The precipitation distribution set by eddy fluxes: the case of boreal winter
The precipitation distribution set by eddy fluxes: the case of boreal winter
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涡通量决定的降水分布：以北半球冬季为例
DOI：
10.1038/s41612-023-00356-9
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发表时间：
2023
影响因子：
9
通讯作者：
Lee, Sukyoung
中科院分区：
文献类型：
--
作者：
Yoo, Changhyun;Lee, Sukyoung
降水量的纬向分布表现为中纬度次高，亚热带最低。这个最小值被广泛地归因于欧拉Hadley环流的下降分支。然而，这项研究表明，降水分布与转换后的欧拉平均（TEM）垂直运动更紧密地结合在一起。在北方半球冬季，TEM最大下降（上升）和降水最小（最大）位置在~20°N（~40°N）。大尺度涡旋的纬向动量通量是副热带下沉的主要驱动力，而中纬度上升则是由涡旋的纬向热量通量驱动的。而当涡动动量通量足够强时，次降水峰值向60°N移动，对应于涡动动量通量驱动的TEM上升位置。降水的水分供应是通过蒸发来帮助的，在TEM下降分支从对流层上部/平流层下部带来干燥空气的地方，蒸发得到加强。这幅图让人想起天气学中的干空气入侵，表明下降分支可能体现了干空气入侵的纬向平均表达。湿空气沿TEM上升分支上升，表明上升分支可解释为暖输送带的纬向平均表达。因此，这项研究提供了一个大尺度的动力学角度的天气学描述的降水系统。这里的研究结果还表明，涡动动量通量的未来变化，这是知之甚少，可以在确定未来的降水分布中发挥关键作用。
The latitudinal precipitation distribution shows a secondary peak in midlatitudes and a minimum in the subtropics. This minimum is widely attributed to the descending branch of the Eulerian Hadley cell. This study however shows that the precipitation distribution aligns more closely with the transformed Eulerian mean (TEM) vertical motion. In Northern Hemisphere winter, maximum TEM descent (ascent) and precipitation minimum (maximum) are collocated at ~20°N (~40°N). The subtropical descent is mostly driven by the meridional flux of zonal momentum by large-scale eddies, while the midlatitude ascent is driven by the meridional flux of heat by the eddies. When the poleward eddy momentum flux is sufficiently strong, however, the secondary precipitation peak shifts to 60°N corresponding to the location of the TEM ascent driven by the eddy momentum flux. Moisture supply for the precipitation is aided by evaporation which is enhanced where the TEM descending branch brings down dry air from the upper troposphere/lower stratosphere. This picture is reminiscent of dry air intrusions in synoptic meteorology, suggesting that the descending branch may embody a zonal mean expression of dry air intrusions. Moist air rises following the TEM ascending branch, suggesting that the ascending branch may be interpreted as a zonal mean expression of warm conveyor belts. This study thus offers a large-scale dynamics perspective of the synoptic description of precipitation systems. The findings here also suggest that future changes in the eddy momentum flux, which is poorly understood, could play a pivotal role in determining the future precipitation distribution.
影响因子：
8.9
作者：
M. Juckes
通讯作者：
M. Juckes
影响因子：
5.2
作者：
Hawcroft, M. K.;Shaffrey, L. C.;Dacre, H. F.
通讯作者：
Dacre, H. F.
以等熵线上方的质量为纵坐标的大气平均经向环流
DOI：
--
发表时间：
2013
期刊：
影响因子：
--
作者：
Gang Chen
通讯作者：
Gang Chen