Raman lidar measurements for boundary layer gradients and atmospheric refraction of millimeter-wave signals

摘要

The atmospheric boundary layer is typically characterized by a higher water vapor content and higher temperature than the free troposphere above it. Its height increases as the size of convection cells grow during the morning due to surface heating, stabilizes during the day, and it collapses as the energy input decreases in the evening. The marine boundary layer emphasizes these aspects. The large temperature gradients, humidity gradients and shear at the top of the boundary layer impact several processes, such as changes in both propagation properties as a function of wavelength and aerosol size distributions. We use Raman lidar to measure the gradients, and investigate several data inversion techniques to determine the best approach to obtain a high accuracy, for high SNR profiles of these gradients. Methods include anisotropic averaging between height and range, and averaging only to the level required for a specific target SNR. Examples that benefit from different time and range averaging will be given. The methods for gradient calculations and the interaction with pre- or post-averaging are also investigated. We model the impact of gradient-profile measurement from errors in the refraction of radar beams as a measure of quality requirements.