Applying PRISM topography and SSTs as anomalies + Lakes

[Alan Haywood]

Applying PRISM topography and SSTs as anomalies + Lakes

There has been some discussion within the Advisory Panel regarding the
best way to implement the Pliocene boundary conditions for topography
and SSTs.

Our view is that Pliocene topography and SSTs should be applied as an
anomaly to whatever topography and SSTs data set each group uses for
modern.

We want anomaly results from different groups to be completely
comparable - i.e. to reflect differences in the models rather than
differences in methodology of creating boundary conditions. If each
group use anomaly Pliocene orography/SST, and their own local standard
modern orography/SST we should be able to achieve this.

This might remove the need for groups to repeat control simulations
which will be particularly welcome for experiment 2.

To create the Pliocene SST/orography please sum the difference between
PRISM Pliocene orography/SST and PRISM modern orography/SST to your
own control modern orography and SST data sets.

E.g.

Orog_Plio = (Orog_Plio_PRISM - Orog_Mod_PRISM) + Orog_Mod_Local

SST_Plio = (SST_Plio_PRISM - SST_Mod_PRISM) + SST_Mod_Local

To create the modern orography/SSTs use your local orography/SST data
sets for modern.

This creates the problem of a potential mismatch of land-sea mask
between Pliocene and modern, but this can be overcome by using
absolute Pliocene orography in regions where there is no modern
orography/SSTs (if there are any such regions).

A further advantage of using the anomaly method is that we should see
lakes disappear. In the absence of any data on Pliocene lake
distribution this is the cleanest way to deal with lakes i.e. to have
none.

Thanks.

Plio-MIP Advisory Panel.