75812 - Radiative Transfer and Remote Sensing

Learning outcomes

At the end of the course the student will possess a solid background in:

- the fundamental laws of the transfer of radiation in presence of absorption and scattering processes, both in clear and cloudy conditions;

- know the diabatic effects of radiative transfer, such as heating and cooling of the surface and of atmospheric layers;

- appreciate the inverse methodologies used to derive geophysical parameters from remote measurements;

- use this knowledge to interpret very complex multispectral radiance data set to derive geophysical information;

The student is able to express orally specific arguments related to the course subjects, using material and lecture notes in English; participate to the lab group sessions to improve the interaction with peers and perform collaborative work;

The student writes a report on the lab activity and discusses its content during the oral examination.

Course contents

Absorption by gaseous molecules: the gaseous molecule as a rigid quantized rotator, the gaseous molecule as a quantized vibrator, vibro-rotational bands. Examples of optical depth spectra of gaseous molecules. Line shapes and the absorption coefficient: natural, collisional and Doppler broadening; Voigt line profile. The computation of transmittance

Formalism to describe a general scattered wave. Modelling atmospheric processes: scattering by air molecules.
Absorption by a small object.
Radiative properties of large objects: scattering and absorption by large spherical particles; scattering and absorption by a distribution of particles; modelling of aerosol physical and radiative properties. The colour of the sky. Visual range.

An introduction to remote sensing: satellite orbit geometry and Kepler's law; orbit perturbations. Classification of weather satellites: geostationary and polar satellites. Instrument parameters: geometry, type of scanning systems, main sensor parameters. Examples of data from modern sensors used for remote sensing of the environment, meteorology and climate.

Schwarzschild’s equation and weighting functions for clear air; idealised weighting functions of real satellite instruments, schematic satellite-observed radiance near an idealised absorption line; examples of satellite (IR) radiances in clear conditions. Infrared radiative transfer in presence of clouds: transmittance and the weighting function; examples of upwelling radiances at TOA from 50 to 3500 cm-1.
Remote sensing in the Microwave and Millimeter-wave spectral region
Shortwave radiative transfer: the general equation, scattering diagram formal solution
An introduction to discrete ordinates method and the adding method. Application of adding method to inhomogeneous atmospheres. Some examples of radiances computed in the shortwave.

Inverse methods: some examples of problems that involve inversion (retrieval of temperature from spectral radiances, aerosol size distribution from extinction measurements); the number of independent measurements.
Using additional information to solve the temperature retrieval problem: constrained linear inversion; operate on the structure of the solution and use “climatological” information.
The estimation problem and the use of constraints; the maximum probability solution.

Readings/Bibliography

Lecture notes (in english, downloadable).

Bohren C.F. and E.E. Clothiaux, Fundamentals of atmospheric radiation, 2006, Wiley-VCH Verlag GmbH

Kuo-Nan Liou, An introduction to atmospheric radiation, 1980, Academic Press Inc.

Michael I. Mishchenko, Larry D. Travis and Andrew A. Lacis, Scattering, Absorption and Emission of Light by Small Particles NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA The electronic edition is available at the following Internet sites: http://www.giss.nasa.gov/~crmim/books.html

Teaching methods

Formal lectures using multimedia material.

Remote sensing data analysis discussed and solved at the remote sensing lab. 

Assessment methods

Written report on lab activities. Final oral examination

Teaching tools

Lectures using pc and projector.

Office hours

See the website of Rolando Rizzi

See the website of Tiziano Maestri