ABSTRACT
Hadley (cell) circulation A circulation in the meridional plane known to exist in the tropics due to the ascending warm air near the equator and descending cold air in high latitudes.
Hadley cell Convection cells within the atmosphere of a body. On planets where most of the atmospheric heating is produced by the sun (such as Earth, Venus, and Mars), air over the equatorial regions will be hotter than air over the poles. This hotter air is less dense than cooler air and thus rises, eventually losing heat as it moves toward the polar regions. Over the poles, the air becomes colder and more dense, thus sinking towards the surface. The cooler air moves back along the planet’s surface towards the equator, where it warms up and the cycle repeats. This basic cycle of warm air rising over the equator and cooler air sinking over the poles is called Hadley Circulation. Rapid rotation and variations in surface temperature (caused, for example, by oceans vs. continents) complicate this basic pattern. Hadley cells fairly accurately describe the atmospheric circulation only for Venus, although they form the basics for physical studies of other planetary atmospheres.
hadron Any particle that interacts with the strong nuclear force. Hadrons are divided into two groups: baryons (“heavy ones,” consisting of three quarks), which are fermions and obey the exclusion principle, and mesons which are bosons, and consist of a quark anti-quark pair. See fermion, boson, quark.
