Abstract
Abstract. Atmospheric aerosols play a key role in the Earth's climate system by scattering and absorbing solar radiation and by acting as cloud condensation nuclei. Satellites are increasingly used to obtain information on properties of aerosol particles with a diameter larger than about 100 nm. However, new aerosol particles formed by nucleation are initially much smaller and grow into the optically active size range on time scales of many hours. In this paper we derive proxies, based on process understanding and ground-based observations, to determine the concentrations of these new particles and their spatial distribution using satellite data. The results are applied to provide seasonal variation of nucleation mode concentration. The proxies describe the concentration of nucleation mode particles over continents. The source rates are related to both regional nucleation and nucleation associated with more restricted sources. The global pattern of nucleation mode particle number concentration predicted by satellite data using our proxies is compared qualitatively against both observations and global model simulations.
Highlights
Atmospheric aerosol particles affect the quality of our life in many different ways
These findings suggest that it might be possible to derive [ORG] in the proxies given by Eqs. (11) and (12) using satellite data on HCHO
We have derived proxies based on physical processes to estimate the concentration of nucleation mode particles
Summary
Atmospheric aerosol particles affect the quality of our life in many different ways. First of all, they influence the Earth’s radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei Detailed aerosol properties can only be measured in situ, and a few ground-based measurement networks for this purpose have been established These include the Global Atmospheric Watch (GAW) aerosol program M. Kulmala et al.: Global nucleation mode aerosol concentrations vertical structure of aerosol properties can be obtained from aircraft, balloon and lidar measurements and from model simulations. Remote sensing with satellite instruments provide aerosol data over large spatial areas, but the information is limited to particles in the optically-active size range, i.e. particles larger than about 100 nm in diameter. In this paper we propose the use of proxies, i.e. parameterizations for the concentrations of nucleated particles in terms of satellite-observable quantities These proxies are developed based on our best understanding on the atmospheric nucleation and growth processes. In terms of the global aerosol number budget, free-troposphere nucleation is probably extremely important as well (e.g. Merikanto et al, 2009), but our approach is not suitable for tracing particles formed in that region due to long times scales associated with the life cycle of these particles
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