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1.
As a component of the Canadian Arctic Haze Study, held coincident with the second Arctic Gas and Aerosol Sampling Program (AGASP II), vertical profiles of aerosol size distribution (0.17 m), light scattering parameters and cloud particle concentrations were obtained with an instrumented aircraft and ground-based lidar system during April 1986 at Alert. Northwest Territories. Average aerosol number concentrations range from about 200 cm–3 over the Arctic ice cap to about 100 cm–3 at 6 km. The aerosol size spectrum is virtually free of giant or coarse aerosol particles, and does not vary significantly with altitude. Most of the aerosol volume is concentrated in the 0.17–0.50 m size range, and the aerosol number concentration is found to be a good surrogate for the SO4 = concentration of the Arctic haze aerosol. Comparison of the aircraft and lidar data show that, when iced crystal scattering is excluded, the aerosol light scattering coefficient and the lidar backscattering coefficient are proportional to the Arctic haze aerosol concentration. Ratios of scattering to backscattering, scattering to aerosol number concentration, and backscattering to aerosol number concentration are 15.3 steradians, 1.1×10–13 m2, and 4.8×10–15 m2 sr–1, respectively. Aerosol scattering coefficients calculated from the measured size distributions using Mie scattering agree well with measured values. The calculations indicate the aerosol absorption optical depth over 6 km to range between 0.011 and 0.018. The presence of small numbers of ice crystals (10–20 crystals 1–1 measured) increased light scattering by over a factor of ten.  相似文献   

2.
北京地区对流层中上部云和气溶胶的激光雷达探测   总被引：39，自引：8，他引：39  
介绍了近年来研制的一台多波长激光雷达及其探测对流层高云和气溶胶的实验,并依据探测结果重点分析了北京2000年1月至4月对流层上部云和气溶胶在532 nm波长的消光系数分布特征.结果表明:从6 km至11 km的气溶胶光学厚度值在0.0152至0.0284之间变化,均值为0.0192.从6 km至11 km的云光学厚度值在0.014至0.23之间变化.观测到的单层高云的厚度最大为6 km.4月6日,近年来最强的一次沙尘暴袭击北京.4月7日北京地区无可见云,激光雷达探测结果表明,从4 km至10 km高度范围内,存在一层厚度约为6 km的气溶胶粒子层,消光系数峰值处于8 km附近,比晴天无云时的消光系数值约大一个数量级.估计这是一层沙尘气溶胶,系由远距离输送至北京形成的.  相似文献   

3.
The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the non-Soviet Arctic in March and April 1986, to study the aerosol, gaseous, chemical, and optical properties of Arctic haze. One component of the program was supported with an instrumented NOAA WP-3D atmospheric research aircraft. Measurements of wind, temperature, ozone, water vapor, condensation nucleus concentration, and aerosol scattering extinction coefficient were used to determine the locations and properties of haze layers. The first three NOAA WP-3D research flights were conducted north of Barrow, Alaska, and over the Beaufort Sea northeast of Barter Island, Alaska. The next three sampled conditions in the high Arctic near Alert, Northwest Territories, Canada. All basic meteorological, gas, and aerosol systems are described. The WP-3D flight tracks and operations are presented.  相似文献   

4.
The current paper introduces an empirical method for estimating the vertical distribution of background stratospheric aerosol extinction profiles covering the latitude bands of 50±5°N,40±5°N,30±5°N,and 20±5°N and the longitude range of 75 135°E based on Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction measurements at wavelengths of 1020 nm,525 nm,452 nm,and 386 nm for the volcanically calm years between 1998 2004.With this method,the vertical distribution of stratospheric aerosol extinction coefficients can be estimated according to latitude and wavelength.Comparisons of the empirically calculated aerosol extinction profiles and the SAGE II aerosol measurements show that the empirically calculated aerosol extinction coefficients are consistent with SAGE II values,with relative differences within 10% from 2 km above the tropopause to 33 km,and within 22% from 33 km to 35 km.The empirically calculated aerosol stratospheric optical depths (vertically integrated aerosol extinction coefficient) at the four wavelengths are also consistent with the corresponding SAGE II optical depth measurements,with differences within 2.2% in the altitude range from 2 km above the tropopause to 35 km.  相似文献   

5.
We compared April to September retrievals of total, fine-mode (sub-micron), and coarse-mode (super-micron) aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) with simulations from a global three-dimensional chemical transport model, the Goddard Earth Observing System (GEOS-Chem), across five Arctic stations and a four-year sampling period. It was determined that the AOD histograms of both the retrievals and the simulations were better represented by a lognormal distribution and that the successful simulation of this empirical feature as well as its consequences (including a better model versus retrieval coefficient of determination in log-log AOD space) represented a general indicator of model evaluation success. Seasonal (monthly averaged) AOD retrievals were sensitive to the way in which the averaging was performed; this was ascribed to the presence of highly variable fine-mode smoke in the western Arctic. The retrieved and modelled station-by-station fine-mode AOD averages showed a peak in April/May that decreased over the summer, while the model underestimated the fine-mode AOD by an average of about 0.004 (～6%). Both the retrievals and simulations showed seasonal coarse-mode AOD variations with a peak in April/May that was attributed to Asian and/or Saharan dust. The model's success in capturing such weak seasonal events helps to confirm the relevance of the separation of the fine and coarse modes and the general validity of model estimates in the Arctic.  相似文献   

6.
灰霾过程中的气溶胶特性观测研究   总被引：13，自引：5，他引：8  
结合太阳光度计、激光雷达以及其他相关数据对河北香河县2007年4月初的一次灰霾天气过程中的气溶胶特性进行了遥感研究。研究表明,在这次灰霾的爆发期间,能见度从20 km下降到3 km左右;气溶胶光学厚度（AOD）在3个波段上都明显增加,特别是380 nm处的AOD从6日的031增长到10日的140;Angstrom指数(ALPHA)也明显下降,例如340~440 nm处的ALPHA从7日的145下降到10日的099。从AOD和ALPHA在短波处的较大变化、体积浓度谱的粗模态粒子的大量增加和PM10浓度值的变化分析来看,这次灰霾过程中的气溶胶数浓度明显增加,其中还含有大颗粒物的大量导入。激光雷达探测消光系数的垂直分布也显示气溶胶在垂直高度上达到了近3 000 m左右。从微物理特征的变化上看,这次灰霾过程中局地气溶胶的散射能力增强,吸收能力减弱。另外,通过HYSPLIT模式对后向轨迹的模拟和对NCEP数据的分析,发现这次灰霾过程中所包含的大颗粒物的主要源地可能是蒙古地区,所以气溶胶呈现了一定的沙尘气溶胶特征。  相似文献   

7.
该文简要介绍了遥感气溶胶光学厚度的宽带消光法, 重点比较与分析了2001～2002年间北京地区宽带消光法和全球气溶胶探测网(AERONET)气溶胶光学厚度的探测结果.对比结果表明, 两类探测结果在无云晴天的条件下具有很好的吻合, 二者的相关系数达到90%以上.另外, 作者还针对宽带消光法反演月平均气溶胶光学厚度问题, 提出了一个减小云对反演结果影响的方法, 即月平均光学厚度约束法, 并与全球气溶胶探测网探测结果做对比分析.二者结果的一致性表明该约束方法的有效性.  相似文献   

8.
为确定新疆博斯腾湖地区气溶胶主要组分,减小辐射传输计算和卫星遥感应用中由于气溶胶模型误判造成的误差,分别取大陆型、背景沙漠型、体积百分比自定义模型和两种动态气溶胶模型,用6S辐射传输算法计算出对应于太阳光度计测量时段的各波段大气气溶胶光学厚度。将模式计算值与测量值进行比较,确定测量地区的大气气溶胶模型。将该方法用于2010年在新疆博斯腾湖地区测量的太阳光度计数据,结果显示该地区在测量时段较为符合体积百分比自定义模型,沙尘性粒子体积百分比均在88%上,符合当地靠近沙尘源地和测量时段浮尘天气频发的实际情况。  相似文献   

9.
Thirty-six aerosol filter samples collected in tropospheric Arctic haze layers, in the stratosphere, and in the marine boundary layer during the 1983 Arctic Gas and Aerosol Sampling Program were analyzed for trace elements using instrumental neutron activation analysis. Average crustal dust concentrations were 540 ng/m3 and 330 ng/m3 for samples collected in Arctic haze over the North American and Norwegian Arctic, respectively. An average marine salt concentration of 120 ng/m3 was obtained for haze samples collected above the marine boundary layer on both sides of the Arctic.Meteorological and wind trajectory information were used to identify specific haze transport pathways, which brought relatively unmixed aerosol from the central Soviet Union into the AGASP sampling areas. Results from individual filters collected within these transport zones are discussed, with emphasis on certain trace metal ratos which have been proposed by other researchers as discriminators of aerosols from different source regions. Our aircraft-collected data are compared with previously-collected ground-based measurements, and show reasonably good agreement for most tracer elements and ratios. Specifically, we have determined the As/Sb ratio tracer, named by other researchers as the most effective elemental discriminator of aerosol from the central Soviet Union, to be approximately 5–6. This relatively high tracer value is consistent with previous ground-based findings. A significantly lower V/Sb ratio was observed throughout this study, possibly indicating a change in the source signature.  相似文献   

10.
小洋山岛位于上海东南面距海岸线约30km处,四面环海,研究其上空的大气气溶胶光学特性对了解我国东部沿海地区及其近海海域的环境和气候影响等都具有重要的意义。对于近岸海岛的气溶胶光学厚度(AOD)观测,至今国内尚未见这方面的实测资料与分析。本次实验利用2006～2007年连续观测得到的AOD值,分析了AOD的季节变化及其与地面风向、湿度和能见度等气象要素的关系,并给出了气溶胶消光谱。分析发现:小洋山地区AOD具有春季最大,冬季次之,秋季较小的特点,而且在低能见度情况下,气溶胶以大粒子为主;盛行西风时,AOD值增大且大粒子比重增加;AOD与湿度有较好的正相关关系。  相似文献   

11.
The interaction of the Aretic winter aerosol (Arctic haze) with solar radiation produces changes in the radiation field that result in the enhancement of scattering and absorption processes which alter the energy balance and solar energy distribution in the Arctic atmosphere-surface system. During the second Arctic Gas and Aerosols Sampling Project (AGASP II) field experiment, we measured radiation parameters using the NOAA WP-3D research aircraft as a platform. State-of-the-art instrumentation was used to measure in situ the absorption of solar radiation by the Arctic atmosphere during severe haze events. Simultaneously with the absorption measurements, we determined optical depths, and total, direct, and scattered radiation fields. All optical measurements were made at spectral bands centered at 412, 500, 675, and 778 nm and with a bandpass of 10 nm. With this selection of spectral regions we concentrated on the measurement of the radiative effects of the aerosol excluding most of the contributions by the gaseous components of the atmosphere. An additional measurement performed during these experiments was the determination of total solar spectrum fluxes. The experimentally determined parameters were used to define an aerosol model that was employed to deduce the absorption by the aerosols over the full solar spectrum and to calculate atmospheric heating rate profiles. The analyses summarized above allowed us to deduce the magnitude of the change in some important parameters. For example, we found changes in instantaneous heating rate of up to about 0.6 K/day. Besides the increased absorption (30 to 40%) and scattering of radiation by the atmosphere, the haze reduces the surface absorption of solar energy by 6 to 10% and the effective planetary albedo over ice surfaces by 3 to 6%. The vertical distribution of the absorbing aerosol is inferred from the flux measurements. Values for the specific absorption of carbon are found to be around 6 m2/g for externally mixed aerosol and about 11.7 m2/g for internally mixed aerosol. A complete study of the radiative effects of the Arctic haze should include infrared measurements and calculations as well as physics of the ice, snow, and water surfaces.  相似文献   

12.
During the second Arctic Gas and Aerosol Sampling Program conducted in April 1986, we performed measurements of the optically absorbing carbonaceous component of the ambient aerosol from the NOAA WP-3D aircraft operating between sea level and 10 km altitude. We collected the aerosol of filters that were exposed for several hours; we also operated the aethalometer to measure the concentration of aerosol black carbon in real time. The filter analyses represent averages over the altitude range and time span during which the filter was collecting. The real-time results were sorted by altitude to calculate vertical profiles of black carbon concentration. Values typically ranged from 300 to 500 ng m–3 at lower altitudes, decreasing gradually to 25 to 100 ng m–3 at 8–10 km. Strong stratification at lower altitudes was frequently observed. The magnitude of these concentrations suggests that the sources are distant regions of considerable fuel consumption. The presence of this material in the tropospheric column and its probable deposition to the high-albedo surface may result in perturbations of the solar radiation balance. The concentrations measured at the highest altitudes may mean that particulate carbon and accompanying emissions for which it is a tracer are mixing into the stratosphere.  相似文献   

13.
The aerosol optical depth of the atmosphere obtained from spectral sun photometer measurements and the integral optical depth determined from standard actinometric observations of direct solar radiation are the parameters of the optical state of the atmosphere. The quantitative estimates of the integral transparency and aerosol optical depth of the atmosphere in Antarctica are presented, their long-term variability over the entire period of observations is analyzed. The comparison of obtained data with the estimates for other natural regions and conditions revealed that during the periods without the impact of volcanic eruptions, the levels of atmospheric aerosol turbidity in Antarctica over the recent decades are minimal on the planet and can be considered as global background characteristics.  相似文献   

14.
This work aims at determining the aerosol particle radii in the atmosphere of Athens. Such a work is carried out in Athens for the first time. For this purpose, solar spectral direct-beam irradiance measurements were used in the spectral range 310–575 nm. To estimate the particle radius from aerosol optical depth retrieval, a minimization technique was employed based on the golden-section search of the difference between experimental and theoretical values of the aerosol optical depth. The necessary Mie computations were performed based on the algorithm LVEC.In this study, the mean particle radius of a given distribution was calculated every 30 min during cloudless days in the period November 1996 to September 1997. The largest particles were observed in the summer and the smallest during winter. The result was verified by the increased values of the aerosol optical depth and the turbidity factors calculated in the summer. The differences in the diurnal variation from season to season are attributed to the prevailing wind regime, pollutant emission and sink rates in the atmosphere of Athens.  相似文献   

15.
Precipitable water measurements made coincident in time and space with direct broadband solar irradiance measurements are used in conjunction with an atmospheric transmission model to derive a parameter whose major dependence is on total aerosol extinction. Irradiance measurements are used to calculate an atmospheric transmission factor (ATF) that is independent of the instrument calibration and the extraterrestrial solar constant. The dependency of the ATF on precipitable water is determined using LOWTRAN5, an atmospheric transmission model with high spectral resolution. Precipitable water measurements are then used to adjust the measured ATF to correspond to an ATF value obtained for a constant precipitable water amount. The remaining variability in the adjusted ATF is due mostly to aerosol extinction. The technique is applied to a 6-year period (1978–1983) for clear-sky mornings at Mauna Loa, Hawaii (MLO). MLO ATF aerosol residuals are compared with independently measured monochromatic aerosol optical depth. Results show that the ATF aerosol residual is nearly equal to the 500 nm aerosol optical depth prior to the eruption of E1 Chichon, at which time a nonlinear time-dependent relationship between the two quantities is evident. ATF aerosol residuals reflect the spectrally integrated aerosol influence on transmission and, therefore, could indicate better than monochromatic optical depth the radiation balance perturbations due to aerosols. The 6-year precipitable water record for MLO, determined from a dual-channel sunphotometer, has a mean value of 0.3 cm. An annual cycle in precipitable water is evident, as is a 4-month 5-standard-deviation drought from December 1982 through March 1983.  相似文献   

16.
提出一套高光谱分辨率激光雷达(HSRL)系统,用于同时测量大气风和气溶胶的光学性质.该HSRL系统中使用碘分子滤波器分离分子和气溶胶后向散射,同时利用双边缘检测技术测量大气风场引起的多普勒频移.文中选用合理的HSRL参数和大气模型数据,模拟和分析了HSRL的测量性能.系统夜晚运行时,可测量20 km以下的大气风速和气溶胶,风速误差小于2 m s-1,气溶胶的后向散射系数相对误差小于30%.在白天工作时,相同误差下的可探测高度为10 km.模拟分析结果表明,该HSRL雷达有较大的应用前景,对天气和气象研究等有重要意义.  相似文献   

17.
Measurements from July 4 to July 8, 2005 by a high resolution visible radiometer, a Raman lidar, a ground particulate matter sampler, and ground meteorological sensors have been combined in synergy to infer the intrusion over south-east Italy, of air masses from north-west Sahara, the Atlantic Ocean, and the continental Europe. It is shown that backscatter coefficient, depolarization-ratio, and lidar ratio vertical profiles represent the best tools to detect the intrusion of long range transported air masses and to monitor their effects on the vertical distribution of aerosol optical and microphysical properties. High resolution radiometers are instead important tools to monitor changes on columnar aerosol properties and size distributions.Backscatter coefficient, depolarization-ratio, and lidar ratio vertical profiles have revealed that aerosol optical and microphysical properties significantly changed with time and space during African dust outbreaks: the intrusion of dust particles that at first occurred above 2 km of altitude extending up to 6 km, affected the all aerosol load down to ground within few hours. Aerosol size distributions showed during dust events a clear bimodality with an accumulation mode maximum at 0.24 µm and a coarse mode maximum at 0.94 μm. Conversely, we have found that during the advection of air masses from the Atlantic and continental Europe, aerosol particles were mainly located below 2 km, their optical and microphysical properties were affected by smaller changes in time and space, and were characterized by depolarization ratios rather close to those due to a pure molecular atmosphere. In this case bimodal size distributions with an accumulation mode showing two sub-modes at 0.16 μm and 0.24 μm, respectively and a coarse mode centred at 0.94 μm have also been observed.  相似文献   

18.
利用2006年3～5月天空辐射计观测数据反演得到北京地区春季大气气溶胶光学性质参数,包括大气气溶胶光学厚度(0.5μm)、Angstrm指数、单次散射反射比和粒子谱分布特征。结果表明:北京地区春季气溶胶平均光学厚度0.67,Angstrm指数0.54,单次散射比0.88,粒子吸收性质较弱,粒子谱呈双峰形,以粗粒子为主,粗、细模态粒子粒径分别集中在0.17μm和7.7μm左右。相比2004年此次观测期间气溶胶粒径较大,粒子体积浓度较高,散射作用在其消光特性中的比重略有下降。光学厚度日变化呈单峰型,日间单次散射比随时间逐渐递减,Angstrm指数在上午递减趋势明显,午后变得稳定。对同时观测的天空辐射计与CE-318不同波长光学厚度结果进行比较,结果显示两者得到的光学厚度相关性很好,各波长小时平均结果的相对误差小于7%。  相似文献   

19.
大气气溶胶光学厚度遥感研究概况   总被引：1，自引：0，他引：1  
宋薇  张镭 《干旱气象》2007,23(3):76-81
大气气溶胶是影响气候变化的重要因子之一,利用遥感手段不仅可以获得气溶胶的分布信息,也可以得到相关的气溶胶光学特性参数。本文阐述了国内外气溶胶遥感的发展动态,介绍了气溶胶遥感的基本情况及气溶胶光学厚度反演的几种方法,提出了存在的问题并对今后的研究进行了展望。  相似文献   

20.
马新成  田伟红  张磊  张蔷 《气象科技》2011,39(6):685-691
2004年秋季在北京地区利用机载大气气溶胶粒子探头进行了大气气溶胶观测,获得了0～7 km气溶胶细粒子数浓度和尺度谱分布的垂直、水平变化特征.结果表明:北京地区上空气溶胶粒子数浓度在1 km左右高度以下的混合层内有均匀的分布,明显递减层的高度范围约在1～2 km之间,2 km以上随高度递减很小,高层气溶胶数浓度变化不大...  相似文献   

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