Weather, Climate, and the Atmosphere

What Is the Atmosphere? The atmosphere is the thin layer of air surrounding the earth 99% of the atmosphere is within 30 km of the surface The atmosphere is vital for life o The air we breathe o Liquid water If no air, water boils away o Temperatures not freezing cold or boiling hot

Altitude of space station: 230 miles (370 km) Kevin Ford, NASA

78% 21% 1% 0.038%0.002% Water vapor concentration varies between 0-4%. Depends on the weather. What Is the Atmosphere?

Other Trace Gases (Less Than 1%) Methane (CH 4 ) o Natural gas Ozone (O 3 ) o Absorbs harmful ultraviolet radiation from sun Chlorofluorocarbons (CFCs) o Formerly used as a coolant in air conditioners o React with and destroy ozone Many others…

Aerosols Small solid or liquid particles suspended in the atmosphere o Both natural and man-made pollutants Component of smog Reduce visibility

History of Meteorology 340 B.C.: Aristotle writes Meteorologica 1600s-1700s: Weather instruments invented 1843: Telegraph invented 1920s: Study of air masses and fronts 1940s: Upper-air observations begin 1950s: Development of weather radar and computers 1960s: First satellites launched

Weather Weather – Atmospheric conditions at a particular time and place o Elements: Temperature, pressure, humidity, cloud cover, precipitation, visibility, wind speed and direction

Weather

Tornado: 10 m – 1 km (not shown) Mid-latitude cyclone: 1000 km Hurricane: 500 km Thunderstorms: km

Climate The average weather over a long (10+ year) period of time o Weather records o Climate changes over long periods of time and is changing now Need to look at long-term trends in weather data to evaluate climate changes o Often requires detailed statistical analysis You CANNOT see climate change by looking out the window!!! Can’t prove anything by cherry picking a few data points either

Weather vs. Climate CANNOT use individual weather events to prove or disprove changes in climate! o Climate is what you expect, weather is what you get

Observing the Weather Weather Instruments Satellites (space) Radar(ground)

Satellites – View clouds from space

Radar – View precipitation from ground Doppler radar – Can sense motion of precipitation particles toward/away from radar

Reflectivity (rain) Velocity GREEN = TOWARD radar RED = AWAY FROM radar Doppler Radar Strong outbound velocities and strong inbound velocities on adjacent radials indicate rotation and potentially a tornado!!!

Data from weather instruments plotted using the station model.

Examine temperature data (colored) to find areas of warm and cold air Masses of warm and cold air meet at fronts (see next slide) Masses of warm and cold air meet at fronts (see next slide) Cold front – Cold air advancesCold front – Cold air advances Warm front – Cold air retreatsWarm front – Cold air retreats

Examine pressure data to find areas of high and low pressure Fronts connect to low pressure centers Low pressure (L): Counter-clockwise and inward circulation and clouds/precipitation Low pressure (L): Counter-clockwise and inward circulation and clouds/precipitation High pressure (H): Clockwise and outward circulation and generally clear skies High pressure (H): Clockwise and outward circulation and generally clear skies

Surface Highs and Lows

Upper-air map (10 km height) Winds generally from west, move weather from west to east Jet stream axis in GREEN