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Diabatic Heating (diabatic + heating)

Distribution by Scientific Domains

Earth and Environmental Science	100%

Selected Abstracts

Onset characteristics of the southwest monsoon over India

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2005
P. V. S. Raju
Abstract Dynamic and thermodynamic characteristics of the Asian summer monsoon during the onset phase over the Indian Peninsula (Kerala coast) and its variability are examined with reanalysis data sets. For this study, daily averaged (0000 and 1200 UTC) reanalysis data sets of National Centre for Environmental Prediction,National Centre for Atmospheric Research for the period 1948,99 are used. Based on 52 years of onset dates of the Indian summer monsoon, we categorized pre-onset, onset and post-onset periods (each averaged 5 days) to investigate the mean circulation characteristics and the large-scale energetics of the Asian summer monsoon. It is found that the strength of the low-level Somali jet and upper tropospheric tropical easterly jet increase rapidly during the time of evolution of the summer monsoon over India. Over the Bay of Bengal and the Arabian Sea, predominant changes are noticed in the large-scale balances of kinetic energy, heat and moisture from the pre-onset to the post-onset periods. Prior to the onset of the summer monsoon over India, a zone of flux convergence of heat and moisture is noticed over the eastern sector of the Bay of Bengal and this intensifies in the onset and post-onset periods. During onset of the monsoon over India, the horizontal flux convergence of heat and moisture, as well as diabatic heating, are enhanced over the Arabian Sea. These subsequently increase with the evolution and advancement of the monsoon over India. Further, the dynamics of the evolution processes (15 days before and 30 days after the onset date of the monsoon over Kerala for each annual cycle) are studied over various sectors, such as the Arabian Sea, Bay of Bengal and Indian Peninsula region. The study reveals that the low-level kinetic energy, vertically integrated generation of kinetic energy and net tropospheric moisture over Arabian Sea can be used as potential predictors for the prediction of the possible onset date of the summer monsoon over the Indian Peninsula. Copyright © 2005 Royal Meteorological Society [source]

Characteristics, evolution and mechanisms of the summer monsoon onset over Southeast Asia

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2004
Zuqiang Zhang
Abstract Based on the 1979,95 mean pentad reanalysis data from the US National Centers for Environmental Prediction, the climatological characteristics and physical mechanism of the Asian summer monsoon (ASM) onset are investigated. Special focus is given to whether the ASM onset starts earlier over the Indochina Peninsula than over the South China Sea (SCS) and why the ASM is established the earliest over Southeast Asia. An examination of the composite thermodynamic and dynamic quantities confirms that the ASM onset commences earliest over the Indochina Peninsula, as highlighted by active convection and rainfall resulting from the convergence of southwesterly flow from the Bay of Bengal (BOB) vortex and easterly winds associated with the subtropical anticyclone over the SCS. Two other important characteristics not previously noted are also identified: the earliest reversal of meridional temperature gradient throughout the entire troposphere and the corresponding establishment of an easterly vertical wind shear, which are due to upper level warming caused by eddy (convective) transport of latent heat. These changes in the large-scale circulation suggest that, in addition to rainfall, a reversal in the planetary-scale circulation should be included in determining the timing of the ASM onset. With such a consideration, the climatological ASM onset occurs first over southeastern BOB and southwestern Indochina Peninsula in early May, and then advances northeastward to reach the SCS by the fourth pentad of May (16,20 May). The monsoon then covers the entire Southeast Asia region by the end of May. Subsequently, a similar onset process begins over the eastern Arabian Sea, India and western BOB, and the complete establishment of the ASM over India is accomplished in mid June. In the process of the onset of each ASM component, the reversal of the upper level planetary-scale circulation depends strongly on that of the meridional temperature gradient. Over the Indochina Peninsula, the seasonal transition of upper level temperature results from convection-induced diabatic heating, whereas over western Asia it is attributed to subsidence warming induced by the active ascending motion over the former region. The steady increase in surface sensible heating over the Indian subcontinent and the latent heating over the tropical Indian Ocean in April to early May appear to be the major impetus for the development of the cyclonic vortex over the BOB. A similar enhancement over the Arabian Peninsula and the surrounding regions is also identified to be crucial to the development of the so-called onset vortex over the Arabian Sea, and then ultimately to the ASM onset over India. Copyright © 2004 Royal Meteorological Society [source]

Towards a consistent numerical compressible non-hydrostatic model using generalized Hamiltonian tools

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 635 2008
Almut Gassmann
Abstract A set of compressible non-hydrostatic equations for a turbulence-averaged model atmosphere comprising dry air and water in three phases plus precipitating fluxes is presented, in which common approximations are introduced in such a way that no inconsistencies occur in the associated budget equations for energy, mass and Ertel's potential vorticity. These conservation properties are a prerequisite for any climate simulation or NWP model. It is shown that a Poisson bracket form for the ideal fluid part of the full-physics equation set can be found, while turbulent friction and diabatic heating are added as separate ,dissipative' terms. This Poisson bracket is represented as a sum of a two-fold antisymmetric triple bracket (a Nambu bracket represented as helicity bracket) plus two antisymmetric brackets (so-called mass and thermodynamic brackets of the Poisson type). The advantage of this approach is that the given conservation properties and the structure of the brackets provide a good strategy for the construction of their discrete analogues. It is shown how discrete brackets are constructed to retain their antisymmetric properties throughout the spatial discretisation process, and a method is demonstrated how the time scheme can also be incorporated in this philosophy. Copyright © 2008 Royal Meteorological Society [source]

Some dynamical aspects of tropical cyclone concentric eyewalls

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 632 2008
Christopher M. Rozoff
Abstract The intensification of tropical cyclones is often interrupted by an eyewall replacement cycle, a process in which an outer eyewall forms, contracts, and replaces an inner eyewall. The radial distributions of inertial stability and diabatic heating change during such events, impacting the transverse circulation. To examine the effects of such changes, an analytical solution of the transverse circulation equation associated with a balanced vortex model is derived using a parameterization that distinguishes five radial regions subdividing the domain by each region's values of inertial stability and diabatic heating. These regions define the eye, inner eyewall, moat, outer eyewall, and far-field. In mature concentric eyewall situations, the solutions do not support the hypothesis that the inner eyewall collapses as a direct result of subsidence from the outer eyewall. However, the results suggest subsidence and warming temperatures in the moat are governed by enhanced inertial stability associated with a strengthening outer eyewall. The model solutions also illustrate how the diabatic heating in the inner eyewall, imbedded in a region of high inertial stability, induces larger temperature tendencies than the diabatic heating in the outer eyewall, which borders the far-field region of low inertial stability. Thus, as the inner eyewall dies, the storm temporarily loses its ability to produce an intense, localized warm region. This ability is restored during the contraction and intensification of the outer eyewall. These results provide a partial dynamical explanation of how an eyewall replacement cycle can act as a temporary brake on tropical cyclone intensification. Copyright © 2008 Royal Meteorological Society [source]

A diagnosis of warm-core and cold-core extratropical cyclone development using the Zwack,Okossi equation

ATMOSPHERIC SCIENCE LETTERS, Issue 4 2009
Roohollah Azad
Abstract In this study, the development of a warm-core and cold-core extratropical cyclone over North Atlantic is examined. The geostrophic relative vorticity tendency used to diagnose the development is calculated utilizing the so-called extended form of the Zwack,Okossi development equation. In both cases, the cyclonic vorticity advection acted to develop the system, but warm-air advection (diabatic heating) made the largest contribution to explosive development in the cold-core (warm-core) case. Further, a vertical cross section of the temperature advection in the warm-core case reveals that the largest values of this contributor are located far and ahead of the cyclone center. Copyright © 2009 Royal Meteorological Society [source]