Record snow of a century ago may be traced to the sun
October 28, 2005
http://www.sierrasun.com/article/200510 ... /110280016
When it comes to weather in the West, averages are hard to come by. More often than not, desiccating droughts are broken by wild winters, when torrential downpours soak the lower elevations and snow falls thick and deep in the High Sierra. The resulting snowmelt invigorates parched rivers, replenishes empty reservoirs, and resuscitates the withered landscape in a natural cycle as old as the West itself.
Drought-busting seasons come along every so often, but after nearly a century, the epic winter of 1906-07 continues to reign as the snowiest on record in the Sierra Nevada. Powerful Pacific storms that year buried elevations above 8,000 feet with a snowpack that averaged 30 feet deep, and established California's greatest seasonal snowfall total of 884 inches - more than 73 feet.
Weather prophets call it
The big winter of 1907 was not entirely unexpected. On December 14, 1906, the Reno Evening Gazette reported, "[Weather] Prophets in various sections of the country and Nevada have been foretelling a long, hard winter, beginning immediately after Thanksgiving." Weather prophets were purveyors of 19th century Victorian meteorology, who foretold weather events based on natural cycles and astronomical techniques. Most prognosticators were reluctant to share the proprietary details behind their forecast methodology. One who did was Montreal-born Henry George Vennor whose forecast method included three components: An intuitively deduced prediction based on his outdoor experience, short trends he noted in recent weather conditions, and a long-term seasonal trend he established over a lifetime of observations.
The two winters prior to 1907 had been drier than normal, so in the fall of 1906, Western farmers, ranchers, and residents were hoping for a big winter to break the drought and fill their rivers and reservoirs again. The long-range forecasts proclaimed by weather prophets were often wrong, but this time they got it right. True to predictions, heavy snow invaded the Sierra Nevada on November 21, 1906, the day before Thanksgiving. When the wintry storm stalled in the Great Basin, northerly winds over Nevada and California drove temperatures down to freezing in Los Angeles and San Diego. Snow fell near San Francisco and ice formed in Golden Gate Park.
On Dec. 11, a tremendous blizzard dumped nearly four feet of snow on the Sierra. Hurricane-force winds snapped power lines in the mountains and plunged Reno, Carson City, and Virginia City into an eerie darkness. The next day, two seasoned Southern Pacific linemen, Peter Robinson and Fred Rogers, were ordered to find and repair the breaks in the mountains west of Reno. They finished their task near dusk and prepared to ski down, but the sun had set leaving a hard, icy crust on the snowpack. When Robinson began his descent, his long pole slipped from his grasp and he soon was hurtling at breakneck speed down the slope. Rogers sped recklessly after his friend. Nearing the bottom of the hill, both skiers aimed for a 20-foot-high snowdrift. The deep snow buried them completely and saved them from serious injury.
On January 5, 1907, two miners were trapped in the mountains east of Gardnerville, Nevada, an abandoned cabin where they had taken refuge from the snowy gales. Chris Jepperson and Jack Reynolds had floundered helplessly in 15-foot drifts, and now they were stranded at an isolated mine. After three days snowbound without food, the men turned to their one possible savior - Jepperson's cocker spaniel. They tied a message around its neck, offered a few encouraging words, and forced the dog out into the drifts to die or reach the town of Gardnerville, about 20 miles away. The heroic canine struggled into town three days later, and then it wandered around for two more days before someone noticed the emergency plea for help. Rescuers trailed the exhausted canine back into the mountains where they found Jepperson and Reynolds unconscious, but still alive.
In February the jet stream shifted north, and the harsh weather and frigid temperatures moderated. The welcome respite didn't last long, however, and March arrived roaring like a lion. Rain and snow fell everyday that month except on the 14th and 15th and from the 28th to 31st. In Nevada, where the greatest monthly precipitation was 16.85 inches at Lewers' Ranch in Washoe County, it was the wettest March on record. High Sierra locations got plastered with wet, heavy snow, which added another 8 feet to the near record snowpack.
or the sun?
At first glance, it might be surprising that the record winter snows of 1906-07 occurred during what climatologists call a "La Niña" event, when sea surface temperatures (SST) in the equatorial Pacific Ocean cool below average. These La Niña cycles in the Pacific generally bring dry conditions to California and Nevada, not heavy snowfall. "El Niño" is the better-known episode of the so-called Southern Oscillation (ENSO) when sea surface temperatures are warmer than normal and the winter precipitation in California is often enhanced.
Further research suggests that another factor may have influenced that year's weather. The exceptional winter of 1906-07 coincided with a distinct dip, or low value point, in the solar constant cycle. The solar constant represents the amount of the sun's energy reaching the Earth's atmosphere and surface. Scientific measurements first began in the mid-1800s, but more recently researchers have analyzed the amount of carbon 14 in tree rings to measure changes in the output of energetic particles from the sun. Today, relatively long and reliable records are now available to profile the fluctuations of solar variability. The word "constant" may be a poor choice - the trend is definitely upwards - with the highest values occurring in the last 50 years.
The sun drives the weather on planet Earth, so the winds and circulations of ocean patterns are all affected by the sun's energy output. From 1890 to 1910, there was a significant drop in the solar constant. Snowfall data from the 124 years of record on Donner Summit indicate that out of the top 21 all-time greatest seasonal snowfalls measured there, seven occurred during this period of diminished solar value. In fact, nine out of the top 23 snowiest winters on Donner Summit occurred during the 1890 to 1910 time span.
Remarkably, despite the heavy amounts of snow, when measured for precipitation (water value), only one of the 20 wettest seasons on Donner Summit occurred between 1890 and 1910. The high accumulation values combined with low water content in these years indicate that winter storms were cold, with light, powdery snow, as opposed to the more typical, high water content snowfall most common in the Sierra. These conditions suggest cold, Alaskan-bred storms as opposed to moist and mild Pacific systems, and lower mountain temperatures during snowfall.
Although no one can say with certainty that a reduced solar value at the turn of the 20th century spawned the record winter of 1906-07, as well as the unusual cluster of snowy winters on Donner Summit around that time, the anecdotal evidence is certainly food for thought.
Mark McLaughlin's column, "Weather Window," appears monthly in the Sierra Sun. His award-winning books, "Western Train Adventures: The Good, the Bad & the Ugly" and "Sierra Stories: Trues Tales of Tahoe, Vol. 1 & 2" are available at local bookstores. Reach him at firstname.lastname@example.org.
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