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Retrieval of aerosol properties from MICROTOPS II sunphotometer data

Retrieval of aerosol properties from MICROTOPS II sunphotometer data

Volcanoes represent one of the most important global sources of gases and particles to the atmosphere. Their emissions provide important information about the physical and chemical conditions of subsurface magma, and have impacts on the atmospheric and terrestrial environments, human health, and climate. Volcanoes present particularly harsh and challenging conditions to work in, and remote sensing techniques often provide the only safe means for data collection. Differential Optical Absorption Spectroscopy has played a key role in monitoring and in quantifying the global budget of several significant gaseous species (SO2, BrO, NO2, ClO etc.) emitted by volcanoes. In contrast, little work has been carried out on volcanic aerosol, except perhaps for important studies of Pinatubo and El Chichón eruptions and their resulting global climatic changes.

Microtops II Sunphotometers are hand held instruments that allow easy and accurate measurement of aerosol optical thickness through the use of five wavelength bands. Read more information on the Microtops II. Microtops II can be inverted to retrieve columnar optical thickness of aerosols.

Plume aerosol optical thickness software

This project presents the Microtops II Inverse software package, which is designed to retrieve columnar optical thickness of aerosols concentrated in plumes (resulting from volcanoes, fires or industrial plants). To investigate the aerosol properties of a plume, it is necessary to make measurements observing the Sun both through the plume and through the background atmosphere (clear from plume). The optical thickness of the plume can then be obtained by subtracting the optical thickness of the background atmosphere from the total through-plume optical thickness.

This methodology has been used to study plumes emitted in resulting from Lascar and Villarrica volcanoes (Mather et al., 2004), Chile, and to examine the atmospheric consequences of the Buncefield Oil Depot fire (Mather et al., 2007 and Mather et al., 2007 - Appendix) in December 2005.

The software package presented here was developed by Dr V.I. Tsanev and Dr T.A. Mather. It is based on FORTRAN77 codes CSIGT, PREPRCES and RADINV, developed by Michael King. These three codes were modified to include calculations of surface and volume distributions, sets of effective radii and an improved structure to the input and output files. The package was created using FORTRAN95 and Basic and the executables are DOS programs. All enquiries for support should be addressed to the software author Dr Vitchko Tsanev [].

If you make use of the software or associated manual in your research, please acknowledge this in publications by referencing the software as:

Tsanev, V.I. and Mather, T.A., 2007. Microtops II Inverse: Software package for retrieving aerosol columnar size distributions using MICROTOPS II data. Available from .

Software downloads

The software manual (in PDF format) and executables (including some example data files) can be downloaded below.

A number of papers, referenced in the manual, are also available to download as PDF files, below.


Software manual

Detailed description of King's algorithm and the MICROTOPS II Inverse software package plus operating instructions.


DOS executables

Compressed executable files together with test tasks and the corresponding result files.


  • Jorge and Ogren, 1996: Evaluation of King's inversion algorithm by numerical experiments.
  • King et al., 1978: Description of the retrieval algorithm.
  • King, 1982: Significance of Lagrange parameters illustrated by numerical tests.
  • Mather et al., 2004: Application of MICROTOPS II sunphotometer and software package to Lascar and Villarrica (Chile) volcanic plumes.
  • Mather et al., 2007 (and Appendix): Application of MICROTOPS II sunphotometer and software package to the Buncefield Oil Depot fire
  • Morys et al., 2001: Detailed description of MICROTOPS II sunphotometer