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The Gas Absorption Spectrometer Correlating Optical Difference—New Generation 4 (GASCOD/NG4) is a multi-axis differential optical absorption spectroscopy (MAX-DOAS) instrument which measures diffuse solar spectra at the Environmental-Climate Observatory (ECO) of the Italian research institute CNR-ISAC, near Lecce. The high-resolution spectra measured in zenith-sky configuration were used to retrieve the NO 2 and O 3 vertical column densities (VCDs) from March 2017 to November 2019. These good-quality data, proven by the comparison with the Ozone Monitoring Instrument (OMI) and TROPOspheric Monitoring Instrument (TROPOMI) satellite measurements, were used to characterize the ECO site by exploiting the sinergy with in situ NO 2 and O 3 concentrations and meteorological data. Although stratospheric processes seem to be the main forces behind the NO 2 and O 3 VCDs seasonal trends, diurnal variabilities revealed the presence of a tropospheric signal in the NO 2 VCDs, which had significant lower values during Sundays. Comparison with wind data acquired at the ECO observatory, at 20 m above the ground, revealed how NO 2 VCDs are influenced by both tropospheric local production and transport from the nearby city of Lecce. On the other hand, no significant tropospheric signal was contained in the O 3 VCDs. [ABSTRACT FROM AUTHOR]

This study analyses the interactions and impacts between multiple factors i.e., urban greening, building layout, and meteorological conditions that characterise the urban microclimate and thermal comfort in the urban environment. The focus was on two neighbourhoods of Lecce city (southern Italy) characterised through field campaigns and modelling simulations on a typical hot summer day. Field campaigns were performed to collect greening, building geometry, and microclimate data, which were employed in numerical simulations of several greening scenarios using the Computational Fluid Dynamics-based and microclimate model ENVI-met. Results show that, on a typical summer day, trees may lead to an average daily decrease of air temperature by up to 1.00 °C and an improvement of thermal comfort in terms of Mean Radiant Temperature (MRT) by up to 5.53 °C and Predicted Mean Vote (PMV) by up to 0.53. This decrease is more evident when the urban greening (in terms of green surfaces and trees) is increased by 1266 m2 in the first neighbourhood and 1988 m2 in the second one, with respect to the current scenario, proving that shading effect mainly contributes to improving the urban microclimate during daytime. On the contrary, the trapping effect of heat, stored by the surfaces during the day and released during the evening, induces an increase of the spatially averaged MRT by up to 2 °C during the evenings and a slight deterioration of thermal comfort, but only locally where the concentration of high LAD trees is higher. This study contributes to a better understanding of the ecosystem services provided by greening with regard to microclimate and thermal comfort within an urban environment for several hours of the day. It adds knowledge about the role of green areas in a Mediterranean city, an important hot spot of climate change, and thus it can be a guide for important urban regeneration plans. [ABSTRACT FROM AUTHOR]