The defender this afternoon completed the move on a temporary deal until the end of the season.
Howe told the Daily Echo: “The thinking behind it is we need to address the balance in the squad.
“We brought in three players last week and, both from a squad management and financial point of view, these decisions must be made and we must balance it.
“From our perspective, we are a League One club and what we can't do is carry a squad that is too big in numbers.
“We have always said that we want a tight, lean squad and a manageable number because you can only pick 18.”
Zubar's exit came after Howe had drafted in Southampton loan man Dan Seaborne to boost his defensive resources, with winger Ryan Fraser and goalkeeper Ryan Allsop also signing.
Centre-half Zubar had seen his first-team opportunities limited after making just three appearances for Cherries this term.
Zubar, who agreed a new three-and-a-half-year contract with Cherries in February, joined the Dorset club as a free agent in September 2011.
Having left Plymouth Argyle, the 26-year-old became a fans' favourite in his debut campaign at Dean Court as he made 25 appearances.
But a combination of injuries and Cherries' form under Howe saw Zubar fall down the pecking order.
Howe added: “He is going to a good club. Hopefully, he will do well, enjoy his loan spell and get what he wants out of it.”