Skip to main content

Advertisement

Log in

Why coupled general circulation models overestimate the ENSO and Indian Summer Monsoon Rainfall (ISMR) relationship?

  • Published:
Climate Dynamics Aims and scope Submit manuscript

Abstract

Interannual variability of the Indian Summer Monsoon Rainfall (ISMR) is modulated by Sea Surface Temperature (SST) anomalies over Indo-Pacific Oceans, especially by the El Niño Southern Oscillation (ENSO). In general, coupled models used for seasonal prediction overestimate the correlation between ENSO and ISMR compared to observations. By analysing the observational data from 1982 to 2017, this study shows that the relationship between ENSO and ISMR is weak during August compared to the other months of the summer monsoon season (June, July, and September). This weak association between ENSO and ISMR during August is due to an increase in the synoptic variability. Thus, the effect of large-scale flow dominated by ENSO is suppressed by the formation of a synoptic system in the Bay of Bengal (BoB), making ENSO-ISMR relation feeble in August. The data analysis of various coupled models shows that all models underestimate synoptic variability, due to which simulated ENSO-ISMR relation is overestimated during August. Coupled model exhibit strong biases in relative humidity and cyclonic circulation over the northern BoB hence underestimating the synoptic variability.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3

taken from Sikka (2006), data is available from 1984 to 2003. GPCP rainfall data is available from Oct 1996. Thus, the data used is from 1997 to 2003.(values are given in percentage). Similarly, MMCFS percentage contribution of LPS days rainfall to seasonal mean rainfall in June (f), July (g), August (h), September (i) and JJAS (j)

Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8

Similar content being viewed by others

Availability of data and material

The datasets generated during and/or analysed during the current study are available from the corresponding author (surya@tropmet.res.in) on reasonable request.

Code availability

Code available upon request to the corresponding author.

References

Download references

Acknowledgements

IITM is a fully-funded institute under the Ministry of Earth Sciences, Govt. of India. The authors acknowledge the Director, IITM, for the support. NCAR is acknowledged for the software NCAR Command Language (NCL) version 6.4.0. The authors would also like to thanks anonymous reviewer whose suggestions helped to improve this manuscript.

Funding

Not applicable.

Author information

Authors and Affiliations

Authors

Contributions

RSD and SAR designed, analysed, and proposed the paper's methodology and prepared the manuscript. PAP, AS, MP, and DAR contributed to the paper's discussion and corrections.

Corresponding author

Correspondence to Suryachandra A. Rao.

Ethics declarations

Conflicts of interest/Competing interests

None.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Appendix 1: low-pressure system tracking algorithm

Appendix 1: low-pressure system tracking algorithm

Studies like Hunt et al. (2016), Hurley and Boos (2015), Praveen et al. (2015), and Srivastava et al. (2017) have identified LPS in reanalysis data using a tracking algorithm. These studies use Mean Sea Level Pressure (MSLP) and vorticity in the algorithm. However, Model simulated MSLP may have bias, and vorticity can be noisy. Recently, Vishnu et al. (2020) have shown that stream function is an optimal variable to track LPS (Vishnu et al. 2020). Their work showed that the stream function of 850 hPa is less noisy and represents the complete non-divergent wind. Thus, this study uses stream function to identify the LPS system.

Procedure to identify the system:

Step 1: Search the system with minima in the stream function.

Step 2: Remove multiple systems within 5 degrees by retaining a low mslp.

Step 3: Ensure the system has relative humidity higher than 80% within 3 degrees of the system.

Step 4: Ensure the system exists for 24 h.

Step 5: Each system is assigned a number.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Das, R.S., Rao, S.A., Pillai, P.A. et al. Why coupled general circulation models overestimate the ENSO and Indian Summer Monsoon Rainfall (ISMR) relationship?. Clim Dyn 59, 2995–3011 (2022). https://doi.org/10.1007/s00382-022-06253-w

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00382-022-06253-w

Keywords

Navigation