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Publications (10 of 17) Show all publications
Karlsson, K.-G., Anttila, K., Trentmann, J., Stengel, M., Meirink, J. F., Devasthale, A., . . . Hollmann, R. (2017). CLARA-A2: the second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data. Atmospheric Chemistry And Physics, 17(9), 5809-5828
Open this publication in new window or tab >>CLARA-A2: the second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data
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2017 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 9, p. 5809-5828Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-4108 (URN)10.5194/acp-17-5809-2017 (DOI)000401103400002 ()
Available from: 2017-06-07 Created: 2017-06-07 Last updated: 2017-06-07Bibliographically approved
Sedlar, J. & Tjernstrom, M. (2017). Clouds, warm air, and a climate cooling signal over the summer Arctic. Geophysical Research Letters, 44(2), 1095-1103
Open this publication in new window or tab >>Clouds, warm air, and a climate cooling signal over the summer Arctic
2017 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 2, p. 1095-1103Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-4035 (URN)10.1002/2016GL071959 (DOI)000395652600058 ()
Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2017-11-29Bibliographically approved
Loewe, K., Ekman, A. M. L., Paukert, M., Sedlar, J., Tjernstrom, M. & Hoose, C. (2017). Modelling micro- and macrophysical contributors to the dissipation of an Arctic mixed-phase cloud during the Arctic Summer Cloud Ocean Study (ASCOS). Atmospheric Chemistry And Physics, 17(11), 6693-6704
Open this publication in new window or tab >>Modelling micro- and macrophysical contributors to the dissipation of an Arctic mixed-phase cloud during the Arctic Summer Cloud Ocean Study (ASCOS)
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2017 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 11, p. 6693-6704Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-4140 (URN)10.5194/acp-17-6693-2017 (DOI)000403213500001 ()
Available from: 2017-08-08 Created: 2017-08-08 Last updated: 2017-08-08Bibliographically approved
Brooks, I. M., Tjernstrom, M., Persson, P. O., Shupe, M. D., Atkinson, R. A., Canut, G., . . . Brooks, B. J. (2017). The Turbulent Structure of the Arctic Summer Boundary Layer During The Arctic Summer Cloud-Ocean Study. Journal of Geophysical Research - Atmospheres, 122(18), 9685-9704
Open this publication in new window or tab >>The Turbulent Structure of the Arctic Summer Boundary Layer During The Arctic Summer Cloud-Ocean Study
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2017 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 122, no 18, p. 9685-9704Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-4463 (URN)10.1002/2017JD027234 (DOI)000416388000009 ()
Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2018-01-09Bibliographically approved
Devasthale, A., Sedlar, J., Kahn, B. H., Tjernstrom, M., Fetzer, E. J., Tian, B., . . . Pagano, T. S. (2016). A DECADE OF SPACEBORNE OBSERVATIONS OF THE ARCTIC ATMOSPHERE Novel. Insights from NASA's AIRS Instrument. BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, 97(11), 2163-2176
Open this publication in new window or tab >>A DECADE OF SPACEBORNE OBSERVATIONS OF THE ARCTIC ATMOSPHERE Novel. Insights from NASA's AIRS Instrument
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2016 (English)In: BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, ISSN 0003-0007, Vol. 97, no 11, p. 2163-2176Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-3910 (URN)10.1175/BAMS-D-14-00202.1 (DOI)000390831500014 ()
Available from: 2017-01-24 Created: 2017-01-24 Last updated: 2017-01-24Bibliographically approved
Leung, W.-Y. -., Savre, J., Bender, F.-M. A., Komppula, M., Portin, H., Romakkaniemi, S., . . . Ekman, A. M. (2016). Sensitivity of a continental night-time stratocumulus-topped boundary layer to varying environmental conditions. QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, 142(700), 2911-2924
Open this publication in new window or tab >>Sensitivity of a continental night-time stratocumulus-topped boundary layer to varying environmental conditions
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2016 (English)In: QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, ISSN 0035-9009, Vol. 142, no 700, p. 2911-2924Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-3912 (URN)10.1002/qj.2877 (DOI)000390652500025 ()
Available from: 2017-01-24 Created: 2017-01-24 Last updated: 2017-01-24Bibliographically approved
Tjernstrom, M., Leck, C., Birch, C. E., Bottenheim, J. W., Brooks, B. J., Brooks, I. M., . . . Wheeler, C. R. (2014). The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design. Atmospheric Chemistry And Physics, 14(6), 2823-2869
Open this publication in new window or tab >>The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design
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2014 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 14, no 6, p. 2823-2869Article in journal (Refereed) Published
Abstract [en]

The climate in the Arctic is changing faster than anywhere else on earth. Poorly understood feedback processes relating to Arctic clouds and aerosol-cloud interactions contribute to a poor understanding of the present changes in the Arctic climate system, and also to a large spread in projections of future climate in the Arctic. The problem is exacerbated by the paucity of research-quality observations in the central Arctic. Improved formulations in climate models require such observations, which can only come from measurements in situ in this difficult-to-reach region with logistically demanding environmental conditions. The Arctic Summer Cloud Ocean Study (ASCOS) was the most extensive central Arctic Ocean expedition with an atmospheric focus during the International Polar Year (IPY) 2007-2008. ASCOS focused on the study of the formation and life cycle of low-level Arctic clouds. ASCOS departed from Longyearbyen on Svalbard on 2 August and returned on 9 September 2008. In transit into and out of the pack ice, four short research stations were undertaken in the Fram Strait: two in open water and two in the marginal ice zone. After traversing the pack ice northward, an ice camp was set up on 12 August at 87 degrees 21' N, 01 degrees 29' W and remained in operation through 1 September, drifting with the ice. During this time, extensive measurements were taken of atmospheric gas and particle chemistry and physics, mesoscale and boundary-layer meteorology, marine biology and chemistry, and upper ocean physics. ASCOS provides a unique interdisciplinary data set for development and testing of new hypotheses on cloud processes, their interactions with the sea ice and ocean and associated physical, chemical, and biological processes and interactions. For example, the first-ever quantitative observation of bubbles in Arctic leads, combined with the unique discovery of marine organic material, polymer gels with an origin in the ocean, inside cloud droplets suggests the possibility of primary marine organically derived cloud condensation nuclei in Arctic stratocumulus clouds. Direct observations of surface fluxes of aerosols could, however, not explain observed variability in aerosol concentrations, and the balance between local and remote aerosols sources remains open. Lack of cloud condensation nuclei (CCN) was at times a controlling factor in low-level cloud formation, and hence for the impact of clouds on the surface energy budget. ASCOS provided detailed measurements of the surface energy balance from late summer melt into the initial autumn freeze-up, and documented the effects of clouds and storms on the surface energy balance during this transition. In addition to such process-level studies, the unique, independent ASCOS data set can and is being used for validation of satellite retrievals, operational models, and reanalysis data sets.

National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-160 (URN)10.5194/acp-14-2823-2014 (DOI)000334104700006 ()
Available from: 2015-04-09 Created: 2015-03-26 Last updated: 2017-12-04Bibliographically approved
Karlsson, K.-G., Riihela, A., Mueller, R., Meirink, J. F., Sedlar, J., Stengel, M., . . . Wolters, E. (2013). CLARA-A1: a cloud, albedo, and radiation dataset from 28 yr of global AVHRR data. Atmospheric Chemistry And Physics, 13(10), 5351-5367
Open this publication in new window or tab >>CLARA-A1: a cloud, albedo, and radiation dataset from 28 yr of global AVHRR data
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2013 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 10, p. 5351-5367Article in journal (Refereed) Published
Abstract [en]

A new satellite-derived climate dataset - denoted CLARA-A1 ("The CM SAF cLoud, Albedo and RAdiation dataset from AVHRR data") - is described. The dataset covers the 28 yr period from 1982 until 2009 and consists of cloud, surface albedo, and radiation budget products derived from the AVHRR (Advanced Very High Resolution Radiometer) sensor carried by polar-orbiting operational meteorological satellites. Its content, anticipated accuracies, limitations, and potential applications are described. The dataset is produced by the EUMETSAT Climate Monitoring Satellite Application Facility (CM SAF) project. The dataset has its strengths in the long duration, its foundation upon a homogenized AVHRR radiance data record, and in some unique features, e. g. the availability of 28 yr of summer surface albedo and cloudiness parameters over the polar regions. Quality characteristics are also well investigated and particularly useful results can be found over the tropics, mid to high latitudes and over nearly all oceanic areas. Being the first CM SAF dataset of its kind, an intensive evaluation of the quality of the datasets was performed and major findings with regard to merits and shortcomings of the datasets are reported. However, the CM SAF's long-term commitment to perform two additional reprocessing events within the time frame 2013-2018 will allow proper handling of limitations as well as upgrading the dataset with new features (e. g. uncertainty estimates) and extension of the temporal coverage.

National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-410 (URN)10.5194/acp-13-5351-2013 (DOI)000319749400019 ()
Available from: 2015-04-01 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
Shupe, M. D., Persson, P. O., Brooks, I. M., Tjernstrom, M., Sedlar, J., Mauritsen, T., . . . Leck, C. (2013). Cloud and boundary layer interactions over the Arctic sea ice in late summer. Atmospheric Chemistry And Physics, 13(18), 9379-9399
Open this publication in new window or tab >>Cloud and boundary layer interactions over the Arctic sea ice in late summer
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2013 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 18, p. 9379-9399Article in journal (Refereed) Published
Abstract [en]

Observations from the Arctic Summer Cloud Ocean Study (ASCOS), in the central Arctic sea-ice pack in late summer 2008, provide a detailed view of cloud-atmosphere-surface interactions and vertical mixing processes over the sea-ice environment. Measurements from a suite of ground-based remote sensors, near-surface meteorological and aerosol instruments, and profiles from radiosondes and a helicopter are combined to characterize a week-long period dominated by low-level, mixed-phase, stratocumulus clouds. Detailed case studies and statistical analyses are used to develop a conceptual model for the cloud and atmosphere structure and their interactions in this environment. Clouds were persistent during the period of study, having qualities that suggest they were sustained through a combination of advective influences and in-cloud processes, with little contribution from the surface. Radiative cooling near cloud top produced buoyancy-driven, turbulent eddies that contributed to cloud formation and created a cloud-driven mixed layer. The depth of this mixed layer was related to the amount of turbulence and condensed cloud water. Coupling of this cloud-driven mixed layer to the surface boundary layer was primarily determined by proximity. For 75% of the period of study, the primary stratocumulus cloud-driven mixed layer was decoupled from the surface and typically at a warmer potential temperature. Since the near-surface temperature was constrained by the ocean-ice mixture, warm temperatures aloft suggest that these air masses had not significantly interacted with the sea-ice surface. Instead, back-trajectory analyses suggest that these warm air masses advected into the central Arctic Basin from lower latitudes. Moisture and aerosol particles likely accompanied these air masses, providing necessary support for cloud formation. On the occasions when cloud-surface coupling did occur, back trajectories indicated that these air masses advected at low levels, while mixing processes kept the mixed layer in equilibrium with the near-surface environment. Rather than contributing buoyancy forcing for the mixed-layer dynamics, the surface instead simply appeared to respond to the mixed-layer processes aloft. Clouds in these cases often contained slightly higher condensed water amounts, potentially due to additional moisture sources from below.

National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-399 (URN)10.5194/acp-13-9379-2013 (DOI)000325283800017 ()
Available from: 2015-04-01 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
Devasthale, A., Sedlar, J., Koenigk, T. & Fetzer, E. J. (2013). The thermodynamic state of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea ice extents of 2007 and 2012. Atmospheric Chemistry And Physics, 13(15), 7441-7450
Open this publication in new window or tab >>The thermodynamic state of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea ice extents of 2007 and 2012
2013 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 15, p. 7441-7450Article in journal (Refereed) Published
Abstract [en]

The record sea ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric thermodynamics. Here, we facilitate comparisons in the evolution of the thermodynamic state of the Arctic atmosphere during these two SIM events using a decade-long AIRS observational record (2003-2012). It is shown that the meteorological conditions during 2012 were not extreme, but three factors of preconditioning from winter through early summer played an important role in accelerating sea ice melt. First, the marginal sea ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea ice melt. All these factors may have lead the already thin and declining sea ice cover to pass below the previous sea ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea ice melting events in the Arctic.

National Category
Meteorology and Atmospheric Sciences
Research subject
Remote sensing
Identifiers
urn:nbn:se:smhi:diva-403 (URN)10.5194/acp-13-7441-2013 (DOI)000323103900012 ()
Available from: 2015-04-01 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-3101-9401

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