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

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

Sample and calibration flow schematic

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

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

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

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

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

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

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

TW vs WV channel comparison

• Good agreement between the two channels TW = 1.04 * WV – 0.08

• Some residual clouds clearly not removed

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

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