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@ARTICLE{Smit:59857,
author = {Smit, H. G. J. and Volz-Thomas, A. and Helten, M. and
Pätz, H.-W. and Kley, D.},
title = {{A}n in-flight {C}alibration {M}ethod for
{N}ear-{R}eal-{T}ime {H}umidity {M}easurements with the
{A}irborne {MOZAIC} sensor},
journal = {Journal of atmospheric and oceanic technology},
volume = {25},
issn = {0739-0572},
address = {Boston, Mass.},
publisher = {AMS},
reportid = {PreJuSER-59857},
pages = {656 - 666},
year = {2008},
note = {Record converted from VDB: 12.11.2012},
abstract = {A new in-flight calibration (IFC) method is described for
the humidity sensor flown routinely since 1994 on the
Measurement of Ozone and Water Vapor by Airbus In-Service
Aircraft (MOZAIC) program's aircraft. The IFC method
corrects the potential drift of the sensor offset at zero
relative humidity, which is the critical parameter in
determining the uncertainty of the measurements. The sensor
offset is determined from the measurements themselves as
obtained during periods when the aircraft is flying in the
lower stratosphere at or above the hygropause, where the H2O
mixing ratio reaches well-defined minimum values of about 5
ppmv and the contribution of atmospheric H2O to the sensor
signal is minimal. The selection of stratospheric data is
achieved with the help of potential temperature, which can
be calculated in situ from measured temperature and
pressure. The IFC method is capable of providing humidity
measurements in near-real time with an uncertainty of
$+/-8\%$ RH at the surface and $+/-7\%$ RH in the upper
troposphere.For validation, the IFC method was applied to 5
yr of archived raw signals from the MOZAIC aircraft. The
resulting humidity data are in good agreement (within $2\%$
RH) with the original MOZAIC data that used monthly pre- and
postflight calibrations of the sensor. The standard
deviation of the differences varies with altitude between
$+/-4\%$ and $+/-6\%$ RH, which is comparable to the
accuracy of the MOZAIC laboratory calibrations. Compared to
MOZAIC operation based on monthly calibrations in the
laboratory, the use of IFC will substantially reduce the
efforts for maintenance and thus will enable operation of
the sensor on a large fleet of in-service aircraft for
near-real-time measurements of humidity in the troposphere.
Because the IFC method will not work on aircraft that never
enter the lower stratosphere, for example, aircraft that fly
exclusively regional routes or in the tropics, regular
offline calibrations will remain important for such
aircraft.},
keywords = {J (WoSType)},
cin = {ICG-2},
ddc = {550},
cid = {I:(DE-Juel1)VDB791},
pnm = {Atmosphäre und Klima},
pid = {G:(DE-Juel1)FUEK406},
shelfmark = {Engineering, Ocean / Meteorology $\&$ Atmospheric Sciences},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000256069000002},
doi = {10.1175/2007JTECHA975.1},
url = {https://juser.fz-juelich.de/record/59857},
}