Marine aerosol influence on clouds in the high Arctic


Project leader


Co-Investigators


Funding source

Swedish Research Council - Vetenskapsrådet (VR)


Project Details

Start date: 01/01/2016
End date: 31/12/2019
Funding: 3885000 SEK


Description

The goal of this project is to investigate if local emissions of aerosol particles from the ocean surface govern the background state of clouds in the summertime high Arctic. This knowledge is fundamental for understanding the response of Arctic clouds to different perturbations, for example increased air pollution or enhanced levels of greenhouse gases. The Arctic is currently warming considerably faster than the rest of the world. Clouds over the Arctic pack ice area can persist for several days and are crucial for the surface energy budget, which controls whether sea ice will freeze or melt. The longevity of Arctic clouds is surprising as they predominantly consist of both liquid droplets and ice crystals, a mixture that is unstable and should make the clouds dissipate. Aerosol particles are necessary to form cloud droplets and ice crystals, but the source of aerosols that dominates the cloud-forming process in the summertime high Arctic is still not well known. Current climate models have problems representing Arctic cloud conditions and thus the surface energy budget. Our hypothesis is that aerosol particles emitted from open leads (water channels) in the pack ice are crucial for governing the background state of Arctic clouds. Consequently, the aerosol sources, and their droplet and ice forming potential, need to be adequately addressed in climate models. Using a three-dimensional large-eddy simulation model, uniquely developed with the aim to study the complex processes governing Arctic cloud properties, we will simulate in detail the evolution of Arctic clouds and compare the model results with observations. Making use of unique high-quality data, extending over decades and obtained from past successful expeditions to the high Arctic, we will extract information on the fluxes of aerosols from the open leads in the pack ice as well as their cloud droplet nucleating properties. With the model, we will examine if a surface source of aerosols can sustain the clouds and how different input parameters, both meteorological and chemical, affect the cloud properties. As no data on the ice crystal forming potential of marine Arctic Ocean aerosols currently exist, laboratory experiments will be performed as a complement to the already available in-situ measurements. These experiments will be a collaborative effort with ETH-Zurich, Switzerland, using a combined aerosol immersion and ice nucleation chamber. Based on the results obtained from the comparison between the simulations and the observations, the numerical descriptions for cloud droplet activation and ice crystal formation will be evaluated and revised, to consider the most crucial processes while still being suitable for application in global models. The results will provide novel insights on the complex processes governing cloud properties in one of the climatically most sensitive regions of the world. The project extends over four years and is led by Dr. Annica Ekman, an expert in cloud-aerosol interactions and their numerical modelling at both the small (large-eddy simulation) and the global (climate model) scales. She has solid experience in integrating observations and models, and is collaborating on a national and international level with both experimental and modelling aerosol-cloud-climate interaction experts. The large-eddy simulation model applied in the project has been developed by Dr. Ekman and her research group. Co-leader of the project will be Prof. Caroline Leck, a world-leading expert on biogeochemical processes in the Arctic and with extensive previous experience of managing large multidisciplinary/institutional Arctic research programs. The project resources will mainly be used to fund a PhD student. Our collaborative partner at ETH-Zurich, Switzerland will be Prof. Ulrike Lohmann.


Last updated on 2017-28-07 at 11:15