MEASUREMENTS OF VERTICAL KINEMATIC EDDY SENSIBLE HEAT-FLUX BY MEANS OF A DOPPLER SODAR AND A CRYOGENIC RADIOMETER

Radiative and dynamical energy exchanges in the planetary boundary lay er are investigated by the simultaneous operation of a triaxial Dopple r sodar, a zenith-pointing cryogenic radiometer with a bandpass centre d around 850 mum wavelength, and additional meteorological equipment f or near-ground reference. The two instruments provide measurements of the wind field and of the atmospheric radiative temperature, respectiv ely. Two measurement campaigns were carried out in the Rome area in th e periods 12-18 Sept. 1990 and 16-22 Sept. 1991. Data were analysed fo r correlation and used to calculate kinematic eddy sensible heat fluxe s. Depending on the meteorological conditions, high values of correlat ion were found between the fluctuations of the height-averaged (300 m) vertical wind speed and the radiative temperature, in the presence of clear-sky convection. The highest values of correlation were obtained for delays of a few minutes, as expected in agreement with typical di mensions of convective structures in the boundary layer. Estimates of the kinematic eddy sensible heat flux gave average values as high as 0 .14 K m s-1 in daytime and 0.005 K m s-1 at night.