Paola Arias
The University of Texas at Austin
Department of Geological Sciences, Jackson School of Geosciences
1 University Station C1100
GEO 5.336
Austin, TX 78712
Education
Ph.D. student, Department of Geological Sciences, The University of Texas at Austin.
M.Sc. Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008.
M.Sc. Engineering: Water Resources, Universidad Nacional de Colombia Sede Medellin, 2005.
B.S. Civil Engineering, Universidad Nacional de Colombia Sede Medellin, 2001.
Research Experience
Faculty Position, Facultad de Ingeniería, Universidad de Antioquia, Colombia, 2006-present.
Graduate Research Assistant, Department of Geological Sciences, The University of Texas at
Austin, 2009-present.
Graduate Research Assistant, School of Earth and Atmospheric Sciences, Georgia Institute of
Technology, 2006-2008.
Graduate Research Assistant, Universidad Nacional de Colombia Sede Medellín, 2002-2005.
Teaching Experience
TA: Introduction to Environmental Sciences (EAS1600), School of Earth and Atmospheric
Sciences, Georgia Institute of Technology, 2006 and 2008.
Linear Algebra, Escuela de Ciencias, Universidad EAFIT, Medellín, Colombia, 2005.
Geometry, Escuela de Ciencias, Universidad Nacional de Colombia Sede Medellín, 2003-2005.
TA: Fluid Mechanics, Escuela de Ingeniería Civil, Universidad Nacional de Colombia Sede
Medellín, 2000.
Honors, awards, and fellowships
Michael Bruce Duchin Centennial Memorial Endowed Presidential Scholarship for the 2009-10
Academic Year, Jackson School of Geosciences, The University of Texas at Austin,
2009.
Faculty Position, Facultad de Ingeniería, Universidad de Antioquia, Medellín, Colombia, 2006.
Master thesis sponsored by Colciencias, Universidad Nacional de Colombia, 2004-2005.
Fellowship sponsored by the program “Best High School Students of Colombia”, Universidad
Nacional de Colombia, 1996-2001.
Research
My research interest deals with recent climate variability over South America. My master thesis
in Colombia focused on intra-annual climate variability over Colombia and its link to
intraseasonal oscillations in the Pacific Ocean. My Ph.D. research is focused on two topics: (i)
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how convective cloudiness has changed over the Amazon forests during the recent decades and
which are the possible causes for these changes and (ii) how North America and South America
Monsoon Systems interact between them. I am currently looking for the possible causes for a
delayed onset of the North American Monsoon with the aim of understanding which mechanisms
play a more important role and linking them to the also observed delayed onset of the wet season
over the Amazon forests.
Decadal changes in cloudiness over the Amazon forests
Tropical forests contain as much as 40% of the carbon stored as terrestrial biomass and account
for 30 to 50% of terrestrial productivity. 54% of the contingent rainforest is located in the
Amazon basin. This river basin also provides 18% of global fresh water discharge. Through its
control on evapotranspiration and runoff, rainforest plays an important role in regulating the
water cycle in this basin. Thus, the fate of Amazon rainforest has important consequence to the
global carbon and water cycle. The fate of the rainforests are primarily influenced by land use
and climate change. The former, especially the conversion of forest to pasture, has been
documented by many previous studies, whereas latter is more subtle and largely unclearly.
Changes in rainforest growth and mortality rates, especially in the deep and least
perturbed forest areas, have been consistently observed across global tropics in recent decades.
Previous studies have suggested that such a change may be caused by an elevated atmospheric
CO2 and increasing surface temperature. However, the rainforests in wet tropical regions are
mostly light limited and changes in atmospheric circulation and radiation balance over tropical
oceans have been reported, although it is not clear how cloudiness has changed over tropical
land. My research has shown a decadal-scale decrease of seasonal mean convection, cloudiness
and shortwave (SW) downwelling radiation during 1984 to 2007 over the Amazon basin. These
changes are consistent with observed increase in surface temperature and reduction of moisture
transport to the Amazon basin. Our analysis suggests that this observed change in cloudiness is
linked to of the Pacific Decadal Oscillation (PDO) and the expansion of the western Pacific
warm pool during December-February season, to the Atlantic Multidecadal Oscillation during
March-May season, and to the tropical Atlantic SST gradient during September-November
season [Arias et al., 2009, in preparation].
Possible causes for a delayed onset of the North American Monsoon
Monsoon precipitation over North America and northwest Mexico has important implications in
both society and economy. Reliable and accurate forecasting is necessary, especially now that
society awareness of global climate change increases. Our preliminary analyses have evidenced a
delay in the onset of the North American Monsoon. Warming in troposphere requires higher
surface air buoyancy to convect and high loss of soil moisture would reduce rainfall during the
dry to wet transition over the monsoon region. On the other hand, higher surface temperature and
precipitable water enhance rainfall intensity during wet season and high loss of soil moisture
increase dryness in the dry season. However, earlier warming of land surface temperature could
lead to earlier monsoon onset in North America. Which mechanism will be stronger is unclear.
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This part of my research aims to identify which possible causes could produce the
observed delay of the North American Monsoon onset. We consider three possible causes: (i)
stronger land-ocean surface temperature contrast, (ii) stronger eastern Pacific ITZC, and (iii)
relaxation of the lapse rate over the monsoon region due to tropospheric warming.
Publications
Arias, P., R. Fu, C. Hoyos, and W. Li, 2009: Decadal changes in cloudiness over the Amazon
forests: Observations and potential causes. In preparation to Climate Dynamics.
Arias, P. A. and G. Poveda, 2007: Estimación de la relación adimensional de Budyko en
Colombia. Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 31
(118), 69-78 (in spanish).
Poveda, G., O. J. Mesa, L. F. Salazar, P. A. Arias, H. Moreno, S. C. Vieira, P.A. Agudelo, V.G.
Toro, and J. F. Álvarez, 2005: Diurnal cycle of precipitation in the tropical Andes of Colombia.
Monthly Weather Review, 133(1), 228-240.
Arias, P. A. and G. Poveda, 2005: Efecto de la desagregacion temporal sobre la coherencia
espacial de la precipitación en Colombia. Avances en Recursos Hidráulicos, No. 12, 135-147 (in
spanish).
Poveda, G., O. J. Mesa, P. A. Agudelo, J. F. Álvarez, P. A. Arias, H. A. Moreno, L. F. Salazar,
V. G. Toro, and S. C. Vieira, 2002: Influencia del ENSO, Oscilación Madden-Julian, Ondas del
Este, Huracanes y Fases de la Luna en el Ciclo Diurno de la Precipitación en los Andes
Tropicales de Colombia. Meteorología Colombiana, No. 5, 3-12 (in spanish).
Poveda, G., O. J. Mesa, P. A. Agudelo, J. F. Álvarez, P. A. Arias, H. A. Moreno, L. F. Salazar,
V. G. Toro, S. C. Vieira, A. Jaramillo, and O. Guzman, 2002: Diagnóstico del Ciclo Diurno de la
Precipitación en los Andes Tropicales de Colombia. Meteorología Colombiana, No. 5, 23-30 (in
spanish).
Poveda, G. O. J. Mesa, P. A. Agudelo, J. F. Álvarez, P. A. Arias, H. A. Moreno, L. F. Salazar,
V. G. Toro y S. C. Vieira, 2002: Diagnóstico del Ciclo Anual y Efectos del ENSO sobre la
intensidad máxima de lluvias de duración entre 1 y 24 horas en los Andes de Colombia.
Meteorología Colombiana, No. 5, 67-74 (in spanish).
Talks and presentations
Arias, P., R. Fu, C. Hoyos, and W. Li. Decadal changes in cloudiness over the Amazon forests:
Observations and potential causes. Accepted for presentation in the 90th AMS Annual Meeting,
Atlanta, GA, January 2010.
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Arias, P., R. Fu, and W. Li. Changes in cloudiness over tropical land during the last decades and
its link to global climate change. AGU Fall Meeting, San Francisco, CA, December 2007.
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