Remote sensing of trace gases with optical correlation spectroscopy and lidar: theoretical and numerical approach

Remote sensing of atmospheric gases with optical correlation spectroscopy and lidar: first experimental results on water vapor profile measurements

“…(1), an integral is performed over an effective wavelength spectral range Dk, defined from the effective width of the amplitude modulation function; therefore, the OCS-lidar methodology does not require a spectrally resolved detector. From the two OCS-lidar signals P C and P NC , a calculus detailed in B. Thomas et al [20] is then performed to retrieve absolute range-resolved atmospheric gas concentrations, with statistical and systematical error assessment. It is important to note that this OCS-lidar methodology does not require a permanent gas calibration as in regular optical correlation spectroscopy [32].…”

“…3 experiment, we here perform a numerical simulation using the OCS-lidar methodology for water vapor concentration retrievals to optimize the precision on the retrieved concentration. We use the numerical model developed in B. Thomas et al [20] to generate OCS-lidar signals. This numerical model has four main inputs: the water vapor absorption crosssection spectrum plotted in Fig.…”

“…The concentration retrieval algorithm is based on a Taylor expansion of the transmission T(r, k) leading to a third-order polynomial equation, whose solution allows to retrieve the water vapor mixing-ratio at a range r from the lidar receiver. It avoids using the ratio of P C (r) to P NC (r) signals, as usually performed in differential absorption spectroscopy [20].…”

“…Among these recent advances, we may mention novel research achievements on remote sensing of greenhouse gases, by using a broadband laser source instead of a narrowband laser. Examples of these new advances are the broadband differential absorption lidar [13][14][15][16][17][18][19] and the optical correlation spectroscopy lidar (OCS-lidar) methodology, introduced by B. Thomas et al [20]. The OCS-lidar methodology is a new differential absorption spectroscopy method based on pioneer work performed on gas correlation lidar [21].…”

“…The OCS-lidar methodology is a new differential absorption spectroscopy method based on pioneer work performed on gas correlation lidar [21]. The OCS-lidar has been extensively described in theoretical papers [20,22] for methane remote sensing. In these papers, it is shown that OCS-lidar differs from the standard differential absorption lidar (DIAL) and also from the wavelength modulation spectroscopy (WMS) [23].…”