 |
| Titel |
Strategies for coupling global and limited-area ensemble Kalman filter assimilation |
| VerfasserIn |
D. Merkova, I. Szunyogh, Edward Ott |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1023-5809
|
| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 18, no. 3 ; Nr. 18, no. 3 (2011-06-27), S.415-430 |
| Datensatznummer |
250013927
|
| Publikation (Nr.) |
 copernicus.org/npg-18-415-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
This paper compares the forecast performance of four strategies for coupling
global and limited area data assimilation: three strategies propagate
information from the global to the limited area process, while the fourth
strategy feeds
back information from the limited area to the
global process. All four strategies are formulated in the Local Ensemble
Transform Kalman Filter
(LETKF) framework.
Numerical experiments are carried out with the model component of the
National Centers for Environmental Prediction (NCEP) Global Forecast System
(GFS) and the NCEP Regional Spectral Model (RSM). The limited area domain
is an extended North-America region that includes part of the north-east
Pacific. The GFS is integrated at
horizontal resolution T62 (about 150 km in the mid-latitudes), while the
RSM is integrated at horizontal resolution 48 km. Experiments are carried out
both under the perfect model hypothesis
and in a realistic setting. The coupling strategies are evaluated by comparing
their deterministic forecast performance at 12-h and 48-h lead times.
The results suggest that the limited area data assimilation system has the
potential to enhance the forecasts at 12-h lead time in the limited area domain
at the synoptic and sub-synoptic scales
(in the global wave number range of about 10 to 40). There is a clear indication
that between the forecast performance of the different coupling strategies those
that cycle the limited area assimilation process produce the most accurate
forecasts. In the realistic setting, at 12-h forecast time the limited area
systems produce more modest improvements compared to the global system than
under the perfect model hypothesis, and at 48-h forecast time the global
forecasts are more accurate than the limited area forecasts. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|