What vehicle did God use for Jonah to receive this word?

>The word of the Lord came to Jonah son of Amittai: 2 “Go to the great city of Nineveh and preach against it, because its wickedness has come up before me.” 3 But Jonah ran away from the Lord and headed for Tarshish. He went down to Joppa, where he found a ship bound for that port. After paying the fare, he went aboard and sailed for Tarshish to flee from the Lord. (Jonah 1:1-3. NIV) It does not say in the text how the word was delivered to Jonah. Can someone explain to me how he received the word. Was it through a vision, dream or direcly from mouth of God? Are there any Christian Traditions that explore this subject.