Cascade Documentation

Cascade documentation

Cathryn Birch

File formats

I have put the data we discussed onto the hard drive. 2m winds were not saved out when the model was run, so these are not included. However, winds on model levels are with the first level at 10m above ground level.

The data consists of the 40 days of 40km param, 12km param and 12km explicit and 10 days of 4km explicit, all starting from 25th July 2006 (you should discount at least the first day to allow for spin up).

The files for 40km param, 12km param and 12km explicit are organised in a similar way – see Appendix one of Cascade_Data_at_Leeds2.docx. Model diagnostics were already organised into different files so instead of extracting the diagnostics you requested I have copied the whole files to your disk. This means you have all the diagnostics in the ph, pj, pf and pa files. The filenames look like this:

xhqwda_ph008.nc

The letters at the start are the model experiment number. The ‘ph’ shows what variables are in the file (as discussed above) and the numbers relate to the number of hours into the run that the files contain e.g. here 8 means the files contain diagnostics between 8 and 12 hours into the simulation.

The files for the 4km explicit simulation are organised differently – there is only one variable in each file, therefore you only have the diagnostics you asked for. The diagnostics are in different folders, which should be self-explanatory. Also see the codes in Appendix 2 of Cascade_Data_at_Leeds2.docx for a list of which codes match which file name.

I suggest downloading a bit of software which will help you see what is in each file (some of the variable names may not come through in the netcdf file headings). Go here:

and click the downloads option, then download the Xconv executable for your platform.

Lat/lon coordinates

For the limited area model domains the poles are rotated to make the grid boxes as square as possible. The lat/lon coordinates in the files are on this rotated system so will not represent reality. They need to be converted. I have put scripts to convert between the two in the folder ‘lat_lon’. These are in matlab and IDL format (should be easy to translate – I managed it!). You also need to know the lat and lon of the rotated poles, which are lat=79.000 and lon = 180.000 for all domains.

Vertical coordinates

The Unified Model has two sets of vertical levels: rho and theta, where theta levels are positioned in the middle of each of the rho levels. U and V winds are on rho levels and everything else is on theta levels. It is a terrain-following coordinate system and therefore you need to know the orography height and some other details to know how high the levels are above mean sea level.

See Joy_of_new_dynamics.ps Appendix B for a description of this. You need to know the orography height at each grid box and some other files that I have put in the folder ‘vertical_levels’. vertlevs_G3 has the parameters needed for the models with 38 vertical levels (40 and 12km param and explicit) and vertlevs_UK4_L70 has the parameters needed for the models with 70 vertical levels (4km).

You will find that in some of the netcdf files for the 4km model the 3D variables are only on 37 levels - lowest 12 rho levels to 600m then every other to 16km. This was to make the files smaller. This shouldn’t be a problem for you (all the lowest levels are there) but if you need the full field let me know and I can get them.

Model surface properties

I have created netcdf files of surface fraction (2 types of tree, 3 types of grassland, urban etc) and roughness length. They are in the folder ‘surface_properties’ (12km param and explicit have the same properties). The 9 surface types are in the order that they are in the table at in the top of p19 in ancillary_file_data_sources.pdf.