I am a Senior Research Scientist in Prof. Sonia Kreidenweis's research group, within the Atmospheric Chemistry Program. My research interests are in the area of aerosol-cloud interactions, particularly ice phase transitions of atmospheric particles for conditions present in various regions of the troposphere, including layer clouds in winter, cumulus clouds, and cirrus clouds. The goals of my research are to understand the way that the physical, chemical, and biological makeup of certain aerosols of natural or anthropogenic origin determine the formation of ice crystals (precursors of precipitation) in clouds and in turn how clouds impact the distribution and nature of ice nucleating particles (INPs)in the atmosphere. This information is important to the fundamental issue of how aerosols affect climate indirectly by impacting the radiative properties of clouds, latent heating of the atmosphere, and precipitation. Other awesome members of our ice phase transitions study group at CSU include Dr. Thomas Hill, Dr. Ezra Levin, Dr. Jessie Creamean (starting October 1!), Dr. Russell Perkins, Dr. Jun Uetake, Ms. Kathryn Moore, and Mr. Kevin Barry. Our research approach involves laboratory and field studies using specialized instrumentation, and numerical modeling studies from the process level to the global scale in collaboration with external investigators. I also serve as an external PI for the Center for Aerosol Impacts on Chemistry of the Environment (CAICE), an NSF Center for Chemical Innovation centered at the University of California, San Diego.

Curriculum Vitae


  • New summer interns enliven our laboratory!.
    Three summer undergraduate interns are working with the Kreidenweis/DeMott group in the laboratory in Summer 2018. We welcome, left to right, Ruby Nelson (U. Massachusetts), sponsored by the CAICE summer studies program, and Samantha Gillette (Portland State) and Marquin Spann (North Carolina A&T) as part of the summer REU program in climate science sponsored by the Earth System Modeling and Education Institute at Colorado State.
  • SOCRATES (Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Studies) field phase completed.
    (SOCRATES) occurred during January and February 2018, as part of a major Southern Ocean (SO) studies period that also included DOE-related studies (see below). Participants from several U.S. universities (funded by NSF), CSIRO, the Australian Bureau of Meteorology, and NCAR based from Hobart, Tasmania for in situ measurement and radar/lidar studies to investigate and help resolve global climate model radiation biases over the SO as having bases from aerosol/cloud microphysical versus dynamical sources. During SOCRATES, our group led comprehensive measurements of ice nucleating particles using equivalent suites of our CFDC instrument and Ice Spectrometer (IS) filter collections on the NSF/NCAR G-V aircraft and on the CSIRO R/V Investigator (CAPRICORN-2018 study – see photo of Ezra Levin and Kathryn Moore during installations). We also operated WIBS-4A instruments (ours and one from Dr. Anne Perring of Colgate University) for bioaerosol measurements on both platforms, and will conduct next-gen sequencing analyses of collected aerosols to assist understanding of cloud response to ocean biogenic aerosol emissions.
  • MARCUS and MICRE campaigns provide unprecedented Southern Ocean data.
    These two projects are funded and supported by the DOE Atmospheric Radiation Measurement Program’s Climate Research Facility. Closely aligned with the multi-agency SOCRATES campaign, one objective of the Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) campaign (Greg McFarquhar, Oklahoma U., PI) is to help in understanding the sources, sinks, and variability of CCN and INPs, the increased bias of absorbed shortwave radiation in summer in models, and conditions conducive to occurrence of extensive supercooled water in the SO region. INP filter collections for offline processing using our IS instrument were deployed alongside the second ARM Mobile Facility's (AMF2) on the Australian Antarctic Division’s Aurora Australis during four Antarctic and Macquarie Island station resupply cruises between October 2017 and March 2018. Whereas MARCUS will provide spatial data over Spring through Fall seasons, the Macquarie Island Cloud and Radiation Experiment (MICRE) (Roj Marchand, U. Washington, PI) will provide seasonal and annual cycles of INPs, aerosol, and cloud properties at a single site (Macquarie station is at 54.6 degrees south latitude and 158.9 degrees east longitude). IS processing is underway to determine the temperature spectrum of the concentrations of INPs active via the immersion freezing mechanism across the temperature regime from 0 to -27°C. Additional analyses (thermal, chemical) will be used to discern the biogenic versus inorganic contributions to INP populations. Aerosol ionic, total carbon and genetic analyses of biological community diversity will also be performed and archived.
  • Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption And Nitrogen (WE-CAN) ready to takeoff!.
    The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen (WE-CAN) study aims to better understand the chemistry of wildfire smoke. The project is funded by the U.S. National Science Foundation (NSF), supported by the National Center for Atmospheric Research (NCAR), and is led by Principal Investigators from Colorado State University, the University of Washington, the University of Colorado at Boulder, the University of Montana, and the University of Wyoming. Agency collaborators include NOAA and NASA, as this project precedes the FIREX and FIRECHEM studies in 2019. A flyer on the full project is here (Flyer). One of the largest instrument packages ever assembled on the NSF/NCAR C-130 aircraft will base from Boise, Idaho from 22 July - 31 August 2018. Our group is specifically addressing how wildfire smoke plume particles of different age affect the behavior and formation of liquid and ice clouds. Elevated wildfire plumes have not previously been sampled in a coordinated manner to evaluate for INP emissions and their evolution. We will be collecting INP measurements (number concentrations and compositions) via our online and offline instrumentation, CCN spectra, aerosol size distribution, and refractory black carbon measurements (SP-2). Sampling will occur from ambient air and a counterflow virtual impactor inlet for sampling smoke that has been ingested in clouds.
  • Dr. Christina McCluskey graduates and starts an NCAR Advanced Studies Program Postdoc!
  • Kathryn Moore was accepted to attend the NCAR Advanced Studies Program Summer Colloquium “Synthesis of Observations and Models in Studies of Shallow and Deep Clouds,” from June 4 to 15, 2018 in Boulder, CO. In July, Kathryn was also selected to attend the 7th International SOLAS Summer School from 23 July to August 4, 2018 in Cargèse, Corsica, France. This biennial event combines lectures and practical workshops by 15 prominent scientists focused on skills and knowledge of the many disciplines needed to understand the nature of ocean-atmosphere interactions and how to link ocean-atmosphere interactions with climate and people.
  • Kevin Barry will be attending the AMS Cloud Physics Conference, , in Vancouver, from July 7 to 14, to present “Ice formation in an atmospheric river event during ACAPEX”. Kevin will also represent our group at the “Workshop on Evaluation of Cloud Probe Processing Software,” being held at the University of British Columbia beforehand, on July 7 to 8, 2018.
  • Paul is greatly looking forward to attending the Telluride Science Research Center's "Aerosols and Clouds: Connections from the Laboratory to the Field to the Globe", to be held from July 30 to August 3rd.
  • Recent publications: "A mesocosm double feature: Insights into the chemical make-up of marine ice nucleating particles" a feature paper on CAICE studies from Christina McCluskey's disseration, was published in the AMS Journal of the Atmospheric Sciences. Christina also led collaborative studies as part of the BACCHUS campaign at Mace Head, Ireland, published in JGR-Atmospheres as "Marine and Terrestrial Organic Ice Nucleating Particles in Pristine Marine to Continentally-Influenced Northeast Atlantic Air Masses". This paper includes the first ever parameterization for marine INPs on the basis of atmospheric measurements. Gregg Schill published "Use of the Single Particle Soot Photometer (SP2) as a pre-filter for ice nucleation measurements: Effect of particle mixing state and determination of SP2 conditions to fully vaporize refractory black carbon" in Atmospheric Measurement Techniques. Kaitlyn Suski's lead paper, "Agricultural harvesting emissions of ice nucleating particles" is now in open discussion in Atmospheric Chemistry and Physics, the first in a series on measurements of arable land emissions of INPs to the atmosphere under prior NSF funding. Finally, Paul's long-coming manuscript ("Overview of results from the Fifth International Workshop on Ice Nucleation part 2 (FIN-02): Laboratory intercomparisons of ice nucleation measurements") on the laboratory study INP measurement phase of the 2015 Fifth International Workshop on Ice Nucleation will open shortly for discussion in Atmospheric Measurement Techniques!

Contact info

Paul J. DeMott
Department of Atmospheric Science
1371 Campus Delivery
Colorado State University
Fort Collins, Colorado 80523
email*: Paul.Demott-AT-colostate.edu
office: (970) 491-8257

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