TITLE:
Assessment of CMIP3-CMIP5 Climate Models Precipitation Projection and Implication of Flood Vulnerability of Bangkok
AUTHORS:
Seree Supharatid
KEYWORDS:
Precipitation Downscaling, CMIP3, CMIP5, The 2011 Great Flood
JOURNAL NAME:
American Journal of Climate Change,
Vol.4 No.1,
March
27,
2015
ABSTRACT: Reliable estimates of precipitation are essential for both research and
practical applications. CMIP3 and CMIP5 climate simulations provide both
historical simulations and future projections of extreme climate. The 2011
monsoon season was one of case studies with exceptionally heavy and led to
extensive and long-lasting flooding in the Chao Phraya river basin, Thailand.
Flooding was exacerbated by the rapid expansion of urban areas into flood
plains and was the costliest natural disaster in the country’s history, with
direct damages estimated at US$45 billion. The present paper focuses on the
precipitation downscaling of CMIP3 and CMIP5 models. The majority of CMIP3 and
CMIP5 models overestimate the dry spell (in June and July) and underestimate
the peak precipitation (in May and September). The interquartile model range for
precipitation, which is spanned by the 25th and 75th quantiles,
is closer to the observed data for CMIP5 than CMIP3 models. However, overall results
suggest that the performance of CMIP5 models cannot be readily distinguished
from of CMIP3 models, although there are clear signals of improvements over
Bangkok. The correlation coefficient is found between 0.6 - 0.8, implying that most
of the models simulate the mean rainfall reasonably well. Both model
generations have approximately the same standard deviation as observed, but
more spatial variability and more RMS error are found for the future
projections. Use of the Multi Model mean shows continuously increased rainfall
from the near future to the far future while the Multi Model Median shows
increased rainfall only for the far future. These findings in changing
precipitation are discussed through the flood behavior in 2011. Results from
flood simulation with several adaptation measures reveal that flood cannot be
completely avoided. One of the best practices for highflood risk communities is
to raise the house with open space in the first floor.