Last Millennium ENSO Diversity and North American Teleconnections: New Insights From Paleoclimate Data Assimilation
Last Millennium ENSO Diversity and North American Teleconnections: New Insights From Paleoclimate Data Assimilation
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DOI：
10.1029/2021pa004283
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发表时间：
2022-02
影响因子：
3.5
通讯作者：
Xinyue Luo;S. Dee;S. Stevenson;Y. Okumura;N. Steiger;L. Parsons
中科院分区：
文献类型：
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作者：
Xinyue Luo;S. Dee;S. Stevenson;Y. Okumura;N. Steiger;L. Parsons
厄尔尼诺-南方涛动（ENSO）变率影响北美水文气候的年与年变化。由于随机的大气变率和不同的海面温度异常，厄尔尼诺事件之间的热带外遥相关并不总是一致的，这使得仅使用基于仪器的记录难以量化遥相关。在这里，我们使用两个跨越上个千年（LM）的古气候数据同化（DA）产品来比较前工业化时期和20世纪世纪不同厄尔尼诺事件的振幅和频率的变化，并评估其对北美水文气候影响的稳定性。使用中太平洋（CP）和东太平洋（EP）厄尔尼诺的几种定义，我们发现，在20世纪世纪EP厄尔尼诺强度显着增加，但没有显着变化的CP或EP厄尔尼诺频率响应于人为强迫。相关的水文气候异常表明：（a）在CP厄尔尼诺期间，美国东部-中部和西北部的干燥条件和EP厄尔尼诺期间相同地区的潮湿条件;（B）美国西南部的潮湿条件对于两种厄尔尼诺类型。区域水文气候遥相关的大小也显示了数十年到百年时间尺度上的大自然变率。然而，当考虑整个LM时，在CP或EP厄尔尼诺期间北美的平均水文气候异常在符号（湿与干）方面是一致的。结果对代理数据和DA产品中使用的模型先验很敏感。厄尔尼诺分类方法之间的差异突出表明，在评估降水遥相关时，需要改进厄尔尼诺/南方涛动多样性分类。
El Niño‐Southern Oscillation (ENSO) variability affects year‐to‐year changes in North American hydroclimate. Extra‐tropical teleconnections are not always consistent between El Niño events due to stochastic atmospheric variability and diverse sea surface temperature anomalies, making it difficult to quantify teleconnections using only instrumentally‐based records. Here we use two paleoclimate data assimilation (DA) products spanning the Last Millennium (LM) to compare changes in amplitudes and frequencies of diverse El Niño events during the pre‐industrial period and 20th century, and to assess the stationarity of their North American hydroclimate impacts on multi‐decadal to centennial timescales. Using several definitions for Central Pacific (CP) and Eastern Pacific (EP) El Niño, we find a marked increase in 20th century EP El Niño intensity, but no significant changes in CP or EP El Niño frequencies in response to anthropogenic forcing. The associated hydroclimate anomalies indicate (a) dry conditions across the eastern‐central and northwestern U.S. during CP El Niño and wetter conditions in the same regions during EP El Niño; (b) wet conditions over the southwestern U.S. for both El Niño types. The magnitude of regional hydroclimate teleconnections also shows large natural variability on multi‐decadal to centennial timescales. However, when the entire LM is considered, mean hydroclimate anomalies in North America during CP or EP El Niño are consistent in terms of sign (wet vs. dry). Results are sensitive to proxy data and model priors used in DA products. Inconsistencies between El Niño classification methods underscore the need for improved ENSO diversity classification when assessing precipitation teleconnections.