MONITORING OF THE NOCTURNAL MIXED-LAYER BY MEANS OF PARTICULATE RADONPROGENY MEASUREMENT

Meteorological and radon concentration data referring to two measureme nt campaigns carried out in Milan, Italy, are reported and discussed. An urban mixing height (UMH) is defined through radio sounding data an d an equivalent mixing height (EMH) is obtained through application of a simple box model obtained with radon measurements, especially in th e meteorological situations found during the campaigns which were char acterized by negligible advection. It is shown that the meteorological and the radon-model estimations of the mixed layer height are highly correlated. It is concluded that a simple beta counter for particulate radon progeny can be regarded as a useful instrument for estimating u rban mixing heights in situations dominated by weak thermally induced turbulence which are also responsible for intense photochemical activi ty and pollution episodes.