Use of an observation-based aerosol profile in simulations of a mid-latitude squall line during MC3E: Similarity of stratiform ice microphysics to tropical conditions
Ann M. Fridlind1, Xiaowen Li2,3, Di Wu3,4, Marcus van Lier-Walqui1,5, Andrew S. Ackerman1, Wei-Kuo Tao3, Greg M. McFarquhar6, Wei Wu6, Xiquan Dong7, Jingyu Wang7, Alexander Ryzhkov8, Pengfei Zhang8, Michael R. Poellot9, Andrea Neumann9, and Jason M. Tomlinson101NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY, USA 2Morgan State University, Baltimore, MD, USA 3NASA Goddard Space Flight Center, Greenbelt, MD, USA 4Science Systems and Applications, Inc., Lanham, MD, USA 5Columbia University, New York, NY, USA 6University of Illinois, Urbana-Champaign, IL, USA 7University of Arizona, Tucson, AZ, USA 8Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, and National Severe Storms Laboratory, Norman, OK, USA 9University of North Dakota, Grand Forks, ND, USA 10Pacific Northwest National Laboratory, Richland, WA, USA
Received: 24 Oct 2016 – Accepted for review: 10 Nov 2016 – Discussion started: 14 Nov 2016
Abstract. Advancing understanding of deep convection microphysics via mesoscale modeling studies of well-observed case studies requires observation-based aerosol inputs. Here we derive hygroscopic aerosol size distribution input profiles from ground- based and airborne measurements for six convection case studies observed during the Midlatitude Continental Convective Cloud Experiment (MC3E) over Oklahoma. We demonstrate use of the aerosol inputs in mesoscale model simulations of the only well-observed case study that produced extensive stratiform outflow, on 20 May 2011. At well-sampled elevations between −10 and −23 °C over widespread stratiform rain, ice crystal number concentrations are consistently dominated by a single mode near ∼ 400 μm in randomly oriented maximum dimension (Dmax). The ice mass at −23 °C is primarily in a closely collocated mode, whereas a mass mode near Dmax ∼ 1000 μm becomes dominant with decreasing elevation to the −10 °C level, consistent with possible aggregation during sedimentation. However, simulations with and without observation-based aerosol inputs systematically overpredict mass peak Dmax by a factor of 3–5 and underpredict ice number concentration by a factor of 4–10. Previously reported simulations with both two-moment and size-resolved microphysics have shown biases of a similar nature. The observed ice properties are notably similar to those reported from recent tropical measurements. Based on several lines of evidence, we speculate that the microphysics pathways associated with deep tropical convection outflow also occurred in the 20 May MC3E case, likely associated with warm-temperature ice multiplication that is not well understood or well represented in models.
Fridlind, A. M., Li, X., Wu, D., van Lier-Walqui, M., Ackerman, A. S., Tao, W.-K., McFarquhar, G. M., Wu, W., Dong, X., Wang, J., Ryzhkov, A., Zhang, P., Poellot, M. R., Neumann, A., and Tomlinson, J. M.: Use of an observation-based aerosol profile in simulations of a mid-latitude squall line during MC3E: Similarity of stratiform ice microphysics to tropical conditions, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-948, in review, 2016.