Elements of Weather

1
Elements of Weather

• air temperature, air pressure
• humidity, clouds
• precipitation, visibility
• wind

Climate

• Average weather
• Extreme

2

Precip, wind, T/Td, rain type, lightning, cloud
base, freezing rain, visibility
3
Instruments

• tipping bucket rain gauge used in ASOS

• It is difficult to capture rain in a bucket when
  thewind is blowing strongly.

4

Fig. 4-1, p. 80
5
Fog

• radiation fog
• cooling from ground
• advection fog
• warm, moist air over cold surface
• upslope fog cooling
• evaporation (mixing) fog
• when moist air from your mouth or nose meets
  the cold air and mixes with it
• haze hygroscopic (water seeking) condensation
  nuclei
• allows water vapor to condense when RH is
  below 100

6
Precipitation Processes
7
Clouds with Vertical Development

• Cumulus puffy, floating cotton with flat base
• cumulus congestus line of towering Cu
• Cumulonimbus thunderstorm with anvils

• Not all cumulus clouds grow to be thunderstorms,
  butall thunderstorms start out as cumulus clouds.

8

Fig. 1-13, p. 17
9
Measuring Air Temperature
While T is as high as 500oC in the upper
atmosphere of 300 km, astronauts still feel very
cold. Why?
10
Why the Earth has Seasons

• earth-sun distance closer in winter
• tilt of the earths axis

• Earth-sun distance has little effect on
  atmospheric temperature.