MODIS AQUA SST unit

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shorion
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MODIS AQUA SST unit

by shorion » Fri Sep 30, 2022 6:13 am America/New_York

Hi all,

I have downloaded the monthly SST time series from Aqua. The values are supposed to be unit of degree Celsius but they are way out of normal ranges (+5000).
I assume that i need to scale them to get to real numbers but I cannot find the information.

Anyone that could help.

Many thanks!

Stephanie

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OB.DAAC - SeanBailey
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Joined: Wed Sep 18, 2019 6:15 pm America/New_York
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Re: MODIS AQUA SST unit

by OB.DAAC - SeanBailey » Fri Sep 30, 2022 8:56 am America/New_York

Did you apply the scaling factor? The SST mapped product is stored as a scaled short integer. To get the correct floating point value, you need to apply the scale_factor and add_offset (although the offset is zero for this product):

short sst(lat, lon) ;
sst:long_name = "Sea Surface Temperature" ;
sst:scale_factor = 0.005f ;
sst:add_offset = 0.f ;
sst:units = "degree_C" ;

Many netCDF readers will automatically apply the scaling, but if your API doesn't you will need to do so after reading in the data:
geophysical_value = scale_factor * scaled_integer + add_offset

Regards,
Sean

shorion
Posts: 2
Joined: Fri Sep 30, 2022 6:07 am America/New_York
Answers: 0

Re: MODIS AQUA SST unit

by shorion » Mon Oct 03, 2022 9:42 am America/New_York

Great - makes total sense.

Have a great day :)

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