Transport–Radiation Feedback Due to Ozone in the Tropical Tropopause Layer

The tropical tropopause layer (TTL) temperature balance is of considerable interest for its control over the amount of water entering the stratosphere, which has impacts on the stratospheric circulation, formation of polar stratospheric clouds, and climate sensitivity. Previous work has indicated a wide variety of processes that affect this temperature balance in both the mean state and seasonal cycle. In particular, the upwelling branch of the Brewer-Dobson circulation (BDC) acts directly on temperature through adiabatic cooling. BDC upwelling also has a second, indirect effect on TTL temperatures through its well-known influence on TTL radiation by ozone transport.

Here, we present the results of an investigation of the BDC ozone transport-radiation feedback, using a a single-column radiative-convective equilibrium model with interactive ozone concentrations calculated by a scheme of simplified stratospheric ozone chemistry and vertical transport. We find that BDC ozone transport is of first-order importance for TTL temperatures. Additionally, we estimate the effect of ozone transport on the cold point tropopause temperature response to changes in BDC upwelling. We find that the ozone transport-radiation feedback is responsible for approximately 20% of the cold point temperature response to BDC upwelling perturbations on timescales longer than about half a year, but that this contribution can be neglected for timescales shorter than about a week.