The Amazonian Low-Level Jet and Its Connection to Convective Cloud Propagation and Evolution

Autor(es)

Anselmo, Evandro M. ^[1] ; Schumacher, Courtney ^[2] ; Machado, Luiz A. T. ^{[3, 1]}

Afiliação do(s) autor(es)

^[1] Inst Nacl Pesquisas Espaciais, Ctr Previsdo Tempo & Estudos Climat, Cachoeira Paulista, SP - Brazil

^[2] Texas A&M Univ, College Stn, TX - USA

^[3] Max Planck Inst Chem, Multiphase Chem Dept, Mainz - Germany

• Tipo de documento: Artigo Científico
• Fonte: MONTHLY WEATHER REVIEW; v. 148, n. 10, p. 4083-4099, OCT 2020.
• Citações Web of Science: 0

Resumo

We describe the existence of an Amazonian low-level jet (ALLJ) that can affect the propagation and life cycle of convective systems from the northeast coast of South America into central Amazonia. Horizontal winds from reanalysis were analyzed during March-April-May (MAM) of the two years (2014-15) of the GoAmazon2014/5 field campaign. Convective system tracking was performed using GOES-13 infrared imagery and classified into days with high and weak convective activity. The MAM average winds show a nocturnal enhancement of low-level winds starting near the coast in the early evening and reaching 1600 km inland by late morning. Mean 3-hourly wind speeds maximize at 9-10 ms(-1) near 900 hPa, but individual days can have nighttime low-level winds exceeding 12ms(-1). Based on objective low-level wind criteria, the ALLJ is present 10%-40% of the time over the Amazon during MAM depending on the location and time of day. The evolution of the ALLJ across the Amazon impacts the frequency of occurrence of cloud clusters and the intensity of the moisture flux. In addition, the ALLJ is associated with the enhancement of northeasterly flow in the midtroposphere during active convective days, when vertical momentum transport may be occurring in the organized cloud clusters. During the weakly active convective period, the ALLJ is weaker near the coast but stronger across the central Amazon and appears to be linked more directly with the South American low-level jet. (AU)

• Processo FAPESP: 15/14497-0 - Previsão imediata de tempestades intensas e entendimento dos processos físicos no interior das nuvens: o SOS-CHUVA (Sistema de Observação e Previsão de Tempo Severo)
• Beneficiário: Luiz Augusto Toledo Machado
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático