scholarly journals Mechanism of Future Spring Drying in the Southwestern United States in CMIP5 Models

2018 ◽  
Vol 31 (11) ◽  
pp. 4265-4279 ◽  
Author(s):  
Mingfang Ting ◽  
Richard Seager ◽  
Cuihua Li ◽  
Haibo Liu ◽  
Naomi Henderson
Keyword(s):  
United States ◽  
Surface Water ◽  
Moisture Flux ◽  
Moisture Convergence ◽  
Cmip5 Models ◽  
Significant Shift ◽  
Southwestern United States ◽  
Budget Analysis ◽  
Near Term ◽  
The U.S

Abstract The net surface water budget, precipitation minus evaporation (P − E), shows a clear seasonal cycle in the U.S. Southwest with a net gain of surface water (positive P − E) in the cold half of the year (October–March) and a net loss of water (negative P − E) in the warm half (April–September), with June and July being the driest months of the year. There is a significant shift of the summer drying toward earlier in the year under a CO2 warming scenario, resulting in substantial spring drying (March–May) of the U.S. Southwest from the near-term future to the end of the current century, with gradually increasing magnitude. While the spring drying has been identified in previous studies, its mechanism has not been fully addressed. Using moisture budget analysis, it was found that the drying is mainly due to decreased mean moisture convergence, partially compensated by the increase in transient eddy moisture flux convergence. The decreased mean moisture convergence is further separated into components as a result of changes in circulation (dynamic changes) and changes in atmospheric moisture content (thermodynamic changes). The drying is found to be dominated by the thermodynamic-driven changes in column-averaged moisture convergence, mainly due to increased dry zonal advection caused by the climatological land–ocean thermal contrast, rather than by the well-known “dry get drier” mechanism. Furthermore, the enhanced dry advection in the warming climate is dominated by the robust zonal mean atmospheric warming, leading to equally robust spring drying in the southwestern United States.

scholarly journals Assessing Future Changes in the East Asian Summer Monsoon Using CMIP5 Coupled Models

2013 ◽  
Vol 26 (19) ◽  
pp. 7662-7675 ◽  
Author(s):  
Kyong-Hwan Seo ◽  
Jung Ok ◽  
Jun-Hyeok Son ◽  
Dong-Hyun Cha
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Moisture Flux ◽  
Moisture Convergence ◽  
Cmip5 Models ◽  
Moisture Flux Convergence ◽  
The North ◽  
Asian Summer

Abstract Future changes in the East Asian summer monsoon (EASM) are estimated from historical and Representative Concentration Pathway 6.0 (RCP6) experiments of the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The historical runs show that, like the CMIP3 models, the CMIP5 models produce slightly smaller precipitation. A moisture budget analysis illustrates that this precipitation deficit is due to an underestimation in evaporation and ensuing moisture flux convergence. Of the two components of the moisture flux convergence (i.e., moisture convergence and horizontal moist advection), moisture convergence associated with mass convergence is underestimated to a greater degree. Precipitation is anticipated to increase by 10%–15% toward the end of the twenty-first century over the major monsoonal front region. A statistically significant increase is predicted to occur mostly over the Baiu region and to the north and northeast of the Korean Peninsula. This increase is attributed to an increase in evaporation and moist flux convergence (with enhanced moisture convergence contributing the most) induced by the northwestward strengthening of the North Pacific subtropical high (NPSH), a characteristic feature of the future EASM that occurred in CMIP5 simulations. Along the northern and northwestern flank of the strengthened NPSH, intensified southerly or southwesterly winds lead to the increase in moist convergence, enhancing precipitation over these areas. However, future precipitation over the East China Sea is projected to decrease. In the EASM domain, a local mechanism prevails, with increased moisture and moisture convergence leading to a greater increase in moist static energy in the lower troposphere than in the upper troposphere, reducing tropospheric stability.

The Russian Federation

2020 ◽  
pp. 155-169
Author(s):  
Matthew Kroenig
Keyword(s):  
United States ◽  
National Security ◽  
Russian Federation ◽  
Political Institutions ◽  
The United States ◽  
Security Threat ◽  
The Russian Federation ◽  
Near Term ◽  
Vladimir Putin ◽  
The U.S

This chapter analyzes the Russian Federation through the lens of its domestic political system. Russia may pose the greatest near-term national security threat to the United States and its allies, but it has a key vulnerability: its domestic political institutions. Its autocratic system is undermining its international effectiveness. Its economy is smaller than Italy’s. It lacks effective alliances. And its military is overly focused on domestic threats and is ill-equipped for the strategic-technological competitions of the 21st century. It is dangerous and it can disrupt the U.S.-led order. But it will not be in a position to be a true peer competitor to the United States any time soon. So long as it continues to be ruled by President Vladimir Putin, or another similar dictator, Russia will not be able to mount a serious challenge to U.S. global leadership.

Impacts of Storm Track Variations on Wintertime Extreme Precipitation and Moisture Budgets over the Ohio Valley and Northwestern United States

2020 ◽  
Vol 33 (13) ◽  
pp. 5371-5391
Author(s):  
Chen-Geng Ma ◽  
Edmund K. M. Chang ◽  
Sun Wong ◽  
Rui Zhang ◽  
Minghua Zhang ◽  
...  
Keyword(s):  
United States ◽  
Extreme Precipitation ◽  
Moisture Flux ◽  
Water Vapor Transport ◽  
Lower Latitude ◽  
Ohio Valley ◽  
Central Pacific ◽  
Budget Analysis ◽  
Extreme Precipitation Events ◽  
Precipitation Events

AbstractPrevious studies have shown that variations in extratropical cyclone activity significantly affect the frequency of extreme precipitation events over the Ohio Valley and northwestern United States. In this study, we examine the similarities and differences between the dynamics governing these events in these two regions. In the Ohio Valley, extreme precipitation events are associated with midlatitude synoptic-scale convergence northeast of cyclones and a southwestward oriented ridge near the Atlantic coast that drives strong water vapor transport from the Gulf of Mexico into the Ohio Valley. In the northwestern United States, extreme precipitation events are associated with a cyclonic and anticyclonic circulation pair aligned northwest to southeast, which together drive a long and strong moisture transport corridor from the lower latitude of the central Pacific Ocean toward the northwestern United States. Moisture budget analysis shows that moisture convergence due to dynamical convergence dominates in the Ohio Valley, whereas moisture advection dominates over the Pacific Northwest. Differences between the cases in the same region are examined by an empirical orthogonal function (EOF) analysis conducted on the vertically integrated moisture flux. Different EOFs highlight shifts in spatial location, orientation, and intensity of the moisture flux but demonstrate consistent roles of dynamics in the two regions. Composites based on these EOFs highlight the range of likely synoptic scenarios that can give rise to precipitation extremes over these two regions.

It's Alive! The Federal Booker-Fix Debate Stirs

2012 ◽  
Vol 24 (5) ◽  
pp. 335-337
Author(s):  
Frank O. Bowman, III
Keyword(s):  
United States ◽  
Sentencing Guidelines ◽  
Federal Sentencing Guidelines ◽  
Federal Sentencing ◽  
Legislative Action ◽  
Near Term ◽  
Institutional Actors ◽  
The U.S

These Editor's Observations introduce Volume 24, Number 5 of the Federal Sentencing Reporter, an issue devoted to renewed discussion in Congress and the U.S. Sentencing Commission about whether there is a need for legislative action to revise or replace the advisory federal sentencing guidelines system judicially created by the U.S. Supreme Court's 2005 decision in United States v. Booker. It describes the basic positions of the main institutional actors, briefly summarizes the articles in the issue, and makes a prediction about the likelihood of action in the near term.

The Physical Mechanisms by Which the Leading Patterns of SST Variability Impact U.S. Precipitation

2010 ◽  
Vol 23 (7) ◽  
pp. 1815-1836 ◽  
Author(s):  
Hailan Wang ◽  
Siegfried Schubert ◽  
Max Suarez ◽  
Randal Koster
Keyword(s):  
United States ◽  
Gulf Of Mexico ◽  
Great Plains ◽  
Moisture Transport ◽  
Diabatic Heating ◽  
Moisture Flux ◽  
Physical Mechanisms ◽  
Sst Variability ◽  
Precipitation Response ◽  
The U.S

Abstract This study uses the NASA Seasonal-to-Interannual Prediction Project (NSIPP-1) AGCM to investigate the physical mechanisms by which the leading patterns of annual mean SST variability impact U.S. precipitation. The focus is on a cold Pacific pattern and a warm Atlantic pattern that exert significant drought conditions over the U.S. continent. The precipitation response to the cold Pacific is characterized by persistent deficits over the Great Plains that peak in summer with a secondary peak in spring, and weakly pluvial conditions in summer over the Southeast (SE). The precipitation response to the warm Atlantic is dominated by persistent deficits over the Great Plains with the maximum deficit occurring in late summer. The precipitation response to the warm Atlantic is overall similar to the response to the cold Pacific with, however, considerably weaker amplitude. An analysis of the atmospheric moisture budget combined with a stationary wave model diagnosis of the associated atmospheric circulation anomalies is conducted to investigate mechanisms of the precipitation responses. A key result is that, while the cold Pacific and warm Atlantic are two spatially distinct SST patterns, they nevertheless produce similar diabatic heating anomalies over the Gulf of Mexico during the warm season. In the case of the Atlantic forcing, the heating anomalies are a direct response to the SST anomalies, whereas in the case of Pacific forcing they are a secondary response to circulation anomalies forced from the tropical Pacific. The diabatic heating anomalies in both cases force an anomalous low-level cyclonic flow over the Gulf of Mexico that leads to reduced moisture transport into the central United States and increased moisture transport into the eastern United States. The precipitation deficits over the Great Plains in both cases are greatly amplified by the strong soil moisture feedback in the NSIPP-1 AGCM. In contrast, the response over the SE to the cold Pacific during spring is primarily associated with an upper-tropospheric high anomaly over the southern United States that is remotely forced by tropical Pacific diabatic heating anomalies, leading to greatly reduced stationary moisture flux convergences and anomalous subsidence in that region. Moderately reduced evaporation and weakened transient moisture flux convergences play secondary roles. It is only during spring that these three terms are all negative and constructively contribute to produce the maximum dry response in spring. The above findings based on the NSIPP-1 AGCM are generally consistent with observations, as well as with four other AGCMs included in the U.S. Climate Variability and Predictability (CLIVAR) project.

scholarly journals Implications of North Atlantic Sea Surface Salinity for Summer Precipitation over the U.S. Midwest: Mechanisms and Predictive Value

2016 ◽  
Vol 29 (9) ◽  
pp. 3143-3159 ◽  
Author(s):  
Laifang Li ◽  
Raymond W. Schmitt ◽  
Caroline C. Ummenhofer ◽  
Kristopher B. Karnauskas
Keyword(s):  
United States ◽  
Soil Moisture ◽  
North Atlantic ◽  
Summer Precipitation ◽  
Moisture Flux ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Southern United States ◽  
Surface Salinity ◽  
The U.S

Abstract Moisture originating from the subtropical North Atlantic feeds precipitation throughout the Western Hemisphere. This ocean-to-land moisture transport leaves its imprint on sea surface salinity (SSS), enabling SSS over the subtropical oceans to be used as an indicator of terrestrial precipitation. This study demonstrates that springtime SSS over the northwestern portion of the subtropical North Atlantic significantly correlates with summertime precipitation over the U.S. Midwest. The linkage between springtime SSS and the Midwest summer precipitation is established through ocean-to-land moisture transport followed by a soil moisture feedback over the southern United States. In the spring, high SSS over the northwestern subtropical Atlantic coincides with a local increase in moisture flux divergence. The moisture flux is then directed toward and converges over the southern United States, which experiences increased precipitation and soil moisture. The increased soil moisture influences the regional water cycle both thermodynamically and dynamically, leading to excessive summer precipitation in the Midwest. Thermodynamically, the increased soil moisture tends to moisten the lower troposphere and enhances the meridional humidity gradient north of 36°N. Thus, more moisture will be transported and converged into the Midwest by the climatological low-level wind. Dynamically, the increases in soil moisture over the southern United States enhance the west–east soil moisture gradient eastward of the Rocky Mountains, which can help to intensify the Great Plains low-level jet in the summer, converging more moisture into the Midwest. Owing to these robust physical linkages, the springtime SSS outweighs the leading SST modes in predicting the Midwest summer precipitation and significantly improves rainfall prediction in this region.

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