Microphysics of Antarctic Clouds

Lead Research Organisation: NERC British Antarctic Survey
Department Name: Science Programmes

Abstract

The largest uncertainties in future climate predictions highlighted by the Intergovernmental Panel on Climate change (IPCC 2007) arise from our lack of knowledge of the interaction of clouds with solar and terrestrial radiation (Dufresene & Bony, 2008).
In Antarctica clouds play a major role in determining the continent's ice sheet radiation budget, its surface mass balance and ozone climatology. However in spite of this there are few in situ measurements of cloud properties, aerosol numbers, Cloud Condensation Nuclei (CCN) or Ice Nuclei (IN) with the main focus being on remote sensing data sets (see the review by Bromwich et al 2012). As a result the skill in climate and forecast models at high latitudes is significantly poorer than at mid latitudes.
In this is project we plan to extend the regions sampled to ones more representative of the Antarctic continent's coastal region. It is in this coastal region that clouds will have the biggest impact on the climate as in the interior of the continent the total cloud cover is less (Lachlan-Cope 2010) and those clouds that exist are more tenuous. To achieve this we will conduct flights from the Halley research station.

Planned Impact

This study addresses an area in which numerical models of the atmosphere over Antarctic are deficient. The results from this study will be used to develop new cloud parametrizations that can be used in high resolution local forecast model and lower resolution global climate and forecast models. The developers of high resolution models such as the Weather Research and Forecasting (WRF) model and global models such as the UK Met Office unified model will be consulted about the development of the field campaign and will be given access both to any new parametrizations developed. Also the microphysical data sets collected during the project will be made freely available.

The results from this project will be disseminated to the general public by talks, both to schools and to the wider community. Also key results from the project will be posted on the well visited BAS web site.

Publications

10 25 50
 
Description The fieldwork component of this projects was postponed for a year due to problems at Halley Station. The fieldwork was eventually completed in November and December 2015 and an interesting data set has been collected. Although analysis is still in an early stage the results seem interesting with both primary and secondary ice cloud particle formation processes identified. The extra year on the project has been used to further analyse the cloud data collected over the Antarctic Peninsula and investigate how well the Weather Research and Forecast numerical model represents these clouds. It has been found that two moment schemes - ones that have a representation of both particle size and numbers - work better than the more simple single moment schemes that have been more commonly used. It is hoped that this work will inform our work with more recent data from MAC. The analysis of the observations taken at Halley have now yielded a paper on the initial results and one on biogenic aerosol observed at the surface. Work on modelling these clouds has continued .
Exploitation Route It is hoped that our findings will be used by the developers of the Antarctic Mesoscale Prediction System (AMPS) that is based on the WRF model, to improve Antarctic Forecasts. Also we would expect the results to improve the cloud over the Southern Ocean in climate models where large errors have been identified.
Sectors Environment

 
Title Microphysics of Antarctic Clouds 
Description Data collected during Microphysics of Antarctic Clouds project that took play at Halley Station, Antarctica during November and December 2015. The data includes aircraft measurements of clouds, aerosols and turbulence as well as surface based measurements of aerosols. This data will be made publicly available during the next year. 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
Impact Papers using this data are being prepared. 
 
Title Microphysics of Antarctic Clouds: Polar-optimised Weather Research and Forecasting (PWRF) model simulations for case study 
Description Microphysics of Antarctic Clouds: Polar-optimised Weather Research and Forecasting (PWRF) model simulations for case study with BAS MASIN twin-otter flights 218 and 219 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact A paper published in GRL - Young, G., Lachlan-Cope, T., O'Shea, S. J., Dearden, C., Listowski, C., Bower, K. N., et al. (2019). Radiative effects of secondary ice enhancement in coastal Antarctic clouds. Geophysical Research Letters, 46. https://doi.org/10.1029/2018GL080551