Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 397-416, 2016
http://www.atmos-chem-phys.net/16/397/2016/
doi:10.5194/acp-16-397-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
18 Jan 2016
Evaluating the skill of high-resolution WRF-Chem simulations in describing drivers of aerosol direct climate forcing on the regional scale
P. Crippa1, R. C. Sullivan2, A. Thota3, and S. C. Pryor2,3 1COMET, School of Civil Engineering and Geosciences, Cassie Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
2Department of Earth and Atmospheric Sciences, Bradfield Hall, 306 Tower Road, Cornell University, Ithaca, NY 14853, USA
3Pervasive Technology Institute, Indiana University, Bloomington, IN 47405, USA
Abstract. Assessing the ability of global and regional models to describe aerosol optical properties is essential to reducing uncertainty in aerosol direct radiative forcing in the contemporary climate and to improving confidence in future projections. Here we evaluate the performance of high-resolution simulations conducted using the Weather Research and Forecasting model with coupled with Chemistry (WRF-Chem) in capturing spatiotemporal variability of aerosol optical depth (AOD) and the Ångström exponent (AE) by comparison with ground- and space-based remotely sensed observations. WRF-Chem is run over eastern North America at a resolution of 12 km for a representative year (2008). A systematic positive bias in simulated AOD relative to observations is found (annual mean fractional bias (MFB) is 0.15 and 0.50 relative to MODIS (MODerate resolution Imaging Spectroradiometer) and AERONET, respectively), whereas the spatial variability is well captured during most months. The spatial correlation of observed and simulated AOD shows a clear seasonal cycle with highest correlation during summer months (r = 0.5–0.7) when the aerosol loading is large and more observations are available. The model is biased towards the simulation of coarse-mode aerosols (annual MFB for AE  =  −0.10 relative to MODIS and −0.59 for AERONET), but the spatial correlation for AE with observations is 0.3–0.5 during most months, despite the fact that AE is retrieved with higher uncertainty from the remote-sensing observations. WRF-Chem also exhibits high skill in identifying areas of extreme and non-extreme aerosol loading, and its ability to correctly simulate the location and relative intensity of extreme aerosol events (i.e., AOD  >  75th percentile) varies between 30 and 70 % during winter and summer months, respectively.

Citation: Crippa, P., Sullivan, R. C., Thota, A., and Pryor, S. C.: Evaluating the skill of high-resolution WRF-Chem simulations in describing drivers of aerosol direct climate forcing on the regional scale, Atmos. Chem. Phys., 16, 397-416, doi:10.5194/acp-16-397-2016, 2016.
Publications Copernicus
Download
Short summary
We evaluate the performance of high-resolution simulations of the Weather Research and Forecasting model coupled with Chemistry in capturing spatiotemporal variability of aerosol optical properties by comparison with ground- and space- based remote-sensing observations and investigate causes of model biases. This work contributes to assessing the model's ability to describe drivers of aerosol direct radiative forcing in the contemporary climate and to improving confidence in future projections.
We evaluate the performance of high-resolution simulations of the Weather Research and...
Share