Study of Atmospheric Dynamics With the new Rotational Raman Lidar of RASC at Shigaraki

*Andreas Behrendt[1] ,Takuji Nakamura [1]
Michitaka Onishi [1],Toshitaka Tsuda [1]
Radio Science Center for Space and Atmosphere, Kyoto University[1]

The new Raman lidar of RASC is a five channel system optimized for the study of atmospheric dynamics in the upper troposphere and the stratosphere. In the upper troposphere and stratosphere, the system measures the atmospheric temperature profile with rotational Raman technique. In heights above 30 km heights where background aerosols are present, another technique, Rayleigh integration lidar, is deployed. In addition, the water vapor mixing ratio and, independently, the particle extinction and the particle backscatter coefficient are detected (rotational Raman technique). The system was set up at (34.8 deg N, 136.1 deg E) near Shigaraki where also the MU (middle and upper atmosphere) radar is located. We will discuss the benefits of the new RASC Raman lidar for the study of atmospheric waves and dynamics and present first measurements.

The new Raman lidar of the Radio Science Center for Space and Atmosphere (RASC) at Kyoto University is a five channel system optimized for the study of atmospheric dynamics in the upper troposphere and the stratosphere. The lidar transmitter is frequency-doubled Nd:YAG laser with 30 W output power at 532 nm. For the detection of the backscattered signal a Cassegrain telescope with a diameter of 0.82 m is used. Detection channels are for the elastic backscatter signal from lower and higher altitudes, two rotational Raman signals with opposite temperature dependency, and a water vapor Raman signal. In the upper troposphere and stratosphere, the system measures the atmospheric temperature profile with rotational Raman technique. Rotational Raman lidar gives the temperature without external assumptions and is the only lidar technique which is unperturbed by the presence of cloud or aerosol particles. With the RASC lidar, rotational Raman signals with, to our best knowledge, at present highest intensity can be taken. This allows nighttime temperature measurements with a resolution of, e.g., 300 m with a few minutes in 10 km height, and made even the first daytime rotational Raman measurements possible. In heights above 30 km, another technique, Rayleigh integration lidar, is deployed. This method leads to higher resolution data than rotational Raman lidar but is perturbed in heights where background aerosols are present. As the upper limit for deriving rotational Raman data is near the stratopause, there is an altitude range where we can compare temperature data of both techniques. In addition to temperature, our system measures the water vapor mixing ratio (Water vapor Raman lidar technique) and, independently, the particle extinction and the particle backscatter coefficient (rotational Raman technique). Commonly, Raman lidar uses the vibrational-rotational Raman backscatter signal as a reference signal. In contrast to this, our system makes use of the approximately 10-times stronger pure-rotational Raman signals for deriving both atmospheric temperature and a temperature independent Raman reference signal. The system was set up at (34.8 deg N, 136.1 deg E) near Shigaraki, Japan, where also the MU (middle and upper atmosphere) radar, one of the world largest atmospheric radars, is located and allows simultaneous radar lidar measurements. We will discuss the benefits of the new RASC Raman lidar for the study of atmospheric waves and dynamics and present first measurements.