if something receives sunlight, then it will increase in temperature & the air around the equator receives direct sunlight ->  the air around the equator will increase in temperature  the air around the equator will increase in temperature & if something increases in temperature, then that something will be warm ->  the air is warm around the equator  the air is warm around the equator & the air mass formed close to the ocean is humid in moisture -> air masses formed over the ocean near the equator are moist / warm