# Reading: WRF SNOW Depth (m) and SNOW Water Equivalent (kg/m^2) data

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#### tesfamichaelb

##### New member
I am having a hard time figuring out how to interpret the hourly Snow depth (m) and Snow Water Equivalent (kg/m^2) data in WRF, whether it is incremental or hourly independent values? Do I have to add the hourly values to get the daily totals or what arithmetic do I need to use to estimate the daily values from WRF hourly results?

When I extracted the text data from WRF for my Jan 2013 period to compare with SNOTEL data, WRF’s every hour of a station has some value greater than zero, (following hour sometimes greater or less than the previous hour in the 0-23 hours of data values listed). SNOTEL seems to show instantaneous daily values, where you get random values that includes zero (in the absence of no snow or rain daily record).

When I tried to add the WRF hourly values to get the 24-hr total to compare to its corresponding SNOTEL site’s daily values, there is a huge disparity between the two.

Tes

Tes,
SHOWH and SNOW are not incremental variables. They are snow depth and snow water equivalent at the actual time. You should't add the hourly data to get their daily values. Probably you can average hourly data o obtain the daily mean.
Note that NoaH snow model is pretty simple. Its performance on snow physics is kind of poor. I suppose NoaHMP and CLM might be a better option for snow physics simulation.

Hi,
May I ask what about SNOWNC (ACCUMULATED TOTAL GRID SCALE SNOW AND ICE)? It is obviously incremental (accumulated), but could it be used as snow depth (height), for example with a ratio of 7:1? What is its exact difference with SNOW (SNOW WATER EQUIVALENT), except being accumated?
Finally, if I want to calculate snow depth, which variable (SNOW, SNOWNC, SNOWH) is the best?

Please let me know if I should create a new topic.
I hope to hear from you.

Sincerely,
Ehsan

P.S. Outputs are from WRFV3 (I think) and NOAH (not NOAH-MP). This is operational and changing it almost impossible.

SNOWH is the snow depth in unit of 'm'. I believe this is the variable you need.
SNOWNC is only snow form resolve scale, and thus the parameterized snow is not included. This variable cannot be used to derive snow depth.