Atmospheric Composition and Structure

by

Justin Schoof

• LAST REVIEWED: 15 April 2021
• LAST MODIFIED: 30 January 2014
• DOI: 10.1093/obo/9780199874002-0087

Introduction

The earth’s atmosphere is the layer of gases and aerosols surrounding the planet and held by the earth’s gravitational force. The composition and structure of the atmosphere define its role, both as a producer of weather and a protector of life. The composition of the atmosphere varies across a range of timescales. For example, tectonic plate movement and volcanic activity have caused substantive changes in atmospheric composition over the earth’s 4.6 billion year history. At shorter timescales, human impacts on composition are evident, and the increasing concentrations of greenhouse gases that contribute to global climate change are currently the focus of intense scientific research. The structure of the atmosphere is usually considered in terms of the three variables that define the state of any fluid: pressure, density, and temperature. The decrease of gravitational force with altitude and the compressibility of air dictate that both pressure and density are greatest at the surface and decrease exponentially with height. Because of vertical variations in atmospheric composition, the temperature profile exhibits more complex behavior, which is described in more detail in this article. The large-scale structure of the atmosphere is also influenced by the uneven receipt of solar energy (more in the tropics and less in the polar regions when averaged annually), the earth’s rotation, and the uneven distribution of land and water. These factors collectively drive the general circulation of both the atmosphere and oceans. Periodic variations in solar radiation received (i.e., the daily and seasonal cycles) also lead to predictable variations in atmospheric structure, such as greater instability in the afternoon relative to nighttime and seasonal variations in the positions of large-scale atmospheric features, such as the jet stream.

General Overviews

A general overview of the atmospheric composition and structure can be found in most introductory atmospheric science textbooks (usually as the first chapter). For example, after defining weather and climate, Aguado and Burt 2013 immediately starts describing the composition of the atmosphere in terms of composition and structure. Such texts traditionally focus on the current composition of the atmosphere and describe it in terms of permanent and variable gases. The former are those for which the concentration does not change substantively from time to time or place to place (e.g., nitrogen). The latter are those with highly varying concentrations either through time, space, or both (e.g., water vapor). Structure in introductory texts is treated rudimentarily, with a description of exponentially decreasing pressure and density followed by a description of four atmospheric layers based on temperature variation: troposphere, stratosphere, mesosphere, and thermosphere. More advanced textbooks, such as Stull 1999 and Wallace and Hobbs 2006, provide a more quantitative overview of the relationship between these variables and height as well as their interrelationships. Introductory texts also present the relatively short observational record of accumulating greenhouse gases, usually shown as the monthly concentration of carbon dioxide at the Mauna Loa Observatory in Hawaii measured continuously since 1958, while peer-reviewed sources, such as Keeling, et al. 1976 and Thoning, et al. 1989, provide a more scientific treatment. Near real-time CO₂ measurements are available online from the Scripps Institute of Oceanography, while data relating to a wide variety of atmospheric chemistry observations are available from the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory. On the other hand, few texts discuss the historical context for the Mauna Loa observations. In an excellent overview of the earth’s climate history, Ruddiman 2008 provides context for contemporary greenhouse gas concentrations.

• Aguado, E., and J. E. Burt. Understanding Weather and Climate. 6th ed. Boston: Pearson, 2013.

  An introductory weather and climate text, Aguado and Burt 2013 covers a broad range of topics, including basic atmospheric composition and structure.

• Keeling, C. D., R. B. Bacastow, A. E. Bainbridge, C. A. Ekdahl, P. R. Guenther, and L. S. Waterman. “Atmospheric Carbon Dioxide Variations at Mauna Loa Observatory, Hawaii.” Tellus 28 (1976): 538–551.

  DOI: 10.1111/j.2153-3490.1976.tb00701.x

  This paper presents ten years of measurements from Mauna Loa and provides some of the earliest measurements confirming an increase in atmospheric carbon dioxide concentrations.

• Pacific Marine Environmental Laboratory.

  The Pacific Marine Environmental Laboratory is a leader in research on biogeochemical cycling between the ocean and atmosphere. As such, it maintains a substantive database on both atmospheric and oceanic chemistry.

• Ruddiman, W. F. Earth’s Climate: Past and Future. New York: W. H Freeman, 2008.

  This book provides a thorough introduction to Earth’s climate history, assessing drivers of climate change over several distinct timescales. Central to this work is the movement of carbon between its various reservoirs within the climate system, including the atmosphere.

• Scripps Institute of Oceanography. The Keeling Curve.

  The Scripps Institute of Oceanography provides near real-time measurements of atmospheric carbon dioxide measured at the Mauna Loa Observatory in Hawaii (the so-called Keeling Curve). Users can also view historical observations on timescales ranging from one week to the full record as well as view carbon dioxide proxy records developed from ice score studies.

• Stull, R. B. Meteorology for Scientists and Engineers. 2d ed. London: Brooks/Cole, 1999.

  Stull 1999 provides a quantitative description of the atmosphere’s structure.

• Thoning, K. W., P. P. Tans, and W. D. Komhyr. “Atmospheric Carbon Dioxide at Mauna Loa Observatory 2: Analysis of the NOAA GMCC Data, 1974–1985.” Journal of Geophysical Research 94 (1989): 8549–8565.

  DOI: 10.1029/JD094iD06p08549

  This paper describes twelve years of data from Mauna Loa and builds on the work of Keeling, et al. 1976 focusing on the seasonal cycle and rate of carbon dioxide increase.

• Wallace, J. M., and P. V. Hobbs. Atmospheric Science: An Introductory Survey. 2d ed. New York: Academic Press, 2006.

  This is an introductory text for students majoring in atmospheric science. It provides an excellent overview of atmospheric structure but assumes that students are comfortable with basic physics and calculus.