Hadley cell
= Hadley cell
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{wiki}
A tropical atmospheric overturning circulation with rising air near the equator, poleward flow aloft, subtropical descent and an equatorward lower return. In its ideal upper branch, <conservation of angular momentum> gives $u=\Omega a\sin^2\phi/\cos\phi$ for air initially at rest relative to the equatorial surface. <Eddies> and <friction> modify this idealization.