1/11/2013

1

All images courtesy of the National Weather Service unless otherwise indicated.

Chapter 18: Water in the Atmosphere

18.2 Clouds

• High: Above 7000 meters

–Cirrus

–Cirrostratus

–Cirrocumulus

Cirrus Cirrostratus

Cirrocumulus Chapter 18: Water in the Atmosphere

18.2 Clouds

• Middle: About 2000 to 7000 meters

–Altostratus

–Altocumulus

1/11/2013

2

Stratus Altostratus

Chapter 18: Water in the Atmosphere

18.2 Clouds

• Low: Below about 2000 meters

–Stratus

–Nimbostratus

–Stratocumulus

–Cumulus

Stratus

Nimbostratus Stratocumulus

1/11/2013

3

Cumulus Cumulonimbus

Cumulonimbus (photo taken from a passenger jet)

Cloud Animation

http://www.clouds365.com/video/

Thunderstorm Animationhttp://vimeo.com/48731737

http://vimeo.com/15084868

Cloud Formation & Satellite Imagery

Cumulus Cloud Formation• Condensation Level: the height

at which clouds form

• Dependent on a constant supply of warm, moist air

• Also dependent on temperature and dew point temperature

1/11/2013

4

Condensation Level

Cumulus Cloud Formation

• Dry-adiabatic lapse rate: the rate at which unsaturated air cools with height (~10°C/km)

• Moist-adiabatic lapse rate: the rate at which saturated air cools with height (~5 to 9°C/km)

Dry-adiabatic Lapse Rate

Moist-adiabatic Lapse Rate

Cumulus Cloud Formation

• Why is the moist rate less than the dry rate?

• Condensation releases heat

• Warms the air around it, increasing the temperature

• This is due to the high heat capacity of water

Cumulonimbus Clouds• Form the same way as cumulus

clouds, except density differences between the surface air and the air aloft is greater (unstable)

• Causes the air inside to rise more quickly and achieve greater heights

Cumulonimbus Cloud Diagram

http://www.uwsp.edu/geo/faculty/ritter/images/atmosphere/severe%20weather/mature_stage_NOAA_nssl1012.jpg

1/11/2013

5

Layer Clouds• Form in stable air; the density

difference between the surface air and the air aloft is small

• Causes the air inside to spread out horizontally rather than vertically like cumulus clouds

Layer Clouds• Can form in 2 ways:

1.Air can be forced slowly upward to its condensation level

2.The layer of air can cool to its dew point by radiating heat or mixing with cooler air

Satellite Imagery GOES Weather Satellites• There are a few satellites

orbiting Earth gathering many types of weather data, including “pictures” of clouds

• Satellites are centered over the equator, over 22,000 miles up

• Geosynchronous: orbits Earth at same rate of Earth’s rotation

Satellite Imagery• There are 3 main types of

images:

1.Visible: visible light from the sun is reflected to the satellite

2.Infrared: infrared light (heat) is sensed

3.Water vapor: detects moisture in mid/upper troposphere

Compare 3 Images

http://www.srh.noaa.gov/jetstream/remote/goes.htm

http://www.weather.gov