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基于朴素贝叶斯方法的浙江省夏季短时强降水潜势预报模型研究

Research of a Naive Bayesian method-based potential forecast model for short-duration heavy rainfall during summer in Zhejiang Province

  • 摘要: 短时强降水是强对流天气的重要类型之一,浙江省地处华东沿海,夏季短时强降水频发。为提高浙江省短时强降水的预报能力,本文利用2010—2023年6—8月浙江省内国家和区域级气象观测站逐小时雨量观测数据、ERA5再分析资料和细网格数值预报产品,首先分析了短时强降水发生前环境参数分布特征;然后利用点双列相关分析优选了预报因子;最后基于朴素贝叶斯方法建立了浙江省夏季短时强降水潜势预报模型,并对模型作评估和不同天气形势下的个例预报检验。结果表明:(1) 对流有效位能(CAPE)、整层大气可降水量(PWAT)、大气低层相对湿度(RH700RH850)、大气低层比湿(q700q850)和中下层垂直风切变(SHR03和SHR06)为浙江省短时强降水优选预报因子。夏季发生短时强降水前,CAPE中位值为738 J·kg−1,PWAT为56.7 mm,RH700和RH850分别为79.8%和86.1%,q700和q850分别为9.5 g·kg−1和14.8 g·kg−1,SHR03和SHR06分别为6 m·s−1和7 m·s−1。(2) 对2023年6—8月浙江省短时强降水天气过程进行试报和检验评估,模型提前3 h、6 h和12 h的POD分别为94.9%、91.6%和90.5%,TS分别为58.4%、64.0%和58.2%,表明该潜势预报模型在短时强降水天气的预报中具有一定的适用性。(3) 模型对2023年夏季梅雨锋型、副高边缘型和高空槽型短时强降水过程不同预报时效的POD均达到95%,MAR均低于8%,对副高控制型强降水过程的POD达到80%,表明该模型对不同天气形势下短时强降水的潜势预报均有一定的指示意义,有较好的应用价值。

     

    Abstract: Short-duration heavy rainfall (SDHR) is one of the types of severe convective weather. Located on the coast of East China, Zhejiang Province experiences frequent SDHR events during summer. To improve the forecasting capability for SDHR in Zhejiang, this study utilizes hour rain gauge data from national and regional meteorological stations in Zhejiang Province, ERA5 reanalysis and fine-grid numerical forecast products during June to August from 2010 to 2023. First, the distribution characteristics of environmental parameters prior to the occurrence of SDHR are analyzed. Then, the forecast predictors are optimized using point-biserial correlation analysis. Finally, a potential forecast model for summer short-duration heavy rainfall in Zhejiang Province is established based on the naive Bayesian method, and the model is evaluated under different weather patterns. The results show that: (1) Convective available potential energy (CAPE), precipitable water (PWAT), lower-level relative humidity (RH700 and RH850), lower-level specific humidity (q700 and q850), and mid-to-lower level vertical wind shear (SHR03 and SHR06) are optimal predictors for SDHR in Zhejiang Province. Before the occurrence of SDHR, the median values of CAPE, PWAT, RH700, RH850, q700, q850, SHR03 and SHR06 are 738 J·kg-1, 56.7 mm, 79.8%, 86.1%, 9.5 g·kg-1, 14.8 g·kg-1, 6 m·s-1 and 7 m·s-1, respectively. (2) The model was tested and evaluated for short-duration heavy rainfall events in Zhejiang Province from June to August 2023. The POD at lead times of 3 h, 6 h, and 12 h is 94.9%, 91.6% and 90.5% respectively, and the TS are 58.4%, 64.0% and 58.2%, indicating that the potential forecast model has reasonable applicability for forecasting SDHR events. (3) For the Meiyu-front-type, subtropical-high-edge-type, and upper-level-trough-type short-duration heavy rainfall events in the summer of 2023, the model achieves a POD of 95% at all lead times, with a MAR below 8% for these three types. For the subtropical-high-controlled-type heavy rainfall event, the POD reaches 80%. These results demonstrate that the model provides useful indications for the potential forecasting of SDHR under different weather patterns and has good application value.

     

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