Clouds, warm air, and a climate cooling signal over the summer Arctic
Clouds, warm air, and a climate cooling signal over the summer Arctic
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夏季北极上空的云、暖空气和气候变冷信号
DOI：
10.1002/2016gl071959
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发表时间：
2017
影响因子：
5.2
通讯作者：
M. Tjernström
中科院分区：
文献类型：
--
作者：
J. Sedlar;M. Tjernström
虽然大气温室效应总是导致地表变暖，但向太空发出的长波辐射（OLR）总是代表冷却。在热量和水分平流进入北极的过程中，对流层温度和水分的增加会影响云层，进而影响长波辐射。最先进的卫星测量和大气再分析一致显示，在热力学平流异常高的月份，夏季北极每月OLR冷却增强1.5-4 W m−2。这种冷却异常被发现是相同的幅度或略大于相关的下降流LW表面变暖异常。我们确定了大尺度环流变率和云特性变化之间的关系，允许大气表面和顶部的LW辐射响应大气热力学的变化。在暖空气异常平流的驱动下，月尺度上OLR冷却信号的增强是北极区域变暖的重要缓冲。
While the atmospheric greenhouse effect always results in a warming at the surface, outgoing longwave radiation (OLR) to space always represents a cooling. During events of heat and moisture advection into the Arctic, increases in tropospheric temperature and moisture impact clouds, in turn impacting longwave (LW) radiation. State‐of‐the‐art satellite measurements and atmospheric reanalysis consistently reveal an enhancement of summer Arctic monthly OLR cooling ranging 1.5–4 W m−2 during months with anomalously high thermodynamic advection. This cooling anomaly is found to be of the same magnitude or slightly larger than associated downwelling LW surface warming anomalies. We identify a relationship between large‐scale circulation variability and changing cloud properties permitting LW radiation at both the surface and top of the atmosphere to respond to variability in atmospheric thermodynamics. Driven by anomalous advection of warm air, the corresponding enhanced OLR cooling signal on monthly time scales represents an important buffer to regional Arctic warming.