MMM SEMINAR NCAR
Statistics of Scalar Fields in the
Atmospheric Boundary Layer
Based on Large-Eddy Simulations of Free
and Forced Convection
Zbigniew
W. Sorbjan
Department of Physics
Free and forced convection in a quasi-steady atmospheric boundary layer is investigated based on a large-eddy simulation (LES) model.
The performed simulations show
that in the upper portion of the mixed layer, the dimensionless (in terms of
the mixed layer scales) vertical gradients of temperature, humidity, and wind
velocity depend on the dimensionless height z/zi and
the Reech number Rn = (zi Ni/w*)2, where Ni is the Brunt-Vaisala
frequency . The peak values of variances and covariances
at the top of the mixed layer, scaled in terms of the interfacial scales depend
on of 1/Ri, where Ri is the
interfacial
Profiles of dimensionless scalar moments in the mixed layer are proposed to be expressed in terms of two empirical similarity functions Fm and Fi, dependent on dimensionless height z/zi, and 1/Ri. The obtained similarity expressions adequately approximate the LES profiles of scalar statistics, and properly represent the impact of stability, shear, and entrainment. They are consistent for both free and forced convection.
Tuesday, 18 October 2005,
3:30 PM
Refreshments
NCAR-Foothills Laboratory
Bldg 2 Auditorium (Rm1022)