Impact of horizontal resolution on monsoon precipitation for CORDEX-South Asia: A regional earth system model assessment

Abstract

For the first time for CORDEX-South Asia, a high-resolution regional earth system model (ROM) is adopted to assess the impact of horizontal resolution (0.22 • and 0.11 • ) in simulating the Indian summer monsoon rainfall (ISMR) and the underlying spatiotemporal variability. ROM at both resolutions bears a close resemblance to observations in simulating the mean precipitation climatology compared to other regional climate models (RCMs) participated in CORDEX-South Asia. ROM shows substantial improvement relative to the ensemble mean of the RCMs included in CORDEX-South Asia. While comparing both simulations with observations, some systematic wet and dry bias over Central India (CI) and Northern Western Ghats is noticed. In general, the wet/dry bias over India is mainly associated with the overestimation/underestimation of the large-scale/convective component. Increasing horizontal resolution from 0.22 • to 0.11 • significantly adds value in simulating the JJAS mean precipitation by reducing the wet bias over western central India (WCI) and southern peninsular India and dry bias over eastern CI. The reduction in wet/dry bias is mainly associated with suppression/enhancement of the large scale/convective precipitation. This improvement in mean precipitation is partially due to the improved representation of the propagation of mesoscale systems such as boreal summer intraseasonal oscillation (eastward and northward). Despite the above improvements, the wet precipitation bias, particularly over WCI, persists. The weaker Findlater Jet associated with weaker land-ocean thermal contrast caused by the warm sea surface temperature (SST) bias over the western Arabian Sea (AS) suggests that AS moisture transport does not contribute to the wet bias over India. The wet bias is possibly associated with favourable atmospheric conditions (atmospheric instability).

Demonstrating the asymmetry of the Indian Ocean Dipole response in regional earth system model of CORDEX-SA

“…From the figure, it can be noticed that the model shows a slightly different pattern of relationship during all decades. The misrepresentation of the ISMR-IOD relationship is one of the possible causes of model limitation in simulating the ISMR (overestimation over southwest-central India) reported in the earlier study of this model (Mishra et al, 2021a(Mishra et al, , 2021b. Most of the ISMR related studies have reported the limited skill of the model to reproduce ISMR correctly.…”

“…1). A detailed description of the model setup can be found in Sein et al (2015Sein et al ( , 2020 and (Mishra et al, 2021b).…”

Regional earth system model for CORDEX‐South Asia: A comparative assessment of RESM and ESM over the tropical Indian Ocean

“…However, it is computationally expensive, and alternatively, high-resolution RESM can be used at a less computational cost. Various RESM having varying complexities have been developed and employed to explore the understanding of atmospheric and oceanic variability over different regions of the globe and suggest improvements (Sein et al, 2015;Wang et al, 2015;Dubey et al, 2021;Mishra et al, 2021aMishra et al, , 2021bSaharwardi et al, 2021;Kumar et al, 2022;Mishra et al, 2022aMishra et al, , 2022bMishra et al, , 2022c. Kumar et al (2022) demonstrated that dynamical and thermodynamical processes including the upper tropospheric circulation associated with the Indian summer monsoon employing the same model used in this study.…”

“…However, it is computationally expensive, and alternatively, high‐resolution RESM can be used at a less computational cost. Various RESM having varying complexities have been developed and employed to explore the understanding of atmospheric and oceanic variability over different regions of the globe and suggest improvements (Sein et al ., 2015; Wang et al ., 2015; Dubey et al ., 2021; Mishra et al ., 2021a, 2021b; Saharwardi et al ., 2021; Kumar et al ., 2022; Mishra et al ., 2022a, 2022b, 2022c). Kumar et al .…”

Does Increasing Climate Model Horizontal Resolution Be Beneficial for the Mediterranean Region?: Multimodel Evaluation Framework for High‐Resolution Model Intercomparison Project

“…Most of the global climate models participating in CMIP5 activities have a nominal resolution of about 150 km in the atmosphere and 1° in the ocean (Eyring et al., 2016; T. Rackow et al., 2018; Taylor et al., 2012) providing a reasonable trade‐off between computing time and model complexity. Various studies noted the improvement in the model performance (either global or regional) by increasing the atmospheric or oceanic resolution over most parts of the world (Bador et al., 2020; de la Vara et al., 2020; Güttler et al., 2015; Hack et al., 2006; Mishra et al., 2021; Moreno‐Chamarro et al., 2022; Strandberg & Lind, 2021; Tsartsali et al., 2022). Strandberg and Lind (2021) show notable improvement in high or moderate precipitation intensities over Europe after increasing atmospheric resolution (downscaling CMIP5 with a regional climate model).…”