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[Coloquios CIMA-DCAO]

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                         Coloquios del
   Departamento de Ciencias de la Atmósfera y los Océanos DCAO)/⁠
         Centro de Investigaciones del Mar y la Atmósfera (CIMA)

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LUNES 18/09, a las 13HS:
Aula 8-⁠DCAO, 2° Piso, Pabellón 2
"Long range transport  of  stratospheric  aerosols  over  Southern 
Hemisphere following the Calbuco eruption in April 2015"

Dr. Nelson Begue (Universidad de la Reunión, Isla de la Reunión, 
Francia). El Dr. Begue está visitando la Argentina como parte del 
proyecto ECOS-Sud titulado "Dinámica e intercambios meridionales dentro 
del Hemisferio Sur: impacto sobre el ozono estratosférico y la radiación 
ultravioleta en superficie y el cambio climático"


Resumen:
The importance of stratospheric aerosol on the chemistry is mostly due 
to their role on ozone budget. Indeed, stratospheric aerosol provide 
sites for heterogeneous chemical reactions leading to  stratospheric  
ozone  depletion, significantly  enhanced  in  periods  of  high  
aerosol  loadings following major volcanic eruptions. After 43 years of 
inactivity, the Calbuco volcano which is located  in  the  southern  
part  of  Chile erupted  on  22  April  2015.  The  spacetime  
evolutions (distribution  and  transport)  of its aerosol  plume are 
investigated  by  combining  satellite 3(CALIOP, IASI, OMPS), in situ 
aerosol counting(LOAC OPC) and lidar observations, and the MIMOSA 
advection model. The Calbuco aerosol plume reached the  Indian Ocean one 
week after  the  eruption.  Over  the  Reunion  Island  site  (21°S;  
55.5°E), the  aerosol  signal  was unambiguously enhanced in comparison 
with “background” conditions with a volcanic aerosol layer extending 
from 18 km to 21km during the May-July period. All the data reveal an 
increase by  a  factor  of  ~2  in  the sAOD  (stratospheric  Aerosol  
Optical  Depth)  with  respect  to  values observed before the eruption. 
The aerosol mass e-folding time is approximately 90 days which is  
rather  close  to  the  value  (~80 days)  reported  for  the  Sarychev  
eruption. Microphysical measurements  obtained  before,  during  and  
after  the  eruption  reflecting the  impact  of  the Calbuco eruption 
on the lower stratospheric aerosol content have been analyzed over 
Reunion site. During the passage of the plume, the volcanic aerosol was 
characterized by an effective radius of 0.16 ±0.02 μm with an unimodal 
lognormal size distribution and the aerosol number concentration appears 
20 times higher than before and one year after the eruption. According 
to  OMPS and  lidar  observations,  a  tendency  toward  conditions  
before  the  eruption  has  been observed since April 2016. The volcanic 
aerosol plume is advected eastward in the Southern Hemisphere and its 
latitudinal extent is clearly bounded by the subtropical barrier and the 
polar vortex. The  transient  behavior  of  the aerosol  layers  
observed  above  Reunion Island between May and July 2015 reflects an 
inhomogeneous spatio-temporal distribution of the plume which is 
controlled by the localization of these dynamical barriers.




MIERCOLES 20/09, a las 13HS:
Aula 8-⁠DCAO, 2° Piso, Pabellón 2
"Topological analysis of geophysical flows"

Dra. Denisse Sciamarella (Institut Franco-Argentin d'études sur le 
climat et ses impacts (IFAECI), UMI 3351)

Resumen:
Topology plays a central role when it comes to unveiling the underlying 
structure of chaotic flows from data. The question: 'are there different 
classes of chaotic behavior?' is intrinsically related with the topology 
of chaotic attractors in phase space. On the other hand, topology also 
plays an important role in fluid mechanics, when it comes to a 
mathematical-physics perspective encompassing applications as diverse as 
airflow behavior in the larynx up to large-scale dispersion of 
pollutants in Earth's atmosphere and oceans. This talk provides an 
overview of scientific progress in both contexts, and examines potential 
applications of topological methods to the analysis of geophysical 
flows, with the goal of understanding the basic processes which are most 
important in describing what we observe, directly or indirectly, in 
these complex systems.


Los esperamos!!


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Grupo Coloquios

Departamento de Ciencias de la Atmósfera y los Océanos (FCEN-UBA)

Centro de Investigaciones del Mar y la Atmósfera (CONICET-UBA)

Ciudad Universitaria, 2do piso.

email: coloquios en cima.fcen.uba.ar

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