Observed Trends in Total Vertical Column Abundances of Atmospheric Gases from IR Solar Spectra Recorded at the Jungfraujoch

Since 1984, about 15000 high quality infrared solar spectra have beenrecorded with state-of-the-art grating and Fourier transform spectrometersat the International Scientific Station of the Jungfraujoch, Switzerland.Nonlinear least squares spectral curve fitting of selected microwindowscontaining isolated and well characterized lines of 20 telluric gases haveallowed to retrieve their total vertical column abundances above thestation, leading to observational data bases essential to derive long- andshort-term changes experienced by these species during the last 12 years. Inthis paper, we focus on atmospheric gases of particular interest within thecontext of the EUROTRAC/TOR (Tropospheric Ozone Research) project; secularevolution as well as seasonal cycles of the minor constituentsCH₄, CO and of the trace gasesC₂H₆, OCS, C₂H₂, HCNand H₂CO are reported and discussed. The long-livedN₂O is included as a tracer of the dynamic activity of theatmosphere.     

Measurement of the NO + O3 Reaction Rate at Atmospheric Pressure Using Realistic Mixing Ratios

Accurate values for the rate and temperature dependence of the reaction NO + O₃ NO₂ + O₂ are important in the chemical modelling of photochemical processes in the atmosphere. Previous measurements have been made at low total pressures and/or with very large mixing ratios relative to those observed in the atmosphere. In this study the reaction rate has been measured using a novel approach under tropospheric conditions of temperature and pressure, and at tens of ppb (mixing ratios of 1 in 10⁸) between 263 and 328 K. The resultant Arrhenius expression (k=Ae^-Ea/RT) gives a larger activation energy (Ea/R=1670 ± 100) than the recommended literature value (Ea/R=1400 ± 200), and a larger pre-exponential factor (A=5.1 ± 1.6 × 10^-12 cf. recommended A=2.0 × 10^-12), but the second-order rate constant at 298 K (1.90 × 10^-14 molecules cm^-3 s^-1 ± 10%) is similar to the recommended value. The results confirm a lack of pressure dependence of the reaction, but were made over too small a range in temperature to address the issue of curvature of the simple Arrhenius expression.     

GPS卫星定位误差分析

GPS测量数据中包含有多种误差,按其产生的来源、性质、大小及对测量产生的影响等进行了介绍和初步分析,提出了相应的措施以便消除或削弱它们对测量结果的影响。     

地基GPS反演水汽影响因素分析

地基GPS(Global Position System)技术日益成熟,气象观测应用此技术逐渐增多,但对此影响因素的分析不是太多。本文首先阐述了地基GPS遥感水汽原理,然后结合雾灵山GPS气象观测试验数据,利用GAMIT软件解算此期间数据的对流层延迟量,主要分析了影响地基GPS遥感水汽的几项因素,得出测站精度与ZTD精度变化趋势图、星历精度与ZTD(Troposphere Zenith Delay)精度变化趋势图和不同参考站对ZTD的影响。其结果对GPS遥感大气水汽有一定的参考价值。     

Atmospheric concentrations and deposition of heavy metals over the North Sea: A literature review

A literature review of the atmospheric concentration rates and dry and wet deposition fluxes of particulate Cd, Cr, Cu, Pb and Zn to the North Sea and adjacent areas is given. The results of direct measurements of dry and wet deposition fluxes are compared to indirect estimates and to modelling values. This work points out the large uncertainties in results of different studies on atmospheric input of trace elements into the North Sea. The current knowledge about the dependence of the deposition velocity upon the particle size and about the processes controlling wet deposition fluxes, and the quality and completeness of the emission data are still inadequate for describing the environmental cycle and impact of heavy metals in the North Sea.     

The distribution of acetaldehyde in the lower troposphere during TROPOZ II

A series of 72 measurements of the acetaldehyde (CH₃CHO) mixing ratio were made in the lower troposphere during TROPOZ II. These measurements are the first ever made of the background level of this trace gas in the free troposphere. The data show a vertical decrease of the CH₃CHO mixing ratio with increasing altitude and indicate higher CH₃CHO concentrations in the Northern Hemisphere — in general agreement with a model-derived average CH₃CHO distribution. Deviations of the observed CH₃CHO mixing ratios from the modelled mean distribution are correlated with similar deviations in the corresponding HCHO mixing ratios.     

Teleconnection of IOD signal in the upper troposphere over southern high latitudes

Evidence has been found for the teleconnection of Indian Ocean Dipole mode (IOD) events in the southern high latitude sea surface pressure field, although the mechanisms that might lead to such far-reaching links remain unresolved. Based on the teleconnection pattern between IOD and the climate anomaly in the upper troposphere, we propose one such mechanism here: the energy propagation theory of the atmospheric planetary wave. Ray traces of the atmospheric planetary waves suggest that the energy propagation of the waves could be responsible for the teleconnection between IOD and tropospheric climate anomalies in southern high latitudes.     

Distribution and Variation of Carbon Monoxide in the Tropical Troposphere and Lower Stratosphere

The authors examine the distribution and varia- tion of carbon monoxide （CO） in the tropics from the sur- face to the lower stratosphere. By analyzing space-borne microwave limb sounder （MLS） measurements, measure- ments of pollution in the troposphere （MOPITT） and mod- em-era retrospective analysis for research and applications （MERRA） meteorological products, and atmospheric chemistry and climate model intercomparison project （ACCMIP） surface emission inventories, the influences of atmospheric dynamics and surface emissions are investi- gated. The results show that there are four centers of highly concentrated CO mixing ratio over tropical areas in differ- ent seasons： two in the Northern Hemisphere and another two in the Southern Hemisphere. All of these centers cor- respond to local deep convective systems and mon- soons/anticyclones. The authors suggest that both deep convections and anticyclones affect CO in the tropical tro- posphere and lower stratosphere--the former helping to transport CO from the lower to the middle troposphere （or even higher）, and the dynamical uplift and isolation effects of the latter helping to build up highly concentrated CO in the upper troposphere and lower stratosphere （UTLS）. Similarly, there are two annual surface emission peaks in- duced by biomass burning emissions： one from the North- ern Hemisphere and the other from the Southern Hemi- sphere. Both contribute to the highly concentrated CO mixing ratio and control the seasonal variabilities of CO in the UTLS, combining the effects of deep convections and monsoons. Results also show a relatively steady emission rate from anthropogenic sources, with a small increase mainly coming from Southeast Asia and lndia. These emis- sions can be transported to the UTLS over Tibet by the joint effort of surface horizontal winds, deep convections, and the Asian summer monsoon system.     

平流层-对流层相互作用的多尺度过程特征及其与天气气候关系——研究进展

在过去5年中,在国家自然科学基金委员会和中国科学院的项目支持下,针对以大气上下层相互作用中的多时空尺度过程特征及其与天气气候的关系为主要关注内容,开展了几个方面的研究。本文介绍其中的一些主要进展与结果,包括:(1)平流层臭氧的探测与分析研究;(2)平流层－对流层质量交换(STME)与对流层顶特征研究;(3)中层大气多尺度波动特征研究;(4)大气辐射传输和中层大气卫星临边遥感新方法研究。     

Formulation and Evaluation of IMS, an Interactive Three-Dimensional Tropospheric Chemical Transport Model 3. Comparison of Modelled C2–C5 Hydrocarbons with Surface Measurements

In part 3 of this series of papers on a new 3-D global troposphericchemical transport model, using an Integrated Modelling System (IMS), anevaluation of the model performance in simulating global distributions andseasonal variations for volatile organic compounds (VOCs) in the atmosphere,is presented. Comparisons of model OH concentrations with previous modelstudies show consistent modelled OH levels from the subtropics tomidlatitudes, while more discrepancies occur over the tropical lowlatitudes, with IMS predicting the highest levels of OH. The close agreementbetween modelled OH concentrations over midlatitudes, where high surfaceNO_xand VOC concentrations are also found, is indicative of the strongphotochemical coupling between NO_x, VOCs and O₃ overthese latitudes. IMSOH concentrations in the Northern Hemisphere (NH) midlatitudes during summerare generally lower than available measurements, implying that models ingeneral are underestimating OH levels at this location and time of year.Substantial differences between model OH concentrations over low latitudesclearly highlight areas of uncertainty between models. IMS OH concentrationsare the highest in general of the models compared, one possible reason isthat biogenic emissions of species such as isoprene and monoterpenes arehighest in IMS, leading to higher O₃ levels and hence higher OH.Generally, the IMS VOC concentrations show a similar seasonality to themeasurements at most locations. In general though, IMS tends to underestimatethe NH wintertime VOC maximum and overestimate the NH summertime VOCminimum. Such an overestimate in summer could be due to IMSunderestimating OH levels, or an overestimation of VOC emissions or possiblya problem with model transport, all of these possibilities are explored.Except for n-pentane, the model underprediction of a VOC maximum during theNH winter month strongly suggests a missing emission mechanism in the modelor an underestimate of an existing one. It is very likely that there is alack of time varying emission sources in the model to account for theseasonal change in emission behaviour such as increasing energy usage (e.g.,electricity and gas), road transportation, engine performance, and otheranthropogenic factors which show strong seasonal characteristics. Theanomalous overprediction of wintertime n-pentane compared with its closesummertime prediction with the measurements suggest that emissions in thiscase may be too high.