scattering/reflectance. it is due to the passage of the e.m. wave from a medium to another of...

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Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends from: - composition (refractive index) of the medium - relative (to the e.m. wavelength) length of the path of the e.m. within the discontinuity: size, shape and orientation of the medium

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Page 1: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering/Reflectance.It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index).It depends from:- composition (refractive index) of the medium- relative (to the e.m. wavelength) length of the path of the e.m. within the discontinuity: size, shape and orientation of the medium

Page 2: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

SCATTERING:

Huygens principle

How many wavelengthsthe wave is spending inside a medium with different propagation characteristics?

Page 3: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering: a geometric optics representation

Page 4: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Yang et al., “Single-scattering properties of complex ice crystals in terrestrial Atmosphere”, Contr. Atmos. Phys., 71, 223-248, 1998.

Page 5: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering

Mie scattering & Geometric Optics: Depends from scattering particleamount, shape, dimension & relative orientation particle-wave

Rayleigh scattering: Depends from scattering particleamount

Negligible Scattering: independent from an particle property

&

non spheric

al partic

les methods

Page 6: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

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Page 7: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

SCATTERING: DEFINIZIONIScattering Singolo

Variabili ottiche di singola particella (SSOP Single scattering optical properties)

- cross sections

- ssa

- phase function

Variabili ottiche di polidispersione

Variabili ottiche di volume

Variabili macroscopiche di strato

Scattering Multiplo

Page 8: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Proprieta’ fisiche delle singole molecole e Aerosols (composizione)

(p,T)Proprieta’ ottiche delle singole molecole e Aerosols (λ,Ω)

Proprieta’ ottiche del volume (λ,Ω)

Equazione del trasporto radiativo (λ,Ω)Proprieta’ ottiche della superficie/boundaries (λ,Ω)

Soluzione (∫ ∫ …dλdΩ)

Page 9: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Proprieta’ fisiche delle singole molecole e Aerosols (composizione)

Proprieta’ ottiche delle singole molecole e Aerosols (λ,Ω)

Proprieta’ ottiche del volume (λ,Ω)

Equazione del trasporto radiativo (λ,Ω)

Soluzione (∫ ∫ …dλdΩ)

Processi radiativi d’interazione

Calcolo delle proprieta’ ottiche di volume:Spessore ottico, albedo di singolo scattering, proprieta’ angolari dello scattering (per es: g o matrice di diffusione) o T,R,A

Risoluzione numerica dell’eq. Del trasporto radiativo

Risoluzione numerica di eventuali integrazioni angolari e spettrali

Page 10: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering: numerical representation

Variabili ottiche di singola particella

- Cross Sections (Efficiencies)

- Single scattering albedo: ω

- Phase function: Scattering Matrix,Tavola P(γ), Coefficienti dei Polinomi di Legendre, Asymmetry factor (g), Approximations (e.g.: HG)

Page 11: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Diffraction limit

Page 12: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends
Page 13: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends
Page 14: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering: Polarization

Page 15: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

http://www.astro.uva.nl/scatter/

Page 16: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Source function (solar, plane parallel)

Page 17: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Metodi numerici per il calcolo delle proprieta’ ottiche di singola particella

• Rayleigh scattering (particelle relativamente piccole)

• Mie scattering (particelle sferiche di dimensioni comparabili con la lunghezza d’onda)

• Metodi numerici per particelle non sferiche (particelle non-sferiche di dimensioni comparabili con la lunghezza d’onda)

• Ottica geometrica (particelle di forma qualsiasi di dimensioni relativamente grandi)

Casi particolari: pr es: coated spherical particles

Page 18: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends
Page 19: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Esempi programma di simulazione per scattering Mie http://omlc.ogi.edu/calc/mie_calc.html

Page 20: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Ottica Geometrica

Page 21: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Discrete Dipole Approximation

Page 22: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Parametri per la descrizione della dipendenza angolare

• Scattering matrix

• Phase function– Tabelle– Coefficienti dei polinomi di Legendre– Asymmetry factor – HG approximation

Page 23: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Accorgimenti numerici: delta-Eddington

Page 24: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering: numerical representation

Definizione di polidispersioneVariabili di polidispersione -> effective radiusEsempi di forme funzionali di distribuzione

dimensionale:- Junge (power law) (aerosols)- Log-normal (aerosols) - Gamma distribution (clouds)- Marshall & Palmer (precipitation)

Page 25: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Una distribuzione dimensionale è definita da:

Distribuzione dimensionale

Esempi di distribuzione dimensionale descritta dalla funzione in basso con 2 valori di a e 3 di b

Page 26: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Calcolo delle proprieta’ di singolo scattering per una polidispersione

Page 27: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends
Page 28: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends
Page 29: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Calcolo dei coefficienti di scattering per 2 specie: A, M.

Page 30: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

(p,T)

La radiazione scatterata da un generico volume dipende dalla intensita’ e distribuzione angolare della radiazione incidente sul volume che pero’ dipende, atraverso lo scattering dei volumi vicini a sua volta dalla radiazione scatterata

Page 31: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Scattering MULTIPLO: METODI NUMERICI

• Ordini di scattering successivi• Doubling or Adding• Invariant imbedding• Funzioni X e Y• Discrete – Ordinate• Armoniche sferiche• Sviluppo in eigenfuction• Montecarlo• Soluzioni analitiche• Pseudo-assorbimento

Page 32: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Accorgimenti numerici: delta-Eddington

Page 33: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends
Page 34: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Doubling or adding method

Page 35: Scattering/Reflectance. It is due to the passage of the e.m. wave from a medium to another of different speed of propagation (refractive index). It depends

Si definisce per la trasmissione diffusa e per la riflessione:

Un prodotto R1R2 implica: