中小尺度强对流系统(含台风环流内强对流)引发的短时强降水、雷雨大风和冰雹等强对流天气是影响我国公共安全的最主要气象灾害.海峡西岸地处我国东南海岸,是我国受强对流天气影响最为显著的地区之一,做好中小尺度强对流系统(含台风环流内强对流)造成的短时强降水、雷雨大风和冰雹监测预警预报,对于海峡西岸气象防灾减灾工作至关重要,同时也是国家气象防灾减灾的重大需求.

2018年5月7日冷锋前暖区暴雨和8月29日华南季风槽暴雨,这两次大暴雨都是由广东和闽南地区的沿岸线状中尺度对流系统产生,对其环境背景与对流系统特征进行对比分析,得到主要结论如下:两次过程均有明显850 hPa和925 hPa低空急流;5月7日过程,对流层中低层条件不稳定较大,大气斜压性较强,对流有效位能和0～6 km垂直风切变相对较大,对流层中部存在明显干层,有利于强降水和雷暴大风的产生;8月29日过程,对流层中下层为弱的条件不稳定,准正压大气,更高的融化层高度,对流有效位能和0～6 km垂直风切变相对较小,垂直整层相对湿度高,有利于强降水而不利于雷暴大风的产生.两次过程风暴承载层平均风均来自西南方向,前者的平流比后者要强很多;厦门及其周边闽南地区大暴雨是由于后向传播导致相继多个较强对流雨团移过同一区域形成的;5月7日后向传播形成是一个对流雨团的阵风锋与另一个对流雨团后侧的水平对流卷相遇触发新的对流导致的,新生对流来自陆地;8月29日后向传播形成则是低层暖湿气流遇到成熟对流雨团的后侧阵风锋触发新的对流,新生对流位于海上,持续移入陆地.5月7日导致大暴雨的对流系统中冰相过程和暖云过程对暴雨产生都很重要,8月29日导致极端暴雨的对流系统中暖云过程对强降水产生起主要作用.在两次过程中,对流系统冷池前沿阵风锋附近都有γ中尺度涡旋形成,与阵风锋辐合上升运动结合产生正的垂直螺旋度,有利于对流系统的维持.低空急流通过其对水汽和热量的输送以及与地形和对流系统冷池的相互作用,对沿岸线状中尺度对流系统的维持起到重要作用.

针对确定性模式和集合预报模式降水产品没有得到最优应用的问题,该文开展多模式降水融合预报研究.应用福建省智能网格预报业务关键点的降水观测资料,对4种确定性模式降水预报和欧洲中期天气预报中心(EC-MWF)集合预报的降水集合统计量产品进行降水分级统计检验,确定融合方案,并根据融合方案产生多模式和集合预报降水融合产品.结果表明,除了后汛期(7～9月)外,大部分产品的TS评分随降水量级的增大而下降,随着预报时效的延长,各量级降水TS有所下降.融合产品在3～4月的表现较确定性预报有一定的性能提升;5～6月融合产品表现最差;7～9月融合产品TS评分基本与最优确定性预报接近.对于个例检验而言,融合产品能够较为准确地刻画强降水的落区,但存在大暴雨落区范围过大等偏差.

Using daily precipitation data from 50 principal weather stations over Fujian from 1960 to 2010, we analysized the spatial and temporal variation trends of extreme precipitation events over Fujian Province. The results show that there are significant differences in the spatial distribution of the extreme precipitation events. The multi-year mean annual extreme precipitation threshold and amount are larger in the middle-southern coast of Fujian than other regions, but the annual-mean extreme precipitation frequency is larger in central-northern Fu-jian than other regions. The regional average of annual extreme precipitation frequency, amount, intensity, and the daily maximum amount all show that a linear increasing trend is statistically significant. M-K test shows the mutation time was in 1996 for extreme precipitation frequen-cy, amount and daily maximum amount, and in 2002 for extreme precipitation intensity.

利用双线性插值与线性回归方法、消除偏差集合平均(bias-removed ensemble mean,BREM)和多模式超级集合预报(Super-ensemble Prediction,SUP)方法对厦门地区的地面气温进行统计降尺度分析,结果表明:在2013年夏季的3个月中,降尺度后三个单模式对厦门地面气温的预报效果显著改善.使用多模式集成预报方法(BREM和SUP)后,预报误差进一步减小.对比整体预报效果最好的单模式ECMWF,降尺度后3～96h预报误差均在3℃以下.此外,结合SUP方法的降尺度预报能最大程度的改善地面气温的预报误差.

Numerical simulations and sensitivity experiments for the effect of Taiwan island terrain on track, precipitation and structure of super typhoon Fanapi (1011) were performed with the WRF-ARW 3.2.1 model. The results indicate that owing to effect of the topographic low pressure at windward slope, the typhoon moved southward and had a motion in the counter-clockwise direction before it landed on the Taiwan island. The topographic low pressure at leeward slope and the bow-shaped positive vorticity zone in northwest side of the typhoon make it move in a V-type track when it was in the Taiwan Straits. The obstruct by Taiwan island terrain makes the water vapor convergence and the positive vorticity decreased in northwest side of the typhoon, but increased in east and south side of the typhoon. The typhoon presents an asymmetric structure of weak in northwest and strong in southeast in its intensity and an inhomogeneous distribute of precipitation. The Ter-rain effects of mountains in the central Taiwan regions on typhoon flow field in the low-level leads to increase of precipitation and an asym-metric precipitation distribution being strong in south and east and weak in northwest Taiwan regions.

Utilizing the NCEP/NCAR reanalysis data,the characteristics of annual south wind over East Asia are investigated.And it is discovered that a key area(22.5°—30°N,105°—110°E) where the south wind prevails all the year is over the southeast of the Tibetan Plateau.The south wind is strong in summer and weak in winter,showing a double peak.A peak occurs in the 15th pentad and the other peak occurs in the 37th pentad.Further research found that there is a good relationship between the south wind on the southeast of Tibetan Plateau and the spring precipitation in southern China.In the 15th pentad,the south wind on the southeast of Tibetan Plateau becomes stronger and expands eastwardly,and then the rainfall in the south of China becomes heavy.The occurring reason for the two peaks of the south wind is different. The south wind peak occurring in the 15th pentad is for a low-level cyclone caused by the Tibetan Plateau heating superimposed over the south wind.It causes the south wind stronger,and then South China comes into rainy period.The south wind peak occurring in the 37 th pentad is while the South China Sea monsoon broke out,the southwest wind in front of the Bay of Bengal trough intensifies the south wind. And then it brings about the rain over the Yangtze River.

Potential monthly predictability on Northwestern Pacific tropical cyclones(TCs) activities for the season(June—October) and associated large scale environment conditions were evaluated by utilizing the are separately 0.77 and 0.82 between the simulation and observation,which show a good potential predictability.The simulated distribution of TC genesis positions is in accordance with the observation and International Pacific Research Center(IPRC) high-resolution regional climate model(IPRC-RegCM) and the results show that the IPRC model exhibited good skill in simulating the associated large-scale environmental conditions.The correlation coefficients of the annual and monthly TC genesis numbers(within the season) the interannual trend of PDI simulation is satisfactory.But the simulated occurrence is obviously more than the observed one in the South China Sea.Fewer TCs move towards to the north than those in the observation.And the simulated peak value section of the maximum speeds is not as good as the observation.