Search Results

You are looking at 1 - 2 of 2 items for

  • Author or Editor: Thomas Hauf x
  • Refine by Access: All Content x
Clear All Modify Search
Thomas Hauf

Abstract

A vertical cross section of 100 km × 10 km through a daytime midlatitude troposphere is analyzed using aircraft turbulence data with 1.5-m spatial resolution. Convectively forced internal gravity waves, also referred to as “convection waves,” were studied with an instrumented aircraft over southern Germany. This is the first quantitative observational study of convection waves over a central European region. Characteristics are found to be in good agreement with results of previous numerical simulations and measurements. Vertical wind amplitudes are +0.5–1 m s−1 and lower than those found over the Great Plains of North America. Convection waves were trapped in midtropospheric levels by a layer of reduced stability aloft. The waves were forced by shallow moist convection penetrating into an overlying shear layer centered around the boundary-layer top. Both speed shear with a value of about 6.5 m s−1 km−1 and directional shear of about 26° km−1 were present. The measurements support the hypothesis that convection waves represent a typical fluid-dynamical mode of a daytime troposphere. They can be observed whenever there is moderate to strong convection in the atmospheric boundary layer and shear aloft.

Full access
Thomas Hauf and Hartmut Höller

Abstract

The theoretical investigations presented in this paper show that the various definitions of potential temperatures, such as the potential temperature of dry air and of moist air, the equivalent potential temperature, the liquid water potential temperature, the ice-liquid water potential temperature and the wet equivalent potential temperature can be unified by one single definition. This general potential temperature is named the entropy temperature as it is a measure of entropy. The entropy state function for a system of cloudy air and the entropy budget are presented and discussed. For each of the potential temperatures the respective thermodynamic equation for which the potential temperature is an integral of the form, θ = constant, is reviewed on the basis of the entropy concept. As one result, it is found that the ice-liquid water potential temperature θil is only an integral of the corresponding thermodynamic equation if saturation or chemical equilibrium between water vapor and liquid water or ice is assumed. A prognostic equation for the entropy temperature is derived using the entropy budget equation. This equation describes irreversible effects and holds also for an open system. From this equation exact prognostic equations for each of the potential temperatures can, at least in principle, be derived.

Full access