We are using the CAMS near real time data for a wildfire application. In the old interface we always had the option to select a finer grid size of the data (0.125°x0.125° was used). In the new interface there is no such option and the user is tied to a more coarse resolution (I think per defualt 0.4°x0.4°).
Can users still access the higher reoluted data? If nor, is it planned to re-add the grid size option to the new ADS web interface?
Is it possible to access the full resolution of the data (0,125°x0,125°) through the python api?
Thank you very much in advance!
Hi Mohamad,
The CAMS Global atmospheric composition forecasts data available from the ADS has been pre-interpolated to a regular 0.4°x 0.4° latitude/longitude grid. The keyword 'grid' is not supported in CDS API requests on the ADS.
See CAMS: Global atmospheric composition forecast data documentation for full details of this dataset,
Thanks,
Kevin
Hello. I have a follow-up question regarding the re-gridding.
What is the best way of re-gridding the ADS provided 0.4 x 0.4 into 0.25 x 0.25 grid we use?
It's really hard to find any good answers for re-gridding. We're not a computer-savvy enough output to figure out the arcane commands for CDO and their brothers.
HI Marine,
I'd say that CDO is a good option for this regridding - do you have the details of the grid you want? do you have CDO installed?
(Note that regridding to a higher resolution does not add any 'extra' information to the data)
Thanks
Kevin
Hi, and thanks for the answer!
I've found this so far:
cdo -v remapnn,r1440x720 ECMWF_CAMS_dust_aerosol_optical_depth_550nm2022011212.grib ECMWF_CAMS_dust_aerosol_optical_depth_550nm2022011212_remapped.grib
This "seems" to work, but creates a grid from (-89.875, -180) to (89,875, 179,75), with 0.25-steps. I guess it means that value is in the "middle" of a 0.25x0.25 point?
We would like to match the output of (-90, -180) to (90, 179.75) that ERA5 weather files generates, where the value is the lower left point.
But perhaps it's as simple as substracting -0.125 from the latitude?
Another question, is if "nn" - nearest neighbour is the correct algorithm to use for the various CAMS values?
Wondering (~2.5y later) if you ever got an answer to this?
I’m also looking to regrid CAMS to be not-0.75x0.75; fortunately I’d settle for either 0.25 or 1x1 which is at least an easy multiple, but it would be exponentially easier if we could just download its native resolution…
Also I’ve been looking for an answer re: the grid points-- I presume it’s the midpoint of a particular grid (rather than top-left/bottom-right corner or something) but haven’t been able to find any explicit confirmation of that.
Thanks in advance!
Hi Kristina (and Mohamad),
While this isn’t possible with the existing system, we are about to launch a new version of the ADS and I will try to make sure it is possible in that one.
See here for latest info: A new ADS soon to be launched - expect some disruptions. More should follow within the next couple of weeks or so.
Luke.
I just realised I didn’t answer your question about grid points. Yes, I can confirm the coordinates given in the files are the grid-point centres.
And on the issue of the native resolution - that’s a reduced Gaussian grid, i.e. a non-rectangular grid in which the number of points on each east-west row reduces as you move further from the equator. Users generally find these very difficult to deal with. Are you sure that would be better for you?