星载微波辐射计反演洋面非降水云区云水总量的研究

云水总量(也可称为液水路径)是一个重要的气象学和云雾物理参数。星载微波辐射计是目前监测全球范围内云水总量分布和变化的最强有力的技术手段。但由于云水总量的实测资料太少,给反演研究带来很大的困难。在本工作中,根据微波辐射传输模式,模拟计算“人工”资料样本,建立了AMSR-E 18.7 GHz~36.5 GHz六个极化通道云天-晴天亮温差与云水总量的线性回归关系,初步对云水总量的反演作了定性的研究。     

利用NOAA卫星AVHRR资料分析云的性质

文章利用NOAA卫星AVHRR的通道3（3.55～3.93 μm）、通道4（10.3～11.3 μm）和通道5（11.5～12.5 μm）所在波长上的亮温（BT3,BT4,BT5）以及它们之间的亮温差（BTD34,BTD45）,分析云的性质。分析表明:对于密蔽的云和无云区,通道间亮温差有极小值,在密实的云区BTD34可出现负值;当存在半透明云时,通道间亮温差大;云与背景地面之间温差点聚图的振幅越大,通道间亮温差越大。     

The water-bearing numerical model and its operational forecasting experiments part I: the water-bearing numerical model

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Coastal CCN measurements at Mace Head with enhanced concentrations in strong winds

Surface measurements of cloud condensation nuclei (CCN) number concentration (cm⁻³) are presented for unmodified marine air and for polluted air at Mace Head, for the years 1994 and 1995. The CCN number concentration active at 0.5% supersaturation is found to be approximately log-normal for marine and polluted air at the site. Values of geometric mean, median and arithmetic mean of CCN number concentration (cm⁻³) for marine air are in the range 124–135, 140–150 and 130–157 for the two years of data. Analysis of CCN number concentration for high wind speed, U, up to 20 m s⁻¹ show enhanced CCN production for U in excess of about 10–12 m s⁻¹. Approximately 7% increase in CCN per 1 m s⁻¹ increase in wind speed is found, up to 17 m s⁻¹. A relationship of the form log₁₀CCN=a+bU is obtained for the periods March 1994 and January, February 1995 for marine air yielding values a of 1.70; 1.90 and b of 0.035 for both periods.     

On the application of the classic Kessler and Berry schemes in Large Eddy Simulation models with a particular emphasis on cloud autoconversion, the onset time of precipitation and droplet evaporation

Many Large Eddy Simulation (LES) models use the classic Kessler parameterisation either as it is or in a modified form to model the process of cloud water autoconversion into precipitation. The Kessler scheme, being linear, is particularly useful and is computationally straightforward to implement. However, a major limitation with this scheme lies in its inability to predict different autoconversion rates for maritime and continental clouds. In contrast, the Berry formulation overcomes this difficulty, although it is cubic. Due to their different forms, it is difficult to match the two solutions to each other. In this paper we single out the processes of cloud conversion and accretion operating in a deep model cloud and neglect the advection terms for simplicity. This facilitates exact analytical integration and we are able to derive new expressions for the time of onset of precipitation using both the Kessler and Berry formulations. We then discuss the conditions when the two schemes are equivalent. Finally, we also critically examine the process of droplet evaporation within the framework of the classic Kessler scheme. We improve the existing parameterisation with an accurate estimation of the diffusional mass transport of water vapour. We then demonstrate the overall robustness of our calculations by comparing our results with the experimental observations of Beard and Pruppacher, and find excellent agreement.     

云微物理特性对云光学和云辐射性质的影响

根据辐射传输理论，计算了不同云滴谱分布时的云光学参数βe，ωo和g，考察了这些光学参数的变化对云的反射率、透过率和吸收率的影响，以及云滴谱分布和云水含量在垂直方向的不均匀对云整体辐射性质、云中辐射通量密度和加热率的影响。     

过冷层状云中飞机播云有效区域的模拟研究

根据飞机人工增雨作业个例 ,利用层状云中催化剂输送扩散的三维时变模式 ,对过冷层状云中播云产生的有效区域、催化剂水平输送和扩散速率等进行了模拟研究。结果表明 :(1)飞机播云 4 5min线长 32 7km ,投影有效面积和有效体积在播云刚结束时 (5 0分 )达到极大 ,其值分别为 70 7km2 和 2 98.0km3 ,有效扩展宽度和厚度为 2 .5 1km和 0 .4 2km ;(2 )有效作用时段为 2 0～ 80min ,其间的投影有效面积平均值为 5 13.3km2 ,平均有效扩展宽度和厚度分别为 2 .4 1km和 0 .4 5km ;(3)在扩散作用下 ,投影有效面积和有效体积先随时间不断增加 ,达到极值后逐渐减小 ,播云结束 (5 5分 )后 ,云中的有效区域消失 ,其间的投影有效面积平均值为 389.7km2 ,平均有效扩展宽度和厚度分别为 2 .34km和 0 .4 4km ;(4)云中催化剂水平输送 1h的平均值达到 6 5km ,仅与风场有关。催化剂扩散速率 1h平均为 0 .82m/s,与风、温、湍流有关 ;(5 )在飞机增雨作业时 ,飞行方案的设计必须是严格科学的 ,以便进一步提高人工增雨的实效     

海-陆-气全球耦合模式能量收支的误差

通过分析GOALS模式两个版本GOALS 1.1和GOALS 2的能量收支 ,并与观测对比 ,结果表明 :模式模拟的地表净短波辐射通量在高纬地区偏低 ,而净长波辐射通量又偏高 ,导致极地表面温度偏低 ,感热通量在高纬地区为很高的负值。而在陆地上感热加热作用显著偏强 ,使地表有较大的向上净能量给大气 ,引起陆地上有些暖中心也偏强 ,这也解释了模式模拟地表面空气温度场的误差原因。海洋上潜热通量偏低 ,特别是在副热带洋面上偏少更明显。陆地上的欧亚和北美大陆大部分地区潜热通量仍偏低。这也是模式降水在大部分地区偏少的重要原因。两模式大气顶OLR偏低的模拟主要是在中低纬度 ,大气顶净短波辐射通量的模拟在中低纬度虽然与NCEP结果接近 ,但与地球辐射收支试验ERBE资料比较仍偏小较多 ,说明改进中低纬度云 辐射参数化方案对改进全球能量收支的模拟有重要意义。GOALS 2模式中诊断云方案模拟的云量除赤道地区外普遍偏小 ,尤以中纬度为甚 ,造成那里能量收支出现大的误差 ,这表明了更好的云参数化方案的引入是今后模式发展的重要任务之一     

The chemical composition of fogs and intercepted clouds in the United States

Over the past decade, the chemical compositions of fogs and intercepted clouds have been investigated at more than a dozen locations across the United States. Sampling sites have been located in the northeast, southeast, Rocky Mountain, and west coast regions of the US. They include both pristine and heavily polluted locations. Frontal/orographic clouds (warm and supercooled), intercepted coastal stratiform clouds, and radiation fogs have all been examined. Sample pH values range from below 3 to above 7. Major ions also exhibit a wide concentration range, with clouds at some locations exhibiting high sea salt concentrations, while composition at other locations is dominated by ammonium and sulfate or nitrate.     

Pollutant concentrations in fog and low cloud water at selected sites of the Czech Republic

In this paper, the basic composition of fog and low cloud water are presented, resulting from the analyses of water samples from 111 fog/cloud events. The samples were collected at five sites located in various regions of the Czech Republic. Two sampling sites are in mountainous regions and three sites represent various urban areas. The mountain stations are located in two regions of the Czech Republic with different industry types. At all the sites, active fog collectors were employed. In the water samples, the conductivity, acidity (pH), cations (H⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺) and anions (F⁻, Cl⁻, NO₃⁻, SO₄²⁻) were determined.A mean pH value of about 4.5 was obtained at mountain sites whereas the measurements in urban areas showed mean pH values from 4.9 to 6.4. The mean conductivity values in the samples from the two mountain stations were 137 and 191.5 μS cm⁻¹. The samples from urban sites showed mean values between 127.7 and 654.4 μS cm⁻¹. The maximum concentration means for the three dominant pollutants (expressed by the ratio mountain sites/urban sites) are 32.9/99.6 mg l⁻¹ for NO₃⁻, 32.5/192.9 mg l⁻¹ for SO₄²⁻ and 18.5/52.7 mg l⁻¹ for NH₄⁺. As expected, we found higher ion concentrations in the northern part of the Czech Republic where larger numbers of lignite-burning power plants, chemical factories and opencast lignite mines are located. A decrease in ion concentrations was observed at higher altitude sites, probably reflecting at least in part higher liquid water contents at these locations.