Local Radiative forcing by Saharan Dust and Forest Fire Aerosols over Portugal

Abstract

It is well known that aerosols directly affect the climate by increasing back-scattered radiation and by absorbing solar and long wave radiation (IPCC, 2001). Continental Portugal is often affected by the long-range transport of desert dust aerosols advected from Africa, and, frequently during summer, smoke from forest fires (Silva et al., 2003). This fraction is very efficient at scattering and absorbing short-wave radiation, being then of primary importance the estimation of radiative forcing due to aerosols. In order to understand climate change implications, in particular to identify major aerosol types, aerosol long-term monitoring is necessary. This is a good way to characterise their spatial and temporal distribution and their optical and physical properties, and to estimate their local and regional radiative forcing. Since 2002, long-term monitoring is being undertaken in Portugal with measurements from ground-based instruments at Évora, and, since December 2003, extended with measurements from Cabo da Roca.