CELLULAR CONVECTION EMBEDDED IN THE CONVECTIVE PLANETARY BOUNDARY-LAYER SURFACE-LAYER

Cellular convection was first studied in the laboratory by Benard [Ann . Chim. Phys. 23 (1901) 62-144] and Rayleigh [Phil. Mag. Ser. 6 (1916) 529-546] investigated these motions from a theoretical perspective. H e defined a dimensionless number, now called the Rayleigh number, whic h is the ratio of convective transport to molecular transport, and fou nd that if a certain critical value is exceeded, cellular convection o ccurs. Mesoscale cellular convection (MCC) is a common occurrence in t he planetary boundary layer. Agee [Dyn. Atmos. Oceans 10 (1987) 317-34 1] discussed the similarities and differences of MCC and classical Ray leigh-Benard convection. A similar cellular pattern can be seen in the convective boundary layer (CBL) surface layer. It is known that in th e CBL, air near the surface converges into thermals producing updrafts . This produces a 'spoke' type pattern similar to the mesoscale cellul ar or Rayleigh-Benard convection. This paper will focus on applying Ra yleigh-Benard convection criteria, using a linearized perturbation met hod, to the CBL surface layer produced by Large Eddy Simulation (LES). We will investigate the length scales of turbulence in the CBL surfac e layer and compare them to those predicted from linear theory. Simila rities and differences will be discussed between the LES produced surf ace layer and classical Rayleigh-Benard convection theory.