Rayleigh-Brillouin scattering profiles of air at different temperatures and pressures

TL;DR

This study measures Rayleigh-Brillouin scattering profiles of air across various temperatures and pressures, demonstrating the potential for atmospheric temperature retrieval and assessing the accuracy of the Tenti S6 model for future LIDAR applications.

Contribution

The paper provides detailed RB scattering measurements of air over relevant atmospheric conditions and evaluates the Tenti S6 model's accuracy, highlighting its use for temperature retrieval.

Findings

RB profiles measured with 1% noise level

Bulk viscosity shows an increasing trend with temperature

Tenti S6 model matches data within 2% accuracy

Abstract

Rayleigh Brillouin (RB) scattering profiles for air have been recorded for the temperature range from 255 to 340 K and the pressure range from 640 to 3300 mbar, covering the conditions relevant for the Earth's atmosphere and for planned atmospheric light detection and ranging (LIDAR) missions. The measurements performed at a wavelength of 366.8 nm detect spontaneous RB scattering at a 90 degree scattering angle from a sensitive intracavity setup, delivering scattering profiles at a 1 percent rms noise level or better. The elusive transport coefficient, the bulk viscosity, is effectively derived by a comparing the measurements to the model, yielding an increased trend. The calculated (Tenti S6) line shapes are consistent with experimental data at the level of 2 percent, meeting the requirements for the future RB scattering LIDAR missions in the Earth's atmosphere. However, the systematic 2 percent deviation may imply that the model has a limit to describe the finest details of RB scattering in air. Finally, it is demonstrated that the RB scattering data in combination with the Tenti S6 model can be used to retrieve the actual gas temperatures.