Professor Gordon’s research group is interested in how atmospheric particulate matter influences weather and climate, both directly and by interacting with clouds. Particles in the atmosphere may come from natural or anthropogenic (air pollution) sources. Every cloud droplet in our atmosphere formed around a particle, and so polluted clouds have more droplets in them. Clouds with more droplets are brighter so reflect more light back to the Sun. Therefore atmospheric particles generally cool the climate. However, some particles, usually those that are mainly soot, can absorb solar radiation and heat clouds up, causing them to evaporate, and this leads to a warming effect because clouds are more reflective than Earth’s surface below them. Particles in the atmosphere also lead to reduced visibility, either as haze or by influencing the properties of fog. It is therefore important for aviation weather forecasts to account for particle concentrations. Finally, particles can also affect precipitation in clouds containing ice, leading to further complicated weather and climate effects. To understand atmospheric particles and their effects, we run simulations with the UK Met Office “Unified Model,” which is used for both weather forecasting and climate prediction. Our research requires adding new code to the model to better represent both particles and clouds.
Hamish Gordon is an assistant professor in chemical engineering and with the Center for Atmospheric Particle Studies. His research interests are focused on the effects of air pollution and natural airborne particles on clouds and climate. He received his first degree from the University of Cambridge in 2009, and his doctorate from the University of Oxford in experimental high energy physics in 2013. He moved to Carnegie Mellon from a postdoc position at the University of Leeds in 2019.
To study the climate effects of atmospheric particles (the focus of the video featuring Professor Gordon, linked below), we are playing a leading role in the development of the double-moment microphysics configuration of the Unified Model, in which both aerosol and cloud particle mass and particle number concentrations are tracked separately. We make extensive use of atmospheric observations (made at the surface, from aircraft, or from satellites in space) to validate and improve our simulations. Professor Gordon was part of a large team observing clouds in the south-east Atlantic using the UK research aircraft, based at Ascension Island in 2017. The smoke aerosols mixing into clouds can be seen on a day of the measurement campaign in the figure opposite, taken by the MODIS instrument on the TERRA satellite. Since these measurements, we have been analysing data from the aircraft and starting research in new directions, including studying aerosol interactions with mid-latitude storm systems. We are grateful for funding for research in these areas from NASA, the US Department of Energy, and the C3 Digital Transformation Institute.
Our group is also interested in how aerosols affect the weather. By scattering and absorbing radiation and changing the properties of clouds, atmospheric particles can strongly affect visibility, as well as Earth’s climate. Professor Gordon is starting collaborations with various researchers studying aerosol effects on visibility using the UK Met Office Unified Model, including some at Delhi’s National Center for Medium Range Weather Forecasting. An example of low visibility in Delhi is pictured. Please see our first publication, Jayakumar et al (2021) under “Recent publications” below.
Professor Gordon’s research in atmospheric science started at the CLOUD experiment at CERN, and his group plays a leading role in understanding the influence of secondary aerosol formation (essentially, gas molecules in the atmosphere sticking together to make particles) on Earth’s climate. The CLOUD chamber at CERN, shown here, is the world’s leading laboratory experiment for aerosol formation studies. The primary aim of the experiment is to measure the rate at which new particle formation occurs from carefully controlled gas mixtures in ultra-clean conditions. The rates are then parameterized and included into atmospheric models to represent the effects of this process on climate and air quality. Professor Gordon was involved in this research while working first at CERN and then at the University of Leeds. We are now funded by the NASA Roses program to continue studying the implications of new aerosol formation for the atmosphere, working in the Center for Atmospheric Particle Studies at CMU with Professor Neil Donahue.
Muhammad Mueed Khan
- Rasmus Erlemann, Postdoc
- Xu-Cheng He, Postdoc
- Aditya Biyani, MS
- Yash Gokhale, MS
- Hanyu Liu, MS
- H. Gordon et al, Development of aerosol activation in the double-moment Unified Model and evaluation with CLARIFY measurements, Atmospheric Chemistry and Physics, 20 10997 (2020)
- H. Gordon, P. R. Field, S. J. Abel, M. Dalvi, D. P. Grosvenor, et al. Large simulated radiative effects of smoke in the south-east Atlantic. Atmospheric Chemistry and Physics, 18(20): 15261-15289, 2018
- H. Gordon, J. Kirkby, U. Baltensperger, F. Bianchi, M. Breitenlechner, et al. Causes and importance of new particle formation in the present-day and preindustrial atmospheres. Journal of Geophysical Research: Atmospheres, 122(16):8739-8760, 2017
- E. M. Dunne, H. Gordon, A. Kuerten, J. Almeida, J. Duplissy, et al. Global atmospheric particle formation from CERN CLOUD measurements. Science, 354:1119-1124, 2016
- H. Gordon, K. Sengupta, A. Rap, J. Duplissy, C. Frege, et al. Reduced anthropogenic aerosol radiative forcing caused by biogenic new particle formation. Proceedings of the National Academy of Sciences, 113:12053-12058, 2016
- J. Trostl, W. K. Chuang, H. Gordon, M. Heinritzi, et al. The role of low-volatility organic compounds in initial particle growth in the atmosphere. Nature, 533(7604):527-531, 2016
- R. Aaij …H. Gordon et al, (the LHCb Collaboration), Search for CP violation in D+->phipi+ and D+->K0Spi decays. JHEP, 1306:112, 2013
- R. Aaij … H. Gordon et al. (the LHCb Collaboration), Measurement of the D+production asymmetry in 7 TeV pp collisions. Phys. Lett., B718, 2013
- R. Aaij… H.Gordon et al. (the LHCb Collaboration), Search for CP violation in D+->K-K+pi+ decays. Phys. Rev., D84: 112008, 2011
- S. J. Doherty, P. E. Saide, .. H. Gordon et al, Modeled and observed properties related to the direct aerosol radiative effect of biomass burning aerosol over the Southeast Atlantic, Atmospheric Chemistry and Physics (2022)
- M. Wang, M. Xiao, … H.Gordon et al, Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation, Nature 605 483-489 (2022)
- A. Jayakumar, H. Gordon, T. Francis, A. A. Hill, S. Mohandas, B. S. Sandeepan, A. K. Mitra and G. Beig, Delhi Model with chemistry and aerosol framework (DM-chem) for high-resolution fog forecasting, Quarterly Journal of the Royal Meteorological Society (2021)
- M. Xiao, C. R. Hoyle, … H. Gordon et al, The driving factors of new particle formation and growth in the polluted boundary layer, Atmos. Chem. Physics 21 14275 (2021)
- A. Ranjithkumar, H. Gordon, C. Williamson, A. Rollins, K. Pringle, A. Kupc, N. L. Abraham, C. Brock and K.S. Carslaw, Constraints on global aerosol number concentration, SO2 and condensation sink in UKESM1 using ATom measurements, Atmos. Chem. Physics 21 4979 (2021)
- H. Lamkaddam, J. Dommen, A. Ranjithkumar, H. Gordon et al, Large contribution to secondary organic aerosol from isoprene cloud chemistry, Science Advances 7 eabe2952 (2021)
- J. Haywood …. H. Gordon et al, Overview: the Cloud Aerosol Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) measurement campaign, Atmospheric Chemistry and Physics 21 1049 (2021)
- H. Che, P. Stier, H. Gordon, D. Watson-Parris and L. Deaconu, The significant role of biomass burning aerosols in clouds and radiation in the South-east Atlantic Ocean, Atmospheric Chemistry and Physics, 21 17 (2021)
- M. Heinritzi, …, H. Gordon, et al, Molecular understanding of the suppression of new-particle formation by isoprene, Atmospheric Chemistry and Physics, 20 11809 2020
- Y. Shinozuka…H.Gordon et al, Modeling the smoky troposphere of the southeast Atlantic: a comparison to ORACLES airborne observations from September of 2016, Atmospheric Chemistry and Physics, 2020
- Zhao, M. Shrivastava, N. Donahue, H. Gordon et al, High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation, Proc. Natl Acad. Sci. (2020)
- Weber, … H.Gordon et al, CRI-HOM: A novel mechanism for simulating Highly Oxygenated Organic Molecules (HOMs) in global chemistry-aerosol-climate models, Atmospheric Chemistry and Physics, 20 10889 (2020)
- Simon, .. H.Gordon et al, Molecular understanding of new-particle formation from alpha-pinene between −50 °C and 25 °C. Atmospheric Chemistry and Physics, 20 9193 (2020)
- I. McCoy, D. McCoy,…and H. Gordon, The hemispheric contrast in cloud microphysical properties constrains aerosol forcing, Proc. Natl. Acad. Sci. (2020)
- D. Stolzenburg, M. Simon, A. Ranjithkumar, A. Kürten, K. Lehtipalo, H. Gordon, et al, Enhanced growth rate of atmospheric particles from sulfuric acid, Atmospheric Chemistry and Physics, 2020
- C. Yan, … H. Gordon et al, Size-dependent influence of NOx on the growth rates of organic aerosol particles, Science Advances 6 22 (2020)
- D. McCoy, P. Field, H. Gordon, G. S. Elsaesser, and D. P. Grosvenor, Untangling causality in midlatitude aerosol-cloud adjustments, Atmospheric Chemistry and Physics (2020)
- X. Wang, H. Gordon, D. P. Grosvenor, M. O. Andreae and K. S. Carslaw, Contribution of regional aerosol nucleation to low-level CCN in an Amazonian deep convective environment: Results from a regionally nested global model, Atmospheric Chemistry and Physics Discussions, 2022
- H. Che, P. Stier, D. Watson-Parris, H. Gordon, L. Deaconu, Source attribution of cloud condensation nuclei and their impact on stratocumulus clouds and radiation in the south-eastern Atlantic, Atmospheric Chemistry and Physics Discussions (2022)
Sullivan and Gordon receive DOE award
MechE’s Ryan Sullivan and Research Accelerator Hamish Gordon have received funding from the Department of Energy to continue studying how wildfire emissions could affect the climate.
Discovery uncovers need for ammonia emission regulations
A new discovery sheds light on one way new particles are forming in the upper troposphere. Published in Nature, the study’s findings suggest that in addition to carbon dioxide, there are other compounds in need of immediate attention and regulation.
DEP declares Code Orange; Gordon explains
The Pennsylvania Department of Environmental Protection (DEP) has declared a Code Orange Air Quality Action Day for fine particulate matter in Pittsburgh and several surrounding counties. Assistant Research Professor, Hamish Gordon, explains what led to the current conditions.
Faculty earn DOE Awards for Atmospheric Research
Carnegie Mellon University’s Coty Jen and Hamish Gordon have earned Department of Energy (DOE) awards for their work in atmospheric research.
Two engineering faculty projects awarded grants
The Accelerator’s Hamish Gordon and ECE’s Amritanshu Pandey were recently announced as winners of the C3.ai Digital Transformation Institute awards, which this year focused on “digital transformation & AI for energy and climate security.”