Digitalizing precipitation data from the image of weather map

Question

I have a set of very old precipitation anomaly maps, from 1995-2006 for Brazil. The data of these maps, is to the best of my knowlegde, lost.

I would like to have them digitalized, ie, to NetCDF or another similar gridded format. Is there any tools recommendend for this job?

The figure below is a recent plot, similar to my files.

Are you sure the data is lost? Have you checked the standard data sources? — user967, Oct 4, 2016 at 20:40
Just three points to remember when it comes to interpretation: In arid to semi-arid areas the spottiness of the rainfall distribution doesn't average out on any useful time-scale, and certainly not over an 11 year time-series. Secondly, in mountainous areas like the Andes the local physiographic effects totally eclipse the true regional variation. Thirdly, the map you show looks suspiciously as if it has been generated by a 'contour package', which is often totally misleading because it treats the rainfall in a small rain-guage as an areal maximum or minimum - which it isn't!. — Gordon Stanger, Oct 5, 2016 at 4:47
@BarryCarter One can always be surer, but I have put some hours in it and could not find data at this resolution going back to 1995. — kurast, Oct 5, 2016 at 12:48
Fair enough. I take it climatedataguide.ucar.edu/climate-data/… and things like ftp.cpc.ncep.noaa.gov/precip/CPC_UNI_PRCP/GAUGE_GLB/V1.0/1985 were unhelpful? — user967, Oct 5, 2016 at 14:16

hichris123 · Accepted Answer · 2016-10-04 23:09:11Z

4

You can convert the image to NetCDF data using gdal_translate. The command line looks something like:

gdal_translate -ot Int16 -of netCDF jpeg_filename nc_filename

You can use ncl example: click here

hichris123♦

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answered Oct 4, 2016 at 22:04

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