Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XXXIX-B8, 109-113, 2012
http://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XXXIX-B8/109/2012/
doi:10.5194/isprsarchives-XXXIX-B8-109-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
 
27 Jul 2012
STEREO DERIVED CLOUD TOP HEIGHT CLIMATOLOGY OVER GREENLAND FROM 20 YEARS OF THE ALONG TRACK SCANNING RADIOMETER (ATSR) INSTRUMENTS
D. Fisher and J.-P. Muller Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, U.K., RH5 6NT
Keywords: Climate, Environment, Atmosphere, Imagery, Matching, Pattern, Stereoscopic Abstract. 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 R2 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.
Conference paper (PDF, 666 KB)


Citation: Fisher, D. and Muller, J.-P.: STEREO DERIVED CLOUD TOP HEIGHT CLIMATOLOGY OVER GREENLAND FROM 20 YEARS OF THE ALONG TRACK SCANNING RADIOMETER (ATSR) INSTRUMENTS, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XXXIX-B8, 109-113, doi:10.5194/isprsarchives-XXXIX-B8-109-2012, 2012.

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