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Cirrus optical thickness and crystal size retrieval from ATSR-2 data using phase functions of imperfect hexagonal ice crystals

Knap, W.H. and Hess, Michael and Stammes, P. and Koelemeijer, R.B.A. (1999) Cirrus optical thickness and crystal size retrieval from ATSR-2 data using phase functions of imperfect hexagonal ice crystals. Journal of Geophysical Research, 104 (24), pp. 31721-31730.

Full text not available from this repository.

Abstract

Along Track Scanning Radiometer-2 (ATSR-2) measurements made over a tropical cirrus anvil (Pacific Ocean, 14° N, 134° E; 6 September 1996) are analysed on the basis of radiative transfer calculations for clouds consisting of imperfect hexagonal ice crystals. Reflectivity measurements made at two wavelengths (0.87 µm, non-absorbing; 1.6 µm, absorbing) and two viewing directions (nadir and forward) are considered. Model calculations for a cloud consisting of single-sized imperfect hexagonal ice crystals (maximum dimension 60 µm) adequately explain the gross features of the ATSR-2 reflectivity measurements. Retrieved values of optical thickness and crystal size reveal no discernible relationship between these quantities. Nadir-derived and forward-derived optical thickness and crystal size are compared for imperfect and near-perfect hexagonal crystals. For these two crystal shapes there appears to be a moderate trade-off in consistent retrieval of crystal size versus retrieval of optical thickness. Consistent retrieval of crystal size is found for imperfect crystals. Averaged over those measurements for which the optical thickness is larger than 10 we find a crystal size (defined as maximum crystal dimension) of 63 +/- 4 µm for a cloud consisting of imperfect hexagonal columns (crystal sizes for optically thin clouds are omitted because of high retrieval errors). For hexagonal plates a somewhat larger value is retrieved: 71 +/- 3 µm. Both retrieved sizes suggest that the cloud system consisted of relatively small ice crystals.

Document Type:Article
Additional Information: LIDO-Berichtsjahr=2001,
Title:Cirrus optical thickness and crystal size retrieval from ATSR-2 data using phase functions of imperfect hexagonal ice crystals
Authors:
AuthorsInstitution or Email of Authors
Knap, W.H.UNSPECIFIED
Hess, MichaelUNSPECIFIED
Stammes, P.UNSPECIFIED
Koelemeijer, R.B.A.UNSPECIFIED
Date:1999
Journal or Publication Title:Journal of Geophysical Research
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:104
Page Range:pp. 31721-31730
Status:Published
Keywords:Cirrus, optical thickness, particle size retrieval, hexagonal ice crystals, phase function
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):UNSPECIFIED
Location: Oberpfaffenhofen
Institutes and Institutions:Remote Sensing Technology Institute
Deposited By: Cornelia Roehl
Deposited On:07 Feb 2006
Last Modified:06 Jan 2010 22:06

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