Database of physicochemical and optical properties of black carbon fractal aggregates 


***** Database abstract *****

In order to estimate the climate impact of black carbon (BC), it is necessary to know its optical properties. The Lorentz-Mie theory, which is often used to calculate the optical properties of BC under the spherical morphological assumption, produces discrepancies when compared to measurements. In light of this, researchers are currently investigating the possibility of computing the optical properties of BC using a realistic fractal aggregate morphology. In order to determine the optical properties of such BC fractal aggregates, the Multiple Sphere T-Matrix method (MSTM) is used which can take more than 24 hours for a single simulation depending on the aggregate properties. In light of this, we developed a comprehensive database for the physicochemical and optical properties of BC fractal aggregates. The database can be directly used for optical simulations in ambient and laboratory studies of BC. The database was also used to provide a highly accurate benchmark machine-learning algorithm that can be used to generate the optical properties of BC fractal aggregate in a fraction of a second. The machine learning algorithm was trained over this database of physicochemical and optical properties of BC fractal aggregates. The extensive training data helped in the development of an ML algorithm that can accurately predict the optical properties of BC fractal aggregates with an average deviation of less than one percent from their true values. The machine learning algorithm is available at ’github...’ (Patil et al., 2023).

***** Database generation *****

The Multi-sphere T-matrix Method (MSTM) calculates electromagnetic properties of a system that consists of a set of spheres (Mishchenko et al., 2004; Mackowski and Mishchenko, 2011). In this study, we use MSTM version 3.0 (Mackowski, 2013) written in FORTRAN to compute the electromagnetic properties for fixed and random orientations. For every BC fractal aggregate, the MSTM algorithm presents an orientational average of the combined spherical expansions of each primary particle. The MSTM code is best suited to calculate the optical properties of coated BCFAs since it consists of nested spheres. A limiting condition in MSTM, however, is that primary particles cannot overlap each other. It is possible to produce aggregates up to a limited size range through tunable DLA software. 


***** Database contents *****

- database_optical_properties_black_carbon_fractal_aggregtates.csv, data file, comma-separated values
- database_header.txt, metadata, text
- README.txt, metadata, text

***** Database contact *****

Baseerat Romshoo, Leibniz Institute for Tropospheric Research (TROPOS), Germany. Email: baseerat@tropos.de
Thomas Müller, Leibniz Institute for Tropospheric Research (TROPOS), Germany. Email: tmueller@tropos.de
Mira Pöhlker, Leibniz Institute for Tropospheric Research (TROPOS), Germany. Email: poehlker@tropos.de

***** Database citation *****

Romshoo, B., Patil, J., Michels, T., Müller, T., Kloft, M., and Pöhlker, M.: Database of physicochemical and optical properties of black
carbon fractal aggregates, Dataset, https://doi.org/10.5281/zenodo.7523058, 2023.