Answer:
1. The cartoonist depicts the atomic threat as a certain occurrence that should be expected as one would rain. The threat is depicted as a dark looming cloud pregnant with a rain of atomic bombs looming over a city. Of course, there is an element of satire that is depicted in the use of an umbrella to shield one's self from bombs. As if to say when the bombs start dropping, all that was needed was a shield from it in form of an umbrella.
2. The umbrella normally is a sheet of fabric stretched over a frame of the metal web. In the cartoon, this sheet of fabric was gone. This was to say that taking a shield from the threat was a laughable solution and impractical.
3. the look on the man's face reeks of fear.
Cheers