Dr. Robert Wood, Professor, Dept. of Atmospheric Sciences, University of Washington, will present.

Current and Future Cloud Brightening from Ships in Subtropical Low Clouds

ABSTRACT: It has long been known that emissions of aerosol particles and precursors from large ships can alter the reflectivity of low clouds over the oceans. The influence of aerosol particles on cloud reflectivity is one of the largest sources of uncertainty in our understanding of anthropogenic climate change. Commercial shipping constitutes a large and relatively concentrated aerosol perturbation that can be used to quantify the impacts of aerosols on cloud reflectivity. In this presentation, I will present an analysis of satellite data that shows a significant increase in cloud reflectivity associated with enhanced cloud droplet number concentrations within a major shipping corridor in the southeast Atlantic. These results are then used to  estimate a global radiative forcing estimate from shipping, which is anticipated to diminish as new fuel-sulfur regulations came into force in 2020. Analysis of clouds brightened by commercial ships (ship tracks) shows a marked reduction in their frequency after 2020. We use the results to make an estimate of the global effective radiative forcing from all anthropogenic sulfate. For the final part of the presentation, I will ask the question of how much more reflective marine clouds could be made if we were to deliberately increase aerosol concentrations over the oceans, a climate intervention proposal known as marine cloud brightening (MCB). This will include a discussion of research being conducted to better quantify the potential efficacy of MCB using field observations and multi-scale modeling. 

Bio:

Dr. Robert Wood is Professor of Atmospheric Sciences at the University of Washington. Wood’s research work focuses upon understanding processes controlling clouds in the Earth’s atmosphere and the roles that clouds play in determining climate variability and change, the formation of rain, and how tiny aerosol particles (both natural and anthropogenic) interact with them and affect their properties. Wood’s research uses a combination of observational data collected with aircraft, satellites and from ground-based remote sensing, together with numerical and theoretical models. Wood also serves as lead scientist for the Marine Cloud Brightening Project, which aims to better understand the feasibility of deliberately seeding marine low clouds as a potential means for cooling the Earth system.

     Wood served in leadership roles on several major field experiment including the VOCALS Regional Experiment and the ORACLES NASA Earth Venture Suborbital 2 mission (2015-2019) to examine the effects of southern African biomass burning aerosols on clouds and climate over the southeastern Atlantic Ocean. Wood served as site scientist for the DOE Eastern North Atlantic (ENA) ARM fixed site on Graciosa Island in the Azores (2015-2020) and was co-principal investigator on the ACE-ENA field experiments in 2017/2018.  

     Dr. Wood was awarded the 2001 L. F. Richardson Prize from the Royal Meteorological Society, the 2010 Henry Houghton Award from American Meteorological Society, “for advancing understanding of the interactions between cloud droplets, aerosols, radiation and precipitation in marine stratocumulus”, and was awarded an AGU Ascent Award in 2017 “for seminal contributions to our understanding of physical processes controlling marine boundary layer clouds and their interactions in the Earth’s climate system”. He became a fellow of the American Meteorological Society in 2021.

Dr. Robert Wood, Professor, Dept. of Atmospheric Sciences, University of Washington, will present.

Current and Future Cloud Brightening from Ships in Subtropical Low Clouds

ABSTRACT: It has long been known that emissions of aerosol particles and precursors from large ships can alter the reflectivity of low clouds over the oceans. The influence of aerosol particles on cloud reflectivity is one of the largest sources of uncertainty in our understanding of anthropogenic climate change. Commercial shipping constitutes a large and relatively concentrated aerosol perturbation that can be used to quantify the impacts of aerosols on cloud reflectivity. In this presentation, I will present an analysis of satellite data that shows a significant increase in cloud reflectivity associated with enhanced cloud droplet number concentrations within a major shipping corridor in the southeast Atlantic. These results are then used to  estimate a global radiative forcing estimate from shipping, which is anticipated to diminish as new fuel-sulfur regulations came into force in 2020. Analysis of clouds brightened by commercial ships (ship tracks) shows a marked reduction in their frequency after 2020. We use the results to make an estimate of the global effective radiative forcing from all anthropogenic sulfate. For the final part of the presentation, I will ask the question of how much more reflective marine clouds could be made if we were to deliberately increase aerosol concentrations over the oceans, a climate intervention proposal known as marine cloud brightening (MCB). This will include a discussion of research being conducted to better quantify the potential efficacy of MCB using field observations and multi-scale modeling. 

Bio:

Dr. Robert Wood is Professor of Atmospheric Sciences at the University of Washington. Wood’s research work focuses upon understanding processes controlling clouds in the Earth’s atmosphere and the roles that clouds play in determining climate variability and change, the formation of rain, and how tiny aerosol particles (both natural and anthropogenic) interact with them and affect their properties. Wood’s research uses a combination of observational data collected with aircraft, satellites and from ground-based remote sensing, together with numerical and theoretical models. Wood also serves as lead scientist for the Marine Cloud Brightening Project, which aims to better understand the feasibility of deliberately seeding marine low clouds as a potential means for cooling the Earth system.

     Wood served in leadership roles on several major field experiment including the VOCALS Regional Experiment and the ORACLES NASA Earth Venture Suborbital 2 mission (2015-2019) to examine the effects of southern African biomass burning aerosols on clouds and climate over the southeastern Atlantic Ocean. Wood served as site scientist for the DOE Eastern North Atlantic (ENA) ARM fixed site on Graciosa Island in the Azores (2015-2020) and was co-principal investigator on the ACE-ENA field experiments in 2017/2018.  

     Dr. Wood was awarded the 2001 L. F. Richardson Prize from the Royal Meteorological Society, the 2010 Henry Houghton Award from American Meteorological Society, “for advancing understanding of the interactions between cloud droplets, aerosols, radiation and precipitation in marine stratocumulus”, and was awarded an AGU Ascent Award in 2017 “for seminal contributions to our understanding of physical processes controlling marine boundary layer clouds and their interactions in the Earth’s climate system”. He became a fellow of the American Meteorological Society in 2021.