Ground-based millimeter-wave radiometer for measuring the stratospheric ozone over Rikubetsu, Japan

A millimeter-wave radiometer was installed at Rikubetsu, Japan (43.5 degrees N, 143.8 degrees E) in March 1999, to monitor the vertical distribution of ozone and temporal ozone variations in the stratosphere. Since November 1999, we have been monitoring vertical profiles of the ozone mixing ratio in the altitude range from 22 to 60 km, with measurements at 2-km altitude intervals. The systematic error was estimated to be 10%-15% positive above 28 km, and the total random error to be 5%-21%. Comparisons of the Rikubetsu radiometer data with ozone sondes at Sapporo, and HALOE show that the ozone-mixing-ratio data, between 22 and 32 km, agree within the calculated 10% systematic error. On February 17, 2001, temporary ozone decreases of 37% and 15% at 22 and 30 km were found, respectively, when the potential vorticity at 550 K and 800 K increased. Suggesting that the ozone decrease may have been due to the arrival of a different airmass. During this event, the temporal variation of the ozone mixing ratio was clearly detected with small scatter, indicating that the Rikubetsu radiometer measurements have sufficient precision and time resolution to detect such short-term variations of stratospheric ozone.