Arctic Summer Cloud Ocean Study (ASCOS) Editor(s): J. W. Bottenheim, W. M. Drennan, M. Tjernström, C. Leck, I. Brooks, G. de Leeuw, E. Swietlicki and A. Hansel Special issue jointly organized between Atmospheric Chemistry and Physics, Atmospheric Measurement Techniques, and Ocean Science
Clouds constitute one of the major uncertainties in understanding the climate system and changes in the clouds as a consequence of global climate change is not well constrained by observations. This is particularly true in the Arctic, where clouds constitute the larges single factor affecting the surface energy balance, and therefore on melting and freezing of sea ice.
ASCOS is a highly interdisciplinary project with a major field experiment in the central Arctic Ocean during August/September 2008, approximately at 87N and 7W, deployed on the Swedish icebreaker Oden as a part of the International Polar Year (IPY). The ASCOS main target is to study the formation and life cycle of Arctic summer low-level clouds. To achieve this we deployed instruments for process level observations in a column from 0.5 km in to the ocean, through the ocean/ice surface up through the atmospheric boundary layer, and to the top of the troposphere (also see http://www.ascos.se). ASCOS measurements range from in-situ observations, to surface-based remote sensing, to airborne observations. The most intense observations were during a 3-week ice drift, starting with typical Arctic summer melt conditions and ending with the initial freeze-up of autumn. ASCOS was also coordinated with the Arctic Mechanisms of Interaction between the Surface and Atmosphere (AMISA) project, providing airborne measurements from the NASA DC8 research aircraft in the vicinity of the ASCOS column, flying in from Kiruna, Sweden.
The science team on Oden consisted of 33 researchers from 14 institutes in 11 different countries; many more are involved in analysis and associated modelling studies. This, and the experimental set-up, makes ASCOS the most extensive atmosphere-oriented experiment in the central Arctic for the entire IPY. ASCOS science cuts across several disciplines, with links to microbial life in ocean and ice, atmospheric chemistry and physics, cloud microphysics, turbulent exchange at the surfaces above and below the ice, and atmospheric circulation. A large part of ASCOS (atmospheric gas and particulate chemistry, aerosol physics, boundary-layer and synoptic meteorology) fall within the remit of ACP while physical oceanography and marine biology/chemistry fall within the remit of OS which is the incentive for a joint ACP/OS issue; only this way will it become possible to develop a special issue spanning the whole width of the science in ASCOS.
T. Mauritsen, J. Sedlar, M. Tjernström, C. Leck, M. Martin, M. Shupe, S. Sjogren, B. Sierau, P. O. G. Persson, I. M. Brooks, and E. Swietlicki Atmos. Chem. Phys., 11, 165-173, 2011 AbstractFinal Revised Paper (PDF, 879 KB)Discussion Paper (ACPD)
10 Jan 2011
Measurements of bubble size spectra within leads in the Arctic summer pack ice
Aerosol composition and sources in the central Arctic Ocean during ASCOS
R. Y.-W. Chang, C. Leck, M. Graus, M. Müller, J. Paatero, J. F. Burkhart, A. Stohl, L. H. Orr, K. Hayden, S.-M. Li, A. Hansel, M. Tjernström, W. R. Leaitch, and J. P. D. Abbatt Atmos. Chem. Phys., 11, 10619-10636, 2011 AbstractFinal Revised Paper (PDF, 7094 KB)Supplement (273 KB)Discussion Paper (ACPD)
27 Oct 2011
Cloud condensation nuclei closure study on summer arctic aerosol
Modelling atmospheric structure, cloud and their response to CCN in the central Arctic: ASCOS case studies
C. E. Birch, I. M. Brooks, M. Tjernström, M. D. Shupe, T. Mauritsen, J. Sedlar, A. P. Lock, P. Earnshaw, P. O. G. Persson, S. F. Milton, and C. Leck Atmos. Chem. Phys., 12, 3419-3435, 2012 AbstractFinal Revised Paper (PDF, 1249 KB)Discussion Paper (ACPD)
11 Apr 2012
The summer aerosol in the central Arctic 1991–2008: did it change or not?
Meteorological conditions in the central Arctic summer during the Arctic Summer Cloud Ocean Study (ASCOS)
M. Tjernström, C. E. Birch, I. M. Brooks, M. D. Shupe, P. O. G. Persson, J. Sedlar, T. Mauritsen, C. Leck, J. Paatero, M. Szczodrak, and C. R. Wheeler Atmos. Chem. Phys., 12, 6863-6889, 2012 AbstractFinal Revised Paper (PDF, 10789 KB)Discussion Paper (ACPD)
01 Aug 2012
Cloud and boundary layer interactions over the Arctic sea ice in late summer
M. D. Shupe, P. O. G. Persson, I. M. Brooks, M. Tjernström, J. Sedlar, T. Mauritsen, S. Sjogren, and C. Leck Atmos. Chem. Phys., 13, 9379-9399, 2013 AbstractFinal Revised Paper (PDF, 12786 KB)Discussion Paper (ACPD)
24 Sep 2013
A method for sizing submicrometer particles in air collected on Formvar films and imaged by scanning electron microscope
Climate and air quality trade-offs in altering ship fuel sulfur content
A. I. Partanen, A. Laakso, A. Schmidt, H. Kokkola, T. Kuokkanen, J.-P. Pietikäinen, V.-M. Kerminen, K. E. J. Lehtinen, L. Laakso, and H. Korhonen Atmos. Chem. Phys., 13, 12059-12071, 2013 AbstractFinal Revised Paper (PDF, 7669 KB)Discussion Paper (ACPD)
12 Dec 2013
Vertical profiling of aerosol particles and trace gases over the central Arctic Ocean during summer
P. Kupiszewski, C. Leck, M. Tjernström, S. Sjogren, J. Sedlar, M. Graus, M. Müller, B. Brooks, E. Swietlicki, S. Norris, and A. Hansel Atmos. Chem. Phys., 13, 12405-12431, 2013 AbstractFinal Revised Paper (PDF, 1955 KB)Discussion Paper (ACPD)
19 Dec 2013
Size-resolved atmospheric particulate polysaccharides in the high summer Arctic
Near-surface meteorology during the Arctic Summer Cloud Ocean Study (ASCOS): evaluation of reanalyses and global climate models
G. de Boer, M. D. Shupe, P. M. Caldwell, S. E. Bauer, O. Persson, J. S. Boyle, M. Kelley, S. A. Klein, and M. Tjernström Atmos. Chem. Phys., 14, 427-445, 2014 AbstractFinal Revised Paper (PDF, 3724 KB)Discussion Paper (ACPD)
13 Jan 2014
The Arctic summer atmosphere: an evaluation of reanalyses using ASCOS data
The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design
M. Tjernström, C. Leck, C. E. Birch, J. W. Bottenheim, B. J. Brooks, I. M. Brooks, L. Bäcklin, R. Y.-W. Chang, G. de Leeuw, L. Di Liberto, S. de la Rosa, E. Granath, M. Graus, A. Hansel, J. Heintzenberg, A. Held, A. Hind, P. Johnston, J. Knulst, M. Martin, P. A. Matrai, T. Mauritsen, M. Müller, S. J. Norris, M. V. Orellana, D. A. Orsini, J. Paatero, P. O. G. Persson, Q. Gao, C. Rauschenberg, Z. Ristovski, J. Sedlar, M. D. Shupe, B. Sierau, A. Sirevaag, S. Sjogren, O. Stetzer, E. Swietlicki, M. Szczodrak, P. Vaattovaara, N. Wahlberg, M. Westberg, and C. R. Wheeler Atmos. Chem. Phys., 14, 2823-2869, 2014 AbstractFinal Revised Paper (PDF, 14910 KB)Discussion Paper (ACPD)
19 Mar 2014
Characteristic nature of vertical motions observed in Arctic mixed-phase stratocumulus
The thermodynamic structure of summer Arctic stratocumulus and the dynamic coupling to the surface
Summary: During ASCOS, clouds are more frequently decoupled from the surface than coupled to it; when coupling occurs it is primary driven by the cloud. Decoupled clouds have a bimodal structure; they are either weakly or strongly decoupled from the surface; the enhancement of the decoupling is possibly due to sublimation of precipitation. Stable clouds (no cloud-driven mixing) are also observed; those are optically thin, often single-phase liquid, with no or negligible precipitation (e.g. fog).