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| Titel |
Ground-based microwave remote sensing of temperature inversions in the Bergen valley, Norway |
| VerfasserIn |
Tobias Wolf, Igor Esau, Joachim Reuder |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250086399
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| Publikation (Nr.) |
 EGU/EGU2014-256.pdf |
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| Zusammenfassung |
| The temperature profiles in the urbanized Bergen valley, Norway, are characterized by
wintertime temperature inversions, which have a strong impact on the surface layer air quality
in the city. We present the results from two years of vertical temperature profile
measurements obtained with the ground-based microwave temperature profiler MTP-5HE
and show the advantages of ground-based remote sensing with this instrument for the
monitoring of atmospheric temperature inversions.
From a subset of the final, filtered dataset we found that the mean difference between
temperatures measured with the MTP-5HE and an automatic meteorological station
(AMS) on a nearby mountain was as low as -0.03 ± 0.78 K during inversion free
conditions and -0.06 ± 0.71 K during ground-based temperature inversions. The
only selection criterion for this subset was a wind speed of more than 5 m/s and
to ensure comparability between the location of the AMS and the central valley
atmosphere.
We found two regimes of ground-based inversions: Non-persistent inversions lasting
shorter than 2 hours that are mostly thinner than 100 m and more persistent inversions often
reaching 270 m above sea level. The height of the shorter inversions was consistent with the
maximum height of inversions found in a previous study based on tethersonde measurements.
Ground-based inversions mostly occurred during situations characterized by weak winds in
the ERA-Interim reanalysis, to a large degree independent from wind direction. A distinct
south-easterly tail in the ERA-Interim wind distribution with wind speeds as high as 16 m/s
might have been connected to a wake effect from a nearby mountain. The strong
channeling effect within the valley that was also found in previous studies was
evident.
The ground-based remote sensing was particularly useful for the monitoring of elevated
temperature inversions between 170 m and 720 m above sea level. This kind of
inversions has not been observed in this valley before. They mostly occurred during
nighttime in spring and summer with northerly low-level winds in ERA-Interim and
only a low correlation in wind direction between the low-level and the 850hPa
ERA-Interim winds. Such wind conditions were unusual for the region under study and
might generally result in a valley-circulation favoring the occurrence of elevated
inversions under conditions with weak enough convection and warm air advection. |
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