Preliminary results obtained by a new Ka-band polarimetric Doppler radar of Nagoya University, Japan

A new Ka-band (34.87 GHz) polarimetric Doppler radar manufactured by Mitsubishi Electric Corporation was installed at Nagoya University (136.97E, 35.17N) in March 2014 and we have started the continuous operation using the radar since September 2014. A transmitter used by a Klystron is operated simultaneously with horizontal (H-) and vertical (V-) polarization signals. The radar are able to obtain horizontal radar reflectivity (ZH), Doppler velocity, differential reflectivity (ZDR), differential propagation phase (ΦDP), correlation coefficient between H- and V-polarization signals (ρHV), and specific differential phase (KDP). Sampling resolutions are 75 m and 0.35 deg. in the direction of the beam and azimuth, respectively. Radius of the observation range is 30 km. Data are collected at a dual pulse repetition frequency (PRF) less than 2500 Hz. We have operated with the rotation rate of the PPI scans of 1.5 rpm, which obtains three-dimensional (3D) volume scans with 12 elevation angles, and a RHI scan along west-east direction in every 10-min interval.

Data of stratiform precipitating clouds obtained on 25 November 2014 show that radar reflectivity below the melting level is critically greater than that above, however, significant bright-band do not appear around the melting level. Data of non-precipitating thick cirrus clouds whose depth between 5 and 12 km obtained on 19 September 2014 show the streak structure of high reflectivity and unevenness of the cloud bottom. The streak structure is expected to the existence of heterogeneous distribution of particle size and number concentration of ice crystals in the cirrus clouds. The unevenness of the cloud bottom suggests the existence of weak convection around the region. In the case of thin cirrus clouds obtained on 12 September, the radar detects the streak structure whose reflectivity less than -10 dBZ.

Now we develop several algorithms for the analysis of the radar data, such as the attenuation correction and checking polarimetric parameters. An X-band polarimetric Doppler radar is also installed near the Ka-band radar whose distance is less than 100 m. During the simultaneous observation period, data obtained by X-band radar will be utilized for the attenuation correction of the Ka-band radar data. Also, the comparison with the satellite radar data, such as GPM and CloudSat-CPR will be conducted.