Universidad de Chile

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Atmospheric Science

The Atmospheric Science Group at the Department of Geophysics, Universidad de Chile, was formally established in 1965, and ever since it has had a leading position in atmospheric research in Chile. The group also shows a long record of participation in in national and international research programs. Our group currently has seven full time researchers and three part-time professors. A similar number of post-docs, research assistants and graduate students collaborate in our activities. The research, teaching and outreach activities of the group are supported by a specialized an updated library, a modern computer network, and meteorological observation systems. The research of our Department focuses on the understanding of atmospheric phenomena and processes in Chile, western South America and the adjacent ocean, using observations as well as numerical models. The bulk of our research activities deals with the understanding of atmospheric phenomena and processes in Chile, South America and the adjacent oceans including:

  • Climate and climate variability;
  • Synoptic, mountain and coastal meteorology;
  • Boundary layer meteorology and urban pollution
  • Atmospheric chemistry and aerosol-cloud interactions

Climate Variability and Climate Change

In this area we have documented the intraseasonal, internannual and interdecadal climate variability (especially air temperature and precipitation) along the west coast of South America. Of particular relevance are the physical and dynamical mechanisms by which large-scale phenomena (ENSO, PDO, AAO) modulate these fluctuations, which provides the foundation for intraseasonal and interannual prediction. More recently, the evaluation of changes in the regional climate system and their model-based projections for the rest of the 21st century has become a major issue in the frame of ongoing anthropogenic climate change. Model simulations also allow us to elucidate the drivers of major climate shifts in the remote past revealed by the many palaeo environmental proxies along our country.

Synoptic, Mountain and Coastal Meteorology

Continental Chile extends from 18°-53°S bounded by the Pacific coast and the Andes cordillera. This varied geography and prominent topography set the stage for distinctive sub-synoptic and mesoscale phenomena that has been only partially investigated using in-situ observations, remote sensed data and numerical simulations. Some of these phenomena result from the interaction of the large-scale flow and the coastal and Andean mountains, including coastal lows, coastal jets, frontal stagnation, orographic precipitation and downslope winds.

Boundary Layer Meteorology and Urban Air Pollution

Atmospheric boundary layer (ABL) research at DGF focuses on description, by means of measurement, data analysis and modeling, of the structure and mechanisms underlying the ABL under the various complex settings generously provided by the geography and climate of Chile. Worth mentioning are the ABL of the Santiago valley, the coastal and marine ABL along the coast of north-central Chile, and the ABL over the extremely arid Atacama Desert. Over Santiago the ABL regularly develops under stable anticylonic conditions, capped by a strong subsidence inversion and flanked by the steep topography of the Andes. Studies have addressed the nocturnal cooling in the valley as well as the growth rate and energy balance of the convective ABL during daytime. Closely related projects have modeled the severe air pollution problem of Santiago city, aimed at better forecasting and managing of the problem. The dynamics of the marine ABL along the north-central Chilean coast has also been a primary interest for the group. There, the interplay of the coastal jet, the marine stratocumulus layer, and the abrupt coastal topography still provides a formidable challenge to mesoscale models to produce realistic results for the evolution of the coastal ABL. Efforts of the group in this area include intensive field campaigns and modeling aimed at better understanding of the principal mechanisms at work there. Finally, the Atacama Desert provides another paradigmatic ABL to study in Chile. Recent work in this area has aimed at the micrometeorological characterization of wind re-suspension of desert dust, in support of paleoclimatological studies. Applied research in ABL at DGF includes several data analysis and modeling projects contracted by environmental agencies, mining companies, and energy agencies, devoted mainly to air pollution and wind energy evaluation problems.

Atmospheric chemistry and aerosol-cloud interactions

The optical properties of the stratus deck over the South East Pacific (SEP) region, and elsewhere, depend on both atmospheric and oceanic dynamics and to the abundance of cloud condensation nuclei (CCN). In fact, air-sea exchange of trace gases and particles, e.g., dimethyl sulfide (DMS, CH3-S-S-CH3) and sea-salt, which provide efficient CCN, is thought to be very important within the Humboldt Current System off Chile and Southern Peru. This is due to the fact that these cold nutrient-rich waters are continuously renewed by wind driven coastal upwelling and exposed to light allowing phytoplankton and zooplankton production, which in turn give rise to the accumulation and degassing of climatically relevant trace species such as carbon dioxide (CO2), dimethylsulfide, nitrous oxide (N2O), etc. Also, the subduction of the Nazca plate under the Andes and the South American continent induces an area of distinct volcanic activity along the Central Andes where numerous volcanoes show persistent fumarolic activity that probably provides a rather continuous source of sulfate, which in connection with down slope winds may supply effective CCN over the stratocumulus deck. Furthermore, there is evidence of a potential perturbation of the subtropical stratocumulus deck due to anthropogenic emissions of oxidized sulfur (SOx) that occur mainly due to copper smelting along the continental strip of Chile and Peru. Anthropogenic sulfate aerosols emitted from smelters located uphill the Andes would reach the stratus deck in connection with strong easterly wind events, whereas coastal emissions would be advected by trade winds. In addition to the copper industry, urban centers, particularly Santiago (33.5S, 70.5W, 500 m.a.s.l.) and Lima (12S, 80W, 50 ma.s.l.), also constitute significant sources of aerosols and trace species that may have an impact on the stratus deck off the coast. Finally, dust, particularly in semi-desertic areas at the Southern bound of the Atacama Desert may also provide particles that may become activated as CCN and perhaps more importantly, affect the coastal biochemistry by means of iron deposition.

 

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