Abstract
This study calculated the Thorpe scale, thickness of turbulent layer, turbulent kinetic energy dissipation rate, and turbulent diffusion coefficient based on the Thorpe method using a set of near-space high-resolution radiosonde data in northwest China, and a case study was conducted to analyze the large-scale turbulent layer in the middle stratosphere. The results showed that the most turbulent layers exist near from the middle and upper troposphere to the tropopause region, accounting for 44.0% of the total turbulence, and the largest Thorpe scale and thickness of turbulent layer also appear in this altitude range. In addition, affected by the large-scale turbulence near the tropopause, the calculated turbulent energy dissipation rate and diffusion coefficient also have maximum values at this altitude, which are 0.003 m2s−3 and 6.94 m2s−1, respectively. By analyzing the meteorological elements, it is found that there is an obvious correlation between precipitation and large-scale turbulence in the stratosphere. When the precipitation occurs, the corresponding two sets of radiosondes detected larger-scale turbulence layers in the middle stratosphere.
Highlights
Fluid motion of the atmosphere can be divided into two basic forms, laminar and turbulent flow (Riveros and Riveros-Rosas, 2010)
The Thorpe method has been considered feasible in turbulence detection (Sunilkumar et al., 2015; Martini et al., 2017)
A group of sounding balloons released in Northwest China in January 2018 were analyzed from two aspects: 1) distribution of Thorpe scale and turbulence thickness; 2) distribution and general trend of turbulent kinetic energy dissipation rate and turbulent diffusion coefficient
Summary
Fluid motion of the atmosphere can be divided into two basic forms, laminar and turbulent flow (Riveros and Riveros-Rosas, 2010). As an important form of the atmospheric motion, turbulence can lead to a certain random overturn and irregular fluctuation in temperature, air pressure, and humidity of each layer (Fritts et al, 2012; Sharman et al, 2012). In the stratified stable atmosphere, when the wind speed and wind shear increase to a certain degree, the gravity wave (Kelvin-Helmholtz wave) becomes unstable in shear and cannot maintain the stable state before, so it breaks into turbulence of different scales, and the kinetic energy is converted into turbulent energy. Case Analysis of Turbulence troposphere, thermal convection caused by uneven surface heating and Kelvin-Helmholtz instability are important sources of turbulence (Fritts and Werne, 2000). Thermal convection, latent heat release, strong wind shears, and other factors produce turbulent layers of different scales, causing the atmospheric elements inside the turbulence to mix in different degrees. How to detect turbulence more accurately is of great significance to better understand the mechanism of turbulence action on matter and energy in the atmosphere as well as the spatial and temporal distribution and variation of turbulence
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