The Microphysical Characteristics of Wintertime Cold Clouds in North China

The microphysical characteristics of wintertime cold clouds in North China were investigated from 22 aircraft observation flights from 2014 to 2017, 2020, and 2021. The clouds were generated by mesoscale weather systems with little orographic component. Over the mixed-phase temperature range (–40°C to 0°C), the average fraction of liquid, mixed-phase, and ice cloud was 4.9%, 23.3%, and 71.8%, respectively, and the probability distribution of ice mass fraction was a half-U-shape, suggesting that ice cloud was the primary cloud type. The wintertime mixed-phase clouds in North China were characterized by large cloud droplet number concentration, small liquid water content (LWC), and small effective diameter of cloud droplets. The main reason for larger cloud droplet number concentration and smaller effective diameter of cloud droplets was the heavy pollution in winter in North China, while for smaller LWC was the lower temperature during flights and the difference in air mass type. With the temperature increasing, cloud droplet number concentration, LWC, and the size of ice particles increased, but ice number concentration and effective diameter of cloud droplets decreased, similar to other mid-latitude regions, indicating the similarity in the temperature dependence of cloud properties of mixed-phase clouds. The variation of the cloud properties and ice habit at different temperatures indicated the operation of the aggregation and riming processes, which were commonly present in the wintertime mixed-phase clouds. This study fills a gap in the aircraft observation of wintertime cold clouds in North China.     

三江源地区秋季典型多层层状云系的飞机观测分析

利用三江源地区一次机载粒子测量系统PMS(Particle Measuring Systems)的分层垂直探测资料,系统研究了该地区秋季典型多层层状云系的微物理特性,结果表明:(1)云系由4层云层组成,Cs(卷层云)和上层As(高层云)为冰云,下层As和Sc(层积云)为过冷混合态云。下层As的云粒子浓度和过冷水含量最大,Sc的云粒子尺寸及谱宽最大,且具有较明显的地区特性;(2)Sc(下层As及对流泡)中中值直径在3.5～18.5 μm(3.5～ 21.5 μm)之间的云粒子为液相,中值直径大于21.5 μm(24.5 μm)的云粒子为冰相;(3)混合态云中高过冷水区与低过冷水区云的粒子谱分布差异明显,Sc高过冷水区有较明显的淞附增长现象;(4)Sc、下层As云底、对流泡顶高过冷水区的云滴有效半径依次增加。Sc高过冷水区的过冷水含量比率均值及标准差为69.9±19.4%,且与过冷水含量存在一定的关联性;下层As云底高过冷水区的过冷水含量比率无明显变化,其均值及标准差为89.2±8.1%;(5)混合态云各高度层FSSP(前向散射粒子谱探头)平均粒子谱均为单峰型伽玛分布,混合态云和冰云各高度层2DC(二维灰度云粒子探头)平均粒子谱基本上都为负指数型分布。     

Comparison of cloud properties between cloudsat retrievals and airplane measurements in mixed-phase cloud layers of weak convective and stratus clouds

Cloud microphysical properties including liquid and ice particle number concentration (NC), liquid water content (LWC), ice water content (IWC) and effective radius (RE) were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear (p1) and two exponential (p2 and p3) functions, which estimate the liquid-phase fraction as a function of subfreezing temperature (from -20°C to 0°C), were tested. The retrieved NC, LWC, IWC and RE using p1 were on average larger than airplane measurements in the same cloud layer. Function p2 performed better than p1 or p3 in retrieving the NCs of cloud droplets in the convective cloud, while function p1 performed better in the stratus cloud. Function p3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the p1 function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function p1.     

Two-moment bulk stratiform cloud microphysics in the grid-point atmospheric model of IAP LASG (GAMIL)

A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG (GAMIL) as an effort to enhance the model’s capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable representation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. Furthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.     

Application of aircraft observations over Beijing in cloud microphysical property retrievals from CloudSat

Cloud microphysical property retrievals from the active microwave instrument on a satellite require the cloud droplet size distribution obtained from aircraft observations as a priori data in the iteration procedure.The cloud lognormal size distributions derived from 12 flights over Beijing,China,in 2008-09 were characterized to evaluate and improve regional CloudSat cloud water content retrievals.We present the distribution parameters of stratiform cloud droplet （diameter ＜500 tm and ＜1500 μm） and discuss the effect of large particles on distribution parameter fitting.Based on three retrieval schemes with different lognormal size distribution parameters,the vertical distribution of cloud liquid and ice water content were derived and then compared with the aircraft observations.The results showed that the liquid water content （LWC） retrievals from large particle size distributions were more consistent with the vertical distribution of cloud water content profiles derived from in situ data on 25 September 2006.We then applied two schemes with different a priori data derived from flight data to CloudSat overpasses in northern China during April-October in 2008 and 2009.The CloudSat cloud water path （CWP） retrievals were compared with Moderate Resolution Imaging Spectroradiometer （MODIS） liquid water path （LWP） data.The results indicated that considering a priori data including large particle size information can significantly improve the consistency between the CloudSat CWP and MODIS CWP.These results strongly suggest that it is necessary to consider particles with diameters greater than 50 tm in CloudSat LWC retrievals.     

山西春季一次层状冷云的微物理结构特征

利用2009年3月11日机载DMT（droplet measurement technology）粒子测量系统获取的山西层状云探测资料,结合天气、卫星、雷达等,分析了降水性冷云的宏微观结构特征.结果表明,降水云系由高层云和层积云组成,液态含水量变化范围为0 0.42 g/m3.CDP（cloud droplet probe;云粒子探头）和CIP（cloud imaging probe;云粒子图像探头）观测到的粒子数浓度偏大,CDP探测到最大粒子数浓度为451.93 cm-3,CIP探测到最大粒子数浓度为162.78 L-1.本次探测适宜的人工增雨作业温度区间为-11.4-7℃、-4.40℃.高层云上部以冰晶的核化和凝华增长为主;高层云的中下部为冰雪晶活跃增长层;通过凝华、碰并机制高层云降落的冰雪晶粒子在层积云进一步长大.层状云水平分布不均匀特性很明显.统计云滴谱谱型分布发现,双峰型、多峰型出现几率较高,指数型主要出现在层积云的中部和顶部,出现单峰型时LWC（liquid water concentration;液态水含量）小于0.03 g/m3或大于0.1 g/m3.     

In situ observations of snow particle size distributions over a cold frontal rainband within an extratropical cyclone

Cloud microphysical properties of a mixed phase cloud generated by a typical extratropical cyclone in the Tongliao area, Inner Mongolia on 3 May 2014, are analyzed primarily using in situ flight observation data. This study is mainly focused on ice crystal concentration, supercooled cloud water content, and vertical distributions of fit parameters of snow particle size distributions (PSDs). The results showed several discrepancies of microphysical properties obtained during two penetrations. During penetration within precipitating cloud, the maximum ice particle concentration, liquid water content, and ice water content were increased by a factor of 2-3 compared with their counterpart obtained during penetration of a nonprecipitating cloud. The heavy rimed and irregular ice crystals obtained by 2D imagery probe as well as vertical distributions of fitting parameters within precipitating cloud show that the ice particles grow during falling via riming and aggregation process, whereas the lightly rimed and pristine ice particles as well as fitting parameters within non-precipitating cloud indicate the domination of sublimation process. During the two cloud penetrations, the PSDs were generally better represented by gamma distributions than the exponential form in terms of the determining coefficient (R²). The correlations between parameters of exponential /gamma form within two penetrations showed no obvious differences compared with previous studies.     

基于CloudSat资料对中国低纬度陆地区域卷云物理特征的研究

利用2008年9月—2016年8月的CloudSat卫星资料对发生在我国低纬度陆地区域(5°~36.5°N,78°~124°E)的卷云物理特征进行统计分析,并分别讨论东部沿海、中部、西部3个子区域的卷云物理特征的季节变化。结果表明:卷云的整层发生率西部地区整体低于中部与东部沿海地区。3个子区域整层发生率均在夏季最高、冬季最低。卷云的主要发生高度在5.04~18.71 km,垂直分布中卷云发生率的最大值出现在春季中部地区,为15.34%,高度为9.83 km。冰水路径最大值出现在夏季的东部沿海,液水路径最大值在秋季的西部地区。冰水含量、冰粒数浓度、冰粒有效半径的主要分布高度与卷云的发生高度一致,液水含量、液滴数浓度、液滴有效半径的主要分布高度在5.04~9.35 km。3个子区域卷云冰水含量、冰粒数浓度、冰粒有效半径垂直分布中大多集中在中上部;液水含量垂直分布主要集中在分布高度的中下部。四季卷云雷达反射率因子的最大值在-19.89~-16.78 dBZ,分布高度在7.19~10.55 km。     

机载热线含水量仪探测数据校验方法

机载含水量仪是目前云中液态水含量唯一的探测仪器,其准确性直接影响人工增雨作业条件判别。基于2015年和2017年四川盆地南部开展的10架次飞机云物理探测试验,考察机载热线含水量仪LWC-100探测数据发现存在异常极大值、负值数量多等问题。通过分析DMT（Droplet Measurement Technologies）公司云粒子探头（cloud droplet probe,CDP）、云粒子图像探头（cloud imaging probe,CIP）、降水粒子图像探头（precipitation imaging probe,PIP）数据,提出对入云前的干功率进行重新计算的3种方法:方法1以CDP探头的不同粒子尺度分档为标准,不低于某一档尺度的粒子数浓度大于0记为入云;方法2以CDP的数浓度大于10 cm-3为入云判定条件;方法3以CDP,CIP,PIP 3种探头探测的粒子数浓度同时大于0记为入云。结果显示:3种方法均有效纠正液态水含量不为0的情况,负值数量也较探测数据明显减少。方法1以不小于5 μm的粒子数浓度大于0记为入云,校验计算得到的液态水含量以负值数量和大小作为评价依据较方法2和方法3更优。     

In-Situ Measurements of Cloud-Precipitation Microphysics in the East Asian Monsoon Region Since 1960

A large number of in-situ measurements of cloud-precipitation microphysical properties have been made since 1960, including measurements of particle size distribution, particle concentration, and liquid water content of clouds and rain. These measurements have contributed to considerable progress in understanding microphysical processes in clouds and precipitation and significant improvements in parameterizations of cloud microphysics in numerical models. This work reviews key findings regarding cloud-precipitation microphysics over China. The total number concentrations of various particles vary significantly, with certain characteristic spatial scales. The size distributions of cloud droplets in stratiform clouds can generally be fit with gamma distributions, but the fit parameters cover a wide range. Raindrop size distributions(RSDs)associated with stratiform clouds can be fit with either exponential or gamma distributions, while RSDs associated with convective or mixed stratiform-cumuliform clouds are best fit with gamma distributions.Concentrations of ice nuclei(IN) over China are higher than those observed over other regions, and increase exponentially as temperature decreases. The particle size distributions of ice crystals, snow crystals, and hailstones sampled at a variety of locations can be reliably approximated by using exponential distributions,while aerosol particle size distributions are best described as the sum of a modified gamma distribution and a Junge power-law distribution. These results are helpful for evaluating and improving the fidelity of physical processes and hydrometeor fields simulated by microphysical parameterizations. The comprehensive summary and analysis of previous work presented here also provide useful guidelines for the design of future observational programs.     

二维粒子形状分类技术在云微物理特征分析中的应用

本文介绍了一种针对飞机粒子探测系统中云二维图像探头开发的二维粒子形状分类技术。该技术利用粒子形状几何参数特征把云粒子分为8种类型,分别为微小状、线形状、聚合状、霰状、球状、六角形状、不规则状和枝状。同时结合冰水质量关系,给出了探头液水含量和冰水含量的计算方法。最后应用该技术对2006年4月6日一次飞机探测获取的数据进行了云微物理结构分析,聚合状、霰状、六角形状、不规则状的总出现频率为78%,其中霰状粒子的出现频率随着温度的降低而增加。非降水云中的液水含量、液滴粒子浓度、冰晶浓度明显小于降水云,非降水云中液水含量的平均值为0.01 g m-3,冰水含量的平均值0.007 g m-3,冰晶粒子浓度的平均值为11.9 L-1。     

华北秋季一次低槽冷锋积层混合云宏微物理特征与催化响应分析

利用2013年10月13日机载粒子测量系统（PMS）在张家口涞源地区对积层混合云中上部进行的增雨探测数据,分析了云的垂直微物理结构、云区的可播性和作业前后液态云粒子、冰晶及降水粒子的微物理变化。结果表明,此次降水性积层混合云的垂直结构由冷、暖两层云配置,云层发展厚实,冷云区云粒子浓度平均为62 cm-3,液态水含量最大0.05 g/m3;2DC和2DP探测的冰晶及降水粒子平均浓度分别为1.9和2.2 L-1;暖云内云粒子数浓度集中在300 cm-3左右,液态水含量约0.1 g/m3。探测区域云粒子数浓度的水平分布不均匀。利用云内过冷水含量和冰晶浓度等参数判断,该降水性积层混合云的播撒作业层具有强可播性。对比作业前后云中粒子浓度及平均直径发现,云粒子在作业前时段内的平均浓度为31 cm-3,远高于作业后平均浓度（17.6 cm-3）;但平均直径变化不大。作业后冰晶粒子通过贝吉龙过程消耗过冷水长大,浓度由之前的0.86 L-1增至4.27 L-1,平均直径也增至550 μm。冰晶粒子逐渐长大形成降水,降水粒子浓度也相应有所升高,谱明显变宽。      

山西一次降雪云物理特征的飞机观测研究

通过飞机直接进入降雪云进行探测,并配合MICPAS（气象信息综合分析处理系统）、雷达和卫星等资料,对2011年11月29日山西一次降雪云宏、微观结构特征进行分析。研究发现:本次降雪过程的雷达回波以10～20 dBZ大片层状云回波为主,镶嵌了超过30 dBZ的块状强回波,雷达径向速度零线呈较强的“S”型弯曲,出现“牛眼”结构,从低层到高层有较强的风垂直切变。液态水含量主要位于3.2 km以下,最大值为0.0697 g m?3,N₅₀（粒子直径大于50 μm的冰雪晶数浓度）、N₂₀₀（粒子直径大于200 μm的冰雪晶数浓度）和冰水含量主要产生于层积混合降雪云的上部,极大值出现在?9.3°C附近,分别为188.4 L?1、33.5 L?1和0.121 g m?3。?14.4°C～?19.7°C冰晶图像以针状、柱状和不规则状为主,以冰晶的凝华增长为主。?9.3°C附近冰雪晶图像以辐枝状、不规则状为主,辐枝状冰晶的聚并碰撞和折裂繁生可能是造成此处冰雪晶高浓度的主要原因。利用指数形式能较好地拟合冰雪晶谱分布,谱拟合参数可以用幂函数N_os=1.021λ1.684表示（其中,N_os、λ分别表示截距和斜率,N_os越大表示小粒子数浓度越大,λ越大表示小粒子数浓度占总粒子数浓度比例越高）,相关系数R2为0.86。3.2 km以下存在三次逆温,逆温层的出现使云微物理特征量和拟合参数N_os减小,抑制了云内凇附增长和凝华增长,导致本次观测谱拟合参数N_os、λ随温度的变化规律与以往的观测不一致,逆温强度越大抑制作用越大。     

辽宁层状云微物理结构的水平变化特征

根据1997年在辽宁利用机载粒子测量系统(PMS)获取的探测资料,探讨了层状云中云滴谱、粒子数浓度在水平方向上的分布变化,并分析了温度、粒子含水量在水平方向上的变化特征。研究表明:云滴数浓度和云滴半径在水平方向上存在着较强的起伏性变化;层状云中温度在水平方向上总体变化不大;云中的云滴谱结构在水平方向上的起伏较大,存在3种变化规律;云中含水量在水平方向上的变化大,且与粒子数浓度存在正相关。     

Aircraft Measurements of the Microphysical Properties of Stratiform Clouds with Embedded Convection

The presence of embedded convection in stratiform clouds strongly affects ice microphysical properties and precipitation formation. In situ aircraft measurements, including upward and downward spirals and horizontal penetrations, were performed within both embedded convective cells and stratiform regions of a mixedphase stratiform cloud system on 22 May 2017. Supercooled liquid water measurements, particle size distributions, and particle habits in different cloud regions were discussed with the intent of characterizing the riming process and determining how particle size distributions vary from convective to stratiform regions. Significant amounts of supercooled liquid water, with maxima up to 0.6 g m~(-3), were observed between -3℃ and-6℃ in the embedded convective cells while the peak liquid water content was generally less than 0.1 g m~(-3) in the stratiform regions.There are two distinct differences in particle size distributions between convective and stratiform regions.One difference is the significant shift toward larger particles from upper -15℃ to lower -10℃ in the convective region, with the maximum particle dimensions increasing from less than 6000 μm to over 1 cm. The particles larger than 1 cm at -10℃ are composed of dendrites and their aggregates. The other difference is the large concentrations of small particles(25–205 μm) at temperatures between -3℃ and-5℃ in the convective region, where rimed ice particles and needles coexist. Needle regions are observed from three of the five spirals, but only the cloud conditions within the convective region fit into the Hallett-Mossop criteria.     

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。     

Importance of the mixed-phase cloud distribution in the control climate for assessing the response of clouds to carbon dioxide increase: a multi-model study

We have conducted a multi-model intercomparison of cloud-water in five state-of-the-art AGCMs run for control and doubled carbon dioxide climates. The most notable feature of the differences between the control and doubled carbon dioxide climates is in the distribution of cloud-water in the mixed-phase temperature band. The difference is greatest at mid and high latitudes. We found that the amount of cloud ice in the mixed phase layer in the control climate largely determines how much the cloud-water distribution changes for the doubled carbon dioxide climate. Therefore evaluation of the cloud ice distribution by comparison with data is important for future climate sensitivity studies. Cloud ice and cloud liquid both decrease in the layer below the melting layer, but only cloud liquid increases in the mixed-phase layer. Although the decrease in cloud-water below the melting layer occurs at all latitudes, the increase in cloud liquid in the mixed-phase layer is restricted to those latitudes where there is a large amount of cloud ice in the mixed-phase layer. If the cloud ice in the mixed-phase layer is concentrated at high latitudes, doubling of carbon dioxide might shift the center of cloud water distribution poleward which could decrease solar reflection because solar insolation is less at higher latitude. The magnitude of this poleward shift of cloud water appears to be larger for the higher climate sensitivity models, and it is consistent with the associated changes in cloud albedo forcing. For the control climate there is a clear relationship between the differences in cloud-water and relative humidity between the different models, for both magnitude and distribution. On the other hand the ratio of cloud ice to cloud-water follows the threshold temperature which is determined in each model. Improved measurements of relative humidity could be used to constrain the modeled representation of cloud water. At the same time, comparative analysis in global cloud resolving model simulations is necessary for further understanding of the relationships suggested in this paper.     

伊宁春季层状云和混合云降水的雨滴谱统计特征分析

利用设在伊宁的激光雨滴谱仪获取的2013年4月的降水资料,对层状云和混合云降水粒子谱的微物理参量平均值和Gamma函数拟合结果以及Z-I关系进行对比分析。计算结果表明,伊宁地区春季降水的微物理参量普遍偏小,小滴对降水浓度的贡献达到92%以上,即降水主要以小滴为主。层状云降水的雨强、雨滴数浓度、雨滴的各类微物理特征参量的平均值均大于混合云降水。函数拟合结果表明,混合云降水的雨滴谱宽大于层状云降水的雨滴谱宽,层状云和混合云降水的雨滴谱都比较符合Gamma分布,在小滴段Gamma分布对实际谱都有一定的低估,在大于1 mm的粒径段,拟合结果有一定的偏差。还讨论了雨滴大小因子Λ和形状因子μ之间的关系以及Z-I关系,Λ-μ关系与粒子尺度有关,根据拟合的二项式得到层状云降水粒子的平均直径大于混合云降水的平均直径。     

Microphysical and radiative properties of mixed-phase altocumulus: A model evaluation of glaciation effects

Using a cloud model with explicit microphysics and radiation, we evaluate the microphysical changes in a supercooled liquid altocumulus cloud with increasing ice content, until glaciation occurs. The properties of the ice and water particle constituents are resolved independently, revealing the relative radiative contributions from the water phase source cloud versus the ice phase virga. Cloud contents are also converted to millimeter-wave radar reflectivities to shed light on the ability of such radars to study these ubiquitous clouds. The results show that the radiative and radar backscattering properties of mixed-phase clouds are dominated by the cloud droplets and ice crystals they contain, respectively.     

太赫兹频段雷达探测的冰云微物理参数反演算法模拟研究

在假设冰云粒子呈球形以及粒子谱服从对数正态分布的条件下,利用离散偶极子近似法(DDA),计算出太赫兹频段(220 GHz)冰云粒子的雷达反射率因子,及其与瑞利假设下雷达反射率因子的比值。忽略衰减和多次散射的影响,根据太赫兹波段冰云的雷达反射率因子,基于最优估计理论反演冰云的微物理参数,并验证该算法的可靠性。反演结果表明,当冰云粒子大小在设定的尺度范围内时,有效粒子半径(r_e)的反演误差小于4%,粒子谱宽(σ)的误差小于2.5%、粒子数密度(N_T)的误差小于1%,冰水含量(IWC)的误差小于5%。还分析了当N_T和σ为定值时,反演结果随粒子尺寸的变化情况,当冰云粒子尺寸在模拟计算设定的范围内时,r_e的反演误差小于0.04%,σ的反演误差小于0.02%,N_T的反演误差小于0.50%,IWC的反演误差小于0.08%,如果冰云粒子大小超出模拟计算设置的范围,反演误差随着r_e增加而增大。该结果证明了基于最优估计理论反演得到的冰云微物理参数与模拟设定值有良好的一致性,说明该方法可应用于太赫兹频段云雷达的冰云观测及云微物理参数的反演和研究。