	SSP Project Summary:

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To parallelise a multi-layer, atmospheric transport model

A computer model has been developed which predicts the concentration and deposition rate of ammonia over Great Britain. Despite optimisation, run times are long (1 - 2 days on Waverley) and this is constraining future development of the model. Parallelising should reduce run times considerably and allow more realisitic processes to be incorporated.

The model is written in FORTRAN 77 (7300lines) and utilises air columns, extending from the surface to a height of 2500m, moving along straight-line trajectories along a series of specified wind directions. Ammonia is introduced into the air columns at the surface from a detailed UK emission inventory. Sulphur dioxide and nitrogen oxides are introduced at various heights from both UK and European source inventories. Vertical diffusion is treated explicitly, with 33 layers of differing depths and with transfer between layers determined by turbulent exchange coefficients. As the air columns move along their trajectories, chemical interactions between ammonia, sulphur dioxide and nitrogen oxides take place and deposition of chemical species occurs at the surface at rates dependent on land use. Wet deposition occurs at rates determined by concentrations, washout coefficients and rainfall rates.

Annual mean concentration maps and deposition maps are determined by combining 24 equally-spaced wind directions, suitably weighted by the frequency of winds from each direction.

Programme

Week 2: Familiarisation with model and existing code.
Weeks 3-5: Development of strategy for parallelising model; adaption of code.
Weeks 6-9: Comparison of results with serial code results**; comparison of runs with more sophisticated wind statistics**; looking at seasonal differences in deposition.
Week 10: Report writing.

** possible drop-out points

Expertise required

No subject area skills required; no difficult maths required of student; just logical thought.

Resources supplied

Serial code; all input datasets.

References

ApSimon et al. (1994) Modelling studies of the atmospheric release and transport of ammonia. Atmospheric Environment, 28, 665-678.

Singles et al. (1995) Fine resolution modelling of ammonia dry deposition in Great Britain. Acid Rain Research, Elsevier Scientific.

Victor Lesk worked on this project.

Compressed PostScript of the project's final report is available here (38 kbytes) .

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