Monsoon Climate Change Projection for the Orographic West Coast of India Using High‐Resolution Nested Dynamical Downscaling Model

Abstract

An efficient, reliable very high resolution dynamical downscaling model, a regional climate model (Weather Research and Forecasting‐Advanced Research Weather Research and Forecasting) one‐way nested into skillful general circulation model (National Center for Atmospheric Research‐Community Climate System Model version 4), is configured and implemented for ecologically sensitive, densely populated west coast of India encompassing Western Ghats (WG) having complex, meridionally oriented orography and wide biodiversity. This model with 3 km resolution resolves orographic features enabling realistic simulation of physical and dynamical characteristics of present‐day Indian summer monsoon (ISM) and extreme events, particularly recent trends in ISM rainfall over WG as observed. Marked skill of this model provides confidence in its future climate projection at regional scale. Future ISM rainfall projection shows significant increase (reduction) over 50.7% (5.8%) of Indian grid points. Significant reduction (10–20% of mean) over WG is due to upper‐tropospheric warming effect that stabilizes the atmosphere. Projected changes in extreme events show overall increase in warm days and warm nights over India with maximum increase over South India. Projected changes show widespread increase in wet days over most of India and reduction over WG. Projection of consecutive dry days implies wetter future for most parts of India but strengthened drought conditions for WG. Wind extreme projection shows strengthened (weakened) low (high) winds probability over WG and increase (decrease) in very high (low) winds over central India. This study establishes the importance of (i) employing sufficiently high‐resolution model, (ii) using bias‐corrected boundary data, and (iii) configuring model for realistic present‐day climate over complex topographic coastlines such as the west coast, in order to obtain useful climate change information for adaptation measures.

Effects of Convection Representation and Model Resolution on Diurnal Precipitation Cycle Over the Indian Monsoon Region: Toward a Convection‐Permitting Regional Climate Simulation

“…In the case of CON, we used the KF (Kain, 2004) cumulus parameterization scheme, which was switched off in COFF. The recent studies of Jayasankar et al (2018) and Ratnam et al (2017) have become our motivation to choose KF scheme in the simulation settings. Other physics configurations were considered according to Sugimoto and Takahashi (2016); they used these settings over the South Asian tropical regions of Bangladesh.…”

Does increasing the spatial resolution in dynamical downscaling impact climate change projection of Indian summer monsoon, population and GDP?

“…To overcome the di culties caused by inadequate horizontal resolution and to study the ner-scale climate features, an alternative way is to downscale those GCMs by using a high-resolution regional climate model (RCM, Wang et al 2004;IPCC 2013). This requires a high-resolution RCM driven by the initial and lateral boundary conditions from the global GCM (Dickinson et al 1989;Giorgi et al 1990;Jayasankar et al 2018;Jayasankar 2019). There are several studies, which attempted to simulate the Indian summer monsoon and its seasonal variability using RCMs through dynamical downscaling technique (Bhaskaran et al 1996;Dash et al 2006;Ratnam et al 2009).…”

“…CORDEX -South Asia (SA) domain covers the Indian region with RCMs are having a spatial resolution of 0.44° (~ 50-km). The inability to represent realistic spatial distribution of the summer monsoon rainfall at regional scale by the coarse resolution CMIP5 models is considerably recti ed through the dynamical downscaling with most suitable physics schemes and domain set up (Jayasankar et al 2018). These high-resolution downscaled simulations can be effectively used to understand the climate change projection at regional scale.…”

“…A detailed analysis of the mean summer monsoon climatology over India revealed that downscaling may not always improve the seasonal averages, and it strongly depends on the choice of the RCM and the driving GCM (Sanjay et al 2017b). However, in a study, Jayasankar et al (2018) showed that employing su ciently high-resolution RCM driven by bias-corrected boundary datasets with a suitable con guration results in realistic present-day ISM simulation as well as useful regional climate change projection.…”

Dynamical downscaling of a multimodel ensemble prediction system: Application to tropical cyclones

“…The weather research and forecasting (WRF) model is widely used for regional studies and is known to have good prediction skill for Indian monsoon region Mukhopadhyay et al (2009); Srinivas et al (2013); Raju et al (2015); Ratnam et al (2017). Several studies addressed the impact of physical parameterizations Osuri et al (2012), monsoon climate change projections Jayasankar et al (2018), basin scale hydro-meteorological applications and flood forecasting Lin et al (2015); Srivastava et al (2015), tropical cyclone cases Mohanty et al (2010); Singh et al (2011), simulations of extreme rainfall events Kumar et al (2008); Routray et al (2010); Alam (2014) using WRF.…”