Collaborative Research: Trace Gas Deposition Processes in the Arctic Boundary Layer

This research is concerned with data analyses and modeling activities to gain further insights on the processes governing atmospheric trace gas dynamics, in particular ozone in the arctic boundary layer. The research activities will lead to improvements in the predictive understanding of tropospheric ozone and other trace gases, which can exert a critical influence in the arctic chemical and radiative balance. Our studies are motivated to derive further understanding of trace gas deposition rates and will achieve the following objectives:

1. to investigate the most appropriate methods for estimating trace gas transport in the surface layer of the arctic atmosphere,

2. to evaluate the suitability of electrochemical ozonesonde data for deriving ozone deposition rates,

3. to study and quantify ozone deposition rates at selected Arctic sites based on ozonesonde routinely obtained at selected arctic sites,

4. and to define the atmospheric conditions when maximum ozone surface deposition rates take place in the arctic boundary layer.

These objectives will be addressed through a combination of data analyses and modeling studies employing three data sets deemed to be of high quality. During spring 2000, we obtained high frequency data at Alert, Nunavut, Canada and Summit, Greenland, Denmark. These two data sets, involving vertical meteorological and chemical profiles from towers and tethered balloons, will be analyzed within the framework of investigating the most appropriate methods to derive trace gas fluxes between the surface and overlying atmosphere and/or vice versa. Additional scientific outputs of these activities relate to the turbulent length scales associated with trace gas fluxes in the arctic boundary layer. Knowledge of turbulent scales is critically essential to understand the atmospheric layer impacted by trace gas emissions from the Arctic snowpack. The third data set involves the archived data from ozonesondes released at selected sites throughout the Arctic. We will employ these extensive historical data to develop a one-dimensional model to derive ozone deposition rates to the snowpack surface. Estimated deposition rates will provide upper threshold values that can then be incorporated in regional and/or global models to constrain ozone budgets in the arctic troposphere. The research will lead to a simple modeling parameterization to routinely derive ozone deposition rates based on the World Meteorological Organization (WMO) ozone monitoring network, and thus provide critical information to decipher the processes governing ozone temporal changes in the Arctic boundary layer. Understanding of ozone dynamics is crucial to define the contribution of ozone in the chemical and radiative balance of the Arctic. Given the recent discovery that the arctic snowpack represents a substantial source of gases such as nitric oxide, nitrogen dioxide, nitrous acid and formaldehyde, this project will also yield methodologies to deduce fluxes of these important trace gases based on ambient (profile) concentrations.