1. VLIDORT and Linearized MIE for the Retrieval of Aerosol Parameters
STCE Workshop, 24 May 2012, Green Room, BIRA-IASB
Retrieval of Aerosol Properties from Satellite and Ground-based Measurements
VLIDORT and Linearized MIE for the Retrieval of Aerosol Parameters
by S. Kochenova, M. De Mazière, V. Letocart, S. Vandenbussche, N. Kumps, T. Kerzenmacher, A.C. Vandaele, Y. Willame, et al.
Within the framework of the Radiative Transfer project funded by the Solar Terrestrial Centre of Excellence, PI M. De Mazière.

2. Summary of the Presentation
A little bit of history – my work on volcanic aerosols
Presentation of the new software: VLIDORT and Linearized MIE (& T-MATRIX)
Example of the use of this new software
Future plans 2

3. IASI data with aerosol/ice cloud signature
The signature is visible if you plot radiance in brightness temperature units.
Eyjafjallajokull volcano, Iceland
IASI pixels (track 16, 12:28h, 15/04/2010)
Aerosol retrievals come together with O3 and H2O retrievals. 3

4. VLIDORT can perfectly function as LIDORT with NSTOKES = 1
AVL (ASIMUT-VLIDORT)
- gas absorption (line-by-line & continua)
- instrument convolution/apodisation
- OEM (Rodgers)
VLIDORT can perfectly function as LIDORT with NSTOKES = 1
aerosols
aerosols
advanced RT + surface BRDF
advanced RT
with pol. + BRDF
1. LIDORT 3.3 and VLIDORT 2.5 (F77) provided by Dr. R. Spurr, RT Solutions, Cambridge, MA, USA
2. SPHER and T-MATRIX provided by Dr. M. Mishchenko, NASA GISS, New York, USA
3. ASIMUT provided by Dr. A.C. Vandaele et al., BIRA-IASB, Belgium 4

5. Retrieval of ice cloud concentration
- One ice cloud layer between km (Clarisse et al., 2010, Applied Optics)
- Gamma model: r = 15.0 m, b = 1/9 (Clarisse et al., 2010, Applied Optics)
- Clear sky IASI to retrieve H2O ( cm-1)  Retrieval of Caer (a priori 0.35 part/cm3) from IASI ( cm-1)  Forward modelling ( cm-1) 5

6. Research done by Others
ULB collaborators: L. Clarisse & P.-F. Coheur (retrieval of aerosol from IASI)
Extended Atmosphit: thermal IR, LBL forward and inverse Atmosphit with double-adding RT + aerosol treatment (MIE  LUT, one layer), spherical atmosphere, retrieval on the basis of Rodgers’s OEM
The slope depends on Radius & Concentration:
L. Clarisse et al., Tracking and quantifying volcanic SO2 with IASI, the September 2007 eruption at Jebel at Tair, Atmos. Chem. Phys., 8, , 2008
L. Clarisse et al., Retrieving radius, concentration, optical depth and mass of different types of aerosols from high-resolution infrared nadir spectra, App. Opt., 49, , 2010 6

7. Can we retrieve radius?
With the help of Finite Differences – a method used for testing Jacobians:
Jacobian w.r.t. r = (Radiance (r + ) – Radiance (r)) / 
Disadvantage:
- the MIE algorithm has to be run twice;
- the forward model has to be run twice (in case of only 1 aerosol layer).
Advantage:
- the FD method can be used to calculate Jacobians w.r.t. any other parameter. 7
End of my work with volcanic aerosols  the code goes to Sophie, Ann Carine & Nicolas

8. Linearized MIE and T-MATRIX
Created by: R. Spurr, RT solutions
Release: 5 April 2012 to scientists at BIRA-IASB
Language: F90
Purpose:
extinction & scattering X-sections, scattering matrix;
analytical derivatives of these optical properties w.r.t. radius, refractive index, etc.
Incorporation:
can be easily combined with VLIDORT F90;
combination with AVL is more difficult, as it would involve the replacement of VLIDORT F77 by VLIDORT F90.
Advantages:
faster than the similar codes written in F77;
the package allows analytical calculation of Jacobians w.r.t. radius, refractive index, etc. 8

9. Calculation of Radiance:
VLIDORT F90
Calculation of Radiance:
subroutines RT and BRDF (to read input, to solve RT, etc.)
You have to combine these subroutines according to your
PHYSICAL SCENARIO
Aerosol & molecular atmosphere have to be supplied from outside
Easy! VLIDORT comes together with examples.
Calculation of Jacobians:
the same as for Radiance +
Formulas to calculate analytical derivatives of - total albedo, - total optical thickness, - total scattering matrix w.r.t. the parameter you want to retrieve 9

10. Analytical Derivatives w.r.t. *
Calculated with Linearized MIE
Significant gain in time! 10 2

11. Example (VLIDORT + Linearized MIE)
Study case: West Coast of Mauritania and Senegal
Reason: MODIS and CALIPSO show a large dust plume on 21 June 2009
Literature: L. Clarisse et al., 2010
Aerosol layer: km 11

12. Example (Continuation - 2)
The same site was measured by PARASOL:
between 14:07h and 14:50h
The same site was measured by AERONET:
Gap between measurements at 9:25h & 16:57h)
Radiance at 856 nm 12

13. Example (Continuation - 3)
1. Simulation of the PARASOL data by using the AERONET data as a-priori;
2. Calculation of Jacobians w.r.t. aerosol vertical profile and model parameters (reff and veff);
3. Checking of the calculated Jacobians with FD. 13
This work was presented at EGU-2012 in Vienna, Austria.

14. Future Plans 1. Upcoming conference: IRS-2012, 6-10 August, Berlin
Poster: Retrieval of volcanic ash and ice cloud physical properties together with gas concentration from IASI measurements with the help of the AVL model
{ Retrieval of H2O, SO2, aerosol concentration, particle radius, and altitude }
2. Further work on the combination of VLIDORT F90 and Linearized MIE (& T-MATRIX) The easiest way is to combine it with absorption and continuum codes written in F90 to create a ‘template’ model, before combining it with more complicated models written in other languages (ASIMUT C/C++)  To be decided
3. Comparison of our RT and aerosol simulations (between BIRA and KMI)  ???
4. We would also like to start working on the earth radiation budget and climate within the framework of the Radiative Transfer project. 14

15. Not limited to the Earth
VLIDORT F90 and Linearized MIE are also applicable to Mars  it’s just another physical scenario.
Relative proof: use of AVL (VLIDORT F77 + MIE) for Mars
VLIDORT F90 replaces all previous versions of LIDORT/VLIDORT! 15

16. The End Many thanks for your attention! Many thanks to our presenters!
Next step: informal discussion during lunch! 16