scholarly journals A 500‐Year Tree Ring‐Based Reconstruction of Extreme Cold‐Season Precipitation and Number of Atmospheric River Landfalls Across the Southwestern United States

2018 ◽  
Vol 45 (11) ◽  
pp. 5672-5680 ◽  
Author(s):  
Scott Steinschneider ◽  
Michelle Ho ◽  
A. Park Williams ◽  
Edward R. Cook ◽  
Upmanu Lall
Keyword(s):  
United States ◽  
Tree Ring ◽  
Cold Season ◽  
Southwestern United States ◽  
Atmospheric River ◽  
Extreme Cold

Dendrochronology

Antiquity ◽  
1937 ◽  
Vol 11 (44) ◽  
pp. 409-426
Author(s):  
F. Martin Brown
Keyword(s):  
United States ◽  
Tree Ring ◽  
Tree Growth ◽  
Southwestern United States ◽  
Annual Increment ◽  
Old Spanish ◽  
The Past ◽  
Spanish Missions ◽  
Characteristic Sequences ◽  
Sun Spots

During the first years of this century an astronomer, Dr A. E. Douglass, started a series of examinations of the annual increment in trees just south of Flagstaff, Arizona, to see if the cyclical nature of sun-spot appearances was reflected in tree growth, through their influence on climate. He found that there was a rather high correlation between tree growth and sun-spots in the living trees he examined. In order to extend his studies into the past—beyond the 500 years recorded by living trees—he collected material taken from beams in the old Spanish Missions that dot the southwestern United States. He had found that it was possible to identify certain characteristic sequences of tree-ring widths with certain years, and thus project into the past his chart of tree growth from timbers cut at an unknown past date. In doing so he discovered a technique that has founded a new branch of science—dendrochronology.

scholarly journals Causes and Implications of Extreme Atmospheric Moisture Demand during the Record-Breaking 2011 Wildfire Season in the Southwestern United States

2014 ◽  
Vol 53 (12) ◽  
pp. 2671-2684 ◽  
Author(s):  
A. Park Williams ◽  
Richard Seager ◽  
Max Berkelhammer ◽  
Alison K. Macalady ◽  
Michael A. Crimmins ◽  
...  
Keyword(s):  
United States ◽  
Moisture Content ◽  
Vapor Pressure ◽  
Coupled Model ◽  
Warm Season ◽  
Cold Season ◽  
Atmospheric Moisture ◽  
Southwestern United States ◽  
Dewpoint Temperature ◽  
Atmospheric Moisture Content

AbstractIn 2011, exceptionally low atmospheric moisture content combined with moderately high temperatures to produce a record-high vapor pressure deficit (VPD) in the southwestern United States (SW). These conditions combined with record-low cold-season precipitation to cause widespread drought and extreme wildfires. Although interannual VPD variability is generally dominated by temperature, high VPD in 2011 was also driven by a lack of atmospheric moisture. The May–July 2011 dewpoint in the SW was 4.5 standard deviations below the long-term mean. Lack of atmospheric moisture was promoted by already very dry soils and amplified by a strong ocean-to-continent sea level pressure gradient and upper-level convergence that drove dry northerly winds and subsidence upwind of and over the SW. Subsidence drove divergence of rapid and dry surface winds over the SW, suppressing southerly moisture imports and removing moisture from already dry soils. Model projections developed for the fifth phase of the Coupled Model Intercomparison Project (CMIP5) suggest that by the 2050s warming trends will cause mean warm-season VPD to be comparable to the record-high VPD observed in 2011. CMIP5 projections also suggest increased interannual variability of VPD, independent of trends in background mean levels, as a result of increased variability of dewpoint, temperature, vapor pressure, and saturation vapor pressure. Increased variability in VPD translates to increased probability of 2011-type VPD anomalies, which would be superimposed on ever-greater background VPD levels. Although temperature will continue to be the primary driver of interannual VPD variability, 2011 served as an important reminder that atmospheric moisture content can also drive impactful VPD anomalies.

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