Modulation of the Seasonal Cycle in Length-of-Day and Atmospheric Angular Momentum
Modulation of the Seasonal Cycle in Length-of-Day and Atmospheric Angular Momentum
复制标题
日长和大气角动量的季节周期调节
DOI：
10.1007/978-3-662-04709-5_76
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发表时间：
2002
影响因子：
3.4
通讯作者：
J. Dickey
中科院分区：
文献类型：
--
作者：
R. Gross;S. Marcus;J. Dickey
根据定义，全球变暖会改变大气温度场。这种温度变化预计不会是均匀的，无论是在地理上，还是在大气中的高度。根据热力风方程，极赤道温度梯度的变化会引起大气纬向风的变化。许多以前的研究表明，在几天到几年的时间尺度上观测到的日长(LOD)变化主要是由大气纬向风波动引起的。特别是，LOD的季节变化以前被证明主要是由大气纬向风的季节变化引起的。本文分析了1962-2000年间观测到的季节LOD强度变化和风致大气角动量信号的变化，发现它们之间存在显著的相关性，并与南方涛动指数显著相关。这表明，观测到的季节LOD信号可以作为季节性纬向风角动量变化的替代测量，从而即使在没有风测量的情况下也可以研究季节性纬向风的变化。此外，研究季节循环强度的十年尺度变化的方法允许LOD测量用于气候变化研究，这些研究由于对核-地幔边界过程引起的LOD的主要十年尺度变化进行建模的不确定性而不能直接进行。
Global warming, by definition, changes the atmospheric temperature field . This temperature change is not expected to be uniform, either geographically, or with height in the atmosphere. By the thermal wind equation, changes in the poleto-equator temperature gradient will cause changes in the atmospheric zonal winds. Numerous previous studies have shown that observed length-of-day (LOD) variations on time scales of a few days to a few years are largely caused by atmospheric zonal wind fluctuations. In particular, seasonal variations in LOD have been previously shown to be dominantly caused by seasonal variations in the atmospheric zonal winds. Here, observed changes in the strength of seasonal LOD and wind-driven atmospheric angular momentum signals during 1962 to 2000 are analyzed and shown to be significantly correlated with each other and with the Southern Oscillation Index. This demonstrates that the observed seasonal LOD signal can be used as a proxy measurement for changes in the angular momentum of the seasonal zonal winds, thereby allowing changes in the seasonal zonal winds to be studied even when wind measurements are not available. In addition, the approach of studying decadal-scale changes in the strength of the seasonal cycle allows LOD measurements to be used in climate change studies, studies that cannot be undertaken directly due to uncertainties in modeling the dominant decadal-scale changes in LOD caused by core-mantle boundary processes.