Solar UV dose patterns in Italy.

Since 1992 solar ultraviolet (UV) spectral irradiance (290-325 nm) has been measured at two Italian stations of Rome (urban site) and Ispra (semirural site) using Brewer spectrophotometry. The data collected under all sky conditions, are compared with the output of a sophisticated radiative transfer model (System for Transfer of Atmospheric Radiation--STAR model). The STAR multiple scattering scheme is able to cope with all physical processes relevant to the UV transfer through the atmosphere. The experience so far acquired indicates that, in spite of the unavoidable uncertainties in the input parameters (ozone, aerosol, surface albedo, pressure, temperature, relative humidity, cloud cover), measured and computed clear sky iradiances are in reasonable agreement. The STAR model is applied to build up the solar UV geographic patterns in Italy: the daily dose in the range 290-325 nm is computed at about 70 sites where a thorough and homogeneous climatology is available. For each month the concept of an idealized "standard day" is introduced and the surface distribution of solar UV field determined. The map of solar UV patterns for Italy, available for the first time, meets the study requirements in the field of skin and eye epidemiology, as well as in other investigations dealing with the impact of UV on the biosphere. The results are interpreted in terms of atmospheric and meteorological parameters modulating UV radiation reaching the ground.

Correlation between SO2 and NO 2 measured in an atmospheric column by a Brewer spectrophotometer and at ground-level by photochemical techniques.

An investigation to determine the correlation of atmospheric amounts of SO2 and NO2 between columnar measurements from the ground and ground point determinations has been performed. The experimental data have been obtained from a Brewer spectrophotometer for columnar measurements and standard analytical techniques for ground measurements.The results show that the Brewer can give a correct indication of the trend of these pollutants on a monthly averaged basis. The possibility of deducing the mixing layer depth from the measured data has also been investigated but the results obtained are not conclusive due to the lack of an accurate experimental verification.

Diode laser system for measurement of gaseous ammonia in ambient air.

The use of a second harmonic diode laser system for monitoring gaseous ammonia in tropospheric air is discussed. Using a 96 m White cell operated at 13 torr pressure in flow mode, a minimum detectable concentration lower than 1 ppbv was obtained.The NH3 mixing ratio was determined by simultaneous spectroscopic analysis of an atmospheric CO2 line used as a built-in calibration standard.