The impact of finer-resolution air-sea coupling on the intraseasonal oscillation of the Indian monsoon

Klingaman, N. P. ORCID: https://orcid.org/0000-0002-2927-9303, Woolnough, S. J. ORCID: https://orcid.org/0000-0003-0500-8514, Weller, H. ORCID: https://orcid.org/0000-0003-4553-7082 and Slingo, J. M. (2011) The impact of finer-resolution air-sea coupling on the intraseasonal oscillation of the Indian monsoon. Journal of Climate, 24 (10). pp. 2451-2468. ISSN 1520-0442 doi: 10.1175/2010JCLI3868.1

Abstract/Summary

The new HadKPP atmosphere–ocean coupled model is described and then used to determine the effects of sub-daily air–sea coupling and fine near-surface ocean vertical resolution on the representation of the Northern Hemisphere summer intra-seasonal oscillation. HadKPP comprises the Hadley Centre atmospheric model coupled to the K Profile Parameterization ocean-boundary-layer model. Four 30-member ensembles were performed that varied in oceanic vertical resolution between 1 m and 10 m and in coupling frequency between 3 h and 24 h. The 10 m, 24 h ensemble exhibited roughly 60% of the observed 30–50 day variability in sea-surface temperatures and rainfall and very weak northward propagation. Enhancing either only the vertical resolution or only the coupling frequency produced modest improvements in variability and only a standing intra-seasonal oscillation. Only the 1 m, 3 h configuration generated organized, northward-propagating convection similar to observations. Sub-daily surface forcing produced stronger upper-ocean temperature anomalies in quadrature with anomalous convection, which likely affected lower-atmospheric stability ahead of the convection, causing propagation. Well-resolved air–sea coupling did not improve the eastward propagation of the boreal summer intra-seasonal oscillation in this model. Upper-ocean vertical mixing and diurnal variability in coupled models must be improved to accurately resolve and simulate tropical sub-seasonal variability. In HadKPP, the mere presence of air–sea coupling was not sufficient to generate an intra-seasonal oscillation resembling observations.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/17968
Item Type	Article
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Uncontrolled Keywords	monsoon
Publisher	American Meteorological Society
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