线性准地转模型中副热带环流对潜热加热的定常响应II.边界约束及风场与层结稳定度的自适应

本文着重研究了线性模型中副热带环流对潜热加热的响应过程中影响高、低压系统中心位置的因子, 剖析出边界层中基本流的垂直切变影响低层环流的根本原因, 并且探讨了线性模式中基本流和静力稳定度自调整过程的重要作用。结果表明, 在β效应和f效应、基本流在经向和垂直方向的二阶切变、以及东、西风基本流作用的非对称性等因素的共同作用下, 高、低压中心位于热源北侧。结果还表明, 当近地面基本流的垂直切变为零或者当风速随高度减小时, 低层气旋和反气旋中心位于地面上, 当风速随高度增大具有类似亚洲季风区的结构时, 低层气旋和反气旋中心抬升离开地面; 进一步考虑热源区附近静力稳定度和基本流自调整过程的作用后, 反气旋中心继续抬升至中层, 证明对流降水对其东侧对流层中低层副高的形成有重要贡献。指出基于传统线性准地转模式来研究副热带高压形成的缺陷在于应用不适当的下边界条件以及缺乏静力稳定度的自调整机制和基本流对热源的反馈机制, 从而得到“潜热加热激发的低层反气旋中心位于洋面上”的不切实际的解。

Stationary Response of the Subtropical Circulation to Latent Heating in a Linear Quasigeostropic Model. II: Boundary Restriction and Self-adaptation of Basic Flow and Stratified Stability

The factors that affect the centers of subtropical cyclone and anticyclone responding to latent heating are explored by using a linear quasigeostropic model. The mechanism that the vertical shear of basic flow in the boundary layer influences the lower troposphere circulation is revealed, and the importance of self-adjustment of basic flow and static stability is discussed. Results show that the centers of the forced cyclone and anticyclone are located on the north of the heating area due to β and f effect, the second order shear of basic flow in the meridional and vertical directions, and the asymmetry of advection of westerly and easterly basic flow. Results also show that the centers appear at the surface when the vertical shear of basic flow is zero at the surface boundary or when wind decreases with height in the boundary layer. The centers lift when wind increases with height, which is similar to the features in the Asia monsoon area in summer. The center of lower anticyclone would lifts further when the self-adjustment processes of basic flow and static stability are considered, which proves that convective precipitation contributes greatly to the formation of anticyclone to its east in the mid or lower troposphere. It is shown that the location of the center of lower anticyclone forced by latent heating appearing at the sea surface is not correct because there is improper lower boundary condition and there are no self-adjustment processes of basic flow and static stability in traditional linear models.