Leibniz MMS Days 2019 - Abstract

Vierinen, Juha

Estimation of the mesospheric wind field correlation and structure functions using multistatic specular meteor radars

A method for estimating the three-dimensional mesospheric wind field covariance structure from a sparse set of specular meteor trail echo measurements is described. The measurements consist of one dimensional projections of the vector wind field measured at random points in space and time. The method for estimating the correlation function relies on cross-correlating pairs of Doppler velocity measurements, which are separated in time and space. These measurements can be used to estimate the correlation function of the mesospheric wind field at different spatial and temporal scales. The method is demonstrated using a multistatic specular meteor radar measurement data set that includes ≈105 meteor detections during a 24 hour time period. To validate the method, the results are compared with an established method for estimating horizontal mean wind. The method is also applied for estimation of high resolution temporal, horizontal, and vertical structure of the mesospheric wind. The results are compared with the expected behavior of atmospheric fluctuations at mesospheric altitudes. The temporal correlation function is used to estimate the power spectrum of mesospheric wind, which includes the semidiurnal mode and a strong peak with a 3 hour period. From the horizontal correlation function of the fluctuating wind, we estimate the structure function for the <4 hour fluctuating component and find that the spectral index is close to -5/3, which is consistent with the Kolmogorov distribution of energy within turbulence. The vertical correlation function for the fluctuating component shows that the vertical scale size of <1 hour waves is approximately 10 km for the horizontal wind components. The method described in this study expands the range of spatial and temporal scales of the mesospheric wind covariance structure that can be studied with specular meteor radars, and it may also be applied to other similar sparse and incomplete measurements of random vector fields.