Characteristics of Frequency‐Power Spectra in the Troposphere and Lower Stratosphere Over Andøya (Norway) Revealed by MAARSY

This study investigates the tropospheric and lower stratospheric 3D wind frequency spectra at Andøya, Norway (69.30°N and 16.04°E) during the years 2017–2020 obtained with the Middle Atmosphere Alomar Radar System. We produce power spectral density S(f) in a broad frequency range (3.5 days−1 > f > 1h−1). We categorize the spectra into different ranges: two frequency ranges (lower and higher than (13 hr)−1 according to the local inertial period of 13 hr), four altitude ranges (lower troposphere, middle troposphere, tropopause region, and lower stratosphere), and four seasons (spring, summer, autumn, and winter). We approximate the power law S(f) ∝ fβ through a least‐square regression. Our results indicate that (a) the spectra of the horizontal winds follow a power law with slopes of about β = −5/3 and −2 at the high and low frequency, respectively, (b) the slopes get steeper around the tropopause and seasonally during the summer (which we report for the first time), and (c) the slope β in the vertical wind is shallow 0 > β > −1, which flattens with altitude. Key Points Frequency spectra of the horizontal winds in the troposphere and lower stratosphere exhibit power laws with slopes of about −2 and −5/3 The horizontal wind slopes steepen in altitude around the tropopause and during summer (particularly at the frequency higher than (13 hr)−1) The power law spectral slopes in the vertical wind are shallower than −1 and flatten with altitude