Joel uses the imagery of what to depict impending invasion?

The correct choice is the depiction of a locust plague. Joel utilizes the image of locusts throughout his book to symbolize an impending invasion, highlighting the devastation and destruction they bring, which serves as a powerful metaphor for the futility of human efforts against divine judgment. This imagery reflects the agricultural context of the time, where locusts could devastate crops and lead to famine, vividly illustrating the consequences of sin and disobedience among the people of Judah.

In the Book of Joel, the description of the locust plague serves as both a warning and a call to repentance, as Joel urges the people to turn back to God in the face of impending disaster. This vivid and relatable imagery resonates with the audience, making the impending threat more immediate and personal.

The other options, while relevant to the themes of the Old Testament, do not specifically encapsulate the central imagery that Joel uses to describe the invasion. For instance, a storm can symbolize chaos and divine intervention, an army usually represents human military strength, and drought refers to a lack of water and fertility, but these do not carry the same weight and specificity in the context of impending invasion as the locust plague does in Joel's prophecies.