Tropical Plumes in the UTLS and Their Connection to Atmospheric Rivers

The Upper Troposphere-Lower Stratosphere (UTLS) of the tropics is a region where there is considerable storage of potential energy drawn from the integral latent heat released by convective and tropical storm activity. We can quantify the energy storage as the Jet Available Potential Energy (JAPE) which is a metric showing the potential energy excess over the long term average potential energy at the same elevation of the extratropics. JAPE is mostly confined to the tropical UTLS by lateral inertial trapping and vertical radiative trapping. Therefore, tropical JAPE takes on the form of a JAPE bubble usually confined between latitudes of and bounded by the Subtropical Jet (STJ).

The integral energy stored in JAPE bubble maintains a long-term equilibrium through periodic exchanges with the extratropics via tropical plumes. Then, plumes of JAPE and low PV flow out of the JAPE bubble into the extratropics. Such a plume produces a poleward arching STJ on its poleward periphery. The tropical plume development process occurs in response to a breach in the inertial wall, which traps JAPE in low latitudes. Such a breach is often associated with the approach of a Rossby wave trough from the extratropical Rossby Wave Train (RWT). As the plume develops, JAPE is fed into and amplifies the RWT. In association with the UTLS tropical plumes, deep circulations result which typically form rivers of precipitable water from near the ITCZ into the RWT, that we recognize as atmospheric rivers.

Analysis of this process will be discussed in the oral presentation.