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1.
Transfer of radiation through cirrus consistingofnon-sphericalice crystals randomly oriented in a plane (2D model) is solved by using the discrete-ordinates method. The model is employed to determine the radiative flux properties and the intensity distribution of cirrus for both solar and thermal infrared radiation. Comparison of the 2D cloud model with the conventional 3D cloud model, i.e., randomly oriented in a three-dimensional space, shows that the preferential orientation of ice crystals has a substantial effect on the cloud solar albedo. The difference in the cloud albedo computed from the two models can be as large as 8% for a cirrus of 2 km chicknss. On the thermal infrared side, although the flux emission for cirrus is less affected by the orientation of ice crystals, the difference in the upward radiance using 2D and 3D models is also significant.  相似文献   

2.
It is verified that there is δ-phase function characteristic in both of TS and SW simplified models, and on the basis of TS model, a more accurate model calculating the albedo and transmissivity of cloud layers is derived.  相似文献   

3.
The data of two cases of the winter stratocumulus cloud over U|¨ru|¨mqi,obtained by aircraft,radio-sonde,radiowind,tethered bolloon and surface observations,are analysed.On the hasis of these,a concep-tual model of the formation,evolution and dissipation of this type of cloud is proposed.  相似文献   

4.
In this paper, a 1-D time dependent cold cumulus chemistry model is presented. In the coldcumulus model, 4 categories of hydrometeors: cloud drops, raindrops, cloud ice crystals, graupelparticles, and 18 microphysical interactions are considered, In the chemical model, the source andsink terms for pollutants include: the complicated interactions between pollutants (gases andaerosol particles) and the hydrometeors (especially ice crystals and graupel particles), the ex-changes of chemical compounds between two hydrometeors accompanying microphysical processesand the aqueous oxidations of S (IV) to S (VI). The two models are combined to study the acidifi-cation processes in cold cumulus clouds.  相似文献   

5.
It is shown that the medium scale cloud cluster is u major one of precipitation systems from analysing the rainstorms along the Changjiang River during the plum rain period of 1980-1983. The medium-scale cloud clusters do not always correspond to the moving vortex, but they are in good agreement with the convergence center for the divergent component of wind at 850 hPa. The favourable environmental conditions for the genesis and development of medium-scale cloud cluster, such as the large-scale circulation situation, patterns of temperature and moisture, potential instability, and the structure of cloud cluster are given. A model on large seaie clond pattern for the genesis of medium scale cloud cluster is presented.  相似文献   

6.
In order to study mechanisms of hailstone formation and hail suppression with seeding and toobtain optimum seeding technique for hail cloud,a 3-D compressive numerical seeding model forhail cloud is developed.The water substance in hail cloud is divided into 8 categories,i.e.,watervapor,cloud droplet,raindrop,ice crystal,snow.graupel,frozen drop and hail,and the detailedmicrophysical processes are described in a spectrum with two variable parameters and morereasonable particle number/size distributions.Then,the model is able to predict concentration andwater content of various particles.Especially.it can calculate the number of hailstones whosecores are graupel or frozen drop and apply to study mechanism of hailstone formation.Additionally,a conservative equation of AgI as seeding or glacigenous agent is found andnucleation by condensation of artificial nucleus,and nucleation by freezing of cloud droplet or raindrop which contact with AgI particle are considered.The dynamic energy flux of hail shooting onground is used to verify seeding effect.Therefore the model is also used to study mechanism of hailsuppression with seeding and the seeding technique,  相似文献   

7.
A new three-dimensional dynamics and electrification coupled model has been developed forinvestigating the characteristics of microphysics,dynamics and electrification insidethunderstorms.This model is basically modified from a three-dimensional,time-dependent,anddual-parameter cloud model originally established in IAP(Institute of Atmospheric Physics)and atwo-dimensional axisymmetric cloud dynamics and electrification coupled model.Primarymodifications to the model include not only the coupling of electrification with dynamical andmicrophysical processes,but also the lightning discharge process and screening layer effect at thecloud top as well.Apart from including a full treatment of small ions with attachment to sixclasses of hydrometeors,the inductive and non-inductive charging mechanisms are more specificallyconsidered.A case simulation of July 19.1981 CCOPE is performed aiming to validate thepotential capability of the model.Comparison between model results and observations reveals thatthe model has the capacity to reproduce many of the observed characteristics of thunderstorms indynamical,microphysical,and electrical aspects.  相似文献   

8.
Ozone chemistry processes are analyzed during a cumulus cloud process with the model(1CCCM)described in Part Ⅰ.The simulation results show that entire cumulus cloud process can bewell described with the development of vertical velocities and liquid water content which are the twomost outstanding features of cumulus clouds.Ozone chemistry is strongly influenced by cumulusclouds.NO_x can be transported upwards above 4 km in the first 20 minutes of the convection eventand form a relative higher concentration area which enhances the production of ozone.Two areas ap-pear during the convection event:area of net ozone production and area of net ozone depletion.Thearea of ozone depletion coincides with the area of liquid water within cloud.Results show that theaqueous phase(cloud water and rainwater)can alter gas ozone level through two ways:one is scav-enging free radicals(HO_2)from the gas phase and thereby inhibiting the reactions of transformationto NO_2 from NO,which results in reduction of the gas source of ozone;the other is aqueous phasechemical reactions which consume ozone in the aqueous phase.Calculations reveal that the reaction O_3+OH→HO_2 is the main pathway of ozone depletion in gas phase during the process of cumulusclouds.  相似文献   

9.
We investigate the role of clouds and radiation in the general circulation of the atmosphere usinga model designed for 30-day predictions.Comprehensive verifications of 30-day predictions for the 500 hPa geo-potential height field have been carried out,using the data from ECMWF objective analyses that cover theperiod from May 5 to June 3,1982.We perform three model simulations,including experiments with interac-tive cloud formation,without clouds,and without radiative heating.The latter two experiments allow us tostudy the effects of cloud/radiation interactions and feedbacks on the predicted vertical velocity,and themeridional and zonal wind profiles,averaged over a 30-day period.We demonstrate that the Hadley circulation is maintained by the presence of clouds.The radiative coolingin the atmosphere intensifies the vertical motion in low latitudes and,to some extent,also strengthens theoverall meridional circulation.The meridional winds are correctly reproduced in the model if clouds areincorporated.The zonal winds are significantly affected by clouds and radiative cooling.Without an appropriate incor-poration of these physical elements,the model results would deviate significantly from observations.Thepresence of clouds strengthens the westerlies in middle and high levels.In May,the northerly movementof the jet stream over eastern Asia is,in part,associated with the presence of clouds.  相似文献   

10.
The application of the explicit microphysical process in the high-resolution mesoscale numerical models makes it necessary to analyze the moisture variables such as the cloud water, cloud ice and rain water to initialize the explicit predicted fields. While the inclusion of moisture variables in initial fields can influence the whole performance of the model significantly, it can also reduce the spin-up time and increase the short-term forecasting ability of the model since the dynamical fields become more accordant with the thermodynamic fields. Now the increase of the observing ability and the abundance of the data promote the development of ways to analyze the moisture variables. A review of some methods to analyze the moisture variables is presented, and the situation and problems of the application in the numerical models are also discussed in this paper.  相似文献   

11.
Based on the two-stream approximation a broad-band parameterization scheme for solar radiative flux calculationis presented.The whole solar spectral region from 0.2 to 3.58 μm is divided into three broad spectral intervals.The effec-tive broad-band optical depths and single scattering albedos in the atmosphere in each spectral interval can be obtainedusing parameterized formulae from known atmospheric parameters.The overlapping scattering and/or absorption ef-fects of two atmospheric constituents are considered properly.In the consideration of radiative effect of clouds in theatmosphere the single scattering albedos and backscattering parameters of clouds in each broad spectral interval are giv-en preliminarily and the cloud optical depths are determined according to the cloud liquid water content.  相似文献   

12.
The impacts of the enhanced model's moist physics and horizontal resolution upon the QPFs(quantitative precipitation forecasts)are investigated by applying the HIRLAM(high resolutionlimited area model)to the summer heavy-rain cases in China.The performance of the control run,for which a 0.5°×0.5°grid spacing and a traditional“grid-box supersaturation removal+Kuo typeconvective paramerization”are used as the moist physics,is compared with that of the sensitivityruns with an enhanced model's moist physics(Sundqvist scheme)and an increased horizontalresolution(0.25°×0.25°),respectively.The results show:(1)The enhanced moist physics scheme(Sundqvist scheme),by introducing the cloud watercontent as an additional prognostic variable and taking into account briefly of the microphysicsinvolved in the cloud-rain conversion,does bring improvements in the model's QPFs.Althoughthe deteriorated QPFs also occur occasionally,the improvements are found in the majority of thecases,indicating the great potential for the improvement of QPFs by enhancing the model's moistphysics.(2)By increasing the model's horizontal resolution from 0.5°×0.5°,which is already quitehigh compared with that of the conventional atmospheric soundings,to 0.25°×0.25°without thesimultaneous enhancement in model physics and objective analysis,the improvements in QPFs arevery limited.With higher resolution,although slight amelioration in locating the rainfall centersand in resolving some finer structures of precipitation pattern are made,the number of the mis-predicted fine structures in rainfall field increases with the enhanced model resolution as well.  相似文献   

13.
A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to computethe atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 1988.Somecharacteristics of atmospheric radiative heating fields during the autumn in Zhangye area have been analysed,and somequestions that merit attention in the future observation are also discussed in this paper.  相似文献   

14.
A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henanare simulated with our microphysical model in a one-dimensional framework.The model,using the radio-sonde data as input,gets its output which shows agreement in many aspects as compared with observationsin each case.The glaciation of small cumulus cloud,low precipitation efficiency of hailstorm and the per-sistence of torrential rain are demonstrated.It is also shown that the Bergeron process has little influence,but the warm-rain process plays an important role in the formation of precipitation in cumulonimbus witha warm cloud base.  相似文献   

15.
In nested nonhydrostatic mesoscale model MM5,the characteristic quantities of atmosphericturbulence,i.e.,the standard deviations of the turbulent fluctuated speeds for three directions inPBL are computed by Mellor-Yamada's level 2.5 closure scheme.The magnitudes and the verticalprofiles of these quantities computed from the model are closely connected with temperature andwind speed profiles as well as the type of the ground with a significant diurnal variation,and are inagreement with known magnitudes and regularities in different stratification conditions.Hence themethod in this paper is reasonable and convincible.Their horizontal distribution depends on thehorizontal distribution of the stratification.The method of predicted characteristic quantities ofturbulence from mesoscale model in this paper can be used in the problem of atmospheric diffusionand atmospheric environment.  相似文献   

16.
In this paper, an equation of the vertical velocity at the top of PBL is derived by use of a PBL model which is based on an analytic and actual form of K. Results show that the vertical velocity is a function of geostrophic vorticity, geostrophic wind speed, Coriolis parameter and the roughness of the ground, thus improving Charney-Eliassen's formula. The order of magnitude of the vertical velocity computed from our equation is in agreement with that from the latter, but more factors affecting the vertical velocity are included.  相似文献   

17.
Depositional growth of ice crystal is one of the major processes for development of precipitation systems and can be represented by depositional growth of cloud ice from cloud water (PIDW) and depositional growth of snow from cloud ice (PSFI) in cloud-resolving model. Four parameterization schemes are analyzed in the cloud-resolving model simulations of four rainfall cases over the tropics and midlatitudes. The comparison of time and model domain mean data shows that Shen’s scheme produces the closest rainfall simulation to the observation. Compared to Zeng’s scheme, Shen’s scheme improves the mean rain-rate simulation significantly through the dramatic decrease in depositional growth of cloud ice from cloud water. Compared to other schemes, Shen’s scheme produces the better rainfall simulation via the reduction in the mean rain rate associated with the enhanced gain of cloud water and ice.  相似文献   

18.
A NUMERICAL MODEL OF MIXED CONVECTIVESTRATIFORM CLOUD   总被引：1，自引：0，他引：1  
A 2-D slab-symmetric model of mixed convective-stratiform cloud is developed bysuperimposing convective cloud-size field on the convergence field,in order to simulate and studythe mixed clouds consisting of stratiform cloud and convective cloud.A deep convective,anelasticand conservative system of equations with basic variables(V,θ,π')is solved by a new method tocalculate dynamic field.The water substance in the cloud is divided into 6 categories and themicrophysical processes are described in spectrum with two variable parameters and morereasonable particle number/size distributions.To compare with measured radar echo intensity andstructure,the model may calculate echo intensity of the model cloud observed by radar.  相似文献   

19.
Ozone chemistry processes are analyzed during a cumulus cloud process with the model（lCCCM）described in Part Ⅰ.The simulation results show that entire cumulus cloud process can be well described with the development of vertical velocities and liquid water content which are the two most outstanding features of cumulus clouds.Ozone chemistry is strongly influenced by cumulus clouds.NOx can be transported upwards above 4 km in the first 20 minutes of the convection event and form a relative higher concentration area which enhances the production of ozone.Two areas appear during the convection event:area of net ozone production and area of net ozone depletion.The area of ozone depletion coincides with the area of liquid water within cloud.Results show that the aqueous phase（cloud water and rainwater）can alter gas ozone level through two ways:one is scavenging free radicals（HO2）from the gas phase and thereby inhibiting the reactions of transformation to NO2 from NO,which results in reduction of the gas source of ozone;the other is aqueous phase chemical reactions which consume ozone in the aqueous phase.Calculations reveal that the reaction O3+OH→HO2 is the main pathway of ozone depletion in gas phase during the process of cumulus clouds.  相似文献   

20.
In this paper,data of solar direct spectral radiance observation in summer and autumn of 1990 and 1991 were usedto derive the average atmospheric extinction spectra for very clear days each year.The difference of these two extinctionspectra is obvious and considered as the contribution of volcanic cloud resulting from Pinatobu's volcanic eruption inmiddle June of 1991.This average size distribution of volcanic cloud was retrieved from the difference spectra and givenin this paper which will be useful for estimation and modeling of the effects of volcanic eruption.  相似文献   

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