Average vertical velocity (in pascals per second) at the 500 hPa pressure height in July from 1979–2001. Ascent (negative values) is concentrated close to the solar equator while descent (positive values) is more diffuse; their distribution is an imprint of the ascending and descending branches of the Hadley circulation.
The Hadley cell, also known as the Hadley circulation, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward near the tropopause at a height of 12–15 km (7.5–9.3 mi) above the Earth's surface, cooling and descending in the subtropics at around 25 degrees latitude, and then returning equatorward near the surface. It is a thermally direct circulation within the troposphere that emerges due to differences in insolation and heating between the tropics and the subtropics. On a yearly average, the circulation is characterized by a circulation cell on each side of the equator. The Southern Hemisphere Hadley cell is slightly stronger on average than its northern counterpart, extending slightly beyond the equator into the Northern Hemisphere. During the summer and winter months, the Hadley circulation is dominated by a single, cross-equatorial cell with air rising in the summer hemisphere and sinking in the winter hemisphere. Analogous circulations may occur in extraterrestrial atmospheres, such as on Venus and Mars.
Global climate is greatly influenced by the structure and behavior of the Hadley circulation. The prevailing trade winds are a manifestation of the lower branches of the Hadley circulation, converging air and moisture in the tropics to form the Intertropical Convergence Zone (ITCZ) where the Earth's heaviest rains are located. Shifts in the ITCZ associated with the seasonal variability of the Hadley circulation cause monsoons. The sinking branches of the Hadley cells give rise to the oceanic subtropical ridges and suppress rainfall; many of the Earth's deserts and arid regions are located in the subtropics coincident with the position of the sinking branches. The Hadley circulation is also a key mechanism for the meridional transport of heat, angular momentum, and moisture, contributing to the subtropical jet stream, the moist tropics, and maintaining a global thermal equilibrium.
The Hadley circulation is named after George Hadley, who in 1735 postulated the existence of hemisphere-spanning circulation cells driven by differences in heating to explain the trade winds. Other scientists later developed similar arguments or critiqued Hadley's qualitative theory, providing more rigorous explanations and formalism. The existence of a broad meridional circulation of the type suggested by Hadley was confirmed in the mid-20th century once routine observations of the upper troposphere became available via radiosondes. Observations and climate modelling indicate that the Hadley circulation has expanded poleward since at least the 1980s as a result of climate change, with an accompanying but less certain intensification of the circulation; these changes have been associated with trends in regional weather patterns. Model projections suggest that the circulation will widen and weaken throughout the 21st century due to climate change.
The Hadleycell, also known as the Hadley circulation, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing...
planet are organised into three cells in each hemisphere—the Hadleycell, the Ferrel cell, and the polar cell. Those cells exist in both the northern and...
rise to the largest scale atmospheric circulations: the Hadleycell, the Ferrel cell, the polar cell, and the jet stream. Weather systems in the middle latitudes...
winds. The ITCZ is effectively a tracer of the ascending branch of the Hadleycell and is wet. The dry descending branch is the horse latitudes. The location...
Winnetka, Illinois Hadley!, a 2010 Australian TV talk show hosted by Ray HadleyHadleycell, a tropical atmospheric circulation Hadley Centre for Climate...
create wind and current charts for the world's oceans. As part of the Hadleycell, surface air flows toward the equator while the flow aloft is towards...
from the collision of the cold Benguela Current and warm air from the HadleyCell create a fog belt that frequently envelops parts of the desert. Coastal...
solar radiation that produces the large-scale polar, Ferrel, and Hadley circulation cells, and the action of the Coriolis force acting on those moving masses...
Subtropical high-pressure zones form under the descending portion of the Hadleycell circulation. Upper-level high-pressure areas lie over tropical cyclones...
the reason the Kalahari is a desert. It is the descending limb of a Hadleycell. George B. Silberbauer (April 30, 1981). Hunter and Habitat in the Central...
and the cell repeats the cycle. Convection cells can form in any fluid, including the Earth's atmosphere (where they are called Hadleycells), boiling...
the polar front is the weather front boundary between the polar cell and the Ferrel cell around the 60° latitude, near the polar regions, in both hemispheres...
of the atmosphere with the tropical-latitude Hadleycell, the mid-latitude Ferrel cell, and the polar cell to describe the flow of energy and the circulation...
000 ft) above sea level. The plateau is sufficiently high to reverse the Hadleycell convection cycles and to drive the monsoons of India towards the south...
30th parallel of both hemispheres. This circulation is known as the Hadleycell and leads to the formation of the subtropical ridge. Many of the world's...
poles. It consists of two primary convection cells, the Hadleycell and the polar vortex, with the Hadleycell experiencing stronger convection due to the...
towards the Equator (an atmospheric circulation feature known as the HadleyCell). At about 30°S, the outward-travelling air sinks to lower altitudes...
in a space as small as a room or as large as a global hemisphere. The Hadleycell is an example of a global-scale thermal loop. Bartell, Patrick (2021-07-22)...
the Intertropical Convergence Zone, itself the ascending branch of the Hadleycell. Mountainous locales near the equator in Colombia are amongst the wettest...
Another significant determinant of tropical desert climate are Hadleycells. Hadleycells concentrate all precipitations in the hotter humid lower pressure...
south. Such a large Hadleycell is only possible on a slowly rotating world such as Titan. The pole-to-pole wind circulation cell appears to be centered...
and the lower temperatures reduced the strength of the HadleyCell. This is a climate cell which causes rising tropical air of the Inter-Tropical Convergence...
The Met Office Hadley Centre was named in his honour. A crater on Mars was also named after him. Hadleycell Anita McConnell, 2004, "Hadley, George (1685–1768)"...
called Hadley circulation. However, the meridional air motions are much slower than zonal winds. The poleward limit of the planet-wide Hadleycell on Venus...
is a result of the convergence of two great air-masses, the Hadleycell and the Ferrel cell. In these near-deserts, the Old Red Sandstone sedimentary beds...
winds and ocean circulation, when distributing heat around the globe. A Hadleycell is an example of a heat engine. It involves the rising of warm and moist...
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