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1.
A combined three-dimensional numerical model of convective cloudiness with detailed microphysics and a model of the transport of atmospheric trace gases with gas- and aqueous-phase chemistry were developed. We consider the main physical mechanisms responsible for the formation of midsized droplet clouds and the transport of gases with differing solubility therein. Test numerical calculations were performed to investigate the sensitivity of the cloud model to variations in input parameters, as well as the variability of the ion composition of cloud drops with regard to their size distribution. The results of numerical calculations are presented with a preliminary analysis.  相似文献   

2.
We present the results of numerical simulation of the action of hygroscopic particles on a convective cloud for obtaining additional precipitation. The correspondence of vertical profiles of cloud parameters to those actually observed under natural atmospheric conditions is achieved within a one-dimensional numerical model by parametrization of the process of heat and moisture entrainment into the upward air flow forming the cloud. The model describes in detail microphysical processes in a cloud with the use of the kinetic equation for the size distribution of cloud droplets. The processes of forming precipitation in convective clouds with a vertical thickness of 3–4 km during their natural development and during the introduction of hygroscopic particles are analyzed using numerical calculations. It is shown that it is actually possible to obtain additional precipitation from convective clouds of continental type under the action of hygroscopic particles with sizes of 1–1.5 μm. The results of calculating the intensity and total amount of precipitation as functions of the vertical thickness of a cloud and the parameters of particles introduced into it are presented. The conditions necessary for obtaining the maximum positive effect are elucidated.  相似文献   

3.
The results of a numerical simulation of the action of hygroscopic particles on a warm convective cloud with the purpose of obtaining additional precipitation are presented. The one-dimensional numerical model considered in this work describes the evolution of the cloud medium in the central part of an axisymmetric convective cloud at the specified height-variable velocity of the upward air flow which forms the cloud. Our model comprehensively describes microphysical processes in the cloud medium with the use of the kinetic equation for the size distribution of cloud droplets. This model makes it possible to obtain the spatiotemporal pattern of the cloud formation and development and to analyze regular features in the cloud evolution under the action of hygroscopic reagents. The cloud characteristics calculated with the use of this model correspond to the cloud parameters observed in natural conditions of the atmosphere. The process of precipitation stimulation by hygroscopic particles in convective clouds with vertical thicknesses of 2.5–4.5 km was analyzed on the basis of the results of numerical calculations. The results of calculations of the dependence of the intensity and total amount of precipitation on the vertical cloud thickness and parameters of particles introduced into the cloud are presented. It is shown that hygroscopic particles with root-mean-cube radii of 1–1.5 μm are the most effective for acting on warm convective clouds with the purpose of obtaining additional precipitation. In this case, the required reagent expenditure is 100–200 kg/km2. The conditions necessary for obtaining the maximal positive effect of the action are elucidated.  相似文献   

4.
An extraordinary experimental fact is presented and analyzed, namely, a rather intense broadband radio noise detected during the passage of an atmospheric front through the field of view of UHF antennas. Local atmospheric properties and possible sources of the extraordinary noise, including the thermal noise from cloudiness and extra-atmospheric sources, are considered. A conclusion is made about the presence of an additional nonthermal source of radio noise in the frontal cloudiness. According to the proposed hypothesis, these are multiple electric microdicharges on hydrometeors in the convective cloud.  相似文献   

5.
The evolution of cloud microstructure initiated by hygroscopic seeding is studied on the basis of numerical simulation of cloud formation in the initial stage of condensation. The influence of both physicochemical properties of atmospheric aerosol and atmospheric conditions controlling the cloud type on the microstructure of a developing cloud (without hygroscopic seeding) is analyzed. It is shown that cloud seeding with additional particles whose sizes exceed the characteristic size of atmospheric condensation nuclei leads to a decrease in the concentration of cloud droplets and an increase in their sizes. This result of cloud seeding represents a positive effect for stimulation of precipitation from convective clouds. It is shown that this positive effect is achieved if there are some relationships between the parameters characterizing the hygroscopic particles and the atmospheric conditions. In particular, the maximum effect of action can be achieved at some optimal concentration of seeded particles. The decrease in the concentration of cloud droplets because of hygroscopic seeding is compared to the results of numerical simulations performed by other authors with allowance for coagulation processes in clouds. It is shown that this decrease can serve as an estimate for the effectiveness of hygroscopic seeding as a means for artificial intensification of precipitation from convective clouds.  相似文献   

6.
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7.
The planetary boundary layer (PBL), which directly interacts with the underlying surface, differs significantly in its nature from the low-turbulent stably stratified free atmosphere. Fluctuations of the Earth’s surface heat balance immediately affect the PBL and assimilate there owing to the effective mechanism of turbulent heat transfer. In this case the upper boundary of the PBL plays the role of a cover, preventing the direct penetration of thermal effects and contaminants into an overlying atmospheric layer. In view of this, air pollution is especially dangerous when associated with shallow PBL. In addition, local peculiarities of climate change are mainly determined by the PBL height due to the high sensitivity of thin stably stratified PBLs to the thermal effects. Deep convective PBLs are not very sensitive to weak thermal effects, but they significantly affect the formation of convective cloudiness and the climate system as a whole by means of the turbulent entrainment of the thermal energy, humidity, aerosols, and other admixtures through the upper boundary. The PBL height and turbulent entrainment must be calculated when simulating and forecasting air pollution, abnormal frosts and heat, and other hazardous phenomena. In this paper we discuss the state-of-the-art knowledge in the area of PBL height simulation and suggest a new model of turbulent entrainment for convective PBLs.  相似文献   

8.
“黑格比”后期异常强降水形成机理分析   总被引：1，自引：0，他引：1  
0814号强台风黑格比2008年9月25日08时减弱成低压进入越南高平后,在外围云系有明显中尺度对流云团发展,引发广西西南部新一轮比热带风暴本身更具破坏力的暴雨到大暴雨降雨。对美国国家环境预报中心(NCEP)提供的再分析资料、常规观测资料及雷达回波等研究结果,认为南亚高压西退造成负涡度向对流层中低层延伸,使500 hPa的西太平洋副热带高压出现减弱东退现象,成为低压后部对流云团在广西西南部停滞发展的背景条件。造成此次暴雨的4个中尺度对流云团,都是沿着暖切变右(北)侧100—200km范围内从东南往西北方向产生、移动的,中尺度降水落区呈东南-西北的带状分布。暖切变、垂直方向上的抽吸作用、θse的高值始终呈漏斗状的湿中性特征以及湿Q矢量对次级环流的激发作用等是此次低压后部中尺度对流云团的加强机制;而湿舌、湿Q矢量辐合区与未来强降水出现区域、出现时间对应较好。  相似文献   

9.
为探究冬季不同背景风场下黑潮锋影响边界层云的机理,采用高分辨率卫星数据和再分析数据,研究了冬季海面背景风为垂直(西北风)和平行(东北风)东海黑潮海表面温度锋(黑潮锋)条件下,边界层云对黑潮锋的响应。结果表明:背景风垂直黑潮锋情况下,黑潮锋强迫的边界层内次级环流明显,黑潮锋暖水侧海面冷平流强,海气温差增大,海气界面潜热感热通量增大,海气界面不稳定性增大,产生上升运动,云底高度抬升。上升运动在边界层底向南北两侧辐散,在冷水侧产生下沉运动与500 hPa高压下沉叠加,使局地云量明显减少,形成晴空少云区(云洞)。在暖水侧以南的下沉支叠加云顶上的下沉运动和边界层退耦效应共同作用,产生另一个云洞。气压调整机制为次级环流产生的主要原因。背景风平行黑潮锋情况下,海面空气温度平流作用小,暖水侧海气温差较小,虽然海洋仍然加热大气,但海气界面不稳定较弱,湍流增强使云底高度抬升,垂直混合机制为该湍流增强的主要原因。  相似文献   

10.
Evaporation and vertical moisture and heat transfer from the underlying surface are the basis of cloud formation. The situation when the coming relatively cold stably stratified air moves over a warm ocean is a typical problem in the development of a turbulent convective layer. The problem of cloud formation is also of scientific and practical interest. This paper considers the problems of the formation of a turbulent convective layer over a warmer ocean and the vertical distribution of relative humidity. The results of the theoretical model are compared with the data of observations of the development of the turbulent convective layer at low latitudes (in the Indian Ocean) and at higher latitudes (in autumn over Lake Michigan). Approximate equations describe well the dynamics of temperature and humidity of the layer as a function of the difference between the temperatures of the approaching and near-surface air layers. The theoretical results are compared with the data on measurements of the condensation heights obtained at the Novosibirsk Tolmachevo Airport. Some discrepancy between them is due to the unsteadiness measurement and the approximations adopted in the theoretical model.  相似文献   

11.
9012号热带气旋维持的卫星云图和垂直结构特征分析   总被引：2，自引：0，他引：2  
本文根据卫星云图的演变和常规天气分析相结合，对9012号热带气旋登陆后维持水消的成因进行了分析。指出该热带气旋经久不消的重要原因为其西南侧对流云团和东北侧高空槽前对流云带与热带气旋云系相衔接在中低层东北气流引导下卷入，热带气旋内部的两条云带的维持，以及利有的环流条件。  相似文献   

12.
On the basis of the radiation-cloudiness model and the available long-term satellite data, we study the correlations of the greenhouse effect with the surface temperature of air and effective cloudiness equal to the product of the cloud amount by the conditional optical density of the clouds. We deduce the relations of satellite monitoring of the behavior of the anomalies of global air temperature caused by the excess amounts of volcanic products and greenhouse gases (formed as a result combustion of the fossil fuel) in the atmosphere. Realistic estimates of the processes of cooling and warming of the currently existing climate are obtained. Under the condition of preservation of the existing linear trends in the behaviors of the short-and long-wave flows of radiation into the outer space (observed according to satellite data for the last 20 yr), the global temperature in the second part of the current century can increase by 1.6–2.0°C. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 13–28, November–December, 2006.  相似文献   

13.
ＯｂｓｅｒｖａｔｉｏｎｏｆｃｌｏｕｄｓａｎｄｓｏｌａｒｒａｄｉａｔｉｏｎｏｖｅｒｔｈｅＰａｃｉｆｉｃＯｃｅａｎａｓｒｅｌａｔｉｏｎｔｏｇｌｏｂａｌｃｌｉｍａｔｅ￥ＦａｒｎＰａｒｕｎｇｏ；ＣｌａｒｅｎｃｅＮａｇａｍｏｔｏ；ＣｅｃｉｌｉａＭ．Ｉ．Ｒ．Ｇｉ...  相似文献   

14.
The sensitivities of two climate-model versions—INMCM4 which participated in the Coupled Model Intercomparison Project, Phase 5 (CMIP5), and a new INMCM5 version with increased vertical and horizontal resolutions in its atmospheric block—to the quadrupled concentration of CO2 are studied. When the CO2 concentration is quadrupled, the equilibrium increase in surface temperature amounts to about 4.2 K for INMCM4, which is lower than that for other models that participated in the CMIP5. When the CO2 concentration increases, the cloud radiative forcing in the model decreases; in this case, one portion of this decrease occurs during the first year after the concentration of CO2 is quadrupled and the other portion almost linearly depends on the value of global warming. The results of additional numerical experiments with the model show that a rapid decrease in cloud-radiative forcing results from variations in stratification in the atmospheric surface boundary layer and associated increased cloudiness. The portion of a linear decrease in cloud-radiative forcing with increased temperature is associated with an increase in the water content of model clouds at higher temperatures. The elimination of these two mechanisms allows one to increase the model sensitivity to the quadrupled concentration of CO2 up to 5.2 K.  相似文献   

15.
The results of experimental investigations into the action of polydispersion salt powders on model cloud media are presented. The results of experiments show a considerable positive effect of the modification of convective clouds by salt powders in order to obtain additional precipitation. The introduction of polydispersion salt powder into a forming cloud medium leads to the appearance of large cloud droplets and to the droplet-spectrum broadening. This result is a positive factor for the stimulation of coagulation processes and further precipitation formation. No “overseeding” phenomenon (when, instead of the enlargement of droplets, their sizes decrease and the concentration of cloud droplets increases) is observed at rather high mass concentrations of the introduced powder.  相似文献   

16.
北极中央区海冰密集度与云量相关性分析   总被引：2，自引：0，他引：2  
纪旭鹏  赵进平 《海洋学报》2015,37(11):92-104
本文使用海冰密集度以及低云、中云、高云的日平均数据,借助滑动相关分析方法,研究了北极中央区海冰密集度与云量之间的相关性,分析了海冰与云的相互作用机制。研究表明,在春季海冰融化季节(4、5月)、秋季海冰冻结季节(10、11月),低云与海冰密集度之间表现为较好的负相关,表明在这段时间内冰区海面蒸发强烈,对低云的形成有重要贡献。在10月和11月,中云与海冰密集度也有很好的负相关,表明秋季低云可以通过抬升形成中云。高云与海冰密集度之间并没有明显的相关性,可能原因:一方面海冰的空间分布对高云无影响,另一方面,高云主要影响到达的短波辐射,从而影响海冰的融化和冻结速度,与海冰厚度有直接显著的关系,而与海冰密集度的关系不明显。此外,在海冰密集度与低云存在较好负相关的情况下会出现某些年份相关性不好的情况,我们的研究发现这是北极中央区与周边海区发生了海冰交换或云交换的结果。  相似文献   

17.
Satellite-based microwave radiometers can measure sea surface temperature (SST) over wide areas, even under cloud cover, owing to the weak absorption of microwaves by cloud droplets. This advantage is not available in the case of infrared observations, hence SST data derived from microwave radiometers have been widely used for operational and research purposes in recent years. This paper reviews the significant algorithms, validations, and applications related to microwave observation of SST. The history and specifications of past and present microwave radiometers are also documented. Various physical properties, including sea surface salinity, sea surface wind, molecules in the atmosphere, and clouds, affect the accuracy of SST data estimated by satellite-based microwave radiometers. Estimation algorithms are designed to correct these effects by using microwave measurements in several frequency channels and by using data of ancillary geophysical parameters. Validation studies have shown that microwave radiometer SST data have high accuracy that is comparable to the accuracy of data obtained from infrared measurements. However, certain persistent problems, such as sea-surface wind correction, remain to be solved.  相似文献   

18.
When long, fast swell waves travel in approximately the same direction as the wind, the surface stress is reduced compared with under wind-sea conditions. Using measurements from the Östergarnsholm site in the Baltic Sea, new expressions of the roughness length were developed for wind sea and swell. These new expressions were implemented in the RCA3 regional climate model covering Europe. A 3-year simulation and two case studies using the wavefield from the ECMWF reanalysis (ERA-40) were analysed using the improved formulations. Wind-following swell led to a significant reduction of mean wind stress and heat fluxes. The mean surface layer wind speed was redistributed horizontally and the marine boundary layer cooled and dried slightly. This cooling was most pronounced over North Sea and the Norwegian Sea (almost 0.2 °C annually on average) whereas the drying was most pronounced over the Mediterranean Sea (almost 0.4 g kg−1). Somewhat less convective precipitation and low-level cloudiness over the sea areas were also indicated, in particular over the Mediterranean Sea. The impact on the atmosphere, however, is significantly locally greater in time and space.  相似文献   

19.
High-frequency propagation close to an active surf line is explored with 12and 100-kHz propagation paths together with measurements of bubble clouds, bubble size distributions, and waves. Breaking waves inject massive bubble plumes that are mixed downwards from the roller region by intense turbulence. If these injections follow one another at intervals less than the time taken for the bubbles to rise to the surface, acoustic signals will be continuously blocked, forming an acoustical barrier that effectively inhibits any propagation. Occasionally, waves break seaward of this barrier. In this case, dense bubble clouds are mixed down beneath the air entrainment zone, but there is sufficient time for them to disappear before succeeding breakers, allowing intermittent high-frequency propagation recharge the bubble field. The duration and shape of signal dropouts are then determined by the selective removal of bubbles by buoyancy and dissolution. In addition to turbulence created by the air entrainment process, a lower level of continuous background turbulence may be generated by interaction of residual currents with the wave boundary layer. Our observations illustrate the variable character of acoustic blocking by bubble clouds and serve as a basis for quantitative analysis of these effects with a 2D propagation model coupled to 2D models of bubble cloud evolution and background turbulence  相似文献   

20.
We analyzed the motions of small sediment particles over a sinusoidal ripple due to an unsteady turbulent boundary layer flow using Large Eddy Simulation. The motions of sediment particles are described in terms of the Lagrangian framework as it is helpful in studying the structure of sediment suspension in detail. Strong coherent vortical structures are well developed along the upslope of the ripple surface during the accelerating flow phase, which effectively drag the particles to the ripple crest. At the maximum flow rate and at the decelerating flow phase, a cloud of vortical structures is developed vertically in the lee area of the ripple. Sediment particles render strong dispersion in the vertical direction when they are captured by these turbulent vortices, causing convective sediment flux that cannot be explained by the mean flows. The convective sediment suspension is strongest at the time of flow deceleration, while over a flat bed at the time of flow reversal. This observation suggests that bed form effect should be considered in modeling convective sediment flux.  相似文献   

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