(大气科学基础)云的分类与形成条件
合集下载
相关主题
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
✓Some CN are also good ice nuclei, others are not.
• Clouds in the Atmosphere ✓Clouds are a collection of water drops and/or ice crystals;
✓Clouds form when water vapor in the atmosphere condenses, condensation only occurs on CN;
• Cloud Formation Imagine an air parcel, rising upward through the atmosphere. The air parcel expands as it rises and this expansion causes the temperature of the air parcel to decrease.
✓ Dew and frost condense on surfaces such as plants or windshields； ✓ In the atmosphere ， water condenses on condensation nuclei (CN).
• 凝结核 Condensation Nuclei (CN) ✓CN are tiny particles suspended in the atmosphere；
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 heated by the sun, bubbles of hot air form (called thermals) and rise upward from the warm surface.
✓Above this point the cloud droplets grow by condensation in the rising air; If the rising motion is sufficiently intense and enough water vapor is present, precipitation will develop.
✓Water vapor condenses 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.
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;
第五章 云物理学基础
• §1 云的分类与形成条件 • §2 主要云属的宏观和微观特征 • §3 云滴的凝结和碰并增长 • §4 自然降水过程 • §5 人工影响天气基础
§1 云的分类与形成条件
（1）云的描述 （2）云的形成 （3）云的分类
(2) 云的形成
• 凝结 Condensation
✓ Condensation occurs when the relative humidity exceeds 100%； ✓ Water only condenses on a surface；
✓CN stay aloft in the air for many days. They are so small that their weight is less than their air resistance.
✓Radius typically from 0.1 to 1 microns (micron = 10-6 meters)
✓Convergence is an atmospheric condition tຫໍສະໝຸດ Baiduat exists when there is a horizontal net inflow of air into a region.
✓When air converges along the earth's surface, it is forced to rise since it cannot go downward.
(3) 云的分类
Cloud
Cumulus
积云
Stratus
or 层云
Cloud
Cirrus
卷云
Low cloud
Middle cloud
✓Some particles cause super-cooled water to freeze, these particles are known as ice nuclei；
✓Without ice nuclei, pure water would need to be – 40F to freeze；
✓Concentrations from 1 to 1000 per cm3 of air
• 冰核 Ice Nuclei ✓Water does not always freeze at 32 F；
✓Water existing at temperatures below freezing is called “super-cooled”；
• Clouds in the Atmosphere ✓Clouds are a collection of water drops and/or ice crystals;
✓Clouds form when water vapor in the atmosphere condenses, condensation only occurs on CN;
• Cloud Formation Imagine an air parcel, rising upward through the atmosphere. The air parcel expands as it rises and this expansion causes the temperature of the air parcel to decrease.
✓ Dew and frost condense on surfaces such as plants or windshields； ✓ In the atmosphere ， water condenses on condensation nuclei (CN).
• 凝结核 Condensation Nuclei (CN) ✓CN are tiny particles suspended in the atmosphere；
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 heated by the sun, bubbles of hot air form (called thermals) and rise upward from the warm surface.
✓Above this point the cloud droplets grow by condensation in the rising air; If the rising motion is sufficiently intense and enough water vapor is present, precipitation will develop.
✓Water vapor condenses 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.
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;
第五章 云物理学基础
• §1 云的分类与形成条件 • §2 主要云属的宏观和微观特征 • §3 云滴的凝结和碰并增长 • §4 自然降水过程 • §5 人工影响天气基础
§1 云的分类与形成条件
（1）云的描述 （2）云的形成 （3）云的分类
(2) 云的形成
• 凝结 Condensation
✓ Condensation occurs when the relative humidity exceeds 100%； ✓ Water only condenses on a surface；
✓CN stay aloft in the air for many days. They are so small that their weight is less than their air resistance.
✓Radius typically from 0.1 to 1 microns (micron = 10-6 meters)
✓Convergence is an atmospheric condition tຫໍສະໝຸດ Baiduat exists when there is a horizontal net inflow of air into a region.
✓When air converges along the earth's surface, it is forced to rise since it cannot go downward.
(3) 云的分类
Cloud
Cumulus
积云
Stratus
or 层云
Cloud
Cirrus
卷云
Low cloud
Middle cloud
✓Some particles cause super-cooled water to freeze, these particles are known as ice nuclei；
✓Without ice nuclei, pure water would need to be – 40F to freeze；
✓Concentrations from 1 to 1000 per cm3 of air
• 冰核 Ice Nuclei ✓Water does not always freeze at 32 F；
✓Water existing at temperatures below freezing is called “super-cooled”；