Present Weather and Climate: Average Conditions offers a snapshot of the region’s current climate—in terms of temperature, precipitation, and snowpack—and reviews the factors that define the range of climates found across the Southwest, and that contribute to climate variability and hazards, such as droughts, floods, wildland fires, diminished air quality, and extreme temperatures.
Citation:
Steenburgh, W. J., K. T. Redmond, K. E. Kunkel, N. Doesken, R. R. Gillies, J. D. Horel, M. P. Hoerling, and T. H. Painter. 2013. “Present Weather and Climate: Average Conditions.” In Assessment of Climate Change in the Southwest United States: A Report Prepared for the National Climate Assessment, edited by G. Garfin, A. Jardine, R. Merideth, M. Black, and S. LeRoy, 56–73. A report by the Southwest Climate Alliance. Washington, DC: Island Press.
W. James Steenburgh (University of Utah)
Kelly T. Redmond (Western Regional Climate Center and Desert Research Institute)
Kenneth E. Kunkel (NOAA Cooperative Institute for Climate and Satellites, North Carolina State University and National Climate Data Center)
Nolan Doesken (Colorado State University)
Robert R. Gillies (Utah State University)
John D. Horel (University of Utah)
Martin P. Hoerling (NOAA, Earth System Research Laboratory)
Thomas H. Painter (Jet Propulsion Laboratory)
Key Findings
The region’s climate is highly varied and strongly influenced by topography, storm tracks, and proximity to oceans (seen here from space).
The North American monsoon is important during the warm season (July through September) and is most prominent in Arizona and New Mexico.
The low-elevation deserts of Southern California, Nevada, and Arizona are the hottest, driest regions of the contiguous United States.
Wind-blown dust accumulation in the Rocky Mountains snowpack increases the sunlight absorbed by the snow, leading to earlier and rapid snowmelt.
Persistent cold-air pools, also known as inversions, sometime form in basins during wintertime, leading to buildup of pollution in some areas.
Figure Gallery
Figure 4.1: Temperature climatology of the Southwest (°F, 1971–2000). Source: PRISM Climate Group, Oregon State University (http://prism.oregonstate.edu).
Figure 4.2: Annual average precipitation in the Southwest, 1971–2000 (in inches). Source: PRISM Climate Group, Oregon State University (http://prism.oregonstate.edu).
Figure 4.3: Major spatial patterns of monthly varying precipitation over the Southwest, 1901–2010. Source: PRISM Climate Group, Oregon State University (http://prism.oregonstate.edu).
Figure 4.4: Dust-covered snow in the Dolores River headwaters, San Juan Mountains, Colorado, 19 May 2009. Photo courtesy of T. H. Painter, Snow Optics Laboratory, JPL/Caltech.
Figure 4.5: 25-year running mean of reconstructed (thin line) and observed (thick line) flows at Lees Ferry, Arizona. Adapted from Meko et al. (2007) with permission from the American Geophysical Union.
Figure 4.6: Counties designated by the Environmental Protection Agency as nonattainment areas for National Ambient Air Quality Standards in April 2010. Source: EPA (n.d.).