id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
519	WARNING: major overhaul of ROMS kernel to include nesting Phase II	arango	arango	"This is a major update of ROMS nonlinear ('''NLM'''), tangent linear ('''TLM'''), representer ('''RPM'''), and adjoint ('''ADM''') models to include the multiple grid nesting (refinement, composed, and mosaics) '''Phase II''' development.
The main goal in '''Phase II''' is to remove all the lateral boundary conditions C-preprocessing options and replace them with logical switches. The changes are extensive because there were periodic boundary conditions ('''EW_PERIODIC''' and '''NS_PERIODIC''') everywhere in the code. This required extensive testing of the '''NLM''', '''TLM''', '''RPM''', and '''ADM''' kernels and provided idealized and realistic test cases.

The actual nesting capabilities are not available yet. This will be released in '''Phase III''' in the near future. There is is still some work ahead. The changes that will be required for full nesting capabilities are very minimal but tricky and will involve changes to '''main2d'''/'''main3d''' and adding new files for the actual nesting.

However, the current update is '''very important''' since it includes changes to the ROMS kernel.  At the beginning, I thought that '''Phase II''' was really easy but tedious. Well, I greatly underestimated the amount of work and time in the debugger during testing. It was as tricky as '''Phase I''' but it only took me five months to finish it.

We are releasing this update at this time to allow the Users time to assimilate, test, and play with the new lateral boundary conditions structure. One of the advantages of the new design is the we can have different lateral boundary conditions for each active (temperature and salinity) and passive (inert, biology, sediment, etc) tracers. I highly recommend that you use the '''same''' lateral boundary conditions for temperature and salinity because they uniquely determine the density of the fluid via the equation of state for seawater.

This version is named '''ROMS 3.6'''. Once we have the full nesting in place and finish other important developments it will become '''ROMS 4.0'''. The current plan is to release '''ROMS 4.0''' sometime this year.

The technical description of the changes is elaborated and will be reported in the ROMS [https://www.myroms.org/forum/viewtopic.php?f=13&t=2401 forum].

'''Good look updating to ROMS Version 3.6 ...'''"	upgrade	closed	major	Nesting/Composed Grids	Release	3.6	Done