Under a previous award, the co-principal investigators studied, using cross correlation techniques, the upper level (tropospheric) circulation anomalies associated with tropical convection over the Indian and Pacific Oceans on various times scales during the Northern Hemisphere winter. Their analyses suggest that tropical convective activity (and the attendant atmospheric heating), on the timescale of 14-30 days, generates planetary scale waves sources in subtropical regions which have a significant impact on the east Asian subtropical jet and planetary scale wave patterns in the midlatitudes. In contrast, it appears that convective activity in the eastern Pacific on shorter timescales (6-14 days) is more likely to be affected by extratropical disturbances. With this award, Drs. Kiladis and Weickmann will extend their previous results (cross correlation) to other seasons and other regions of the globe. They also will begin some studies using a simple linear model to explore the mechanism(s) by which tropical heating influences extratropical circulation patterns. This research should provide insights into the dynamical links between the tropics and extratropics and ultimately contribute to improving the models used for medium range forecasting.
