Associations between low frequency variability modes and winter temperature extremes in Canada
Associations between low frequency variability modes and winter temperature extremes in Canada
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低频变异模式与加拿大冬季极端温度之间的关联
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
B. Bonsal
中科院分区：
文献类型：
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作者：
A. Shabbar;B. Bonsal
摘要研究了1950- 1998年期间，包括厄尔尼诺-南方涛动（ENSO）、北极涛动（AO）和准两年期涛动（QBO）在内的低频气候变率模式与加拿大冬季极端温度发生之间的关系。综合分析表明，ENSO在冷暖期的频率和持续时间上起着主导作用。特别是，厄尔尼诺/南方涛动的暖相与加拿大大部分地区暖（冷）期和极端暖（冷）日数的显著增加（减少）有关。研究结果通常与冷ENSO阶段相反。奇异值分解（SVD）技术进一步表明，类似ENSO的年代际海表温度变率在加拿大冬季寒冷和温暖的变化中起着重要的作用。AO的高和低指数阶段之间的差异显示出显着较高的频率和持续时间的寒冷期在加拿大东部在积极AO冬季，而冬季温暖期的频率增加在加拿大大草原。这些结果也被使用北方半球1000 hPa环流的SVD分析所证实。QBO，确定的平流层风的相位，有加拿大极端温度的空间格局的影响，是类似的AO。最重要的结果涉及增加的频率温暖的法术和极端温暖的天数在南部大草原在西风阶段的QBO。本研究的诊断结果提高了对低频变率模态对加拿大极端温度影响的认识。它们还可能有助于确定过去的趋势和极端事件的变异性，并有可能提供对极端温度事件未来变化的深入了解。
Abstract Relationships between patterns of low frequency climate variability including the El Niño‐Southern Oscillation (ENSO), the Arctic Oscillation (AO) and the Quasi‐Biennial Oscillation (QBO), and the occurrence of Canadian winter temperature extremes are examined for the 1950–98 period. Composite analyses reveal that ENSO plays a dominant role in the frequency and duration of both cold and warm spells. In particular, the warm phase of ENSO is associated with a significant increase (decrease) in the occurrence of warm (cold) spells and the number of extreme warm (cold) days across most of Canada. The findings are generally the opposite for the cold ENSO phase. The singular value decomposition (SVD) technique further shows that ENSO‐like interdecadal sea surface temperature variability plays a significant role in the variability of winter cold and warm spells over Canada. Differences between the high and low index phases of the AO show a significantly higher frequency and duration of cold spells over eastern Canada during positive AO winters, while the frequency of winter warm spells increases over the Canadian Prairies. These results are also confirmed by the SVD analysis using northern hemisphere 1000‐hPa circulation. The QBO, as determined by the phase of the stratospheric winds, has an effect on the spatial pattern of Canadian extreme temperatures that is similar to that of the AO. The most significant result involves increases in the frequency of warm spells and the number of extreme warm days over the southern Prairies during the westerly phase of the QBO. The diagnostic results from this study improve the understanding of the imapact of the low frequency variability modes on temperature extremes over Canada. They may also assist in the attribution of past trends and variability in extremes, and potentially, provide insight into future changes to extreme temperature events.