Numerical study of penetrative and "solid lid" nonpenetrative convective boundary layers

Abstract

A large eddy simulation model was used to generate and compare statistics of turbulence during nonpenetrative and penetrative dry convection. In penetrative convection dimensionless vertical velocities in updrafts were found to have almost the same values as in the nonpenetrative case. The countergradient transport of heat and moisture was found to be present during nonpenetrative convection at z/zi > 0.6. For penetrative convection the countergradient transport of heat occurred only in a layer 0.5 < 0.75, while the countergradient transport of humidity was not present. During nonpenetrative convection, temperature and humidity were perfectly correlated. In penetrative convection the correlation coefficient was found to be less than unity, varying from about 0.9 near the surface to about -0.7 at the top of the mixed layer. © 1996 American Meteorological Society.