Scientific activity of Prof. Claudio Cassardo

Main activities

Physical exchange processes (momentum, heat and water vapour) in the surface boundary layer.

This theme constitutes the primary research argument since 1989. The parametrizations of physical exchange processes in the surface boundary layer involving vegetation, bare soil, snow, ice and water surfaces and related to the radiative budget, the energy and hydrological budgets have been analyzed and implemented in a numerical model. The original version of this model was called LSPM (acronym of Land Surface Process Model) and was regularly updated and improved by adding new processes, parameterizations and algorythms. Each parameterization was submitted to a series of tests, validations and sensitivity experiments in order to check eventual errors and evidentiate the most sensitive parameters for the initialization.
The first stable version of the LSPM was obtained in the 1994 and publshed one year later ([Cassardo et al., 1995]). That version, however, did not yet allow the treatment of the snow layer. Among the several intercomparison experiments with measurements carried out in several meteorological stations displaced in the world, or other models, we can report the one with the model BATS in the Po Valley [Ruti et al., 1997]. The dependence on the initialization has also been investigated [Cassardo et al., 1998].
The snow parameterization was considered in the 1998, and tested using 6 years of Russian observations carried out in Siberia [Cassardo and Balsamo, 1999]. The question of the initialization was again investigated some years later, due to its influence in the results quality ([Cassardo et al., 2002]). One of the output variables tested by an intercomparison with observations was the leaf wetness ([Cassardo et al., 2003]). Again, a sensitivity analysis [Cassardo et al., 2005] was performed on the LSPM in order to check the dependence of the results (namely, energy and hydrological budget components) from the initial conditions (namely, soil temperature and moisture) on the synoptic scale; the results were used to identify the minimum spinup time of the model.
The last documented version of the LSPM is the 2006 ([Cassardo, 2006]).
One of the last studies performed with the LSPM was the calibration of the canopy resistance in a vineyard in which specific measurements were carried out on the individual leaves, allowing to determine the dependence from the air temperature and humidity, the solar radiation and the atmospheric carbon dioxide concentration ([Cassardo et al., 200XX??]).
At the January 2010, the LSPM changed its name in UTOPIA, acronym of the University of TOrino land surface Process Interaction model in Atmosphere. Despite the change of its name, there is a continuity between the two models, and the UTOPIA can be considered as the evolution of the old LSPM. The last documented version of the UTOPIA is the 2011 ([Cassardo, 2011]).
The UTOPIA has recently been used to assess the energy and hydrological budget in three vineyards located in the Piemonte region, which were differing not only for their location but also for their characteristics ([Francone ...]).
The UTOPIA, as well its ancestor LSPM, is currently operational at the Regional Meteo Center of ARPA Piemonte, where the personnel uses its output data for evaluating specific informations useful for agrometeorological purposes.
The current collaborators of UTOPIA include the Regional Meteo Center of ARPA Piemonte, the Agrometeorological service of Piemonte region, the Department of Forestry of the University of Torino and the CCCPR of the Ewha Womans University at Seoul.

Analysis of extreme meteorological events

A preliminary introduction explains the role of the meteorological models in the physical and climatological analyses [Cassardo, 2009)].
The energy and hydrological budget components (net radiation, sensible and latent heat fluxes, conductive heat flux, precipitation, evapotranspiration, surface runoff, underground runoff and bottom drainage, soil temperature and moisture, canopy temperature) have been investigated in occasion of recent extreme meteorological events, such as droughts or floods.
The capability of the model (UTOPIA or its ancestor LSPM) in reproducing accurately the energy/hydrological budget components in occasion of extremely dry or wet spells had been preliminarly tested [Feng et al. 1997], [Qian et al., 2001].
In particular, the floods occurred in Piemonte on the 3-5 November 1994 (which caused victimes ans big damages in the cities of Asti and Alessandria and in several other smaller towns) [Cassardo et al., 2002], that of 14-18 October 2000 (which caused victimes and several damages in the province of Torino) [Cassardo et al., 2006] and the four episodes occurred in the hydrological year 2009-2010 [Cassardo et al., 2009] have been investigated using the UTOPIA, driven by the meteorological observations carried out over the territory or by a mesoscale model.
The model UTOPIA has been applied to evaluate the hydrological budget during a typical summer monsoon season in Korea, where there was the availability of several meteorological stations for driving the model in standalone version [Cassardo et al., 2009].
The exceptional summer of 2003, extremely arid and hot over southwestern Europe in general and over Piemonte region in particular, has been also analyzed in the same way [Cassardo et al., 2007].
Several other studies have been performed using mesoscale meteorological models, generally driven by ECMWF or other GCM data. In some cases, these models have been coupled or with land surface models, or with ocean models.
In the study of the 1999 Christmas storm, a mesoscale meteorological model (the WRF) has been applied to simulate the two events [Cassardo et al., 2008] occurred over western Europe.
The mesoscale meteorological model WRF has been coupled with the ocean model DieCAST in order to simulate the onset of Bora and Sirocco events on the Adriatic sea ([Ferrarese et al., 2008], [Loglisci et al., 2004]).
A spcific study about the importance of surface fluxes in convective episodes has been performed by using the WRF model and selecting the land surface schemes [Zhang and Cassardo, 2007].
The most recent application is the coupling of the LSPM with the Weather Research and Forecast (WRF) model and the application of the coupled model WRF-LSPM on a flash flood caused by a landfalled typhoon [Zhang, 2009] and to the exceptionally wet period 2008-9 in the northwestern Italy ([Cassardo et al., 2009] and [Zhang et al., 2009]).

Regional climate aspects: the surface layer

The researches carried out in this section are based on the assumption that, at regional scale, the local effects can assume a considerable importance on the assessment of future climatic conditions in a given region.
The most recent study, yet unpublished, has specifically analized the energy and hydrological budget in the Alpine area. The method has been to run the UTOPIA in standalone way, driven by the output of a regional climate model (RegCM3), in turn driven by the output of a General Climate Model. For future climate, the scenario A2 has been chosen and compared with the present climate [Cassardo et al., 2009]. The results seem indicate that the method is able to identify the main characteristics of the physical processes in the surface layer.
This study was based on the results of previous studies, which had analyzed in more detail the importance of the initialization of soil parameters for preparing long term runs of land surface models. The aim was to get from these simulations some surface layer data difficult to be measured for long time and over a mesoscale area. In this way, the land surface scheme selected, which must be a trusted one, becomes a sort of surrogate of the observations. The model used in these studies ([Cassardo et al., 1999], [Cassardo et al., 1997]) was the LSPM, and the method was called CLIPS (CLImatology of Parameters at the Surface).
The usefulness of the CLIPS methodology was demonstrated also in the detailed determination of the present day climate ([Ruti et al., 1998]).
As the availability of data is always the most important source for performing climate studies, in previous papers the long term (more than one century) precpitation and temperature series collected in Alessandria, Italy, has been digitized and checked on daily basis Cassardo et al., 2003], allowing to discover some errors in the montly series available.
A most recent study has instead analyzed the time series of records performed in neighboring stations (managed by different institutions and containing different sensors) in the overlapped period ([Acquaotta et al., 2008]), showing the importance of having contemporary measurements when a station changes its position.

Pollutants in the surface layer, in troposphere and stratosphere

The distribution of major troposheric pollutants (methane, carbon bioxide, ozone) was analyzed using two different methods. In an early stage, we checked directly the distribution of the trajectories arriving at the station in which the observations were carried out (in the preliminary studies, it was Plateau Rosa, while in the following other remote stations have been considered). These studies were able to reveal just the direction of arrival of the air masses ([Longhetto et al., 1995]).
In a second stage, a source-receptor methodology originally developed by Stohl was adopted, adapted and applied to generate the pollutant field distribution using as input data the 3-D air trajectories arriving at the site and the pollutant measurement time trends ([Ferrarese et al., 2002], [Longhetto et al., 1997], [Apadula et al., 2003]).
A detailed study was then performed on the tropospheric/stratospheric ozone data, thanks to the availability of a large aircraft database of measurements along the routes on the international company Lufthansa ([Cacopardo et al., 2004]).
Both methods are based on the evaluation of backwards air trajectories starting from the output of a General Circulation Model (in all cases, the ECMWF).
The algorithm for generating such trajectories, called TRAJECT, has been widely used at the beginning of the study in order to verify its capability to generate reliable trajectories ([[Anfossi et al., 1988]]). Subsequently, a climatological analysis of the directions of provenance of the backwards air trajectories at Plateau Rosa station ([[Anfossi et al., 1989] and [Villone et al., 1992]]).
Other specific studies regarded some peculiar events or measurements of pollutants in the surface layer, such as the case of Torino immediately after a foehn event ([Natale et al., 1999]), or the data at thew Svalbards ([Mabilia et al., 2007]), or finally the statistics calculated on the pollutants in the urban area of Torino before and after the Olimpic games ([Cassardo et al., 2008]).

Measurements of physical parameters in the surface layer

The activity carried out in this section is, and has been, maily experimental. However, in several occasion the treatment of data has required the development of special software, sometimes different for different field experiments, for the data analysis. Another important part of the data elaboration, specifically required by the use with models, despite it has never been published, has been the interpolation of the data missing periods.
A special software named SONELA was elaborated to calculate the turbulent heat and momentum fluxes from the measurements collected by fast-response sonic anemometers and other sensors (thermometers and hygrometers) ([Cassardo et al., 1995]). With the availability of net radiation and atmosphere-ground heat flux data, SONELA algorythm is able to evaluate reliable estimates of turbulent quantities that can be used to test numerical surface layer models or parametrizations.
Several field experiments were subsequently performed, studied and analyzed in the following years, giving several useful informations on the evolution of the boundary layer deduced by the analysis of the turbulent heat fluxes, over land and over the sea near the coast ([Qian et al., 1998]; [Ferrarese et al., 1998] and [Ferrarese et al., 1998]).
A special method for evaluate the values of sensible heat flux and other similarity parameters during convective conditions in the Po valley (Italy) by the measurements of SODAR has been developed and tested ([Fiacconi et al., 1996] and [Fiacconi et al., 1997]).
The entire dataset collected during a wide experimental campaign lasted three months in the 1993 in the center of the Po valley, at San Pietro Capofiume, in Italy, has been analyzed and reanalyzed subsequently on the basis of the results obtained ([Cassardo et al., 2006]).
Thanks to the six field experiments carried out by the two technicians of our group in the Italian basis in Antarctica, the large database of conventional (in the atmospheric surface layer and in the uppermost ice layer) and remote sensing (fast response data from sonic anemometers, thermometers and hygrometers) physical variables measured have allowed to determine the energy budget in the Antarctic surface layer ([Ferrarese et al., 1999]; [Qian et al., 2000] and [Ferrarese et al., 2002]).
An attempt of deducing the snow cover by interpreting the satellite images at different channels, both during daytime and nighttime, has been done by using both MODIS sensor on Terra and Aqua satellites, as well as the SEVIRI sensor on the MSG and MSG2. The data derived in this way have been compared with each other (using the two different satellite types) and also with the observations carried out in the meteorological stations, with useful indications about the potentiality of the method ([Bechini et al., 2007] and [Terzago et al., 2009]).
Last, but not least, the management of the meteorological stations. Historically, the first station managed was an amatorial one, located in the vicinity of my house, at Baldissero Torinese. The data were collected (with some interruptions) from the 1979 to the 2000. A recent intercomparison with the data of temperature and precipitation collected in neighboring hilly stations has shown that the data have a quality comparable to that of the professional stations. On this site there are some more informations regarding this station, with some sample plots. On this page is summarized a list of observed foehn episodes occurred at Baldissero Torinese in the period 1995-1999.
During the period in which I was researcher at the University of Eastern Piemonte at Alessandria, Italy, I installed a meteorological station on the roof of the University. This station collected data from the 1996 to the end of the 2000 (year in which I moved to the University of Torino). Subsequently, it was managed by a collegue and is currently active. The analysis of data showed that the data of this station possess a climatological characteristics more similar to the historical data collected in the old observatory, also located on a roof of a tall building in the center of Alessandria, with respect to the data collected by the official meteorological station of the Regional Meteorological Service of ARPA Piemonte, located in the suburban area of the city and over a grass field.
Since my arrival in Torino, I became the responsible of the meteorological stations of the Department of Physics. One of them, which required too high resources to be kept active (in terms of funding and personnel) was closed, while the other is still active nowadays. This station is located over the roof of the building of the Department of Physics, and also in this case the analyses performed by the Italian Meteorological Society on all data recorded in the city of Torino since the 1780 have shown that, concerning the data of temperature and precipitations, the climatological characteristics of our station are the ones most similar to those of the historical stations. By the way, in the period between the two WW, the station of the Institute of Physics was the official meteorological station of Torino.
Since the beginning of the millennium I have organized the creation of the web page of this station, which contains both on-line and archived data. Since the autumn 2010, I have organized also a specialized, even if yet experimental, service of meteorological forecasts, in Italian language, which is hosted on the same web page.

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