I'm using the TRMM 3B43 precipitation data. I have downloaded individual NetCDF files depicting yearly accumulation in mm for each year from 2000 to 2015 (16 files). I have imported each file into ArcGIS as a raster file, and each shows a different min & max. I now want to calculate the average annual precipitation from 2000 to 2015. How would you recommend I do this?

Annual accumulated precipitation in mm

2 Answers 2


The alternative to doing this in the raster calculator is to use the Cell Statistics tool in ArcToolbox. You can select all of your rasters at once and then pick which ever summary statistic you are interested in. It saves a lot of typing!


In Raster Calculator:

( "raster_1"+"raster_2"+...+"raster_n" )/n

Where n is the number of rasters.

  • Thank you - but I receive the error message 'list object has no attribute to save.' How do I fix this?
    – leaf27
    Jul 13, 2016 at 14:26
  • so maybe try "raster_1" etc., I've forgoten syntax for 10.1. You can just choose rasters from the list.
    – dmh126
    Jul 13, 2016 at 14:35
  • 1
    Even when I choose them from the list it still does not work - any other options?
    – leaf27
    Jul 13, 2016 at 14:41
  • Try first to do only the addition, save it to file and than divide this new file by n. I don't know what is going wrong, I've done this before this way and this syntax should be correct.
    – dmh126
    Jul 13, 2016 at 14:50

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