首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 94 毫秒
1.
基于激光雷达资料的气溶胶辐射效应研究   总被引：2，自引：0，他引：2  
利用新型激光雷达气溶胶探测资料及综合数值模式,以地形复杂的兰州市及周边地区冬季典型天气形势下的大气边界层为研究对象,通过理想试验模拟研究了城市气溶胶辐射效应与大气边界层的相互作用。结果表明:夜间,低空(50~600 m)气溶胶所在气层冷却效应明显,温度降低0.13~0.18℃,600 m高度以上,气溶胶浓度较低,其冷却效应较小,温度降低不足0.1℃;白天,受气溶胶短波辐射效应影响,边界层内增温明显,增温最大值位于低层脱地逆温层顶300 m高度附近,600 m以上由于气溶胶浓度减小,加热率亦降低,增温由0.2℃减至0.1℃。此外,气溶胶的存在使得所在层的风速降低。可见,激光雷达探测资料在边界层模式中有很好的应用价值,对于研究气溶胶辐射效应的大气边界层响应有重要意义。  相似文献   

2.
不同污染条件下气溶胶对短波辐射通量影响的模拟研究   总被引：1，自引：0，他引：1  
将高光谱分辨率的气溶胶光学参数化方案应用于高精度的辐射传输模式BCC_RAD（974带）中,研究不同污染状况下气溶胶在地表与近地层大气中造成的直接辐射强迫与辐射强迫效率。发现气溶胶在地表产生的直接辐射强迫为负,在近地层大气中产生的直接辐射强迫为正,且随气溶胶浓度的升高变大,说明大气气溶胶的含量越高,单位气溶胶光学厚度产生的直接辐射强迫越大。将短波划分为3个波段:紫外、可见光和近红外,发现在紫外、可见光和近红外波段中,不同污染状况下气溶胶在地表造成的直接辐射强迫范围分别为:-1.36—-13.66、-3.03—-32.41和-2.74—-28.62 W/m2,在近地层大气中产生的直接辐射强迫范围分别为0.44—4.26、0.99—9.80和0.93—8.87 W/m2。通过进一步对比自然和人为气溶胶的影响,发现人为气溶胶在地表和大气层顶产生的负直接辐射强迫以及对整层和近地面大气造成的正直接辐射强迫均大于自然气溶胶的影响,且上述两种排放源的气溶胶对整层大气辐射收支的影响主要集中在800 hPa高度以下的大气中。按照地表直接辐射强迫大小来分析不同种类气溶胶的影响,结果为硫酸盐>有机碳>黑碳>海盐>沙尘;按照近地层大气直接辐射强迫大小排序则为黑碳>有机碳>沙尘>海盐>硫酸盐。最后,通过分析散射型气溶胶与吸收型气溶胶对辐射通量的影响,还探究了大气中散射与吸收过程的异同。   相似文献   

3.
2017年12月22日至2018年1月18日利用无人机携带温、湿和颗粒物浓度探测仪对南京地区灰霾污染条件下大气边界层垂直结构开展加密观测。通过比较不同灰霾污染条件下温度、湿度和PM2.5（直径小于2.5微米的颗粒物）浓度的垂直结构差异,结合地面热通量、2米空气温度、相对湿度、风速、风向及主要大气污染物（如臭氧和PM2.5）浓度,定量评估了气溶胶辐射效应对边界层和夹卷过程的影响。分析表明,灰霾或气溶胶削弱到达地表太阳辐射,减小地表感热通量,延迟边界层发展,增加近地层大气稳定度,降低边界层高度,并加重灰霾污染。灰霾污染物在混合层顶处累积,导致PM2.5浓度最大变化出现在边界层顶部而不是近地层。气溶胶辐射效应对夹卷特征及其特征参数有重要影响。灰霾浓度升高时,夹卷区厚度增加;无量纲化夹卷速度随对流理查逊数的变化不再符合负1次方幂函数关系,与大涡模拟结果一致。本研究进一步指出,为提高重霾污染条件下天气和空气质量数值预报水平,必须考虑气溶胶辐射效应对边界层和夹卷参数化的影响。  相似文献   

4.
复杂地形城市冬季边界层对气溶胶辐射效应的响应   总被引：6，自引：3，他引：6  
郑飞  张镭  朱江 《大气科学》2006,30(1):171-179
作者着眼于城市气溶胶辐射效应与大气边界层的相互作用问题,针对地形复杂的兰州市及周边地区,开发应用了WRF(Weather Research and Forecasting,天气研究和预报)模式,使之与包含了大气气溶胶辐射效应和气溶胶粒子扩散的综合大气边界层数值模式嵌套起来.通过个例分析,揭示了冬季气溶胶辐射效应对边界层结构的定量影响.主要特征为夜间气溶胶的长波辐射效应使地面附近的气温增高,增温幅度为0.1～0.3 K/h,使低空(25～300 m)大气层冷却,降温幅度为0.08～0.15 K/h,风速在150 m以下减小;白天气溶胶的短波辐射效应使地面层内明显增温,1 h内升温约0.5 K,增温最大值在混合层顶500～600 m高度.受增温影响,垂直风场和水平风场随之调整,风速在450 m以下增大约0.1 m/s左右,而在450 m以上风速减小0.1 m/s左右.  相似文献   

5.
A 3-D mesoscale numerical model of cloud formation, fog, and aerosol transport in an orographically inhomogeneous atmospheric boundary layer (ABL) has been considered. Streamlining of the flow around isolated obstacles in steady-state stratified flow has been studied. An account of radiation transfer in the ABL has made it possible to analyze the combined effect of orography and radiation on the formation of fog and cloud, to analyze the interaction between radiation and cloudiness, as well as their effect on the change of mesoscale circulation in the atmosphere and on variations in the optical characteristics of the atmosphere. The transport of aerosols from various sources has been modelled. The impact of orography, cloudiness and atmospheric stratification, governed by the radiative regime of the ABL, on the propagation of admixtures and surface deposition has been studied. The atmospheric aerosol turbidity in zones of intensive industrial pollution has been assessed.  相似文献   

6.
As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS,and the transport model of BC aerosols has also been established and combined with the RIEMS model.Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July.  相似文献   

7.
一维辐射对流模式对云-辐射强迫的数值模拟研究   总被引：1，自引：9，他引：1  
利用一维辐射－对流气候模式, 详细研究了云量、云光学厚度以及云高等要素的变化对大气顶和地面太阳短波辐射和红外长波辐射通量以及云的辐射强迫的影响, 给出了计算这些物理量的经验拟合公式。结果表明, 云具有极为重要的辐射－气候效应。云量、云光学厚度以及云高即使只有百分之几的变化, 所带来的辐射强迫也可以与大气二氧化碳浓度加倍所产生的辐射强迫（3.75 W/m2）相比拟。例如, 当分别给它们+3%的扰动时, 即取云量变化0.015, 云光学厚度变化0.27, 以及云高变化0.15 km时（在实际的地球大气中, 这种尺度的变化是完全可能发生的）, 那么,可以得到地气系统的太阳短波辐射强迫-3.10 W/m2以及红外长波辐射强迫-1.77 W/m2, 二者之和为-4.78 W/m2, 已经完全可以抵消大气二氧化碳浓度加倍所产生的辐射强迫。但是, 当云量、云光学厚度以及云高向相反方向产生类似扰动时, 所产生的辐射强迫可能极大地放大二氧化碳浓度增加所产生的增强温室效应。因此, 研究结果揭示出, 不管是为了解释过去的气候变化, 还是预测未来的气候变化, 亟待加强在一个变化了的气候环境（例如地面温度升高）下, 云将发生何种变化的研究。  相似文献   

8.
Simplified numerical models of the atmospheric boundary layer (ABL) are useful both for understanding the underlying dynamics and potentially providing parsimonious modelling approaches for inclusion in larger models. Herein the governing equations of a simplified slab model of the uniformly mixed, purely convective, diurnal ABL are shown to allow immediate solutions for the potential temperature and specific humidity as functions of the ABL height and net radiation when expressed in integral form. By employing a linearized saturation vapour relation, the height of the mixed layer is shown to obey a non-linear ordinary differential equation with quadratic dependence on ABL height. A perturbation solution provides general analytical approximations, of which the leading term is shown to represent the contribution under equilibrium evaporation. These solutions allow the diurnal evolution of the height, potential temperature, and specific humidity (i.e., also vapour pressure deficit) of the mixed layer to be expressed analytically for arbitrary radiative forcing functions.  相似文献   

9.
The climatic effects of the atmospheric boundary aerosols are studied by the use of a three-dimensional climatemodel.Simulated results show that the climate states both at the surface and in the atmosphere change remarkably whenthe aerosols with different optical thicknesses and properties are introduced into the atmospheric boundary layer of themodel.The aerosols absorb and scatter the solar shortwave radiation,therefore,they reduce the solar energy reachingthe ground surface and decrease the surface and the soil temperatures.The temperature in the boundary layer increasesbecause of the supplementary absorption of radiation by the boundary aerosols.In the atmosphere,the temperatures atall isobaric surfaces rise up except for the 100 hPa level.The atmospheric temperatures below the 500 hPa level aredirectly influenced by the boundary aerosols,while the atmospheric temperatures above the 500 hPa level are influencedby the heating due to convective condensation and the changes in the vertical motion field.Cyclonic differential circula-tions appear over the desert areas at the low levels,and anticyclonic differential circulations exist at the upper levels inthe horizontal flow fields.The vertical motions change in correspondence with the differential circulations.The changesin precipitation are directly related to that of vertical motions.The mechanisms of climate effects of the boundaryaerosols are also discussed in this paper.  相似文献   

10.
北京秋季一次降雪前污染天气的激光雷达观测研究   总被引：1，自引：0，他引：1  
以2009年11月5~8日北京地区发生的一次特殊天气形势下的重污染天气过程为例,研究分析本次污染特点和大气边界层结构特征以及此天气过程的大气温度和相对湿度结构特点。激光雷达是探测大气边界层及气溶胶的一个高效工具,利用ALS300激光雷达系统测量信号,应用Fernald方法反演大气消光系数,根据反演的气溶胶消光系数的最大突变,即最大递减率的高度来确定大气边界层的高度。利用其观测的退偏比分析大气污染物特性。利用微波辐射计数据,确定大气温度和湿度时空特征。研究结果表明:在本次污染天气下,大气具有很强的逆温结构,逆温最大可达近1 K(100 m)-1,500 m以上的大气相对湿度很低,在这种天气特征下的大气边界层高度在400 m左右,非常稳定。污染结束降雪开始前,大气逆温结构消失,大气湿度大幅度增加,接近饱和。根据lidar(light detection and ranging)退偏比的分析,本次污染天气是一次典型的烟尘类颗粒物的污染,污染具有区域性特点。PM2.5(空气动力学当量直径小于等于2.5μm的颗粒物)与AOT(Aerosol Optical Thickness)之间有明显的线性关系,相关系数达到0.72。该lidar系统能够反演出秋季降雪前本次污染天气背景下北京城区上空的大气污染特性和大气边界层高度。  相似文献   

11.
The climatic effects of the atmospheric boundary aerosols are studied by the use of a three-dimensional climate model.Simulated results show that the climate states both at the surface and in the atmosphere change remarkably when the aerosols with different optical thicknesses and properties are introduced into the atmospheric boundary layer of the model.The aerosols absorb and scatter the solar shortwave radiation,therefore,they reduce the solar energy reaching the ground surface and decrease the surface and the soil temperatures.The temperature in the boundary layer increase because of the supplementary absorption of radiation by the boundary aerosols.In the atmosphere,the temperatures at all isobaric surfaces rise up except for the 100 hPa level.The atmospheric temperatures below the 500 hPa level are directly influenced by the boundary aerosols,while the atmospheric temperatures above the 500 hPa level are influenced by the heating due to convective condensation and the changes in the vertical motion field.Cyclonic differential circulations appear over the desert areas at the low levels,and anticyclonic differential circulations exist at the upper levels in the horizontal flow fields.The vertical motions change in correspondence with the differential circulations.The changes in precipitation are directly related to that of vertical motions.The mechanisms of climate effects of the boundary aerosols are also discussed in this paper.  相似文献   

12.
During a haze event in Baltimore, U.S.A. from July 6 to 8, 2002, smoke from forest fires in the Québec region (Canada), degraded air quality and impacted upon local climate, decreasing solar radiation and air temperature. The smoke particles in and above the atmospheric boundary layer (ABL) served as a tracer and provided a unique opportunity to investigate the ABL structure, especially entrainment. Elastic backscatter lidar measurements taken during the haze event distinctly reveal the downward sweeps (or wisps) of smoke-laden air from the free atmosphere into the ABL. Visualisations of mechanisms such as dry convection, the entrainment process, detrainment, coherent entrainment structures, and mixing inside the ABL, are presented. Thermals overshooting at the ABL top are shown to create disturbances in the form of gravity waves in the free atmosphere aloft, as evidenced by a corresponding ripple structure at the bottom of the smoke layer. Lidar data, aerosol ground-based measurements and supporting meteorological data are used to link free atmosphere, mixed-layer and ground-level aerosols. During the peak period of the haze event (July 7, 2002), the correlation between time series of elastic backscatter lidar data within the mixed layer and the scattering coefficient from a nephelometer at ground level was found to be high (R=0.96 for z =324 m, and R=0.89 for z=504 m). Ground-level aerosol concentration was at a maximum about 2 h after the smoke layer intersected with the growing ABL, confirming that the wisps do not initially reach the ground.  相似文献   

13.
The atmospheric boundary layer (ABL) is characterized by the turbulence eddies that transport heat, momentum, gaseous constituents and particulate matter from Earth’s surface to the atmosphere and vice versa. Thus, the determination of its height has a great importance in a wide range of applications like air quality forecasting and management. This study aims at estimating the height of the ABL in a suburban environment and at investigating its temporal variation and its relationship with meteorological variables, like temperature and wind. For this purpose, radiosonde data from the suburban area of Thessaloniki, Greece, are analyzed. The data analysis reveals that ABL height is usually below 200 m in the morning hours during all seasons of the year and that is also low when near-surface temperature and wind speed are low too. Additionally, noon ABL height exhibits a strong seasonal variation, reaching higher values during summer than during winter.Very high values of ABL height, of the order of ~3,000 m, are occasionally observed in Thessaloniki during summer. Moreover, sea breeze development during summer is related to a slight reduction of the ABL height.  相似文献   

14.
污染大气边界层的长波冷却率模式   总被引：2，自引：0，他引：2  
考虑大气气溶胶在长波窗区的散射和吸收作用以及水汽的连续吸收作用，建立了一个适用于污染大气边界层的长波冷却率模式。计算结果表明：当单位面积气柱中气溶胶含量为７８５．９ｍｇ／ｍ２时，气溶胶的作用可使到达地面的长波向下辐射增大３９Ｗ／ｍ２。在大气窗区，大气气溶胶和水汽的连续吸收对长波冷却率的影响是同等重要的。在水汽含量和气溶胶浓度较大的大气边界层内，水汽连续吸收的冷却率最大时可达１．３Ｋ／ｄ，气溶胶的冷却率最大时可达到１．６６Ｋ／ｄ，二者对长波冷却率的贡献均不容忽视  相似文献   

15.
Among anthropogenic perturbations of the Earths atmosphere, greenhouse gases and aerosols are considered to have a major impact on the energy budget through their impact on radiative fluxes. We use three ensembles of simulations with the LMDZ general circulation model to investigate the radiative impacts of five species of greenhouse gases (CO2, CH4, N2O, CFC-11 and CFC-12) and sulfate aerosols for the period 1930–1989. Since our focus is on the atmospheric changes in clouds and radiation from greenhouse gases and aerosols, we prescribed sea-surface temperatures in these simulations. Besides the direct impact on radiation through the greenhouse effect and scattering of sunlight by aerosols, strong radiative impacts of both perturbations through changes in cloudiness are analysed. The increase in greenhouse gas concentration leads to a reduction of clouds at all atmospheric levels, thus decreasing the total greenhouse effect in the longwave spectrum and increasing absorption of solar radiation by reduction of cloud albedo. Increasing anthropogenic aerosol burden results in a decrease in high-level cloud cover through a cooling of the atmosphere, and an increase in the low-level cloud cover through the second aerosol indirect effect. The trend in low-level cloud lifetime due to aerosols is quantified to 0.5 min day–1 decade–1 for the simulation period. The different changes in high (decrease) and low-level (increase) cloudiness due to the response of cloud processes to aerosols impact shortwave radiation in a contrariwise manner, and the net effect is slightly positive. The total aerosol effect including the aerosol direct and first indirect effects remains strongly negative.  相似文献   

16.
This paper analyzes trends of temperatures over Africa and seeks to quantify the most significant processes. Observations of air temperature reveal significant warming trends in the 925–600 hPa layer over tropical west Africa and the east Atlantic. This is related to the influence of desert dust and biomass burning emissions on the atmospheric energy budget. We calculate a net radiative absorption of ～??20 W m???2. The southern (northern) plume is rich in short-lived greenhouse gases (dust aerosols), and the atmospheric response, according to a simplified radiative transfer model, is a >3°C heating of the 2–4 km layer. The observed pattern of warming coincides with a mixture of dust, black carbon and short-lived greenhouse gases in space, time and height. Physical forcing provides a secondary source of regional warming, with sinking motions over the Sahel. The elevated warm layer stabilizes the lower atmosphere over and west of Africa, so drying trends may be anticipated.  相似文献   

17.
Anthropogenic aerosols in the lower troposphere increase the absorption and scattering of solar radiation by air and clouds, causing a warmer atmosphere and a cooler surface. It is suspected that these effects contribute to slow down the hydrological cycle. We conducted a series of numerical experiments using a limited area atmospheric model to understand the impacts of aerosol radiative forcing on the rainfall process. Experiments with different radiative conditions under an idealized setting revealed that increasing atmospheric forcing and decreasing surface forcing of radiation causes reductions in rainfall. There was no relationship of top of the atmosphere forcing to the rainfall yield. The model was then used to simulate a domain covering southern part of Sri Lanka, over for the period from November 2002 to July 2003. For a given radiative forcing, instances with lower rainfall yields showed larger fractional reductions in rainfall. The trends in seasonal rainfall observed over the site in past 30 years in a different study confirms this finding. We conclude that the negative impact of increase of anthropogenic aerosols on rainfall would be more severe on regions and seasons with lower rainfall yields. The consequences of this problem on the industries that critically depend on well-distributed rainfall like non-irrigated agriculture and on the general livelihood of societies in low-rain areas can be serious.  相似文献   

18.
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   

19.
本文利用—维地气耦合模式研究了大气边界层气溶胶和云的气候效应。模拟结果表明,边界层内低云和气溶胶都能使地面和土壤温度下降;而低云还能使云下大气降温。当云和气溶胶并存时,气溶胶的作用不明显。云和气溶胶的温度效应不仅取决于它们的光学厚度和光学特性,还与下垫面的物理特性有关,沙漠下垫面所受的影响要比一般性裸土下垫面的大。   相似文献   

20.
Aerosol optical properties and direct radiative effects on surface irradiance were examined using seven years(2006–2012)of Cimel sunphotometer data collected at Panyu—the main atmospheric composition monitoring station in the Pearl River Delta(PRD) region of China. During the dry season(October to February), mean values of the aerosol optical depth(AOD)at 550 nm, the ?ngstr?m exponent, and the single scattering albedo at 440 nm(SSA) were 0.54, 1.33 and 0.87, respectively.About 90% of aerosols were dominated by fine-mode strongly absorbing particles. The size distribution was bimodal, with fine-mode particles dominating. The fine mode showed a peak at a radius of 0.12 μm in February and October(~0.10μm~3μm~(-2)). The mean diurnal shortwave direct radiative forcing at the surface, inside the atmosphere(FATM), and at the top of the atmosphere, was-33.4 ± 7.0, 26.1 ± 5.6 and-7.3 ± 2.7 W m~(-2), respectively. The corresponding mean values of aerosol direct shortwave radiative forcing per AOD were-60.0 ± 7.8, 47.3 ± 8.3 and-12.8 ± 3.1 W m~(-2), respectively. Moreover,during the study period, FATMshowed a significant decreasing trend(p 0.01) and SSA increased from 0.87 in 2006 to 0.91 in 2012, suggesting a decreasing trend of absorbing particles being released into the atmosphere. Optical properties and radiative impacts of the absorbing particles can be used to improve the accuracy of inversion algorithms for satellite-based aerosol retrievals in the PRD region and to better constrain the climate effect of aerosols in climate models.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号