Studying aerosol indirect effects by combining CM-SAF cloud microphysical property data with NO2 retrievals

In this study the correlation between OMI tropospheric NO2 and cloud physical parameters was investigated, motivated by the idea to use OMI NO2 as a proxy for AOT in observing the aerosol indirect effect. OMI NO2 observations were compared to MODIS AOT and cloud physical parameters from SEVIRI and PATMOS-x over Europe, Africa and China. No clear correlation is found in the daily observations, but for monthly averaged measurements higher NO2 values correspond to smaller SEVIRI r_e over eastern Europe and the Po-valley, the decrease of re levels off for NO2 columns exceeding 3x10^15 molecules/cm2. Over China and selected biomass burning regions in Africa higher NO2 values correlate with smaller monthly averaged r_e observations from PATMOS-x, although in case of Africa this relation can also result from climatology as biomass burning predominantly occurs in summer.