NWP normalization seems off

[jacobbieker]

Describe the bug
The NWP normalization, copied directly from Power Perceiver, doesn't result in a range of -1 to 1 in the test data, but instead -60ish to 1. This is using the same mean and std as in PP, and the same method of normalization, so not sure why its different. Downsampling before running the normalization doesn't seem to help with it.

To Reproduce
Steps to reproduce the behavior:

1. Run the nwp normalization test and add some prints

Expected behavior
A clear and concise description of what you expected to happen.

Additional context
Add any other context about the problem here.