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| Titel |
Simulating 3-D radiative transfer effects over the Sierra Nevada Mountains using WRF |
| VerfasserIn |
Y. Gu, K. N. Liou, W.-L. Lee, L. R. Leung |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 20 ; Nr. 12, no. 20 (2012-10-30), S.9965-9976 |
| Datensatznummer |
250011546
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| Publikation (Nr.) |
 copernicus.org/acp-12-9965-2012.pdf |
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| Zusammenfassung |
| A surface solar radiation parameterization based on deviations between 3-D
and conventional plane-parallel radiative transfer models has been
incorporated into the Weather Research and Forecasting (WRF) model to
understand the solar insolation over mountain/snow areas and to investigate
the impact of the spatial and temporal distribution and variation of surface
solar fluxes on land-surface processes. Using the Sierra-Nevada in the
western United States as a testbed, we show that mountain effect could
produce up to −50 to + 50 W m−2 deviations in the surface solar
fluxes over the mountain areas, resulting in a temperature increase of up to
1 °C on the sunny side. Upward surface sensible and latent heat
fluxes are modulated accordingly to compensate for the change in surface
solar fluxes. Snow water equivalent and surface albedo both show decreases on
the sunny side of the mountains, indicating more snowmelt and hence reduced
snow albedo associated with more solar insolation due to mountain effect.
Soil moisture increases on the sunny side of the mountains due to enhanced
snowmelt, while decreases on the shaded side. Substantial differences are
found in the morning hours from 8–10 a.m. and in the afternoon around
3–5 p.m., while differences around noon and in the early morning and late
afternoon are comparatively smaller. Variation in the surface energy balance
can also affect atmospheric processes, such as cloud fields, through the
modulation of vertical thermal structure. Negative changes of up to
−40 g m−2 are found in the cloud water path, associated with
reductions in the surface insolation over the cloud region. The day-averaged
deviations in the surface solar flux are positive over the mountain areas and
negative in the valleys, with a range between −12~12 W m−2.
Changes in sensible and latent heat fluxes and surface skin temperature
follow the solar insolation pattern. Differences in the domain-averaged
diurnal variation over the Sierras show that the mountain area receives more
solar insolation during early morning and late afternoon, resulting in
enhanced upward sensible heat and latent heat fluxes from the surface and a
corresponding increase in surface skin temperature. During the middle of the
day, however, the surface insolation and heat fluxes show negative changes,
indicating a cooling effect. Hence overall, the diurnal variations of surface
temperature and surface fluxes in the Sierra-Nevada are reduced through the
interactions of radiative transfer and mountains. The hourly differences of
the surface solar insolation in higher elevated regions, however, show
smaller magnitude in negative changes during the middle of the day and
possibly more solar fluxes received during the whole day. |
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