Is your feature request related to a problem? Please describe.
In horiz_interp and interpolator, some variables with the type of pointer are being allocated storage space with the use of the allocate statement. With newer versions of Fortran, we now have access to the allocatable type. The allocatable type is safer to use as storage will automatically be deallocated at end of a program. With the pointer type, we can potentially cause memory leaks if we do not deallocate the pointer.

Describe the solution you'd like
Change any allocated pointers to allocatables.

Describe alternatives you've considered
N/A

Additional context
N/A