Page 264 - 《高原气象》2025年第5期

高 原 气 象 44 卷
1382

A new India-Burma Trough Index and its Relationship with Interdecadal

Changes of Precipitation over Southern China

1
1
1
WANG Hongwu ， ZHANG Jiwei ， YANG Teng ， LI Bingchen ，
1
ZHANG Yi ， SONG Minhong ， LIN Zhiqiang 3
2
3
（1. Yunnan Power Grid Co. ， Ltd. Transmission Branch， Kunming 650000， Yunnan， China；
2. Yuxi Power Supply Bureau of Yunnan Power Grid Co. ， Ltd， Yuxi 653100， Yunnan， China；
3. School of Atmospheric Sciences， Chengdu University of Information Technology， Chengdu 610225， Sichuan， China）
Abstract： The India-Burma Trough （IBT）， a semi-permanent low-pressure system situated on the southern
flank of the Qinghai-Xizang （Tibetan） Plateau during the winter half-year， plays a crucial role in modulating
winter and spring precipitation patterns across China. To quantitatively characterize IBT activity， researchers
have proposed multiple indices from diverse methodological perspectives. While data source selection and isobar‐
ic surface choices exert limited influences， the principal distinctions among these indices stem from their utiliza‐
tion of different atmospheric variables， notably geopotential height， relative vorticity， and vertical velocity
fields. The regionally mean geopotential height index of the IBT is particularly susceptible to the isobaric surface
uplift caused by global warming. Its persistent weakening trend essentially reflects the increasing geopotential
height of tropospheric isobaric surface under global warming. Consequently， this necessitates the implementation
of zonal correction procedures to accurately capture the trough’s activity charcteristics and its interannual-to-
decadal variability. The revised index demonstrates interannual and decadal variation patterns comparable to
those derived from relative vorticity and vertical velocity， while effectively mitigating the confounding effects of
climate warming on geopotential height fields. It reveals a robust correlation between IBT intensity and winter
precipitation in South China， with coherent decadal-scale fluctuations observed in both parameters. This revised
geopotential height-based index achieves dual objectives： （1） Effectively eliminating global warming-induced
isobaric surface uplift artifacts， and （2） Maintaining clear physical interpretability by capturing the localized geo‐
potential height depression characteristic of meridionally elongated trough systems like the IBT. Notably， while
detrending methods can reduce climate changes impacts on geopotential height indices， they may inadvertently
introduce spurious weakening trends in interannual variability due to discrepancies between short-term atmo‐
spheric fluctuations and long-term climate trajectories. This study highlights a critical implication that the validity
of regional mean geopotential height as a climate system metric requires rigorous verification. And the isobaric
surface rising effects by global warming must be explicitly accounted for to distinguish genuine climate system
characteristics from warming-induced artifacts.
Key words： India-Burma trough； large-scale circulation index； rising troposphere pressure； precipitation over
South China