  The universal velocity log law first proposed by von K\'arm\'an in the
near-wall region of turbulent shear flows is one of the cornerstones of
turbulence theory. When buoyancy effects are important, the universal velocity
log law is typically believed to break down according to Monin-Obukhov
similarity theory (MOST), which has been used in almost all global weather and
climate models to describe the dependence of the mean velocity profiles on
buoyancy in the atmospheric boundary layer. In contrast to MOST, we propose new
logarithmic profiles of near-wall mean velocity in the stably stratified
atmospheric boundary layers based on direct numerical simulations and field
observations across a wide range of buoyancy effects. We find that buoyancy
does not change the logarithmic nature of velocity profiles but instead
modifies the slope of the log law in stably stratified conditions.
