Opened 7 years ago
Last modified 5 years ago
#168 reopened Support
the coordinate transfo error exceeds 0.02*dx
Reported by: | victoria.sinclair@… | Owned by: | adingwell |
---|---|---|---|
Priority: | minor | Milestone: | |
Component: | FP other | Version: | FLEXPART-WRF |
Keywords: | coordinate transform, mercator grid | Cc: |
Description
I am trying to run FLEXPART-WRF (forward) using WRF input data on a mercator grid. I keep getting the error:
test_xyindex_to_ll_wrf calling map_set -- map_proj_id, map_set_proj_code = 3 1
test_xyindex_to_ll_wrf -- lgrid, rmserr (km) = 0 1.03E+03
- *
- WARNING - the coordinate transfo error exceeds 0.02*dx *
- *
problem with the projection. wrf+flexpart stops.
I have attached my input file I am using. The WRF output is at 9km grid spacing and has 249 points in the east-west direction and 255 points in the north-south direction. Any advice in how to solve this problem would be appreciated.
Attachments (1)
Change History (6)
Changed 7 years ago by victoria.sinclair@…
comment:1 Changed 7 years ago by adingwell
- Owner set to adingwell
- Status changed from new to assigned
Hi Victoria,
the error you get is due to large scaling errors from your map projection. FLEXPART-WRF makes a test for this to prevent the user from setting up too distorted grids. You can view the scaling errors in your WRF-output (the MAPFAC_* fields). FLEXPART-WRF is hard-coded to abort if the error is above 2%.
You can solve this problem by:
- Changing the map projection to something more suitable for the region you're studying
- Setting up a smaller model domain in flexpart-wrf (the highest errors are usually near the domain borders unless you're using an unsuitable map projection)
- Changing the threshold in map_proj_wrf.f90 (not recommended)
comment:2 Changed 7 years ago by adingwell
- Resolution set to fixed
- Status changed from assigned to closed
I'm marking this as solved due to inactivity.
comment:3 follow-up: ↓ 4 Changed 5 years ago by ahilboll
We're running in the same problem here with WRF output on 40m resolution. The MAPFAC_ values are all below 1.0002, using Lambert projection. So in principle, the domain should not affected by scaling.
So I don't understand how come that the RMS is above 2%. Do WRF and FLEXPART-WRF use different formulas to calculate lat/lon from the map projection parameters?
And, for now, more importantly: Can we safely use the WRF output in this situation?
comment:4 in reply to: ↑ 3 ; follow-up: ↓ 5 Changed 5 years ago by pesei
- Resolution fixed deleted
- Status changed from closed to reopened
Replying to ahilboll:
So I don't understand how come that the RMS is above 2%. Do WRF and FLEXPART-WRF use different formulas to calculate lat/lon from the map projection parameters?
They should not but maybe there have been changes in newer versions of WRF? Might be worthwhile to compare.
comment:5 in reply to: ↑ 4 Changed 5 years ago by ahilboll
Replying to pesei:
Replying to ahilboll:
So I don't understand how come that the RMS is above 2%. Do WRF and FLEXPART-WRF use different formulas to calculate lat/lon from the map projection parameters?
They should not but maybe there have been changes in newer versions of WRF? Might be worthwhile to compare.
I just compared map_proj_wrf_subaa.f90 from FLEXPART-WRF v3.3.2 to module_llxy.F from WRF v4.1 and the respective ijll_lc subroutines seem to be equivalent.
input file