The effect of uniform zonal winds on tropical cyclone (TC) genesis is examined on a beta plane using an idealized mesoscale model. The simulation results show that uniform easterly and westerly flows are both favorable for TC genesis. However, uniform easterly flows result in a faster TC genesis rate compared with uniform westerly flows. It is found that faster TC genesis is associated with greater surface heat fluxes and convection during the early stage. The superposition of uniform easterly flows and the beta effect results in greater surface heat fluxes and convection around the TC center compared with uniform westerly flows. Meanwhile, TC genesis is closely associated with the size and intensity of a mid-level circulation. The joint greater convection induced by the easterly flows and beta effect results in enhancement of the vertical temperature gradient, which is associated with the intensification of mid-level circulation. The strong and compact mid-level circulation is more favorable for efficient conversion of latent heat energy to the kinetic energy of the lower-level cyclonic winds. Thus, uniform easterly flows are more favorable for TC genesis than uniform westerly flows.
本文利用理想的中尺度模式考察了beta平面下一致的纬向风对热带气旋生成的影响。模拟结果显示一致的东风和西风均有利于热带气旋的生成。然而，一致的东风可以引起更快的热带气旋的生成。造成热带气旋更快生成的主要原因是更大的地面热通量和对流，以及与中层环流的大小和强度也有密切的关系。研究发现东风和beta效应可以引起更大的对流，以及造成更大的垂直温度梯度，从而引起中层环流的加强，中层环流的加强有利于潜热能量向动能的转化，从而更快的形成热带气旋。