请问,The rainbow dissolve as the sun came fully out from behin

请问,The rainbow dissolve as the sun came fully out from behind the clouds.中的“dissolve...请问,The rainbow dissolve as the sun came fully out from behind the clouds.中的“dissolve”该怎么理解?实在是无法理解可是太阳的出现不正是彩虹出现的原因吗？如果理解为“消散”，那dissipate为什么又不行了呢？