Ground-Based Millimeter-Wave Radiometer for Measuring the Stratospheric Ozone over Rikubetsu, Japan

Abstract

A millimeter-wave radiometer was installed at Rikubetsu, Japan (43.5 N, 143.8 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, Corresponding author: Tomoo Nagahama, SolarTerrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. E-mail: nagahama@stelab.nagoya-u.ac.jp ( 2007, Meteorological Society of Japan 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.

Observations of stratospheric and mesospheric O3 with a millimeter-wave radiometer at Rikubetsu, Japan

“…The operation timeline of the instrument is listed in Table 1. The details of the instrument until October 2005 are described in Nagahama et al (2007), and we present the changes that were made after October 2005. As for the receiver, a tunable SIS mixer was replaced with a sideband-separating SIS mixer (2SB mixer) made of two double sideband (DSB) mixers and two 90° hybrid couplers (Asayama et al 2004) in October 2005.…”

“…The a priori uncertainties (square roots of the diagonal elements of S a ) of the O 3 profile were assumed to be 30 % of the mixing ratios at each altitude. The uncertainty was estimated from the variability (deviation from the 30-day average) of O 3 mixing ratio in the stratosphere in a short term (Nagahama et al 2004). The off-diagonal elements of the a priori covariance matrix were set to decrease exponentially with a correlation length of 6 km.…”

“…It shifts from summer maximum in the middle stratosphere (~35 km) to winter maximum in the upper stratosphere and the lower mesosphere (~45-55 km). During winter months, the O 3 mixing ratio in the upper stratosphere might be more variable than during the other seasons because sudden stratospheric warming induces large variability of O 3 (Flury et al 2009) and the polar vortex occasionally moves toward mid-latitudes (Nagahama et al 2007). …”

“…The instrument has been tuned to the frequency of 110.836 GHz to observe the 6 1,5 -6 0,6 transition of O 3 . Nagahama et al (2007) reported O 3 observation at Rikubetsu with this instrument during the period from November 1999 to June 2002.…”

GROMOS-C, a novel ground-based microwave radiometer for ozone measurement campaigns

“…Nowadays there are a few ground-based ozone radiometers sites in the world. Most of them are gathered under the international organization NDACC (Network for the Detection of Atmospheric Composition Change) with permanent instruments located at observation stations in NyAlesund (Spitsbergen) (Palm et al, 2010), Bern (Switzerland) (Studer et al, 2013), Payerne (Switzerland) (Maillard Barras et al, 2009), Mauna Loa (Hawaii), Lauder (New Zealand) and Rikubetsu (Japan) (Nagahama et al, 2007). In addition, other ozone radiometers are located in Thule (Greenland), Seoul (Korea), Kiruna (Sweden), Moscow (Russia) and in Antarctica.…”