Vertical wind profiling from the troposphere to the lower mesosphere based on high-resolution heterodyne near-infrared spectroradiometry

Abstract

We propose a new technique of remote wind measurements based on Doppler analysis of a CO2 absorption line in the 1.605 µm overtone band measured in the direct Sun observation geometry. Heterodyne spectroradiometric measurements of the solar radiation passing through the atmosphere provide an unprecedented spectral resolution up to λ/δλ∼6×107, with a signal-to-noise ratio of more than 100. The shape of the individual rotational line profile provides an unambiguous relationship between the offset from the line center and the altitude at which the respective part of the line profile is formed. Therefore, an inverse problem may be posed in order to retrieve the vertical distribution of wind because with retrievals the vertical resolution is compromised by a spectral resolution and the signal-to-noise ratio of the measurements. A close coincidence between the measured and synthetic absorption line is reached, with retrieved wind profiles between the surface and 50 km being in good agreement with reanalysis models. This method may pose an alternative to widely employed lidar and radar techniques.