= Dry adiabatic lapse rate
{title2=$\Gamma_{\rm dry}=g/C_p$}
For a homogeneous dry <ideal gas> in a hydrostatic adiabat, $dT/dz=-g/C_p$, where $z$ increases upwards and $C_p$ is the <specific heat capacity at constant pressure> per unit mass. It follows from $dT/dP=1/(\rho C_p)$ and <hydrostatic equilibrium>. The altitude version of the <Schwarzschild criterion> is $dT/dz<-g/C_p$ for instability; equality is marginal. Moisture, composition gradients and nonideal equations of state modify the criterion.
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