cdo trend map
Added by Jerry Kuntz over 3 years ago
Hello!
I am hoping to calculate a trend over the period between 1990-2019 for a precipitation variable over the U.S. using cdo. I would like to have a trend value for each latitude/longitude so I could create a map to see where there has been a positive or negative trend over time.
Is this possible?
I tried using cdo trend infile.nc outfile1.nc outfile2.nc (with my data file replacing infile.nc), subtracting the outfile1.nc from the outfile2.nc and mapping that but the trend values do not seem to be right. Some other information that may be useful is that the data is on a mesh grid for latitude longitude (which I am not too familiar with). I am not sure if this makes a difference.
Please let me know if you have any ideas or suggestions, it would be greatly appreciated!
-J
Replies (2)
RE: cdo trend map - Added by Karin Meier-Fleischer over 3 years ago
Hi Jerry,
I guess you are looking for the operator subtrend (see https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf#section.2.10).
cdo trend infile.nc a.nc b.nc cdo subtrend infile.nc a.nc b.nc out_subtrend.nc
-Karin
RE: cdo trend map - Added by Jerry Kuntz over 3 years ago
Hi Karin,
Thank you for your response!
So this subtrend operator gives me the monthly means minus the trend value, is that correct?
If so, if I wanted to create a map showing trends over time, would I then average these subtrend values over latitude and longitude to get one number for each grid box?
Thanks again
- J