夏季青藏高原北部对流层臭氧垂直分布的观测研究

对流层臭氧垂直分布变化对气候环境有重要的影响,然而观测数据一直较为稀缺。利用2016年7月下旬—8月青海省格尔木市对流层臭氧探空观测资料开展夏季青藏高原北部对流层臭氧垂直分布变化特征及其形成机制的大气背景研究。结果表明,在大气背景的转换下对流层臭氧垂直分布整体上呈现高（低）臭氧与低（高）水汽和高（低）位势涡度的对应。除7月25—27日高空低压槽过境导致的平流层向下输送使对流层臭氧浓度升高明显外,阻塞暖高压反气旋和源自青藏高原主体地区的强对流天气过境也对对流层臭氧分布有影响:阻塞暖高压在观测点东北部形成后导致7月31日至8月8日格尔木对流层连续出现罕见东风,但对流层臭氧浓度仅在8月2日因东北—西南方向反气旋切变而出现较高值,其中6 km高度以下则因为东风输送而出现高臭氧、高比湿的污染性气团;强对流天气过境影响使得8月12—14日10 km高度以上出现臭氧最低值和比湿最高值。与西宁历史夏季（1996年7—8月初）臭氧探空测值比较,格尔木对流层臭氧浓度8月偏低,该特征与季风影响青藏高原纬度最高地区所在月份一致。与林芝（2014年7月）、那曲（2011年7月末—8月中旬）和拉萨（1998年8月）历史夏季臭氧探空测值比较发现,纬度效应对青藏高原地区对流层臭氧浓度有影响。      

一次典型蒙古气旋沙尘暴的对流层顶演变及沙尘垂直输送特征

利用高分辨率中尺度数值模拟结果,对一次蒙古气旋沙尘暴过程的对流层顶折叠和沙尘对流层-平流层输送特征进行分析研究。结果发现:本次过程蒙古气旋的发展由对流层中低层斜压强迫引发,对流层中高层高空位涡下传是蒙古气旋发展的另一影响因素。蒙古气旋发展阶段,对流层中高层为低压槽,对流层顶折叠呈漏斗状;随着蒙古气旋的成熟及高空切断低涡的形成,对流层顶折叠变为双漏斗状,位置偏于低涡区南侧,分别位于低槽槽线中段和低涡中心附近。之后的气旋减弱阶段,对流层顶折叠逐渐与低涡区趋于重合。高空急流位于漏斗状对流层顶折叠区南支附近,当对流层顶折叠加强时,高空急流核向下拉伸,反之,高空急流核则趋于水平。对流层顶折叠呈漏斗状的气旋发展阶段,对流层-平流层输送气流位于漏斗东侧、北侧,即气旋暖区螺旋上升气流,位置越偏东、偏北,输送气流的强度和范围越大;气旋成熟阶段,对流层顶折叠呈双漏斗状(经向)和平直带状(纬向),低涡中心附近的准垂直上升气流、低涡中心以东的低涡区偏南上升气流、以及低涡前部槽前强上升气流均产生明显的对流层-平流层输送。气旋减弱阶段,偏南上升气流、准垂直上升气流导致的对流层-平流层输送明显减弱,低涡东北象限偏东气流则能够形成不可逆的对流层-平流层输送。     

东亚地区平流层、对流层交换对臭氧分布影响的模拟研究

首先将区域酸沉降模式(RADM)进行改造,加入平流层化学模块以替代对流层模块.然后用MM5单向耦合改造后的化学模式M-RADM,对东亚地区一次切断低压(2000年4月8～12日)引起的对流层顶折叠对上对流层、下平流层臭氧分布形式的影响进行模拟.结果显示:(1)随着高空槽的发展与切断,高空槽的底部及切断低压四周臭氧有显著增加.对流层顶折叠使高空臭氧向下输送,这种向下的输送可以到达对流层中部,对上对流层的臭氧影响最大.(2)模式可以成功地模拟出在北京地区探测到的臭氧垂直廓线的双峰结构.250 hPa处的臭氧分压比背景值增加近5倍.模拟表明改造后的区域化学模式M-RADM可以用于研究天气过程引起的对流层顶附近臭氧的演变情况.(3)上对流层臭氧分布形势的变化主要是由动力过程中的水平平流作用引起的,但是对流层顶附近臭氧的化学过程是不可忽略的.     

西宁夏季对流层臭氧垂直分布变化与气象要素的关系

根据臭氧、气象探空观测数据,分析了1996年7月5日至8月3日西宁（36°44’N,101°45＇E,海拔高度2296m）上空对流层臭氧垂直分布变化与气象要素之间的关系。对流层臭氧浓度的增加（减少）总伴随着干、冷（暖、湿）气流的输送变化,而这又与大气垂直方向的运动是紧密联系在一起的。分析表明天气动力输送过程对对流层臭氧垂直分布变化有重要作用。     

动力传输和地表排放对北京地区对流层臭氧长期变化的影响

利用2003—2013年北京地区臭氧探空资料和多种再分析资料,结合CAM-chem模式模拟分析了北京地区对流层臭氧的长期变化趋势及影响因子。结果表明:近11 a来,北京地区对流层臭氧整体呈明显增加趋势,对流层臭氧总量每年增加约0.98 DU,且地表排放对该地区对流层臭氧增加的贡献相比动力过程更大。其中,由平流层向下输送造成的对流层臭氧总量每年增加约为0.13×10~(-3)~0.17×10~(-3)Tg,对北京地区对流层臭氧总量的增加贡献约20%;由水平输送造成的臭氧增加每年约为0.06×10~(-3)Tg,对臭氧总量增加贡献约10%;而由地表排放造成的对流层臭氧增加约占该地区对流层臭氧总增加量的60%。     

春季南极昭和站上空增温与臭氧含量和分布的关系

本文利用南极昭和站1966—1979年的臭氧和高空气象资料,讨论了春季南极大气爆发性增温及其与臭氧总量、臭氧分压垂直分布的关系,发现如下事实:1.平流层爆发性增温与臭氧总量突变有三种类型,即一次突变型,两次突变型和一次突变与一次缓变混合型;2.平流层爆发性增温3—5天后,对流层上部也有一次剧烈升温;3.增温过程自平流层上部向对流层下传时,伴随着臭氧分压增压中心逐渐向下传递;在平流层各等压面上,臭氧分压变化与气温变化值之间有较好的正相关,相关系数为0.85.     

青藏高原及附近区域穿越对流层顶的质量和臭氧通量研究

利用等熵坐标下的Wei公式对青藏高原及附近地区穿越动力学和热力学定义下对流层顶的质量和臭氧通量的时空分布变化进行了计算分析。结果表明,采用这两种定义下的对流层顶时,穿越对流层顶的质量和臭氧通量都表现出在热带纬度带为TST通量,到了副热带则转换为STT通量。由于热力学定义下的对流层顶位置稍高,造成了穿越热力学对流层顶的质量和臭氧通量变化幅度大于动力学对流层顶的情况。另外,还发现在所研究的区域穿越对流层顶质量和臭氧通量交换具有明显的年代际变化特征,在1958—2001年时段内交换是先减弱后增强。青藏高原南部及南侧地区向上的质量和臭氧输送经历了逐渐减弱过程,青藏高原北部地区向下的质量和臭氧通量交换也表现为逐渐减弱的过程,这些区域作为通量输送的通道作用是在减弱的。而接近青藏高原西北侧的塔里木盆地附近的向上输送则是逐渐加强的,表明这一区域交换通道作用在青藏高原及附近地区的质量和臭氧交换过程中起着越来越重要的作用。     

东亚季风及台风过程与臭氧含量变化的关系分析

文中用2001~2015年东亚区域的气压场和对流层顶臭氧含量的资料,选用并计算了最能代表东亚地区季风活动的两种指数,应用统计分析和个例分析的方法,对东亚地域内季风运动及台风过程与臭氧浓度变化的相关性进行了分析。得到如下结论:东亚的夏季风强度指数SMC与对流层顶臭氧含量两者在40°~50°N的高纬度地区有明显的正相关关系,赤道附近存在着负相关区。东亚IWT冬季风指数与对流层顶臭氧含量在南海—西北太平洋的海域有很好的正相关。在对流层上层受台风中心强上升气流影响最频繁的地区臭氧浓度低,而受到台风外围下沉气流影响最多的地区臭氧浓度高。      

一次昌吉地区春季强寒潮天气分析及数值模拟

先基于常规天气观测资料和美国FNL1°×1°逐6h再分析资料,对2014年4月23~24日昌吉地区一次寒潮天气过程进行分析和总结,而后利用WRF3.7中尺度数值模式对10米风场和地形作用进行分析,结果表明：（1）这次寒潮天气过程出现在欧洲高压脊东南衰退、西西伯利亚低槽东南下进入新疆爆发的大尺度环流背景下。（2）这次强寒潮过程的高位涡强冷空气来自欧亚北部和北极地区的平流层下部和对流层上部。（3）本次天气受西南水汽通道影响明显,从印度洋经过长途跋涉经过四川盆地以东地区,沿着西北方向在输送中绕过青藏高原,地形阻挡引起的损失相对较少,顺着甘肃地区到达41°N附近与北支带来的水汽相遇后向西输送进入昌吉地区。（4）低层强西北风急流向山脉辐合,造成暖湿气流在天山迎风坡强烈爬升,是暴雪发生的触发机制。通过地形敏感性试验表明天山地形的抬升作用减弱所引起的降水变小。     

北半球冬季副热带高压带维持的涡度机制

本文利用涡度平衡方程讨论北半球冬季副热带高压的维持,计算发现,30°N副热带高压带地区,大型扰动所造成的涡度输送的辐散是维持这地区反气旋涡度的主要因子,这种辐散作用所造成的反气旋涡度主要发生在对流层上层,平均经圈环流对地转祸度的输送可以把它引导到对流层下层来。此外,我们还根据涡度输送的计算,讨论了西风急流的维持。向北的扰动涡度输送在45°N上空达极大值,因此它对中纬度西风和纬向平均急流的维持起着重要作用。但30°N上空,扰动的涡度输送为零,而平均经圈环流对地转涡度和相对涡度的输送都比较大,因此,可以认为副热带急流是在平均经圈环流作用下维持的。     

INTERCOMPARISON OF OZONE VERTICAL PROFILES BETWEEN ECC OZONESONDE AND BREWER UMKEHR MADE OVER QINGHAI PLATEAU OF CHINA*

From October 1995 to August 1996.a total of 50 ECC(electrochemical concentration cell) ozonesoundings were made in Xining(36.43°N,101.45°E,2296 m ASL)to study the distribution and seasonal characteristics of ozone profile,and intercompare the Brewer Umkehr ozone profiles obtained at Waliguan Baseline Station over the Qinghai Plateau.It was demonstrated that(1) Umkehr produced estimates of the ozone comparing with ECC profiles were accurate to better than 25% in the 20-38 km altitude range,and where 23-33 km region was the most accurate,within about 15% of the ECC ozonesonde:(2)higher differences between Brewer Umkehr and ECC ozonesonde occurred in the troposphere and lower stratosphere;and ozone amounts were overestimated in Umkehr layers 1,2 and 3,and were underestimated in Umkehr layers 6 and 7 by Brewer Umkehr method.     

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

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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。     

Downward transport and modification of tropospheric ozone through moist convection

This study estimated the largely unstudied downward transport and modification of tropospheric ozone associated with tropical moist convection using a coupled meteorology-chemistry model. High-resolution cloud resolving model simulations were conducted for deep moist convection events over West Africa during August 2006 to estimate vertical transport of ozone due to convection. Model simulations realistically reproduced the characteristics of deep convection as revealed by the estimated spatial distribution of temperature, moisture, cloud reflectivity, and vertical profiles of temperature and moisture. Also, results indicated that vertical transport reduced ozone by 50% (50 parts per billion by volume, ppbv) in the upper atmosphere (12–15 km) and enhanced ozone by 39% (10 ppbv) in the lower atmosphere (<2 km). Field observations confirmed model results and indicated that surface ozone levels abruptly increased by 10–30 ppbv in the area impacted by convection due to transport by downdrafts from the upper troposphere. Once in the lower troposphere, the lifetime of ozone decreased due to enhanced dry deposition and chemical sinks. Ozone removal via dry deposition increased by 100% compared to non-convective conditions. The redistribution of tropospheric ozone substantially changed hydroxyl radical formation in the continental tropical boundary layer. Therefore, an important conclusion of this study is that the redistribution of tropospheric ozone, due to deep convection in non-polluted tropical regions, can simultaneously reduce the atmospheric loading of ozone and substantially impact the oxidation capacity of the lower atmosphere via the enhanced formation of hydroxyl radicals.     

Study of ozone distribution over the south-eastern France (ESCOMPTE campaign): discrimination between ozone tendencies due to chemistry and to transport

Ozone tendencies due to chemistry and transport are calculated by a mesoscale model using a fine horizontal resolution (3 km × 3 km), over South-Eastern France. Over that region where the anthropogenic emissions are very strong, ozone pollution is highlighted during two intensive observations periods of the ESCOMPTE campaign, when the sea breeze penetrates far into the Durance and Rhone valleys and the up-slope breezes are developed. From a fine analysis of time series of ozone concentration at different ground stations along these valleys and from numerical results, it is possible to discriminate the tendency due to chemistry from the tendency due to dynamical processes. We can distinguish both processes, either local chemical production/loss or dynamical increase/decrease (transport, deposition) on maps of ozone budget according to the meteorological conditions. In particular, we show that the variations due to transport can be have the same order of magnitude than those due to chemistry, reaching 20 ppbv h⁻¹, whereas those due to chemistry are around 30 ppbv h⁻¹.     

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。     

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.     

Formation of the Summertime Ozone Valley over the Tibetan Plateau: The Asian Summer Monsoon and Air Column Variations

The summertime ozone valley over the Tibetan Plateau is formed by two influences,the Asian summer monsoon(ASM) and air column variations.Total ozone over the Tibetan Plateau in summer was ～33 Dobson units(DU) lower than zonal mean values over the ocean at the same latitudes during the study period 2005-2009.Satellite observations of ozone profiles show that ozone concentrations over the ASM region have lower values in the upper troposphere and lower stratosphere(UTLS) than over the non-ASM region.This is caused by frequent convective transport of low-ozone air from the lower troposphere to the UTLS region combined with trapping by the South Asian High.This offset contributes to a ～20-DU deficit in the ozone column over the ASM region.In addition,along the same latitude,total ozone changes identically with variations of the terrain height,showing a high correlation with terrain heights over the ASM region,which includes both the Tibetan and Iranian plateaus.This is confirmed by the fact that the Tibetan and Iranian plateaus have very similar vertical distributions of ozone in the UTLS,but they have different terrain heights and different total-column ozone levels.These two factors(lower UTLS ozone and higher terrain height) imply 40 DU in the lower-ozone column,but the Tibetan Plateau ozone column is only ～33 DU lower than that over the non-ASM region.This fact suggests that the lower troposphere has higher ozone concentrations over the ASM region than elsewhere at the same latitude,contributing ～7 DU of total ozone,which is consistent with ozonesonde and satellite observations.     

青藏高原东北侧臭氧垂直分布与平流层-对流层物质交换

利用臭氧和温度探空廓线,结合NCEP/NCAR资料、TOMS臭氧总量卫星观测资料和NOAAHYSPLIT后向轨迹模式资料,通过个例分析探讨了影响青藏高原(下称高原)附近臭氧垂直分布的因子和过程。结果表明,动力过程是影响高原上空臭氧垂直分布的主要因子,特别是中高纬度高臭氧浓度的空气向南入侵会导致高原上空臭氧浓度的升高,影响高原上空臭氧低谷的范围大小和形态;尽管大气化学过程对高原上空的平流层下层臭氧垂直分布的影响并不显著,但是高原上空的平流层臭氧变化与温度变化具有较好的一致性。同时还发现,对流层上层的强反气旋系统,特别是中高纬度阻塞高压的边缘有明显的平流层空气向对流层入侵,从而导致对流层内臭氧浓度的增加。