Computer code long path method for long path differential-absorption predictions using CO 2 laser lines

A computer program LPM (Long Path Method) has been developed for imitative modeling of the concentration at gases (H2O, CO2, O3, NH3, C2H4) in the atmosphere using a long‐path double‐wavelength laser system equipped with two tunable CO2 lasers. The model is designed for four different lasing isotopes of CO2 (12C16O2, 13C16O2, 12C18O2, 13C18O2). The program determines optimal pairs of CO2 laser wavelengths, and the gas concentration retrieval errors from sounding data caused both by detector noise and systematic inaccuracy. The program was written in MS FORTRAN and Visual Basic languages for Windows 3.1 and an IBM‐compatible PC. © 1995 American Institute of Physics.