Thursday, 13 February 2003: 4:30 PM
Tropical precipitation anomalies: ENSO teleconnections vs. global warming
New theory for tropical teleconnections has recently been proposed that highlights the importance of moist processes in producing remote precipitation anomalies during El Niņo and La Niņa. The traditionally assumed mechanism of anomalous radiative cooling balanced by anomalous descent has been relegated to a lesser role, while changes in moisture advection and surface fluxes interacting with convective heating and cloud radiative effects have come to the fore. In projections of global warming, substantial regional precipitation anomalies are also found. Teleconnection mechanisms are in principle testable on shorter time scales than those of global warming, so it is tempting to seek parallels. Global warming changes are fundamentally driven by greenhouse gas radiative effects and so on the face of it, it would appear that the mechanisms should differ from those of teleconnections. However, the shifts in convection zones do share at least some dynamics with those of teleconnections. With this in mind, the differences and parallels in the dynamics of the two cases are contrasted. Diagnostics and experiments in an intermediate complexity climate model are used to quantify the analysis.