Rapid intensification and propagation of the dayside aurora: Large scale interplanetary pressure pulses (fast shocks)

Abstract This study investigates the variation of tropical cyclone (TC) rapid intensification (RI) in the western North Pacific (WNP) and its relationship with large-scale climate variability. RI events have exhibited strikingly multidecadal variability. During the warm (cold) phase of the Pacific decadal oscillation (PDO), the annual RI number is generally lower (higher) and the average location of RI occurrence tends to shift southeastward (northwestward). The multidecadal variations of RI are associated with the variations of large-scale ocean and atmosphere variables such as sea surface temperature (SST), tropical cyclone heat potential (TCHP), relative humidity (RHUM), and vertical wind shear (VWS). It is shown that their variations on multidecadal time scales depend on the evolution of the PDO phase. The easterly trade wind is strengthened during the cold PDO phase at low levels, which tends to make equatorial warm water spread northward into the main RI region rsulting from meridional ocean advection associated with Ekman transport. Simultaneously, an anticyclonic wind anomaly is formed in the subtropical gyre of the WNP. This therefore may deepen the depth of the 26°C isotherm and directly increase TCHP over the main RI region. These thermodynamic effects associated with the cold PDO phase greatly support RI occurrence. The reverse is true during the warm PDO phase. The results also indicate that the VWS variability in the low wind shear zone along the monsoon trough may not be critical for the multidecadal modulation of RI events.

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Destructiveness of pyroclastic surges controlled by turbulent fluctuations

Nature Communications ◽

10.1038/s41467-021-27517-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Ermanno Brosch ◽

Gert Lube ◽

Matteo Cerminara ◽

Tomaso Esposti-Ongaro ◽

Eric C. P. Breard ◽

...

Keyword(s):

High Pressure ◽

Large Scale ◽

Dynamic Pressure ◽

Low Frequency ◽

Turbulent Energy ◽

Turbulent Structures ◽

Mean Values ◽

Flow Energy ◽

Pyroclastic Surges ◽

Pressure Pulses

AbstractPyroclastic surges are lethal hazards from volcanoes that exhibit enormous destructiveness through dynamic pressures of 100–102 kPa inside flows capable of obliterating reinforced buildings. However, to date, there are no measurements inside these currents to quantify the dynamics of this important hazard process. Here we show, through large-scale experiments and the first field measurement of pressure inside pyroclastic surges, that dynamic pressure energy is mostly carried by large-scale coherent turbulent structures and gravity waves. These perpetuate as low-frequency high-pressure pulses downcurrent, form maxima in the flow energy spectra and drive a turbulent energy cascade. The pressure maxima exceed mean values, which are traditionally estimated for hazard assessments, manifold. The frequency of the most energetic coherent turbulent structures is bounded by a critical Strouhal number of ~0.3, allowing quantitative predictions. This explains the destructiveness of real-world flows through the development of c. 1–20 successive high-pressure pulses per minute. This discovery, which is also applicable to powder snow avalanches, necessitates a re-evaluation of hazard models that aim to forecast and mitigate volcanic hazard impacts globally.

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Large-Scale Flow Patterns and Their Influence on the Intensification Rates of Western North Pacific Tropical Storms*

Monthly Weather Review ◽

10.1175/mwr3327.1 ◽

2007 ◽

Vol 135 (3) ◽

pp. 1110-1127 ◽

Cited By ~ 25

Author(s):

Justin D. Ventham ◽

Bin Wang

Keyword(s):

North Pacific ◽

Western North Pacific ◽

Large Scale ◽

Early Stage ◽

Flow Patterns ◽

Reanalysis Data ◽

Tropical Storm ◽

Tropical Storms ◽

Rapid Intensification ◽

Stage Of Development

Abstract NCEP–NCAR reanalysis data are used to identify large-scale environmental flow patterns around western North Pacific tropical storms with the goal of finding a signal for those most favorable for rapid intensification, based on the hypothesis that aspects of the horizontal flow influence tropical cyclone intensification at an early stage of development. Based on the finding that intensification rate is a strong function of initial intensity (Joint Typhoon Warning Center best track), very rapid, rapid, and slow 24-h intensification periods from a weak tropical storm stage (35 kt) are defined. By using composite analysis and scalar EOF analysis of the zonal wind around these subsets, a form of the lower-level (850 mb) combined monsoon confluence–shearline pattern is found to occur dominantly for the very rapid cases. Based on the strength of the signal, it may provide a new rapid intensification predictor for operational use. At 200 mb the importance of the location of the tropical storm under a region of flow splitting into the midlatitude westerlies to the north and the subequatorial trough to the south is identified as a common criterion for the onset of rapid intensification. Cases in which interactions with upper-level troughs occurred, prior to and during slow and rapid intensification, are studied and strong similarities to prior Atlantic studies are found.

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The Relationship Between Solar Wind Dynamic Pressure Pulses and Solar Wind Turbulence

Frontiers in Physics ◽

10.3389/fphy.2021.750410 ◽

2021 ◽

Vol 9 ◽

Author(s):

Mengsi Ruan ◽

Pingbing Zuo ◽

Zilu Zhou ◽

Zhenning Shen ◽

Yi Wang ◽

...

Keyword(s):

Solar Wind ◽

Large Scale ◽

Dynamic Pressure ◽

Solar Wind Dynamic Pressure ◽

Occurrence Rate ◽

Time Lags ◽

Gaussian Distributions ◽

Solar Wind Turbulence ◽

Wind Turbulence ◽

Pressure Pulses

Solar wind dynamic pressure pulses (DPPs) are small-scale plasma structures with abrupt and large-amplitude plasma dynamic pressure changes on timescales of seconds to several minutes. Overwhelming majority of DPP events (around 79.13%) reside in large-scale solar wind transients, i.e., coronal mass ejections, stream interaction regions, and complex ejecta. In this study, the intermittency, which is a typical feature of solar wind turbulence, is determined and compared during the time intervals in the undisturbed solar wind and in large-scale solar wind transients with clustered DPP events, respectively, as well as in the undisturbed solar wind without DPPs. The probability distribution functions (PDFs) of the fluctuations of proton density increments normalized to the standard deviation at different time lags in the three types of distinct regions are calculated. The PDFs in the undisturbed solar wind without DPPs are near-Gaussian distributions. However, the PDFs in the solar wind with clustered DPPs are obviously non-Gaussian distributions, and the intermittency is much stronger in the large-scale solar wind transients than that in the undisturbed solar wind. The major components of the DPPs are tangential discontinuities (TDs) and rotational discontinuities (RDs), which are suggested to be formed by compressive magnetohydrodynamic (MHD) turbulence. There are far more TD-type DPPs than RD-type DPPs both in the undisturbed solar wind and large-scale solar wind transients. The results imply that the formation of solar wind DPPs could be associated with solar wind turbulence, and much stronger intermittency may be responsible for the high occurrence rate of DPPs in the large-scale solar wind transients.

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Different Climatological Characteristics, Inner-Core Structures, and Intensification Processes of Simulated Intense Tropical Cyclones between 20-km Global and 5-km Regional Models

Journal of Climate ◽

10.1175/jcli-d-16-0093.1 ◽

2017 ◽

Vol 30 (5) ◽

pp. 1583-1603 ◽

Cited By ~ 1

Author(s):

Sachie Kanada ◽

Akiyoshi Wada

Keyword(s):

Tropical Cyclones ◽

General Circulation ◽

Large Scale ◽

Atmospheric General Circulation Model ◽

Inner Core ◽

Circulation Model ◽

Maximum Intensity ◽

Rapid Intensification ◽

Nonhydrostatic Model ◽

Before And After

Abstract Climatological characteristics of simulated intense tropical cyclones (TCs) in the western North Pacific were explored with a 20-km-mesh atmospheric general circulation model (AGCM20) and a 5-km-mesh regional atmospheric nonhydrostatic model (ANHM5). From the AGCM20 climate runs, 34 intense TCs with a minimum central pressure (MCP) less than or equal to 900 hPa were sampled. Downscaling experiments were conducted with the ANHM5 for each intense TC simulated by the AGCM20. Only 23 developed into TCs with MCP ≤ 900 hPa. Most of the best-track TCs with an MCP ≤ 900 hPa underwent rapid intensification (RI) and attained maximum intensities south of 25°N. The AGCM20 simulated a similar number of intense TCs as the best-track datasets. However, the intense AGCM20 TCs tended to intensify longer and more gradually; only half of them underwent RI. The prolonged gradual intensification resulted in significant northward shifts of the location of maximum intensity compared with the location derived from two best-track datasets. The inner-core structure of AGCM20 TCs exhibited weak and shallow eyewall updrafts with maxima below an altitude of 6 km, while downscaling experiments revealed that most of the intense ANHM5 TCs underwent RI with deep and intense eyewall updrafts and attained their maximum intensity at lower latitudes. The altitudes of updraft maxima simulated by the AGCM20 descended rapidly during the phase of greatest intensification as midlevel warming markedly developed. The change in major processes responsible for precipitation in AGCM20 TCs before and after maximum intensification suggests close relationships between the large-scale cloud scheme and midlevel warming and prolonged gradual intensification.

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Synoptic-Scale Precursors to Tropical Cyclone Rapid Intensification in the Atlantic Basin

Advances in Meteorology ◽

10.1155/2015/814043 ◽

2015 ◽

Vol 2015 ◽

pp. 1-16 ◽

Cited By ~ 6

Author(s):

Alexandria Grimes ◽

Andrew E. Mercer

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Potential Temperature ◽

Vertical Shear ◽

Specific Humidity ◽

Support Vector ◽

Rapid Intensification ◽

Synoptic Scale ◽

Atlantic Basin ◽

And Cluster Analysis

Forecasting rapid intensification (hereafter referred to as RI) of tropical cyclones in the Atlantic Basin is still a challenge due to a limited understanding of the meteorological processes that are necessary for predicting RI. To address this challenge, this study considered large-scale processes as RI indicators within tropical cyclone environments. The large-scale processes were identified by formulating composite map types of RI and non-RI storms using NASA MERRA data from 1979 to 2009. The composite fields were formulated by a blended RPCA and cluster analysis approach, yielding multiple map types of RI’s and non-RI’s. Additionally, statistical differences in the large-scale processes were identified by formulating permutation tests, based on the composite output, revealing variables that were statistically significantly distinct between RI and non-RI storms. These variables were used as input in two prediction schemes: logistic regression and support vector machine classification. Ultimately, the approach identified midlevel vorticity, pressure vertical velocity, 200–850 hPa vertical shear, low-level potential temperature, and specific humidity as the most significant in diagnosing RI, yielding modest skill in identifying RI storms.

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Dynamics of the Electron Belts

10.1007/978-3-030-82167-8_7 ◽

2021 ◽

pp. 213-240

Author(s):

Hannu E. J. Koskinen ◽

Emilia K. J. Kilpua

Keyword(s):

Solar Wind ◽

Large Scale ◽

Geomagnetic Storms ◽

Radiation Belts ◽

Satellite Observations ◽

Interplanetary Shocks ◽

Outer Electron ◽

Structure And Dynamics ◽

The Earth ◽

Pressure Pulses

AbstractIn this chapter we discuss the overall structure and dynamics of the electron belts and some of their peculiar features. We also consider the large-scale solar wind structures that drive geomagnetic storms and detail the specific responses of radiation belts on them. Numerous satellite observations have highlighted the strong variability of the outer electron belt and the slot region during the storms, and the energy and L-shell dependence of these variations. The belts can also experience great variations when interplanetary shocks or pressure pulses impact the Earth, even without a following storm sequence.

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A Numerical Study of Typhoon Megi (2010). Part I: Rapid Intensification

Monthly Weather Review ◽

10.1175/mwr-d-13-00070.1 ◽

2014 ◽

Vol 142 (1) ◽

pp. 29-48 ◽

Cited By ~ 75

Author(s):

Hui Wang ◽

Yuqing Wang

Keyword(s):

Large Scale ◽

Structural Changes ◽

Inner Core ◽

Numerical Study ◽

Convective Available Potential Energy ◽

Heat Content ◽

Vertical Shear ◽

Rapid Intensification ◽

Upper Troposphere ◽

Spiral Rainbands

Abstract Typhoon Megi (15W) was the most powerful and longest-lived tropical cyclone (TC) over the western North Pacific during 2010. While it shared many common features of TCs that crossed Luzon Island in the northern Philippines, Megi experienced unique intensity and structural changes, which were reproduced reasonably well in a simulation using the Advanced Research Weather Research and Forecasting Model (ARW-WRF) with both dynamical initialization and large-scale spectral nudging. In this paper processes responsible for the rapid intensification (RI) of the modeled Megi before it made landfall over Luzon Island were analyzed. The results show that Megi experienced RI over the warm ocean with high ocean heat content and decreasing environmental vertical shear. The onset of RI was triggered by convective bursts (CBs), which penetrate into the upper troposphere, leading to the upper-tropospheric warming and the formation of the upper-level warm core. In turn, CBs with their roots inside of the eyewall in the boundary layer were buoyantly triggered/supported by slantwise convective available potential energy (SCAPE) accumulated in the eye region. During RI, convective area coverage in the inner-core region was increasing while the updraft velocity in the upper troposphere and the number of CBs were both decreasing. Different from the majority of TCs that experience RI with a significant eyewall contraction, the simulated Megi, as the observed, rapidly intensified without an eyewall contraction. This is attributed to diabatic heating in active spiral rainbands, a process previously proposed to explain the inner-core size increase, enhanced by the interaction of the typhoon vortex with a low-level synoptic depression in which Megi was embedded.

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