Air

Air
NASA Earth Observatory · Public domain · source
Name	Air

Air is the gaseous mixture that surrounds planetary bodies and supports aerobic life, mediates weather, and enables flight. It plays a central role in the dynamics of the Earth system, interacts with planetary surfaces such as Amazon Rainforest and Sahara Desert, and factors into human endeavors from navigation to industry represented by entities like Boeing and General Electric.

Composition and Properties

The modern bulk composition of near-surface air over Earth is dominated by Nitrogen (≈78%), Oxygen (≈21%), with smaller but critical fractions of Argon, Carbon dioxide, and trace gases referenced by organizations such as the Intergovernmental Panel on Climate Change and World Meteorological Organization. Properties such as density, viscosity, specific heat, and refractive index vary with temperature and pressure measured in standards maintained by National Institute of Standards and Technology and applied in models by groups like NASA and European Space Agency. Molecular-scale behavior is described by kinetic theory developed in the tradition of Ludwig Boltzmann and thermodynamic relations used by Sadi Carnot and Rudolf Clausius. Isotopic composition (e.g., Oxygen-18/Oxygen-16, Carbon-13/Carbon-12) provides proxies used by paleoclimate studies associated with IPCC assessments and paleooceanography projects such as those at Lamont–Doherty Earth Observatory.

Atmospheric Structure and Layers

Planetary atmospheres are stratified; Earth’s troposphere, stratosphere, mesosphere, thermosphere, and exosphere are delineated using temperature gradients characterized in campaigns by NOAA and observatories like Mauna Loa Observatory. The troposphere hosts weather systems influenced by circulation cells first described by George Hadley and modified by studies at institutions including Met Office and Max Planck Institute for Meteorology. The stratosphere contains the ozone layer studied in the context of the Montreal Protocol and monitored by instruments on satellites from European Space Agency and NASA. Interfaces such as the tropopause and mesopause govern exchange processes considered in research by World Meteorological Organization and in field experiments at Sierra Nevada Observatory.

Physical and Chemical Processes

Dynamical processes—turbulence, convection, and large-scale advection—are treated in the frameworks developed by Andrey Kolmogorov and Lewis Fry Richardson and implemented in numerical codes at NOAA and ECMWF. Radiative transfer involving scattering and absorption by molecules and aerosols follows formalisms by Chandrasekhar and is central to climate modeling by Hadley Centre and IPCC reports. Chemical cycles include the nitrogen cycle investigated by Rachel Carson-era ecologists, the carbon cycle quantified by programs at Scripps Institution of Oceanography, and photochemistry driven by solar ultraviolet flux measured by instruments on Orbiting Carbon Observatory. Heterogeneous chemistry on aerosol surfaces links to studies by Paul Crutzen and mechanisms that affect stratospheric ozone.

Biological Interactions and Ecology

Air mediates exchanges between ecosystems—photosynthesis by plants studied from Kew Gardens to Smithsonian Tropical Research Institute consumes Oxygen and Carbon dioxide, while respiration by animals and microbes returns gases monitored in long-term sites such as FLUXNET and NEON. Pollination by insects like those documented in Royal Society publications depends on wind and atmospheric cues, and airborne pathogens tracked by public health agencies including Centers for Disease Control and Prevention influence disease dynamics in cities like New York City and Mumbai. Avian migration studied by Cornell Lab of Ornithology and aerobiology research at Johns Hopkins University examine how atmospheric conditions shape species distributions.

Human Uses and Technologies

Humans exploit air for propulsion, energy, and industrial processing. Aeronautical engineering by companies such as Airbus and Lockheed Martin leverages aerodynamic principles formalized by Isaac Newton and Daniel Bernoulli. Wind energy farms operated by firms like Vestas and researched at National Renewable Energy Laboratory convert kinetic energy into electricity. Air separation units produce industrial gases used by BASF and Air Liquide; HVAC systems designed by firms such as Trane regulate indoor climates in buildings by standards from ASHRAE. Life-support systems aboard International Space Station and submarines by navies like United States Navy recycle and condition breathing gases.

Environmental Issues and Air Quality

Air quality concerns include pollution from fossil fuel combustion addressed by regulations such as the Clean Air Act and mitigation strategies coordinated by United Nations Environment Programme. Emissions of greenhouse gases from sectors tracked by IPCC produce radiative forcing studied in international policy forums such as UNFCCC and observed by networks including Global Atmosphere Watch. Particulate matter, ozone precursors, and persistent organic pollutants are the focus of monitoring by agencies like EPA and remediation by projects at European Environment Agency. Transboundary pollution events exemplified by smog episodes in Los Angeles and haze in Beijing prompt air-quality indices and public-health advisories issued by municipal authorities.

Measurement and Instrumentation

Quantifying atmospheric constituents and dynamics uses instruments ranging from ground-based gas analyzers developed at Scripps Institution of Oceanography to satellite sensors deployed by NOAA, ESA, and JAXA. Lidar systems pioneered at facilities like National Center for Atmospheric Research measure aerosols and wind profiles; radiosondes launched by national services including Met Office provide vertical profiles of temperature and humidity. Flux measurements in ecosystems are coordinated by FLUXNET; mass spectrometers at laboratories such as Lawrence Berkeley National Laboratory analyze isotopic signatures. Standardization and calibration are overseen by organizations like World Meteorological Organization and National Institute of Standards and Technology to ensure data interoperability for research and policy.

Category:Atmosphere