Upon examining the spatial plots and analyzing the trends in annual rainfall, it is
clear that there is neither a fixed increase nor a decrease of annual rainfall over the
basin. However, the grids toward the Western Ghats region (Maharashtra state) lying
in the Upper Bhima (K5) show the increasing trends (positive tau values) in rainfall.
Annual mean rainfall varies between 2000 and 2500 mm, and the maximum daily
rainfall of 450 mm is also evidence of the occurrence of extreme events; the Lower
Bhima (K6) has altogether a decreasing trend of annual rainfall. The spatial grids on
the downstream side (Karnataka state) have annual mean rainfall values between
500 and 1000 mm with maximum daily rainfall of 100–150 mm. Further, as we
examine the annual rainfall, the best fit line for the range of data has a mean value of
850 mm with a decreasing rainfall trend up to 2004. Interestingly, in the year 2005,
the annual maximum rainfall reached 2300 mm and declined subsequently. The
average slope of yearly time series data as per the linear equation is À0.2086,
resulting in 0.044% of decline of annual rainfall for every decade. The annual
maximum rainfall trends, however, show a positive trend and with an occurrence
of an extreme event during 2005. Flooding was a norm in Upper Bhima as the tau
values are positive and even more in the magnitude than Lower Bhima (negative
values of tau); this could have resulted in drought conditions in the Lower Bhima
regions.
Materials and Methods
This study uses the Coupled Model Intercomparison Project Phase-5 (CMIP5), a
GCM model used extensively in studies of climate changes associated with scenarios
at global and regional scales (Zhang et al. 2019). IPCC developed four new
pathways under representative concentration pathway (RCP) scenarios for longterm and near-term climate modeling experiments based on future climate projections until 2100, with radiative forcing values in the range 2.6–8.5 W/m
2 and named
sequentially as RCP 2.6–8.5. These RCPs include one alleviation scenario priming a
low driving level (RCP 2.6), two stabilization scenarios (RCP 4.5 and RCP 6), and
one scenario with high GHG emissions (RCP 8.5): scenarios are based on GHG and
socioeconomic development (Nilawar and Waikar 2019). The RCP development
process and main characteristics have been summarized by van Vuuren et al. (2011).
GCM models used for this study for climate projections are at coarse resolution
(150–250 km) and poor in the ability to resolve important subgrid scale features
required at the regional scale (20–25 km), so that the projections may not be reliable
for regional impact assessment studies. Downscaling methods are robust techniques
to overcome this problem to obtain regional-scale weather and climate information,
particularly at the surface level. Downscaling techniques are broadly classified as
dynamic downscaling and statistical downscaling (Wilby et al. 1998).
2 Regional Assessment of Impacts of Climate Change: A Statistical Downscaling. . .
25
clear that there is neither a fixed increase nor a decrease of annual rainfall over the
basin. However, the grids toward the Western Ghats region (Maharashtra state) lying
in the Upper Bhima (K5) show the increasing trends (positive tau values) in rainfall.
Annual mean rainfall varies between 2000 and 2500 mm, and the maximum daily
rainfall of 450 mm is also evidence of the occurrence of extreme events; the Lower
Bhima (K6) has altogether a decreasing trend of annual rainfall. The spatial grids on
the downstream side (Karnataka state) have annual mean rainfall values between
500 and 1000 mm with maximum daily rainfall of 100–150 mm. Further, as we
examine the annual rainfall, the best fit line for the range of data has a mean value of
850 mm with a decreasing rainfall trend up to 2004. Interestingly, in the year 2005,
the annual maximum rainfall reached 2300 mm and declined subsequently. The
average slope of yearly time series data as per the linear equation is À0.2086,
resulting in 0.044% of decline of annual rainfall for every decade. The annual
maximum rainfall trends, however, show a positive trend and with an occurrence
of an extreme event during 2005. Flooding was a norm in Upper Bhima as the tau
values are positive and even more in the magnitude than Lower Bhima (negative
values of tau); this could have resulted in drought conditions in the Lower Bhima
regions.
Materials and Methods
This study uses the Coupled Model Intercomparison Project Phase-5 (CMIP5), a
GCM model used extensively in studies of climate changes associated with scenarios
at global and regional scales (Zhang et al. 2019). IPCC developed four new
pathways under representative concentration pathway (RCP) scenarios for longterm and near-term climate modeling experiments based on future climate projections until 2100, with radiative forcing values in the range 2.6–8.5 W/m
2 and named
sequentially as RCP 2.6–8.5. These RCPs include one alleviation scenario priming a
low driving level (RCP 2.6), two stabilization scenarios (RCP 4.5 and RCP 6), and
one scenario with high GHG emissions (RCP 8.5): scenarios are based on GHG and
socioeconomic development (Nilawar and Waikar 2019). The RCP development
process and main characteristics have been summarized by van Vuuren et al. (2011).
GCM models used for this study for climate projections are at coarse resolution
(150–250 km) and poor in the ability to resolve important subgrid scale features
required at the regional scale (20–25 km), so that the projections may not be reliable
for regional impact assessment studies. Downscaling methods are robust techniques
to overcome this problem to obtain regional-scale weather and climate information,
particularly at the surface level. Downscaling techniques are broadly classified as
dynamic downscaling and statistical downscaling (Wilby et al. 1998).
2 Regional Assessment of Impacts of Climate Change: A Statistical Downscaling. . .
25