三维对流云对大气光化学组分的再分布作用及其化学效应

利用一个三维的冰雹云模式与化学组分输送模块耦合，得到云输送引起大气光化学组分的再分布，然后用一个包含详细气相化学反应机制的箱模式研究了云输送引起的气相体积分数的变化及其对大气化学系统产生的影响。结果表明，云输送后O3体积分数大于无云个例，但其后两天内两者的变化趋势相差不大；HNO3、NO2、NO3、PAN等的体积分数均明显高于无云个例，分别增长了87％、70％、62％和49％，其中NO2体积分数的增加主要由于云输送造成，而NO3、HNO3、PAN主要是输送对化学扰动的结果。两天内OH和HO2自由基体积分数比无云个例平均增长了13％和11％。     

基于秒级探空资料的中国地区浮力频率分布

浮力频率用来描述大气层结稳定性,反映大气扰动强弱。利用2014年6月-2017年5月中国地区高垂直分辨率的秒级探空资料,分析了中国地区浮力频率的时空分布特征。结果表明:中国地区大气浮力频率总体随高度的增加而增大,低平流层值大于对流层值;对流层和低平流层中浮力频率随高度变化均较小可视为常数,过渡层浮力频率随高度变化较大,对流层中浮力频率受地形影响较平流层大。对流层中北方地区5 km高度以下的浮力频率随时间呈现出较弱的周期变化,周期为1年,峰值出现在冬季,南方地区随时间无明显变化;在过渡层中南北地区的浮力频率随时间均呈现出1年的周期变化,峰值出现在冬季,谷值出现在夏季;在低平流层中南北地区浮力频率随时间均无明显变化。浮力频率的大小变化对重力波参数有较大影响,秒级探空资料计算的的浮力频率和风速切变更精细,较常规探空资料更准确地反映大气稳定度的变化。     

Climatology of Ozone, PAN, CO, and NMHC in the Free Troposphere Over the Southern North Atlantic

Free tropospheric measurements of ozone, peroxyacetylnitrate andprecursors (CO, NMHC) that were made within the framework of the EUROTRACsub-project TOR (Tropospheric Ozone Research) between 1990 and 1995 at theGAW station Izana, Tenerife (28°18N, 16°30W) arediscussed. The average annual cycles reveal the importance of transport fromnorthern mid-latitudes and the role of photo-chemistry. According toair-mass trajectories, which were supplied to us from AEROCE(Atmosphere/Ocean Chemistry Experiment), transport from northernmid-latitudes is associated with high precursor concentrations in winter,whereas ozone concentrations in winter are not much influenced by transportpatterns, suggesting a rather uniform distribution over the northern part ofthe Northern Hemisphere around mean value of 43 ± 5 ppb. In summer,high ozone concentrations of up to 90 ppb are often encountered duringtransport from north, while the levels of precursors are much lower than inwinter, because of photochemical destruction. Trajectories from southerlylatitudes and the Sahara usually have the lowest ozone concentrationsassociated with them.     

中国地区闪电和对流层上部NOx的时空分布特征及其相关性分析

为了解闪电对对流层上部NO_x的贡献,本文利用美国全球水资源和气候中心（GHRC）提供的1995年4月~2005年12月的闪电卫星格点资料及高层大气研究卫星 (UARS) 上的卤素掩星试验装置 (HALOE) 1991年10 月~2005 年11月的观测资料,分析了中国地区闪电与对流层上部NO_x体积混合比的时空分布特征及两者的相关性.结果表明:中国地区闪电和对流层上部的NO_x在季节分布、年际分布和空间分布上保持很好的一致性,闪电是对流层上部NO_x的重要来源;NO极值高度在350 hPa左右,云闪直接产生的NO是极值产生的主要原因,NO₂的极值高度在250 hPa左右,因为闪电产生的NO在传输过程中会被氧化成NO₂并通过雷暴的垂直输送作用抬升到更高高度;强对流活动有利于NO_x的传输,而人类活动产生的NO_x一般较难输送到对流层上部,因此闪电多发区的NO_x极值较大,所在的高度也较高.     

中国东部高空颠簸时空分布特征及其与热带中东太平洋海温的关系

本文利用1979～2014年NCEP-DOE日平均再分析资料和中国区域2375份航空器空中颠簸报告资料,研究中国东部区域高空颠簸的时空分布特征及其与热带中东太平洋海温异常（简称“海温异常”;空间范围:5°S～5°N,120°～170°W）的关系以及产生这种关系的可能原因。结果表明:中国东部地区高空颠簸与东亚副热带西风急流之间存在显著时空相关关系,其原因是高空纬向风引起的垂直风切变是构成高空颠簸时空分布的主导因素。中国东部夏季高空颠簸与海温异常存在正相关关系;冬季呈现南北两个正负相关区:以30°N为界,北部区域存在显著的负相关,南部区存在显著的正相关,在30°N急流轴附近区域无显著相关关系。海温异常影响中国高空颠簸时空分布的可能原因是海温变化引起对流层高层温度出现异常,进而影响温度的经向梯度,导致东亚副热带西风急流强度和位置出现异常（夏季,急流轴南侧出现西风异常;冬季,急流轴北侧出现东风异常,南侧出现西风异常）。高空纬向风的变化导致纬向风的垂直梯度和经向梯度出现异常,最终影响高空颠簸的时空分布特征。对流层高层温度的异常变化可能是由与热带海温异常相关的平流层水汽变化所引起。     

CHARACTERISTICS OF UT/LS CARBON MONOXIDE INTRASEASONAL OSCILLATIONS AND THEIR IMPACT FACTORS OVER THE TIBETAN PLATEAU AND ITS ADJACENT AREAS IN SUMMER

The study presented herein investigated the main characteristics of carbon monoxideintraseasonal variability and evaluated its possible impact factors using the upper troposphere and lowerstratosphere (UT/LS) Aura Microwave Limb Sounder (MLS) observations over Tibetan Plateau and itsadjacent areas in summer (June to August) of 2005 and 2006. Observations show a persistent constituentextreme extending up into the UT/LS throughout summer, as well as a temporally reversed phase variationbetween the carbon monoxide and ozone in UT/LS. The intraseasonal oscillations (ISOs) of carbonmonoxide during summer are investigated by using methods of wavelet and band pass filter analysis. It isfound that ISOs over the Tibetan Plateau have periods of 10 to 20 days and 30 to 60 days. The formermainly appeared in upper troposphere while the latter in lower stratosphere. Further analysis shows thatthese two periods of ISOs in UT/LS are mainly in phase to the activities of convection over the south of theplateau and the variation of South Asia High, respectively. The above two factors and their dynamicalcoupling may be responsible for the tracer ISOs at different levels.     

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.     

Atmospheric nuclei in the remote free-troposphere

During May-June of 1990 an extensive flight series to survey aerosol present in the upper-troposphere was undertaken aboard the NASA DC-8 as part of the CLObal Backscatter Experiment (GLOBE). About 50,000 km were characterized between 8–12 km altitude and between 70°N and 58°S. Aerosol with diameters greater than 3nm were counted and sized with a combination of condensation nuclei counters and optical particle counters. Aerosol number and mass concentrations were separately identified with regard to both refractory and volatile components. Regions of the free-troposphere with the lowest mass concentrations were generally found to have the highest number concentrations and appeared to be effective regions for new particle production. These new particle concentrations appear inversely related to available aerosol surface area and their volatility suggests a sulfuric acid composition. The long lifetime of these new particles aloft can result in their growth to sizes effective as CN and CCN that can be mixed throughout the troposphere.     

Barotropic processes associated with the development of the Mei-yu precipitation system

The barotropic processes associated with the development of a precipitation system are investigated through analysis of cloud-resolving model simulations of Mei-yu torrential rainfall events over eastern China in mid-June 2011. During the model integration period, there were three major heavy rainfall events: 9–12, 13–16 and 16–20 June. The kinetic energy is converted from perturbation to mean circulations in the first and second period, whereas it is converted from mean to perturbation circulations in the third period. Further analysis shows that kinetic energy conversion is determined by vertical transport of zonal momentum. Thus, the prognostic equation of vertical transport of zonal momentum is derived, in which its tendency is associated with dynamic, pressure gradient and buoyancy processes. The kinetic energy conversion from perturbation to mean circulations in the first period is mainly associated with the dynamic processes. The kinetic energy conversion from mean to perturbation circulations in the third period is generally related to the pressure gradient processes.     

Static Stability of the Troposphere Over the Southeastern Beaufort Sea–Amundsen Gulf Region of the Western Maritime Arctic

The characterization of the static stability of the troposphere over the western maritime Arctic remains limited in spite of its significance to both atmospheric thermodynamics and dynamics. Field observations of microwave radiometric temperature profiles from the International Polar Year, Circumpolar Flaw Lead System Study (late November 2007 to mid-July 2008) and the ArcticNet field campaign (mid-July to early November 2009) provided a unique opportunity to characterize the static stability of the troposphere over the southeastern Beaufort Sea–Amundsen Gulf region. Notably, the monthly median atmospheric boundary layer (<2000?m) static stability profile for April and the profile for May clearly revealed an inversion elevated above a thermal internal boundary layer, whereas the median summer static stability profiles had very strong surface-based inversions. These profiles have been linked to the seasonal evolution of sea-ice cover in Amundsen Gulf. The monthly static stability profiles for the free atmosphere (2000–10,000?m) revealed an annual cycle. The average static stability of the lower troposphere (2000–5000?m) had a minimum of 3.3?±?0.5?K?km^?1 in July and a maximum of 4.5?±?0.5?K?km^?1 in January and February. In the upper troposphere (>5000–8000?m), the average static stability had a minimum of 2.9?±?0.6?K?km^?1 in June and August and a maximum of 5.3?±?0.8?K?km^?1 in January. The monthly median heights of the tropopause also had an annual cycle. The maximum of 9750?m occurred in June, July, and August. The minimum tropopause height of 8000?m occurred in December, January, and March. The seasonal cycles of static stability in the free atmosphere and the seasonal cycle in the height of the tropopause can be attributed to regional as well as synoptic-scale forcing. This analysis will contribute to the understanding of the thermodynamics and dynamics of a data-sparse region of the Arctic by providing a “snapshot” of the state of the atmosphere through a composite annual cycle.