A Strategy for Assessing Potential Future Changes in Climate, Hydrology, and Vegetation in the Western United States.
R.S. Thompson, S.W. Hostetler, P.J. Bartlein and K.H. Anderson (1998),
U.S. Geoglogical Survey Circular 1153 (20 p.)

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Abstract

Alternative versions of selected figures

	Figure 1.  Maps illustrating spatial and topographic resolution of the two climate models--A, the GENESIS global atmospheric general circulation model (AGCM) and B, the regional climate model (RegCM)--relative to actual topography in the Western United States. The latter, shown in C, is displayed by elevations on a 15-km grid, sampled from the 5-minute ETOPO5 data set (Edwards, 1992). The GENESIS map (A) shows how the complex topography of the Western United States is greatly smoothed and reduced in elevation in this model. The RegCM map (B), in comparison with the map of observed topography (C), shows how many physiographic features in the real landscape that have an important mesoscale climatic influence, such as the Sierra Nevada, Colombia Basin, and Snake River Plain, are explicitly represented in the model. Some features, such as the Cascade Range and the individual basins and ranges, are still not well represented by RegCM. (Fig1.gif, 63KB / Fig1.pdf, 250KB)
	Figure 2.  Maps showing comparison of present-day climate (average or mean January and July temperature and precipitation) as depicted by A-D, GENESIS; E-H, RegCM; and I-L, observed conditions. Observed present-day climate data (I-L) is interpolated onto a 15-km grid from climate stations using a locally weighted trend-surface regression approach (e.g., Lipsitz, 1988). The GENESIS maps (A-D) show, in part, how the crude depiction of topography in the model (see fig. 1A) is translated into the simulation of temperature and precipitation. Because of the reduction in overall elevation in the smoothed representation of topography in the model, lower values of January temperatures are not simulated correctly and the overall representation of topography as a broad dome centered over Wyoming, Colorado, and Utah spreads out areas of higher precipitation relative to those of the observed present-day climate. The RegCM maps (E-H), on the other hand, show that this higher resolution model, even though forced by the coarse-resolution GENESIS, produces simulations that are closer in overall appearance to observed climatic patterns (I-L). (Fig2.gif, 137KB / Fig2.pdf, 729KB)
	Figure 3. RegCM simulation of January and July temperature and precipitation for the present-day climate (A-D), for the 2 X CO2 climate (E-H), and the difference (anomalies) between the 2 X CO2 climate and the present-day climate (I-L). The RegCM present-day climate simulation (A-D) used the GENESIS simulation of present-day climate (see figs. 2A-2D) as lateral boundary conditions or inputs, whereas the RegCM 2 X CO2 climate simulation (E-H) used the GENESIS 2 X CO2 simulation for lateral boundary conditions. The climate anomalies (RegCM of 2 X CO2 climate minus RegCM of present-day climate) are shown in I-L. The temperature anomalies show greater warming in winter than in summer, with the maximum warming in winter in the interior of the continent (I). Precipitation anomalies reveal increases of precipitation in the 2 X CO2 simulation relative to the present-day climate along the West Coast in January (K), and in a broad region extending from the Pacific Northwest to the Great Plains in July (L), with generally drier conditions simulated elsewhere in the interior. A hint of a stronger summer monsoon in the 2 X CO2 climate is also apparent. (Fig3.gif, 145KB / Fig3.pdf, 295KB)
	Figure 9. Observed present-day (A-D) and simulated 2 X CO2 (E-H) climates illustrated on 15-km grid. These latter values were formed by interpolating the RegCM climate anomalies (see bottom row of fig. 3) onto the 15-km grid and adding interpolated values to present-day values. (Fig9.gif, 107KB / Fig9.pdf, 1130KB)
	Observed and simulated distribution, and response surface for Artemisia tridentata See Figure 11. (Artr.gif, 80KB / Artr.pdf, 394KB)
	Observed and simulated distribution, and response surface for Pseudotsuga meziesii See Figure 11. (Psme.gif, 85KB / Psme.pdf, 316KB)
	Simulated present distributions. (Wclift.gif, 178KB / Wclift.pdf, 2266KB)

	Simulated future distributions. (W2xfit.gif, 162KB / W2xfit.pdf, 2271KB)
	Potential changes in distributions. See Figure 12. (Wchange.gif, 153KB / Wchange.pdf, 513KB)