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El Niño Impacts Precipitation Recycle Ratio over Tibetan Plateau at Interannual Timescale

Feb 25, 2021

The water cycle over the Tibetan Plateau (TP) is vital to regional and downstream climate and ecosystem. According to a new study by researchers from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, the interannual variability of the summer precipitation recycle ratio over the TP is influenced by the El Niño events in preceding winters.

The study was published in Journal of Geophysical Research: Atmospheres.

The precipitation recycle ratio is the contribution rate of the local evaporation to the total precipitation. "It's an important indicator of the water cycle process in the atmosphere. However, previous studies about precipitation recycle ratio over the TP remain inconclusive," said Dr. ZHOU Tianjun, the corresponding author of the study. "The key point is the reasonable consideration of the atmospheric water vapor mixture processes."

Using the advanced reanalysis data ERA5 of the high resolution and a bulk model method, the team analyzed the interannual variability of the precipitation recycle ratio over the TP.

"The results show the impact of ENSO, the most significant variability of the climate system at interannual timescale," said Dr. ZHOU. "In the El Niño decaying summers, the large-scale anomalous anticyclone spans over the Indo-Northwest Pacific and the westerly anomalies along the north flank of the anticyclone transport more moisture into the TP. The increased external inflow and decreased local evaporation lead to a decrease in the precipitation recycle ratio over the TP."

 

The schematic diagram of the atmospheric water cycle and its changes with ENSO events over the TP in summer (Image by ZHAO Yin)

"The change in the recycle ratio induced by the preceding El Niño events explains 60% of its interannual variability, but the response of precipitation recycle ratio over the TP in summer to the preceding El Niño and La Niña events is asymmetric," said Dr. ZHOU. "We hope this study is useful to reach the consensus on the climatic precipitation recycle ratio over the TP and advance our knowledge about its interannual variability mechanism."

This work is supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, National Natural Science Foundation of China, and the Second Tibetan Plateau Scientific Expedition and Research (STEP) Program.

Contact

LIN Zheng

Institute of Atmospheric Physics

E-mail:

Interannual variability of precipitation recycle ratio over the Tibetan Plateau

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