Role of winter jet stream in the middle atmosphere energy balance

Abstract

We consider physical mechanisms responsible for forming plain-layered jet streams in the winter stratosphere. Unlike the conventional notion about the balance between the energy of the solar UV radiation energy absorbed by the stratospheric ozone within the Hartley band and the energy of loss due to infrared emission from СО2, О3, and Н2О molecules, such a balance is shown not to persist. It is shown that the bias of these energies observed in satellite experiments can be explained by dynamic mechanism increasing the air gravity potential in the tropical stratosphere and forming equator/winter pole baroclinic instability, which generates the jet stream. Jet streams transport energy and pulse from equatorial to polar region and facilitate the descending part of the Brewer-Dobson global circulation. Potential energy release, when the stratospheric jet stream lowers, is ∼1018 W/day; the air mass transported by the jet stream to the winter tropopause region is estimated as being ∼1014 kg/day. Based on the ECMWF ERA-Interim reanalysis data, we analyzed the temporal characteristics of the stratospheric air motion from the region of gravity potential abundance generation in the summer tropical stratosphere to the polar winter tropopause altitudes, where the stratospheric air ends its motion, thus participating in cyclogenesis. Duration of the descending part of the Brewer-Dobson circulation in the winter stratosphere/troposphere averages 50–70 days.