speed up grid loading and cell searches for smc grid generation

[ukmo-ansaulter]

• ww3-grid version: 0.1
• Python version: 3
• Operating System: RHEL7

Description

For larger SMC grids (N512 and bigger) and multiple levels grid loading and cell amendment using gridgen.py can be relatively slow. The main hold ups are:

• [major] searching for and amending cells adjacent to dry land/tier cells (fillCells, chkAdj)
• [minor] setting up cell corners and centres arrays when loading the netCDF files (setCellBoundsSMC, setCellMidsSMC)

Planned code updates

TBC