Lisan Yu's Homepage

Surface air-sea heat exchange is a result of a number of processes: incoming solar radiation, outgoing longwave radiation, sensible heat transfer by conduction and convection, and latent heat release by evaporation of sea surface temperature. The transport of heat by ocean currents resulting from the imbalance of these exchanges is of great interest to studies of present climate and its potential changes. Therefore, an accurate estimate of heat flux exchange at the air-sea interface is needed. Work has been ongoing to develop a gridded product of surface heat fluxes over global oceans with good accuracy by using innovative approach.

Westerly winds bursts (WWB) are synoptic atmospheric events that occur preferably during the period from October to April. On interannual timescales they are most active during the warm phase of El Nino - Southern Oscillation. Why do WWB have year-to-year variations in association with ENSO phases? Whether and how does this low-frequency component of WWB affect the ENSO dynamics, irregularity, and predictability? These issues are the focus of my research.

Atmosphere-ocean interactions occur on various time and space scales, both within the tropics and between the tropics and midlatitudes. Due to nonlinear nature of the climate system, some seemingly regional/local processes on synoptical and mesoscales can interact actively with longer time scale and larger space scale processes, and such interactions often have considerable impacts on the large-scale climate system. My research emphasizes on analyzing and understanding possible dynamical interactions between synoptic-intraseasonal atmospheric processes and interannual-decadal coupled climate variations in the tropical Indo-Pacific regions.

Data assimilation is a powerful tool to combine model with observations that allows the estimation of unobserved quantities from observables, filling in information in data-poor regions, and generation of assimilated oceanic datasets with physical consistency. My research combines data assimilation method with various oceanic models to derive ocean surface heat fluxes and oceanic eddy viscosity profile and to study the oceanic circulation constrained by observations.