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Exploiting the favourable alignment of CALIPSO's descending orbital tracks over Sweden to study aerosol characteristics

Manu Anna Thomas ; Abhay Devasthale ; Michael Kahnert (Institutionen för rymd- och geovetenskap, Global miljömätteknik och modellering)
Tellus Series B - Chemical and Physical Meteorology ( 0280-6509). Vol. 65 (2013),
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: aerosols; CALIPSO; vertical distribution; air quality



Denna post skapades 2013-11-13. Senast ändrad 2014-10-13.
CPL Pubid: 186555

 

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Projekt

Denna publikation är ett resultat av följande projekt:


Aerosol Optics in Global Earth System Modelling (AGES) (VR//2011-3346)