Evolution of the atmospheric convective boundary layer monitored by the metric RASS

The automatic metric RASS (Radio Acoustic Sounding System), operating at an acoustic wavelength ∼1 m, proved to be able to measure continuously the thermal vertical profiles as far as about 1 km in 50% of soundings with an accuracy generally within a few tenths of K degrees and with an altitude resolution of (30÷40) m. A set of triennal data of the diurnal evolution of the convective boundary layer (CBL) during Summer, as monitored by a metric RASS operating in the Po Valley (Italy) is presented and discussed. Although atmospheric turbulence, pertinent to the considered unstable conditions, is one of the main factors limiting the radio-acoustic sounding range, by means of the metric RASS it is possible to follow the growth of the mixing layer and to estimate the multilayered structure of the CBL. In addition to the RASS data, the measurements of wind speed, temperature, radiation, humidity and so on, performed by conventional equipments near ground level, are considered.