Singh et al. (2026) Accounting for the bias in the median track of Indian Summer monsoon low-pressure systems in an Earth system model

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Climate
• Year: 2026
• Date: 2026-03-31
• Authors: Mahendra Singh, Govindasamy Bala, Ashwin K Seshadri
• DOI: 10.1175/jcli-d-25-0510.1

Research Groups

Not explicitly mentioned in the abstract. Studies involving CESM typically involve researchers from institutions like the National Center for Atmospheric Research (NCAR) and universities contributing to climate modeling.

Short Summary

This study investigates systematic biases in Monsoon Low-Pressure Systems (LPSs) and associated dry biases in the Community Earth System Model (CESM2.1.3) during the Indian Summer Monsoon. It finds a southward shift in LPS activity in CESM2.1.3, linked to biases in the low-level westerly jet and dry air intrusion, which are common across CMIP model generations.

Objective

• To identify and understand the systematic biases in Monsoon Low-Pressure System (LPS) activity and the associated dry bias over the monsoon core zone of the Indian Summer Monsoon (ISM) in the Community Earth System Model (CESM2.1.3).
• To account for the mechanisms driving these biases in CESM2.1.3.

Study Configuration

• Spatial Scale: Regional to continental scale, covering large parts of India, northwest India, the Arabian Sea, and western Asia.
• Temporal Scale: Present-day climate simulations, focusing on the Indian Summer Monsoon (ISM) season and seasonal averages of LPS activity.

Methodology and Data

• Models used: Community Earth System Model (CESM2.1.3), and comparison with Coupled Model Intercomparison Project (CMIP) Phase 3, 5, and 6 models.
• Data sources: ERA5 reanalysis and various other reanalysis datasets for comparison.

Main Results

• The present-day simulation using CESM2.1.3 exhibits a southward shift in Monsoon Low-Pressure System (LPS) activity compared to ERA5 reanalyses.
• Biases in simulating LPS activity in CESM2.1.3 are linked to a southward bias in the low-level westerly jet and a dry bias over northwest India.
• A bias towards larger dry air intrusion from the north and west of the Arabian Sea into India, associated with a high-pressure bias over western Asia, leads to a southward displacement of the monsoon low-level jet.
• This southward shift adversely impacts LPS genesis and propagation towards northern and northwestern India, resulting in the observed southward bias in LPS activity in the model.
• The southward shift in LPS activity and the dry air intrusion into northwest India are identified as common biases across CMIP3, CMIP5, and CMIP6 climate models.

Contributions

• Provides a detailed analysis of the mechanisms (e.g., low-level westerly jet bias, dry air intrusion, western Asia high-pressure bias) contributing to the southward shift in LPS activity and dry bias in CESM2.1.3.
• Highlights the persistence and commonality of these specific biases across three generations of CMIP climate models (CMIP3, CMIP5, CMIP6), underscoring a long-standing challenge in climate modeling of the Indian Summer Monsoon.
• Offers critical insights for future model development aimed at improving the simulation of synoptic-scale phenomena and rainfall distribution over India.

Funding

• Not explicitly mentioned in the abstract.

Citation

@article{Singh2026Accounting,
  author = {Singh, Mahendra and Bala, Govindasamy and Seshadri, Ashwin K},
  title = {Accounting for the bias in the median track of Indian Summer monsoon low-pressure systems in an Earth system model},
  journal = {Journal of Climate},
  year = {2026},
  doi = {10.1175/jcli-d-25-0510.1},
  url = {https://doi.org/10.1175/jcli-d-25-0510.1}
}