Shipboard C-band polarimetric radar onboard R/V Mirai: Outline and preliminary results

The new shipboard C-band polarimetric radar was installed on research vessel Mirai, operated by Japan Agency for Marine-Earth Science and Technology (JAMSTEC) as successor of the Doppler radar which operated for 15 years. As same as previous shipboard Doppler radar, the pointing direction of the antenna is stabilized by cancelling the ship motion in which the high-precision laser gyro detects. The polarimetric planes, which cannot be stabilized mechanically, were corrected mathematically. The radar also equipped solid-state transmitter to enable the continuous observation without frequent supply of expensive expendables.

The radar is in operation since June 2014. In its first year, the data were obtained continuously for three cruises in mid-latitude (North Pacific), Arctic Ocean, and tropics (western Pacific / eastern Indian Ocean). As an example of the captured phenomenon, the case of typhoon Phanfone in the western Pacific was examined. Phanfone was in the extratropical transition when it passed over Mirai. The radar-observed RhoHV is successfully utilized to detect the 0 degree-C height. Found spatial / temporal variations of 0 degree-C height can be estimated as a frontal structure in the lower troposphere.