Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

Applied Optics (Impact Factor: 1.78). 04/1991; 30(12):1517-24. DOI: 10.1364/AO.30.001517
Source: PubMed


Recently measured properties of water vapor (H(2)O) absorption lines have been used in calculations to evaluate the temperature sensitivity of differential absorption lidar (DIAL) H(2)O measurements. This paper estimates the temperature sensitivity of H(2)O lines in the 717-733-nm region for both H(2)O mixing ratio and number density measurements, and discusses the influence of the H(2)O line ground state energies E'', the H(2)O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for sixty-seven H(2)O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E'' values in the 100-300-cm(-1) range were found to be optimum for DIAL measurements of H(2)O number densities, while E'' values in the 250-500-cm(-1) range were found to be optimum for H(2)O mixing ratio measurements.

Download full-text


Available from: Edward V. Browell
  • Source
    • "The evaluation of the temperature sensitivities of water vapor absorption lines in the 820–840-nm spectral region were studied using the methods presented by Browell et al. (1991), leading to the selection of this water vapor absorption line for number density profiles at 828.187 nm (vacuum) (the online wavelength). A summary of the water vapor DIAL transmitter and the receiver specifications are shown in Table 2, where the laser transmitter requirements for accurate water vapor profiling are also shown for comparison. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Coordinated observational data of atmospheric aerosols were collected over a 24-h period between 2300 mountain daylight time (MDT) on 27 August 2009 and 2300 MDT on 28 August 2009 at Bozeman, Montana (45.66 degrees N, 111.04 degrees W, elevation 1530 m) using a collocated two-color lidar, a diode-laser-based water vapor differential absorption lidar (DIAL), a solar radiometer, and a ground-based nephelometer. The optical properties and spatial distribution of the atmospheric aerosols were inferred from the observational data collected using the collocated instruments as part of a closure experiment under dry conditions with a relative humidity below 60%. The aerosol lidar ratio and aerosol optical depth retrieved at 532 and 1064 nm using the two-color lidar and solar radiometer agreed with one another to within their individual uncertainties while the scattering component of the aerosol extinction measured using the nephelometer matched the scattering component of the aerosol extinction retrieved using the 532-nm channel of the two-color lidar and the single-scatter albedo retrieved using the solar radiometer. Using existing aerosol models developed with Aerosol Robotic Network (AERONET) data, a thin aerosol layer observed over Bozeman was most likely identified as smoke from forest fires burning in California; Washington; British Columbia, Canada; and northwestern Montana. The intrusion of the thin aerosol layer caused a change in the atmospheric radiative forcing by a factor of 1.8 +/- 0.5 due to the aerosol direct effect.
    Full-text · Article · Mar 2011 · Journal of Atmospheric and Oceanic Technology
  • Source
    • "Our procedure for selecting a water vapor absorption line closely followed the methods of Browell et al., 1991 [41]. Temperature sensitivity analysis involves calculating the error in the absorption cross section with temperature, dσ/dT [cm 2 /K], where σ = KV [cm 2 ], across a range of temperatures, pressures, and ground-state transitional energies, E " [cm -1 ]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This work describes the design and testing of a highly-tunable differential absorption lidar (DIAL) instrument utilizing an all-semiconductor transmitter. This new DIAL instrument transmitter has a highly-tunable external cavity diode laser (ECDL) as a seed laser source for two cascaded commercial tapered amplifiers. The transmitter has the capability of tuning over a range of ~ 17 nm centered at about 832 nm to selectively probe several water vapor absorption lines. This capability has been requested in other recent DIAL experiments for wavelengths near 830 nm. The transmitter produces pulse energies of approximately 0.25 μJ at a repetition rate of 20 kHz. The linewidth is exceptionally narrow at <0.3 MHz, with frequency stability that has been shown to be +/-88 MHz and spectral purity of 0.995. Tests of the DIAL instrument to prove the validity of its measurements were undertaken. Preliminary water vapor profiles, taken in Bozeman, Montana, agree to within 5-60% with profiles derived from co-located radiosondes 800 meters above ground altitude. Below 800 meters, the measurements are biased low due to a number of systematic issues that are discussed. The long averaging times required by low-power systems have been shown to lead to biases in data, and indeed, our results showed strong disagreements on nights when the atmosphere was changing rapidly, such as on windy nights or when a storm system was entering the area. Improvements to the system to correct the major systematic biases are described.
    Full-text · Article · Mar 2010
  • Source
    • "). The temperature sensitivity for the number density measurement is calculated using the expression (Browell et al. 1991) "
    [Show abstract] [Hide abstract]
    ABSTRACT: A differential absorption lidar (DIAL) instrument for automated profiling of water vapor in the lower troposphere has been designed, tested, and is in routine operation at Montana State University. The laser transmitter for the DIAL instrument uses a widely tunable external cavity diode laser (ECDL) to injection seed two cascaded semiconductor optical amplifiers (SOAs) to produce a laser transmitter that accesses the 824-841-nm spectral range. The DIAL receiver utilizes a 28-cm-diameter Schmidt - Cassegrain telescope; an avalanche photodiode (APD) detector; and a narrowband optical filter to collect, discriminate, and measure the scattered light. A technique of correcting for the wavelength-dependent incident angle upon the narrowband optical filter as a function of range has been developed to allow accurate water vapor profiles to be measured down to 225 m above the surface. Data comparisons using the DIAL instrument and collocated radiosonde measurements are presented demonstrating the capabilities of the DIAL instrument.
    Full-text · Article · Apr 2009 · Journal of Atmospheric and Oceanic Technology
Show more