Vertical Profile Comparison of Aerosol and Cloud Optical Properties in Dominated Dust and Smoke Regions over Africa Based on Space-Based Lidar

This study evaluates the vertical profiles of aerosol and cloud optical properties in 40 dominated dust and smoke regions in Western-Northern Africa (WNA) and Central-Southern Africa (CSA), respectively, from the surface to 10km and from 2008 to 2011 based on LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies). Aerosol extinction (AE), aerosol backscatter (AB), and aerosol depolarization (AD) generally increase from the surface to 1.2 km and decrease from 1.2 km to the upper layers in both WNA and CSA. AE and AB in CSA (maximum of 0.13 km-1, 0.14 km-1, 0.0021 km-1‧sr-1, 0.0033 km-1‧sr-1) are higher than in WNA (maximum of 0.07 km-1, 0.08 km-1, 0.0017 km-1‧sr-1, 0.0015 km-1‧sr-1) at 532 and 1064 nm respectively. AD in WNA (maximum of 0.25) is significantly higher than in CSA (maximum of 0.05). There is a smooth change with the height of cloud extinction and backscatter in WNA and CSA, while there is a remarkable increase of cloud depolarization with height, whereby it is high in CSA and low in WNA due to high and low fraction of cirrus respectively. Altocumulus has the highest extinction in NA (0.0139 km-1), CA (0.058 km-1), WA (0.013 km-1), while low overcast transparent (0.76 km-1) below 1 km in SA. The major findings of this study may contribute to the improvement of our understanding of aerosol-cloud interaction studies in dominated dust and smoke aerosol regions.

Vertical distribution characteristics of dust aerosol mass concentration in the Taklimakan Desert hinterland

The different height mass concentrations of dust aerosol data from the atmosphere environment observation station （Ta- zhong Station） was continuously observed by instruments of Grimm 1.108, Thermo RP 1400a and TSP from January of 2009 to February of 2010 in the Taklimakan Desert hinterland. Results show that： （1） The mass concentration value of 80 m PMl0 was higher, but PM2.5 and PM1.0 concentrations at 80 m was obviously lower than 4 m PMl0, and the value of 80 m PM1.0 mass concentration was the lowest. （2） The PM mass concentrations gradually decreased from night to sunrise, with the lowest concentration at 08：00, with the mass concentration gradually increased, up to the highest concentration around 18：00, and then decreased again. It was exactly the same with the changes of wind speed. （3） The high monthly average mass concentration of TSP mainly appeared from March to September, and the highest concentration was in April and May, subsequently gradually decreased. Also, March-September was a period with high value area of PM monthly average mass concentration, with the highest monthly average mass concentration of 846.0 p.g/m3 for 4 m PM^0 appeared in May. The concentration of PM10 was much higher than those of PM2.5 and PM1.0 at 80 m. There is a small difference between the concentration of PM2.5 and PM~ 0. Dust weather was the main factor which influenced the concentration content of the different diameter dust aerosol, and the more dust weather days, the higher content of coarse particle, conversely, fine particle was more. （4） The mass concentration of different diameter aerosols had the following sequence during dust weather： clear day 〈 blowing dust 〈 floating and blowing dust 〈 sandstorm. In different dust weather, the value of PM^o/TSP in fine weather was higher than that in floating weather, and much higher than those in blowing dust and sandstorm weather. （5） During the dust weather process, dust aerosol concentration gradually decreased with particle size decreasing. The dust aerosol mass concentration at different heights and diameter would have a peak value area every 3-4 days according to the strengthening process of dust weather.

Synergistic Use of AIRS and MODIS for Dust Top Height Retrieval over Land

It is nontrivial to extract the dust top height（DTH） accurately from passive instruments over land due to the complexity of the surface conditions. The Moderate Resolution Imaging Spectroradiometer（MODIS） deep blue（DB） algorithm can be used to infer the aerosol optical depth（AOD） over high-reflective surfaces. The Atmospheric Infrared Sounder（AIRS） can simultaneously obtain the DTH and optical depth information. This study focuses on the synergistic use of AIRS observations and MODIS DB results for improving the DTH by using a stable relationship between the AIRS infrared and MODIS DB AODs. A one-dimensional variational（1DVAR） algorithm is applied to extract the DTH from AIRS. Simulation experiments indicate that when the uncertainty of the dust optical depth decreases from 50% to 20%, the improvement of the DTH retrieval accuracy from AIRS reaches 200 m for most of the assumed dust conditions. For two cases over the Taklimakan Desert, the results are compared against Cloud-Aerosol Lidar with Orthogonal Polarization（CALIOP） measurements. The results confirm that the MODIS DB product could help extract the DTH over land from AIRS.

Vertical dynamic and thermodynamic characteristics of urban lower boundary layer and its relationship with aerosol concentration over Beijing

By utilizing observational data from a 325 m tower of the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS) on March 19-29, 2001 and August 11-25, 2003, a comprehensive study was conducted on the vertical dynamical and thermodynamic characteristics of the urban lower boundary layer (ULBL) and its relationship with aerosol concentration over Beijing. Firstly, a comparative analysis was made on the gradient data (wind, temperature and humidity), ultrasonic data (atmospheric turbulences) and air-quality observations at different tower heights (47, 120 and 280 m). Secondly, a diagnosis was made to reveal the major features of normalized variances of velocity and temperature, turbulence kinetic energy as well as their relationship with aerosol concentrations. Furthermore, the characteristics of the ULBL vertical structure and the TSP concentration/distribution variations during a sand/dust weather process were also analyzed. The outcome of the study showed that under unstable stratification, the normalized variances of velocity (σu/u*, σv/u*, σw/u*) and temperature (σT/T*) at 47 and 120 m heights fit the Monin-Obukhov similarity (MOS) framework and the fitting formulas were given out accordingly. According to the stratification parameter (z′/L), the stable ULBL could be divided into 2 zones. With z′/L<0.1, it was a weakly stable zone and MOS framework was applicable. The other was a highly stable zone with z′/L>0.1 and the normalized velocity variances tended to increase along with higher stability, but it remained constant for normalized temperature variances. At daytime, the near-surface layer includes two heights of 47 and 120 m, while 280 m has been above it. The ULBL analysis in conjunction with a sand/dust weather process in Beijing in March 2001 indicated that the maximum concentration of Total Suspended Particulates (TSP) at 320 m reached 913.3 μg/m3 and the particles were transported from the upper to lower ULBL, which was apparently related to the development process of a low-level jet and its concomitant strong sinking motion.

2021年3月中国北方两次强沙尘天气污染特征

为探究沙尘天气发展规律和污染特征,以石家庄和济南为例,基于偏振-米散射激光雷达观测数据和城市颗粒物小时质量浓度等数据,分析2021年3月中国北方发生的两次强沙尘过程(3月15日与27日强沙尘过程,简称“3·15”过程与“3·27”过程)。结果表明:(1)两次过程沙尘入境时,两市PM10质量浓度快速上升,PM2.5与PM10质量浓度比迅速减小。(2)两次过程期间,两市PM10质量浓度符合正态分布,“3·15”过程石家庄和济南PM10质量浓度高斯拟合的决定系数分别为0.92和0.76,“3·27”过程分别为0.83和0.89。(3)沙尘爆发期,近地面消光系数和退偏比都明显增大。(4)因沙尘沉降和多沙尘源,沙尘传输过程中出现多层结构,可分为近地面沙尘层、低空沙尘层和高空沙尘层。近地面沙尘层出现时间和地面颗粒物质量浓度急剧上升时间基本一致。(5)离地面近且雷达数据质量可靠的195 m高度处,“3·15”过程(“3·27”过程)石家庄和济南退偏比最大分别为0.29、0.23(0.28、0.20),消光系数最大分别为3.94、3.84 km^(-1)(3.10、1.83 km^(-1))。表明沙尘在传输过程中强度变弱,大粒子不断减少。该高度退偏比开始快速上升时间比地面颗粒物质量浓度开始快速上升时间早约1 h。(6)根据沙尘天气污染特征可将其发展分为前期、爆发期、维持期和后期4个阶段,综合利用PM10质量浓度、PM2.5与PM10质量浓度比、消光系数和退偏比等能很好地识别沙尘的不同阶段。

河西走廊地区一次典型夏季沙尘过程分析

通过分析2020年甘肃省河西走廊地区夏季一次持续时间较长的沙尘天气,结合天气形势和颗粒物激光雷达监测数据,探究了沙尘过程中各城市空气质量的变化情况、污染成因及沙尘传输特征。结果表明:6月29日至7月3日,南疆盆地产生的沙尘在偏西风作用下输入河西地区,沙尘气团自西向东传输,造成河西五市PM 10小时浓度峰值达1000μg/m^(3)以上,空气质量指数(AQI)严重污染级别持续时间较长,雷达消光系数和退偏振比同步升高。

Analysis on the temporal-spatial distribution character and effect factors of PM10 in the hinterland of Taklimakan Desert and surrounding area

In recent years, the physical and chemical properties of dust aerosols from the dust source area in northem China have attracted increased attention. In this paper, Thermo RP 1400a was used for online continuous observation and study of the hinterland of Taldimakan, Tazhong, and surrounding areas of Kurnul and Hotan from 2004 to 2006. In combination with weather analysis during a sandstorm in the Tazhong area, basic characteristics and influencing factors of dust aerosol PMl0 have been summarized as below： （1） The occurrence days of floating dust and blowing dust appeared with an increasing trend in Kumul, Tazhong and Hotan, while the number of dust storm days did not significantly change. The frequency and intensity of dust weather were major factors affecting the concentration of dust aerosol PMI0 in the desert. （2） The mass concentration of PM10 had significant regional distribution characteris- tics, and the mass concentration at the eastern edge of Taklimakan, Kumul, was the lowest; second was the southern edge of the desert, Hotan; and the highest was in the hinterland of the desert, Tazhong. （3） High values of PM10 mass concentration in Kumul was from March to September each year; high values of PM^0 mass concentration in Tazhong and Hotan were distributed from March to August and the average concenlration changed from 500 to 1,000 gg/m3, respectively. （4） The average seasonal concentration changes of PM10 in Kumul, Tazhong and Hotan were： spring 〉 summer 〉 autumn 〉 winter; the highest average concentration of PMl0in Tazhong, was about 1,000 gg/m3 in spring and between 400 and 900 gg/m3 in summer, and the average concentration was lower in autumn and winter, basically between 200 and 400 gg/m3. （5） PMl0 concentration during the sandstorm season was just over two times the con- centration of the non-sandstorm season in Kumul, Tazhong and Hotan. The average concentrations of sandstorm season in Tazhong were 6.2 and 3.6 times the average concentrations of non-sandstorm season in 2004 and 2008, respectively. （6） The mass concentra- tion of PM10 had the following sequence during the dust weather： clear day 〈 floating dust 〈 floating and blowing dust 〈 sandstorm. The wind speed directly affects the concentration of PM10 in the atmosphere, the higher the wind speed, the higher the mass concen- tration. Temperature, relative humidity and bammelric pressure are important factors affecting the strength of storms, which could also indirectly affect the concentration change of PM~ 0 in the atmosphere.

合肥上空卷云和沙尘气溶胶退偏振比的激光雷达探测

研制了一台L30 0偏振激光雷达 ,用于卷云和沙尘气溶胶后向散射光退偏振比的探测研究。介绍了偏振激光雷达的探测原理 ,叙述了L30 0偏振激光雷达的结构、技术参数、测量方法和数据处理方法。初步的探测结果表明 ,合肥西郊上空高度在 1 0km左右的卷云的退偏振比在 0 4～ 0 5之间 ,沙尘气溶胶的退偏振比在 0 2～ 0 3范围内 ,但是剧烈沙尘暴的气溶胶的退偏振比可达到 0

北京春季强沙尘过程前后的激光雷达观测

利用激光雷达、PM2.5和地面气象要素等综合观测资料,分析了北京地区2012年3月30—31日的强沙尘过程前后的天气形势和PM2.5的污染特征,反演了雷达探测期间得到的消光系数,探讨了沙尘过程中气溶胶的时空分布特征及输送特征.结果表明:沙尘过境时,地面风速最大达到6 ms,沙尘沉降时ρ(PM2.5)增至289μgm3,相对湿度和能见度明显降低,大气低层逆温和近地面风速等气象条件对沙尘影响地面的时间和程度起到了重要作用;沙尘层雷达反演的气溶胶消光系数最大为0.96 km-1,偏振比最大为0.4,近地面消光系数变化与地面ρ(PM2.5)变化规律吻合较好,其探测可以精确反映不同天气形势下气溶胶的垂直结构和时空变化信息;高空输送至北京的沙尘以粗颗粒物为主,细粒子主要来源于本地及周边地区细粒子源;西北方向的内蒙及外蒙地区沙尘输送是导致此次北京强沙尘过程的主要原因.

石家庄一次沙尘气溶胶污染过程及光学特性

为掌握沙尘气溶胶远距离输送特征及其规律,对2015年4月15日影响石家庄空气质量的沙尘天气背景、污染特征进行了分析,利用HYSPLIT—4模式分析了沙尘气溶胶的后向轨迹,并利用微脉冲激光雷达和太阳光度计CE318监测资料分析了沙尘气溶胶的垂直分布和光学特性演变,与大风无沙尘沉降另一过程进行了对比,探讨了沙尘沉降对消光系数的影响,估算了沙尘沉降对地面PM10浓度的贡献.结果表明：来自蒙古国的沙尘气溶胶以西北路径远距离输送沉降是导致石家庄PM10浓度骤升的主要因素;沙尘沉降对消光系数和地面PM10浓度具有重要贡献;气溶胶快速沉降时间与冷锋过境、冷空气下沉相一致;微脉冲激光雷达监测到整个沙尘气溶胶输送沉降过程,沉降之前沙尘气溶胶主要分布在1500～3000m高空,气溶胶消光系数随高度上升而增大,输送飘浮空中到沉降持续时间较长,为沙尘污染预警提供了＂强信号＂特征;气溶胶光学厚度随沙尘到达明显上升,浑浊度较高,粒径偏大,地面能见度随气溶胶光学厚度呈幂指数递减.

利用激光雷达观测兰州沙尘气溶胶辐射特性

利用微脉冲激光雷达CE370-2与太阳光度计CE-318,在兰州观测分析了2007年3月27~29日扬沙过程沙尘气溶胶辐射特性,并利用HYSPLIT-4模式分析了沙尘过程气溶胶粒子的后向轨迹。分析表明,此沙尘过程气溶胶粒子的传输路径主要有两条:一条起源于青海西北经西宁抵兰州,另一条起源于塔克拉玛干沙漠经河西走廊抵兰州;沙尘气溶胶主要集中于离地1.5 km高度层内;沙尘气溶胶消光系数随高度先增加,到0.2 km左右高度达到最大,然后急剧减小。沙尘气溶胶光学厚度的时间演变呈双峰型,最高峰出现在28日12:00,次高峰在27日22:00。验证表明由CE370-2得到的气溶胶光学厚度与CE-318得到的很接近;雷达观测资料的处理方法可以较好地反演气溶胶消光系数和光学厚度。

激光雷达在沙尘观测中的应用——2004年春季北京和呼和浩特沙尘天气的解析

2004年春季（2003年12月至2004年5月）利用激光雷达在北京和呼和浩特对沙尘天气进行了连续观测。利用激光雷达的数据导出了沙尘和大气污染物气溶胶消光系数的关系，对两个地点的沙尘天气特征和大气污染特征进行了探讨。该期间在呼和浩特观测到较大型的沙尘事件（消光系数大于0．3·km^-1）有9次，这些起源于蒙古国/内蒙古的沙尘事件晚于呼和浩特6～10h在北京被观测到。在呼和浩特观测到的沙尘云块的高度普遍较低（由地表至高空1～2km），而在北京较高一般可达到2～4km，同一沙尘事件的最高浓度（消光系数）是呼和浩特高于北京。在北京观测到的沙尘天气共有17次，其中包括数次小规模的沙尘事件在呼和浩特未观测到。从北京及呼和浩特的观测结果可以看出，北京地区3～5月沙尘的背景浓度高于呼和浩特，北京地区具有明显的区域规模大气污染特征，而呼和浩特只具有局部规模的大气污染特征。

激光雷达对一次沙尘天气探测与分析

利用中韩合作沙尘暴监测项目的微脉冲激光雷达(MPL)观测了2005年4月28日影响大连的一次沙尘天气过程。MPL遥感发现影响大连的沙尘气溶胶层位于0～5km的高度,厚度达5km多。通过激光雷达对大气气溶胶探测与分析,得到了一些沙尘过程对流层气溶胶分布的典型结果,并分析和讨论了沙尘过程气溶胶消光系数的垂直分布和演变特征。基本分析表明,本次沙尘过程的外源性特征明显,并且大气层结对气溶胶(沙尘)的扩散、沉降起着重要作用。

激光雷达观测2005年春季北京沙尘天气

利用激光雷达对2005年春季北京地区沙尘天气进行了连续观测,表征了沙尘气溶胶的时空分布以及沙尘天气特征。2月至5月间北京共发生沙尘天气26次,其中强沙尘天气12次。并将激光雷达观测结果和GT-521光学粒子计数器的测定结果进行了对比。

利用紫外Mie散射激光雷达探测澳门地区沙尘暴事件

研制了一台工作波长为355nm的紫外高能Mie散射激光雷达,并利用该激光雷达在2010年一次沙尘暴事件期间对澳门上空的大气进行了探测,得到了澳门地区不同时刻的气溶胶消光系数垂直廓线。利用Fernald方法反演得到的气溶胶近地面消光系数随时间的变化与当地气象数据具有较好的一致性,气溶胶消光系数与当地可吸入颗粒物浓度的相关性达到了0.93。气溶胶垂直廓线显示,在沙尘暴来临期间存在明显的沙尘气溶胶凝集层。通过气溶胶轨迹倒推,分析了沙尘气溶胶的来源及路径。观测结果表明,该激光雷达可以在特殊天气条件下对澳门地区气溶胶进行有效探测,这将有助于深化对澳门上空气溶胶特性的研究。

北京风沙天气的气溶胶特征

利用常规气象观测资料、卫星云图以及 1 988、1 990、1 992、1 993、1 995、2 0 0 0年等年北京风沙天气期间所采集的气溶胶样品的分析结果 ,研究了北京的风沙天气分布特征 ,风沙期间大气污染状况 ,产生风沙天气的主要原因及沙尘的来源等。初步得出 :北京的风沙天气主要出现在春季 ,是造成春季大气污染的重要原因之一 ;北京春季风沙天气是由沙尘暴、浮尘和扬沙造成 ,但以扬尘引起的频率为最高 ,占 71 .4% ;风沙期间大气气溶胶与无风沙时气溶胶的物理化学特征有明显的差异 ;大气气溶胶的物理化学特征显示出 ,风沙期间的大气气溶胶主要来源于自然源 ,以局地尘源为主 。

银川上空大气气溶胶光学特性激光雷达探测研究

小型米散射激光雷达是广泛使用的探测大气气溶胶光学特性的有效工具。作者研制了一台小型米散射激光雷达,并利用该激光雷达于2009年4月1日至4月10日期间对宁夏银川地区(北纬38°29′,东经106°06′)上空的大气气溶胶光学特性以及时空分布进行了观测。系统选用532 nm波长激光作为光源,采用Fernald法对接收到的大气回波信号进行反演,得到了气溶胶消光系数的高度分布廓线及24 h内气溶胶消光系数相对浓度的时空变化特性;并对期间一次明显的沙尘天气进行了观测和分析。观测结果表明,该小型米散射激光雷达能够对大气气溶胶及其时空分布情况进行有效、连续的观测,其观测结果有利于分析该地区气溶胶及沙尘天气的变化趋势。

激光雷达观测北京大气气溶胶的垂直分布

利用激光雷达对北京2005年4月26—30日大气气溶胶进行了连续观测,对气溶胶光学特性进行了测量和分析,讨论了大气污染物气溶胶和沙尘气溶胶的垂直分布,以及沙尘气溶胶的传输和沉降过程。因此,激光雷达是研究阴霾天气和沙尘天气特征的有效手段。

塔克拉玛干沙漠腹地沙尘气溶胶质量浓度的观测研究

对塔克拉玛干沙漠腹地塔中地区进行了长达6a的试验观测研究,获得了该地区沙尘气溶胶的基本特征:塔中地区浮尘、扬沙出现日数呈上升趋势,而沙尘暴日数呈下降趋势,沙尘天气出现的频率和强度是影响沙漠地区沙尘气溶胶浓度的主要因素.可吸入颗粒物(PM10)月平均质量浓度峰值区分布在春夏两个季节,3～5月是主峰值区域,7～8月是次峰值区,春季PM10平均浓度在1000μg/m3左右变化,夏季在400～900μg/m3之间,秋冬两季浓度较低基本上在200～400μg/m3之间变化.每年的3～9月是总悬浮颗粒物(TSP)质量浓度较高的月份,4～5月是主峰值区,7～8月为次峰值区;2005年TSP质量浓度最低,年平均值为1105.0μg/m3,2009年略高于2008年,年平均浓度为1878.0μg/m3,2008年5月TSP平均质量浓度是全年最高值,浓度值达到7415.0μg/m3.沙尘天气过程中大气颗粒物浓度变化具有以下规律:晴天<浮尘天气<浮尘、扬沙天气<沙尘暴天气.风速大小直接影响大气中颗粒物浓度,风速越大颗粒物浓度越高.气温、相对湿度和气压是影响沙尘暴强度的重要因素,也间接影响大气中颗粒物浓度的变化.

中国春季北方大气气溶胶浓度特征

采用2008年和2009年春季10个气溶胶观测站资料,分析了我国北方3个代表区域的气溶胶浓度特征与空间分布特点以及气溶胶粒子粒径的异同,并结合一次典型的沙尘天气过程,利用气溶胶和气象资料,讨论了沙尘天气对ρ(TSP)的影响以及各观测站点ρ(TSP)的变化特点.结果表明:西北区域站点ρ(TSP)最高,达到0.488 mg/m3,其中以沙尘和土壤等粗模态粒子为主,占ρ(TSP)的50.7%;北部区域站点ρ(TSP)为0.350 mg/m3,主要由PM2.5及沙尘、土壤等粗模态粒子组成,它们分别占ρ(TSP)的55.7%和30.9%;北京地区ρ(TSP)最低,平均值为0.252 mg/m3,ρ(PM10)占ρ(TSP)比例较高,达到94.4%,其中ρ(PM2.5)占ρ(TSP)的54.7%;沙尘天气强度和发生次数对气溶胶浓度年际变化影响明显,而天气形势对沙尘天气的发生发挥重要作用.