An update on the 4D-LETKF data assimilation system for the whole neutral atmosphere
<p>The four-dimensional local ensemble transform Kalman filter (4D-LETKF) data assimilation system for the whole neutral atmosphere is updated to better represent disturbances with wave periods shorter than 1 d in the mesosphere and lower thermosphere (MLT) region. First, incremental analysis...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-03-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/15/2293/2022/gmd-15-2293-2022.pdf |
| Summary: | <p>The four-dimensional local ensemble transform Kalman
filter (4D-LETKF) data assimilation system for the whole neutral atmosphere
is updated to better represent disturbances with wave periods shorter than 1 d in the mesosphere and lower thermosphere (MLT) region. First,
incremental analysis update (IAU) filtering is introduced to reduce the
generation of spurious waves arising from the insertion of the analysis
updates. The IAU is better than other filtering methods, and also is
commonly used for middle atmospheric data assimilation. Second, the order of
horizontal diffusion in the forecast model is changed to reproduce the more
realistic tidal amplitudes that were observed by satellites. Third, the
Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and
Special Sensor Microwave Imager/Sounder (SSMIS) observations in the
stratosphere and mesosphere also are assimilated. The performance of the
resultant analyses is evaluated by comparing them with the mesospheric winds
from meteor radars, which are not assimilated. The representation of
assimilation products is greatly improved not only for the zonal mean field
but also for short-period and/or horizontally small-scale disturbances.</p> |
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| ISSN: | 1991-959X 1991-9603 |