武汉与海口地区对流层顶的变化特征

通过对武汉和海口地区2000-2004年Radiosonde常规观测数据的分析,讨论了当地对流层顶温度与高度的年变化特征,并与热带地区站点的结果进行了比较.各等压面温度的扰动、温度递减率及对流层厚度的年变化特征显示,对流层顶更多地受到了平流层的影响.通过对武汉地区2006年1月11-15日Radiosonde加密观测数据的分析,对武汉地区对流层顶周日变化的特征进行了探讨,结果表明武汉地区对流层顶的温度存在显著的周日变化.     

利用COSMIC数据分析全球对流层顶温度和高度的变化特性

利用COSMIC卫星无线电掩星观测的温度数据分析了全球范围的对流层顶参量的变化特性.COSMIC多颗卫星连续观测的温度数据有很好的全球覆盖和很好的垂直分辨率,是分析全球范围对流层顶变化的重要探测数据.经过数据筛选,得到日平均温度的全年分布数据.采用大气温度递减率判据得到对流层顼温度和对流层顶高度的全球分布和变化.结果表明,全球范国内的对流层顶温度和对流层顶高度分布的基本结果与利用无线电探空资料和欧洲气象局再分析数据得到的结果基本一致;对流层项温度和对流层顶高度呈现明显的季节变化,赤道附近和中纬度地区的对流层顶高度变化与高纬地区的对流层顶高度变化出现反相:对流层顶温度和高度的变化呈现明显的南北半球不对称性.     

中国不同地区剩余臭氧及臭氧探空订正因子

根据中国不同地点臭氧探空数据，研究气球炸点臭氧浓度定值（CMR）法、卫星（SBUV和MLS）纬向平均法确定的剩余臭氧Ω_res及其对订正因子C_ref的影响，同时检验臭氧垂直分布对C_ref的贡献.结果显示: CMR法对气球炸点高度依赖性明显，且易高估Ω_res使C_ref整体低于100%；卫星纬向平均Ω_res对气球炸点高度不敏感，但在中国东部的臭氧总量高值区或青藏高原及低纬度臭氧低值地区，Ω_res呈现近10DU以上低值，这是经向臭氧总量及其垂直分布差异在卫星遥感数据上的反映.地面到100hPa的对流层臭氧（Ω_tro），100~10hPa的平流层臭氧（Ω_str）以及10hPa以上的Ω_res对C_ref贡献平均分别为（16±3.4）%，（65±2.3）%，（19±3.3）%.表明基于C_ref评估或订正探空仪平流层臭氧测值时，需考虑对流层臭氧及确定Ω_res方法的影响.卫星纬向平均法，特别是近似实测的SBUV臭氧廓线的值适用于确定Ω_res.      

利用WACCM-3模式对平流层动力、热力场及微量化学成分季节变化的数值模拟研究

利用美国NCAR最新的化学-气候耦合模式WACCM-3对平流层风场、温度场以及平流层臭氧等多种微量气体成分(O3, CH4, N2O, H2O, HCl, HNO3)的季节变化进行了数值模拟, 并使用ECMWF再分析资料与美国UARS卫星 搭载的HALOE, MLS, CLAES等探测器的观测资料, 对模式输出的动力、热力及化学成分浓度的气候平均值进行了验证. 结果表明, 在气候平均海表温度值驱动下, WACCM-3模式能够很好地再现ECMWF资料中平流层纬向平均风场与温度场的季节变化. 模拟结果中平流层化学成分的经向-垂直分布及其季节变化与卫星观测结果基本一致. 模式的动力、热力场在极地平流层以及热带对流层顶等区域存在一定的偏差. 这些偏差对于微量气体成分分布 的模拟具有一定影响, 特别是南半球冬(7月)、春(10月)季节南极平流层低层极夜 急流偏强, 造成极地地区附近的输送障碍增强, 从而导致CH4, N2O, H2O浓度比观测偏低. 此外, WACCM-3缺少热带平流层风场的准两年振荡(QBO) 机制, 这对于热带平流层东风急流以及低纬度平流层O3, CH4, N2O, H2O等成分经向输送的模拟结果也有一定影响.      

基于SABER的平流层顶温度的时空特征分析

利用SABER探测器2002—2017年超过一个太阳活动周的数据,以大气垂直方向上40～60km的最大温度作为平流层顶温度（T_sp）,分析50°S—50°N T_sp的时空分布特征.结果表明:T_sp具有明显的纬度特征和季节特征,在赤道和南北半球夏季温度较高,而在南北半球冬季的40°—50°纬度附近温度有最低值.再利用EOF方法分析T_sp,发现其第一模态的解释率达91%,且时间系数与平流层顶高度相关性最大,为-0.75,与平流层顶臭氧体积混合比相关性约0.49,与日地距离相关性为0.44,与太阳活动性（太阳活动指数,太阳黑子数）的相关性约0.33.依据该相关关系,进一步分析各变量原始场,发现T_sp和平流层顶臭氧体积混合比的纬度变化近似相反;与日地距离的季节变化有明显的负相关,约-0.81,且这种相关性与日地距离有弱的正相关关系;年平均T_sp在2002—2017年的变化约为2K,与F_10.7的相关系数为0.6,在南北纬20°附近与太阳活动指数F_10.7的相关性最大,约0.74.      

台风与电离层f_0F_2相关性的探讨

本文分析了1969、1970、1972、1973四年中,21次台风影响海南岛时,该地区电离层F_2层临频f_oF_2的日变化曲线;找到了台风与电离层f_oF_2变化之间的有规律的相关现象。文中设想了这种相关的定性机制,即台风引起的对流层内的强烈垂直气流可以改变平流层、中间层内的局地环流系统,影响湍流层顶的高度及气体成分比,从而使电离层的电子浓度发生变化。我们认为,通过台风对高层大气的影响,研究上、下层大气耦合是比较现实的手段。     

基于MST雷达数据的中纬对流层和低平流层大气行星波研究

通过分析中国河北香河站MST (Mesosphere-Stratosphere-Troposphere)雷达 2012-2014年的水平风场数据, 研究了北半球中纬地区对流层和低平流层 (Troposphere and Lower Stratosphere, TLS)区域大气行星波的特性. 谱分 析发现, 在这一区域准16天波和准10天波占据主导地位, 准16天波更为显著. 在 对流层区域, 行星波具有丰富的频谱成分, 活动具有间断性, 持续时间一般不 超过三个月, 并没有明显的季节性变化特征, 其中纬向分量的振幅大于经向分量. 在 平流层区域(高度17km以上), 行星波一般出现在冬季, 并且主要在纬向分量中. 通常平流层区域的振幅要小于对流层区域. 结合MERRA再分析资料分 析了强行星波传播特性, 结果表明: 2014年2-3月纬向分量中的准16天波垂 直向上传播, 垂直波长约为64km, 纬圈波数约为2, 纬向传播方向自西向东, 水平波长约为15324.7km, 对应的相速度为11.1m·s-1 (向东为正); 2014年5月纬向分量中的准10天波在10~18km高度范围内向下传播, 垂直波长约为50km, 纬圈波数约为1, 传播方向自西向东, 水平波长约为 30649.4km, 对应相速为35.5m·s-1.      

平流层臭氧和辐射场的季节分布特征

利用美国NCAR化学气候耦合模式WACCM3对平流层温度场、风场、臭氧及辐射场进行了模拟.结果表明,在适宜飞艇长期驻留的准零风层高度20～22km(对应大气压强范围为50～30hPa,以下均采用气压值表征对应大气高度),7-8月风速小于5m·s-1的风带可长期稳定在40°N以北.臭氧空间分布显示,在30hPa气压高度处中国地区臭氧浓度出现了带状分布,30hPa高度以下低纬度地区臭氧浓度低于中纬度地区.平流层太阳加热率的时空变化表明,在平流层上层,太阳加热率可达100×10-6K·s-1,而在平流层下层,只有10×10-6K·s-1.6-8月中国区域的太阳加热率大于9月;在100～30hPa高度内,中纬度地区太阳加热率高于低纬度地区,在30hPa高度以上,低纬度地区太阳加热率高于中纬度地区;8-9月30～40hPa高度处,太阳加热率的空间变化较小.在30hPa高度上,太阳加热率在40°N昼夜变化最大;50hPa高度处,太阳加热率的昼夜变化小于30hPa高度处,而且白天太阳加热率出现极大值的纬度明显靠北.平流层低纬度地区的长波加热率小于中纬度地区.青藏高原由于地形特殊,其6-7月的臭氧浓度、太阳加热率和长波加热率均小于同纬度其他地区.      

基于钠激光雷达观测数据的中间层顶大气温度分布特性研究

作为中间层和热层的边界层,中间层顶存在多种能量交换方式,是大气能量耦合的重要区域。本文利用部署于中国科学院廊坊临近空间大气探测站的钠荧光多普勒激光雷达2013年的观测数据,研究了廊坊上空中间层顶区域大气温度的年度和季节分布特性,并分析了影响温度分布的多种因素。年平均温度廓线图显示,中间层顶位于约97.5 km高度处,温度约191.2 K。受放热化学反应的影响,年平均温度廓线91 km高度处出现了一个198 K的相对温度高点。中间层顶区域大气温度的季节分布受太阳辐射和大气动力学因素综合影响,夏季在大气动力学影响下,中间层顶高度较低,位于88 km高度处,温度也较低,约177 K;冬季太阳辐射起主导作用,中间层顶位于99 km高度处,温度为181 K。通过拟合月平均温度分析了中间层顶区域大气温度年变化和半年变化的振幅和相位特征。结果显示,中间层顶区域上部温度分布主要受太阳辐射的影响;在中间层顶区域下部,大气波动主导了温度分布。      

日全食期间中间层大气臭氧光化过程试验

利用包括活O_x、HO_x、和NO_x等成份在内的一维时变光化模式,研究了日全食时上中层大气臭氧和O₂(1△g)的变化特性,并通过与观测资料的比较进行了光化模式的试验.结果表明,日全食时太阳辐照变化对1.27μm气晖影响的高度比曙暮期间明显偏低,利用1.27μm气晖光度计测量大气臭氧的高度范围约为52-67km.1997年3月9日漠河日全食时测量的大气臭氧含量变化幅度为50％.这与考虑O_x、HO_x、和NO_x等成份的光化模式理论模拟结果基本一致.它表明在52-67km高度范围不存在臭氧亏损现象.      

High vertical resolution water vapour profiles in the upper troposphere and lower stratosphere retrieved from MAESTRO solar occultation spectra

An algorithm has been developed that retrieves water vapour profiles in the upper troposphere and lower stratosphere from optical depth spectra obtained by the Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instrument onboard the SCISAT satellite as part of the Atmospheric Chemistry Experiment (ACE) mission. The retrieval relies on ro-vibrational absorption of solar radiation by water vapour in the 926–970 nm range. During the iterative inversion process, the optical depth spectra are simulated at the spectral resolution and sampling frequency of MAESTRO using the correlated-k approximation. The Chahine inversion updates the water vapour volume mixing ratio (VMR), adjusting all retrieval layers simultaneously, to match the observed differential optical depth due to absorption by water vapour and ozone at each tangent height. This approach accounts for significant line saturation effects. Profiles are typically obtained from ∼22 km down to the cloud tops or to 5 km, with relative precision as small as 3% in the troposphere. In the lower stratosphere, the precision on water vapour VMR is ∼1.3 μmol/mol in an individual retrieval layer (∼1 km thick). The spectral capability of MAESTRO allows for the clear separation of extinction due to water vapour and aerosol, and for the fitting quality to be quantified and used to determine an altitude-dependent convergence criterion for the retrieval. In the middle troposphere, interhemispheric differences in water vapour VMR are driven by oceanic evaporation whereas in the upper troposphere, deep convection dominates and a strong seasonal cycle is observed at high latitudes.     

Periodic and aperiodic ozone variations in the middle and upper stratosphere

Umkehr, ozonesonde and satellite observations were used to determine the height/latitude distribution of the amplitude and phase of the periodic components of the variation of the ozone mixing ratio in the middle and upper stratosphere. The amplitude of the first (annual) harmonic is small in the subtropics and increases to a maximum at polar latitudes. It also increases with height in the mid and upper stratosphere to an apparent maximum just below the stratopause. The second (semi-annual) harmonic has an amplitude that is largest in tropical regions and in subpolar regions at a level of about 40 km. There seems to be very little ozone variation above 30 km with dominant periods close to the quasi-biennial period of total ozone observed in the tropics. The percent of the total variance of the ozone mixing ratio accounted for by the first harmonic is larger than 60 percent at all heights from 20° – 60° latitude in both hemispheres (except near 40 km in the Northern Hemisphere). The percent of the total variance accounted for by the second harmonic is maximum at a height of about 40 km in the tropics and at subpolar latitudes where, as mentioned, its amplitude is also largest.The phase of the first harmonic shows a marked transition from a winter/spring maximum below 30 km to a summer maximum at 30 km, changing rapidly to a maximum in winter in both hemispheres. The regions of minimum amplitude of the annual variation and the marked phase shifts with height both indicate the separation by levels of the dominant physical control mechanisms on the periodic changes of the ozone mixing ratio in the middle and upper stratosphere. Changes below 30 km respond primarily to dynamic influences in the lower stratosphere while above 30 km the periodic variations result mainly from photochemical processes. Above 40 km these variations are strongly temperature dependent.     

Vertical wavenumber spectra of atmospheric ozone measured from ozonesonde observations

Vertical profiles of ozone have been measured at balloon altitudes. Our purpose is to examine the character of vertical wavenumber spectra of ozone fluctuations, to assess the possible roles of gravity wave field in ozone fluctuations, and to determine dominant vertical wavelengths of ozone spectra. Vertical wavenumber spectra of 12 ozone fluctuations obtained during June–August 2003 are presented. Results indicate that mean spectral slopes in the wavenumber range from 4.69 × 10⁻⁴ to 2.50 × 10⁻³ cyc/m are about −2.91 in the troposphere and −2.87 in the lower stratosphere, which is close to the slope of −3 predicted by current gravity wave saturation models. The consistency of the observed spectral slopes with the value of −3 predicted by current gravity wave saturation models suggests that the observed ozone fluctuations are due primarily to atmospheric gravity waves. At m = 1/(1000 m) the mean spectral amplitude is over 30 times larger in the lower stratosphere than in the troposphere. Mean vertical wavenumber spectra in area-preserving form reveal dominant vertical wavelengths of ∼2.6 km in the troposphere and ∼2.7 km in the lower stratosphere, which is consistent with the values varying between 1.5 and 3.0 km estimated from the velocity field and temperature field at these heights.     

Ozone mini-hole observation over the Balkan Peninsula in March 2005

Areas with dimensions of 1000–3000 km in which the total ozone content (TOC) decreases fast are called ozone mini-holes. They are generated mainly dynamically in two ways, either by poor-ozone air mass transport from the tropics to higher latitudes by planetary wave activity or, they are connected with strong adiabatic uplifting of the tropopause height. An ozone mini-hole, generated by the second mechanism, was observed over the Balkan Peninsula on 19/21 March 2005. In the middle of March, the polar vortex was strongly disturbed by Rossby waves, reaching up to the lower stratosphere. Warming episodes over a geographical area, covering the Barents Sea and the Polar Sea north from Central Siberia, displaced a polar vortex fragment extremely southwards. However, the vorticity was weak and the stratospheric temperatures did not reach low values, providing conditions for ozone chemical destruction via heterogenic reactions. At the same time, a Rossby wave ridge was located below the European polar fragment. In the period from 13 to 19 March, the thermal tropopause over Sofia was uplifted almost by 3 km. Ozone distributions observed by the SCIAMACHY instrument on 18–21 March show a fast TOC decrease westwards from Ireland, which was moving eastwards during the next days, increasing the area in which the ozone content decreased. On 20/21 March low ozone content was observed above the Stara Zagora (42°N, 25°E) ground-based station by means of the GASCOD instrument, using DOAS technique. The TOMS Earth probe instrument detected 237 DU over Sofia. This is a record low March value from the beginning of the TOMS instrument measurements in 1978. In March/April the ozone distribution was characterized by its mean annual maximum of 360 DU at 42°N.     

Global pictures of the ozone field,from high altitudes,from DE-I

Using the imaging instrumentation aboard the Dynamics Explorer spacecraft (DE-I), total column ozone densities are obtained in the sunlit hemisphere by measuring the intensities of backscattered solar ultraviolet radiation with multiple filters and multiple photometers. The high apogee altitude (23,000 km) of the eccentric polar orbit allows high resolution global-scale images of the terrestrial ozone field to be obtained within 12 minutes. Previous ozone-monitoring spacecraft have required much longer time periods for comparable spatial coverage because of their lower altitudes (<1200 km). The much higher altitude of DE-I also provides hours of continuous imaging of features compared to minutes or seconds with previous spacecraft. Near perigee, high resolution images can be gained with pixel size as small as 3 km to view mesoscale atmospheric variations. Utilizing these data, the effects of planetary-scale, synoptic-scale, and mesoscale dynamical processes, which control the distribution of ozone near the tropopause, can be studied. Preliminary results show short-term (less than one day) variations in the synoptic ozone field and these variations appear to be in accord with meteorological data. Spatial variations in the ozone field are found to be highly negatively correlated with tropopause altitude.     

Measurements of the upper troposphere and lower stratosphere during tropical cyclones using the GPS radio occultation technique

Water vapour transport to the upper troposphere and lower stratosphere by deep convective storms affects the radiation balance of the atmosphere and has been proposed as an important component of climate change. The aim of the work presented here is to understand if the GPS radio occultation technique is useful for characterization of this process. Our assessment addresses the question if severe storms leave a significant signature in radio occultation profiles in the upper troposphere/lower stratosphere. Radio occultation data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) were analyzed, focusing on two particular tropical cyclones with completely different characteristics, the hurricane Bertha, which formed in the Atlantic Basin during July 2008 and reached a maximum intensity of Category 3, and the typhoon Hondo, which formed in the south Indian Ocean during 2008 reaching a maximum intensity of Category 4. The result is positive, suggesting that the bending angle of a GPS radio occultation signal contains interesting information on the atmosphere around the tropopause, but not any information regarding the water vapour. The maximum percentage anomaly of bending angle between 14 and 18 km of altitude during tropical cyclones is typically larger than the annual mean by 5–15% and it can reach 20% for extreme cases. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.     

Long term solar induced variations in total ozone, stratospheric temperatures and the tropopause

The variations of total ozone, stratospheric temperature and tropopause temperature are presented for the past 3 solar cycles for the summer months of the northern hemisphere. Ground-based, 30-year total column ozone series, filtered from its seasonal, QBO, El Nino/Southern Oscillation (ENSO) and trend components are found to be correlated to the 11-year solar cycle. Model calculations with a 2D chemical transport model are consistent with the observations. Mean stratospheric temperature variations, between levels 100 and 10 hPa, show also the same variation, correlated with the observed 11-year solar cycle, and the tropopause temperature increases in the same manner, in response to a warmer stratosphere during solar maxima.     

Boundary of nighttime ozone chemical equilibrium in the mesopause region: Improved criterion of determining the boundary from satellite data

A modified derivation of the criterion of nighttime ozone chemical equilibrium (NOCE) in the mesopause region is presented. According to 3D model calculations, the improved criterion reproduces the lower boundary of the equilibrium much better than its earlier version. Processing of the SABER/TIMED data of 2021 has shown that the modified criterion elevates the NOCE boundary by ～ 0.1–1.7 km, depending on latitude and season. The proposed method of determining the condition of chemical equilibrium can be used to analyse the equilibrium of many trace gases in the stratosphere and troposphere important for different practical applications.     

Tropopause analysis over the Iranian region using GPS radio occultation data

Near-tropopause phenomena like upper level fronts and cyclones, penetrative cumulus convection and mesoscale mechanisms of exchange make important contributions to the mixing processes in the atmosphere. Spatio-temporal monitoring of the tropopause height, temperature and pressure is an appropriate tool to show the running processes in the atmosphere. In this study, GPS radio occultation data is used to investigate the tropopause height fluctuations and the relation between the stratosphere–troposphere exchange and the aforementioned phenomena over the Iranian region. The paper shows how the position of the sub-tropical jet has changed with time, using GPS radio occultation observations. The tropopause height changes latitudinally, and three different bimodal probability distribution functions are observed. The results also show that the mixing region in the south of Iran is associated with the subtropical jet in winter. However, this region shifts north of Iran due to changes in the position of the subtropical jet during the summer. Consistency of the mixing region from the radio occultation data and the total ozone of TOMS over the Iranian region is also observed.     

Gravity wave propagation studies using the Indian MST radar observations

The Indian MST radar facility at Gadanki (13.5°N, 79.2°E) has been utilised to study the propagation of gravity waves from the troposphere/lower stratosphere to the mesosphere and their interaction with the radar backscattered signal variations. The main objective is to correlate vertically propagating gravity waves derived from the tropospheric velocity fields with the dynamics of mesospheric scattering centres. The tropospheric wind velocities and signal strengths over the entire height range have been subjected to power spectral and wavelet analysis to determine the predominant wave periods/amplitudes and the coupling between the lower atmosphere and mesosphere. Results show that (a) the gravity waves are clearly detectable near tropopause heights, (b) while relatively higher period gravity waves (20–50 min) interact with mesospheric scattering centres, the lower period waves (<20 min) are absorbed in the troposphere itself, (c) the mesospheric scattering layers are affected by gravity waves of complementary periods.