Background

Stratospheric transport, and in particular barriers to transport, largely determines the distribution of radiatively active gases (e.g. ozone) and hence their fingerprint on the warming of the atmosphere. These processes are often not well simulated in atmosphere-ocean global climate models.

Hundreds of long-duration stratospheric balloons were flown by Google to provide internet access to remote locations (see here) .

Bodeker Scientific used Loon balloon position data to reveal in unprecedented detail the transport processes, and small-scale turbulent diffusion processes, active in the southern high latitude stratosphere. Our research contributed to fundamental understanding of stratospheric dynamics and its role in climate. This was a small (1 year) research project funded through the New Zealand Antarctic Research Institute.

Research Aims

The main purpose of this project was to analyse an unprecedented database of stratospheric air parcel trajectories obtained from a suite of many hundreds (eventually many thousands) of stratospheric long-duration balloons to identify, describe, and better understand large-scale transport processes and small-scale turbulent diffusion processes that drive irreversible mixing of air masses in the stratosphere.

Transport processes are resolved by current models (e.g. 0.5°×0.5° model grids) and are therefore also resolved in reanalyses which assimilate available observations into these models. On the other hand, small-scale turbulent diffusion processes, and other processes smaller than the grid resolution such as gravity waves, are not resolved at current model resolution and must be parameterized. Improved understanding of these processes is the foundation for better simulating the morphology of fields of radiatively active gases and their fingerprint on the climate system.

Our goals:

• Greatly add to fundamental understanding of the physical processes that drive large-scale transport resolved by models and processes that drive small-scale turbulent diffusion that causes irreversible mixing and is unresolved in models.

• Provide much needed validation of meteorological reanalyses products over Southern Hemisphere middle and high latitudes. The outcomes from this study may then contribute to the SPARC (Stratosphere-troposphere Processes And their Role in Climate) reanalysis intercomparison project (S-RIP).

• Better understand the dynamical containment properties of the Antarctic stratospheric vortex which determine the steepness of tracer gradients across the vortex edge, the pattern of radiative forcing, and hence the strength of stratospheric jets.