CMA-GFS模式对东北半球环流形势预报能力的检验评估

Forecast Assessment of CMA-GFS on the Meteorological Elements in the Northeast Hemisphere

基于CMA全球模式(CMA-GFS)2019年10月至2020年12月逐日20:00(北京时)起报的数据,对东北半球高空气象要素预报进行检验评估,检验的要素包括500 hPa位势高度场和风场、850 hPa温度场和700 hPa相对湿度场。结果表明:(1)从模式预报效果的时间变化来看,预报效果有明显的季节变化,500 hPa位势高度和850 hPa温度的预报场和分析场的相似度在夏季最低,700 hPa相对湿度场的相似度在冬季最低;随着预报时效的增加,各要素的误差幅度在夏季最小。(2)从模式预报效果的空间变化来看,500 hPa位势高度场在东北半球大部分地区预报场与分析场具有较高相似度,且中高纬地区相对低纬地区更相似,预报误差的幅度则在低纬地区相对较小高纬地区相对较大,且预报偏差以大范围负偏差为主。相比而言,模式对东亚地区的位势高度及其梯度具有更高预报技巧。850 hPa温度场预报相似度和误差幅度与500 hPa位势高度场分布相似,预报偏差则主要表现为中高纬地区温度预报整体偏低,中低纬地区偏高。在预报前期(24~48 h),20°N以北的中高纬地区温度预报场与分析场相似度较高,均方根误差基本在2℃以内,预报效果较好。500 hPa纬向风场和经向风场预报相似度和误差幅度也具有随纬度增加而增大的特点,但对于纬向风场,模式在20°N-30°N存在一个明显的预报技巧高值带,对于经向风场,模式在20°N以南大部分地区预报效果较差。模式对700 hPa相对湿度场在24 h时效下具有一定预报效果,随着预报时效增加,对湿度场的预报只在北非至南亚一带存在一些参考价值。

Based on the daily forecast data initialized at 20:00(Beijing time)of the CMA global forecast system(CMA-GFS)during the period from October,2019 to December,2020,the forecasting quality of the upper air meteorological elements in the Northeast Hemisphere are verified.The verified meteorological elements include geopotential height and wind fields at 500 hPa,temperature field at 850 hPa and relative humidity field at 700 hPa.The results show that:(1)From the characteristics of time variability,there were obviously seasonal variation of the forecasting performance.The similarity between the forecast field and analysis field of 500 hPa geopotential height and 850 hPa temperature is the lowest in summer,and the similarity of 700 hPa relative humidity field is the lowest in winter.With the increase of forecasting time,the root mean square error of each field is the smallest in summer.(2)From the characteristics of spatial variability,500 hPa geopotential height has high similarity between the forecast field and analysis field in most areas of the Northeast Hemisphere,and the similarity of mid-high latitudes are more similar than the low latitudes.The root mean square error of geopotential height is relatively small in the low latitudes and large in the high latitudes,and the mean error is mainly a large-scale negative deviation in the Northeast Hemisphere.In contrast,the model has higher forecasting skill in East Asia for the geopotential height and its gradient.The distribution of forecasting similarity and root mean square error of 850 hPa temperature field are like that of 500 hPa geopotential height,and the mean error is lower in the midhigh latitudes and higher in the low latitudes.In former forecast period(for the 24~48 hours),the similarity of temperature field is higher and the root mean square error is basically within 2℃in the north of 20°N,which means the forecast effect here is preferable.The distribution of forecasting similarity and root mean square error of 500 hPa zonal wind and meridional wind fields also increase with increasing latitude.However,for zonal wind,there is an obvious high value belt of forecasting skill between 20°N-30°N,and for meridional wind,the forecast effect is poor in the south of 20°N.For 700 hPa relative humidity field,the model has a certain forecast effect for the 24 hours.But with the increase of forecasting time,the forecast of humidity field only has some reference significance in North Africa to South Asia.