Introduction to Atmospheric Thermodynamics and Dynamics

Overview

This lecture provides a historical survey of the development of meteorology and atmospheric sciences, tracing key concepts from ancient philosophy to modern scientific understanding. The focus is on the evolution of ideas about the atmosphere, weather phenomena, and the physical laws governing them.

Meteorology: Old

Aristotle's Contributions

• Meteorology (Meteorologica or Meteora): A treatise by Aristotle (384–322 BC) containing early theories about earth sciences, including water evaporation, weather phenomena, and earthquakes.

• Main topics covered by Aristotle:

  • Physics

  • Four elements

  • Atmosphere

    • Water vapor

    • Weather

  • Geology

  • Geography

  • Hydrology

  • Spherical Earth

Four Elements

Ancient Elemental Theory

• Definition: Aristotle proposed that all terrestrial matter consists of four elements: fire, air, water, earth.

• Structure: Fire occupies the highest place, earth the lowest, with air nearest to fire and water to earth.

• Mixed and Same Origin: Each element can originate from the others and exists potentially in each, resolved into a common substrate.

• Diversity from Simplicity: Various ratios of these elements combine to create the diverse materials found in nature.

• Example: The combination of fire and water in different proportions leads to phenomena such as steam or mist.

Water Vapor

Aristotle's Observations

• Evaporation: Not all vapor formed during the day rises; the ability to rise depends on the ratio of fire (heat) to water.

• Dew and Hoar-Frost: These phenomena occur when the sky is clear and there is no wind, allowing vapor to condense.

• Altitude Effects: Hoar-frost is not found on mountains because vapor does not rise high enough; it originates from low, watery places and is limited by the heat available to lift it.

• Example: Dew forms on grass during clear, calm nights due to condensation of water vapor.

Weather

Ancient Explanations of Weather Phenomena

• Thunderbolt: Occurs when a large quantity of exhalation (vapor) is squeezed out in the cloud itself.

• Whirlwind: Results from the failure of an incipient hurricane to escape its cloud, generating an eddy and forming a spiral that descends to earth, dragging the cloud and moving objects by wind and circular motion.

• Example: Aristotle's description of whirlwinds is an early attempt to explain tornadoes and cyclones.

Additional info:

• Aristotle's theories, while not scientifically accurate by modern standards, laid the groundwork for later scientific inquiry into atmospheric phenomena.

• The transition from qualitative elemental theory to quantitative physical laws marks the evolution of meteorology into a rigorous scientific discipline.