ALBERT

Description: We apply a coupled modelling system composed of a state-of-the-art hydrodynamical model and a low-complexity biogeochemical model to an idealized Iberian Peninsula upwelling system to identify the main drivers of dissolved-oxygen variability and to study its response to changes in the duration of the upwelling season and in the phytoplankton growth regime. We find that the export of oxygenated waters by upwelling front turbulence is a major sink for nearshore dissolved oxygen. In our simulations of summer upwelling, when the phytoplankton population is generally dominated by diatoms whose growth is boosted by nutrient input, net primary production and air–sea exchange compensate dissolved-oxygen depletion by offshore export over the shelf. A shorter upwelling duration causes a relaxation of upwelling winds and a decrease in offshore export, resulting in a slight increase of net dissolved-oxygen enrichment in the coastal region as compared to longer upwelling durations. When phytoplankton is dominated by groups less sensitive to nutrient inputs, growth rates decrease, and the coastal region becomes net heterotrophic. Together with the physical sink, this lowers the net oxygenation rate of coastal waters, which remains positive only because of air–sea exchange. These findings help in disentangling the physical and biogeochemical controls of dissolved oxygen in upwelling systems and, together with projections of increased duration of upwelling seasons and phytoplankton community changes, suggest that the Iberian coastal upwelling region may become more vulnerable to hypoxia and deoxygenation.

Description: The increasing availability of free-access satellite data represents a relevant opportunity for the analysis and assessment of natural hazards. The systematic acquisition of spaceborne imagery allows for monitoring areas prone to geohydrological disasters, providing relevant information for risk evaluation and management. In cases of major landslide events, for example, spaceborne radar data can provide an effective solution for the detection of slope failures, even in cases with persistent cloud cover. The information about the extension and location of the landslide-affected areas may support decision-making processes during emergency responses. In this paper, we present an automatic procedure based on Sentinel-1 Synthetic Aperture Radar (SAR) images, aimed at facilitating the detection of landslides over wide areas. Specifically, the procedure evaluates changes of radar backscattered signals associated with land cover modifications that may be also caused by mass movements. After a one-time calibration of some parameters, the processing chain is able to automatically execute the download and preprocessing of images, the detection of SAR amplitude changes, and the identification of areas potentially affected by landslides, which are then displayed in a georeferenced map. This map should help decision makers and emergency managers to organize field investigations. The process of automatization is implemented with specific scripts running on a GNU/Linux operating system and exploiting modules of open-source software. We tested the processing chain, in back analysis, on an area of about 3000 km2 in central Papua New Guinea that was struck by a severe seismic sequence in February–March 2018. In the area, we simulated a periodic survey of about 7 months, from 12 November 2017 to 6 June 2018, downloading 36 Sentinel-1 images and performing 17 change detection analyses automatically. The procedure resulted in statistical and graphical evidence of widespread land cover changes that occurred just after the most severe seismic events. Most of the detected changes can be interpreted as mass movements triggered by the seismic shaking.

Description: The Balloon Lidar Experiment (BOLIDE) was the first high-power lidar flown and operated successfully on board a balloon platform. As part of the PMC Turbo payload, the instrument acquired high-resolution backscatter profiles of polar mesospheric clouds (PMCs) from an altitude of ∼ 38 km during its maiden ∼ 6 d flight from Esrange, Sweden, to northern Canada in July 2018. We describe the BOLIDE instrument and its development and report on the predicted and actual in-flight performance. Although the instrument suffered from excessively high background noise, we were able to detect PMCs with a volume backscatter coefficient as low as 0.6×10-10 m−1 sr−1 at a vertical resolution of 100 m and a time resolution of 30 s.

Description: Several record-breaking precipitation events have struck the mountainous area of the Emilia–Romagna region (northern Apennines, Italy) over the last 10 years. As a consequence, severe geomorphological processes such as debris avalanches and debris flows, shallow landslides, and overbank flooding have affected the territory, causing severe damage to human-made structures. The unusual intensity of these phenomena prompted an investigation into their frequency in the past, beyond instrumental time. In the quest for an understanding of whether these phenomena are unprecedented in the region, peat bog and lake deposits were analyzed to infer the frequency of extreme precipitation events that may have occurred in the past. We present the results of a dedicated field campaign performed in summer 2017 at Lake Moo in the northern Apennines, a 0.15 km2 peat bog located at an altitude of 1130 m a.s.l. During the extreme precipitation event of 13–14 September 2015, several debris flows generated by small streams affected the Lake Moo plain. In such a small drainage basin (

Description: The evaporation flux Jev(H2O) of H2O from HCl-doped typically 1.5 µm or so thick vapor-deposited ice films has been measured in a combined quartz crystal microbalance (QCMB)–residual gas mass spectrometry (MS) experiment. Jev(H2O) has been found to show complex behavior and to be a function of the average mole fraction χHCl of HCl in the ice film ranging from 6×1014 to 3×1017 molecule cm−2 s−1 at 174–210 K for initial values χHCl0 ranging from 5×10-5 to 3×10-3 at the start of the evaporation. The dose of HCl on ice was in the range of 1 to 40 formal monolayers and the H2O vapor pressure was independent of χHCl within the measured range and equal to that of pure ice down to 80 nm thickness. The dependence of Jev(H2O) with increasing average χHCl was correlated with (a) the evaporation range rb∕e parameter, that is, the ratio of Jev(H2O) just before HCl doping of the pure ice film and Jev(H2O) after observable HCl desorption towards the end of film evaporation, and (b) the remaining thickness dD below which Jev(H2O) decreases to less than 85 % of pure ice. The dependence of Jev(H2O) with increasing average χHCl from HCl-doped ice films suggests two limiting data sets, one associated with the occurrence of a two-phase pure ice/crystalline HCl hydrate binary phase (set A) and the other with a single-phase amorphous HCl∕H2O binary mixture (set B). The measured values of Jev(H2O) may lead to significant evaporative lifetime extensions of HCl-contaminated ice cloud particles under atmospheric conditions, regardless of whether the structure corresponds to an amorphous or crystalline state of the HCl∕H2O aggregate.

Description: Anthropogenic volatile organic compounds (AVOCs) often dominate the urban atmosphere and consist to a large degree of aromatic hydrocarbons (ArHCs), such as benzene, toluene, xylenes, and trimethylbenzenes, e.g., from the handling and combustion of fuels. These compounds are important precursors for the formation of secondary organic aerosol. Here we show that the oxidation of aromatics with OH leads to a subsequent autoxidation chain reaction forming highly oxygenated molecules (HOMs) with an O : C ratio of up to 1.09. This is exemplified for five single-ring ArHCs (benzene, toluene, o-/m-/p-xylene, mesitylene (1,3,5-trimethylbenzene) and ethylbenzene), as well as two conjugated polycyclic ArHCs (naphthalene and biphenyl). We report the elemental composition of the HOMs and show the differences in the oxidation patterns of these ArHCs. A potential pathway for the formation of these HOMs from aromatics is presented and discussed. We hypothesize that AVOCs may contribute substantially to new particle formation events that have been detected in urban areas.

Description: The ion composition at high altitude (3454 m a.s.l.) was measured with an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF) during a period of 9 months, from August 2013 to April 2014. The negative mass spectra were dominated by the ions of sulfuric, nitric, malonic, and methanesulfonic acid (MSA) as well as SO5−. The most prominent positive ion peaks were from amines. The other cations were mainly organic compounds clustered with a nitrogen-containing ion, which could be either NH4+ or an aminium. Occasionally the positive spectra were characterized by groups of compounds each differing by a methylene group. In the negative spectrum, sulfuric acid was always observed during clear sky conditions following the diurnal cycle of solar irradiation. On many occasions we also saw a high signal of sulfuric acid during nighttime when clusters up to the tetramer were observed. A plausible reason for these events could be evaporation from particles at low relative humidity. A remarkably strong correlation between the signals of SO5− and CH3SO3− was observed for the full measurement period. The presence of these two ions during both the day and the night suggests a non-photochemical channel of formation which is possibly linked to halogen chemistry. Halogenated species, especially Br− and IO3−, were frequently observed in air masses that originated mainly from the Atlantic Ocean and occasionally from continental areas based on back trajectory analyses. We found I2O5 clustered with an ion, a species that was proposed from laboratory and modeling studies. All halogenated ions exhibited an unexpected diurnal behavior with low values during daytime. New particle formation (NPF) events were observed and characterized by (1) highly oxygenated molecules (HOMs) and low sulfuric acid or (2) ammonia–sulfuric acid clusters. We present characteristic spectra for each of these two event types based on 26 nucleation episodes. The mass spectrum of the ammonia–sulfuric acid nucleation event compares very well with laboratory measurements reported from the CLOUD chamber. A source receptor analysis indicates that NPF events at the Jungfraujoch take place within a restricted period of time of 24–48 h after air masses have had contact with the boundary layer. This time frame appears to be crucial to reach an optimal oxidation state and concentration of organic molecules necessary to facilitate nucleation.

Description: In the last years coupled atmospheric ocean climate models have remarkably improved medium range seasonal forecasts, especially on middle latitude areas such as Europe and the Mediterranean basin. In this study a new framework for medium range seasonal forecasts is proposed. It is based on circulation types extracted from long range global ensemble models and it aims at two goals: (i) an easier use of the information contained in the complex system of atmospheric circulations, through their reduction to a limited number of circulation types and (ii) the computation of high spatial resolution probabilistic forecasts for temperature and precipitation. The proposed framework could be also useful to lead predictions of weather-derived parameters, such as the risk of heavy rainfall, drought or heat waves, with important impacts on agriculture, water management and severe weather risk assessment. Operatively, starting from the ensemble predictions of mean sea level pressure and geopotential height at 500 hPa of the NCEP – CFSv2 long range forecasts, the third-quantiles probabilistic maps of 2 m temperature and precipitation are computed through a Bayesian approach by using E-OBS 0.25∘ gridded datasets. Two different classification schemes with nine classes were used: (i) Principal Component Transversal (PCT9), computed on mean sea level pressure and (ii) Simulated Annealing Clustering (SAN9), computed on geopotential height at 500 hPa. Both were chosen for their best fit concerning the ground-level precipitation and temperature stratification for the Italian peninsula. Following this approach an operative chain based on a very flexible and exportable method was implemented, applicable wherever spatially and temporally consistent datasets of weather observations are available. In this paper the model operative chain, some output examples and a first attempt of qualitative verification are shown. In particular three case studies (June 2003, February 2012 and July 2014) were examined, assuming that the ensemble seasonal model correctly predicts the circulation type occurrences. At least on this base, the framework here proposed has shown promising performance.

Description: Climate variability and change are recognised as a major threat for West African agriculture, particularly for smallholder farmers. Moreover, population pressure, poverty, and food insecurity, are worsening the vulnerability of production systems to climate risks. Application of Climate Services in agriculture, specifically Agrometeorological Services, is acknowledged as a valuable innovation to assist decision-making and develop farmers' specific adaptive capacities. In West Africa, the World Meteorological Organisation and National Meteorological Services deployed considerable efforts in the development of Agrometeorological Services. Nevertheless, the impacts of such services on West African farming communities are still largely unknown. This paper aims to delineate the added value of agrometeorological services for farmers within the Agriculture Innovation System of Mauritania. The results of this quali-quantitative assessment demonstrate that farmers use agrometeorological information for a variety of choices: making strategic choice on the seed variety and on the geographical distribution of plots, choosing the most appropriate planting date, better tuning crop development cycle with the rhythm of the rains and choosing favourable periods for different cultural operations. Globally, the effects of all these good practices can be summarized by an increase of crops productivity and a decrease of cropping costs (including opportunity cost) in terms of inputs and working time.

Description: The Department of Earth Sciences of Florence (DST) has developed a new type of drone chassis., Several survey campaigns were performed in Ricasoli village, in the Upper Arno river Valley (Tuscany, Italy) with the drone equipped with an optical camera, to understand the possibility of this rising technology to map and to characterize landslides. The aerial RGB images were analysed and combined using SfM (Structure from Motion) software. The comparative analysis of the obtained DTMs allowed an accurate reconstruction and mapping of the detected landslides. The collected data also allowed to precisely detect some slope portions prone to failure and to evaluate the area and volume of the involved masses.