Foto del docente

Tiziano Maestri

Associate Professor

Department of Physics and Astronomy "Augusto Righi"

Academic discipline: FIS/06 Physics of the Earth and of the Circumterrestrial Medium


Keywords: remote sensing radiative transfer in multiple scattering environment clouds and aerosols cloud identification and classification retrievals

Atmsopheric radiative tansfer and high spectral resolution forward models

Multiple scattering of electromagnetic waves

Single scattering properties of ice crystals and aerosols

Polarimetric properties of particles and polarization

Characterization of cloud optical properties from microwave to UV

Satellite data analysis and machine learning techniques for the identification and classification of the scenes (clear, cloudy, aerosol)

Retrieval techniques fot optical physical and microphysical properties of clouds

Radiative energetic balance in presence of clouds

Satellite measurements collocation and algorithms for the comparison of cloud products from multiple sensors

Statistical analysis of backscatter profiles of thin cirrus clouds from satellite lidar measurements

Water vapour absorption continuum parameterization and validation of cloud optical properties in the far infrared part of the spectrum

Evaluation of Climate Model perfomances in reproducing cloud cover and comparison with satellite measurements 



1.     Forward computing

Part of the research work is based on the development and improvement of algorithms for the computation of radiances and fluxes at high spectral resolution in presence of multiple scattering layers.  The forward radiative transfer code (RTX) includes the status of the art of the knowledge about gas spectroscopy, radiation-matter interaction and atmospheric physical thermodynamics processes. RTX is used as a reference for theoretical investigations and for calibration/validation experiment of satellite sensors at infrared wavelengths. In the last years RTX has been modified to work at microwave and solar wavelengths and lots of efforts have been put to model the emissivity and reflectance of the surface (in particular the sea surface bi-directional reflectance and its dependence on speed and direction of the wind).


2.     Single Scattering Properties

Techniques for the computation of the single scattering properties for liquid water (homogeneous or with an ice core, precipitating or non-precipitating) and aerosols (hygroscopic or non-hygroscopic) using the Mie Method have been developed. Single scattering properties of non- spherical ice crystals are continually updated and a database of in-situ measured particles size distributions benefits of new data from field experiments.

Recently the Discrete Dipole Approximation methodology for the computation of optical properties of ice crystal (extinction and scattering efficiency and Mueller matrix) at large wavelengths has been adopted. The sensitivity of single scattering properties of ice particles to shape and orientation has been evaluated. The optical properties of crystals with respect to specific direction of the incident electromagnetic field have been used to study radar polarimetric parameters.


3.     Inversion Techniques

Development of inversion techniques to infer optical and microphysical properties of multiple scattering layers from remote sensing measurements is the most important line of research.

It has been recently developed a new retrieval algorithm (RT-RET) which exploits measurements from multiple sensors (passive and active) operating at infrared and solar wavelengths. Advantages and disadvantages of infrared retrieval with respect to those working at solar wavelengths have been studied. An error analysis has been performed and sensitivity to atmospheric, surface and cloud physical parameters has been evaluated.

A climatology of backscatter profile has been defined so that the vertical distribution of the ice-water-content in the cloud depth could be better retrieved. New cloud properties inversion techniques using passive and active measurements in the shortwave and at microwave are investigated.




The research activity also includes other lines of research. Among them:

  • Definition of machine learning algorithms for the identification of liquid water, ice phase or precipitating clouds (in particular on Artic surface) exploiting high spectral resolution measurements from ground based or satellite sensors (microwave and infrared).
  • Development of cloud optical properties parameterizations for numerical weather prediction and climate models based on in-situ particle size distribution data and single scattering databases.
  • Evaluation of IPCC Climate Models performances in reproducing ice cloudy fields
  • Analysis of solar system planets' atmospheres at shortwave and long wave wavelengths for the retrieval of clear and cloudy sky properties.






Forward (RTX) and inverse (RT-RET) radiative transfer models are applied to satellite sensors data and to measurements collected in experimental field campaigns (i.e. EAQUATE, COBRA-ECOWAR, P-THORPEX, M-PACE and others).

Main activities performed during data analysis are resumed in what follows:

•        {Clear Sky}: (1) validation of water vapour continuum absorption parameterization in the far infrared (100-600 cm-1); (2) validation of new parameterization of the marine surface reflectance at solar wavelengths; (3) validation of snow and iced surface emissivity at microwave regions; (4) impact of tropospheric aerosols on solar radiances at the surface or at the top of the atmosphere and evaluation of sensitivity to composition and relative humidity.

•        {Cloudy Sky}: (1) spectral fluxes and energetic balances at all atmospheric levels; (2) ice crystals mixture optical properties validation over the whole spectrum; (3) inversion of radiances in presence of cloudy fields and development of new techniques for comparing cloudy sky data from multiple sensors and platforms (4) new retrieval methodology for the derivation of ice cloud optical properties from ground-based measurements in the far infrared and building of new ice cloud optical properties parameterizations.


Ice clouds are studied from satellite and global measurements (in particular from sensor on the NASA A-Train). The research activity includes collocation of multiple instrumentations and cloud retrieval products comparisons and identification of limits and advantages of various retrieval techniques and reference databases.

A classification of ice clouds is performed based on their backscattering characteristics. A full year of data from the satellite CALIOP (on board CALIPSO) has been used to identify common features in the vertical backscatter profile of Mid Latitude and Tropical cirrus clouds and their dependence on other cloud and atmospheric parameters.





2019-21: Local PI for the FORUM-Scienza project funded by the Italian Space Agency (ASI). Accordo Quadro n-2018-6-Q.0 with ASI and CNR-INO Florence (I). Responsible for the generation of scattering properties of clouds and aerosols for Line-by-Line and fast radiative transfer codes.

2020: Local PI for the E2E Simulator for FORUM CCN2 the future 9th Earth Explorer Track Mission (FORUM_E2ES_CCN2-ECP for ESA Contract n° 4000123810/18/NL/CT CCN2) sub-contractor with DEIMOS Elecnor (Spain).

2018-20: Local PI in the MIUR PNRA16_00189 (FIRCLOUDS - Esperimento di chiusura nel lontano infrarosso per le nubi antartiche).


2018-19: Scientific responsible and Local PI for the E2E Simulator for FORUM the future 9th Earth Explorer Track Mission (ESA_E2E_ITT AO/1-9220/18/NL/CT) sub-contractor with DEIMOS Elecnor (Spain). Responsible for the Scene Generator Module, L2 classification, ATBD definition.

2018-9: Local PI for the ESA Express Procurement (EXPRO) “FORUM - Testing models and retrieving cloud properties from aircraft observations of cirrus” (ESA-EOPSM-FORM-SOW-3306). Sub-contractor with Imperial College London (UK).

2017-18: Local PI in the ASI (Italian Space Agency) DC-OST-2015-045 (SCIEF - Sviluppo delle Competenze Italiane per l’Esperimento FORUM). Sub-contractor with IFAC-CNR Florence (I).

2017: Local PI (Co- Investigator) for the FORUM project in response of the ESA Earth Explorer Mission EE-9 accepted by ESA for Phase-A competition.

2016-18: Local PI for the ESA Tender AO/1-8236/15/NL/RA (Characterisation of Particulates in the Upper Troposphere / Lower Stratosphere, contract 4000116779). Sub-contractor with Julich Forschungzentrum (D).

2007: Member of the COBRA-ECOWAR project (Italian Ministry of the University and Research, DM n. 287 23 feb. 2005, project # 2005025202): Earth Cooling by water vapour emission.

2006-07: EUMETSAT contract EUM/CO/06/1529/PS (Reference tool for simulation of VIS/NIR spectral radiances) in support of the post EPS mission on Cloud, Precipitation and large scale Land surface imaging.

2006: Member (Co-I.) of the TC-ROSES Roses A.9 (NRC 2006)

2001: Member of the project REFIR Radiation Explorer in the Far Infrared funded by ASI Piccole Missioni Scientifiche (PMS-II)

2000-2012: Worked for the accomplishment of the goals of many International projects such as REFIR (EU and ASI funding) and AEROCLOUDS (MIUR-FISR funding).