Comparison of atmospheric boundary layer soundings by a metric and a decimetric RASS

Abstract

The vertical thermal profile of the lower atmosphere can be remotely measured by the Radio Acoustic Sounding System (RASS). A RASS operating at the acoustic wavelength λ_a ∼ 1 m was designed and developed twenty years ago. It is suitable for monitoring the temperature profile of the lower troposphere and has been utilised for studies of the atmospheric boundary layer in different conditions and for the application of control strategies to air pollution emissions. The acoustic antenna is composed by 9 folded horns covering an area of 7x7 m²; the two radar antennas are composed by arrays of dipoles with square reflector of 2.8x2.8 m² for each antenna. Therefore the metric RASS can be utilised only in a settled station. Recently we have designed and developed a decimetric RASS (λ_a = 0.34 m) with smaller antennas, which can be used as a mobile system. It can be housed and carried by a trailer. As it is known, increasing the sounding frequency gives a decreasing of the sounding range. Comparisons of results obtained by both the metric and the decimetric RASS in different atmospheric conditions are presented and discussed.