Hadley circulation
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| Hadley circulation | |
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 Kaidor · CC BY-SA 3.0 · source | |
| Name | Hadley circulation |
| Type | Atmospheric circulation |
| Discovered | 1735 (George Hadley) |
| Region | Tropics and subtropics |
| Driving forces | Solar heating, Coriolis effect, convection |
| Typical extent | Equator to ~30° latitude (variable) |
| Typical time scale | Seasonal to annual |
Hadley circulation is a large-scale tropical atmospheric overturning circulation that transports heat and moisture between the equator and subtropics. It plays a central role in the distribution of tropical precipitation, trade winds, and subtropical aridity across continents and oceans. The Hadley circulation interacts with the Intertropical Convergence Zone, midlatitude jet streams, and oceanic phenomena to modulate climate on seasonal to multi-decadal timescales.
Overview and Definition
The Hadley circulation is classically defined as a zonally averaged overturning cell in the meridional plane characterized by ascending motion near the equator, poleward flow aloft, descending motion in the subtropics, and return flow near the surface. Early theoretical explanations trace to George Hadley and later formalization by scientists associated with the Royal Society, the Royal Society of London, and the Philosophical Transactions of the Royal Society. Modern observational and modeling frameworks derive from research by figures affiliated with institutions such as the National Aeronautics and Space Administration, the National Oceanic and Atmospheric Administration, the Met Office, the Scripps Institution of Oceanography, and the Max Planck Institute for Meteorology. Empirical descriptions use diagnostics developed by researchers connected to universities like University of Cambridge, Massachusetts Institute of Technology, University of Oxford, Harvard University, and Stanford University.
Mechanism and Dynamics
The dynamical drivers include differential solar heating between the tropics and higher latitudes, buoyant convection over warm sea surfaces and continents, and the influence of planetary rotation via the Coriolis force. Key theoretical frameworks involve work by contributors linked to Princeton University, California Institute of Technology, University of Chicago, and the Lamont–Doherty Earth Observatory, and draw on mathematical formalisms from researchers at Imperial College London and ETH Zurich. Interactions with baroclinic eddies and angular momentum conserving flows are central concepts developed in studies associated with Woods Hole Oceanographic Institution, University of Washington, National Center for Atmospheric Research, and Geophysical Fluid Dynamics Laboratory. The role of moist convection has been elucidated through campaigns and projects run by World Climate Research Programme, Global Atmosphere Watch, and Tropical Ocean Global Atmosphere programs.
Meridional Extent and Seasonal Variability
The poleward edge and strength of the circulation vary with season, sea surface temperature patterns, and forcings such as volcanic eruptions and anthropogenic greenhouse gas increases. Observational synthesis from satellites operated by European Space Agency, Japan Aerospace Exploration Agency, Indian Space Research Organisation, and Russian Federal Space Agency complement field experiments supported by agencies like Australian Bureau of Meteorology and Environment and Climate Change Canada. The interannual variability links to phenomena researched at International Research Institute for Climate and Society, including connections with the El Niño–Southern Oscillation, the Indian Ocean Dipole, and the Atlantic Multidecadal Oscillation. Longer-term shifts relate to studies by Intergovernmental Panel on Climate Change, United Nations Environment Programme, and national climate centers such as Met Office Hadley Centre.
Interaction with Other Atmospheric Circulation Cells
The Hadley circulation interacts with the Walker circulation, polar cells, and midlatitude Ferrel circulation studied by collaborators across European Centre for Medium-Range Weather Forecasts, Centre National de Recherches Météorologiques, and Deutsches Klima-Konsortium. These interactions influence the position of the subtropical jet and tropical easterly jet and are central to research by groups at NOAA’s Geophysical Fluid Dynamics Laboratory, National Center for Atmospheric Research, and university departments at Columbia University, University of California, Los Angeles, and Yale University. Teleconnections such as those identified in research from Potsdam Institute for Climate Impact Research and International Centre for Theoretical Physics link the Hadley circulation to monsoon systems examined by institutions like Indian Institute of Tropical Meteorology, China Meteorological Administration, and Centro de Investigación Científica y de Educación Superior de Ensenada.
Impacts on Climate, Weather, and Biomes
Variations in the Hadley circulation modulate the location and intensity of tropical rainfall belts, influencing ecosystems studied by researchers at Smithsonian Institution, Royal Botanic Gardens, Kew, and World Wildlife Fund. Expansion or contraction affects subtropical aridity, with implications for agriculture and water resources in regions monitored by Food and Agriculture Organization, International Water Management Institute, and United States Agency for International Development. Links to extreme events have been examined by teams at European Commission’s Joint Research Centre, National Institutes of Health, and disaster agencies such as Federal Emergency Management Agency and United Nations Office for Disaster Risk Reduction.
Observations, Modeling, and Measurement Methods
Measurement techniques combine in situ observations from research vessels and stations managed by Scripps Institution of Oceanography, British Antarctic Survey, and Lamont–Doherty Earth Observatory with satellite retrievals by NASA, ESA, JAXA, and NOAA. Climate models from centers such as Met Office Hadley Centre, GFDL, MPI-M, NCAR, and CSIRO are used to simulate Hadley cell behavior, while reanalysis products from ECMWF and NCEP provide gridded diagnostics. Field campaigns like those led by Tropical Atmosphere Ocean program and observational networks including Argo, Global Atmospheric Watch, and Tropical Rainfall Measuring Mission supply critical data. Advances in parameterizations and high-resolution modeling have been pursued at Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and major universities including Princeton University and Massachusetts Institute of Technology.