上对流层/下平流层GPS掩星资料与我国探空温度对比

本文使用CDAAC(COSMIC Data Analysis and Archival Center)提供的1995—2010年GPS掩星干反演大气温度和我国无线电探空温度资料,选择临近的廓线进行匹配,以掩星资料为基准,分析上对流层/下平流层区域(200～30 hPa)探空温度与掩星温度之间的偏差。分析多种时空匹配条件下总的温度偏差和标准差的结果表明,匹配条件对偏差平均值影响较小,主要影响偏差标准差,选择探空和掩星廓线时间差小于3 h、距离小于200 km作为匹配条件。就全国平均而言,探空温度和掩星温度相差很小,其中在上对流层的偏差大于下平流层,偏差的标准差随高度增加而变大。在上对流层昼夜偏差都为正,下平流层白天为正、夜间为负,温度偏差和标准差在白天大于夜间,说明掩星资料具有足够的精度可以识别出太阳辐射对我国探空温度的影响。偏差在低纬较大,随纬度升高逐渐减小,与使用掩星资料计算的大气垂直减温率有较好的对应关系,其变化特征与探空滞后误差比较一致,说明使用掩星资料可以辨别滞后误差对探空资料的影响。就全国平均而言,L波段探空仪和59型探空仪的平均温度偏差都相对较小,但在不同纬度表现不同;在低纬地区二者偏差对比明显,59型探空仪具有较大的偏差,L波段探空仪偏差较小,高纬地区二者偏差相对都较小;59型探空仪的偏差标准差始终大于L波段探空仪。结果说明掩星资料可以分辨仪器换型对温度偏差的影响,探空仪的升级使我国探空资料的精准度提高,特别在纬度较抵的区域,偏差的改进更加明显。     

东亚副热带季风雨带建立特征及其降水性质分析

利用1961—2006年NCEP/NCAR再分析数据集和TRMM、CMAP多年平均逐候降水资料,分析了中国东部副热带季风雨季的起始时间、建立特征及其降水性质。结果表明,第16—18候,在中国江南南部和华南北部地区(25°30°N)日降水率达到6 mm/d,且范围较大,在低层该雨带的水汽主要来源于西太平洋副热带高压南侧转向的西南水汽输送,其源地即为西太平洋副热带季风雨季开始。雨带建立同时,东亚副热带地区中东太平洋的纬向海平面气压梯度首先在中纬度发生反转,即西低东高(相应于西暖东冷)。中国东部副热带地区出现加热中心并伴有上升运动,强度逐渐增强,并伸展至对流层顶,其强度及对流高度与热带地区相当,对流层中低层大气呈对流不稳定,降水已具有对流性降水性质。与此同时,南海西太平洋地区仍在副热带高压控制之下,盛行下沉运动,无降水产生,南海夏季风及其相应的水汽输送尚未建立。东亚副热带季风雨带的建立(3月底4月初)早于热带夏季风雨带,两雨带分别具有独立的热源中心和上升运动。南海夏季风即将爆发之际,赤道地区加热中心快速北移至南海地区,与副热带地区热源相互作用。     

Measurements and modelling of atmospheric pollution over the Paris area: an overview of the ESQUIF Project

The Étude et Simulation de la QUalité de lair en Ile de France (ESQUIF) project is the first integrated project dedicated to the study of the processes leading to air pollution events over the Paris area. The project was carried out over two years (summer 1998 to winter 2000) to document all types of meteorological conditions favourable to air quality degradation, and in particular to photo oxydant formation. The goals of ESQUIF are (1) to improve our understanding of the relevant chemical and dynamical processes and, in turn, improve their parametrizations in numerical models, and (2) to improve and validate existing models dedicated to pollution analysis, scenarios and/or forecasting, by establishing a comprehensive and thorough database. We present the rationale of the ESQUIF project and we describe the experimental set-up. We also report on the first experiments which took place during the summer of 1998 involving surface networks, and remote sensing instruments as well as several aircraft. Focusing on three days of August 1998, the relative contributions of long-range transported and locally-produced ozone to the elevated ozone concentrations observed during this period are discussed and chemistry-transport model preliminary results on this period are compared to measurements.     

Connections between the distribution of prevailing winds in the winter Northern Hemisphere, solar/geomagnetic activity and the QBO phase

The effect of solar/geomagnetic activity and QBO phase on the distribution of winds prevailing in the winter periods (January–March) in the Northern Hemisphere at the altitude of 850 mb was studied. Analysis has shown that the zonal flow over the North Atlantic under high geomagnetic activity intensifies and under low solar/geomagnetic activity weakens. Flow deviations, associated with geomagnetic activity, are more marked under the QBO-east phase, and flow deviations, associated with solar activity, are more marked under the QBO-west phase. The results reported by Venne and Dartt (1990) concerning the wind distribution in the winter (February–March) Northern Hemisphere under high and low solar activity and a QBO-west phase, have been confirmed, and supplemented with wind distributions under high and low geomagnetic activity.     

RELATIONSHIPS BETWEEN ZONAL WIND ANOMALIES IN HIGH AND LOW TROPOSPHERE AND ANNUAL FREQUENCY OF NW PACIFIC TROPICAL CYCLONES

Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition.It is indicated that when △ U200-△U850 ＞0 in the eastern tropical Pacific and △ U200- △U850 ＜0 in western tropical Pacific, the Walker cell is stronger in the Pacific tropical region and the annual frequency of NW Pacific tropical cyclone are above normal. In the years with zonal wind anomalies, the circulation of high and low troposphere and the vertical motions in the troposphere have significant characteristics. In the time scale of short-range climate prediction, zonal wind anomalies in high and low troposphere are useful as a preliminary signal of the annual frequency prediction of NW Pacific tropical cyclones.     

福建入夏早晚异常的风场特征分析

本文以850 hPa、200 hPa月平均风场和西太平洋副热带高压脊线北抬至25°N日期资料及福建省25个代表站(县)5—7月的降水资料为基本分析素材。首先标定福建入夏异常的标准与年例,其次揭示850 hPa2、00 hPa 6月风场与异常年例的基本特征,进而探讨了对福建入夏早晚的影响关系。结果表明:在低层索马里-阿拉伯海区的越赤道气流强劲,南海至东亚低纬区域西南风偏大,西太平洋区域低纬度地区南风减弱、东风强劲,且东西风交汇区偏西;而在高层辐合区东风范围偏大,索马里-阿拉伯海区的区域东风风速强劲,青藏高原南侧和副高主体季节性位移的关键区以吹东风为主,东亚区域经向度小,位于青藏高原至我国东部区域范围内,形成一逆时针“距平”风环流;在此高低层风场特征的匹配下,有利于福建提早进入夏季;反之亦然。     

利用卫星资料分析对流层臭氧柱总量分布特征及其可能的原因

利用卫星资料计算得到的对流层臭氧柱总量数据分析了近20年来全球对流层臭氧柱总量的全球分布特征，并对我国对流层臭氧的季节变化做了研究。利用对流层污染测量仪（MOPITT）的CO和全球臭氧监测仪（GOME）和大气制图扫描成像吸收光谱仪（SCIAMACHY）的NO₂数据分析了关于对流层臭氧的分布特征及其原因。得出中高纬度地区对流层臭氧浓度存在规律的年内变化，对流层臭氧高浓度值的分布及变化与人类活动有密切关切。     

应用查表法模拟区域对流层O3、Nox分布和演化的研究

应用STEM-II气相光化学模式探讨了影响对流层O3、NOx气相光化学转化率的各物理、化学因子。表明在我国多数地区光化学污染物特征(NMHC/NOx较高)下,光辐射强度、温度、初始O3浓度和NOx浓度是影响O3、NOx气相光化学转化率的主要因子。将以上因子分档组合,计算并建立了各种情况下O3、NOx气相光化学转化率的查算表,并将之用于模拟区域O3、NOx的演化和分布。结果表明,与光化学模式直接耦合计算法相比,该方法既能显著缩短计算时间,又能基本反映大气化学反应的非线性过程,并与直接耦合法符合得较好。     

Convective Redistribution of Ozone and Oxides of Nitrogen in the Troposphere over Europe in Summer and Fall

The fluxes of ozone and NO_x out of the atmospheric boundary layer (ABL) over Europe are calculated in a mesoscale chemical transport model (MCT) and compared with the net chemical production or destruction of ozone and the emissions of precursors within the ABL for two 10 days' periods which had quite different synoptic situations and levels of photochemical activity (1–10 July 1991 (JUL91) and 26 October–4 November 1994 (ON94)). Over the European continent, about 8% of the NO_x emissions were brought from the ABL to the free troposphere as NO_x, while about 15% of the NO_x emissions were brought to the free troposphere as NO_y–NO_x, i.e. as PAN or HNO₃. The convection dominates over the synoptic scale vertical advection as a transport mechanism both for NO_x and NO_y out of the boundary layer in the summertime high pressure situation (JUL91), while in the fall situation (ON94) the convective part was calculated to be the smallest. NO_x was almost completely transformed to NO_y–NO_x or removed within the ABL. Also for NO_y the major part of the atmospheric cycle is confined to the ABL both for JUL91 and ON94. The vertical transport time out of the ABL is of the order of 100h both for the total model domain and over the European continent. The net convective exchange of ozone from the ABL is not a dominant process for the amount of ozone in the ABL averaged over 10 days and the whole domain, but convection reduces the maximum ozone concentration in episodes significantly. The ozone producing efficiency of NO_x is calculated to increase with height to typically 15–20 in the upper half of the troposphere from around 5 in the ABL, but in the middle free troposphere the concentration of NO_x is often too low to cause net chemical formation of ozone there.     

Atmospheric measurements during Polarstern cruise ANT VII/1, 54° N to 32° S: An overview

A comprehensive set of trace gas concentrations and meteorological parameters were measured simultaneously during a cruise of the research vessel Polarstern from Bremerhaven (54° N, 8° E) to Rio Grande (32° S, 52° W) during the period from 15 September to 9 October 1988. This paper describes the general features of the cruise and summarizes the measurements made, the techniques employed, and the placement of the instruments on board the ship. The synoptic data base is used to characterize the nature and possible origins of the air masses encountered during the cruise and to draw some general conclusions from the measurements.