Low-Frequency Eddy Kinetic Energy Spectrum in the Deep Western North Pacific

Tropical cloud clusters (TCCs) are embryos of tropical cyclones (TCs) and may have the potential to develop into TCs. The genesis productivity (GP) of TCCs is used to quantify the proportion of TCCs that can evolve into TCs. Recent studies have revealed a decrease in GP of western North Pacific (WNP) TCCs during the extended boreal summer (July–October) since 1998. Here, we show that the changing tendencies in GP of WNP TCCs have obvious seasonality. Although most months could see recent decreases in GP of WNP TCCs, with October experiencing the strongest decreasing trend, May is the only month with a significant recent increasing trend. The opposite changing tendencies in May and October could be attributed to different changes in low-level atmospheric circulation anomalies triggered by different sea surface temperature (SST) configurations across the tropical oceans. In May, stronger SST warming in the tropical western Pacific could prompt increased anomalous westerlies associated with anomalous cyclonic circulation, accompanied by the weakening of the WNP subtropical high and the strengthening of the WNP monsoon. Such changes in background atmospheric circulations could favor the enhancement of atmospheric eddy kinetic energy and barotropic energy conversions, resulting in a recent intensified GP of WNP TCCs in May. In October, stronger SST warming in the tropical Atlantic and Indian Oceans contributed to anomalous easterlies over the tropical WNP associated with anomalous anticyclonic circulation, giving rise to the suppressed atmospheric eddy kinetic energy and recent weakened GP of WNP TCCs. These results highlight the seasonality in recent changing tendencies in the GP of WNP TCCs and associated large-scale atmospheric-oceanic conditions.

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Factors of boreal summer latent heat flux variations over the tropical western North Pacific

Climate Dynamics ◽

10.1007/s00382-021-05835-4 ◽

2021 ◽

Author(s):

Yuqi Wang ◽

Renguang Wu

Keyword(s):

Heat Flux ◽

Wind Speed ◽

North Pacific ◽

High Frequency ◽

Western North Pacific ◽

Surface Wind ◽

Low Frequency ◽

Boreal Summer ◽

Wind Intensity ◽

Tropical Western North Pacific

AbstractSurface latent heat flux (LHF) is an important component in the heat exchange between the ocean and atmosphere over the tropical western North Pacific (WNP). The present study investigates the factors of seasonal mean LHF variations in boreal summer over the tropical WNP. Seasonal mean LHF is separated into two parts that are associated with low-frequency (> 90-day) and high-frequency (≤ 90-day) atmospheric variability, respectively. It is shown that low-frequency LHF variations are attributed to low-frequency surface wind and sea-air humidity difference, whereas high-frequency LHF variations are associated with both low-frequency surface wind speed and high-frequency wind intensity. A series of conceptual cases are constructed using different combinations of low- and high-frequency winds to inspect the respective effects of low-frequency wind and high-frequency wind amplitude to seasonal mean LHF variations. It is illustrated that high-frequency wind fluctuations contribute to seasonal high-frequency LHF only when their intensity exceeds the low-frequency wind speed under which there is seasonal accumulation of high-frequency LHF. When high-frequency wind intensity is smaller than the low-frequency wind speed, seasonal mean high-frequency LHF is negligible. Total seasonal mean LHF anomalies depend on relative contributions of low- and high-frequency atmospheric variations and have weak interannual variance over the tropical WNP due to cancellation of low- and high-frequency LHF anomalies.

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V3: Structure and vibrations from density functional theory, Franck–Condon factors, and the pulsed-field ionization zero-electron-kinetic energy spectrum

The Journal of Chemical Physics ◽

10.1063/1.1337859 ◽

2001 ◽

Vol 114 (9) ◽

pp. 4036-4044 ◽

Cited By ~ 43

Author(s):

Patrizia Calaminici ◽

Andreas M. Köster ◽

Tucker Carrington ◽

Pierre–Nicholas Roy ◽

Nino Russo ◽

...

Keyword(s):

Density Functional Theory ◽

Energy Spectrum ◽

Kinetic Energy ◽

Density Functional ◽

Field Ionization ◽

Functional Theory ◽

Kinetic Energy Spectrum ◽

Pulsed Field Ionization ◽

Condon Factors ◽

Franck Condon

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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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Measurement of turbulent spatial structure and kinetic energy spectrum by exact temporal-to-spatial mapping

Physics of Fluids ◽

10.1063/1.4999102 ◽

2017 ◽

Vol 29 (8) ◽

pp. 085109 ◽

Cited By ~ 3

Author(s):

Preben Buchhave ◽

Clara M. Velte

Keyword(s):

Energy Spectrum ◽

Kinetic Energy ◽

Spatial Structure ◽

Spatial Mapping ◽

Kinetic Energy Spectrum

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Calculating Energy Spectra from Drifters

10.20944/preprints201607.0087.v1 ◽

2016 ◽

Author(s):

Joseph H. LaCasce

Keyword(s):

Energy Spectrum ◽

Kinetic Energy ◽

Structure Function ◽

Two Dimensions ◽

Longitudinal Structure ◽

Kinetic Energy Spectrum ◽

Longitudinal Structure Function ◽

Large Pair ◽

Non Local ◽

Lagrangian Data

The relations between the kinetic energy spectrum and the second order longitudinal structure function in two dimensions are derived, and several examples are considered. The forward conversion (from spectrum to structure function) is illustrated first with idealized power law spectra, representing turbulent inertial ranges. The forward conversion is also applied to the zonal kinetic energy spectrum of Nastrom and Gage (1985) and the result agrees well with the longitudinal structure function of Lindborg (1999). The inverse conversion (from structure function to spectrum) is tested with data from 2D turbulence simulations. When applied to the theoretical structure function (derived from the forward conversion of the spectrum), the result closely resembles the original spectrum, except at the largest wavenumbers. However the inverse conversion is much less successful when applied to the structure function obtained from pairs of particles in the flow. This is because the inverse conversion favors large pair separations, which are typically noisy with particle data. Fitting the structure function to a polynomial improves the result, but not sufficiently to distinguish the correct inertial range dependencies. Furthermore the inversion of non-local spectra is largely unsuccessful. Thus it appears that focusing on structure functions with Lagrangian data is preferable to estimating spectra.

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