TITLE:
Surrogate Climate Change Scenario and Projections with a Regional Climate Model: Impact on the Aridity in South America
AUTHORS:
Sergio H. Franchito, Julio P. Reyes Fernandez, David Pareja
KEYWORDS:
Aridity in South America, Surrogate Climate-Change Scenario, Regional Climate Model
JOURNAL NAME:
American Journal of Climate Change,
Vol.3 No.5,
December
31,
2014
ABSTRACT: The
impact of global warming on the aridity in South America (SA) is investigated.
For this purpose, the methodology for generating surrogate climate-change
scenarios with a RCM is employed. For the present climate (CTRL) the RCM is
initialized with and driven by ECMWF/ERA-Interim reanalysis data. Two aridity
indices are used: the Budyko and the UNEP indices. The results for the CTR are
in agreement with other model studies which indicate future warming;
rainfall increases in southeastern South America, Ecuador and Peru and
decreases in the central and eastern Amazon. In general the model reproduces the aridity
in the continent compared with the observed data for both indices. The
distribution of aridity over SA in surrogate climate-change scenario shows an
increase of the dryness in the continent. Over Amazonia the aridity increases
23.9% (for the UNEP index) and 3.1% (for the Budyko index), suggesting that
portions of the Amazonia forest are replaced by dry land area. The semi-arid
zone over northeast Brazil expands westward, attaining the interior of north
Brazil. In this region the aridity increases 20% (for the UNEP index) and 0.6%
(for the Budyko index) indicating that areas of humid regime may be occupied by
areas with dry land regime. The RCM was also integrated driven by the AOGCM
ECHAM5/MPI-OM for the reference climate (CTRL2) and under A1B SRES scenario.
The results for the present-day climate are similar in CTRL2 and CTRL, and are
in agreement with CRU data. The distribution of the aridity for the present
climate seems to be better represented in CTRL using both Budyko and UNEP indices.
The changes in aridity (future climate minus control) are higher in the run
forced by the A1B SRES scenario. Although the UNEP and Budyko indices show
potentialities and limitations to represent the aridity distribution over SA,
the changes in aridity due to a pseudo-scenario of global warming are higher
using the UNEP index.