Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments

Current algorithms for the determination of cloud top height and cloud fraction in Polar Regions tend to provide unreliable results, particularly in the presence of isothermal conditions within the atmosphere. Alternative methods to determine cloud top heights in such regions effectively, from space...

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Main Authors: Fisher, D, Muller, J-P
Format: Report
Language:unknown
Published: 2012
Subjects:
Online Access:http://discovery.ucl.ac.uk/1420871/
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record_format openpolar
spelling ftucl:oai:eprints.ucl.ac.uk.OAI2:1420871 2023-05-15T16:28:20+02:00 Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments Fisher, D Muller, J-P 2012 http://discovery.ucl.ac.uk/1420871/ unknown In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives. (pp. 109 - 113). (2012) Proceedings paper 2012 ftucl 2015-03-26T23:11:28Z Current algorithms for the determination of cloud top height and cloud fraction in Polar Regions tend to provide unreliable results, particularly in the presence of isothermal conditions within the atmosphere. Alternative methods to determine cloud top heights in such regions effectively, from space borne sensors, are currently limited to stereo-photogrammetry and active sensing methods, such as LiDAR. Here we apply the modified census transform to one month of AATSR stereo data from June 2008. AATSR is unique in that it is the only space borne stereo capable instrument providing data continuously in both the visible, near infrared and thermal channels. This allows for year round imaging of the poles and therefore year round cloud top height and cloud fraction estimation. We attempt a preliminary validation of the stereo retrieved cloud top height measurements from AATSR against collocated cloud height measurements from the CALIOP LiDAR instrument. CALIOP provides an excellent validation tool due to its excellent height resolution of between 30-60 meters. In this validation, a pair of collocated swaths is assessed with a total of 154 inter-comparisons; the results show that AATSR correlates well with CALIOP cloud base layers with an R score of 0.71. However, in all cases AATSR appears to be underestimating the cloud top height compared to CALIOP, the causes for this are currently not fully understood and more extensive inter-comparisons are required. Once validation is completed a processing chain is in place to process the entire ATSR time-series data generating a 20 year cloud top height dataset for Greenland. Report Greenland University College London: UCL Discovery Greenland
institution Open Polar
collection University College London: UCL Discovery
op_collection_id ftucl
language unknown
description Current algorithms for the determination of cloud top height and cloud fraction in Polar Regions tend to provide unreliable results, particularly in the presence of isothermal conditions within the atmosphere. Alternative methods to determine cloud top heights in such regions effectively, from space borne sensors, are currently limited to stereo-photogrammetry and active sensing methods, such as LiDAR. Here we apply the modified census transform to one month of AATSR stereo data from June 2008. AATSR is unique in that it is the only space borne stereo capable instrument providing data continuously in both the visible, near infrared and thermal channels. This allows for year round imaging of the poles and therefore year round cloud top height and cloud fraction estimation. We attempt a preliminary validation of the stereo retrieved cloud top height measurements from AATSR against collocated cloud height measurements from the CALIOP LiDAR instrument. CALIOP provides an excellent validation tool due to its excellent height resolution of between 30-60 meters. In this validation, a pair of collocated swaths is assessed with a total of 154 inter-comparisons; the results show that AATSR correlates well with CALIOP cloud base layers with an R score of 0.71. However, in all cases AATSR appears to be underestimating the cloud top height compared to CALIOP, the causes for this are currently not fully understood and more extensive inter-comparisons are required. Once validation is completed a processing chain is in place to process the entire ATSR time-series data generating a 20 year cloud top height dataset for Greenland.
format Report
author Fisher, D
Muller, J-P
spellingShingle Fisher, D
Muller, J-P
Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments
author_facet Fisher, D
Muller, J-P
author_sort Fisher, D
title Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments
title_short Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments
title_full Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments
title_fullStr Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments
title_full_unstemmed Stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (ATSR) instruments
title_sort stereo derived cloud top height climatology over greenland from 20 years of the along track scanning radiometer (atsr) instruments
publishDate 2012
url http://discovery.ucl.ac.uk/1420871/
geographic Greenland
geographic_facet Greenland
genre Greenland
genre_facet Greenland
op_source In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives. (pp. 109 - 113). (2012)
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