Interannual variability of aerosols and its relationship with downward shortwave radiation

Aerosols influence directly the earth's radiation budget by absorbing solar radiation and heating the atmosphere. Also, aerosols modulate indirectly the hydrological cycle modifying cloud properties, precipitation and ocean heat storage. Several studies have pointed out influences throughout surface cooling by reducing solar radiation at the surface with an enhanced warming of the lower troposphere by absorption leading to dynamical responses of the atmosphere. Different studies have reported the existence of a global reduction of aerosol and a consistent increase of the amount of solar radiation at the earth's surface. Aerosol load also varies from year two year. However, the regional effects of aerosol interannual variability and trends have not been studied in detail. In this work we use satellite information of aerosol concentrations in terms of the Aerosol Index from the Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI); Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS); downwelling shortwave radiation from the International Satellite Cloud Climatology Project (ISCCP) and from the NASA/GEWEX Surface Radiation Budget (SRB) to evaluate the annual climatology and interannual variability of aerosols and their influences on the global climatology of downwelling solar radiation reaching the earth's surface. Analysis of the spatial distribution of the recent trends in aerosol concentration is estimated using a nonparametric approach. Preliminary results show positive trends over eastern Atlantic Ocean, northern Africa, the Middle East and northwestern India and negative trends for the equatorial Africa and the Sahel region. Diversity in those interannual trends produce different regional influences over the observed downwelling shortwave radiation, further affecting the global climatology of sea surface temperature (SST), atmospheric circulation and precipitation. Analysis of SST, streamflow at different levels and precipitation with the climatology of aerosols observed by satellites using multivariate EOFs and canonical correlations give us insight on the observed relationships. Results of this work are useful in order to better understand the response of the energy budget, precipitation and atmospheric circulation to changes in aerosol load.