The fingerprint of the 2018 drought in Europe on ground-based atmospheric CO2 measurements.

During the summer of 2018, a widespread drought developed over Northern and Central Europe. The increase in temperature and the reduction of soil moisture have influenced carbon dioxide (CO2) exchange between the atmosphere and terrestrial ecosystems in various ways, such as a reduction of photosynthesis, changes in ecosystem respiration, or allowing more frequent fires. In this study, we characterize the resulting perturbation of the atmospheric CO2 seasonal cycles. 2018 has a good coverage of European regions affected by drought, allowing the investigation of how ecosystem flux anomalies impacted spatial CO2 gradients between stations. This density of stations is unprecedented compared to previous drought events in 2003 and 2015, particularly thanks to the deployment of the Integrated Carbon Observation System (ICOS) network of atmospheric greenhouse gas monitoring stations in recent years. Seasonal CO2 cycles from 48 European stations were available for 2017 and 2018. Earlier data were retrieved for comparison from international databases or national networks. Here, we show that the usual summer minimum in CO2 due to the surface carbon uptake was reduced by 1.4 ppm in 2018 for the 10 stations located in the area most affected by the temperature anomaly, mostly in Northern Europe. Notwithstanding, the CO2 transition phases before and after July were slower in 2018 compared to 2017, suggesting an extension of the growing season, with either continued CO2 uptake by photosynthesis and/or a reduction in respiration driven by the depletion of substrate for respiration inherited from the previous months due to the drought. For stations with sufficiently long time series, the CO2 anomaly observed in 2018 was compared to previous European droughts in 2003 and 2015. Considering the areas most affected by the temperature anomalies, we found a higher CO2 anomaly in 2003 (+3 ppm averaged over 4 sites), and a smaller anomaly in 2015 (+1 ppm averaged over 11 sites) compared to 2018. This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'.

Optical properties of tropospheric aerosols determined by lidar and spectrophotometric measurements (Photochemical Activity and Solar Ultraviolet Radiation campaign).

We present the results of the aerosol measurements carried out over the Aegean Sea during the Photochemical Activity and Solar Ultraviolet Radiation campaign held in Greece during June 1996. Simultaneous observations performed with a lidar and a double-monochromator spectrophotometer allowed us to retrieve the optical depth, the Angström coefficient, and the backscatter-to-extinction ratio. The Sun photometric data can be used to improve quantitative aerosol measurements by lidar in the Planetary Boundary Layer. Systematic errors could arise otherwise, because the value of the backscatter-to-extinction ratio has to be supplied. Instead this ratio can be retrieved experimentally by use of an iterative solution of the lidar equation.

Computerized system for nuclear emergency response in the ENEA Nuclear Research Center of Frascati.

At the National Committee for Research and Development of Nuclear Energy and Alternate Energy Sources (ENEA) Center of Frascati, there are several radiation-producing machines: two tokamaks and three electron accelerators; moreover, a neutron generator will begin to operate in a short time. A completely automatic monitoring system has been developed. Radiation control is performed by means of classical active and passive detectors. An automatic acquisition system has been developed: Measured quantities are acquired and stored in a specific data base; information regarding radioactivity levels, machines status, personnel dosimetry and meteorological parameters are available in real time. If any of the radiometric quantities exceeds appropriate reference levels, the following operations automatically activate: An automatic switch turns off the machines and an alarm signal is broadcast to the Health Physics group. In addition, the "Nuclear Emergency" software module starts if a radionuclide emission is detected. This module has been implemented to provide response to radiological emergencies in the ENEA nuclear research centers. The modularity of the computer-based system allows its utilization also in other nuclear centers, such as at nuclear power plants. When activated, the "Nuclear Emergency" displays an alarm signal and informs the Health Physics group about the monitor's location and characteristics and the measured data exceeding the reference level. If emission of radionuclides occurs, a preliminary evaluation of their diffusion in the atmosphere and an estimation of the population dose are performed. Statistical analysis of the event is also possible.