Raffaele Marino joined the Nature Publishing Group as editor of “Scientific Reports“
Go to the website: https://www.nature.com/srep/
Author: fferaco
Harikrishnan Charuvil Asokan PhD Thesis defense (09/2023)
Harikrishnan Charuvil Asokan PhD thesis defense: Investigations of Mesosphere and Lower Thermosphere Mesoscale Dynamics Using Ground-based Measuring Techniques
Thesis advisors
– CHAU Jorge Luis, Research Director (Leibniz Institute for Atmospheric Physics)
– MARINO Raffaele, Head of Research (CNRS)
Summary
Mesoscale dynamics in the mesosphere and lower thermosphere (MLT) region are mainly due to atmospheric gravity waves (GWs) and stratified turbulence. GWs are assumed to be the dominant drivers of MLT mesoscale dynamics. However, characterising and observing these scales is challenging due to their scales and intermittent nature. This thesis investigates the mesoscale dynamics of the MLT region using ground-based observations. The main dataset used in this work is from multistatic specular meteor radars (SMRs). The study is complemented with observations from airglow imagers and satellites and with direct numerical simulations as well as high-resolution model data. This thesis uses a novel second-order statistics approach to investigate the correlation functions in temporal and spatial scales from one-dimensional projections of three-dimensional wind velocities. In a case study, we found that unexpected large horizontal scales dominate the dynamics. Intriguing high vertical velocity estimates using multistatic SMRs at different latitudes are also addressed through a validation study by constructing virtual multistatic radar systems based on winds from a high-resolution general circulation model.
Meet Us @ EGU General Assembly 2022, 23-27/05, Wien (Aus)
Meet Us @ EGU General Assembly 2022, 23-27/05, Wien (Aus)
The European Geophysical Union General Assembly 2022 will bring together geoscientists from all over the world for one meeting covering all disciplines of the Earth, planetary, and space sciences. The EGU aims to provide a forum where scientists, especially early career scientists, can present their work and discuss their ideas with experts in all fields of geoscience.
Find out more @ EGU official website
- Oral Presentation, R. Foldes, S.S. Cerri, E. Camporeale, F. Feraco and R. Marino et al.: “(EGU22-11160) Local energy release by extreme vertical drafts in stratified geophysical flows“
- Oral Presentation, E. Pietropaolo, R. Foldes, A. Del Corpo, R. Marino and M. Vellante et al.: “(EGU22-5411) Automated tool for estimating field line resonance frequencies using ground-based magnetometer measurements“
LETMA – CeLyA Spring School 2022: Waves & geosciences
LETMA – CeLyA Spring School 2022: Waves & geosciences
General Information
The spring school is proposed in the framework of LETMA, which is a joint laboratory between CEA, Sorbonne University and Centrale Lyon. LETMA studies the propagation of low frequency waves in the atmosphere. In order to raise awareness of the subjects studied in relation to environmental issues, LETMA’s partners propose a spring school Waves & geosciences: Infrasound and beyond for students and researchers.
The spring school will take place from 28 March 2022 to 1 April 2022 at the Valpré seminar centre in Ecully near Lyon, France. The number of participants is expected to be around 50.
This spring school, in the format of a research school, is aimed at students, researchers and engineers. The objective is to present the state-of-the-art on different topics: physics of the atmosphere and propagation, statistical methods and machine learning, quantification of uncertainties, etc. An important aspect will be dedicated to the presentation of dual problems (identification of acoustic sources for environmental problems, contribution to climate modelling, etc.). Some of the lectures will be complemented by practical sessions. Collaborative work and scientific presentations will allow exchanges between participants.
Find out more @Centre for Acoustic Research
Fabio Feraco PhD Thesis defense
Fabio Feraco PhD thesis defense: Dynamics driven by emerging vertical drafts in stratified turbulent flows
Committee
– Bertoglio Jean-Pierre, Research Director (CNRS, Emeritus) – Thesis Supervisor
– Marino Raffaele, Head of Research (CNRS) Thesis Supervisor
– Primavera Leonardo, Professor (University of Calabria, Italy) – Thesis Supervisor
– Lanotte Alessandra, Researcher (CNR, Italy) – Rapporteur
– Liu Hanli, Senior Scientist and Professor (NCAR-CU Boulder, US) – Rapporteur
– Moisy Frédéric, Professor (University of Paris-Saclay) – Examiner
– Bourgoin Mickaël, Head of Research (CNRS, École Normale Supérieure of Lyon) – Examiner
– Folini Doris, Senior scientist at Lecturer (ETH) – Examiner
Summary
Intermittency is a characteristic feature of turbulent flows.
Typically observed as the localized enhancement of small-scale field fluctuations, it is at the origin of the bursty behavior of the energy dissipation in fluids. However, the intermittent character of the velocity and of the temperature fields has been reported in many observations in geophysical flows also in the large scales.
The purpose of this thesis is precisely to characterize the emergence of large-scale intermittent vertical velocity drafts and temperature bursts in stratified turbulent flows of geophysical interest, as detected in the atmosphere and the oceans. In particular, using direct numerical simulations (DNSs) of the Boussinesq equations (with or without rotation), I explore the parameter space with the aim of investigating dynamics and energetics in stratified flows in which the interplay of internal waves and turbulent motions produces powerful enhancements of the vertical velocity and temperature at large-scale. This phenomenon, resulting from a resonant mechanism that I describe through a simple one-dimensional model, feeds back on the energy transport and dissipation property of the flow, influencing mixing. The large-scale intermittency detected in stratified flows has been investigated here by means of high order statistics of the prognostic fields, and in particular through the kurtoses of the vertical velocity and temperature, which are found to have a non-monotonic behavior with the Froude number, that is, the control parameter of the turbulent system viewed as a superposition of waves and nonlinear eddies.
The Eulerian fields are used to characterize the distribution of the energy across the scales and the exchanges between kinetic and potential energies within the resonant regime. Lagrangian tracers have also been released in DNSs to investigate their dispersion in stratified turbulent flows developing extreme vertical drafts.
The first radar observation of an extreme event in the vertical velocity field in the mesosphere and lower thermosphere, interpreted here as a “super-bore”, is finally presented together with a study of the diffusion of a passive scalar in a turbulent flow, preliminary to future characterizations of the passive scalar diffusion in a stratified environment in the resonant regime identified as before in terms of the Froude number.
Keywords: stratified turbulence, waves, geophysical flows, mixing, intermittence, rotation, Lagrangian particles
New Article on EOS Vol. 103
New Article on EOS (Science News by AGU) Vol. 103: A New Journey Around (and Around) the Sun
Daniele Telloni, Francesco Valentini and Raffaele Marino
The Solar Orbiter just completed its commissioning phase while en route to the Sun. It has already provided valuable looks at solar campfires and Venus’s magnetic fields, and it promises much more.
Find out more on EOS
New Article on Physics Review Fluids Vol. 7 (3), p. 033801
New Publication on Physical Review Fluids, Vol. 7 (3), p. 033801: Turbulence generation by large-scale extreme vertical drafts and the modulation of local energy dissipation in stably stratified geophysical flows
R. Marino, F. Feraco, L. Primavera, A. Pumir, A. Pouquet, D. Rosenberg, P. Mininni
We observe the emergence of strong vertical drafts in direct numerical simulations of the Boussinesq equations in a range of parameters of geophysical interest. These structures, which appear intermittently in space and time, generate turbulence and enhance kinetic and potential energy dissipation, providing a possible explanation for the observed variability of the local energy dissipation in the bulk of oceanic flows and the modulation of its probability distribution function. We show how, due to the extreme drafts, in runs with Froude numbers observable in geophysical scenarios, roughly 10% of the domain flow can account for up to 50% of the global volume dissipation, reminiscent of estimates based on oceanic models.
