In the present work an analytical model of the vortex motion elementary state of the dry atmosphere with nonzero air velocity divergence is constructed. It is shown that the air parcel moves along the open curve trajectory of spiral geometry. It is found that for the case of nonzero velocity divergence the atmospheric elementary state presents an unlimited sequence of vortex cells transiting from one to another. On the other hand, at zero divergence, the elementary state presents a pair of connected vortices, and the trajectory is a closed curve. If in some cells the air parcel moves upward then in the adjacent cells it will move downward and vice versa. At reaching the cell middle height the parcel reverses the direction of rotation. When parcel moves upward, the motion is of anticyclonic type in the lower part of the vortex cell and of the cyclonic type in the upper part. When parcel moves downward, the motion is of anticyclonic type in the upper part of the vortex cell and of the cyclonic type in the lower part. Full article

Acetylene is a simple molecule of interest for interstellar medium (ISM) and planetary atmospheres. The presence of C₂H₂ was detected by IR spectroscopic measurements. Acetylene was also found as a minor component in the atmosphere of gas giants like the planet Jupiter, in the atmosphere of Saturn’s satellite Titan, and in comets, where photochemical experiments have demonstrated that this simple hydrocarbon is a likely precursor of C₂, a widely observed component in such environments. It has to be noted that the presence in planetary atmospheres and ISM of Vacuum Ultra Violet (VUV) light’s photons as well as cosmic rays makes highly probable the double photoionization of molecular species with the production of molecular dications producing subsequent dissociation into ionic fragments having a high kinetic energy content of several eV. This translational energy is sufficient in some cases to allow ions escape from the upper atmosphere of some planet of the Solar System, as Venus, Mars and Titan, into space. In this contribution we present the experimental study of the microscopic dynamics of the two-body dissociation reactions of the C₂H₂⁺² dication, induced by the double ionization of acetylene molecules by VUV photons in the energy range of 31.9–50.0 eV. The photoionizing agent was a tunable synchrotron radiation beam, while ion products are revealed by coupling photoelectron-photoion-photoion-coincidence and ion imaging techniques. The measured angular distributions and kinetic energy of product ions exhibit significant changes (as the photon energy increases) for the three leading dissociation reactions producing H⁺+C₂H⁺, C⁺+CH₂⁺, and CH⁺+CH⁺, providing detailed information on the fragmentation dynamics of the C₂H₂²⁺ dication. Full article

Some weather extremes can be the result of atmospheric blocking, which can be responsible for the stagnation of weather patterns. These large-scale quasi-stationary mid-latitude flow regimes can result in significant temperature and precipitation anomalies in the regions that the blocking event impacts. The ability to predict periods of anomalous weather conditions due to atmospheric blocking is a major problem for medium-range forecasting. Analyzing the NCEP Ensemble 500-mb pressure heights (240 h) ten-day forecasts, and using the University of Missouri blocking archive to identify blocking event, the forecasted duration and intensity of model blocking events are compared to observed blocks. Comparing these differences using four case studies occurring over a one-year period across the Northern Hemisphere has shown the continued need for improvement of the duration and intensity of blocking events. Additionally, a comparison of the block intensity to a diagnostic known as the Integrated Regional Enstrophy (IRE) was performed in order to determine if there is a correlation between these quantities. Having a better understanding of knowing how long each block will last and their associated anomalies can help society prepare for the damage they can cause. Simulating and identifying blocks correctly is important in improving forecast issues. Full article

According to IPCC reports, a greater frequency, intensity and duration of heat waves in urban areas are expected. This is related to the dynamical evolution of the cities, due the changes of the natural surface modifies the roughness pattern reduce the wind intensity, modify the available humidity in the soil and the radiative properties. These topics characterize the formation of the urban heat island (UHI). A dynamical downscaling of A2 and B1 future scenarios was made for Londrina, a medium-size city of Southern Brazil, using Weather Research Forecasting model, to investigate the impact of this projections on the UHI formation and intensity, as well for rural area, which consistent an important agricultural landscape. For this, an evaluation of the model and the scenarios were done to investigate the current trends. The results shows a tendency of following the worst proposed scenarios (A2), and a drier rural area for the sustainable projection, which has directly influence on the urban heat island intensity and formation, and in the agriculture of the region. Full article

The role of the single PM components in inducing the catalytic generation of reactive oxygen species (ROS), has not yet been clarified. Different a-cellular assay are currently used in the literature for the determination of the PM oxidative potential (OP), which is considered as a predictive index of its capacity to generate ROS in biological organisms. In order to better understand the existing correlations between PO and PM generated by specific emission sources, the water soluble and insoluble fractions of seven dust coming from specific sources were chemically characterised and analysed by three PO assays: the dithiothreitol (DTT, the acid ascorbic (AA) and the 2′,7′-dichlorofluorescin (DCFH) assays. PO and chemical data were elaborated by principal constituent analysis. The three methods responded in a very different way to each dust; they are then no-interchangeable and probably none of them is able to correctly predict the ROS generation in biological organisms. DTT was particularly sensitive to organic compounds, while AA was mostly influenced by inorganic components. DCFH results are more difficult to interpret and need to be further deepened. Furthermore, the results confirmed the important role played by the insoluble components of dusts in generating oxidative processes. Full article

Τhe main purpose of this research is to study the sensitivity of regional climate model RegCM4.4.5.1 to the different physics parameterization schemes in the Mediterranean region. The spatial resolution of the model is 25 × 25 km. Different ERA-Interim-driven simulations were performed with changes in the model’s configurations for the time period 1981–1990. The different simulated data of temperature and precipitation were processed seasonally and the differences between the simulations were examined. The statistical significance of the differences is calculated with Student’s t-test. Aiming a more detailed evaluation of the changes that occur, a division of the area of study into five sub-regions was performed according to the common EURO-CORDEX analysis domain and the Taylor diagrams for the examined parameters were calculated. From the analysis of the results it was found that Grell, Mixed, UW-PBL and CORINE simulations present a cold bias, while in BATS1e run temperature is increased. Additionally, Grell, Mixed and UW-PBL simulations present a decrease of precipitation except for winter, where in Grell simulations total precipitation is increased. In BATS1e run an increase of the parameter is detected. Finally, changes in land cover led to a reduction of the parameter during winter and an increase in summer. Full article

There is a strong need for long term observations of land surface fluxes, especially the latent heat flux (λE), or actual evapotranspiration (ETa), a key component of both the surface energy balance and the hydrological cycle. The eddy covariance (EC) method is widely used to provide measurements of land surface fluxes. However, missing data are inherent to EC measurements and several gap-filling methods have been proposed. Nevertheless, observing ETa by EC and testing gap-filling methods in hilly watersheds received little attention. This study aimed at obtaining continuous ETa time series from EC measurements collected within a small hilly watershed, which implied adapting gap-filling techniques to these particular conditions. The experiment took place within the agricultural watershed Kamech (Northeast Tunisia) which belongs to the OMERE environmental observatory. A 9.6-m-high EC flux tower was installed in the center of the 2.45 km² area watershed. Sensible and latent heat fluxes data collected from 2010 to 2013 were quality controlled. The software REddyProc was used to gap-fill the fluxes at hourly timescale. To account for the combined effects of wind direction and topography, REddyProc was applied after separating the two dominant wind directions, which notably improved the estimated fluxes. Aggregating the hourly λE estimates at daily and monthly timescales allowed analyzing the temporal variability of ETa over the seasons and between years. Full article

Nowadays, the Internet of Things (IoT) is a rapidly growing technology that allows to integrate digital devices into a network. Using the IoT technology to collect information from a variety of Internet connected GNSS receivers provides a unique opportunity to obtain real-time information about the special and temporal distribution of ionospheric characteristics with high resolution. The ability to create a dense sensor network is achieved through the usage of cheap single-frequency GNSS receivers based on the Arduino technology. This approach can be implemented to obtain real-time data on the total electron content (TEC) of the ionosphere. The determination of the ionospheric delay of the radio signal of GLONASS/GPS satellite and the calculation of the ionospheric TEC are carried out directly in the GNSS receiver. The results are transmitted over a wireless communication channel via Internet to a cloud server, where maps of the TEC of the ionosphere are constructed. Full article

Not all precipitation, falling above the trees, reach the ground. Part of it is retained in the canopy and eventually evaporates back into the atmosphere. This is known as intercepted rainfall. The process is influenced by various meteorological parameters of which we have mainly focused on drop diameter and velocity. Rainfall in the open and throughfall under birch and pine trees have been measured since 2014 in Ljubljana, Slovenia. The results demonstrate that birch has intercepted 41% (±32%) and pine 70% (±24%) of rainfall on average per event. During the 146 individual events between 297 and 724,905 rain drops were recorded with the average drop diameter 0.73 mm (±0.23 mm) and average drop velocity 3.71 m/s (±0.49 m/s). We have closely analyzed the effect of drop size and velocity on interception by pine during two rainfall events in June and July 2014. In June event drops with larger drop diameter (6.5–8.5 mm) were observed in the open causing an instant reduction of rainfall interception by pine for 30%. Furthermore, twice during the both events the groups of drops with higher velocity (7.6–10.4 m/s) were observed, causing the reduction in rainfall interception. Full article

Evaluation of the performance of the parameterization schemes used in the WRF model is assessed for temperature and precipitation over Europe at 36 km by 36 km grid resolution using gridded data from the ECA & D 0.25° regular grid. Simulations are performed for a winter (i.e., January 2015) and a summer (i.e., July 2015) month using the two way nesting approach. A step-wise decision approach is followed, beginning with 18 simulations for the various microphysics schemes followed by 45 more, concerning all of the model’s PBL, Cumulus, Long-wave, Short-wave and Land Surface schemes. The best performing scheme at each step is chosen by integrating the entropy weighting method ‘Technique for Order Performance by Similarity to Ideal Solution’ (TOPSIS). The concluding scheme set consists of the Mansell-Ziegler-Bruning microphysics scheme, the Bougeault-Lacarrere PBL scheme, the Kain-Fritsch cumulus scheme, the RRTMG scheme for short-wave, the New Goddard for long-wave radiation and a seasonal-variable sensitive option for the Land Surface scheme. Full article

Elements of surface atmospheric electricity have never been used to solve problems of applied geophysics. A physical model representation of hydrogen, methane, radon, and elements of surface atmospheric electricity is constructed. Bubble formations of volatile gases capture from the depth of 4–6 m soil radon and carry it into the near-surface layers of the soil and atmosphere. The increase in the density of carrier gases over the ore body, oil field, fault zones, karst cavities leads to a fall in the atmospheric electric field and an increase in the polar air conductivities. The pumping of artesian water causes an increase in the atmospheric electric field. The injection of fluid into the ground leads to the reverse process—the fall of the atmospheric electric field. Full article

Increasing the amount of anthropogenic aerosols over the Himalayas modulate cloud properties, thereby altering cloud phase and cloud height, consequently influence formation and distribution of orographic precipitation. Moreover, further rises in global temperature may influence cloud properties by the ‘Clausius—Clapeyron effect’, which increases moisture holding capacity of air. This study presents sensitivity of simulated cloud properties to aerosol and temperature perturbations using the Weather Research and Forecasting (WRF) model, coupled with a bulk microphysics scheme, in a convection permitting configuration applied to a complex topographical region, the Nepal Himalayas. We find that the effect of aerosol on the simulated rainfall is nonlinear, ranging from −3% to +4% depending on the investigated aerosol perturbation scenarios. The model results highlight a realistic simulation of the 1st indirect (Twomey) effect. However, the rainfall was not overly sensitive to the aerosol perturbations and not statistically significant at the 95% confidence interval. The oversimplified parameterization of ice phase processes, a dominant cloud formation process over the Himalayas, appears to play a crucial role in buffering the sensitivity to increased aerosol loading. Our results, however, show that aerosol perturbations may modify shape, size and spatial distribution of individual cloud and their precipitation production. In contrast, the impact of temperature perturbations is more than the aerosol effect, ranging from −17% to +93%, which is statistically significant at the 95% confidence interval, suggesting that more intense rain events are likely as the climate warms in this region. Full article

The main objective of this paper is to implement different methods to assess the salient features of the data trend for a CO₂ and CH₄ data series. Said series was obtained at the Low Atmosphere Research Centre (41°48′49″ N, 4°55′59″ W) using a Picarro analyser (G1301). Different functions were employed to determine and quantify the data trend. The first was a harmonic function based on a third-degree polynomial. An increasing trend, below 2.30 ppm year⁻¹ for CO₂ and below 11.90 ppb year⁻¹ for CH₄, was reported. Epanechnikov, Gaussian, biweight, tricubic, rectangular and triangle kernels, were applied with a 500-day bandwidth for the trend. The best fit was obtained by the biweight kernel (r > 0.20), with an increasing trend around 1.80 ppm year⁻¹ for CO₂ and around 7.15 ppb year⁻¹ for CH₄. The final analysis, which included local linear regression functions also applying a 500-day bandwidth, revealed increasing trends for both CO₂, around 1.98 ppm year⁻¹, and CH₄, around 10.85 ppb year⁻¹. Trend values were far more accelerated in the latter years of the series, regardless of the chosen function. This paper demonstrated the usefulness of the mathematical functions, allowing for an accurate determination of the data trend. Full article

Diabatic heating from deep moist convection in the hurricane eyewall produces a towering annular structure of elevated potential vorticity (PV), known as a hollow PV tower. For sufficiently thin annular structures, eddies can extract energy from the mean flow, leading to hollow tower breakdown with significant changes in vortex structure and intensity. A forced primitive equation model in isentropic coordinates is used to understand the role of diabatic heating in the generation, maintenance, and breakdown of the hurricane PV tower. It is shown that diabatic heating produces a strengthening and thinning PV tower in time due to the combined effects of the diabatic heating and the radial PV advection by the induced secondary circulation. If the forcing makes the eyewall thin enough, then the PV tower can become dynamically unstable and cause air parcels with high PV to be mixed preferentially into the eye at lower levels, where unstable PV wave growth rates are largest. The breakdown of the hollow PV tower leads to a transient break in vortex intensification, a decrease in minimum central pressure, and an inward shift and tilt of absolute angular momentum surfaces. It is shown that the maintenance of the PV tower structure depends on the strength of the heating-induced secondary circulation. Full article

Snowfall events are considered as a factor of spatial distribution of snow cover thickness, its snow water equivalent and stratigraphy formation. Under the term of snowfall it is understood an event of solid atmospheric precipitation (snow) with duration of certain period of time (up to one or several days) with intensity of not less than 0.1 mm per day and the temperature below zero, i.e. under condition of snow cover presence. Snowfalls’ intensity is characterized as a sum of precipitation (its snow water equivalent) during this snowfall. For the time period of 1960–2016 on the basis of meteorological data for 45 stations situated on the territory of Russia (not less than two in each of 19 climatic regions) the events of snowfalls are determined, as well as their frequency and averaged intensity for each winter season. Snowfalls’ spatial and temporal distribution is analyzed on the basis of the compiled maps of averaged frequency (number per season) of all snowfalls and snowfalls of defined intensity (0.1–2.5, 2.5–5, 5–10, 10–20 and more than 20 mm). The materials of obtained distribution allow revealing the features in distribution of snowfalls of different intensity for the various regions and the possibility to model generalized regional stratigraphy of snow cover. Full article

Spatiotemporal conditions that rule hydro-climatology over northern South America and the Caribbean Sea are influenced by a large amount of phenomena taking place at different timescales. Characterizing the activity of the AEWs over northern South America and the Caribbean is an imperative work to do in order to improve our understanding of the tropical atmospheric dynamics involved in hydrology and climate features over the region. The latter regulates the availability of very important resources such as water. Furthermore, AEWs activity plays an important role on air quality characteristics as a consequence of its connections with dust transport. In order to approach an adequate characterization of the AEWs activity over the region, this work addresses the relationship between these atmospheric perturbations and the occurrence or inhibition of precipitation, as well as possible connections with dust transport, when the AEW’s oscillations take place over northern South America and the Caribbean region. In particular, relative vorticity and outgoing long-wave radiation are used to identify AEW’s activity during the 1983–2013 period, together with daily precipitation anomalies, surface divergence, vertical integrated moisture flux, and Aerosol Optical Depth, in order to understand how the passage of AEWs could influence meteorological interactions in the region. Full article

Air pollution is a major environmental risk to health. In particular, exposure to high concentrations of small particulates (PM₁₀ and PM_2.5) is related to increased mortality and morbidity. In Argentina, only at Buenos Aires city (34.4° S 58.3° W), which together with the surrounding districts accounts for the 30% of the total country population, continuous measurements of air quality are carried out. Though ground-based stations provide very accurate PM concentration values, they have very limited spatial coverage and may not be sufficient to assess the level of population exposure. Satellite-based is a valid alternative to fill these observational gaps. In this work, the MODIS 3 km × 3 km AOD retrievals for 2014, for both Terra and Aqua, were employed to evaluate the spatio-temporal variation of atmospheric aerosols over Buenos Aires and its metropolitan area in a year period. The MODIS AOD dataset is validated using the AOD dataset reported by the CEILAP_BA AERONET station (34.5° S 58.5° W). Satellite data show some areas with higher AOD values throughout the year-period in which no PM monitoring is not actually being carried out. These areas correspond mainly to a west zone within Buenos Aires territory and two other areas, at west and south Buenos Aires districts. Buenos Aires local government and the surrounding districts should make an effort to expand the monitoring network in order to make it representative of the actual exposure to particulate matter of the whole population. Full article

The atmosphere at North-Central Argentina Andes range is exceptionally clear for the placement of astrophysical/astronomical/solar observatories (Piacentini et al., Advances Space Research, 2016). However, this region is part of the Pacific fire belt, due to the large number of active volcanoes. Consequently, the possibility of having strong sporadic emissions of different gases and aerosols needs to be investigated. In the present work, we analyze in particular the SO₂ trace gas, since it can affect significantly the solar UVB (280–320 nm) radiation. Also, particulate matter can attenuate this radiation in the UV-visible ranges. One of the most significant contributions to volcanic eruptions that could arrive at the selected San Antonio de los Cobres (SAC) location is the near Lascar volcano. We used satellite images form the OMI/KMNI/Aura/NASA satellite instrument, for deriving the intensity of the eruption at the SAC geographical point. An important eruption was that of the Puyehue/ Cordón Caulle volcanic complex at Chile Patagonia, in June 2011. No significant influence on the other selected El Leoncito (LEO) location was registered. We present aerosol optical depth (AOD550) satellite data obtained with the Deep Blue Level 2 data provided by the SeaWiFS/SeaStar/NASA satellite instrument for SAC and LEO places, showing that AOD550 for the whole period is extremely low (0.0262 for SAC and 0.0266 for LEO). We also present ground atmospheric aerosol concentration measurements as a function of aerosol diameter with a high quality GRIMM laser instrument for some days of campaign performed in those sites. Full article

We study wintertime blocking events in 2004–2016 over Western Siberia (WS) and their influence on the surface temperature. The period 2004–2016 is very interesting for study because there has been an increase in the blocking frequency over WS beginning with 2004. We used data ECMWF ERA-Interim and blocking criterion proposed by Tibaldi and Molteni. We investigated blockings events with duration of 5 days or more for winter interval (1 November–31 March). We have chosen 15 blockings events. For each event we calculate surface temperature anomaly in the grid points for two sectors 60–90 E; 50–60 N (southern part of WS) and 60–90 E; 60–70 N (northern part of WS). To estimate advective transfer for studied events we analyzed the potential temperature on the dynamical tropopause. We showed that wintertime blocking events over WS lead to the surface temperature increase in the northern part of West Siberia and to the surface temperature decrease in the southern part of WS. This feature apparently due to warm air masses advection from south-west on the western periphery of the blocking ridge and arctic air masses intrusion to the southern part of the WS on the eastern periphery of this ridge. Full article

A global blocking climatology published by this group for events that occurred during the late 20th century examined the comprehensive list of characteristics that included block intensity. In addition to confirming the results of other published climatologies, they found that Northern Hemisphere blocking was stronger than Southern Hemisphere events and winter events are stronger than summer ones. This work also examined the interannual variability of blocking as related to El Niño. Since this time, there is evidence that the occurrence of blocking has increased globally. A comparison of blocking characteristics during the first part of the 21st century to those in the late 20th century shows that the number of blocking events and their duration have increased in the Northern and Southern Hemisphere. The intensity of blocking has decreased by about nine percent in the Northern Hemisphere, but there was little change in the intensity of Southern Hemisphere events. Additionally, there is little or no change in the genesis regions of blocking. An examination of variability related to El Niño and Southern Oscillation reveals that the variability found in the earlier work has reversed. This could either be the result of interdecadal variability or a change in the climate. Full article

A study of spatial variability of PM₁₀ elemental components was conducted in Terni city (Central Italy), situated in an intramountain depression characterized by the presence of several particulate matter emission sources. The meteorological conditions of Terni basin limit the dispersion and enhance the accumulation of the atmospheric pollutants. Thanks to the utilization of new smart samplers, used for the first time and working in parallel at 23 sampling sites, spatially resolved data were obtained. Localizations of the samplers were chosen in order to evaluate the impact of different local PM₁₀ sources. Chemical composition of the samples was determined in combination with a chemical fractioning procedure, that allowed us to discriminate water-soluble and residual fractions of analyzed elements in which proved to be a valuable approach for increasing selectivity of elements as source tracers. Spatial variability of elements underlined the contribution of local emission sources and the different dispersion capacity of each element. Terni city resulted to be an ideal area to test and validate a new experimental method for the acquisition of spatially resolved data providing the possibility to properly evaluate the spatial variability of PM₁₀ and its chemical components. Full article

Extreme rainfall is one of the most devastating natural events. The frequency and intensity of these events has increased. This trend will likely continue as the effects of climate change become more pronounced. As a consequence, it is necessary to evaluate the different statistical methods that assess the occurrence of the extreme rainfalls. This research evaluates some of the most important statistical methods that are used for the analysis of the extreme precipitation events. Extreme Value Theory is applied on ten station data located in the Mediterranean region. Furthermore, its two main fundamental approaches (Block-Maxima and POT) and three commonly used methods for the calculation of the extreme distributions parameters (Maximum Likelihood, L-Moments, and Bayesian) are analyzed and compared. The results showed that the Generalized Pareto Distribution provides better theoretical justification to predict extreme precipitation compared to Generalized Extreme Value distribution while in the majority of stations the most accurate parameters for the highest precipitation levels are estimated with the Bayesian method. Extreme precipitation for return period of 50, 150 and 300 years were finally obtained which indicated that Generalized Extreme Value Distribution with Bayesian estimator presents the highest return levels for western stations, while for the eastern Mediterranean stations the Generalized Pareto Distribution with Bayesian estimator presents the highest ones. Full article

Seasonal range prediction over North America has been based on intraseasonal and interannual variability related to the Pacific North America (PNA) pattern and El Niño and Southern Oscillation (ENSO), respectively. These phenomena have an impact on the occurrence of atmospheric blocking and the long-term conditions for North America. Similar relationships may be found for seasonal range prediction over South America. Previous studies have examined ENSO-related variability of the South Pacific Jetstream as well as atmospheric blocking. Using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalyses, the character of the monthly circulations were studied over the South Pacific/South America sector from 2000–2016. Initial results show that there is a negative correlation in the upper air circulation over the East Pacific and South America during winter for ENSO. Also, the interannual variability in the jet-stream pattern for the region as related to ENSO shows a 180° phase difference. Finally, there is evidence that the circulation pattern for the 2000–2016 may be different from that of the latter part of the 20th century as indicated by a recent reversal of the interdecadal variability of atmospheric blocking over the South Pacific Region. Full article