 |
| Titel |
Validation of HRDI MLT winds with meteor radars |
| VerfasserIn |
F. Hasebe, T. Tsuda, T. Nakamura, M. D. Burrage |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 15, no. 9 ; Nr. 15, no. 9, S.1142-1157 |
| Datensatznummer |
250012944
|
| Publikation (Nr.) |
 copernicus.org/angeo-15-1142-1997.pdf |
|
|
|
|
|
| Zusammenfassung |
| A validation study of the mesospheric and
lower-thermospheric (MLT) wind velocities measured by the High-Resolution
Doppler Imager (HRDI) on board the Upper-Atmosphere Research Satellite (UARS)
has been carried out, comparing with observations by meteor radars located at
Shigaraki, Japan and Jakarta, Indonesia. The accuracy of the HRDI winds relative
to the meteor radars is obtained by a series of simultaneous wind measurements
at the time of UARS overpasses. Statistical tests on the difference in the wind
vectors observed by HRDI and the meteor radars are applied to determine whether
the wind speed has been overestimated by HRDI (or underestimated by the MF
radars) as previously noticed in HRDI vs. MF radar comparisons. The techniques
employed are the conventional t-test applied to the mean values of the
paired wind vector components as well as wind speeds, and two nonparametric
tests suitable for testing the paired wind speed. The square-root transformation
has been applied before the t-tests of the wind speed in order to fit the
wind-speed distribution function to the normal distribution. The overall results
show little evidence of overestimation by HRDI (underestimation by meteor
radars) of wind velocities in the MLT region. Some exceptions are noticed,
however, at the altitudes around 88 km, where statistical differences
occasionally reach a level of significance of 0.01. The validation is extended
to estimate the precision of the wind velocities by both HRDI and meteor radars.
In the procedure, the structure function defined by the mean square difference
of the observed anomalies is applied in the vertical direction for the profile
data. This method assumes the isotropy and the homogeneity of variance for the
physical quantity and the homogeneity of variance for the observational errors.
The estimated precision is about 6ms–1 for the Shigaraki meteor
radar, 15ms–1 for the Jakarta meteor radar, and 20ms–1 for
HRDI at 90-km altitude. These values can be used to confirm the statistical
significance of the wind field obtained by averaging the observed winds. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|