Transcript Tools and Techniques for Precipitation Prediction in

Dirty Little Secrets of the Greatest Snow on
Earth and the Future of the Great Salt Lake
Jim Steenburgh
Department of Atmospheric Sciences
University of Utah
[email protected]
Contributors: Tom Painter, Trevor Alcott, John
Horel, Thomas Reichler, Leigh Jones, Chris
Landry, Jeff Deems, Annie Bryant, McKenzie
Skiles, Ashley Powell, Jayne Belnap, Mark Miller,
Jason Wolf, and many more...
Words of Wisdom
Prediction is very difficult,
especially about the future
- Danish Physicist Niels Bohr
And more so the
Great Salt Lake
- Jim Steenburgh
Global Temperature Change
Source: Climatic Research Unit, University of East Anglia

Earth’s average surface temperature has increased
1.4°F since 1900
7/17/2015
3
Utah Temperature Change
1993

Last decade 2°F warmer than 100 year average
–
Warming trend larger than global average trend
Frequency of “warm” years increasing
 Frequency of “cold” years decreasing
 Mother nature playing with loaded dice

2008
Utah Mountain Snowpack
Courtesy: Randy Julander, NRCS



No clear linkage between global warming and long-term (75+ year)
trends in Utah’s upper-elevation mountain snowpack
Recent fluctuations are within range of past variability
Graph uncorrected and does not include 2006-2010
Streamflow & Lake Level
GSLB Hydrologic Observatory Prospectus



Decadal-scale variability continues to dominate lake levels
Lake levels currently low, but remain with range of past variability
Linkages between recent fluctuations and warming remain unclear
Key Points: Recent Climate Change

Earth is warming
– Utah warming faster than global
average, but with more variability

Temperature dice are “loaded”
– Odds of warm seasons and years
increasing
– Odds of cold seasons and years
decreasing

Year-to-year and decadal variability
still dominate Utah snowpack and
GSL level fluctuations
– Unclear if snowpack and GSL dice
are loaded yet
Casinosupply.com
7
The Future

We are confident about warming but
– How fast will it warm?
– How sensitive is Utah snowfall & runoff to
warming?
– Will the storm tracks & lake-effect change?
– What about variability/extremes?
 More big years? More droughts?
– What about climate feedbacks, surprises, and
dirty little secrets?
– What does this mean for the GSL?
Utah Climate Prediction Challenges
Unique local climate – transition zone
 Modeling precipitation very challenging

– Complex terrain/lake effects
Warren Washington, NCAR
Have this: 60x90 miles
Want this: Reality
9
Wasatch Snowfall Sensitivity
+1°C
+2°C
+3°C
+4°C
PC Base
PC Base
PC Base
PC Base
PC Top
PC Top
PC Top
PC Top
Alta
Base
Alta
Base
Alta
Base
Alta
Base
Mt. Baldy
Mt. Baldy
Mt. Baldy
Mt. Baldy
10% 20% 30% 40% 50%
Percent of snow that will instead fall as rain
with warming
Courtesy: John Horel and Leigh Jones, Univ. of Utah
Temperature Change by 2050
A1B, 1980-1999 vs. 2040-2059
Nov-Apr
+2°C
2040-2059
1980-1999
PC Base
°C
SLC
3°C
38°F
St. George
8°C
46°F
PC Top
Alta
Base
Mt. Baldy
°C
SLC
5°C
41°F
St. George
10°C
50°F
10% 20% 30% 40% 50%
Courtesy Thomas Reichler
Univ. of Utah
Range of Possibilities
Temperature Change °C
PC Base
6
PC Top
4
Alta
Base
2
+3°C
Mt. Baldy
0
PC Base
-2
2000
2020
2040
2060
2080
Northern Utah Winter (Nov-Apr)
Temperature Change Relative to 1980-1999
2100 CO2 = 2.5x Pre-Industrial (~700 ppm)
PC Top
Alta
Base
Mt. Baldy
+1°C
Precipitation Changes
You
Are
Here
Average Winter Precip Change
A1B, 2040-2059 minus 1980-1999
Nov-Apr
mm
Absolute
5” more
No Change
Relative
12% Increase
%
No Change
Courtesy
Thomas Reichler
Univ. of Utah
Dirty Climate Secrets
&
Thinking beyond CO2
Snow Optics Lab-Alta Site (SOLA)
30 April, 2009
Courtesy
Tom Painter
Dust
Plumes
Sevier Lake
Milford Flat Fire
Courtesy
Tom Painter
The Intermountain Haboob
Impact of Dust: A Perfect Storm
Rabbit Ears Pass,
Colorado
Dust decreases snow albedo
(reflectivity)
43 ppmw
Dust deposition comes
generally in the spring (Neff et
al, 2005)
52 ppmw
306 ppmw
406 ppmw
- solar irradiance is
increasing
- snowpack is warming
April, 2009
Courtesy
Tom Painter
May, 2009
Dust generally accumulates in
surface layers and is not
entrained in melt - therefore,
the surface continues to
darken
Changes in dust loading
Neff et al (2008), Nature
High Wind + Vulnerable Soils =
Dust Storms
Plants: rainfall timing,
temperatures critical
Rocks: cover low in many places
Physical crusts: do not occur on
sandy soils, easily crushed
Biological crusts: occur on all
soils, but easily crushed
Senator Beck Basin Study Area
Courtesy
Tom Painter
Concluding Thoughts

Trends expected to emerge during the 21st century include
– Reduced snowfall and snowpack in low-to-mid elevation
mountain areas
 Upper elevation trends less clear
– Earlier and less intense spring runoff
– Increased demand for residential and agricultural irrigation
– Lower average GSL levels and increased salinity

How quickly these trends dominate local climate variability
remains an important area of research
– Natural variability in the GSL system is very large and needs to
be better understood
– There is more to the story than GHG related warming

A comprehensive observing and modeling system is needed
for the Great Salt Lake Basin
Snowfall Sensitivity: Snowbird
Snowfall decrease (%) per Dec C at 9650 ft
Courtesy: John Horel and Leigh Jones, Univ. of Utah
Concluding Thoughts

Future warming is already in the
pipeline
– Climate inertia
– Socio-economic inertia

Efforts to reduce CO2 emissions
will only have an impact after
~2040

New modeling systems are
needed to improve our
understanding and prediction of
the GSL basin
– Need to consider decadal-scale
prediction in addition to longterm trends
– Must think beyond CO2
 Consider regional climate change
as a multifaceted problem
Precipitation Change (in)
The Trend?
10
5
0
5
10
2000
2020
2040
2060
2080
Northern Utah Winter (Nov-Apr)
Precipitation Change Relative to 1980-1999
2100 CO2 = 2.5x Pre-Industrial (~700 ppm)
Slight Loading of Dice for “Wet” Winters
But Is the Storm Track Right?
No Lake-Effect
Courtesy
Thomas Reichler
Univ. of Utah