A cryogenically operated laser diode spectrometer for airborne measurement of stratospheric trace gases

A cryogenically operated laser diode spectrometer (COLD) for the airborne measurement of carbon monoxide is described. The instrument is designed, and fully qualified, for operation on a high-altitude aircraft and the scientific mission is the in situ measurement of trace gases in the upper troposphere and lower stratosphere. Sensitivities achieved so far during in-flight operation are a few ppbV with a time resolution of 4 s, coupled with a good reliability. Airborne data, obtained by COLD during research campaigns in Australia and Brazil in the frame of international projects, are also presented to demonstrate COLD in-flight performance. PACS 82.80.Gk; 42.62.Fi; 07.88.+y     

High spatial and temporal resolution mobile incoherent Doppler lidar for sea surface wind measurements

A mobile Doppler lidar based on an injection-seeded diode-pumped Nd:YAG pulsed laser with a high repetition rate was developed to measure the sea surface wind (SSW) with high spatial and temporal resolution. The system was operated during the 2007 Qingdao International Regatta to measure the distribution of SSW in the racing area in real time with 50-100 m horizontal resolution and 2-10 min temporal resolution. An observation of nonuniform distribution of SSW is presented. The lidar results are compared with both buoy and wind tower measurements, which show good agreement. This lidar can be used advantageously for the 2008 Olympic sailing games as well as for observing mesoscale and microscale meteorology processes.     

Study of ozone concentration variations in the upper stratosphere using millimeter wave spectroscopy methods

New results of the study of ozone concentration variations in the upper stratosphere over Moscow in the layer at a height of 40 km, which is most sensitive to anthropogenic impacts, are presented. Changes in the ozone concentration and its relation to other atmospheric parameters in cold periods of 2008–2009 and 2009–2010 are analyzed. It was shown that there exist regions with decreased ozone content in the polar vortex and outside of it in air with higher temperature in the upper stratosphere. These phenomena cause deformations of vertical ozone distribution profiles and an appreciable shift of the maximum of the relative content of ozone to lower stratosphere layers.     

基于改进格子Boltzmann焓法模型的霜层生长数值研究

采用介观尺度格子Boltzmann方法数值研究壁面的表面特性对霜层生长的影响.将成核概率模型和改进的焓法相变模型相耦合，建立基于成核概率理论的霜层生长过程格子Boltzmann模型.该模型能够在宏观尺度上模拟霜层生长的加密加厚过程，也可以从微观尺度上描述局部的冰枝生长导致的霜层结构的动态变化，应用该模型能够获得霜层平均厚度、平均密度、结霜量等内部非稳态物理量.开展冷壁面上霜层形成及生长过程的数值研究，获得霜层的拓扑结构时空演化特性，得到不同时刻下结霜量以及霜层的平均厚度、平均密度、平均固相体积分数，探讨冷壁面温度、相对湿度、冷表面浸润性能对结霜的影响.     

国外差分吸收激光雷达探测大气水汽廓线的研究进展

水汽含量是大气最基本的物理参量之一,大气水汽垂直分布结构对于大气过程的研究十分有意义。差分吸收激光雷达可以昼夜获取高精度、高距离分辨率的大气水汽垂直分布廓线,是最有潜力的探测手段。国际上已经发展出几种类型的差分吸收激光雷达,对它们的发展路径做一梳理,理清发展脉络,具有有益的参考价值。其中,稍早时期水汽差分吸收激光雷达工作在4ν振动吸收带720～730 nm频域,以Alexandrite为主流的激光器或者Nd∶YAG/ruby固体激光器泵浦的染料激光器作为发射光源,光电倍增管仍然可以在这个波段担任探测器,代表性的仪器是法国的机载LEANDRE Ⅱ。此后发展的820 nm波段的水汽差分吸收激光雷达,以钛宝石激光器或钛宝石光放大器为发射机,以硅的雪崩二极管作为探测器,紧跟前置放大和数据的AD采集器,如德国Hohenheim大学的车载扫描激光雷达,可以获得对流层300～4 000 m之间水汽两维或三维分布结构;德国Institutfür Meteorologie und Klimaforschung所建立的差分吸收激光雷达可以探测3～12 km高度之间大气的水汽垂直分布。720和820 nm波段水汽吸收截面较小,更适合于地基或车载的对流层水汽廓线探测。而水汽3ν振动谱935 nm区域吸收截面较大,是为了空间探测大气对流层上、平流层下相对干燥区域的水汽分布而准备的,且可以安排多个探测波长,和一个参考波长,它们对水汽的吸收截面大小呈梯度分布,以应对空间对地观测时不同高度大气水汽浓度的差别。基于种子注入的光参量振荡器或Nd∶YGG全固态激光器的935 nm差分吸收激光雷达,以德国Deutsches Zentrumfür Luft- und Raumfahrt的研究最为成功,推动了欧洲空间局立项发展空间水汽差分吸收激光雷达WALES（Water Vapour Lidar Experiment in Space）,测量从地球表面到平流层下、高垂直分辨率和高精度水汽浓度分布。机载多波长水汽差分吸收激光雷达1999年建立起来,担当空间WALES任务的模拟器,2006年完成了机载飞行试验。以823～830 nm分布布拉格反射半导体激光器和半导体光放大器为核心、采用雪崩二极管盖格光子计数技术的微脉冲差分吸收激光雷达,是差分吸收激光雷达面向商业化、可普及的方向迈出的重要一步,目前已经发展到第四代产品。发射机激光工作波长的长期稳定十分重要而棘手,以窄带连续波种子激光注入脉冲激光器的谐振腔锁定其的腔长,种子激光的波长以水汽的多通道光吸收池为参照标准,或以高精度波长计为误差获取手段,通过负反馈进行主动稳频;其次,需要仔细考虑大气对激光的后向散射光谱线型,显然Rayleigh后向散射光的多普勒展宽与水汽吸收光谱线宽度可以比拟,所以其吸收截面σ_on和σ_off必需加以修正;水汽的空间垂直分布梯度大,因此差分吸收激光雷达应该实行分通道探测。     

Influence of interactive stratospheric chemistry on large-scale air mass exchange in a global circulation model

A new globally uniform Lagrangian transport scheme for large ensembles of passive tracer particles is presented and applied to wind data from a coupled atmosphere-ocean climate model that includes interactive dynamical feedback with stratospheric chemistry. This feedback from the chemistry is found to enhance large-scale meridional air mass exchange in the northern winter stratosphere as well as intrusion of stratospheric air into the troposphere, where both effects are due to a weakened polar vortex.     

A new algorithm for reconstructing the three-dimensional flow field of the oceanic mesoscale eddy

A new algorithm for reconstructing the three-dimensional flow field of the oceanic mesoscale eddies is proposed in this paper, based on variational method. Firstly, with the numerical differentiation Tikhonov regularizer, we reconstruct the continuous horizontal flow field on discrete grid points at each layer in the oceanic region, in terms of the horizontal flow field observations. Secondly, benefitting from the variational optimization analysis and its improvement, we reconstruct a three-dimensional flow field under the constraint of the horizontal flow and the vertical flow. The results of simulation experiments validate that the relative error of the new algorithm is lower than that of the finite difference method in the case of high grid resolution, which still holds in the case of unknown observational errors or in the absence of vertical velocity boundary conditions. Finally, using the reanalysis horizontal data sourcing from SODA and the proposed algorithm, we reconstruct three-dimensional flow field structure for the real oceanic mesoscale eddy.     

Simultaneous measurement of atmospheric temperature,humidity, and aerosol extinction and backscatter coefficients by a combined vibrational–pure-rotational Raman lidar

Implementation of the pure-rotational Raman (PRR) lidar method for simultaneous measurement of atmospheric temperature, humidity, and aerosol extinction and backscatter coefficients is reported. The isolation of two wavelength domains of the PRR spectrum and the suppression of the elastically scattered light is carried out by a double-grating polychromator. Experiments involving elastic backscatter from dense clouds and a solid target confirm the high level of suppression of the elastic light in the corresponding acquisition channels of the two selected PRR domains. Calibration of the temperature channel was done both by comparison with an experimentally verified atmospheric temperature model profile and by inter-comparison with radiosondes. Night-time temperature profiles with high vertical resolution were obtained up to the lower stratosphere. The PRR temperature profile combined with the water vapor mixing ratio obtained from the ro-vibrational Raman channel is used to estimate the relative humidity. PACS 42.68.Wt; 42.68.Mj; 33.20.Fb     

温度对CrIS热红外卫星资料反演臭氧廓线的影响分析

臭氧是地球大气中一种重要的痕量气体,在光化学反应和气候变化中都扮演着非常重要的角色。高光谱红外卫星可以观测到较高垂直分辨率的大气臭氧信息,但是由于热红外受大气温度影响较大,臭氧反演精度会有所下降。为此详细讨论和分析了温度对臭氧吸收光谱和权重函数的敏感性,以及对臭氧反演精度的影响。首先利用逐线积分辐射传输模型LBLRTM,分别模拟计算了六种不同标准大气模式下,1K的随机温度误差对大气透过率和辐射值的影响,发现1 K温度随机误差和臭氧浓度5%～6%的变化引起的辐射值变化量一致。接着利用CRTM辐射传输模型,针对搭载于美国对地观测卫星Suomi NPP(National Polar-orbiting Partnership)平台上的CrIS(Cross-track Infrared Sounder)红外高光谱观测数据,计算了1K的随机温度误差对大气臭氧权重函数的影响,并计算了由1K温度误差所导致的热红外高光谱资料大气臭氧廓线反演误差,结果显示CrIS对于臭氧的敏感区位于10～100 hPa之间,且1 K的温度误差和6%的臭氧浓度变化引起的权重函数变化量相当。最后以CrIS作为实验数据,在最优估计法框架下,通过特征向量统计法获取臭氧廓线的先验知识,并将大气温度廓线和大气臭氧廓线都作为未知量,进行同步迭代反演。将反演结果和配对的世界臭氧紫外数据中心WOUDC的站点数据进行比较,发现在反演中加入大气温度廓线进行同步迭代后,反演结果有显著提高,尤其在平流层与真值几乎一致,最大相对误差不超过20%,在对流层反演结果相对较差,最大相对误差不超过50%,优于欧洲中期天气预报中心ECMWF(European Center for Medium-range Weather Forecasting)臭氧模式数据集ERA-Interim。     

Bioacoustic spatial perception by humans: a controlled laboratory measurement of spatial resolution without distal cues

The angular spatial resolution of a wide-angle air sonar using a continuous transmission frequency-modulated radiation, with the output coupled binaurally to the auditory system of a user, was measured under restrained controlled conditions. This was done to determine the effect of adding a narrow central field of view of 9 deg to a wide-angle sonar. The target objects were three equidistant vertical rods initially spaced apart by 10 deg. This was varied down to a spacing of 4 deg. Ten nonvisual subjects achieved an angular resolution of 6 deg. Four of these ten subjects continued learning to achieve an unexpected spatial resolution of 4 deg within the 9 deg central field. A mean error of approximately 1 deg in direction accuracy was achieved. It is inferred that the unique variations in the octave band ultrasonic echoes within the narrow field, and the invariance of the on-axis echo as one's head is turned, enables this angular resolution and accuracy to be achieved within the wide binaural field of view of 50 deg. This ability to resolve specula objects within a narrow angular resolution element of 9 deg is linked to the bat's ability to seemingly resolve object glints within a distal resolution element of less than 2 wavelengths.     

Statistics of some synthetic parameters of vertical profiles of pressure and temperature obtained by one year of ECMWF's analysis over Europe

Summary In this paper monthly distributions of synthetic parameters of vertical profiles of temperature and pressure over Europe are shown. The data have been obtained by fits of one-year data analysis of the ECMWF model. In particular, distributions of lapse rates, distributions of heights of the layers and distributions of temperature and dry-air pressure of the lower level are reported. Within the precision of the input data and by disregarding the boundary layer, a finer subdivision of a layered troposphere and lower stratosphere has been obtained. Paper presented at the IX Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 8–10, 1992, Rome.     

Middle-atmospheric Doppler lidar using an iodine-vapor edge filter

We present both modeled capabilities of and experimental data from a Doppler lidar for the stratosphere and the lower mesosphere that uses the edge of a molecular iodine filter in a differential measurement to provide frequency discrimination. Modeled results show a capability for wind measurements to an altitude of 55 km with 1.5-km resolution in 30 min. Experimentally, wind-vector components from 18 to 45 km are measured every 20 min. The molecular-vapor filter provides great advantages with regard to system stability, operation in less-than-optimum weather conditions, and simplicity of data analysis.     

Fourier spectroscopy of the stratospheric emission

Emission spectra of the stratosphere have been recorded from balloon altitude with an unapodized resolution of 0.0033 cm^–1 in the submillimeter (SM) spectral range. Preliminary results on constituent identification are presented in this paper.     

星光掩星剥洋葱法反演臭氧密度

星光掩星技术探测恒星光经大气层消光、折射等作用后的恒星光光谱,利用大气中不同成分对不同波长的光吸收的差异反演得到大气密度信息。低轨卫星与恒星分别位于地球两侧,低轨卫星接收到不同切线高度上光谱,即构成星光掩星观测。光谱探测高度可从平流层至低热层,其中不同波段可用于不同大气痕量成分密度反演。星光掩星技术具有探测参数多、全球覆盖、垂直分辨率高、无需定标等优点。GOMOS(global ozone monitoring by occultation of stars)是搭载在欧洲航天局ENVISAT卫星上的平流层臭氧检测仪器。GOMOS利用星光掩星技术进行探测,设计精密,分辨率高,在轨稳定运行十年（2002年-2012年）,探测波长跨越紫外到可见光波段,采用光谱反演和垂直反演迭代的方法反演大气成分密度,得到了大量关于临近空间区域大气资料,对长期监测平流层至低热层区域变化提供了可靠的数据支持。利用GOMOS掩星数据,提出一种简单的反演方法--剥洋葱法,反演临近空间高度上臭氧数密度。剥洋葱法假设地球大气对称且水平分层,利用单个波段光谱进行反演,假设在此波长上光谱的大气吸收效应全部由臭氧造成,即选择臭氧吸收占据绝对优势的波长。经分析,在50～100 km高度上可以利用290 nm波段进行反演,在15～50 km高度上可以利用600 nm波段进行反演。根据Beer-Lambert定律,随切点高度自上而下,对恒星光光谱透过率利用剥洋葱法进行反演得到臭氧数密度。将剥洋葱法反演结果与GOMOS官方发布结果相对比,两者符合得很好。     

Infrared absorption cross-sections for acetaldehyde (CH3CHO) in the 3 μm region

A series of infrared absorption cross-sections for acetaldehyde has been measured in the 3 μm region from spectra obtained using a high-resolution Fourier transform spectrometer (Bruker IFS 125/HR). Results presented are for mixtures of acetaldehyde vapor combined with pure synthetic air taken at various temperatures and pressure to simulate atmospheric conditions found principally in the Earth's troposphere and lower stratosphere. Spectra were recorded at a resolution of 0.005 cm⁻¹ and intensities were calibrated using three acetaldehyde spectra (measured at 278, 298 and 323 K) provided by the Pacific Northwest National Laboratory (PNNL) IR database.     

On the quality of the Nimbus 7 LIMS version 6 ozone for studies of the middle atmosphere

The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) radiance profile dataset of 1978/79 was reconditioned and reprocessed to Version 6 (V6) profiles of temperature and species that are improved significantly over those from Version 5 (V5). The LIMS V6 dataset was archived for public use in 2002. Improvements for its ozone include: (1) a more accurate accounting for instrument and spacecraft motion effects in the radiances, (2) the use of better spectroscopic line parameters for its ozone forward model, (3) retrievals of all its scans, (4) more accurate and compatible temperature versus pressure profiles (or T(p)) that are needed for the registration of the ozone radiances and for the removal of temperature effects from them, and (5) a better accounting for interfering species in the lower stratosphere. The retrieved V6 ozone profiles extend from near cloud top altitudes to about 80 km and from 64S to 84N latitude with better sampling along the orbit than for the V5 dataset. Calculated estimates of the single-profile precision and accuracy are provided; precision estimates based on the data themselves are of order 3% or better from 1 to 30 hPa. Estimates of total systematic error are hard to generalize because the separate sources of error may not all be of the same sign, and they depend somewhat on the atmospheric state. It is estimated that the accuracy of the V6 zonal mean ozone distribution is within ±9% from 50-10 hPa, improving to ±7% in the uppermost stratosphere. Simulation studies show that the LIMS T(p) retrievals are underestimating slightly the small amplitudes of the atmospheric temperature tides, which affect the retrieved day/night ozone differences. There are also small biases in the middle to lower stratosphere for the ascending versus descending node LIMS ozone, due principally to not accounting for the asymmetric weighting of its radiance within the tangent layer. The total accuracy for the LIMS ozone was assessed by comparing its daily zonal mean, daytime distributions against those from the Nimbus 7 SBUV Version 8 (V8) dataset for the same period. The LIMS V6 ozone agrees well with SBUV, except between 2 and 5 hPa where the LIMS ozone is greater. That bias is related to the differing vertical resolutions and forward models for the two experiments. The accuracy for LIMS V6 ozone in the lower stratosphere is improved over that reported for V5, as indicated by a small set of V6 comparisons with ECC ozonesonde profiles. Comparisons of diurnal, photochemical model calculations with the monthly-averaged, upper stratospheric ozone obtained with LIMS V6 indicate only a slight ozone deficit for the model at about 2 hPa. However, that deficit exhibits little to no seasonal variation and is in good agreement with similar model comparisons for a seasonal time series of ozone obtained with ground-based microwave instruments. Because the LIMS V6 ozone has improved accuracy and sampling versus that of V5 for the lower stratosphere it should now be possible to conduct quantitative studies of ozone transport and chemistry for the northern hemisphere, polar winter/spring of 1978/79—a time period when the catalytic loss of ozone due to reactive chlorine should not have been a major factor for the Arctic stratosphere.     

First experimental evidence for chaos-assisted tunneling in a microwave annular billiard

We report on first experimental signatures for chaos-assisted tunneling in a two-dimensional annular billiard. Measurements of microwave spectra from a superconducting cavity with high frequency resolution are combined with electromagnetic field distributions experimentally determined from a normal conducting twin cavity with high spatial resolution to resolve eigenmodes with properly identified quantum numbers. Distributions of quasidoublet splittings serve as basic observables for the tunneling between whispering gallery-type modes localized to congruent, but distinct tori which are coupled weakly to irregular eigenstates associated with the chaotic region in phase space.     

Energy resolution of CsI(Na) scintillators

The presented paper on CsI(Na) scintillators is a continuation of systematical studies of alkali halide crystals exhibiting more than one exponential decay time. The CsI(Na) crystals are known to have short (～550 ns) and long (few microseconds) components in the scintillation pulse. Previous studies showed that integration of slow components of the light pulse improved the light output, non-proportionality and energy resolution of CsI(Tl), NaI(Tl) in lower temperatures and undoped NaI crystal at liquid nitrogen temperature. In this work, an influence of the shaping time in the spectroscopy amplifier on the light output, non-proportional response to γ-rays, and energy resolution of two different size CsI(Na) scintillators is examined. Each crystal was coupled to the Photonis XP5212 PMT with a photocathode blue sensitivity of 12.2 μA/l mF. The data analysis showed improved proportionality of the crystal response, higher number of photoelectrons/MeV-γ, and consequently, a better overall energy resolution obtained for 12 μs shaping time constant. Finally, the CsI(Na) characteristics are compared to that obtained previously for NaI(Tl).     

Sampling a terahertz dipole transition with subcycle time resolution

We present a time-resolved technique to measure optical excitation processes with a time resolution shorter than the oscillation period of the exciting light. Our terahertz (THz) experiments fully resolve the polarization dynamics of electrons in semiconductor heterostructures when they are excited by a THz pulse. The time resolution of the polarization enables us to deduce the population dynamics of the excited state, which includes the dynamics of a virtual population in the case of off-resonant excitation.