Test Case 1: Dry, neutral boundary layer with backscatter

This test case is 3D and does not require the radiation code. This page provides the background information on test case 1 and examples of run of test case 1 on various machines.

Background information (from Jon Petch)

This standard case simulates a dry, neutral boundary layer with a constant geostrophic wind using backscatter in the subgrid model. Backscatter is an important option in the LEM subgrid model as it stochastically puts energy back on the gridscale, which is in the opposite sense to the usual dissipative drain of energy. Using backscatter gives a much better simulation of the dry, neutral boundary layer problem than the basic subgrid model. This is illustrated in the diagrams below, blue showing diagnostics without backscatter and green showing diagnostics with. For example, the spin-up of the energy time-series in the top-left hand corner is much smoother under backscatter, whereas in the bottom plots the energy/turbulence peak is eroneously lifted from the surface without backscatter and the wind profile shows too strong shear near the surface.

As well as providing a rigorous test of the backscatter code, this case is representative of the model in its simplest mode - with no moisture, microphysics or radiation - solving problems for which the LEM was originally designed.

Files required to run test case 1

The files needed to run this test case can be found in /home/lem/VER2.3/TEST_CASES/TEST1_2.3 and the table below indicates which files you'll need for which machines

	Turing (T3E - no longer available)	Department machines	Origins (i.e. wren, fermat or green)	Newton
run...f	runTEST1_2.3.f	runTEST1_2.3-m.f	runTEST1_2.3.f	runTEST1_2.3.f
end...f	endTEST1_2.3.f	endTEST1_2.3.f	endTEST1_2.3.f	endTEST1_2.3.f
nmlsetup...	nmlsetupTEST1_2.3	nmlsetupTEST1_2.3	nmlsetupTEST1_2.3	nmlsetupTEST1_2.3
nmlchain...	nmlchainTEST1_2.3	nmlchainTEST1_2.3	nmlchainTEST1_2.3	nmlchainTEST1_2.3
model...	modelTEST1_2.3	modelTEST1_2.3	modelTEST1_2.3-n	modelTEST1_2.3-n

Runs for Test Case 1

Computer	Run No	Version	PEs	IIP, JJP, KKP	Time Taken	Results
Newton	140 & 141	2.3	8	48, 32, 64	1.27 & 0.70 hrs	With backscatter No Backscatter
Origins	33 & 34	2.3	8	48, 32, 64	4.15 & 2.22 hrs	With backscatter No Backscatter
GRID	52 & 51	2.3	1	48, 32, 64	~63.1 & 27.6 hrs	With backscatter No Backscatter
T3E at Met Office	N/A	2.2	8	48, 32, 64	unknown	With backscatter Without backscatter
Turing	705	2.2	8	48, 32, 64	unknown	With backscatter
Stokes	700	2.2	1	48, 32, 64	unknown	With backscatter