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1.
Effects of vertical wind shear, radiation, and ice clouds on cloud microphysical budget associated with torrential rainfall during landfall of severe tropical storm Bilis (2006) are investigated by using a series of analysis of two-day grid-scale sensitivity experiment data. When upper-tropospheric upward motions and lower-tropospheric downward motions occur on 15 July 2006, the removal of vertical wind shear and ice clouds increases rainfall contributions from the rainfall type (CM) associated with positive net condensation and hydrometeor loss/convergence, whereas the exclusion of cloud radiative effects and cloud-radiation interaction reduces rainfall contribution from CM. The elimination of vertical wind shear and cloud-radiation interaction increases rainfall contribution from the rainfall type (Cm) associated with positive net condensation and hydrometeor gain/divergence, but the removal of cloud radiative effects and ice clouds decreases rainfall contribution from Cm. The enhancements in rainfall contribution from the rainfall type (cM) associated with negative net condensation and hydrometeor loss/convergence are caused by the exclusion of cloud radiative effects, cloud-radiation interaction and ice clouds, whereas the reduction in rainfall contribution from cM results from the removal of vertical wind shear. When upward motions appear throughout the troposphere on 16 July, the exclusion of all these effects increases rainfall contribution from CM, but generally decreases rainfall contributions from Cm and cM.  相似文献   

2.
In this study,the effects of key ice microphysical processes on the pre-summer heavy rainfall over southern China during 3-8 June 2008 were investigated.A series of two-dimensional sensitivity cloud-resolving model simulations were forced with zonally uniform vertical velocity,zonal wind,horizontal temperature,and water vapor advection data from the National Centers for Environmental Prediction(NCEP)/Global Data Assimilation System(GDAS).The effects of key ice microphysical processes on the responses of rainfall to large-scale forcing were analyzed by comparing two sensitivity experiments with a control experiment.In one sensitivity experiment,ice crystal radius,associated with depositional growth of snow from cloud ice,was reduced from 100 μm in the control experiment to 50 μm,and in the other sensitivity experiment the efficiency of the growth of graupel from the accretion of snow was reduced to 50% from 100% in the control experiment.The results show that the domain-mean rainfall responses to these ice microphysical processes are stronger during the decay phase than during the onset and mature phases.During the decay phase,the increased mean rain rate resulting from the decrease in ice crystal radius is associated with the enhanced mean local atmospheric drying,the increased mean local hydrometeor loss,and the suppressed mean water vapor divergence.The increased mean rain rate caused by the reduction in accretion efficiency is related to the reduced mean water vapor divergence and the enhanced mean local hydrometeor loss.  相似文献   

3.
This study investigates the effects of vertical wind shear on the torrential rainfall response to the large-scale forcing using a rainfall separation analysis of a pair of two-dimensional cloud-resolving model sensitivity experiments for a pre-summer heavy rainfall event over southern China from 3-8 June 2008 coupled with National Centers for Environmental Prediction(NCEP)/Global Data Assimilation System(GDAS) data.The rainfall partitioning analysis based on the surface rainfall budget indicates that the exclusion of vertical wind shear decreases the contribution to total rainfall from the largest contributor,which is the rainfall associated with local atmospheric drying,water vapor divergence,and hydrometeor loss/convergence,through the reduction of the rainfall area and reduced rainfall during the rainfall event.The removal of vertical wind shear increases the contribution to total rainfall from the rainfall associated with local atmospheric drying,water vapor convergence,and hydrometeor loss/convergence through the expansion of the rainfall area and enhanced rainfall.The elimination of vertical wind shear enhances heavy rainfall and expands its area,whereas it reduces moderate rainfall and its area.  相似文献   

4.
At present,parameterization methods to describe cloud and precipitation processes are widely used in cloud and mesoscale models,but with different drop size distributions.When precipitation formation mechanism,weather modification technique,and mechanism of hail suppression with seeding are studied by using these models,a question that needs to be addressed is:what is the influence of different drop size distributions and related parameters on cloud and precipitation?In this paper,by using a three-dimensional hail cloud numerical model developed by the Institutes of Atmospheric Physics,Chinese Academy of Sciences, we performed numerical experiments with varied drop size distribution parameters for two hail storms,and analyzed the influence of shape parameters(ar,ai,and ag)of raindrops,ice crystal,and graupel size distributions on rainfall,hail amount,and microphysical processes in clouds.The results show that the variation of ar has no effect on precipitation formation on the whole,but affects directly the production rates for the physical processes related to raindrop.The ag variation has a less obvious effect on rainfall amount,but has a significant effect on hail amount,hailfall rate,and rainfall intensity.It impacts noticeably on the generation rate of the number and mass of ice crystal,graupel,and hail,and also to various degrees on all the microphysical processes in clouds.The ag variation also influences the growing process of the hydrometeors.The effects of the ai variation on part of the generation and growing processes of all the hydrometeors are significant,and even dramatic,such as the collection process of cloud water to rain through melting ice crystal(T CLcir).However,for clouds located in different geographic regions,the variation of ai has different effects on precipitation,which reflects the complexity of the impact of drop size distribution on cloud and precipitation.At last,some issues about the application of cloud models are also discussed.  相似文献   

5.
The effects of vertical wind shear on tropical cyclone (TC) intensity change are examined based on the TC data from the China Meteorological Administration and the NCEP reanalysis daily data from 2001 to 2006. First, the influence of wind shear between different vertical levels and averages in different horizontal areas are compared. The results indicate that the effect of wind shear between 200 and 850 hPa averaged within a 200–800 km annulus on TC intensity change is larger than any other calculated vertical wind shear. High-latitude and intense TCs tend to be less sensitive to the effects of VWS than low-latitude and weak TCs. TCs experience time lags between the imposition of the shear and the weakening in TC intensity. A vertical shear of 8–9 m/s (9–10 m/s) would weaken TC intensity within 60 h (48 h). A vertical shear greater than 10 m/s would weaken TC intensity within 6 h. Finally, a statistical TC intensity prediction scheme is developed by using partial least squares regression, which produces skillful intensity forecasts when potential predictors include factors related to the vertical wind shear. Analysis of the standardized regression coefficients further confirms the obtained statistical results.  相似文献   

6.
A thunderstorm that produced severe wind, heavy rain and hail on 23 August 2001 in Beijing was studied by a three-dimensional cloud model including hail-bin microphysics. This model can provide important information for hail size at the surface, which is not available in hail parameterization cloud models. The results shows that the cloud model, using hail-bin microphysics, could reasonably reflect the storm's characteristics such as life cycle, rainfall distribution and the diameter of the hailstones and also can reproduce developing processes of downbursts, where they can then be compared with the observed features of the storm. The downburst formation mechanism was investigated based on the cloud microphysics of the simulated storm and it was found that the downburst was primarily produced by hail-loading and enhanced by cooling processes that were due to hail melting and rain evaporation. The loading and melting of hail played crucial roles in the formation of downbursts within the storm.  相似文献   

7.
Both water vapor and heat processes play key roles in producing surface rainfall.While the water vapor effects of sea surface temperature and cloud radiative and microphysical processes on surface rainfall have been investigated in previous studies,the thermal effects on rainfall are analyzed in this study using a series of two-dimensional equilibrium cloud-resolving model experiments forced by zonally-uniform,constant,large-scale zonal wind and zero large-scale vertical velocity.The analysis of thermally-related surface rainfall budget reveals that the model domain mean surface rain rate is primarily associated with the mean infrared cooling rate.Convective rainfall and transport of hydrometeor concentration from convective regions to raining stratiform regions corresponds to the heat divergence over convective regions,whereas stratiform rainfall corresponds to the transport of hydrometeor concentration from convective regions and heat divergence over raining stratiform regions.The heat divergence over convective regions is mainly balanced by the heat convergence over rainfall-free regions,which is,in turn,offset by the radiative cooling over rainfall-free regions.The sensitivity experiments of rainfall to the effects of sea surface temperature and cloud radiative and microphysical processes show that the sea surface temperature and cloud processes affect convective rainfall through the changes in infrared cooling rate over rainfall-free regions and transport rate of heat from convective regions to rainfall-free regions.  相似文献   

8.
The impact of different cloud microphysics parameterization schemes on the intensity and structure of the Super-strong Typhoon Rammasun (1409) in 2014 is investigated using the Weather Research and Forecasting model version 3.4 with eight cloud microphysics parameterization schemes. Results indicate that the uncertainty of cloud microphysics schemes results in typhoon forecast uncertainties, which increase with forecast time. Typhoon forecast uncertainty primarily affects intensity predictions, with significant differences in predicted typhoon intensity using the various cloud microphysics schemes. Typhoon forecast uncertainty also affects the predicted typhoon structure. Greater typhoon intensity is accompanied by smaller vortex width, tighter vortex structure, stronger wind in the middle and lower troposphere, greater height of the strong wind region, smaller thickness of the eyewall and the outward extension of the eyewall, and a warmer warm core at upper levels of the eye. The differences among the various cloud microphysics schemes lead to the different amounts and distributions of water vapor and hydrometeors in clouds. Different hydrometeors have different vertical distributions. In the radial direction, the maxima for the various hydrometeors forecast by a single cloud microphysics scheme are collocated with each other and with the center of maximum precipitation. When the hydrometeor concentration is high and hydrometeors exist at lower altitudes, more precipitation often occurs. Both the vertical and horizontal winds are the strongest at the location of maximum precipitation. Results also indicate that typhoon intensities forecast by cloud microphysics schemes containing graupel processes are noticeably greater than those forecast by schemes without graupel processes. Among the eight cloud microphysics schemes investigated, typhoon intensity forecasts using the WRF Single-Moment 6-class and Thompson schemes are the most accurate.  相似文献   

9.
Cloud structure and evolution of Mesoscale Convective Systems(MCSs) retrieved from the Tropical Rainfall Measuring Mission Microwave Imager(TRMM TMI) and Precipitation Radar(PR) were investigated and compared with some pioneer studies based on soundings and models over the northern South China Sea(SCS).The impacts of Convective Available Potential Energy(CAPE) and environmental vertical wind shear on MCSs were also explored.The main features of MCSs over the SCS were captured well by both TRMM PR and TMI.However,the PR-retrieved surface rainfall in May was less than that in June,and the reverse for TMI.TRMM-retrieved rainfall amounts were generally consistent with those estimated from sounding and models.However,rainfall amounts from sounding-based and PR-based estimates were relatively higher than those retrieved from TRMM-TMI data.The Weather Research and Forecasting(WRF) modeling simulation underestimated the maximum rain rate by 22% compared to that derived from TRMM-PR,and underestimated mean rainfall by 10.4% compared to the TRMM-TMI estimate,and by 12.5% compared to the sounding-based estimate.The warm microphysical processes modeled from both the WRF and the Goddard Cumulus Ensemble(GCE) models were quite close to those based on TMI,but the ice water contents in the models were relatively less compared to that derived from TMI.The CAPE and wind shear induced by the monsoon circulation were found to play critical roles in maintaining and developing the intense convective clouds over SCS.The latent heating rate increased more than twofold during the monsoon period and provided favorable conditions for the upward transportation of energy from the ocean,giving rise to the possibility of inducing large-scale interactions.  相似文献   

10.
The effects of the initial cloud condensation nuclei(CCN) concentrations(100–3000 mg~(-1)) on hail properties were investigated in an idealized non-severe hail storm experiment using the Weather Research and Forecasting(WRF) model, with the National Severe Storms Laboratory 2-moment microphysics scheme. The initial CCN concentration(CCNC) had obvious non-monotonic effects on the mixing ratio, number concentrations, and radius of hail, both in clouds and at the surface, with a CCNC threshold between 300 and 500 mg~(-1). An increasing CCNC is conducive(suppressive) to the amount of surface hail precipitation below(above) the CCNC threshold. The non-monotonic effects were due to both the thermodynamics and microphysics. Below the CCNC threshold, the mixing ratios of cloud droplets and ice crystals increased dramatically with the increasing CCNC, resulting in more latent heat released from condensation and frozen between 4 and 8 km and intensified updraft volume. The extent of the riming process, which is the primary process for hail production, increased dramatically. Above the CCNC threshold, the mixing ratio of cloud droplets and ice crystals increased continuously, but the maximum updraft volume was weakened because of reduced frozen latent heating at low level. The smaller ice crystals reduced the formation of hail and smaller clouds, with decreased rain water reducing riming efficiency so that graupel and hail also decreased with increasing CCNC, which is unfavorable for hail growth.  相似文献   

11.
Microphysical and radiative effects of ice clouds on diurnal variations of tropical convective and stratiform rainfall are examined with the equilibrium simulation data from three experiments conducted with a two-dimensional cloud resolving model with imposed temporally and zonally invariant winds and sea surface temperature and zero mean vertical velocity. The experiment without ice radiative effects is compared with the control experiment with ice microphysics (both the ice radiative and microphysical effects) to study effects of ice radiative effects on diurnal rainfall variations whereas it is compared with the experiment without ice microphysics to examine ice microphysical effects on the diurnal rainfall variations. The ice radiative processes mainly affect diurnal cycle of convective rainfall whereas the ice microphysical processes have important impacts on the diurnal cycles of both convective and stratiform rainfall. Turning off the ice radiative effects generally enhances convective rainfall during the morning and evening and suppresses convective rainfall in the afternoon whereas turning off the ice microphysical effects generally suppresses convective and stratiform rainfall during the morning and enhances convective and stratiform rainfall in the afternoon and evening. The ice radiative and microphysical effects on the diurnal cycle of surface rainfall are mainly associated with that of vapor condensation and deposition, which is controlled by air temperature through saturation specific humidity. The ice effects on the diurnal cycle of local temperature tendency are largely explained by that of latent heating since the diurnal cycle of radiation is insensitive to the ice effects.  相似文献   

12.
The effects of ice microphysics on tropical atmospheric and oceanic variability are investigated with a two-dimensional coupled ocean-cloud resolving atmosphere model forced by the large-scale vertical velocity and zonal wind derived from Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). The experiment without ice microphysics is compared to a control experiment with ice microphysics. Compared to the control experiment, the experiment without ice microphysics generates a more humid and colder atmosphere by suppressing stratiform clouds and rainfall and associated latent heating; the experiment without ice microphysics produces a saltier mixed layer by a larger saline forcing associated with a weaker stratiform rainfall. Ocean mixed-layer temperature is insensitive to the atmospheric variability associated with ice microphysics.  相似文献   

13.
采用二维和三维完全弹性参数化冷云数值模式模拟研究了低层单向切变风场中积云的发展演变过程和地面降水特征。结果表明:在低层切变风场中,用热泡扰动方式激发对流的启动条件提高,而冷出流方式激发对流则更加容易。适当强度的低层切变使对流峰值强度减小,但积云生命史延长,地面累计总降水量增大,雨区拓宽,峰值雨强则减小。采用二维模式来模拟单向切变风场的对流活动虽然存在严重歪曲,但积云最大升速以及地面总降水随时间的演变特征与三维模拟结果一致。  相似文献   

14.
Ice clouds are an important component in precipitation systems. The radiative processes of ice clouds directly impact radiation in heat budget and the microphysical processes of ice clouds directly affect latent heat and net condensation through deposition processes, which may eventually change surface rainfall. Thus, torrential rainfall responses to radiative and microphysical processes of ice clouds during a landfall of severe tropical storm Bilis (2006) are investigated with the analysis of sensitivity experiments. The two-dimensional cloud-resolving model is integrated for 3 days with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature and vapor advection from NCEP/GDAS data. One sensitivity experiment excludes the radiative effects of ice clouds and the other sensitivity experiment excludes ice microphysics and associated radiative and microphysical processes. Model domain mean surface rain rate is barely changed by the exclusion of radiative effects of ice clouds due to the small decrease in net condensation associated with the small reduction in latent heat as a result of the offset between the increase in radiative cooling and the decrease in heat divergence. The exclusion of microphysical effects of ice clouds decreases the mean rain rate simply through the suppression of latent heat as a result of the removal of deposition processes. The total exclusion of ice microphysics decreases the mean rain rate mainly through the exclusion of microphysical effects of ice clouds.  相似文献   

15.
"98.5"华南前汛期暴雨云微物理场数值模拟分析   总被引:2,自引:1,他引:2  
为了进一步理解暴雨发生过程中云微物理场的演变和云微物理过程与动力、热力过程的相互作用,利用非静力中尺度数值模式MM5对1998年5月23~24日的华南暴雨过程进行了模拟,并详细分析了模拟结果。分析结果表明:利用混合冰相显式物理方案比其它方案模拟的降水更接近实际情况;云微物理场的模拟显示没有雪出现,这可能是华南降水云微物理的特点;每小时降水量有先减弱后又增强的趋势,暴雨过程中云的各微物理量的变化趋势与其一致;云的发展与良好的热力动力条件互相作用、共同加强,由南风带来的充足的水汽和热量为其发展提供前提条件,凝结潜热使上升运动向更高处伸展。  相似文献   

16.
The effects of sea surface temperature (SST), radiation, cloud microphysics, and diurnal variations on the vertical structure of tropical tropospheric temperature are investigated by analyzing 10 two-dimensional equilibrium cloud-resolving model simulation data. The increase of SST, exclusion of diurnal variation of SST, and inclusion of diurnal variation of solar zenith angle, radiative effects of ice clouds, and ice microphysics could lead to tropical tropospheric warming and increase of tropopause height. The increase of SST and the suppression of its diurnal variation enhance the warming in the lower and upper troposphere, respectively, through increasing latent heat and decreasing IR cooling. The inclusion of diurnal variation of solar zenith angle increases the tropospheric warming through increasing solar heating. The inclusion of cloud radiative effects increases tropospheric warming through suppressing IR cooling in the mid and lower troposphere and enhancing solar heating in the upper troposphere. The inclusion of ice microphysics barely increases warming in the mid and lower troposphere because the warming from ice radiative effects is nearly offset by the cooling from ice microphysical effects, whereas it causes the large warming enhancement in the upper troposphere due to the dominance of ice radiative effects. The tropopause height is increased mainly through the large enhancement of IR cooling.  相似文献   

17.
Summary A systematic modeling study investigates the effects of cloud condensation nuclei (CCNs) on the evolution of mixed-phase deep convective storms. Following previous studies the environmental conditions like buoyancy and vertical wind shear are varied to simulate different storm types like ordinary single cells, multicells and supercells. In addition, the CCN characteristics are changed from maritime to continental conditions. The results reveal very different effects of continentality on the cloud microphysics and dynamics of the different storms. While a negative feedback on total precipitation and maximum updraft velocity is found for ordinary single cells and supercell storms, a positive feedback exists for multicell cloud systems. The most important link between CCN properties, microphysics and dynamics is the release of latent heat of freezing.  相似文献   

18.
霰粒子参数对强对流云降水和催化影响的数值模拟研究   总被引:1,自引:0,他引:1  
楼小凤  孙晶  史月琴  师宇 《大气科学》2015,39(3):474-488
本文利用三维对流云AgI催化模式, 开展了霰粒子密度和落速参数的敏感性模拟试验, 以研究高凇附度时霰粒子参数的选取对催化模拟结果的影响。敏感性试验中对七个霰微物理过程进行了调整。分析发现改变霰落速参数和霰密度, 可以引起3小时模拟的总降水量增加4.9%。催化后改变了敏感性试验中霰落速和上升气流的配置, 并影响到霰碰并云水和冰晶的过程, 及霰融化成雨水的过程。在高凇附度云中如果只增加霰密度而没有增加相应的落速系数, 将使云中霰含量大幅增加。霰参数也影响了自然云和催化云的降水效率。过量催化使得催化云的降水效率低于自然云。增加霰密度的同时也增加霰落速系数, 将使其降水效率高于对照试验, 从而影响催化效果。在高凇附度云中采用大密度和较大下落系数, 并且利用比数浓度平均落速计算霰粒子比数浓度的下落过程, 会使催化效率从25%减少到15%, 极大地改变催化效果。所以在高凇附度的暴雨个例中, 应当采用高霰密度和相应的高霰落速, 否则减雨的催化效果将会被大幅夸大。  相似文献   

19.
Summary Cloud microphysical processes associated with the diurnal variations of tropical convection are investigated based on hourly data from a 2D coupled ocean-cloud resolving atmosphere simulation. The model is forced by the large-scale vertical velocity and zonal wind derived from TOGA COARE for a 50-day period. The diurnal composites are carried out in weak diurnal SST variations (case W) and strong diurnal SST signals (case S). The ice water path is larger than the liquid water path in case W than it is in case S. The difference is enhanced in the morning in case W and in the early afternoon in case S when the surface rain rates reach their peaks. Further comparison of cloud microphysics budgets, associated with rainfall peaks, between cases S and W shows that solar heating in case S warms air to reduce the contribution of vapor deposition to cloud growth, which decreases ice water path compared to those in case W. While the collection of cloud water by rain is a major contributor to the surface precipitation in both cases, the melting of precipitation ice (sum of snow and graupel) contributes less to the rainfall in case S than in case W.  相似文献   

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