Seminar
Using artificial sky glow to retrieve night time aerosol optical depth

Resumen

Measuring the Aerosol Optical Depth (AOD) is of particular importance in monitoring aerosol contributions to global radiative forcing and air quality. Most measuring methods are based on direct or indirect observation of sunlight and thus are only available for use during daylight hours. Attempts have been made to measure AOD behavior at night from star photometry, and more recently moon photometry. Star photometry method uses spectrally calibrated stars as reference targets this provides somewhat more flexibility than a sun photometer but there are low-signal and calibration issues which can make these measurements problematic. Moon photometry is only possible when the moon is present in the sky. We suggest a complementary method, based on the observation of artificial sky glow generated by light pollution. The methodology requires (1) the implementation of an heterogeneous 3D light pollution model and (2) the design of an automated light pollution spectrometer which will be presented here. The instrument designated as the Spectrometer for Aerosol Night Detection (SAND) is now in its third version. Basically, SAND-3 is an automated CCD based, long-slit spectrometer protected from inclement weather by an acrylic dome. SAND have been used successfully in many astronomical sites along with some urban sites. Our first day/night (continuity) AOD measurements comparisons with AERONET/AEROCAN sunphotometer data will be shown for Sherbrooke university (Quebec, Canada) atmospheric optical observatory.