2011 - Cooperative Institute for Research in Environmental Sciences ...

ADVANCED MODELING AND OBSERVING SYSTEMS
AMOS-01 Instrumentation Design,
Prototyping and Analysis
n CSD-01 Instrumentation for
Atmospheric Observations and Analysis
n PSD-08 Sensor and Technique Development
n CET-01 Remote Hydrology Sensing
CSD-01InstrumentationforAtmospheric
ObservationandAnalysis
FEDERAL LEADS: MICHAEL HARDESTY,
STEVEN BROWN AND DAN MURPHY
CIRES LEAD: CHRISTINE ENNIS
NOAA Goals 2 and 3: Climate and Weather and Water
Project Goal: Design and evaluate new approaches and
instrumentation to make atmospheric observations of hard-tomeasure
species and parameters that are important players in
the chemistry of the troposphere and stratosphere.
Milestone 1. Develop and test a new, fully automated instrument
to measure water vapor on board a high-altitude
research aircraft. Impact: The new instrument will include inflight
calibration to ensure that water vapor measurements
made over a wide dynamic range (1–200 parts per million)
have known, high accuracy.
A new chemical ionization mass spectrometry (CIMS)
technique was developed for the measurement of low mixing
ratios of water vapor in the upper troposphere and lower
stratosphere (UT/LS). The instrument sample flow is passed
through a radioactive alpha particle source, and the resulting
ion-molecule reactions lead to the production of H3O+ ions
that are used to quantify the water vapor mixing ratio. This
ionization scheme required the design of a custom alpha particle
source capable of efficient operation at low pressure. An
existing CIMS instrument, designed for automated operation
onboard research aircraft, was modified to use the new ion
source and related flow system. To calibrate the instrument
during flight, a new calibration system was constructed using
catalytic oxidation of hydrogen to produce an accurate
and adjustable source of water vapor on demand. The H2O
CIMS instrument is currently the only UT/LS water vapor
instrument that conducts in-flight calibration at low water
vapor mixing ratios.
The H2O CIMS instrument was flown on the NASA WB-
57 high-altitude research aircraft during the NASA Mid-
Latitude Airborne Cirrus Properties Experiment (MAC-
PEX) campaign in March and April 2011. The MACPEX
campaign provided a rare opportunity to intercompare a
number of different water vapor measurements in order
to assess the community’s ability to accurately measure
water vapor in the UT/LS region. Data reduction from the
MACPEX flights is currently in progress, and analysis of
the data will begin soon.
Product: Rollins, AW, TD Thornberry, R-S Gao, BD
Hall, and DW Fahey (2011), Catalytic oxidation of H2 on
platinum: A method for in situ calibration of hygrometers,
Atmos. Meas. Tech. Discuss., 4, 3083-3095, doi:10.5194/
amtd-4-3083-2011.
Thornberry, TD, AW Rollins, R-S Gao, LA Watts, SJ Ciciora,
RJ McLaughlin, and DW Fahey, A chemical ionization
mass spectrometer for in situ measurement of water
vapor in the upper troposphere and lower stratosphere, in
preparation.
Milestone 2. Construct and deploy a three-wavelength, photoacoustic/cavity
ring-down combination to measure single
scattering albedo. Impact: Single scattering albedo controls
whether the direct radiative effect of aerosols is a warming
or cooling. This instrumentation will make measurements of
CIRES Annual Report 2011 83