Proceedings - C-SRNWP Project

either with a 1-dimensional observation operator which assumes local horizontal homogeneity
for the radiative transfer calculations, or with a 2-dimensional observation operator which
takes into account horizontal gradients along the limb-viewing plane.
The first set of experiments assimilating CHAMP GPS radio occultation (GPSRO)
measurements with 2-dimensional bending angle observation operators has been completed.
The 2-dimensional operators improved the bending angle departure statistics in the lower
troposphere by around ~5% compared with a 1-dimensional bending angle operator, although
this did not translate into a clear, statistically significant improvement in the forecast scores.
COSMIC data (which has been seen to be of high quality) have been received from August
and should be used in operations soon.
Green dots – COSMIC GPSRO locations over a 24 hour period. Red dots: radiosondes
Observing System Experiments (OSEs) coordinated by EUCOS have been performed to
examine the various components of the terrestrial Observing System, in the presence of the
current satellite-based Observing System. Results from a summer period (46 days) are
currently being assessed. The winter studies indicate a large impact of the radiosondes (wind
and temperature) and aircraft (wind and temperature), a marginal impact of radiosonde
humidity information, and a contrasted impact (with negative spells) from the wind profilers.
REANALYSIS
The ERA-interim reanalysis has started. It covers the period from 1989 and will be continued
in near-real time when it reaches the present (“climate data assimilation mode”).
• It uses Cycle 31r1 of the IFS 12-hour window 4D-Var and T255 resolution in the outer
loops. Currently two versions exist: 60 and 91 levels. Only the best version will be
continued in near-real time.
• The set of observations and SST/ice information used is the same as in ERA-40 until 2002,
then operational datasets will be used.
• It also uses Meteosat AMV´s reprocessed by Eumetsat and ERS-1 and ERS-2 altimeter and
scatterometer data reprocessed by ESA.
• It uses 1dVar+4dvar assimilation of rain-affected SSMI radiances.
• It uses variational bias correction of all clear sky satellite radiances and automated bias
correction for surface pressure observations.
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