Raman/Rayleigh lidar measurements during a major stratwarm in Greenland

Abstract

Rayleigh lidar observations of atmospheric temperatures below 30 km are contaminated by the Mie backscattering from the sulphate stratospheric aerosols that normally exist between 12 and 25 km. Consequently, the fact that nitrogen Raman lidar returns for vibrational and rotational Raman backscattering are red-shifted offers the opportunity to extend the Rayleigh lidar measurements to lower altitudes by joining the two relative density profiles at a height where the Mie backscattering contamination may be ignored. This technique was applied by us previously with the aim of providing an improved means of normalizing lidar measurements of upper atmosphere densities against simultaneous balloon measurements. Because lower stratosphere temperatures below 195 °K will support the production of polar stratospheric clouds (PSC) designated as Type 2 nitric acid trihydrate (NAT) and for temperatures below the frost point, nominally 190 °K, the production of Type 1 water ice PSCs. To study the possible formation and evolution of these polar stratospheric clouds, we undertook to make measurements of temperatures in the winter Arctic with a Raman augmentation of our mobile Rayleigh lidar facility. While the results did not show any indications of the production of PSCs, the profiles did show substantial dynamic activity in connection with the progression of a major stratospheric warming.