CLouds and Aerosol Radiative Impacts and Forcing: Year 2016 (CLARIFY-2016)
Lead Research Organisation:
University of Leeds
Department Name: School of Earth and Environment
Abstract
Biomass burning aerosol (BBA) exerts a considerable impact on climate by impacting regional radiation budgets as it significantly reflects and absorbs sunlight, and its cloud nucleating properties perturb cloud microphysics and hence affect cloud radiative properties, precipitation and cloud lifetime. However, BBA is a complex and poorly understood aerosol species as it consists of a complex cocktail of organic carbon and inorganic compounds mixed with black carbon and hence large uncertainties exist in both the aerosol-radiation-interactions and aerosol-cloud-interactions, uncertainties that limit the ability of our current climate models to accurately reconstruct past climate and predict future climate change.
The African continent is the largest global source of BBA (around 50% of global emissions) which is transported offshore over the underlying semi-permanent cloud decks making the SE Atlantic a regional hotspot for BBA concentrations. While global climate models agree that this is a regional hotspot, their results diverge dramatically when attempting to assess aerosol-radiation-interactions and aerosol-cloud-interactions. Hence the area presents a very stringent test for climate models which need to capture not only the aerosol geographic, vertical, absorption and scattering properties, but also the cloud geographic distribution, vertical extent and cloud reflectance properties. Similarly, in order to capture the aerosol-cloud-interactions adequately, the susceptibility of the clouds in background conditions; aerosol activation processes; uncertainty about where and when BBA aerosol is entrained into the marine bundary layer and the impact of such entrainment on the microphysical and radiative properties of the cloud result in a large uncertainty. BBA overlying cloud also causes biases in satellite retrievals of cloud properties which can cause erroneous representation of stratocumulus cloud brightness; this has been shown to cause biases in other areas of the word such as biases in precipitation in Brazil via poorly understood global teleconnection processes.
It is timely to address these challenges as both measurement methods and high resolution model capabilities have developed rapidly over the last few years and are now sufficiently advanced that the processes and properties of BBA can be sufficiently constrained. This measurement/high resolution model combination can be used to challenge the representation of aerosol-radiation-interaction and aerosol-cloud-interaction in coarser resolution numerical weather prediction (NWP) and climate models. Previous measurements in the region are limited to the basic measurements made during SAFARI-2000 when the advanced measurements needed for constraining the complex cloud-aerosol-radiation had not been developed and high resolution modelling was in its infancy.
We are therefore proposing a major consortium programme, CLARIFY-2016, a consortium of 5 university partners and the UK Met Office, which will deliver a suite of ground and aircraft measurements to measure, understand, evaluate and improve:
a) the physical, chemical, optical and radiative properties of BBAs
b) the physical properties of stratocumulus clouds
c) the representation of aerosol-radiation interactions in weather and climate models
d) the representation of aerosol-cloud interactions across a range of model scales.
The main field experiment will take place during September 2016, based in Walvis Bay, Namibia. The UK large research aircraft (FAAM) will be used to measure in-situ and remotely sensed aerosol and cloud and properties while advanced radiometers on board the aircraft will measure aerosol and cloud radiative impacts. While the proposal has been written on a stand-alone basis, we are closely collaborating and coordinating with both the NASA ORACLES programme (5 NASA centres, 8 USA universities) and NSF-funded ONFIRE programme (22 USA institutes).
The African continent is the largest global source of BBA (around 50% of global emissions) which is transported offshore over the underlying semi-permanent cloud decks making the SE Atlantic a regional hotspot for BBA concentrations. While global climate models agree that this is a regional hotspot, their results diverge dramatically when attempting to assess aerosol-radiation-interactions and aerosol-cloud-interactions. Hence the area presents a very stringent test for climate models which need to capture not only the aerosol geographic, vertical, absorption and scattering properties, but also the cloud geographic distribution, vertical extent and cloud reflectance properties. Similarly, in order to capture the aerosol-cloud-interactions adequately, the susceptibility of the clouds in background conditions; aerosol activation processes; uncertainty about where and when BBA aerosol is entrained into the marine bundary layer and the impact of such entrainment on the microphysical and radiative properties of the cloud result in a large uncertainty. BBA overlying cloud also causes biases in satellite retrievals of cloud properties which can cause erroneous representation of stratocumulus cloud brightness; this has been shown to cause biases in other areas of the word such as biases in precipitation in Brazil via poorly understood global teleconnection processes.
It is timely to address these challenges as both measurement methods and high resolution model capabilities have developed rapidly over the last few years and are now sufficiently advanced that the processes and properties of BBA can be sufficiently constrained. This measurement/high resolution model combination can be used to challenge the representation of aerosol-radiation-interaction and aerosol-cloud-interaction in coarser resolution numerical weather prediction (NWP) and climate models. Previous measurements in the region are limited to the basic measurements made during SAFARI-2000 when the advanced measurements needed for constraining the complex cloud-aerosol-radiation had not been developed and high resolution modelling was in its infancy.
We are therefore proposing a major consortium programme, CLARIFY-2016, a consortium of 5 university partners and the UK Met Office, which will deliver a suite of ground and aircraft measurements to measure, understand, evaluate and improve:
a) the physical, chemical, optical and radiative properties of BBAs
b) the physical properties of stratocumulus clouds
c) the representation of aerosol-radiation interactions in weather and climate models
d) the representation of aerosol-cloud interactions across a range of model scales.
The main field experiment will take place during September 2016, based in Walvis Bay, Namibia. The UK large research aircraft (FAAM) will be used to measure in-situ and remotely sensed aerosol and cloud and properties while advanced radiometers on board the aircraft will measure aerosol and cloud radiative impacts. While the proposal has been written on a stand-alone basis, we are closely collaborating and coordinating with both the NASA ORACLES programme (5 NASA centres, 8 USA universities) and NSF-funded ONFIRE programme (22 USA institutes).
Planned Impact
CLARIFY-2016: Impact Summary
1. The Beneficiaries of the Research and how they will benefit from it:-
Scientific community:
CLARIFY will be of significant scientific interest nationally and internationally as evident by the synergistic proposed research under the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) and NSF ONFIRE (ObservatioNs of Fires Impact on the southeast atlantic REgion) proposals and the level of support from the Met Office. CLARIFY data will be placed on the BADC for use initially by project partners, but will be available to the entire community subsequent to completion of the project. Specifically:-
1) The ONFIRE consortium consists of a total of 22 US universities and research institutes who plan complementary measurements with the C-130 aircraft from Sao Tome Island (2000km north of Walvis Bay). CLARIFY measurements will provide vital cloud-aerosol-radiation observations in stratocumulus, rather than cumulus-dominated cloud regimes hence extending the geographical extent and applicability of their study. They will be granted access to bespoke Numerical Weather Prediction model forecasts, and CLARIFY data (ODMP), and will provide the same to CLARIFY in a reciprocal data sharing agreement.
2)The ORACLES consortium consists of 5 NASA Research Centres and 8 US universities. They plan deployment of the NASA P3 and ER-2 high altitude aircraft to Walvis Bay. They will benefit from intercomparison/validation of aircraft data, synergistic planning of the aircraft measurements with potential dual-aircraft flights planned, NWP forecasts and CLARIFY data (ODMP). They will provide the same to CLARIFY in a reciprocal agreement.
3) The AEROCOM community. There are 22 global atmospheric models/groups contributing to Phase II of AEROCOM who will benefit from a full range of validation data, and comparisons against an optimised version of HadGEM3.
4) Project partners in the satellite community; the provision of accurate aerosol microphysical properties, cloud retrievals and biases caused by overlying BBA will be utilised by the satellite community.
Operational Weather Forecasting Centres:
5) The Met Office will benefit from (i) sharing costs of aircraft deployment costs (ii) validation and improvement of satellite retrievals, Met Office large eddy simulation model (LEM), limited area and global NWP models, and the HadGEM3 climate model leading to better weather, seasonal forecasts, and climate projections at local, regional, and continental scales.
6)The South Africa Weather Service (SAWS) provides weather forecasts for southern Africa, using a licensed version of the Met Office limited area NWP model.
7) The European Centre for Medium Range Weather Forecasting (ECMWF, PP) will collaborate and benefit from provision of forecast validation data (see letter of support).
General public / media:
8) There has been significant publicity in recent years on aerosols, clouds and climate. However, there remains a significant lack of knowledge surrounding these issues and clear information needs to be conveyed to the public to enable greater appreciation of the uncertainties in regional and global climate prediction.
9) Improved forecasts by SAWS will improve NWP forecasts for southern Africa, while the global NWP model improvements will improve forecasts in other areas by better representing global teleconnections in weather patterns.
Policymakers:
10) There is considerable interest from policy-makers on the impacts of absorbing aerosol on the radiative forcing of climate with suggestions for black carbon emission reduction as a mitigation strategy to counter global warming. The measurements will lead to a greater knowledge of the impacts of black carbon-rich absorbing aerosol above reflective cloud over the SE Atlantic hot-spot. The measurement and modelling integration will provide policy makers with evidence for potential effectiveness of mitigation strategies.
1. The Beneficiaries of the Research and how they will benefit from it:-
Scientific community:
CLARIFY will be of significant scientific interest nationally and internationally as evident by the synergistic proposed research under the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) and NSF ONFIRE (ObservatioNs of Fires Impact on the southeast atlantic REgion) proposals and the level of support from the Met Office. CLARIFY data will be placed on the BADC for use initially by project partners, but will be available to the entire community subsequent to completion of the project. Specifically:-
1) The ONFIRE consortium consists of a total of 22 US universities and research institutes who plan complementary measurements with the C-130 aircraft from Sao Tome Island (2000km north of Walvis Bay). CLARIFY measurements will provide vital cloud-aerosol-radiation observations in stratocumulus, rather than cumulus-dominated cloud regimes hence extending the geographical extent and applicability of their study. They will be granted access to bespoke Numerical Weather Prediction model forecasts, and CLARIFY data (ODMP), and will provide the same to CLARIFY in a reciprocal data sharing agreement.
2)The ORACLES consortium consists of 5 NASA Research Centres and 8 US universities. They plan deployment of the NASA P3 and ER-2 high altitude aircraft to Walvis Bay. They will benefit from intercomparison/validation of aircraft data, synergistic planning of the aircraft measurements with potential dual-aircraft flights planned, NWP forecasts and CLARIFY data (ODMP). They will provide the same to CLARIFY in a reciprocal agreement.
3) The AEROCOM community. There are 22 global atmospheric models/groups contributing to Phase II of AEROCOM who will benefit from a full range of validation data, and comparisons against an optimised version of HadGEM3.
4) Project partners in the satellite community; the provision of accurate aerosol microphysical properties, cloud retrievals and biases caused by overlying BBA will be utilised by the satellite community.
Operational Weather Forecasting Centres:
5) The Met Office will benefit from (i) sharing costs of aircraft deployment costs (ii) validation and improvement of satellite retrievals, Met Office large eddy simulation model (LEM), limited area and global NWP models, and the HadGEM3 climate model leading to better weather, seasonal forecasts, and climate projections at local, regional, and continental scales.
6)The South Africa Weather Service (SAWS) provides weather forecasts for southern Africa, using a licensed version of the Met Office limited area NWP model.
7) The European Centre for Medium Range Weather Forecasting (ECMWF, PP) will collaborate and benefit from provision of forecast validation data (see letter of support).
General public / media:
8) There has been significant publicity in recent years on aerosols, clouds and climate. However, there remains a significant lack of knowledge surrounding these issues and clear information needs to be conveyed to the public to enable greater appreciation of the uncertainties in regional and global climate prediction.
9) Improved forecasts by SAWS will improve NWP forecasts for southern Africa, while the global NWP model improvements will improve forecasts in other areas by better representing global teleconnections in weather patterns.
Policymakers:
10) There is considerable interest from policy-makers on the impacts of absorbing aerosol on the radiative forcing of climate with suggestions for black carbon emission reduction as a mitigation strategy to counter global warming. The measurements will lead to a greater knowledge of the impacts of black carbon-rich absorbing aerosol above reflective cloud over the SE Atlantic hot-spot. The measurement and modelling integration will provide policy makers with evidence for potential effectiveness of mitigation strategies.
Organisations
Publications
Toll V
(2017)
Volcano and ship tracks indicate excessive aerosol-induced cloud water increases in a climate model.
in Geophysical research letters
McCoy IL
(2020)
The hemispheric contrast in cloud microphysical properties constrains aerosol forcing.
in Proceedings of the National Academy of Sciences of the United States of America
Haywood J
(2021)
The CLoud-Aerosol-Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) measurement campaign
in Atmospheric Chemistry and Physics
Grosvenor D
(2017)
The relative importance of macrophysical and cloud albedo changes for aerosol-induced radiative effects in closed-cell stratocumulus: insight from the modelling of a case study
in Atmospheric Chemistry and Physics
Gordon H
(2018)
Large simulated radiative effects of smoke in the south-east Atlantic
in Atmospheric Chemistry and Physics
Gordon H
(2020)
Development of aerosol activation in the double-moment Unified Model and evaluation with CLARIFY measurements
in Atmospheric Chemistry and Physics
| Description | Analysis performed of the PCASP data for all profiles runs (239 runs) and calculations made of the mean values of aerosol between the inversion base and the surface, the mean between the inversion top and 5000 m, the maximum values between the inversion top and 5000 m and their height. Cluster analysis found that the flights can be classified into two groups: relatively clean free troposphere and polluted BL, polluted free troposphere and relatively clean BL. The latter can further be classified into two groups. |
| Exploitation Route | The cluster analysis is a different technique that can be used by others. More later -- it's early days yet. |
| Sectors | Environment |
| Title | A major combustion aerosol event had a negligible impact on the atmospheric ice-nucleating particle population |
| Description | Clouds containing supercooled water are important for both climate and weather, but our knowledge of which aerosol particle types nucleate ice in these clouds is far from complete. Combustion aerosols have strong anthropogenic sources and if these aerosol types were to nucleate ice in clouds they might exert a climate forcing. Here, we quantified the atmospheric ice-nucleating particle (INP) concentrations during the UK's annual Bonfire Night celebrations, which are characterised by strong anthropogenic emissions of combustion aerosol. We used three immersion mode techniques covering more than six orders of magnitude in INP concentration over the temperature range from -10 °C to homogeneous freezing. We found no observable systematic change in the INP concentration on three separate nights, despite more than a factor of 10 increase in aerosol number concentrations, up to a factor of 10 increase in PM10 concentration and more than a factor of 100 increase in black carbon (BC) mass concentration relative to pre-event levels. This implies that BC and other combustion aerosol such as ash did not compete with the INPs present in the background air. Furthermore, the upper limit of the ice-active site surface density, ns(T), of BC was shown to be consistent with several other recent laboratory studies, showing a very low ice-nucleating activity of BC. We conclude that combustion aerosol particles similar to those emitted on Bonfire Night are at most of secondary importance for the INP population relevant for mixed-phase clouds in typical mid-latitude terrestrial locations. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| URL | https://archive.researchdata.leeds.ac.uk/756/ |
| Title | Diurnal cycle of the semi-direct effect from a persistent absorbing aerosol layer over marine stratocumulus in large-eddy simulations: supporting dataset |
| Description | Relevant data for reproducing figures and tables from Herbert et al., 2020, Atmospheric Chemistry and Physics: "Diurnal cycle of the semi-direct effect from a persistent absorbing aerosol layer over marine stratocumulus in large-eddy simulations". The tar file contains the relevant netcdf files that contain simulation output from the MET Office large eddy model (LEM). Each netcdf file corresponds to a single model setup and experiment - details of which can be found within the published manuscript. Information concerning the LEM, and details on how to obtain access to the code, can be found at http://appconv.metoffice.com/LEM/index.html. The file 'relevant_information.pdf' contains two tables. The first provides the names of each netcdf file that was used to produce each figure in the manuscript. The second provides the metadata for the netcdf variables that were used to produce the figures and tables. The netcdf filename provides information on the experiment setup as follows: run-identifier-number _ length-of-run _ AOD-of-layer _ GAP-between-cloud-and-layer _ THICKNESS-of-layer _ 'bigarray' _ special-setups-for-sensitivity-experiments For example, r1360_8day_transient_aod02_0dz_250th_bigarray_nodrizz is run number r1360, simulating 8 days, with the aerosol layer properties AOD=0.2, cloud-to-aerosol gap of 0m, layer thickness of 250m, in the sensitivity setup where precipitation has been switched off. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| URL | https://zenodo.org/record/3630557 |
| Title | Diurnal cycle of the semi-direct effect from a persistent absorbing aerosol layer over marine stratocumulus in large-eddy simulations: supporting dataset |
| Description | Relevant data for reproducing figures and tables from Herbert et al., 2020, Atmospheric Chemistry and Physics: "Diurnal cycle of the semi-direct effect from a persistent absorbing aerosol layer over marine stratocumulus in large-eddy simulations". The tar file contains the relevant netcdf files that contain simulation output from the MET Office large eddy model (LEM). Each netcdf file corresponds to a single model setup and experiment - details of which can be found within the published manuscript. Information concerning the LEM, and details on how to obtain access to the code, can be found at http://appconv.metoffice.com/LEM/index.html. The file 'relevant_information.pdf' contains two tables. The first provides the names of each netcdf file that was used to produce each figure in the manuscript. The second provides the metadata for the netcdf variables that were used to produce the figures and tables. The netcdf filename provides information on the experiment setup as follows: run-identifier-number _ length-of-run _ AOD-of-layer _ GAP-between-cloud-and-layer _ THICKNESS-of-layer _ 'bigarray' _ special-setups-for-sensitivity-experiments For example, r1360_8day_transient_aod02_0dz_250th_bigarray_nodrizz is run number r1360, simulating 8 days, with the aerosol layer properties AOD=0.2, cloud-to-aerosol gap of 0m, layer thickness of 250m, in the sensitivity setup where precipitation has been switched off. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| URL | https://zenodo.org/record/3630556 |
| Title | Polluted cloud tracks detected in MODIS satellite images |
| Description | The dataset contains positions and time of occurrence of polluted cloud tracks. These cloud tracks polluted by aerosols have increased cloud droplet number concentrations compared to the nearby unpolluted clouds. The locations of polluted cloud tracks in MODIS satellite images have been hand-logged at various anthropogenic and natural aerosol sources over land and ocean. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2019 |
| Provided To Others? | Yes |