99081 - TRASFERIMENTO RADIATIVO: TEORIA E MODELLISTICA

Learning outcomes

At the end of the course the Student:

- knows the main physical processes governing the interaction between solar and terrestrial radiation with atmospheric and surface matter;

- knows the fundamentals laws of the radiative transfer in atmosphere. He learns the phenomenology and equations governing the physics of the radiative energy transfer by electromagnetic waves in a multiple scattering environment;

- is able to apply approximations to the radiative transfer general equation in order to interpret radiance fieldsin different regimes

- is able to implement numerical modelling techniques for radiative transfer algorithm;

- knows the basics of the satellite remote sensing and is capable to use geolocated calibrated radiances and create surface, atmospheric and cloud products for climate and meteorology;

- uses texts and lecture notes written in English and she/he is able to communicate about radiative transfer in atmosphere using the proper terminology

Course contents

1. Introduction, basic definitions

• Summary of the RT basics
• Radiometry and Photometry

2. Spectroscopy for atmospheric observations

• Molecular energy levels
• Electric dipole
• Rotational transitions
• Vibrational transitions
• Line Shapes
  
• Modelling: from the HITRAN database to layer optical depth

3.Thermodynamic equilibrium

• LTE e NLTE
• Curve of Growth
• Schwarzschild’s equation
• Complex refractive index
• Modelling: infrared upwelling radiances in clear sky

4. Absorption of shortwave Radiation

• Absorption processes in UV and visible
• The Ozone layer and the Chapman model
• Heating rates
• Modelling: downwelling solar irradiance absorption

5. Introduction to scattering

• Overview of scattering processes
• Rayleigh scattering
• Airlight
• Modelling: molecular scattering

6. RT equation and Scattering

• RT equation in a multiple scattering environment
• The Mie solution
• Stokes parameters

7. Cloud properties

• Single scattering properties of single particles
• Particle size distributions
• Bulk properties
• Modelling: parametrization of cloud and aerosols optical properties

8. Reflectance from surface and thin clouds

• Reflectance and transmission function
• BDRF
• Albedo
• Single scattering approximation
  

9. Polarization and Radar-lidar equation

• Light polarization
• Active sensors
• Depolarization
• Modelling: cloud base height from lidar backscatter data

10. Longwave RT in clear sky

• IR absorption and weighting functions
• LbL computations
• Modelling: from monochromatic layer optical depth to band transmittances

11. Cooling rates

• LW cooling rates
• Cooling rates in presence of clouds

12. Inversion methods

• Direct linear inversion
• Optimal estimation
• Modelling: inversion of temperature profile

13. General RT equation

• General form of the RT equation
• Azimuth decomposition
• Legendre polynomial

14. Advanced topics in RT modelling

• Two-stream approximation
• Similarity principle and 𝛿-function approximation
• Scaling methods
• Modelling: scaling methods for fast radiative transfer in presence of clouds

15. Satellite data analysis techniques

• Introduction to weather satellites and missions
• Detection of essential climate variables
• Water vapor from sw data
• Sea and land surface temperature

Readings/Bibliography

* T. Maestri, lectures notes on radiative transfer and remote sensing

* K.N.Liou: An introduction to atmospheric radiation. Academic Press

* K.N.Liou: Radiation and cloud processes in the atmosphere. Oxford University Press

Teaching methods

The program content (6 ects) will be discussed by using both the blackboard and the video projector.

Simple problems will be solved during the classes (or suggested as homework) to facilitate the understanding of the theoretical part of the program. During the lessons, the student will implement in coded algorithm the solving equations of the multiple problems proposed.

Possibly, Satellite data will be made available to the students to facilitate the interpretation of remote sensing measurements.

Assessment methods

The assessment of the student's learnings is performed by an oral test which serves to evaluate the achievements of the main objectives of the course:

*) understanding the fundamental laws regulating the radiative transfer in atmosphere

*) the ability to implement numerical solution of the proposed problems

*) the ability to interpret satellite remote sensing data and products of atmosphere and surface

The test will cover the whole program. The student can start the test by discussing a written work concerning a specific topic of radiative transfer modelling. The oral test will last at about 1 hour.

Teaching tools

The following items will be available to the Students:

* Lectures notes (in pdf format).

* Scientific articles useful for the investigation of specific lines of research.

* Software algorithms (in MATLAB) for the numerical solution of specific problems.

 * Bibliography and references

Office hours

See the website of Tiziano Maestri