The Sahelian region is located southern the Sahara Desert and the wet tropical belt of central Africa, and it is affected by a monsoonal regime. It is well known that the Sahel is one of the most vulnerable areas due its annual strong climatic variations. In essence, to bring precipitation over a region, the atmosphere needs moisture to condense. So, it is necessary to know where the supply of moisture that precipitates over the Sahel come from to understand the rainfall variability. In a previous paper by Nieto et al. [1] they defined, using a lagrangian method of diagnosis, the sources of moisture that reach the Sahel (10°–20° N; 20° E–18° W) calculating changes in the specific humidity along trajectories of a lot of atmospheric-particles. The analysis was done using the observational data from the ECMWF for a 5-year period (2000–2004), but the shorter time period used impeded the study of interannual variability or possible relationships with modes of climate variability as ENSO or NAO. Based in those lacks in this following paper we provide an extensively revisited analysis to determine and analyze in an improved way the sources of moisture for the Sahel. In order to carry out this aim, we have used here: (a) a longer climatological period of time from 1980 to 2012 (three decades) to redefine the sources of moisture; (b) the nowadays best-considered database to reproduce the atmospheric branch of the hydrological cycle: the ERA-Interim Reanalysis data to track atmospheric moisture changes along trajectories; (c) a definition of the sources using a moving threshold in the field of E-P for annual, seasonal and monthly scales. This new extended and improved data allowed us to redo, among others, the time series of E-P day by day calculated backward for the moisture over the Sahel area and integrated over the moisture sources determined in the previous steps. But now the most important is the possibility to analyze the relationship with between the amount of the moisture over the sources and the field of real precipitation over the Sahel, and to have concrete outcomes about the modulation by the main patterns of climate variability on the sources as ENSO, NAO and the local West African Monsoon (WAM).

Impacts of atmospheric halogens on the ozone depletion events (ODEs) in polar boundary layer have been under investigation since the discovery of negative correlation between atmospheric ozone and bromine. By simulating an ODE in a box model KINAL, this study focuses on the influence of natural organic sources on the ozone depletion. An estimation of bromine flux from Arctic plantation is given as 6.3 x 106 molec. Br/(cm²
s). Since there exists huge fluctuation in the flux, the bromine input is set to be adjustable, by which the impact of Arctic biological behavior on the tropospheric ozone can be predicted. Meanwhile, another nitrogen flux emitted from plants is also included in the model as the plants release considerable amount of nitrogen into the atmosphere, which alters the process of the ozone depletion. Different from the Br flux, the nitrogen flux implemented in the model remains relatively stable around 1 x 108 molec. NO/(cm²
s). The simulation results indicate that the type of the Br flux plays a relatively important role in the depletion of ozone. An average level of Br input may cause approximately a 1.0 day antedate to the ODE. In contrast to that, NO exerts minor impact on the ozone concentration, but an obvious force to the mixing ratio of Br species.

The ozone depletion events (ODEs) in the spring of Arctic has been investigated since the 1980s. It is found that the depletion of ozone is highly associated with the release of halogens especially bromine containing compounds from various substrates such as the ice/snow-covered surfaces in Arctic. In the present study, the dependence of the mixing ratios of ozone and principal bromine species during ODEs on the initial composition of the atmosphere in the boundary layer of Arctic is investigated by using a concentration sensitivity analysis, which is performed by implementing a reaction mechanism representing the ozone depletion and halogen release in a box model KINAL. The ratio between the relative change of the mixing ratios of particular species such as ozone and the variation in the initial concentration of each  atmospheric component is calculated, which reveals the relative importance of each initial species in the chemical kinetic system. The simulation results show that the impacts of various chemical species are different for ozone and bromine containing compounds during the depletion of ozone. It is found the species CH₃CHO is the most influential species which critically controls the time scale of the complete removal of ozone. However, the rate of ozone depletion and the maximum values of bromine species are only slightly influenced by the presence of CH₃CHO. Besides, according to the concentration sensitivity analysis, the reduction of initial Br₂ is found to cause a significant retardant of the ODE while the initial mixing ratio of HBr exerts minor influence on both ozone and bromine species. In addition, it is also interesting to note that the increase of C₂H₂ would significantly raise the amount of HOBr and Br in the atmosphere while the ozone depletion is hardly changed.

Nitrogen oxides (NO_x) play a major role in the atmospheric oxidation processes leading to ozone and secondary organic aerosol formation in the lower atmosphere. Wildfires are one of the important sources of NO_x emissions; however, knowledge of NO_x emissions from fires is currently insufficient and available estimates provided by emission inventories have mostly not been validated against atmospheric measurements. Recent studies indicated that useful observational constraints to biomass burning (BB) NO_x emissions are provided by satellites measurements of nitrogen dioxide (NO₂), but available BB NO_x emission estimates inferred from such measurements involve quantitative assumptions regarding the atmospheric NO_x lifetime. In this study, we investigated NO_x emissions from the extreme wildfires that occurred in the European part of Russia in summer 2010. To this end, we analyzed tropospheric NO₂ retrievals from measurements performed by the OMI satellite instrument in the framework of an original inverse modeling method. A quantitative relationship between BB NO_x emissions and tropospheric NO₂ columns was simulated using the mesoscale CHIMERE chemistry transport model. Our analysis indicated that such a relationship depends strongly on BB emissions of volatile organic compounds and that a dependence of the effective NO_x lifetime on the NO_x fluxes can be essentially nonlinear. Our estimates of the total NO_x emissions in the study region are found to be at least 40% larger compared to the respective data from the GFASv1.0 and GFED4.1s global fire emission inventories.

Polycyclic aromatic hydrocarbons were measured near Interstate 40, just east of Research Triangle Park, North Carolina. One hundred seven 8-h integrated samples were collected on 20 sampling days over a 2 month period in Fall 2014. The 8-h samples were collected by low flow (16.7 L/min) fine particulate samplers. The samples were analyzed using gas chromatography-mass spectrometry. Temporal distribution of the PAHs (0.1–21.6 ng/m³ ± 9.0 std) were compared to meteorological and pollutant data collected at the near roadway station. There is a weak but significant correlation between the sum of the measured PAHs with ozone, nitrogen dioxide and nitric oxide, with the R² values being 0.0049, 0.0187 and 0.0788 respectively. However the p-values (α = 0.05) were 0.044, 0.002 and 0.044, which are significant. Wind rose analysis illustrated the morning hours which were predominantly southern winds, while the afternoon hours illustrated southerly and easterly winds, which suggests that the automobile traffic as the main source of PAHs. The nighttime hours wind rose shows winds from northerly and easterly direction, which are predominantly from the RDU International Airport. PAH concentration found in this study compare favorably to other research studies (0.1 to 193.6 ng/m³) both nationally and internationally.

The IPCC Fifth Assessment Report suggests that the projected increase in the global temperature in future scenarios could cause different impacts in different regions of the world. For the Polar Regions the global models are being adapted to measure these changes, but the preliminary results indicate large heating for the Arctic region. The changes on Arctic region are not a problem just for a future climate: the Arctic amplification, the decrease on Arctic sea ice extent and on snow cover extent is a present concern for climatologists. Studies suggest a link between Arctic changes and mid-latitude weather, as the changes on Arctic Region where observed accompanied by changes in other regions of the world, especially in the Northern Hemisphere mid-latitude. Some mechanisms are proposed to explain this link, and one of then is related to changes in the atmospheric moisture transport from middle latitudes. Recent studies have shown that the Mediterranean Sea, North Atlantic Ocean and North Pacific Ocean appear as the main regions that contribute as moisture sources to the Arctic Region. The objective of this work is to use the output of GFDL/CM3 Model for 2046–2075 and 2070–2099 periods to identify the regions of the main change on moisture sources that contributes to the Arctic Region in a future scenario (RCP4.5) compared to a present climate (1980–2005). For both future periods analysed, the results suggest that the contribution for Arctic moisture by the regions located on North Atlantic Ocean, North Africa and Middle East enhanced. This may indicate an increase in moisture transport from mid-latitude to Arctic that could lead to several changes in Arctic climate: warming, decrease on sea ice extent and on snow cover.

Fundamental properties of multiply charged molecular ions, such as energetics, structure, stability, lifetime and fragmentation dynamics, are relevant to understand and to model the behavior of gaseous plasmas as well as ionosphere and astrophysical environments. Experimental determinations of the Kinetic Energy Released (KER) for ions originating from dissociations reactions, induced by Coulomb explosion of doubly charged molecular ions (molecular dications) produced by double photoionization of CO₂, N₂O and C₂H₂ molecules of interest in planetary atmospheres, are reported. The KER measurement as a function of the ultraviolet (UV) photon energy in the range of 28-65 eV are extracted from the electron-ion-ion coincidence spectra obtained by using tunable synchrotron radiation coupled with ion imaging techniques at the ELETTRA Synchrotron Light Laboratory Trieste, Italy. These experiments allow assessing the probability of escape for simple ionic species in the upper atmosphere of Mars, Venus and Titan. The measured KER in the case of H⁺, C⁺, CH⁺, CH₂⁺, N⁺, O⁺, CO⁺, N₂⁺ and NO⁺ fragment ions are ranging between 1.0 and 5.5 eV, being large enough to allow these ionic species in participating in the atmospheric escape from such planets into space.

The Niger River basin (NRB) is located on the important climatic region of the African Sahel. In this work we use the Lagrangian tridimensional model FLEXPART v9.0, to identify and characterize the moisture sources for the NRB. The method allowed integrating the evaporation minus precipitation budget through 10 days backward trajectories and thus, identifying the origin of air masses residing over the NRB. The analysis was performed for 35 years from 1980 to 2014. There were identified the main seasonal climatological moisture sources of the NRB and quantify their contribution to the total moisture influx. At first day backward in time the NRB appears as the main moisture source, contributing less and less humidity to the particles during last days, suggesting the importance of local moisture supply to recycling process. Through the 10 days backward, the pattern of (E – P) shows the spatial expansion of sources and sinks regions. Across the year, the moisture supply to the NRB mainly comes from itself and the tropical-east south Atlantic Ocean, but are also important the rest of the sources located on the tropical-east north Atlantic Ocean near Africa, the Sahel surrounded regions, the Mediterranean Sea, the east Africa, the north-east Africa and less important small regions on central-equatorial Africa and the
tropical-west Indian Ocean.

The year 2015 is considered the hottest on records at the global scale, since reliable temperature measurements are available. Ambient air quality is strongly influenced by meteorological conditions, and daytime surface ozone concentrations are generally positively correlated with temperatures. We thus analysed 2015 ozone data over Italy to check if exceptional ozone values reflected the exceptional temperatures. To this end, we evaluated the ozone season in 2015 compared to the 2002–2015 trend, using data from 24 selected monitoring stations and analyzing the exceedances of limit values imposed by the European directive. We found that 2015 was one of the hottest years over Italy, and the ozone season was one of the most severe in the last ten years. In 2015, the average duration of ozone episodes (the number of consecutive days with daily maximum 8-hour-average values higher than the threshold of 120 µg·m⁻³) was about 4 days, similar to that of 2006 and less than that of 2003 which was about 5 days. This duration is longer than the average observed in recent years, which is less than 3 days. Furthermore, the mean maximum concentration of ozone events was the second on record together with 2006, after the notable heatwave of 2003.

Bangkok Metropolitan Region - Thailand (BMR), one of the major metropolitan areas in the world, is a bustling upper-middle class megacity composed of Bangkok city proper and five surrounding provinces. With an actual population of approximately 15 million, it is the central hub for commerce and tourism in the Southeast Asian (SEA) region. In the past decades, Bangkok has experienced extraordinary economic development and urban expansion, all the while displaying notable concern regarding the ambient air pollution and its adverse effects on human health. In this study, 16-years of air quality monitoring data were collected from 25 stations in BMR, which are operated by the Thailand’s Pollution Control Department. Data for O₃, PM₁₀, NOx, CO and SO^₂ were analyzed temporally with a particular focus on long-term, seasonal and diurnal variations. The data were also analyzed spatially to identify the hotspots and flow of air pollution in the region. These investigations were performed to assess the evolution of air quality in BMR over the past 16 years and identify areas of potential concern. Analysis of the data indicated that PM₁₀, NOx , CO and SO₂ were in a moderate decline over the 16 years, while O₃ concentration has risen steadily throughout this time period. The results and findings of these investigations are discussed with a perspective to provide policy recommendations for air quality improvements in BMR.