Dynamical Instability of Pressure-truncated Polytropes of Index 5

The Asian monsoon anticyclone, which develops in the upper troposphere and lower stratosphere during boreal summer, exhibits significant subseasonal variability with a characteristic spatial structure. The dynamics of this variability is investigated using a nonlinear β-plane shallow-water model. The equivalent depth is estimated using reanalysis data to relate the three-dimensional dynamics in isentropic coordinates to the shallow-water model. Composite analysis reveals the resemblance of the horizontal structures between the Montgomery streamfunction and thickness on the 360-K level. However, the coefficients of the linear regressions between those two variables are strongly dependent on latitude. The estimated equivalent depths of the northern region are more than 2 times greater than those of the southern region. This is attributable to the background thermal structure around the tropopause. Based on this, a latitude-dependent mean depth is incorporated into the shallow-water model to numerically investigate responses to a steady localized forcing in the subtropics. With the inclusion of the latitudinal dependence of the mean depth, the vortex shedding state is able to have a longitudinally confined structure, which differs from the conventional case of constant mean depth. The spatial structure of this numerical solution corresponds to the observed structure, in which low-PV air is largely confined to finite longitudes within the Asian monsoon anticyclone. This suggests the possible role of dynamical instability and the interaction with the subtropical jet in determining the characteristic structure of the Asian monsoon anticyclone.

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A statistical study of gravity waves from radiosonde observations at Wuhan (30° N, 114° E) China

Annales Geophysicae ◽

10.5194/angeo-23-665-2005 ◽

2005 ◽

Vol 23 (3) ◽

pp. 665-673 ◽

Cited By ~ 37

Author(s):

S. D. Zhang ◽

F. Yi

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Extreme Values ◽

Dynamical Instability ◽

Strong Wind ◽

Data Set ◽

Height Range ◽

Wave Parameters ◽

Thermal Structures ◽

Radiosonde Observation

Abstract. Several works concerning the dynamical and thermal structures and inertial gravity wave activities in the troposphere and lower stratosphere (TLS) from the radiosonde observation have been reported before, but these works were concentrated on either equatorial or polar regions. In this paper, background atmosphere and gravity wave activities in the TLS over Wuhan (30° N, 114° E) (a medium latitudinal region) were statistically studied by using the data from radiosonde observations on a twice daily basis at 08:00 and 20:00 LT in the period between 2000 and 2002. The monthly-averaged temperature and horizontal winds exhibit the essential dynamic and thermal structures of the background atmosphere. For avoiding the extreme values of background winds and temperature in the height range of 11-18km, we studied gravity waves, respectively, in two separate height regions, one is from ground surface to 10km (lower part), and the other is within 18-25km (upper part). In total, 791 and 1165 quasi-monochromatic inertial gravity waves were extracted from our data set for the lower and upper parts, respectively. The gravity wave parameters (intrinsic frequencies, amplitudes, wavelengths, intrinsic phase velocities and wave energies) are calculated and statistically studied. The statistical results revealed that in the lower part, there were 49.4% of gravity waves propagating upward, and the percentage was 76.4% in the upper part. Moreover, the average wave amplitudes and energies are less than those at the lower latitudinal regions, which indicates that the gravity wave parameters have a latitudinal dependence. The correlated temporal evolution of the monthly-averaged wave energies in the lower and upper parts and a subsequent quantitative analysis strongly suggested that at the observation site, dynamical instability (strong wind shear) induced by the tropospheric jet is the main excitation source of inertial gravity waves in the TLS.

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SIGNATURES OF DYNAMICAL INSTABILITY OF BOSE–EINSTEIN CONDENSATES IN 1D OPTICAL LATTICES

Fluctuation and Noise Letters ◽

10.1142/s0219477513400063 ◽

2013 ◽

Vol 12 (02) ◽

pp. 1340006

Author(s):

DONATELLA CIAMPINI ◽

OLIVER MORSCH ◽

ENNIO ARIMONDO

Keyword(s):

Interference Pattern ◽

Optical Lattices ◽

Time Of Flight ◽

Dynamical Instability ◽

Bose Einstein ◽

Dynamical Instabilities

The onset of dynamical instabilities of Bose–Einstein condensates in optical lattices due to the dephasing of the condensate wavefunction is observed through the decay of the visibility of the interference pattern in time-of-flight and the growth of the radial width of the condensate.

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Effects of Na+ and K+ channel blockade on vulnerability to and termination of fibrillation in simulated normal cardiac tissue

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00241.2005 ◽

2005 ◽

Vol 289 (4) ◽

pp. H1692-H1701 ◽

Cited By ~ 29

Author(s):

Zhilin Qu ◽

James N. Weiss

Keyword(s):

Action Potential ◽

Cardiac Tissue ◽

Theoretical Perspective ◽

Conduction Block ◽

Dynamical Instability ◽

K Channel ◽

Channel Blockade ◽

Wave Instability ◽

Transient Time ◽

Underlying Mechanisms

Na+ and K+ channel-blocking drugs have anti- and proarrhythmic effects. Their effects during fibrillation, however, remain poorly understood. We used computer simulation of a two-dimensional (2-D) structurally normal tissue model with phase I of the Luo-Rudy action potential model to study the effects of Na+ and K+ channel blockade on vulnerability to and termination of reentry in simulated multiple-wavelet and mother rotor fibrillation. Our main findings are as follows: 1) Na+ channel blockade decreased, whereas K+ channel blockade increased, the vulnerable window of reentry in heterogeneous 2-D tissue because of opposing effects on dynamical wave instability. 2) Na+ channel blockade increased the cycle length of reentry more than it increased refractoriness. In multiple-wavelet fibrillation, Na+ channel blockade first increased and then decreased the average duration or transient time (<Ts>) of fibrillation. In mother rotor fibrillation, Na+ channel blockade caused peripheral fibrillatory conduction block to resolve and the mother rotor to drift, leading to self-termination or sustained tachycardia. 3) K+ channel blockade increased dynamical instability by steepening action potential duration restitution. In multiple-wavelet fibrillation, this effect shortened <Ts> because of enhanced wave instability. In mother rotor fibrillation, this effect converted mother rotor fibrillation to multiple-wavelet fibrillation, which then could self-terminate. Our findings help illuminate, from a theoretical perspective, the possible underlying mechanisms of termination of different types of fibrillation by antiarrhythmic drugs.

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