromsφ,Norway;69.6°N,19.2°E)and radar(EISCAT[European Incoherent Scatter Scientific Association]very high frequency,224 MHz).The heating patterns of both PMWE and PMSE were found to be similar;however,PMSE was more greatly affected by HF heating.Polar mesosphere summer echoes showed recovery and overshoot more frequently than did PMWE.In addition,the mean recovery and overshoot of PMSE were greater than those of PMWE.The associated electron temperature enhancement was estimated for both PMWE and PMSE and showed that,compared with PMWE,the electron temperature enhancement was more significant in PMSE.The strong heating effects on PMSE may be due to the considerable increase in electron temperature.
基金supported by National Natural Science Foundation of China(Nos.41104097 and 41304119)by the National Key Laboratoryof Electromagnetic Environment,China Research Institute of Radiowave Propagation(CRIRP)
文摘Radar echoes intensity of polar mesosphere summer echoes（PMSE） is greatly affected by the temperature of dusty plasma and the frequency of electromagnetic wave about the radar.In this paper,a new method is developed to explain the active experiment results of PMSE.The theory of wave propagation in a layered media is used to study the propagation characteristics of an electromagnetic wave at different electron temperatures.The simulation results show that the variation tendency of the reflected power fraction almost agrees with the results observed by radar in the European Incoherent Scatter Scientific Association（EISCAT）.The radar echoes intensity of PMSE greatly decreases with the increase of the radio frequency and the enhancement of the electron temperature.
基金the National Key R&D Program of China(Grant No.2022YFF0503702)the National Natural Science Foundation of China(Grant Nos.42004132,42074195 and 42074183)+1 种基金the open funding of the Ministry of Natural Resources Key Laboratory for Polar Science(Grant No.KP202104)the China Geological Survey(Grant No.ZD20220145).
文摘Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.
基金supported by the National Natural Science Foundation of China(No.61671116,61771096,11905026)National Key Research and Development Program of China(No.2019YFA 0210202)Fundamental Research Funds for the Central Universities(No.ZYGX2019Z006,ZYGX2019J012).
文摘Polar mesosphere summer echoes(PMSE)are observed simultaneously with Digisonde and EISCAT VHF radar.The phenomenon of irregular Es layers is called PMSE-like or PMSE-Es(Polar Mesosphere Summer Echoes-Es)and has some relationship with real PMSE.In this paper,the characteristics of irregular Es layers at 80–100 km were observed by Digisonde at Tromsøduring 2003–2014 are statistically analyzed with ionograms.The diurnal,day-to-day and year-to-year variations and discrepancies of occurrence rate between PMSE and PMSE-Es are compared with the statistical results observed by Esrange MST radar(ESRAD),and the reasons are discussed.The results show that the trends in the occurrence rate of PMSE-Es are similar to the trends in the occurrence rate of PMSE,but there are some notable differences.The occurrence rate of PMSE-Es is much lower than the occurrence rate of PMSE.The minimum value of PMSE-Es appears 1–2 hours earlier than the minimum value of the PMSE occurrence rate,while PMSE-Es appear earlier than PMSE in the year.In addition,there is a significant positive correlation between the annual average occurrence rates of PMSE and PMSE-Es.PMSEEs is a relatively important occurrence in the polar mesopause.Analysis of its characteristics can provide new ideas and methods for studying the formation mechanism of PMSE.
基金the National Natural Science Foundation of China(NSFC)with grant No.61601419.
文摘This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.
