Simultaneous diode laser based in situ quantification of oxygen, carbon monoxide, water vapor, and liquid water in a dense water mist environment

Abstract. A unique feature of the VOCALS Regional Experiment was the inclusion of a small, inexpensive, zenith-pointing millimeter-wavelength passive radiometer on the fourteen research flights of the NCAR C-130 plane, the G-band (183 GHz) Vapor Radiometer (GVR). The radiometer permitted above-cloud retrievals of water vapor path, and cloud liquid water path retrievals at 1 Hz resolution for the sub-cloud and cloudbase aircraft legs when combined with in-situ thermodynamic data. Retrieved free-tropospheric (above-cloud) water vapor paths possessed a strong longitudinal gradient, with off-shore values of one to two mm and near-coastal values reaching one cm. Overall the free-troposphere was drier than that sampled by radiosondes in previous years. For the sub-cloud legs, the absolute (between-leg) and relative (within-leg) LWP accuracy was estimated at 20–25 and 5 g m−2 respectively for well-mixed conditions, with greater uncertainties expected for decoupled conditions. Clouds with retrieved liquid water paths between 200 to 400 g m−2 matched adiabatic values derived from coincident cloud thickness measurements exceedingly well. A significant contribution of the GVR dataset is the extended information on the thin clouds, with 66 % of the retrieved LWPs < 100 g m−2. Nevertheless, the overall LWP cloud fraction of 62 % was less than the 92 % cloud cover determined by airborne cloud lidar and radar combined.

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Lightweight diode laser spectrometer CHILD (Compact High-altitude In-situ Laser Diode) for balloonborne measurements of water vapor and methane

Applied Optics ◽

10.1364/ao.44.000091 ◽

2005 ◽

Vol 44 (1) ◽

pp. 91 ◽

Cited By ~ 42

Author(s):

Wolfgang Gurlit ◽

Rainer Zimmermann ◽

Carsten Giesemann ◽

Thomas Fernholz ◽

Volker Ebert ◽

...

Keyword(s):

Water Vapor ◽

High Altitude ◽

Diode Laser ◽

Laser Diode ◽

Laser Spectrometer ◽

Diode Laser Spectrometer

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Comparison of Water Vapor Measurements by Airborne Sun Photometer and Diode Laser Hygrometer on the NASA DC-8

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2008jtecha1047.1 ◽

2008 ◽

Vol 25 (10) ◽

pp. 1733-1743 ◽

Cited By ~ 4

Author(s):

J. M. Livingston ◽

B. Schmid ◽

P. B. Russell ◽

J. R. Podolske ◽

J. Redemann ◽

...

Keyword(s):

Water Vapor ◽

Diode Laser ◽

Free Stream ◽

Vapor Density ◽

Aircraft Fuselage ◽

Sun Photometer ◽

Local Water ◽

Highly Correlated ◽

First Time

Abstract In January–February 2003, the 14-channel NASA Ames airborne tracking sun photometer (AATS) and the NASA Langley/Ames diode laser hygrometer (DLH) were flown on the NASA DC-8 aircraft. The AATS measured column water vapor on the aircraft-to-sun path, while the DLH measured local water vapor in the free stream between the aircraft fuselage and an outboard engine cowling. The AATS and DLH measurements have been compared for two DC-8 vertical profiles by differentiating the AATS column measurement and/or integrating the DLH local measurement over the altitude range of each profile (7.7–10 km and 1.1–12.5 km). These comparisons extend, for the first time, tests of AATS water vapor retrievals to altitudes >∼6 km and column contents <0.1 g cm−2. To the authors’ knowledge, this is the first time suborbital spectroscopic water vapor measurements using the 940-nm band have been tested in conditions so high and dry. Values of layer water vapor (LWV) calculated from the AATS and DLH measurements are highly correlated for each profile. The composite dataset yields r 2 0.998, rms difference 7.7%, and bias (AATS minus DLH) 1.0%. For water vapor densities AATS and DLH had r 2 0.968, rms difference 27.6%, and bias (AATS minus DLH) −4.2%. These results for water vapor density compare favorably with previous comparisons of AATS water vapor to in situ results for altitudes <∼6 km, columns ∼0.1 to 5 g cm−2, and densities ∼0.1 to 17 g m−3.

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In-Situ Optical Measurements of Water Vapor Concentration and Temperature in a Proton Exchange Membrane Fuel Cell at Steady State and Under Dynamic Cycling

ASME 2009 7th International Conference on Fuel Cell Science, Engineering and Technology ◽

10.1115/fuelcell2009-85093 ◽

2009 ◽

Author(s):

Ritobrata Sur ◽

Thomas J. Boucher ◽

Michael W. Renfro ◽

Baki M. Cetegen

Keyword(s):

Water Vapor ◽

Fuel Cell ◽

Partial Pressure ◽

Diode Laser ◽

Pem Fuel Cell ◽

Tunable Diode Laser ◽

Cathode Side ◽

Vapor Concentration ◽

Water Vapor Concentration

A robust, accurate and fast in-situ sensor was developed for detection of water vapor partial pressure and temperature simultaneously at the anode and cathode channels of a PEM fuel cell. Tunable diode laser absorption spectroscopy (TDLAS) utilizing wavelength modulation (WMS) was employed for these measurements. This method determines the ratio of the second and first harmonics (2f/1f) of the spectroscopic absorption profile of water vapor by the aid of a software lock-in amplifier. Measurements were taken using a diode laser emitting around a wavelength of 1471 nm where the water vapor absorption exhibits significant sensitivity to partial pressure and temperature. Measurements of water vapor concentration and temperature in were taken at steady and dynamic operating conditions in the anode and cathode gas channels near the inlet and outlet ports of a serpentine channel PEM fuel cell with Nafion membrane of active area 50 cm2. Different load and inlet humidity conditions were tested to characterize the operation at different conditions. The partial pressure of water vapor increases towards the exit of both the gas channels, but the increase is found to be more significant on the cathode side. The dynamic operation of the fuel cell was also examined in this study as well as the simultaneous measurements at the anode and cathode gas channels.

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