81754 - CLIMATOLOGY

Learning outcomes

At the end of the course the student: - knows the basics of physical climatology; - knows the main statistical methods used in climate analysis; - can use the results of both numerical global climate simulations and regional climate models for future climate scenarios evaluation: - acquires abilities in communication on the subject and becomes familiar with the English terminology used in climatology; - knows how to use scientific literature.

Course contents

The course is organized in two modules delivered by two instructors run in parallel (2+2 hours of each module per week)

Module 1: Prof Michele Brunetti
Module 2: Prof. Paolo Ruggieri

Below the course contents for the two modules:

 

Module 1

The Global Energy Balance

• The nature of electromagnetic radiation and the physical laws of radiation
• Planck’s Law of Blackbody Emission
• Emission temperature of a planet
• Greenhouse effect
• Distribution of insolation
• The global energy balance (incoming solar radiation, outgoing long-wave radiation, albedo)

Atmospheric Energy Transfer and Climate

• Selective Absorption and Emission by Atmospheric Gases
• The Lambert-Bouguet-Beer Law
• Absorption rate and heating rate
• Schwarzchild's Equation
• Heuristic Model of Radiative Equilibrium
• Radiative-Convective Equilibrium Temperature Profiles

Clouds and radiation

• The radiative properties of clouds
• A Simple Model for the Net Radiative Effect of Cloudiness
• Observed Role of Clouds in the Energy Balance of Earth

The Energy Balance of the Surface

• The Surface Energy Budget
• Storage of Heat in the Surface
• Sensible and Latent Heat Fluxes
• Variation of Energy Balance Components with Latitude

Aerosols and Climate

• Aerosol distribution
• Volcanic Eruptions and Stratospheric Aerosols
• Anthropogenic Aerosols and Atmospheric Sulfur

The Hydrologic Cycle

• Water in the climate system
• Terrestrial branch of the hydrologic cycle
• Atmospheric branch of the hydrologic cycle
• Latitudinal distribution of the water balance
• The concept of evapotranspiration

The General Circulation of the Atmosphere

• The energy balance of the atmosphere and the general circulation
• The mean meridional circulation
• Eddy circulation
• The meridional transport of energy
• The meridional transport of moisture
• Angular momentum balance

The Orbital Parameter Theory of Ice Ages

• Historical introduction
• Eccentricity and the Sun-Earth distance
• Obliquity and insolation
• The variation of annual mean insolation
• Orbital parameter evolution
• Testing the theory
• The middle pleistocene transition

Geochemical cycles

• Early evolution of the atmosphere
  
• The nitrogen cycle
• the oxygen cycle
• the carbon cycle

• rate of storage and removal of gases in the atmosphere

The Earth Observation

• The International Geophysical Year and the Global Observation System
• A brief history of the ground base observation networks with a focus on the Italian network

Proxy Data

• What proxy data are
• Documentary reconstructions
• The delta-O18 isotope ratio
• Some examples of proxies: Corals, Palynology, Dendroclimatology, Ice cores, Sediments

The Problem of the Data Quality in Climatology

• The importance of data quality in climatology
• The example of ground based stations
• Data error sources (instruments change, instrument and station relocation, solar radiation sheltering, in situ changes, observation rules changes)
• The metadata
• Some homogenization techniques

Principal Component Analysis/Empirical Orthogonal Functions (PCA/EOF)

• What PCA is
• Diagonalization of the covariance matrix (eigenvalues and eigenvectors)
• Covariance and correlation matrix
• Varimax rotation
• Some example of PCA

Extreme Events Theory

• General aspects of the extreme events theory
• Extremal Types Theorem
• The Generalized Extreme Value (GEV) distribution
• Above threshold models and the Generalized Pareto distribution

Module 2

Introduction

• The components of the climate system
• Energy balance and circulation
• Zonal mean, temporal mean and eddie

Governing equations of the atmosphere and the ocean

• Recap of primitive equations and scale analysis for the ocean and the atmosphere
• Thermodynamic equation, conservation of angular momentum and thermal wind equation for a steady axisymmetric flow
  

Axisymmetric tropical circulation

• Observed mean state of the tropical atmosphere
• Hide’s theorem and the angular momentum conserving wind
• Hadley cell and the sub-tropical jet, the Held-Hou mode

Quasi-geostrophy

• A quasi-geostrophic zonally averaged model of the middle-atmosphere
• The Transformed Eulerian Mean
• The Eliassen-Palm theorem, the non-acceleration theorem and eddy-balanced circulations
  

The extra-tropics

• Observed mean state of the extra-tropical atmosphere
• Eddy potential vorticity flux, surface winds and vertical wind shear
  

The stratosphere

• Observed mean state of the stratosphere and chemistry of the stratospheric ozone
• The Brewer-Dobson circulation, the Charney-Drazin criterion and the Rossby-wave pumping
  

The ocean

• Observed mean state of the ocean
• The Overturning Circulation and the wind driven circulation
  

The cryosphere

• Observed state of the cryosphere and physical properties of the ice
• The role of ice in the energy balance, the ice feedback and the Budyko-Sellers model
  

E Zonal asymmetries in the Earth climate

• The orography of the Earth and orographically forced stationary waves
• Phenomenology of the the Walker Circulation and the Monsoon
  

E The eddy-driven jet, the extra-tropical storm tracks

• The rationale of an eddy-driven jet
• The North Atlantic Oscillation
• Oceanic frontal regions
  

E El Nino Southern Oscillation

• Phenomenology of ENSO, the Bjerknes’ Hypothesis and the delayed oscillator model
• Diagnosing teleconnections
  

E Overview of interannual and multi-decadal climate variability

Readings/Bibliography

Dennis L. Hartmann: Global Physical Climatology ; Academic Press

Peixoto and Oort: Physics of Climate; American Institute of Physics; 1st edition (February 1, 1992)

Wilks: Statistical Methods in the Atmospheric Sciences, 3rd Edition (2011)

Teaching methods

Frontal lectures

Assessment methods

The final exam is inteded to verify the understanding/comprehension of all phenomenological, mathematical/statistical aspects of the topics dealt during the two modules.

The final exam consists of an oral examination during which the student will be asked generally three questions selected between the two modules.

The exam lasts 50 minutes on average.

Teaching tools

PC and Projector

Office hours

See the website of Michele Brunetti

See the website of Paolo Ruggieri