WIND AND TEMPERATURE PROFILES IN THE RADIX LAYER - THE BOTTOM 5TH OF THE CONVECTIVE BOUNDARY-LAYER

In the middle of the convective atmospheric boundary layer is often a deep layer of vertically uniform wind speed (M-UL), wind direction, an d potential temperature (theta(UL)). A radix layer is identified as th e whole region below this uniform layer, which includes the classic su rface layer as a shallower subdomain. An empirical wind speed (M) equa tion with an apparently universal shape exponent (A) is shown to cause observations from the 1973 Minnesota field experiment to collapse int o a single similarity profile, with a correlation coefficient of rough ly 0.99. This relationship is M/M-UL = F(z/z(R)), where F is the profi le function, is height above ground, and z(R) is depth of the radix la yer. The profile function is F = (z/z(R))(A) exp[A(1 - z/z(R))] in the radix layer (z/z(R) less than or equal to 1), and F = 1 in the unifor m layer (z(R )<( )z < 0.7z(i)). The radix-layer equations might be of value for calculation of wind power generation, wind loading on buildi ngs and bridges, and air pollutant transport. The same similarity func tion F with a different radix-layer depth and shape exponent is shown to describe the potential temperature (theta) profile: (theta - theta( UL))/(theta(0) - theta(UL)) = 1 - F(z/z(R)), where theta(0) is the pot ential temperature of the air near the surface. These profile equation s are applicable from 1 m above ground level to the midmixed layer and include the little-studied region above the surface layer but below t he uniform layer. It is recommended that similarity profiles be formul ated as mean wind or potential temperature versus height, rather than as shears or gradients versus height because shear expressions disguis e errors that are revealed when the shear is integrated to get the spe ed profile.