Projected Changes in Daily Variability and Seasonal Cycle of Near-Surface Air Temperature over the Globe during the Twenty-First Century
Projected Changes in Daily Variability and Seasonal Cycle of Near-Surface Air Temperature over the Globe during the Twenty-First Century
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DOI：
10.1175/jcli-d-19-0438.1
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发表时间：
2019-12-01
影响因子：
4.9
通讯作者：
Zhang, Yaocun
中科院分区：
文献类型：
--
作者：
Chen, Jiao;Dai, Aiguo;Zhang, Yaocun
大气中温室气体的增加不仅会使地球温度升高，而且还可能改变其变化和季节循环。在这里，CMIP 5模式数据进行分析，以量化这些变化的地面空气温度（Tas）和调查的基础过程。这些模型很好地捕捉了平均Tas季节性周期和变率及其在再分析中的变化，这表明从1979年到2017年，北极和南大洋的Tas季节性振幅和变率都在下降。预计在21世纪，高纬度地区的Tas日变率和季节振幅将减少（除了北方夏季Tas变率增加），但在低纬度地区会增加。最大或最小Tas日在高纬度海洋有较大的延迟，而在低纬度变化不大。高纬度地区的这些Tas变化与变暖和海冰损失的极地放大有关，由于寒冷季节海洋的额外加热，冬季的变暖比夏季更大。海冰覆盖的减少也降低了其引起Tas变化的能力，有助于降低高纬度Tas的变化。在中低纬度海洋，冬季表面蒸发的增加比夏季大（由于冬季强风，南半球冬季风增强，北方半球低纬度地区冬季表面湿度梯度增加），加上冬季强烈的海洋混合，导致冬季表面变暖比夏季小，从而增加了季节振幅。这些变化导致高（低）纬Tas分布变窄（变宽），这可能对其他相关领域具有重要意义。
Increases in atmospheric greenhouse gases will not only raise Earth's temperature but may also change its variability and seasonal cycle. Here CMIP5 model data are analyzed to quantify these changes in surface air temperature (Tas) and investigate the underlying processes. The models capture well the mean Tas seasonal cycle and variability and their changes in reanalysis, which shows decreasing Tas seasonal amplitudes and variability over the Arctic and Southern Ocean from 1979 to 2017. Daily Tas variability and seasonal amplitude are projected to decrease in the twenty-first century at high latitudes (except for boreal summer when Tas variability increases) but increase at low latitudes. The day of the maximum or minimum Tas shows large delays over high-latitude oceans, while it changes little at low latitudes. These Tas changes at high latitudes are linked to the polar amplification of warming and sea ice loss, which cause larger warming in winter than summer due to extra heating from the ocean during the cold season. Reduced sea ice cover also decreases its ability to cause Tas variations, contributing to the decreased Tas variability at high latitudes. Over low-midlatitude oceans, larger increases in surface evaporation in winter than summer (due to strong winter winds, strengthened winter winds in the Southern Hemisphere, and increased winter surface humidity gradients over the Northern Hemisphere low latitudes), coupled with strong ocean mixing in winter, lead to smaller surface warming in winter than summer and thus increased seasonal amplitudes there. These changes result in narrower (wider) Tas distributions over the high (low) latitudes, which may have important implications for other related fields.