16.1 WEATHER AND ATMOSPHERIC WATER

Learning Targets

1. Discuss the difference between weather and climate

2. Describe the relationship between air temperature and humidity, including the concept of dew point

3. List the basics of the different cloud types and what they indicate about current and future weather

4. Explain how the different types of precipitation form

Weather vs. Climate

1. Weather: condition of the atmosphere at any given time

2. Climate: long term averages of weather

Weather

1. Weather depends on:a) Air temperatureb) Air pressurec) Dew pointd) Humiditye) Cloud coverf) Precipitationg) Wind speed and direction

2. All are directly related to amount of energy in system

Humidity

1. Humidity - Amount of water vapor in air

a) Usually ~3%

2. Relative humidity - % of water vapor certain volume of air is holding relative to maximum amount it can contain

Humidity

1. Precipitation occurs when relative humidity is over 100%

2. Dew point = 100% humidity

3. Two ways to reach dew pointa) Lower temperatureb) Increase water content

Clouds

1. Clouds form when air reaches its dew point2. Serve several roles

a) Preventing solar radiation from reaching ground

b) Absorbing warmth that is re-emitted from ground

c) Source of precipitation3. Classified based on height

a) Strato (low), Alto (middle), Cirro (high)4. Classified based on shape

a) Cumulus, stratus, cirrus

Cloud Height

1. Cirro – High2. Alto – Middle3. Strato - Low

Cloud Shapes

1. Cumulus: puffy cotton ball

2. Stratus: even layers

3. Cirrus: wispy tufts

Fog

1. Radiation foga) Cold ground cools air beyond its

dew pointb) Most common

2. Steam foga) Forms over lakes and ponds at

night because water is warm and air is cool

Precipitation

1. Dewa) Warm air contacting cold surface

2. Rain/Snowa) Drops/flakes too heavy to be held up

by air currentsb) Melt or remain frozen depending on

temperature

3. Haila) Extremely strong currents push water

back up into the cloud several times