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| Titel |
Development of a Cloud-Top Height Estimation Method by Geostationary Satellite Split-Window Measurements Trained with CloudSat Data |
| VerfasserIn |
Atsushi Hamada, Noriyuki Nishi, Toshiro Inoue |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039454
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| Zusammenfassung |
| Estimation of cloud-top height and visible optical thickness of upper-tropospheric clouds by
brightness temperature (TB) measurements of geostationary satellite at two infrared
split-window wavelengths was conducted. These cloud parameters were estimated by
regressing the measurements of 94-GHz cloud radar onboard CloudSat satellite in terms of
TB at 10.8 um (T11) and its difference from TB at 12 um (ÎT = T11 -T12) measured by
geostationary satellite MTSAT-1R.
Estimation by geostationary satellite measurements are fairly useful in field
campaigns aiming mesoscale cloud systems, where cloud-top heights are compared
with the vertical profiles of ground-based measurements such as wind and cloud
condensates in a short time interval. Hamada et al. (2008) conducted the estimation of
cloud-top height by T11 and ÎT measured by GMS-5, using ship-borne cloud radar
measurements. However, their ground-based result was limited to the non-rainy clouds, since
cloud radar signal is heavily attenuated by precipitation particles. Spaceborne radar
measurements enables an estimation of cloud-top height without concern for the existence of
precipitation.
We examined the dependences of the estimates of cloud-top height on latitude, season,
satellite zenith angle, day-night, and land-sea differences. It was shown that these
dependences were considered as being uniform in tropics, except for the region with large
satellite zenith angle. The dependences on latitude and season were negligible in
tropics, while they became the most significant factor affecting the estimates at higher
latitudes.
Estimation of visible optical thickness was also conducted, although limited to the
non-rainy high clouds. The distributions of estimates in TB-ÎT space were qualitatively
consistent with those expected from a simplified radiative transfer equation, although the
standard deviations of measurements were slightly large.
The near real-time products has already been provided on our Website
(http://www-clim.kugi.kyoto-u.ac.jp/hamada/ctop/). Since the CloudSat conducts cloud radar
observations on a global scale, the method adopted in this study can easily be applied to other
current geostationary satellites with split-window channels, yielding hourly estimation map
of cloud-top and optical thickness in global scale. We will show the results also using
Meteosat Second Generation measurements. |
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