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1.
黄土高原半干旱区典型日吸收性气溶胶综合观测分析 总被引:2,自引:0,他引:2
利用兰州大学半干旱气候与环境观测站的太阳光度计、激光雷达、微波辐射计综合观测资料,结合辐射传输模式分析了该地区秋季典型日2012年9月3~4日、21日和28日气溶胶物理特性、垂直分布特征,及其与气象条件的关系。研究时期的气溶胶主要为局地沙尘与人为污染混合气溶胶,吸收性明显,尺度较小。其中,4日西北风增强,远距离传输沙尘气溶胶,气溶胶光学厚度最大,粒子尺度明显增大。尝试利用灰色关联度法确定参考高度,分别为7.41 km、8.47 km、7.13 km和7.66 km,反演气溶胶消光系数,由此积分得到的光学厚度与太阳光度计观测值相关性可达0.975,反演效果较好。研究时期气溶胶的抬升主要受白天热力湍流作用,边界层发展,气溶胶向上传输,每日12时(当地时间,下同)至14时传输至最大高度,气溶胶抬升的高度对应大气加热率的高值区,低层加热率可达1 K d-1。气溶胶在大气层顶和地面造成负辐射强迫,分别为-12.707 W m-2、-25.398 W m-2,大气中表现为正辐射强迫,为12.692 W m-2,大气层顶的辐射强迫对气溶胶的物理特性最为敏感,当气溶胶吸收性明显时,大气层顶的瞬时辐射强迫会出现正值。 相似文献
2.
The atmospheric general circulation model ECHAM-4 is coupled to a chemistry model to calculate sulfate mass distribution
and the radiative forcing due to sulfate aerosol particles. The model simulates the main components of the hydrological cycle
and, hence, it allows an explicit treatment of cloud transformation processes and precipitation scavenging. Two experiments
are performed, one with pre-industrial and one with present-day sulfur emissions. In the pre-industrial emission scenario
SO2 is oxidized faster to sulfate and the in-cloud oxidation via the reaction with ozone is more important than in the present-day
scenario. The atmospheric sulfate mass due to anthropogenic emissions is estimated as 0.38 Tg sulfur. The radiative forcing
due to anthropogenic sulfate aerosols is calculated diagnostically. The backscattering of shortwave radiation (direct effect)
as well as the impact of sulfate aerosols on the cloud albedo (indirect effect) is estimated. The model predicts a direct
forcing of −0.35 W m-2 and an indirect forcing of −0.76 W m-2. Over the continents of the Northern Hemisphere the direct forcing amounts to −0.64 W m-2. The geographical distribution of the direct and indirect effect is very different. Whereas the direct forcing is strongest
over highly polluted continental regions, the indirect forcing over sea exceeds that over land. It is shown that forcing estimates
based on monthly averages rather than on instantaneous sulfate pattern overestimate the indirect effect but have little effect
on the direct forcing.
Received: 16 October 1996/Accepted: 24 October 1996 相似文献
3.
On summing the components of radiative forcing of climate change 总被引:1,自引:0,他引:1
Radiative forcing is a useful concept in determining the potential influence of a particular mechanism of climate change.
However, due to the increased number of forcing agents identified over the past decade, the total radiative forcing is difficult
to assess. By assigning a range of probability distribution functions to the individual radiative forcings and using a Monte-Carlo
approach, we estimate the total radiative forcing since pre-industrial times including all quantitative radiative forcing
estimates to date. The resulting total radiative forcing has a 75–97% probability of being positive (or similarly a 3–25%
probability of being negative), with mean radiative forcing ranging from +0.68 to +1.34 W m−2, and median radiative forcing ranging from +0.94 to +1.39 W m−2.
Received: 14 March 2001 / Accepted: 1 June 2001 相似文献
4.
Climate forcing by carbonaceous and sulfate aerosols 总被引:3,自引:0,他引:3
An atmospheric general circulation model is coupled to an atmospheric chemistry model to calculate the radiative forcing
by anthropogenic sulfate and carbonaceous aerosols. The latter aerosols result from biomass burning as well as fossil fuel
burning. The black carbon associated with carbonaceous aerosols is absorbant and can decrease the amount of reflected radiation
at the top-of-the-atmosphere. In contrast, sulfate aerosols are reflectant and the amount of reflected radiation depends nonlinearly
on the relative humidity. We examine the importance of treating the range of optical properties associated with sulfate aerosol
at high relative humidities and find that the direct forcing by anthropogenic sulfate aerosols can decrease from −0.81 W m-2 to −0.55 Wm-2 if grid box average relative humidity is not allowed to increase above 90%. The climate forcing associated with fossil fuel
emissions of carbonaceous aerosols is calculated to range from +0.16 to +0.20 Wm-2, depending on how much organic carbon is associated with the black carbon from fossil fuel burning. The direct forcing of
carbonaceous aerosols associated with biomass burning is calculated to range from −0.23 to −0.16 Wm-2. The pattern of forcing by carbonaceous aerosols depends on both the surface albedo and the presence of clouds. Multiple
scattering associated with clouds and high surface albedos can change the forcing from negative to positive.
Received: 29 September 1997 / Accepted: 10 June 1998 相似文献
5.
Dong Xia Ling Chen Huizhong Chen Xuyu Luo Tao Deng 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(4):341-352
The atmospheric aerosols can absorb moisture from the environment due to their hydrophilicity and thus affect atmospheric radiation fluxes. In this article, the ultraviolet radiation and relative humidity (RH) data from ground observations and a radiative transfer model were used to examine the influence of RH on ultraviolet radiation flux and aerosol direct radiative forcing under the clear-sky conditions. The results show that RH has a significant influence on ultraviolet radiation because of aerosol hygroscopicity. The relationship between attenuation rate and RH can be fitted logarithmically and all of the R2 of the 4 sets of samples are high, i.e. 0.87, 0.96, 0.9, and 0.9, respectively. When the RH is 60%, 70%, 80% and 90%, the mean aerosol direct radiative forcing in ultraviolet is ?4.22W m?2, ?4.5W m?2, ?4.82W m?2 and ?5.4W m?2, respectively. For the selected polluted air samples the growth factor for computing aerosol direct radiative forcing in the ultraviolet for the RH of 80% varies from 1.19 to 1.53, with an average of 1.31. 相似文献
6.
Impacts of Internally and Externally Mixed Anthropogenic Sulfate and Carbonaceous Aerosols on East Asian Climate 总被引:1,自引:0,他引:1 下载免费PDF全文
A coupled regional climate and aerosol-chemistry model, RIEMS 2.0 (Regional Integrated Environmental Model System for Asia),
in which anthropogenic sulfate, black carbon, and organic carbon were assumed to be externally mixed (EM), internally mixed
(IM) or partially internally mixed (IEM), was used to simulate the impacts of these anthropogenic aerosols on East Asian climate
for the entire year of 2006. The distributions of aerosol mass concentration, radiative forcing and hence the surface air
temperature and precipitation variations under three mixing assumptions of aerosols were analyzed. The results indicated that
the mass concentration of sulfate was sensitive to mixing assumptions, but carbonaceous aerosols were much less sensitive
to the mixing types. Modeled results were compared with observations in a variety of sites in East Asia. It was found that
the simulated concentrations of sulfate and carbonaceous aerosols were in accord with the observations in terms of magnitude.
The simulated aerosol concentrations in IM case were closest to observation results. The regional average column burdens of
sulfate, black carbon, and organic carbon, if internally mixed, were 11.49, 0.47, and 2.17 mg m−2, respectively. The radiative forcing of anthropogenic aerosols at the top of the atmosphere increased from −1.27 (EM) to
−1.97 W m−2 (IM) while the normalized radiative forcing (NRF) decreased from −0.145 (EM) to −0.139 W mg−1 (IM). The radiative forcing and NRF were −1.82 W m−2 and −0.141 W mg−1 for IEM, respectively. The surface air temperature changes over the domain due to the anthropogenic sulfate and carbonaceous
aerosols were −0.067, −0.078, and −0.072 K, with maxima of −0.47, −0.50, and −0.49 K, for EM, IM, and IEM, respectively. Meanwhile,
the annual precipitation variations were −8.0 (EM), −20.6 (IM), and −21.9 mm (IEM), with maxima of 148, 122, and 102 mm, respectively,
indicating that the climate effects were stronger if the sulfate and carbonaceous aerosols were internally mixed. 相似文献
7.
Ahmed A. Balogun Jimmy O. Adegoke Sajith Vezhapparambu Matthias Mauder Joseph P. McFadden Kevin Gallo 《Boundary-Layer Meteorology》2009,133(3):299-321
Previous measurements of urban energy balances generally have been limited to densely built, central city sites and older
suburban locations with mature tree canopies that are higher than the height of the buildings. In contrast, few data are available
for the extensive, open vegetated types typical of low-density residential areas that have been newly converted from rural
land use. We made direct measurements of surface energy fluxes using the eddy-covariance technique at Greenwood, a recently
developed exurban neighbourhood near Kansas City, Missouri, USA, during an intensive field campaign in August 2004. Energy
partitioning was dominated by the latent heat flux under both cloudy and near clear-sky conditions. The mean daytime Bowen
ratio (β) values were 0.46, 0.48, and 0.47 respectively for the cloudy, near clear-sky and all-sky conditions. Net radiation (R
n
) increased rapidly from dawn (−34 and −58W m−2) during the night to reach a maximum (423 and 630W m−2) after midday for cloudy and near clear-sky conditions respectively. Mean daytime values were 253 and 370W m−2, respectively for the cloudy and near clear-sky conditions, while mean daily values were 114 for cloudy and 171W m−2 for near clear-sky conditions, respectively. Midday surface albedo values were 0.25 and 0.24 for the cloudy and near clear-sky
conditions, respectively. The site exhibited an angular dependence on the solar elevation angle, in contrast to previous observations
over urban and suburban areas, but similar to vegetated surfaces. The latent heat flux (Q
E
), sensible heat flux (Q
H
), and the residual heat storage ΔQ
s
terms accounted for between 46–58%, 21–23%, and 18–31% of R
n
, respectively, for all-sky conditions and time averages. The observed albedo, R
n
, and Q
E
values are higher than the values that have been reported for suburban areas with high summer evapotranspiration rates in
North America. These results suggest that the rapidly growing residential areas at the exurban fringe of large metropolitan
areas have a surface energy balance that is more similar to the rural areas from which they were developed than it is to the
older suburbs and city centres that make up the urban fabric to which they are being joined. 相似文献
8.
A group of twenty-four leading atmospheric and climate scientists provided subjective probability distributions that represent
their current judgment about the value of planetary average direct and indirect radiative forcing from anthropogenic aerosols
at the top of the atmosphere. Separate estimates were obtained for the direct aerosol effect, the semi-direct aerosol effect,
cloud brightness (first aerosol indirect effect), and cloud lifetime/distribution (second aerosol indirect effect). Estimates
were also obtained for total planetary average forcing at the top of the atmosphere and for surface forcing. Consensus was
strongest among the experts in their assessments of the direct aerosol effect and the cloud brightness indirect effect. Forcing
from the semi-direct effect was thought to be small (absolute values of all but one of the experts' best estimates were ≤0.5
W/m2). There was not agreement about the sign of the best estimate of the semi-direct effect, and the uncertainty ranges some
experts gave for this effect did not overlap those given by others. All best estimates of total aerosol forcing were negative,
with values ranging between −0.25 W/m2 and −2.1 W/m2. The range of uncertainty that a number of experts associated with their estimates, especially those for total aerosol forcing
and for surface forcing, was often much larger than that suggested in 2001 by the IPCC Working Group 1 summary figure (IPCC,
2001). 相似文献
9.
Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by nu- merical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth’s Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products. We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were -1.03±0.48 W m-2 and -0.34 ±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases. 相似文献
10.
Summary ?The analysis of ground-based measurements of solar erythemal ultraviolet (UV) irradiance with a Solar Light 501 biometer,
and total (300–3000 nm) irradiance with an Eppley B&W pyranometer at the Argentine Antarctic Base “Almirante Brown”, Paradise
Bay (64.9° S, 62.9° W, 10 m a.s.l.) is presented. Measurement period extends from February 16 to March 28 2000. A relatively
high mean albedo and a very clean atmosphere characterise the place. Sky conditions were of generally high cloud cover percentage.
Clear-sky irradiance for each day was estimated with model calculations, and the effect of the cloudiness was studied through
the ratio of measured to clear-sky value (r). Two particular cases were analysed: overcast sky without precipitation and overcast sky with rain or slight snowfall, the
last one presenting frequently dense fog. Total irradiance was more attenuated than UV by the homogeneous cloudiness, obtaining
mean r values of 0.54 for erythemal irradiance and 0.30 for total irradiance in the first case (without precipitation) and 0.27
and 0.17 respectively in the second case (with precipitation). Mean r values for the complete period were 0.58 for erythemal irradiance and 0.43 for total irradiance. Erythemal and total daily
insolations reduce quickly at this epoch due to the increase of the noon solar zenith angle and the decrease of daylight time.
Additionally, they were strongly modulated by cloudiness. Measured maxima were 2.71 kJ/m2 and 18.42 MJ/m2 respectively. Measurements were compared with satellite data. TOMS-inferred erythemal daily insolation shows the typical
underestimation with respect to ground measurements at regions of high mean albedo. Measured mean total daily insolation agrees
with climatological satellite data for the months of the campaign.
Received August 9, 2002; revised January 4, 2003; accepted January 28, 2003
Published online May 20, 2003 相似文献
11.
Summary Vertical profile of surface radiative fluxes in an area of heterogeneous terrain in south-west Germany is presented. Main
data sets utilized for the study were recorded during the REgio KLIma Projekt (REKLIP). Supporting observational data were
provided by the German weather service and German geophysical consultant service. Elevation of the study sites ranged from
212 m a.s.l. to 1489 m a.s.l. From May to September, monthly mean albedo was generally low at the study sites, ranging from
19% to 24%. For the other months, monthly mean albedo lie between 22% and 25% at the lowland site but extended between 27%
and 71% at the highly elevated mountain site. Following the altitudinal increase in surface albedo, net radiative flux and
radiation efficiency declined with elevation at an annual mean of 1.15 Wm−2/100 m and 0.008/100 m respectively. Absorbed shortwave radiation and effective terrestrial radiation showed mean decline
of 1.54 Wm−2/100 m and 0.34 Wm−2/100 m, respectively, with the mean sky-to-earth radiation deficit amounting to about 52 Wm−2 for the lowland site and 73 Wm−2 for the highest elevated site.
Some empirical models which express shortwave and longwave radiative fluxes in terms of meteorological variables have been
validated for the lowland and mountain sites. Monthly mean daily total estimates of solar radiation obtained from ?ngst?m-Prescott
relation were quite consistent with observed values. Parameterisation of downward atmospheric radiation under all sky condition
was achieved by extending Brutsaert clear sky atmospheric model. Relationship between outgoing longwave radiation and screen
temperature at the study sites was best described by an exponential function unlike the linear relationship proposed by Monteith
and Unsworth. Net radiative flux for the lowland and mountain sites has been expressed in terms of absorbed shortwave radiation,
cloud amount and screen temperature.
Received March 5, 2001 Revised October 29, 2001 相似文献
12.
THE IMPACT OF RELATIVE HUMIDITY ON THE RADIATIVE PROPERTY AND RADIATIVE FORCING OF SULFATE AEROSOL* 下载免费PDF全文
With the data of complex refractive index of sulfate aerosol,the radiative properties of the aerosol under 8 relative humidity conditions are calculated in this paper.By using the concentration distribution from two CTM models and LASG GOALS/AGCM,the radiative forcing due to hygroscopic sulfate aerosol is simulated.The results show that:(1)With the increase of relative humidity,the mass extinction coefficiency factor decreases in the shortwave spectrum;single scattering albedo keeps unchanged except for a little increase in longwave spectrum,and asymmetry factor increases in whole spectrum.(2)Larger differences occur in radiative forcingsimulated by using two CTM data,and the global mean forcing is -0.268 and -0.816 W/m2,respectively.(3)When the impact of relative humidity on radiative property is taken into account,the distribution pattern of radiative forcing due to the wet particles is very similar to that of dry sulfate,but the forcing value decreases by 60%. 相似文献
13.
用MODIS反演北京城市地区地表反照率精度以及算法改进 总被引:3,自引:2,他引:1
MODIS(MODerate-resolution Imaging Spectroradiometer)地表反照率的精度在乡村地区已经得到了检验,但是至今没有在城市地区的有关研究。地表反照率的精度在很大程度上取决于大气订正的精度,作者利用2002年以来的北京AERONET(国际气溶胶检测网络)站点Cimel气溶胶观测资料对反射率进行大气订正,通过对比来评价MODIS地表反照率算法中大气订正的精度。结果发现,MODIS大气订正在蓝光波段具有明显的过度订正现象,MODIS大气订正后地表反射率平均偏低0.03。MODIS地表反照率在冬季有约75%的缺测,这是因为冬季严重的空气污染使得MODIS云检测得到晴空观测较少。MODIS使用三参数双向反射率函数(BRDF)要求16天以内至少有3次以上的晴空观测(MODIS算法中要求7次)。通过分析MODIS反演得到的三参数,发现虽然它们的绝对值具有明显的季节变化,但是它们的比值是十分稳定的,这样使BRDF函数降低到只需要一个参数,有效降低了对晴空观测次数的要求,这一思想可以应用到热带等晴空日数较少的地区。 相似文献
14.
采用大气辐射传输模式SES2以及2013年1月—2015年10月欧洲中期天气预报中心细网格再分析资料计算了北京地区4个观测站地面接收的短波辐射通量,分析了晴天和云天北京城郊气溶胶对总辐射的定量影响时空变化特征。结果表明:北京城区和近郊区气溶胶对总辐射的影响约为远郊区的2倍,北京南部和西部气溶胶对辐射的影响较大,晴天和云天北京城区和近郊区气溶胶对总辐射的削减值分别为146.23~180.99 W·m-2和202.11~217.02 W·m-2,晴天总辐射削减空间差异较大;秋冬季气溶胶对总辐射的影响明显大于春夏季,北京市观象台秋冬季气溶胶对总辐射的削减作用最大可达60%,较春夏季高10%~20%;北京城郊总辐射和直接辐射削减率与气溶胶光学厚度变化均呈线性关系,近地面PM2.5浓度对辐射的影响不容忽视。 相似文献
15.
Summary This paper summarizes results from a mesoscale modeling study to quantify the possible meteorological and energy-use impacts
of large-scale increases in surface albedo and vegetative fraction. Ten regions in the U.S. were characterized and simulated
in base- and modified-surface conditions. Time- and space-dependent meteorological variables were simulated for each region
in four 3-day episodes to represent a range of seasonal variations.
Using a simple interpolative procedure, a complete year of hourly weather data was created for each region (based on episodic
meteorological simulation results) and input into energy-use models. The modified weather input was used to assess the effects
of large-scale albedo and vegetative fraction changes on annual energy consumption in each of the ten areas targeted in this
study. The simulations suggest annual electricity savings of between 1and 6.7 kWh m−2 (of roof area) in residential neighborhoods and between 2 and 6.1 kWh m−2 in office areas, depending on region. Annual gas penalties amount to up to 34.8 MJ m−2 (of roof area) in residential neighborhoods and up to 21.1 MJ m−2 in office areas.
Received December 1, 1996 Revised May 11, 1998 相似文献
16.
Seasonal carbon dioxide balance and respiration of a high-arctic fen ecosystem in NE-Greenland 总被引:2,自引:0,他引:2
C. Nordstroem H. Soegaard T. R. Christensen T. Friborg B. U. Hansen 《Theoretical and Applied Climatology》2001,70(1-4):149-166
Summary Turbulent fluxes of CO2 were continuously measured by eddy correlation for three months in 1997 over a gramineous fen in a high-arctic environment
at Zackenberg (74°28′12″N, 20°34′23″W) in NE-Greenland. The measurements started on 1 June, when there was still a 1–2 m cover
of dry snow, and ended 26 August at a time that corresponds to late autumn at this high-arctic site. During the 20-day period
with snow cover, fluxes of CO2 to the atmosphere were small, typically 0.005 mg CO2 m−2 s−1 (0.41 g CO2 m−2 d−1), wheres during the thawed period, the fluxes displayed a clear diurnal variation. During the snow-free period, before the
onset of vegetation growth, fluxes of CO2 to the atmosphere were typically 0.1 mg CO2 m−2 s−1 in the afternoon, and daily sums reached values up to almost 9 g CO2 m−2 d−1. After 4 July, downward fluxes of CO2 increased, and on sunny days in the middle of the growing season, the net ecosystem exchange rates attained typical values
of about −0.23 mg m−2 s−1 at midday and max values of daily sums of −12 g CO2 m−2 d−1. Throughout the measured period the fen ecosystem acted as a net-sink of 130 g CO2 m−2. Modelling the ecosystem respiration during the season corresponded well with eddy correlation and chamber measurements.
On the basis of the eddy correlation data and the predicted respiration effluxes, an estimate of the annual CO2 balance the calender year 1997 was calculated to be a net-sink of 20 g CO2 m−2 yr−1.
Received October 6, 1999 Revised May 2, 2000 相似文献
17.
Xiaoyan WU Jinyuan XIN Wenyu ZHANG Chongshui GONG Yining MA Yongjing MA Tianxue WEN Zirui LIU Shili TIAN Yuesi WANG Fangkun WU 《大气科学进展》2020,37(12):1310-1322
Industrial pollution has a significant effect on aerosol properties in Changsha City, a typical city of central China. Therefore, year-round measurements of aerosol optical, radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed. During the observation period, the energy structure was continuously optimized, which was characterized by the reduction of coal combustion. The aerosol properties have obvious seasonal variations. The seasonal average aerosol optical depth (AOD) at 500 nm ranged from 0.49 to 1.00, single scattering albedo (SSA) ranged from 0.93 to 0.97, and aerosol radiative forcing at the top of the atmosphere (TOA) ranged from ?24.0 to 3.8 W m?2. The chemical components also showed seasonal variations. Meanwhile, the scattering aerosol, such as organic carbon, SO42?, NO3?, and NH4+ showed a decrease, and elemental carbon increased. Compared with observation in winter 2012, AOD and TOA decreased by 0.14 and ?1.49 W m?2 in winter 2014. The scattering components, SO42?, NO3? and NH4+, decreased by 12.8 μg m?3 (56.8%), 9.2 μg m?3 (48.8%) and 6.4 μg m?3 (45.2%), respectively. The atmospheric visibility and pollution diffusion conditions improved. The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol. The results indicate that Changsha is an industrial city with strong scattering aerosol. The energy structure optimization had a marked effect on controlling pollution, especially in winter (strong scattering aerosol). 相似文献
18.
Auromeet Saha Marc Mallet Jean Claude Roger Philippe Dubuisson Jacques Piazzola Serge Despiau 《Atmospheric Research》2008,90(2-4):195-ICNAA07
We present results of direct aerosol radiative forcing over a French Mediterranean coastal zone based on one year of continuous observations of aerosol optical properties during 2005–2006. Monthly-mean aerosol optical depth at 440 nm ranged between 0.1 and 0.34, with high Angstrom coefficient (α > 1.2). The single scattering albedo (at 525 nm) estimated at the surface ranged between 0.7 and 0.8, indicating significant absorption. The presence of aerosols over the Mediterranean zone during summer decreases the shortwave radiation reaching the surface by as much as 26 ± 3.9 W m− 2, and increases the top of the atmosphere reflected radiation by as much as 5.2 ± 1.0 W m− 2. The shortwave atmospheric absorption translates to an atmospheric heating of 2.5 to 4.6 K day− 1. Concerted efforts are needed for investigating the possible impact of the increase in heating rate on the maintenance of heat-waves frequently occurring over this coastal region during summer time. 相似文献
19.
Yu Zheng Huizheng Che Leiku Yang Jing Chen Yaqiang Wang Xiangao Xia Hujia Zhao Hong Wang Deying Wang Ke Gui Linchang An Tianze Sun Jie Yu Xiang Kuang Xin Li Enwei Sun Dapeng Zhao Dongsen Yang Zengyuan Guo Tianliang Zhao Xiaoye Zhang 《Acta Meteorologica Sinica》2017,31(6):1045-1061
The optical and radiative properties of aerosols during a severe haze episode from 15 to 22 December 2016 over Beijing, Shijiazhuang, and Jiaozuo in the North China Plain were analyzed based on the ground-based and satellite data, meteorological observations, and atmospheric environmental monitoring data. The aerosol optical depth at 500 nm was < 0.30 and increased to > 1.4 as the haze pollution developed. The Ångström exponent was > 0.80 for most of the study period. The daily single-scattering albedo was > 0.85 over all of the North China Plain on the most polluted days and was > 0.97 on some particular days. The volumes of fine and coarse mode particles during the haze event were approximately 0.05–0.21 and 0.01–0.43 μm3, respectively—that is, larger than those in the time without haze. The daily absorption aerosol optical depth was about 0.01–0.11 in Beijing, 0.01–0.13 in Shijiazhuang, and 0.01–0.04 in Jiaozuo, and the average absorption Ångström exponent varied between 0.6 and 2.0. The aerosol radiative forcing at the bottom of the atmosphere varied from –23 to –227,–34 to –199, and –29 to –191 W m–2 for the whole haze period, while the aerosol radiative forcing at the top of the atmosphere varied from –4 to –98, –10 to –51, and –21 to –143 W m–2 in Beijing, Shijiazhuang, and Jiaozuo, respectively. Satellite observations showed that smoke, polluted dust, and polluted continental components of aerosols may aggravate air pollution during haze episodes. The analysis of the potential source contribution function and concentration-weighted trajectory showed that the contribution from local emissions and pollutants transport from upstream areas were 190–450 and 100–410 μg m–3, respectively. 相似文献
20.
Ülle Kikas Aivo Reinart Anna Pugatshova Eduard Tamm Vidmantas Ulevicius 《Atmospheric Research》2008,90(2-4):211-ICNAA07
The microphysical structure, chemical composition and prehistory of aerosol are related to the aerosol optical properties and radiative effect in the UV spectral range. The aim of this work is the statistical mapping of typical aerosol scenarios and adjustment of regional aerosol parameters. The investigation is based on the in situ measurements in Preila (55.55° N, 21.00° E), Lithuania, and the AERONET data from the Gustav Dalen Tower (58 N, 17 E), Sweden.Clustering of multiple characteristics enabled to distinguish three aerosol types for clear-sky periods: 1) clean maritime–continental aerosol; 2) moderately polluted maritime–continental aerosol; 3) polluted continental aerosol. Differences between these types are due to significant differences in aerosol number and volume concentration, effective radius of volume distribution, content of SO4− ions and Black Carbon, as well as different vertical profiles of atmospheric relative humidity. The UV extinction, aerosol optical depth (AOD) and the Ångstrom coefficient α increased with the increasing pollution. The value α = 1.96 was observed in the polluted continental aerosol that has passed over central and eastern Europe and southern Russia. Reduction of the clear-sky UV index against the aerosol-free atmosphere was of 4.5%, 27% and 41% for the aerosol types 1, 2 and 3, respectively. 相似文献