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

O Uchino,K Shibata,Y Sasano,K Kita,M Nakazato,S Kawakami,S Takubo,T Akaho,H Okumura,T Matsunaga,T Nagai,T Sakai,T Maki,K Arai,I Morino,M Deushi,M Kajino,T Yokota,T Kawasaki

doi:10.5194/amt-7-1385-2014

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 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 (19.1 DU on average) from January to March, and increased to 26.7 DU from late April to July. From mid-July through August, ozone column amounts decreased greatly to 14.3 DU because of exchanges of continental and maritime air masses. Then in mid-September they increased again to 22.1 DU within 1−6 km, and subsequently decreased slowly to 17.3 DU, 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 volume 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 volume 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.

Highlights

Ozone is an important air pollutant that at high concentrations impacts on human health and ecosystems including crops (Parrish et al, 2012)
Ozone volume mixing ratios predicted by MRICCM2 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 DIfferential Absorption Lidar (DIAL)
With our improved DIAL system, 44 ozone profiles were observed in the 1–6 km altitude range over Saga in 2012

Summary

Introduction

Ozone is an important air pollutant that at high concentrations impacts on human health and ecosystems including crops (Parrish et al, 2012). The system’s transmitter transmits laser beams at three Stokes lines (276.2 nm, 287.2 nm, and 299.1 nm) of the SRS of carbon dioxide (CO2) with vibrational shift of 1385 cm−1 pumped by the fourth harmonic (266 nm) of a Nd:YAG laser (Nakazato et al, 2007; Seabrook et al, 2011) We used this transmitter with a coaxial receiving system with a 49 cm diameter Newtonian reflecting telescope to measure ozone profiles from a few hundred meters to about 10 km altitude. In this case, vertical profiles of the ozone number density and volume mixing ratio are plotted together with their statistical errors (precision) calculated from the lidar signal-to-noise ratios (Uchino and Tabata, 1991). The average and one standard deviation of the difference between DIAL and ozonesonde data are 14±10 % below 2 km, 6 ± 4 % for 2–7 km, and 20 ± 13 % above 7 km

MRI-CCM2

Findings

Concluding remarks