A review of global stratospheric aerosol: Measurements, importance, life cycle, and local stratospheric aerosol

Stratospheric aerosol, noted after large volcanic eruptions since at least the late 1800s, were first measured in the late 1950s, with the modern continuous record beginning in the 1970s. Stratospheric aerosol, both volcanic and non-volcanic are sulfuric acid droplets with radii (concentrations) on the order of 0.1–0.5 µm (0.5–0.005 cm^− 3), increasing by factors of 2–4 (10–10³) after large volcanic eruptions. The source of the sulfur for the aerosol is either through direct injection from sulfur-rich volcanic eruptions, or from tropical injection of tropospheric air containing OCS, SO₂, and sulfate particles. The life cycle of non-volcanic stratospheric aerosol, consisting of photo-dissociation and oxidation of sulfur source gases, nucleation/condensation in the tropics, transport pole-ward and downward in the global planetary wave driven tropical pump, leads to a quasi steady state relative maximum in particle number concentration at around 20 km in the mid latitudes. Stratospheric aerosol have significant impacts on the Earth's radiation balance for several years following volcanic eruptions. Away from large eruptions, the direct radiation impact is small and well characterized; however, these particles also may play a role in the nucleation of near tropopause cirrus, and thus indirectly affect radiation. Stratospheric aerosol play a larger role in the chemical, particularly ozone, balance of the stratosphere. In the mid latitudes they interact with both nitrous oxides and chlorine reservoirs, thus indirectly affecting ozone. In the polar regions they provide condensation sites for polar stratospheric clouds which then provide the surfaces necessary to convert inactive to active chlorine leading to polar ozone loss. Until the mid 1990s the modern record has been dominated by three large sulfur-rich eruptions: Fuego (1974), El Chichón (1982) and Pinatubo (1991), thus definitive conclusions concerning the trend of non-volcanic stratospheric aerosol could only recently be made. Although anthropogenic emissions of SO₂ have changed somewhat over the past 30 years, the measurements during volcanically quiescent periods indicate no long term trend in non-volcanic stratospheric aerosol.     

两类极区平流层异常增温的特征及其与850hPa温度的关系

采用NCEP/NCAR逐日再分析资料,将冬季极区平流层增温分为两种类型:Ⅰ型和Ⅱ型,并分析了两种类型增温的特征、机制及其与850hPa温度的关系。结果表明,波动强迫的强度和对流层的热量能否向上到达平流层是决定两类平流层异常增温的两个主要因素。Ⅰ型平流层增温期间,对流层也表现出了明显的增温特征,850hPa与平流层温度距平场呈现相当正压结构,极区和中纬度异常表现为反位相的振荡,呈现典型的北极涛动的特征;Ⅱ型平流层异常增温期间,增温异常仅局限在平流层范围内,平流层的中低层与高层呈现反位相的距平分布,850hPa温度距平场呈现无规则的分布特征。     

A note on the Aitken nuclei and ion flow measurements in the lower stratosphere

In the light of new measurements of small aerosol particles in the lower stratosphere, some of the old investigations—which were only published in part in scientific journals—are reviewed and compared. The discussion focuses on whether the Aitken nuclei (AN) size distribution up to 20 km can be described by Junge’s or log-normal density functions and under what circumstances one can find a bimodal distribution of these particles. The ion flow in correlated to the stratospheric pollution (intercept with the jet aircraft, volcanic activity) and is, in mean, directly proportional to the aircraft altitude in the undisturbed lower stratosphere. Note: The GCCPR, Univ. Missouri at Rolla, reports quoted in the article can be obtained from the author.     

Correlated seasonal and climatic variations of trace constituents in the stratosphere

Summary Spectrometric experiments performed, in November 1976, within the framework of the Latitude Survey Mission on board the NASA Convair 990 from Ames Research Center are briefly deseribed. The results presented concern odd nitrogen molecules, HCl and water vapor. In terms of vertical column density, HNO₃ is predominant over NO+NO₂ at all latitudes higher than 40 degrees. A seasonal variation of NO₂ abundance is observed, with larger values in the summer hemisphere at high latitude. The mean zenith column density of HCl above 11 km is 1.5×10¹⁵ mol.cm^–2, with no evidence for any seasonal or climatic variation. Local number densities as high as 1.4×10¹⁰ mol.cm^–3 for HNO₃ and 5.4×10¹⁴ mol.cm^–3 for water vapor have been measured during the same flight near 11 km.     

Depth profiles of chlorofluoromethanes in the Norwegian sea

Depth profiles of the chlorofluoromethanes (CFM), CFCl₃ and CF₂Cl₂, have been obtained together with tritium profiles from water samples collected in the Norwegian Sea between surface and 2800 m depth. CFM analysis was performed by vacuum extraction of the dissolved gases from 500 ml samples of seawater and subsequent gaschromatographic measurement. The CFM concentration decreases with depth to about 10 percent of surface concentration at depths below 2000 m. The same behaviour is found for the tritium content. From a correlation of the CFM and tritium concentration the upper limit of the preindustrial atmospheric CFM levels can be estimated to 5 percent of the present day concentrations.     

XLS-Ⅱ型系留气艇探测系统

简单描述了系留气艇运动的基本力学原理，较详细地介绍了国产XLS-Ⅱ型系留气艇探测系统的基本组成、结构和主要技术指标。系统的绞车重36kg，电机功率600W，拉线最大拉力为175kg。与系统配套的有气象要素、大气臭氧和大气气溶胶等探测单元。给出了主要气象和某些环境要素的探测精度和应用实例并简单讨论了系留气艇探测系统在实际应用的某些问题。     

An Isentropic Mass Circulation View on the Extreme Cold Events in the 2020/21 Winter

Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isentropic mass circulation(IMC)perspective.Results show that the midlatitude cold surface temperature anomalies always co-occurred with the high-latitude warm anomalies,and this was closely related to the strengthening of the low-level equatorward cold air branch of the IMC,particularly along the climatological cold air routes over East Asia and North America.Specifically,the two cold surges over East Asia in early winter were results of intensification of cold air transport there,influenced by the Arctic sea ice loss in autumn.The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures(SSTs)explained the concurrent anomalous warmth there.This enhanced a wavenumber-1 pattern and upward wave propagation,inducing a simultaneous and long-lasting stronger poleward warm air branch(WB)of the IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming(SSW)event on 4 January.The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch,hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February.Results do not yield a robust direct linkage from La Ni?a to the SSW event,IMC changes,and cold events,though the extratropical warm SSTs are found to contribute to the February cold surge in North America.     

与东北冷涡相伴的高空急流诱发平流层重力波的数值模拟研究

使用中尺度数值模式WRF-ARW,针对2010年6月发生在中国东北地区一例伴随对流层高空西风急流（位于~9 km高度）演变过程出现的平流层重力波活动特征开展了数值模拟. 事件发生期间,对流层区域环流处在一个东北冷涡系统的控制之下. 模拟结果再现了该东北冷涡的发展和维持过程,以及与之相伴的高空急流的特征. 模拟结果揭示出在急流区域上空的平流层中存在显著重力波活动现象. 分析结果显示,重力波活动与急流存在紧密联系,在水平方向上,重力波呈显著的二维结构,出现在急流出口区上部并逆背景流向西传播. 功率谱分析结果表明盛行波动具有~700 km水平尺度、9~12 h时间尺度以及4~5 km垂直波长. 由于急流的存在,造成其与平流层中下部之间存在显著的水平风速垂直切变,与切变相伴的耗散使得上传的重力波动量通量数值随着高度升高而递减. 同时,在18~20 km高度间出现的西风-东风转换带极大地抑制了波动在垂直方向的传播,形成显著动量通量沉积效应. 估算结果表明,在11~20 km高度之间,这种效应的整体作用相当于对该层背景流施加强度为0.86 m·s-1·day-1的动力阻曳.     

北京夏季夜间低空急流特征观测分析

利用三年夏季系留气艇探测结果,分析了北京夏季夜间低空急流的一般特征.30％的夜间观测记录出现了低空急流.急流平均高度为200 m,其最大频率出现在140 m左右,90％急流出现在320 m以下.W、SW、SE是夜间低空急流的主要风向.不同观测地点低空急流在速度、风向和高度上存在明显差异.城区低空急流高度大部分时间比郊区高.个例分析表明,在夜间稳定边界层条件下,低空急流与局地山谷风环流强弱变化有很好相关.进一步成因分析认为,斜坡地形产生的热成风、山谷风环流可能是北京夏季夜间低空急流形成的主要原因.     

大气准定常行星波异常传播及其在平流层影响东亚冬季气候中的作用

东亚季风区同时受世界上最广阔的大洋和陆地的影响,这种行星尺度的海陆热力对比以及青藏高原大地形的作用,从而产生很强的行星尺度扰动,并且这种扰动具有准定常的性质。利用再分析资料研究了准定常行星波活动的变化对东亚地区冬季气候异常的影响,主要侧重于年际和季节内时间尺度上的变化。在年际时间尺度上,冬季行星波两支波导的变化存在反相关的振荡关系,这种年际振荡一方面影响了北半球环状模的位相,另外一方面导致了东亚地区的气候异常。当有异常强的低纬波导时,一般对应有西伯利亚高压的减弱和我国东北、华北地区的增温;反之当有异常弱的低纬波导时,我国东北和华北温度则普遍偏低。研究还表明,行星波传播的年际振荡与东亚地区气候异常的关系显著地受到热带平流层准两年周期振荡（QBO）的调制,只是当QBO处于东风位相时,行星波传播的年际振荡才与东亚气候异常有显著的关系。在季节内时间尺度上,准定常行星波的变化与平流层极涡的低频变化密切相关,并且这种平流层极涡的异常通过和行星波的相互作用,可以自上而下影响到对流层的短期气候;平流层极涡异常下传对对流层大气环流有明显的影响,并且这种影响在东亚地区非常显著。由于平流层变化通常维持时间长,并且平流层极涡异常下传领先于对流层,因此这为东亚冬季短期气候异常的预报提供了一个新的预报依据。