Indicators and trends of polar cold airmass
Indicators and trends of polar cold airmass
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DOI：
10.1088/1748-9326/aaf42b
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发表时间：
2019-02
影响因子：
6.7
通讯作者：
Y. Kanno;J. Walsh;M. R. Abdillah;J. Yamaguchi;T. Iwasaki
中科院分区：
文献类型：
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作者：
Y. Kanno;J. Walsh;M. R. Abdillah;J. Yamaguchi;T. Iwasaki
对1959-2018年60年期间北极和北方半球冷气团数量的趋势和变化进行了评估。这两个指标是（1）极地冷空气质量（PCAM），这是低于潜在温度阈值的空气量，以及（2）负热含量（NHC），其中包括冷度加权。由于寒冷的指标是基于大气中的多个层，因此它们为评估变暖提供了一个比单独的地表气温更全面的框架。当阈值为245 K而不是280 K时，PCAM和NHC的负趋势更强（每十年的百分比），表明极冷空气的损失比中等冷空气的损失更快。冷空气的损失已经加速，因为NHC的损失是近几十年来（1989-2018）最快的。PCAM和NHC趋势的空间模式提供了北极放大的另一种表现。在各种遥相关指数中，大西洋年代际涛动与空间综合指标的中度寒冷相关性最强。若干太平洋指数也与这些指标密切相关。然而，极冷空气质量的数量与这里使用的内部变率指数没有显着的相关性。
Trends and variations in the amount of cold airmass in the Arctic and the Northern Hemisphere are evaluated for the 60 year period, 1959–2018. The two indicators are (1) polar cold air mass (PCAM), which is the amount of air below a potential temperature threshold, and (2) negative heat content (NHC), which includes a weighting by coldness. Because the metrics of coldness are based on multiple layers in the atmosphere, they provide a more comprehensive framework for assessment of warming than is provided by surface air temperatures alone. The negative trends of PCAM and NHC are stronger (as a % per decade) when the threshold is 245 K rather than 280 K, indicating that the loss of extremely cold air is happening at a faster rate than the loss of moderately cold air. The loss of cold air has accelerated, as the most rapid loss of NHC has occurred in recent decades (1989–2018). The spatial patterns of the trends of PCAM and NHC provide another manifestation of Arctic amplification. Of the various teleconnection indices, the Atlantic Multidecadal Oscillation shows the strongest correlations with the spatially integrated metrics of moderate coldness. Several Pacific indices also correlate significantly with these indicators. However, the amount of extremely cold air mass does not correlate significantly with the indices of internal variability used here.