YetAnotherCoupler 3.1.1
Loading...
Searching...
No Matches
Conservative interpolation

Table of Contents

Description

This interpolation method assumes that the source field values are fluxes defined on the source grid cells.

For each target cell, this method searches for all overlapping source cells. Based on the overlap areas between the source and target grid cell the flux values for the target field will be computed.

A first order following Jones (1999) and a second order following Kritsikis et al. (2017) are supported.

When computing the intersection areas between source and target cells, YAC differentiates between edges defined on great circles and latitude circles. This is especially important for cells from regular grids that are located close to the poles. Therefore, in contrast to other software that also provides this interpolation method, YAC does not require the usage of coordinate transformations close to the poles.

Source Field

Options

  • Order (default: order: 1)
    • 1

      First order conservative interpolation

Target field
  • 2

    Second order conservative interpolation.

    In contrast to first order conservative, this option generates a much bigger stencil. In order to do that, a gradient of the source field is computed for each source cell based on its neighbouring cells. If the gradient computation fails, a zero-gradient will be used for the respective source cell, which is basically a fallback to first order conservative interpolation.

Target field
  • Enforced conservation (default: enforced_conservation: false)

    If true, all weights for a target cell will be scaled such that the sum of them is 1.0.

    For second order this option is not supported and only the value false is allowed.

  • Partial coverage (default: partial_coverage: false)

    If the value is false, target cells that are not completely covered by non-masked source cells will not be interpolated.

  • Area normalisation (default: normalisation: destarea)

    Selects the area normalisation method as described in the SCRIP User manual (Jones, Philip. (1998). A User's Guide for SCRIP: A Spherical Coordinate Remapping and Interpolation Package, Version 1.4.).

    Only for target cells that are partially covered by non-masked source cells the different options produce different results.

    • fracarea

      The sum of the area of the non-mask source cells overlapping with the target cell is used to normalise the respective target field value.

      This option gives reasonable flux values but may not be locally conservative.

    • destarea

      The target cell area is used to normalise the target field value.

      This option might generate unreasonable flux values but it ensures local conservation of the source flux.

YAML example

interpolation:
- conservative:
order: 1
enforced_conservation: false
partial_coverage: false
normalisation: fracarea