10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Modelling the Effects of Natural and Anthropogenic Sources of Aerosols on Weather
PAUL MAKAR, Wanmin Gong, Craig A. Stroud, Ayodeji Akingunola, Balbir Pabla, Jack Chen, Radenko Pavlovic, Michael Moran, Chris McLinden, Junhua Zhang, Jason Milbrandt, David Sills, Katherine Hayden, Shao-Meng Li, Philip Cheung, Qiong Zheng, Environment and Climate Change Canada
Abstract Number: 1453 Working Group: Aerosol Modeling
Abstract The “fully coupled” configuration of the Global Environmental Multiscale – Modelling Air-quality and CHemistry (GEM-MACH) chemical weather model was used with two nested grids to examine the relative impacts of anthropogenic versus natural sources of atmospheric particles on weather across North America (outer grid), and in particular the Canadian provinces of Alberta and Saskatchewan (inner grid). This model configuration employs a 12-bin sectional approach for representing the aerosol size distribution, and incorporates direct-effect feedbacks using a Mie scattering approach. Indirect-effect feedbacks are represented through the cloud microphysics’ cloud droplet nucleation process making use of the model-generated particle properties, the resulting cloud droplet distribution influencing radiative transfer and in-cloud particle scavenging, and the resulting precipitation rate influencing below-cloud particle removal. Both the North American 10-km horizontal grid spacing simulations, and the Alberta + Saskatchewan 2.5-km horizontal grid spacing simulations made use of these direct and indirect effect parameterizations.
Five sets of simulations were carried out for the 5-week period June 1st through July 6th, 2018: (1) a “no-feedback/all emissions” simulation, in which the direct and indirect effects of feedbacks were disabled; and emissions include biogenic, anthropogenic, and forest fire sources; (2) a “feedbacks, all emissions” simulation wherein the feedbacks were enabled; (3) a “feedbacks, no anthropogenic emissions” simulation; (4) a “feedbacks, no biogenic emissions” simulation; and (5) a “feedbacks, no forest fire emissions” simulation. Differences between the predictions of these simulations for 2-m and 3-D temperature, 10m and 3D winds, total cloud liquid water content, and surface precipitation were used to show the incremental and relative impacts of anthropogenic, biogenic and forest fire emissions on weather, for both North America the highest resolution nest over Alberta and Saskatchewan. Comparisons will be shown between each model simulation and the available meteorological and air-quality observation data to demonstrate their relative forecast skill.
Each of the 24-hour simulations were initialized from 10-km horizontal grid spacing meteorological analyses updated daily – and hence the resulting variations in the predicted weather examined here describe the relatively short-term impacts on the resulting forecasts. However, these impacts were found to be significant, particularly near large local sources of anthropogenic and forest fire emissions, but also over the larger region of Alberta and Saskatchewan.