Greg McFarquhar                                                             University of Illinois

Professor Greg McFarquhar

Department of Atmospheric Sciences

University of Illinois

105 S. Gregory Street

Urbana, IL 61801-3070

PH: 217-265-5458

FX: 217-244-4393

Email: mcfarq at


Picture of the Month: Check back each month for a new picture about our group's activities.

This month Prof. McFarquhar is shown with research scientist Junshik Um and Prof. Ed Zipser of the University of Utah in the aircraft conference room at the Cayenne Airport in French Guiana. Supported by a grant from the National Science Foundation, they are part of an international consortium conducting a flight campaign to better understand the causes of high ice water contents in the absence of high reflectivity issues.

Prior Pictures of the Month

Recent Publication: Um, J., G.M. McFarquhar, Y.P. Hong, S.-S. Lee, R.P. Lawson, and Q. Mo, 2015: Dimensions and aspect ratios of natural ice crystals in cirrus. Atmos. Chem. Phys., 15, 3933-3956, doi:10.5194/acp-15-3933-2015.

- this paper, written using funding from the Department of Energy, describes how the morphological features of ice particles vary with environmental conditions using data collected in cloud over Alaska, Australia and Oklahoma. In particular, we determined how the aspect ratios (length to width ratios) and distributions of habits varied with temperature, geographic location, and cloud formation mechanism (convective vs. synoptic)


Greg McFarquhar received his B.Sc. in mathematics and physics from the University of Toronto, Canada in 1987. Thereafter, he changed his field of study to atmospheric sciences and received his M.Sc. (1989) and Ph.D. (1993) from the University of Toronto, specializing in cloud physics. Greg spent two years as a postdoctoral fellow at the Scripps Institute of Oceanography in La Jolla, California (1993-94) and worked at the National Center for Atmospheric Research in Boulder, Colorado (1995-2001) before joining the faculty at the University of Illinois in the fall of 2001. He is the outgoing chair of the American Meteorological Society Committee on Cloud Physics and a member of the International Commission on Clouds and Precipitation. He is the chief editor for the American Meteorological Society's Monographs Collection, an associate editor for the Quarterly Journal of the Royal Meteorological Society and the Journal of Climate, and has active research grants from the National Science Foundation (NSF), the Department of Energy (DOE), and the National Aeronautics and Space Administration (NASA). He has formerly served as Chair of the DOE Atmospheric Radiation Measurement (ARM) program Cloud properties working group, and has been Chief Scientist for the ARM Uninhabited Aerospace Vehicle Program (ARM UAV), the ARM Aerial Vehicle Program (AVP) and the ARM Aerial Facilities (AAF). He was formerly a Richard and Margaret Romano Professorial Scholar at the University of Illinois. He has 107 publications in the refereed literature and has made over 380 presentations at conferences and working group meetings. Interested candidates for graduate studies or postdoctoral positions are encouraged to contact him for more information.



The most fundamental and complex problems in climate and weather research today are our poor understandings of the basic properties of clouds and our inability to determine quantitatively the many effects cloud processes have on weather and climate. Current climate models indicate that Earth's average surface temperature will warm from 1.5 to 4.5°C by 2100 due to increases in greenhouse gases, with the large uncertainty attributed to different treatments of clouds in climate models. Winter weather significantly impacts the transportation and power industries, schools and businesses, and severe thunderstorms can cause significant damage and flooding. Improved quantitative precipitation forecasts require a greater understanding of how cloud processes and the related energy release affect the structure and dynamics of storms. Research within the McFarquhar group addresses the overarching theme of clouds and their relation to climate and weather using a combination of field observations, satellite retrievals and numerical modeling studies.Prof. McFarquhar's work at Illinois aims at making fundamental advances in our understanding of cloud properties and processes, and improving our ability to represent clouds in weather and climate models.


Current projects are advancing our understanding of 1) the microphysical structure of snow bands in winter cyclones; 2) the properties of tropical clouds generated by deep convection; 3) the operating characteristics of probes measuring cloud properties; 4) the transmission of radiation through the cloudy atmosphere; 5) the representation of clouds in climate and weather models; 6) the dependence of arctic cloud properties on aerosol properties; 7) the impact of cloud and aerosol processes on hurricane evolution; and 8) the dependence of fair weather cumuli properties on land-surface and aerosol characteristics. Funding is received from the National Science Foundation (NSF), the Department of Energy (DOE), and the National Aeronautics and Space Administration (NASA) for this research. In the past few years, my graduate students and I have participated in field projects in Darwin Australia (tropical cirrus), Barrow Alaska (arctic mixed-phase clouds), Ponca City Oklahoma (fair weather cumuli and cirrus), Peoria Illinois (winter storms), and Boulder Colorado (performance of cloud probes). Data collected during these projects are being linked with numerical models having a variety of temporal and spatial scales, including cloud resolving, mesoscale and single column models.


Arctic Clouds Tropical Clouds
Snow Bands Indirect Effects Radiation Transmission Probe Operating Characteristics

Future modeling and observational studies are being planned for Darwin Australia, Salina Kansas, the Galapagos Islands, and the Smokey Mountains in Tennessee. Graduate students and postdoctoral research associates are active collaborators in all projects, presenting their research at conferences and publishing papers in the scientific literature. I am always looking for more students to join my group so that we can improve our knowledge of clouds together.


Current Group

Current Graduate/Undergraduate Students

Amador, Robert UG Properties of multi-layer and single-layer arctic clouds
Brown, Tyra
Using wavelets to represent ice crystals
Choate, Davis M.S. Elevated nocturnal convection
Crowleyfarenga, Remy UG Aerosol effects on hurricane evolution
Dong, Jiayin
Cloud probe intercomparison
Duffy, George
Remote sensing of ice clouds
Finlon, Joe M.S. Retrieving cloud properties in winter storms
Haapanala, Päivi (Helsinki)
Radiative transfer in cirrus clouds
Keeler, Jason
Modeling mid-latitude wintertime cyclones
Lee, Heewoong UG Shape analysis of ice crystals
Murphy, Amanda UG Microphysics of snowbands
Norris, Bethany
Microphysics in deep nocturnal convective systems
Pham, Casey UG Equilibrium raindrop size distributions
Rosenow, Andrew
Snowbands in mid-latitude cyclones
Stechman, Dan M.S. Elevated nocturnal convection
White, Charles UG Dependence of cloud properties on land-surface properties
Wu, Wei
Representation of ice clouds in climate models
Yang, Hee-Jung
Indirect effects in trade wind cumuli
Zhu, Shichu
High ice water content clouds in Tropics


Current Postdocs/Staff/Associates


Individual Topic
Jewett, Brian Hurricane and mid-latitude cyclone studies
Um, Junshik Cloud/radiative interactions


Former Students/Postdocs/Staff

Year Topic Current Employer
Bae, Kenny
2010 Microphysics of arctic clouds Wolcott High School, Chicago, IL
Birky, Josh
2002-03 Lidar observations of clouds University of South Florida, Tampa, FL
Dooley, Amanda
2008 Hurricane cloud microphysics Rutgers University, Rutgers, NJ
Fitzgerald, Andrea
2014 Aerosol effects on hurricanes University of Illinois, Urbana, IL
Freer, Matt
2003-07 Cloud physics probe processing DMT, Boulder, CO
Grim, Joe
2008 MCS microphysics NCAR, Boulder, CO
Guarente, Bryan
2007 MCS modeling NCAR, Boulder, CO
Guerero, Spencer UG 2013 Characterizing cloud particles as fractals University of Illinois, Urbana, IL
Hampton, Justin
2009 Mid-latitude snowband properties Elmhurst College, Elmhurst, IL
Hseih, Tsung-Lin UG 2011-13 Techniques for fitting size distributions Princeton University, Princeton, NJ
Jackson, Robert
2011 Indirect effects in ice clouds University of Wyoming, Laramie, WY
Jackson, Robert Ph.D. 2015 Accuracy of cloud probes University of Wyoming, Laramie, WY
Kim, Sun Kyu
2013-14 Image analysis of ice crystals Seoul, Korea
Kruk, Michael
2005 Bow echo damage patterns NOAA, Ashville, NC
Macomber, Matt
2013-14 Frontal structure of mid-latitude cyclone University of Illinois, Urbana, IL
Maliawco Jr., Richard
2012 Predictability of tropical cyclones NWS, Montana
Mascio, Jeana M.S. 2013 Ice size distributions in tropical cyclones University of Utah, Salt Lake City, UT
Mauno, Päivi
2010 Radiative transfer in ice clouds (Helsinki) University of Helsinki, Helsinki, Finland
Nousiainen, Timo Postdoc 2002-04 Scattering from small ice crystals University of Helsinki, Helsinki, Finland
Peterson, Melissa
2012 Stability characteristics of wintertime cyclones Avmet, Reston, VA
Pitcel, Michelle
2010 Numerical models of gravity waves University of Illinois, Urbana, IL
Plummer, David
2014 Microphysics of snowbands University of Wyoming, Laramie, WY
Rosenow, Andrew
2011 Snowbands in mid-latitude cyclones University of Illinois, Urbana, IL
Scheff, Jack
2007-08 Cloud particles as fractals University of Washington, Seattle, WA
Silver, Amanada  UG  2011-13 Rapid intensification of hurricanes Water Quality Association, Chicago, IL
Smith, Andrea
2007 Microphysics of MCSs Univ of Northern Colorado, Greeley, CO
Timlin, Mike
2002-06 Cloud probe analysis Midwestern Climate Center, Urbana, IL
Turner, Bill UG 2013 Icing conditions in mid-latitude cyclones University of Illinois, Urbana, IL
Um, Junshik
2004 Cloud-radiation interactions University of Illinois, Urbana, IL
Um, Junshik
2009 Tropical cirrus microphysics/radiation University of Illinois, Urbana, IL
Wang, Hailong
2007 Indirect effects in trade wind cumuli PNNL, Richland, WA
Wegman, Joe
2012 Electrification of winter storms NWS, Anchorage, Alaska
Weingartner, Fiona
2010 History of cloud physics University of Illinois, Urbana, IL
Yaffe, Kyle    UG 2013 Automated identification of ice crystals Scott Air Force Base, Pasquotah, IL
Zhang, Henian
2004 Models of hurricane microphysics Georgia Dept. of Transport, Atlanta, GA
Zhang, Henian
2008 Saharan dust impacts on hurricanes Georgia Dept. of Transport, Atlanta, GA