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| Titel |
Effective boundary layer temperature from atmospheric water vapour emission |
| VerfasserIn |
J. Gröbner, S. Wacker, L. Vuilleumier |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028014
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| Zusammenfassung |
| Measurements of the atmospheric boundary layer (ABL) temperature are obtained from
concurrent measurements of two pyrgeometers: One standard pyrgeometer sensitive to the 3
μm to 50 μm wavelength range and one modified pyrgeometer sensitive only in the
atmospheric window, e.g. from 8 μm to 14 μm. By combining the two measurements we
retrieve the effective temperature of the saturated atmospheric water vapor from the radiation
emitted by the atmosphere in the wavelength range 3 μm to 8 μm and 14 μm to 50 μm for
four sites in Switzerland, Davos, Payerne, Locarno-Monti and Jungfraujoch. The radiation in
this wavelength range is emitted from the layers of the atmosphere closest to the Earth’s
surface which form the ABL. The temperature derived from these measurements can be
considered as an effective temperature of the saturated atmospheric water vapor, which
depends directly on the profiles of humidity and temperature. We show that this
effective saturated water vapor temperature is a powerful indicator for the state of the
ABL when it is compared to the synoptic temperature measured at the surface. The
ABL temperature measurements obtained from the pyrgeometers were validated at
the BSRN site of Payerne using air temperature measurements obtained from a
meteorological tower at 10 m and 30 m. The measurements show clearly the stable
inversion layer during the night and the break-up of the ABL during daylight due
to solar heating. The measurements at Jungfraujoch do not show any systematic
diurnal variation of the atmospheric temperature relative to synoptic temperature
which is due to the absence of a stable boundary layer at Jungfraujoch. This is
consistent with observations that the Jungfraujoch at 3580 m.a.s.l. is located in the free
troposphere. Our observations of the ABL temperature using infrared radiation
emission of saturated water vapour are a crucial parameter for the parametrization of
atmospheric longwave radiation models and can be used to improve cloud cover
algorithms using longwave radiation measurements from standard pyrgeometers. |
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