Preprints
https://doi.org/10.5194/egusphere-2024-22
https://doi.org/10.5194/egusphere-2024-22
09 Jan 2024
 | 09 Jan 2024
Status: this preprint is open for discussion and under review for Weather and Climate Dynamics (WCD).

Using regional relaxation experiments to understand the development of errors in the Asian Summer Monsoon

Gill M. Martin and Jose M. Rodriguez

Abstract. We describe the use of regional relaxation (“nudging”) experiments carried out in initialised hindcasts to shed light on the contribution from particular regions to the errors developing in the Asian Summer Monsoon. Results so far confirm previous hypotheses that errors in the Maritime Continent region contribute substantially to the East Asia Summer Monsoon (EASM) circulation errors through their effects on the Western North Pacific Subtropical High. Locally forced errors over the Indian region also contribute to the EASM errors. Errors arising over the Maritime Continent region also affect the circulation and sea surface temperatures in the Equatorial Indian Ocean region, contributing to a persistent error pattern resembling a positive Indian Ocean Dipole phase. This is associated with circulation errors over India and the strengthening and extension of the westerly jet across southeast Asia and the South China Sea into the Western Pacific, thereby affecting the ASM circulation and rainfall patterns as a whole. However, errors developing rapidly in the deeper equatorial Indian Ocean, apparently independently of the atmosphere errors, are also contributing to this bias pattern. Preliminary analysis of nudging increments over the Maritime Continent region suggests that these errors may at least partly be related to deficiencies in the convection and boundary layer parametrisations.

Gill M. Martin and Jose M. Rodriguez

Status: open (until 06 Mar 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-22', Anonymous Referee #1, 20 Feb 2024 reply
  • RC2: 'Comment on egusphere-2024-22', Anonymous Referee #2, 28 Feb 2024 reply
Gill M. Martin and Jose M. Rodriguez
Gill M. Martin and Jose M. Rodriguez

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Short summary
Using sensitivity experiments, we show that model errors developing in the Maritime Continent region contribute substantially to the Asian Summer Monsoon (ASM) circulation and rainfall errors through their effects on the Western North Pacific subtropical high-pressure region and the winds and sea surface temperatures in the Equatorial Indian Ocean, exacerbated by local coupled feedback. Such information will inform future model developments aimed at improving model predictions for the ASM.