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1.
The second field campaign of the Cloud Ice Mountain Experiment (CIME) project took place in February 1998 on the mountain Puy de Dôme in the centre of France. The content of residual aerosol particles, of H2O2 and NH3 in cloud droplets was evaluated by evaporating the drops larger than 5 μm in a Counterflow Virtual Impactor (CVI) and by measuring the residual particle concentration and the released gas content. The same trace species were studied behind a round jet impactor for the complementary interstitial aerosol particles smaller than 5 μm diameter. In a second step of experiments, the ambient supercooled cloud was converted to a mixed phase cloud by seeding the cloud with ice particles by the gas release from pressurised gas bottles. A comparison between the physical and chemical characteristics of liquid drops and ice particles allows a study of the fate of the trace constituents during the presence of ice crystals in the cloud.In the present paper, an overview is given of the CIME 98 experiment and the instrumentation deployed. The meteorological situation during the experiment was analysed with the help of a cloud scale model. The microphysics processes and the behaviour of the scavenged aerosol particles before and during seeding are analysed with the detailed microphysical model ExMix. The simulation results agreed well with the observations and confirmed the assumption that the Bergeron–Findeisen process was dominating during seeding and was influencing the partitioning of aerosol particles between drops and ice crystals. The results of the CIME 98 experiment give an insight on microphysical changes, redistribution of aerosol particles and cloud chemistry during the Bergeron–Findeisen process when acting also in natural clouds.  相似文献   

2.
Phase Two of the Integrative Monsoon Frontal Rainfall Experiment(IMFRE-II)was conducted over the middle and lower reaches of the Yangtze River during the period 16 June to 19 July 2020.This paper provides a brief overview of the IMFRE-II field campaign,including the multiple ground-based remote sensors,aircraft probes,and their corresponding measurements during the 2020 mei-yu period,as well as how to use these numerous datasets to answer scientific questions.The highlights of IMFRE-II are:(1)to the best of our knowledge,IMFRE-II is the first field campaign in China to use ground-based,airborne,and spaceborne platforms to conduct comprehensive observations over the middle and lower reaches of the Yangtze River;and(2)seven aircraft flights were successfully carried out,and the spectra of ice particles,cloud droplets,and raindrops at different altitudes were obtained.These in-situ measurements will provide a“cloud truth”to validate the ground-based and satellite-retrieved cloud and precipitation properties and quantitatively estimate their retrieval uncertainties.They are also crucial for the development of a warm(and/or cold)rain conceptual model in order to better understand the cloud-to-rain conversion and accretion processes in mei-yu precipitation events.Through an integrative analysis of ground-based,aircraft,and satellite observations and model simulations,we can significantly improve our cloud and precipitation retrieval algorithms,investigate the microphysical properties of cloud and precipitation,understand in-depth the formation and dissipation mechanisms of mei-yu frontal systems,and improve cloud microphysics parameterization schemes and model simulations.  相似文献   

3.
The chemistry of cloud multiphase systems was studied within the Kleiner Feldberg Cloud Experiment 1990. The clouds encountered during this experimental campaign could be divided into two categories according to the origin of air masses in which the clouds formed. From the chemical point of view, clouds passing the sampling site during the first period of the campaign (26 October-4 November) were characterized by lower pollutant loading and higher pH, as compared to clouds during the final period of the experimental campaign (10–13 November). The study of multiphase partitioning of the main chemical constituents of the cloud systems and of atmospheric acidity within the multiphase systems themselves (gas + interstitial aerosol + liquid droplets) are presented in this paper. A general lack of gaseous NH3 was found in these cloud systems, which caused a lack of buffer capacity toward acid addition. Evidence supports the hypothesis that the higher acidity of the cloud systems during this final period of the campaign was due to input of HNO3. Our measurements, however, could not determine whether the observed input was due to scavenging of gaseous HNO3 from the air feeding into the cloud, or to heterogeneous HNO3 formation via NO2 oxidation by O3 to NO3 and N2O5. Sulfate in cloud droplets mainly originated from aerosol SO 4 2– scavenging, since S(IV) to S(VI) liquid phase conversion was inhibited due to both lack of H2O2 and low pH of cloud droplets, which made O3 and metal catalyzed S(IV) oxidation inefficient.  相似文献   

4.
金莲姬  银燕  王盘兴 《大气科学》2007,31(5):793-804
利用中国科学院大气物理研究所发展的三维强风暴模式,对Egrett Microphysics Experiment with Radiation Lidar and Dynamics（EMERALD）试验期间的一次长寿命热带深对流个例进行对流产生、发展、消亡过程以及云砧的数值模拟,并与实测资料［包括C波段双线偏振雷达图像资料、机载云粒子成像仪（CPI）探测的云砧卷云微物理特性以及激光雷达探测的云砧宏观特性资料］进行了细致的对比,然后通过改变模式中最大云滴数浓度进行有关云凝结核数浓度影响云砧卷云冰晶含水量和数浓度的敏感性试验。模式较好地模拟出系统的一些重要宏观特征,如爆发性增长阶段、各高度雷达水平反射率因子的最大值、对流云主体移动方向、云砧底部和顶部高度。对云砧冰相粒子含水量、数浓度以及平均直径等微观特征的模拟结果与实测也比较接近。对于本文个例而言,异质核化为冰晶形成的最主要方式,其次为过冷云滴的均质核化。敏感性试验结果表明:当云凝结核数浓度增加时,爆发性增长阶段的垂直速度减小,使得对流云从中低层向高层的水物质输送量减少,从而使云砧卷云冰晶的数量减少。  相似文献   

5.
To date, the intraseasonal variation of raindrop size distribution(DSD) in response to the Madden–Julian Oscillation(MJO) has been examined only over the Indonesian Maritime Continent, particularly in Sumatra. This paper presents the intraseasonal variation of DSD over the Indian Ocean during the Cooperative Indian Ocean experiment on Intraseasonal Variability in the Year 2011(CINDY 2011) field campaign. The DSDs determined using a Joss–Waldvogel disdrometer,which was installed on the roof of the anti-rolling system of the R/V Mirai during stationary observation(25 September to 30 November 2011) at(8°S, 80.5°E), were analyzed. The vertical structure of precipitation was revealed by Tropical Rainfall Measuring Mission Precipitation Radar(version 7) data. While the general features of vertical structures of precipitation observed during the CINDY and Sumatra observation are similar, the intraseasonal variation of the DSD in response to the MJO at each location is slightly different. The DSDs during the active phase of the MJO are slightly broader than those during the inactive phase, which is indicated by a larger mass-weighted mean diameter value. Furthermore, the radar reflectivity during the active MJO phase is greater than that during the inactive phase at the same rainfall rate. The microphysical processes that generate large-sized drops over the ocean appear to be more dominant during the active MJO phase, in contrast to the observations made on land(Sumatra). This finding is consistent with the characteristics of radar reflectivity below the freezing level, storm height, bright band height, cloud effective radius, and aerosol optical depth.  相似文献   

6.
Summary In autumn 1999 during the field phase of the Mesoscale Alpine Programme (MAP), the geostationary satellite Meteosat-6 performed 5-minute rapid scan imagery over central Europe. The rapid scan data of 11 heavy precipitation events are investigated by analyzing the spatial and temporal characteristics of cloud top structures. The objectives are to separate convective from stratiform cloud regions by satellite data alone and to gain insight into the life cycle of heavy precipitation systems. For verification of the satellite-based results, radar data from the operational Mt. Lema C-band radar is interpolated on the spatial grid of the infrared and visible Meteosat images. The interpolated radar data of each single grid cell is then classified by a convective-stratiform algorithm and compared to the analysed rapid scan imagery.The satellite- and radar-based approaches do only rarely produce matching classifications concerning the identification of convective areas. Since convection during the field phase of MAP occurred mostly embedded within stratiform cloud regions, no temporal and spatial characteristics of convective activity within clouds can be systematically derived from satellite imagery. This lack of characteristic cloud top structures prevented the unambiguous identification of typical cloudiness associated with stratiform precipitation. It is one of the major findings of this study, that in several cases being classified as stratiform by radar, strong cloud development is observed in satellite imagery. The preferred area of strong cloud development is located ahead of the Alpine barrier in a precipitation-free atmosphere. Two contrasting examples of life cycles of heavy precipitation systems are given based on the complementary information extracted from satellite and radar data.  相似文献   

7.
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.  相似文献   

8.
毫米波测云雷达作为一种新型的气象探测装备,在云粒子的探测上具有一定的优势。基于毫米波测云雷达的探测数据和探空仪获取的温度数据,设计云粒子相态识别算法。采用该算法,对2017年1月19日、2月7日、3月20日的毫米波测云雷达探测数据进行了云粒子相态识别和过冷水等数据产品反演。分析结果表明,逆温层与过冷水层高度正相关,过冷水和冰晶交汇区附近会出现湿冰相和混合相,过冷水含量与融化层亮带呈一定的负相关关系,整体相态识别结果与实际相吻合,验证了粒子相态识别算法的有效性。  相似文献   

9.
The influence of meteorology on clouds at Kleiner Feldberg   总被引：1，自引：0，他引：1  
  相似文献   

10.
Based on airborne observations during the Baltex Bridge Cloud (BBC) campaign in September 2001, the impact of two layer cloud systems, gas absorption and surface albedo on cloud radiative smoothing is investigated. Multispectral nadir radiance measurements have been conducted which cover the visible and near infrared wavelength range. The observed radiances are transformed into Fourier space where ranges of scale-invariance are identified. Associated slopes and scale breaks are determined and used to characterize the impacts on cloud radiative smoothing. The results reveal that an increase of gas absorption reduces the small scale slope and the scale break due to a decreasing likelihood of horizontal photon transport. Another impact is that the increasing gas absorption reduces the cloud surface interaction, which is indicated by an increase of the large scale slope. An increasing surface albedo results in large scale cloud radiative smoothing and is associated with a decrease of the large scale slope. This effect depends on the cloud height and the cloud morphology. Two layer cloud systems exhibit a similar behaviour in Fourier space as large surface albedos beneath a single cloud deck. It is argued that the impact of two layer cloud systems on large scale cloud radiative smoothing may not be typical for two layer clouds.  相似文献   

11.
The cloud processes of a simulated moderate snowfall event in North China   总被引：1，自引：0，他引：1  
The understanding of the cloud processes of snowfall is essential to the artificial enhancement of snow and the numerical simulation of snowfall. The mesoscale model MM5 is used to simulate a moderate snowfall event in North China that occurred during 20–21 December 2002. Thirteen experiments are performed to test the sensitivity of the simulation to the cloud physics with different cumulus parameterization schemes and different options for the Goddard cloud microphysics parameterization schemes. It is shown that the cumulus parameterization scheme has little to do with the simulation result. The results also show that there are only four classes of water substances, namely the cloud water, cloud ice, snow, and vapor, in the simulation of the moderate snowfall event. The analysis of the cloud microphysics budgets in the explicit experiment shows that the condensation of supersaturated vapor, the depositional growth of cloud ice, the initiation of cloud ice, the accretion of cloud ice by snow, the accretion of cloud water by snow, the deposition growth of snow, and the Bergeron process of cloud ice are the dominant cloud microphysical processes in the simulation. The accretion of cloud water by snow and the deposition growth of the snow are equally important in the development of the snow.  相似文献   

12.
In this study, the temporal structure of the variation of North Atlantic Oscillation （NAO） and its impact on regional climate variability are analyzed using various datasets. The results show that blocking formations in the Atlantic region are sensitive to the phase of the NAO. Sixty-seven percent more winter blocking days are observed during the negative phase compared to the positive phase of the NAO. The average length of blocking during the negative phase is about 11 days, which is nearly twice as long as the 6-day length observed during the positive phase of the NAO. The NAO-related differences in blocking frequency and persistence are associated with changes in the distribution of the surface air temperature anomaly, which, to a large extent, is determined by the phase of the NAO. The distribution of regional cloud amount is also sensitive to the phase of the NAO. For the negative phase, the cloud amounts are significant, positive anomalies in the convective zone in the Tropics and much less cloudiness in the mid latitudes. But for the positive phase of the NAO, the cloud amount is much higher in the mid-latitude storm track region. In the whole Atlantic region, the cloud amount shows a decrease with the increase of surface air temperature. These results suggest that there may be a negative feedback between the cloud amount and the surface air t.emperature in the Atlantic region.  相似文献   

13.
The mei-yu season,typically occurring from mid-June to mid-July,on average,contributes to 32%of the annual precipitation over the Yangtze-Huai River Valley(YHRV)and represents one of the three heavy-rainfall periods in China.Here,we briefly review the large-scale background,synoptic pattern,moisture transport,and cloud and precipitation characteristics of the mei-yu frontal systems in the context of the ongoing Integrative Monsoon Frontal Rainfall Experiment(IMFRE)field campaign.Phase one of the campaign,IMFRE-I,was conducted from 10 June to 10 July 2018 in the middle reaches of the YHRV.Led by the Wuhan Institute of Heavy Rain(IHR)with primary support from the National Natural Science Foundation of China,IMFRE-I maximizes the use of our observational capacity enabled by a suite of ground-based and remote sensing instruments,most notably the IHR Mesoscale Heavy Rainfall Observing System(MHROS),including different wavelengths of radars,microwave radiometers,and disdrometers.The KA350(Shanxi King-Air)aircraft participating in the campaign is equipped with Ka-band cloud radar and different probes.The comprehensive datasets from both the MHROS and aircraft instruments are combined with available satellite observations and model simulations to answer the three scientific questions of IMFRE-I.Some highlights from a previously published special issue are included in this review,and we also briefly introduce the IMFRE-II field campaign,conducted during June-July 2020,where the focus was on the spatiotemporal evolutions of the mei-yu frontal systems over the middle and lower reaches of the YHRV.  相似文献   

14.
夏季催化对流云雷达回波特征对比分析   总被引：2，自引：0，他引：2  
袁野  冯静夷  蒋年冲  吴汪毅 《气象》2008,34(1):41-47
对"江淮地区对流云人工增雨外场试验"中3次催化作业过程,催化云和对比云新一代天气雷达回波特征的对比分析结果表明:催化云的平均维持时间比对比云长51.2%,平均回波面积比对比云多17%,催化云每个体扫的平均总液态含水量要高于对比云,整个维持时间的总液态含水量高出对比云46%.从而认为:催化作业可以达到增加回波面积,延长回波的持续时间,增加云中液态含水量的目的.并且,从其中一组对比中发现,对流云催化作业要掌握好催化时机,对于处在减弱期的对流云,催化作业达不到增加含水量、延长生命期的目的.  相似文献   

15.
Summary A method for the calculation of atmospheric turbulent diffusivity over complex terrain during day-time is presented, which may improve the predictions based on diagnostic meteorological models. The proposed procedure takes into account the geographic location of the area (latitude and longitude), the time of the day, the inclination and exposition of the surface, the soil type and the cloud cover. These data are used to compute the amount of solar heat flux contributing to the heating of the air mass above the ground level, and, consequently, the atmospheric turbulence. The model accounts for the effect of shadows generated by mountain profiles, which determine a differential heating at the valley floor and induce spatial and temporal variations of turbulent diffusivity. Model calibration has been performed through ground data collected during a field campaign in the Adige valley in the surrounding of the town of Trento.  相似文献   

16.
人工影响暖云过程吸湿性催化研究   总被引：1，自引：0，他引：1  
卢炯  袁冬梅 《河南气象》2008,31(1):80-84
介绍了近年来吸湿性催化的一些最新理论、新催化剂研制和播撒方法的研究,并分析了近期4个不同地区吸湿性作业试验结果：南非和墨西哥试验试图引入吸湿性凝结核,增宽云滴谱,加速凝结过程;泰国和印度试验试图引入活跃的凝结核,跳跃性地开启碰并过程。两类试验均促进云滴早期发展,产生比自然状态下更多的降水。此外通过暖云借化试剂在云室中催化湿空气的试验,来初步评估吸湿性催化的效率。  相似文献   

17.
A ground-based seeding experiment using carbon dioxide and propane sprayed from pressurized bottles was carried out under supercooled cloud conditions on a small spatial and short time scale. Water vapor deposition on the artificially generated dry ice and propane ice germs as the main ice formation process (nucleation and growth) is consistent with the experimental results. After nucleation, diffusional growth of the ice particles, partly at the expense of evaporating small droplets, was identified during the mixing of the seeding line with the ambient supercooled cloud. Within the seeding plume, ice water contents up to 80% of the total condensed water are observed, although the size of the formed ice particles did not exceed 25 μm. From the changes of the ice and supercooled liquid phase with time under mixed-phase conditions, liquid water content (LWC) evaporation, ice water content (IWC) formation, and ice crystal growth rates are estimated, which are not affected by the artificial nucleation process. Thus, these rates are assessed to be applicable for a growing ice phase of small ice particles in a young mixed-phase cloud, where other growth mechanisms, like riming or aggregation, are negligible.  相似文献   

18.
A strong precipitation event caused by the southwest vortex(SWV), which affected Sichuan Province and Chongqing municipality in Southwest China on 10–14 July 2012, is investigated. The SWV is examined using satellite observations from AIRS(Atmospheric Infrared Sounder), in situ measurements from the SWV intensive observation campaign, and MICAPS(Marine Interactive Computer-Aided Provisioning System) data. Analysis of this precipitation process revealed that:(1)heavy rain occurred during the development phase, and cloud water content increased significantly after the dissipation of the SWV;(2) the area with low outgoing longwave radiation values from AIRS correlated well with the SWV;(3) variation of the temperature of brightness blackbody(TBB) from AIRS reflected the evolution of the SWV, and the values of TBB reduced significantly during the SWV's development; and(4) strong temperature and water vapor inversions were noted during the development of the SWV. The moisture profile displayed large vertical variation during the SWV's puissant phase,with the moisture inversion occurring at low levels. The moisture content during the receding phase was significantly reduced compared with that during the developing and puissant phases. The vertical flux of vapor divergence explained the variation of the moisture profile. These results also indicate the potential for using AIRS products in studying severe weather over the Tibetan Plateau and its surroundings, where in situ measurements are sparse.  相似文献   

19.
Ground-based measured solar radiation fluxes are used to derive simultaneously cloud water content and cloud fraction cover. In this paper we present a new method for prognostically inferring cloud microphysical properties based on previous work of Chou and Suarez. A look up table method combined with simulated annealing process is associated with the Chou and Suarez radiation transfer model called CLIRAD-SW. This model which is of great sensitivity has been validated for several atmospheres. Calculations here are conducted for an equivalent period of one year of measurement realized by the MINREST-LRE program for the Yaoundé meteorological station during the year 1984 and are focused on the previously derived average solar days similar to those proposed by Klein and more representative of the monthly solar radiation profile. In order to reduce computational time, mean values of liquid, mixed phase and ice cloud effective radius are used according to those proposed by Chou M.D. As part of our retrieving method, diffuse and global fluxes calculated for each set of cloud and aerosol microphysical characteristics are compared with the fluxes measured during the corresponding period. The obtained results are in very good agreement with those fluxes with relative errors ranging from 0.001% to 1.9% for diffuse flux and from 0.0009% to 2% for global flux. Mean cloud fraction profile obtained was generally well correlated with seasons whereas the correlation of cloud water content with seasons was not very good. However, the characteristic trend was in good agreement with the change in seasons. The overall agreement observed suggests that the method is capable of characterizing cloud water content and fraction for the given period of the day and the year although the lack of in situ measurements was a limitation for a valuable verification of the accuracy of the method.  相似文献   

20.
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.  相似文献   

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