适宜太湖蓝藻水华形成的风场辐散特征及其形成机制

对太湖周边17个气象观测站的7年常规观测资料聚类分析发现,在适宜蓝藻水华形成的高温、微风气象条件下,太湖湖面风场往往出现辐散特征,在此辐散风场的驱动下,蓝藻水华迁移过程必然与均匀风场驱动下有所不同；数值模拟结果显示,这种辐散风场是由于非绝热加热不均匀造成的局地次级环流叠加在弱的背景风场之上引起的；其强弱程度是受湖陆温差和背景风速共同决定的,并据此给出了湖面风场辐散强度指数.

Divergence characteristics and formation mechanism of wind field appropriate for the cyanobacteria bloom in Taihu Lake

Based on conventional observational data from the 17 meteorological stations in 7 years around Taihu Lake, a cluster analysis is carried out. The analysis indicates that there is divergence wind field (DWF) above the water surface under the weather condition of high temperature and gentle breeze, which is suitable for the cyanobacteria bloom. Being driven by DWF, the transportation of the algae must be different with the situation under the single wind field. Based on this phenomenon, typical cases are selected for the numerical simulation. The simulation result shows that nonuniform diabatic heating process causes local thermodynamic sub-circulation which is superimposed upon weak background wind field. It is the formation mechanism of DWF. The intensity of the DWF depends on the lake-land thermal difference and the speed of the background wind field.