近沙尘源区气溶胶光学特性的季节变化及其统计学描述

利用天空辐射计测定了敦煌地区1999年1月至2001年3月期间太阳直接辐射和散射辐射,采用“SKYRAD”反演模式同时反演了敦煌地区气溶胶光学厚度、体积尺度分布和折射指数实部,分析了其季节变化及统计学特性。结果表明,光学厚度存在明显季节变化,大致从12月开始存在明显的上升,3月或4月达到最大值,5—8月光学厚度逐渐减小,9—10月又有所上升,11月达到最小值,而波长指数的变化与光学厚度的变化基本相反;敦煌地区气溶胶光学厚度和波长指数的概率分布与其季节变化具有很好的相关性,并近似满足对数正态分布和正态分布;4个季节的气溶胶波长指数与光学厚度表现出一种相似的关系,并可以简单地利用一个指数函数加以描述;气溶胶尺度分布表现出双峰型结构,一种是位于半径0.25 μm附近的积聚态,另一种是半径7.7 μm左右的粗模态,且春季积聚态与粗模态之间存在着一个假模态;折射指数实部春季明显升高,对波长的敏感性较低,且4个季节的概率分布最大值均处在1.54～1.56范围内;两种情况下对实部值的概率分布进行拟合,发现其概率分布同样可以利用高斯模型加以描述,但是两种情况下春季与其他季节明显不同。     

沙尘天气中气溶胶光学特性的时空分布特征

选取内蒙古境内额济纳旗、乌拉特中旗、东胜、朱日和、锡林浩特5个站的几次沙尘天气过程和晴朗天气下CE-318太阳光度计资料,计算出大气气溶胶光学厚度,结合气象资料分析在沙尘天气发生过程中气溶胶光学厚度的时空分布特征。分析结果显示,在沙尘天气发生过程中,气溶胶光学厚度是一个相当敏感的变量,其随沙尘的发生、发展和消亡表现出明显不同的日变化特征,且光学厚度值随着沙尘天气的发生和发展,在其空间分布变化上与沙尘天气本身的空间分布变化具有很好的一致性,可以很好的反映沙尘输送过程。此外气溶胶光学厚度与大气稳定度也有一致的日变化趋势。因此,对于大气气溶胶光学厚度的监测可以为沙尘天气的预报提供较为准确的客观依据。     

沙尘源区与下游地区沙尘期间气溶胶光学特性分析

为了解沙尘传输过程中气溶胶粒子光学性质的变化,利用2001-2008年中国北方4个站点沙尘期间的数据资料,比较分析了沙尘源区与下游地区气溶胶光学特性的差异。结果表明,沙尘期间大量粗粒子对总消光具有强烈贡献,沙尘源区和下游地区粗粒子消光分别占总消光的85.2%和65.8%。沙尘期间沙尘源区与下游地区均表现出较高的气溶胶光学厚度;而源区的Angstrom波长指数明显低于下游地区,当沙尘暴出现时会下降到零甚至负值。沙尘源区与下游区气溶胶体积尺度谱以粗模态峰为主模态峰。在波长440~1 020 nm时,气溶胶单次散射反照率随波长增大而增大,源区与下游地区的单次散射反照率分别达到0.95和0.92。沙尘源区气溶胶的不对称因子大于下游地区,4个波段的平均不对称因子分别为0.73和0.70。     

气溶胶光学厚度的分布特征及其与沙尘天气的关系

 利用MODIS卫星遥感光学厚度资料，分析了中国大气气溶胶光学厚度的时空分布特征，并与同期沙尘天气进行了对比和相关分析，结果表明：①中国主要内陆地区的气溶胶光学厚度(Aerosol Optical Thickness，简称AOT)分布有4个高值区：①分别位于南疆盆地和青海\,甘肃、内蒙古中西部地区、四川盆地和长江黄河下游地区。②春季北方特别是西北的AOT值明显高于南方，冬季南北AOT值差别不大。③南疆盆地和内蒙古中东部地区AOT值随季节变化明显，而四川盆地、长江黄河下游地区AOT值没有明显的季节变化。④南疆盆地、青海、内蒙古等地区沙尘天气过程与AOT值同步变化。⑤在沙尘天气的多发区，气溶胶光学厚度与沙尘天气有较好的相关性；沙尘天气的少发区，气溶胶光学厚度与沙尘天气基本不相关。因此可以推断，中国北方，特别是干旱荒漠区，大气气溶胶主要来自沙尘天气过程引起的地面沙尘释放。     

半干旱区气溶胶散射特性研究

利用2005年1月至9月锡林浩特观象台积分浊度计的观测资料,结合同期的PM10质量浓度、能见度以及常规气象资料,分析了半干旱地区气溶胶的散射系数变化特征,讨论了它的季节变化、日变化、不同沙尘天气下气溶胶散射系数的变化情况,以及散射系数与PM10质量浓度、能见度的关系。结果表明1月至9月散射系数总体呈先下降再升高的趋势,日变化呈明显的双峰型;散射系数能很好的反映沙尘天气的强度;它与PM10质量浓度变化规律基本一致,两者之间具有很好的相关性;散射系数与能见度呈指数相关关系。     

中国西北干旱半干旱区气溶胶分类及特征

基于2013—2015年CALIPSO星载激光雷达的Level 2数据集资料,对中国西北干旱半干旱区的气溶胶进行了分类研究,并对不同种类气溶胶在不同光学厚度下的年均发生频率做以分析。结果表明：沙尘气溶胶整体随气溶胶光学厚度值增大呈下降趋势;而污染沙尘型气溶胶在6类型气溶胶出现频率最高;大陆污染型气溶胶频率集中在[0.1,0.35],随气溶胶光学厚度值的增大频率呈升高趋势;烟尘型气溶胶频率集中在[0.2,0.4],在不同气溶胶光学厚度值情况下,频率较大陆污染型气溶胶高,随气溶胶光学厚度值的增大频率呈上升趋势;从四季来看,秋季和冬季当气溶胶光学厚度值大于0.1时,大陆污染型气溶胶频率明显高于沙尘气溶胶。春季,河西地区的气溶胶光学厚度高于其他三季,而在研究区域的南部和东南部,秋、冬季的气溶胶光学厚度值高于春、夏季。气溶胶光学厚度秋季 > 春季 > 夏季 > 冬季。     

半干旱区冬春季黑碳气溶胶吸收特性的观测研究

利用2006年4月和12月锡林浩特观象台黑碳灰度仪的观测资料,分析了半干旱地区黑碳气溶胶浓度的变化特征,讨论了引起这些变化特征的影响因子。结果表明,黑碳气溶胶浓度冬季远大于春季,日变化呈明显的双峰型;讨论了风速对黑碳气溶胶浓度不同影响的范围,可知风速在较小的情况下（小于3.5 m·s-1）,黑碳气溶胶浓度值随风速的增大而减小;在3.5~4.5 m·s-1之间,风速增大,黑碳气溶胶浓度值也增大;风速较大（大于4.5 m·s-1）后,黑碳气溶胶浓度与风速之间没有明显的相关性。冬季12月由于黑碳气溶胶吸收作用造成的消光占总气溶胶消光的25%。     

河西走廊干旱区春季沙尘气溶胶对辐射的影响初步研究

利用2008年春季中美沙尘暴联合观测实验中张掖站晴朗少云天正午的地表辐射和太阳光度计资料,计算分析了沙尘气溶胶对太阳辐射和大气逆辐射的影响,结果表明：沙尘对太阳总辐射有一定程度的削弱作用,经估算,大气浑浊度每增加0.1,太阳总辐射平均减少约10.45 W·m^-2;当大气浑浊度一定时,沙尘粒子越小,对太阳总辐射的削弱效率就越高;大气浑浊度小于0.3时,大气逆辐射有随大气浑浊度的增加而增加的趋势,大气浑浊度大于0.3时,大气逆辐射随大气浑浊度增加有减小的趋势。     

南极长城站云和气溶胶光学特性的遥感和分析

本文根据光度计和半球辐射计观测的资料、分析了1988年12月至1989年2月南极长城站云和气溶胶光学厚度以及气溶胶的谱分布。结果表明,在长城站夏季,云和气溶胶的光学厚度都较大,其均值分别为12.7和0.094。     

Seasonal variation in dust events and the causes of the variation in the Tarim Basin, China

We analyzed dust event occurrence and its seasonal distribution at 16 sites in the Tarim Basin,China.Although the overall frequency of dust events was the highest in spring in this region,its variation in other seasons could be classified into three patterns:(1) frequency of dust events in autumn > that in summer > that in winter(at the Kashi and Kuche sites);(2) frequency in summer > that in winter > that in autumn(at the Ruoqiang site);and(3) frequency in summer > that in autumn > that in winter(at all other areas of the Tarim Basin).The frequency of dust events and their seasonal variations in the Tarim Basin were mainly controlled by wind speed and locally available dust sources;the former was the key control when dust sources did not differ significantly.The seasonal variation in evaporation had a smaller,but still significant effect on the frequency of dust events.     

Seasonal variation of sedimentation in the Changjiang Estuary mud area

Seasonal distributions of suspended matter and their sedimentary effect on the Changjiang Estuary mud area of the East China Sea were discussed, based on three cruise data of total suspended matter, temperature and salinity collected from the Changjiang Estuary and its adjacent area in summer and winter. The results show that the basic pattern of distributions of suspended matter in the study area is almost the same in winter and in summer. Sediments from Changjiang (Yangtze River) to the sea are chiefly trapped to the west of 123o15'E due to a strong obstruction of the Taiwan Warm Current. This suggests that these sediments are mainly transported and deposited in the inner shelf. The sediment supply, Taiwan Warm Current, and Zhejiang Coastal Current show a strong seasonal variation, which results in a strong seasonal variation of the sedimentary effect on this mud area. This mud area is a "sink" of the Changjiang's sediment discharge to the sea and its sedimentation is stronger in summer and weaker in winter.     

长江口泥质区的季节性沉积效应

1IntroductionThe continental shelf of the East China Sea (ECS) is one of the widest shelves in the world. There are several mud areas distributing like patches on a background of widespread coarser ambient sediments of silt and sand on the continental shelf of the ECS. The coastal mud area can be divided into two parts, namely, the Changjiang Estuary mud area (CEMA) in the north and Zhejiang coastal mud area in the south. Between these two parts there is a silt area (Figure 1). The CE…     

The impacts of urbanization on soil erosion in the Loess Plateau region

1 IntroductionThe Loess Plateau region covers an area of 62.4(104 km2 and lies in the center of northern China. Urbanization and economic development have been quickened in recent decades. Both the number of towns established and scale of cities have increased. Although the pace of urbanization has been accelerated, the eco-environmental control in urban areas still lags behind relatively. Moreover, the construction and development of cities damaged the already vulnerable eco-environment to …     

The impacts of urbanization on soil erosion in the Loess Plateau region

The accelerated urbanization has resulted in new soil erosion in the Loess Plateau region since the 1980s. A concept of urban erosion and its impacts on environment are discussed. The experimental studies and field investigations show that those loose silt and earth piles formed by urban construction can be eroded seriously: Under stormy rain, the amount of sediment from steep man-dumped slope is 10.8–12.2 times that of from uncovered slope land; the result of experiments with the wind tunnel also shows that the damage to the surface structure of dry loess can cause serious soil erosion by wind in some cities of the region. Even if in the urban built-up area, there are many loose sandy soil, mud and silt, which are washed into rivers by city’s ground flow in the rainy season. So, anthropogenically induced soil erosion has made soil erosion more serious around the urban areas. And the urban eroded environment has several characteristics such as fragility, complexity, seasonality and quick variability. Urban areas witness a quick economic growth and have more construction projects than rural areas, which brings more intensive changes of environments during a short period of time or adds some new elements to the erosion system. Therefore erosion has experienced more intensive impact by human activities. So, the possible impact of urbanization on erosion environment must be taken into consideration when designing or planning to exploit natural resources or to develop urban areas in the Loess Plateau.     

The impacts of urbanization on soil erosion in the Loess Plateau region

The accelerated urbanization has resulted in new soil erosion in the Loess Plateau region since the 1980s. A concept of urban erosion and its impacts on environment are discussed. The experimental studies and field investigations show that those loose silt and earth piles formed by urban construction can be eroded seriously: Under stormy rain, the amount of sediment from steep man-dumped slope is 10.8-12.2 times that of from uncovered slope land; the result of experiments with the wind tunnel also shows that the damage to the surface structure of dry loess can cause serious soil erosion by wind in some cities of the region. Even if in the urban built-up area, there are many loose sandy soil, mud and silt, which are washed into rivers by city’s ground flow in the rainy season. So, anthropogenically induced soil erosion has made soil erosion more serious around the urban areas. And the urban eroded environment has several characteristics such as fragility, complexity, seasonality and quick variability. Urban areas witness a quick economic growth and have more construction projects than rural areas, which brings more intensive changes of environments during a short period of time or adds some new elements to the erosion system. Therefore erosion has experienced more intensive impact by human activities. So, the possible impact of urbanization on erosion environment must be taken into consideration when designing or planning to exploit natural resources or to develop urban areas in the Loess Plateau.     

准噶尔盆地梭梭群落地上生物量及季节变化研究——以克拉玛依农业综合开发区为例

根据样地调查资料,对位于准噶尔盆地的克拉玛依农业开发区外围荒漠植被的生物量及季节变化进行了研究。通过对梭梭自然群落地上生物量的研究表明,梭梭群落在一年的生长周期内没有明显的生长变化,只有两个生长高峰分别在6月下旬和8月下旬出现,但是绿色同化速率快。梭梭地上生物量中,多年生枝条比例最多占地上生物量的60%,当年生绿色同化枝生物量较少,一般占30%以下。5月份梭梭当年生绿色同化枝生长比较缓慢,地上生物量42 052．197g/m~2；7～8月份达到高峰76 457．18～92 922．598g/m~2,这是梭梭当年生绿色同化枝生长最旺盛、最有活力的时期；进入9月份随光合作用的下降生物量也下降至86 794．669g/m~2；10月份生物量迅速下降11月接近零,准备冬眠,脱落大部分枝条被并入非同化系统。梭梭群落地上生物量增长规律符合Logistic增长模型；其地上现存量季节动态呈二次抛物线方程y=a bx cx~2形式；梭梭绿色同化系统(AS)和非同化系统(UAS)的现存量集中分布于地面8～60cm和20～90cm的范围内,属典型的中繁型群落。梭梭群落的生物量及其季节变化与梭梭当年生绿色同化枝的萌发、生长、脱落有密切的关系。     

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.     

乌鲁木市PM2.5浓度与MODIS气溶胶光学厚度相关性分析

选择西北干旱区城市乌鲁木齐市为研究区,利用MODIS气溶胶产品（AOD）数据和地面监测站PM_2.5浓度数据进行相关性分析,结果表明：二者相关性良好,对AOD数据进行垂直订正和湿度订正后,发现相关性进一步提升（0.49～0.80,p<0.01）。对订正后AOD数据与地面PM_2.5浓度进行建模并选取最优模型,结果均为一元三次模型且模型R²在0.27～0.69之间,其中春秋两季模型R²较高,夏季较低。对模型精度进行验证结果,显示春季与秋季模型精度良好,夏季较差,说明MODIS气溶胶光学厚度数据可以用于反演干旱区地面PM_2.5浓度值,对卫星遥感在干旱区地面空气监测应用提供了新的方法和思路。