共查询到20条相似文献，搜索用时 31 毫秒
1.
Differences in the radiative feedback from clouds account for much of the variation in climate sensitivity amongst General
Circulation Models (GCMs). Therefore metrics of model performance which are demonstrated to be relevant to the cloud response
to climate change form an important contribution to the overall evaluation of GCMs. In this paper we demonstrate an alternative
method for assigning model data to observed cloud regimes obtained from clustering histograms of cloud amount in joint cloud
optical depth—cloud top pressure classes. The method removes some of the subjectivity that exists in previous GCM cloud clustering
studies. We apply the method to ten GCMs submitted to the Cloud Feedback Model Intercomparison Project (CFMIP), evaluate the
simulated cloud regimes and analyse the climate change response in the context of these regimes. We also propose two cloud
regime metrics, one of which is specifically targeted at assessing GCMs for the purpose of obtaining the global cloud radiative
response to climate change. Most of the global variance in the cloud radiative response between GCMs is due to low clouds,
with 47% arising from the stratocumulus regime and 18% due to the regime characterised by clouds undergoing transition from
stratocumulus to cumulus. This result is found to be dominated by two structurally similar GCMs. The shallow cumulus regime,
though widespread, has a smaller contribution and reduces the variance. For the stratocumulus and transition regimes, part
of the variance results from a large model spread in the radiative properties of the regime in the control simulation. Comparison
with observations reveals a systematic bias for both the stratocumulus and transition regimes to be overly reflective. If
this bias was corrected with all other aspects of the response unchanged, the variance in the low cloud response would reduce.
The response of some regimes with high cloud tops differ between the GCMs. These regimes are simulated too infrequently in
a few of the models. If the frequency in the control simulation were more realistic and changes within the regimes were unaltered,
the variance in the cloud radiative response from high-top clouds would increase. As a result, use of observations of the
mean present-day cloud regimes suggests that whilst improvements in the simulation of the cloud regimes would impact the climate
sensitivity, the inter-model variance may not reduce. When the cloud regime metric is calculated for the GCMs analysed here,
only one model is on average consistent with observations within their uncertainty (and even this model is not consistent
with the observations for all regimes), indicating scope for improvement in the simulation of cloud regimes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
2.
Buoyancy reversal, decoupling and the transition from stratocumulus to shallow cumulus topped marine boundary layers 总被引：1，自引：0，他引：1
The transition in a marine boundary layer (MBL) from stratocumulus topped to shallow cumulus topped is investigated by using a large eddy simulation (LES) model. The experiments performed aim to examine the influence on the transition of (1) the probability of buoyancy reversal at the MBL top (i.e. situations in which the mixture of two air parcels becomes denser than either of the original parcels due to phase change or other nonlinear processes involved in the mixing), and (2) the degree of decoupling in the MBL (i.e. the strength of a shallow stably stratified layer near cloud base). Our results suggest that a stratocumulus-topped MBL is most likely to transit to a cumulus-topped one when (1) there exists high probability of buoyancy reversal at the MBL top, and (2) the MBL is decoupled due to large surface evaporation. We argue that a parameterization that includes representation of those two effects combined has the potential to provide a simple way of predicting the MBL transition in climate models. 相似文献
3.
The impact of increased vertical resolution in the Hadley Centre Climate Model upon the simulation of stratocumulus is investigated
in experiments using single column (SCM) and general circulation (GCM) model configurations. A threefold enhancement of vertical
resolution in the boundary layer leads to improvements in the vertical structure of the cloud-topped boundary layer produced
by the SCM and GCM in both well-mixed and decoupled situations. However, single and decoupled mixed layers in the marine stratocumulus
subsidence regions are still too shallow and, despite increasing, layer cloud amounts remain generally too low. Moreover,
closer examination of GCM data and SCM timeseries reveals an underlying sensitivity to vertical resolution in model interactions
between boundary layer and convection processes which appears unrealistic. Stratocumulus simulation is thus unlikely to improve
significantly as a result of enhanced resolution alone and further work is being undertaken to improve the Hadley Centre model’s
boundary layer scheme and, in particular, its interaction with the convection scheme. Nevertheless, this study shows that
the full benefit of an improved boundary layer scheme will not be realized if the boundary layer structure is constrained
by the rather poor lower troposphere resolution of the standard 19-level climate model. Future Hadley Centre model versions
will seek to combine the added flexibility of a better resolved structure with improvements to the subgrid boundary layer
parametrizations.
Received: 14 April 1998 / Accepted: 5 November 1998 相似文献
4.
The Naval Research Laboratory Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) has been extended to perform as a large-eddy simulation (LES) model. It has been validated with a series of boundary-layer experiments spanning a range of cloud nighttime, and includes a nighttime stratocumulus case, a trade wind cumulus layer, shallow cumulus convection over land, and a mixed regime consisting of cumulus clouds under broken stratocumulus. COAMPS-LES results are in good agreement with other models for all the cases simulated. Exact numerical budgets for the vertical velocity second\((\overline{w^{'2}})\) and third moment\((\overline{w^{'3}})\) have been derived for the stratocumulus and trade wind cumulus cases. For the\(\overline{w^{'3}}\) budget in the stratocumulus, the buoyancy contribution from the updraughts and downdraughts largely cancel each other due to their similar magnitudes but opposite signs. In contrast, for the cumulus layer, the negative buoyancy contribution from the environmental downdraughts is negligible and the positive contribution from the updraughts completely dominates due to the conditional instability in the environment. As a result,\(\overline{w^{'3}}\) is significantly larger in the cumulus than in the stratocumulus layer. 相似文献
5.
This paper aims at characterizing how different key cloud properties (cloud fraction, cloud vertical distribution, cloud reflectance, a surrogate of the cloud optical depth) vary as a function of the others over the tropical oceans. The correlations between the different cloud properties are built from 2?years of collocated A-train observations (CALIPSO-GOCCP and MODIS) at a scale close to cloud processes; it results in a characterization of the physical processes in tropical clouds, that can be used to better understand cloud behaviors, and constitute a powerful tool to develop and evaluate cloud parameterizations in climate models. First, we examine a case study of shallow cumulus cloud observed simultaneously by the two sensors (CALIPSO, MODIS), and develop a methodology that allows to build global scale statistics by keeping the separation between clear and cloudy areas at the pixel level (250, 330?m). Then we build statistical instantaneous relationships between the cloud cover, the cloud vertical distribution and the cloud reflectance. The vertical cloud distribution indicates that the optically thin clouds (optical thickness <1.5) dominate the boundary layer over the trade wind regions. Optically thick clouds (optical thickness >3.4) are composed of high and mid-level clouds associated with deep convection along the ITCZ and SPCZ and over the warm pool, and by stratocumulus low level clouds located along the East coast of tropical oceans. The cloud properties are analyzed as a function of the large scale circulation regime. Optically thick high clouds are dominant in convective regions (CF?>?80?%), while low level clouds with low optical thickness (<3.5) are present in regimes of subsidence but in convective regimes as well, associated principally to low cloud fractions (CF?<?50?%). A focus on low-level clouds allows us to quantify how the cloud optical depth increases with cloud top altitude and with cloud fraction. 相似文献
6.
The radiative feedback from clouds remains the largest source of variation in climate sensitivity amongst general circulation
models (GCMs). A cloud clustering methodology is applied to six contemporary GCMs in order to provide a detailed intercomparison
and evaluation of the simulated cloud regimes. By analysing GCMs in the context of cloud regimes, processes related to particular
cloud types are more likely to be evaluated. In this paper, the mean properties of the global cloud regimes are evaluated,
and the cloud response to climate change is analysed in the cloud-regime framework. Most of the GCMs are able to simulate
the principal cloud regimes, however none of the models analysed have a good representation of trade cumulus in the tropics.
The models also share a difficulty in simulating those regimes with cloud tops at mid-levels, with only ECHAM5 producing a
regime of tropical cumulus congestus. Optically thick, high top cloud in the extra-tropics, typically associated with the
passage of frontal systems, is simulated considerably too frequently in the ECHAM5 model. This appears to be a result of the
cloud type persisting in the model after the meteorological conditions associated with frontal systems have ceased. The simulation
of stratocumulus in the MIROC GCMs is too extensive, resulting in the tropics being too reflective. Most of the global-mean
cloud response to doubled CO2 in the GCMs is found to be a result of changes in the cloud radiative properties of the regimes, rather than changes in the
relative frequency of occurrence (RFO) of the regimes. Most of the variance in the global cloud response between the GCMs
arises from differences in the radiative response of frontal cloud in the extra-tropics and from stratocumulus cloud in the
tropics. This variance is largely the result of excessively high RFOs of specific regimes in particular GCMs. It is shown
here that evaluation and subsequent improvement in the simulation of the present-day regime properties has the potential to
reduce the variance of the global cloud response, and hence climate sensitivity, amongst GCMs. For the ensemble of models
considered in this study, the use of observations of the mean present-day cloud regimes suggests a potential reduction in
the range of climate sensitivity of almost a third.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
A Parameterization of Dry Thermals and Shallow Cumuli for Mesoscale Numerical Weather Prediction 总被引：3，自引：1，他引：2
Julien Pergaud Valéry Masson Sylvie Malardel Fleur Couvreux 《Boundary-Layer Meteorology》2009,132(1):83-106
For numerical weather prediction models and models resolving deep convection, shallow convective ascents are subgrid processes
that are not parameterized by classical local turbulent schemes. The mass flux formulation of convective mixing is now largely
accepted as an efficient approach for parameterizing the contribution of larger plumes in convective dry and cloudy boundary
layers. We propose a new formulation of the EDMF scheme (for Eddy Diffusivity\Mass Flux) based on a single updraft that improves
the representation of dry thermals and shallow convective clouds and conserves a correct representation of stratocumulus in
mesoscale models. The definition of entrainment and detrainment in the dry part of the updraft is original, and is specified
as proportional to the ratio of buoyancy to vertical velocity. In the cloudy part of the updraft, the classical buoyancy sorting
approach is chosen. The main closure of the scheme is based on the mass flux near the surface, which is proportional to the
sub-cloud layer convective velocity scale w
*. The link with the prognostic grid-scale cloud content and cloud cover and the projection on the non- conservative variables
is processed by the cloud scheme. The validation of this new formulation using large-eddy simulations focused on showing the
robustness of the scheme to represent three different boundary layer regimes. For dry convective cases, this parameterization
enables a correct representation of the countergradient zone where the mass flux part represents the top entrainment (IHOP
case). It can also handle the diurnal cycle of boundary-layer cumulus clouds (EUROCS\ARM) and conserve a realistic evolution
of stratocumulus (EUROCS\FIRE). 相似文献
8.
Simultaneous wind and droplet measurements have been made in three cloudy boundary layers using tethered balloon-borne instrumentation. The types of clouds studied ranged from small thin cumulus to medium cumulus (non precipitating) and stratocumulus formed by the spreading out (shelving) of cumulus. Available synoptic data have been analysed in order to investigate the relative importance of advection and subsidence over scales of order 100 km in the local boundary-layer development. The factors which influenced the extent of cloud cover are also discussed together with the effect of condensation on vertical air motions in the upper half of the boundary layer. Within individual clouds, horizontal variations in droplet spectra were observed to occur over distances of a few metres being related to both position within cloud and height above local cloud base. These results highlight difficulties which may arise in the interpretation of droplet data of horizontal resolution greater than a few metres. Different clouds sampled on the same day showed different amounts of variability in the droplet parameters but no systematic differences between the various case studies were detected. 相似文献
9.
Analyses of aircraft observations of the stratocumulus-topped boundary layer during the First ISCCP (International Satellite
Cloud Climatology Project) Regional Experiment (FIRE I) show the frequent presence of clear, but relatively moist, air patches
near the stratocumulus cloud-top interface. A conditional sampling of measurements in these clear air patches shows that their
thermodynamic properties do more resemble boundary-layer air characteristics than those of free troposphere air. From an aircraft
leg through cloud tops it is demonstrated that turbulent mixing across the cloud-top interface can lead to the local dissipation
of the cloud top. Analogous to the terminology used for shallow cumulus parameterizations this process can be considered as
detrainment, with which we mean that after a mixing event across the cloud-top boundaries, mixed unsaturated parcels become
part of the clear environment of the cloud. 相似文献
10.
本文利用A-Train卫星队列中的Cloudsat卫星所提供的二级云分类产品资料(结合了CALIPSO卫星气溶胶激光雷达)2B-CLDCLASS-LIDAR,选取2007年3月至2017年2月的样本数据进行统计分析,研究北半球主要的气溶胶排放源区(中国东部,美国东部和欧洲西部)不同云型出现频率的分布特征。结果表明,在以单层云出现的8种云类中卷云,层积云和积云的发生频率总和高达50%~70%,其次为高层云、高积云和雨层云,而深对流云和层云这两种云仅占10%以下。各类云的发生频率的空间分布可看出卷云和层积云的发生频率可高达90%以上,高层云的发生频率在70%~80%左右,高积云和积云的发生频率则接近70%以上,深对流云和层云的发生频率则在20%以下。其中,卷云、深对流云和积云主要出现在低纬度的海洋上;高层云和高积云主要出现在中低纬工业发达的陆地上;层积云、层云和雨层云主要出现在中高纬地区,其中层积云和层云出现在海洋上居多,雨层云出现频次的海陆差别不大。不同云型在不同的季节出现频次差异明显,在夏季出现较多的云型以卷云、深对流云,积云和层云为主;在冬季则是高层云、层积云和雨层云这样稳定型的云型占据主导,同时还发现卷云和层积云发生频率的月变化相反,而高层云和雨层云发生频率的月变化相似。 相似文献
11.
12.
Organization of tropical convection in a GCM with varying vertical resolution; implications for the simulation of the Madden-Julian Oscillation 总被引：7，自引：0，他引：7
P. M. Inness J. M. Slingo S. J. Woolnough R. B. Neale V. D. Pope 《Climate Dynamics》2001,17(10):777-793
Experiments using a GCM with two different vertical resolutions show differences in the amount of variability in the tropical
upper tropospheric zonal wind component associated with the Madden-Julian Oscillation (MJO). The GCM with lower vertical resolution
shows very little variability in this quantity whereas when the vertical resolution is doubled in the free troposphere, the
GCM produces variability which is of the same strength as observations. However, the eastward propagation of an enhanced convective
region from the Indian Ocean into the west Pacific is not well represented in either simulation of this atmospheric GCM. A
water-covered or “aqua-planet” version of the same GCM is used to investigate the behaviour of tropical convection when the
vertical resolution is doubled. When the vertical resolution is increased, the spectrum of tropical cloud types changes from
a bimodal distribution with peaks representing shallow cumulus and deep cumulonimbus clouds to a trimodal distribution with
a third peak in mid-troposphere near the melting level. Associated with periods when these mid-level congestus clouds are
dominant, the detrainment from these clouds significantly moistens the mid-troposphere. The appearance of these congestus
clouds is shown to be partly due to improved resolution of the freezing level and the convective processes occurring at this
level. However, due to the way in which convective detrainment is parametrized in this model, the vertical profile becomes
rather noisy and this too contributes to the change in the nature of the convective clouds. The resulting cloud distribution
more closely resembles observations, particularly during the suppressed phase of the MJO when cumulus congestus is the dominant
cloud type.
Received: 17 April 2000 / Accepted: 30 November 2000 相似文献
13.
毫米波雷达云回波的自动分类技术研究 总被引：1，自引：0，他引：1
毫米波雷达在云探测方面比厘米波天气雷达和激光雷达具有显著优势,可获得更多的云粒子信息,是研究云特性的主要遥感探测设备。为了开展对毫米波雷达探测的云回波进行自动分类的研究,利用161次云回波的个例数据,统计得到了卷云、高层云、高积云、层云、层积云和积云6类云型的特征量和其他参量的数值范围,利用分级的多参数阈值判别方法,达到了自动分类的目标,通过与人工分类的初步验证,两种分类结果的一致性达到84%,其中,层云和积云的识别一致较低的原因在于样本数据有限,仅有6次层云和8次积云的个例样本数据。通过更多样本的处理,提取的特征参量更可靠,自动分类的准确率会得到提高,以便将基于毫米波雷达的云分类技术应用于将来的云观测自动化业务。 相似文献
14.
本文利用拉萨地区1981 ～2010年汛期5～9月4个台站的地面观测资料,统计分析了汛期5～9月各类积云的发生频率及其降水过程,分析了各类积云的降水能力;从卫星云图、天气雷达图识别及目测三个方面对拉萨地区汛期适宜高炮（火箭）人工增雨作业云系做了初步探讨.结果表明：拉萨地区平均每年有40d以上的积云降水;其中伴随碎雨云的积雨云（Cb＋Fn）降水概率最大.各县区平均积云降水过程占总降水过程的52.6％,平均积云降水量占总降水量的54.8％;汛期降水过程中由积云带来的降水占一半以上,一般产生小雨及小到中雨的雨量,产生大雨及暴雨的概率极小.降水性积云不仅人工增雨潜力很大,实施人工增雨催化作业的机会也较多.适合人工增雨作业影响的积云降水云系按其对降水量的贡献大小依次为伴随碎雨云出现的积雨云（Cb＋ Fn）、伴随碎积云出现的混合层积云（Sc＋Fc）、积雨云（Cb）、层积云（Sc）. 相似文献
15.
Yoko Tsushima Mark A. Ringer Mark J. Webb Keith D. Williams 《Climate Dynamics》2013,41(9-10):2679-2696
An extended cloud-clustering method to assess the seasonal variation of clouds is applied to five CMIP5 models. The seasonal variation of the total cloud radiative effect (CRE) is dominated by variations in the relative frequency of occurrence of the different cloud regimes. Seasonal variations of the CRE within the individual regimes contribute much less. This is the case for both observations, models and model errors. The error in the seasonal variation of cloud regimes, and its breakdown into mean amplitude and time varying components, are quantified with a new metric. The seasonal variation of the CRE of the cloud regimes is relatively well simulated by the models in the tropics, but less well in the extra-tropics. The stratocumulus regime has the largest seasonal variation of shortwave CRE in the tropics, despite having a small magnitude in the climatological mean. Most of the models capture the temporal variation of the CRE reasonably well, with the main differences between models coming from the variation in amplitude. In the extra-tropics, most models fail to correctly represent both the amplitude and time variation of the CRE of congestus, frontal and stratocumulus regimes. The annual mean climatology of the CRE and its amplitude in the seasonal variation are both underestimated for the anvil regime in the tropics, the cirrus regime and the congestus regime in the extra-tropics. The models in this study that best capture the seasonal variation of the cloud regimes tend to have higher climate sensitivities. 相似文献
16.
In this study, we evaluate the ability of the Weather Research and Forecasting model to simulate surface energy fluxes in the southeast Pacific stratocumulus region. A total of 18 simulations is performed for the period of October to November 2008, with various combinations of boundary layer, microphysics, and cumulus schemes. Simulated surface energy fluxes are compared to those measured during VOCALS-REx. Using a process-based model evaluation, errors in surface fluxes are attributed to errors in cloud properties. Net surface flux errors are mostly traceable to errors in cloud liquid water path (LWPcld), which produce biases in downward shortwave radiation. Two mechanisms controlling LWPcld are diagnosed. One involves microphysics schemes, which control LWPcld through the production of raindrops. The second mechanism involves boundary layer and cumulus schemes, which control moisture available for cloud by regulating boundary layer height. In this study, we demonstrate that when parameterizations are appropriately chosen, the stratocumulus deck and the related surface energy fluxes are reasonably well represented. In the most realistic experiments, the net surface flux is underestimated by about 10 W m?2. This remaining low bias is due to a systematic overestimation of the total surface cooling due to sensible and latent heat fluxes in our simulations. There does not appear to be a single physical reason for this bias. Finally, our results also suggest that inaccurate representation of boundary layer height is an important factor limiting further gains in model realism. 相似文献
17.
Hyelim Yoo Zhanqing Li Yu-Tai Hou Steve Lord Fuzhong Weng Howard W. Barker 《Climate Dynamics》2013,41(5-6):1595-1613
The objective of this study is to investigate the quality of clouds simulated by the National Centers for Environmental Prediction global forecast system (GFS) model and to examine the causes for some systematic errors seen in the simulations through use of satellite and ground-based measurements. In general, clouds simulated by the GFS model had similar spatial patterns and seasonal trends as those retrieved from passive and active satellite sensors, but large systematic biases exist for certain cloud regimes especially underestimation of low-level marine stratocumulus clouds in the eastern Pacific and Atlantic oceans. This led to the overestimation (underestimation) of outgoing longwave (shortwave) fluxes at the top-of-atmosphere. While temperature profiles from the GFS model were comparable to those obtained from different observational sources, the GFS model overestimated the relative humidity field in the upper and lower troposphere. The cloud condensed water mixing ratio, which is a key input variable in the current GFS cloud scheme, was largely underestimated due presumably to excessive removal of cloud condensate water through strong turbulent diffusion and/or an improper boundary layer scheme. To circumvent the problem associated with modeled cloud mixing ratios, we tested an alternative cloud parameterization scheme that requires inputs of atmospheric dynamic and thermodynamic variables. Much closer agreements were reached in cloud amounts, especially for marine stratocumulus clouds. We also evaluate the impact of cloud overlap on cloud fraction by applying a linear combination of maximum and random overlap assumptions with a de-correlation length determined from satellite products. Significantly better improvements were found for high-level clouds than for low-level clouds, due to differences in the dominant cloud geometry between these two distinct cloud types. 相似文献
18.
Mickey Man-Kui Wai 《Boundary-Layer Meteorology》1987,40(3):241-267
A one-dimensional grid-level model including longwave radiative transfer and a level-4 second-order turbulent transfer closure which contains prognostic equations for turbulent quantities, is used to study the physics and dynamics of inversion-capped marine stratocumulus clouds.A set of numerical experiments had been performed to examined the role of sea surface temperature, large-scale vertical velocity, wind speed, and vertical wind shear in the formation and the structure of low-level clouds. For a given sea surface and geostrophic wind speed, stratocumulus clouds can grow higher with smaller large-scale subsidence as less dry air entrains into the cloud. Clouds grow higher with higher sea surface temperature for a given geostrophic wind speed and large-scale subsidence as a result of enhanced moist convection. In high wind speeds, the entire cloud deck is lifted up because of larger surface energy flux. In the budget studies of the turbulent kinetic energy (TKE), the buoyancy term is a major source term when the wind speed and the vertical shear are small across the inversion top. When the wind speed and the vertical wind shear across the inversion top become large, the mixed layer is decoupled into a cloud and a subcloud layer. In the TKE budget studies, the shear generation term becomes an important term in the budgets of the TKE and the variance of vertical velocity. 相似文献
19.
层积云覆盖的海洋边界层云详细微物理过程的数值模拟 总被引：1，自引：0，他引：1
文中建立了一个含显式分档的云微物理模式和辐射传输模式的一维 3阶湍流闭合模式 ,该模式可用于研究海洋边界层云中气溶胶和云的相互作用过程 ,同时提出了一种新的动力模式和微物理模式耦合方法 ,该方法可使动力模式中液态水相关项可以直接由微物理模式变量计算得到。作为模式的初步应用模拟了 2 0 0 1年APEX/ACE Asia在西太平洋上所观测到的一个个例。模拟结果和观测资料比较表明该模式基本上模拟出层积云覆盖的海洋边界层的基本结构 相似文献
20.
In this study, a one-dimensional ensemble-average model is used to simulatethe Atlantic Stratocumulus Transition Experiment firstLagrangian, where the same airmass was followed from the subtropical high pressure region en route towards the trade wind region. The airmass experiences increasing sea-surface temperature and achange from subsidence to weak ascent on its way south. Thiscauses the marine boundary layer (MBL)to grow and the cloud deck to change from a solid stratocumulus deck tomore broken stratocumulus clouds with cumulus cloudsdeveloping beneath, and reaching up into the stratocumulus clouds.A control run is analyzed and compared in detail with theobservations. Both a statistical evaluation and a more subjective evaluation are performed, where both establish confidencein the model performance. The model captures the MBL growth and the cloudliquid water, as well as the drizzle flux, is well predicted by the model.A sensitivity study was performed with the objective of examining theMBL and the cloud response to external and internal 'forces'.The results show that, if drizzle formation is not allowed,unrealistically high cloud liquid water mixing ratios are predicted. Even though the drizzle flux is very small, it is still important for the water budget of the MBL and for the boundary-layer dynamics.We also found that the sea-surface temperature increase is more important for the increasing cloud top height than the synoptic-scale divergence fields. However, the synoptic-scale subsidence is crucial during the first day, when the sea-surface temperature was constant, in keepingthe cloud top at a constant height. Drizzle evaporation below the cloud base seems to be important for below-cloud condensation. The drizzle predictions are significantly altered when the prescribed cloud droplet and/or drizzle drop numbers are altered. 相似文献