FAMOUS

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Variable Solar Forcing

The latitudinal distribution of solar forcing varies over long timeperiods. This has been implemented in FAMOUS by backporting the UM6.1 code, wrapped up in some custom code. The options, under Atmosphere→Science→General Physics→Solar in the UMUI are as follows:

1) Fixed, modern defaults. Hardcoded into model, exact values for Julian2000 from UM6.1

2) Fixed, user specified year. Specify a year via the UMUI (and a calculation option, see below) and the model will calculate appropriate orbital params and stay fixed at those values for the course of the run

3) Varying, calculated online. Calculate orbital parameters based on the model year every new year, using the Berger78 method as implemented at UM6.1 (valid ± 1Myr BP)

4) Varying, using precalculated tables. Calculate orbital parameters based on the model year every new year, derived from precalculated tables i.e. Laskar04 (valid for whenever you can find values for. Laskar 04 claims some use up to −100Myr→20Myr)

Options 3) and 4) can additionally use an “acceleration” factor where the orbital forcing is speeded up. For example, with a factor of 10, 20kyr of orbital forcing would be applied over a 2000yr run

Negative and long paleo-dates in FAMOUS currently can’t be post-processed by xconv/conv.sh -based programs. This limitation is apparently hard-coded, and will probably not get fixed. A number of workarounds exist.

Page last modified on August 16, 2011, at 11:00 AM by robin