Meteorology Basics

Meteorology

• Meteorology is the study and forecasting of weather changes resulting from large-scale atmospheric circulation.

Chemical Composition of the Atmosphere

• Nitrogen: 78%
• Oxygen: 21%
• Argon: 0.9%
• Carbon Dioxide: 0.03%
• Water Vapor: Trace substances

Vertical Structure of Atmosphere

• Troposphere: lowest layer of Earth's atmosphere, where nearly all weather conditions take place
• Troposphere contains 75% of the atmosphere's mass and 99% of the total mass of water vapor and aerosols
• Average height of the troposphere:
  • 18 km (11 mi; 59,000 ft) in the tropics
  • 17 km (11 mi; 56,000 ft) in the middle latitudes
  • 6 km (3.7 mi; 20,000 ft) in the polar regions in winter
• Tropopause: boundary region between the troposphere and the stratosphere

Variables Influencing the Atmosphere

• Temperature: measure of heat, average kinetic energy of molecules
• Pressure:
  • High Pressure: Region where air has piled up, warmer and dryer than surrounding air
  • Low Pressure: Region where air has stretched out, tends to rise and cool, vapor condenses into clouds
• Humidity: relative humidity – the ratio of the amount of water vapor in air at current temperature to the maximum amount vapor air can hold at that temperature
• Cloudiness: water droplets, ice crystals, warm air rises, cools, and condenses (phase change)
• Winds: due to differential heating of the earth's surface, warm air rises, cooler air flows in

Global Air Circulation Patterns

• Warmer near the Earth's equator and colder near the poles due to differential heating of the earth's surface

Weather Forecasting

• National Weather Service
• World Weather Building in Camp Springs, Maryland
• Media weather specialists
• Instruments: Thermometer, Hygrometer, Barometer, Weathervane, Anemometer
• Instrument Carriers:
  • 10,000 land-based stations
  • 7,000 ocean-based buoys
  • Automated Weather Stations (about 1,000)
  • Doppler Radar
  • Satellites
• Reading a Weather Map:
  • Pressure Centers
  • Fronts
  • Precipitation
  • Temperature Readings
  • Surface Winds

Air Masses

• Winter Air Masses:
  • Continental Polar
  • Maritime Polar
  • Maritime Tropical
• Summer Air Masses:
  • Continental Polar
  • Maritime Tropical
  • Continental Tropical

Fronts

• Cold Front: digs in underneath a warm air mass, warm air rises, mixes with colder air, and condenses into clouds
• Warm Front: rides up above the cold air, in the rising warm air, clouds form far ahead of advancing warm front

Quiz on the fundamentals of meteorology, including the distinction between weather, seasons, and climate, and the chemical composition of the atmosphere.