A Composite Analysis of Cross-Equatorial Total Energy Transports by Tropical Cyclones

Abstract:

Discussions of tropical cyclones (TCs) in relation to climate have typically assumed that TC activity does not feed back upon the climate. However, recent research has suggested that TCs may play a significant role in atmospheric meridional heat transport given the strong correlation between aggregate TC activity and meridional heat transport during the following winter. Building upon prior research, the present study seeks to advance our understanding of the potential role of TCs in aggregate transport of atmospheric energy by quantifying whether the upper-tropospheric outflow of TCs is responsible for transporting significant quantities of total energy (i.e., sum of kinetic energy, latent energy, potential energy, and sensible heat) in the upper troposphere from the Northern Hemisphere (NH) tropics into the Southern Hemisphere tropics during the peak of NH TC season (i.e., late summer and early fall).

Storm-relative composites of western North Pacific TCs reveal that the upper-tropospheric outflow jet of the TC is responsible for significant southward total energy transport at the equator primarily in the form of dry static energy (i.e., sum of potential energy and sensible heat). Zonal integration of the meridional total energy transport anomalies over a global domain suggests that the TC is the dominant contributing factor at the equator, resulting in instantaneous southward energy transport anomalies of −0.5 PW. For comparison, time-averaged climatological meridional energy transport is approximately −1.0 to −2.0 PW at the equator during the peak of NH TC season, suggesting that TCs temporarily enhance climatological southward energy transport at the equator.