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 rep- resentation 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. ~rthermore, 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.

A STUDY OF THE INFLUENCE OF MICROPHYSICAL PROCESSES ON TYPHOON NIDA(2016) USING A NEW DOUBLE-MOMENT MICROPHYSICS SCHEME IN THE WEATHER RESEARCH AND FORECASTING MODEL

The basic structure and cloud features of Typhoon Nida(2016) are simulated using a new microphysics scheme(Liuma) within the Weather Research and Forecasting(WRF) model. Typhoon characteristics simulated with the Liuma microphysics scheme are compared with observations and those simulated with a commonly-used microphysics scheme(WSM6). Results show that using different microphysics schemes does not significantly alter the track of the typhoon but does significantly affect the intensity and the cloud structure of the typhoon. Results also show that the vertical distribution of cloud hydrometeors and the horizontal distribution of peripheral rainband are affected by the microphysics scheme. The mixing ratios of rain water and graupel correlate highly with the vertical velocity component and equivalent potential temperature at the typhoon eye-wall region. According to the simulation with WSM 6 scheme,it is likely that the very low typhoon central pressure results from the positive feedback between hydrometeors and typhoon intensity. As the ice-phase hydrometeors are mostly graupel in the Liuma microphysics scheme, further improvement in this aspect is required.

NUMERICAL SIMULATION OF CLOUD MICROPHYSICAL CHARACTERISTICS OF LANDFALL TYPHOON KROSA

In this study,the super typhoon KROSA(2007)was simulated using a mesoscale numerical model Global and Regional Assimilation and Prediction System(GRAPES)with a two-moment mixed-phase microphysics scheme.Local rainfall observations,radar and satellite data were also used to analyze the precipitation structure and microphysical features.It was shown that low-level jets and unstable temperature stratification provided this precipitation process with favorable weather condition.Heavy rainfall centers were located in the north and east part of KROSA with the maxima of 6-hourly total rainfall during the simulation more than 100 mm.The quantities of column solid water and column liquid water were generally equivalent,indicating the important role of ice phase in precipitation formation.Results of CloudSat showed that strong convection occurred in the eyewall around the cyclonic center.According to the simulation results,heavy precipitation in the northeast part of the typhoon was mainly triggered by convective clouds,accompanied by the strongest updraft under the melting level.In the southwest part of KROSA,precipitation intensity was rather homogeneous.The ascending center occurred in high-level cold clouds,favoring the formation and growth of ice particles.

SENSITIVITY OF LANDFALLING TYPHOON STRUCTURE AND PRECIPITATION TO VARYING CLOUD MICROPHYSICAL PROCESSES

Typhoon KROSA in 2007 is simulated using GRAPES,a mesoscale numerical model,in which a two-parameter mixed-phase microphysics scheme is implanted.A series of numerical experiments are designed to test the sensitivity of landfalling typhoon structure and precipitation to varying cloud microphysics and latent heat release.It is found that typhoon track is sensitive to different microphysical processes and latent heat release.The cloud structures of simulated cyclones can be quite different with that of varying microphysical processes.Graupel particles play an important role in the formation of local heavy rainfall and the maintenance of spiral rainbands.Analysis reveals that the feedback of latent heat to dynamic fields can significantly change the content and distribution of cloud hydrometeors,thus having an impact on surface precipitation.

Aerosol Microphysical and Radiative Effects on Continental Cloud Ensembles

Aerosol-cloud-radiation interactions represent one of the largest uncertainties in the current climate assessment. Much of the complexity arises from the non-monotonic responses of clouds, precipitation and radiative fluxes to aerosol perturbations under various meteorological conditions. In this study, an aerosol-aware WRF model is used to investigate the microphysical and radiative effects of aerosols in three weather systems during the March 2000 Cloud Intensive Observational Period campaign at the US Southern Great Plains. Three simulated cloud ensembles include a low-pressure deep convective cloud system, a collection of less-precipitating stratus and shallow cumulus, and a cold frontal passage. The WRF simulations are evaluated by several ground-based measurements. The microphysical properties of cloud hydrometeors, such as their mass and number concentrations, generally show monotonic trends as a function of cloud condensation nuclei concentrations. Aerosol radiative effects do not influence the trends of cloud microphysics, except for the stratus and shallow cumulus cases where aerosol semi-direct effects are identified. The precipitation changes by aerosols vary with the cloud types and their evolving stages, with a prominent aerosol invigoration effect and associated enhanced precipitation from the convective sources. The simulated aerosol direct effect suppresses precipitation in all three cases but does not overturn the aerosol indirect effect. Cloud fraction exhibits much smaller sensitivity （typically less than 2%） to aerosol perturbations, and the responses vary with aerosol concentrations and cloud regimes. The surface shortwave radiation shows a monotonic decrease by increasing aerosols, while the magnitude of the decrease depends on the cloud type.

RADIATIVE AND MICROPHYSICAL EFFECTS OF ICE CLOUDS ON A TORRENTIAL RAINFALL EVENT OVER HUNAN,CHINA

The radiative and microphysical effects of ice clouds on a torrential rainfall event over Hunan,China in June 2004 are investigated by analyzing the sensitivity of cloud-resolving model simulations.The model is initialized by zonally-uniform vertical velocity,zonal wind,horizontal temperature and vapor advection from National Centers for Environmental Prediction(NCEP) /National Center for Atmospheric Research(NCAR) reanalysis data.The exclusion of radiative effects of ice clouds increases model domain mean surface rain rates through the increase in the mean net condensation associated with the increase in the mean radiative cooling during the onset phase and the increases in the mean net condensation and the mean hydrometeor loss during the mature phase.The decrease in the mean rain rate corresponds to the decreased mean net condensation and associated mean latent heat release as the enhanced mean radiative cooling by the removal of radiative effects of ice clouds cools the mean local atmosphere during the decay phase.The removal of microphysical effects of ice clouds decreases the mean rain rates through the decrease in the mean net condensation during the onset phase,while the evolution of mean net condensation and the mean hydrometeor changes from decrease to increase during the mature phase.The reduction in the mean rain rate is primarily associated with the mean hydrometeor change in the absence of microphysical effects of ice clouds during the decay phase.

基于云微物理过程的北方冻雨的模拟与形成机制研究

本文通过耦合AFWA(Air Force Weather Agency)冻雨参数化方案的WRF模式,对2020年冬季因暖锋引发的中国北方严重冻雨灾害个例进行了模拟,结果显示模式能够很好地模拟此次冻雨过程中降水相态的空间分布。通过分析暖锋的演变、水成物云微物理特征以及降水相态的变化,得到:在辽宁中北部—吉林中东部地区,暖锋导致中低空形成“冷—暖—冷”的温度层结,该区冻雨形成机制以“冰相机制”为主,即高空的雪花落入大于0℃暖层内融化、再降落到次冻结层后形成冻雨。同时,发现存在高空无固态水成物、逆温层内暖雨下落到次冻结层在地面形成冻雨的现象,这种新机制被定义为“暖雨机制”,更多水成物垂直剖面与同期地面观测降水相态的比对,验证了新机制的存在,并解释了该机制形成的可能原因。为更深入理解冻雨形成机理以及北方冻雨的预报、预警提供科学支撑。

Improvement of cloud microphysical parameterization and its advantages in simulating precipitation along the Sichuan-Xizang Railway

The Sichuan-Xizang Railway is an important part of the railway network in China, and geological disasters, such as mountain floods and landslides, frequently occur in this region. Precipitation is an important cause of these disasters;therefore,accurate simulation of the precipitation in this region is highly important. In this study, the descriptions for uncertain processes in the cloud microphysics scheme are improved;these processes include cloud droplet activation, cloud-rain autoconversion, rain accretion by cloud droplets, and the entrainment-mixing process. In the default scheme, the cloud water content of different sizes corresponds to the same cloud droplet concentration, which is inconsistent with the actual content;this results in excessive cloud droplet size, unreasonable related conversion rates of microphysical process(such as cloud-rain autoconversion), and an overestimation of precipitation. Our new scheme overcomes the problem of excessive cloud droplet size. The processes of cloudrain autoconversion and rain accretion by cloud droplets are similar to the stochastic collection equation, and the mixing mechanism of cloud droplets is more consistent with that occurred during the actual physical process in the cloud. Based on the new and old schemes, multiple precipitation processes in the flood season of 2021 along the Sichuan-Xizang Railway are simulated, and the results are evaluated using ground observations and satellite data. Compared to the default scheme, the new scheme is more suitable for the simulation of cloud physics, reducing the simulation deviation of the liquid water path and droplet radius from 2 times to less than 1 time and significantly alleviating the overestimation of precipitation intensity and range of precipitation center. The average root-mean-square error is reduced by 22%. Our results can provide a scientific reference for improving precipitation forecasting and disaster prevention in this region.

不同云微物理方案对飞机结冰气象条件预测评估分析

飞行安全在复杂气象条件下易受结冰影响而受到威胁。能够结合地形特征并准确预测结冰气象条件是保障飞行安全的重要因素。本文利用中尺度天气预报模型模式,以4种不同的云微物理方案组合对美国华盛顿山地区的两次结冰事件进行了数值模拟。结果表明:预测的液态水含量和温度与现有文献匹配较好,而Morrison方案组合在误差分析中表现最佳。此外,讨论了水平分辨率和云微物理方案对液态水含量和云中液滴平均有效直径预测的敏感性。由于地形所引起的垂直运动是产生云水的主要动因,较高的水平分辨率能够做出更为准确的预测。最后利用IC指数对结冰强度进行了分析,表明结冰严重程度具有明显的时空多变特性,以及对云微物理方案的敏感性。本文工作有望加强对云微物理方案的理解和认识,并为选择适合的云微物理方案进行结冰天气预测提供了依据。

不同污染背景下云滴谱离散度对云降水模拟影响的个例研究

云滴谱离散度是云雨自动转化过程参数化中不可忽视的重要参数,对地面降水有着重要的影响。本文利用WRF-Chem(Weather Research and Forecast coupled with Chemistry)模式,对发生在2019年1月3~6日长江中下游地区的一次降水过程进行了模拟。在清洁和污染的气溶胶背景下,设定不同的云滴谱离散度的数值(0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9和1.0),研究云降水微物理的变化。结果表明,该个例降水主要来源于云雨自动转化以及云雨碰并过程。在清洁条件下的地面累计降水量大于在污染条件下的累计降水量,这是因为在清洁条件下云滴数浓度小,有利于云雨自动转化以及云雨碰并过程。虽然云雨自动转化以及云雨碰并过程占主导,但导致地面累计降水量随云滴谱离散度增大而增大的主要原因是:随着云滴谱离散度的增大,冰粒子质量浓度增大,导致融化过程增强,产生更多的雨滴,从而增强地表降水。所得结果将提高我们对云降水对气溶胶和离散度响应过程的理论认识。

Influence of multi-chemical-component aerosols on the microphysics of warm clouds in North China

An adiabatic bin-sized cloud parcel model is developed by incorporating the multi-chemical-component (MCC) aerosol effects into the UWyo single-chemical-component (SCC) parcel model. The effects of MCC aerosols on the warm cloud microphysics in North China are investigated with the model. The simulations are initialized using the data on chemical components and number size distribution of aerosols measured during the IPAC (Influence of Pollution on Aerosols and Cloud Microphysics in North China) campaign in spring 2006. It is found that the MCC aerosols in North China increase the cloud droplet number concentration (CDNC) and decrease the effective radius more efficiently than pure ammonium-sulfate aerosols. It is also shown that the MCC aerosols in North China can narrow the cloud droplet spectra (CDS) by increasing CDNC in small size and decreasing CDNC in large size. Our results indicate that aerosol chemical components and their size distributions can influence the microphysics of warm clouds, and thus affect atmospheric radiation and precipitation. This should attract more attentions in weather and climate change research in the future.

冰晶核化对雷暴云微物理过程和起电影响的数值模拟研究

本文在已有的二维对流云模式中采用了一种与气溶胶有关的冰晶核化方案替代原有的冰晶核化经验公式,并选取个例,分别就两种方案进行了模拟对比试验。模拟结果表明:(1)新方案所得冰晶比含水量主要分布在-0.1^-7.6°C温区之间,高于原方案所得的-50.1^-24.2°C温区;在整个雷暴云的发展过程中新方案冰晶的分布高度、温度区间以及最大浓度值均大于原方案。(2)在新方案中,温度相对较高的过冷区产生大量冰晶,其争食云中水汽抑制了云滴、雨滴的增长。此外,与原方案相比,霰增长受雨滴大幅减小的影响进一步得到限制,导致生成的霰小于原方案,且空间分布具有较大区别。(3)两方案在雷暴云初期形成的电荷结构不同;在发展旺盛与消散阶段新方案中电荷空间分布区域和电荷量均大于原方案,此外,在不同时刻主正电荷区和主负电荷区的中心高度存在差异。本文对云微物理过程及起电的分析为后继探讨气溶胶与雷暴云起放电过程、电荷结构之间的相互关系提供了有利条件。

贵州地区冰雹云微物理过程及发展机制数值模拟研究

为了进一步探究贵州地区冰雹云的形成、发展机制和冰雹增长的微物理转化条件,运用三维冰雹云模式对该地区2012—2015年12个冰雹个例进行数值模拟研究,结果发现:各种水成物有利的空间分布是雹粒增长的物质基础,且上升气流与水汽相变之间存在一个正反馈效应,冰雹粒子主要以霰粒子为胚胎进行增长,增长方式以霰自动转化成雹为主。在再生冰雹云发展过程中,雹云首次发展过程结束时,高空仍维持4 km及以下很低的0℃层高度,是再生冰雹云发展的热力环境条件。降雹区地面气流辐散,导致两侧区域形成较强的气流辐合上升,是再生冰雹云发展的动力条件。气流在辐合的同时,又使原降雹区的水汽源源不断地向两侧气流辐合区汇合,是再生冰雹云发展的水汽来源。冰雹云中冰晶和霰粒子含量的迅速增加,为冰雹的再次增长提供了有利的微物理物质转化条件。

云凝结核浓度对WRF模式模拟飑线降水的影响:不同云微物理参数化方案的对比研究

采用WRF模式模拟一次影响中国广东省的飑线过程,分别选取Morrison、Thompson07、Thompson09和WDM6云微物理方案实施了四组试验,每组试验包括不同云凝结核(CCN)浓度的三次模拟,称为"低浓度"、"中浓度"和"高浓度",将模拟区域划分为深对流、浅对流和层云区域,对比分析四组试验中CCN浓度变化对模拟的总降水量、不同区域降水率和不同区域面积的影响,进一步分析了云微物理过程、动力环流强度等受CCN浓度变化的影响。发现:(1)由于不同云微物理过程与CCN浓度有着直接或间接的联系、不同云微物理过程之间存在复杂的关联、云微物理过程与动力环流之间发生非线性耦合,采用不同的云微物理方案导致模拟的CCN—降雨影响既有相似、也有差异;(2)模拟的CCN—降水影响在采用Thompson09和Thompson07方案时更显著,采用WDM6方案时最小;(3)四组模拟试验均出现CCN浓度增加延迟降水产生、初期降水减弱的情况,在模拟后期降水量也随着CCN浓度增加而减小,而飑线成熟阶段CCN—降水影响更加复杂。

华北地区气溶胶混合状态对暖云微物理特征的影响

在UWyo单组分气溶胶的绝热气块分档云模式基础上,发展了多种化学组分气溶胶的绝热气块分档云模式。利用2006年春季华北地区地面气溶胶分级采样的离子成分分析数据和同时段高空气溶胶、云微物理飞机观测资料,研究了气溶胶混合状态对暖云微物理特征的影响。模拟结果表明,华北地区气溶胶内部混合比外部混合有利于增加云凝结核数浓度、降低气块水汽最大饱和比、增加云滴数浓度。气溶胶的混合状态不同,形成的云滴谱的特征差异较大,主要体现在云滴谱的平均尺度和峰值的突出程度;云滴谱相对离散度在0.3附近变化,且随着云滴数浓度的增加,云滴谱相对离散度呈现减小的趋势。气溶胶混合状态能够影响暖云微物理特征,从而影响大气辐射和降水过程,在天气和气候变化的研究中应予以关注。

祁连山夏季地形云结构和云微物理过程的模拟研究(I):模式云物理方案和地形云结构

对三维非静力中尺度模式ARPS的云降水微物理方案进行了改进,利用改进后的ARPS模式模拟了祁连山地区夏季的两个地形云个例,通过对各自模拟结果的对比分析并结合实况资料研究了夏季祁连山地区地形云的发展状况、动力场特征、降水特征以及云微物理结构特征。研究结果表明,地形云的发展受地形影响很大,地形的抬升促进了云和降水的发展,地形的作用也改变了地面降水特征,使云的宏、微观物理结构发生较大变化。

华南区域高分辨率模式中不同雷达回波反演技术方案的比较试验

结合一次比较典型的华南前汛期暴雨过程,对目前常用的几种雷达回波反演技术进行比较,试图得到一种适用于华南区域高分辨率模式的技术方案。首先比较了两种不同的水凝物反演技术对短期降水预报的影响,发现基于暖雨假设构造的经验公式反演得到的云微物理量进行Nudging以后预报降水比实况偏弱,而利用LAPS系统可以反演出高层的固态粒子,这些云粒子通过冰相过程可以产生强度与实况相当的降水。仅仅引入初始场的凝结物只对第一小时降水预报改进比较明显。通过对两种不同的水汽反演技术进行比较,发现1D+3D方法反演得到的水汽场并不适用于高分辨率模式,按该方法调整初始场水汽之后反而导致降水预报效果变差,而根据雷达回波调整水汽饱和的方法却可以有效提高前6小时的降水评分,这种改进主要来自降水漏报现象的减少。总体来说,结合利用LAPS系统反演云物理量以及水汽饱和调整方法是一套比较适合华南区域高分辨率模式的技术路线。

中尺度山脉对流群的动力和微物理数值模拟

大山脉春夏季受太阳加热和地形抬升作用易于形成对流过程。为研究这类对流特点，在沙特阿拉伯ＡＳＩＲ山区组织了一个ＳＡＣＰＥＸ实验计划。本文应用中国强风暴实验室ＭＢＧ（ＭＥＳＯ—Ｂｅｔａ＆Ｇａｍｍａ）非静力模式，选取适当模拟通道模拟了该计划中１９９０年５月３日一次对流降水过程。模拟结果揭示了大山脉气流强迫与对流环流相互作用的一些基本特点，展示了大山脉对流过程多种复杂的宏微观特征及其生消演变。包括山坡激发对流，大对流对小对流的抑制，云自然引晶效应等，并指出在这类对流系统中ＣＣＮ浓度对其降水类型的重要影响。此外，本文还进行了采取细致的雹云微物理参数化和采用简单的暖云微物理参数化的对比试验，结果表明两者模拟的动力场差别甚小，而云形态和降水发展有明显差异。上述结果总体上与该个例外场观测一致。

黄河上游河曲地区对流云催化增雨的数值模拟研究

应用中国科学院大气物理研究所开发的三维对流云模式 ,对青藏高原河曲地区强对流云的催化增雨效果及催化云的动力特征、微物理机制进行了模拟研究。模拟结果显示 :黄河上游河曲地区的对流云具备一定的催化潜力。如果催化时机、部位选择适当 ,降水总量增加有望达到 30 %～ 5 0 % ,催化所产生的动力效果比较显著。催化剂的加入使得云中凝华潜热释放量增加 ,上升气流加强 ,云顶升高 ,云水平尺度也有所加大 ,地面降水区域扩大 ,降水时间延长。由于云中冰晶大量生成 ,导致过冷云水、雨水减少 ,暖雨过程迅速减弱 ,云中霰和冻滴量增多 ,其融化过程加强引起的降水增加远远超过了暖雨量的减少 ,总的增雨效果比较显著。敏感性实验表明 ,催化高度对增雨效果的影响最为显著 ,高于某一催化高度 ,有可能产生增雨防雹的好效果 ;低于某一催化高度 ,则会在防雹的同时使地面降水减少。对流云早期催化的增雨效果较好。一定范围内催化剂量的变化对增雨量影响不大 ,小剂量催化也有可能达到较好的增雨效果。

一次冰雹过程及雹云物理结构的数值模拟研究

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