The influence of tropical cyclone outflow on the Northern Hemisphere subtropical and tropical general circulation

Diabatic redistribution of potential vorticity (PV) in tropical cyclones (TCs) is associated with the formation of the TC's cyclonic PV tower and a lens of anticyclonic PV in the upper troposphere. When viewed on the dynamic tropopause, the region of anticyclonic PV is manifest as an area of anomalously high (equivalent) potential temperature accompanied by an anticyclonic circulation. For developing TCs, this potential temperature anomaly is observed to expand. The balanced response to the expanding area of high potential temperature is a concomitant increase in the area of the anticyclonic circulation which surmounts the TC. Long after the demise of the TC, the upper-tropospheric anticyclonic circulation remains.

In this presentation, we explore the effects these diabatically generated anticyclones had on the large-scale circulation of the subtropical and tropical Northern Hemisphere during the summer and fall of 2005. The factors which govern the spatial scale of these anticyclonic events as well as their maintenance is explored. In addition, we describe the role these features have on the downstream development of upper tropospheric Rossby waves, and their contribution to the stationary wave pattern over the subtropics.