Velocity and length scales that apply to the atmospheric boundary layer during conditions of a statically unstable atmosphere with vigorous thermal circulations and negligible shear-generation of turbulence, such as during a sunny day over land with calm winds. The length scale is zi, the mixed-layer depth, and the velocity scale is w* the Deardorff velocity. A free convection timescale can be created as t* = zi/w*. A free convection temperature scale can be found using the surface kinematic heat flux,. Similar scales can be generated for other variables such as humidity.