南海中尺度大气海浪耦合模式及其对该区一次强台风过程的模拟研究

利用中尺度大气模式MM5(V3)和第3代海浪模式WWATCH建立考虑大气-海浪相互作用的风浪耦合模式.在耦合模式中引入考虑波浪影响的海表粗糙度参数化方案,大气模式分量提供海面10 m风场驱动海浪模式分量运行,并利用海浪模式分量反馈的波龄参数计算海表粗糙度.利用耦合模式模拟南海的一次台风过程,通过3组对比试验,检验耦合模式对台风过程的模拟效果并研究大气-海浪相互作用对台风过程的影响.结果表明:耦合模式能够较好地模拟南海的台风过程,与非耦合大气模式相比,其模拟的台风强度略有增强,路径变化不大;耦合模式对台风过程中海表热通量及降水影响显著,在台风充分发展过程中,耦合模式模拟的海表热通量增强,台风螺旋雨带上尤其是台风路径的右侧,耦合模式模拟的降水强于非耦合模式;耦合模式较好地模拟了台风过程海浪场的分布和演变,与非耦合模式相比,其模拟的海浪场增强,与实际更为接近;考虑了海表粗糙度对波浪的依赖关系后,海浪场同时影响海表的动力过程和热力过程,从本次个例看,在台风发展初期,海浪对海表动力作用影响显著,其反馈作用使台风系统减弱,但在台风充分发展后,耦合系统中海表热通量增加,热力作用显著增强,海浪的反馈作用有利于台风系统的发展和维持.     

东亚夏季气溶胶—云—降水分布特征及其相互影响的资料分析

东亚季风气候受到自然因素和人类活动的共同影响,而人类活动因子中气溶胶的作用尤为关键,采用诊断分析的手段研究东亚地区气溶胶的特征及其与云和降水的相互关系具有重要的科学意义。本文利用MODIS(moderate-resolution imaging spectroradiometer)气溶胶和云资料以及TRMM(Tropical Rainfall Measuring Mission)降水数据,分析了东亚夏季气溶胶、云、降水的时空分布特征,研究了气溶胶与云和降水的相互关系。结果表明:中国四个典型地区(珠三角、长三角、四川盆地、京津唐)2001～2011年夏季(6～8月)平均气溶胶光学厚度(Aerosol Optical Depth, AOD)变化范围为0.40～0.68,云光学厚度平均值为18.7～23.6,水云云滴有效粒子半径在20.2～25.6 μm,冰云有效粒子半径在12.9～15.3 μm,云水路径为222.2～243.8 g m-2,降水强度平均值3.6～8.6 mm d-1;珠三角气溶胶光学厚度有显著降低趋势,年倾向为-3.31%,四川盆地云滴有效粒子半径(冰云、水云)和云水路径年变化趋势为-0.42%、-0.49%和-1.26%,京津唐夏季降水量年增幅为3.24%。气溶胶光学厚度和云光学厚度呈正相关,相关系数最大为0.77;在相对湿度较低(30%～50%)情况下,气溶胶光学厚度与云滴有效粒子半径呈负相关;气溶胶光学厚度与云水路径呈正相关,相关系数最大为0.92;相对于低污染情况(AOD<0.5),高污染情况(AOD>0.5)下出现大雨(>10 mm d-1)的频率增加了6.6%～19.1%,小雨(<1 mm d-1)的频率减少了0.72%～7.3%。在水汽含量较少的情况下,气溶胶的增加导致云滴有效粒子半径的减少;气溶胶增强了南方地区的对流性降水,抑制了北方地区层云降水。     

A modeling study of the effects of aerosols on clouds and precipitation over East Asia

The National Center for Atmospheric Research Community Atmosphere Model (version 3.5) coupled with the Morrison?CGettelman two-moment cloud microphysics scheme is employed to simulate the aerosol effects on clouds and precipitation in two numerical experiments, one representing present-day conditions (year?2000) and the other the pre-industrial conditions (year?1750) over East Asia by considering both direct and indirect aerosol effects. To isolate the aerosol effects, we used the same set of boundary conditions and only altered the aerosol emissions in both experiments. The simulated results show that the cloud microphysical properties are markedly affected by the increase in aerosols, especially for the column cloud droplet number concentration (DNC), liquid water path (LWP), and the cloud droplet effective radius (DER). With increased aerosols, DNC and LWP have been increased by 137% and 28%, respectively, while DER is reduced by 20%. Precipitation rates in East Asia and East China are reduced by 5.8% and 13%, respectively, by both the aerosol??s second indirect effect and the radiative forcing that enhanced atmospheric stability associated with the aerosol direct and first indirect effects. The significant reduction in summer precipitation in East Asia is also consistent with the weakening of the East Asian summer monsoon, resulting from the decreasing thermodynamic contrast between the Asian landmass and the surrounding oceans induced by the aerosol??s radiative effects. The increase in aerosols reduces the surface net shortwave radiative flux over the East Asia landmass, which leads to the reduction of the land surface temperature. With minimal changes in the sea surface temperature, hence, the weakening of the East Asian summer monsoon further enhances the reduction of summer precipitation over East Asia.     

Retrieval of Liquid Water Path Inside Nonprecipitating Clouds Using TMI Measurements

Quantitative estimates of liquid water path （LWP） in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature （TB） and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager （TMI） onboard the Tropical Rainfall Measuring Mission （TRMM）, together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0- and 85.5-GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single,channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover,by using TMI measurements （1Bll）, this algorithm is applied to retrieving respectively LWPs for clear sky, nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP cl~anges from -1 to 1 g m-2, and its mean value is about 10^-5 g m^-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough. The LWP values varying from 0 to 1000 g m^-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner （VIRS） on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h^-1, the LWP increases with increasing rainfall rate.     

庐山云雾及降水的日、季节变化和宏微观物理特征观测研究

庐山云雾观测站2015年重新开始观测试验。利用2015年11月—2018年2月庐山云雾试验站观测的云物理资料和九江站的雷达资料,统计研究了庐山云雾及降水的日、季节变化和宏微观物理特征。结果表明,庐山强降水多发生在夏季,降水强度超过100 mm/h,而云雾天多发生在秋冬春季,最高云和雾天数达25 d/月,最低能见度仅20 m,东北风有利于水汽的冷却凝结。云雾辐射影响下的日最低温度出现在09时前后,即云雾消散前。利用雷达资料对降水分类,庐山秋冬季层状云、积层混合云和对流云降水分别占29%、44%和27%,春夏季的对流云和积层混合云降水分别占83%和17%。与城市降水和雾相比,庐山降水的中、小雨滴多,云雾滴谱的数浓度较低,双峰结构显著,且谱较宽。随着云内降水量级的增大,雨滴的数浓度和尺度不断增加,更易于启动碰并机制,使小于11 μm和大于30 μm云雾滴减少,导致11 μm的峰值更为显著。降雪期间的小云雾滴较为丰富,固态降水更容易通过凇附过程消耗大的过冷云滴。      

Model Analysis of the Anthropogenic Aerosol Effect on Clouds over East Asia

A coupled meteorology and aerosol/chemistry model WRF-Chem(Weather Research and Forecast model coupled with Chemistry) was used to conduct a pair of simulations with present-day(PD) and preindustrial(PI) emissions over East Asia to examine the aerosol indirect effect on clouds.As a result of an increase in aerosols in January,the cloud droplet number increased by 650 cm-3 over the ocean and East China,400 cm-3 over Central and Southwest China,and less than 200 cm-3 over North China.The cloud liquid water path(LWP) increased by 40-60 g m-2 over the ocean and Southeast China and 30 g m-2 over Central China;the LWP increased less than 5 g m-2 or decreased by 5 g m-2 over North China.The effective radius(Re) decreased by more than 4 μm over Southwest,Central,and Southeast China and 2μm over North China.In July,variations in cloud properties were more uniform;the cloud droplet number increased by approximately 250-400 cm-3,the LWP increased by approximately 30-50 g m-2,and Re decreased by approximately 3 ?m over most regions of China.In response to cloud property changes from PI to PD,shortwave(SW) cloud radiative forcing strengthened by 30 W m-2 over the ocean and 10 W m-2 over Southeast China,and it weakened slightly by approximately 2-10 W m-2 over Central and Southwest China in January.In July,SW cloud radiative forcing strengthened by 15 W m-2 over Southeast and North China and weakened by 10 W m-2 over Central China.The different responses of SW cloud radiative forcing in different regions was related to cloud feedbacks and natural variability.     

Modeling of the Second Indirect Effect of Anthropogenic Aerosols in East Asia

This study investigated the second indirect climatic effect of anthropogenic aerosols,including sulfate,organic carbon(OC) ,and black carbon(BC) ,over East Asia.The seasonal variation of the climatic response to the second indirect effect was also characterized.The simulation period for this study was 2006.Due to a decrease in autoconversion rate from cloud water to rain as a result of aerosols,the cloud liquid water path(LWP) ,and radiative flux(RF) at the top of the atmosphere(TOA) changed dramatically,increasing by 14.3 g m-2 and decreasing by-4.1 W m-2 in terms of domain and annual average.Both LWP and RF changed most in autumn. There were strong decreases in ground temperature in Southwest China,the middle reaches of the Yangtze River in spring and autumn,while maximum cooling of up to-1.5 K occurred in the Chongqing district.The regional and annual mean change in ground temperature reached-0.2 K over eastern China.In all seasons except summer,precipitation generally decreased in most areas north of the Yangtze River,whereas precipitation changed little in South China.Precipitation changed most in summer,with alternating bands of increasing(～40 mm) and decreasing(～40 mm) precipitation appearing in eastern China.Precipitation decreased by 1.5-40 mm over large areas of Northeast China and the Huabei Plain.The domain and annual mean change in precipitation was approximately-0.3 mm over eastern China.The maximum reduction in precipitation occurred in summer,with mean absolute and relative changes of-1.2 mm and-3.8%over eastern China.This study revealed considerable climate responses to the second indirect effect of aerosols over specific regions of China.     

Effect of aerosol pollution on clouds and its dependence on precipitation intensity

In this study, simulations performed with a large-eddy resolving numerical model are used to examine the effect of aerosol on cumulus clouds, and how this effect varies with precipitation intensity. By systematically varying the surface moisture fluxes, the modeled precipitation rate is forced to change from weak to strong intensity. For each of these intensities, simulations of a high-aerosol case (a polluted case with a higher aerosol concentration) and a low-aerosol case (a clean case with a lower aerosol concentration) are performed. Whether or not precipitation and associated sub-cloud evaporation and convective available potential energy (CAPE) are large, liquid–water path (LWP) is larger in the high-aerosol case than in the low-aerosol case over the first two-thirds of the entire simulation period. In weak precipitation cases, reduction in aerosol content leads to changes in CAPE in the middle parts of cloud layers, which in turn induces larger LWP in the low-aerosol case over the last third of the simulation period. With strong precipitation, stronger stabilization of the sub-cloud layers in the low-aerosol case counters the CAPE changes in the middle parts of cloud layers, inducing smaller LWP in the low-aerosol case over the last third of the simulation period. The results highlight an interaction between aerosol effects on CAPE above cloud base and those in sub-cloud layers, and indicate the importance of a consideration of aerosol effects on CAPE above cloud base as well as those in sub-cloud layers. In the high-aerosol case, near the beginning of the simulation period, larger environmental CAPE does not necessarily lead to larger in-cloud CAPE and associated larger cloud intensity because aerosol-induced increase in cloud population enhances competition among clouds for the environmental CAPE. This demonstrates the importance of the consideration of cloud population for an improved parameterization of convective clouds in climate models.     

东亚地区云微物理量分布特征的CloudSat卫星观测研究

本文利用2007~2010年整四年最新可利用的CloudSat卫星资料, 对东亚地区(15°~60°N, 70°~150°E)云的微物理量包括冰/液态水含量、冰/液态水路径、云滴数浓度和有效半径等的分布特征和季节变化进行了分析。本文将整个东亚地区划分为北方、南方、西北、青藏高原地区和东部海域五个子区域进行研究, 结果显示:东亚地区冰水路径值的范围基本在700 g m-2以下, 高值区分布在北纬40度以南区域, 在南方地区夏季的平均值最大, 为394.3 g m-2, 而在西北地区冬季的平均值最小, 为78.5 g m-2;而液态水路径的范围基本在600 g m-2以下, 冬季在东部海域的值最大, 达到300.8 g m-2, 夏季最大值为281.5 g m-2, 分布在南方地区上空。冰水含量的最高值为170 mg m-3, 发生在8 km附近, 南方地区夏季的值达到最大, 青藏高原地区的季节差异最大;而液态水含量在东亚地区的范围小于360 mg m-3, 垂直廓线从10 km向下基本呈现逐渐增大的趋势, 峰值位于1~2 km高度上。冰云云滴数浓度在东亚地区的范围在150 L-1以下, 水云云滴数浓度的值小于80 cm-3, 垂直廓线的峰值均在夏季最大。冰云有效半径在东亚地区的最大值为90 μm, 发生在5 km左右;水云有效半径在东亚地区的值分布在10 km以下, 最大值为10~12 μm, 基本位于1~2 km高度上。从概率分布函数来看, 东亚地区冰/水云云滴数浓度的分布呈现明显的双峰型, 其他量基本为单峰型。本文的结果可以为全球和区域气候模式在东亚地区对以上云微物理量的模拟提供一定的观测参考依据。     

中国东部大陆和邻近海域暖云特性时空分布及其与气象条件的关系

基于2003~2016年MODIS/Aqua（MODerate resolution Imaging Spectroradiometer）云产品资料（MYD08_D3）,分析了中国东部大陆及其邻近海域云量（CF）、云滴有效半径（CER）、和液水路径（LWP）的空间分布以及季节变化,并结合同期ERA-Interim再分析资料的850 hPa垂直速度（ω_850hPa）、低对流层稳定度（LTS）、以及MODIS/Aqua水汽产品中的大气可降水量（PWV）资料,分析了云宏微观物理量与动力、热力及水汽条件之间的关系。从空间分布来看,夏季由日本海至中南半岛存在一个东北西南走向的云量高值区,覆盖我国东部地区,冬季云量高值区位于我国南方地区和东部海域上空;云滴有效半径冬、夏分布类似,均为由东南洋面至西北内陆递减;夏季液水路径分布较为均一,冬季空间差异很大,30°N是明显的高低值分界线,这与冬季水汽的分布密切相关。陆地和海洋上云量均呈冬高夏低的变化趋势,陆地大于海洋,而云滴有效半径和液水路径则为夏高冬低,海洋大于陆地。总体来说,云量与PWV和LTS均表现为正相关、与ω_850hPa呈负相关,表明低层的上升运动有利于水汽向上输送、凝结形成云,但稳定的大气层结又会阻碍云进一步向上发展,使其被限制在底层空间,由于本文的研究对象为暖云,多为中低云,因而云量较高;云滴有效半径和液水路径均与LTS、ω_850hPa表现为负相关,但是对PWV的变化不是很敏感,表明水汽并不是影响云滴尺度和液水路径的主导因素,其主要受动力、热力抬升作用的影响;以上关系在不同区域、不同季节的表现存在一定差异。     

Seasonal Variation of Columnar Aerosol Optical Properties in Yangtze River Delta in China

In order to understand the seasonal variation of aerosol optical properties in the Yangtze River Delta,5 years of measurements were conducted during September 2005 to December 2009 at Taihu,China.The monthly averages of aerosol optical depth were commonly >0.6;the maximum seasonal average(0.93) occurred in summer.The magnitude of the Angstr¨om exponent was found to be high throughout the year;the highest values occurred in autumn(1.33) and were the lowest in spring(1.08).The fine modes of volume size distribution showed the maxima(peaks) at a radius of ～0.15 μm in spring,autumn,and winter;at a radius of ～0.22 μm in summer.The coarse modes showed the maxima(peaks) at a radius of 2.9 μm in spring,summer,and autumn and at a radius of 3.8 μm in winter.The averages of single-scattering albedo were 0.92(spring),0.92(summer),0.91(autumn),and 0.88(winter).The averages of asymmetry factor were found to be larger in summer than during other seasons;they were taken as 0.66 at 440-1020 nm over Taihu.The real part of the refractive index showed a weak seasonal variation,with averages of 1.48(spring),1.43(summer),1.45(autumn),and 1.48(winter).The imaginary parts of the refractive index were higher in winter(0.013) than in spring(0.0076),summer(0.0092),and autumn(0.0091),indicating that the atmosphere in the winter had higher absorbtivity.     

Compensating Errors in Cloud Radiative and Physical Properties over the Southern Ocean in the CMIP6 Climate Models

The Southern Ocean is covered by a large amount of clouds with high cloud albedo. However, as reported by previous climate model intercomparison projects, underestimated cloudiness and overestimated absorption of solar radiation (ASR) over the Southern Ocean lead to substantial biases in climate sensitivity. The present study revisits this long-standing issue and explores the uncertainty sources in the latest CMIP6 models. We employ 10-year satellite observations to evaluate cloud radiative effect (CRE) and cloud physical properties in five CMIP6 models that provide comprehensive output of cloud, radiation, and aerosol. The simulated longwave, shortwave, and net CRE at the top of atmosphere in CMIP6 are comparable with the CERES satellite observations. Total cloud fraction (CF) is also reasonably simulated in CMIP6, but the comparison of liquid cloud fraction (LCF) reveals marked biases in spatial pattern and seasonal variations. The discrepancies between the CMIP6 models and the MODIS satellite observations become even larger in other cloud macro- and micro-physical properties, including liquid water path (LWP), cloud optical depth (COD), and cloud effective radius, as well as aerosol optical depth (AOD). However, the large underestimation of both LWP and cloud effective radius (regional means ~20% and 11%, respectively) results in relatively smaller bias in COD, and the impacts of the biases in COD and LCF also cancel out with each other, leaving CRE and ASR reasonably predicted in CMIP6. An error estimation framework is employed, and the different signs of the sensitivity errors and biases from CF and LWP corroborate the notions that there are compensating errors in the modeled shortwave CRE. Further correlation analyses of the geospatial patterns reveal that CF is the most relevant factor in determining CRE in observations, while the modeled CRE is too sensitive to LWP and COD. The relationships between cloud effective radius, LWP, and COD are also analyzed to explore the possible uncertainty sources in different models. Our study calls for more rigorous calibration of detailed cloud physical properties for future climate model development and climate projection.     

First Surface-based Estimation of the Aerosol Indirect Effect over a Site in Southeastern China

The deployment of the U.S. Atmospheric Radiation Measurement mobile facility in Shouxian from May to December2008 amassed the most comprehensive set of measurements of atmospheric, surface, aerosol, and cloud variables in China.This deployment provided a unique opportunity to investigate the aerosol–cloud interactions, which are most challenging and, to date, have not been examined to any great degree in China. The relationship between cloud droplet effective radius(CER) and aerosol index(AI) is very weak in summer because the cloud droplet growth is least affected by the competition for water vapor. Mean cloud liquid water path(LWP) and cloud optical depth(COD) significantly increase with increasing AI in fall. The sensitivities of CER and LWP to aerosol loading increases are not significantly different under different air mass conditions. There is a significant correlation between the changes in hourly mean AI and the changes in hourly mean CER,LWP, and COD. The aerosol first indirect effect(FIE) is estimated in terms of relative changes in both CER(FIECER) and COD(FIECOD) with changes in AI for different seasons and air masses. FIECODand FIECERare similar in magnitude and close to the typical FIE value of ~ 0.23, and do not change much between summer and fall or between the two different air mass conditions. Similar analyses were done using spaceborne Moderate Resolution Imaging Spectroradiometer data. The satellite-derived FIE is contrary to the FIE estimated from surface retrievals and may have large uncertainties due to some inherent limitations.     

基于Ka波段云雷达的六盘山顶云特征分析

利用宁夏六盘山气象站2017年9月至2018年8月的Ka波段云雷达观测资料,统计分析了六盘山顶不同云的出现频率及宏观特征。结果表明：六盘山顶云出现频率最高值在7月,为61%,最低值在12月,为26%;按云层数划分,六盘山顶出现的云主要以1层云、2层云及3层云为主,相对总云的月平均出现频率分别为68%—86%、14%—27%及0.4%—4.8%;按云底高度及云层厚度划分,六盘山顶低云、中云、高云及直展云相对总云的月平均出现频率分别为29%—53%、14%—58%、6%—22%及2%—20%。云底高度在冬春季节高于夏秋季节,云顶高度在夏秋季节高于冬春季节,云层厚度为1.6—3.6 km,年变化特征与云顶高度类似。整体来看,春、夏、秋季云厚在白天大于夜间,冬季云厚在夜间大于白天,其中夏、秋季云厚日变化特征较为明显。     

Enhanced aerosol-cloud relationships in more stable and adiabatic clouds

Modification of cloud microphysics and cloud albedo by cloud-active aerosol is generally identified and accepted, but the nature and magnitude of aerosol-cloud interactions are vaguely understood and thought to include a myriad of processes that vary regionally and confound the application of simple physical models of cloud-aerosol sensitivity. This paper presents observations demonstrating that cloud top stability through its regulation of mixing and vertical development is one of the critical mechanisms that regulate cloud response to cloud-active aerosol in some cloud systems. Strong above-cloud inversions are shown to buffer marine stratocumulus from the effects of mixing with drier, warmer inversion air. This buffering reduces the variability of the cloud liquid water path (LWP) and enables the clouds to remain nearly adiabatic. While weaker above-cloud inversions in continental stratocumulus promote variability in the LWP and sub-adiabatic LWPs, stronger inversions in marine stratocumulus enables a relatively adiabatic existence that increases the relationship of cloud microphysical alteration to cloud-active aerosol. This study has important implications for Geoengineering in that it demonstrates that cloud systems overlain by strong thermal inversions are more likely to respond predictably to intentional manipulation of the in-cloud concentration of cloud-active aerosol.     

京津冀地区夏季降水冰云和非降水冰云云特征对比分析

利用2013～2016年的Aqua MODIS卫星和CloudSat卫星的二级产品资料,对发生在京津冀地区夏季的降水冰云和非降水冰云进行了统计。基于此,对比分析了两类冰云的云类型,研究了二者在云特征参数、云层数及垂直结构上的差异,并且探究了二者在不同通道下云特征参数的相对大小。结果表明:1）京津冀地区的降水冰云以深对流云和雨层云为主,分别占48.63%和34.65%,而非降水冰云以高层云和卷云为主,分别占55.62%和31.58%。2）降水冰云和非降水冰云的平均云顶温度、云顶高度、光学厚度、积分云水总量、有效粒子半径分别为230.99 K、10.90 km、53.26、937.98 g/m2、31.45m和236.17 K、10.10 km、12.81、209.00 g/m2、27.54 μm。3）降水冰云以单层云为主,占80.39%,双层云占18.75%;而非降水冰云仍以单层云为主,占85.35%,双层云则占14.38%,比降水冰云低。4）相较于非降水冰云,降水冰云中卷云和高积云云体位置较高,而高层云和深对流云位置较低。5）随高度变化,降水冰云冰水含量是双峰结构,而非降水冰云是单峰结构;二者的粒子数浓度则差异不大;非降水冰云的粒子有效半径在5～7.5 km随高度变化不大,而降水冰云则随高度减小。6）降水冰云的积分云水总量、光学厚度和粒子有效半径>≥模态[、、分别代表该云特征参数在1.6、2.1、3.7 μm通道中的数值,当n=1, 2, 3时,分别代表光学厚度（b₁）、积分云水总量（b₂）、有效半径这三种（b₃）]的比例都高于非降水冰云,而二者在云参数≥≥模态的比例则有差异。     

秦岭地区气溶胶对地形云降水的抑制作用

以华山站为影响站, 周围的西安、渭南和华阴作为对比站, 通过影响站与对比站降水之比——地形强化因子(Ro)的变化趋势以及Ro与能见度关系的分析, 定量研究了秦岭地区气溶胶对地形云降水的抑制作用。Ro的演变分析表明: 有观测以来Ro逐年递减, 减幅为14%～20%, 即影响站与对比站相比降水量减少了14%～20%; Ro的减少趋势与能见度递减、气溶胶递增相吻合, 说明气溶胶的增加抑制了地形云降水。Ro的递减主要是减少了中小雨 (日雨量小于30 mm) 的天数, 这种影响对浅薄的生命期较短的地形云降水作用更明显, 对于华山站, 30 mm以下的降水都会受到入云气溶胶的抑制作用, 而西安站为5 mm以下, 入云气溶胶浓度越高, 就有越厚的降水云受气溶胶影响而抑制降水; 在以动力强迫抬升为主的春秋季, 气溶胶抑制华山地形云降水20%左右, 最大可达25%; 在热对流条件下, 气溶胶对地形云和对平原地区云的抑制作用基本相当。不同风速风向下Ro的变化趋势表明, Ro递减随风速增大而加快, 迎风向 (240°～30°) 大风 (≥5 m/s) 时减少降水超过30%。由Ro与能见度关系的定量分析发现, 当能见度在14 km时Ro为1.8左右, 随着能见度的降低Ro逐渐减小, 当能见度小于8 km时,R0约为1.2, 减小了30%左右; 华山对于华阴的Ro与能见度呈线性关系, 相关系数达0.81。最后, 根据研究结果归纳出气溶胶抑制秦岭地区地形云降水的初步物理模型。     

华北地区一次气溶胶与浅积云微物理特性的飞机观测研究

2014年8月15日,山西省人工降雨防雹办公室在山西忻州开展了气溶胶和浅积云的飞机观测,本文利用机载云物理资料,详细分析了华北地区气溶胶、云凝结核（CCN）和浅积云微物理特性及其相互影响。主要结论有:（1）此次过程的边界层高度约为3600 m,不同层结情况下,0.1～3 μm尺度范围内的气溶胶粒子浓度N_a、有效直径D_a和CCN数浓度的垂直廓线明显不同,近地面N_a可达2500 cm?3。（2）CCN的主要来源为积聚模态、爱根模态或者核模态的气溶胶颗粒,0.2%过饱和度下,气溶胶活化率（AR）在各高度层的结果变化不大;0.4%过饱和度下,AR随着高度增加而降低。（3）后向轨迹模式分析表明,2 km以下的气溶胶主要来自于当地城市排放,由细颗粒污染物组成;2 km以上的气溶胶主要来源于中国西北和蒙古地区的沙漠,由亚微米沙尘组成,溶解度相对较低,可作为潜在的冰核。（4）本文细致分析了两块相邻浅积云（Cu-1和Cu-2）的云物理特性。Cu-1云底高度约4500 m,云厚约600 m,云体松散,夹卷较多;云中液态含水量（LWC）基本保持在0.5 g m?3,云粒子浓度N_c平均值为278.3 cm?3,云滴有效直径D_c整体在15 μm以内;毛毛雨滴粒子浓度最大值为0.002 cm?3,云中几乎无降水粒子;粒子谱宽随着高度增加而增大,主要集中在30 μm以内。Cu-2云底高度约3900 m,云厚约1200 m,云体密实;云中过冷水丰沛,LWC有多个超过1 g m?3的区域,云顶附近出现冰晶,云中粒子从凝结增长状态直接进入到混合相态;积云内部粒子水平分布不均,同一高度N_c相差较大,最大可达1240 cm?3。D_c随着高度增加而增大;粒子谱宽随着高度增加而拓展,最大可达1100 μm,谱型由单峰向多峰转变;降水粒子和冰晶图像大多为霰粒子、针状和板状。     

华北中部夏季气溶胶和云分布特征

气溶胶与云的垂直分布特征是气溶胶间接气候效应关注的重点。基于2018年7—8月华北中部6架次飞机观测数据,研究气溶胶和云滴的垂直和水平分布特征。结果表明:华北中部780~5687 m高度内气溶胶数浓度( N_a )平均值为821.36 cm-3,最大量级可达到104 cm-3,云中气溶胶数浓度(N_acc)占总颗粒浓度的80%以上,表明细颗粒占大多数,气溶胶粒子算术平均直径( D_m )平均值为0.12~0.52 μm;大气层结对气溶胶垂直分布影响较大,逆温阻挡气溶胶垂直输送,高空(高度2000 m以上) D_m 的垂直分布受到相对湿度影响较大; N_a 和 D_m 在垂直方向波动较大,水平方向波动较小;低层云中云滴数浓度(N_c)较大、液态水含量(L)较小,而中层和高层云中N_c较小、L较大,N_c和云滴有效半径(R_e)的概率密度函数均为双峰型分布,L的概率密度函数为单峰型分布;气溶胶数浓度谱基本呈现多峰型分布,而云滴数浓度谱多呈现单峰型分布。     

基于美国AMF寿县观测的云特性研究

美国能源部大气辐射观测计划移动观测ARMAMF（atmospheric radiation measurement mobile facility）2008年首次在我国寿县开展综合观测,为研究云特性提供了很好的资料平台。本文在此次云雷达等观测资料基础上,研究了寿县秋末冬初云高、云厚、云量及其辐射特性,结果发现,寿县有76．3％的观测日有云出现,54．0％的观测时间有云覆盖,中云（以下简称M云）和高云（以下简称H云）出现频率占全部云系的76．7％,天气系统对寿县云系形成有较大影响;云底高度大于3km的降水性云（以下简称P云）出现频率占全部P云的67．7％,是云底高度小于3kmP云的5．3倍,发生在下午的降水占全部P云的47．8％,气溶胶可能对P云的这种分布有较大影响;云和气溶胶减少地面短波辐射的日均值达一99．1W／m。,其中气溶胶减少约占25．1％。不同高度和厚度云对地面辐射通量的影响有较大差异,P云产生最大的冷却效应（一201．9W／m。）,厚度小于2km的H云对地面辐射通量的减少量最少（一32．9w／m。）。另外,用地面单点云辐射观测与中分辨率成像光谱仪MODIS（moderate resolution imaging spectroradiometer）资料估计结果对比发现,两种资料有较大差异,差异可达-1．9～-36．9W／m。