The metadata includes the following variables from the .info.txt file for
daily, monthly, and annual data:
Additionally, two local variables are added identifying where the file is
located on the local system:
The annual and monthly normals data includes different keys in
the .info.txt, so they are renamed to be the same as those found in the
other temporal data. The keys/variables are renamed as follows:
PRISM_FILENAME --> PRISM_DATASET_FILENAME
PRISM_CREATE_DATE --> PRISM_DATASET_CREATE_DATE
PRISM_DATASET --> PRISM_DATASET_TYPE
PRISM_VERSION --> PRISM_CODE_VERSION
PRISM_REMARKS --> PRISM_DATASET_REMARKS
Additionally, the normals does not include PRISM_DATASET_VERSION, so that
variable is added with NA
values.