[ferret_users] Average with ferret vs nco

[Tony Jolibois <tjolibois@xxxxxx>]

       Hi all,

I have to compute averages on longitude and latitude axes to have a one value result, data are ocean model outputs (depth=0).
When I use ferret and nco to compute these averages, I don't find the same result, I don't understand why. With nco I find a temperature_averaged = 14.06548 and with ferret I find 14.38.

Source file : mercatorPsy3v1R1v_med_levitus_1998_M01.nc (levitus climatology over Mediterranean sea)

• With nco :

ncwa -a latitude,longitude -d depth,0,0 mercatorPsy3v1R1v_med_levitus_1998_M01.nc mercatorPsy3v1R1v_med_levitus_1998_M01_averaged.nc
result : temperature_averaged = 14.06548

• With ferret :

yes? use mercatorPsy3v1R1v_med_levitus_1998_M01.nc
yes? define variable/unit="degC"/title="Temperature (degC)" temperature_averaged = temperature[x=@AVE,y=@AVE,z=0]
yes? list temperature_averaged
             VARIABLE : Temperature (degC) (degC)
             DATA SET : MERCATOR PSY3V1R1 VITRINE CLIM (with bathy mask)
             FILENAME : mercatorPsy3v1R1v_med_levitus_1998_M01.nc
             LONGITUDE: 6.1W(-6.1) to 45.1E(45.1)
             LATITUDE : 30N to 48N
             DEPTH (m): 0
          14.38
yes?

Can someone help me ?
Tony

-- 
Tony Jolibois

CLS - Direction Océanographie Spatiale
8-10 rue hermès - 31520 Ramonville Saint-Agne
tjolibois@cls.fr

Tél : +33 (0) 561 393 797
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