Observed Characteristics of the Standard Deviation of the Vertical Wind Velocity in Upper Part of the Atmospheric Boundary Layer

Abstract

To clarify the behavior of the standard deviation of vertical velocity *w under various meteorological conditions, many data obtained by tethered balloon, high tower and light airplane were analized. Relations between *w, wind speed U, and many meteorological elements, for example, insolation, local lapse rate, Pasquill's stability categories, classification of cloud and inversion base height, were checked. It has been found from observations at height of 50 m that *w was proportional to U in case of weak insolation while with increasing of insolation, * w tended to show characteristics caused by free convective fluctuations. Temperature gradient at the observation height of *w can not explain variation of the relation between *w and U with stability. Pasquill's stability categories are not explanatory index either for the *w-U relations, except at 50m. Three different relations between *w and U were found from observations taken at various heights. First is the relation for strong convective layer; second, in the layer below inversion base; and third, in the inversion layer. In the case of second group, there is a critical wind speed Uc*. When U is weaker than Uc*, free convection is predominant and *w is independent of wind speed. When U is stronger than Uc*, however, forced convection is predominant and * w/U tends to be constant. The height dependency of Uc* was observed.

Growth of the Mixing Depth and the Diurnal Variation of Vertical Profiles of Temperature and Turbulence Characteristics in the Mixing Layer

“…Fig. 5 shows the comparison of hm defined by Yokoyama et al with hi estimated by temperature profiles by Gamo et al (1976a). The mixing layer height hm defined by Yokoyama et al (1977a) is a little larger than hi in this observation.…”

“…We regard hi as the upper side of the strong echo in the chart paper. The value of hi(t) increases with the root of the integrated insolation (in detail, see Gamo et al (1976b)). The same results during morning hours were obtained by Moriguchi et al (1977).…”

“…(2), the vertical profile of heat flux is described by Q=Q0*. Yokoyama et al (1977a) obtained *'s from airborne measurements of turbulence (Gamo et al (1976a)), as follows: (25), turbulence quantities below hm are represented by Q0, hm, g, T0, Cp, p and z. Since g, T0, Cp and p are assumed to be constant up to the height of 1,000m or so, the profiles of the above-mentioned quantities are determined by two external parameters; Q0 and hm, and *(instead of z).…”

“…First, we will see the turbulence structure of the mixing layer. Gamo et al (1976a) observed turbulence by airborne measurements and classified the atmospheric boundary layer below the inversion base into two groups: free and forced convective atmospheric boundary layer. It was found that vertical profiles of turbulence quantities, such as the energy dissipation rate *, rms of the vertical component of wind fluctuations model for the free convective atmospheric boundary layer.…”

Notes on the Turbulence Closure Model for Atmospheric Boundary Layers

“…For the sake of comparison, we refer the observational result of the Eulerian scale length l e obtained by Gamo et al (1975). They showed that the vertical distribution of le is quite similar to (8.1) and le is about 100m at z=500m* 1,000m.…”