Scientists investigate California’s worst drought

Using measurements and computer simulations, researchers seek answer to the question: Is climate change behind the state's dry spell? California's parched landscapes are receiving a much-needed soaking this week as heavy rainstorms roll across the West Coast. The break in the state's dry spell is due to a weakening of an atmospheric anomaly that has been hovering above the northern Pacific Ocean. Dubbed the "ridiculously resilient ridge" by a Stanford graduate student, this enormous region of atmospheric high pressure has been squatting off the coast of western Canada since January 2013, diverting storms northward, away from California and toward Alaska. In recent weeks, however, this blocking ridge has begun dissipating enough to allow a highly concentrated "atmospheric river" of moisture originating near Hawaii - nicknamed the "Pineapple Express" - to break through and soak Northern California in early February, and for a new round of storms to penetrate the state this week. But the much-needed downpour won't be nearly enough to end the state's current drought, which is the worst in its recorded history. "It's the driest period in San Francisco since at least the Gold Rush," said Daniel Swain , a graduate student in the lab of Noah Diffenbaugh , an associate professor of environmental Earth system science at Stanford. "At this point, we would need at least 10 fairly big storms to achieve normal precipitation levels.