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

This study investigates the tropospheric and lower stratospheric 3D wind frequency spectra at Andoya, Norway (69.30 degrees N and 16.04 degrees 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) proportional to f(beta) through a least-square regression. Our results indicate that (a) the spectra of the horizontal winds follow a power law with slopes of about beta = -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 beta in the vertical wind is shallow 0 > beta > -1, which flattens with altitude.