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The role of potential vorticity anomalies in the Somali Jet on Indian summer monsoon intraseasonal variability

Rai, P., Joshi, M., Dimri, A. P. and Turner, A. (2018) The role of potential vorticity anomalies in the Somali Jet on Indian summer monsoon intraseasonal variability. Climate Dynamics, 50 (11-12). pp. 4149-4169. ISSN 0930-7575

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To link to this item DOI: 10.1007/s00382-017-3865-9

Abstract/Summary

The climate of the Indian subcontinent is dominated by rainfall arising from the Indian summer monsoon (ISM) during the summer season (June to September). Intraseasonal variability during the monsoon is characterized by periods of heavy rainfall interspersed by drier periods, known as active and break events respectively. Understanding and predicting such events is of vital importance for forecasting human impacts such as water resources. The Somali Jet is a key regional feature of this circulation. In the present study, we find that the spatial structure of Somali Jet potential vorticity (PV) anomalies varies considerably during active and break periods. Analysis of these anomalies shows a mechanism whereby sea surface temperature (SST) anomalies propagate north/northwestwards through the Arabian Sea, caused by a positive feedback loop joining anomalies in SST, convection, modification of PV by diabatic heating and mixing in the atmospheric boundary layer, wind stress curl, and upwelling processes. The feedback mechanism is consistent with observed coupled ocean-atmosphere system variability timescales of approximately 20 days. This research suggests that better understanding and prediction of monsoon subseasonal variability in the South Asian monsoon may be gained by analysis of the day-to-day dynamical evolution of PV in the Somali Jet.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > NCAS
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:68484
Publisher:Springer
Publisher Statement:The DOI will be: 10.1007/s00382-017-3865-9

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