Abstract. A large part of the research in the radar meteorology is devoted to the evaluation of the radar data quality and to the radar data processing. Even when, a set of absolute quality indexes can be produced (like as ground clutter presence, beam blockage rate, distance from radar, etc.), the final product quality has to be determined as a function of the task and of all the processing steps. In this paper the emphasis lies on the estimate of the rainfall at the ground level taking extra care for the correction for ground clutter and beam blockage, that are two main problems affecting radar reflectivity data in complex orography. In this work a combined algorithm is presented that avoids and/or corrects for these two effects. To achieve this existing methods are modified and integrated with the analysis of radar signal propagation in different atmospheric conditions. The atmospheric refractivity profile is retrieved from the nearest in space and time radiosounding. This measured profile is then used to define the `dynamic map' used as a declutter base-field. Then beam blockage correction is applied to the data at the scan elevations computed from this map. Two case studies are used to illustrate the proposed algorithm. One is a summer event with anomalous propagation conditions and the other one is a winter event. The new algorithm is compared to a previous method of clutter removal based only on static maps of clear air and vertical reflectivity continuity test. The improvement in rain estimate is evaluated applying statistical analysis and using rain gauges data. The better scores are related mostly to the ``optimum" choice of the elevation maps, introduced by the more accurate description of the signal propagation. Finally, a data quality indicator is introduced as an output of this scheme. This indicator has been obtained from the general scheme, which takes into account all radar data processing steps.
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 agreements between the national authorities and regional administrations and of the PREPAIR project itself, in the overall context of the application of the current legislation of the European Union. The combination of these measures will lead to the reduction of direct emissions of PM10 in the Po Valley and of the main precursors emitted in the area (NOx, nitrogen oxides and NH3, and ammonia) by 38% for PM10, 39% for NOx and 22% for NH3, respectively. This lowering corresponds to a reduction of about 30.000 tons of primary PM10, 150.000 tons of NOx, 54.000 tons of NH3 and 1700 tons of SO2. The results show that these expected reductions should allow us to achieve the EU PM10 limit value in the Po Valley by the year 2025.
Convective precipitation events in northern Italy during 1996 and
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.
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