Hemispheric transport and influence of meteorology on global aerosol climatology
1Key Lab of Atmospheric Physics and Environment, CMA, Nanjing University of Information Science & Technology, Nanjing, Jiangsu, 210044, China
2Air Quality Research Division, Science & Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario M3H 5T4, Canada
3Chinese Academy of Meteorological Sciences, China Meteorological Administration (CMA), Beijing 100081, China
4DL Modeling & Research, Brampton, Ontario, Canada
Abstract. Based on a 10-yr simulation with the global air quality modeling system GEM-AQ/EC, the inter-annual and seasonal variability as well as the mean climate of hemispheric aerosol transport (HAT) was investigated. The intercontinental aerosol transport is predominant in the zonal direction from west to east with the magnitudes of inter-annual variability between 14% and 63%, and are 0.5–2 orders of magnitude weaker in the meridional direction but with larger inter-annual variability. The HAT is found to fluctuate seasonally with a factor of 5–8 between the maximum in late winter and spring and the minimum in late summer and fall. Three meteorological factors controlling the inter-annual aerosol variations in the source-receptor (S-R) relationships are identified from the modeling results: (1) Anomalies in the mid-latitude westerlies in the troposphere. (2) Variations of precipitation over the intercontinental transport pathways and (3) Changes of meteorological conditions in the boundary layer. Changed only by the meteorology, the aerosol column loadings in the free troposphere over the HTAP-regions vary inter-annually with the highest magnitudes of 30–37% in January and December and the lowest magnitudes of 16–20% in August and September, and the magnitudes of inter-annual variability within the boundary layer influencing the surface concentrations over the HTAP-regions are 30–70% less than in the free troposphere and more region-dependent. As the strongest climatic signal, the El Niño–Southern Oscillation (ENSO) can lead the anomalies in the S-R relationships for intercontinental aerosols in the Northern Hemisphere (NH) with the strong/weak transport in the mid-latitude westerlies and the low latitude easterlies for the HAT in El Niño/ La Niña-years.