Simulated austral winter response of the Hadley circulation and stationary Rossby wave propagation to a warming climate

Autor(es)

Freitas, Ana C. V. ; Frederiksen, Jorgen S. ; O'Kane, Terence J. ; Ambrizzi, Tercio

• Tipo de documento: Artigo Científico
• Fonte: Climate Dynamics; v. 49, n. 1-2, p. 521-545, JUL 2017.
• Citações Web of Science: 4

Resumo

Ensemble simulations, using both coupled ocean-atmosphere (AOGCM) and atmosphere only (AGCM) general circulation models, are employed to examine the austral winter response of the Hadley circulation (HC) and stationary Rossby wave propagation (SRW) to a warming climate. Changes in the strength and width of the HC are firstly examined in a set of runs with idealized sea surface temperature (SST) perturbations as boundary conditions in the AGCM. Strong and weak SST gradient experiments (SG and WG, respectively) simulate changes in the HC intensity, whereas narrow (5A degrees S-5A degrees N) and wide (30A degrees S-30A degrees N) SST warming experiments simulate changes in the HC width. To examine the combined impact of changes in the strength and width of the HC upon SRW propagation two AOGCM simulations using different scenarios of increasing carbon dioxide (CO2) concentrations are employed. We show that, in contrast to a wide SST warming, the atmospheric simulations with a narrow SST warming produce stronger and very zonally extended Rossby wave sources, leading to stronger and eastward shifted troughs and ridges. Simulations with SST anomalies, either in narrow or wide latitude bands only modify the intensity of the troughs and ridges. SST anomalies outside the narrow latitude band of 5A degrees S-5A degrees N do not significantly affect the spatial pattern of SRW propagation. AOGCM simulations with 1 %/year increasing CO2 concentrations or 4 times preindustrial CO2 levels reveal very similar SRW responses to the atmospheric only simulations with anomalously wider SST warming. Our results suggest that in a warmer climate, the changes in the strength and width of the HC act in concert to significantly alter SRW sources and propagation characteristics. (AU)

• Processo FAPESP: 12/14231-1 - Relação entre a circulação de Hadley e as ondas quase-estacionárias em um cenário de aquecimento global no hemisfério sul
• Beneficiário: Ana Carolina Vasques Freitas
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Processo FAPESP: 08/58101-9 - Impact of the Southwestern Atlantic Ocean on South American climate for the 20th and 21st centuries
• Beneficiário: Tercio Ambrizzi
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático