Origin and dynamics of global atmospheric wavenumber-4 in the Southern mid-latitude during austral summer

Senapati, B. ORCID: https://orcid.org/0000-0001-5029-9731, Deb, P., Dash, M. K. and Behera, S. K. (2022) Origin and dynamics of global atmospheric wavenumber-4 in the Southern mid-latitude during austral summer. Climate Dynamics, 59 (5). pp. 1309-1322. ISSN 1432-0894 doi: 10.1007/s00382-021-06040-z

Abstract/Summary

Using empirical orthogonal function analysis, a stationary atmospheric wavenumber-4 (AW4) pattern is identified in the Southern mid-latitudes during austral summer. The generation mechanism and its linkage to Southern Hemisphere climate is explored using a linear response model and composite analysis. It is found that, AW4 pattern is forced by a Rossby wave source in the upstream region of the upper-tropospheric westerly wave-guide. The vortex stretching associated with the anomalous convection over subtropical western Pacific Ocean (near the New Zealand coast) adjacent to the westerly jet triggers the Rossby wave train around mid-November. This disturbance gets trapped in the Southern Hemisphere westerly jet waveguide and circumnavigates the globe. Around 15-25 days later (in early December), a steady AW4 pattern is established in the Southern mid-latitudes. Further, correlation analysis suggests the AW4 pattern is independent of other natural variabilities such as El Niño/Southern Oscillation, Southern Annular Mode, and Indian Ocean Dipole. The AW4 pattern is found to influence the rainfall over different parts of South America and Australia by modulating upper-level divergence.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/118927
Item Type	Article
Refereed	Yes
Divisions	No Reading authors. Back catalogue items Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Springer
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