Konstantin M. Firsov

Parametrization of transmittance for application in atmospheric optics

Abstract Different ways of improving the line-by-line method are described. Peculiarities of the application of the k-distribution method to parametrization of transmittance of overlapping bands for atmospheric gases are discussed. An expansion of the transmittance in exponential series with parameters determined on the basis of absorption coefficients is proposed.

THE COMPUTER CODE SAGDAM FOR SIMULATING THE LASER SOUNDING OF ATMOSPHERIC GASES

Abstract The description of the dialogue package for modeling laser sounding of atmospheric gases by the differential adsorption method is presented in this paper. The package allows to investigate the potentialities of laser measurements both the spatially distributed and integral content of gas with the help of ground-based, airborne and satellite laser systems. The package is written in FORTRAN and Visual Basic for Windows 3.1.

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.

The computer codes LARA and AIRA for simulating the atmospheric transmittance and radiance: Current status

Abstract The two compter codes for atmospheric transmittance/radiance simulations are briefly outlined. The first package (LARA) is based on a line-by-line method and makes possible the calculation of the transmittance and radiance with high spectral resolution. The second package (AIRA) is based on an approximate method and intended for calculations of the transmittance and radiance with low spectral resolution. The results of simulation and comparison are presented.

A fast line-by-line method

Abstract A new spectral line selection algorithm is developed. The algorithm makes it possible to decrease the number of spectral lines with the increase in altitude. In order for the computer code based on a line-by-line method to operate efficiently two line selections must be carried out. The first selection is rough. This enables the most weak lines not contributing to the optical thickness of the layer z 1 – z 2 to be eliminated. The other lines are subjected to the second selection. In this case the maximum height up to which the line should be taken into account is determined. At the same time for each line at each altitude the maximum resonance frequency difference within the limits of which the contribution of the line to absorption should be taken into account is determined. The gain in the time of calculation of the integral transmittance may be of five times or greater. The calculation error of the integral transmittance is not larger than 0.5%.

Simulation of operation of multiwave remote gas-analyzer based on NH3-laser

Abstract Numerical analysis of a multiwave path gas-analyzer, based on a NH3-laser pumped by CO2-laser radiation, is performed for model detection of concentrations of a series of molecular species such as NH3, HCN, phosgene, NHO3, CO2, and H2O. The potentialities of the gas analyzer and uncertainty of the gas concentration detection were estimated for a 4 km horizontal atmospheric path. The estimation took into account the absorption of laser radiation by the atmospheric aerosol and molecular gases under study and distortion of the laser beam due to atmospheric turbulence.

Parameterization of transmission functions in problems of radiative transfer in the Earth's atmosphere

This paper generalizes the results of development of few- parameter models of transmittance, which provide both the needed accuracy close to that given by the LBL method and the high computational speed. Particular emphasis is placed on the latest advances connected with the Laplace transformation and presentation of the transmission function as exponential series.

Effective parametrization of overlapping water vapor and carbon dioxide absorption bands

This report presents a new effective method which can be used to compute both the transmittance and the atmospheric radiation fluxes in the overlapping water vapor and carbon dioxide absorption bands.

Determination of content of columnar CO2 from solar transmission measurements

The retrieval technique for sensing the columnar content of CO2 via differential solar transmission measurements in and out absorption bands is presented. The calibration procedure based on the line-by-line method is described. The k-distribution method is used for acceleration calculation. The multiwavelength Sun-photometer has six channels for measurements in and out the H2O, CO2, CH4 absorption bands. The interferometer filters are used for spectral selection with resolution (Delta) (lambda) /(lambda) approximately equals 0.01 - 0.02. The wavelengths are centered at 0.87, 0.94, 1.06, 2.06, 2.18, 2.32 micrometers. Errors of the columnar content retrieval connected with the parametrization of atmospheric transmittance and uncertainties of the spectroscopy information are analyzed. The correction of signal on the basis of the measurements of aerosol optical depth is described.

Sounding of atmospheric gases by differential absorption method: computer code SAGDAM

The dialog package SAGDAM (sounding of atmospheric gases by differential absorption method) is intended for simulation of the potentialities of the DAS method for sounding water vapor and ozone on the vertical and slant directions with ground-based, airborne, and spaceborne lidars. Moreover, the package enables one to model the ground-based, airborne, and spaceborne systems for sounding the integral gas content by a long-path differential absorption method. The spectral range is near UV, visible, and infrared spectral ranges. The program calculates: a) vertical profiles of the absorption coefficients and transmittance of the gas under study and the foreign gases, as well as the transmittance of aerosol and Rayleigh atmosphere; b) spatially resolute error including random error and systematic error. The program enables one to determine the optimal pairs of wavelengths for sounding a gas in the specified altitude range and the minimum-detectable concentration of the gas under study (for the long-path method).