Previous studies have noted the asymmetry in the annual cycle of zonal mean surface air temperature, defined as the difference in the lengths of warming and cooling periods. Pronounced north-south hemispheric differences in this asymmetry, by up to 40 days, were attributed to the eccentricity of Earth's orbit. However, we propose that the dominant factor comes from the difference in the land-sea fraction between hemispheres, because the asymmetry is strongly influenced by the annually varying heat capacity and land-sea interactions. The oceanic temperature annual cycle generally features a longer cooling period than warming due to the seasonal variation in ocean mixed layer depth, and exhibits the opposite situation when there is seasonal sea ice. Land-sea interactions impact the zonal mean temperature annual cycle by resulting in an earlier winter trough of the downstream oceanic temperature and delaying the summer peak in west coasts.

中文翻译：

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是什么导致温度年周期不对称的半球差异？


以前的研究已经注意到纬向平均地表气温年周期的不对称性，纬向平均地表气温被定义为变暖和变冷周期长度的差异。这种不对称性中南北半球的明显差异长达 40 天，这归因于地球轨道的偏心率。然而，我们认为主导因素来自半球之间陆地-海洋分数的差异，因为不对称性受到每年变化的热容量和陆地-海洋相互作用的强烈影响。由于海洋混合层深度的季节性变化，海洋温度年周期通常具有比变暖更长的冷却期，当有季节性海冰时则表现出相反的情况。陆海相互作用通过导致下游海洋温度的冬季槽提前并延迟西海岸的夏季高峰来影响纬向平均温度的年周期。