用双时次GMS/IR通道数据合成动态云图的研究

数值化动态云图是一种在保留常规云图的基本信息的基础上,增加同窗定量化显示中尺度对流系统（MCS）静态与动态特征功能的新型云图,它比通常的GMS-IR云图具有更多的信息荷载,更丰富的信息内含与更好的实用性。文中提出了以双时次GMS/IR通道数据合成数值化动态云图的技术原理和技术模式。     

Seasonal cycle of cloud cover analyzed using Meteosat images

A cloud-detection method was used to retrieve cloudy pixels from Meteosat images. High spatial resolution (one pixel), monthly averaged cloud-cover distribution was obtained for a 1-year period. The seasonal cycle of cloud amount was analyzed. Cloud parameters obtained include the total cloud amount and the percentage of occurrence of clouds at three altitudes. Hourly variations of cloud cover are also analyzed. Cloud properties determined are coherent with those obtained in previous studies.     

Subpixel fractional cloud cover and inhomogeneity effects on microwave beam-filling error

Using synthetic geometrical clouds and radiative microwave model, we examine the possibility to correct the estimations of liquid water path (LWP) or rain rate with cloud cover measurement. This information may be gotten by co-localized measurements of microwave and infrared/visible measurements on new satellites (TRMM, ADEOS 2, …). In a first step, the effects of fractional cloud cover on microwave brightness temperatures (TB) are investigated in three typical cases of nonprecipitating and precipitating (stratiform and convective) clouds. The beam-filling error (BFE) on brightness temperatures may be analyzed with the known spatial variability using 1D or 3D radiative transfer model. Relationships between BFE and subpixel cloud fraction (CF) are discussed according to the cloud type. We tested several parameters that characterize the horizontal cloud inhomogeneity within a radiometer field of view. BFE was found very sensitive to cloud type and inhomogeneity and is maximum for raining cloud with open spatial structure. In order to account for the uncertainty introduced by the spatial distribution, dependence of BFE on textural-based parameters is also discussed using homogeneity, entropy and an indicator of CF horizontal gradient.     

中国地区云对地-气系统辐射强迫温度效应的气候研究

文中利用地球辐射平衡试验 (ERBE)和国际卫星云气候计划 (ISCCP)提供的地 气系统行星反射率、射出长波辐射 (OLR)和云量资料 ,计算了中国地区年、月平均总云量对地 气系统短波辐射、长波辐射以及净辐射强迫的温度效应和敏感性系数 ,并讨论了云对各辐射分量强迫的温度效应与总云量的关系。结果表明 :地 气系统云辐射强迫温度效应与总云量间具有较明显的曲线相关。云辐射强迫温度效应及其敏感性系数具有明显的时空变化特点。就中国全国平均而言 ,各月地 气系统云辐射强迫净温度效应一般表现为降温作用。     

Organic compounds in radiation fogs in Davis (California)

New stainless steel active fogwater collectors were designed and used in Davis (CA, USA) to collect fogwater for the speciation of organic matter. Organic compounds in fog samples were extracted by liquid–liquid extraction and analyzed by gas chromatography coupled to mass spectrometry. Numerous organic compounds, including various alkanes, polycyclic aromatic hydrocarbons (PAH) and alkanoic acids, have been identified in the fogwater samples. Higher molecular weight (MW) compounds are preferentially associated with an insoluble phase inside the fog drops, whereas lower molecular weight and more polar compounds are found predominantly in the dissolved phase. Concentrations in the dissolved phase were sometimes much higher than estimated by the compounds' aqueous solubilities.     

Effects of organic aerosol constituents on extinction and absorption coefficients and liquid water contents of fogs and clouds

We have speculated on the influence of organic material on extinction and absorption coefficients and liquid water content of fogs and of clouds immediately after their condensational stage. It results therefore, that the reduction of the speed of growth from fog to cloud droplets due to the presence of organic films largely reduces the properties mentioned. Compared to that their increase coming from the surface tension reduction due to organic material being dissolved or building up films is expected to be less effective.     

Experimental evaluation of the coalescence efficiencies of colliding water drops

The coalescence of water drops of sizes comparable to rain drops (200–2500 m diameter) was investigated. The method used provided a good separation between collision and coalescence effects. The result suggests a dependence of the coalescence efficiency on both the size of the large drop and the ratio of the radii of the interacting drops (p-ratio). The coalescence was observed to rapidly decrease due to bouncing and partial coalescence as the angle of impact increased from head-on to grazing angle. However, some bouncing was observed at very low impact angles.The results of the coalescence efficiency were fitted with an empirical equation for use in numerical models of cloud growth and precipitation development.On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Parameterizations of cloud feedback in a radiative-convective model

The effect of cloud feedback on the response of a radiative-convective model to a change in cloud model parameters, atmospheric CO₂ concentration, and solar constant has been studied using two different parameterization schemes. The method for simulating the vertical distribution of both cloud cover and cloud optical thickness, which depends on the relative humidity and on the saturation mixing ratio of water vapor, respectively, is the same in both approaches, but the schemes differ with respect to modeling the water vapor profile. In scheme I atmospheric water vapor is coupled to surface parameters, while in scheme II an explicit balance equation for water vapor in the individual atmospheric layers is used. For both models the combined effect of feedbacks due to variations in lapse rate, cloud cover, and cloud optical thickness results in different relationships between changes in surface temperature, planetary temperature, and cloud cover. Specifically, for a CO₂ doubling and a 2% increase in solar constant, in both models the surface warming is reduced by cloud feedback, in contrast to no feedback, with the greater reduction in scheme I as compared to that of scheme II.     

云系模式研究:云场的宏微观结构模拟

用计算物理方法设计构造了一个云系模式，并用一个实例作为初始场进行了模拟，模拟的云场宏观特征与实况观测比较一致，微观结构比较合理，配套的模式输出数据处理和绘图程序包能给出云系的点（粒子谱）、线（垂直廓线）、面（结构剖面）、体（云场，云型，云量，云系形状）的多维宏微观结构的云场图象。     

卫星云图和数值预报产品及雷达资料相结合作短时预报

在短期和短时天气预报工作中，本文通过对卫生云图的定量分析和研究，结合天气形势、数值预报产品及雷达回波资料，给出了运城市短时降水预报指标，以提高云图在短时预报中的可用性。