Course teached as: B028842 - FISICA DELL'ATMOSFERA Second Cycle Degree in PHYSICAL AND ASTROPHYSICAL SCIENCES Curriculum FISICA NUCLEARE E SUBNUCLEARE
Teaching Language
Italian
Course Content
Evolution, structure and composition of the mean atmosphere. Radiative transfer, energy balances in atmosphere. Green-house effect and climate change. Ozonosphere and ionosphere.
Atmospheric fluid dynamics, instability and transition to turbulence. Boundary layer. Rotating fluids, general circulation, vorticity. Elements of meteorological forecast.
Cloud formation and microphysics, global electric circuit and lightnings, precipitation phenomena and instruments for meteo observations.
An Introduction to Dynamic Meteorology
Author: James R. Holton
Publisher: Elsevier, ISBN: 0123848660
An Introduction to Atmospheric Physics
Author: David G. Andrews
Publisher: Cambridge University Press, ISBN: 0521693187
Atmospheric Science, An introductory survey
Authors: John M. Wallace e Peter V. Hobbs
Publisher: Academic Press, ISBN 9780127329512
Physics and dynamics of clouds and precipitation
Author: P. K. Wang
Publisher: Cambridge Univ. Press, ISBN: 9781107005563
Microphysics of clouds and precipitation
Authors: H. R. Pruppacher and J.D.Klett
Publisher: Springer, ISBN: 9780792342113
Learning Objectives
The course is intended as an introduction to Atmospheric Physics, to provide the physical foundations that regulate the behavior of the Earth's atmosphere and the mathematical tools underlying their modeling. Specific attention is paid to geophysical fluid dynamics, instability phenomena, fluid dynamics, microphysical phenomena in the atmosphere and thermodynamic transformations connected to phenomena of major meteorological interest.
The choice of topics covered is largely the result of the experience gained by the LaMMA Consortium (regional meteorological service of Tuscany) in the operational activity of numerical forecasting of meteorological conditions, with which students will be able to deal with internships and/or theses that they may eventually want to undertake on the subject. However, the topics will also be treated with the aim of enhancing the connections with the knowledge acquired in other subjects of the degree course, relating to the study of dynamic systems, computational physics and the parts of atmospheric physics covered in the astrophysics courses.
At the end of the course students will have acquired knowledge on the structure of the atmosphere with elements of climatology, will be able to understand the physical processes that regulate its dynamics and determine the phenomena of major meteorological interest by managing the main mathematical tools on which these processes are based. They will therefore possess the tools from which to start to face problems connected to meteorological observations and forecasts, on which, if interested, they will be able to try themselves within the proposed internships or thesis works.
Prerequisites
Classical Mechanics, Fluid dynamics, Thermodynamics, Mathematical Methods of Physics, as done in the basic courses of the three-year degree in Physics.
Teaching Methods
Frontal teaching with computer support.
Possible supplementary seminars in relation to the students's specific interests
Further information
As a possible integration to the topics covered in the course, the organization of seminars could be arranged on topics of current interest, such as, for example: meteorological measurement systems, climate change, oceanography, air quality.
As a possible supplement to the course for students interested in deepening the application of knowledge to applied meteorology, internships are proposed in which a part will be dedicated (about 1/3 of the internship time) to introduce them to numerical meteorological forecasting, as a problem to the initial and boundary conditions, in connection with the availability and evolution of Earth observation and computational tools. Students will then be introduced to the main equation discretization schemes, the closure problem, the concept of parameterization and the principles of data assimilation in numerical prediction models. The problem of the strong dependence on the initial conditions will be related to the non-linearity of the Navier-Stokes equations and the consequent problem of meteorological predictability will be addressed, arriving at the introduction of modern Ensemble Prediction Systems approaches. The practical part of the internships could then be focused on trying one of the problems described above, through simulating some significant cases.
Type of Assessment
Oral presentation (about 45 minutes) of a thematic proposed by the student, widely argued through skills and data acquired during the degree course. The presentation can be supported by slides. The exam also includes questions (3-5) for in-depth analysis on the presented topics or of a more general nature on the topics covered in the course, connected to the chosen thematic. The assessment will take into account the student's ability to argue the chosen thematic and to answer to the questions with clarity of exposition, scientific rigor and mastery of the matter, and to explain the selection and the logical connections of the presented topics in relation to the main motivation for the choice of the developed thematic.
Course program
The course is essentially organized in three modules, grouped according to the themes.
The first module (about 16 hours of lessons) consists of introductory lessons on evolution and present structure of the Earth's atmosphere, radiative transport, thermodynamics, elements of climatology, and it is organized in two parts. The first introduces the hypothesis of the formation of the atmosphere in relation to its average structure and the main processes that determine its present composition and structure. The second deals with the basic elements of radiative transport and energy balances underlying the thermal structure of the atmosphere, also recalling the elements of thermodynamics, already known from the preparatory courses, thus focusing on the most relevant for the treatment of atmospheric phenomena. The ozonosphere and ionosphere are also introduced with the main processes that characterize them.
The second module (about 16 hours of lessons) deals with the geophysical fluid dynamics. Also this module is organized in two distinct parts, related to fluid mechanics and to rotating fluids and geophysical systems. In the first part, the fundamental aspects of basic fluid dynamics are summarized in a synthetic way, as a reminder of what already covered in some preparatory courses. The deepening of some peculiar details of the physics of the atmosphere will be carried out, remaining within these limits, in particular on the aspects related to the transition to turbulence, starting from the description of Newtonian fluids through the Navier-Stokes equations. These aspects play an important role in geophysical fluid dynamics, also in light of the instabilities of hydrodynamic and geophysical flows. In this framework, the experiments of Rayleigh-Benard and Taylor-Couette will be described, taking up important issues in the field of Dynamical Systems Theory, in particular as regards the transition paths to chaos and turbulence.
The second part aims to provide the fundamental notions of the dynamics of rotating fluids and to use it to synthetically but rigorously describe and explain the general circulation of the atmosphere, also highlighting the relationship with the oceanographic analogue, framing the different space-time scales through the use of the dimensional analysis of the fundamental equations for rotating fluids. The fundamental role of vorticity will be highlighted, also mentioning its role in numerical forecasting in meteorology. The complex sequence of meteorological systems at various scales, present in the general circulation and interacting with it, will be briefly described, making use of the concepts related to the instabilities of geophysical flows. In this context, the boundary layer and atmospheric turbulence will be treated.
The third module (about 16 hours of lessons) deals with atmospheric instability and cloud physics. In the latter module the main mechanisms of cloud formation and related precipitation phenomena are analyzed in relation to atmospheric instability processes. For the structures of major meteorological interest, the microphysical processes of cloud formation are presented (from the nucleation process to the growth of the various types of hydrometeors and their mutual interactions) and the models with which to describe them are analysed. The global terrestrial electrical circuit and atmospheric electrical phenomena are explained, too. Finally, current measurement instruments are introduced, that are used to observe these processes and to quantify the associated phenomena, both from the ground and remotely
Summary of the topics covered.
Introduction to the evolution and present composition of the atmosphere: origin of the Earth's atmosphere, composition and structure of the standard atmosphere, balance of the main components.
Radiative transport and thermodynamics of the atmosphere: absorption, emission and scattering processes, radiation balances at the ground and in high atmosphere, thermal structure of the atmosphere. Greenhouse effect and climate change. Basic processes in ozonosphere and ionosphere. Thermodynamics of dry and humid air, and applications to the atmospheric system
Fluid mechanics: review of kinematics of continuous systems, atmospheric conservation laws, strain tensor and stress tensor, Newtonian fluids, dimensional analysis of Navier-Stokes equations: Reynolds and Froude numbers, viscosity and boundary layer, hydrodynamic instabilities, transition paths to chaos and turbulence, Salzmann-Lorenz '63 model and its dynamic analogues.
Rotating fluids and geophysical systems: Navier-Stokes equations in rotating systems, Coriolis force and conservation of angular momentum, vorticity equations. Dimensionless analysis in rotating systems: Rossby and Ekman numbers, Taylor-Proudman theorem, general circulation of the atmosphere.
Atmospheric instability and cloud physics: instability and phenomenology at different scales, cloud and hydrometeor formation processes, liquid and solid precipitation, terrestrial electrical circuit and lightnings, role of atmospheric aerosol, introduction to the instruments for meteorological measurements.