The YAK-AEROSIB transcontinental aircraft campaigns: new insights on the transport of CO2, CO and O3 across Siberia

Two airborne campaigns were carried out to measure the tropospheric concentrations and variability of CO₂, CO and O₃ over Siberia. In order to quantify the influence of remote and regional natural and anthropogenic sources, we analysed a total of 52 vertical profiles of these species collected in April and September 2006, every ∼200 km and up to 7 km altitude. CO₂ and CO concentrations were high in April 2006 (respectively 385–390 ppm CO₂ and 160–200 ppb CO) compared to background values. CO concentrations up to 220 ppb were recorded above 3.5 km over eastern Siberia, with enhancements in 500–1000 m thick layers. The presence of CO enriched air masses resulted from a quick frontal uplift of a polluted air mass exposed to northern China anthropogenic emissions and to fire emissions in northern Mongolia. A dominant Asian origin for CO above 4 km (71.0%) contrasted with a dominant European origin below this altitude (70.9%) was deduced both from a transport model analysis, and from the contrasted ΔCO/ΔCO₂ ratio vertical distribution. In September 2006, a significant O₃ depletion (∼–30 ppb) was repeatedly observed in the boundary layer, as diagnosed from virtual potential temperature profiles and CO₂ gradients, compared to the free troposphere aloft, suggestive of a strong O₃ deposition over Siberian forests.     

农田近地面层CO2和湍流通量特征研究

利用１９８５年５月至６月在北京郊区中国科学院农业生态试验研究站的麦田中实测的小麦不同生长期的ＣＯ２浓度梯度、光合有效辐射、净辐射、土壤热通量和温度、湿度及风速梯度等量的数据，采用空气动力学方法，计算了ＣＯ２通量、感热通量、潜热通量和动量通量。并对观测场地、仪器设备、校准方法及误差分析进行了描述。结果表明：从５月１４日到６月１５日，在１ｍ，２ｍ和１０ｍ处，ＣＯ２浓度振幅的日变化分别为１０３．４到２７．５，８７．５到２７．３和６９．８到１１．５ｐｐｍ；光合型和呼吸型的平均ＣＯ２浓度分别为３４５．３，３５０．６，３５７．５ｐｐｍ和３７３．９，３６９．７，３６２．１ｐｐｍ。在白天，ＣＯ２通量和梯度的输送方向是从大气向植被，在中午（１１时到１３时）输送达到负的最大值。在夜间，ＣＯ２通量和梯度输送的方向与白天相反，并且，在早晨（４时到６时）达到正的最大值。ＣＯ２通量与净辐射（Ｒｎ）、可利用能（Ｈ＋ＬＥ）、光合有效辐射和动量通量之间有较好的相关关系     

2008年冬季北京上空上对流层/下平流层臭氧的异常特征

利用国产GPSO3臭氧探空系统观测的大气臭氧探空资料和NCEP再分析资料,结合对天气形势、大气环流背景、高空位涡变化及对流层顶高度扰动的分析,深入研究了2008年冬季北京地区10~14 km高度范围内持续出现的臭氧次峰值及大气臭氧含量异常现象。结果表明:在2008年我国南方雪灾这一特殊时期,引起臭氧垂直分布持续出现次峰值现象及臭氧含量异常的主要原因是平流层空气强烈下沉运动及其与对流层的交换作用,而引起这种下沉运动及平流层-对流层交换则是由于该阶段特殊的天气背景,乌拉尔阻塞高压长时间维持,贝加尔湖到巴尔喀什湖一带横槽稳定存在,里海以东切断低压长期维持,造成冷空气长时间、稳定地南下影响北京上空臭氧的垂直分布。加之副热带急流的出现,北京正处于其入口区左侧,其上空有强烈的辐合下沉运动,有利于平流层空气向下输送。此次臭氧次峰值及臭氧含量异常的现象很好地说明,在冷空气天气过程的影响下,北京地区上空的平流层空气运动及其与对流层的交换十分活跃。     

Climatic changes associated with a global “2°C-stabilization” scenario simulated by the ECHAM5/MPI-OM coupled climate model

In this study, concentrations of the well-mixed greenhouse gases as well as the anthropogenic sulphate aerosol load and stratospheric ozone concentrations are prescribed to the ECHAM5/MPI-OM coupled climate model so that the simulated global warming does not exceed 2°C relative to pre-industrial times. The climatic changes associated with this so-called “2°C-stabilization” scenario are assessed in further detail, considering a variety of meteorological and oceanic variables. The climatic changes associated with such a relatively weak climate forcing supplement the recently published fourth assessment report by the IPCC in that such a stabilization scenario can only be achieved by mitigation initiatives. Also, the impact of the anthropogenic sulphate aerosol load and stratospheric ozone concentrations on the simulated climatic changes is investigated. For this particular climate model, the 2°C-stabilization scenario is characterized by the following atmospheric concentrations of the well-mixed greenhouse gases: 418 ppm (CO₂), 2,026 ppb (CH₄), and 331 ppb (N₂O), 786 ppt (CFC-11) and 486 ppt (CFC-12), respectively. These greenhouse gas concentrations correspond to those for 2020 according to the SRES A1B scenario. At the same time, the anthropogenic sulphate aerosol load and stratospheric ozone concentrations are changed to the level in 2100 (again, according to the SRES A1B scenario), with a global anthropogenic sulphur dioxide emission of 28 TgS/year leading to a global anthropogenic sulphate aerosol load of 0.23 TgS. The future changes in climate associated with the 2°C-stabilization scenario show many of the typical features of other climate change scenarios, including those associated with stronger climatic forcings. That are a pronounced warming, particularly at high latitudes accompanied by a marked reduction of the sea-ice cover, a substantial increase in precipitation in the tropics as well as at mid- and high latitudes in both hemispheres but a marked reduction in the subtropics, a significant strengthening of the meridional temperature gradient between the tropical upper troposphere and the lower stratosphere in the extratropics accompanied by a pronounced intensification of the westerly winds in the lower stratosphere, and a strengthening of the westerly winds in the Southern Hemisphere extratropics throughout the troposphere. The magnitudes of these changes, however, are somewhat weaker than for the scenarios associated with stronger global warming due to stronger climatic forcings, such as the SRES A1B scenario. Some of the climatic changes associated with the 2°C-stabilization are relatively strong with respect to the magnitude of the simulated global warming, i.e., the pronounced warming and sea-ice reduction in the Arctic region, the strengthening of the meridional temperature gradient at the northern high latitudes and the general increase in precipitation. Other climatic changes, i.e., the El Niño like warming pattern in the tropical Pacific Ocean and the corresponding changes in the distribution of precipitation in the tropics and in the Southern Oscillation, are not as markedly pronounced as for the scenarios with a stronger global warming. A higher anthropogenic sulphate aerosol load (for 2030 as compared to the level in 2100 according to the SRES A1B scenario) generally weakens the future changes in climate, particularly for precipitation. The most pronounced effects occur in the Northern Hemisphere and in the tropics, where also the main sources of anthropogenic sulphate aerosols are located.     

Long-range transport of carbon monoxide from tropical ground to upper troposphere: a case study for South East Asia in October 1997

High concentrations of carbon monoxide (CO) were observed in October 1997 at the upper troposphere of the western tropical Pacific. Transport from the potential sources of CO due to biomass burnings in the tropics was investigated by using a global chemical transport model (CTM) driven by assimilated meteorological data provided from European Centre for Medium-Range Weather Forecasts (ECMWF). A CTM evaluation simulation using water vapor showed that the amount of vertical transport of moisture by large-scale flow was consistent with the precipitation predicted at the convective zone. A series of CTM simulations using 10-day emission periods of an artificial material with lifetime of 60 days indicated that vertical lifting of surface air at the Indonesian archipelago occurred in the concentrated convections west of Sumatra Island. No evidence was found that CO from the Amazon region or Africa significantly contributed to high concentrations in the western tropical Pacific. Transport formed a large-scale anvil below the tropopause by rapid vertical transport and by divergence flow. The average time required for the transport from Kalimantan and Sumatra Island to the point of high CO concentration was about 15 days. High concentrations at an altitude of 10 km in the Southern Hemisphere were transported by large-scale subsidence from the upper tropospheric maximum, which was presumably produced from the sources at Kalimantan and Sumatra Island. Estimated emissions of CO in September and October from Kalimantan and Sumatra were substantially larger than the previous estimates. Omission of chemical reaction was a possible problem for the overestimate, but not significant. The possible problems in the transport were incorrect CTM transport due to insufficient horizontal (2.5×2.5°) and vertical resolution of the CTM, and to inaccuracy in the wind fields at the upper part of the troposphere and a divergent flow pattern in the upper part of the troposphere.     

Observation of a summer tropopause fold by ozonesonde at Changchun,China: Comparison with reanalysis and model simulation

Tropopause folds are one of the key mechanisms of stratosphere-troposphere exchange (STE) in extratropical regions, transporting ozone-rich stratospheric air into the middle and lower troposphere. Although there have been many studies of tropopause folds that have occurred over Europe and North America, a very limited amount of work has been carried out over northeastern Asia. Ozonesondes produced by the Institute of Atmospheric Physics were launched in Changchun (43.9°N, 125.2°E), Northeast China, in June 2013, and observed an ozone-enriched layer with thickness of 3 km and an ozone peak of 180 ppbv at 6 km in the troposphere. The circulation field from the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim) dataset shows that this ozone peak was caused by a tropopause fold associated with a jet stream at the eastern flank of the East Asian trough. By analyzing the ozone data from the ozone monitoring instrument and Weather Research and Forecasting model with Chemistry (WRF-Chem) simulations, it was found that a high ozone concentration tongue originating from the lower stratosphere at high latitude (near central Siberia) intruded into the middle troposphere over Changchun between 5 and 8 km on 12 June 2013. The high-resolution WRF-Chem simulation was capable of describing events such as the tropopause fold that occurred on the cyclonic shear side of the jet stream. In addition, the TRAJ3D trajectory model was used to trace the origin of measured secondary ozone peaks in the middle troposphere back, for example, to stratospheric intrusion through the tropopause fold.     

The possible influences of the increasing anthropogenic emissions in India on tropospheric ozone and OH

A 3-D chemical transport model (OSLO CTM2) is used to investigate the influences of the increasing anthropogenic emission in India. The model is capable of reproducing the observational results of the INDOEX experiment and the measurements in summer over India well. The model results show that when NOx and CO emissions in India are doubled, ozone concentration increases, and global average OH decreases a little. Under the effects of the Indian summer monsoon, NOx and CO in India are efficiently transported into the middle and upper troposphere by the upward current and the convective activities so that the NOx, CO, and ozone in the middle and upper troposphere significantly increase with the increasing NOx and CO emissions. These increases extensively influence a part of Asia, Africa, and Europe, and persist from June to September.     

夏季亚洲季风区对流层向平流层输送的源区、路径及其时间尺度的模拟研究

基于NCEP/NCAR分析资料和拉格朗日轨迹输送模式FLEXPART, 通过气块轨迹计算, 对2005年夏季亚洲季风区对流层向平流层输送 (Troposphere to Stratosphere Transport, 简称TST) 的近地层源区、 输送路径及其时间尺度问题进行了一些初步探讨。结果表明: (1) 夏季亚洲季风区TST两个主要的边界层源区, 一个是热带西太平洋地区; 另一个是青藏高原南部、 孟加拉湾以及印度半岛中北部等地区, 上述两个区域与夏季强对流的分布相一致。在对流层顶高度附近 (约16 km高度), 两个近地层源区的垂直输送贡献相当。但进一步分析发现, 穿越对流层顶高度的质量输送只有约10％能够进入20～22 km高度的平流层中, 且主要源于以青藏高原南侧为代表的南亚季风区 (约贡献75%), 这进一步强调了青藏高原及其周边区域在全球TST过程中的重要地位。 (2) 轨迹分析显示, 夏季亚洲季风区对流层进入平流层的 “入口区” 主要在 (25°N～35°N, 90°E～110°E) 区域的青藏高原及其周边区域。TST路径受对流层上层南亚高压闭合环流、 北半球副热带西风急流和赤道东风急流的共同控制。 (3) 亚洲季风区TST两个主要的过程, 一个是和夏季湿对流抬升直接联系的快速输送过程, 它可以使近地层大气在1～2天内输送到平流层中, 贡献了整个TST的10%～30%; 另一个是大气辐射加热所致的大尺度垂直输送, 该输送是一个相对的慢过程, 时间尺度一般为5～30天。此结果意味着, 源于地表的短生命周期的大气污染物可通过光化学反应过程对该区域平流层臭氧及其他大气痕量成分平衡产生重要影响。     

梅雨期高位涡源区及其传播过程

分析了气候平均意义下梅雨前期及期间东亚地区等熵位涡（isentropic potential vorticity,简称IPV）的源区和演变过程。结果表明:梅雨发生前,东亚地区对流层高层经向位涡梯度减弱,而后这里的IPV开始向南延伸出高值带,形成“舌区”。同期对流层低层,经向位涡梯度出现反向,与南边位涡梯度大值带形成经向偶极子型并伴随梅雨发生发展。梅雨期40°N,120°E附近对流层顶折叠处有明显的位涡输送和质量交换。用10~90 d带通滤波和超前相关追踪IPV异常源区和传播路径发现,345 K的IPV异常场和梅雨期前后降水异常的相关系数最大值出现在前者超前后者10 d左右,位置在贝加尔湖东侧,这里是影响梅雨期降水的位涡源区。其向南输送高位涡空气主要在梅雨发生前的6月10日左右,高位涡异常空气沿2 PVU等位涡面以东北—西南路径向南输送,在2 PVU面最陡峭处堆积,然后穿越物质面快速下沉侵入40°N以南,并在对流层呈扇状铺开。因而,贝加尔湖东侧可能是影响梅雨的主要冷空气源区,是梅雨降水中期预报的一个关键区。     

Carbon dioxide concentration and flux in an urban residential area in Seoul,Korea

The carbon dioxide （CO2） concentrations and fluxes measured at a height of 17.5 m above the ground by a sonic anemometer and an open-path gas analyzer at an urban residential site in Seoul, Korea from February 2011 to January 2012 were analyzed. The annual mean CO2 concentration was found to be 750 mg m-3, with a maximum monthly mean concentration of 827 mg m-3 in January and a minimum value of 679 mg m-3 in August. Meanwhile, the annual mean CO2 flux was found to be 0.45 mg m-2 s-1, with a maximum monthly mean flux of 0.91 mg m-2 s-1 in January and a minimum value of 0.19 mg m-2 s-1 in June. The hourly mean CO2 concentration was found to show a significant diurnal variation; a maximum at 0700-0900 LST and a minimum at 1400-1600 LST, with a large diurnal range in winter and a small one in summer, mainly caused by diurnal changes in mixing height, CO2 flux, and surface complexity. The hourly mean CO2 flux was also found to show a significant diurnal variation, but it showed two maxima at 0700-0900 LST and 2100-2400 LST, and two minima at 1100-1500 LST and 0300-0500 LST, mainly caused by a diurnal pattern in CO2 emissions and sinks from road traffic, domestic heating and cooking by liquefied natural gas use, and the different horizontal distribution of CO2 sources and sinks near the site. Differential advection with respect to wind direction was also found to be a cause of diurnal variations in both the CO2 concentration and flux.     

强对流天气对O3和CO的垂直输送作用

利用ACTIVE（aerosol and chemical transport in tropical convection）试验资料,取2006年1月20日澳大利亚北部达尔文岛附近发生的一次飑线强对流天气的AE17航次和2006年1月27日无对流天气的AE21航次飞行路径中的探测资料,对澳大利亚达尔文地区夏季风盛行期间发生的有无强对流发生时O₃和CO浓度垂直分布变化进行对比,考察强对流性天气发生对O₃和CO浓度垂直输送作用。深对流云内强烈的垂直上升运动将O₃和CO等化学气体携带输送至对流层上部并在对流层顶堆积,从而在对流层上部产生浓度峰值。当有强对流发生,飞机进入对流云上层时,O₃浓度和CO浓度升高,O₃和CO浓度变率增大,在对流层上部浓度出现峰值;当飞机飞出对流云时,O₃和CO浓度相对较低,在对流云外出现谷值。在无对流发生的条件下O₃和CO浓度相对较小,浓度变率也较小,无峰值产生。分析表明:O₃和CO浓度分布不仅与强对流的垂直输送作用关系密切,且与气象要素垂直和水平分布以及动力输送过程密切相关。     

Stratosphere-troposphere exchange and its specific features at extratropical latitudes

A review of the papers dealing with various aspects of stratosphere-troposphere exchange (STE) is presented. The development of STE concepts is described and quantitative estimates of STE obtained by different authors are given. Typical time scales and geographic features of STE are described. Special attention is given to the specific features of STE at extratropical latitudes where active vertical air transport is observed in both directions. The air ascent through the tropopause occurs there in the zones of warm conveyor belts, and the air descent takes place in the zones of stratospheric intrusions. Exchange processes in the key region including the upper troposphere and the lowermost stratosphere are described. The mechanisms of large-scale stratospheric intrusions in the systems of tropopause folds or cut-off lows are presented as well as the mechanisms of the mixing of the stratospheric air with the tropospheric one. Specific features of deep stratospheric intrusions are discussed which are based on the analysis of such indicators of stratospheric air as high concentrations of ozone and stratospheric radionuclide 7Be. Some aspects of stratosphere-troposphere energy exchange are considered.     

深对流系统对污染气体CO垂直动力输送作用的数值模拟研究

本文采用高分辨率WRF-Chem模式模拟了2014年7月27日和8月24日发生于长三角地区的两次强度不同的深对流系统对污染气体CO的再分布作用,对比分析了模拟的两次深对流系统在CO垂直输送过程中的差异。通过与实际雷达回波的比较发现,两次模拟的深对流发生时间、回波强度等都与实际观测接近。8月24日深对流过程发生前的对流有效位能和0～6 km垂直风切变强度均高于7月27日个例,因此 8月24日深对流系统更不稳定,发展高度更高。从CO浓度垂直剖面、质量通量随高度的变化特征发现,7月27日的深对流系统最高可以将CO输送到14 km高度处,8月24日的深对流系统最高可以将CO输送到16 km高度处。对CO浓度的垂直通量散度平均垂直廓线分析看出,7月27的深对流系统主要将CO输送到12 km附近,导致7月27日个例对流层中层的CO浓度更高,8月24日的深对流系统主要将CO输送到15 km附近,导致8月24日个例对流层上层的CO浓度更高。对垂直通量求和的分析表明,8月24日的深对流系统每小时垂直输送的CO浓度是7月27的1.3倍,而考虑到8月24日的深对流系统持续时间更长,8月24日的深对流系统对CO的垂直输送作用远远大于7月24日的深对流系统的垂直输送作用。     

Ozone structure over the equatorial Andes from balloon-borne observations and zonal connection with two tropical sea level sites

In this paper we present first-time measurements of ozone profiles from a high altitude station in Quito, Ecuador (0.19°S, 78.4°W, and 2391 masl) taken from June 2014 to September 2015. We interpret ozone observations in the troposphere, tropopause, and stratosphere through a zonal comparison with data from stations in the Atlantic and Pacific (Natal and San Cristobal from the SHADOZ network). Tropospheric ozone concentrations above the Andes are lower than ozone over San Cristobal and Natal for similar time periods. Ozone variability and pollution layers are also reduced in the troposphere above the Andes. We explain these differences in terms of reduced contributions from the boundary layer and from horizontal transport. In the tropical tropopause layer, ozone is well-mixed up to near the cold point tropopause level. In this regard, our profiles do not show constraints to deep mixing above 14 km, as has been consistently observed at other tropical stations. Total column ozone and stratospheric column ozone are comparable among the three sites. However, the contribution of tropospheric column ozone to total column ozone is significantly lower above the Andes. Our comparisons provide a connection between observations from tropical stations in equatorial South America separated by the wide continental mass. Identified differences in ozone throughout the atmospheric column demonstrate the global benefit of having an ozone sounding station at the equatorial Andes in support of global monitoring networks.     

Vertical profiles of biospheric and fossil fuel-derived CO2 and fossil fuel CO2 : CO ratios from airborne measurements of Δ14C, CO2 and CO above Colorado, USA

Measurements of  Δ¹⁴C  in atmospheric CO₂ are an effective method of separating CO₂ additions from fossil fuel and biospheric sources or sinks of CO₂. We illustrate this technique with vertical profiles of CO₂ and  Δ¹⁴C  analysed in whole air flask samples collected above Colorado, USA in May and July 2004. Comparison of lower tropospheric composition to cleaner air at higher altitudes (>5 km) revealed considerable additions from respiration in the morning in both urban and rural locations. Afternoon concentrations were mainly governed by fossil fuel emissions and boundary layer depth, also showing net biospheric CO₂ uptake in some cases. We estimate local industrial CO₂:CO emission ratios using in situ measurements of CO concentration. Ratios are found to vary by 100% and average 57 mole CO₂:1 mole CO, higher than expected from emissions inventories. Uncertainty in CO₂ from different sources was ±1.1 to ±4.1 ppm for addition or uptake of −4.6 to 55.8 ppm, limited by  Δ¹⁴C  measurement precision and uncertainty in background  Δ¹⁴C  and CO₂ levels.     

Main Detrainment Height of Deep Convection Systems over the Tibetan Plateau and Its Southern Slope

Deep convection systems (DCSs) can rapidly lift water vapor and other pollutants from the lower troposphere to the upper troposphere and lower stratosphere. The main detrainment height determines the level to which the air parcel is lifted. We analyzed the main detrainment height over the Tibetan Plateau and its southern slope based on the CloudSat Cloud Profiling Radar 2B_GEOPROF dataset and the Aura Microwave Limb Sounder Level 2 cloud ice product onboard the A-train constellation of Earth-observing satellites. It was found that the DCSs over the Tibetan Plateau and its southern slope have a higher main detrainment height (about 10?16 km) than other regions in the same latitude. The mean main detrainment heights are 12.9 and 13.3 km over the Tibetan Plateau and its southern slope, respectively. The cloud ice water path decreases by 16.8% after excluding the influences of DCSs, and the height with the maximum increase in cloud ice water content is located at 178 hPa (about 13 km). The main detrainment height and outflow horizontal range are higher and larger over the central and eastern Tibetan Plateau, the west of the southern slope, and the southeastern edge of the Tibetan Plateau than that over the northwestern Tibetan Plateau. The main detrainment height and outflow horizontal range are lower and broader at nighttime than during daytime.     

Typical Structure, Variety, and Multi-Scale Characteristics of Meiyu Front

Meiyu front plays an important role in summer rainfall in central China. Based on the GMS-5 satellite images, NCEP reanalyses （2.5°×2.5°） and final analyses （1°×1°） data, and meteorological conventional sounding observations, the horizontal and vertical structures of the Meiyu front were summarized using multiple diagnostic variables, including winds, temperature, jet stream, front, pseduo-equivalent potential temperature, divergence, vertical motion, static instability, etc. In this paper, four cases were selected and analyzed, two of which are in 26-28 June and 23 July 2002 during the Experiment on Heavy Rain in the Meiyu period in the lower reaches of the Yangtze River, and the others are in May and July 1998. The two cases in July 1998 and July 2002 are the secondary Meiyu front cases. The results show that the structures and characteristics of the Meiyu front are different for various cases, or at various places and time, or at various stages of one case, and the frontal characteristics can be converted from the polar front to the equatorial front. Because of the interaction of the different scale circulations in the high and low latitudes, the horizontal structure of the Meiyu front has various forms.
The results in this paper also show that the typical Meiyu front consists of a narrow band with a high gradient of potential equivalent temperature below 500 hPa, south of which is warm and moist air mass, and north of which is the transformed air mass from the midlatitude ocean or polar continent. Below the mid troposphere, south of the front blows southwesterlies, while north blows easterlies. The ascending motion and precipitation usually occur ahead of the Meiyu front. In the upper troposphere, the subtropical front is above the Meiyu front, but two fronts are separated. In addition, the upper westerly jet stream and the easterlies to the south of the Meiyu front result in the upper divergent flow field.
The multi-scale characteristics of the horizontal structure of the Meiyu front can     

The variability of the horizontal circulation in the troposphere and stratosphere – a comparison

Summary The variability of the horizontal circulation in the stratosphere and troposphere of the Northern Hemisphere (NH) is compared by using various approaches. Spatial degrees of freedom (dof) on different time scales were derived. Modes of variability were computed in geopotential height fields at the tropospheric and stratospheric pressure levels by applying multivariate statistical approaches. Features of the spatial and temporal variability of the winterly zonal wind were studied with the help of recurrence and persistence analyses. The geopotential height and zonally-averaged zonal wind at the 50-, 500- and 1000-hPa level are used to investigate the behavior of the horizontal circulation in the lower stratosphere, mid-troposphere and at the near surface level, respectively. It is illustrated that the features of the variability of the horizontal circulation are very similar in the mid-troposphere and at the near surface level. Due to the filtering of tropospheric disturbances by the stratospheric and upper tropospheric zonal mean flow, the variability of the stratospheric circulation exhibits less spatial complexity than the circulation at tropospheric pressure levels. There exist enormous differences in the number of degrees of freedom (or free variability modes) between both atmospheric layers. Results of the analyses clearly show that the concept of a zonally symmetric AO with a simple structure in the troposphere similar to the one in the stratosphere is not valid. It is concluded that the spatially filtered climate change signal can be detected earlier in the stratosphere than in the mid-troposphere or at the near surface level. Received June 28, 2000/Revised March 10, 2001     

Numerical Simulation of CO2 Concentrations in East Asia with RAMS-CMAQ

The regional air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module(VPRM) and used to simulate temporal-spatial variations in atmospheric CO2 concentrations in East Asia,with prescribed surface CO2 fluxes(i.e.,fossil fuel emission,biomass burning,sea-air CO2 exchange,and terrestrial biosphere CO2 flux).Comparison of modeled CO2 mixing ratios with eight ground-based in-situ measurements demonstrated that the model was able to capture most observed CO2 temporal-spatial features.Simulated CO2 concentrations were generally in good agreement with observed concentrations.Results indicated that the accumulated impacts of anthropogenic emissions contributed more to increased CO2 concentrations in urban regions relative to remote locations.Moreover,RAMS-CMAQ analysis demonstrates that surface CO2 concentrations in East Asia are strongly influenced by terrestrial ecosystems.     

Ozone Vertical Profile Characteristics over Qinghai Plateau Measured by Electrochemical Concentration Cell Ozonesondes

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