降水日变化, 业务数值模式, 偏差特征

Evaluating the bias characteristics of numerical models in the diurnal variation of precipitation is helpful to understand the

forecasting ability of the model. The key parameters such as precipitation frequency, precipitation intensity, its peak value and amplitude are calculated by using the 3 h observation data of summer precipitation, combined with the 3 h precipitation of the 12-36 h forecast time of the model in the complex terrain of the Taihang Mountains, Funiu Mountains and the areas to their east. Using the methods of deviation analysis and spatial correlation analysis, the forecast characteristics of the ECMWF (European Centre for Medium-Range Weather Forecasts) numerical forecast model, NCEP-GFS (National Centers for Environmental Prediction-Global Forecast System), CMA-TYM (the China Meteorological Administration Regional Typhoon Numerical Forecast System) and CMA-SH9 (the China Meteorological Administration Shanghai Numerical Forecast Model System) are compared with the observations, and the causes of the deviations are analyzed preliminarily. The results show that the regional models CMA-TYM and CMA-SH9 have the characteristics of “low frequency and high intensity” in precipitation forecast, while the global models ECMWF and NCEP-GFS feature “high frequency and low intensity”. Moreover, the spatial correlation between each model and the observational data is weak. In the regional models, the bias of precipitation forecast about CMA-TYM is relatively small and it fluctuates near 0, and the peak time and diurnal variation amplitude of precipitation frequency are better. The CMA-SH9 has the largest positive deviation of precipitation most of the time, and the predicted peak time and diurnal variation amplitude of precipitation intensity are the best, but the frequency of precipitation is larger and its peak time is basically in the early night, while the peak time of observations in the North China Plain, central and eastern Shandong Province and northern Huanghuai Plain mainly occurs in the early morning with a difference of nearly 12 h. In the global model, the precipitation forecast of NCEP-GFS is smaller than observation in most of the time, and the absolute value of negative deviation from night to early morning and afternoon is the largest. The precipitation frequency of NCEP-GFS has the largest positive deviation most of the time, while the absolute value of the negative deviation of precipitation intensity is the largest. The ECMWF underestimates the precipitation from evening to night and overestimates the precipitation from early morning to noon, where the precipitation frequency is positive deviation, and the precipitation intensity of each time is negative deviation. According to the comprehensive analysis of the tem⁃

perature and wind field with or without precipitation, the rapid increase of precipitation in the model is mainly due to the high temperature forecasted by CMA-SH9 at night and ECMWF at noon, combined with the southeast warm and humid airflow, which is easy to form unstable stratification in the near surface layer, thus triggering convective weather and producing large precipitation, especially large precipitation frequency.

daily variation of precipitation, operational numerical prediction, deviation characteristics