The relationship between surface kinematic flux of any meteorological variable to the product of wind speed times the difference of that variable between the surface and some reference height, usually taken as 10 m AGL. For example, the bulk transfer law for kinematic heat flux at the surface is , where CH is the bulk transfer coefficient for heat, M is wind speed, θs is the potential temperature of the surface, w′ is the fluctuation in vertical velocity, θs′ is the fluctuation in potential temperature, the overbar indicates an average, and θ10m is the potential temperature at height 10 m AGL.