Future projections of heatwave characteristics and dynamics over India using a high-resolution regional earth system model.

This study using a high resolution (~ 25 km) regional coupled earth system model ROM (REMO-OASIS-MPIOM), addresses the future projections of heatwave characteristics (frequency, duration, and severity) and associated dynamics over India for the AMJ (April–May–June) season. The near-surface maximum temperature (Tmax) is used to identify the prominent regions of large fluctuations using rotated empirical orthogonal function analysis. The averaged heatwave characteristics simulated by ROM is compared against the Indian Meteorological Department (IMD) Tmax observational data for the historical period 1980–2005. The ROM simulated heatwave characteristics largely agree with observations though few deviations are also noticed. The typical synoptic features associated with the heatwave days for the identified regions show the presence of elevated geopotential height (thickness; Z) with an anomalous anticyclonic structure which forms an atmospheric blocking over each region except south east coast. The daily evolution of potential vorticity and Z suggests eastward propagation of blocks that remain persistent during heatwave days. ROM is able to simulate these features with systematic higher magnitude and minor location changes. The future projections (RCP 8.5) of heatwave characteristics show a gradual increase for different time-slices during 2020–2099. The projected frequency will be doubled, and the average duration will increase by 8–12 days per season at the end of the century. The severity will also increase by 2°–3 °C. Similarly, future dynamical features will be associated with an increase in geopotential height (thickness) in the future along with a gradual decrease in potential vorticity. The future patterns of anomalous potential vorticity indicate the presence of omega block in all-time slices with a decrease in negative magnitude. [ABSTRACT FROM AUTHOR]