Required units for precipitation unclear

[kvantricht]

Hi guys,

we're still working on setting up the first Presto encoder attempt from our side and we're facing issues with precipitation as an input. In general, I think there's a bit a of lack on documentation with regards to expected units for inputting data into Presto (like Sentinel-2 required to be in 1E4 scaling, Sentinel-1 required to be in decibels, etc.). I think we figured out most on our own, but for precipitation we're puzzled.
We see the ERA5_DIV_VALUES being 0.03 for precipitation. At the moment, we are feeding just the monthly sum in mm, but after normalization, the values in x explode due to this 0.03 factor. So what's the expected units?

https://github.com/nasaharvest/presto/blob/613265efac15c8c97a28d94fc2110a2d38e8a5e0/presto/dataops/pipelines/s1_s2_era5_srtm.py#L53:L55

Also note that the commented notebook where the values supposedly come from is inaccessible to us.

[gabrieltseng]

Hi @kvantricht ,

We are using the ERA5 Land monthly averaged values - in this case, the unit for the precipitation (total_precipitation) is in metres.

I'll make a note in construct_single_presto_input making this more explicit.

[kvantricht]

We're using ÀgERA5 instead which is derived ERA5 so I think fairly compatible. But precipitation is daily in mm which we accumulated to monthly values. Thanks for clarifying, I'll convert to m!