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Auxiliary material for
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Observed and projected changes in absolute temperature records across the contiguous United States
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John T. Abatzoglou1
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Renaud Barbero1
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Department of Geography, University of Idaho, Moscow, Idaho, USA
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Geophysical Research Letters, 2014
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Introduction
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The auxiliary material is composed of one table and four figures. Auxiliary Table S1 shows linear trends
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in extent of absolute temperature records simulated by 20 CMIP5 GCMs for 1950-2013. Auxiliary Figure
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S1 illustrates the cumulative distribution of absolute temperature records and their distribution for couple
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example years. Auxiliary Figure S2 shows decadal variability in absolute temperature records for both
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observations and simulations for 1950-2013. Auxiliary Figure S3 shows the Palmer Drought Severity
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Index (PDSI) for the month concurrent with the absolute highest maximum temperature record from
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USHCN stations for 1920-2013. PDSI were calculated following Kangas and Brown (2007) using
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monthly data from Parameter-elevation Regressions on Independent Slopes Model (Daly et al., 2008) on a
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4-km grid. We extracted the 4-km voxel co-located with each station and map those in Auxiliary Figure
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S3. Auxiliary Figure S4 shows the composite standardized 500-hPa geopotential height anomalies for
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absolute temperature records from USHCN stations from 1920-2013. Geopotential height data were
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obtained from the 20th century reanalysis V2 (Compo et al., 2011) and standardized anomalies were
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computed using means and standard deviations calculated along a moving 21-day window. To create the
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composite, standardized anomalies of 500-hPa height were centered relative to the geolocation of each
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USHCN station.
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1. Table S1: Linear trends in the % of spatial extent of the US with absolute temperature records from
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CMIP5 simulations for 1950-2013. Trends are expressed as the difference between the last and the first
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values from the least square line. * indicates that the trend observed is significant according to a Monte-
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Carlo test, that is, more than 95% of the simulated trends agree on the sign of the trend.
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1.1 Column Official acronyms of Global Climate Models used.
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1.2 Column Linear least squares trend in the highest absolute maximum temperature record.
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1.3 Column Linear least squares trend in the lowest absolute maximum temperature record.
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1.4 Column Linear least squares trend in the highest absolute minimum temperature record.
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1.5 Column Linear least squares trend in the lowest absolute minimum temperature record.
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2. (Auxiliary Figure S1) The cumulative distribution of absolute daily records by year for (a) maximum
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temperature and (b) minimum temperature for the 1920-2013 period from aggregated station data. The
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extent of the domain that set or tied records for (c) absolute highest maximum temperatures in 1936, and
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(d) absolute lowest maximum temperatures in 1985.
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3. (Auxiliary Figure S2) Decadal variability in the spatial extent of absolute records in (a) highest
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maximum temperatures, (b) lowest maximum temperatures, (c) highest minimum temperatures, and (d)
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lowest minimum temperatures for GHCN and 20 different climate models from 1950-2013. Data is
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expressed as a departure from an assumed uniform distribution of records. Climate model results are
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depicted by the box plots where the interquartile range is shown by the grey envelope, the 20-model mean
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shown by the black horizontal line and individual model results shown by small circles.
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4. (Auxiliary Figure S3) Palmer Drought Severity Index (PDSI) for month during which absolute highest
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maximum temperature was recorded for each USHCN station 1920-2013. PDSI values less than -3 are
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shown by larger circles to emphasize severe drought.
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5. (Auxiliary Figure S4) Composite standardized 500-hPa geopotential height anomalies for absolute
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temperature records set from 1920-2012 centered relative to the geographic location of USHCN stations
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(denoted by the black x on each plot). Solid red (dashed blue) contours are plotted every 0.2σ starting
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from 0.6σ (-0.6σ) with the 1σ isoline shown in bold. Geopotential height data were obtained from the 20th
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century reanalysis V2.
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References
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Compo, G.P., and coauthors, 2011: The Twentieth Century Reanalysis Project. Quarterly J. Roy.
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Meteorol. Soc., 137, 1-28. DOI: 10.1002/qj.776.
Daly, C., M. Halbleib, J.I. Smith, W. P. Gibson, M. K. Doggett, G. H. Taylor, J. Curtis, and P. A. Pasteris
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(2008) Physiographically-sensitive mapping of temperature and precipitation across the conterminous
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United States. International Journal of Climatology, 28: 2031-2064.
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Kangas, R.S. and T.J. Brown (2007) Characteristics of U.S. Drought and Pluvials from a High-Resolution
Spatial Dataset, International Journal of Climatology, 27, 1303-1335.
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bcc-csm1-1
canESM2
CCSM4
CNRM-CM5
CSIRO-Mk3-6-0
GFDL-ESM2M
HadGEM2-ES365
HadGEM2-CC365
inmcm4
IPSL-CM5A-LR
IPSL-CM5A-MR
MIROC5
MIROC-ESM
MIROC-ESM-CHEM
MRI-CGCM3
NorESM1-M
bcc-csm1-1-m
BNU-ESM
IPSL-CM5B-LR
GFDL-ESM2G
Highest TMAX
Lowest TMAX
Highest TMIN
Lowest TMIN
3.13*
4.55*
4.42*
3.14*
4.32*
4.23*
3.96*
3.85*
3.00*
4.86*
4.33*
2.99*
0.49
1.86*
1.87*
3.66
4.49*
5.61*
4.43*
4.97*
-1.94*
-1.11
-0.05
0.55
-1.10
0.10
-0.02
-0.56
-0.87
0.14
-0.65
-0.65
-1.21*
0.35
-2.64*
-0.91
-0.28
-1.57*
-0.56
-0.53
1.36*
2.97*
3.15*
1.79*
3.10*
2.15*
3.07*
1.42*
1.86*
3.33*
3.20*
2.33*
2.75*
2.69*
1.29*
2.11*
1.92
3.69
3.31
1.98
-2.03*
-0.86
-1.48*
1.14
-0.84
0.19
-0.07
-1.00*
0.92
-0.48
-1.22
-0.63
-2.16*
0.19
-2.52*
0.23
-1.31
-1.07*
-0.03
-1.22*
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Table S1: Linear trends in the % of spatial extent of the US with absolute temperature records from
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CMIP5 simulations for 1950-2013. Trends are expressed as the difference between the last and the first
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values from the least square line. * indicates that the trend observed is significant according to a Monte-
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Carlo test, that is, more than 95% of the simulated trends agree on the sign of the trend.
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f(# of absolute records)
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a) CDF of record years (TMAX)
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0.8
0.8
0.6
0.6
0.4
0.4
0.2
01
Highest TMAX
Lowest TMAX
920 1930 1940 1950 1960 1970 1980 1990 2000 2010
c) Highest TMAX in 1936
0.2
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b) CDF of record years (TMIN)
Highest TMIN
Lowest TMIN
920 1930 1940 1950 1960 1970 1980 1990 2000 2010
d) Lowest TMAX in 1985
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Figure S1: The cumulative distribution of absolute daily records by year for (a) maximum temperature
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and (b) minimum temperature for the 1920-2013 period from aggregated station data. The extent of the
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domain that set or tied records for (c) absolute highest maximum temperatures in 1936, and (d) absolute
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lowest maximum temperatures in 1985.
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Figure S2: Decadal variability in the spatial extent of absolute records for (a) highest maximum
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temperatures, (b) lowest maximum temperatures, (c) highest minimum temperatures, and (d) lowest
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minimum temperatures for GHCN and 20 different climate models from 1950-2013. Data is expressed as
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a departure from an assumed uniform distribution of records. Climate model results are depicted by the
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box plots where the interquartile range is shown by the grey envelope, the 20-model mean shown by the
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black horizontal line and individual model results shown by small circles.
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Figure S3: Palmer Drought Severity Index (PDSI) for month during which absolute highest maximum
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temperature was recorded for each USHCN station 1920-2013. PDSI values less than -3 are shown by
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larger circles to emphasize severe drought.
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Figure S4: Composite standardized 500-hPa geopotential height anomalies for absolute temperature
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records set from 1920-2012 centered relative to the geographic location of USHCN stations (denoted by
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the black x on each plot). Contours are plotted every 0.2σ starting from 0.6σ with the 1σ isoline boldened.
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Geopotential height data were obtained from the 20th century reanalysis V2. All contours plotted were
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statistically significant at p<0.05.