Use jovial to describe people who show good humor and are full of joy. Santa Claus, with his constant "ho-ho-hoing" is a jovial figure.
Jocose and jocular are similar words, but they refer more to things that actually cause laughter. Jovial is from Middle French, from Late Latin jovialis "relating to Jupiter, the ancient Roman god of the sky," from Jupiter "Jupiter" plus the Latin prefix -alis "relating to." In astrology, people born under the sign of Jupiter are joyful.