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Forecast and analysis assessment through skill scores
Author(s)
Language
English
Obiettivo Specifico
4A. Oceanografia e clima
Status
Published
JCR Journal
JCR Journal
Title of the book
Issue/vol(year)
/5 (2009)
Publisher
EGU
Pages (printed)
649–660
Issued date
2009
Keywords
Abstract
This paper describes a first comprehensive evaluation of the quality of the ten days
ocean forecasts produced by the Mediterranean ocean Forecasting System (MFS).
Once a week ten days forecasts are produced. The forecast starts on Tuesday at noon
and the prediction is released on Wednesday morning with less then 24 hr delay. 5 In this
work we have considered 22 ten days forecasts produced from the 16 August 2005 to
the 10 January 2006. All the statistical scores have been done for the Mediterranean
basin and for 13 regions in which the Mediterranean sea has been subdivided.
The forecast evaluation is given here in terms of root mean square (rms) values.
10 The main skill score is computed as the root mean square of the difference between
forecast and analysis (FA) and forecast and persistence (FP), where the persistence
is defined as the average of the day of the analysis corresponding to the first day of
the forecast. A second skill score (SSP) is defined as the ratio between rms of FA and
FP, giving the percentage of accuracy of the forecast with respect to the persistence
15 (Murphy 1993).
The rms of FA is always better than FP and the FP rms error is double than the
rms of FA. It is found that in the surface layers the error growth is controlled mainly by
the atmospheric forcing inaccuracies while at depth the forecast errors could be due to
adjustments of the data assimilation scheme to the data insertion procedure. The pre20
dictability limit for our ocean forecast seems to be 5–6 days connected to atmospheric
forcing inaccuracies and to the data availability for assimilation.
ocean forecasts produced by the Mediterranean ocean Forecasting System (MFS).
Once a week ten days forecasts are produced. The forecast starts on Tuesday at noon
and the prediction is released on Wednesday morning with less then 24 hr delay. 5 In this
work we have considered 22 ten days forecasts produced from the 16 August 2005 to
the 10 January 2006. All the statistical scores have been done for the Mediterranean
basin and for 13 regions in which the Mediterranean sea has been subdivided.
The forecast evaluation is given here in terms of root mean square (rms) values.
10 The main skill score is computed as the root mean square of the difference between
forecast and analysis (FA) and forecast and persistence (FP), where the persistence
is defined as the average of the day of the analysis corresponding to the first day of
the forecast. A second skill score (SSP) is defined as the ratio between rms of FA and
FP, giving the percentage of accuracy of the forecast with respect to the persistence
15 (Murphy 1993).
The rms of FA is always better than FP and the FP rms error is double than the
rms of FA. It is found that in the surface layers the error growth is controlled mainly by
the atmospheric forcing inaccuracies while at depth the forecast errors could be due to
adjustments of the data assimilation scheme to the data insertion procedure. The pre20
dictability limit for our ocean forecast seems to be 5–6 days connected to atmospheric
forcing inaccuracies and to the data availability for assimilation.
Type
article
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