Evolution of equatorial and tropical disturbances in nonuniform environments

In this study we focus on the evolution of tropical waves and disturbances in various inhomogeneous background environments within the context of three different situations: (i) MRG waves within the environment created by the MJO in the western Pacific; (ii) Easterly waves and disturbances in zonally inhomogeneous environment over the Atlantic and the Caribbean; and (iii) Easterly waves within the MJO environment over the eastern Pacific and the Gulf of Mexico.; A linear shallow water model is used to simulate the evolution of mixed Rossby gravity (MRG) waves in background states representative of the convective phase of the Madden-Julian Oscillation (MJO). Initial MRG wave structures are obtained analytically. The MJO basic state is defined by the steady response of the tropical atmosphere to localized heating. Results from the simulations reveal that variations in the background flow play a significant role in the evolution of the MRG waves.; The behavior of easterly waves and disturbances within the Atlantic and the Caribbean environments is first examined by compiling a climatology of their frequency of occurrence. Two procedures are used to track the disturbances. The first method consists of identifying coherent PV centers and is similar to the procedure used in past work, while the second method locates troughs in easterlies in the streamfunction fields. These results suggest that a relatively more informative description of AEW tracks can be obtained by combining the results from both PV center and trough climatologies than by considering coherent PV or vorticity centers alone.; The role of the MJO in the genesis of tropical storms in the Gulf of Mexico and eastern Pacific during August and September, 1998 is examined. This is motivated by the formation of five tropical storms within a short span of 18 days between August 31–September 17 1998. This period was characterized by a dramatic evolution of the environment, defined here as the 20 day low-pass filtered fields, over the eastern Pacific and the Gulf of Mexico. This variation is documented and is shown to be consistent with the evolution of the MJO described in past studies. (Abstract shortened by UMI.)...