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| Titel |
Collocating GRAS with AMSU onboard of Metop: An assessment for instrument and climate monitoring |
| VerfasserIn |
F. Ladstädter, H. Gleisner, K. Kinch, K. B. Lauritsen, U. Foelsche, C. Marquardt, J. Ackermann, A. von Engeln |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067947
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| Zusammenfassung |
| Satellite observations of upper-air temperature have been dominated by the MSU and the
AMSU instrument for the last several decades. These instruments flying on NOAA polar
orbiting satellites were the only source for long-term temperature measurements of global
coverage. The calibration of time series containing data from only one source is
inevitably a demanding task. In this context, the series of METOP satellites provides
unique opportunities to both meteorological and climatological applications. They
carry both state-of-the-art instruments such as GRAS or IASI, and instruments
which have been in use for a longer time period within the NOAA satellite program,
such as AMSU or HIRS. The inherent precision of the RO technique employed
by the GRAS instrument makes it a candidate for providing potential reference
measurements.
Observing from the same platform gives a high number of collocated measurements
from the different types of instruments, and avoids uncertainties stemming from
different sampling characteristics. The nadir sounders AMSU-A, HIRS, IASI are
collocated, but GRAS observes in limb sounding view either ahead of the satellite
(rising occultations) or behind the satellite (setting). Most of the occultations are
actually on the nadir swath, but with a few minutes ahead or delayed. The hosting of a
radio occultation instrument along with nadir sounders opens an opportunity to use
these continuous collocations for instrument monitoring. In particular collocations
of the AMSU-A with GRAS are promising since AMSU (and previously MSU)
are instruments used to generate long term data sets for climate monitoring. The
AMSU-A channel primarily used for these long term data sets is peaking in the upper
troposphere/lower stratosphere, thus the use of GRAS radio occultation measurements can
be restricted to altitudes where no ambiguity of water vapor and temperature is
present.
In this initial study, the opportunity of having the GRAS RO instrument alongside AMSU
shall be used to assess the prospect of inter-calibration and instrument monitoring using
GRAS. This can potentially also improve the contribution of AMSU to weather forecasting
and climate monitoring. |
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