EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Multifaceted Aerosol Effects on Precipitation

Philip Stier1 and the GEWEX Aerosol Precipitation (GAP) initiative expert workshop team*
Philip Stier and the GEWEX Aerosol Precipitation (GAP) initiative expert workshop team
  • 1Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK (
  • *A full list of authors appears at the end of the abstract

A wide range of aerosol effects on precipitation have been proposed, from the scale of individual clouds to that of the globe.

This presentation, based on the findings of an expert workshop under the umbrella of the GEWEX Aerosol Precipitation initiative, reviews the evidence and scientific consensus behind these effects and the underlying set of physical mechanisms, categorised into i) radiative effects via modification of radiative fluxes and the energy balance and ii) microphysical effects via modification of cloud droplets and ice crystals.

There exists broad consensus and strong theoretical evidence that, because global mean precipitation is constrained by energetics and surface evaporation, aerosol radiative effects (aerosol-radiation interactions and aerosol-cloud interactions) act as drivers of precipitation changes. Likewise, aerosol radiative effects cause well-documented shifts of large-scale precipitation patterns, such as the Inter-Tropical Convergence Zone (ITCZ). The extent to which aerosol effects on precipitation are applicable at smaller scales and driven or buffered by compensating microphysical and dynamical mechanisms and budgetary constraints is less clear. Although there exists broad consensus and strong evidence that suitable aerosol perturbations increase cloud droplet numbers, reducing the efficiency of warm rain formation across cloud regimes, the overall aerosol effect on cloud microphysics and dynamics as well as the subsequent impact on local, regional and global precipitation is less constrained.

This presentation provides a review of the physical mechanisms of aerosol effects on precipitation backed up by evidence from recent cloud-resolving and global modelling simulations as well as from satellite observations.

GEWEX Aerosol Precipitation (GAP) initiative expert workshop team:

Philip Stier1, Susan C. van den Heever2, Matthew Christensen1,a, Edward Gryspeerdt3, Guy Dagan1,now at 19, Massimo Bollasina4, Leo Donner5, Kerry Emanuel6, Annica M. L. Ekman7, Graham Feingold8, Paul Field9,10, Piers Forster11, Jim Haywood12,10, Ralph Kahn13, Ilan Koren14, Christian Kummerow2, Tristan L'Ecuyer15 , Ulrike Lohmann16, Yi Ming5, Gunnar Myhre17, Johannes Quaas18, Daniel Rosenfeld19, Bjorn Samset17, Axel Seifert20, Graeme Stephens21, Wei-Kuo Tao22 1 Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, UK a Now at Pacific Northwest National Laboratory, Richland, WA 99354, United States. 2 Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA 3 Space and Atmospheric Physics Group, Imperial College London, London SW7 2AZ, UK 4 School of GeoSciences, The University of Edinburgh, Grant Institute, West Mains Road, Edinburgh EH9 3JW, UK 5 NOAA/GFDL, Princeton University Forrestal Campus, 201 Forrestal Road, Princeton, New Jersey 08540, USA 6 Lorenz Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 7 Department of Meteorology, and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden 8 National Oceanic and Atmospheric Administration, Chemical Sciences Laboratory, Boulder, CO 80305, USA 9 School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK 10 Met Office, Fitzroy Rd, Exeter EX1 3PB, UK 11 Priestley International Centre for Climate, University of Leeds, Leeds, LS2 9JT, UK 12 CEMPS, University of Exeter, Exeter, UK 13 NASA Goddard Space Flight Center, Greenbelt, MD, USA 14 Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel 15 Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA 16 ETH Zürich, Institute for Atmospheric and Climate Science, Zürich, Switzerland 17 Center for International Climate Research—Oslo (CICERO), Pb. 1129 Blindern, N-0318 Oslo, Norway 18 Institute for Meteorology, Universität Leipzig, Leipzig, Germany 19 Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel 20 Deutscher Wetterdienst, Offenbach, Germany 21 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA 22 Mesoscale Atmospheric Processes Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA

How to cite: Stier, P. and the GEWEX Aerosol Precipitation (GAP) initiative expert workshop team: Multifaceted Aerosol Effects on Precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2856,, 2022.