Scavenging Efficiency of ‘Aerosol Carbon’ and Sulfate in Supercooled Clouds at Mt. Sonnblick (3106 m a.s.l., Austria)

Cloud water and interstitial aerosol samples collected at Mt. Sonnblick (SBO) were analyzed for sulfate and aerosol carbon to calculate in-cloud scavenging efficiencies. Scavenging efficiencies for sulfate (_SO) ranged from 0.52 to 0.99 with an average of 0.80. Aerosol carbon was scavenged less efficiently with an average value (_AC) of 0.45 and minimum and maximum values of 0.14 and 0.81, respectively. Both _SO and _AC showed a marked, but slightly different, dependence on the liquid water content (LWC) of the cloud. At low LWC, _SO increased with rising LWC until it reached a relatively constant value of 0.83 above an LWC of 0.3 g/m³. In the case of aerosol carbon, we obtained a more gradual increase of _AC up to an LWC of 0.5 g/m³. At higher LWCs, _{_} remained relatively constant at 0.60. As the differences between _SO and _A varied across the LWC range observed at SBO, we assume that part of the aerosol carbon was incorporated into the cloud droplets independently from sulfate. This hypothesis is supported by size classified aerosol measurements. The differences in the size distributions of sulfate and total carbon point to a partially external mixture. Thus, the different chemical nature and the differences in the size and mixing state of the aerosol particles are the most likely candidates for the differences in the scavenging behavior.     

青海秋季对流云降水及催化过程数值模拟研究

利用CAMS三维对流云模式和青海省河南县秋季外场试验取得的资料，对自然云的发展演变过程进行了数值模拟试验。进一步就催化时间、催化剂量对增雨效果的影响进行了数值试验。结果表明，该地区秋季对流云降水主要为冷云降水，冰晶是霰产生的主要来源，冰霰自动转化是霰产生的最主要方式，冰晶与霰的碰并又促进了霰的进一步增长，霰是云中过冷水消耗的主要因素。人工播撒催化剂应在冰核活化过程大量开始以前进行，以达到增加冰晶浓度，消耗过冷云水，从而增加降水的目的。     

东南沿海地区中α尺度雷暴云团卫星云图特征分析

利用GMS-5卫星IR、VIS、WV和分裂窗云图资料及常规天气图对1996～1999年3～9月发生在我国东南沿海地区的对流(雷暴)天气进行分析表明，对流(雷暴)天气主要发生在静止锋等六种不同的天气形势下，它们在卫星云图上的基本数字特征有相同之处，也存在明显的差异。通过对卫星云图中α尺度雷暴云团的灰度和局地标准差等基本数字特征的分析，发现局地标准差极大值或红外一分裂≤0极小值的出现，预示4h左右后雷暴云团将达最强。由此，可以较好的把握雷暴云团的发展阶段以及发展趋势，提高雷暴的预报水平。     

Comparison Between Computer Simulation of Transport and Diffusion of Cloud Seeding Material Within Stratiform Cloud and the NOAA-14 Satellite Cloud Track

A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 kin, 8.3 and 11 kin, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time,are simulated. The model results at the satellite receiving time axe compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track.The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, width, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L^-1 are simulated in order to understand the variations of influencing range.     

强对流云新概念在积云人工增雨作业中的运用

在对强对流(积云)增雨作业中,引用防雹新概念方法是利用多普勒雷达不同仰角的反射率(R)图及反射率剖面(RCS)图、径向速度剖面(VCS)图等资料,对强对流云流场特征进行定性分析,判定其主位置,通过主入流区位置和态势,确定“0”线的类型,给出增雨作业的时机和部位。用这一新概念,结合天津地区积云增雨的实际情况,在2003~2005年期间进行了应用。当流场、温度场和水凝物粒子场适当配置时,会形成大量降水粒子的集中累积,产生阵性暴雨。     

对流云人工增雨潜力初步探讨

利用在古田水库建立的以新一代天气雷达为主,包括稠密地面雨量站网等人工增雨综合监测技术系统,结合古田水库“蓄水型”人工增雨外场试验研究对流云降水量、降水效率和人工增雨潜力。研究表明:①试验区对流云自然降水效率平均约为1222×103m3,最大为1626×103m3;②人工催化后18~36 min,平均降水效率提高6个百分点,每次作业降水量增加395.5×103m3;相对增加28.36%,最大分别增加10个百分点,为972×103m3和59.78%;③每次作业水库入库流量增加143×103m3;④综合12年(1975~1986)古田人工增雨试验和2004年古田水库“蓄水型”人工增雨效果分析,可以认为对流云云内含水量大,有明显的增雨潜力。     

A bin-microphysics cloud model with high-order, positive-definite advection

An axisymmetric, anelastic model of a convective cloud is described. The model comprises prognostic equations for the azimuthal vorticity, the perturbation potential temperature, the perturbation water vapor mixing ratio, 44 categories of cloud condensation nuclei, and 100 categories of liquid-phase hydrometeors. Results from a control simulation show that the model is capable to reproduce realistically the life cycle of a convective cloud including the production of warm rain.A discussion of the role of advection in bin-microphysics models is presented and sensitivity tests were performed regarding the order of advection. The results show that, although the global characteristics of all simulated clouds were similar, significant differences occur with respect to their microstructure, particularly close to the cloud edges, when the order of the advective scheme changes. The conclusion is that intermediate-order advection schemes can indeed be used in cloud-resolving simulations, as far only as the gross characteristics of the cloud/cloud system are being investigated, but not poor, low-order schemes. On the other hand, the sensitivity with respect to the advection suggests that the evaluation of cloud phenomena that occur in fine-scales, such as entrainment and certain microphysical and radiational processes, must require the use of accurate, higher-order schemes.     

提高小概率事件预报成功率的一条途径

在给出小概率事件定义与评估小概率事件预报成功率参数的基础上,根据参数变换后的表达式推断,变小概率事件为条件概率下的大概率事件,是提高小概率事件预报成功率的一条途径。     

孟加拉湾低压造成云南强降水的中尺度分析

通过对１９８１～１９９１年春秋两季孟加接湾低压影响云南强降水的１６个个例的ＴＢＢ资料进行等值线分析及云北度、云降水效率的计算和对中－α尺度对流进行了尺度及结构分析、对云顶温度、温度梯度、地理区域与降水关系的分析,给出了一些孟加拉湾低压影响云南并造成强降水时的云图特征量与降水的相互关系。     

连续冰雹天气的物理量场特征分析

对１９９７年４月２８～２９日山东连续两天出现大范围冰雹天气的天气系统和热力及动力场特征进行了分析。结果表明,这次连续性大范围冰雹天气过程是由冷性低涡影响产生的。冷锋触发对流不稳定能量释放,产生强对流。冰雹产生在中低层对流不稳定、高能舌和低层暖平流、高层冷平流以及低层辐合、高层辐散的上升运动区。对流有效位能和高层正涡度平流对冰雹的产生起主要作用。