Scheduled Downtime
On Tuesday 24 October 2023 @ 5pm MT the forums will be in read only mode in preparation for the downtime. On Wednesday 25 October 2023 @ 5am MT, this website will be down for maintenance and expected to return online later in the morning.
Normal Operations
The forums are back online with normal operations. If you notice any issues or errors related to the forums, please reach out to help@ucar.edu

latixy values in clm h0 history files - what is the actual output grid?

The h0 files delineate an extent of -0.625,359.375,-90,90 (west, east, south north) with 288 longitude and 192 latitude points. If these points all represent same-size cells, this gives consistent resolution of 1.25x0.9375 (lon, lat). The longxy and latixy variables hold the cell-center values (presumably), and while the longitude layout is awkward due to the first center at 0.0 degrees, the longxy values do align with 288 cells. The latixy values, however, do not. There are 192 latixy values ranging from -90 to 90 degrees, which leaves only 191 cells (0.9424... resolution), and -90 and 90 cannot be cell centers if the boundaries are at -90 and 90 degrees.

Are the latixy values incorrect? Should I treat the clm grid as all equal-sized cells at 0.9375 degree resolution and boundaries at -90 and 90 degrees?

It turns out that the atmosphere history files also include cell boundary variables, and the lat_bnds values show 192 cells, but the northernmost and southernmost rows are half of 0.9424... degrees, and the other 190 cells are 0.9424... degrees. The latixy values are the same as for the clim history files, and align with the 190 inner rows but have the same problem at +-90 (which is understandable in this case). Does the atmosphere operate on the grid described by its history files, and does clm also operate on this grid? Or does clm operate on an even-sized grid and its latixy value are just a legacy from the atmosphere grid?

Thanks,
Alan
 

slevis

Moderator
Could you diagnose the answer by writing out lat/lon values using print statements in parts of the cam and clm codes where the lat/lon values matter? Sorry for not offering more help with this...Sam
 
Top