Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century
Seasonal hindcast experiments, using prescribed SSTs, are analysed for Northern Hemisphere winters from 1900-2010. Ensemble mean Pacific/North American index (PNA) skill varies dramatically, dropping towards zero during the mid-twentieth century, with similar variability in North Atlantic Oscillatio...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Published: |
American Geophysical Union
2017
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| _version_ | 1826263043772776448 |
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| author | O'Reilly, C Heatley, J MacLeod, D Weisheimer, A Palmer, T Schaller, N Woollings, T |
| author_facet | O'Reilly, C Heatley, J MacLeod, D Weisheimer, A Palmer, T Schaller, N Woollings, T |
| author_sort | O'Reilly, C |
| collection | OXFORD |
| description | Seasonal hindcast experiments, using prescribed SSTs, are analysed for Northern Hemisphere winters from 1900-2010. Ensemble mean Pacific/North American index (PNA) skill varies dramatically, dropping towards zero during the mid-twentieth century, with similar variability in North Atlantic Oscillation (NAO) hindcast skill. The PNA skill closely follows the correlation between the observed PNA index and tropical Pacific SST anomalies. During the mid-century period the PNA and NAO hindcast errors are closely related. The drop in PNA predictability is due to mid-century negative PNA events, which were not forced in a predictable manner by tropical Pacific SST anomalies. Overall, negative PNA events are less predictable and seem likely to arise more from internal atmospheric variability than positive PNA events. Our results suggest that seasonal forecasting systems assessed over the recent 30-year period may be less skillful in periods, such as the mid-twentieth century, with relatively weak forcing from tropical Pacific SST anomalies. |
| first_indexed | 2024-03-06T19:45:25Z |
| format | Journal article |
| id | oxford-uuid:22245d66-d0c7-4eee-ab4c-b6b8cf066266 |
| institution | University of Oxford |
| last_indexed | 2024-03-06T19:45:25Z |
| publishDate | 2017 |
| publisher | American Geophysical Union |
| record_format | dspace |
| spelling | oxford-uuid:22245d66-d0c7-4eee-ab4c-b6b8cf0662662022-03-26T11:37:08ZVariability in seasonal forecast skill of Northern Hemisphere winters over the 20th centuryJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:22245d66-d0c7-4eee-ab4c-b6b8cf066266Symplectic Elements at OxfordAmerican Geophysical Union2017O'Reilly, CHeatley, JMacLeod, DWeisheimer, APalmer, TSchaller, NWoollings, TSeasonal hindcast experiments, using prescribed SSTs, are analysed for Northern Hemisphere winters from 1900-2010. Ensemble mean Pacific/North American index (PNA) skill varies dramatically, dropping towards zero during the mid-twentieth century, with similar variability in North Atlantic Oscillation (NAO) hindcast skill. The PNA skill closely follows the correlation between the observed PNA index and tropical Pacific SST anomalies. During the mid-century period the PNA and NAO hindcast errors are closely related. The drop in PNA predictability is due to mid-century negative PNA events, which were not forced in a predictable manner by tropical Pacific SST anomalies. Overall, negative PNA events are less predictable and seem likely to arise more from internal atmospheric variability than positive PNA events. Our results suggest that seasonal forecasting systems assessed over the recent 30-year period may be less skillful in periods, such as the mid-twentieth century, with relatively weak forcing from tropical Pacific SST anomalies. |
| spellingShingle | O'Reilly, C Heatley, J MacLeod, D Weisheimer, A Palmer, T Schaller, N Woollings, T Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century |
| title | Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century |
| title_full | Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century |
| title_fullStr | Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century |
| title_full_unstemmed | Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century |
| title_short | Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century |
| title_sort | variability in seasonal forecast skill of northern hemisphere winters over the 20th century |
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