One of my cats howls during the night, and more than once a night.
What I did, was purchase a large dog crate, and put a litter pan in it, and her pillow. At night, she gets her treats when we "go to bed" she walks into the kennel has her treats, and things are quiet until she hears me up in the morning.
It might sound cruel but, that makes her sleep, and lets me have my sleep as well.
She didn't really like it at first, and that is why I started giving treats, and using the command "go to bed".
Hope you find something that works for you