Friday, 22 September 2017

Standard two letter codes for meteorological variables

For the file names of the Parallel Observations Science Team (ISTI-POST) we needed short codes for the meteorological variables in the file.

Two letter codes are used quite often in the scientific literature, which suggests there exists a standard, but I was unable to find a WMO standard. Thus we would suggest to follow standard two-letter conventions.

CodeElementUnit
Wind
ddwind direction[in degrees; calm = -1]
ffwind speed[in m/s]
Temperatures
tmmean temperature[in °C]
tnminimum temperature[in °C]
txmaximum temperature[in °C]
trread temperature (at a specific time)[in °C]
twwet-bulb temperature[in °C]
tssurface temperature[in °C]
Radiation
snsunshine duration[in h]
sdsolar radiation flux down[in W m-2]
susolar radiation flux up[in W m-2]
hdinfra-red (heat) radiation flux down[in W m-2]
huinfra-red (heat) radiation flux up[in W m-2]
Snow
tstotal snow[in mm]
nsnew snow[in mm]
Diverse
rhrelative humidity[in %]
pppressure[in mbar]
rrprecipitation[in mm per day]
nncloud cover[in %]

If you know of an existing system, please say so. Many codes are quite common in the literature, but some also less. If you have suggestion for other codes for these or would like to propose abbreviations for other variables, please contact us or write a comment below.

7 comments:

Bob Kelly said...

Hi, Victor,
I was thinking the weather observation synoptic code might be useful http://atmo.tamu.edu/class/atmo251/LandSynopticCode.pdf , but many of of the variables are more than two digits. -bob bkellysky.wordpress.com

Victor Venema said...

Thanks. The synoptic code may explain why we use dd and ff for wind and not just d and f because it is specified in two digits. That may explain this custom; I was wondering whether it indicated an existing standard.

I would not mind if the codes were 3 or 4 characters, but I would prefer them to have the same length, otherwise I would have to add delimiters to the file names to make them easy to read automatically. And the names are already quite long.

Victor Venema said...

Twitter suggested to use wd and wf for wind direction and speed. My impression is that dd and ff are used more.

Bob Kelly said...

Right. I can see why you'd prefer 2 characters!

Mark McCarthy said...

Why do you need codes? Why not just use the human readable names, even if they are a little long. What is the problem caused by a long filename?

jon said...

ecmwf's grib tables have many abbreviation, some two letters, most three, some 4 (at most) and the names are rather meaningful

Victor Venema said...

Mark, what is a need? ;-) It can naturally be done differently. It would be nice if all variables names/codes are the same length. The filenames also denote the station, averaging scale, processing stage and a directory with one parallel measurement would contain several files. If the codes are all the same length, it is easier to compare them with each other in a directory and see what you have.

Jon, the nice thing about GRIB is that it is a real standard, except maybe for the tables the weather services use individually. But some codes are also longer. Just found "mean2t24" for "Mean temperature at 2 metres in the last 24 hours". Probably unavoidable in case of model data because there are so many variables.