UKCA & UMUI Tutorial 5

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Adding Emissions into a Tracer

At the end of the previous tutorial you will now know how to create new tracers for use by UKCA. However, after completing the tasks, your tracers will still be empty, as nothing has been put into those tracers. This tutorial will teach you how to create an emissions ancillary file that the UM will read, and that you can then tell UKCA to use and emit into your tracer(s).

Making a new Emissons Ancillary File

The UM uses its own format to read-in intial and emissions data, the ancillary file. UKCA makes use of these files for the surface and aircraft emissions, and these files can easily be made up from netCDF data using the Xancil program.

Xancil is installed on both MONSooN (on the postproc03 machine) at

/projects/um1/linux/bin/xancil

and on HECToR at

/work/n02/n02/hum/bin/xancil

You may already have this location in your PATH and so can just launch Xancil from the command line. However, before we can use Xancil to create our emissions ancillary, we must first use [http:/75/badc.nerc.ac.uk/help/software/xconv/ Xconv] to view (and possibly regrid) the raw data to the correct resolution of the UM configuration that you are using.

Regridding data with Xconv

We are using a model at N96L85 resolution. In the horizonal this is 1.875 degrees by 1.25 degrees. There are 85 vertical levels.

The N96 UM grid

1. Has 192 points in longitude (x) and 145 points in latitude (y)
2. Starts at 0.0 longitude with a spacing of 1.875 degrees
3. Starts at -90.0 latitude with a spacing of 1.25 degrees

Horizontal Regridding

Figure 1: The Xconv Trans window.

Horizontal regridding in Xconv is straight-forward. First, open your dataset in Xconv by

xconv -i file.nc

and double-click on the field that you want to regrid.

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Written by Luke Abraham 2013