基于CMA-BJ数值预报模式产品的复杂地形下冬奥站点地面气温和风速预报方法研究

Forecasting surface temperature and wind speed at Winter Olympics stations over complex terrain based on the CMA-BJ model products

  • 摘要: 北京冬奥服务对站点气象要素预报提出了明确需求,2 m气温预报偏差在±2℃以内,10 m风速预报平均偏差小于观测的30%,文中提出一种基于相似集合嵌套一元线性回归的预报方法—嵌套相似集合(AnEn-Ne),该方法基于相似集合思路,在满足一定条件时,启动其嵌套一元线性回归提供订正预报。冬奥赛期(2021年11月1日—2022年3月15日)实时业务预报表明,嵌套相似集合具有较好的预报效果,相对业务数值模式(CMA-BJ)预报,预报精度显著提高,相对相似集合预报和一元线性回归预报精度明显提高,其预报结果满足冬奥服务需求。复杂地形下的要素预报检验表明,CMA-BJ模式预报2 m气温虽然存在较明显的系统偏差,但与观测相关较强,对观测的表征意义明显,订正后能有效消除复杂地形影响,10 m风速模式预报偏差振荡明显,模式预报与观测相关较弱,表征意义差,订正后站间差异明显;改进CMA-BJ模式复杂地形区近地面风速预报对观测的表征意义,可进一步提高该预报方法对10 m风速订正预报的精度。

     

    Abstract: Beijing Winter Olympic service has made a clear request for prediction of weather elements at individual sites. The 2 m temperature forecast bias is less than ±2℃, and 10 m wind speed forecast bias is less than 30% of observation average. This paper proposes a forecast method based on analog ensemble (AnEn) nested linear regression (LR)—analog ensemble nested linear regression (AnEn-Ne). When certain conditions are met, the nested linear regression is activated to provide revised forecasts. The real-time operational forecasts during the Winter Olympic period (1 November 2021 to 15 March 2022) show that the AnEn-Ne method has a better forecast effect. Compared with that of the CMA-BJ, the forecast accuracy of the AnEn-Ne is improved significantly; compared with that of AnEn and LR, the forecast accuracy of the AnEn-Ne is obviously improved, and the forecasts meet the service demand at the Winter Olympic stations. The verification of forecasted elements in complex terrain area shows that, despite an obvious systematic deviation of 2 m temperature in the forecast by the CMA-BJ, the forecasts are strongly correlated with observations and show an obvious representation of observations, and the influence of complex terrain can be effectively eliminated after correction. The CMA-BJ forecast Bias of 10 m wind speed demonstrates an oscillation feature, and the correlation between the model forecasts and observations is weak, indicating a poor model representation of surface wind. The differences in 10 m wind speed between stations are obvious after correction. Improving the representation of the CMA-BJ model on surface wind speed prediction in complex terrain areas can further improve the accuracy of the method for the correction of 10 m wind speed prediction.

     

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