A new India-Burma Trough Index and its Relationship with Interdecadal Changes of Precipitation over Southern China 

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  • 1. Yunnan Power Grid Co. Ltd. Transmission BranchKunming 650000YunnanChina
    2. Yuxi Power Supply Bureau of Yunnan Power Grid Co. LtdYuxi 653100YunnanChina
    3. School of Atmospheric SciencesChengdu University of Information TechnologyChengdu 610225SichuanChina

Online published: 2025-04-11

Abstract

The India-Burma TroughIBT),a semi-permanent low-pressure system situated on the southern flank of the Qinghai-XizangTibetanPlateau during the winter half-yearplays a crucial role in modulating winter and spring precipitation patterns across China. To quantitatively characterize IBT activityresearchers have proposed multiple indices from diverse methodological perspectives. While data source selection and isobaric surface choices exert limited influencesthe principal distinctions among these indices stem from their utilization of different atmospheric variablesnotably geopotential heightrelative vorticityand 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. Consequentlythis necessitates the implementation of zonal correction procedures to accurately capture the trough’s activity charcteristics and its interannual-todecadal variability. The revised index demonstrates interannual and decadal variation patterns comparable to those derived from relative vorticity and vertical velocitywhile 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 Chinawith coherent decadal-scale fluctuations observed in both parameters. This revised geopotential height-based index achieves dual objectives:(1Effectively eliminating global warming-induced isobaric surface uplift artifactsand2Maintaining clear physical interpretability by capturing the localized geo‐ potential height depression characteristic of meridionally elongated trough systems like the IBT. Notablywhile detrending methods can reduce climate changes impacts on geopotential height indicesthey may inadvertently introduce spurious weakening trends in interannual variability due to discrepancies between short-term atmospheric 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.

Cite this article

WANG Hongwu, ZHANG Jiwei, YANG Teng, LI Bingchen, ZHANG Yi, SONG Minhong, LIN Zhiqiang . A new India-Burma Trough Index and its Relationship with Interdecadal Changes of Precipitation over Southern China [J]. Plateau Meteorology, 0 : 1 . DOI: 10.7522/j.issn.1000-0534.2025.00023

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