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Exploiting the favourable alignment of CALIPSO's descending orbital tracks over Sweden to study aerosol characteristics
SMHI, Research Department, Air quality.ORCID iD: 0000-0002-5709-7507
SMHI, Research Department, Atmospheric remote sensing.ORCID iD: 0000-0002-6717-8343
SMHI, Research Department, Air quality.ORCID iD: 0000-0001-5695-1356
2013 (English)In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 65, 21155Article in journal (Refereed) Published
Abstract [en]

One of the key knowledge gaps when estimating aerosol forcing and their role in air quality is our limited understanding of their vertical distribution. As an active lidar in space, the CALIOP-CALIPSO is helping to close this gap. The descending orbital track of CALIPSO follows elongated semi-major axis of Sweden, slicing its atmosphere every 2-3 d, thus providing a unique opportunity to characterise aerosols and their verticality in all seasons irrespective of solar conditions. This favourable orbital configuration of CALIPSO over Sweden is exploited in the present study. Using five years of night-time aerosol observations (2006-2011), we investigated the vertical distribution of aerosols. The role of temperature inversions and winds in governing this distribution is additionally investigated using collocated AIRS-Aqua and ERA-Interim Reanalysis data. It is found that the majority of aerosols (up to 70%) are located within 1 km above the surface in the lowermost troposphere, irrespective of the season. In summer, convection and stronger mixing lift aerosols to slightly higher levels, but their noticeable presence in the upper free troposphere is observed in the winter half of the year, when the boundary layer is decoupled due to strong temperature inversions separating local sources from the transport component. When southerly winds prevail, two or more aerosol layers are most frequent over southern Sweden and the polluted air masses have higher AOD values. The depolarisation ratio and integrated attenuated backscatter of these aerosol layers are also higher. About 30-50% of all aerosol layers are located below the level where temperature inversions peak. On the other hand, relatively cleaner conditions are observed when the winds have a northerly component.

Place, publisher, year, edition, pages
2013. Vol. 65, 21155
Keyword [en]
aerosols, CALIPSO, vertical distribution, air quality
National Category
Meteorology and Atmospheric Sciences
Research subject
URN: urn:nbn:se:smhi:diva-400DOI: 10.3402/tellusb.v65i0.21155ISI: 000325709700001OAI: diva2:800028
Available from: 2015-04-01 Created: 2015-03-31 Last updated: 2016-11-22Bibliographically approved

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Thomas, Manu AnnaDevasthale, AbhayKahnert, Michael
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