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| Titel |
The effects of the RAW filter on the climatology and forecast skill of the SPEEDY model |
| VerfasserIn |
Javier Amezcua, Eugenia Kalnay, Paul Williams |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052364
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| Zusammenfassung |
| In a recent study, Williams (2009) introduced a simple modification to the widely
used Robert–Asselin (RA) filter for numerical integration. The main purpose of the
Robert–Asselin–Williams (RAW) filter is to avoid the undesired numerical damping of the
RA filter and to increase the accuracy.
In this presentation, the effects of the modification are comprehensively evaluated in the
SPEEDY atmospheric general circulation model. First, we search for significant changes in
the monthly climatology due to the introduction of the new filter. After testing both at the
local level and at the field level, we find no significant changes, which is advantageous in the
sense that the new scheme does not require a retuning of the parameterized model
physics.
Second, we examine whether the new filter improves the skill of short and medium term
forecasts. January 1982 data from the NCEP Reanalysis are used to evaluate the
forecast skill. Improvements are found in all the model variables (except the relative
humidity, which is hardly changed). The improvements increase with lead time and
are especially evident in medium-range forecasts (96 to 144 hours). For example,
in tropical surface pressure predictions, five-day forecasts made using the RAW
filter have approximately the same skill as four-day forecasts made using the RA
filter.
The results of this work are encouraging for the implementation of the RAW filter in other
models currently using the RA filter.
References
Amezcua, Kalnay and Williams (2011) The effects of the RAW filter on the climatology
and forecast skill of the SPEEDY model. Monthly Weather Review, in press.
http://dx.doi.org/10.1175/2010MWR3530.1
Williams (2009) A proposed modification to the Robert–Asselin time filter. Monthly Weather
Review 137(8), pp 2538–2546. http://dx.doi.org/10.1175/2009MWR2724.1
Williams (2011) The RAW filter: An improvement to the Robert–Asselin filter in semi-implicit
integrations. Monthly Weather Review, in press. http://dx.doi.org/10.1175/2010MWR3601.1 |
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