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Abstract This study investigates Gulf Stream (GS) sea surface temperature (SST) anomalies associated with the extratropical transition (ET) of tropical cyclones (TCs) in the North Atlantic. Composites of western North Atlantic TCs indicate that GS SSTs are warmer, and both large‐ and fine‐scale SST gradients are weaker than average, for TCs that begin the ET process but do not complete it, compared with TCs that do. Further analysis suggests that the associated fine‐scale GS SST gradient anomalies are related to atmospheric processes but not the same as those that are typically associated with the onset of ET. As sensible heat flux gradients and surface diabatic frontogenesis are shown to generally scale with the local SST gradient strength, these results suggest that knowledge of the fine‐scale GS SST gradient in the weeks prior to the arrival of a TC might potentially provide additional information regarding the likelihood of that system completing ET.
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Air‐Sea Heat Flux Gradients Over the Gulf Stream Lead the Late Winter North Atlantic Oscillation
Abstract Previous studies have suggested that variability in the Gulf Stream (GS) region can lead North Atlantic atmospheric variability. However, it remains unclear what GS characteristic is most important in driving this lead time. Here, we show that the GS sensible heat flux (SHF) gradient specifically leads the North Atlantic Oscillation (NAO) by 1 month. This lag relationship occurs only when climatological sea‐surface temperature and SHF gradients are largest in late winter. Further analysis reveals that fine‐scale gradients (∼50 km) are critical. A month prior to a negative NAO, stronger than normal diabatic frontogenesis associated with anomalously strong SHF gradients is observed over the separated GS region. This is collocated with a North Atlantic eddy‐driven jet located in its Southern regime. These results suggest that knowledge of fine‐scale air‐sea heat flux gradients in late winter can potentially provide useful information about the NAO in weather forecasts and climate prediction systems.
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- Award ID(s):
- 2023585
- PAR ID:
- 10642868
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 52
- Issue:
- 18
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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