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Rotated lat-lon: stand_lon meaning and CLONG shift

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New member

I've recently been tinkering with WRF's rotated lat-lon projection. I am however facing two issues:

1) The coordiantes CLONG (computational or rotated domain longitude) values are shifted by some amount from a zero or 180 center. Where does this shift come from?

2) The rotated lat-lon has a few parameters: pole_lat, pole_lon, stand_lat, ref_lat and ref_lon. The ref_lat and ref_lon are coordinates of the studied domain within geographical coordinates. The paremters pole_lat, pole_lon and stand_lon on the other hand are needed to define the rotated coordinates. According to WRF's User's Guide's recommendation (as well as the common sense), it's best to use pole_lat (geogrpahic pole latitude within rotated coordinates) as 90-ref_lat and pole_lon (geogrpahic pole longitude within rotated coordinates) as 180 degrees. However, the aformentioned choices do not actually fix the rotated coordinate system, an initial rotated coordiante parameter needs to be input as well ... Therefore, this is where the stand_lon parameter comes in. WRF defines this to be -ref_lon. Our actual guess is that stand_lon is the inverse (negative) of date line longitude of the rotated coordinates in standard coordinates. However, there may be something that we are missing here and the defintion of the stand_lon is different than the above. Can you let us know if this's the case?

P.S. In all these statements, we assume the domain center's within the northern hemisphere.

Best Regards,