Sampling Error in Aircraft Flux Measurements Based on a High-Resolution
Large Eddy Simulation of the Marine Boundary Layer
Abstract
A high-resolution (1.25 m) LES simulation of the nocturnal cloud-topped
marine boundary layer is used to evaluate random error as a function of
continuous track length L for virtual aircraft measurements of turbulent
fluxes of sensible heat, latent heat, and horizontal momentum. Results
are compared with the theoretically derived formula of Lenschow and
Stankov (1986). In support of these comparisons , we also evaluate and
document the relevant integral length scales and correlations and show
that for heights up to approximately 100 m (z/z i = 0.12), the length
scales are accurately predicted by empirical expressions of the form I f
= Az^b. The Lenschow and Stankov expression is found to be remarkably
accurate at predicting the random error for shorter flight tracks, but
our empirically determined errors decay more rapidly with L than the
L^−1/2 relationship predicted from theory. Consistent with earlier
findings, required track lengths to obtain useful precision increase
sharply with altitude.