Atmospheric Turbulence Determined From High-resolution Radiosonde Dataset

Turbulent flows in the lower atmosphere are important for the understanding of the dynamical processes in the lower atmosphere.Turbulence dramatically varies in the spatiotemporal domain.Therefore,a statistical analysis of the turbulent kinetic energy dissipation rate is crucial.The association between Thorpe sort method and high-resolution radiosonde datasets is interesting and makes gathering insights into the climatological distributions of turbulence possible.The present study aims to investigate the statistical characteristics of turbulence in 2-30 km altitude by analyzing numerous radiosonde datasets.The research results of present study are organized as three parts.The first part is to prove the statistical usage of Thorpe sort method in atmospheric turbulence study and predict the optimal constant value in Thorpe analysis.The second part is to presents the long-term variations of turbulence and their associations with local instabilities and gravity waves by using a high-resolution radiosonde dataset from Miramar Nas(32.8° N,117.1° W).The third part is to determine the latitudinal and topographical dependencies of turbulent flow.The main results of present study include:1.If the ratio between Ozmidov length OL and Thorpe length TL(i.e.,c~2)is a lognormal distribution,then energy dissipation rate can be simulated by the Monte Carlo method.The approximate proportionalities between the energy dissipation rates revealed by a constant c~2 and a lognormally distributed c~2 that is based on the results from Schneider et al.[2015] exist in the middle,low,and high latitudes.These results suggest that,even for a highly variable c~2,the Thorpe analysis can be statistically applied to the stably stratified free atmosphere.2.The optimal value of c~2 is 0.54 at all heights and latitudes.3.The propagating gravity waves in the lower atmosphere,especially in the middle troposphere and the tropopause regions,can reduce Ri.Therefore,enhanced turbulent mixing is expected.Other role of gravity waves in turbulent flow is that breaking waves may be occasionally transferred to turbulence.4.The spatial variabilities of turbulence above the four areas are similar to a certain extent,i.e.,a dramatic decrease in the lower free troposphere and an enhancement above the middle troposphere.5.The energy dissipation rate exhibits evident seasonal cycles at mid-latitudes and follows a lognormal distribution.6.The magnitude and variance of the energy dissipation rate can be considerably influenced by underlying terrain.