Statistical parameters of the spatiotemporal variability of the wind direction in the surface layer

Abstract

Multipoint measurements of wind direction were carried out during the expedition of the Institute of Atmospheric Physics, Russian Academy of Sciences (IPA RAS), in Tsimlyansk in 2012. Spatial correlation functions for the transverse direction and temporal correlation functions for the longitudinal direction are plotted under stable and unstable stratification of the atmosphere. The longitudinal correlation radius is much higher than the transverse one, and radii in daytime realizations are larger than in nighttime. To determine the stratification conditions, an ultrasonic anemometer–thermometer was used. Autospectra of wind direction fluctuations were plotted. They include long segments of power dependence on the frequency. The spectral correlation coefficients of variations in the wind direction versus intersensor distance in the transverse direction are also calculated. A set of fast-response thermometers was used in the experiment. They allowed temperature mapping, i.e., plotting the time variations in the isothermal surface altitude. That analysis was also applied to visualization of the spatiotemporal variability of wind direction. The resulting data were used for planning the helicity measurements in the Tsimlyansk expedition in 2014.