DOASIS: a framework design for DOAS

The Differential Optical Absorption Spectroscopy (DOAS) is a simple, sensitive and robust method to measure trace gas concentrations by analyzing the spectrum of light that has passed through the atmosphere. Due to these advantages, DOAS gains more and more popularity for environmental monitoring in both cities and on a global scale. To use DOAS, an efficient software basis is necessary. The existing DOAS tools either concentrate only on a certain part of the whole DOAS analysis process or lack support of new devices or evaluation methods. This work will show a way to unify the already well known measurement and evaluation methods. The DOASIS Framework (DOAS Intelligent System) covers the whole range from hardware support, data management to the evaluation process. This framework offers an easy to extend basis to cover the DOAS evaluation process as a whole including automation support through a standardized scripting language. One of the major aspects in a DOAS analysis is the evaluation of the measured data. Especially in scientific environments it is necessary to have an easy, fast and reliable way to test and integrate new evaluation methods. A framework will be presented that supports these needs for the non-linear evaluation process of a DOAS analysis while still providing the performance and stability of already existing software tools. Besides the improvements in the evaluation process from a technical point of view, a new method for evaluating spectral data is proposed. Using the Laplace pyramid an optimal bandwidth filter is determined for NO2 evaluation. Instead of using a polynomial to remove certain broadband structures in a spectrum and preprocessing the spectra with highand lowpass filters, which both require user estimated parameters, the bandpass filter eliminates these.