Spatio-temporal variability of aerosol in the tropics and its relationship with the hydrological cycle

Aerosols influence directly the earth's radiation budget by absorbing solar radiation and heating the atmosphere. Also, aerosols modulate the hydrological cycle indirectly by modifying cloud properties, precipitation and ocean heat storage. In spite of recent advances in the study of aerosols, uncertainty in their spatial and temporal distributions still presents a challenge in the understanding of climate variability. For example, aerosol loading varies not only from year to year but also on intraseasonal time scales with a strong interaction of local to regional atmospheric variability. Furthermore, the impact of spatial variability has not been studied in detail. Here, we use the Aerosol Index from the Total Ozone Mapping Spectrometer (TOMS) and the Ozone Monitoring Instrument (OMI), and Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) to evaluate the annual climatology and interannual variability of aerosols as well as their influences on the variability of different parameters that characterize the dynamic and thermodynamic state of the climate system. Data from ERA-40 and ERA-interim reanalyses are used in the analysis. A nonparametric approach is used to examine the spatial distribution of the recent trends in aerosol concentration. Composite analysis, multivariate EOF and canonical correlation analysis of surface temperature, atmospheric wind, geopotential height, OLR and precipitation together with the climatology of aerosols provide insight on how the variables interact. Different modes of variability, especially in intraseasonal time scales appear as strong modulators of the aerosol distribution. Interaction with atmospheric waves (e.g. African Easterly waves) is also explored. Results of this work are useful in order to understand more precisely the response of the energy budget, precipitation and atmospheric circulation to changes in aerosol loading.