High-Order statistics of wiNDs in the lower and middle Atmosphere (HONDA)

• Applicants: Victor Avsarkisov, Ph.D.; Professor Jorge Chau, Ph.D., since 8/2025
• Subject Area: Atmospheric Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552554225

The highly nonlinear, stochastic, and dissipative (disordered) geophysical flows, like those in the atmosphere and ocean, are the subject of turbulence theory. These features strongly influence the small-scale dynamics from centimeters to several hundreds of meter scales and significantly affect larger meso- and synoptic scales, typically associated with wave dynamics. A vivid example of the latter is observed in the power spectrum of mesoscale horizontal wind observations, which behave statistically similar to meter scales, matching the predictions of classic 3D isotropic turbulence, as found in the seminal 1984 work by Nastrom and Gage. This finding created the need for novel turbulence theories, that could offer an alternative to the conventional gravity waves explanation, to understand the physics behind the mesoscale dynamics in geophysical flows, such as stratified turbulence (ST) theory. A powerful exploration tool of the ST theory is the analysis of high-order statistics of state variables that characterize the mean flow behavior. In particular, the structure function (SF), which synthetizes measurements of the same parameters at different times and positions on a single value, by means of ensemble averages estimation. However, a key limitation to studying the winds’ mesoscale dynamics by means of the estimation of high-order SFs at various atmospheric altitudes, is the lack of proper measurement capabilities that can map horizontal mesoscales with high enough resolution, and continuously in time. In the Mesosphere and Lower Thermosphere (MLT) region in particular, multistatic specular meteor radar systems (SMRs) have been recently proven to fulfill these requirements. In this project, we devise two main lines of work. The first one is the extensive analysis and characterization of second-order SFs of horizontal mesoscale winds from multistatic SMRs observations in the MLT region. We want to assess the validity of the horizontal isotropy property and evaluate its effects on the dynamics of rotational and divergent modes. Measurements at middle and high latitudes are available for use on these tasks. The second line of work is the implementation of winds high-order SFs beyond second order, using MST radar wind data from a single location. Employment of the Taylor approximation method will facilitate the exploration of spatial displacements, obtained from temporal lags. The method will be implemented using winds in the upper troposphere and lower stratosphere region and then extended to the mesospheric winds. The findings of this project will shed light on the differences and similarities in the statistical behavior of mesoscale winds at different atmospheric altitudes. In addition, they will help to validate the underlying physical mechanisms and will play a crucial role in the future parameterization strategies of the mesoscale dynamics and accompanying dynamical processes, such as isopycnal turbulent mixing and horizontal intermittency.

• DFG Programme: Research Grants
• International Connection: Japan, Norway
• Cooperation Partners: Dr. Njal Gulbrandsen; Dr. Satonori Nozawa; Professor Dr. Masaki Tsutsumi; Professor Dr. Juha Vierinen
• Ehemaliger Antragsteller: Dr. Facundo Leandro Poblet, until 7/2025