Remote<scp>R</scp>aman Spectroscopy. Profiling Water Vapor and Aerosols in the Troposphere Using<scp>R</scp>aman Lidars

Turner, David D.; Whiteman, David N.

doi:10.1002/0470027320.s6803

Cited by 5 publications

(4 citation statements)

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“…pulsed Light Detection and Ranging (LIDAR) lasers, and exploited for many years in atmospheric physics experiments [see e.g. [39][40][41][42][43][44][45]. Specifically, laser photons lose through the inelastic collision with O 2 or N 2 molecules a quantized amount of energy through the excitation of the fundamental ν 1←0 rotational-vibrational (rovibrational) modes of these diatomic molecules [46][47][48].…”

Section: The First Detection Of Laser-induced Atmospheric Raman Scatt...mentioning

confidence: 99%

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

et al. 2017

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Laser guide stars employed at astronomical observatories provide artificial wavefront reference sources to help correct (in part) the impact of atmospheric turbulence on astrophysical observations. Following the recent commissioning of the 4 Laser Guide Star Facility (4LGSF) on the Unit Telescope 4 (UT4) of the Very Large Telescope (VLT), we characterize the spectral signature of the uplink beams from the 22 W lasers to assess the impact of laser scattering from the 4LGSF on science observations. We use the Multi-Unit Spectroscopic Explorer (MUSE) optical integral field spectrograph mounted on the Nasmyth B focus of UT4 to acquire spectra at a resolution of R ∼ =3000 of the uplink laser beams over the wavelength range of 4750Å → 9350Å. We report the first detection of laser-induced Raman scattering by N2, O2, CO2, H2O and (tentatively) CH4 molecules in the atmosphere above the astronomical observatory of Cerro Paranal. In particular, our observations reveal the characteristic spectral signature of laser photons -but 480Å to 2210Å redder than the original laser wavelength of 5889.959Å -landing on the 8.2m primary mirror of UT4 after being Raman-scattered on their way up to the sodium layer. Laser-induced Raman scattering, a phenomenon not usually discussed in the astronomical context, is not unique to the observatory of Cerro Paranal, but common to any astronomical telescope employing a laser-guide-star (LGS) system. It is thus essential for any optical spectrograph coupled to a LGS system to handle thoroughly the possibility of a Raman spectral contamination via a proper baffling of the instrument and suitable calibrations procedures. These considerations are particularly applicable for the HARMONI optical spectrograph on the upcoming Extremely Large Telescope (ELT). At sites hosting multiple telescopes, laser collision prediction tools also ought to account for the presence of Raman emission from the uplink laser beam(s) to avoid the unintentional contamination of observations acquired with telescopes in the vicinity of a LGS system.Popular summary: Atmospheric turbulence strongly affects the sharpness of astronomical observations from the ground. Specially-equipped telescopes (and their associated instruments) can reduce this effect by directing lasers up into the sky, causing sodium atoms in the upper atmosphere to glow. Deformable mirrors can then use these "artificial guide stars" to help correct for the impact of turbulence on observations.Four such lasers were recently installed at the Very Large Telescope (VLT) at Cerro Paranal in Chile. For the first time, we characterized the astronomical consequences of laser-induced inelastic Raman scattering, a process through which the laser photons lose energy by exciting air molecules. This isa possible source of contamination for astrophysical observations, appearing in the data as complex groups of emission lines.We used the Multi-Unit Spectroscopic Explorer (MUSE) integral field spectrograph -an instrument that obtains a spectrum for each pixel of an image in a...

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Section: The First Detection Of Laser-induced Atmospheric Raman Scatt...mentioning

confidence: 99%

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

et al. 2017

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“…[16] Turner and Whiteman [2002] provide a historical overview of atmospheric Raman lidar observations. The Raman lidar is an active, vertically pointing remote sensing instrument that estimates atmospheric q through the measured ratio of the Raman shifted signals of H 2 O and N 2 molecules.…”

Section: Raman Lidarmentioning

confidence: 99%

Ability to quantify coherent turbulent structures in the convective boundary layer using thermodynamic profiling instruments

et al. 2006

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[1] Water vapor mixing ratio data from the Raman lidar and Atmospheric Emitted Radiance Interferometer (AERI) are analyzed toward inferring the presence of organized, three-dimensional, turbulent features within convective boundary layers (CBLs). The Raman lidar and AERI instruments provide unique, high-quality data sets, from 200-m to $3-km altitude at 1-min temporal resolution profiles of water vapor. CBLs under the influence of solar heating for two fair-weather days over the Atmospheric Radiation Measurement (ARM) Central Facility near Lamont, Oklahoma, during the International H 2 0 Project 2002 (IHOP_2002), and 1 day during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL)-Florida Area Cirrus Experiment (FACE) 2002 experiment, are evaluated. This research provides a means of inferring the presence of coherent, convectively driven circulation (momentum) signatures exclusively from hightemporal resolution water vapor profiles. Spectral and statistical analysis of Raman lidar water vapor-time series reveal the passage of coherent turbulent structures, including horizontal convective rolls (HCRs), within the CBL over the ARM site at $8 and 12 min intervals for 2 days during IHOP_2002. AERI data collected during CRYSTAL-FACE also indicate similar structures, with meteorological conditions on this day also dictating the presence of cloud streets over the AERI (every 12 and 28 min). Radiosonde, satellite, and ceilometer analyses provide information about the favored stability and CBL cloud patterns, as well as a check on our spectral analysis. Evidence within the perturbation water vapor time series from these two instruments is well correlated with HCRs and other cumulus patterns seen in 1 km resolution GOES visible satellite imagery.

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“…(2) using the known scattering cross section σ W V of the H 2 O Raman line at 3599 cm −1 which is 6×10 −30 cm 2 sr −1 (Turner and Whiteman, 2002). Accordingly, the peak at 13 km (Fig.…”

Section: Fluorescence Lidarmentioning

confidence: 99%

Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the stratosphere

Immler¹,

Engelbart²,

Schrems³

2004

Preprint

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Abstract. With a lidar system that was installed in Lindenberg/Germany, we observed in June 2003, an extended aerosol layer at 13 km altitude in the lowermost stratosphere. This layer created an inelastic backscatter signal which we interpret as laser induced fluorescence from aerosol particles. Also, we find evidence for inelastic scattering in a smoke plume from a forest fire that we observed in the troposphere. Fluorescence from ambient aerosol had not yet been considered detectable by lidar. However, organic compounds such as polycyclic aromatic hydrocarbons sticking to the aerosol particles, or bioaerosol such as bacteria, spores or pollen fluoresce when excited with UV-radiation in a way that is detectable by our lidar system. Therefore, we conclude that fluorescence from organic material released by biomass burning creates the inelastic backscatter signal that we measured with our instrument and thus demonstrate a new and powerful way to characterize aerosols by a remote sensing technique. The stratospheric aerosol layer that we have observed in Lindenberg for three consecutive days is likely to be a remnant from Siberian forest fire plumes lifted across the tropopause and transported around the globe.

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RemoteRaman Spectroscopy. Profiling Water Vapor and Aerosols in the Troposphere UsingRaman Lidars

Abstract: Water vapor and aerosols are two important parameters in atmospheric science. They both participate strongly in processes that influence weather and climate and can be measured with high accuracy and high spatial and temporal resolution by Raman lidar.

Cited by 5 publications

References 84 publications

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

Ability to quantify coherent turbulent structures in the convective boundary layer using thermodynamic profiling instruments

Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the stratosphere

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