Some reasons that God has behind the suffering and disasters that he controls:

1. Disaster can remind us that this world has been infected by sin and its consequences (Rom. 8:20-22).

2. Disasters that directly result from sin remind us of the terrible character of sin

    and can teach us to take more seriously the importance of avoiding sin ourselves (Rom. 6:23).

3. Disasters warn us of the coming of God's final judgment (Lk. 13:1-5).

4. For Christians, suffering can increase our appreciation for what Christ suffered for us. 

    We suffer in fellowship with Christ (Phil. 3:10).

5. Suffering can remind us of the importance of Christ's compassion for us, because he himself suffered (Heb. 4:15; 5:7).  He compassionately understands our suffering.

6. Sufferings can be used by God to sanctify our character (Rom. 5:3-5; James 1:2-4).

7. Sufferings can refine our faith and give glory to God (1 Pet. 1:6-7).

[Vern S. Poythress, "Chance and the Sovereignty of God"]