scholarly journals Increased turbulence in the Eurasian upper‐level jet stream in winter: past and future

2020 ◽  
Author(s):  
Yanmin Lv ◽  
Jianping Guo ◽  
Jian Li ◽  
Yi Han ◽  
Hui Xu ◽  
...  
Keyword(s):  
Jet Stream ◽  
Upper Level ◽  
Upper Level Jet

scholarly journals Potential Vorticity Diagnosis of the Severe Convective Regime. Part II: The Impact of Idealized PV Anomalies

2008 ◽  
Vol 136 (5) ◽  
pp. 1582-1592 ◽  
Author(s):  
John W. Nielsen-Gammon ◽  
David A. Gold
Keyword(s):  
Potential Vorticity ◽  
Severe Weather ◽  
Jet Stream ◽  
Balance Equations ◽  
Upper Level ◽  
Height Fields ◽  
Upper Level Jet ◽  
The Impact ◽  
Analysis Errors ◽  
Pv Gradient

Abstract Idealized numerical experiments are conducted to understand the effect of upper-tropospheric potential vorticity (PV) anomalies on an environment conducive to severe weather. Anomalies are specified as a single isolated vortex, a string of vortices analogous to a negatively tilted trough, and a pair of string vortices analogous to a position error in a negatively tilted trough. The anomalies are placed adjacent to the tropopause along a strong upper-level jet at a time just prior to a major tornado outbreak and inverted using the nonlinear balance equations. In addition to the expected destabilization beneath and adjacent to a cyclonic PV anomaly, the spatial pattern of the inverted balanced streamfunction and height fields is distorted by the presence of the horizontal PV gradient along the upper-tropospheric jet stream. Streamfunction anomalies are elongated in the cross-jet direction, while height and temperature anomalies are elongated in the along-jet direction. The amplitude of the inverted fields, as well as the changes in CAPE associated with the inverted temperature perturbations, are linearly proportional to the amplitudes of the PV anomalies themselves, and the responses to complex PV perturbation structures are approximated by the sum of the responses to individual simple PV anomalies. This is true for the range of PV amplitudes tested, which was designed to mimic typical 6-h forecast or analysis errors and produced changes in CAPE beneath the trough of well over 100 J kg−1. Impacts on inverted fields are largest when the PV anomaly is on the anticyclonic shear side of the jet, where background PV is small, compared with the cyclonic shear side of the jet, where background PV is large.

scholarly journals Characteristics of Explosive Cyclones over the Northern Pacific

2017 ◽  
Vol 56 (12) ◽  
pp. 3187-3210 ◽  
Author(s):  
Shuqin Zhang ◽  
Gang Fu ◽  
Chungu Lu ◽  
Jingwu Liu
Keyword(s):  
Cold Season ◽  
Early Spring ◽  
Occurrence Frequency ◽  
Northwestern Pacific ◽  
Jet Stream ◽  
Central Pacific ◽  
Positive Vorticity ◽  
Northern Pacific ◽  
Upper Level ◽  
Upper Level Jet

AbstractExplosive cyclones (ECs) over the northern Pacific Ocean during the cold season (October–April) over a 15-yr (2000–15) period are analyzed by using the Final (FNL) Analysis data provided by the National Centers for Environmental Prediction. These ECs are stratified into four categories according to their intensity: weak, moderate, strong, and super ECs. In addition, according to the spatial distribution of their maximum-deepening-rate positions, ECs are further classified into five regions: the Japan–Okhotsk Sea (JOS), the northwestern Pacific (NWP), the west-central Pacific (WCP), the east-central Pacific (ECP), and the northeastern Pacific (NEP). The occurrence frequency of ECs shows evident seasonal variations for the various regions over the northern Pacific. NWP ECs frequently occur in winter and early spring, WCP and ECP ECs frequently occur in winter, and JOS and NEP ECs mainly occur in autumn and early spring. The occurrence frequency, averaged maximum deepening rate, and developing and explosive-developing lifetimes of ECs decrease eastward over the northern Pacific, excluding JOS ECs, consistent with the climatological intensity distributions of the upper-level jet stream, midlevel positive vorticity, and low-level baroclinicity. On the seasonal scale, the occurrence frequency and spatial distribution of ECs are highly correlated with the intensity and position of the upper-level jet stream, respectively, and also with those of midlevel positive vorticity and low-level baroclinicity. Over the northwestern Pacific, the warm ocean surface also contributes to the rapid development of ECs. The composite analysis indicates that the large-scale atmospheric environment for NWP and NEP ECs shows significant differences from that for the 15-yr cold-season average. The southwesterly anomalies of the upper-level jet stream and positive anomalies of midlevel vorticity favor the prevalence of NWP and NEP ECs.

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 Effect of Mid-Latitude Jet Stream on the Intensity of Tropical Cyclones Affecting Korea: Observational Analysis and Implication from the Numerical Model Experiments of Typhoon Chaba (2016)

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1061
Author(s):  
Gunwoo Do ◽  
Hyeong-Seog Kim
Keyword(s):  
Tropical Cyclones ◽  
Vertical Wind Shear ◽  
Jet Stream ◽  
Rapid Reduction ◽  
Large Intensity ◽  
Intensity Changes ◽  
Secondary Circulations ◽  
Upper Level ◽  
Numerical Model Experiments ◽  
Upper Level Jet

The effect of the jet stream on the changes in the intensity of tropical cyclones (TC) affecting Korea is discussed. We classified the TCs into three categories based on the decreasing rate of TC intensity in 24 h after TC passed 30° N. The TCs with a large intensity decrease had a more vigorous intensity when the TCs approached the mid-latitudes. The analysis of observational fields showed that the strong jet stream over Korea and Japan may intensify TCs by the secondary circulations of jet entrance but induces a large decrease in TC intensity in the mid-latitudes by the strong vertical wind shear. We also performed the numerical simulation for the effect of the jet stream on the intensity changes of Typhoon Chaba (2016). As a result, the stronger jet stream induced more low-level moisture convergence at the south of the jet stream entrance, enhancing the intensity when the TC approached Korea. Furthermore, it induced a rapid reduction in intensity when TC approached in the strong jet stream area. The results suggest that the upper-level jet stream is one of the critical factors modulating the intensity of TC affecting Korea in the vicinity of the mid-latitudes.

scholarly journals Derecho and MCS Development, Evolution, and Multiscale Interactions during 3–5 July 2003

2010 ◽  
Vol 138 (8) ◽  
pp. 3048-3070 ◽  
Author(s):  
Nicholas D. Metz ◽  
Lance F. Bosart
Keyword(s):  
Gravity Wave ◽  
Cold Pool ◽  
Jet Stream ◽  
Surface Boundary ◽  
Initial Surface ◽  
Synoptic Scale ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Upper Level ◽  
Upper Level Jet

Abstract From 3 to 5 July 2003 during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX), multiple mesoscale convective systems (MCSs 1 and 2) and derechos (derechos AN, AS, A, BW, and BE) progressed across a preferred upper Midwest corridor. The derechos evolved in a favorable synoptic-scale environment. However, the environmental details associated with each derecho, such as the characteristics of the initial surface boundary, the formation position relative to the upper-level jet stream, the presence of an upper-level mesoscale disturbance, and the CAPE/shear environment varied from derecho to derecho. The MCSs and derechos composed three distinct convective episodes. Multiple mesoscale interactions between the MCSs and derechos and the environment altered the character and longevity of these episodes. The first convective episode consisted of derecho A, which formed from merging derechos AN and AS (northern and southern systems, respectively). The ∼200-hPa-deep cold pool associated with derecho A decreased surface potential temperatures by 4–8 K. MCS 1 dissipated upon entering this cold pool and an inertia–gravity wave was emitted that helped to spawn MCS 2. This inertia–gravity wave connected MCSs 1 and 2 into a compound convective episode. As derecho BW (western system) approached a strong surface boundary across Iowa created by the cold pools of derecho A and MCS 1, derecho BE (eastern system) formed. The remnants of derecho BW merged with derecho BE creating another compound convective episode. The upscale effects resulting from this active convective period directly affected subsequent convective development. Upper-level diabatic heating associated with derecho A resulted in NCEP GFS 66-h negative 1000–500-hPa thickness errors of 4–8 dam (forecast too cold) and negative 200-hPa wind errors of 10–20 m s−1 (forecast too weak). The resulting stronger than forecast 200-hPa jet stream likely increased synoptic-scale forcing for the formation and evolution of derecho BW.

scholarly journals Increased shear in the North Atlantic upper-level jet stream over the past four decades

Nature ◽  
2019 ◽  
Vol 572 (7771) ◽  
pp. 639-642 ◽  
Author(s):  
Simon H. Lee ◽  
Paul D. Williams ◽  
Thomas H. A. Frame
Keyword(s):  
North Atlantic ◽  
Jet Stream ◽  
The Past ◽  
The North ◽  
The North Atlantic ◽  
Upper Level ◽  
Upper Level Jet

First observations of Kelvin-Helmholtz billows in an upper level jet stream using VHF frequency domain interferometry

Radio Science ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 1149-1160 ◽  
Author(s):  
Phillip B. Chilson ◽  
Andreas Muschinski ◽  
Gerhard Schmidt
Keyword(s):  
Frequency Domain ◽  
Jet Stream ◽  
Upper Level ◽  
Upper Level Jet
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