Relationships between aerosol index, ozone, solar zenith angle and surface reflectivity: a case study of satellite observations over Lagos

Abstract

Surface reflectivity (RFL), solar zenith angle (SZA), ozone and aerosol index (AI) daily data over Lagos (6.60° N, 3.33° E) measured by the Total Ozone Mapping Spectrometer (TOMS) were examined to determine the relationship between the parameters. We found that aerosol distribution can fully account for changes in RFL in the presence of ozone when other factors are held constant. We also showed that dust distribution over Lagos varies seasonally, reaching a maximum during the local dry season and a minimum during the local wet season whereas ozone peaks during the wet season and decreases to a minimum during the dry season. Aerosol variation was further linked to the seasonal transport of sahelian dust by the northeasterly wind that arrives at the location during the dry season and the eventual cloud washout during the wet season while the ozone distribution was attributed to the near balance between production and loss of the pollutant as a consequent of local wind transport.

Acknowledgements

We thank the Ozone Processing Team (OPT) of the NASA/Goddard Space Flight Center for making the TOMS data available. The comments and suggestions from two anonymous reviewers are gratefully acknowledged.