vai al contenuto della pagina vai al menu di navigazione
 

Atmospheric Physics

The research activity carried out by the members of the Atmospheric Physics group deals with fundamental issues related to the dynamics, radiative transfer and thermodynamics of the atmosphere. The ultimate goal is to improve our knowledge on fundamental processes regulating the evolution of the terrestrial atmosphere, both in the short-term (meteorology) and long-term (climate).

The group is involved in the definition of innovative methods used to extract the maximum information content from in-situ and remote sensing measurements of the atmosphere either from active or passive sensors.

Research is fully integrated in the national and international context, it is funded by national and international projects. The group is active in numerous collaborations with several research institutions (local, national or international).

 

Physics of the Stratosphere

M. Ridolfi (Assoc. Prof.), M. Valeri (PhD Student), F. Fabiano (PhD Student)

Accurate knowledge of the distribution and time evolution of minor stratospheric constituents is the basis to understand the chemical and physical processes that drive important issues such as stratospheric ozone depletion, climate change and global warming.

Spectrally resolved remote measurements of the atmospheric radiance are considered one of the most powerful tools to measure the composition of the atmosphere, and particularly of the stratosphere, on a global scale, with short re-visit time. Our specialization is in the design and implementation of state of the art inversion techniques for remote sensing emission and absorption measurements of the atmospheric spectrum, from mid- to far-infrared. These techniques allow to infer from measured spectra the vertical distribution of several atmospheric minor constituents. For inversion, analysis and characterization of data acquired by atmospheric experiments we developed algorithms that implement:

  • Radiative transfer through inhomogeneous, clear sky atmosphere (used for forward model simulations).
  • Retrieval of the spatial distribution of geophysical parameters (temperature, pressure and concentration of atmospheric constituents), with both one-dimensional (global-fit) and two-dimensional (tomography, with geo-fit) retrieval models. State-of-the-art self-adapting regularization techniques are developed to constrain ill-conditioned or ill-posed inversions.
  • Modeling of the whole chain of an atmospheric experiment with sensitivity functions. These allow to predict the quality of the retrieval results, on the basis of averaging kernels and covariance matrices.

In the frame of in international project, our team developed the algorithm used by the European Space Agency (ESA) to process the measurements acquired by MIPAS (Michelson Interferometer for Passive Atmospheric Sounding). This is a mid-infrared limb emission sounder that successfully operated on board of the ENVISAT satellite in the years from 2002 to 2012.

Web links: MIPAS sensor: https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/envisat/instruments/mipas

Scientific Collaborations:

  • Consiglio Nazionale delle Ricerche, Istituti IFAC (Firenze) e ISAC (Bologna), I
  • LISA – CNRS, Paris, Fr
  • KIT – Karlsruhe, D
  • Univ. of Oxford and Univ. of Leicester, UK
  • European Space Agency: ESRIN, ESTEC, N

Funding: European Space Agency (ESA), UniBo

 

Tropospheric Clouds

R. Rizzi (Assoc. Prof.), T. Maestri (Assist. Prof.), E. Tosi (Assist. Prof.)

Condensed phases in the Troposphere are studied through the exploitation of active and passive remotes sensing measures, in-situ data and theoretical modelling.

The research activity 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.  Line-by-Line codes are used as a reference for theoretical investigations and for calibration/validation experiments of remote sensing sensors at microwave, infrared and shortwave wavelengths. A continually updated database for non-spherical ice crystals’ single scattering properties is used within an innovative inversion technique to infer optical and microphysical properties of ice clouds from remote sensing measurements at infrared wavelengths. This allows comparisons of cloud retrieval products from multiple data, the check of limits and consistency of available cloud radiative properties databases and the definition of cloud parameterizations for numerical weather prediction and climate models.

The research activity also includes the: I) Characterisation of Particulates in the Upper Troposphere/Lower Stratosphere with focus on the detectability and optical/microphysical properties derivation of sub-visible cirrus clouds from limb observations; II) application of statistical retrieval models to infer Venus tropospheric clouds’ properties and the use of radiative transfer Monte Carlo models at limb geometry to study the Venusian upper haze properties, III) investigation of the average ice distribution vertical structure of cirrus clouds by means of active data aiming at developing a parameterization, depending on both physical and geographical parameters, implemented into inversion codes.

Scientific Collaborations:

  • SSEC-CIMSS Univ. of Wisconsin-Madison, Madison, USA (http://cimss.ssec.wisc.edu)
  • ISAC-CNR, Bologna
  • JSC, Forschungszentrum Jülich, Germany
  • INAF-IAPS, Roma, I (http://www.iaps.inaf.it)

Funding: PRIN, Eumetsat, ESA, UniBo

 

Radiance in the Far Infra-Red

R. Rizzi (Assoc. Prof.), T. Maestri (Assist. Prof.)

The Far InfraRed emission from the Earth is highly characteristic of our planet as a system seen from space, and it is of fundamental significance for planetary energy balance considerations and therefore for understanding the Earth's climate.

The study of FIR emission and of the main physical processes acting upon it is a long-term research project of APG. This line of research involves the characterization of the long-term downwelling radiance in the far infrared both in clear and cloudy conditions. This is fundamental either for the validation of water vapour continuum absorption parameterization and for the definition of the cloud optical properties databases in the 100-600 cm-1 spectral interval.

Data in the FIR are currently collected by the Fourier Transform Spectrometer REFIR-PAD (Radiation Explorer in the Far InfraRed - Prototype for Applications and Development) instrument that has successfully performed observations from high mountain sites and a balloon borne platform.

High spectral resolution radiance data in the infrared are also used for the definition of methodologies for the identification of clear sky, not-precipitating and precipitating clouds (in particular in the Artic region) by means of Linear Discriminant Analysis and Support Vector Machine algorithms.  The Italian Space Agency is supporting (SCIEF project) the scientific and technical development of the REFIR-PAD within the call “Bando per attività preparatorie per future missioni e payload di osservazione della terra” (preparatory activities for future missions and payload for the Earth observation).

Web links:

  • ECOWAR-COBRA experiment: http://www2.unibas.it/gmasiello/cobra/index.htm
  • PRANA expriment: http://www.ino.it/en/?p2=funding&p=project-detail&passo=151

Scientific Collaborations:

  • Dipartimento di Ingegneria e Fisica dell'Ambiente - Università della Basilicata, I
  • Istituto Nazionale di Ottica –CNR, Firenze, I

Funding: PRIN, PNRA-PRANA, Italian Space Agency, UniBo

 

Precipitation retrieval and Snowflake Modelling

F. Porcù (Assist. Prof.), T. Maestri (Assist. Prof.)

Precipitation is one of the atmospheric parameters with highest variability at all scales, and thus difficult to measure with the accuracy requested for climate and weather studies.

The group is involved in the characterization of microphysical and radiative properties of precipitation particles, as measured in different experimental campaigns with disdrometers and ground based radar, with the goal to improve the knowledge of the involved microphysical processes, and the remote sensing of precipitation characteristics. Recent interest is devoted to the study of snow detection and characterisation from remote sensors: a model to generate complex snow aggregates was developed to reproduce the evolution of a distribution of snow particles growing by collisions and uses a combined Monte Carlo aggregation model. Radar variables of statistical particles size distributions of snowflakes, obtained by a discrete dipole approximation, are used to implement retrieval algorithm for satellite radars measures and are used in fuzzy logic quantitative snow-rate retrieval algorithms of meteorological ground based radars. Particular interest is on the study of severe convective systems, carried on with remote sensing (satellite sensors and radar) and in situ instruments, such as lightning detectors, disdrometers and raingauges.

Further applications of precipitation studies are devoted to the prevention and mitigation of hydrogeological disasters, to the study of the hydrological cycle over remote areas (such as Tibetan Plateau and Antarctica) and to the relationship between precipitation and lightning.

Web links: Eumetsat H-SAF: hsaf.meteoam.it

Scientific Collaborations:

  • ARPA Emilia Romagna, Bologna, I (http://www.arpa.emr.it/sim/)
  • NASA-GSFC Greenbelt, USA (https://www.nasa.gov/centers/goddard/home/index.html)
  • University of Maryland, Baltimore County, Baltimore, MA, USA
  • ISAC-CNR, Bologna e Roma, I
  • Dipartimento della Protezione Civile, I

Funding: EU-FP7, PNRA, UniBo, EUMETSAT

 

Urban meteorology and climatology; Environmental fluid dynamics

S. Di Sabatino (Assoc. Prof.)

The focus is on the understanding and modelling of flow and dispersion phenomena in the lower atmosphere and their role and feedbacks in climate.  The emphasis is on the thermodynamics of atmospheric/environmental systems at various spatial-temporal scales ranging from few meters to several kilometers and from fraction of seconds (turbulence) to years (climate). Specific effort is devoted to the urban environment tailored to the understanding of city system as a whole from its “breathability” i.e. to its ability ventilate itself and to the understanding on how both flow and energy is exchanged, transported and distributed within it. In the context of urban meteorology and climatology the research developed within the group tackles different aspects: the connection between urban form, vegetation and the atmospheric processes; the urban heat island, air quality and their role on the climate systems. Of applied nature is the development of numerical and smart tools to co-adiuvate urban planners to construct sustainable yet smart cities. To this scope the research group is also engaged in translating theoretical knowledge of atmospheric processes to real world-applications. The tools utilised include numerical modelling (computational fluid dynamics and mesoscale modelling) field measurement techniques, and laboratory investigations.

Web links: http://www3.nd.edu/~dynamics/materhorn/contact.html

Scientific Collaborations:

  • University of Notre Dame, South Bend (IN, USA),
  • University of Hong Kong, Hong Kong (CHINA),
  • University of Gavle, Gavle (Svezia),
  • CIEMAT, Madrid Spain,
  • Caledonian University, Glasgow (UK),
  • Lahti University, Lahti (Finland).

Funding: Unibo, EU-INTERREG, TELECOM, EU-LLP

Contacts

Silvana Di Sabatino

Associate Professor

Dipartimento di Fisica e Astronomia - DIFA

Viale Berti Pichat 6/2

Bologna (BO)

tel: +39 051 20 9 5215

Tiziano Maestri

Assistant professor

Dipartimento di Fisica e Astronomia - DIFA

Viale Berti Pichat 6/2

Bologna (BO)

tel: +39 051 20 9 5212

Federico Porcù

Assistant professor

Dipartimento di Fisica e Astronomia - DIFA

Viale Berti Pichat 6/2

Bologna (BO)

tel: +39 051 20 9 5214

Marco Ridolfi

Associate Professor

Dipartimento di Fisica e Astronomia - DIFA

Viale Berti Pichat 6/2

Bologna (BO)

tel: +39 051 20 9 5194

tel: +39 051 20 9 5215

tel: +39 051 20 9 3693

tel: +39 055 5226351

fax: +39 051 252774

Rolando Rizzi

Associate Professor

Dipartimento di Fisica e Astronomia - DIFA

Viale Berti Pichat 6/2

Bologna (BO)

tel: +39 051 20 9 5216

Ennio Tosi

Docente dell’Università di Bologna fino al 2017

Dipartimento di Fisica e Astronomia - DIFA

Viale Berti Pichat 6/2

Bologna (BO)

tel: +39 051 20 9 5214