Abstract
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.
Highlights
In spite of the tremendous progress in remote sensing during the last decades, atmospheric dynamics still remain hard to assess by direct measurements
Thermal profiles based on the NCEP/NCAR reanalysis were adopted for the radiative transfer calculations as well
Reanalysis data with a horizontal resolution of 1 km and 37 layers in the vertical were interpolated to the location of the instrument seen above, while their lateral variations along the line of sight during Sun observations were neglected
Summary
In spite of the tremendous progress in remote sensing during the last decades, atmospheric dynamics still remain hard to assess by direct measurements. The authors argue that in the stratosphere and lower mesosphere passive high-resolution spectroradiometry in the microwave remains one of the most effective techniques of direct wind monitoring. This provides heterodyne spectroscopy information about the wind field in the Earth’s atmosphere and in the atmospheres of other planets. By taking advantage of passive observations capabilities of sounding remote objects at arbitrary distances, high-resolution heterodyne spectroscopy in the microwave and mid-infrared spectral ranges has provided an opportunity to measure winds in the atmospheres of Venus, Mars, and Titan by means of ground-based telescopes (Kostiuk and Mumma, 1983; Sornig et al, 2012). High-resolution spectroscopic studies with traditional echelle or Fabry–Pérot spec-
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