P33  A WRF-Chem Realtime Modeling System for Monitoring CO2 Emissions

Deng, Aijun, Thomas Lauvaux, Ken Davis, Natasha Miles, Scott Richardson and David Stauffer, Penn State University, USA

Atmospheric inversions, used to infer atmospheric sources and sinks of greenhouse gases, require highly accurate modeling of atmospheric transport, particularly when applied to urban scales.  Towards that end, the Penn State team has developed a time-lagged WRF-Chem realtime modeling system and used it for a realtime CO2 monitoring mission during the World Economic Forum (WEF) Annual Meeting 2012 over Davos, Switzerland.  The WRF-Chem realtime modeling system for this application consists of a 36-/12-/4-/1.33-km grid configuration, with the outermost grid encompassing most of Europe, and the innermost grid, with the grid dimension of 202x202x50, covering Switzerland and centered over Davos.  The system uses the multi-scale FDDA capabilities that involve both analysis and observation nudging, and assimilates available meteorological observations during the entire model simulation.  The first guess of the CO2 emissions from Davos comes from a previous study that presents emissions inventory data specifically for Davos.  For the entire week of the WEF meeting, the WRF-Chem realtime system was run twice a day for 24 hours in a time-lagged fashion so that it ends at the current real time, and simulated the most accurate meteorological conditions possible, critical to simulating the atmospheric CO2 concentrations in space and time throughout the Davos region.

The simulated CO2 concentrations are compared to the observations at two different locations, with a first site in the city used to evaluate the emissions from Davos, and a second at higher altitude measuring the background concentrations. Using a simplified inverse approach, the difference between the observed- and simulated-CO2 concentrations allowed the evaluation of the reported CO2 emissions at the daily time scale. We will present the main findings on local emissions and discuss the modeling performance in the valley of Davos, in particular the stable atmospheric conditions which limit the modeling performance of the Planetary Boundary Layer dynamics.  Some modeling issues such as those related to dealing with complex terrain will also be discussed.