Energy budgets on the interactions between the mean and eddy flows during a persistent heavy rainfall event over the Yangtze River valley in summer 2010
Energy budgets on the interactions between the mean and eddy flows during a persistent heavy rainfall event over the Yangtze River valley in summer 2010
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2010年夏季长江流域持续强降雨过程中平均流与涡流相互作用的能量收支
DOI：
10.1007/s13351-016-5121-3
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发表时间：
2016
影响因子：
3.2
通讯作者：
Zhang Yuanchun
中科院分区：
文献类型：
--
作者：
Fu Shenming;Wang Huijie;Sun Jianhua;Zhang Yuanchun
在这项研究中，一次持续了9天左右(从2010年0000UTC 17到0000UTC 26时)的持续强降雨过程(PHRE)在长江流域造成了600 mm以上的累积降水，这一过程被高级研究WRF模式合理地再现。在模拟的基础上，计算了一组能量收支方程，将实际气象场划分为平均流和涡流，以了解与降水相关的涡流及其背景环流(BCS)之间的相互作用。结果表明，在PHRE过程中，与降水相关的涡流与其BCS发生了强烈的相互作用。在不同层次上，能量循环表现出明显的特征。在对流层高层，出现了低尺度的能量级联过程，有利于高层涡流的维持；同时，也发生了斜压能量转换，减少了高层急流。在对流层中层，出现了明显的高尺度能量级联过程，反映了涡流对其边界层边界条件的反作用。对于BCS的演化来说，这些效应是不能忽略的，并且在动力场中的反应性效应比在热力学中的要强。在对流层低层，一条长时间的准静止低层切变线是PHRE的直接触发。相应的涡流主要通过与对流活动相关的斜压能量转换来维持。此外，反映BCS对与降水有关的涡流的直接影响的低尺度动能级联过程也是有利的。对流层下部还出现了尺度减小的(火用)能量级联，通过斜压能量转换间接有利于与降水相关的涡流。
In this study, a persistent heavy rainfall event (PHRE) that lasted for around 9 days (from 0000 UTC 17 to 0000 UTC 26 June 2010) and caused accumulated precipitation above 600 mm over the Yangtze River valley, was reasonably reproduced by the advanced research WRF model. Based on the simulation, a set of energy budget equations that divided the real meteorological field into the mean and eddy flows were calculated so as to understand the interactions between the precipitation-related eddy flows and their background circulations (BCs). The results indicated that the precipitation-related eddy flows interacted with their BCs intensely during the PHRE. At different layers, the energy cycles showed distinct characteristics. In the upper troposphere, downscaled energy cascade processes appeared, which favored the maintenance of upper-level eddy flows; whereas, a baroclinic energy conversion, which reduced the upper-level jet, also occurred. In the middle troposphere, significant upscaled energy cascade processes, which reflect the eddy flows’ reactionary effects on their BCs, appeared. These effects cannot be ignored with respect to the BCs’ evolution, and the reactionary effects were stronger in the dynamical field than in the thermodynamical field. In the lower troposphere, a long-lived quasi-stationary lower-level shear line was the direct trigger for the PHRE. The corresponding eddy flows were sustained mainly through the baroclinic energy conversion associated with convection activities. Alongside this, the downscaled energy cascade processes of kinetic energy, which reflect the direct influences of BCs on the precipitation-related eddy flows, were also favorable. A downscaled energy cascade of exergy also appeared in the lower troposphere, which favored the precipitation-related eddy flow indirectly via the baroclinic energy conversion.