RTTOV-7 : A Satellite Radiance Simulator for the New Millennium

One of the essential tools to exploit satellite radiance data in an NWP model assimilation system is a fast radiative transfer (RT) model. This includes both the forward model, which computes satellite radiances for a given profile vector, and its jacobian which computes the change in radiances with respect to the input profile variables. The RTTOV fast RT model has been developed for many years now and recently this has been supported as part of the EUMETSAT NWP Satellite Application Facility (SAF) activities. The last version of RTTOV, RTTOV-6, was released in March 2000 and has been distributed to over 40 users worldwide. In February 2002 RTTOV-7 was released by the NWP-SAF and has several improvements that are described briefly in this paper and other papers in this proceedings (see references below). The main upgrades are: improved water vapour channel simulation, improved microwave surface emissivity model, support for AIRS, MODIS and SSM/I(S), additional RTTOV routines for simulating cloudy radiances, code rewritten in standard Fortran-90 and simpler coefficient ingest.

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