Ändra sökning
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Characterization of AVHRR global cloud detection sensitivity based on CALIPSO-CALIOP cloud optical thickness information: demonstration of results based on the CM SAF CLARA-A2 climate data record
SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.ORCID-id: 0000-0001-8256-0228
SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
2018 (Engelska)Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 11, nr 1, s. 633-649Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The sensitivity in detecting thin clouds of the cloud screening method being used in the CM SAF cloud, albedo and surface radiation data set from AVHRR data (CLARA-A2) cloud climate data record (CDR) has been evaluated using cloud information from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite. The sensitivity, including its global variation, has been studied based on collocations of Advanced Very High Resolution Radiometer (AVHRR) and CALIOP measurements over a 10-year period (2006-2015). The cloud detection sensitivity has been defined as the minimum cloud optical thickness for which 50% of clouds could be detected, with the global average sensitivity estimated to be 0.225. After using this value to reduce the CALIOP cloud mask (i.e. clouds with optical thickness below this threshold were interpreted as cloud-free cases), cloudiness results were found to be basically unbiased over most of the globe except over the polar regions where a considerable underestimation of cloudiness could be seen during the polar winter. The overall probability of detecting clouds in the polar winter could be as low as 50% over the highest and coldest parts of Greenland and Antarctica, showing that a large fraction of optically thick clouds also remains undetected here. The study included an in-depth analysis of the probability of detecting a cloud as a function of the vertically integrated cloud optical thickness as well as of the cloud's geographical position. Best results were achieved over oceanic surfaces at mid-to high latitudes where at least 50% of all clouds with an optical thickness down to a value of 0.075 were detected. Corresponding cloud detection sensitivities over land surfaces outside of the polar regions were generally larger than 0.2 with maximum values of approximately 0.5 over the Sahara and the Arabian Peninsula. For polar land surfaces the values were close to 1 or higher with maximum values of 4.5 for the parts with the highest altitudes over Greenland and Antarctica. It is suggested to quantify the detection performance of other CDRs in terms of a sensitivity threshold of cloud optical thickness, which can be estimated using active lidar observations. Validation results are proposed to be used in Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulation Package (COSP) simulators for cloud detection characterization of various cloud CDRs from passive imagery.

Ort, förlag, år, upplaga, sidor
2018. Vol. 11, nr 1, s. 633-649
Nationell ämneskategori
Meteorologi och atmosfärforskning
Forskningsämne
Fjärranalys
Identifikatorer
URN: urn:nbn:se:smhi:diva-4502DOI: 10.5194/amt-11-633-2018ISI: 000423980700002OAI: oai:DiVA.org:smhi-4502DiVA, id: diva2:1183972
Tillgänglig från: 2018-02-20 Skapad: 2018-02-20 Senast uppdaterad: 2018-02-20Bibliografiskt granskad

Open Access i DiVA

fulltext(30479 kB)46 nedladdningar
Filinformation
Filnamn FULLTEXT01.pdfFilstorlek 30479 kBChecksumma SHA-512
e92e41fd89e02e5b329040fa686f2ba999173cd285ea0e4873a6b573fc57c18ab3d25479aac32d45918e9f6d86f777916dec42ad7e8dd9bf3fba9e9dd449ec7f
Typ fulltextMimetyp application/pdf

Övriga länkar

Förlagets fulltext

Personposter BETA

Karlsson, Karl-GöranHåkansson, Nina

Sök vidare i DiVA

Av författaren/redaktören
Karlsson, Karl-GöranHåkansson, Nina
Av organisationen
Atmosfärisk fjärranalys
I samma tidskrift
Atmospheric Measurement Techniques
Meteorologi och atmosfärforskning

Sök vidare utanför DiVA

GoogleGoogle Scholar
Totalt: 46 nedladdningar
Antalet nedladdningar är summan av nedladdningar för alla fulltexter. Det kan inkludera t.ex tidigare versioner som nu inte längre är tillgängliga.

doi
urn-nbn

Altmetricpoäng

doi
urn-nbn
Totalt: 183 träffar
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
v. 2.35.7
|