Where’s the Snow?

COLORADO WATER CONGRESS ANNUAL CONVENTION

Denver, Colorado – February 1, 2013

Real Weather

Nolan Doesken, Colorado State climatologist, provided a look back at the weather patterns of 2012.  With 2012 being the fifth driest year since 1895, Doesken explored the details of Colorado’s current drought.  The only other winter with similarly high temperatures occurred in 1939.  The current drought most severely affects Southern Colorado, which experienced two of its driest years back to back.

Doesken’s presentation walked through weather patterns from each month in 2012.  After a mild and dry January, February saw a lot of snow, with snow packs nearly returning to average by the end of the month.  However, March was unusually warm with little snow, leading to early snowmelt.  As a result, spring storms proved ineffective, because snow falling on bare ground lead to less accumulation.  June weather was terribly hot and dry while July gave some Colorado regions a small amount of moisture.  However, in August the drought returned with full force.  The fall provided a little rainfall, allowing farmers to plant wheat.  Doesken described December as a “wimpy beginning” to the winter of 2012-2013.

Thus, temperature averages of 2012 were well above the long-term average in Colorado.  The dry year led to a diminished snowpack, demonstrating the importance of spring precipitation to maintaining snowpack levels.  Typically, the highest snowpack accumulation occurs in April, but not so for 2012.  Doesken presented a picture showing the top of Copper Mountain in late March 2012. The mountain peaks lay bare with only man-made and groomed snow visible.

Furthermore, the flows of the Colorado and Yampa River dropped dramatically between 2011 and 2012.  Colorado reservoirs similarly dropped to below average levels, despite attaining above-average levels in 2011.  Doesken ended his presentation by stating that while Colorado is still in a drought, there are signs of improvement for 2013.

What’s Up with the Weather?

Brian Bledsoe, Chief Meteorologist at KKTV, presented his long-term weather projections for Colorado.  Bledsoe specifically forecasted that Colorado can expect further drought based on: (1) El Nino and La Nina cycles, (2) Madden Julian Oscillation (“MJO”) and (3) temperature oscillations of the Atlantic and Pacific Oceans.

The El Nino and La Nina cycles result in opposing weather patterns for Colorado.  El Nino brings in the Pacific jet-stream, which rolls across the southern states bringing wet and cool weather.  La Nina develops a ridge of high pressure, pushing storms north of Colorado, leaving eastern part of the state windy and dry.  Bledsoe explained that while Colorado is technically in between the two cycles, current projections suggest that weather will remain in a La Nina cycle.

The MJO tracks storm activity originating over the Indian Ocean.  This weather pattern often correlates to weather events in Colorado.  Recently, the MJO is not particularly active, which Bledsoe explained has him concerned because an inactive MJO typically results in fewer storms in Colorado.

Bledsoe also discussed the multi-decadal temperature cycles of the temperatures of the Pacific and Atlantic Oceans.  The Pacific Ocean shifted to its cold phase in 2005, which typically results in more frequent La Nina cycles.  Currently, the Atlantic Ocean remains in its warm phase, leading to more frequent storms, especially hurricanes.  According the Bledsoe, the current cold Pacific Ocean and warm Atlantic Ocean configuration is similar to ocean temperatures in the 1950s.  Incidentally, one of the largest droughts in recent Western history occurred during the 1950s.  Bledsoe further argued that the Atlantic Ocean is likely to shift to a cold phase in the next three to eight years.  He suggested that this temperature shift will lead to a generally wetter United States, except for an intense drought in the high plains.  Thus, Bledsoe advised that Colorado, especially the Eastern plains, is entering a long-term drought phase and that the state must plan accordingly.

Dust in Western Snow Cover: What’s In It and Where Did It Come From?

Rich Reynolds, from the U.S. Geological Survey (“USGS”), discussed the increasing problem of dust on Western snow packs.  Dust particles absorb solar radiation, instead of reflecting the radiation as snow does, which warms and melts the pack.  Dust-covered snow packs lead to serious problems including: decrease in the albedo (reflectivity) of snow cover, triggering earlier and faster snow melt, and smaller late season water supplies.

The USGS analyzes the mineral content of dust on the snow pack, and has more recently focused on the Wasatch Range in Utah.  Milford Flats, south of the Wasatch Range, experienced a large wildfire in 2007 and is now one of the best documented dust sources in North America.  After the fire, Utah land managers began rehabilitating the land to prevent erosion and to improve forage for cattle grazing by seeding and applying herbicide.  Dust from Milford Flats settling in the Wasatch Range actually comes from the treated part of the soil, not the remaining burned areas.

USGS’s study of the mineral composition of the dust on the Wasatch Range revealed that particles contained both iron oxide minerals and carbonaceous material, such as black carbon.  The study found high levels of iron oxide in the Milford Flats area and USGS believes that the carbonaceous material comes from industrial and transportation sources in the heavily populated near the Wasatch Range.  Reynolds explained that the presence of both materials led to lower reflectance of solar energy by the snow pack.  Hence, the dust is absorbing heat from solar radiation and promoting snowmelt.  As a result the USGS currently works with the Bureau of Land Management to create dust risk maps.  These maps intend to avoid the mistakes made by the land rehabilitation efforts at Milford Flats.

Reynolds then turned to discuss dust issues in Colorado, where large dust events have occurred more frequently over the past decade.  Colorado experiences dust moving from southern Colorado plateaus northeast into the mountains.  Reynolds identified numerous sources where this dust may be coming from.  For instance, regional groundwater withdrawal, overgrazing, and increasing regional aridity may all contribute to the increased dust.  Reynolds pointed to Tolani Lake, a dried-up lake in Arizona, as large contributor of dust into Colorado’s mountains.  The USGS is testing sediment from Colorado snow pack and using the types of iron oxide materials in an attempt to trace the largest contributors of dust in the state.

Reynolds ended his presentation by listing possible solutions to the increasing dust on the snowpack, such as stabilizing soil and sand dunes with perennial vegetation and maintaining high groundwater levels.  Reynolds made it clear that any solution is going take a lot of “will power, knowledge, resources, and collaboration.”