Data compression in the presence of observational error correlations
Numerical weather prediction (NWP) models are moving towards km-scale (and smaller) resolutions in order to forecast high-impact weather. As the resolution of NWP models increase the need for high-resolution observations to constrain these models also increases. A major hurdle to the assimilation of...
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| Format: | Article |
| Language: | English |
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Stockholm University Press
2019-01-01
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| Series: | Tellus: Series A, Dynamic Meteorology and Oceanography |
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1080/16000870.2019.1634937 |
| _version_ | 1811292271626158080 |
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| author | A.M. Fowler |
| author_facet | A.M. Fowler |
| author_sort | A.M. Fowler |
| collection | DOAJ |
| description | Numerical weather prediction (NWP) models are moving towards km-scale (and smaller) resolutions in order to forecast high-impact weather. As the resolution of NWP models increase the need for high-resolution observations to constrain these models also increases. A major hurdle to the assimilation of dense observations in NWP is the presence of non-negligible observation error correlations (OECs). Despite the difficulty in estimating these error correlations, progress is being made, with centres around the world now explicitly accounting for OECs in a variety of observation types. This paper explores how to make efficient use of this potentially dramatic increase in the amount of data available for assimilation. In an idealised framework it is illustrated that as the length-scales of the OECs increase the scales that the analysis is most sensitive to the observations become smaller. This implies that a denser network of observations is more beneficial with increasing OEC length-scales. However, the computational and storage burden associated with such a dense network may not be feasible. To reduce the amount of data, a compression technique based on retaining the maximum information content of the observations can be used. When the OEC length-scales are large (in comparison to the prior error correlations), the data compression will select observations of the smaller scales for assimilation whilst throwing out the larger scale information. In this case it is shown that there is a discrepancy between the observations with the maximum information and those that minimise the analysis error variances. Experiments are performed using the Ensemble Kalman Filter and the Lorenz-1996 model, comparing different forms of data reduction. It is found that as the OEC length-scales increase the assimilation becomes more sensitive to the choice of data reduction technique. |
| first_indexed | 2024-04-13T04:42:55Z |
| format | Article |
| id | doaj.art-01ec943b8ae64dd3a3cdafcf4e7f4c95 |
| institution | Directory Open Access Journal |
| issn | 1600-0870 |
| language | English |
| last_indexed | 2024-04-13T04:42:55Z |
| publishDate | 2019-01-01 |
| publisher | Stockholm University Press |
| record_format | Article |
| series | Tellus: Series A, Dynamic Meteorology and Oceanography |
| spelling | doaj.art-01ec943b8ae64dd3a3cdafcf4e7f4c952022-12-22T03:01:56ZengStockholm University PressTellus: Series A, Dynamic Meteorology and Oceanography1600-08702019-01-0171110.1080/16000870.2019.16349371634937Data compression in the presence of observational error correlationsA.M. Fowler0University of ReadingNumerical weather prediction (NWP) models are moving towards km-scale (and smaller) resolutions in order to forecast high-impact weather. As the resolution of NWP models increase the need for high-resolution observations to constrain these models also increases. A major hurdle to the assimilation of dense observations in NWP is the presence of non-negligible observation error correlations (OECs). Despite the difficulty in estimating these error correlations, progress is being made, with centres around the world now explicitly accounting for OECs in a variety of observation types. This paper explores how to make efficient use of this potentially dramatic increase in the amount of data available for assimilation. In an idealised framework it is illustrated that as the length-scales of the OECs increase the scales that the analysis is most sensitive to the observations become smaller. This implies that a denser network of observations is more beneficial with increasing OEC length-scales. However, the computational and storage burden associated with such a dense network may not be feasible. To reduce the amount of data, a compression technique based on retaining the maximum information content of the observations can be used. When the OEC length-scales are large (in comparison to the prior error correlations), the data compression will select observations of the smaller scales for assimilation whilst throwing out the larger scale information. In this case it is shown that there is a discrepancy between the observations with the maximum information and those that minimise the analysis error variances. Experiments are performed using the Ensemble Kalman Filter and the Lorenz-1996 model, comparing different forms of data reduction. It is found that as the OEC length-scales increase the assimilation becomes more sensitive to the choice of data reduction technique.http://dx.doi.org/10.1080/16000870.2019.1634937observation network designdata assimilationdegrees of freedom for signalmutual information |
| spellingShingle | A.M. Fowler Data compression in the presence of observational error correlations Tellus: Series A, Dynamic Meteorology and Oceanography observation network design data assimilation degrees of freedom for signal mutual information |
| title | Data compression in the presence of observational error correlations |
| title_full | Data compression in the presence of observational error correlations |
| title_fullStr | Data compression in the presence of observational error correlations |
| title_full_unstemmed | Data compression in the presence of observational error correlations |
| title_short | Data compression in the presence of observational error correlations |
| title_sort | data compression in the presence of observational error correlations |
| topic | observation network design data assimilation degrees of freedom for signal mutual information |
| url | http://dx.doi.org/10.1080/16000870.2019.1634937 |
| work_keys_str_mv | AT amfowler datacompressioninthepresenceofobservationalerrorcorrelations |