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CN 11-1768/O4

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引发强降水的一次东移高原云团的能量演变特征研究
作者:
作者单位:

1.中国气象局武汉暴雨研究所;2.中国科学院大气物理研究所;3.黄岛区气象局

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基金项目:

(91637211,41975058,41620104009,41775046),科技部国家重点研究计划项目(2018YFC1507200)Funded by National Nature Science Foundation of China (Grant 91637211,41975058, 41620104009,and 41775046), and the National Key Research and Development Plan (Grant 2018YFC1507200)


Energy evolution characteristics of an eastward-moving convective cloud cluster producing heavy precipitation that originates from the Tibetan Plateau
Author:
Affiliation:

1.Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research,Institute of Heavy Rain,China Meteorological Administration;2.Institute of Atmospheric Physics,Chinese Academy of Sciences;3.Huangdao Sub-administration of Qingdao Meteorological Administration

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    摘要:

    利用日本气象厅葵花-8卫星资料、欧洲中心ERA5再分析资料,根据时间尺度分解的局地能量诊断方法,本文从能量学等多个角度研究了2016年6月5日至6日(持续40小时)一次东移并引发强降水的高原对流云团,得到了以下主要结论。本次事件中,高原东移对流云团在不同阶段的主要影响系统有所不同。移出高原前,其主要受高原涡和高原短波槽的共同影响,随着云团移出高原,高原涡消亡,而高原短波槽则随时间发展加强,成为东移云团的最主要影响系统。高原东移对流云团具有显著的深对流特征,自西向东引发了一系列的降水,移出高原后,其对流重心显著降低,降水达到最强。不同阶段高原东移对流云团的能量转换特征显著不同。云团位于高原上时,背景场通过动能的降尺度能量级串为造成强降水的扰动流直接提供能量,这是此阶段扰动流动能维持的主要方式;云团移出高原过程中,降水凝结潜热明显增强,由此制造的扰动有效位能也显著增强。在垂直运动配合下,扰动有效位能斜压释放所制造的动能是本阶段造成强降水扰动流动能维持的最主要能量来源;云团移出高原后,背景场对造成强降水扰动流的影响再次增强,但是不同于第一阶段直接影响方式,该阶段背景场的作用是一种间接的影响方式出现。其首先通过有效位能的降尺度级串将背景场的有效位能转换为扰动流的有效位能,然后通过扰动有效位能的斜压能量释放为扰动流的动能维持不断地提供能量。此外,本阶段内还出现了扰动流向背景场动能的升尺度级串供给(即扰动流的反馈),但其强度不足以对背景场的演变产生显著影响。

    Abstract:

    Based on the Himawari-8 satellite TBB data from the Japan Meteorological Agency, the ERA5 reanalysis data from ECMWF and a new energy diagnostic method that uses temporal scale for scale separation, evolutionary characteristics of a convective cloud cluster (lasted 40 hours from 05:00 June 5th to 06:15 6th, 2016) that formed over the Tibetan Plateau (TP), moved eastward and induced heavy precipitation in downstream regions was investigated in this study. Main findings are listed as follows: the main influencing systems for the eastward-moving convective cloud cluster at different stages of its lifespan were different. Before moving out of the plateau, the cloud cluster was mainly affected by a plateau vortex and a short-wave trough. As the cloud cluster vacated the plateau, the plateau vortex dissipated, whereas the short-wave trough intensified with time, and finally the short-wave trough became the main influencing system of the cloud. The deep convection features of the eastward-moving cloud cluster were significant. The eastward-moving cloud cluster induced a series of precipitation from west to east, with the strongest precipitation occurred after it had moved out of the plateau and its convective barycenter lowered in height. The energetics characteristics of the eastward-moving convective cloud cluster experienced notable changes during its lifespan, and the associated precipitation characteristics were also significantly different. When the cloud cluster was over the TP (the first stage), the contribution from the background field was a dominant factor. The background filed provided energy for the evolution of eddy flow [by downscale kinetic energy (KE) cascade] which induced heavy precipitation directly. During the second stage, the precipitation-related latent heating was greatly enhanced, which significantly increased available potential energy (APE) of eddy flow. Under the influences of vertical motion, APE of eddy flow was released and converted to KE of eddy flow. This acted as a dominant factor for the sustainment of the precipitation-related eddy flow. When the cloud cluster moved out of the TP, the influence from background field on eddy flow enhanced again, however it was different from the direct influencing way that appeared at the first stage. In this stage, the influence from background environment favored the persistence of precipitation-related eddy flow indirectly. First, APE of the background filed transferred to APE of eddy flow through a downscale energy cascade. Then, a baroclinic energy conversion from APE of the eddy flow to its KE occurred. This acted as a dominant energy source for KE of eddy flow. Furthermore, in the third stage, a remarkable upscale energy cascade of KE was found, which reflected the feedback of eddy flow on its background field. However, the feedback intensity was not enough to affect evolution of the background field obviously.

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  • 收稿日期:2019-09-18
  • 最后修改日期:2019-12-18
  • 录用日期:2019-12-18
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