Variations in parameters of aerosol optical thickness in Dushanbe

The results of studies of aerosol optical thickness (AOT) in Dushanbe conducted from July 2010 to March 2011 within the AERONET program are discussed. The statistical characteristics of AOT have been shown to significantly vary during dust intrusions. The seasonal variations in the dustiness of the atmosphere have been analyzed.     

Features of optical characteristics of atmospheric aerosol in the Middle Urals

The results of studies into the aerosol optical depth (AOD) for the atmosphere in the Middle Urals in the spectrum range of 0.34–1.02 μm for 2004–2010 is presented. The interannual, annual, seasonal, and daily variations in the AOD are analyzed. The major statistical characteristics of the AOD, the parameters of the probability density function of distributions over different wave lengths, and the parameters of Angstrom’s formula for the different seasons are calculated. The monitoring stations in the Russian segment of the AERONET network are ranked with respect to the AOD value. A shift from March to May in the spring maximum of the AOD is revealed in comparison with the results of the actinometric observations for the period of 1960–1986. A qualitative assessment is given to the influence of forest and peat fires in the region on the AOD. A classification of the states of aerosol haze in the atmosphere according to the AOD values is proposed.     

Chemical composition and microphysical characteristics of atmospheric aerosol over moscow and its vicinity in June 2009 and during the fire peak of 2010

The microphysical characteristics of aerosol were measured in the atmospheric surface layer simultaneously over the center of Moscow and its vicinity (Zvenigorod Scientific Station, Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences) from June 15 to June 30, 2009, in order to compare the mass concentrations, particle-size distribution functions, and elemental compositions of aerosol over the megapolis and the background zone. During the fire peak of 2010, on August 8, aerosol samples were taken in the center of Moscow and their chemical composition was determined. Comparing results obtained from the simultaneous measurements of the concentrations of aerosol and its elemental composition made it possible to determine their interdiurnal variability, which suggests that the features of time variations are of a regional character and they are determined mainly by the dynamics of the synoptical processes of air-mass exchange. The chemical composition of obtained samples was determined using the method of atomic absorption spectrometry. The measurement results obtained in June 2009 revealed an increase in the content of anthropogenic elements in the atmosphere over Moscow when compared to their content in the atmosphere over the background zone. In Moscow, during the summer fires of 2010, the concentration of sulfur exceeded its concentration in June 2009 by an order of magnitude, and the concentrations of Na, Mg, Al, Si, K, Ca, and Fe increased several times. The mean mass concentration of aerosol amounted to 917 μg/m³ in August 2010 and 50–70 μg/m³ in June 2009.     

台湾海峡及周边海区MODIS气溶胶光学厚度有效性验证

大气气溶胶通常是指悬浮在大气中直径小于10μm的液态或固态的微小粒子.对流层气溶胶是陆地-大气-海洋系统的重要组成部分.它通过直接或间接辐射强迫强烈地影响着地-气系统的辐射收支平衡,进而影响全球环境和气候,是气候变化研究的一个重要因子.气溶胶光学厚度是气溶胶最重要的参数之一,是表征大气浑浊度的重要物理量,也是确定气溶胶气候效应的一个关键因子和大气模型的一个重要参量[1].探测气溶胶光学厚度可以采用陆基探测方法,如太阳辐射计、天空辐射计、日射强度计等,也可以采用卫星遥感观测的方法.     

厦门海域大气气溶胶光学厚度地基观测分析及卫星遥感检验

利用设立于厦门岛西南部沿海的气溶胶地基观测站点2008年1月7日至2009年4月30日的观测资料,对厦门海域气溶胶光学厚度的每日逐时变化、逐日变化、逐月变化进行了分析研究,并利用观测结果对MODIS L2级气溶胶光学厚度(AOT)产品进行检验。结果表明,厦门海域气溶胶光学厚度每日逐时变化和逐月变化有一定的季节规律,而逐日变化随气象条件的不同有很大差异。一年中气溶胶光学厚度月平均值呈现春秋季双峰分布趋势,4月份最大,超过0.9,空气较为混浊;6月份呈现谷值,AOT小于0.3,空气相对清洁。夏季气溶胶主控粒子的粒径较大,而其余各月份的波长指数在平均值1.21附近波动,混浊系数年平均值为0.25。利用该地基观测资料对MODIS L2级AOD产品进行检验,MODIS反演的厦门海域气溶胶光学厚度逐月变化趋势和地基观测结果完全一致,表明MODIS卫星遥感气溶胶光学厚度能比较好地反映厦门海域的气溶胶季节变化特征。     

SeaWiFS遥感资料分析中国海域气溶胶光学厚度的季节变化和分布特征

通过与地基气溶胶观测数据的对比,确认了SeaWiFS气溶胶光学厚度产品用于研究中国海域气溶胶分布和变化特征的有效性。在此基础上,分析了中国海域气溶胶光学厚度的季节变化和地理分布特征。研究结果表明,中国东部海域平均气溶胶光学厚度存在以中纬度为中心的纬向分布;受沙尘、季风气候的影响,中国海域气溶胶光学厚度存在季节变化,不同海区有不同的季节变化和分布特征。渤海、黄海及东海有类似的变化特征,春季都受到沙尘气溶胶的影响,使中国东部海域气溶胶光学厚度普遍高于0.160,且对东海的影响最大;夏、秋季逐渐减小,冬季有所回升。南海气溶胶光学厚度均值为0.150,随时间变化不明显,但地理分布变化显著;受季风气候的影响,从春季到冬季,气溶胶光学厚度高值中心从高纬海域向低纬海域转移,范围也逐渐扩大。冬季南海大部分海域气溶胶光学厚度都达到0.160以上,是整个中国海域冬季气溶胶光学厚度最大的海区。气溶胶光学厚度的季节变化和地理分布特征为研究中国海区域气候变化和海洋生态提供了依据。     

浊度对活体叶绿素荧光检测的影响及修正方法

本文研究了泥沙悬浮液浊度对叶绿素荧光计测定水样中活体叶绿素荧光的影响。结果表明,浊度产生的荧光效应和遮蔽效应对活体叶绿素荧光测定具有显著影响。在100 NTU浊度范围内,浊度会导致荧光效应使活体叶绿素荧光值测量结果随着浊度的增大而增大,并构成良好的线性关系;实际测定水体中硅藻的活体叶绿素荧光值时,泥沙悬浮液的浊度会导致遮蔽效应使活体叶绿素荧光值测量结果随着浊度的增大而减小,水体中硅藻质量浓度越高遮蔽效应越显著,在1 000 mV(约10 μg/L)硅藻质量浓度,100 NTU浊度条件下,浊度遮蔽效应可导致活体叶绿素荧光值偏低20%。根据近海泥沙实验数据,本文提出了一种活体叶绿素荧光检测的浊度影响修正方法,在100 NTU浊度内,修正后叶绿素荧光值偏差率都下降到±10%以内,校准后的荧光值与真实叶绿素荧光值较为接近。     

海滩碎波带悬沙浊度短期变化特征分析

基于珠江口荷包岛南湾海滩碎波带垂向上的悬沙浊度和同步实测潮位资料,本文利用谱分析和小波分析方法对碎波带的悬沙浊度变化特征和影响因素进行分析.结果表明:(1)碎波带近底层和中层的悬沙浊度变化表现为周期性振荡特征,其中处于低频部分的近底层悬沙浊度周期约为中层悬沙浊度的1.25倍,但处于高频振荡部分的近底层和中层悬沙浊度变化周期基本一致.此外,近底层悬沙浊度峰值滞后于中层的悬沙浊度变化.(2)碎波带的中层悬沙浊度与潮位变化呈明显的负相关,且滞后于潮位变化.(3)近底层的悬沙浊度变化主要受控于波浪动力作用,而潮位变化引起的潮流作用是中层悬沙浊度变化的主要因素.     

Specific features of the size distribution of atmospheric aerosol in the continent-ocean transition zone

The distribution functions of atmospheric aerosol obtained on the basis of lidar sounding and photometric measurements over marine water areas in continental and transition zones are analyzed. Changes in the microphysical parameters of the distribution function in the continent-ocean transition zone with height are considered on the basis of data taken from three-frequency lidar sounding. Specific features of changes in the particle size distribution with height during intense dust storms and records of volcanogenic aerosol in the tropopause region in the summer of 2008 are described.     

Structure and optical properties of soot aerosol in a moist atmosphere: 1. Structural changes of soot particles in the process of condensation

A laboratory setup and a procedure for measuring the volume coefficients and mean cross sections of extinction, scattering, and absorption of soot particles in the medium of saturated water vapor are described. A method for hydrophilization of the surface of soot particles, which makes it possible to obtain model objects with specified hygroscopic properties, is presented. The processes of transformation of soot particles are analyzed with the use of data of electron-microscopic investigations on the basis of the fractal approach. The structural parameters of hydrophobic soot are shown to depend on the conditions of moistening, whereas hydrophilic particles are subject to substantial structural changes indicative of their watering. Investigation of the coagulation of soot particles with drops shows that hydrophobic particles form a weakly bound system; they coagulate on the surface of drops and cause no changes in the structure of soot aggregates. During the coagulation, hydrophilic soot particles penetrate inside a drop and irreversibly form a mixed system.     

Long-period variations in the optical and microphysical parameters of surface aerosol in a Moscow suburb

The mass concentration M of surface submicron aerosol and its condensation activity χ were measured at the Zvenigorod Scientific Station of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, in 2001–2006. Variations in these quantities on scales of several days to several months are analyzed. It is shown that the occurrence of dense and superdense hazes over central Russia became more frequent during these years. This resulted in a change in the character of the seasonal dependence of the mass aerosol concentration M: ordered oscillations whose amplitude increases from year to year appeared in the seasonal cycle of M. Due to more frequent cases of dense and superdense hazes in 2002–2006, a significant monotonic increase is observed in the annual means of M. The annual mean of M increased more than twofold in 2005 (56 μm/m³) compared to 2001 (23 μm/m³). The time regimes of M and χ are characterized by variations with periods in the vicinity of 10, 20, and 40–50 days, as well as variations with longer periods within 70–100 days. In addition, the variability of mass concentration is of a strongly intermittent character. A cross-spectral analysis has shown that, on the whole, variations in M are coherent with those in χ. If the parameters M and χ vary on the same time scales, then, as a rule, variations in M lag behind variations in χ by several days. To understand the relationship between the parameters M and χ, special investigations, including studies of aerosol composition, are needed.     

大气垂直速度计算中校正方法的探讨

本文对大气运动中垂直速度ｗ计算中的几种校正方法作了分析比较，并在前人工作的基础上，对校正方法作了改进，提出了进行低通滤波、散度校正和法线风分量校正的方法。通过这些校正，使计算出的平均散度和垂直速度的垂直廓线能维持原计算曲线的形式，并能满足整个气层连续方程积分为零的条件，也符合误差随高度增大的情况。     

Landsat-8 OLI卫星数据的大气校正检验及其应用

本文检验了Vanhellemont和Ruddick算法在浑浊的海洋沿岸水体中的适用性。采用基于Vanhellemont和Ruddick算法对2013—2015年黄河口水体的landsat-8 OLI数据进行大气校正,该算法得到的OLI反射率与黄河口高光谱实测反射率较一致, R为0.95,在483 nm(蓝)、561 nm(绿)、655 nm(红)波段处平均相对误差为16.4%、17.3%和25.7%。MODIS和Landsat-8 OLI数据获取的悬浮物浓度之间一致性较好, R为0.85,平均相对误差为20.5%,表明该算法适用于黄河口水体。基于时间序列OLI数据,得到了悬浮物浓度时空分布特征。黄河口悬浮物浓度变化差异主要由风速和输沙量引起的,风速和输沙量对悬浮物浓度的影响存在一定的时间滞后现象。     

长江口及东海海域大气气溶胶中水溶性离子的分布特征

2006年夏季、冬季和2007年春季、秋季在长江口及东海海域进行了大面积走航采样,通过离子色谱法分析了气溶胶中主要水溶性离子的质量浓度,探讨了其季节变化和海域分布.分析结果表明,K+和Ca2+季节变化显著,海域分布呈现近岸高外海低的趋势,Na+和Mg2+海域分布差异显著;NH4+-N,NO3--N和SO42--S的春、...     

海冰快速减退背景下大气动量输入对波弗特流涡长期变化的影响

随着北冰洋海冰快速减退,气–冰–海系统发生显著变化,波弗特流涡也发生显著变化。本文使用实测资料和海洋大气再分析数据,探讨北冰洋波弗特流涡的长期变化和大气动量输入对波弗特流涡变化的影响。波弗特流涡的长期变化可以分为3个典型时期(1980–1995年,1996–2007年,2008–2018年)。最近时期(2008–2018年),波弗特流涡平均流涡强度达到4.39×10–7,相较于第1个时期(1980–1995年),流涡强度增加近2倍,达到稳定的状态。波弗特流涡范围扩大,主体向西北移动;上层海洋斜压性增强。与此同时,上层海洋环流主模态已发生显著转变:1980–1995年,环流主模态为影响整个加拿大海盆的加拿大海盆模态;2008–2018年的主模态则转变为影响整个研究海域的太平洋扇区模态。最近时期,表征气–海之间动量输入的气–海应力显著增加,尤其是夏末秋初的8–10月,与冰–海应力几乎相当。增加的大气动量输入带来平均动能增加,埃克曼泵压效应增强,下盐跃层深度加深,增加的大气动量输入进而导致近年来波弗特流涡的显著增强。加拿大海盆南部是大气动量输入的关键区。     

Long-term changes in microbial and biochemical parameters in the Central Indian Basin

Natural kilometer-scale spatial variability and seasonal variability in deep-sea sediments at ∼5000 m depth was studied at two reference sites in the Central Indian Basin. Biochemical parameters such as the labile organic matter (LOM) (consisting of carbohydrates, protein and lipids) and total organic matter (TOM) and biological parameters such as total counts of bacteria and adenosine triphosphate (ATP) were estimated after an interval of 54 months. These were compared with nine locations (12–17 km away) where an artificial sediment disturbance was created by a hydraulic benthic disturber. Besides the above-mentioned parameters, extracellular enzymes, alkaline phosphatase, aminopeptidase and lipase were also monitored at these nine locations. Post-disturbance (PoD1) observations were carried out immediately after the benthic disturbance experiment and compared with the pre-disturbance (PreD) pattern. The restoration process in the test site was studied after a period of 44 months (PoD2). There was a drastic reduction in total counts of bacteria, ATP, carbohydrates and lipids accompanied by a two- to four-fold increase in protein content at the undisturbed reference sites after 54 months. A similar reduction in these parameters was observed in the PoD1 compared to the PreD stage at the test site. An initial increase in TOM content and in the activities of three extracellular enzymes in the PoD1 stage was followed by a reduction in TOM, ATP and organic P content and activities of the extracellular enzymes in the PoD2 phase (i.e. after 44 months). Reduction in ATP levels suggests a negative impact of resedimentation on living biomass in the sediments. Although LOM, protein concentrations and the protein/carbohydrate ratio increased in the PoD2 phase relative to the PoD1 phase, the bacterial numbers were below the concentrations in the PreD stage, indicating slow restoration of benthic conditions. Long-term analyses of the indicator parameters thus showed mixed effects of sediment disturbance. A similar pattern at the undisturbed reference location suggests that natural (seasonal) variability outweighed artificial variability caused by the benthic disturbance in the Central Indian Basin and the former is responsible for bringing about changes in deep-sea benthic ecosystem on long-time scales.     

On the influence of atmospheric chemical reactions on the ion composition of aerosol particles in the Baikal region

Monitoring data on the ion composition of aerosols and gas admixtures in the background and polluted atmosphere of the Lake Baikal region are presented. The ion composition and morphology of aerosols are affected by heterogeneous chemical reactions and variations in relative humidity. Two types of aerosol particles are revealed over this region. The fraction of solid particles recorded in most episodes includes primarily carbonates of alkaline and alkaline-earth metals. With increased atmospheric humidity, these particles are engaged in heterogeneous chemical reactions with gas-phase NH₃ and H₂SO₄, proceeding through the phase of watering. As a result, the composition of these aerosols is changed, and a fraction of aqueous H₂O/H₂SO₄/(NH₄)₂SO₄ aerosol particles of a different composition is formed. On the basis of a physical and chemical analysis of monitoring data on the aerosol composition and concentrations of gas admixtures, the average aerosol-size distribution of different types is estimated. For the first time, the mean acidity of aqueous aerosol particles is estimated.