(大气科学基础)云的分类与形成条件课件.ppt
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1、第五章第五章 云物理学基础云物理学基础 1 云的分类与形成条件云的分类与形成条件 2 主要云属的宏观和微观特征主要云属的宏观和微观特征 3 云滴的凝结和碰并增长云滴的凝结和碰并增长 4 自然降水过程自然降水过程 5 人工影响天气基础人工影响天气基础1 云的分类与形成条件云的分类与形成条件(1)云的描述)云的描述(2)云的形成)云的形成(3)云的分类)云的分类 Observed Cloud Cover station reporting symbol The symbol highlighted in yellow indicates the amount of cloud cover obse
2、rved at the time the observation is taken.In this case,broken clouds were reported(1 1)云的描述)云的描述 凝结核凝结核 Condensation Nuclei(CN)CN are tiny particles suspended in the atmosphere;CN stay aloft in the air for many days.They are so small that their weight is less than their air resistance.Radius typical
3、ly from 0.1 to 1 microns(micron=10-6 meters)Concentrations from 1 to 1000 per cm3 of air 冰核冰核 Ice NucleiWater does not always freeze at 32 F;Water existing at temperatures below freezing is called“super-cooled”;Some particles cause super-cooled water to freeze,these particles are known as ice nuclei
4、;Without ice nuclei,pure water would need to be 40F to freeze;Some CN are also good ice nuclei,others are not.Clouds in the AtmosphereClouds are a collection of water drops and/or ice crystals;Clouds form when water vapor in the atmosphere condenses,condensation only occurs on CN;Water vapor condens
5、es when the relative humidity exceeds 100%;This can happen if one or both of the following occurs:1)The air is cooled,reducing the saturation vapor pressure;2)Water vapor is added to the air.Cloud FormationImagine an air parcel,rising upward through the atmosphere.The air parcel expands as it rises
6、and this expansion causes the temperature of the air parcel to decrease.Temperature As the parcel rises,it cools,and the humidity increases until it reaches 100%;When this occurs,cloud droplets begin forming as the excess water vapor condenses on CN particles;Above this point the cloud droplets grow
7、 by condensation in the rising air;If the rising motion is sufficiently intense and enough water vapor is present,precipitation will develop.Why does air rise?An air parcel will rise naturally if the air within the parcel is warmer than the surrounding air(like a hot air balloon).As the earth is hea
8、ted by the sun,bubbles of hot air form(called thermals)and rise upward from the warm surface.Convergence is an atmospheric condition that exists when there is a horizontal net inflow of air into a region.When air converges along the earths surface,it is forced to rise since it cannot go downward.Clo
9、udCumulusStratusCirrusCloudLow cloudMiddle cloudHigh cloudor积云层云卷云 老云结了驾,不阴也要下。云吃雾有雨,雾吃云好天。云吃火有雨,火吃云晴天。乌云接日头,半夜雨不愁。乌云脚底白,定有大雨来。低云不见走,落雨在不久。西北恶云长,冰雹在后晌。暴热黑云起,雹子要落地。黑云起了烟,雹子在当天。黑黄云滚翻,冰雹在眼前。黑黄云滚翻,将要下冰蛋。满天水上波,有雨跑不脱。蓝色的天空,漂浮着一朵朵白色的淡积云淡积云,个体较小,云底较平有阴影,云顶凸起,水平宽度大于垂直高度 9000米高空拍摄的淡积云淡积云云场,大小不同的云块分布在低空呈白色;距飞机
10、较近的淡积云云块较大,边缘也比较零散,远方的淡积云个体显得很小;排列也不整齐,远方白色云条是密卷云。云南石林冬季出现的碎积云碎积云,形状多变,边缘破碎,轮廓很不完整,靠左边一大块碎积云,正向淡云发展。海南永兴岛海面上形成众多淡积云淡积云和碎积云碎积云,淡积云个体较大,边缘有些零散,由于逆光淡积云云体呈暗灰色,碎积云个体很小,云体零散而形状多变,远处高空是匀卷层云。一块发展旺盛的浓积云浓积云,顶部的对流泡体正向上凸起,好似花椰菜的形状,云的底部较宽,云底部平整呈暗黑色,上部有几块碎积云。图中前排是三块浓积云浓积云,云体垂直高度大于水平宽度,云底较平整并有暗影;中间一块浓积云正在向上发展,另外两块
11、浓积云云顶向左倾斜;前排后边还有几个浓积云正处于发展阶段,初看起来好似互相联接,高空有几条密卷云。从飞机上观测浓积云浓积云个体庞大,顶部向上凸起好似一座小山,云体周围分布着很多淡积云,右侧上方有一块浓积云处于发展阶段。图中上部远方是密卷云 图中三块浓积云浓积云正处于发展阶段,由于云中上升气流很强,云顶迅速上升,使云顶上比较潮湿的气层迅速冷却凝结,形成覆盖在云顶上的轻纱似的云幕,即幞状云,这三块云很快又发展成秃积雨云 积雨云是对流云发展到极盛阶段,常产生较强的阵性降水,并伴有大风、雷电等现象,有时还出现强的降雹(叫冰雹云),有时有龙卷风产生。积雨云积雨云发展很旺盛,由南向北移动,云顶伸展很高,云
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