Atmsopheric radiative tansfer and high spectral resolution
forward models
Multiple scattering of electromagnetic waves and fast radiative transfer solutions (scaling methods)
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) and surfaces from infrared high resolution observations
Retrieval techniques fot optical physical and microphysical
properties of clouds
Radiative energetic balance in presence of clouds.
Parametrization of cloud properties
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
THEORETICAL
STUDIES
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.
Various
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.
DATA ANALYSIS
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.
