Satellite- and ground-based atmospheric water vapor measurements: a comparative study

Simultaneous water vapor measurements from satellite and ground based systems, have been performed in Napoli and Potenza throughout the last two years. Night-time water vapor profiles were provided by two lidar systems based on the Raman technique. The lidar system in Napoli, Italy is based on Xe:F excimer laser ((lambda) equals 351 nm), the system in Potenza, Italy is based on a Nd:YAG laser operating both on the 2nd (532nm) and 3rd (355nm) harmonics. Precipitable water (PW) measurements were provided during daytime by a grating spectrometer observing solar spectral irradiance at differentially absorbing channels in the wing of (rho) (sigma) (tau) water vapor band. Night and daytime PW measurements were provided using TOVS and AVHRR packages flying on NOAA satellites. Split window technique on two differentially absorbing AVHRR channels in the 11 micrometers region has been used in order to provide PW amounts with a spatial resolution of approximately 2 Km. The standard ITPP processing for TOVS package has been used in order to obtain PW estimates at lower spatial resolution (about 40 Km). Night and daytime radiosonde measurements have been performed during the last part of the campaign. All the simultaneous independent measurements have been analyzed and the results compared.