Seasonal Asymmetries in the Lag between Insolation and Surface Temperature
Seasonal Asymmetries in the Lag between Insolation and Surface Temperature
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DOI：
10.1175/jcli-d-19-0329.1
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发表时间：
2020-05-01
影响因子：
4.9
通讯作者：
Rhines, Andy
中科院分区：
文献类型：
--
作者：
Donohoe, Aaron;Dawson, Eliza;Rhines, Andy
我们分析了地球仪表面气温的气候季节循环的时间结构。我们发现，在地球的大部分地区，地表温度的季节性周期偏离了年度谐波：秋季和春季的持续时间相差多达2个月。我们的特点是这种不对称的度量ASYM，定义为相对于夏至减去相对于冬至的季节性最低温度的相位滞后的季节性最高温度的相位滞后。我们提出了一个全球分析的ASYM从气象站数据和大气再分析，发现ASYM是很好的代表在再分析。ASYM通常在陆地上为正值，在海洋上为负值，表明春季在陆地上的持续时间较长，而秋季在海洋上的持续时间较长。然而，与欧洲相比，ASYM在北美也具有更多的正值，在极地地区的冰盖和海冰上具有负值。了解气候ASYM的根本原因可能会进一步加深我们对温度季节循环及其未来/过去变化的控制的理解。我们探讨了几个候选机制来解释ASYM的空间结构，包括1）云厚度的季节性演变对地面太阳辐射季节性循环的修改，2）海洋和陆地上空大气边界层深度季节性循环的差异，以及3）季节性演变的大气环流对温度平流的影响。
We analyze the temporal structure of the climatological seasonal cycle in surface air temperature across the globe. We find that, over large regions of Earth, the seasonal cycle of surface temperature departs from an annual harmonic: the duration of fall and spring differ by as much as 2 months. We characterize this asymmetry by the metric ASYM, defined as the phase lag of the seasonal maximum temperature relative to the summer solstice minus the phase lag of the seasonal minimum temperature relative to winter solstice. We present a global analysis of ASYM from weather station data and atmospheric reanalysis and find that ASYM is well represented in the reanalysis. ASYM generally features positive values over land and negative values over the ocean, indicating that spring has a longer duration over the land domain whereas fall has a longer duration over the ocean. However, ASYM also features more positive values over North America compared to Europe and negative values in the polar regions over ice sheets and sea ice. Understanding the root cause of the climatological ASYM will potentially further our understanding of controls on the seasonal cycle of temperature and its future/past changes. We explore several candidate mechanisms to explain the spatial structure of ASYM including 1) modification of the seasonal cycle of surface solar radiation by the seasonal evolution of cloud thickness, 2) differences in the seasonal cycle of the atmospheric boundary layer depth over ocean and over land, and 3) temperature advection by the seasonally evolving atmospheric circulation.