AOD-to-PM2.5 conversion

Estimating ground‐level concentrations of PM2.5 from satellite observations of total‐column AOD requires a conversion factor that accounts for their spatially and temporally varying relationship. This conversion factor is a function of aerosol size, aerosol type, relative humidity, and the vertical structure of aerosol.

We plan to implement a two‐step procedure: a) conversion of the SEVIRI‐AOD to total column PM2.5 considering one single aerosol type in the atmospheric column, and b) calculation of the near‐surface PM2.5 based on the WRF‐Chem simulated PM2.5 cross sections. The logical scheme of the algorithm for the AOD to PM2.5conversion is shown in Fig.1.

Fig. 1: Logical scheme of the algorithm for AOD to PM2.5 conversion
Fig. 1: Logical scheme of the algorithm for AOD to PM2.5 conversion

In the first step WRF‐Chem aerosol species will be grouped to reconstruct the aerosol components defined in GADS, for which microphysical parameters are available. T‐Matrix computation will be applied to calculate the mass‐to‐extinction conversion factors for a wide range of aerosol classes in various humidity conditions and mass proportions. The mass‐to‐extinction conversion factor LUT’s (Look-Up-Table) will then be used to calculate the column PM2.5 from the SEVIRI‐AOD.