Equatorial Wave Expansion of Instantaneous Flows for Diagnosis of Equatorial Waves from Data： Formulation and Illustration

• Published in: Advances in atmospheric sciences Vol. 34; no. 10; pp. 1219 - 1234
• Main Authors: Barton, Cory, Cai, Ming
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01-10-2017; Springer Nature B.V; Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, Florida, 32306, USA; Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, Florida, 32306, USA
• Subjects: Advection; Amplitude; Atmospheric Sciences; Biennial; Cylinders; Data; Earth and Environmental Science; Earth Sciences; Equatorial waves; Geophysics; Geophysics/Geodesy; Illustrations; Meteorology; Methods; Ocean waves; Original Paper; Quasi-biennial oscillation; Shallow water; Solutions; Spatial filtering; Stratosphere; Waves; Zonal winds; 公式; 动态约束; 图解; 抛物柱面; 时间序列; 瞬时流量; 诊断; 赤道波; 即时波动; 赤道平面浅水模式; channel shallow-water model; Equatorial wave expansion; 赤道波展开; Instantaneous flows; equatorial; equatorial β-channel shallow-water model
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/s00376-017-6323-z

This paper presents a method for expanding horizontal flow variables in data using the free solutions to the shallow-water system as a basis set. This method for equatorial wave expansion of instantaneous flows（EWEIF） uses dynamic constraints in conjunction with projections of data onto parabolic cylinder functions to determine the amplitude of all equatorial waves.EWEIF allows us to decompose an instantaneous wave flow into individual equatorial waves with a presumed equivalent depth without using temporal or spatial filtering a priori.Three sets of EWEIF analyses are presented. The first set is to confirm that EWEIF is capable of recovering the individual waves constructed from theoretical equatorial wave solutions under various scenarios. The other two sets demonstrate the ability of the EWEIF method to derive time series of individual equatorial waves from instantaneous wave fields without knowing a priori exactly which waves exist in the data as well as their spatial and temporal scales using outputs of an equatorial β-channel shallow-water model and ERA-Interim data. The third set of demonstrations shows, for the first time, the continuous evolutions of individual equatorial waves in the stratosphere whose amplitude is synchronized with the background zonal wind as predicted by quasi-biennial oscillation theory.