i3d/InterpolationType

The interpolation type is specified in the configuration file i3d.inp (line 3):

0 - only one nearest neighbor from the CLaMS grid is used (i.e. this interpolation does not cause any numerical diffusion)
1 - weighted interpolation over two triangles (i.e. 6 neighbors). The contribution of these 6 points depends on the horizontal distance within the upper and lower triangle as well as on the absolute vertical differences of these 6 points to the considered air parcel, i.e. APs with smallest -values have the higher contribution where is defined as
$r = \sqrt{(x_{exp}-x)^2+(y_{exp}-y)^2+(z_{exp}-z)^2+((\theta_{exp}-\theta)/\Delta{\theta}ratio)^2)}$
Here, index denotes the coordinates of a given AP where the interpolation from the external (CLaMS) grid should be determined. $\theta_{exp}-\theta$ and are the distances in the $\theta$ -space (absolute difference in $\zeta$ -space) and on the unit sphere (i.e., points are on a unit sphere but the distance is defined in ), respectively. $\Delta{\theta}ratio$ is the aspect ratio (horizontal/vertical resolution) of the simulation. In July 2010 i3d was updated to ensure interpolation between the values of $\theta_{exp}$
2 - Interpolation type 0 and 1 (two output files per date are created)

The earlier definition 1 of the weight is not supported after July 2010 (but could be re-created from CVS):

former type 1 - weighted interpolation over two triangles (i.e. 6 neighbors). The contribution of these 6 points depends on the horizontal distance within the upper and lower triangle as well as on the absolute vertical differences of these 6 points to the considered air parcel, i.e. APs with smallest -values have the higher contribution where is defined as
- $r = |\theta_{exp}-\theta|r_s, \quad r_s^2=(x_{exp}-x)^2+(y_{exp}-y)^2+(z_{exp}-z)^2$