National Consortium of Universities for Atmospheric and Hydrospheric Physics

Rome, Italy

National Consortium of Universities for Atmospheric and Hydrospheric Physics

Rome, Italy
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Laiti L.,University of Trento | Laiti L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2014

This study investigates the thermal structures of the atmospheric boundary layer (ABL) and the near-surface wind field associated with a lake-valley circulation in the south-eastern Italian Alps-the so-called Ora del Garda. Two flights of an equipped motorglider allowed for the exploration of the diurnal evolution of this circulation, from the onset, on Lake Garda's shoreline, throughout its development along the Sarca Valley and Lakes Valley (Valle dei Laghi), to the outflow into the Adige Valley. At the same time, surface observations, both from a targeted field campaign and from routinely operated weather stations, supported the analysis of the development of the Ora del Garda at the valley floor. In particular, in the valleys typical ABL vertical structures, characterized by rather shallow convective mixed layers (∼500 m) and (deeper) weakly stable layers above, up to the lateral crest height, are identified in the late morning. In contrast, close to the lake the ABL is stably stratified down to very low heights, as a consequence of the intense advection of colder air associated with the Ora del Garda flow (up to 6ms-1). The combined analysis of surface and airborne observations (remapped over 3-D high-resolution grids) suggests that the lake-breeze front propagating up-valley from the shoreline in the late morning penetrates slightly later at the eastern end of the valley inlet (delay: ∼1 h), probably due to the asymmetric radiative forcing caused by the N-S valley orientation. On the other hand, in the early afternoon the Ora del Garda overflows through an elevated gap, producing an anomalous, strong cross-valley wind (5ms-1) at the Adige Valley floor north of Trento, which overwhelms the local upvalley wind. This feature is associated with a strong deepening of the local mixed layer (from 400 to 1300 m). The potential temperature 3-D field suggests that the intense turbulent mixing may be attributed to the development of a downslope wind across the gap, followed by a hydraulic jump downstream. © 2014 Author(s).


Laiti L.,University of Trento | Laiti L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 5 more authors.
Atmospheric Research | Year: 2013

The paper investigates a coupled lake-breeze and valley-wind system, known as Ora del Garda. The latter typically originates on clear-sky days over the northern shore of Lake Garda in the Alps. After channelling into the nearby Sarca Valley and Lakes Valley, this airflow finally breaks out, through an elevated saddle, into the adjacent Adige Valley, where it strongly interacts with the local valley wind. Two flights of an instrumented motorglider explored, under different synoptic conditions, the thermal structure of the atmospheric boundary layer (ABL) associated with this wind at selected vertical sections-namely over the lake shore, at mid-valley, and at the junction with the Adige Valley. Data from airborne measurements, as well as from weather stations disseminated along the valley floor, provided the basis for mapping 3D fields of potential temperature over high-resolution grids by means of a Residual Kriging (RK) technique. This representation allowed the identification of site-specific ABL features associated with the Ora del Garda. In particular, a typical daytime coastal-breeze structure is detected in the lake shore region, where the advection of colder air tends to stabilize the atmosphere throughout the ABL depth. Mid-valley vertical profiles from both flights display shallow convective mixed layers, surmounted by deeper weakly stable layers. On the other hand, RK-gridded temperature maps show cross-valley thermal asymmetries, amenable to the complex topography and to the inhomogeneous surface coverage, as well as to a curvature of the valley axis. Finally, in the area where the upper Lakes Valley joins the Adige Valley, specific features associated with the complex interaction between the Ora del Garda and the local up-valley wind are found. © 2013 Elsevier B.V.


Laiti L.,University of Trento | Laiti L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 5 more authors.
Atmospheric Science Letters | Year: 2013

Residual kriging (RK) is applied to data from measurements performed with an instrumented motorglider in an Alpine Valley, where a coupled lake and valley wind develops. Results provide an insight into a typical mean vertical structure of the valley boundary layer, displaying a rather shallow convective mixed layer, surmounted by a deep stable layer. Mapping with RK allows to detect spatial temperature anomalies associated with the local development of diurnal winds over each explored valley cross section. Local scale features, such as cross-valley thermal asymmetries, amenable to surface inhomogeneities and their effects on heat fluxes, are also identified. © 2013 Royal Meteorological Society.


Estevez J.,University of Cordoba, Spain | Gavilan P.,Center Alameda del Obispo | Garcia-Marin A.P.,University of Cordoba, Spain | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics
International Journal of Climatology | Year: 2015

Tipping-bucket rain gauges are convenient and reliable sensors of rainfall measurements; however, like all other field sensors, they are subject to different kinds of errors. Due to their location, rain gauges in this research can record accidental pulses produced by vibrations from works of farm machineries near the station, or may receive water from sprinkler irrigation systems. These spurious inputs are recorded as precipitation data, although they do not correspond to rain, so it is necessary to detect them in order to avoid their inclusion in the future soil-water balance. The main objective of this work is to design a simple quality control procedure to validate precipitation data generated in several stations of the Agroclimatic Information Network of Andalusia (southern Spain), and valid for similar agro-meteorological station networks. The relationship between the degree of cloudiness through attenuation of solar radiation (atmospheric transmittance coefficient), relative humidity and rainfall measurements has been studied in order to separate true and false precipitation records. Meteorological data from 2002 to 2011 were used for the study. © 2014 Royal Meteorological Society.


Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Serafin S.,University of Vienna
Quarterly Journal of the Royal Meteorological Society | Year: 2015

The article examines the flow generated by time-periodic variations in surface temperature along an infinite slope in an initially unperturbed, stably stratified atmosphere at rest. Uniform boundary conditions at the surface are conducive to an along-slope parallel flow, governed by a periodically reversing local imbalance between along-slope advection and slope-normal fluxes of momentum and heat. It is shown that solutions include both a transient part and a periodic regime and that three different flow regimes may occur. The properties of the solutions in each regime are examined and discussed, outlining novelties with respect to previously known results. © 2015 Royal Meteorological Society.


Giovannini L.,University of Trento | Giovannini L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 3 more authors.
International Journal of Climatology | Year: 2014

High-resolution simulations are performed with the Weather Research and Forecasting (WRF) model, coupled with an advanced urban parameterization scheme, to evaluate the modifications induced by the urban area of Trento on boundary-layer processes in the Alpine Adige Valley in a typical summer sunny day. Specific gridded datasets of urban morphology parameters and anthropogenic heat releases were created to provide high-resolution input information for the urban scheme. Comparison of model results against measurements from surface weather stations shows that the model simulates reasonably well the development of valley winds, as well as the complex interaction occurring north of Trento between the up-valley wind of the Adige Valley and a lake breeze flowing from a tributary valley. The urban heat island of the city is also well captured by the model, with stronger intensities at night and lower values during daytime. Comparisons with an idealized simulation, where all the urban land use grid points are replaced by cropland, suggest that the city inhibits the development of the ground-based thermal inversion at night and also affects valley winds, modifying both the typical down-valley wind, and the interaction between the up-valley wind of the Adige Valley and the lake breeze. Further sensitivity tests are performed to evaluate the impacts of the gridded datasets of urban morphology and anthropogenic heat releases, and to assess what are the benefits of using the advanced urban scheme against a simple bulk parameterization. Results highlight that even the moderate anthropogenic heat releases present in Trento appreciably affect nocturnal temperatures in the city, while gridded information on urban parameters is not essential in the present case, because urban morphology does not display a high spatial variability. However, it is shown that the choice of the urban scheme may have significant impacts on both temperature and wind fields. © 2013 Royal Meteorological Society.


Giovannini L.,University of Trento | Giovannini L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Laiti L.,University of Trento | Laiti L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 4 more authors.
International Journal of Climatology | Year: 2015

The Ora del Garda is a coupled lake and valley breeze regularly blowing from the northern shorelines of Lake Garda, in the Italian Alps, especially during warm-season clear-sky days. The climatological characteristics of this wind are investigated through the analysis of 10years of observations collected at two representative surface weather stations - one on Lake Garda's shore and the other 30 km inland. Furthermore, the possible influences of the land-water temperature contrast and of the synoptic wind on the development and the propagation of the Ora del Garda are analysed. Lake-breeze days are identified by means of a set of objective criteria based on observations of solar radiation, wind speed and direction at the two stations. The analysis highlights that, on the lake's shoreline, the breeze develops on about 70% of the days in the warmest months, while it rarely occurs from October to February. Moreover, in the warmest months, the Ora del Garda reaches the inland weather station on about 80-90% of the days on which it blows on the lake's shore, after 3.5 h on average. It displays rather strong intensities, reaching average velocities of 5 ms-1 and gusts of 10 ms-1, respectively, in summer on the lake's shore and in spring at the inland weather station. No clear relationship is found between the land-water temperature contrast and the lake-breeze strength. On the other hand, synoptic winds are observed to affect significantly the development of the breeze. In particular, onshore synoptic winds are associated with stronger intensities at the lake's shore. Moreover, in these situations the Ora del Garda propagates faster and is detected earlier at the inland weather station. © 2015 Royal Meteorological Society.


Panziera L.,University of Trento | Panziera L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Giovannini L.,University of Trento | Giovannini L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 4 more authors.
International Journal of Climatology | Year: 2015

A comprehensive data set of surface temperature, rainfall, solar radiation and wind measurements was composed to investigate the relation between synoptic circulation types and the climate of Trentino, a mountainous region in the South-Eastern Alps. Synoptic patterns are classified over different levels by means of an existing classification method according to their degree of zonality, meridionality and vorticity. Distinct seasonal anomalies of mean daily temperature, total daily rainfall, daily solar irradiation and mean daily wind intensity are associated with most circulation types. Their magnitude varies not only among weather types, but also within the same type for different isobaric levels and seasons. The largest positive temperature anomalies are observed in correspondence with high-pressure and westerly circulations, whereas southerly circulation in the upper levels and low-pressure systems at lower altitudes produce the largest positive deviations of daily rainfall. Daily solar irradiation and mean daily wind intensity are larger than average with northerly circulations. Particular emphasis is given to extreme meteorological events, which occur with preferential circulation types. In fact, the frequency of occurrence of extremes of any variable for each synoptic pattern rarely coincides with the climatological value. Even though extremes in daily rainfall are observed with almost all synoptic circulations, most of them occur with the south-westerly circulation at 500 hPa, a frequent configuration contributing more than 50% to the total rainfall. Moreover, they occur with a larger variety of weather types at the lower levels and in spring and summer with respect to the upper levels and the colder seasons. The large number of statistical indices presented in this paper reveals that the climate of Trentino is strongly influenced not only by the synoptic circulation, but also by the mesoscale mechanisms resulting from the interaction of the large-scale flow with the local orography. © 2015 Royal Meteorological Society.


Giovannini L.,University of Trento | Giovannini L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 2 more authors.
Urban Climate | Year: 2014

The paper presents a combined analysis of results from field measurements and numerical simulations aimed at supporting the reconstruction of the temperature time series of the city of Trento in the Alps. This project is challenging, due to various relocations of the observational sites and the increasing effects of urbanisation.Identical temperature sensors were placed at the historical observational sites of the city, to detect systematic differences between these places under various seasonal patterns and weather conditions. However, since differences measured nowadays may not be representative of those occurring in the past, numerical simulations were also run with the WRF model, using a historical land use. Furthermore simulations with the present land use were performed and validated against the observations carried out during the field campaign.The comparison between "present" and "historical" simulations suggests that temperature differences between the sites more embedded in the urban area have not changed significantly from the past, whereas greater modifications have occurred at a location on the valley slope, progressively incorporated into the city. Moreover it is shown that the progressive urbanisation has played a significant role in Trento's temperature record, the effect being more significant under sunny conditions, when the UHI is stronger. © 2014 Elsevier B.V.


Giovannini L.,University of Trento | Giovannini L.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | Zardi D.,University of Trento | Zardi D.,National Consortium of Universities for Atmospheric and Hydrospheric Physics | And 2 more authors.
Journal of Applied Meteorology and Climatology | Year: 2013

The results of measurement campaigns are analyzed to investigate the thermal structure in an urban canyon and to validate a simplified model simulating the air and surface temperatures from surface energy budgets. Starting from measurements at roof-top level, the model provides time series of air and surface temperatures, as well as surface fluxes.Two campaignswere carried out in summer 2007 and in winter 2008/09 in a street of the city of Trento (Italy). Temperature sensors were placed at various levels near the walls flanking the canyon and on a traffic light in the street center. Furthermore, the atmosphere above themean roof-top level was monitored by a weather station on top of a tower located nearby. Air temperatures near the walls, being strongly influenced by direct solar radiation, display considerable contrasts between the opposite sides of the canyon. On the other hand, when solar radiation is weak or absent, the temperature field remains mostly homogeneous. Moreover, air temperature inside the canyon is generally higher than above roof level, with larger differences during summertime. Air temperatures from the above street measurements are well simulated by the model in both seasons. Furthermore, the modeled surface temperatures are tested against a dataset of wall surface temperatures fromtheAdvanced Tools for RationalEnergyUse Towards Sustainability-Photocatalytic Innovative Coverings Applications for Depollution (ATREUS-PICADA) experiment, and a very good agreement is found. Results suggest that the model is a reliable and convenient tool for simplified assessment of climatic conditions occurring in urban canyons under various weather situations. © 2013 American Meteorological Society.

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