| Summary: | International audience During the POLARCAT summer campaign in 2008, two episodes (2-5 July and 7-10 July 2008) occurred where low-pressure systems traveled from Siberia across the Arctic Ocean towards the North Pole. The two cyclones had extensive smoke plumes from Siberian forest fires embedded in their associated air masses, creating an excellent opportunity to use satellite and aircraft observations to validate the performance of atmospheric transport models in the Arctic, which is a challenging model domain due to numerical and other complications. Here we compare transport simulations of carbon monoxide (CO) from the Lagrangian transport model FLEXPART, the Eulerian chemical transport model TOMCAT, and the limited-area chemical transport model WRF-Chem. Retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite are used as a total column CO reference for the two simulations. Analysis of CALIPSO lidar curtains and in situ aircraft measurements provide further independent reference points to assess how reliable the model simulations are and what the main limitations are. The horizontal structure of mid-latitude pollution plumes agrees well between the IASI total column CO and the two model simulations. Thereby, finer-scale structures are too quickly diffused in the Eulerian model. In absolute numbers the total CO fields is highest in the satellite observations, followed by the FLEXPART and the TOMCAT model. Aircraft data suggest that the satellite data are biased high. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. Results indicate very good agreement between simulated and observed total column CO fields, but also highlight the difficulty to identify a data set that most realistically represents the actual state of the atmosphere.
|
|---|