Dr. Chen will study the forcing of stationary waves in both Northern and Southern hemispheres using a steady state model. The model employs a lower boundary condition (LBC) which incorporates what is probably the most important nonlinear effect, namely, allowing flow to go around as well as over the orography. The specific objectives are: 1. to further explore the dynamics and the responses of the planetary waves by the more complete LBC (wave.coupled LBC) in the linear model used by Chen and Trenberth (1988a,b) and the issue of flow going "around" or "over" a mountain from both theoretical and computational point of views; 2. to elaborate on the interpretation of the wintertime Northern Hemisphere (NH) subtropical jet streams by momentum budget studies and the theory relating the "rotational and divergent geopotentials and planetary vorticity advection potential" in a linear balance system (Trenberth and Chen, 1988); 3. to simulate the observed planetary waves in the NH summertime and Southern Hemisphere wintertime, and to explore the reasons for the observed differences in planetary waves between the two hemispheres in wintertime; 4. to investigate the kinematic destabilizing effect of the Himalayas on the abrupt onset of the southwest.Asian monsoon.
