Effects of Coriolis force, vorticity and divergence on nonlinear energy  conversions during different phases of July 1979 monsoon

ABSTRACT. Kinetic energy (KE) of the rotational and divergent flows and the nonlinear energy conversion between them due to the action of Coriolis force, divergence and vorticity, partition) further into stationary and transient motions are computed in the Fourier spectral domain during different phases of July 1979 monsoon over the latitudinal belt 10° S - 30° at 850 and 200 hPa and studied. It is found that nonlinear divergent to rotational KE exchange due to the action of Coriolis force is the primary contributor for all categories of stationary and transient waves at both the levels over tropics. Our results indicate that in the transient scale dynamics the wave-wave interaction plays a dominant role at 850 hPa. Divergent to rotational KE conversion by zonal-wave interaction due to divergence and wave-wave interaction due to Coriolis force are identified as important mechanisms for maintenance of rotational stationary planetary and transient synoptic scale waves respectively at 200 hPa. It is inferred that nonlinear energy conversions due to Coriolis force and vorticity oppose each other at 200 hPa. The results support that the energy conversion phenomenon may not be entirely barotropic. The importance of ageostrophic effect at different stages of monsoon activities is also shown.

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The Role of Multiscale Interaction in Synoptic-Scale Eddy Kinetic Energy over the Western North Pacific in Autumn

Journal of Climate ◽

10.1175/jcli-d-13-00380.1 ◽

2014 ◽

Vol 27 (10) ◽

pp. 3750-3766 ◽

Cited By ~ 11

Author(s):

Chih-Hua Tsou ◽

Huang-Hsiung Hsu ◽

Pang-Chi Hsu

Keyword(s):

Kinetic Energy ◽

Energy Conversion ◽

North Pacific ◽

Western North Pacific ◽

Intraseasonal Oscillation ◽

Lower Troposphere ◽

Synoptic Scale ◽

Multiscale Interactions ◽

Barotropic Energy Conversion ◽

Mean Circulation

Abstract This study formulates a synoptic-scale eddy (SSE) kinetic energy equation by partitioning the original field into seasonal mean circulation, intraseasonal oscillation (ISO), and SSEs to examine the multiscale interactions over the western North Pacific (WNP) in autumn. In addition, the relative contribution of synoptic-mean and synoptic-ISO interactions to SSE kinetic energy was quantitatively estimated by further separating barotropic energy conversion (CK) into synoptic-mean barotropic energy conversion (CKS−M) and synoptic-ISO barotropic energy conversion (CKS−ISO) components. The development of tropical SSE in the lower troposphere is mainly attributed to CK associated with multiscale interactions. Mean cyclonic circulation in the lower troposphere consistently provides kinetic energy to SSEs (CKS−M > 0) during the ISO westerly and easterly phases. However, CKS−ISO during the ISO westerly and easterly phases differs considerably. During the ISO westerly phase, the enhanced ISO cyclonic flow converts energy to SSEs (CKS−ISO > 0). The magnitude of the downscale energy conversion from mean and ISO to SSEs is related to the strength of the SSEs. During the ISO westerly phase, a stronger SSE extracts more kinetic energy from mean and ISO circulation. This positive feedback between SSE-mean and SSE–ISO interactions causes further strengthening of SSEs during the ISO westerly phase. By contrast, upscale energy conversion from SSEs to ISO anticyclonic flow (CKS−ISO < 0) was observed during the ISO easterly phase. The weaker SSE activity during the ISO easterly phase occurred because the mean circulation provides less energy to SSEs and, at the same time, SSEs lose energy to ISO during the ISO easterly phase. The two-way interaction between the ISO and SSEs has considerable effects on the development of tropical SSEs over the WNP in autumn.

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Interactions between Boreal Summer Intraseasonal Oscillations and Synoptic-Scale Disturbances over the Western North Pacific. Part I: Energetics Diagnosis*

Journal of Climate ◽

10.1175/2010jcli3833.1 ◽

2011 ◽

Vol 24 (3) ◽

pp. 927-941 ◽

Cited By ~ 77

Author(s):

Pang-chi Hsu ◽

Tim Li ◽

Chih-Hua Tsou

Keyword(s):

Kinetic Energy ◽

Energy Conversion ◽

Tropical Cyclones ◽

North Pacific ◽

Western North Pacific ◽

Intraseasonal Oscillation ◽

Active Phase ◽

Boreal Summer ◽

Synoptic Eddies ◽

Barotropic Energy Conversion

Abstract The role of scale interactions in the maintenance of eddy kinetic energy (EKE) during the extreme phases of the intraseasonal oscillation (ISO) is examined through the construction of a new eddy energetics diagnostic tool that separates the effects of ISO and a low-frequency background state (LFBS; with periods longer than 90 days). The LFBS always contributes positively toward the EKE in the boreal summer, regardless of the ISO phases. The synoptic eddies extract energy from the ISO during the ISO active phase. This positive barotropic energy conversion occurs when the synoptic eddies interact with low-level cyclonic and convergent–confluent ISO flows. This contrasts with the ISO suppressed phase during which the synoptic eddies lose kinetic energy to the ISO flow. The anticyclonic and divergent–diffluent ISO flows during the suppressed phase are responsible for the negative barotropic energy conversion. A positive (negative) EKE tendency occurs during the ISO suppressed-to-active (active-to-suppressed) transitional phase. The cause of this asymmetric EKE tendency is attributed to the spatial phase relation among the ISO vorticity, eddy structure, and EKE. The southwest–northeast-tilted synoptic disturbances interacting with cyclonic (anticyclonic) vorticity of ISO lead to a positive (negative) EKE tendency in the northwest region of the maximum EKE center. The genesis number and location and intensification rate of tropical cyclones in the western North Pacific are closely related to the barotropic energy conversion. The enhanced barotropic energy conversion favors the generation and development of synoptic seed disturbances, some of which eventually grow into tropical cyclones.

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Numerical simulation and decomposition of kinetic energy in the Central Mediterranean: insight on mesoscale circulation and energy conversion

Ocean Science ◽

10.5194/os-7-503-2011 ◽

2011 ◽

Vol 7 (4) ◽

pp. 503-519 ◽

Cited By ~ 51

Author(s):

R. Sorgente ◽

A. Olita ◽

P. Oddo ◽

L. Fazioli ◽

A. Ribotti

Keyword(s):

Numerical Simulation ◽

Kinetic Energy ◽

Energy Conversion ◽

Ocean Model ◽

Eddy Kinetic Energy ◽

Tyrrhenian Sea ◽

Central Mediterranean ◽

Baroclinic Energy Conversion ◽

Sicily Channel ◽

Mean Kinetic Energy

Abstract. The spatial and temporal variability of eddy and mean kinetic energy of the Central Mediterranean region has been investigated, from January 2008 to December 2010, by mean of a numerical simulation mainly to quantify the mesoscale dynamics and their relationships with physical forcing. In order to understand the energy redistribution processes, the baroclinic energy conversion has been analysed, suggesting hypotheses about the drivers of the mesoscale activity in this area. The ocean model used is based on the Princeton Ocean Model implemented at 1/32° horizontal resolution. Surface momentum and buoyancy fluxes are interactively computed by mean of standard bulk formulae using predicted model Sea Surface Temperature and atmospheric variables provided by the European Centre for Medium Range Weather Forecast operational analyses. At its lateral boundaries the model is one-way nested within the Mediterranean Forecasting System operational products. The model domain has been subdivided in four sub-regions: Sardinia channel and southern Tyrrhenian Sea, Sicily channel, eastern Tunisian shelf and Libyan Sea. Temporal evolution of eddy and mean kinetic energy has been analysed, on each of the four sub-regions, showing different behaviours. On annual scales and within the first 5 m depth, the eddy kinetic energy represents approximately the 60 % of the total kinetic energy over the whole domain, confirming the strong mesoscale nature of the surface current flows in this area. The analyses show that the model well reproduces the path and the temporal behaviour of the main known sub-basin circulation features. New mesoscale structures have been also identified, from numerical results and direct observations, for the first time as the Pantelleria Vortex and the Medina Gyre. The classical kinetic energy decomposition (eddy and mean) allowed to depict and to quantify the permanent and fluctuating parts of the circulation in the region, and to differentiate the four sub-regions as function of relative and absolute strength of the mesoscale activity. Furthermore the Baroclinic Energy Conversion term shows that in the Sardinia Channel the mesoscale activity, due to baroclinic instabilities, is significantly larger than in the other sub-regions, while a negative sign of the energy conversion, meaning a transfer of energy from the Eddy Kinetic Energy to the Eddy Available Potential Energy, has been recorded only for the surface layers of the Sicily Channel during summer.

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Hydraulic Kinetic Energy Conversion (HKEC) Systems

Journal of Energy Engineering ◽

10.1061/(asce)0733-9402(1990)116:1(17) ◽

1990 ◽

Vol 116 (1) ◽

pp. 17-38 ◽

Cited By ~ 5

Author(s):

Jaro J. Vocadlo ◽

Brian Richards ◽

Michael King

Keyword(s):

Kinetic Energy ◽

Energy Conversion

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Numerical simulation and decomposition of kinetic energies in the Central Mediterranean Sea: insight on mesoscale circulation and energy conversion

Ocean Science Discussions ◽

10.5194/osd-8-1161-2011 ◽

2011 ◽

Vol 8 (3) ◽

pp. 1161-1214 ◽

Cited By ~ 3

Author(s):

R. Sorgente ◽

A. Olita ◽

P. Oddo ◽

L. Fazioli ◽

A. Ribotti

Keyword(s):

Numerical Simulation ◽

Kinetic Energy ◽

Energy Conversion ◽

Mediterranean Sea ◽

Ocean Model ◽

Eddy Kinetic Energy ◽

Central Mediterranean ◽

Central Mediterranean Sea ◽

Baroclinic Energy Conversion ◽

Mean Kinetic Energy

Abstract. The spatial and temporal variability of eddy and mean kinetic energy of the Central Mediterranean Sea has been investigated, from January 2008 to December 2010, by mean of a numerical simulation mainly to quantify the mesoscale dynamics and their relationships with physical forcing. In order to understand the energy redistribution processes, the baroclinic energy conversion has been analysed, suggesting hypotheses about the drivers of the mesoscale activity in this area. The ocean model used is based on the Princeton Ocean Model implemented at 1/32° horizontal resolution. Surface momentum and buoyancy fluxes are interactively computed by mean of standard bulk formulae using predicted model Sea Surface Temperature and atmospheric variables provided by the European Centre for Medium Range Weather Forecast operational analyses. At its lateral boundaries the model is one-way nested within the Mediterranean Forecasting System operational products. The model domain has been subdivided in four sub-regions: Sardinia channel and southern Tyrrhenian Sea, Sicily channel, eastern Tunisian shelf and Libyan Sea. Temporal evolution of eddy and mean kinetic energy has been analysed, on each of the four sub-regions composing the model domain, showing different behaviours. On annual scales and within the first 5 m depth, the eddy kinetic energy represents approximately the 60 % of the total kinetic energy over the whole domain, confirming the strong mesoscale nature of the surface current flows in this area. The analyses show that the model well reproduces the path and the temporal behaviour of the main known sub-basin circulation features. New mesoscale structures have been also identified, from numerical results and direct observations, for the first time as the Pantelleria Vortex and the Medina Gyre. The classical the kinetic energy decomposition (eddy and mean) allowed to depict and to quantify the stable and fluctuating parts of the circulation in the region, and to differentiate the four sub-regions as function of relative and absolute strength of the mesoscale activity. Furthermore the Baroclinic Energy Conversion term shows that in the Sardinia Channel the mesoscale activity, due to baroclinic instabilities, is significantly larger than in the other sub-regions, while a negative sign of the energy conversion, meaning a transfer of energy from the Eddy Kinetic Energy to the Eddy Available Potential Energy, has been recorded only for the surface layers of the Sicily Channel during summer.

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Intensification and Northward Extension of Northwest Pacific Anomalous Anticyclone in El Niño Decaying Mid-Summer: An Energetic Perspective

10.21203/rs.3.rs-195970/v1 ◽

2021 ◽

Author(s):

Haosu Tang ◽

Kaiming Hu ◽

Gang Huang ◽

Ya Wang ◽

Weichen Tao

Keyword(s):

Energy Conversion ◽

El Niño ◽

El Nino ◽

Dominant Role ◽

North Indian Ocean ◽

Northwest Pacific ◽

Mean Flow ◽

The North ◽

Anomalous Anticyclone ◽

Circulation Anomalies

Abstract The Northwest Pacific (NWP) anomalous anticyclone (AAC) intensifies and extends northward from El Niño decaying early to mid- summer despite the dissipating sea surface temperature anomalies in the North Indian Ocean, North Atlantic and tropical NWP. The present study investigates these two intraseasonal variations of AAC from the perspective of energetics. The efficiency of dry energy conversion from background mean flow to perturbations in the El Niño decaying mid-summer is high and well explains the intensification of El Niño-induced circulation anomalies over the East Asia (EA)-NWP. The baroclinic energy conversion plays a more dominant role in this process than barotropic energy conversion. Besides, mean state changes over the EA-NWP from early to mid- summer are found in favor of the northward shift of the preferred latitude of the circulation anomalies. Thus, the El Niño induced circulation anomalies over the EA-NWP are more northward-extended in the later period. Empirical orthogonal function analyses further confirm that the northward extension of El Niño-induced circulation anomalies over the EA-NWP stems from local optimal mode change from early to mid- summer.

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Long-Term Analysis of Atmospheric Energetics Components over the Mediterranean, Middle East and North Africa

Atmosphere ◽

10.3390/atmos11090976 ◽

2020 ◽

Vol 11 (9) ◽

pp. 976

Author(s):

Silas Michaelides

Keyword(s):

Middle East ◽

Kinetic Energy ◽

Energy Conversion ◽

Internal Energy ◽

North Africa ◽

Climatic Data ◽

Monthly Means ◽

Seasonal Behavior ◽

Long Term Changes

In this research, one aspect of the climate that is not commonly referred to, namely, the long-term changes in the components of the atmospheric energy, is investigated. In this respect, the changes in four energy forms are considered, namely, Kinetic Energy (KE), Thermal Energy (TE), Internal Energy (IE), Potential Energy (PE) and Latent Energy (LE); the Energy Conversion (EC) between Kinetic Energy and Potential plus Internal Energy (PIE) is also considered. The area considered in this long-term energetics analysis covers the entire Mediterranean basin, the Middle East and a large part of North Africa. This broad geographical area has been identified by many researchers as a hot spot of climate change. Analyses of climatic data have indeed shown that this region has been experiencing marked changes regarding several climatic variables. The present energetics analysis makes use of the ERA-Interim database for the period from 1979 to 2018. In this 40-year period, the long-term changes in the above energetics components are studied. The monthly means of daily means for all the above energy forms and Energy Conversion comprise the basis for the present research. The results are presented in the form of monthly means, annual means and spatial distributions of the energetics components. They show the dominant role of the subtropical jet-stream in the KE regime. During the study period, the tendency is for KE to decrease with time, with this decrease found to be more coherent in the last decade. The tendency for TE is to increase with time, with this increase being more pronounced in the most recent years, with the maximum in the annual mean in KE noted in 2015. The sum of Potential and Internal energies (PIE) and the sum of Potential, Internal and Latent energies (PILE) follow closely the patterns established for TE. In particular, the strong seasonal influence on the monthly means is evident with minima of PIE and PILE noted in winters, whereas, maxima are registered during summers. In addition, both PIE and PILE exhibit a tendency to increase with time in the 40-year period, with this increase being more firmly noted in the more recent years. Although local conversion from KE into PIE is notable, the area averaging of EC shows that the overall conversion is in the direction of increasing the PIE content of the area at the expense of the KE content. EC behaves rather erratically during the study period, with values ranging from 0.5 to 3.7 × 102 W m−2. Averaged over the study area, the Energy Conversion term operates in the direction of converting KE into PIE; it also lacks a seasonal behavior.

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