Showing papers by "Yutaka Kondo published in 2001"

Arctic ozone loss in threshold conditions: Match observations in 1997/1998 and 1998/1999

Abstract: Chemical ozone loss rates inside the Arctic polar vortex were determined in early 1998 and early 1999 by using the Match technique based on coordinated ozonesonde measurements. These two winters provide the only opportunities in recent years to investigate chemical ozone loss in a warm Arctic vortex under threshold conditions, i.e., where the preconditions for chlorine activation, and hence ozone destruction, only occurred occasionally. In 1998, results were obtained in January and February between 410 and 520 K. The overall ozone loss was observed to be largely insignificant, with the exception of late February, when those air parcels exposed to temperatures below 195 K were affected by chemical ozone loss. In 1999, results are confined to the 475 K isentropic level, where no significant ozone loss was observed. Average temperatures were some 8°–10° higher than those in 1995, 1996, and 1997, when substantial chemical ozone loss occurred. The results underline the strong dependence of the chemical ozone loss on the stratospheric temperatures. This study shows that enhanced chlorine alone does not provide a sufficient condition for ozone loss. The evolution of stratospheric temperatures over the next decade will be the determining factor for the amount of wintertime chemical ozone loss in the Arctic stratosphere.

High-sensitivity instrument for measuring atmospheric NO2.

Abstract: We report on the development of a high-sensitivity detection system for measuring atmospheric NO2 using a laser-induced fluorescence (LIF) technique around 440 nm. A tunable broad-band optical parametric oscillator laser pumped by the third harmonic of a Nd:YAG laser is used as a fluorescence excitation source. The laser wavelength is tuned at peak and bottom wavelengths around 440 nm alternatively, and the difference signal at the two wavelengths is used to extract the NO2 concentration. This procedure can give a good selectivity for NO2 and avoid interferences of fluorescent or particulate species other than NO2 in the sample air. The NO2 instrument developed has a sensitivity of 30 pptv in 10 s and S/N = 2. The practical performance of the detection system is tested in the suburban area for 24 h. The intercomparisons between the LIF instrument and a photofragmentation chemiluminescence (PF-CL) instrument have been performed under laboratory conditions. The correlation between the two instruments is mea...