An Evaluation of Some Condensation Trail Observations

1955 ◽  
Vol 36 (2) ◽  
pp. 73-79
Author(s):  
Hal H. Dunning ◽  
N. E. La Seur
Keyword(s):  
Lower Stratosphere ◽  
Theoretical Work ◽  
Polar Front ◽  
Jet Streams ◽  
Upper Troposphere ◽  
Subtropical Jet ◽  
Synoptic Features ◽  
Trail Formation ◽  
Polar Front Jet

Observations made on ten routine B-47 training missions are used to evaluate present theoretical work on formation of exhaust condensation trails, and these observations are then correlated with the structure of the upper troposphere and lower stratosphere, to determine synoptic features typically associated with favorable and unfavorable conditions for trail formation For the altitudes considered broad areas of trail formation were found to occur only between the polar front and the sub-tropical jet streams. Broad areas unfavorable to trail formation were found to be located on the cyclonic shear side of the polar front jet and on the anticyclonic shear side of the subtropical jet. Agreement between these observations and theory is good.

scholarly journals The Impact of the East Asian Subtropical Jet and Polar Front Jet on the Frequency of Spring Persistent Rainfall over Southern China in 1997–2011

2015 ◽  
Vol 28 (15) ◽  
pp. 6054-6066 ◽  
Author(s):  
Dan-Qing Huang ◽  
Jian Zhu ◽  
Yao-Cun Zhang ◽  
Jun Wang ◽  
Xue-Yuan Kuang
Keyword(s):  
Water Vapor ◽  
Southern China ◽  
East Asian ◽  
Lower Troposphere ◽  
Polar Front ◽  
Remarkable Feature ◽  
Upper Troposphere ◽  
Subtropical Jet ◽  
The Impact ◽  
Polar Front Jet

Abstract Spring persistent rainfall (SPR) over southern China has great impact on its society and economics. A remarkable feature of the SPR is high frequency. However, SPR frequency obviously decreases over the period of 1997–2011. In this study, the possible causes have been investigated from the perspective of the individual and concurrent effects of the East Asian subtropical jet (EASJ) and East Asian polar front jet (EAPJ). A close relationship is detected between SPR frequency and EASJ intensity (but not EAPJ intensity). Associated with strong EASJ, abundant water vapor is transported to southern China by the southwesterly flow, which may trigger the SPR. Additionally, frequencies of both strong EASJ and weak EAPJ events are positively correlated with SPR frequency. Further investigation of the concurrent effect indicates a significant positive correlation between the frequencies of SPR and the strong EASJ–weak EAPJ configuration. Associated with this configuration, southwesterly flow strengthens in the lower troposphere, while northerly wind weakens in the upper troposphere. This provides a dynamic and moist condition, as enhanced ascending motion and intensified convergence of abundant water vapor over southern China, which favors the SPR. All analyses suggest that the EASJ may play a dominant role in the SPR occurrence and that the EAPJ may play a modulation role. Finally, a possible mechanism maintaining the strong EASJ–weak EAPJ configuration is proposed. Significant cooling over the northeastern Tibetan Plateau may induce a cyclone anomaly in the upper troposphere, which could result in an accelerating EASJ and a decelerating EAPJ.

scholarly journals Local Mixing Events in the Upper Troposphere and Lower Stratosphere. Part I: Detection with the Lyapunov Diffusivity

2009 ◽  
Vol 66 (12) ◽  
pp. 3678-3694 ◽  
Author(s):  
Francesco d’Ovidio ◽  
Emily Shuckburgh ◽  
Bernard Legras
Keyword(s):  
Lyapunov Exponent ◽  
Lower Stratosphere ◽  
Effective Diffusivity ◽  
Strong Mixing ◽  
Longitudinal Variation ◽  
Western Atlantic ◽  
Upper Troposphere ◽  
Subtropical Jet ◽  
Active Mixing ◽  
The Western Pacific

Abstract A new diagnostic (the “Lyapunov diffusivity”) is presented that has the ability to quantify isentropic mixing in diffusion units and detects local mixing events by describing latitude–longitude variability. It is a hybrid diagnostic, combining the tracer-based effective diffusivity with the particle-based Lyapunov exponent calculation. Isentropic mixing on the 350-K surface shows that there is significant longitudinal variation to the strength of mixing at the northern subtropical jet, with a strong mixing barrier over Asia and the western Pacific, a weaker mixing barrier over the western Atlantic, and active mixing regions at the jet exits over the eastern Pacific and Atlantic.

scholarly journals Study of Clear Air Turbulence Related to Tropopause Folding over the Romanian Airspace

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1099
Author(s):  
Sabina Ștefan ◽  
Bogdan Antonescu ◽  
Ana Denisa Urlea ◽  
Livius Buzdugan ◽  
Meda Daniela Andrei ◽  
...  
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Meteorological Data ◽  
Horizontal Temperature Gradient ◽  
Jet Streams ◽  
Mountain Waves ◽  
Upper Troposphere ◽  
Air Turbulence ◽  
Upper Level ◽  
Tropopause Folding

Clear air turbulence (CAT) poses a significant threat to aviation. CAT usually occurs in the lower stratosphere and the upper troposphere. It is generally associated with large scale waves, mountain waves, jet streams, upper-level fronts and tropopause folds. Aircraft can experience CAT when flying in proximity of a tropopause fold. To better understand and diagnose tropopause fold- associated CAT we selected a series of cases from among those reported by pilots between June 2017 and December 2018 in the Romanian airspace. Data on turbulence were used in conjunction with meteorological data, satellite imagery, and vertical profiles. Additionally, a set of indices as Ellrod, horizontal temperature gradient, Dutton, and Brown were computed to diagnose CAT associated with tropopause folding. These indices were also analyzed to test the physics mechanisms that may explain the occurrence of severe turbulence. Results show that out of the 420 cases announced by pilots, severe turbulence was reported in 80 cases of which 13 were associated with tropopause folding.

scholarly journals Global large-scale stratosphere–troposphere exchange in modern reanalyses

2017 ◽  
Vol 17 (9) ◽  
pp. 5537-5559 ◽  
Author(s):  
Alexander C. Boothe ◽  
Cameron R. Homeyer
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Radiative Properties ◽  
Lapse Rate ◽  
Polar Regions ◽  
Transport Mechanisms ◽  
Upper Troposphere ◽  
Subtropical Jet ◽  
The Tropics

Abstract. Stratosphere–troposphere exchange (STE) has important impacts on the chemical and radiative properties of the upper troposphere and lower stratosphere. This study presents a 15-year climatology of global large-scale STE from four modern reanalyses: ERA-Interim, JRA-55, MERRA-2, and MERRA. STE is separated into three regions (tropics, subtropics, and extratropics) and two transport directions (stratosphere-to-troposphere transport or STT and troposphere-to-stratosphere transport or TST) in an attempt to identify the significance of known transport mechanisms. The extratropics and tropics are separated by the tropopause break. Any STE occurring between the tropics and the extratropics through the tropopause break is considered subtropical exchange (i.e., in the vicinity of the subtropical jet). In addition, this study employs a method to identify STE as that which crosses the lapse-rate tropopause (LRT), while most previous studies have used a potential vorticity (PV) isosurface as the troposphere–stratosphere boundary. PV-based and LRT-based STE climatologies are compared using the ERA-Interim reanalysis output. The comparison reveals quantitative and qualitative differences, particularly for TST in the polar regions. Based upon spatiotemporal integrations, we find STE to be STT dominant in ERA-Interim and JRA-55 and TST dominant in MERRA and MERRA-2. The sources of the differences are mainly attributed to inconsistencies in the representation of STE in the subtropics and extratropics. Time series during the 15-year analysis period show long-term changes that are argued to correspond with changes in the Brewer–Dobson circulation.

scholarly journals Study of the jet stream over India and to its north in winter: Part I

MAUSAM ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 1-14
Author(s):  
SQN. LDR. M. S. SINGH
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Polar Front ◽  
Maximum Speed ◽  
Jet Stream ◽  
Jet Streams ◽  
Model Cross Section ◽  
Average Maximum ◽  
The One ◽  
Polar Front Jet

Characteristics of the jet streams over India and to its north in winter were studied with the daily vertical cross sections (1200 GMT) along 75°E from 8oN to 60°N for the period I to 15 February 1967, It was observed that there are three separate jet cores present in this latitl1de belt on most of the days, located on an average at 43°N, 31°N and 23°N. of these three, the most stable and persistent one is the second which is located between Delhi and Srinagar, at 200-mb level with an average maximum speed of 140-150 kt. The one to its south is weaker and quite variable in location as well as altitude. The jet at 31°N, therefore, has been called the primary sl1b-tropical jet over India and its characteristics studied. Based on this study, a. model cross-section has been. prepared for this STJ, The descriptions of the STJ at 23°N and also of PFJ (Polar Front Jet) at 43°N are included.

scholarly journals Local Mixing Events in the Upper Troposphere and Lower Stratosphere. Part II: Seasonal and Interannual Variability

2009 ◽  
Vol 66 (12) ◽  
pp. 3695-3706 ◽  
Author(s):  
Emily Shuckburgh ◽  
Francesco d’Ovidio ◽  
Bernard Legras
Keyword(s):  
Lower Stratosphere ◽  
Southern Oscillation ◽  
Positive Phase ◽  
Strong Mixing ◽  
Atmospheric Variability ◽  
Upper Troposphere ◽  
Rossby Wave Breaking ◽  
The North ◽  
Subtropical Jet ◽  
The Pacific

Abstract The Lyapunov diffusivity is used to investigate local isentropic mixing events in the upper troposphere–lower stratosphere (UTLS) region. The diagnostic highlights the seasonal cycle of the longitudinally varying mixing properties, in particular those associated with the monsoon circulations and the westerly ducts in the subtropics. The results are broadly consistent with studies of Rossby wave–breaking frequencies. The mixing structure is shown to be modulated by modes of atmospheric variability. El Niño–Southern Oscillation (ENSO) is found to strongly influence the mixing structure throughout the tropics and subtropics. The subtropical jet is associated with longitudinal bands of mixing minima (isentropic mixing barriers) separated by synoptic-scale regions of strong mixing activity. The greatest ENSO modulation in December–February is confined to the Pacific sector, where the barriers associated with the subtropical jets extend farther into the eastern Pacific, and in the western Pacific a barrier is found at the equator during the positive phase. During June–August, the influence is seen to extend beyond the Pacific region, with the barrier at the subtropical jet in the Southern Hemisphere increasing in strength at all longitudes and with an increase in strength (and isolation of) monsoon-related mixing over Asia and North America. The local influence of the North Atlantic Oscillation in wintertime is investigated. During the positive phase, a double-barrier structure is associated with the subtropical jet, the northern branch crosses the Atlantic toward Scandinavia, and the southern branch tends toward North Africa. The Antarctic Oscillation is shown to influence whether the subvortex region is isolated from midlatitudes.

Sign in / Sign up

Export Citation Format

Share Document