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. The sign reversal of the radial gradient of PV satisfies the Charney-Stern necessary condition for combined barotropic-baroclinic instability. For sufficiently thin annular structures, small perturbations grow exponentially, extract energy from the mean flow, and lead to hollow tower breakdown, with significant vortex structural and intensity change. A forced primitive equation model in isentropic coordinates is used to understand the role of diabatic and frictional effects in the generation, maintenance, and breakdown of the hurricane PV tower. Diabatic heating is parameterized as an annular heating ring of variable width, depth, and magnitude, and the nonlinear evolution of tropical storm–like vortices is examined under this forcing. Diabatic heating produces a strengthening and thinning PV tower in time due to the combined effects of the diabatic heating and radial PV advection by the induced secondary circulation. If the forcing makes the eyewall thin enough, then it 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, an inward shift of absolute angular momentum surfaces at low levels, and the development of warm anomalies within the center of the vortex. Horizontal and vertical diffusion are shown to help stabilize and maintain the PV tower by reducing the eyewall PV and the unstable-mode barotropic growth rate. Finally, it is shown that the heating-induced secondary circulation helps to maintain the PV tower structure.

In West Africa, is located the Niger River Basin (NRB). Dry and wet conditions were investigated in this basin during the rainy (May-October) and dry (November-April) seasons, from 1980 to 2014. To do this was, calculated the Standardized Precipitation-Evapotranspiration Index (SPEI) at the time scale of 6-months for the whole NRB. The Lagrangian model FLEXPART v9.0 has been used to compute over the main semi-annual climatological moisture sources of the NRB, the budget of evaporation minus precipitation (E-P) over 10-day backward trajectories from the NRB itself. Positive (negative) (E-P) values indicate moisture uptake (loss). This permit evaluating the role of continental and oceanic sources of moisture separately for composites of extremely and severely dry and wet conditions in the basin. The results show for the dry season the negative trend of the April-SPEI6 values and the (E-P)>0 values obtained over the tropical east-north Atlantic Ocean (NAtl), the western Sahel and the Mediterranean region. Over these sources, the anomalies of (E-P) for driest and wettest composites indicate their direct response. On the contrary, for the rainy season, the October-SPEI6 values trend is positive, as well it occurs for the moisture uptake over the South Sahel (SSah) and the NRB itself. The anomalies of the (E-P) values for driest and wettest rainy seasons composites suggest a direct relationship with those obtained mainly over SSah, SAtl and the NRB itself.

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, due to the huge solar radiation income throughout the year as a result of their geographical location. 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, which represents an important resource for economic activities and social dynamics of the populations that occupy these regions. Furthermore, AEWs activity plays an important role on air quality characteristics during the boreal summer, as a consequence of this disturbances connections with dust transport. 

In order to approach an adequate characterization of the AEWs activity over northern South America and the Caribbean Sea, this work intends to address 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 the 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.

Air pollution is a major health environmental risk. In particular, daily exposure to high concentrations of microscopic atmospheric particles (PM10 and PM2.5), is related to increased mortality and morbidity. Many countries are concerned about this issue and have extensive monitoring networks and specific air-quality legislation to establish limit values for PM concentration. In Argentina, very few cities have carried out continuous measurements of air quality. In particular, Buenos Aires city (34.4°S, 58.3°W) has three monitoring stations located at different locations. Buenos Aires and its metropolitan area is the most populated area in the country (12.806.866 inhabitants in 2010 Census). Though ground-based stations provide accurate PM concentration values, they are strongly influenced by local emission sources and do not characterize completely the actual spatial distribution of pollutants in the city. So, this type of monitoring is insufficient to assess the actual level of population exposure. Satellite-based aerosol optical depth (AOD) dataset represent a valid alternative to fill these observational gaps. Several satellites offer AOD products, being the dataset from the MODIS sensors on board TERRA and AQUA (NASA) spacecrafts among the most used for regional air quality studies. In this work, the MODIS 3 Km x 3 Km AOD retrievals for 2014 were employed to evaluate the spatio-temporal variation of atmospheric aerosols over Buenos Aires metropolitan area in a year period. The MODIS dataset was  validated using as ground truth the AOD dataset available from the AERONET CEILAP station (34.5°S,58.5°W) (https://aeronet.gsfc.nasa.gov/). In order to evaluate how well satellite data represent surface measurements, the seasonal AOD maps retrieved from MODIS data were compared with PM measurements at the particular locations of ground-based stations. In this way, the spatio-temporal variation during a whole year of atmospheric aerosols over the largest urban area in Argentina was determined. 

 The atmosphere at North-Central Argentinean Andes range is exceptionally clear and well adapted 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, it exists the possibility of strong sporadic emissions of different gases and aerosols. 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 Chileean 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 (analyzed with the Deep Blue algorithm) taken by the SeaWiFS/SeaStar/NASA satellite  instrument for SAC and LEO  places, showing that AOD₅₅₀ for the whole period is extremely low (0.026 for SAC and  0.030 for LEO). We also present ground atmospheric aerosol concentration measurements as function of aerosol diameter with a high quality GRIMM laser instrument in typical days. In conclusion, our results show that the proposed SAC and LEO sites are of high quality for Southern Hemisphere night (astrophysical/astronomical) and day (solar) observations, even if they are placed in a mountain range with active volcanoes. Also, the results are of importance for the evaluation of the Visibility quality of the region and its possible future evolution, due to the increase in atmospheric contamination.

A global blocking climatology published by this group for events that occurred during the late 20^th 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 Nino. 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 21^st century to those in the late 20^th 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 Nino 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.  Additionally, a more detailed investigation of seasonal and regional characteristics are examined.