东北夏季天气分型及EC降水预报空间检验

利用SANDRA（SAN）方法将东北地区2018年5—9月环流背景分型，并在此基础上对EC模式预报的较强降水（>10 mm/24 h）进行空间检验和定量分析。东北地区主要的形势背景分为北部扰动低压型、副热带高压北抬型、东北扰动低涡型、扰动低压东移型。其中，前3类环流型对应较强降水过程发生频率相对较高；将3种类型对应的模式预报较强降水过程进行分析。结果表明：模式对于北部扰动低压型过程中大雨以上量级降水落区面积的预报较实况普遍偏小45%—60%；中雨量级降水落区面积，36 h时效预报较实况偏大40%，84 h时效偏小19%；36 h、60 h、84 h时效，较强降水预报位置偏西分别为0.19°、0.53°、1.39°，平均强度预报分别偏低2.9 mm、3.1 mm、3.4 mm，极值预报分别偏低7.3 mm、8.1 mm、9.4 mm；副热带高压北抬型过程预报面积与实况之间的偏差没有一致的倾向性，预报位置较实况分别偏南0.25°、0.15°、0.37°，降水强度上有65%—72%的个例表现为平均强度及极值预报较实况偏弱的特征；东北扰动低涡型过程，预报位置偏差分别为36 h偏东0.18°、偏南0.55°，60 h偏东0.20°、偏南0.58°和84 h偏东0.74°；另外，3个时效对应平均强度预报分别偏低3.3 mm、3.7 mm、3.9 mm，极值预报平均偏低为10.2 mm、10.6 mm、11.6 mm。

Classification of synoptic circulations and spatial verification of the ECMWF model precipitation forecast over Northeast China during summer

Background synoptic circulations over Northeast China from May to September in 2018 were classified using a SANDRA (SAN) method, and heavy precipitation (>10 mm/24 h) forecast using the European Center for Medium-range Weather Forecast (ECMWF) model was spatially verified and quantitatively analyzed.Dominant background synoptic circulation over Northeast China can be classified into the North Low Disturbance (NLD) pattern, the Subtropical High Northward Shift (SHNS) pattern, the Northeast Low Vortex Disturbance (NLVD) pattern, and the Low Disturbance Eastward Shift (LDES) pattern.Heavy precipitation events occur more frequently in the presence of the former three patterns, hence we specifically analyze these precipitation events predicted by the ECMWF model.The results indicate that rainfall areas of medium-heavy precipitation events and above under the NLD pattern are generally underestimated by 45%-60%, and that of medium precipitation events is overestimated by 40% for 36 h forecast and is underestimated by 19% for the 84 h forecast.In 36 h, 60 h, and 84 h forecast, the locations of heavy precipitation are deviated by 0.19°, 0.53°, and 1.39° westward, respectively, and the average (maximum) precipitation values are underestimated by 2.9 (7.3) mm, 3.1 (8.1) mm, and 3.4 (9.4) mm, respectively.Under the SHNS pattern, the deviations between the predicted and observed precipitation areas are not always consistent in signs, the predicted rainfall locations are deviated by 0.19°, 0.53°, and 1.39° southward in 36 h, 60 h, and 84 h forecast, respectively, and weaker average and maximum precipitation values occur among 65%-72% forecast cases.While under the NLVD pattern, the predicted precipitation locations are deviated by 0.18° eastward and 0.55° southward in 36 h forecast, by 0.20° eastward and 0.58° southward in 60 h forecast, and by 0.74° eastward in 84 h forecast.In addition, for the three forecast periods, the underestimation separately reaches 3.3 mm, 3.7 mm, and 3.9 mm for average precipitation values, and 10.2 mm, 10.6 mm, and 11.6 mm for maximum precipitation values.