Aerosol-Cloud Interactions - A Directed Programme to Reduce Uncertainty in Forcing through a Targeted Laboratory and Modelling Programme
Lead Research Organisation:
University of Bristol
Department Name: Chemistry
Abstract
Aerosol particles act as sites for cloud droplet and ice particle formation. Cloud properties can be perturbed through the addition of aerosol particles into the atmosphere from anthropogenic and natural processes. This addition influences cloud microphysical properties, and subsequently affects cloud dynamics and thermodynamics, and the way the cloud interacts with radiation. The Earth's radiation budget is very greatly affected by clouds, and human-induced changes to the particle loading affecting them, known as indirect effects, are large and highly uncertain. A large part of this uncertainty is the result of poor knowledge of the fundamental aerosol and cloud properties and processes, leading to their poor representation in models. A programme of research is proposed here to i) directly investigate these processes in the laboratory, ii) evaluate the sensitivity of climate relevant parameters to the studied processes, iii) interpret the laboratory studies with detailed model investigations and iv) to incorporate and test new descriptions of the studied processes in cloud-scale and, where possible, global scale models. The programme will thereby reduce the uncertainty in estimates of radiative forcing and climate feedbacks relating to aerosol and cloud processes. The studies are split into those affecting warm clouds (those containing only liquid droplets) and those affecting clouds containing ice particles. The programme brings together an interdisciplinary team of researchers with expertise in 'warm' and 'cold' cloud and aerosol processes combining laboratory and multiscale modelling activities to deliver the improved predictive capability. The 'warm' laboratory work focuses on two major aspects i) the rate at which water is taken up by growing aerosol particles as they become cloud droplets (or 'activate) and ii) the ability of aerosol particles of various compositions to act as seeds for cloud droplets. These studies use a number of techniques including single particle optical levitation and investigations in a large photochemical chamber coupled to a large number of chemical and physical probes of ensembles of particles formed in simulated atmospheric chemical processes. The 'cold' work uses a similar coupling of a large, well-instrumented cloud chamber experiments and single particle levitation studies. The chambers used in both aspects will be coupled to investigate the impacts of aerosol transformation conditions on warm and cold cloud formation, using the instrumental payload from both chambers. A range of detailed models will be used to explicitly describe the processes by which aerosol particles interact with increasing relative humidity and reducing temperature to form cloud droplet and ice crystals and to their properties. The processes and properties will be represented in dynamical frameworks to predict the interactions between aerosols and clouds and their radiative effects at cloud resolving scales and radiative forcing of some of the investigated properties on global radiative forcing and feedbacks. The sensitivity of climate relevant parameters to the fundamental parameters investigated in the laboratory programme and their improved quantification will be evaluated using a simplified model 'emulator'.
People |
ORCID iD |
Jonathan Reid (Principal Investigator) |
Publications
Davies J
(2014)
Temperature dependence of the vapor pressure and evaporation coefficient of supercooled water Water evaporation/condensation kinetics
in Journal of Geophysical Research: Atmospheres
Davies JF
(2012)
Bulk, surface, and gas-phase limited water transport in aerosol.
in The journal of physical chemistry. A
Davies JF
(2013)
Influence of organic films on the evaporation and condensation of water in aerosol.
in Proceedings of the National Academy of Sciences of the United States of America
Dennis-Smither B
(2012)
Oxidative aging of mixed oleic acid/sodium chloride aerosol particles
in Journal of Geophysical Research: Atmospheres
Dennis-Smither BJ
(2014)
Volatility and oxidative aging of aqueous maleic acid aerosol droplets and the dependence on relative humidity.
in The journal of physical chemistry. A
Julin J
(2013)
Mass accommodation of water: bridging the gap between molecular dynamics simulations and kinetic condensation models.
in The journal of physical chemistry. A
Mason BJ
(2012)
Comparison of the accuracy of aerosol refractive index measurements from single particle and ensemble techniques.
in The journal of physical chemistry. A
Miles RE
(2012)
Retrieval of the complex refractive index of aerosol droplets from optical tweezers measurements.
in Physical chemistry chemical physics : PCCP
Miles RE
(2012)
Comparison of approaches for measuring the mass accommodation coefficient for the condensation of water and sensitivities to uncertainties in thermophysical properties.
in The journal of physical chemistry. A
Miles RE
(2016)
The influence of the surface composition of mixed monolayer films on the evaporation coefficient of water.
in Physical chemistry chemical physics : PCCP
Rickards AM
(2015)
Variabilities and uncertainties in characterising water transport kinetics in glassy and ultraviscous aerosol.
in Physical chemistry chemical physics : PCCP
Rickards AM
(2013)
Measurements of the sensitivity of aerosol hygroscopicity and the ? parameter to the O/C ratio.
in The journal of physical chemistry. A
Description | We have resolved the long standing issue as to the evaporation coefficient of water and mass accommodation of water from aerosol droplet surfaces, better constraining the kinetics of cloud droplet growth and evaporation. This has been published in peer reviewed articles. In addition, we have examined the influence of organic films on the evaporation coefficient, observing a significant suppression in mass transfer rates when aerosol droplets are coated in a condensed organic film. |
Exploitation Route | The results are being exploited by other collaborators in ACID-PRUF in cloud resolving and climate models. |
Sectors | Environment |
URL | http://www.bristol.ac.uk/chemistry/research/barc/research-projects/mass-accommodation/ |
Description | During this project we have demonstrated that the mass accommodation coefficient of water (equal to the evaporation coefficient) is larger than 0.5. This resolves a longstanding issue in quantifying the kinetics of water condensation on aerosol and the formation of cloud droplets, an uncertainty that has been shown to have an effect on cloud droplet number and leads to an uncertainty in the radiative forcing of clouds. Further, we have shown that the formation of organic films on aqueous droplets can slow the evaporation kinetics of aqueous aerosol considerably, by up to 5 orders of magnitude. |
First Year Of Impact | 2013 |
Sector | Environment,Other |
Title | Electron microscopy 3DR of T3SS needle tip complex |
Description | Includes programmes, instructions and test datasets |
Type Of Material | Database/Collection of data |
Year Produced | 2014 |
Provided To Others? | Yes |
Title | Evaporation Mixed Monolayer PCCP (2016) Paper |
Description | We explore the dependence of the evaporation coefficient of water from aqueous droplets on the composition of a surface film, considering in particular the influence of monolayer mixed component films on the evaporative mass flux. Measurements with binary component films formed from long chain alcohols, specifically tridecanol (C13H27OH) and pentadecanol (C15H31OH), and tetradecanol (C14H29OH) and hexadecanol (C16H33OH), show that the evaporation coefficient is dependent on the mole fractions of the two components forming the monolayer film. We also show that the addition of a long chain alcohol to an aqueous-sucrose droplet can facilitate control over the degree of dehydration achieved during evaporation. This work was undertaken as part of the NERC grant NE/I020075/1 |
Type Of Material | Database/Collection of data |
Year Produced | 2016 |
Provided To Others? | Yes |
Description | Collaboration with Prof. Ilona Riipinen |
Organisation | Stockholm University |
Country | Sweden |
Sector | Academic/University |
PI Contribution | Prof. Riipinen has considerable expertise in modelling the condensation/evaporation processes central to understanding aerosol in the atmosphere. The water transport work is progressing through a collaboration with her. |
Start Year | 2012 |
Description | Berkeley Atmospheric Sciences Symposium |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Invited talk |
Year(s) Of Engagement Activity | 2013 |
Description | Invited seminars at Universities of Cardiff, Leeds and Oxford |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Invited talks |
Year(s) Of Engagement Activity | 2014 |
Description | Lecture tour in US (MIT, Harvard, University of Wisconsin and Carnegie Mellon) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Invited talks |
Year(s) Of Engagement Activity | 2014 |
Description | University of California, Irvine |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Invited talk at University |
Year(s) Of Engagement Activity | 2013 |
Description | University of California, San Diego |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Talk at University |
Year(s) Of Engagement Activity | 2013 |