Correlation Analysis of Evapotranspiration, Emissivity Contrast and Water Deficit Indices: A Case Study in Four Eddy Covariance Sites in Italy with Different Environmental Habitats

Evapotranspiration (ET) represents one of the essential processes controlling the exchange of energy by terrestrial vegetation, providing a strong connection between energy and water fluxes. Different methodologies have been developed in order to measure it at different spatial scales, ranging from individual plants to an entire watershed. In the last few years, several methods and approaches based on remotely sensed data have been developed over different ecosystems for the estimation of ET. In the present work, we outline the correlation between ET measured at four eddy covariance (EC) sites in Italy (situated either in forest or in grassland ecosystems) and (1) the emissivity contrast index (ECI) based on emissivity data from thermal infrared spectral channels of the MODIS and ASTER satellite sensors (CAMEL data-set); (2) the water deficit index (WDI), defined as the difference between the surface and dew point temperature modeled by the ECMWF (European Centre for Medium-Range Weather Forecasts) data. The analysis covers a time-series of 1 to 7 years depending on the site. The results showed that both the ECI and WDI correlate to the ET calculated through EC. In the relationship WDI-ET, the coefficient of determination ranges, depending on the study area, between 0.5 and 0.9, whereas it ranges between 0.5 and 0.7 when ET was correlated to the ECI. The slope and the sign of the latter relationship is influenced by the vegetation habitat, the snow cover (particularly in winter months) and the environmental heterogeneity of the area (calculated in this study through the concept of the spectral variation hypothesis using Rao’s Q heterogeneity index)

Effects of COVID‐19 lockdown measures on nitrogen dioxide and black carbon concentrations close to a major Italian motorway

Abstract During the first half of 2020, the Italian government imposed several restrictions to limit the spread of the COVID‐19 pandemic: at the beginning of March, a heavy lockdown regime was introduced leading to a drastic reduction of traffic and, consequently, traffic‐related emissions. The aim of this study is to evaluate the effects of these restrictions on pollutant concentrations close to a stretch of the Italian A22 motorway lying in the Alpine Adige valley. In particular, the analysis focuses on measured concentrations of nitrogen dioxide (NO2) and black carbon (BC). Results show that, close to the motorway, NO2 concentrations dropped by around 45% during the lockdown period with respect to the same time period of the previous 3 years. The equivalent analysis for BC shows that the component related to biomass burning, mostly due to domestic heating, was not particularly affected by the restrictions, while the BC component related to fossil fuels, directly connected to traffic, plummeted by almost 60% with respect to the previous years. Since atmospheric concentrations of pollutants depend both on emissions and meteorological conditions, which can mask the variations in the emission regime, a random forest algorithm is also applied to the measured concentrations, in order to better evaluate the effects of the restrictions on emissions. This procedure allows for obtaining business‐as‐usual and meteorologically normalized time series of both NO2 and BC concentrations. The results derived from the random forest algorithm clearly confirm the drop in NO2 emissions at the beginning of the lockdown period, followed by a slow and partial recovery in the following months. They also confirm that, during the lockdown, emissions of the BC component due to biomass burning were not significantly affected, while those of the BC component related to fossil fuels underwent an abrupt drop

Wind profiles from Doppler Wind-LiDAR during the field campaign of the Bolzano Tracer EXperiment (BTEX)

During BTEX a Doppler Wind–LIDAR (WindCube 100S, manufactured by Leosphere, France) was installed in the Bolzano basin (46.498192 N, 11.364963 E, 267 m ASL) on the roof of a public building at 18 m AGL. The Wind-LIDAR provided every 5 s the vertical profiles of the wind speed components, measured by means of the Doppler Beam Swinging (DBS) technique. In particular, each profile is composed of 110 vertical levels, one every 10 m, from 50 m above the Wind–LIDAR (i.e. 335 m ASL) to 1100 m (i.e. 1385 m ASL). In addition to the vertical profiles of the wind speed components, the Wind–LIDAR also provided the Carrier–to– Noise Ratio profile, corresponding to the ratio of the power of the received signal to the noise powe

Tracer concentrations and meteorological observations from the Bolzano Tracer EXperiment (BTEX)

The data set contains ground concentrations and related meteorological measurements collected during the field campaign of the Bolzano Tracer EXperiment (BTEX). The experiment was performed to characterize the dispersion of pollutants emitted by a waste incinerator in the basin of the city of Bolzano in the Alps. As part of the experiment two controlled releases of a passive gas tracer (sulfur hexafluoride, SF6) were performed through the stack of the incinerator on 14 February 2017 at two different times, starting respectively at 7:00 and 12:45. Samples of ambient air were collected at target sites by means of vacuum-filled glass bottles and plastic bags, and later analysed using a mass spectrometer (detectability limit 30 ppt). Meteorological conditions were monitored by means of a network of 15 ground weather stations, 1 temperature profiler, 1 SODAR and 1 Doppler Wind-LIDAR. The data set represents one of the few examples available in the literature concerning dispersion processes in a typical mountain valley environment and provides a useful benchmark for testing and calibration of dispersion models in such a complex terrain

Emission discharge and emission temperature of the incinerator during the field campaign of the Bolzano Tracer EXperiment (BTEX)

This dataset contains information concerning the incinerator and its working conditions, i.e. the coordinates and the height of the stack, along with the discharge and temperature of the emissions. The data set covers a period of 24 h, from 2017-02-14 00:00 [UTC+1] to 2017-02-15 00:00 [UTC+1], with a time resolution of 30 min. In particular, each row in the file provides the 30 min–average of the corresponding quantity, and the time–stamp refers to the end of the averaging period. The data provided in the data set were collected from the daily reports of the incinerator, that can also be freely downloaded from the web page of the company operating the plant, eco center S.p.A.: https://www.eco-center.it/it/attivita-servizi/ambiente/impianti/impianto-di-termovalorizzazione/reports/reports-giornalieri-795.htm

Temperature profiles during the field campaign of the Bolzano Tracer EXperiment (BTEX)

Temperature profiles were measured by means of a MTP-5HE passive microwave radiometer, manifactured by Attex (Russia). The MTP-5HE is installed in the airfield of Bolzano (46.459843 N, 11.323169 E, 238 m ASL) on the roof of a building 12 m high. The device was operated so as to provide every 10 min the vertical profile of the temperature with a maximum range of 1000 m and with a vertical resolution of 50 m. Temperature profiles are provided by the Physical Chemistry Laboratory of the Environmental Protection Agency of the Autonomous Province of Bolzano (http://www.provincia.bz.it/it/contatti.asp?orga_orgaid=882)

Wind profiles of MFAS mini-SODAR during the field campaign of the Bolzano Tracer EXperiment (BTEX)

During BTEX a MFAS mini–SODAR (manufactured by Scintec, Germany) was installed on the roof of the incinerator of Bolzano (46.468463 N, 11.308782 E, 245 m ASL) at 40 m AGL. In particular, the SODAR was installed close to the chimney of the incinerator, in order to monitor the wind field at the outlet of the stack, where emissions are released into the atmosphere. The SODAR investigated an atmospheric layer 400 m-deep along 38 10 m-spaced vertical levels. Indeed, the lowest datum is provided at 30 m above the antenna, i.e. 70 m AGL and 315 m ASL, whereas the highest one is provided at 400 m above the antenna, i.e. 685 m ASL. Actually, at each vertical level, the SODAR provides a measure averaged over an atmospheric layer 30 m–thick and centered at the elevation of the level. Raw data were processed by means of the software APRun, provided by Scintec, in order to obtain the vertical profiles of: 1. mean wind quantities, i.e. wind speed components, wind intensity, wind direction; 2. standard deviations of the wind speed components; 3. back scatter. Due to the environmental noise affecting the site, raw data were processed and averaged over a time–window of 30 min, in order to obtain reliable profiles of the above quantities. The time-stamp refers to the end of the averaging period

SF6 releases and ground concentration during the field campaign of the Bolzano Tracer EXperiment (BTEX)

On 2017-02-14, two controlled releases of a passive and inert gas tracer (SF6) were performed into the stack of the incinerator (46.468345 N, 11.308716 E, 307 m ASL): one in the morning (under stable atmospheric conditions and light northerly winds) and one in afternoon (under weak unstable conditions and light southerly winds). At each release, samples of ambient air were collected at selected points in the surrounding area by means of vacuum-filled glass bottles and plastic bags. Tracer concentration in each sample was measured in the laboratories of Eco-Research s.r.l. by means of a GC-MS tipple quadrupole mass spectrometer (TSQ 8000 EVO from Thermo Scientific) with chemical ionization (CI) with methane as reagent gas. The obtained sensitivity allowed to measure down to background levels. In the year 2017 the background SF6 levels in the Bolzano basin were close to 10 ppt. To avoid the influence of the background, the quantification was performed at levels above 30 ppt

Meteorological observations of ground weather stations during the field campaign of the Bolzano Tracer EXperiment (BTEX)

Meteorological observations from the ground weather stations are provided as 10-min averages. The time-stamp refers to the end of the averaging period. Data collected by the ground weather stations can be also freely downloaded from the open data web-service of the Autonomous Province of Bolzano (http://dati.retecivica.bz.it/it/group/weather)