Part%201.%20Energy%20and%20Mass

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Part 1. Energy and Mass

• Chapter 1.
• Composition and Structure of the Atmosphere

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Introduction

• The Atmosphere
• A mixture of gas molecules, suspended particles,
  and falling precipitation
• The atmosphere strongly affects our day-to-day
  lives

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• Meteorology
• The study of the atmosphere and the processes
  that cause weather
• Climatology
• Examines weather elements over long time periods

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Variable Gases

• Water Vapor
• Most abundant variable gas
• Added/ removed to air through the hydrologic
  cycle
• Concentrations nearly 0 to nearly 4
• Important to energy balance and many atmospheric
  processes

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• Carbon Dioxide
• A trace gas
• 0.038 of atmospheres mass
• Important to Earths energy balance
• Added through biologic respiration, volcanic
  activity, decay, and natural and human-related
  combustion
• Removed through photosynthesis
• Increasing at a rate of 1.8 ppm/year

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Temporal increases due to human
activities Seasonal variations related to
biological activity
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• Ozone
• Tri-atomic form of oxygen
• Absorbs ultraviolet radiation
• Chlorofluorocarbons (CFCs) destroy ozone
• Destruction peaks over southern hemisphere
• Antarctic circumpolar vortex limits latitudinal
  mixing
• Leads to an O3 hole

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Vertical Structure of the Atmosphere

• Density
• Mass (kg) per unit volume (m3)
• Sea level average 1.2 kg/m3
• Near surface air is more dense
• Compressibility
• Mean free path
• At surface 0.0001 mm
• At 150 km 10 m

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Compressibility of gases relates to density
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Thermal Layers of the Atmosphere

• Four distinct atmospheric layers
• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Each has particular temperature characteristics
  with height.

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• Troposphere
• Lowest layer
• Steady temperature decrease with height
• -6.5oC/km (-3.6oF/1000ft)
• Virtually all weather processes
• Contains 80 of atmospheric mass
• Tropopause top of troposphere

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Violent updrafts may penetrate cloud tops into
the stratosphere. The flattened top of this
cumulonimbus cloud is in the stratosphere.
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• Stratosphere
• Little actual weather
• Temperature inversion
• Caused by absorption of UV radiation by O3
• Stratopause top of stratosphere

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• Mesosphere and Thermosphere
• Combined 0.1 of total mass
• The mesosphere
• Decreasing temperatures with height
• Coldest layer
• The thermosphere
• Slowly merges into space
• Increasing temperatures with height
• Temperature molecular kinetic energy

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Some Weather Basics

• Weather information is abundant
• Pressure and wind
• Wind horizontal movement of air
• Caused by unequal pressures

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• Pressure units
• Millibar (mb), Kilopascal (kPa)
• Isobars
• Station Models
• Portray weather information

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• Temperature
• Most obvious weather component
• Fronts
• Humidity
• May be expressed as relative humidity
• Dew point temperature

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