Dalhousie Geodynamics Group

Author: Chris Beaumont
2010-08-19: new

subroutine eperturb_t_lvlslope perturbs the current E-temperature field according to a level_slope_level perturbation function.

Inputs are:

1. Eulerian grid, x and y coordinates - x1(*), y1(*)
2. Eulerian Temperature field (Kelvin) - t1(*)
3. An isotherm (Kelvin) to which the perturbation is applied.
4. A level-slope-level perturbation function defined by x1_pert, level1, x2_pert, level2

For x < x1_pert a uniform perturbation equal to level1 is applied to t1(ij)

For x > x2_pert a uniform perturbation equal to level2 is applied to t1(ij)

For x1_pert < x < x2 the perturbation is equal to a linear interpolation between level1 and level2 between x1_pert and x2_pert

The perturbation is defined as follows. level is the value of the perturbation for the current column of the temperature field at x(i). level is a number,

Assuming level < 1.0d0 E-grid positions for y-positions greater than that of isothermk_pert are proportionately squeezed in an accordion manner by factor level (y measured +ve upward). E-grid positions for y-positions less than that of isothermk_pert are modified according to adiabat_opt

If adiabat_opt ≤ 1.0d-12 E-grid positions are proportionately stretched in an accordion manner.

If adiabat_opt > 1.0d-12 the value of adiabat_opt is interpreted as the required adiabatic temperature gradient below isothermk-pert. This means that isothermk_pert must be the isotherm that is the interface between conductive and convective regions of the model and may require that the thermal conductivity be temperature dependent in order to represent convection.

Not yet implemented. For the present adiabat_opt should be ≤ 1.0d12

Perturbing the E-grid positions moves the corresponding E-temperature field. The perturbed E-temperature field is then linearly interpolated back onto the E-grid (current E-grid, as it was at the beginning of the subroutine).

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