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Atmospheric initial conditions: For
real-time forecasts: ECMWF
operational analysis. For back statistics: ERA40
when available, otherwise ECMWF operational analysis.
Oceanic initial conditions: Last
ocean analysis + real time forecast
The oceanic initial conditions lag about 12 days behind real time. They
are produced by the ECMWF ocean assimilation system called ODASYS.
The lag is partially due to the fact that the weekly OIv2 SSTs produced
by NCEP can be up to 11 days behind real-time. A first option would be
to wait for the oceanic initial conditions to be created by the data assimilation
system to start the forecast, as in seasonal forecasting. A second option
would be to persist the SST anomalies of the latest ocean analysis. However,
we have some information about the wind stress and heat fluxes during
the last 12 days, from the ECMWF atmospheric analysis; this information
can be used to help determine the present ocean initial state. Therefore,
the option chosen for monthly forecasting is to integrate the ocean model
from the last ocean analysis, forced by analyzed wind stress, heat fluxes
and P-E. During this 'ocean forecast', the sea surface temperature is
relaxed towards persisted SST, with a damping rate of 100 W/m2/K.
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