Episodes of cross-polar transport in the Arctic troposphere during July 2008 as seen from models, satellite, and aircraft observations

Abstract

Abstract. 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 and anthropogenic sources in East Asia 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 and the Eulerian chemical transport model TOMCAT with retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite. The main aspect of the comparison is how realistic horizontal and vertical structures are represented in the model 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 model simulations. However, finer-scale structures are too quickly Correspondence to: H. Sodemann (hso@nilu.no) diffused in the Eulerian model. Applying the IASI averaging kernels to the model data is essential for a meaningful comparison. Using aircraft data as a reference suggests that the satellite data are biased high, while TOMCAT is biased low. FLEXPART fits the aircraft data rather well, but due to added background concentrations the simulation is not independent from observations. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. In addition to the very good agreement between simulated and observed total column CO fields, the results also highlight the difficulty to identify a data set that most realistically represents the actual pollution state of the Arctic atmosphere.

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

“…Studies that have used FLEXPART CO concentration fields (χ CO ) have found satisfactory agreement between model output and measurements (Stohl, 2006;Paris et al, 2009;Hirdman et al, 2010;Sodemann et al, 2011;Stohl et al, 2013Stohl et al, , 2015Eckhardt et al, 2015). In the Alaskan Arctic for the day of 18 April 2008, Warneke et al (2009) described a slope of 0.9 for a linear fit between FLEXPART model output of χ CO and airborne measurements of CO with a least-squares correlation coefficient of 0.63.…”

Hyperspectral Earth Observation from IASI: Five Years of Accomplishments

“…CO columns are now assimilated operationally at ECMWF in the Global Monitoring for Environment and Security (GMES)/Monitoring Atmospheric Composition and Climate (MACC) forecasting model to produce a chemical forecast of CO fields, and are also used in a variational Bayesian system to infer the global distribution of CO emissions (Fortems-Cheiney et al 2009). They have also served as reference for the Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport (POLARCAT) International Polar Year (IPY) activities to plan aircraft campaigns and to study the transport of pollution plumes from boreal fires moving toward the Arctic (Pommier et al 2010;Sodemann et al 2011).…”

Assessment of WRF/Chem Simulated Vertical Distributions of Particulate Matter from the 2009 Minto Flats South Wildfire in Interior Alaska by CALIPSO Total Backscatter and Depolarization Measurements

“…Fractional cloudiness derived from CALIPSO data revealed shortcomings in simulated cloudiness by a climate model in a more pronounced fashion than evaluations based on passive observations [9]. CALIPSO lidar curtains and in situ aircraft measurements were analyzed to assess the model performance during the POLARCAT field campaign [11]. CALIOP data were used to evaluate Weather Research and Forcasting model [13] inline with chemistry (WRF/Chem) [14] simulated wildfire-plume heights over Asia [12].…”