海表温度与低层气温对江苏沿海冬季近地层风场特征影响研究

THE INFLUENCE ON JIANGSU COASTAL WIND FIELD FEATURES OF LOW LAYER AIR IN WINTER BY SST AND LOW-LAYER TEMPERATURE

统计分析与数值模拟的江苏省沿海地区冬季风场状况显示,近地层风场对海表温度与低层气温的季节性以及短时过程演变都有显著响应。风速场表现为风速自内陆向海上增加,等值线与海岸线走向一致,风速梯度在沿海岸线的近海最强。季节性特征为:夏季低风速频次多,冬季高风速频次多;随着高度的增加,相同等级的大风风速在冬季出现频次明显高于夏季。寒潮入侵时,江苏自北向南气温降温幅度递减,海温响应的演变趋势类似,但降温幅度小。具有冷锋与副冷锋的寒潮降温呈三个阶段:(1)先缓降后速降,(2)弱回升,(3)再次降温。大风伴随降温,风速的明显减弱滞后于气温的速降,随着气温回升风速增大,对应副冷锋的降温风速有二次滞后减弱。当近海SST数值增大后,海上风速极大值区强度减弱。同一纬度上,内陆地区风速增加,近海海域风速减小,大值中心仍处于江苏近海海上。当低层气温温差加大、冷锋强度增强时,气旋式风场的切变线后方的风向由偏西北转为偏北风,整体风场的响应强度增大,大值风速带主要位于江苏沿海中部。

According to statistical analysis and numerical modeling, it is shown that low-layer winds response significantly to the seasonal and short-term changes of sea surface temperature and low-layer temperature. The wind is small inland and increases towards the sea, with the isolines in parallel with the coast line and becoming the densest near the coast. The wind is the slowest in summer and fastest in winter. With the increase of heights, winds of the same level of force occur much more frequently in winter than in summer. During a cold wave event, the strength of cold air descends from the northern part of Jiangsu to the southern part, and the SST responses in a similar way but with a smaller magnitude. Cold waves that are marked with a main and a secondary cold front experience three stages in which temperature （1） drops gradually and then rapidly, （2） mildly rises, and （3） remarkably drops again. High winds are accompanied with temperature drops, and the decrease of wind speed lags behind that of temperature. With the increase of temperature, wind speed increases. In association with to the temperature drop caused by the second cold front, wind speed reduces again afterwards. When offshore SST increases, maximum wind speed weakens at sea. At the same latitude, wind speeds increase inland and decreases at sea, but large-value centers remain just offshore. When low-layer temperature difference increases and cold fronts increase, wind direction changes to north from northwest in the area behind the cyclone shear line. The wind strength increases the overall wind field, and the maximum wind speed zone is located in the middle part of Jiangsu coast.