Local and Regional Climatic Impacts of Heat Emission

Abstract

The impact of anthropogenic heat emission on properties of the planetary boundary layer has been investigated experimentally by air-borne meteorological measurements. These investigations covered a wide range of scales of heat emission: Individual stack plumes, cooling tower plumes, urban thermal plumes, and plumes from area sources in highly industrialized cities. Due to the very rapid dissipation of spatial temperature differences in the developing plumes, point sources of heat emission hardly influence the atmosphere. Moisture emission produces its well known impact on sunshine duration in the immediate vicinity of cooling towers. Thermal plumes originating from heat sources within towns and cities were investigated frequently. However, even in such cases, the spatial temperature differences were extremely small if they could be detected at all. A large number of profile flights in the Upper Rhine area indicated that even in the most industrialized parts of this region the natural spatial variations of meteorological parameters are much larger than the man-made ones. This is not true with respect to the fields of vertical motions, however; the thermal plumes of large industrialized cities are built up by a large number of intense thermal plumes of small size. In many cases the normal thermal activity is enhanced considerably. This fact led to the construction of a simple one-dimensional model for mean vertical velocity fields produced by local heat emission. By comparison with vertical velocities found in natural meteorological phenomena, estimates of man-made heat impacts on the atmosphere and on climate are possible.