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| Titel |
Future humidity trends over the western United States in the CMIP5 global climate models and variable infiltration capacity hydrological modeling system |
| VerfasserIn |
D. W. Pierce, A. L. Westerling, J. Oyler |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 5 ; Nr. 17, no. 5 (2013-05-14), S.1833-1850 |
| Datensatznummer |
250018875
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| Publikation (Nr.) |
 copernicus.org/hess-17-1833-2013.pdf |
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| Zusammenfassung |
| Global climate models predict relative humidity (RH) in the western US will
decrease at a rate of about 0.1–0.6 percentage points per decade,
albeit with seasonal differences (most drying in spring and
summer), geographical variability (greater declines in the interior),
stronger reductions for greater anthropogenic radiative forcing, and notable
spread among the models. Although atmospheric moisture content increases,
this is more than compensated for by higher air temperatures, leading to
declining RH. Fine-scale hydrological simulations driven by the global model
results should reproduce these trends. It is shown that the MT-CLIM
meteorological algorithms used by the Variable Infiltration Capacity (VIC)
hydrological model, when driven by daily Tmin, Tmax,
and precipitation (a configuration used in numerous published studies), do
not preserve the original global model's humidity trends. Trends are biased
positive in the interior western US, so that strong RH decreases are changed
to weak decreases, and weak decreases are changed to increases. This happens
because the MT-CLIM algorithms VIC incorporates infer an overly large
positive trend in atmospheric moisture content in this region, likely due to
an underestimate of the effect of increasing aridity on RH. The result could
downplay the effects of decreasing RH on plants and wildfire. RH trends along
the coast have a weak negative bias due to neglect of the ocean's moderating
influence. A numerical experiment where the values of Tdew are
altered to compensate for the RH error suggests that eliminating the
atmospheric moisture bias could, in and of itself, decrease runoff up to
14% in high-altitude regions east of the Sierra Nevada and Cascades, and
reduce estimated Colorado River runoff at Lees Ferry up to 4% by the end
of the century. It could also increase the probability of large fires in the
northern and central US Rocky Mountains by 13 to 60%. |
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