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 layer are investigated by the simultaneous operation of a triaxial Doppler sodar, a zenith-pointing cryogenic radiometer with a bandpass centred around 850 mum wavelength, and additional meteorological equipment for near-ground reference. The two instruments provide measurements of the wind field and of the atmospheric radiative temperature, respectively. Two measurement campaigns were carried out in the Rome area in the periods 12-18 Sept. 1990 and 16-22 Sept. 1991. Data were analysed for correlation and used to calculate kinematic eddy sensible heat fluxes. Depending on the meteorological conditions, high values of correlation 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 dimensions 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.