不同纬度天气尺度扰动影响2020年夏季梅汛期降水的数值模拟
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国家重点研发计划项目(2018YFC1505802);国家自然科学基金重点项目(41930969)


Numerical simulation of effects of synoptic scale disturbances at different latitudes on Meiyu precipitation in 2020
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    摘要:

    利用观测资料和区域气候模式RegCM4.6,研究了高纬和低纬天气尺度扰动对2020年梅雨期降水的可能影响。观测分析表明:2020年6月、7月长江中下游降水在周期上表现为10 d以下的天气尺度扰动,在降水过程中存在多次中高纬度天气尺度扰动的南传与低纬扰动的北传。在此基础上,设计改变不同纬度天气尺度扰动(<10 d)输入的侧边界敏感性试验。数值模拟结果表明:从平均环流来看,当中高纬西北侧边界的天气尺度扰动减弱时,大气平均环流动能向天气尺度扰动动能转换的位置发生北移,影响副高北侧纬向西风带北移,使得梅雨期降水中心从长江中下游地区北移到淮河流域;从时间演变来看,当去除中高纬西北侧边界的天气尺度扰动时,850 hPa上E矢量散度南传减弱,低纬纬向风异常能够向北传播。纬向风异常产生的涡度变化有利于副热带高压北抬,使得雨带可以较早北抬到34°N以北,标志江淮地区出梅。低纬南侧边界的天气尺度扰动减弱时,梅雨期降水略有增强,但对雨带的进退影响较小。因此,观测和数值模拟结果表明,2020年夏季梅雨期降水强度和雨带的维持主要与中高纬度天气尺度扰动异常密切相关,中国北部尤其中国西北部到巴尔喀什湖地区天气尺度扰动偏强且南传是此次梅雨强度偏强和雨带维持的重要原因。

    Abstract:

    Based on the observations and the regional climate model (RegCM4.6),this paper analyzes the possible effects of synoptic scale disturbances at mid-high latitudes and low latitude on the precipitation of Meiyu period in 2020.The observation analysis shows that in June and July of 2020,the precipitation in the middle and lower reaches of the Yangtze River shows a synoptic scale disturbance of less than 10 d in the period,and there are many times of synoptic scale disturbances in middle and high latitudes (low latitude) propagating southward (northward).On this basis,the side boundary sensitivity experiments are designed to change the input of synoptic scale disturbances (<10 d) at different latitudes.Numerical simulation results show that from the perspective of average circulation,when the synoptic scale disturbances on the northwest boundary of middle and high latitudes weaken,the conversion position from the kinetic energy of atmospheric average circulation to the kinetic energy of synoptic scale disturbance moves northward,which affects the northward movement of the westerly belt on the north side of the subtropical high,and makes the precipitation center move northward from the middle and lower reaches of the Yangtze River to the Huaihe River Basin during the Meiyu period.From the perspective of time evolution,when the synoptic scale disturbances on the northwest boundary of middle and high latitudes is removed,the southward propagation of E vector divergence at 850 hPa weakens,and the low latitude zonal wind anomaly can propagate to the north.The vorticity change caused by zonal wind anomaly is beneficial to the northward uplift of subtropical high,which makes the rain belt move northward to the north of 34°N earlier,marking the end of Meiyu season in Jianghuai region.However,when the synoptic scale disturbances on the south boundary of low latitude weaken,the precipitation increases lightly,but there is little influence on the advance and retreat of rain belt during the Meiyu period.It can be seen that the intensity of precipitation and the maintenance of rain belt during the Meiyu period in the summer of 2020 are closely related to the synoptic scale disturbance anomalies in the middle and high latitudes.The strong synoptic scale disturbances in northern China,especially from Northwest China to Lake Balkhash,and its southward propagation are the important reasons for the strong intensity of the Meiyu precipitation and the maintenance of the rain belt.

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王晨宇,姚素香,黄安宁,高千惠.2021.不同纬度天气尺度扰动影响2020年夏季梅汛期降水的数值模拟【J】大气科学学报.44.2:228.239

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  • 收稿日期:2020-11-22
  • 最后修改日期:2020-12-20
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  • 在线发布日期: 2021-04-25
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