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.

scholarly journals Rossby wave breaking, the upper level jet, and serial clustering of extratropical cyclones in western Europe

2017 ◽  
Vol 44 (1) ◽  
pp. 514-521 ◽  
Author(s):  
Matthew D. K. Priestley ◽  
Joaquim G. Pinto ◽  
Helen F. Dacre ◽  
Len C. Shaffrey
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Western Europe ◽  
Extratropical Cyclones ◽  
Rossby Wave Breaking ◽  
Upper Level ◽  
Upper Level Jet

scholarly journals A global climatological perspective on the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events

2021 ◽  
Author(s):  
Andries Jan De Vries
Keyword(s):  
Rossby Wave ◽  
Extreme Precipitation ◽  
Wave Breaking ◽  
Moisture Transport ◽  
Synoptic Scale ◽  
Rossby Wave Breaking ◽  
Extreme Precipitation Events ◽  
The World ◽  
Upper Level ◽  
Precipitation Events

<p>Extreme precipitation events (EPEs) frequently cause flooding with dramatic socioeconomic impacts in many parts of the world. Previous studies considered two synoptic-scale processes, Rossby wave breaking and intense moisture transport, typically in isolation, and their linkage to such EPEs in several regions. This study presents for the first time a global and systematic climatological analysis of these two synoptic-scale processes, in tandem and in isolation, for the occurrence of EPEs. To this end, we use 40-year ERA-Interim reanalysis data (1979-2018) and apply object-based identification methods for (i) daily EPEs, (ii) stratospheric potential vorticity (PV) streamers as indicators of Rossby wave breaking, and (iii) structures of high vertically integrated horizontal water vapor transport (IVT). First, the importance of these two synoptic-scale processes is demonstrated by case studies of previously documented flood events that inflicted catastrophic impacts in different parts of the world. Next, a climatological quantification shows that Rossby wave breaking is associated with > 90 % of EPEs near high topography and over the Mediterranean, whereas intense moisture transport is linked to > 95 % of EPEs over many coastal zones, consistent with findings of atmospheric river-related studies. Combined Rossby wave breaking and intense moisture transport contributes up to 70 % of EPEs in several subtropical and extratropical regions, including (semi)arid desert regions where tropical-extratropical interactions are of key importance for (heavy) rainfall. A detailed analysis shows that five categories with different combinations of wave breaking and intense moisture transport can reflect a large range of EPE-related weather systems across various climate zones. Odds ratios of EPEs linked to the two synoptic-scale processes suggest that intense moisture transport is stronger associated with the occurrence of EPEs than wave breaking. Furthermore, the relationship between the PV and IVT characteristics and the precipitation volumes shows that the depth of the wave breaking and moisture transport intensity are intimately connected with the extreme precipitation severity. Finally, composites reveal that subtropical and extratropical EPEs, linked to Rossby wave breaking, go along with the formation of upper-level troughs and cyclogenetic processes near the surface downstream, reduced static stability beneath the upper-level forcing (only over water), and dynamical lifting ahead (over water and land). This study concludes with a concept that reconciles well-established meteorological principles with the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events. The findings of this study may contribute to an improved understanding of the atmospheric processes that lead to EPEs, and may find application in climatic studies on extreme precipitation changes in a warming climate.</p>

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 Multiscale Dynamics of the February 11-12, 2010, Deep South US Snowstorm Event

2017 ◽  
Vol 2017 ◽  
pp. 1-26
Author(s):  
Stephany M. Taylor ◽  
Michael L. Kaplan ◽  
Yuh-Lang Lin
Keyword(s):  
Surface Flux ◽  
Surface Fluxes ◽  
Deep South ◽  
Synoptic Scale ◽  
Orographic Effects ◽  
Southern Us ◽  
Multiscale Dynamics ◽  
Heating Effects ◽  
Upper Level ◽  
Upper Level Jet

This study investigates the synoptic/mesoscale dynamics responsible for an unusually heavy southern US snowstorm that occurred on February 11-12, 2010, using reanalysis, observations, and numerical simulations. This record breaking snowfall event represents an example of multiple upper level and low-level jets (LLJs) and their accompanying baroclinic zones. The analysis reveals the following synoptic scale processes as significant contributors: (1) upper level jet splitting and merging, (2) advection of cold arctic air at low levels by a large anticyclone, and (3) an incoming upper level shortwave trough. In addition to the synoptic scale processes, the following mesoscale features played a major role in this snowstorm event: coexisting potential (convective) instability and conditional symmetric instability, terrain blocking, and a double LLJ development process. Sensitivity experiments including (1) limiting the orographic effects of elevated plateau in Texas and the Sierra Madre Mountains in Mexico by reducing the terrain height to 225 meters, (2) the microphysics/latent heating effects, and (3) surface fluxes on the development and intensity of the snowstorm were also conducted by turning these options off in the numerical model. Of all three experiments, the surface flux experiment displays the least amount of influence on the developing frozen precipitation bands.

Synergistic Interactions between an Upper-Level Jet Streak and Diabatic Processes that Influence the Development of a Low-Level Jet and a Secondary Coastal Cyclone

1987 ◽  
Vol 115 (10) ◽  
pp. 2227-2261 ◽  
Author(s):  
Louis W. Uccellini ◽  
Ralph A. Petersen ◽  
Paul J. Kocin ◽  
Keith F. Brill ◽  
James J. Tuccillo
Keyword(s):  
Low Level ◽  
Synergistic Interactions ◽  
Diabatic Processes ◽  
Low Level Jet ◽  
Upper Level ◽  
Upper Level Jet ◽  
Jet Streak

scholarly journals A global climatological perspective on the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events

2020 ◽  
Author(s):  
Andries Jan De Vries
Keyword(s):  
Rossby Wave ◽  
Extreme Precipitation ◽  
Wave Breaking ◽  
Moisture Transport ◽  
Synoptic Scale ◽  
Rossby Wave Breaking ◽  
Extreme Precipitation Events ◽  
Upper Level ◽  
High Topography ◽  
Precipitation Events

Abstract. Extreme precipitation events (EPEs) cause frequently flooding with dramatic socioeconomic impacts in many parts of the world. Previous studies considered two synoptic-scale processes, Rossby wave breaking and intense moisture transport, typically in isolation, and their linkage to such EPEs in several regions. This study presents for the first time a global and systematic climatological analysis of these two synoptic-scale processes, in tandem and in isolation, for the occurrence of EPEs. To this end, we use 40-year ERA-Interim reanalysis data (1979–2018) and apply object-based identification methods for (i) daily EPEs, (ii) stratospheric potential vorticity (PV) streamers as indicators of Rossby wave breaking, and (iii) structures of high vertically integrated horizontal water vapor transport (IVT). First, the importance of these two processes is demonstrated by case studies of previously documented flood events that inflicted catastrophic impacts in different parts of the world. Next, a climatological quantification shows that Rossby wave breaking is associated with > 90 % of EPEs near high topography and over the Mediterranean, intense moisture transport is linked to > 90 % of EPEs over many coastal zones, and their combined occurrence contributes to > 70 % of EPEs in several subtropical and extratropical regions. A more detailed analysis shows that a majority of EPEs associated with (1) only Rossby wave breaking are confined to higher-latitude regions that are deprived from remote moisture supplies by high topography and deserts, (2) only intense moisture transport are found circumglobally at the outer tropics, associated with tropical cyclones, tropical easterly waves, and monsoon lows, (3) combined Rossby wave breaking and intense moisture transport dominate a large part of the globe, in particular over dry subtropical regions where tropical-extratropical interactions are of key relevance, (4) remote, far upstream Rossby wave breaking and intense moisture transport occur over mountainous extratropical west coasts, reminiscent of landfalling atmospheric rivers, and (5) neither of the two synoptic-scale processes are concentrated over the inner tropics and high topography at lower latitudes, where EPEs arise under the influence of local forcing. Accordingly, different combinations of wave breaking and intense moisture transport can reflect a large range of weather systems with relevance to EPEs across various climate zones. Furthermore, the relationship between the PV and IVT characteristics and the precipitation volumes shows that the strength of the wave breaking and moisture transport intensity are intimately connected with the extreme precipitation severity. Finally, composites reveal that subtropical and extratropical EPEs, linked to Rossby wave breaking, go along with the formation of upper-level troughs and cyclogenetic processes near the surface downstream, reduced static stability beneath the upper-level forcing (only over water), and dynamical lifting ahead (over water and land). This study concludes with a concept that reconciles well-established meteorological principles with the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events. The findings of this study may contribute to an improved understanding of the atmospheric processes that lead to EPEs, and may find application in climatic studies on extreme precipitation changes in a warming climate.

scholarly journals The Multi-Scale Dynamics Organizing a Favorable Environment for Convective Density Currents That Redirected the Yarnell Hill Fire

Climate ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 170
Author(s):  
Michael L. Kaplan ◽  
Curtis N. James ◽  
Jan Ising ◽  
Mark R. Sinclair ◽  
Yuh-Lang Lin ◽  
...  
Keyword(s):  
Vertical Wind Shear ◽  
Density Currents ◽  
Intermountain West ◽  
Synoptic Scale ◽  
Direct Flow ◽  
Multi Scale ◽  
Gust Fronts ◽  
Upper Level ◽  
Jet Streak ◽  
Wave Break

The deadly shift of the Yarnell Hill, Arizona wildfire was associated with an environment exhibiting gusty wind patterns in response to organized convectively driven circulations. The observed synoptic (>2500 km) through meso-β (approximately 100 km) scale precursor environment that organized a mid-upper tropospheric cross-mountain mesoscale jet streak circulation and upslope thermally direct flow was examined. Numerical simulations and observations indicated that both circulations played a key role in focusing the upper-level divergence, ascent, downdraft potential, vertical wind shear favoring mobile convective gust fronts, and a microburst. This sequence was initiated at the synoptic scale by a cyclonic Rossby Wave Break (RWB) 72 h prior, followed by an anticyclonic RWB. These RWBs combined to produce a mid-continent baroclinic trough with two short waves ushering in cooler air with the amplifying polar jet. Cool air advection with the second trough and surface heating across the Intermountain West (IW) combined to increase the mesoscale pressure gradient, forcing a mid-upper tropospheric subsynoptic jet around the periphery of the upstream ridge over Southern Utah and Northern New Mexico. Convection was triggered by an unbalanced secondary jetlet circulation within the subsynoptic jet in association with a low-level upslope flow accompanying a mountain plains solenoidal circulation above the Mogollon Rim (MR) and downstream mountains.

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.

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