Comparing wavelet and Fourier perspectives on the decomposition of meridional energy transport into synoptic and planetary components

• Published in: Quarterly journal of the Royal Meteorological Society 2020-07, Vol.146 (731), p.2717-2730
• Main Authors: Heiskanen, Tuomas, Graversen, Rune Grand, Rydsaa, Johanne Hope, Isachsen, Pål Erik
• Format: Article
• Language: English
• Subjects: Arctic amplification; Arctic climates; Arctic temperatures; Arctic zone; Climate change; Cyclones; Decomposition; Energy; Energy transport; Fysikk: 430; Ice cover; latent heat; Matematikk og Naturvitenskap: 400; Mathematics and natural science: 400; Physics: 430; Planetary waves; Polar environments; synoptic waves; Transport; VDP; wave decomposition; wavelets; Waves
• ISSN: 0035-9009; 1477-870X; 1477-870X
• DOI: 10.1002/qj.3813

The Arctic region shows some of the world's most significant signs of climate change; for instance, a negative trend in summer sea‐ice cover of around 15% per decade and Arctic amplified surface‐air warming that is three times the global average. The atmospheric energy transport plays an important role in the Arctic climate. Recently a Fourier‐based method for studying the atmospheric energy transport contribution by planetary‐ and synoptic‐scale waves has been proposed. Recent studies based on this method show that planetary waves contribute more than synoptic waves to the atmospheric energy transport into the Arctic. However, this Fourier method suffers from being incapable of resolving spatially localized systems such as cyclones. Here an attempt to evaluate this problem is presented by applying the method on synthetic and reanalysis data. In addition, an alternative method based on a wavelet decomposition is proposed and compared with the Fourier‐based method. The wavelet method is based on localized basis functions which should be capable of resolving these localized systems. The wavelet method shows an impact of synoptic‐scale transport on Arctic temperatures which is not captured by the Fourier method, whilst the planetary‐scale effect of both methods appears similar. Two methods for decomposition of atmospheric energy transport are evaluated and compared. The new wavelet method seems to capture the effects of synoptic‐scale transport on Arcitc temperatures better than does the Fourier method. The effect of planetary‐scale transport found in previous studies is still present in both methods.