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1: Atmospheric Basics

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    Classical Newtonian physics can be used to describe atmospheric behavior. Namely, air motions obey Newton’s laws of dynamics. Heat satisfies the laws of thermodynamics. Air mass and moisture are conserved. When applied to a fluid such as air, these physical processes describe fluid mechanics. Meteorology is the study of the fluid mechanics, physics, and chemistry of Earth’s atmosphere.

    The atmosphere is a complex fluid system — a system that generates the chaotic motions we call weather. This complexity is caused by myriad interactions between many physical processes acting at different locations. For example, temperature differences create pressure differences that drive winds. Winds move water vapor about. Water vapor condenses and releases heat, altering the temperature differences. Such feedbacks are nonlinear, and contribute to the complexity. But the result of this chaos and complexity is a fascinating array of weather phenomena — phenomena that are as inspiring in their beauty and power as they are a challenge to describe. Thunderstorms, cyclones, snow flakes, jet streams, rainbows. Such phenomena touch our lives by affecting how we dress, how we travel, what we can grow, where we live, and sometimes how we feel. In spite of the complexity, much is known about atmospheric behavior. This book presents some of what we know about the atmosphere, for use by scientists and engineers.

    • 1.0: Pressure Instruments
      This page explains barometers, which measure atmospheric pressure against a reference. There are two main types: aneroid barometers with a corrugated can and mercury barometers using a mercury column. Modern versions use safer fluids and include temperature corrections. Electronic barometers employ strain gauges or capacitance for measurements, with digital versions available for computer use. For more information, refer to the WMO-No. 8 Guide.
    • 1.1: Review
      This page explores the thermodynamic state of air, highlighting the relationships between pressure, temperature, and density via the ideal gas law. It covers the exponential decrease of atmospheric pressure with height due to hydrostatic equilibrium and variations in temperature linked to solar radiation. The page introduces the standard atmosphere model for atmospheric layering and offers homework tips to ensure clarity and maximize credit through careful formatting in problem-solving.
    • 1.2: Homework Exercises
      This page highlights the significance of current data in meteorology, focusing on the use of satellite images and weather maps for problem-solving. It promotes internet research skills and proper citation to avoid plagiarism, alongside practical exercises that incorporate mathematical concepts. It also emphasizes critical thinking in evaluating atmospheric equations, exploring hypothetical scenarios in meteorology and physics, and applying the Scientific Method.
    • 1.3: Introduction
      This page presents the five essential components of meteorology: thermodynamics, physical meteorology, observation and analysis, dynamics, and weather systems. It emphasizes thermodynamics' role in atmospheric conditions influenced by pressure, density, and temperature, and explains how minor variations affect weather and climate.
    • 1.4: Meteorological Concentions
      This page covers René Descartes' influential scientific method, focusing on truth validation, problem simplification, and bias avoidance. It also presents statistical data on weather disasters from 1970 to 2012, underscoring the impact of storms.
    • 1.5: Earth Frameworks Reviewed
      This page describes Earth's shape as an oblate spheroid with specific polar and equatorial radii, coordinates for sky positioning, and standard time zones based on UTC. It explains how to convert UTC to local time in Reno, accounting for daylight savings and highlights the 24-hour clock system.
    • 1.6: Thermodynamic State
      This page covers the thermodynamic state of air, defined by pressure (P), density (ρ), and temperature (T). It explains the relationship between temperature and molecular motion, pressure as force per unit area, and the significance of absolute units like Kelvin. The effects of atmospheric pressure on structures are illustrated with calculations and the concept of isotropic nature in fluids.
    • 1.7: Atmospheric Structure
      This page covers the structure and characteristics of the atmosphere, focusing on the 1976 U.S. Standard Atmosphere as a reference for atmospheric conditions at different altitudes. It explains geopotential height and gravitational effects with examples for temperature and pressure calculations.
    • 1.8: Equation of State-Ideal Gas Law
      This page explains the Equation of State relating pressure, density, and temperature in gases, highlighting the Ideal Gas Law for dry air and the influence of water vapor in moist air. It introduces virtual temperature to aid calculations involving humidity and provides sample applications for determining standard surface temperature, absolute humidity, and virtual temperature, demonstrating the practical uses of these concepts.
    • 1.9: Hydrostatic Equilibrium
      This page explains the pressure gradient in a column of air, detailing how pressure decreases with height and results in an upward pressure gradient force that balances gravitational force, creating hydrostatic equilibrium. It includes equations for pressure change relative to height and stresses the need for consistent directional calculations. Additionally, it addresses the shift from finite-difference to differential equations for enhanced understanding of pressure gradients.
    • 1.10: Hypsometric Equation
      This page explains the hypsometric equation, which integrates the ideal gas law and hydrostatic principles to determine pressure variations with height under different temperature profiles. It employs average virtual temperature for height approximations and enables detailed pressure drop analyses in smaller segments. In uniform dry conditions, it exhibits exponential pressure decrease.
    • 1.11: Process Terminology
      This page covers thermodynamic processes in meteorology, defining concepts like isothermal and isobaric conditions, and introducing relevant terms such as isotherms and isobars on weather maps. It includes a table summarizing processes with constant parameters like density, and briefly discusses the hypsometric equation, explaining its derivation from the hydrostatic equation and the ideal gas law, highlighting the role of calculus in advanced studies of meteorology.

    This page titled 1: Atmospheric Basics is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Roland Stull via source content that was edited to the style and standards of the LibreTexts platform.