Influence of Nonlinear Moisture Advection on April Precipitation Anomalies over Indochina Peninsula during 2015/2016 Super El Niño

Abstract

Extreme weather and climate events caused by El Niño have significant impacts on socio-economic conditions and the safety of people’s lives and properties.Between 2014 and 2016， a super El Niño event occurred， leading to frequent extreme weather and climate events worldwide.This study focuses on the Indochina Peninsula region and explores the potential reasons for abnormally decreased precipitation in April 2016， against the backdrop of the super El Niño event.The research utilizes monthly observations and reanalysis data of sea temperatures， precipitation， wind fields， and specific humidity to investigate circulation patterns and abnormal moisture transport.The results indicate that in April 2016， the ICP experienced anomalous sinking currents due to the influence of a developing and robust Western North Pacific Anti-Cyclone and subtropical high-pressure systems.These conditions hindered moisture convergence necessary for precipitation formation.Furthermore， through dynamic diagnostic analysis， the study finds that the product of the Nino3.4 index and the zonal gradient of SST anomalies （GSSTA） between the equatorial East Indian Ocean and the equatorial Western Pacific Ocean effectively indicates the super El Niño event.Additionally， the modulation of nonlinear moisture advection over the ICP plays a vital role in the abnormally low precipitation in the region in April.During the 2015/2016 El Niño event， conflicting wind patterns emerged between the easterly winds on the southern side of the WNPAC and the anomalous westerly moisture transport guided by GSSTA.This conflict weakened the moisture transport from the Pacific Ocean and the Bay of Bengal to the ICP.Over the ICP， most of the moisture exhibited a pattern of being less in the south and more in the north， with higher levels in the east and lower in the west.This led to moisture divergence， which was unfavorable for precipitation formation.In summary， this study emphasizes the significant influence of a super El Niño event on extreme weather and climate events， particularly focusing on the abnormally decreased precipitation over the Indochina Peninsula in April 2016.By examining circulation patterns and moisture transport anomalies， the research contributes to understanding the underlying causes and dynamics of these events.The findings have implications for future weather predictions， climate change assessments， and the development of effective strategies to mitigate the impacts of extreme weather events in the Indochina Peninsula region.In April 2016， under the combined action of the Bay of Bengal anomalous anticyclonic and the Western North Pacific Anti-Cyclone， the Indochina Peninsula convection was suppressed， and the warm and wet air was transported to South China under the guidance of the anomalous south wind.

Keywords

• indochina peninsula
• el niño
• precipitation anomalies
• circulation anomalies
• moisture transport