April 28, 2014

The entire state of California is now suffering from moderate to exceptional drought conditions, according to a recent report from the United States Drought Monitor (USDM). The drought is the worst in the 15-year history of the USDM, which is a joint project by the National Drought Mitigation Center, the National Ocean and Atmospheric Agency, the U.S. Department of Agriculture, and drought observers across the country. The USDM found that the area of California experiencing “extreme drought” has jumped from zero percent in April 2013 to 76.68 percent this month. The area experiencing “exceptional drought” has risen from zero percent to 24.77 percent during the same period. Government officials are deeply concerned about the effect of the drought on drinking water for California communities as well as the state’s valuable agricultural industry. California produces more agricultural products than any other U.S. state. A vast farming region, the Central Valley, is the leading region in the United States for growing fruits, nuts, and vegetables.

Although winter is normally California’s wettest season, 2013 was the driest year in that state’s recorded history, the U.S. National Weather Service (NWS) has reported. The state’s snowpack (snow that accumulates on mountaintops during the winter) was measured at less than one-third of its historical average, according to April data collected by NASA‘s Airborne Snow Observatory.

All of California is now experiencing drought. (U.S. Drought Monitor)

The immediate cause for California’s parched condition is a weather phenomenon that meteorologists have nicknamed the Ridiculously Resilient Ridge. This massive wall of high-pressure air is nearly 4 miles (6.4 kilometers) high and 2,000 miles (3,200 kilometers) long. The ridge, which developed in December 2012, has prevented Pacific winter storms from coming ashore in California. Instead, the storms have been deflected to Alaska and British Columbia. “It’s like the Sierra–a mountain range just sitting off the West Coast–only bigger,” Bob Benjamin, a NWS forecaster told the San Jose Mercury News. “This ridge is sort of a mountain in the atmosphere. In most years, it comes and goes.” This time, however, it came and stayed. Some scientists have speculated that climate change may be keeping the ridge in place.

Additional World Book articles:

• Irrigation
• Losing Ground (a Special Report)
• Parched Earth (a Special Report)