scholarly journals Understanding the processes that control the interannual variability of the Northern Hemisphere wintertime polar front and subtropical jet streams

2021 ◽  
Author(s):  
Xinhuiyu Liu ◽  
Kevin M Grise ◽  
Daniel F Schmidt ◽  
Robert E. Davis
Keyword(s):  
Interannual Variability ◽  
Northern Hemisphere ◽  
Polar Front ◽  
Jet Streams ◽  
Subtropical Jet

scholarly journals A study on the maintenance of the winter subtropical jet streams in the northern hemisphere

1988 ◽  
Vol 40 (5) ◽  
pp. 392-397
Author(s):  
Tsing-Chang Chen ◽  
Ren-Yow Tzeng ◽  
Harry Van Loon
Keyword(s):  
Northern Hemisphere ◽  
Jet Streams ◽  
Subtropical Jet

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 A network-based detection scheme for the jet stream core

2017 ◽  
Vol 8 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Sonja Molnos ◽  
Tarek Mamdouh ◽  
Stefan Petri ◽  
Thomas Nocke ◽  
Tino Weinkauf ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Probability Distributions ◽  
Reanalysis Data ◽  
Western Hemisphere ◽  
Jet Stream ◽  
Jet Streams ◽  
Detection Scheme ◽  
The North ◽  
Eastern Hemisphere ◽  
Subtropical Jet

Abstract. The polar and subtropical jet streams are strong upper-level winds with a crucial influence on weather throughout the Northern Hemisphere midlatitudes. In particular, the polar jet is located between cold arctic air to the north and warmer subtropical air to the south. Strongly meandering states therefore often lead to extreme surface weather. Some algorithms exist which can detect the 2-D (latitude and longitude) jets' core around the hemisphere, but all of them use a minimal threshold to determine the subtropical and polar jet stream. This is particularly problematic for the polar jet stream, whose wind velocities can change rapidly from very weak to very high values and vice versa. We develop a network-based scheme using Dijkstra's shortest-path algorithm to detect the polar and subtropical jet stream core. This algorithm not only considers the commonly used wind strength for core detection but also takes wind direction and climatological latitudinal position into account. Furthermore, it distinguishes between polar and subtropical jet, and between separate and merged jet states. The parameter values of the detection scheme are optimized using simulated annealing and a skill function that accounts for the zonal-mean jet stream position (Rikus, 2015). After the successful optimization process, we apply our scheme to reanalysis data covering 1979–2015 and calculate seasonal-mean probabilistic maps and trends in wind strength and position of jet streams. We present longitudinally defined probability distributions of the positions for both jets for all on the Northern Hemisphere seasons. This shows that winter is characterized by two well-separated jets over Europe and Asia (ca. 20° W to 140° E). In contrast, summer normally has a single merged jet over the western hemisphere but can have both merged and separated jet states in the eastern hemisphere. With this algorithm it is possible to investigate the position of the jets' cores around the hemisphere and it is therefore very suitable to analyze jet stream patterns in observations and models, enabling more advanced model-validation.

A study on the maintenance of the winter subtropical jet streams in the northern hemisphere

1988 ◽  
Vol 40A (5) ◽  
pp. 392-397 ◽  
Author(s):  
TSING-CHANG CHEN ◽  
REN-YOW TZENG ◽  
HARRY LOON
Keyword(s):  
Northern Hemisphere ◽  
Jet Streams ◽  
Subtropical Jet

scholarly journals A Synoptic Climatology of Northern Hemisphere, Cold Season Polar and Subtropical Jet Superposition Events

2017 ◽  
Vol 30 (18) ◽  
pp. 7231-7246 ◽  
Author(s):  
Croix E. Christenson ◽  
Jonathan E. Martin ◽  
Zachary J. Handlos
Keyword(s):  
Northern Hemisphere ◽  
Structural Characteristics ◽  
Cold Season ◽  
Hadley Cell ◽  
Synoptic Climatology ◽  
Jet Streams ◽  
Subtropical Jet ◽  
Wave Development ◽  
Different Origins ◽  
Subtropical Jets

Abstract Narrow, tropopause-level wind speed maxima known as jet streams or jets are among the most ubiquitous structural characteristics of Earth’s atmosphere. Two species, the polar and subtropical jets, can be observed on any given day. The polar jet is tied, via eddy momentum flux convergence associated with extratropical wave development, to the troposphere-deep baroclinicity of the midlatitudes, while the subtropical jet is tied, by angular momentum constraints, to the poleward edge of the tropical Hadley cell. As a consequence of their different origins, the polar and subtropical jets are separated by both latitude and elevation. However, there are times when these two usually separate features become vertically superposed to form a single, intense jet core designated as a jet superposition or superposed jet. An objective method for identifying tropopause-level jets is employed in the construction of 50-yr cold season (November–March) synoptic climatologies of the Northern Hemisphere polar jet, subtropical jet, and jet superpositions. The analysis demonstrates that while superposition events are relatively rare, there are clear geographical maxima. Superpositions are most frequent in the western Pacific from December through February, with a secondary peak in southern North America and along its eastern seaboard. Consistent with expectations, the spatiotemporal maxima in jet superpositions appear to be coincident with maxima in the polar and subtropical jets.

scholarly journals Interannual variability of precipitable water

1996 ◽  
Vol 14 (4) ◽  
pp. 464-467 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Precipitable Water ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Zonal Winds ◽  
Low Latitudes ◽  
Linear Trends

Abstract. The 12-month running means of the surface-to-500 mb precipitable water obtained from analysis of radiosonde data at seven selected locations showed three types of variability viz: (1) quasi-biennial oscillations; these were different in nature at different latitudes and also different from the QBO of the stratospheric tropical zonal winds; (2) decadal effects; these were prominent at middle and high latitudes and (3) linear trends; these were prominent at low latitudes, up trends in the Northern Hemisphere and downtrends in the Southern Hemisphere.

scholarly journals Dynamical Processes Related to the Appearance of Quasi-Stationary Waves on the Subtropical Jet in the Midsummer Northern Hemisphere

2006 ◽  
Vol 19 (8) ◽  
pp. 1531-1544 ◽  
Author(s):  
Naoki Sato ◽  
Masaaki Takahashi
Keyword(s):  
Middle East ◽  
Northern Hemisphere ◽  
Wave Train ◽  
Stationary Wave ◽  
Stationary Waves ◽  
Statistical Features ◽  
Basic Field ◽  
Subtropical Jet ◽  
Anomaly Pattern ◽  
Highly Correlated

Abstract Statistical features of quasi-stationary planetary waves were examined on the subtropical jet in the midsummer Northern Hemisphere by using objectively analyzed data and satellite data. As a result, a quasi-stationary wave train that is highly correlated with the midsummer climate over Japan was identified. A clear phase dependency of the appearance of waves was also confirmed. An analysis of temporal evolution and wave activity flux revealed that the eastward propagation of the wave packet starts in the Middle East, passes over East Asia, and reaches North America. The anomaly pattern is strengthened through kinetic energy conversion near the entrance of the Asian jet over the Middle East. The interaction between the anomaly pattern and the basic field contributes to the appearance of the anomalous wavelike pattern. Although the wave train is correlated with the anomaly of convective activity over the western North Pacific and the Indian Ocean, it is implied that internal dynamics are important in determining the statistical features of the appearance of anomalous quasi-stationary waves on the subtropical jet.

scholarly journals Interannual Variability of the Winter Stratosphere and Troposphere in the Northern Hemisphere

1996 ◽  
Vol 74 (3) ◽  
pp. 365-382 ◽  
Author(s):  
Kunihiko Kodera ◽  
Masaru Chiba ◽  
Hiroshi Koide ◽  
Akio Kitoh ◽  
Yoshinobu Nikaidou
Keyword(s):  
Interannual Variability ◽  
Northern Hemisphere
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