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| Titel |
A WRF simulation of the impact of 3-D radiative transfer on surface hydrology over the Rocky Mountains and Sierra Nevada |
| VerfasserIn |
K. N. Liou, Y. Gu, L. R. Leung, W. L. Lee, R. G. Fovell |
| 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 ; 13, no. 23 ; Nr. 13, no. 23 (2013-12-03), S.11709-11721 |
| Datensatznummer |
250085851
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| Publikation (Nr.) |
 copernicus.org/acp-13-11709-2013.pdf |
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| Zusammenfassung |
| We investigate 3-D mountains/snow effects on solar flux
distributions and their impact on surface hydrology over the western United
States, specifically the Rocky Mountains and Sierra Nevada. The Weather
Research and Forecasting (WRF) model, applied at a 30 km grid resolution, is
used in conjunction with a 3-D radiative transfer parameterization covering
a time period from 1 November 2007 to 31 May 2008, during which abundant
snowfall occurred. A comparison of the 3-D WRF simulation with the observed
snow water equivalent (SWE) and precipitation from Snowpack Telemetry
(SNOTEL) sites shows reasonable agreement in terms of spatial patterns and
daily and seasonal variability, although the simulation generally has a
positive precipitation bias. We show that 3-D mountain features have a
profound impact on the diurnal and monthly variation of surface radiative
and heat fluxes, and on the consequent elevation-dependence of snowmelt and
precipitation distributions. In particular, during the winter months, large
deviations (3-D-PP, in which PP denotes the plane-parallel approach) of the monthly mean surface solar flux are found in
the morning and afternoon hours due to shading effects for elevations below
2.5 km. During spring,
positive deviations shift to the earlier morning. Over mountaintops higher than 3 km,
positive deviations are found throughout the day, with the largest
values of 40–60 W m−2 occurring at noon during the snowmelt season of
April to May. The monthly SWE deviations averaged over the entire domain
show an increase in lower elevations due to reduced snowmelt, which leads to a
reduction in cumulative runoff. Over higher elevation areas, positive SWE
deviations are found because of increased solar radiation available at the
surface. Overall, this study shows that deviations of SWE due to 3-D
radiation effects range from an increase of 18% at the lowest elevation
range (1.5–2 km) to a decrease of 8% at the highest elevation range
(above 3 km). Since lower elevation areas occupy larger fractions of the
land surface, the net effect of 3-D radiative transfer is to extend snowmelt
and snowmelt-driven runoff into the warm season. Because 60–90% of
water resources originate from mountains worldwide, the aforementioned
differences in simulated hydrology due solely to 3-D interactions between
solar radiation and mountains/snow merit further investigation in order to
understand the implications of modeling mountain water resources, and these
resources'
vulnerability to climate change and air pollution. |
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