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CN 11-1768/O4

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WRF模式边界层参数化方案对川渝盆地西南涡降水预报的检验分析
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1.重庆市气象台;2.中国气象局成都高原气象研究所

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基金项目:

国家自然科学基金重大研究计划重点支持项目(编号:91644226);中国科学院战略性先导科技专项A类(编号:XDA23090103);四川省科技计划项目( 编号:2016JY0046);四川省气象局与南京信息工程大学局校合作项目(编号:SCJXHZ03)


Evaluation of different Planetary Boundary Layer Schemes in Simulating Precipitation Caused by Southwest China Vortex in Sichuan basin based on the WRF Model
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Institute of Plateau Meteorology

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    摘要:

    利用WRFv4.0五种边界层参数化方案(YSU、MYJ、MYNN2、ACM2和SH),对2016年所有典型的并在川渝盆地东部造成灾害性暴雨的西南涡过程进行数值模拟,检验分析了它们对各量级降水的预报能力,并采用加密的L波段秒级探空资料对比分析了模拟与实况边界层结构的差异,结合各方案对湍流运动的算法特点探讨了其差异的原因,最后对ACM2方案进行了湍流强度调整,尝试改善川渝盆地边界层与低涡降水预报。结果表明:ACM2和YSU方案Threat Score(TS)表现较好,相对其它方案ACM2空报较少,这种可以根据周围环境的稳定性切换局地或非局地算法的方案似乎更适合盆地降水模拟,然而所有边界层方案都对西南涡降水空报较普遍,尤以大量级降水明显。精细的探空资料进一步显示,所有边界层方案都对白天边界层高度模拟偏高,湍流混合强度偏强。通过参数调整而降低混合强度的ACM2方案,其边界层温湿结构更加符合实际观测,此时边界层下部温度更低、湿度更高,降低了大量级降水的空报,使盆地降水模拟有一定改善。不同边界层参数化方案对西南涡预报的差别主要体现在不同的低涡位置与降水强度,但归根结底都源于方案的局地或非局地特性,以及方案的混合强度这两方面原因,因此,根据不同下垫面环境与气候状况选择方案的特性和混合强度是对边界层结构准确模拟的关键。

    Abstract:

    Five Planetary Boundary Layer(PBL) parameterization schemes [Yonsei University(YSU), Mellor–Yamada–Janjic (MYJ), Mellor–Yamada–Nakanishi–Niino Level 2.5 (MYNN2), Shin-Hong(SH) and the Asymmetric Convective Model, version 2 (ACM2)] in Weather Research and Forecast model (WRFv4.0) are used to simulate well-developed Southwest China Vortex(SWCV) processes that caused rainstorms in the eastern Sichuan basin in 2016.Each level of precipitation prediction are verified, and the L-band radiosonde data, which has the temporal resolution by 1 second, are used to reveal the fine structure of PBL in the midday, the difference between observation and simulation are assessed, and the reason are discussed based on the characteristics of turbulence algorithm in each scheme. Finally, a parameter of turbulence intensity are adjusted for the ACM2 scheme in order to improve the structure of PBL and precipitation in Sichuan basin. The results show that: The ACM2 and YSU schemes have relatively better Threat Score(TS) performance. Compared with other schemes, ACM2 has less false alarms. The attribute of ACM2, which can switch local or non-local algorithms according to the stability of the surrounding environment, seems to be more suitable for Sichuan basin precipitation simulation. However, all PBL schemes show a high false alarm rate in prediction of the Southwest China Vortex precipitation, especially in heavier precipitation. The fine sounding data further shows that all the PBL schemes predict higher Planetary Boundary Layer Height(PBLH) than the observations, which means the simulation has stronger mixing intensity compare to the real atmosphere. Through the parameter adjustment, the ACM2 scheme with reduced mixing intensity, the potential temperature and humidity structure in PBL is more in line with the observation. Then, the potential temperature of the lower PBL is lower, the humidity is higher, and the false alarm report of heavier precipitation is reduced, so that the precipitation simulation in Sichuan basin get some improvement. The different character of the PBL schemes in simulate the Southwest China vortex is mainly lead to different position of the vortex and the precipitation intensity, but essentially, it is derived from the local or non-local attribute and the intensity of vertical mixing. The selection based on the features of research object is the key to accurate simulation of the PBL structure.

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  • 收稿日期:2019-06-13
  • 最后修改日期:2020-04-17
  • 录用日期:2020-06-10
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