Quantifying trace atmospheric gases using open path FTIR measurements combined with a nonlinear least squares fitting algorithm: A feasibility study

A Nonlinear Least Squares (NLLS) method for retrieving trace gas concentrations is tested using horizontal open path Fourier Transform Infrared (FTIR) measurement simulations. The method involves the use of the Doesn't Use Derivatives (DUD) NLLS technique to invert the measurement simulations and solve for trace gas concentrations. The returned concentration is compared to the value used to create the measurement simulation to show the feasibility of the retrieval technique for actual open path FTIR measurements.