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NOAA Water:Instrument and Data
Troy Thornberry, Drew RollinsRu-Shan Gao, Laurel Watts, Steve Ciciora,
Rich McLaughlin, David Fahey
NOAA ESRL CSD and CIRES, University of Colorado
ATTREX Science Team Meeting24 October 2013
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The visible NOAA Water
Main Enclosure: 48 cm x 43 cm x 35 cm, designed for Zone 12
Total Instrument weight (incl. inlet and pumps): 40 kg
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Sample and calibration flow schematic
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P
Optical absorption cell
• 39 cm physical path, 78 cm optical path• 2.694 µm DFB diode laser• WMS spectroscopy with 2f detection• Cell held at constant P, T, and flow• 0.6 s sample residence time at 600 sccm
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TDL scan
• Scan approximately 1 cm-1 at 10 Hz, co-average spectra to 1 Hz
• Two H2O lines with a factor of ~20 difference in line strength
• One or two CO2 lines
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Inlet pylon
27 cm
• Inlet pylon extends 27 cm from fuselage into the free stream
• WV inlet rejects particles• TW inlet samples subisokinetically
⇨ Enhanced sampling efficiency for large particles
• Sharp 90° and heated to 180°C to evaporate particles
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WV inlet particle rejection
• Inlet perpendicular to flow stream to prevent sampling of cloud particles
• Design used successfully in the past with CIMS H2O and SP2 (MACPEX), CIMS HNO3
• Curve based on empirical study reported by Brixey et al., 2004 – application requires extrapolation from low U/U0
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TW inlet enhancement factor
• Function of airspeed, pressure, temperature, volumetric sample flow, particle density
• In TTL, typical values:
– U = 4.47 m/s, U0 = 180 m/s
• Based on CFD models from Krämer and Afchine, 2004 and Eddy et al., 2006
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Calibration vs MBW
• Primary calibration by comparison with MBW 373LX reference cryogenic mirror hygrometer on the ground
• Performed before, during and after ATTREX 2 deployment
• MBW CMH instrument compared with PTB reference during AquaVIT2
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In-flight calibration
• In-flight calibration used to assess stability of sensitivity
• Range of mixing ratios generated by H2 oxidation on Pt catalyst
• Only WV channel calibrated
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TW vs WV channel comparison
• Good agreement between the two channels TW = 1.04 * WV – 0.08
• Some residual clouds clearly not removed
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Data Status
• RF01 and RF02 there was a leak in the exhaust line for the WV channel resulting in pressure/flow problems. TW data good.
• RF01 – RF03: TW measurement following thick clouds was compromised by condensation on the cold hatch interface flange.
• Only need to finalize uncertainty statement to submit final data– WV channel has better precision and lower uncertainty than TW
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Summary
• NOAA Water is a new 2-channel TDL H2O instrument designed and built for GH
• Measures both water vapor and enhanced total water (from which cirrus IWC can be calculated)
• Utilizes in situ calibration to verify stability of instrument sensitivity and background
• ATTREX 2 was a successful first deployment of the new NOAA Water instrument
• Final data only awaiting final error analysis/formulation