Arnobio G. Poblete

Latitudinal positioning of the subtropical anticyclone along the Chilean coast

In the past various authors have investigated climatic change (CC) by using the latitude of the subtropical ridge in the mean sea-level pressure (MSLP) for a range of geographic regions. In this paper the index L is defined as the latitudinal position of the subtropical anticyclone along the Chilean coast. This L index on the South American coast of the South Pacific is analysed using an instrumental record, covering the 1901-2004 period. An objective methodology is proposed for estimating L, and the physical consistency is assessed with the SOI and pressure at sea level in Valdivia, Chile. The analysis of a shorter period is compared with other authors’ results. The L variable can be useful in CC studies or in the analysis of low-frequency fluctuations in climate variability, and it is analysed as a dependent and independent time series. L was displaced towards the south over the last century but not to a statistically significant extent. Natural fluctuations of 50 years and another, shorter, of 16-22 years were also observed. In this paper, the greatest persistence and distant associations between anomalies of monthly L are shown; these associations can be useful for climate forecasting.

Elemental composition of PM 2.5 in the urban environment of San Juan, Argentina

This study contributes to the current knowledge about air pollution in the province of San Juan, Argentina. Sampling was carried out to measure the fine particulate matter in the atmosphere (PM2.5) of the city of San Juan. PM2.5 was collected continuously during the winter and spring seasons of 2014 and 2015, and the concentrations of 14 elements (Pb, Ca, K, Cd, Ni, Cr, Mn, V, Cu, Ti, Ba, Co, Sr, and Fe) were determined in PM2.5 filters using the technique of X-ray fluorescence by synchrotron radiation (SR-XRF). The results revealed that PM2.5 presented annual and seasonal variations, showing a higher concentration during the winter seasons. In addition, for the elements quantified in the filters, a multivariate analysis (Positive Matrix Factorization) was performed to identify the main sources of emission of these elements in the study area, with a series of components being obtained that corresponded to their compositions, which were assigned physical meanings. The first factor, which was the most important in contribution of the sum of the measured elements (45%), was determined mainly by the elements K, Ti, V, Mn, and Fe, which came predominantly from soil particles. The second factor contributed 30% to the measured species in PM2.5, with higher Ba and Zn content perhaps being related to emissions from vehicular traffic. Finally, the third factor, in which Pb, Cr, and Ca predominated, may be an indicator of industrial activity and contributed 25% of the sum of the measured elements of PM2.5. The results of this study provide the first PM composition database in the province, and this can now be used in the development of mitigation and prevention programs.

Trends of the Drought Indices in Southern Hemisphere Subtropical Regions

With the use of droughts indexes on Subtropical South Hemisphere, we have detected: a) statistically stationary conditions on average during the period 1880-1980 and b) an important positive tendency to droughts between 1980-2013. This recent tendency to regional droughts is coincident with the actual processes of Global Warming. The hypothesis of an acceleration of the Hadley Circulation (HC) is present with global warming, which would reduce precipitation in subtropical aridsemi arid zone and increase rainfall in the Intertropical Convergence. This process was confirmed by the precipitation data of Reanalysis I, with an inverse correlation between the two regions. These droughts indexes also show the more presence of an interdecadal variability signal (PDO) and El Niño/South Oscillation (ENSO) at low and high frequencies. Most of the variances in these regions have been explained by long climate changes. ENSO high frequency changes are present and they behaved in an inverse way as expected between both South Pacific Ocean coasts. When the group was analyzed as a subtropical anticyclone band or regional in Chile, Australia and South of Africa, it did not disturb the large-scale signs that are highlighted in this study. KeywordsTrends; Droughts Index; Subtropical South Hemisphere