LES STUDY ON THE ENERGY IMBALANCE PROBLEM FOR HETEROGENEOUS SURFACE

Abstract

The so-called energy imbalance problem is investigated through numerical experiments using Large Eddy Simulation (LES). LES experiments are done for daytime atmospheric boundary layers over a flat surface with inhomogeneous heat flux. The heat flux is represented by a one-dimensional sinusoidal curve with a variable wavelengtha nd amplitude.The following are the main results. 1) When the amplitude is enough, the bias and variance of imbalance is increase. A weak inhomogenity of surface heating, however, may relax the negative bias of imbalance. This is attributed to the heat transport efficiency of vertical mean wind. 2) Although longer wavelengths generally give a smallerb ias of imbalance, the 2km wavelength singularly increases the bias of imbalance. 3) The bias and variance of imbalance decrease in accordance with horizontal wind. Longer averaging time gives a smaller bias but a larger variance of imbalance. The tendency of these two results is almost the same as in the homogeneoush eatingc ase.