西北太平洋台风在S2S时间尺度预报效果评估

使用世界气象组织季节内至季节尺度（Subseasonal to Seasonal, S2S）预测项目数据库评估了多个集合预报系统在S2S时间尺度对台风的预报能力。评估的时间段为1999—2010年期间每年5月1日—10月31日。为评估S2S时间尺度台风的预报技巧，使用了台风密集度来描述台风的生成及移动状况。台风密集度定义为一段时间内500 km范围内台风出现的概率。台风密集度由6个S2S集合预报系统后报结果计算得出，它们分别由BoM、CMA、ECMWF、JMA、CNRM和NCEP开发使用。这6个预报系统台风密集度的预报技巧评分表明，当预报时效为11~30天时，ECMWF预报系统的评分为正值，比基于气候状态的参考预报能略好地预报台风。 

EVALUATING NORTHWESTERN PACIFIC TROPICAL STORM FORECASTING WITH THE SUBSEASONAL TO SEASONAL PREDICTION PROJECT DATABASE

To assess the potential of tropical storm forecasting on Subseasonal to Seasonal (S2S) timescales, the forecast skill of tropical storm is evaluated using S2S Prediction Project Database. The evaluation period is from May 1 to Oct 31 during 1999—2010. To evaluate the forecast skill of tropical storm on S2S timescales, tropical storm density, defined as the probability of tropical storm occurrence within 500 km, is used to describe the generation and movement of tropical storms. Tropical storm density is computed from the ensemble forecasts from six operational centers including BoM, CMA, ECMWF, JMA, CNRM and NCEP. The debiased Brier skill score is used to compare the tropical storm density forecast skill of these models. The ECMWF model shows positive debiased Brier skill score when forecast lead time is from 11 to 30 days, indicating better tropical storm forecast than reference forecast based on climatology.