ALEXANDRIA, VA — Haboobs, giant dust storms, walloped Arizona last summer — some close to 2 kilometers high and 160 kilometers wide — knocking out electricity, creating traffic jams, and grounding airplanes. Even old-timers say they can’t remember anything quite like this year’s aerial assaults. Meanwhile, Texas is experiencing one of the most extreme droughts in recent history, with almost 90 percent of the state in the most extreme level of drought.