D39 Initial evaluation of the observation operator.
This is part of work-package 6300, the purpose of which is observation
operator development for slant delays.
Objectives: To develop a slant delay observation operator
Methodology/Work Description: The actual GPS signal delays are
measured on slant-profiles of the atmosphere. The aim in the NWP variational
data assimilation is to make use of the measurements close to the raw data
format with little data pre-processing. The natural first step towards using
slant-delay measurements in NWP is to properly evaluate them against the
model counterparts. For this task an appropriate observation operator is
needed. The zenith delay observation operator is simple to develop, as the
observation geometry is relatively straightforward and similar to the NWP
model geometry. The slant-delay observation operator, in contrast, requires
a model profile along a slanted path with unknown intersects with the model
levels. Once the iterative problem of interpolating the model variables on
a slanted path is solved, the associated delay can be fairly easily solved.
* FMI will develop a demonstration version of observation operator in
co-operation with the expertise of the KNMI
* FMI, together with KNMI, will adjust a three-dimensional variational
data assimilation system of for the HIRLAM-model for assimilation of (simulated)
slant delays. Special attention will be paid to the selection of sources
of data that can constrain the solution(s) (e.g. Meteosat WV, radiosonde and
other satellite methods).
* FMI will make the initial evaluation of the functionality of the observation
operator against the slant-delay measurements
Deliverable. The slant delay observation operator developed by
FMI has been evaluated. The report on the evaluation is available here: d39-fmi.pdf. For further information contact
Reima Eresmaa at Reima.Eresmaa@fmi.fi.