Forcing and impact of the Northern Hemisphere continental snow cover in 1979–2014
Forcing and impact of the Northern Hemisphere continental snow cover in 1979–2014
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DOI：
10.5194/tc-17-2157-2023
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
G. Gastineau;C. Frankignoul;Yongqi Gao;Yu‐Chiao Liang;Young‐Oh Kwon;A. Cherchi;R. Ghosh;E. Manzini-E.
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文献类型：
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作者：
G. Gastineau;C. Frankignoul;Yongqi Gao;Yu‐Chiao Liang;Young‐Oh Kwon;A. Cherchi;R. Ghosh;E. Manzini-E.
抽象的。对 1979 年至 2014 年期间北半球大陆积雪的主要驱动因素进行了调查。使用四个观测数据集以及两个仅大气模拟的大型多模型集合，具有规定的海面温度（SST）和海冰浓度（SIC）。第一个集合使用 1979-2014 年观测到的年际变化的 SST 和 SIC 条件，而第二个集合则相同，除了使用重复气候周期的 SIC 之外。海表温度和外部强迫通常可以解释模型模拟中 10% 至 25% 的积雪变化，在此期间，主要强迫来自热带和北太平洋海表温度。就积雪异常对气候的影响而言，观测和模型均显示11月和4月积雪变化与1个月后的大气环流之间没有牢固的联系。另一方面，一月份欧亚积雪变化的第一个模式，即欧亚大陆西部地区积雪时间更长，被发现先于大气环流模式一个月，类似于负北极振荡（AO）。对模型模拟中变异性的分解表明，这种关系主要是由于内部气候变异性造成的。其中一个模型的详细输出表明，欧亚大陆西部积雪异常之前出现了负 AO 阶段，并伴有乌拉尔阻塞模式和平流层极地涡旋减弱。 AO与积雪变化之间的联系与平流层极地涡旋的伴随作用密切相关，欧亚积雪对冬季AO变化起到正反馈作用。没有发现 SIC 变化的强烈影响，因为这些模拟中的海冰损失只导致了一小部分积雪异常，模型之间几乎没有达成一致。
Abstract. The main drivers of the continental Northern Hemisphere snow cover are investigated in the 1979–2014 period. Four observational datasets are used as are two large multi-model ensembles of atmosphere-only simulations with prescribed sea surface temperature (SST) and sea ice concentration (SIC). A first ensemble uses observed interannually varying SST and SIC conditions for 1979–2014, while a second ensemble is identical except for SIC with a repeated climatological cycle used. SST and external forcing typically explain 10 % to 25 % of the snow cover variance in model simulations, with a dominant forcing from the tropical and North Pacific SST during this period. In terms of the climate influence of the snow cover anomalies, both observations and models show no robust links between the November and April snow cover variability and the atmospheric circulation 1 month later. On the other hand, the first mode of Eurasian snow cover variability in January, with more extended snow over western Eurasia, is found to precede an atmospheric circulation pattern by 1 month, similar to a negative Arctic oscillation (AO). A decomposition of the variability in the model simulations shows that this relationship is mainly due to internal climate variability. Detailed outputs from one of the models indicate that the western Eurasia snow cover anomalies are preceded by a negative AO phase accompanied by a Ural blocking pattern and a stratospheric polar vortex weakening. The link between the AO and the snow cover variability is strongly related to the concomitant role of the stratospheric polar vortex, with the Eurasian snow cover acting as a positive feedback for the AO variability in winter. No robust influence of the SIC variability is found, as the sea ice loss in these simulations only drives an insignificant fraction of the snow cover anomalies, with few agreements among models.