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Abstract Key questions remain about the atmospheric response to variability in the oceanic western boundary currents (WBCs). Here we exploit a unique high‐resolution slab‐ocean coupled climate model to investigate how ocean heat transport (OHT) anomalies in the major WBCs of both hemispheres affect the atmospheric circulation. Prescribed OHT anomalies lead to robust changes in convective precipitation anomalies equatorward of the maximum surface warming. The response is deepest and most pronounced over the Northern Hemisphere (NH) WBCs, where it is associated with significant changes in upper tropospheric vertical motion, condensational heating and geopotential heights. The response is relatively shallow over the Southern Hemisphere (SH) WBCs. The findings reveal the robustness of the atmospheric response to OHT anomalies and highlight key hemispheric differences: in the NH, OHT anomalies are balanced by deep atmospheric vertical motion; in the SH, they are balanced primarily by shallow horizontal temperature advection.
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Hemisphere-Dependent Impacts of ENSO and Atmospheric Eddies on Hadley Circulation
Abstract The variability of the Hadley circulation strength (HCS), crucial to tropical climate variability, is attributed to both oceanic and atmospheric forcings. El Niño–Southern Oscillation (ENSO) and variations in the extratropical upper-tropospheric eddies are the known drivers of the interannual HCS variability. However, the relative contributions of these oceanic and atmospheric forcings to the hemispheric HCS variability are not well understood. In particular, how much anomalous wind stress–driven ocean dynamics, including ENSO, impact HCS variability remains an open question. To address these gaps, we investigate the drivers of the interannual HCS variability using global coupled model experiments that include or exclude anomalous wind stress–driven ocean circulation variability. We find that the anomalous wind stress–driven ocean circulation variability significantly amplifies HCS variability in the Southern Hemisphere (SH). ENSO is the leading modulator of the SH HCS variability, which offers the potential to improve the predictability of Hadley circulation (HC)–related hydrological consequences. On the other hand, the Northern Hemisphere (NH) HCS variability is predominantly influenced by the eddy-driven internal atmospheric variability with little role in ocean dynamics. We hypothesize that the large eddy variability in the NH and concentrated ENSO-associated heating and precipitation in the SH lead to the hemisphere-dependent differences in the interannual HCS variability.
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- Award ID(s):
- 1951713
- PAR ID:
- 10555757
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 37
- Issue:
- 24
- ISSN:
- 0894-8755
- Format(s):
- Medium: X Size: p. 6533-6548
- Size(s):
- p. 6533-6548
- Sponsoring Org:
- National Science Foundation
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