A 45‐Yr climatology of extratropical cyclone locations relative to upper‐level jet streak determined by an automatic procedure

2021 ◽  
Author(s):  
Jan Degirmendžić
Keyword(s):  
Extratropical Cyclone ◽  
Upper Level ◽  
Upper Level Jet ◽  
Jet Streak

scholarly journals TROCA ESTRATOSFERA-TROPOSFERA COMO UMA FONTE DE OZÔNIO PARA A CAMADA LIMITE PLANETÁRIA

2016 ◽  
Vol 38 ◽  
pp. 257
Author(s):  
Letícia De Oliveira dos Santos ◽  
Lucas Vaz Peres ◽  
Franciano Scremin Puhales ◽  
Vagner Anabor ◽  
Damaris Kirsch Pinheiro
Keyword(s):  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Lower Latitude ◽  
Jet Stream ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Upper Level ◽  
Upper Level Jet ◽  
Jet Streak ◽  
Total Column

Stratosphere-troposphere exchange (STE) events were identified over southern Brazil acting as a stratospheric ozone source to the Planetary Boundary Layer (PBL) during 2011-2013 period. There were 13 events with direct influence between 29° and 31° S (center of Rio Grande do Sul), with increase in ozone total column. In these cases, 4 occurred in 2011, 5 in 2012 and 4 in 2013. They were divided: in relation to the exchange latitude, the upper-level Jet Stream act, altitude of source and arrive of air parcels. The air parcels cross the tropopause between 120 and 320 hPa (dynamic tropopause), entering troposphere until the lower troposphere. Most cases (30,8%) reached 1000 hPa and the rest between 600 and 900 hPa. Just in one day the STE occurred in a lower latitude than 29° S; in all the other days (92,3%), STEs occurred in higher latitudes than 31° S (the closer it gets to the pole, the bigger is the ozone concentration, except in Ozone Hole Influence events) or between 29° and 31° S. In most cases (61,5%) it was observed STE along with the Jet Streak act.

scholarly journals Synoptic-Scale and Mesoscale Environments Conducive to Forest Fires during the October 2003 Extreme Fire Event in Southern California

2009 ◽  
Vol 48 (3) ◽  
pp. 553-579 ◽  
Author(s):  
Chenjie Huang ◽  
Y-L. Lin ◽  
M. L. Kaplan ◽  
J. J. Charney
Keyword(s):  
Forest Fires ◽  
Wave Breaking ◽  
Southern California ◽  
Synoptic Scale ◽  
Fire Event ◽  
Dry Air ◽  
Upper Level ◽  
Upper Level Jet ◽  
Wave Induced ◽  
Jet Streak

Abstract This study has employed both observational data and numerical simulation results to diagnose the synoptic-scale and mesoscale environments conducive to forest fires during the October 2003 extreme fire event in southern California. A three-stage process is proposed to illustrate the coupling of the synoptic-scale forcing that is evident from the observations, specifically the high pressure ridge and the upper-level jet streak, which leads to meso-α-scale subsidence in its exit region, and the mesoscale forcing that is simulated by the numerical model, specifically the wave breaking and turbulence as well as the wave-induced critical level, which leads to severe downslope (Santa Ana) winds. Two surges of dry air were found to reach the surface in southern California as revealed in the numerical simulation. The first dry air surge arrived as a result of moisture divergence and isallobaric adjustments behind a surface cold front. The second dry air surge reached southern California as the meso-α- to meso-β-scale subsidence and the wave-induced critical level over the coastal ranges phased to transport the dry air from the upper-level jet streak exit region toward the surface and mix the dry air down to the planetary boundary layer on the lee side of the coastal ranges in southern California. The wave-breaking region on the lee side acted as an internal boundary to reflect the mountain wave energy back to the ground and created severe downslope winds through partial resonance with the upward-propagating mountain waves.

scholarly journals Synoptic-Scale Environments of Predecessor Rain Events Occurring East of the Rocky Mountains in Association with Atlantic Basin Tropical Cyclones*

2013 ◽  
Vol 141 (3) ◽  
pp. 1022-1047 ◽  
Author(s):  
Benjamin J. Moore ◽  
Lance F. Bosart ◽  
Daniel Keyser ◽  
Michael L. Jurewicz
Keyword(s):  
Tropical Cyclones ◽  
Rocky Mountains ◽  
Composite Analysis ◽  
Synoptic Scale ◽  
Atlantic Basin ◽  
Upper Level ◽  
Rain Events ◽  
Upper Level Jet ◽  
Jet Streak ◽  
Baroclinic Zone

Abstract The synoptic-scale environments of predecessor rain events (PREs) occurring to the east of the Rocky Mountains in association with Atlantic basin tropical cyclones (TCs) are examined. PREs that occurred during 1988–2010 are subjectively classified based upon the synoptic-scale upper-level flow configuration within which the PRE develops, with a focus on the following: 1) the position of the jet streak relative to the TC, 2) the position of the jet streak relative to trough and ridge axes, and 3) the positions of trough and ridge axes relative to the PRE and to the TC. Three categories were identified from this classification procedure: “jet in ridge,” “southwesterly jet,” and “downstream confluence.” PRE-relative composite analysis for each category reveals that, consistent with previous studies, PREs typically occur near a low-level baroclinic zone, beneath the equatorward entrance region of an upper-level jet streak, and in the presence of a stream of water vapor from a TC. Despite these common characteristics, key differences exist among the three PRE categories related to the phasing of a TC with the synoptic-scale flow and to the interactions between a TC and its environment. Brief case studies of PREs associated with TC Rita (2005), TC Wilma (2005), and TC Ernesto (2006) are presented as specific examples of the three PRE categories.

Multiscale aspects of the 26–27 April 2011 tornado outbreak. Part II: Environmental modifications and upscale feedbacks arising from latent processes

2021 ◽  
Author(s):  
Manda B. Chasteen ◽  
Steven E. Koch
Keyword(s):  
Large Scale ◽  
Vertical Wind Shear ◽  
Convective Systems ◽  
Upper Level ◽  
Large Scale Flow ◽  
Jet Streaks ◽  
Upper Level Jet ◽  
Jet Structure ◽  
Tornado Outbreaks ◽  
Jet Streak

AbstractOne of the most prolific tornado outbreaks ever documented occurred on 26–27 April 2011 and comprised three successive episodes of tornadic convection that culminated with the development of numerous long-track, violent tornadoes over the southeastern U.S. during the afternoon of 27 April. This notorious afternoon supercell outbreak was preceded by two quasi-linear convective systems (hereafter QLCS1 and QLCS2), the first of which was an anomalously severe nocturnal system that rapidly grew upscale during the previous evening. In this Part II, we use a series of RUC 1-h forecasts and output from convection-permitting WRF-ARW simulations configured both with and without latent heat release to investigate how environmental modifications and upscale feedbacks produced by the two QLCSs contributed to the evolution and exceptional severity of this multi-episode outbreak.QLCS1 was primarily responsible for amplifying the large-scale flow pattern, inducing two upper-level jet streaks, and promoting secondary surface cyclogenesis downstream from the primary baroclinic system. Upper-level divergence markedly increased after QLCS1 developed, which yielded strong isallobaric forcing that rapidly strengthened the low-level jet (LLJ) and vertical wind shear over the warm sector and contributed to the system’s upscale growth and notable severity. Moreover, QLCS2 modified the mesoscale environment prior to the supercell outbreak by promoting the downstream formation of a pronounced upper-level jet streak, altering the midlevel jet structure, and furthering the development of a highly ageostrophic LLJ over the Southeast. Collectively, the flow modifications produced by both QLCSs contributed to the notably favorable shear profiles present during the afternoon supercell outbreak.

scholarly journals Climatology of Storm Reports Relative to Upper-Level Jet Streaks

2009 ◽  
Vol 24 (4) ◽  
pp. 1032-1051 ◽  
Author(s):  
Adam J. Clark ◽  
Christopher J. Schaffer ◽  
William A. Gallus ◽  
Kaj Johnson-O’Mara
Keyword(s):  
Vertical Velocity ◽  
Conceptual Models ◽  
Temporal Trends ◽  
Vertical Motion ◽  
Upper Level ◽  
Jet Streaks ◽  
Upper Level Jet ◽  
Four Quadrant ◽  
The Right ◽  
Jet Streak

Abstract Using quasigeostrophic arguments and numerical simulations, past works have developed conceptual models of vertical circulations induced by linear and curved jet streaks. Because jet-induced vertical motion could influence the development of severe weather, these conceptual models, especially the “four quadrant” model for linear jet streaks, are often applied by operational forecasters. The present study examines the climatology of tornado, hail, and severe wind reports relative to upper-level jet streaks, along with temporal trends in storm report frequencies and changes in report distributions for different jet streak directions. In addition, composite fields (e.g., divergence, vertical velocity) are analyzed for jet streak regions to examine whether the fields correspond to what is expected from conceptual models of curved or linear jet streaks, and whether the fields help explain the storm report distributions. During the period analyzed, 84% of storm reports were associated with upper-level jet streaks, with June–August having the lowest percentages. In March and April the left-exit quadrant had the most storm reports, while after April the right-entrance quadrant was associated with the most reports. Composites revealed that tornado and hail reports are concentrated in the jet-exit region along the major jet axis and in the right-entrance quadrant. Wind reports have similar maxima, but the right-entrance quadrant maximum is more pronounced. Upper-level composite divergence fields generally correspond to what would be expected from the four-quadrant model, but differences in the magnitudes of the vertical velocity between the quadrants and locations of divergent–convergent centers may have resulted from jet curvature. The maxima in the storm report distributions are not well collocated with the maxima in the upper-level divergence fields, but are much better collocated with low-level convergence maxima that exist in both exit regions and extend into the right-entrance region. Composites of divergence–convergence with linear, cyclonic, and anticyclonic jet streaks also generally matched conceptual models for curved jet streaks, and it was found that wind reports have a notable maximum in the right-entrance quadrant of both anticyclonic and linear jet streaks. Finally, it was found that the upper-level divergence and vertical velocity in all jet-quadrants have a tendency to decrease as jet streak directions shift from SSW to NNW.

scholarly journals The Dynamic and Thermodynamic Structures Associated with a Series of Heavy Precipitation Events over China during January 2008

2010 ◽  
Vol 25 (4) ◽  
pp. 1124-1141 ◽  
Author(s):  
Xiaohui Shi ◽  
Xiangde Xu ◽  
Chungu Lu
Keyword(s):  
Large Scale ◽  
East Coast ◽  
Heavy Precipitation ◽  
Chinese History ◽  
Physical Processes ◽  
Ice Storms ◽  
Upper Level ◽  
Upper Level Jet ◽  
The Western Pacific ◽  
Precipitation Events

Abstract In the winter of 2008, China experienced once-in-50-yr (or once in 100 yr for some regions) snow and ice storms. These storms brought huge socio economical impacts upon the Chinese people and government. Although the storms had been predicted, their severity and persistence were largely underestimated. In this study, these cases were revisited and comprehensive analyses of the storms’ dynamic and thermodynamic structures were conducted. These snowstorms were also compared with U.S. east coast snowstorms. The results from this study will provide insights on how to improve forecasts for these kinds of snowstorms. The analyses demonstrated that the storms exhibited classic patterns of large-scale circulation common to these types of snowstorms. However, several physical processes were found to be unique and thought to have played crucial roles in intensifying and prolonging China’s great snowstorms of 2008. These include a subtropical high over the western Pacific, an upper-level jet stream, and temperature and moisture inversions. The combined effects of these dynamic and thermodynamic structures are responsible for the development of the storms into one of the most disastrous events in Chinese history.

scholarly journals Association of the Poleward Shift of East Asian Subtropical Upper-Level Jet with Frequent Tropical Cyclone Activities over the Western North Pacific in Summer

2017 ◽  
Vol 30 (14) ◽  
pp. 5597-5603 ◽  
Author(s):  
Xian Chen ◽  
Zhong Zhong ◽  
Wei Lu
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
East Asian ◽  
Teleconnection Pattern ◽  
Reanalysis Dataset ◽  
Poleward Shift ◽  
Upper Level ◽  
Upper Level Jet

The NCEP–NCAR reanalysis dataset and the tropical cyclone (TC) best-track dataset from the Regional Specialized Meteorological Center (RSMC) Tokyo Typhoon Center were employed in the present study to investigate the possible linkage of the meridional displacement of the East Asian subtropical upper-level jet (EASJ) with the TC activity over the western North Pacific (WNP). Results indicate that summertime frequent TC activities would create the poleward shift of the EASJ through a stimulated Pacific–Japan (PJ) teleconnection pattern as well as the changed large-scale meridional temperature gradient. On the contrary, in the inactive TC years, the EASJ is often located more southward than normal with an enhanced intensity. Therefore, TC activities over the WNP are closely related to the location and intensity of the EASJ in summer at the interannual time scale.

Multiscale aspects of the 26–27 April 2011 tornado outbreak. Part I: Outbreak chronology and environmental evolution

2021 ◽  
Author(s):  
Manda B. Chasteen ◽  
Steven E. Koch
Keyword(s):  
Mississippi Valley ◽  
Environmental Evolution ◽  
Rossby Wave Breaking ◽  
Convective Systems ◽  
South Central ◽  
Rapid Flow ◽  
Low Level Jet ◽  
Upper Level ◽  
Tornado Outbreaks ◽  
Jet Streak

AbstractOne of the most prolific tornado outbreaks ever documented occurred on 26–27 April 2011 and comprised three successive episodes of tornadic convection that primarily impacted the southeastern U.S., including two quasi-linear convective systems (hereafter QLCS1 and QLCS2) that preceded the notorious outbreak of long-track, violent tornadoes spawned by numerous supercells on the afternoon of 27 April. The ~36-h period encompassing these three episodes was part of a longer multiday outbreak that occurred ahead of a slowly moving upper-level trough over the Rocky Mountains. In this Part I, we detail how the environment evolved to support this extended outbreak, with particular attention given to the three successive systems that each exhibited a different morphology and severity.The amplifying upper-level trough and attendant jet streak resulted from a Rossby wave breaking event that yielded a complex tropopause structure and supported three prominent shortwave troughs that sequentially moved into the south-central U.S. QLCS1 formed ahead of the second shortwave and was accompanied by rapid flow modifications, including considerable low-level jet (LLJ) intensification. The third shortwave moved into the lee of the Rockies early on 27 April to yield destabilization behind QLCS1 and support the formation of QLCS2, which was followed by further LLJ intensification and helped to establish favorable deep-layer shear profiles over the warm sector. The afternoon supercell outbreak commenced following the movement of this shortwave into the Mississippi Valley, which was attended by a deep tropopause fold, cold front aloft, and dryline that promoted two prominent bands of tornadic supercells over the Southeast.

scholarly journals Polar Winds: Airborne Doppler Wind Lidar Missions in the Arctic for Atmospheric Observations and Numerical Model Comparisons

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1141
Author(s):  
Steven Greco ◽  
George D. Emmitt ◽  
Alice DuVivier ◽  
Keith Hines ◽  
Michael Kavaya
Keyword(s):  
Wrf Model ◽  
The Arctic ◽  
Weather Research And Forecasting ◽  
Dynamic Features ◽  
Wind Retrieval ◽  
Atmospheric Observations ◽  
Wind Lidar ◽  
Upper Level ◽  
Upper Level Jet ◽  
Doppler Wind Lidar

During October–November 2014 and May 2015, NASA sponsored and conducted a pair of airborne campaigns called Polar Winds to investigate atmospheric circulations, particularly in the boundary layer, over the Arctic using NASA’s Doppler Aerosol WiNd (DAWN) lidar. A description of the campaigns, the DAWN instrument, wind retrieval methods and data processing is provided. During the campaigns, the DAWN instrument faced backscatter sensitivity issues in the low aerosol conditions that were fairly frequent in the 2–6 km altitude range. However, when DAWN was able to make measurements, comparisons with dropsondes show good agreement and very low bias and supports the use of an airborne Doppler wind lidar such as DAWN that can provide profiles with high velocity precision, ~65 m vertical resolution and horizontal spacing as fine as 3–7 km. Case study analyses of a Greenland tip jet, barrier winds and an upper level jet are presented and show how, despite sensitivity issues, DAWN data can be confidently used in diagnostic studies of dynamic features in the Arctic. Comparisons with both an operational and research Weather Research and Forecasting (WRF) model for these events also show the potential for utilization in model validation. The sensitivity issues of the DAWN laser have since been corrected.

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