Structure of the Atmospheric Boundary Layer Derived from Airborne Measurements of the Energy Dissipation Rate

Abstract

To clarify the structure of the atmospheric boundary layer, airborne measurements were carried out above the Kanto Plain in the vicinity of Tokyo, in March and August, 1972. We analised characteristics of the atmospheric boundary layer, using the rate of turbulent energy dissipation *, which can be calculated from the isotropic region of the power spectrum, where an airplane can be regarded as a fixed platform. We define H*, which is the height where * decreases rapidly, as a thickness of the atmospheric boundary layer. H* in many cases coinsides with the base height of inversion layer Hi during daylight measurements. H* from sunrise to about 1500 hrs can be described as a function of the root of an integral quantity of insolation, which shows H* is strongly correlated with the heat flux from the ground. We clarified relations between vertical temperature profiles and characteristics of turbulance. In the atmospheric boundary layer up to H* or Hi, temperature profiles show nearly neutral stratification, even when a free convection is predominant. However profiles of * show the difference between a free convection case (AA (strong), A (moderate)), and a forced convection case (B). In case AA and A, * is nearly constant up to H* (averaging

On the Turbulence Quantities in the Neutral Atmospheric Boundary Layer

“…In order to clarify the vertical change of u* in the neutral boundary layer, observed data are investigated. Gamo et al (1976) have shown by the observations that, in most cases, *w decreases sharply with height in the forced convective planetary boundary layer. The data cited in Table 1 have been selected from their data.…”

“…Therefore, the possibility of encountering an adiabatic planetary boundary layer and observing it is not large. Nevertheless, in the latest few years, turbulence quantities such as the RMS of the vertical wind speed *w, the dissipation rate of kinetic energy to heat * and the vertical diffusion coefficient for momentum KM in whole planetary boundary layer have been observed by many investigators (e.g., Koprov and Tsvang, 1966;Volkov et al, 1965;Clarke, 1970;Volkovitskaya et al, 1970;Rayment, 1972;Gamo et al, 1976) and we can select observed data taken under nearly adiabatic conditions from this data. In this paper, we propose a model of the adiabatic planetary boundary layer which describes the approximate relation between the turbulence quantities and the fundamental quantity of the vertical momentum flux, on the basis of the observation by extending the similarity theory attributed to Monin and Obukhov (1954) where Cw is a universal constant and approximately equal to 1.2 by Yokoyama (1971).…”

“…In these cases, there exists river Arakawa about 5km up wind direction and beyond the river is the urban area of Tokyo, so that horizontal homogeneity for the forced convective boundary layer may not be sufficient. Excluding these cases, 7 observations have been classified as the forced convective conditions by Gamo et al (1976) which were determined empirically by the relation between * and mean wind speed. Among these 7 observations, * w of 5 cases (Run number 6,11,12,15 and 19 in their paper) show the decreasing with height in the layer below 700 to 1,000 m approximately but above this height, *w increases with height again.…”

“…Table 1. Observed values of the RMS of vertical speed *w and the dissipation rate in near neutral boundary layer (after Gamo et al, 1976).…”

“…in cm2/s3, *w and u*0 in m/s, h is the depth of the layer (m) Table 2. Observed values of * by several authors (Data have been summarized by Gamo et al, 1976).…”