Interdecadal Changes in Atmospheric Low-Frequency Variability with and without Boundary Forcing
The concept of persistent and recurrent large-scale atmospheric flow regimes, or "weather regimes", is used to investigate the response of an atmospheric general circulation model (GCM) to a prescribed decade-long anomaly in sea-surface temperature (SST) over the North Atlantic during wint...
| Main Authors: | , , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1997
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.38.9513 http://uniblab.atmos.ucla.edu/~andy/echam3/echam3_wr.text.ps |
| Summary: | The concept of persistent and recurrent large-scale atmospheric flow regimes, or "weather regimes", is used to investigate the response of an atmospheric general circulation model (GCM) to a prescribed decade-long anomaly in sea-surface temperature (SST) over the North Atlantic during winter. The model's weather regimes are first determined from a 100-year control run of the Max-Planck Institute's ECHAM3 model with seasonally varying climatological SST. Both bump hunting on the probability density function and a K-means algorithm are applied to low-pass filtered daily 700-mb height fields for the winter season over the North Atlantic sector. The resulting six regimes are surprisingly realistic, validating the GCM's low-frequency variability. Decade-to-decade variations in the weather regimes' frequency of occurrence are found to be substantial. A 10-year experiment with an observed decadal SST anomaly over the North Atlantic (30 o --50 o N) is then projected onto the subspace of t. |
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