双月刊

ISSN 1006-9895

CN 11-1768/O4

BSISO演变特征及其与华北夏季降水的关系
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天津市气候中心

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中国气象局创新发展专项“华北夏季降水监测预测及应用技术研究”,国家重点专项(2018YFA0606300),中国科学院战略性先导科技专项(XDA20100304),国家自然科学基金重大项目(41790471)


Evolution characteristics of BSISO and its relationship withsummer precipitation in North China
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Tianjin Climate Center,Tainjin City,300074.

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    摘要:

    本文采用1981-2010年夏季5-10月逐日的10°S-50°N、40-160°E范围内向外长波辐射OLR资料和850 hPa层纬向风速u资料作经验正交分解(简称EOF),重新定义计算了北半球夏季大气低频振荡(boreal summer intraseasonal oscillation,简称BSISO)BSISO指数,并分析了其演变特征及其与对华北夏季降水的影响规律。结果如下:(1)在北半球夏季印度洋-西北太平洋地区存在两种明显的低频信号,一种是BSISO1,空间分布呈西北-东南倾斜状,从热带印度洋向东北方向传播,振荡周期约为45d左右;另一种是BSISO2,空间分布呈西南-东北倾斜状,从西北太平洋向西北方向传播,振荡周期约为15d左右。(2)BSISO主要是通过影响环流异常和水汽输送异常来影响华北夏季降水过程。在500hPa层,BSISO信号会造成华北地区东部副热带高压位置南北移动和强度发生变化来影响华北夏季降水过程的;在850 hPa层,BSISO信号会通过伴随的气旋性或反气旋性异常环流影响向华北的水汽输送以及辐合辐散来影响华北夏季降水过程的。(3)虽然MJO信号在全年都存在,但其变化在冬半年尤其冬季振幅最大,在夏季最小。而BSISO信号变化在夏半年尤其夏季振幅最大。因此,利用热带大气低频信号开展延伸期预测,冬半年可以重点考虑MJO的影响,夏半年重点考虑BSISO的影响。

    Abstract:

    In this paper, we redefine and calculate boreal summer intraseasonal oscillation(BSISO)index by making empirical orthogonal decomposition (EOF) using the OLR data and the 850 hPa zonal wind velocity u data over 10°S-50°N, 40-160°E from May to October in 1981-2010. The evolution characteristics of BSISO and its influence on summer precipitation in North China are analyzed. The results are as follows: (1) there are two obvious low frequency signals in the Indian Ocean-Northwest Pacific region in summer. One is BSISO1, which is inclined from northwest to southeast and propagates from the tropical Indian Ocean to northeast with an oscillation period of about 45 days. The other is BSISO2, which is inclined from southwest to northeast and propagates from the Northwest Pacific to the northwest with an oscillation period of about 15 days. (2) BSISO affects the summer precipitation process in North China mainly by influencing circulation anomalies and water vapor transport anomalies. At 500hPa, BSISO signal will cause the North-South movement and intensity change of the subtropical high in the east of North China to affect the summer precipitation process in North China. At 850 hPa, BSISO signal will affect the water vapor transport to North China and the convergence and divergence through the associated cyclonic or anticyclonic anomalous circulation to influence the summer precipitation process in North China. (3) Although MJO signal exists throughout the year, its amplitude is the largest in winter half year, especially in winter, and the minimum in summer. The amplitude of BSISO signal is the largest in summer half year, especially in summer. Therefore, using the low frequency signal of tropical atmosphere to predict the extension period, winter half year can focus on consideration the impact of MJO and summer half year focus on consideration the impact of BSISO.

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  • 收稿日期:2020-12-02
  • 最后修改日期:2021-01-11
  • 录用日期:2021-02-23
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