My research interests are in atmospheric dynamics, with a special emphasis on the use of observations and models to develop a theoretical understanding of important processes and balances that influence weather and climate. My work to date has been rooted in the tropics and has emphasized two particular scales (mesoscale and large-scale), but I find it difficult to attribute a particular interest to a specific scale. I am particularly interested in monsoons, because of the variety of scales they embody and the exciting research avenues they provide. Two specific projects have absorbed most (but not all) of my time so far:
High resolution satellite derived data, such as near surface ocean winds derived from QuikSCAT, the GPCP 1DD precipitation dataset, AVHRR SST, as well as reanalysis data are used to study the North American Monsoon. These data allow not only to resolve with unprecedented accuracy the structure and climatology of the monsoonal circulation, but also to investigate the role that distinct transient features at its core, known as gulf surges, play in shaping important features such as the distribution and the northward extent of the monsoonal precipitation. Gulf surges are found to be often triggered by easterly waves and other disturbances in the tropical NorthEast Pacific, providing a pathway through which deep tropical processes can directly influence the summertime continental precipitation over North America SouthWest.
Having worked for some time on what some might call a minor monsoon, I found myself wondering about what aspects of monsoonal circulations have some generality. One of the most notable features that all monsoons have in common and that, despite its importance, remains to date poorly understood, is the rapid onset of the summertime precipitation and the rapid associated circulation changes. What drives the sudden onset of monsoons? And what determines the intensity and location of the monsoonal precipitation zones? Traditionally the monsoon has been interpreted as a planetary scale sea-breeze driven by the thermal contrast between land and ocean. While still widely accepted, the land-sea breeze paradigm cannot account for rapid onset and end of monsoons. Using idealized aquaplanet GCM experiments, we are able to simulate transitions in the tropical overturning circulation that in all essential aspects resemble the onset and end of observed monsoons. The results from the numerical experiments suggest that the reorganization of the large-scale circulation leading to the abrupt onset of monsoons is mainly driven, rather than by the contrast in the thermal properties between land and ocean as traditionally thought, by the interaction of the large-scale energy containing midlatitude eddies with the mean flow.