''(back to [[Dec07|XCPSA Release Page]])''
!!! Various notes on individual changes
Overall, the model's climate sensitivity (as specified by ''Gregory et al., GRL 31 (2004)'') has decreased slightly, bringing it closer to that of [=HadCM3=], probably mainly due to the sea-ice changes
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|| '''Change''' || '''Sci details''' || '''Tech Details''' ||
|| Ozone ||After much experimentation, we've ended up with only a minor tweak on the idealised, original FAMOUS 3level O3. The tropopause-finding diagnostic TROPIN is relaxed so as to find the tropopause lower, the "above tropopause" value of O3 specified is slightly lower, and a slightly higher O3 concentration is then placed in the top model layer, everywhere. This results in a much improved "stratospheric" temperature profile at low latitudes, and provides for at least some kind of temperature inversion at high latitudes, although significant cold bias still remains near the poles (see [[Summer07Plots#vtemp|vertical temperature plots]]). Everything else tried, along the lines of realistic climatologies or more layers, looked no better aloft than this mod, and frequently had detrimental impacts on the surface temperature. Ozone concentrations are thus still lower than those observed (see [[Summer07Plots#o3|ozone plots]]), but this seems to be required to get a sensible longwave response in FAMOUS.||'''mods''': ozone_mod-3levcustom, tropin11.mod. Replace standard modsets ozone_mod and tropin11 ||
|| Sea Ice ||Much of the northern latitude cold bias is linked to excessive ice production. Encouraging the melting of the ice thus improves the high latitude surface temperatures considerably (see [[Summer07Plots#stemp|surface temperature plots]]). Sea-ice albedo is tempertaure dependent, between a low "melting" value and a high "frozen" value. Here, the melting value has been lowered from 0.5 to 0.2. This is a bit extreme, although individual meltponds may have albedoes this low. This value was found to help temperature and ice fraction the most, through a short-ish series of sea-ice parameter tests. The overall Northern Hemisphere ice albedo in summer is now a little unrealistically low, but it's actually better than it was for the rest of the year (see [[Summer07Plots#ice|ice albedo scatter plots]]), and temperatures, year-round, are much improved. There's also a slight average improvement in the Southern Hemisphere ice coverage. There's still too much ice cover for much of the year in the Northern Hemisphere, then too little after the summer melt (see [[Summer07Plots#ice|ice fraction plots]]). Interestingly, the excessive ice in the Pacific really isn't impacted much by this - really, it's good for the temperatures via the ice albedo change, rather than by the actual removal of ice fraction. In addition, the tunable parameter of the minimum ice thickness of 0.5m is also reduced, to 0.25m.||'''UMUI changes''': Albedo is in ''Atmosphere -> Scientific Parameters -> Section by section -> SW Radiation -> Minimum Albedo of Sea Ice''. Minimum ice thickness is at ''Ocean -> Scientific Parameters -> Sea Ice Model -> Minimum Local Ice Depth''||
|| Orography ||The original, less smoothed N24 orography was dusted off and tried - we think the more smoothed version was created to (unsuccessfully) reduce model instabilities, and then never changed back. It's slightly peakier (see [[Summer07Plots#orog|orog plot]]), and helps both surface temperatures and midlatitude variablility a bit (see [[Summer07Plots#eke|EKE plot]]). ||'''ancil''': qparm.orog.4837 - currently needs to be reconfigured into atmos dump, release dump should contain the new land already||
|| Orbital variability ||a framework is now provided to allow parameters for the orbitally forced seasonalities of different paleo periods to be set. The parameters can either be fixed at a given year, or allowed to vary as time progresses. Varying parameter sets can be "accelerated" by a given factor. The actual parameters are calculated from the model year via either an online calculation, or using published sets of values from extended, offline orbital calculations. See [[Summer07Instructions|new feature instructions]] ||'''mod''': calc_solar_params.mod - '''handedit''': orbital_parameters.sh - '''ancil''': (e.g.) solar_params_laskar04 (table of values. Not a UM ancil) ||
|| Longfilenames/Dates ||changes the date convention in the output filenames to allow real paleodates to be used - including negative years. e.g. xbyvra@pyo71c1-> xbyvra#py000002471c1+. Negative years end in "-" instead of "+". See [[Summer07Instructions|new feature instructions]]||'''mod''': long_output_names.mod - '''handedit''': long_output_names.sh - for full continuation run functioning, some of the small execs need to be rebuilt with this mod as well. The release version ''may'' have rebuilt execs supplied with it. ||
|| [=HadOCC=] ||Ocean biogeochemistry that works (?!) (see [[Summer07Valnote|TCO2, Alk fields in the validation note]]) in FAMOUS. Can be turned off pretty easily, imposes a ~10% running cost from moving around all the tracers. ||'''mods''': alk2.mod, tuning_2.mod, self_shade.mod (parameter tweaks, simple selfshading req'd because the coupled model doesn't use the banded radiation req'd for the full shading - '''dump''': needs an ocean dump with the tracer fields in i.e. adbip||
|| Iceberg Calving ||The freshwater flux adjustment field used to keep the global salinity drift at 0 in [=HadCM3=] (justified as an iceberg calving parameterisation) has been simply rescaled to fit the salinity drift in FAMOUS due to accumulation of snow on land. Together with the vflux_drift_xccgb mod that removes the artificial tracer drift caused by the rigid-lid numerics, this ensures a zero salinity drift in the modern FAMOUS control run. And I now have to redo the entire release control run on the bank holiday weekend because I've only just remembered we were going to include it.||'''ancil''': icecalv_FAMOUS.anc. ||