Rotational vibrational-rotational Raman lidar:: Design and performance of the RASC Raman lidar at Shigaraki (34.8° N, 136.1° E), Japan

The design and the performance of the new Raman lidar of the Radio Science Center for Space and Atmosphere (RASC) at Kyoto University are presented. The system is located at (34.8degrees N, 136.1degrees E) near Shigaraki, Japan, where also one of the world largest atmospheric radars, the MU (middle and upper atmosphere) radar, is operated. Measurement parameters of the lidar are atmospheric temperature (with rotational Raman and with Rayleigh integration technique), water vapor mixing ratio (H2O Raman lidar technique), and optical particle properties. Common Raman lidar takes vibrational-rotational Raman backscatter of nitrogen 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. This modification leads to a significant reduction of measurement uncertainties. With the RASC lidar, rotational Raman signals with, to our best knowledge, unprecedented intensity can be taken by means of a high-throughput receiver. This allows not only nighttime temperature measurements with a resolution of, e.g., a few minutes near the tropopause, but made also, to our knowledge, the first daytime measurements possible.