Airflow Configurations of Warm Season Southerly Low-Level Wind Maxima in the Great Plains. Part I: Spatial and Temporal Characteristics and Relationship to Convection

Walters, Claudia K.; Winkler, Julie A.

doi:10.1175/1520-0434(2001)016<0513:acowss>2.0.co;2

Cited by 41 publications

(41 citation statements)

References 41 publications

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“…While negative precipitation deviations are seen in most months for Cluster 2, in line with its more western location, mean monthly precipitation for Cluster 4 is larger than the UGLR average from April to August. This pattern is in concordance with the climatological precipitation maximum extending from eastern Kansas northeastward into southeastern Minnesota and western Wisconsin in summer (Kunkel et al , ), which is associated with moisture advection from the Gulf of Mexico around a semi‐permanent high pressure system in the subtropical Atlantic (Kunkel et al , ), initiation of convection by nocturnal southerly low‐level wind maxima (Walters and Winkler, ) and the frequent occurrence of precipitation‐producing mesoscale convective complexes (Fritsch et al , ). Cluster 3 also experiences summertime precipitation greater than the UGLR average for many of the same reasons as Cluster 4, although the positive deviations occur somewhat later from June to October.…”

Section: Analysis and Resultssupporting

confidence: 72%

Selection of climate information for regional climate change assessments using regionalization techniques: an example for the Upper Great Lakes Region, USA

Perdinan

Winkler

2014

Intl Journal of Climatology

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Climate change assessments often utilize only a small number of climate stations within the assessment region. Consequently, the selection of representative stations that capture the spatial variability of climate is an essential first step of the assessment. Furthermore, climate observations and scenarios frequently need to be linked with other (e.g. agricultural, biological, socioeconomic) datasets available at varying spatial resolutions in order to assess regional‐scale impacts and vulnerability. This study illustrates the utility of well‐known objective climate classification techniques in facilitating regional‐scale climate change assessments, using the Upper Great Lakes region (UGLR) of the United States as an example. A combination of principal components analysis and cluster analysis was employed to group climate stations from the US Historical Climatology Network into a small number of climate regions. The regionalization initially was performed on long‐term averages of monthly maximum and minimum temperatures and precipitation for 1971–2000, and then applied to two earlier time periods (1911–1940 and 1941–1970) to assess the sensitivity of the regionalization to the development period. The spatial variability of average monthly temperature and precipitation in the UGLR was found to be effectively represented by seven climate types. Potential applications of the regionalization for climate change assessments are illustrated. First, Euclidean distance, employed within a geographic information system (ArcGIS), provided a convenient means of assigning political units (counties) within the UGLR to the climate regions to facilitate the integration of point‐scale climate information with spatially‐aggregated datasets. Second, a minimum number of climate stations for an assessment were selected based on the climate regionalization. Finally, the regionalization was used to evaluate the spatial representativeness of a subset of climate stations that were initially chosen based on the completeness of daily observations.

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Section: Analysis and Resultssupporting

confidence: 72%

Selection of climate information for regional climate change assessments using regionalization techniques: an example for the Upper Great Lakes Region, USA

Perdinan

Winkler

2014

Intl Journal of Climatology

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“…The SLP anomalies correspond to a marked increase in mean low-level (0.5-1.5 km) southerly flow over the southern and central Great Plains. In fact, the wet composite mean lowlevel isotach-streamline configuration over the central United States (not shown) strongly resembles a contemporary warm season Great Plains southerly lowlevel jet configuration (Walters and Winkler 2001). This indicates that the low-level jet is an important moisture transport mechanism at the LGM with the Gulf of Mexico and Caribbean serving as primary moisture sources for cyclones along the Laurentide Ice Sheet southern margin.…”

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confidence: 89%

“…Yet, model resolution can have an important impact on a model's ability to accurately represent large-scale features, such as the atmospheric longwave pattern and storm tracks (Shinn and Barron 1989;Kageyama et al 1999;Dong and Valdes 2000). Furthermore, mesoscale processes such as low-level jet maxima, which play a critical role in moisture transport and convective development in the central United States (e.g., Walters and Winkler 2001), become prevalent in the warm season but may not be adequately captured in coarse-resolution GCMs. Over the southwestern United States, Yang et al (2001) find significant deficiencies in a GCM simulation of the summertime North American monsoon.…”

Section: Introductionmentioning

confidence: 99%

LGM Summer Climate on the Southern Margin of the Laurentide Ice Sheet: Wet or Dry?*

et al. 2005

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Regional climate simulations are conducted using the Polar fifth-generation Pennsylvania State University (PSU)-NCAR Mesoscale Model (MM5) with a 60-km horizontal resolution domain over North America to explore the summer climate of the Last Glacial Maximum (LGM: 21 000 calendar years ago), when much of the continent was covered by the Laurentide Ice Sheet (LIS). Output from a tailored NCAR Community Climate Model version 3 (CCM3) simulation of the LGM climate is used to provide the initial and lateral boundary conditions for Polar MM5.LGM boundary conditions include continental ice sheets, appropriate orbital forcing, reduced CO 2 concentration, paleovegetation, modified sea surface temperatures, and lowered sea level.The simulated LGM summer climate is characterized by a pronounced low-level thermal gradient along the southern margin of the LIS resulting from the juxtaposition of the cold ice sheet and adjacent warm ice-free land surface. This sharp thermal gradient anchors the midtropospheric jet stream and facilitates the development of synoptic cyclones that track over the ice sheet, some of which produce copious liquid precipitation along and south of the LIS terminus. Precipitation on the southern margin is orographically enhanced as moist southerly low-level flow (resembling a contemporary Great Plains low-level jet configuration) in advance of the cyclone is drawn up the ice sheet slope. Composites of wet and dry periods on the LIS southern margin illustrate two distinctly different atmospheric flow regimes. Given the episodic nature of the summer rain events, it may be possible to reconcile the model depiction of wet conditions on the LIS southern margin during the LGM summer with the widely accepted interpretation of aridity across the Great Plains based on geological proxy evidence.

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“…Several mechanisms, such as thermal gradients over sloping terrains, planetary boundary layer (PBL) oscillations, 11 and land-surface features, have been proposed to explain LLJs immersed in a dormant environment. Large-scale forcing, such as the coupling of upper jet streams with LLJs, their interaction with convective activity, 12 and the synoptic and subsynoptic-scale environment, have been analyzed to explain observed events of the GPLLJ. 13 In the Americas, some of these jet streams, such as the Gulf of California (GC) LLJ, [14][15][16][17] the Chocó jet (CJ) in the eastern tropical Pacific (ETP), 18 and the GPLLJ, have been intensively studied through observations 3,4,16,17,[19][20][21] and numerical studies.…”

Section: Introductionmentioning

confidence: 99%

The Intra‐Americas Sea Low‐level Jet

Amador

2008

Annals of the New York Academy of Sciences

202

225

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A relevant climate feature of the Intra-Americas Sea (IAS) is the low-level jet (IALLJ) dominating the IAS circulation, both in summer and winter; and yet it is practically unknown with regard to its nature, structure, interactions with mid-latitude and tropical phenomena, and its role in regional weather and climate. This paper updates IALLJ current knowledge and its contribution to IAS circulation-precipitation patterns and presents recent findings about the IALLJ based on first in situ observations during Phase 3 of the Experimento Climático en las Albercas de Agua Cálida (ECAC), an international field campaign to study IALLJ dynamics during July 2001. Nonhydrostatic fifth-generation Pennsylvania State University National Center for Atmospheric Research Mesoscale Model (MM5) simulations were compared with observations and reanalysis. Large-scale circulation patterns of the IALLJ northern hemisphere summer and winter components suggest that trades, and so the IALLJ, are responding to land-ocean thermal contrasts during the summer season of each continent. The IALLJ is a natural component of the American monsoons as a result of the continent's approximate north-south land distribution. During warm (cold) El Niño-Southern Oscillation phases, winds associated with the IALLJ core (IALLJC) are stronger (weaker) than normal, so precipitation anomalies are positive (negative) in the western Caribbean near Central America and negative (positive) in the central IAS. During the ECAC Phase 3, strong surface winds associated with the IALLJ induced upwelling, cooling down the sea surface temperature by 1-2 degrees C. The atmospheric mixed layer height reached 1 km near the surface wind maximum below the IALLJC. Observations indicate that primary water vapor advection takes place in a shallow layer between the IALLJC and the ocean surface. Latent heat flux peaked below the IALLJC. Neither the reanalysis nor MM5 captured the observed thermodynamic and kinematic IALLJ structure. So far, IALLJ knowledge is based on either dynamically initialized data or simulations of global (regional) models, which implies that a more systematic and scientific approach is needed to improve it. The Intra-Americas Study of Climate Processes is a great regional opportunity to address trough field work, modeling, and process studies, many of the IALLJ unknown features.

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Airflow Configurations of Warm Season Southerly Low-Level Wind Maxima in the Great Plains. Part I: Spatial and Temporal Characteristics and Relationship to Convection

Cited by 41 publications

References 41 publications

Selection of climate information for regional climate change assessments using regionalization techniques: an example for the Upper Great Lakes Region, USA

Selection of climate information for regional climate change assessments using regionalization techniques: an example for the Upper Great Lakes Region, USA

LGM Summer Climate on the Southern Margin of the Laurentide Ice Sheet: Wet or Dry?*

The Intra‐Americas Sea Low‐level Jet

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