On Eastern Asian Dust Storm

In this paper, the characteristics of eastern Asian dust storm are examined with emphasis on the satellite measurements of aerosol optical thickness. The reflectivity of solar radiation from the earth's atmosphere depends on the optical thickness. The satellite measurement of radiance of sunlight, scattered by the earth and its atmosphere, is used to derive the properties of aerosol on oceanic surfaces. This paper involves the following: (1) investigation of the measurement of dust storm over the oceanic surface by GMS satellite; (2) investigation of the measurement of dust storm over the land surface by ground-based instruments such as actinometer, lidar, etc.; (3) for comparison, deriving an atmospheric aerosol size distribution over the oceanic surface of calm weather through measurements of NOAA satellite; and (4) the weather process and its mass load of eastern Asian dust storm.

Effect of Asian Dust Storms on the Ambient SO₂Concentration over North-East India: A Case Study

Ambient SO2 concentration at a high rain fall site, Shillong (25.67oN, 91.91oE, 1064 m ASL), located in North-East India, was measured during March 2009 and January 2010 with the aim to understand the effect of long range transport of pollutants from North-East Asia on the ambient SO2 levels at this relatively clean site. The concentrations recorded during the former sampling period were very high (Max: 262.3 ppb)—which decayed down gradually towards the end the sampling period—whereas those during the latter sampling period were well within the acceptable limits (Max: 29.7 ppb). This elevated SO2 concentrations during March 2009 is proposed to have association with a major cold air outbreak and an associated cyclone preceding one of the dust storm events reported in China, and a resultant sudden change in wind trajectory leading to the long range transport of pollutants to the sampling site. The argument is formulated on the basis of the back trajectory analysis performed using HYSPLIT for the month of March 2009—the plots clearly showed a drastic change in wind trajectories between 8th and 15th of March 2009 wherein the winds traveled over some of the highly polluted regions such as the Perm region of Russia—and on the results from model runs performed using the global 3-D model of tropospheric chemistry, GEOS-Chem (v8-03-01)—it clearly showed the tropospheric SO2 over Perm region in Russia peaking during Nov, Dec, Jan, Feb and Mar every year, possibly due to central heating. The observation of long range transport of SO2 from the highly industrialized areas of Perm in Russia to North-East India during dust storm events has important implications to the present understanding on its relative contribution to the Asian pollutant outflow to the Pacific during spring as the GEOS-Chem model runs also showed regions in and around Russia with relatively high concentrations of atmospheric NOx, Peroxyacetyl Nitrate, Lumped Peroxypropionyl Nitrate, HNO3, HNO4,C3H8, C2H6, SO4, NH4, Inorganic Sulphur Nitrates and Lumped Alkyl Nitrate.

Mineralogy and Possible Sources of Dust Particles During One Asian Dust Episode

A severe Asian Dust Storm(ADS)event occurred on April 16-17th,2006 in northem China.Mineral components of dust samples were analyzed using X-ray diffraction(XRD).The result indicates that dust particles were dominated by quartz(37.4%)and clay (32.9%),followed by plagioclase(13.7%),with small amounts of calcite,K-feldspar,dolomite,homblende, and gypsum(all【10%).The clay fractions with diameter less than 2μm were separated from the

The Mineralogy and Possible Sources of Spring Dust Particles over Beijing

A severe Asian Dust Storm （ADS） event occurred on 16-17 April 2006 in northern China. The mineral compositions of dust samples were analyzed using X-ray diffraction （XRD）. The results indicated that dust particles of the ＂17 April 2006＂ dust storm were dominated by quartz （37.4%） and clay （32.9%）, followed by plagioclase （13.7%）, with small amounts of calcite, K-feldspar, dolomite, hornblende and gypsum （all less than 10%）. The clay fractions with diameter less than 2 μm were separated from the dust storm particles by centrifuging and were further analyzed by XRD. The results revealed that the clay species were mainly illite/smectite mixed layers （I/S） （49%） and illite （34%）, with small amount of kaolinite （8%） and chlorite （9%）. In order to evaluate the feasibility of using the mineralogy to trace the sources of dust particles, the XRD results of the ＂17 April 2006＂ dustfall particles were compared with the dust particles over past years. The results confirmed that the finer dust particles represented by the ADS PM10 displayed a smaller quartz/clay ratio than the dustfall particles. The dust storm particles, either from the ADS PM10 or from the ＂17 April 2006＂ dustfall, showed a lower level of dolomite contents and lower dolomite/clay ratios compared with the non-dust storm dustfall particles. This implies that dolomite could be used to distinguish between the dust contributions from local and non-local sources. Similar trends were found for the gypsum and the gypsum/clay ratio. Moreover, the two dustfall samples had a lower level of illite/smectite mixed layers and a higher level of illite than airborne PM10, implying that the dustfall particles tend to be enriched with illite in its clay fraction.

Element and mineral characterization of dust emission from the saline land at Songnen Plain, Northeastern China

Recent observations of Asian dust storms show an eastern expansion of the source area to degraded lands, where dust emissions have been little studied. The dust concentrations over the saline land of the western Songnen Plain （SSL）, Northeastern China, are circumstantially higher than those from the northwestern Chinese deserts. These concentrations are sensitive to the surface soil conditions and wind velocity on the ground. The dust samples collected during dust storm events on the SSL contain abundant Na, Mg, A1, K, Ca, Fe and Ti, as well as toxic elements such as Cu, V, Zn and Ba. Individual particle analysis reveals that fine saline particles （〈 10 μm in diameter） on the saline land, consisting largely of carbonate, halite and sulfate together with lithogenic minerals such as SiO2 and aluminosilicate, are eventually uplifted during the interval from spring to autuum. The predominantly fine saline particles uplifted from the SSL are likely transported eastward by the winter monsoon circulation and westerlies. Recent degradation of saline lands in Northeastern China would not only increase the frequency of dust storm events in the downwind area, but also might change the chemical composition of the Asian dust emissions.

Mineralogical characteristics of airborne particles collected in Beijing during a severe Asian dust storm period in spring 2002

Asian dust storm (ADS) samples were collected on March 20,2002 in Beijing,China. High-resolution field emission scanning electron microscopy with energy dispersive X-ray detector (FESEM-EDX) and X-ray diffraction (XRD) were used to study the morphology,chemical compositions,number-size dis-tributions and mineralogical compositions of ADS particles. The mineral particles were major compo-nents in the ADS samples,accounting for 94% by number. The XRD analysis indicated that the dust particles were dominated by clay (40.3%),and quartz (19.5%),followed by plagioclase (8.4%),calcite (7.5%),K-feldspar (1.5%),hematite (0.9%),pyrite (0.9%),hornblende (0.4%) and gypsum (0.3%),with a certain amount of noncrystalline materials (20.3%). Clay minerals were mainly illite/smectite mixed lay-ers (78%),followed by illite (9%),kaolinite (6%),and chlorite (7%). In addition to these main minerals,FESEM-EDX also detected some trace minerals,such as dolomite,pyrite,thenardite,as well as heavy minerals represented by rutile,ilmenite and apatite. The mineralogical compositions of the 2002-03-20 Asian dust storm and the Saharan dust plumes were similar but the clay mineralogy showed a great distinction,with the illite/smectite mixed layers being common in the Asian dust storm but illite being common in the Saharan dust plumes.

内陆输送过程中沙尘单颗粒类型及其非均相反应

采用单颗粒分析方法对2004年2～3月发生在北京的3次沙尘暴的样品中沙尘颗粒物的化学成分进行了测定.3次沙尘暴的反向轨迹图显示,它们主要来自于中国北部、西北部和蒙古的戈壁沙漠地区,且这些沙尘颗粒主要通过高空长距离输送到下游区域.使用带能谱的扫描电镜对481个沙尘颗粒进行分析,并根据成分特征,把这些沙尘颗粒划分为8种类型,主要类型有“富Si”、“富Ca”、“富S”、“富Fe”.将北京样品分析结果与呼和浩特、塔克拉玛干和敦煌的结果进行对比,结果显示,长距离输送的沙尘颗粒表面发生了SO2的非均相化学反应,导致部分颗粒局部的表面发生化学修改作用,且“富Ca”的碱性矿物为非均相化学反应提供了更有利的反应界面.

青藏高原北部可可西里地区近4000年来尘暴事件初探——来自库赛湖沉积物粒度的证据

通过分析库赛湖近4000年来湖相沉积物粒度组成特征,对比人工俘获风成物粒度特征,表明库赛湖沉积物中粗颗粒组分(>64μm)主要由风力搬运作用进入湖泊沉积,记录了该地区尘暴事件历史。重建的尘暴事件序列表明:2500～800cal aBP时段为该地区近4000年来尘暴事件高频发生的阶段,4000～2500cal aBP和800cal aBP以来的时段尘暴事件发生频率较低;近千年来的尘暴事件主要发生于小冰期内的3次降温时段。与贵州董歌洞石笋氧同位素对比分析表明,库赛湖地区近4000年来气候变化受亚洲季风的影响,尘暴事件多发生于夏季风较弱的气候干冷时段。

碳酸盐碳测定在沙尘暴来源地识别中的应用

根据中国大气颗粒物特点 ,在国内沙尘暴研究中首次尝试利用碳酸盐碳进行沙尘暴来源地识别。测定了一系列黄沙、大气颗粒物和沙尘暴源区土壤样品。初步了解了上述样品中碳酸盐碳含量情况 。

利用Terra和Aqua双星MODIS数据协同研究沙尘暴

利用2005-04-28上午星Terra和下午星Aqua白天和晚上共4景MODIS数据对影响华北地区的一次沙尘暴进行了研究。对于白天的MODIS数据,利用热红外亮度温度差值法结合可见光近红外波段反射率阈值法,可以很好地把沙尘与背景地物和云分离开来;对于夜晚的MODIS数据,利用热红外亮度温度差值法也能较好地提取沙尘信息。研究表明,MODIS数据在沙尘暴等灾害研究方面具有很大的潜力。

中国的人为沙漠化因素对亚洲沙尘暴的贡献

以数值模拟与大规模网络观测的对比结果为基础，通过对“去除”已经沙化土地获得的近地面层粉尘浓度的进一步分析，结合已获得的亚洲沙尘暴各源区粉尘释放量结果，提出我国的人为沙漠化因素对亚洲沙尘暴的贡献约为6％的观点。

Analysis on the decadal scale variation of the dust storm in North China

In this paper, the temporal variation characteristics of the dust storm in North China are investigated. Based on power spectrum analysis and wavelet analysis, 1956-1970 and 1985-1999 are chosen as the high-frequency and low-frequency dust storm decades respectively. Analysis results clearly show that the spring and wintertime anomalous atmospheric circulation between these two dec-ades are significantly different. Compared with the former decade, there are a strengthened polar vortex, enhanced westerlies near 50°N, and a weak East Asian major though in the winter of the latter decade. The north and center parts of the Siberian high and the Aleutian low become weak. The southerly and easterly wind anomalies appear over the north and east parts of China, which implies the weakening of East Asian winter monsoon. Meanwhile, northern China experiences warmer winters and wetter springs, which are in favor of the weakening of dust storm intensity in North China. There are significant out-of-phase relationships between dust frequency and wintertime westerly intensity, as well as between dust frequency and Arctic Oscillation. It is also found that the frequency of dust weather is strongly re-lated to winter-springtime East Asian monsoon intensity.

Geochemical studies on the source region of Asian dust

The North China and the neighbouring Mongolia in Asian Interior is characterized by extremely dry climate, resulted in one of the world's major dust emission centres. Deciphering the source region of Asian dust is critical for revealing the mechanism of the dust production, interpreting the paleo-environmental records of eolian deposits, predicting the overall environmental effects of dust, and setting the strategies for the control of contemporary dust storms. This paper summarizes the geochemical methods applied to the source tracing of Asian dust. Nd-Sr isotopes were the most extensively studied source tracer of Asian dust and have been successfully applied in many cases. Geochemistry of detrital monomineral shows great theoretical advantages in source tracing and deserves further studies. The short-range transportation of Chinese loess with direction similar to that of the prevailing near surface wind is revealed. Source tracing also shows that the Asian dust has two ultimate material sources from the northern margin of the Tibetan Plateau and the Central Asian Orogen, which confirms the importance of mountain processes in the production of silt eolian particles. Based on the recent progresses on the source tracing of Asian dust, discussions are expanded on the natural background of Asian dust storms and potential anthropogenic influence, the materials evolution of the source regions of Asian dust and its relationships with climate changes and Tibetan uplift, and the role of Tibetan uplift in the Asian dust system.

Climatology of yellow sand (Asian sand, Asian dust or Kosa) in East Asia

In order to study climatology of yellow sand (Asian sand, Asian dust or Kosa) in EastAsia, secular fluctuation in China, Korea and Japan in the recent 30 years was presented. Thenumber of days with sand-dust storm at five stations in China-Hotan, Zhangye, Minqin, Jurhand Beijing, decreases a lot at the former three stations, but changed little at the latter two stations.Suggesting that the recent global warming is more evident in Xinjiang and Gansu, where the fre-quency of cold air invasions from the higher latitudes is decreasing. But, the eastern parts ofMongolia, inner Mongolia, and North China encounter stronger cyclones in early spring as a resultof global warming. These cyclones bring cold air from higher latitudes, causing severe duststorms. Secular variation in the annual days with sand-dust storms in China and Kosa days in Ko-rea and Japan show a parallel change with higher frequency from 1975 to 1985. This may be re-lated to the higher frequency of La Nina years. However, different tendency was shown in theperiod from 1986 to 1996. Since 1996 or 1997, a sharp increase is clear, which may be caused bythe developed cyclones in East Asia as well as human activities, and stronger land degradationunder La Nina conditions. Anomalies of the total number of stations with Kosa days were dis-cussed in accordance with some synoptic meteorological conditions such as the differences be-tween Siberian anticyclone and Aleutian cyclone center at 500 hPa level during the previous winter.

Compound-specific carbon isotope compositions of individual long-chain n-alkanes in severe Asian dust episodes in the North China coast in 2002

The molecular compositions and com- pound-specific carbon isotope compositions of indi- vidual long-chain n-alkanes of atmospheric aerosols collected during two severe Asian dust episodes in Qingdao in spring of 2002 were analyzed using gas chromatography/mass spectrometry (GC/MS) and gas chromatography/isotope ratio mass spectrometry (GC/IRMS). Typical plant wax n-alkanes (C29 and C31) had lower δ 13C values than those from anthropo- genic (engine exhaust) sources (C21―C23). The av- erage δ 13C value of plant wax n-alkane C29 in non-dust episode periods was -30.5‰ (?30.3‰― ?31.9‰), while -31.3‰ (?31.1‰―?31.5‰) in dust episode periods; for C31, it was ?31.4‰ (?31.1‰― ?33.0‰) in non-dust episode periods, and ?31.7‰ (?31.3‰―?32.6‰) in dust episode periods. Plant wax in the dust episode samples was mainly from herbaceous plants via long-range transport, while local plant wax was mainly from deciduous plants and woody plants. In North China coast, 83.3% of the plant wax in the severe dust episode samples was from C3 plants while 80.0% for the non-dust samples, indicating that plant wax transported to the north- western Pacific Ocean by airborne dust from East Asia was mainly from C3 plants. The results suggestthat the molecular and molecular-isotopic composi- tions of individual long-chain n-alkanes can, as an effective indicator, identify the terrestrial organic components in the dust from East Asia and sedi- ments in the northwest Pacific Ocean.

RELATIONSHIPS BETWEEN DUST STORMS AND DRYNESS-WETNESS IN MIDDLE–EASTERN CHINA DURING 1470–1950

Based on 481-year records of historical dust storm （DS） and Dryness-Wetness Index （DWI） at 120 sites, spatial distribution characteristics of dryness-wetness （DW） in typical dust storm years （DS years） and in non-dust storm years （non-DS years） were derived for continental China. In DS years, most of the sites were drier than in normal years while in non-DS years wetter than normal, and the variation of DWI in DS years was larger than that in non-DS years. The relative instability and increased regional difference of atmospheric circulation in DS years might have induced more frequent DS events and dry-wet abnormality in continental China. In DS years the latitudinal （north-south） dry-wet difference was larger than that in non-DS years, that is, north China was even much drier than south China. This might be attributed to increased latitudinal differences of thermal and pressure gradients in DS years, resulting in the southward withdrawal of precipitation and increase of DS events.

U-Pb ages of zircon grains reveal a proximal dust source of the Xiashu loess, Lower Yangtze River region, China

Deciphering the eolian sources is critical to understand the paleo-significance of the Quaternary eolian deposits(the Xiashu loess)in the lower reaches of the Yangtze River.Both a local source from the fluvial sediments of the Yangtze River and a distal source from the northern deserts similar to that of the loess on the Chinese Loess Plateau(CLP)have been proposed.Recent researches show great advantages of detrital zircon ages as a source tracer for Asian dust based on the laser ablation U-Pb isotopic dating technique.This work presents the U-Pb ages of zircon grains extracted from the Xiashu loess.The results indicate that the Xiashu loess has a very different age distribution of zircon grains from that of the loess on the CLP as well as the materials in the arid lands of the Asian Interior.Instead,the zircon ages of the Xiashu loess are indistinguishable from the fluvial sediments of the Yangtze River,indicating the dominance of proximal dust source.Proximal source of the Xiashu loess implies that extensive eolian processes might have existed in the currently wet South China,possibly in response to the full glacial conditions after the middle Pleistocene transition of global climate.

沙尘暴粒子的非球形模型及其对激光的多次散射特性研究

计算沙尘暴对电磁波的衰减特性,以及利用卫星反射率遥感反演沙尘暴的光学厚度时,通常假设沙尘粒子为球形,但实验室和现场测量结果都表明,自然界中的沙尘粒子为非球形,因此利用球形粒子模型模拟沙尘暴对激光的散射和衰减特性将带来较大误差。利用具有一定尺寸分布、形状分布、随机取向的椭球粒子模型模拟自然界中的沙尘粒子,利用T矩阵方法计算了其单次散射特性,并与球形粒子模型进行了比较,结果表明,混合椭球粒子的相函数随角度分布是平滑的、无特征的、且在侧散射方向上是平坦的,这和自然界中的沙尘粒子散射特性非常类似。最后利用累加法计算了沙尘暴对激光的多次散射特性,结果表明,利用任何一种单一形状的粒子模拟沙尘粒子的散射特性都会带来较大的误差。

中国北方全新世沙尘暴演化:从自然驱动转向人为驱动

亚洲强沙尘暴事件能显著地降低空气质量,改变到达地面的太阳辐射,对人体健康产生严重的潜在危害,受到国内外的广泛关注.然而,目前对于全新世不同时间尺度亚洲沙尘暴的驱动机制以及是否存在由自然驱动向人为驱动的转变仍不清楚.黄土高原是世界上最大的粉尘堆积区,该区域未受人类活动直接影响的湖泊沉积是研究沙尘暴变化的理想载体.基于黄土高原上的高山湖泊岩芯,我们发现全新世沙尘暴频率总体呈增加趋势,并在过去2000年达到最高值且伴随着剧烈波动.其中,11~2 cal ka BP沙尘暴频率与东亚夏季风降水、植被覆盖、东亚冬季风强度均呈负相关,揭示出不同于冬季风控制沙尘暴变化的观点,认为东亚夏季风是控制千年尺度沙尘暴变化的自然驱动因子.从~2 cal ka BP开始,沙尘暴频率与粉尘源区人口数量、季风降雨量同步变化,人类活动的增强使得在强夏季风阶段却出现强沙尘暴现象,揭示出年代际尺度人类活动对地表系统的影响已超过夏季风的影响.沙尘暴由自然驱动向人为驱动的转变,支持中国北方"早期人为假说",可能至少开始于~2 cal ka BP.

Preface

Deciphering the eolian sources is critical to understand the paleo-significance of the Quaternary eolian deposits(the Xiashu loess)in the lower reaches of the Yangtze River.Both a local source from the fluvial sediments of the Yangtze River and a distal source from the northern deserts similar to that of the loess on the Chinese Loess Plateau(CLP)have been proposed.Recent researches show great advantages of detrital zircon ages as a source tracer for Asian dust based on the laser ablation U-Pb isotopic dating technique.This work presents the U-Pb ages of zircon grains extracted from the Xiashu loess.The results indicate that the Xiashu loess has a very different age distribution of zircon grains from that of the loess on the CLP as well as the materials in the arid lands of the Asian Interior.Instead,the zircon ages of the Xiashu loess are indistinguishable from the fluvial sediments of the Yangtze River,indicating the dominance of proximal dust source.Proximal source of the Xiashu loess implies that extensive eolian processes might have existed in the currently wet South China,possibly in response to the full glacial conditions after the middle Pleistocene transition of global climate.