Dynamic downscaling techniques based on physical/dynamical links between climates at large and at small scales and statistical downscaling methods using empirical relationships between large-scale atmospheric variables and observed daily local weather variables are the two main techniques used. The statistical downscaling (SD) technique is a method used to derive local-scale information from a larger scale through inference from the cross-scale relationship using some random and/or deterministic functions [12]. One method of statistical downscaling is through stochastic rainfall modelling. The model can be used with the parameters that have probability distributions, conditionally based on the coarse-scale climatic predictor. The parameters of the stochastic model are obtained from statistical analysis of time series and can be altered in accordance with climate model
simulation results. This study uses the LARS-WG model as the main weather generator model for
predicting the future rainfall. LARS-WG is a stochastic WG based on the series approach [13], with a
detailed description given in Semenov (2007) [14]. LARS-WG produces synthetic daily time series of
maximum and minimum temperatures, precipitation and solar radiation. The WG uses observed daily
weather for a given site to compute a set of parameters for probability distributions of weather
variables, as well as correlations between them [15]. The LARS-WG model has been successfully
applied in many similar case studies [15–18]. The LARS-WG model itself consists of 15 different
AOGCM model results according to different emission scenarios. However, only six AOGCMs have
all three Special Range of Emissions Scenarios (SRES) scenarios (A1B, A2, B1) available. Therefore,
this study utilizes these six models for performing the analysis (Table 1). The outputs from these
AOGCMs are available as monthly means of climatic variables, including precipitation, maximum and
minimum temperatures and radiation for the baseline period corresponding to 1960–1990 and the
periods 2011–2030, 2046–2065 and 2081–2100 [15].