DIAL measurement of lower tropospheric ozone over Saga (33.24° N, 130.29° E), Japan, and comparison with a chemsitry-climate model

Abstract

Abstract. We have improved an ozone DIfferential Absorption Lidar (DIAL) system, originally developed in March 2010. The improved DIAL system consists of a Nd:YAG laser and a 2 m Raman cell filled with 8.1 × 105 Pa of CO2 gas which generate four Stokes lines (276, 287, 299, and 312 nm) of stimulated Raman scattering, and two receiving telescopes with diameters of 49 and 10 cm. Using this system, 44 ozone profiles were observed in the 1–6 km altitude range over Saga (33.24° N, 130.29° E) in 2012. High ozone concentration layers were observed at around 2 km altitude during April and May. Ozone column amounts within the 1–6 km altitude range were almost constant from January to March, and increased from late April to July. From mid-July through August, ozone column amounts decreased greatly because of exchanges of continental and maritime air masses. Then in mid-September they increased again within 1–6 km, and subsequently decreased slowly, becoming almost constant by December. The Meteorological Research Institute's Chemistry-Climate Model version 2 (MRI-CCM2) successfully predicted most of these ozone variations with the following exceptions. MRI-CCM2 could not predict the high ozone-mixing ratios measured at around 2 km altitude on 5 May and 11 May, possibly in part because emissions were assumed in the model to be constant (climatological data were used). Ozone-mixing ratios predicted by MRI-CCM2 were low in the 2–6 km range on 7 July and high in the 1–4 km range on 19 July compared with those measured by DIAL.