Key Processes on Triggering the Moderate 2020/21 La Niña Event as Depicted by the Clustering Approach

Abstract

The 2020/21 La Niña was not well predicted by most climate models when it started in early-mid 2020. This paper adopted an El Niño-Southern Oscillation (ENSO) ensemble prediction system to evaluate the key physical processes in the development of this cold event by performing a clustering analysis of 100 ensemble member predictions 1 year in advance. The abilities of two clustering approaches were first examined in regard to capturing the development of the 2020/21 La Niña event. One approach was index clustering, which adopted only the 12-month Niño3.4 indices in 2020 as an indicator, and the other was pattern clustering through contrasting the evolution of sea surface temperature (SST) anomalies over the tropical Pacific in 2020 for clustering. Pattern clustering surpasses index clustering in better describing the evolution over the off-equatorial and equatorial regions during the 2020/21 La Niña. Consequently, based on the pattern clustering approach, a comparison of the selected most (five best) and least (five worst) representative ensemble members illustrated that the predominance of anomalous southeasterly winds over the central equatorial Pacific in spring 2020 played a crucial role in initiating the moderate La Niña event in 2020/21, by preventing the development of westerly winds over the warm pool. Moreover, the inherent spring predictability barrier (SPB) was still a major challenge for improving the prediction skill of the 2020/21 La Niña event when the prediction occurred across the spring season.

Dynamics of Peatland Fires in South Sumatra in 2019: Role of Groundwater Levels

“…During El Niño episodes, fisherfolk experience a decrease in their catch, whereas La Niña episodes lead to increased fish catch. This can be attributed to the occurrence of upwelling during the evolution of El Niño and La Niña [22][23][24]. As mentioned previously, ENSO evolution comprises three phases: El Niño, La Niña, and neutral.…”

Doses de nitrogênio na produção de pré-secado e grãos de trigo duplo propósito para nutrição animal

“…A partir do mês de agosto, período no qual a planta entrou no espigamento/florescimento (Figura 1) houve forte estiagem. A precipitação acumulada para o período experimental foi de aproximadamente 400 mm, enquanto o esperado era de 700 mm (Inmet, 2020) gerando um clima seco característico de anos com La Niña (Cao;. Além disso, as altas temperaturas registradas no período geraram estresse térmico ao trigo (Figura 1), comprometendo os processos metabólicos e reduzindo a fotossíntese, o que acarretou em diminuições na produtividade dos grãos (Ribeiro et al, 2012).…”

On the Role of Indian Ocean SST in Influencing the Differences in Atmospheric Variability Between 2020–2021 and 2021–2022 La Niña Boreal Winters

“…2020-2022 boreal winters were a continuation of La Niña, with 2020/21 years being a moderate La Niña event and 2021/22 a comparable La Niña event (Cao et al, 2022;Li et al, 2022Li et al, , 2023. For these two consecutive La Niña winters, sea surface temperatures (SSTs) in 2021/22 relative to 2020/21 were warmer over the central North Pacific, the North Atlantic, the Indian Ocean and the equatorial central Pacific, and were colder over the equatorial eastern Pacific (Figure 1, bottom left).…”