Tropical intraseasonal oscillations are important to the short-term climate variability of tropical latitudes and have connections with low-frequency oscillations throughout the global atmosphere. Dr. Crum plans to pursue a broad research effort aimed better understanding of the nature of these oscillations. Conditional heating, where forcing of the large-scale circulation by organized convection occurs in regions of large-scale moisture convergence, has a significant nonlinear effect in determining the structure and horizontal scale of these oscillations. Dr. Crum will expand upon previous results on conditional heating using linear models which have been modified to allow for interaction of the tropical waves with the stratosphere and boundary layer. He plans to examine factors which control the amplitude of these oscillations, focussing on the roles of moisture and static stability. The possible cooperative interaction between convective clouds and the large scale, crucial to many theories, also will be tested in a model with explicitly resolved clouds. A better understanding of the tropical intraseasonal oscillation will lead eventually to a better prediction of a variety of weather phenomena.
