基于DERF2.0的中天山北坡经济带秋季延伸期强降温过程预报检验

基于观测及DERF2.0预报数据,应用多种气候检验指标,针对1983—2013年间中天山北坡经济带8个代表站的秋季日最低气温进行检验,结果表明:(1)秋季日最低气温的预报效果存在空间和年际差异。东部奇台、木垒预报效果优于中西部6站;整体预报能力延伸期弱于中短期,且随预报时效延长而减弱。(2)预报与观测的相关程度较高,但滤除秋季降温背景趋势后日最低气温预报与观测之间的相关程度降低明显,在延伸期时段相关系数从0.8降至0.3以下。不论是否去趋势,温度序列由暖向冷转变的季节趋势越明显,预报的相关性就越好。(3)逐日最低气温预报偏差以偏低为主,随季节推进由9月初的最大-6℃逐渐转变为11月底的2℃以内;多年综合预报PS评分普遍低于60分,站点之间差别较大,奇台站评分相对最高,乌鲁木齐最低,乌鲁木齐的逐年PS评分与其秋季年平均温度分布反向对应,年平均温度越高(低),评分越低(高)。(4)24 h变温的预报偏差整体小于逐日温度,但预报的整体相关程度和相对于观测的离散程度均较逐日温度差,预报时效在5 d内的24 h变温预报效果相对最好。(5)强降温过程的预报能力整体偏弱,初始过程的温度预报偏低,结束过程的温度预报偏高,过程降温幅度预报偏小,过程降温幅度越大,偏小程度越严重,预报时效越长,预报偏差越大。DERF2.0模式的延伸期预报产品对于中天山北坡经济带的秋季强降温过程预报具有一定的参考价值,但是支持能力有限,需要考虑更多方法来探讨提高延伸期预报水平。

DERF2.0 Extension Assessment for Autumn strong cooling process in the North slope economic belt of Mid_Tianshan Mountain

Based on observation and DERF2.0 data of autumn minimum temperature during 1983-2013,using different climate test methods,a preliminary assessment of DERF2.0 prediction ability for 8 typical stations in the North slope economic belt of Mid-Tianshan Mountains is made.The results show that:(1)The prediction ability of daily autumn minimum temperature has obvious spatial and time differences between stations and years.The prediction effect of Qitai and Mulei in the east is better than the other 6 stations in the middle and west,the overall forecast ability of extended period is lower than the mid-short-term evidently,and the total testing ability is decrease with the impel of forecasting time.(2)The correlation between the forecast and observation of daily minimum temperature is high,but it is decreased significantly after filtering out the cooling background trend of autumn,in extended period,the correlation coefficient decreased from 0.8 to less than 0.3;the seasonal trend of weather is filtering out or not,the more obvious the seasonal trend of temperature series from warm to cold is,the better the relevance of prediction is.(3)The forecast bias of daily minimum temperature is mainly cold and gradually changed from-6℃at the beginning of September to within 2℃at the end of November;the Ps score of prediction is generally lower than 60 and scores have obviously differences between stations,in comparison,the score of Qitai is the highest and Urumqi is the lowest,the yearly Ps score of Urumqi is inversely corresponding to the autumn annual average temperature.The higher(lower)the annual average temperature is,the lower(higher)the score is.(4)The comprehensive forecast bias of 24-hour variable temperature is less than daily temperature,but the correlation and dispersion are worse than daily temperature,the forecast effect of 24-hour variable temperature is relatively best when the forecasting time is within 5 days.(5)The forecasting ability of strong cooling process is totally weak,the prediction bias of initial temperature is low,the ending temperature is high,and cause the cooling range bias is small,the stronger the cooling range is,the more serious the bias degree is,the longer the forecasting time is,the larger the prediction bias is.The extended period forecast products of DERF2.0 model have certain reference value for the forecast of strong cooling process in autumn in the north slope economic belt of the Mid-Tianshan Mountains,but the support ability is limited,more methods need to be considered to discuss improving the extended period forecast level.