open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I want to use Telemac-2d to simulate storm surge. Since the simulation domain is large, I want the Coriolis force to vary spatially. Therefore, I decided to use spherical coordinates. However, I'm not fully understanding the meaning of LATITUDE OF ORIGIN POINT. Should I use the default value, or adjust it based on the latitude of my mesh? (My mesh spans latitudes from 20 to 25 degrees.)

Thanks advanced!

Hello,

It depends in which geographic system the geometry file is written:
- if already in Mercator projection, use LATITUDE OF ORIGIN POINT you have chosen to build the coordinates in Mercator projection. In that case, it is recommended to have chosen LATITUDE OF ORIGIN POINT and LONGITUDE OF ORIGIN POINT around the "center" of the extent of the domain,
- if in longitude/latitude, choose LATITUDE OF ORIGIN POINT and LONGITUDE OF ORIGIN POINT around the "center" of the extent of the domain (for you, you can choose 22.5).

You can see in PROSOU subroutine how Coriolis force is computed (if SPHERICAL COORDINATES = YES or NO). If SPHERICAL COORDINATES = YES, TELEMAC-2D uses MESH%SINLAT array, which is computed by LATITU subroutine (called by INBIEF subroutine, which is called by TELEMAC2D_INIT subroutine). This uses LATITUDE OF ORIGIN POINT.
Moreover, LATITUDE OF ORIGIN POINT is used to convert longitude/latitude to Mercator projection (if providing a geometry file in longitude/latitude as TELEMAC-2D computes everything in plane projection). See the call to POINT_TELEMAC2D, then ALMESH, then READ_MESH_COORD.

Hope this helps,

Chi-Tuan