Atmospheric turbidity west of the West African coast in January and July - a comparison

Abstract

Solar radiation data recorded during two cruises of the R/V Meteor on both sides of the ITCZ in the Central Atlantic Ocean (January/February 1997) and west of the West African coast (June/July 1998) were used for calculating atmospheric turbidity in these areas. The LINKE-turbidity factor TL describing the atmospheric turbidity within the entire solar spectrum as well as the broad-band spectral turbidity factors Tk (short-turbidity factor) and Tr (red-turbidity factor) were studied. Air masses loaded with aerosol reaching the ship's position were examined with the help of radiosonde observations launched twice a day during the cruises as well as by 108 hour-backward-trajectories computed in the German Meteorological Computing Centre of the German Weather Service (DWD) for the 0 UTC-ship's position. Both daily cycles and seasonal and spatial differences of the turbidity factors are discussed in this study. Goal of this paper is to place measured data of broad-band spectral atmospheric turbidity at the disposal of those scientists using satellite-data for their ground-truth.