A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region
Abstract We compare the consistency between eight reanalyses: CERA20C, ERA5, ERA‐Interim, ERA20C, NCEP‐DOE, MERRA2, JRA55, and 20CRV2c. This comparison uses daily surface winds near Antarctica to classify synoptic patterns using the self‐organizing map technique. The relative frequency of occurrence...
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ftdoajarticles:oai:doaj.org/article:6d1203dda6b045eb8fd356a8193010f9 2023-05-15T13:40:56+02:00 A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region Adrian J. McDonald Luke H. Cairns 2020-01-01T00:00:00Z https://doi.org/10.1029/2019EA000794 https://doaj.org/article/6d1203dda6b045eb8fd356a8193010f9 EN eng American Geophysical Union (AGU) https://doi.org/10.1029/2019EA000794 https://doaj.org/toc/2333-5084 2333-5084 doi:10.1029/2019EA000794 https://doaj.org/article/6d1203dda6b045eb8fd356a8193010f9 Earth and Space Science, Vol 7, Iss 1, Pp n/a-n/a (2020) self‐organizing maps synoptic climatology reanalyses Antarctica entropy coefficient Astronomy QB1-991 Geology QE1-996.5 article 2020 ftdoajarticles https://doi.org/10.1029/2019EA000794 2022-12-31T05:43:15Z Abstract We compare the consistency between eight reanalyses: CERA20C, ERA5, ERA‐Interim, ERA20C, NCEP‐DOE, MERRA2, JRA55, and 20CRV2c. This comparison uses daily surface winds near Antarctica to classify synoptic patterns using the self‐organizing map technique. The relative frequency of occurrence (RFO) of these patterns are very similar during the satellite era in each reanalysis. The three most common patterns are the same in each reanalysis and changes between the reanalyses only display a 12% relative variation. Examination of the RFOs over time highlights that the CERA20C and 20CRV2c reanalyses display large changes previous to 1957. These changes are likely connected to model relaxation toward their climatology because of a lack of observational constraints. Primarily, we introduce the entropy coefficient (U) which quantifies the consistency between reanalyses in their representation of synoptic patterns. Examination of U shows current reanalyses (ERA5, ERA‐Interim, JRA55, and MERRA2) are highly consistent in the satellite era likely due to good observational coverage. However, centennial reanalyses (CERA20C, ERA20C, and 20CRV2c) show two upward step changes in consistency as measured by U at around 1957 and to a lesser extent 1979. Low values of U before 1957 suggest that centennial reanalyses are of limited use before this date, but may be useful after 1957 in this region. We also show that the entropy coefficient displays an inverse relationship with ensemble spread metrics of individual reanalyses. We conclude that the entropy coefficient provides a powerful quantification of the influence of changes in observation density on reanalysis quality in data sparse regions. Article in Journal/Newspaper Antarc* Antarctica Ice Shelf Ross Ice Shelf Ross Sea Directory of Open Access Journals: DOAJ Articles Ross Ice Shelf Ross Sea Earth and Space Science 7 1 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
self‐organizing maps synoptic climatology reanalyses Antarctica entropy coefficient Astronomy QB1-991 Geology QE1-996.5 |
spellingShingle |
self‐organizing maps synoptic climatology reanalyses Antarctica entropy coefficient Astronomy QB1-991 Geology QE1-996.5 Adrian J. McDonald Luke H. Cairns A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region |
topic_facet |
self‐organizing maps synoptic climatology reanalyses Antarctica entropy coefficient Astronomy QB1-991 Geology QE1-996.5 |
description |
Abstract We compare the consistency between eight reanalyses: CERA20C, ERA5, ERA‐Interim, ERA20C, NCEP‐DOE, MERRA2, JRA55, and 20CRV2c. This comparison uses daily surface winds near Antarctica to classify synoptic patterns using the self‐organizing map technique. The relative frequency of occurrence (RFO) of these patterns are very similar during the satellite era in each reanalysis. The three most common patterns are the same in each reanalysis and changes between the reanalyses only display a 12% relative variation. Examination of the RFOs over time highlights that the CERA20C and 20CRV2c reanalyses display large changes previous to 1957. These changes are likely connected to model relaxation toward their climatology because of a lack of observational constraints. Primarily, we introduce the entropy coefficient (U) which quantifies the consistency between reanalyses in their representation of synoptic patterns. Examination of U shows current reanalyses (ERA5, ERA‐Interim, JRA55, and MERRA2) are highly consistent in the satellite era likely due to good observational coverage. However, centennial reanalyses (CERA20C, ERA20C, and 20CRV2c) show two upward step changes in consistency as measured by U at around 1957 and to a lesser extent 1979. Low values of U before 1957 suggest that centennial reanalyses are of limited use before this date, but may be useful after 1957 in this region. We also show that the entropy coefficient displays an inverse relationship with ensemble spread metrics of individual reanalyses. We conclude that the entropy coefficient provides a powerful quantification of the influence of changes in observation density on reanalysis quality in data sparse regions. |
format |
Article in Journal/Newspaper |
author |
Adrian J. McDonald Luke H. Cairns |
author_facet |
Adrian J. McDonald Luke H. Cairns |
author_sort |
Adrian J. McDonald |
title |
A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region |
title_short |
A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region |
title_full |
A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region |
title_fullStr |
A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region |
title_full_unstemmed |
A New Method to Evaluate Reanalyses Using Synoptic Patterns: An Example Application in the Ross Sea/Ross Ice Shelf Region |
title_sort |
new method to evaluate reanalyses using synoptic patterns: an example application in the ross sea/ross ice shelf region |
publisher |
American Geophysical Union (AGU) |
publishDate |
2020 |
url |
https://doi.org/10.1029/2019EA000794 https://doaj.org/article/6d1203dda6b045eb8fd356a8193010f9 |
geographic |
Ross Ice Shelf Ross Sea |
geographic_facet |
Ross Ice Shelf Ross Sea |
genre |
Antarc* Antarctica Ice Shelf Ross Ice Shelf Ross Sea |
genre_facet |
Antarc* Antarctica Ice Shelf Ross Ice Shelf Ross Sea |
op_source |
Earth and Space Science, Vol 7, Iss 1, Pp n/a-n/a (2020) |
op_relation |
https://doi.org/10.1029/2019EA000794 https://doaj.org/toc/2333-5084 2333-5084 doi:10.1029/2019EA000794 https://doaj.org/article/6d1203dda6b045eb8fd356a8193010f9 |
op_doi |
https://doi.org/10.1029/2019EA000794 |
container_title |
Earth and Space Science |
container_volume |
7 |
container_issue |
1 |
_version_ |
1766143446214508544 |