硫酸盐气溶胶间接效应对中国东部冬季气候的影响

气溶胶间接效应通过对云的作用来影响气候,其过程复杂且不确定性较大。本研究利用美国国家大气研究中心（NCAR）的公共大气模式CAM5.1,通过改变模式中硫酸盐气溶胶转化为云凝结核数浓度的数量,设计了硫酸盐气溶胶间接效应的敏感性试验,通过与控制试验对比来研究其间接效应对中国东部地区冬季云、降水和季风强度的影响。结果表明：在东亚地区云凝结核形成过程中,硫酸盐气溶胶占绝对的主导地位。硫酸盐气溶胶间接效应导致中国东部地区冬季云凝结核和云滴数浓度显著增加,海洋和陆地低层的云滴有效半径减小和总云液水路径的增加,导致了云反照率的增加。引起的负辐射强迫使地表和大气降温,海平面气压升高,增加的海陆气压梯度导致中国南方地区东亚冬季风增强,总降水率减少。硫酸盐气溶胶间接效应可能不是东亚冬季风在20世纪80年代中期年际变率减弱的原因。     

黑碳气溶胶气候效应的研究进展

 黑碳气溶胶能吸收从可见光到红外波段的太阳辐射,已经被部分研究认为是造成全球变暖的一个潜在因子。黑碳气溶胶既可以通过直接气候效应改变地-气系统的辐射平衡,又可以作为云凝结核或冰核改变云的微物理特性,间接影响区域或全球气候。对黑碳气溶胶的辐射强迫及其气候效应的研究现状进行总结和分析后,指出了目前黑碳气溶胶气候效应研究中存在的不确定性,并对未来的相关研究提出了一些建议。     

基于MODIS的春、夏季中国近海气溶胶对于云参数的影响差异研究

通过分析中国近海MODIS数据中气溶胶参数与云参数的相互关系,讨论了该区域气溶胶的间接效应及其对于云的可能影响.结果表明,在中国近海,气溶胶具有明显的间接效应,而且由于气溶胶种类和水汽的季节变化,使得气溶胶的间接作用具有很强的时间变化特征.在夏季,由于人为气溶胶占主导,它作为有效的云凝结核,使得气溶胶光学厚度（AOT）分别与云凝结核数（CCN）有正相关、与云滴有效半径（CER）有负相关性、与云光学厚度（COT）也存在着正相关,气溶胶的间接效应明显;在春季,由于沙尘气溶胶盛行,同时沙尘并不是很好的云凝结核,使得气溶胶光学厚度（AOT）分别与云凝结核数（CCN）的正相关减弱、与云滴有效半径（CER）则由夏季的负相关变为正相关、与云光学厚度（COT）存在弱的负相关,气溶胶的间接效应不明显.     

基于层积云飞机观测资料评估气溶胶间接效应

利用2009年4、5月美国浅薄低云观测项目(RACORO)的层积云飞机观测资料,使用两种方法对气溶胶间接效应进行了估算:根据云滴数浓度定义的值(AIE_n)和根据有效半径定义的值(AIE_s)。AIE_n几乎都比AIE_s大,尤其在中等含水量条件下。理论推导表明,AIE_n与AIE_s的偏差应与气溶胶对云滴谱离散度的影响有关,即离散度效应。当AIE_n加上离散度效应后,数值与AIE_s十分接近,证实了理论预期。离散度效应对气溶胶间接效应的贡献主要为抵消作用,这种抵消作用在中等含水量时最大,当含水量为0.24 g/m~3时达到37%左右。该研究成果增强了对气溶胶-云相互作用的理论认识,将有助于增强对模式和观测中气溶胶间接效应的准确评估。     

基于CMIP6强迫模拟分析人为气溶胶的气候效应(二)——诊断方法在分类评估中的重要性

对气溶胶气候效应开展分类评估并探讨诊断方法的合理性。人为气溶胶辐射效应对计算云辐射强迫的影响为0.38 W·m~(-2)。诊断评估气溶胶对云辐射强迫的影响需要排除这个偏差。两种基于不同试验设计诊断得出的半直接效应分别为0.21和0.09 W·m~(-2),存在显著差异。主要原因可能是人为气溶胶影响云辐射强迫的不同机制之间在模式模拟过程中不断地相互交织,不是简单的线性叠加关系。模式诊断得出的Twomey效应不仅包括Twomey效应本身,还包括Twomey效应引起的部分快速调整。总之,利用模式评估分析人为气溶胶气候效应需要注意审查试验设计和诊断方法的合理性。     

气溶胶影响云和降水的机理和观测研究进展

气溶胶对云和降水的影响,对于气候系统、大气环境以及水循环至关重要。气溶胶粒子作为云凝结核和大气冰核影响云的微物理过程,进而影响雨、雪、雹和其他形式的降水。近年来,在理解气溶胶的化学成分,气溶胶微物理特性以及气溶胶作为云凝结核和大气冰核影响云降水等方面已取得重大进展。本文对于气溶胶的概念、来源以及气溶胶的直接和间接效应进行了简要概述,重点总结了国内外在气溶胶影响云和降水的机理研究方面的成果,回顾了近年来利用卫星、地面观测设备、机载探测设备等对气溶胶和云进行遥感观测和直接观测所获得的观测事实并讨论了其可能的物理机制,在总结前人研究成果的基础上对未来的研究方向进行了讨论。     

大气气溶胶变化对农业影响的研究进展

随着工业化和城市化的迅速发展,大气气溶胶含量和种类明显增加,它们通过直接吸收和反射太阳辐射以及改变其它辐射强迫因子(云、臭氧)的大小间接影响地气系统的能量收支,从而影响气候。气溶胶变化对气候的影响已有较多的研究,而对植被(农业)的影响是一个相对较新的研究领域,文章简要概述了大气气溶胶辐射强迫效应和大气气溶胶对农业的影响研究现状及国内外主要研究成果,并对气溶胶监测方法及模式评估方面可能存在的问题作了简单的分析。     

RegCM3引入气溶胶间接气候效应模拟效果对比

利用2006年区域气候模式RegCM3和Streets气溶胶排放源清单,在原模式中引入间接气候效应模块,改进云降水方案,对硫酸盐气溶胶的时空分布、辐射强迫效应进行了模拟研究。结果表明：硫酸盐气溶胶辐射强迫有明显季节变化;直接效应使地表温度降低,冬春季大值区出现在四川盆地,夏季大值区出现在华北平原。对降水的影响,主要表现在西南—东北水汽输送带上降水减少;其间接气候效应主要表现在使南方地区温度上升、北方地区温度下降;珠江流域和黄河流域降水减少,长江流域和东北地区降水增加。总的来说,直接效应大于间接效应。     

气候模式分辨率对气溶胶气候效应模拟结果的影响

气候模式分辨率作为影响模式模拟结果的重要因素,其对气溶胶与云相互作用的影响尚未全面认识。利用公共大气模型CAM5.3在3种分辨率（2°、1°、0.5°）下,分别采用2000年和1850年气溶胶排放情景进行试验,检验提高分辨率是否能改进气候模式的模拟能力,分析不同分辨率下气溶胶气候效应的异同,探索模式分辨率对气溶胶气候效应数值模拟结果的影响。通过观测资料与模式结果对比发现,提高分辨率可以明显改进模式对总云量、云短波辐射强迫的模拟能力,0.5°分辨率下模拟结果与观测更接近,其他变量并无明显改善。在不同分辨率下,全球平均的气溶胶气候效应较为一致,总云量、云水路径均增加,云短波和长波辐射强迫均加强,而云顶的云滴有效半径和降水均减小,地面气温降低。不同分辨率下,气溶胶增加引起的气溶胶光学厚度、云水路径、地面温度、云短波和长波辐射强迫变化的纬向平均分布相似但大小存在差异;而降水和云量变化的纬向分布与大小均存在较大差异,在区域尺度上还存在较大的不确定性。全球平均而言, 0.5°分辨率下气溶胶的间接辐射强迫相比1°分辨率下的结果降低了2.5%,相比2°分辨率下的结果降低了6.4%。提高模式分辨率可以部分改进模式模拟能力,同时,气溶胶的间接效应随着模式分辨率的提高而减弱。但气溶胶引起的云量、降水的变化在不同分辨率下差异较大,存在较大的不确定性。      

全国各省市气象科技期刊文章摘编46

1RegCM3引入气溶胶间接气候效应模拟效果对比 气象与环境学报2012年第l期徐萌柳浙江国际海运职业技术学院316021 摘要：采用高分辨率模式和最新资料对硫酸盐的辐射强迫和气候效应重新评估很有意义。利用2006年区域气候模式RegCM3和Streets气溶胶排放源清单,在原模式中引入间接气候效应模块,改进云降水方案,对硫酸盐气溶胶的时空分布、辐射强迫效应进行了模拟研究。     

A Review of Aerosol Optical Properties and Radiative Effects

Atmospheric aerosols influence the earth's radiative balance directly through scattering and absorbing solar radiation, and indirectly through affecting cloud properties. An understanding of aerosol optical properties is fundamental to studies of aerosol effects on climate. Although many such studies have been undertaken, large uncertainties in describing aerosol optical characteristics remain, especially regarding the absorption properties of different aerosols. Aerosol radiative effects are considered as either positive or negative perturbations to the radiation balance, and they include direct, indirect (albedo effect and cloud lifetime effect), and semi-direct effects. The total direct effect of anthropogenic aerosols is negative (cooling), although some components may contribute a positive effect (warming). Both the albedo effect and cloud lifetime effect cool the atmosphere by increasing cloud optical depth and cloud cover, respectively. Absorbing aerosols, such as carbonaceous aerosols and dust, exert a positive forcing at the top of atmosphere and a negative forcing at the surface, and they can directly warm the atmosphere. Internally mixed black carbon aerosols produce a stronger warming effect than externally mixed black carbon particles do. The semi-direct effect of absorbing aerosols could amplify this warming effect. Based on observational (ground-and satellite-based) and simulation studies, this paper reviews current progress in research regarding the optical properties and radiative effects of aerosols and also discusses several important issues to be addressed in future studies.     

Elicitation of Expert Judgments of Aerosol Forcing

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).     

Impacts of greenhouse gases and aerosol direct and indirect effects on clouds and radiation in atmospheric GCM simulations of the 1930–1989 period

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.     

Assessment of the first indirect radiative effect of ammonium-sulfate-nitrate aerosols in East Asia

A physically based cloud nucleation parameterization was introduced into an optical properties/radiative transfer module incorporated with the off-line air quality modeling system Regional Atmospheric Modeling System (RAMS)-Models-3 Community Multi Scale Air Quality (CMAQ) to investigate the distribution features of the first indirect radiative effects of sulfate, nitrate, and ammonium-sulfate-nitrate (ASN) over East Asia for the years of 2005, 2010, and 2013. The relationship between aerosol particles and cloud droplet number concentration could be properly described by this parameterization because the simulated cloud fraction and cloud liquid water path were generally reliable compared with Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved data. Simulation results showed that the strong effect of indirect forcing was mainly concentrated in Southeast China, the East China Sea, the Yellow Sea, and the Sea of Japan. The highest indirect radiative forcing of ASN reached ?3.47 W m^?2 over Southeast China and was obviously larger than the global mean of the indirect forcing of all anthropogenic aerosols. In addition, sulfate provided about half of the contribution to the ASN indirect forcing effect. However, the effect caused by nitrate was weak because the mass burden of nitrate was very low during summer, whereas the cloud fraction was the highest. The analysis indicated that even though the interannual variation of indirect forcing magnitude generally followed the trend of aerosol mass burden from 2005 to 2013, the cloud fraction was an important factor that determined the distribution pattern of indirect forcing. The heaviest aerosol loading in North China did not cause a strong radiative effect because of the low cloud fraction over this region.     

中国地区云光学厚度和云滴有效半径变化趋势

利用ISCCP最新的D2云气候资料集和MODIS云的资料,给出中国地区云的光学厚度和云滴有效半径的分布特征;分别对季节平均和年平均时间序列进行线性趋势分析,并进行了显著性检验。结果表明：夏季云的光学厚度和有效半径的变化趋势最显著。结合云量变化情况,可发现云滴有效半径的变化对云光学厚度的影响可能在夏季最大,也就是说,气溶胶的间接气候效应可能在夏季最强;云量、云光学厚度和云滴有效半径的变化也表明长江以南地区和青藏高原地区可能是气溶胶间接气候效应比较显著的地区。中国地区冰云光学厚度与有效直径的相关具有很强的区域特征,说明冰云的微物理机制比水云更复杂。     

Cloud optical thickness and albedo retrievals from bidirectional reflectance measurements of POLDER instruments during ACE‐2

The POLDER instrument is devoted to global observations of the solar radiation reflected by the Earth–atmosphere system. The airborne version of the instrument was operated during the ACE‐2 experiment, more particularly as a component of the CLOUDYCOLUMN project of ACE‐2 that was conducted in summer 1997 over the subtropical northeastern Atlantic ocean. CLOUDYCOLUMN is a coordinated project specifically dedicated to the study of the indirect effect of aerosols. In this context, the airborne POLDER was assigned to remote measurements of the cloud optical and radiative properties, namely the cloud optical thickness and the cloud albedo. This paper presents the retrievals of those 2 cloud parameters for 2 golden days of the campaign 26 June and 9 July 1997. Coincident spaceborne ADEOS‐POLDER data from 2 orbits over the ACE‐2 area on 26 June are also analyzed. 26 June corresponds to a pure air marine case and 9 July is a polluted air case. The multidirectional viewing capability of airborne POLDER is here demonstrated to be very useful to estimate the effective radius of cloud droplet that characterizes the observed stratocumulus clouds. A 12 μm cloud droplet size distribution appears to be a suitable cloud droplet model in the pure marine cloud case study. For the polluted case the mean retrieved effective droplet radius is of the order of 6–10 μm. This only preliminary result can be interpreted as a confirmation of the indirect effect of aerosols. It is consistent with the significant increase in droplet concentration measured in polluted marine clouds compared to clean marine ones. Further investigations and comparisons to in‐situ microphysical measurements are now needed.