Long-Term Sodar Observations in Moscow and a New Approach to Potential Mixing Determination by Radiosonde Data

Abstract

The experimental data about thermal stratification of a low layer of atmosphere, received by the sodar sounding and direct measurements simultaneously, are summarized and discussed. The conclusion was made that sodar records of small-scale turbulent structures can be efficiently explained in terms of a thermal stratification type. The statistics of the thermal stratification in the lowest 800-m air layer are presented by the data of long-term sodar observations during 10 years at Moscow University, which were analyzed separately per hour. According to these data, the climatology of inversions, thermal convection, and weak-stable stratification is described. The mixing layer height, estimated by margins of turbulent structures on sodar records, was analyzed and compared with the one derived by traditional Holzworth method using radiosonde measurements. Climatology of the mixing-layer height in Moscow by the sodar data, as well as its variations due to synoptic effects, is discussed. A new approach is the usage of integral parameters (e.g., the instability energy) instead of heights to determine the potential mixing more precisely. This method allows us to eliminate errors of the height determination, when the temperature profile and dry-adiabatic line are close to each other. Moreover, instability energy in any case represents more realistic estimations of mixing because inertial lifting was taken into account.