INVESTIGADORES
NUÑEZ Mario Nestor
congresos y reuniones científicas
Título:
REGIONAL CLIMATE CHANGE EXPERIMENT OVER SOUTHERN SOUTH AMERICA: PART I: PRESENT CLIMATE CONDITIONS (1981-1990)
Autor/es:
SILVINA SOLMAN; MARIO N. NUÑEZ; MARIA F. CABRÉ
Lugar:
Foz do Iguacu, PR, Brazil
Reunión:
Congreso; 8th International Conference on Southern Hemisphere Meteorology and Oceanography; 2006
Institución organizadora:
American Meteorological Society
Resumen:
This study presents the results from a regional
climate simulation of the present-day climate,
corresponding to the period 1981-1990, over
southern South America, using the MM5 regional
climate model nested within a high resolution
version of the Hadley Centre global atmospheric
model HadAM3. The analysis of the simulation is
focused on evaluating the capability of the nested
modelling system in representing spatial patterns of
seasonal mean climate and its annual cycle, with
two main objectives. First, to quantify the capability
of the dynamical downscaling tool to represent
present-day climate conditions and to assess the
feasibility to produce useful estimates of regional
climate change projections. This simulation is the
basis to examine the climate change simulations
resulting for the A2 and B2 forcing scenarios which
are reported in a separate study. Second, to
identify critical aspects of regional climate simulation
over a barely unexplored region.
The regional simulation reproduces many
mesoscale climate features that are triggered by
regional forcings, not well captured by the low resolution
driving model. Overall, the regional
model improves the representation of the mean
climate upon the general circulation model in many
aspects. In particular, significant improvements
have been found in the regional simulation for near surface
circulation features. The first feature to note
is that the regional model exhibits a better
performance in the representation of the low-level
circulation, not well represented in the driving
model, such as the topographically-induced low
level cyclonic circulation during summer months
over northern Argentina. Nevertheless, it fails in
reproducing the correct position of the low pressure
system, and, in consequence, this results in a large
bias in the precipitation field. The misrepresentation
of this system induces a poor representation of the
low-level jet, which is critical in determining summer
precipitation in subtropical South America, as it
serves as conduit of moisture supply from the
Amazon basin. Thus, much of the deficiency in the
simulation of rainfall may be caused by the
deficiency of the regional model in simulating this
pattern.