GRAPES-TCM业务试验结果分析

An Analysis of GRAPES-TCM's Operational Experiment Results

应用数值模式GRAPES-TCM2.1(GT2.1)的升级版GRAPES-TCM2.6(GT2.6)对2005年西北太平洋及南海热带气旋路径进行了后报试验和性能检验。在检验预报路径时考察了平均距离误差、系统偏差、距离误差的地理分布和平均移速误差,并在总体检验的基础上,根据与热带气旋路径相关的重要因素(路径类型、强度、有无登陆过程以及有无移向或移速突变)进行了分类检验。结果表明,GT2.6表现出良好的预报性能,其对所有样本的24、48和72小时平均距离误差分别为135.8、230.7和336.0km,但前12小时距离误差较大(近100km)。用系统偏差订正GT2.6对转向类样本的预报路径可获得明显的改进。GT2.6对130°E以西区域特别是靠近我国东南沿海的热带气旋路径预报表现较好。GT2.6的总体平均预报移速在48小时内都比最佳路径移速偏快,初始的12小时内偏快最多(近1m.s-1),在48小时后转为偏慢。GT2.6和GT2.1的前48小时路径预报性能的稳定性相当,总体误差特征相似,GT2.6对所有样本的48小时预报有显著改进,平均距离误差减小17km。初步分析表明,对GT2.6的改进应主要集中在数值预报初始场的改进方面,比如在初始化过程中采用较准确的涡旋分离方案、加入引导向量改进初始移动以及适当考虑加入非对称Bogus涡旋;扩大预报区域,并适当选取预报区域起始位置等。

GRAPES_ TCM2.6（GT2.6）, the updated version of the numerical model GRAPES_ TCM2.1 （GT2.1）, is used to post-forecast tracks of TCs occurred over the Northwestern Pacific and the South China Sea during 2005. A series of detailed performance verifications for the numerical prediction of tropical cyclone tracks is presented. The results show that GT2.6 has a good performance on TC track prediction. The total mean forecast errors （MFE） at 24, 48 and 72h are 135.8, 230.7and 336.0km, respectively. The result also shows that the MFE at 12h is somewhat large （ about 100kin）. The significant improvement of GT2.6＇ s track prediction for the turning TC can be obtained through the modification of the forecast tracks with systematic bias. The model is found to have very good forecast skill for the cases that occurred in the west of 130E, especially for those close to the southeast of China. In general, the forecast track of GT2.6 is faster （slower） before （after） 48 hours than the optimal track, and the speed bias at 12 hour is larger during the forecast period （approximately lm/s）. In comparison with GT2.1, GT2.6 has similar performance stability and MFE characteristics on 0-48h TC track prediction, except that the 48h forecast of GT 2.6 is significantly better than that of GT 2.1. Primary results indicate that several essential measures should be taken to further improve the track forecast skill of GT2.6. They are replacing the vortex - environment separation scheme with a stricter one, adding persistence vector to improve the initial motion and an asymmetric bogus vortex in the initial time, as well as enlarging the forecast domain and properly setting its position.