G2 is currently using Met Office ancillaries. These use the standard GLOBE30 orography with all its problems over Australia (wiki:access/HighResolutionAustralianOrography). Also Fiji is missing from the land-sea mask (​https://code.metoffice.gov.uk/trac/TI/ticket/7).
fiji_orography.png​ (44.3 KB) - added by Martin Dix 4 years ago.
treefrac_fiji_new.png​ (43.2 KB) - added by Martin Dix 4 years ago.
treefrac_fiji_std.png​ (42.6 KB) - added by Martin Dix 4 years ago.
treefrac_hawaii_new.png​ (40.0 KB) - added by Martin Dix 4 years ago.
treefrac_hawaii_std.png​ (39.9 KB) - added by Martin Dix 4 years ago.
aust_orog_std.png​ (78.4 KB) - added by Martin Dix 4 years ago.
aust_orog_new.png​ (77.3 KB) - added by Martin Dix 4 years ago.
aust_orog_diff.png​ (87.7 KB) - added by Martin Dix 4 years ago.
The ancillary program can optionally use a list of mask overrides. Standard Met Office N512 set is /projects/access/apps/cap/7.9/control/changes/mask/mask_changes.n512.
Appended to the standard Met Office set to create a new override file /projects/access/apps/cap/7.9/control/changes/mask/mask_changes.n512_access_G2.
However the vegetation fractions for Fiji looked strange with much more bare soil than expected. This was also true for Hawaii (and similar at several resolutions).
The CAP vegetation interpolation code searches for the nearest defined points. For Hawaii this is somewhere on the Mexican coast. Apart from any question of how reasonable it is to take values from this far away, a code error in calculating the weights means that many points in the island block get very small values that are rounded down to zero, leaving only bare soil.
​http://glcf.umd.edu/data/lc has IGBP vegetation classes derived from MODIS data with proper values for Hawaii and Fiji. The vegetation code doesn't have the same sort of point override as the mask, so the simplest fix was to overwrite the missing values in the master 1km data set with the MODIS values. There's not much variation from year to year. For N512 it doesn't seem worth using the highest resolution (500m) data so I used the more convenient 5' data.
The modified file is /projects/access/data/master/vegetation/cover/igbp/v2/qrdata.igbp.island_fix.
Note that if I'd used this corrected master vegetation from the start the mask overrides wouldn't have been necessary.
Even using the standard GLOBE30 data the orography generated here showed some small differences compared to the Met Office file (e.g. /g/data/dp9/da/access-g/um/ancil/atmos/n512/orography/globe30/ukmo/v1/qrparm.orog. This was mainly over Antarctica and is likely due to some difference in the filtering. At the moment the source of the difference is still unexplained. To avoid these extra differences complicating the comparison, the Australia + Fiji region was copied from the new orography to the standard orography, so the final file only has differences over the expected region.
The HWSD master soil dataset (2.5 minute = 0.04167 degree resolution) includes both Fiji and Hawaii so there's no problem with trying to fill missing data from distant points.
Following fields are not used by the cycling suite but possibly used for cold start?
Fiji gets plausible soil moisture values, similar to Queensland coast. Snow simply zero.
Fields identical to standard files except for Fiji being now masked out.
Version numbers were chosen to match Met Office files.
The rose suite au-aa388 generates the ancillaries. Rev 1302 generates the versions described above. Rev 1305 uses the modified vegetation to generate the mask too. This includes Fiji though it's not quite the same shape as with the override. This approach isn't really recommended but more saved as a record of what's possible.