Optical and geometrical properties of cirrus clouds in Amazonia derived from 1 year of ground-based lidar measurements

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dc.citation.issue5
dc.citation.volume17
dc.contributor.authorGouveia, Diego A.
dc.contributor.authorBarja, Boris
dc.contributor.authorBarbosa, Henrique M. J.
dc.contributor.authorSeifert, Patric
dc.contributor.authorBaars, Holger
dc.contributor.authorPauliquevis, Theotonio [UNIFESP]
dc.contributor.authorArtaxo, Paulo
dc.coverageGottingen
dc.date.accessioned2020-07-17T14:02:39Z
dc.date.available2020-07-17T14:02:39Z
dc.date.issued2017
dc.description.abstractCirrus clouds cover a large fraction of tropical latitudes and play an important role in Earth's radiation budget. Their optical properties, altitude, vertical and horizontal coverage control their radiative forcing, and hence detailed cirrus measurements at different geographical locations are of utmost importance. Studies reporting cirrus properties over tropical rain forests like the Amazon, however, are scarce. Studies with satellite profilers do not give information on the diurnal cycle, and the satellite imagers do not report on the cloud vertical structure. At the same time, ground-based lidar studies are restricted to a few case studies. In this paper, we derive the first comprehensive statistics of optical and geometrical properties of upper-tropospheric cirrus clouds in Amazonia. We used 1 year (July 2011 to June 2012) of ground-based lidar atmospheric observations north of Manaus, Brazil. This dataset was processed by an automatic cloud detection and optical properties retrieval algorithm. Uppertropospheric cirrus clouds were observed more frequently than reported previously for tropical regions. The frequency of occurrence was found to be as high as 88% during the wet season and not lower than 50% during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle of precipitation. The mean values of cirrus cloud top and base heights, cloud thickness, and cloud optical depth were 14.3 +/- 1.9 (SD) km, 12.9 +/- 2.2 km, 1.4 +/- 1.1 km, and 0.25 +/- 0.46, respectively. Cirrus clouds were found at tem-peratures down to 90 degrees C. Frequently cirrus were observed within the tropical tropopause layer (TTL), which are likely associated to slow mesoscale uplifting or to the remnants of overshooting convection. The vertical distribution was not uniform, and thin and subvisible cirrus occurred more frequently closer to the tropopause. The mean lidar ratio was 23.3 +/- 8.0 sr. However, for subvisible cirrus clouds a bimodal distribution with a secondary peak at about 44 sr was found suggesting a mixed composition. A dependence of the lidar ratio with cloud temperature (altitude) was not found, indicating that the clouds are vertically well mixed. The frequency of occurrence of cirrus clouds classified as subvisible (tau < 0 : 03) were 41.6 %, whilst 37.8% were thin cirrus (0 : 03 < tau < 0 : 3) and 20.5% opaque cirrus (tau > 0 : 3). Hence, in central Amazonia not only a high frequency of cirrus clouds occurs, but also a large fraction of subvisible cirrus clouds. This high frequency of subvisible cirrus clouds may contaminate aerosol optical depth measured by sun photometers and satellite sensors to an unknown extent.en
dc.description.affiliationUniv Sao Paulo, Inst Phys, Dept Appl Phys, Sao Paulo, SP, Brazil
dc.description.affiliationMeteorol Inst Cuba, Atmospher Opt Grp Camaguey, Camaguey, Cuba
dc.description.affiliationUniv Magallanes, Atmospher Res Lab, Punta Arenas, Chile
dc.description.affiliationLeibniz Inst Tropospher Res TROPOS, Leipzig, Germany
dc.description.affiliationUniv Fed Sao Paulo, Dept Environm Sci, Diadema, SP, Brazil
dc.description.affiliationUnifespUniv Fed Sao Paulo, Dept Environm Sci, Diadema, SP, Brazil
dc.description.sourceWeb of Science
dc.description.sponsorshipCNPq fellowship program
dc.description.sponsorshipCAPES project on the program Science without Frontiers
dc.description.sponsorshipSAVERNET project
dc.description.sponsorshipFAPESP Research Program on Global Climate Change
dc.description.sponsorshipIDCAPES: A016_2013
dc.description.sponsorshipIDFAPESP Research Program on Global Climate Change: 2008/58100-1
dc.description.sponsorshipIDFAPESP Research Program on Global Climate Change: 2009/15235-8
dc.description.sponsorshipIDFAPESP Research Program on Global Climate Change: 2012/16100-1
dc.description.sponsorshipIDFAPESP Research Program on Global Climate Change: 2013/50510-5
dc.description.sponsorshipIDFAPESP Research Program on Global Climate Change: 2013/05014-0
dc.format.extent3619-3636
dc.identifierhttp://dx.doi.org/10.5194/acp-17-3619-2017
dc.identifier.citationAtmospheric Chemistry And Physics. Gottingen, v. 17, n. 5, p. 3619-3636, 2017.
dc.identifier.doi10.5194/acp-17-3619-2017
dc.identifier.fileWOS000397928200001.pdf
dc.identifier.issn1680-7316
dc.identifier.urihttps://repositorio.unifesp.br/handle/11600/54924
dc.identifier.wosWOS:000397928200001
dc.language.isoeng
dc.publisherCopernicus Gesellschaft Mbh
dc.relation.ispartofAtmospheric Chemistry And Physics
dc.rightsinfo:eu-repo/semantics/openAccess
dc.titleOptical and geometrical properties of cirrus clouds in Amazonia derived from 1 year of ground-based lidar measurementsen
dc.typeinfo:eu-repo/semantics/article
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