The average annual rainfall of Mumbai is 2142 mm with monsoon rainfall accounting for 96% of the total annual

rainfall (Rana et al., 2012). During the monsoon, it usually rains uniformly over the city and severe flooding occurs in many parts. The duration of a rainfall event usually ranges from 30 min to 120 min, however in some cases they can be as long as 3–4 h (Rana et al., 2013). Daily rainfall amounts of up to 250 mm are common during monsoon season (Rana et al., 2012). Observed daily rainfall data for the Colaba station (18°54′ N, 72°49′ E, 11 m.a.s.l) in Mumbai, covering the period 1975–2005, was obtained from the India Meteorological Department (IMD). The daily volume resolution is 0.1 mm and there is no missing daily data. Further, daily rainfall data from nine GCM projections (see Table selleck inhibitor 1) was extracted from the CMIP5 database, provided by MOHC (Met Office Hadley Centre) (http://badc.nerc.ac.uk/home/) and we refer to the “WCRP Coupled Model Intercomparison GSK-3 beta phosphorylation Project” report and its references for details about the data (CLIVAR Exchanges; WCRP, 2011). All GCMs were driven

by the Representative Concentration Pathway (RCP) 4.5. The RCP 4.5 is a stabilisation scenario where total radiative forcing is stabilised before 2100 by employment of a range of technologies and strategies for reducing greenhouse gas emissions (Van Vuuren et al., 2011). A large climate model ensemble of outputs driven by different models helps in quantifying the uncertainties in a comprehensive way and reduces errors associated with the GCMs. Time series in the period 1975–2099 from the GCM grid cell covering Mumbai were extracted from each projection. We use the period 1975–2004 as the reference period, and the three periods 2010–2040, 2041–2070 and 2071–2099 as projection periods representing near, intermediate and far future, respectively. We have used the Distribution-based Carbachol Scaling (DBS) Method (Yang et al., 2010) to downscale and bias-correct the GCM data for both historical and future projections. As for most bias-correction

methods, it was assumed that simulations generated by GCMs for the control period cover the full range of climate processes and events that occur in the present climate, and is thus representative of present climate conditions up to a systematic and stationary bias. The DBS approach includes two steps. In the first step, the wet fraction (i.e. proportion of time steps with a non-zero precipitation) is adjusted to match the reference observations. A common feature of climate models is generation of “spurious drizzle”, an excessive number of time steps with very low precipitation intensities (e.g. Maraun et al., 2010). The excessive drizzle can be quantified by comparing climate model output with gridded observations with the same spatial resolution.