大气科学学报2025，Vol.48Issue(2)：312-327,16.DOI:10.13878/j.cnki.dqkxxb.20240407002
非线性阻塞指数的定义与应用
Definition and application of nonlinear blocking index
摘要
Abstract
Atmospheric blocking is a significant large-scale anticyclonic circulation system in midlatitude,charac-terized by prolonged duration beyond synoptic timescales and strong nonlinearity.Blocking events often occur at the exit of jet stream,exerting substantial meteorological impacts such as cold surges,heat waves,and flooding,and pollutants stagnation,both locally and downstream.Understanding blocking dynamics is thus of critical scien-tific and practical importance.Since the 1950s,extensive observational and statistical studies have been conducted to characterized blocking patterns,leading to the development of multiple detection indices.These indices generally fall into two main types:one capturing the meridional gradient reversal of the zonal wind anomalies at latitude of the eddy-driven jet,and the other quantifying the anomalous amplitude of the large scale circulation.However,discrepancies in blocking frequency,location,and intensity due to index-specific sensitivities pose chal-lenges for both observational and simulation studies.In this study,we introduce the instantaneous blocking index(IBA)formulated within the anti-cyclonic local finite-amplitude wave activity(ALWA)framework.As a nonlin-ear diagnostic based on quasi-geostrophic potential vorticity(QGPV),IBA effectively quantify the polar displace-ment of QGPV relative to the eddy-free reference state,while maintain as inverse correlation with the spatial-tem-poral variability of the eddy-driven jet.Consequently,IBA integrates the key attributes of conventional blocking in-dices,capturing both westerly flow reversals and wave amplitude anomaly.Furthermore,it addresses limitations of existing indices by accurately characterizing jet variability,and prevents misidentification of unrelated large-scale systems,such as cut-off low,weak trough,and subtropical or subpolar highs.Most importantly,IBA possesses in-trinsic dynamical significance which can be used to quantify the blocking variability directly through the LWA budget.Statistical analysis of IBA for winter blocking over North Atlantic and Urals reveals a significant increase in Ural blocking frequency and duration since 1990.On interannual timescale,North Atlantic blocking exhibits a sig-nificantly negatively correlated with the NAO(North Atlantic Oscillation),with increased frequency,intensity,and lifespan during the negative NAO period.Similarly,Ural blocking shows negatively correlated with EA/WR(East Atlantic/West Russia)and ENSO(El Niño-Southern Oscillation),with higher frequency during negative EA/WR and negative La Niña phases,and extended lifespan during negative EA/WR phase.These teleconnections correspond to more intense evolution of trough/ridges and intensified cold air activity over East Asia. This study represents a fundamental application of ALWA in describing the strongly nonlinear atmospheric system such as blocking.This nonlinear dynamical framework offers significant advantages for quantifying blocking dynamics and variability.Furthermore,by utilizing its budget,it allows for quantifying the internal dy-namical processes,diabatic heating effects,wave-breaking dissipation,and other nonconservative processes in the further research.关键词
大气阻塞/阻塞动力学/局地有限振幅波作用量/长期变率/涡旋驱动流Key words
atmospheric blocking/blocking dynamics/local finite-amplitude wave activity/long-term variability/eddy-driven jet引用本文复制引用
汪梦凌,孔海妹,李银娥..非线性阻塞指数的定义与应用[J].大气科学学报,2025,48(2):312-327,16.基金项目
湖北省自然科学基金青年项目(2023AFB541) （2023AFB541）
湖北省气象局青年基金项目(2023Q01) （2023Q01）
湖北省气象局科技发展基金项目(2021Z02) （2021Z02）
