Aircraft Studies of Horizontal and Inclined Spectra of Wind Velocity Fluctuations in the Stably-Stratified Troposphere

Abstract

In this paper, we study tropospheric wind velocity fluctuation spectra measured both along horizontal aircraft tracks over Greenland and along inclined aircraft tracks during their ascents and descents. This study is done based on the analysis of the global and long-term high-resolution dataset of meteorological parameters measured by civil aircrafts. The transition from the Nastrom-Gage spectrum with a slope of -5/3 in the horizontal scale-range of 6–200 km to a steeper part of the spectrum at shorter scales is analyzed. Based on the results of wind measurements along 82 inclined trajectories of airplanes during their ascent and descent in the troposphere, the vertical wave number spectra of wind velocity fluctuations measured along these trajectories as a function of height (hereinafter referred to as inclined spectra) were obtained. From the obtained horizontal and inclined spectra of the wind velocity fluctuations their anisotropy (the ratio of horizontal-to-vertical scale) is estimated. The obtained spectra are interpreted using models of 3-D and 1-D (horizontal and vertical) wavenumber spectra of the wind velocity fluctuations. The tropospheric vertical wave number spectra of anisotropic wind velocity fluctuations obtained from the aircraft measurements during ascents and descents (altitudes 5–10 km) are compared to the vertical wave number spectra of the wind velocity fluctuations in the stratosphere and mesosphere retrieved from the infrasound signals generated by ground-based explosions and volcanic eruptions. The general physical mechanism of formation of the fine layered structure of wind velocity for both the stably-stratified layers of the troposphere and the stratosphere-mesosphere is discussed.