Ozone and nitric acid variability in the Upper Troposphere and Lower Stratosphere measured during the Polar Aura Validation Experiment

Understanding the response of stratospheric and tropospheric constituents to climate and chemical change requires synthesizing a complex combination of physical and chemical processes that operate simultaneously on a wide range of spatial and temporal scales to produce the large-scale global distributions observed by satellites. However, retrieval algorithms are difficult to develop in the critical upper tropospheric, tropopause and lower stratospheric regions, where the radiative properties of trace gases most affect the global climate. This is because most retrieval algorithms depend on an initial a priori profile assumption based on a geographical measurement climatology, but the actual vertical mixing ratio gradients are large across the tropopause, which varies in height based on the location of geophysical features.

In this presentation we show high-resolution, accurate in situ correlative ozone and nitric acid measurements from the NASA DC-8 during the Polar Aura Validation Experiment (PAVE) in January-February of 2005. In addition to providing calibrated correlative measurements, these high-resolution measurements help to characterize the variability of ozone and nitric acid in the near-tropopause region. We use our measurements to illustrate both vertical and horizontal variability under various synoptic conditions encountered during the mission. During late winter ozone acts as a conserved dynamical tracer in the lower stratosphere, and we examine correlations of ozone with measured nitric acid and modeled potential vorticity, as well as calculate the observed ozone variance power spectrum and structure functions to better quantify mixing and eddy dissipation rates at scales that are too fine for the satellite instruments and ozone lidars to resolve, but that span the subrange between the inertial (isotropic) and buoyant (anisotropic) turbulent mixing scales. Accurate characterization of mixing of chemical species and energy dissipation in this subrange (200m - 20km) is critical to the accurate quantification of irreversible material exchange across the tropopause. We also hope to identify dynamical structures where atmospheric inhomogeneity may present a particular challenge to satellite retrieval algorithms.