Development of a Web Site for Analyzing Temperatures in Mountain Regions over the Last 100 Years
Jeffrey A. Hicke
Natural Resource Ecology Laboratory, Colorado State University
jhicke@nrel.colostate.edu; 970-491-2104
1. Introduction
ƒ Changes in temperature greatly affect mountain regions through influences on
precipitation, snow pack, ecosystems
ƒ Several issues exist in mountains with regard to long-term monitoring of
climate change
o regions are not well represented in observing networks
o topographic effects
o timing of any change is important for determining effects on snow pack
and ecosystems
ƒ To address these issues, efforts to generate spatially complete climate data sets
have filled in gaps in mountainous regions by accounting for topography (e.g.,
VEMAP, PRISM, Daymet)
ƒ Here I describe a web site (see title box for address) for plotting temperature
time series across the United States and show examples of plots from this web
site that reveal long-term temperature change in mountainous regions
2. Plotting options
ƒ Data sources
• US Historical Climate Network (monthly and daily)
High-quality, long-term station data (back ~100 years)
• SNOTEL
High elevation, short-term station data (back to 1980s)
• Vegetation Analysis and Mapping Project (VEMAP)
Long-term (1895-1993), gridded (0.5°) data; emphasis
on spatial completeness, not temporal quality
ƒ Min, max, mean temperatures
ƒ Annual, seasonal, or monthly temperatures
ƒ Time period to plot (beginning and ending years)
ƒ Geographic regions
• nearest station or grid cell to input latitude, longitude
• ecoregion (with optional elevation range)
www.nrel.colostate.edu/~jhicke/climate_data
3. Example: Seasonal timing of increases
ƒ Four example mountain ecoregions,
distributed across the western US, were
selected to analyze long-term annual
temperatures
winter
spring
o VEMAP better accounts for topography
and higher elevations
ƒ However, the seasonal timing of warming differentially affects
the physical and biological environment
o all seasons show evidence of warming in 1930s and in last
decades
ƒ USHCN and VEMAP records were utilized
o USHCN are of higher quality (screened
and adjusted for biases)
ƒ In the Southern Rockies ecosystem, annual temperatures have
increased over the last 100 years (see #5 at right)
ƒ In this ecoregion,
5. Example: Long-term temperatures in mountain ranges of the western US
summer
fall
o substantial winter warming of ~2°C began around 1990
o spring increase is smaller (1°C) and began earlier
o summer, fall warming is only 0.5°C, comparable to 1930s
warm period
4. Example: Temperatures nearest a point (Loch Vale, Rocky Mountain NP)
ƒ Loch Vale is a highelevation site (>3000 m)
ƒ The nearest highquality, long-term
USHCN station is at
1800 m
ƒ VEMAP accounts for mean elevation; the mean
elevation in the overlying grid cell is 2943 m, though it
covers a very large region (0.5° by 0.5°)
ƒ The nearest SNOTEL station is at 2895 m, but only goes
back to 1990
ƒ Mean annual temperatures in this region have increased
since the early 1980s by 1°C in HCN, VEMAP data; by
0.5°C since early 1990s at SNOTEL site
ƒ Comparison with the onsite weather station reveals reasonable agreement with the
HCN, VEMAP, and SNOTEL behavior
ƒ The lack of high elevation stations is evident
(see elevation histograms in lower right of
each panel); SNOTEL data may fill in some
gaps in the 1980s and 1990s
ƒ Between 6 (AZ-NM) and 30 (Cascades and S.
Rockies) USHCN stations covered these
ecoregions (lower left of each panel)
ƒ Ecoregions exhibited similar temperature
trends over the last 100 years
o overall increase of 1-1.5°C
o warm periods in the 1930s and in the last
several decades
ƒ Cascades and Sierra Nevada temperature
records suggested a slight cooling in the last
years of the record
6. Future work
• Add more detailed gridded data sources (PRISM, Daymet)
• Include additional climate variables (precipitation)
• Expand to global coverage with available data sets
7. Acknowledgements
Lee Casuto provided programming support. This work was funded by the USGS Western Mountain Initiative, USGS Cooperative
Agreement 04CRAG0004/4004CS0001, and USDA Forest Service Cooperative Agreement 03-CS-11222033-315.