Impact of Developing ENSO on Tibetan Plateau Summer Rainfall

Abstract

The year-to-year variations of Tibetan Plateau (TP) summer rainfall have tremendous climate impacts on the adjoining and even global climate, attracting extensive research attention in recent decades to understand the underlying mechanism. In this study, we investigate an open question of how the El Niño-Southern Oscillation (ENSO) influences the TP precipitation. We show that the developing ENSO has significant impacts on the summer rainfall over the southwestern TP (SWTP), which is the second EOF mode of the interannual variability of summer rainfall over the TP. Moisture budget indicates that both the suppressed vertical motion and the deficit of moisture contribute to the reduction of SWTP rainfall during El Niño’s developing summer, with the former contribution four times larger than the latter. Moist static energy analyses indicate that the anomalous advection of climatological moist enthalpy by anomalous zonal wind is responsible for the anomalous descending motions over the SWTP. The El Niño-related southward displacements of the South Asian high and the upper-level cyclonic anomalies over the west of TP stimulated by the suppressed Indian summer monsoon precipitation are two key processes dominating the anomalous zonal moist enthalpy advection over SWTP. Meanwhile, the India-Burma monsoon trough is strengthened during El Niño developing summer, which prevents the water vapor into the SWTP, and thus contributes to the deficit of summer SWTP rainfall. Our results help to understand the complicated ENSO-related air-sea interaction responsible for the variability of TP precipitation and have implications for seasonal prediction of the TP climate.

Toward role of westerly‐monsoon interplay in linking interannual variations of late spring precipitation over the southeastern Tibetan Plateau

“…The SETP, which is located in the fertile river valleys, is a densely populated region with famous agro‐economy (Wu, 2003). Although the precipitation over TP is mainly concentrated in summer (Bothe et al, 2011; Chen & You, 2017; Hu et al, 2021), the sudden increase of late spring precipitation over SETP and its marked year‐to‐year fluctuations could also exert profound impacts on local agriculture and animal husbandry development, as well as the water resources management (Chen et al, 2006; Chen & You, 2017; Webster & Hoyos, 2004). Therefore, a better understanding of the late spring precipitation variations in SETP associated with WMI can provide scientific support for flood/drought mitigation and agricultural planning, which is of great socioeconomic importance.…”

Climate variability and change in Tibetan Plateau within a warming climate

“…The last row shows the correlation between ENSO index and average precipitation and average surface temperature, both values are not very close to 1 or -1, indicating they do not have a strong linear association. Although there is no very significant linear relationship between ENSO and mean temperature and mean precipitation on the Tibetan Plateau in correlation calculations, other researchers have found through other specialized studies that ENSO-related precipitation on the Tibetan Plateau plays an important role in the regulation of hydroclimate on the Tibetan Plateau (Hu et al, 2021).…”

Seasonal‐Interannual Predictions of Summer Precipitation Over the Tibetan Plateau in North American Multimodel Ensemble

“…The positive phase of the IOBM, characterized by SST warming in the tropical southwest Indian Ocean (SWIO) weakens the land–sea thermal contrast between the Eurasian continent and the Indian Ocean, and contributes to suppressed precipitation over TP in early summer (Chen & You, 2017; Zhao et al., 2018). The Indian monsoon rainfall variation, driven by an eastward shift of the Walker circulation due to warm anomalies in the equatorial central‐eastern Pacific during the El Niño developing summer, has striking impacts on the precipitation anomalies over the southwestern TP (Hu et al., 2021, 2022). The decreasing central Pacific La Niña accompanied by persistent cooling of SST anomalies in the equatorial Pacific leads to a strong eastern North Pacific summer monsoon, causing an anomaly in the easterly transport of water vapor from the Sea of Japan to Tibet and increased rainy season precipitation in Tibet (C. Wang & Ma, 2018).…”