Look−up tables resolved by complex refractive index to correct particle sizes measured by common research−grade optical particle counters

Optical particle counters (OPC) are widely used to measure the aerosol particle number size distribution at atmospheric ambient conditions and over a large size range. Their measurement principle is based on the dependence of light scattering on particle size. However, this dependence is not monotonic at all sizes and light scattering also depends on the particle composition (i.e., the complex refractive index, m) and morphology. Therefore, the conversion of the measured scattered intensity to the desired particle size depends on the microphysical properties of the sampled aerosol population and might not be unique at all sizes. While these complexities have been addressed before, corrections are typically applied ad-hoc and are not standardised. These datasets address this issue by providing a consistent and extended database of pre−computed correction factors for a wide range of complex refractive index values representing the composition variability of atmospheric aerosols. Correction factors are calculated for five different commercial OPCs (USHAS, PCASP, FSSP, GRIMM and its airborne version Sky− GRIMM, CDP) by assuming Mie theory for homogeneous spherical particles, and by varying the real part of the complex refractive index between 1.33 and 1.75 in steps of 0.01 and the imaginary part between 0.0 and 0.4 in steps of 0.001. For each OPC, two zip files are provided. Each of them contains files in ASCII format. The OPC_ intensity.zip files are organised as: 1/ For each OPC, the values of scattering cross section Csca for particle diameters comprised between 0.02 and 200 µm in logarithmically−equal steps of 0.004 and as a function of m (n=1.33−1.75; ∆n=0.01, k=0.0-0.4; ∆k=0.001) are provided in ascii files whose generic name is OPC_intensity_real_imag.txt, where OPC is the acronym of the particle counter, real is the value of the real part and imag is the imaginary part of the complex refractive index. Each file contains four columns, namely - the real part of m - the imaginary part of m - the particle diameter used in Equations 1 and 2 (in µm) - the corresponding value of Csca (in µm2) The OPC_ size.zip files are organised as: 2/ The values of the corrected bin diameter as a function of m (n=1.33−1.75; ∆n=0.01, k=0.0-0.4; ∆k=0.001) are provided in text files whose generic name is OPC_Diameter_real_imag.out, where OPC is the acronym of the particle counter, real is the value of the real part of the CRI, and imag is the imaginary part of the m. Each file contains four columns, namely - the nominal bin diameter (in µm) of the calibration m - the bin diameter (in µm) calculated for the atmospheric m - the bin midpoint diameter (Dmid, in µm) calculated for the atmospheric m - the bin width (dlogD) calculated for the atmospheric m.