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| Titel |
Assessing Northern Hemisphere Land-Atmosphere Hotspots Using Dynamical Adjustment |
| VerfasserIn |
Anna Merrifield, Flavio Lehner, Clara Deser, Shang-Ping Xie |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250139599
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| Publikation (Nr.) |
 EGU/EGU2017-2869.pdf |
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| Zusammenfassung |
| Understanding the influence of soil moisture on surface air temperature (SAT) is made more
challenging by large-scale, internal atmospheric variability present in the midlatitude summer
atmosphere. In this study, dynamical adjustment is used to characterize and remove summer
SAT variability associated with large-scale circulation patterns in the Community
Earth System Model large ensemble (CESM-LE). The adjustment is performed
over North America and Europe with two different circulation indicators: sea level
pressure (SLP) and 500mb height (Z500). The removal of dynamical “noise" leaves
residual SAT variability in the central U.S. and Mediterranean regions identified as
hotspots of land-atmosphere interaction (e.g. Koster et al. 2004, Seneviratne et al.
2006). The residual SAT variability “signal" is not clearly related to modes of sea
surface temperature (SST) variability, but is related to local soil moisture, evaporative
fraction, and radiation availability. These local relationships suggest that residual SAT
variability is representative of the aggregate land surface signal. SLP dynamical
adjustment removes ∼15% more variability in the central U.S. hotspot region than Z500
dynamical adjustment. Similar amounts of variability are removed by SLP and Z500
in the Mediterranean region. Differences in SLP and Z500 signal magnitude in
the central U.S. are likely due to the modification of SLP by local land surface
conditions, while the proximity of European hotspots to the Mediterranean sea
mitigates the land surface influence. Variations in the Z500 field more closely resemble
large-scale midlatitude circulation patterns and therefore Z500 may be a more suitable
circulation indicator for summer dynamical adjustment. Changes in the residual SAT
variability signal under increased greenhouse gas forcing will also be explored. |
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