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Remote Sensing of Clouds and the Atmosphere V
... Analysis of lidar performance is traditionally based on examination of the signal-to-noise ratio (SNR) at the photodetector output [1,2,[4][5][6][7][9][10][11][12]. SNR is a frequently used comprehensive criterion for lidar instrument efficiency and is presented in Fig. 1. ...
We present a general methodology for evaluating the capabilities of a general lidar system encompassing both backscatter (elastic and Raman lidar) and topographic targets. By introducing a well-defined atmospheric reference medium and by individually examining and decomposing the contributions of lidar system parameters including lidar transmitter power, field of view, receiver noise, atmospheric conditions, and sky background on the signal-to-noise ratio, we obtain a simple dimensionless parameterization of the lidar system. Using this parameterization, numerical simulations are carried out to determine achievable lidar performance including operation range, minimum detectable gas concentration, and so on.
This work presents new measurements of HDO line parameters in the near-infrared and visible regions (11 500–23 000 cm-1). The measurements consist in high-resolution Fourier transform absorption spectra of H2O/HDO/D2O vapor mixtures, obtained using a long absorption path. Spectra with and without nitrogen as the buffer gas were recorded. Due to the simultaneous presence of the three isotopologues H2O, D2O, and HDO, the H2O lines removal and the D2O lines identification were two necessary preliminary steps to derive the HDO line parameters. The D2O contribution was small and confined to the well-known 4n1 + n3 band. An extensive listing of HDO spectroscopic parameters was obtained, for the first time, by fitting some 3256 observed lines to Voigt line profiles. The list contains calibrated line positions, absorption cross-sections and, for many of the lines, N2-broadening coefficients, as well as N2-induced frequency shifts. As a result of the low HDO vapor pressures, it was not possible to retrieve the self-broadening parameters. The list is available on the http://www.ulb.ac.be/cpmhttp://www.ulb.ac.be/cpm website.
A general methodology for evaluating the capabilities of a general lidar system encompassing both backscatter (elastic and Raman lidar) and topographic targets is presented. By introducing a well defined atmospheric reference medium and by individually examining and decomposing the contribution of lidar system parameters including lidar transmitter power, fields of view, receiver noise, atmospheric conditions, and sky background on the signal-to-noise-ratio (SNR), we obtain a simple dimensionless parameterization of the lidar system. Using this parameterization, numerical simulations are carried out to determine achievable lidar performance including operation range, minimum detectable gas concentration etc.
The absorption spectrum of N2O, at room temperature, was recorded in the 5400–11 000 cm–1 region at resolutions ranging from 0.008 cm–1 near 5400 to 0.023 cm–1 near 11 000 cm–1 using a Bruker IFS120HR Fourier transform spectrometer. Sample pressure/absorption path length products ranging from 200 to 4700 mbar×m were used. More than 6000 absolute line intensities have been measured in 64 different bands of 14N216O. Using wavefunctions previously determined from a global fit of an effective Hamiltonian to more than 18 000 line positions [Tashkun SA, Perevalov VI, and Teffo JL, to be published], the experimental intensities measured in this work and by Toth [J Mol Spectrosc 1999;197:158–87] were fit using 62 parameters of a corresponding effective dipole moment, with residuals very close to the experimental uncertainty.
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