MCSpectra*: An online tool for line-by-line spectral simulations with uncertainty quantification

Line-by-line databases such as HITRAN enable the simulation of high-resolution molecular absorbance and emission spectra, which are indispensable for the development and application of spectroscopic diagnostics. Multiple tools reported in the literature have been built to assist with calculating absorbance and emission spectra based on line-by-line data. However, the available tools lack the essential function of propagating the uncertainty in line parameters into simulated spectra. This work presents MCSpectra: an online tool which aims at addressing this critical shortcoming. The main highlight of the presented tool is the implementation of the Monte Carlo method to estimate uncertainties in simulated spectra. Line parameter uncertainties reported in the HITRAN database and/or uncertainties in experimental conditions are propagated by simulating a large number of spectra each corresponding to a set of randomly sampled spectral parameters. In addition, MCSpectra introduces a few unique features not offered by previous tools, such as manual control of line parameters which enables the user to selectively over-ride HITRAN database parameters. The utility of this new tool to the community is showcased by presenting and interpreting representative simulated spectra. The results emphasize that the uncertainties associated with simulated absorbance and emission spectra vary considerably depending on the species, wavelength range, temperature and pressure.