The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques
The cloud cover in a set of summertime and wintertime AVHRR data from the Arctic and Antarctic regions was analyzed using a pattern recognition algorithm. The data were collected by the NOAA-7 satellite on 6 to 13 Jan. and 1 to 7 Jul. 1984 between 60 deg and 90 deg north and south latitude in 5 spec...
Main Authors: | , |
---|---|
Format: | Other/Unknown Material |
Language: | unknown |
Published: |
1990
|
Subjects: | |
Online Access: | http://hdl.handle.net/2060/19900013552 |
id |
ftnasantrs:oai:casi.ntrs.nasa.gov:19900013552 |
---|---|
record_format |
openpolar |
spelling |
ftnasantrs:oai:casi.ntrs.nasa.gov:19900013552 2023-05-15T13:12:05+02:00 The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques Smith, William L. Ebert, Elizabeth Unclassified, Unlimited, Publicly available May 1, 1990 application/pdf http://hdl.handle.net/2060/19900013552 unknown Document ID: 19900013552 Accession ID: 90N22868 http://hdl.handle.net/2060/19900013552 No Copyright CASI METEOROLOGY AND CLIMATOLOGY NASA-CR-183300 NAS 1.26:183300 1990 ftnasantrs 2019-07-21T09:13:11Z The cloud cover in a set of summertime and wintertime AVHRR data from the Arctic and Antarctic regions was analyzed using a pattern recognition algorithm. The data were collected by the NOAA-7 satellite on 6 to 13 Jan. and 1 to 7 Jul. 1984 between 60 deg and 90 deg north and south latitude in 5 spectral channels, at the Global Area Coverage (GAC) resolution of approximately 4 km. This data embodied a Polar Cloud Pilot Data Set which was analyzed by a number of research groups as part of a polar cloud algorithm intercomparison study. This study was intended to determine whether the additional information contained in the AVHRR channels (beyond the standard visible and infrared bands on geostationary satellites) could be effectively utilized in cloud algorithms to resolve some of the cloud detection problems caused by low visible and thermal contrasts in the polar regions. The analysis described makes use of a pattern recognition algorithm which estimates the surface and cloud classification, cloud fraction, and surface and cloudy visible (channel 1) albedo and infrared (channel 4) brightness temperatures on a 2.5 x 2.5 deg latitude-longitude grid. In each grid box several spectral and textural features were computed from the calibrated pixel values in the multispectral imagery, then used to classify the region into one of eighteen surface and/or cloud types using the maximum likelihood decision rule. A slightly different version of the algorithm was used for each season and hemisphere because of differences in categories and because of the lack of visible imagery during winter. The classification of the scene is used to specify the optimal AVHRR channel for separating clear and cloudy pixels using a hybrid histogram-spatial coherence method. This method estimates values for cloud fraction, clear and cloudy albedos and brightness temperatures in each grid box. The choice of a class-dependent AVHRR channel allows for better separation of clear and cloudy pixels than does a global choice of a visible and/or infrared threshold. The classification also prevents erroneous estimates of large fractional cloudiness in areas of cloudfree snow and sea ice. The hybrid histogram-spatial coherence technique and the advantages of first classifying a scene in the polar regions are detailed. The complete Polar Cloud Pilot Data Set was analyzed and the results are presented and discussed. Other/Unknown Material albedo Antarc* Antarctic Arctic Sea ice NASA Technical Reports Server (NTRS) Antarctic Arctic |
institution |
Open Polar |
collection |
NASA Technical Reports Server (NTRS) |
op_collection_id |
ftnasantrs |
language |
unknown |
topic |
METEOROLOGY AND CLIMATOLOGY |
spellingShingle |
METEOROLOGY AND CLIMATOLOGY Smith, William L. Ebert, Elizabeth The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques |
topic_facet |
METEOROLOGY AND CLIMATOLOGY |
description |
The cloud cover in a set of summertime and wintertime AVHRR data from the Arctic and Antarctic regions was analyzed using a pattern recognition algorithm. The data were collected by the NOAA-7 satellite on 6 to 13 Jan. and 1 to 7 Jul. 1984 between 60 deg and 90 deg north and south latitude in 5 spectral channels, at the Global Area Coverage (GAC) resolution of approximately 4 km. This data embodied a Polar Cloud Pilot Data Set which was analyzed by a number of research groups as part of a polar cloud algorithm intercomparison study. This study was intended to determine whether the additional information contained in the AVHRR channels (beyond the standard visible and infrared bands on geostationary satellites) could be effectively utilized in cloud algorithms to resolve some of the cloud detection problems caused by low visible and thermal contrasts in the polar regions. The analysis described makes use of a pattern recognition algorithm which estimates the surface and cloud classification, cloud fraction, and surface and cloudy visible (channel 1) albedo and infrared (channel 4) brightness temperatures on a 2.5 x 2.5 deg latitude-longitude grid. In each grid box several spectral and textural features were computed from the calibrated pixel values in the multispectral imagery, then used to classify the region into one of eighteen surface and/or cloud types using the maximum likelihood decision rule. A slightly different version of the algorithm was used for each season and hemisphere because of differences in categories and because of the lack of visible imagery during winter. The classification of the scene is used to specify the optimal AVHRR channel for separating clear and cloudy pixels using a hybrid histogram-spatial coherence method. This method estimates values for cloud fraction, clear and cloudy albedos and brightness temperatures in each grid box. The choice of a class-dependent AVHRR channel allows for better separation of clear and cloudy pixels than does a global choice of a visible and/or infrared threshold. The classification also prevents erroneous estimates of large fractional cloudiness in areas of cloudfree snow and sea ice. The hybrid histogram-spatial coherence technique and the advantages of first classifying a scene in the polar regions are detailed. The complete Polar Cloud Pilot Data Set was analyzed and the results are presented and discussed. |
format |
Other/Unknown Material |
author |
Smith, William L. Ebert, Elizabeth |
author_facet |
Smith, William L. Ebert, Elizabeth |
author_sort |
Smith, William L. |
title |
The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques |
title_short |
The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques |
title_full |
The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques |
title_fullStr |
The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques |
title_full_unstemmed |
The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques |
title_sort |
analysis of polar clouds from avhrr satellite data using pattern recognition techniques |
publishDate |
1990 |
url |
http://hdl.handle.net/2060/19900013552 |
op_coverage |
Unclassified, Unlimited, Publicly available |
geographic |
Antarctic Arctic |
geographic_facet |
Antarctic Arctic |
genre |
albedo Antarc* Antarctic Arctic Sea ice |
genre_facet |
albedo Antarc* Antarctic Arctic Sea ice |
op_source |
CASI |
op_relation |
Document ID: 19900013552 Accession ID: 90N22868 http://hdl.handle.net/2060/19900013552 |
op_rights |
No Copyright |
_version_ |
1766250314699112448 |