Laser sounding of aerosols using airborne and space facilities

The paper presents the results of laser sounding of water droplet crystal and mixed clouds carried out using an airborne lidar. A new method of determining the phase state of a cloud is described. The results are given on numerical experiments of laser sounding of various clouds using a polarization lidar for large variety of geometrical parameters of sounding schemes and optical characteristics of clouds. Numerical simulation of the results of laser sounding of aerosols from outer space for different lidar parameters and geometrical schemes of sounding is carried out using new models of vertical profiles of aerosol characteristics.     

Global monitoring of tropospheric water vapor with GPS radio occultation aboard CHAMP

The global positioning system radio occultation (GPS RO) technique provides a powerful tool for atmospheric sounding which requires no calibration, is not affected by clouds, aerosols or precipitation, and provides an almost uniform global coverage. The paper deals with application of GPS RO measurements from CHAllenging Minisatellite Payload (CHAMP) for the retrieval of tropospheric water vapor profiles. CHAMP RO data are available since 2001 with up to 200 high resolution atmospheric profiles per day. We introduce a new direct method for water vapor retrieval from GPS RO data. Additionally, a 1Dvar algorithm is used for this purpose. The so derived CHAMP water vapor profiles are validated with radiosonde data on a global scale. Here, both methods come to statistically comparable results revealing a negative bias of less than 0.1 g/kg and a standard deviation of less than 1 g/kg specific humidity in the mid troposphere. Potentials of CHAMP RO retrievals for monitoring the mean tropospheric water vapor distribution on a global scale are presented.     

武汉上空对流层与平流层大气密度和温度探测的初步结果

利用武汉大学Rayleieh/钠荧光散射激光雷达和无线电探空仪进行联合探测的数据,反演出武汉地区上空(30.5°N,114.4°W)0—65km处的密度和温度分布曲线,并简单阐述了激光雷达的工作原理。将测量结果和MSISE-90参考大气模式比较,二者结果基本符合,温度廓线在中层顶附近和模式的差别约为3K。同时利用激光雷达探测到了中层大气中的重力波活动。     

瑞利激光雷达反演中层大气温度算法

瑞利激光雷达是探测中层大气温度的重要设备,具有高时空分辨率且不存在探测盲区的优点.为充分利用激光雷达探测到的原始数据,改进了传统的Chanin-Haunchecorne方法,采用由均匀搜索生成温度初值的方式反演大气温度.位于北京延庆（40.3°N,116.2°E）的瑞利激光雷达具有589nm和532nm两个通道,将589nm通道用于计算,532nm通道作为参考.在150~250K区间等间隔选取多个温度初值,利用589nm通道反演60~70km高度范围内的大气温度廓线和大气密度廓线,利用参考密度廓线选取准确的温度初值,反演得到准确的大气温度廓线.将589nm通道和532nm通道反演的温度廓线相比较,发现二者具有较高的一致性.改进后的方法有效利用了信噪比较差的光信号,使589nm通道的温度探测上限从60km提高到70km.      

Rocket studies of atmospheric scattering and the aerosol size distribution in the troposphere and lower stratosphere over Thumba

Measurements have been made of the atmospheric scattering in the ultraviolet (λ = 0.31 μm) during the 16 February 1980 solar eclipse rocket campaign. The amplitude of the scattered fluxes as well as the angular distribution could be measured from ground up to an altitude of about 24 km. The Rayleigh scattering component was estimated using standard atmospheric models and the observations have been used to study the scattering due to aerosols at tropospheric and lower stratospheric altitudes.     

A comprehensive study on middle atmospheric thermal structure over a tropic and sub-tropic stations

The general characteristics of middle atmospheric thermal structure have been studied by making use of the Rayleigh lidar data collected over the period of about four years (1998–2001). Here, the data has been used from two different stations in the Indian sub-continent in tropics (Gadanki; 13.5°N, 79.2°E) and in sub-tropics (Mt. Abu; 24.5°N, 72.7°E). The observed monthly mean temperature profiles are compared with different model atmospheres (CIRA-86 and MSISE-90). We observed, the mean temperature profiles have closer agreement with MSISE-90 than CIRA-86. The temperature profiles measured by lidar and HALOE satellite overpass nearby lidar site are generally in agreement with each other. The systematic and statistical errors in deriving temperature are found to be uniform for both the stations, as 1 K at 50 km, 3 K at 60 km and 10 K at 70 km. The special features of mesospheric temperature inversion (MTI) and double stratopause structure (DBS) are also addressed for both the stations.     

不同上边界条件下的极区电离层数值模拟

利用一维自洽的极区电离层模型,研究了沿磁力线方向不同电离层-磁层耦合条件下极区电离层的响应.此模型在110-610km的电离层空间区域内,综合求解描述极区电离层的连续性方程、动量方程和能量方程,以得到电离层数值解.研究发现,上边界条件在200 km以上的高度能显著地影响电离层参量的形态.较高的O+上行速度对应较低的F层峰值和较高的电子温度.不同边界O+上行速度对应的温度高度剖面完全不同.200km以上电子温度高度剖面不但由来自磁层的热流通量所控制,同时还受到场向O+速度的影响.对利用电离层模型研究电离层内部物理过程提出了建议.      

High resolution limb observations of clouds by the CRISTA-NF experiment during the SCOUT-O3 tropical aircraft campaign

The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere – New Frontiers (CRISTA-NF) experiment on board the Russian research aircraft Geophysica measures limb emission spectra with an unprecedented vertical and horizontal resolution in the 4–15 μm wavelength region. The IR spectra measured during the SCOUT-O3 Tropical Aircraft Campaign have been analysed with respect of cloud occurrence, cloud vertical and horizontal extent, cloud spatial structures and their utilisation for trace gas retrievals. In addition indicators for ice water content and optical thickness of the clouds have been adopted. These new kinds of measurements in the upper troposphere/lower stratosphere region are especially valuable for the design and development of future space borne high resolution limb sounders.     

Seasonal Variations of Mesospheric Densities Observed by Rayleigh Lidar at Golmud,Qinghai

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 1616 hours 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.      

Preliminary calibration results of VEGA 1 and 2 SIGMA-3 gas chromatograph

SIGMA - 3 gas chromatograph on board VEGA 1 and 2 landing probes has been operated successfully in the 60 - 50 km altitude range, providing several in - situ chemical analysis of the gas and the aerosols of Venus cloud layers. Post flight calibration required to derive atmospheric abundancies from gas chromatograms were carried out using the SIGMA - 3 spare model. A Venus atmospheric aerosol simulation chamber was used in which sulfuric acid droplets were generated. Preliminary results of these calibration experiments indicate that the concentration of sulfuric acid in the upper part of the clouds ( 60 to 55 km) is about 1 mg/m³ and suggest that an additional constituant must be present in noticeable amount in the aerosols. From these experiments the mixing ratio upper limits of SO₂ is 100 ppmV and of H₂S and COS is few 10 ppmV.     

Aerosol observations for climate studies

The SAM II and SAGE satellite systems have provided to date more than 5 years and almost 3 years, respectively, of data on atmospheric aerosol profiles on a near-global scale. Studies with these unique data sets are developing a global aerosol climatology for the first time and have shown the existence and quantification of polar stratospheric clouds (PSC's) and tropical stratospheric cirrus. In addition, a tropospheric cirrus climatology is evolving. Since these two experiments were launched, a series of large volcanic eruptions have occurred which have greatly impacted the stratospheric aerosol loading. The aerosol layer produced by the eruption of El Chichon, for example, increased the 30 mb temperatures in the northern tropics by as much as 4°C for 6 months after the eruption. This paper will describe in detail, from a climate perspective, the evolving aerosol and cloud climatologies as a function of space and time, and show the stratospheric dynamics of volcanic injections and their enhancements on stratospheric optical depth and mass loading.     

Structure of the middle atmosphere of Venus from analysis of Fourier spectrometer measurements aboard Venera 15

Infrared spectra of Venus measured by means of the Fourier spectrometer aboard Venera 15 orbiter were used for retrievals of temperature profiles of the atmosphere in the altitude range from 60 to 95 km. Monotonous profiles are typical for latitudes lower than 60° latitude, but on the dayside near the equator some traces of the upper atmospheric inversion were found in the profiles. At latitudes greater than 60°N the profiles contain an isothermal or inversional part between 10 and 100 hPa pressure levels. Temperature profiles inside the “warm dipole” maxima are the same as outside of this region and consequently these optical properties should be explained only by peculiarities of cloud structure there.     

Validation of aerosol measurements by the satellite sensors SAM II and SAGE

The satellite sensors SAM II and SAGE have been developing a global data base on stratospheric aerosols since they were launched in October 1978 and February 1979, respectively. The validity of this data base has been tested by numerous comparisons with other measurements made by lidars, balloon-borne particle counters, and aircraft-borne impactors and filters. Because the satellite sensors measure extinction and the correlative sensors measure other properties (e.g., backscatter, number, mass), special techniques are required to convert each measured property to other properties and to quantify conversion uncertainties and measurement uncertainties. Use of these techniques in two major comparative experiments shows that the SAM II and SAGE extinction measurements agree with each other and with values derived from dustsonde, lidar, and filter measurements. In addition, the comparative experiments have highlighted the uncertainties of each type of sensor and stimulated further efforts to reduce these uncertainties.     

Validation of the operational IASI level 2 processor using AIRS and ECMWF data

The algorithms being implemented in EUMETSAT’s IASI Level 2 Product Processing Facility are validated with real case situations using AIRS data and comparing the retrieved atmospheric states with ECMWF analyses. The tests have been performed for clear-sky ocean scenes during daytime.

The Empirical Orthogonal Function (EOF) retrievals show very good performance, with retrieved atmospheric states standard deviations between 1 and 2 K in temperature and 10% and 20% in relative humidity when compared with ECMWF analysis in the troposphere. The EOF retrievals show relatively smooth profiles.

Results from an iterative retrieval show a standard deviation between 2 and 3 K in temperature and 10% and 30% in relative humidity when compared with ECMWF analyses in the troposphere. They tend to show meteorologically reasonable discontinuities in both temperature and relative humidity. This seems to be the reason why they do not compare as well with ECMWF analyses as the EOF retrievals do. Whether they are closer to reality or not will have to be tested with co-located radiosondes or similar more accurate data, which generally do not exhibit such smooth vertical profiles as ECMWF analyses do.     

Estimation of the bias of the Minimum Variance technique in the determination of magnetic clouds global quantities and orientation

Magnetic clouds (MCs) are highly magnetized plasma structures that have a low proton temperature and a magnetic field vector that rotates when seen by a heliospheric observer. More than 25 years of observations of magnetic and plasma properties of MCs at 1 AU have provided significant knowledge of their magnetic structure. However, because in situ observations only give information along the trajectory of the spacecraft, their real 3D magnetic configuration remains still partially unknown. We generate a set of synthetic clouds, exploring the space of parameters that represents the possible orientations and minimum distances of the satellite trajectory to the cloud axis, p. The synthetic clouds have a local cylindrical symmetry and a linear force-free magnetic configuration. From the analysis of synthetic clouds, we quantify the errors introduced in the determination of the orientation/size (and, consequently, of the global magnetohydrodynamic quantities) by the Minimum Variance method when p is not zero.     

激光雷达观测的武汉上空对流边界层高度与夹卷层厚度

基于地基偏振激光雷达2011年1月至2017年12月对武汉中心城区的观测资料，研究了超大城市对流边界层高度与夹卷层厚度的变化特征.采用Fernald方法进行数据反演获得了1min时间分辨率、30m空间分辨率的后散比剖面，通过方差法确定了对流边界层高度和夹卷层厚度.结果表明，武汉上空对流边界层高度和夹卷层厚度具有明显的季节变化特征.对流边界层顶的均值最大处在春季为1.14km，夏季为1.25km，秋季为1.06km，冬季为0.74km；夹卷层厚度均值最大处在春季为0.40km，夏季为0.51km，秋季为0.34km，冬季为0.26km.这些特征与武汉地区地表温度的周年变化特征具有很强的相关性.      

A new non-LTE retrieval method for atmospheric parameters from mipas-envisat emission spectra

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution limb sounder on board the European polar platform ENVISAT, scheduled to be launched in 2001. A large number of atmospheric trace gases relevant to stratospheric ozone chemistry and global change are expected to be retrieved from the IR spectra covering a wide spectral range. While operational data analysis under responsibility of the European Space Agency is limited to conditions of local thermodynamic equilibrium (LTE), the analysis of limb radiances affected by non-LTE is left to scientific institutions. In this paper we present an innovative non-LTE retrieval method as part of the MIPAS semi-operational data processor developed at the Institut für Meteorologie und Klimaforschung (IMK). The new approach enables the treatment of vibrational, rotational, and spin non-LTE as well as a dependence of the non-LTE state distribution on the retrieval target quantities. In a case study, the method has been tested for its application to the non-LTE analysis of 5.3 μm MIPAS radiances. The fundamental ro-vibrational band of nitric oxide emitting at 5.3 μm shows strong non-LTE effects arising from vibrational excitation of stratospheric NO and superposed thermospheric non-LTE emissions. A conventional non-LTE retrieval approach using ab initio vibrational temperatures of NO cannot be applied due to rotational and spin non-LTE in the thermosphere, and the dependence of stratospheric vibrational temperatures on the NO abundance itself. The ability of the developed non-LTE inversion tool to retrieve stratospheric NO abundances is demonstrated by retrieval simulations. The further application of this method to the simultaneous retrieval of NO and kinetic temperature in the thermosphere and the retrieval of important non-LTE process parameters has also been tested.     

基于HITRAN数据库的大气激光雷达信号仿真

信号仿真研究是大气激光雷达研究的重要环节，结果可为激光雷达系统的设计和研制提供基础.本文仿真系统可用于激光雷达回波信号模拟.该仿真系统利用HITRAN数据库中的吸收谱线计算大气分子对激光的吸收光谱，并采用大气辐射传输模型中的气溶胶模式模拟气溶胶对激光的衰减.利用激光雷达方程，数值模拟了355nm，532nm以及1064nm的回波信号，并将532nm的数值模拟结果与实测结果进行对比，评估了激光雷达系统的光学效率.      

Thermal structure of the Martian atmosphere retrieved from the IR spectrometry in the 15 μm CO2 band: input to MIRA

This paper describes one of the sources of the data concerning the thermal structure of the Martian atmosphere, based on the thermal IR spectrometry method. It allows to investigate the Martian atmosphere below 55 km by retrieving the temperature profiles from the 15 μm CO₂ band. This approach enables to reach the vertical resolution of several kilometers and the temperature accuracy of several Kelvins. An aerosol abundance, which influences the temperature profile, is obtained from the continuum of the same spectrum parallel with the temperature profile and is taken into account in the temperature retrieval procedure in a self consistent way. Although this method has the limited vertical resolution, it possesses a significant advantage: the thermal IR spectrometry allows to monitor the temperature profiles with a good coverage both in space and local time. The Planetary Fourier spectrometer on board of Mars Express has the spectral range from 250 to 8000 cm⁻¹ and a high spectral resolution of about 2 cm⁻¹. Vertical temperature profiles retrieval is one of the main scientific goals of the experiment. The important data are expected to be obtained on the vertical thermal structure of the atmosphere, and its dependence on latitude, longitude, season, local time, clouds and dust loadings. These results should give a significant input in the future MIRA, being included in the Chapter “Structure of the atmosphere from the surface to 100 km”.     

简单强磁云的结构特征

本文讨论了1980年12月19日和3月19日两次无大型共转流相联系的行星际简单强磁云事件的磁流体动力学结构特征。此两磁云均以高温、高密度的湍流结构为先导,接着是低温、低密度,磁场很强且倾角单调旋转的磁云本体,后随另一密度稍高的结构。磁云本体内Alfvén波速及磁压对动能密度和热压的比值异常地增高,有利于磁云后的扰动迅速穿越磁云向前传播并向前边界集结。磁云边界上的巨大磁压梯度力及MHD波动在高密度结构内的耗散有可能对磁云前的太阳风进行加速和加热,形成双锯齿流速图象。简单磁云的结构很象典型的日冕质量抛射事件。此外,还简要地分析了磁云引起的地磁暴和宇宙线下降。