scholarly journals Spatial and Seasonal Variations in Aridification across Southwest North America

2016 ◽  
Vol 29 (12) ◽  
pp. 4637-4649 ◽  
Author(s):  
Shannon M. Jones ◽  
David S. Gutzler
Keyword(s):  
United States ◽  
North America ◽  
Warm Season ◽  
Cold Season ◽  
Base Flow ◽  
First Century ◽  
Strongly Correlated ◽  
Southwest United States ◽  
The North ◽  
Twenty First Century

Abstract Southwestern North America (SWNA) is projected to become drier in the twenty-first century as both precipitation (P) and evaporation (E) rates change with increasing greenhouse gas concentration. The authors diagnose the relative contributions of changes in P and E to the local surface moisture balance (P − E) in cold and warm halves of the year across SWNA. Trends in P − E vary spatially between the arid southern subregion (mostly northern Mexico) and the more temperate northern subregion (southwest United States), although both subregions exhibit a negative trend in P − E (trending toward more arid conditions) in CMIP5 projections for the twenty-first century. The P − E trend is biggest in the cold season, when much of the base flow to rivers in the southwest United States is generated. The downward trend in cold season P − E across SWNA is caused primarily by increasing E in the north and decreasing P in the south. Decreasing P is the primary contributor to modest warm season drying trends in both northern and southern subregions. Also, P accounts for most of the interannual variability in SWNA P − E and is strongly correlated with modes of oceanic natural variability during the cold season. SWNA aridification is therefore most readily distinguished from the region’s large natural climate variability in the cold season in the northern subregion, where the projected temperature-driven increase in E is greater than the projected decrease in P.

scholarly journals An anomalous atmospheric river linked to the late June 2021 western North America heatwave

2022 ◽  
Author(s):  
Ruping Mo ◽  
Hai Lin ◽  
Frédéric Vitart
Keyword(s):  
North America ◽  
Water Vapour ◽  
Warm Season ◽  
Lower Troposphere ◽  
Heavy Precipitation ◽  
Cold Season ◽  
Feedback Mechanism ◽  
Western North America ◽  
Water Vapour Flux ◽  
The North

Abstract Atmospheric rivers (ARs) are long and narrow bands of enhanced water vapour flux concentrated in the lower troposphere. Many studies have documented the important role of cold-season ARs in producing heavy precipitation and triggering extreme flooding in many parts of the world. However, relatively little research has been conducted on the warm-season ARs and their impacts on extreme heatwave development. Here we show an anomalous warm-season AR moving across the North Pacific and its interaction with the western North American heatwave in late June 2021. We call it an “oriental express’’ to highlight its capability to transport tropical moisture to the west coast of North America from sources in Southeast Asia. Its landfall over the Alaska Panhandle lasted for more than two days and resulted in significant spillover of moisture into western Canada. We provide evidence that the injected water vapour was trapped under the heat dome and may have formed a positive feedback mechanism to regulate the heatwave development in western North America.

scholarly journals Future Changes in Convective Storm Days over the Northeastern United States Using Linear Discriminant Analysis Applied to CMIP5 Predictions

2016 ◽  
Vol 29 (12) ◽  
pp. 4327-4345 ◽  
Author(s):  
Harrison Li ◽  
Brian A. Colle
Keyword(s):  
United States ◽  
Discriminant Analysis ◽  
Linear Discriminant Analysis ◽  
Warm Season ◽  
First Century ◽  
Historical Period ◽  
Northeastern United States ◽  
Convective Storm ◽  
Linear Discriminant ◽  
Twenty First Century

Abstract Future changes in the frequency of environmental conditions conducive for convective storm days (“CE days”) are determined for the northeastern United States (NEUS) during the warm seasons (April–September) of the twenty-first century. Statistical relationships between historical runs of seven models in phase 5 of the Coupled Model Intercomparison Project (CMIP5) and radar-classified convective storm days are developed using linear discriminant analysis (LDA), and these relationships are then applied to analyze changes in the convective environment under the high-emissions representative concentration pathway 8.5 (RCP8.5) scenario over the period 2006–99. The 1996–2007 warm seasons are used to train the LDA thresholds using convective precipitation from two reanalysis datasets and radar data, and the 1979–95 and 2008–10 warm seasons are used to verify these thresholds. For the CMIP5 historical period (1979–2005), the frequency of warm season CE days averaged across the CMIP5 models is slightly greater than that derived using reanalysis data, although both methods indicate a slight increasing trend through the historical period. Between 2006 and 2099, warm season CE day frequency is predicted to increase substantially at an average rate of 4–5 days decade−1 (50%–80% increase over the entire period). These changes are mostly attributed to a predicted 30%–40% increase in midlevel precipitable water between the historical period and the last few decades of the twenty-first century. Consistent with previous studies, there is decreasing deep-layer vertical wind shear as a result of a weakening horizontal temperature gradient, but this is outweighed by increases in instability led by the moisture increases.

scholarly journals Model Projections of the Changes in Atmospheric Circulation and Surface Climate over North America, the North Atlantic, and Europe in the Twenty-First Century

2013 ◽  
Vol 26 (23) ◽  
pp. 9603-9620 ◽  
Author(s):  
Ngar-Cheung Lau ◽  
Jeffrey J. Ploshay
Keyword(s):  
Climate Change ◽  
North America ◽  
North Atlantic ◽  
Storm Track ◽  
First Century ◽  
The North ◽  
Sst Forcing ◽  
The North Atlantic ◽  
Twenty First Century ◽  
North America North

The impacts of climate change on the North America–North Atlantic–Europe sector are studied using a coupled general circulation model: the Climate Model, version 3 (CM3) and a high-resolution atmosphere-only model, the High Resolution Atmospheric Model (HiRAM)—both developed at the Geophysical Fluid Dynamics Laboratory. The CM3 experiment is conducted under two climate change scenarios for the 1860–2100 period. The sea surface temperature (SST) forcing prescribed in the “time slice” integrations with HiRAM is derived from observations for the 1979–2008 period and projection by CM3 for the 2086–95 period. The wintertime response in the late twenty-first century is characterized by an enhancement of the positive phase of the North Atlantic Oscillation in sea level pressure (SLP) and poleward and eastward displacements of the Atlantic jet stream and storm track. The forcing pattern due to eddy vorticity fluxes in the perturbed storm track matches well with the response pattern of the SLP field in the late twenty-first century. The model results suggest that the above circulation changes are linked to the gradient of the altered SST forcing in the North Atlantic. In summer, the projected enhancement of convection over the eastern tropical Pacific is accompanied by a wave train spanning the North America–North Atlantic–Europe sector. This quasi-stationary circulation pattern is associated with diminished storm track activity at 40°–50°N and an eddy forcing pattern similar to the summertime SLP response in the late twenty-first century.

scholarly journals Spatial Variability of Sea Level Rise in Twenty-First Century Projections

2010 ◽  
Vol 23 (17) ◽  
pp. 4585-4607 ◽  
Author(s):  
Jianjun Yin ◽  
Stephen M. Griffies ◽  
Ronald J. Stouffer
Keyword(s):  
North America ◽  
Southern Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
North Atlantic ◽  
North Pacific ◽  
First Century ◽  
The North ◽  
The North Atlantic ◽  
Twenty First Century

Abstract A set of state-of-the-science climate models are used to investigate global sea level rise (SLR) patterns induced by ocean dynamics in twenty-first-century climate projections. The identified robust features include bipolar and bihemisphere seesaws in the basin-wide SLR, dipole patterns in the North Atlantic and North Pacific, and a beltlike pattern in the Southern Ocean. The physical and dynamical mechanisms that cause these patterns are investigated in detail using version 2.1 of the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Model (CM2.1). Under the Intergovernmental Panel on Climate Change’s (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario, the steric sea level changes relative to the global mean (the local part) in different ocean basins are attributed to differential heating and salinity changes of various ocean layers and associated physical processes. As a result of these changes, water tends to move from the ocean interior to continental shelves. In the North Atlantic, sea level rises north of the Gulf Stream but falls to the south. The dipole pattern is induced by a weakening of the meridional overturning circulation. This weakening leads to a local steric SLR east of North America, which drives more waters toward the shelf, directly impacting northeastern North America. An opposite dipole occurs in the North Pacific. The dynamic SLR east of Japan is linked to a strong steric effect in the upper ocean and a poleward expansion of the subtropical gyre. In the Southern Ocean, the beltlike pattern is dominated by the baroclinic process during the twenty-first century, while the barotropic response of sea level to wind stress anomalies is significantly delayed.

Biosurveillance: A Modern Look

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
James Lee Brooks
Keyword(s):  
United States ◽  
Homeland Security ◽  
The United States ◽  
First Century ◽  
Direct Result ◽  
Current State ◽  
Twenty First Century ◽  
Security Operations

AbstractThe early part of the twenty-first century saw a revolution in the field of Homeland Security. The 9/11 attacks, shortly followed thereafter by the Anthrax Attacks, served as a wakeup call to the United States and showed the inadequacy of the current state of the nation’s Homeland Security operations. Biodefense, and as a direct result Biosurveillance, changed dramatically after these tragedies, planting the seeds of fear in the minds of Americans. They were shown that not only could the United States be attacked at any time, but the weapon could be an invisible disease-causing agent.

Defining the Center—Finding the Boundaries: The Challenge of Re-Visioning the Church in North America for the Twenty-First Century

1994 ◽  
Vol 22 (3) ◽  
pp. 317-337
Author(s):  
Craig Van Gelder
Keyword(s):  
North America ◽  
North American ◽  
American Culture ◽  
First Century ◽  
New Paradigm ◽  
Twenty First Century ◽  
Mission Field ◽  
The Church

It is becoming increasingly clear that we are experiencing a shift in North American culture that requires the church to think of North America as mission field. The thesis of this article is that the church will need to develop a new paradigm of mission to accomplish this. This article identifies 18 issues which such a paradigm of mission will need to address. These issues are discussed in terms of three aspects: (1) the context in which we live, (2) the gospel we seek to proclaim, and (3) the church which seeks to proclaim this gospel.

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