The first estimates of global nucleation mode aerosol concentrations based on satellite measurements

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.

Cloud condensation nuclei production associated with atmospheric nucleation: a synthesis based on existing literature and new results

“…Global estimates based on observations are extremely challenging, since satellites and other remote sensing instruments detect only particles larger than ∼100 nm, and cannot differentiate the fractional contribution of nucleation in this size range (e.g. Kulmala et al, 2011a). On the other hand, only a few global model studies have thus far investigated the topic Kazil et al, 2010;Fatima et al, 2011;Makkonen et al, 2012a, b).…”

“…The small size of nucleated particles poses a major challenge in applying remote sensing for investigating the connection between atmospheric nucleation and CCN production. Approaches for tracking nucleation mode particles and CCN from space have, however, been suggested (Andreae, 2009;Kulmala et al, 2011a), so this issue is worth being explored in more detail. In addition to satellite data, active remote sensing from the Earth's surface provides many kinds of vertically-resolved data that might be useful in investigating atmospheric nucleation and resulting CCN production.…”

Two decades of satellite observations of AOD over mainland China using ATSR-2, AATSR and MODIS/Terra: data set evaluation and large-scale patterns

“…Very large particles, larger than several tens of micrometers, occur in very low concentrations and therefore contribute little to the radiance measured at TOA. Hence, the particles observed from satellites, during clear-sky conditions, are in the size range of about 100 nm to several tens of micrometers and thus do not include newly formed particles , unless proxies are used (Kulmala et al, 2011;Sundström et al, 2015). On the other hand, cloud droplets with sizes on the order of 10 µm do affect the thermal infrared (TIR) radiances, and this is used for cloud detection.…”

Forecasting ultrafine particle concentrations from satellite and in situ observations

“…We estimate UFP concentrations by using lagged estimates of UFP and concurrent satellite-based observations of aerosol optical properties, ultraviolet solar radiation flux, and trace gas concentrations, wherein an expectation maximization algorithm is used to impute missing values in the satellite observations. The resulting model of UFP (derived by using an autoregressive moving average model with exogenous inputs) explains 51 and 28% of the day-to-day variability in concentrations at two sites in eastern North America.Recent innovations in remote sensing technologies and data retrievals offer the potential for predicting UFP concentrations from satellite-borne radiometer measurements Kulmala et al, 2011a;Sundstrom et al, 2015]. The major methodological assumptions and primary findings from previous research in this field can be summarized as follows:1.…”

“…Recent innovations in remote sensing technologies and data retrievals offer the potential for predicting UFP concentrations from satellite-borne radiometer measurements Kulmala et al, 2011a;Sundstrom et al, 2015]. The major methodological assumptions and primary findings from previous research in this field can be summarized as follows:…”