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Your search keyword '"JONSSON, H. H."' showing total 4 results
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4 results on '"JONSSON, H. H."'

2. Differentiating natural and anthropogenic cloud condensation nuclei in the California coastal zone.

Author

HEGG, D. A., COVERT, D. S., JONSSON, H. H., and WOODS, R.

Subjects
AEROSOLS, CONDENSATION, ATMOSPHERIC boundary layer, CLOUDS
Abstract

Aerosol samples were collected and cloud condensation nuclei (CCN) concentrations at five supersaturations were measured along and off the central California coast within the cloud-topped, marine boundary layer from aircraft flights during August 2007. Receptor modelling has been applied to estimate the natural versus anthropogenic source contribution of cloud condensation nuclei in this region, a region of climatically important marine stratocumulus. The results suggest that anthropogenic CCN accounted for about 50% of the CCN active at 0.3% supersaturation in this region during the measurement period. [ABSTRACT FROM AUTHOR]

Published
2009
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3. Factors influencing the mesoscale variations in marine stratocumulus albedo.

Author

Hegg, D. A., Nielsen, K., Covert, D. S., Jonsson, H. H., and Durkee, P. A.

Subjects
AEROSOLS, AIR pollution, SOBOLEV gradients, CLOUDS, THERMODYNAMICS
Abstract

Measurements of both horizontal gradients and vertical profiles of aerosols, cloud droplets and thermodynamic parameters in the cloud topped marine boundary layer off of central California are presented. They suggest that, while aerosols can indeed modulate cloud albedo, other parameters such as sea surface temperature may similarly affect cloud albedo. Additionally, the impact of aerosols, through sedimentation and precipitation, on cloud optical depths and thus albedo is not always in accord with conventional expectations and can either enhance or decrease the albedo, depending on ambient conditions. Taken together, these results suggest that current estimates of indirect forcing by aerosols could be significantly in error. [ABSTRACT FROM AUTHOR]

Published
2007
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4. On the link between ocean biota emissions, aerosol, and maritime clouds: Airborne, ground, and satellite measurements off the coast of California

Author

Sorooshian, A., Padro, L. T., Nenes, Athanasios, Feingold, G., McComiskey, A., Hersey, S. P., Gates, H., Jonsson, H. H., Miller, S. D., Stephens, G. L., Flagan, R. C., and Seinfeld, J. H.

Subjects
Chlorophyll, Water uptake, Porphyrins, Diethylamines, aerosol, Chlorophyll a, Secondary organic aerosols, cloud droplet, marine atmosphere, Cloud droplet number, cloud microphysics, Oceanography, Wind effects, complex mixtures, California, Wind speed, Clouds, Satellite measurements, size distribution, Aerosol composition, Effective radius, cloud condensation nucleus, satellite data, organic matter, Pacific Ocean (East), Atmospheric dynamics, Landforms, Ocean chlorophyll, Pacific Ocean, Chlorophyll-a concentration, Cloud droplets, Cloud condensation nuclei, Methanesulfonates, Atmospheric aerosols, Eastern pacific Ocean, wind velocity, Hygroscopic growth, airborne survey, marine ecosystem, Organic components, carbon emission, sense organs, Drop formation
Abstract

Surface, airborne, and satellite measurements over the eastern Pacific Ocean off the coast of California during the period between 2005 and 2007 are used to explore the relationship between ocean chlorophyll a, aerosol, and marine clouds. Periods of enhanced chlorophyll a and wind speed are coincident with increases in particulate diethylamine and methanesulfonate concentrations. The measurements indicate that amines are a source of secondary organic aerosol in the marine atmosphere. Subsaturated aerosol hygroscopic growth measurements indicate that the organic component during periods of high chlorophyll a and wind speed exhibit considerable water uptake ability. Increased average cloud condensation nucleus (CCN) activity during periods of increased chlorophyll a levels likely results from both size distribution and aerosol composition changes. The available data over the period of measurements indicate that the cloud microphysical response, as represented by either cloud droplet number concentration or cloud droplet effective radius, is likely influenced by a combination of atmospheric dynamics and aerosol perturbations during periods of high chlorophyll a concentrations. Copyright 2009 by the American Geophysical Union.

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