The Alaska Blocking Index, version 2: Analysis and covariability with statewide and large-scale climate from 1948 to 2020,International Journal of Climatology

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The Alaska Blocking Index, version 2: Analysis and covariability with statewide and large-scale climate from 1948 to 2020
International Journal of Climatology ( IF 3.5 ) Pub Date : 2022-09-12 , DOI: 10.1002/joc.7864
Thomas J. Ballinger ₁ , John E. Walsh ₁ , Vladimir A. Alexeev ₁ , Peter A. Bieniek ₁ , Jordan T. McLeod ₂

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Monitoring and quantifying high-latitude atmospheric circulation variability and trends are important towards understanding the anatomy of extreme events and constraining their probabilities under continued Arctic change. The greater Alaska region stands out as one region of enhanced warming and environmental changes over the Arctic amplification era, which has shown proclivity to extreme events and speaks to the need to consistently monitor overlying atmospheric variability. In this paper, we describe the creation and analysis of an updated, daily mid-tropospheric Alaska Blocking Index (ABI) time series from 1948 to 2020. Sensitivity testing and index modifications from the initial dataset are discussed, and the new ABI is evaluated over the full period and subperiods. Additionally, we assess the role of the ABI as a regional climate indicator by analysing its variability against surface air temperature and precipitation from 13 climate divisions across Alaska as well as broader-scale hemispheric temperatures. Months of the highest ABI means mainly transpired in the most recent climatological period, 1991–2020, and most notably during the spring and autumn transition seasons, reflecting the nonstationary nature of the jet stream magnitude through time atop Alaska. ABI trends are positive across all months, seasons, and annually only in the 1991–2020 period. Contemporaneous ABI values are strongly and positively correlated with air temperature across all Alaskan climate divisions during the warm season, but negatively correlated with winter temperatures over southeastern Alaska. Meanwhile, the ABI is significantly anticorrelated with summer precipitation over Interior and southern Alaska, but only over southeastern Alaska in other seasons. The ABI is statistically differentiated from the primary modes of atmospheric variability as shown by its generally weak correlations with the Arctic Dipole and the Arctic Oscillation (r ≤ 0.40).

中文翻译：

阿拉斯加阻塞指数，第 2 版：1948 年至 2020 年全州和大尺度气候的分析和协变性

监测和量化高纬度大气环流变率和趋势对于了解极端事件的解剖结构和限制北极持续变化下的概率非常重要。大阿拉斯加地区作为北极放大时代变暖和环境变化加剧的地区之一脱颖而出，该地区显示出极端事件的倾向，并说明需要持续监测上层大气变化。在本文中，我们描述了从 1948 年到 2020 年更新的每日对流层中层阿拉斯加阻塞指数 (ABI) 时间序列的创建和分析。讨论了对初始数据集的敏感性测试和指数修改，并评估了新的 ABI全期和分期。此外，我们通过分析 ABI 对阿拉斯加 13 个气候分区的地表气温和降水以及更广泛的半球温度的变异性，来评估 ABI 作为区域气候指标的作用。最高 ABI 的月份主要发生在最近的气候时期，即 1991-2020 年，尤其是在春季和秋季过渡季节，反映了阿拉斯加顶部急流强度随时间变化的非平稳性。ABI 趋势在所有月份、季节和每年仅在 1991-2020 年期间都是积极的。在温暖季节，同期的 ABI 值与阿拉斯加所有气候分区的气温呈强烈正相关，但与阿拉斯加东南部的冬季气温呈负相关。同时，ABI 与阿拉斯加内陆和南部的夏季降水显着反相关，但仅在其他季节与阿拉斯加东南部的降水相关。ABI 在统计上与大气变率的主要模式不同，如其与北极偶极子和北极涛动的相关性普遍较弱所示（r ≤ 0.40)。

更新日期：2022-09-12

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