Roberta Amorati - Academia.edu (original) (raw)
Papers by Roberta Amorati
Atmosphere
Air quality in Europe continues to remain poor in many areas, with regulation limits often exceed... more Air quality in Europe continues to remain poor in many areas, with regulation limits often exceeded by many countries. The EU Life-IP PREPAIR Project, involving administrations and environmental protection agencies of eight regions and three municipalities in Northern Italy and Slovenia, was designed to support the implementation of the regional air quality plans in the Po Valley, one of the most critical areas in Europe in terms of pollution levels. In this study, four air quality modelling systems, based on three chemical transport models (CHIMERE, FARM and CAMx) were applied over the Po Valley to assess the sensitivity of PM2.5 concentrations to NOx and NH3 emission reductions. These two precursors were reduced (individually and simultaneously) from 25% up to 75% for a total of 10 scenarios, aimed at identifying the most efficient emission reduction strategies and to assess the non-linear response of PM2.5 concentrations to precursor changes. The multi-model analysis shows that r...
. A standardized methodology for the validation of short-term air quality forecast applications w... more . A standardized methodology for the validation of short-term air quality forecast applications was developed in the framework of FAIRMODE activities. The proposed approach, focusing on specific features to be checked when evaluating a forecasting application, investigates the model capability to detect sudden changes of pollutants concentrations levels, to predict threshold exceedances and to reproduce air quality indices. The proposed formulation relies on the definition of specific forecast Modelling Quality Objective and Performance Criteria, defining the minimum level of quality to be achieved by a forecasting application when it is used for policy purposes. The persistence model, which uses the most recent observed value as predicted value, is used as benchmark for the forecast evaluation. The validation protocol has been applied to several forecasting applications across Europe, using different modelling paradigms and covering a range of geographical contexts and spatial scales. The method is successful, with room for improvement, in highlighting shortcomings and strengths of forecasting applications. This provides a useful basis for using short-term air quality forecast as a supporting tool for correct information to citizens and regulators.
Springer proceedings in complexity, 2022
Atmosphere, 2020
The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit v... more The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit values for PM (particulate matter), NO2 (nitrogen dioxide) and O3 (ozone). This area covers the territory of most Italian northern regions and includes several urban agglomerates, such as Milan, Turin, Venice and Bologna. The area is densely populated and heavily industrialized. The paper summarizes the assessment of the impact of the current (2013) and future (2025) emissions and of the meteorological conditions on the air quality of the Po Valley. This study is one of the first outcomes of the EU LIFE-IP Clean Air Program Po Regions Engaged to Policies of Air (PREPAIR) project. The project, involving administrations and environmental agencies of eight regions and three municipalities in Northern Italy and Slovenia, started in 2017 and will end in 2024. Future emission scenarios consider the emissions reduction due to the air-quality action plans of the regions involved, of the agreement...
Rendiconti online della Società Geologica Italiana, 2015
During the October 2014 alluvial event in Parma province, which also caused the city of Parma to ... more During the October 2014 alluvial event in Parma province, which also caused the city of Parma to be partially flooded, several debris flows affected the upper Val Parma and Val Baganza (northern Apennines, Italy) causing severe and widespread damages to check-dams, roads and other infrastructures. The meteorological event reached intensities as high as 80 mm/hour, which is well above the thresholds presented in literature for the alpine area. The result was the occurrence of tens of debris flow along the Mt. Cervellino – Mt. Vitello relief, which were triggered in zones of failure of slope debris coverage along the streams, remobilized and scoured debris along the track and destroyed several check dams and damaged roads that were overflown by debris. Since debris flows in the northern Apennines are considered quite rare events, their hazard is generally underestimated or overlooked. The event in the Parma province, at the opposite, warns against this potentially destructive events that, in a changing meteorological framework, might result much more frequent and widespread than expected also in the northern Apennines.
Optical Spectroscopic Techniques, Remote Sensing, and Instrumentation for Atmospheric and Space Research IV, 2002
Broad band radiance measurements at top of the atmosphere are simulated using two diverse line-by... more Broad band radiance measurements at top of the atmosphere are simulated using two diverse line-by-line codes for a number of standard atmospheric conditions to evaluate the sensitivity of broad band spectral and spectrally integrated radiometry to realistic changes of water vapor content in the troposphere and of other parameters of climatic significance. . It is shown that the rotational band
Applied Optics, 2002
A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interact... more A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interaction for any number of cloud layers. Layer cloud fraction and transmittance are treated separately and combined with that of gaseous transmittances. RTF is tested against a reference procedure that uses line-by-line gaseous transmittances and solves the radiative transfer equation by use of the adding-doubling method to handle multiple-scattering conditions properly. The comparison is carried out for channels 8, 12, and 14 of the High Resolution Infrared Radiation Sounder (HIRS/2) and for the geostationary satellite METEOSAT thermal infrared and water vapor channels. Fairly large differences in simulated radiances by the two schemes are found in clear conditions for upper- and mid-tropospheric channels; the cause of the differences is discussed. For cloudy situations an improved layer source function is shown to be required when rapid changes in atmospheric transmission are experienced within the model layers. The roles of scattering processes are discussed; results with and without scattering, both obtained by use of a reference code, are compared. Overall, the presented results show that the fast model is capable of reproducing the cloudy results of the much more complex and time-consuming reference scheme.
Meteorology and Atmospheric Physics, 2014
ABSTRACT The spectral characteristics of hourly precipitation fields are studied for a number of ... more ABSTRACT The spectral characteristics of hourly precipitation fields are studied for a number of meteorological events, classified depending on the precipitation process involved, namely stratiform, convective or mixed stratiform–convective. The study focuses on the comparison between spatial spectral characteristics of observed precipitation fields, obtained from hourly radar estimates, and modelled hourly predictions of the same field by the nonhydrostatic model COSMO. The results show that the power spectra of radar hourly precipitation are characterised by invariance within ranges of horizontal spatial scales that are different for the three classes of events. COSMO reproduces some basic characteristics of the radar spectra in all cases. Nevertheless, in stratiform events, COSMO spectra present a well-defined scale break at about 15 km with no counterpart in radar data. It is suggested that this model feature is related to the presence of spurious horizontal smoothing introduced by the semi-lagrangian advection scheme for precipitation. Smoothing affects all scales up to the maximum length scale of precipitation and horizontal advection by the wind. An analysis of wind intensity in the lower troposphere over the region supports this interpretation. Discrepancies in precipitation spectra between radar and COSMO data in convective events are interpreted as a consequence of the inadequacy of the model resolution for a correct representation of convection.
On the afternoon of May 27th, 2009 a severe storm hit the city of Parma and its surroundings, cau... more On the afternoon of May 27th, 2009 a severe storm hit the city of Parma and its surroundings, causing widespread damages due to strong winds, hail and heavy downpours. In the first part of the work, a volumetric analysis of this deep convective system was carried out by using ARPA-SIMC Polarimetric-Doppler radar data, focusing on the microphysical and dynamical structure
... Contract n°: EVK1-CT-2000-00058 A Review of Satellite-based Rainfall Estimation Methods by Vi... more ... Contract n°: EVK1-CT-2000-00058 A Review of Satellite-based Rainfall Estimation Methods by Vincenzo Levizzani and Roberta Amorati Istituto di Scienze dell'Atmosfera e del Clima-CNR, Bologna and Francesco Meneguzzo Istituto di Biometeorologia-CNR, Firenze ...
A considerable advantage offered by the presence of two (or more) radar exploring the same area, ... more A considerable advantage offered by the presence of two (or more) radar exploring the same area, is the possibility to improve the quality of the final product, by adopting procedures of data composition. Radar data mosaicking is normally performed using simply range-related or value related algorithms of selection and combination. Usually, the followed ways are: a-b) to attribute to the common cell the mean or the maximum value of reflectivity; c) to assign to the common cell the reflectivity value of the nearest radar; d) to combine the data through a weighted average, where the weight is inversely proportional to the second power of the distance from the radar. The first approach distributes equally the probability to fail to the two radars, the second one handles only the problem of attenuation (which could be produced by mountains or rain), the third and the fourth are based on the assumption that radar data reliability diminishes only with the distance. Hence, these methods ta...
Many methods for estimating parametrically the intensity function for inhomogeneous spatial point... more Many methods for estimating parametrically the intensity function for inhomogeneous spatial point processes are available in the literature. Almost all papers consider the setting where the number of covariates is moderate. More and more applications involve a large number of covariates. Our paper considers feature selection procedures based on convex and non-convex regularization techniques to deal with such data. We investigate theoretical and computational aspects. We provide general conditions on the spatial point processes and on penalty functions which ensure consistency, sparsity, and asymptotic normality. In particular, from a theoretical point of view, we consider asymptotic properties which make our results available for several penalty functions and large classes of spatial point processes. Joint work with Jean-François Coeurjolly and Frédérique Letué. Passenger flows through airport terminals
The radar estimate of precipitation is recognized to be of great value for operational use, the h... more The radar estimate of precipitation is recognized to be of great value for operational use, the high spatial and temporal resolution being a key point in nowcasting procedures. It is also well known that the radar precipitation estimate suffers for different sources of error that have to be removed in order to fulfill meteorological and hydrological requirements. First of all reflectivity corrections are necessary, but benefits may be achieved by blending other sensor measurements (see among the others Chumchean et al., 2006). Merging the radar estimate with precipitation observed by a dense rain gauge network seems to be a solution. On the other side, often the merging techniques are not only inadequate, but even misleading. The correction by means of a sparse network has to take into account the complexity of the precipitation field itself and instrument limits that may lead to a non-uniform bias field, particularly in areas with complex orography. Moreover different precipitation...
Atmosphere
The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit v... more The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit values for PM (particulate matter), NO2 (nitrogen dioxide) and O3 (ozone). This area covers the territory of most Italian northern regions and includes several urban agglomerates, such as Milan, Turin, Venice and Bologna. The area is densely populated and heavily industrialized. The paper summarizes the assessment of the impact of the current (2013) and future (2025) emissions and of the meteorological conditions on the air quality of the Po Valley. This study is one of the first outcomes of the EU LIFE-IP Clean Air Program Po Regions Engaged to Policies of Air (PREPAIR) project. The project, involving administrations and environmental agencies of eight regions and three municipalities in Northern Italy and Slovenia, started in 2017 and will end in 2024. Future emission scenarios consider the emissions reduction due to the air-quality action plans of the regions involved, of the agreement...
Proc. ERAD, 2004
... Bech, J., Codina, B., Lorente, J., and Bebbington, D.: The sensitiv-ity of single polarizatio... more ... Bech, J., Codina, B., Lorente, J., and Bebbington, D.: The sensitiv-ity of single polarization weather radar beam blockage correction to variability in the ... Marshall, J. S and Palmer, W. McK.: The distribution of raindrops with size, J. Meteor., 5, 165–166, WMO Publications, No. ...
Rainfall is a phenomenon difficult to model and predict, for the strong spatial differences in da... more Rainfall is a phenomenon difficult to model and predict, for the strong spatial differences in data and the presence of many zero collected values. Observed data come from rain gauges, sparsely distributed on ground. These observations can be accompanied by other measurements, like reflectivity radar data. Rainfall prediction is a fundamental issue: all available data ought to be treated together for obtaining more precise results. In this work, we investigate whether radar data can contribute to improve spatial statistical prediction, comparing kriging estimates based on rain gauges with kriging on rain gauges and radar rainfall data acting as an external drift. Results are encouraging about enriching prediction with radar information.
An extensive evaluation of system analysis techniques for obtaining short-term quantitative preci... more An extensive evaluation of system analysis techniques for obtaining short-term quantitative precipitation nowcasting based on radar maps is presented. The analysis considers four rainfall events monitored through radar scans collected at San Pietro Capofiume (northern Italy). These maps have temporal and spatial resolutions equal to 15 minutes and 1 x 1 km2, respectively. The nowcasting is performed by considering four different approaches, ranging from purely heuristic techniques to system analysis methods for modelling storm advection and dynamic storm evolution in a Lagrangian reference frame, travelling along with the storm. Stochastic models of the autoregressive type, as well as neural networks, are applied for modelling the Lagrangian storm dynamic. The dependence of the forecasting skills on prediction lead time and spatial size of the radar map pixels is investigated.
Atmosphere
Air quality in Europe continues to remain poor in many areas, with regulation limits often exceed... more Air quality in Europe continues to remain poor in many areas, with regulation limits often exceeded by many countries. The EU Life-IP PREPAIR Project, involving administrations and environmental protection agencies of eight regions and three municipalities in Northern Italy and Slovenia, was designed to support the implementation of the regional air quality plans in the Po Valley, one of the most critical areas in Europe in terms of pollution levels. In this study, four air quality modelling systems, based on three chemical transport models (CHIMERE, FARM and CAMx) were applied over the Po Valley to assess the sensitivity of PM2.5 concentrations to NOx and NH3 emission reductions. These two precursors were reduced (individually and simultaneously) from 25% up to 75% for a total of 10 scenarios, aimed at identifying the most efficient emission reduction strategies and to assess the non-linear response of PM2.5 concentrations to precursor changes. The multi-model analysis shows that r...
. A standardized methodology for the validation of short-term air quality forecast applications w... more . A standardized methodology for the validation of short-term air quality forecast applications was developed in the framework of FAIRMODE activities. The proposed approach, focusing on specific features to be checked when evaluating a forecasting application, investigates the model capability to detect sudden changes of pollutants concentrations levels, to predict threshold exceedances and to reproduce air quality indices. The proposed formulation relies on the definition of specific forecast Modelling Quality Objective and Performance Criteria, defining the minimum level of quality to be achieved by a forecasting application when it is used for policy purposes. The persistence model, which uses the most recent observed value as predicted value, is used as benchmark for the forecast evaluation. The validation protocol has been applied to several forecasting applications across Europe, using different modelling paradigms and covering a range of geographical contexts and spatial scales. The method is successful, with room for improvement, in highlighting shortcomings and strengths of forecasting applications. This provides a useful basis for using short-term air quality forecast as a supporting tool for correct information to citizens and regulators.
Springer proceedings in complexity, 2022
Atmosphere, 2020
The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit v... more The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit values for PM (particulate matter), NO2 (nitrogen dioxide) and O3 (ozone). This area covers the territory of most Italian northern regions and includes several urban agglomerates, such as Milan, Turin, Venice and Bologna. The area is densely populated and heavily industrialized. The paper summarizes the assessment of the impact of the current (2013) and future (2025) emissions and of the meteorological conditions on the air quality of the Po Valley. This study is one of the first outcomes of the EU LIFE-IP Clean Air Program Po Regions Engaged to Policies of Air (PREPAIR) project. The project, involving administrations and environmental agencies of eight regions and three municipalities in Northern Italy and Slovenia, started in 2017 and will end in 2024. Future emission scenarios consider the emissions reduction due to the air-quality action plans of the regions involved, of the agreement...
Rendiconti online della Società Geologica Italiana, 2015
During the October 2014 alluvial event in Parma province, which also caused the city of Parma to ... more During the October 2014 alluvial event in Parma province, which also caused the city of Parma to be partially flooded, several debris flows affected the upper Val Parma and Val Baganza (northern Apennines, Italy) causing severe and widespread damages to check-dams, roads and other infrastructures. The meteorological event reached intensities as high as 80 mm/hour, which is well above the thresholds presented in literature for the alpine area. The result was the occurrence of tens of debris flow along the Mt. Cervellino – Mt. Vitello relief, which were triggered in zones of failure of slope debris coverage along the streams, remobilized and scoured debris along the track and destroyed several check dams and damaged roads that were overflown by debris. Since debris flows in the northern Apennines are considered quite rare events, their hazard is generally underestimated or overlooked. The event in the Parma province, at the opposite, warns against this potentially destructive events that, in a changing meteorological framework, might result much more frequent and widespread than expected also in the northern Apennines.
Optical Spectroscopic Techniques, Remote Sensing, and Instrumentation for Atmospheric and Space Research IV, 2002
Broad band radiance measurements at top of the atmosphere are simulated using two diverse line-by... more Broad band radiance measurements at top of the atmosphere are simulated using two diverse line-by-line codes for a number of standard atmospheric conditions to evaluate the sensitivity of broad band spectral and spectrally integrated radiometry to realistic changes of water vapor content in the troposphere and of other parameters of climatic significance. . It is shown that the rotational band
Applied Optics, 2002
A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interact... more A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interaction for any number of cloud layers. Layer cloud fraction and transmittance are treated separately and combined with that of gaseous transmittances. RTF is tested against a reference procedure that uses line-by-line gaseous transmittances and solves the radiative transfer equation by use of the adding-doubling method to handle multiple-scattering conditions properly. The comparison is carried out for channels 8, 12, and 14 of the High Resolution Infrared Radiation Sounder (HIRS/2) and for the geostationary satellite METEOSAT thermal infrared and water vapor channels. Fairly large differences in simulated radiances by the two schemes are found in clear conditions for upper- and mid-tropospheric channels; the cause of the differences is discussed. For cloudy situations an improved layer source function is shown to be required when rapid changes in atmospheric transmission are experienced within the model layers. The roles of scattering processes are discussed; results with and without scattering, both obtained by use of a reference code, are compared. Overall, the presented results show that the fast model is capable of reproducing the cloudy results of the much more complex and time-consuming reference scheme.
Meteorology and Atmospheric Physics, 2014
ABSTRACT The spectral characteristics of hourly precipitation fields are studied for a number of ... more ABSTRACT The spectral characteristics of hourly precipitation fields are studied for a number of meteorological events, classified depending on the precipitation process involved, namely stratiform, convective or mixed stratiform–convective. The study focuses on the comparison between spatial spectral characteristics of observed precipitation fields, obtained from hourly radar estimates, and modelled hourly predictions of the same field by the nonhydrostatic model COSMO. The results show that the power spectra of radar hourly precipitation are characterised by invariance within ranges of horizontal spatial scales that are different for the three classes of events. COSMO reproduces some basic characteristics of the radar spectra in all cases. Nevertheless, in stratiform events, COSMO spectra present a well-defined scale break at about 15 km with no counterpart in radar data. It is suggested that this model feature is related to the presence of spurious horizontal smoothing introduced by the semi-lagrangian advection scheme for precipitation. Smoothing affects all scales up to the maximum length scale of precipitation and horizontal advection by the wind. An analysis of wind intensity in the lower troposphere over the region supports this interpretation. Discrepancies in precipitation spectra between radar and COSMO data in convective events are interpreted as a consequence of the inadequacy of the model resolution for a correct representation of convection.
On the afternoon of May 27th, 2009 a severe storm hit the city of Parma and its surroundings, cau... more On the afternoon of May 27th, 2009 a severe storm hit the city of Parma and its surroundings, causing widespread damages due to strong winds, hail and heavy downpours. In the first part of the work, a volumetric analysis of this deep convective system was carried out by using ARPA-SIMC Polarimetric-Doppler radar data, focusing on the microphysical and dynamical structure
... Contract n°: EVK1-CT-2000-00058 A Review of Satellite-based Rainfall Estimation Methods by Vi... more ... Contract n°: EVK1-CT-2000-00058 A Review of Satellite-based Rainfall Estimation Methods by Vincenzo Levizzani and Roberta Amorati Istituto di Scienze dell'Atmosfera e del Clima-CNR, Bologna and Francesco Meneguzzo Istituto di Biometeorologia-CNR, Firenze ...
A considerable advantage offered by the presence of two (or more) radar exploring the same area, ... more A considerable advantage offered by the presence of two (or more) radar exploring the same area, is the possibility to improve the quality of the final product, by adopting procedures of data composition. Radar data mosaicking is normally performed using simply range-related or value related algorithms of selection and combination. Usually, the followed ways are: a-b) to attribute to the common cell the mean or the maximum value of reflectivity; c) to assign to the common cell the reflectivity value of the nearest radar; d) to combine the data through a weighted average, where the weight is inversely proportional to the second power of the distance from the radar. The first approach distributes equally the probability to fail to the two radars, the second one handles only the problem of attenuation (which could be produced by mountains or rain), the third and the fourth are based on the assumption that radar data reliability diminishes only with the distance. Hence, these methods ta...
Many methods for estimating parametrically the intensity function for inhomogeneous spatial point... more Many methods for estimating parametrically the intensity function for inhomogeneous spatial point processes are available in the literature. Almost all papers consider the setting where the number of covariates is moderate. More and more applications involve a large number of covariates. Our paper considers feature selection procedures based on convex and non-convex regularization techniques to deal with such data. We investigate theoretical and computational aspects. We provide general conditions on the spatial point processes and on penalty functions which ensure consistency, sparsity, and asymptotic normality. In particular, from a theoretical point of view, we consider asymptotic properties which make our results available for several penalty functions and large classes of spatial point processes. Joint work with Jean-François Coeurjolly and Frédérique Letué. Passenger flows through airport terminals
The radar estimate of precipitation is recognized to be of great value for operational use, the h... more The radar estimate of precipitation is recognized to be of great value for operational use, the high spatial and temporal resolution being a key point in nowcasting procedures. It is also well known that the radar precipitation estimate suffers for different sources of error that have to be removed in order to fulfill meteorological and hydrological requirements. First of all reflectivity corrections are necessary, but benefits may be achieved by blending other sensor measurements (see among the others Chumchean et al., 2006). Merging the radar estimate with precipitation observed by a dense rain gauge network seems to be a solution. On the other side, often the merging techniques are not only inadequate, but even misleading. The correction by means of a sparse network has to take into account the complexity of the precipitation field itself and instrument limits that may lead to a non-uniform bias field, particularly in areas with complex orography. Moreover different precipitation...
Atmosphere
The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit v... more The Po Valley (Northern Italy) represents an important exceedance zone of the air-quality limit values for PM (particulate matter), NO2 (nitrogen dioxide) and O3 (ozone). This area covers the territory of most Italian northern regions and includes several urban agglomerates, such as Milan, Turin, Venice and Bologna. The area is densely populated and heavily industrialized. The paper summarizes the assessment of the impact of the current (2013) and future (2025) emissions and of the meteorological conditions on the air quality of the Po Valley. This study is one of the first outcomes of the EU LIFE-IP Clean Air Program Po Regions Engaged to Policies of Air (PREPAIR) project. The project, involving administrations and environmental agencies of eight regions and three municipalities in Northern Italy and Slovenia, started in 2017 and will end in 2024. Future emission scenarios consider the emissions reduction due to the air-quality action plans of the regions involved, of the agreement...
Proc. ERAD, 2004
... Bech, J., Codina, B., Lorente, J., and Bebbington, D.: The sensitiv-ity of single polarizatio... more ... Bech, J., Codina, B., Lorente, J., and Bebbington, D.: The sensitiv-ity of single polarization weather radar beam blockage correction to variability in the ... Marshall, J. S and Palmer, W. McK.: The distribution of raindrops with size, J. Meteor., 5, 165–166, WMO Publications, No. ...
Rainfall is a phenomenon difficult to model and predict, for the strong spatial differences in da... more Rainfall is a phenomenon difficult to model and predict, for the strong spatial differences in data and the presence of many zero collected values. Observed data come from rain gauges, sparsely distributed on ground. These observations can be accompanied by other measurements, like reflectivity radar data. Rainfall prediction is a fundamental issue: all available data ought to be treated together for obtaining more precise results. In this work, we investigate whether radar data can contribute to improve spatial statistical prediction, comparing kriging estimates based on rain gauges with kriging on rain gauges and radar rainfall data acting as an external drift. Results are encouraging about enriching prediction with radar information.
An extensive evaluation of system analysis techniques for obtaining short-term quantitative preci... more An extensive evaluation of system analysis techniques for obtaining short-term quantitative precipitation nowcasting based on radar maps is presented. The analysis considers four rainfall events monitored through radar scans collected at San Pietro Capofiume (northern Italy). These maps have temporal and spatial resolutions equal to 15 minutes and 1 x 1 km2, respectively. The nowcasting is performed by considering four different approaches, ranging from purely heuristic techniques to system analysis methods for modelling storm advection and dynamic storm evolution in a Lagrangian reference frame, travelling along with the storm. Stochastic models of the autoregressive type, as well as neural networks, are applied for modelling the Lagrangian storm dynamic. The dependence of the forecasting skills on prediction lead time and spatial size of the radar map pixels is investigated.