View source for GA4.0 N216 Development

As part of the GA4.0 UKCA development, in Cambridge we are developing a N216L85 GA4.0 model using the CheT(+GLOMAP) [[Developing_releases#2013_TropIsop.2FCheT_.2B_GLOMAP_.28Co-ordinator:_Graham_Mann.29|configuration]]. However, there is no GA4.0 N216 base model existing at MetUM version 8.4.

==Create a GA4.0 N216 Base model==

There are a number of steps that need to be made before a base GA4.0 N216 model is ready for UKCA to be included:

# Assess the models available at the [http://collab.metoffice.gov.uk/trac/GA/wiki/GADocumentation/GA4.0#Jobs GA development page]
#* This shows that the only existing N216 job available is [http://collab.metoffice.gov.uk/trac/GA/wiki/GAJobs/xhcea '''xhcea'''] on MONSooN
#** This job ran for 30 years, and the output is available on MOOSE
#** The original UKMO version of this job is '''ajthw'''.
#* There are however GA4.0 N96 jobs available at vn8.0 ([http://collab.metoffice.gov.uk/trac/GA/wiki/GAJobs/aliur '''aliur''']) and vn8.4 ([http://collab.metoffice.gov.uk/trac/GA/wiki/GAJobs/amche '''amche''']) 
# It is therefore necessary to regrid '''amche''' to N216 for use by UKCA
#* There is a [http://collab.metoffice.gov.uk/trac/GA/wiki/GASettings/GA4.0_HRes guide on how change the horizontal resolution] on the GA twiki.
#** The ancillary files can be taken from '''xhcea''' which already exist on MONSooN.
#** There may be other changes that have been made between '''aliur''' and '''xhcea''' which are not represented in the guide. I have therefore asked Jeremy Walton to port '''aliur''' as well as '''amche''' over to MONSooN to check the differences.
#* The new job '''xjgva''' has been created which is a GA4.0 N216L85 AMIP candidate, based on '''amche''' and using the differences from the [http://collab.metoffice.gov.uk/trac/GA/wiki/GASettings/GA4.0_HRes guide] and the differences between '''aliur''' and '''xhcea'''.
#** Differences between vn8.0 GA4.0 N216 ('''xhcea''') and N96 ('''aliur'''): [[diff.xjgvx.xjgvz]]
#** Differences between vn8.4 GA4.0 N216 ('''xjgva''') and N96 ('''amche'''): [[diff.xjgva.xjgvy]]
#* It should be noted that the settings were mainly taken from the guide rather than the differences between vn8.0 jobs. Notable differences between '''xjgva''' and '''xhcea''', or '''xjgva''' and '''amche''', are:
#*# In '''xjgva''' soil moisture has been initialised to <code>$USER_ANCIL/N216/orca025/smc_snow/v1/ajthma.smc_scaled</code> whereas '''amche''' sets this from the dump.
#*# '''xjgva''' uses the same start dump as '''xhcea''': <code>$USER_ANCIL/N216/start_dumps/v1/ajthma.dai1910</code>.
#*# In the ''Large Scale Precipitation'' section, '''xjgva''' uses '''7 substeps over full column''', rather than 10 in '''xhcea'''.
#*# '''xjgva''' uses the standard vn8.4 spectral files, rather than the vn7.9 spectral files used by '''xhcea'''. There should be no difference in the components of the file used however.
# '''xjgva''' compiled successfully and has been sent off for an equivalent 30-year run to '''xhcea'''.
#* '''xjgva''' runs at approximately 2400 +/- 51 seconds for each 10-day jobstep, giving a maximum throughput of 12 model months per day.
#* However, the actual throughput is quite variable, having between 3 and 12 model months per day with an average turnover of 9 model months at present.