scholarly journals On the onset of summer monsoon over India in relation to interactions of the monsoon stationary wave with transient baroclinic waves leading to monsoon cyclogenesis

MAUSAM ◽  
2021 ◽  
Vol 51 (1) ◽  
pp. 1-16
Author(s):  
KSHUDIRAM SARA ◽  
SURANJANA SARA
Keyword(s):  
Detailed Analysis ◽  
Summer Monsoon ◽  
Late Onset ◽  
Stationary Wave ◽  
Travelling Wave ◽  
Thermal Contrast ◽  
Baroclinic Waves ◽  
Wave Disturbances ◽  
Interaction Processes ◽  
Monsoon Depressions

The important problem of the early or late onset of summer monsoon over India is addressed in the present study and found to be related to the structure and behaviour of a monsoon stationary wave that forms over the region due to land-sea thermal contrast and interacts with travelling wave disturbances in the westerlies and the easterlies associated with the subtropical belt over Asia. Depending upon the type of coupling and decoupling that occurs between the interacting waves, monsoon advances towards India either slowly or speedily. Since northward-propagating monsoon depressions are found to accelerate the onset processes. the study carries out a detailed analysis of the interaction processes which give rise to such disturbances and determine their development and movement.

scholarly journals Computational and traveling wave analysis of Tzitzéica and Dodd-Bullough-Mikhailov equations: An exact and analytical study

2021 ◽  
Vol 10 (1) ◽  
pp. 272-281
Author(s):  
Hülya Durur ◽  
Asıf Yokuş ◽  
Kashif Ali Abro
Keyword(s):  
Traveling Wave ◽  
Evolution Equations ◽  
Three Dimensional ◽  
Traveling Wave Solutions ◽  
Expansion Method ◽  
Stationary Wave ◽  
Travelling Wave ◽  
Nonlinear Evolution Equations ◽  
Travelling Wave Solutions ◽  
Wave Solutions

Abstract Computational and travelling wave solutions provide significant improvements in accuracy and characterize novelty of imposed techniques. In this context, computational and travelling wave solutions have been traced out for Tzitzéica and Dodd-Bullough-Mikhailov equations by means of (1/G′)-expansion method. The different types of solutions have constructed for Tzitzéica and Dodd-Bullough-Mikhailov equations in hyperbolic form. Moreover, solution function of Tzitzéica and Dodd-Bullough-Mikhailov equations has been derived in the format of logarithmic nature. Since both equations contain exponential terms so the solutions produced are expected to be in logarithmic form. Traveling wave solutions are presented in different formats from the solutions introduced in the literature. The reliability, effectiveness and applicability of the (1/G′)-expansion method produced hyperbolic type solutions. For the sake of physical significance, contour graphs, two dimensional and three dimensional graphs have been depicted for stationary wave. Such graphical illustration has been contrasted for stationary wave verses traveling wave solutions. Our graphical comparative analysis suggests that imposed method is reliable and powerful method for obtaining exact solutions of nonlinear evolution equations.

scholarly journals Vortex Layer on the β-Plane in the Miles – Ribner Formulation. Pole on the Real Axis

2021 ◽  
Vol 28 (5) ◽  
Author(s):  
V. G. Gnevyshev ◽  
T. V. Belonenko ◽  
◽  
Keyword(s):  
Rossby Waves ◽  
Zonal Flow ◽  
Stationary Wave ◽  
Linear Wave ◽  
Background Flow ◽  
Pure Radiation ◽  
New Class ◽  
Vortex Layer ◽  
Wave Disturbances ◽  
Definition Of

Purpose. The problem of a non-zonal vortex layer on the β-plane in the Miles – Ribner formulation is considered. It is known that in the absence of the β-effect, the vortex layer has no neutral eigenmodes, and the available two ones (varicose and sinusoidal) are unstable. Initially, generalization of the problem to the β-plane concerned only the zonal case. The problem for a non-zonal vortex layer is examined for the first time in the paper. It is known that in the WKB approximation for the linear wave disturbances (regardless of whether a zonal or non-zonal background flow is considered), there is an adiabatic invariant in the form of the law of the enstrophy (vorticity) conservation. For the zonal vortex layer, the enstrophy conservation law also holds, and no vorticity exchange occurs between the waves and the flow in the zonal case. The non-zonal vortex layer has qualitatively different features; particularly, it does not retain enstrophy. Thus, as a result, there appears a new class of solutions which can be interpreted as pure radiation of the Rossby waves by a non-zonal flow. Generalizing the vortex layer problem on the β-plane to the non-zonal case constitutes the basic aim of the present study. Methods and Results. A new class of linear stationary wave solutions, namely the Rossby waves, is found. It is shown a non-zonal flow can be directed in one way, whereas the stationary wave disturbances can move in the opposite (contrary) direction. The coexistence of such solutions for the shear non-zonal flow and stationary wave disturbances takes place due to the influence of the external force and mathematically comes from a non-self-adjoining character of the linear operator for a non-zonal background flow. Conclusions. There exists a new class of solutions that can be interpreted as pure radiation of the Rossby waves by a non-zonal flow. There is no such solution for a zonal flow. It is just non-zoning that gives the effect of pure radiation and corresponds to the classical definition of radiation. This approach makes it possible to eliminate inconsistency in terminology, when instabilities are mistakenly called radiation, and radiation – pure radiation.

Affective Disorder Arising in the Senium II. Physical Disability As an Aetiological Factor

1956 ◽  
Vol 102 (426) ◽  
pp. 141-150 ◽  
Author(s):  
Martin Roth ◽  
D. W. K. Kay
Keyword(s):  
Detailed Analysis ◽  
Affective Disorder ◽  
Old Age ◽  
Physical Disability ◽  
Late Onset ◽  
Physical Illness ◽  
Aetiological Factor ◽  
Affective Psychosis ◽  
Cerebral Degeneration

In previous papers (Roth and Morrissey, 1952; Roth, 1955) evidence for the importance of affective psychosis in old age was presented. It was shown further that in some half of those admitted after the age of 60 no attacks had occurred before this age, and that no new aetiological factor such as cerebral degeneration was associated with these cases of late onset (Kay, Roth and Hopkins, 1955). The problem is to elucidate why it is that defences against illness effective throughout most of these patients' lives prove inadequate in old age. Now in the study just referred to, a tendency for physical illness to be commoner in patients having their first attack after 60 was noted. A more detailed analysis of the incidence of physical illness in the two groups has therefore been carried out in order to investigate its possible aetiological role in old age affective disorder.

Dynamic Effect of Last Glacial Maximum Ice Sheet Topography on the East Asian Summer Monsoon

2020 ◽  
Vol 33 (16) ◽  
pp. 6929-6944 ◽  
Author(s):  
Yu Gao ◽  
Zhengyu Liu ◽  
Zhengyao Lu
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Wave ◽  
Westerly Jet ◽  
Asian Summer ◽  
Ice Sheet Topography

AbstractThe effect of ice sheet topography on the East Asian summer monsoon (EASM) during the Last Glacial Maximum is studied using CCSM3 in a hierarchy of model configurations. It is found that receding ice sheets result in a weakened EASM, with the reduced ice sheet thickness playing a major role. The lower ice sheet topography weakens the EASM through shifting the position of the midlatitude jet, and through altering Northern Hemisphere stationary waves. In the jet shifting mechanism, the lowering of ice sheets shifts the westerly jet northward and decreases the westerly jet over the subtropics in summer, which reduces the advection of dry enthalpy and in turn precipitation over the EASM region. In the stationary wave mechanism, the lowering of ice sheets induces an anomalous stationary wave train along the westerly waveguide that propagates into the EASM region, generating an equivalent-barotropic low response; this leads to reduced lower-tropospheric southerlies, which in turn reduces the dry enthalpy advection into East Asia, and hence the EASM precipitation.

The role of surface air temperature over the east Asia on the early and late Indian Summer Monsoon Onset over Kerala

2020 ◽  
Author(s):  
Devanil Choudhury ◽  
Debashis Nath ◽  
Wen Chen
Keyword(s):  
East Asia ◽  
Air Temperature ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Late Onset ◽  
Southern China ◽  
Surface Air Temperature ◽  
Monsoon Onset ◽  
Low Level ◽  
Summer Monsoon Onset

<p>We investigated the physical mechanism for late Indian Summer Monsoon onset over Kerala<br>(MOK). 14 early and 9 late onset years are selected based on the criteria when the onset is 5 days or<br>more prior and after normal onset date (i.e 1 st June according to India Meteorological Department)<br>respectively. Then, we perform composite analyses of mean May monthly and daily evolution during<br>early and late onset years to examine the differences in monsoon circulation features prior to the MOK.<br>We find that advection of Surface Air Temperature (SAT) from the northern to the southern China and<br>the eastern Tibetan Plateau (TP) plays an important role to modulate the MOK processes. In the late<br>onset years, more low-level jet (LLJ) from the Bay of Bengal (BOB) divert towards the east Asia before<br>the onset, which is due to an extension of the low sea level pressure and high SAT over the east Asia<br>(eastern TP, east-central China). This strengthens the low-level convergence and upper level divergence<br>over the eastern TP and southern China. As a result, a significant amount of moisture from the BOB<br>is transported towards the eastern TP and southern China. Thereby, a comparatively weaker LLJ and<br>deficit low-level moisture supply over the eastern BOB maintain the key roles in modulating the MOK<br>processes.</p>

scholarly journals Disentangling fast and slow responses of the East Asian summer monsoon to reflecting and absorbing aerosol forcings

2017 ◽  
Author(s):  
Zhili Wang ◽  
Lei Lin ◽  
Meilin Yang ◽  
Yangyang Xu ◽  
Jiangnan Li
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Sea Surface ◽  
Slow Response ◽  
Total Response ◽  
Thermal Contrast ◽  
Response Component ◽  
Asian Summer

Abstract. We examine the roles of fast and slow responses in shaping the total equilibrium response of the East Asian summer monsoon (EASM) to reflecting (sulfate, SO4) and absorbing (black carbon, BC) aerosol forcings over the industrial era using the Community Earth System Model version 1. Our results show that there is a clear distinction between fast and slow responses of the EASM to aerosol forcings and the slow climate response due to aerosol-induced change in sea surface temperature plays an important role in the impacts of aerosols on the EASM. The EASM is weakened by a decrease in land-sea surface thermal contrast in the fast response component to SO4 forcing, whereas the weakening is more intensive by the changes in tropospheric thermodynamic and dynamic structures in the slow response component to SO4. The total climate adjustment caused by SO4 is a significant weakening of the EASM and a decrease in precipitation. The BC-induced fast adjustment strengthens the EASM both by increasing the local surface land-sea thermal contrast and shifting the East Asian subtropical jet northwards. BC-induced slow climate adjustment, however, weakens the EASM through altering the atmospheric temperature and circulation. Consequently, the EASM is enhanced north of 30° N but slightly reduced south of 30° N in the total response to BC. The spatial patterns of precipitation change over East Asia due to BC are similar in total response and slow response. This study highlights the importance of ocean response to aerosol forcings in driving the changes of the EASM.

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