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.
Jonah chapter 4 does not say, but suggests strongly, that God spoke to Jonah audibly while Jonah was awake, so it was not a dream.


  4 But to Jonah this seemed very wrong, and he became angry. 2 He
  prayed to the Lord, “Isn’t this what I said, Lord, when I was still at
  home? That is what I tried to forestall by fleeing to Tarshish. I knew
  that you are a gracious and compassionate God, slow to anger and
  abounding in love, a God who relents from sending calamity. 3 Now,
  Lord, take away my life, for it is better for me to die than to live.”
  
  4 But the Lord replied, “Is it right for you to be angry?”
  
  5 Jonah had gone out and sat down at a place east of the city. There
  he made himself a shelter, sat in its shade and waited to see what
  would happen to the city. 6 Then the Lord God provided a leafy
  plant and made it grow up over Jonah to give shade for his head to
  ease his discomfort, and Jonah was very happy about the plant. 7 But
  at dawn the next day God provided a worm, which chewed the plant so
  that it withered. 8 When the sun rose, God provided a scorching east
  wind, and the sun blazed on Jonah’s head so that he grew faint. He
  wanted to die, and said, “It would be better for me to die than to
  live.”
  
  9 But God said to Jonah, “Is it right for you to be angry about the
  plant?”
  
  “It is,” he said. “And I’m so angry I wish I were dead.”
  
  10 But the Lord said, “You have been concerned about this plant,
  though you did not tend it or make it grow. It sprang up overnight and
  died overnight. 11 And should I not have concern for the great city of
  Nineveh, in which there are more than a hundred and twenty thousand
  people who cannot tell their right hand from their left—and also many
  animals?”


The evidence is that the Lord caused a miracle - the growth and death of the plant - so the communication was in the phycical realm, not a dream or vision. Certainly Jonah is speaking aloud. There is no mention of a whirlwind, fire, earthquake, smoke, cloud, or other physical phenomena associated with messages received by Moses, Elijah or others. Yet these physical details are give - the hot wind, the sunrise, the tree Jonah is sitting against. Since so many details of the setting are given and no mention of a visible form is described for God, then an auditory event is the most likely. Jonah heard God speak while awake but did not see a vision of Him.

(For completeness, the only other mention of Jonah in the Old Testament is in 2 Kings 14:25, but nothing there seems to shed light on this question.)