Measurement of tropospheric O₃, SO₂ and aerosol from a volcanic emission event using new multi-wavelength differential-absorption lidar techniques

Abstract

We present measurements of tropospheric O₃, SO₂ and aerosol from a volcanic emission event using new multi-wavelength differential absorption lidar (DIAL) techniques that enable us to remove the mutual effects between O₃ and SO₂ from the raw measurements. The aerosol extinction coefficient is retrieved directly from the lidar return signal at the “off” wavelength and is used to estimate aerosol effects on O₃ and SO₂measurements. Null error, statistical error, and absorption cross-section error are also analyzed. The O₃ and SO₂ concentrations at height between 1000 m and 2000 m for a volcanic event on September 10, 2001 were about 20 ppb and 10–35 ppb, respectively, with an error less than 10 ppb. The measured SO₂ concentration was much higher than the normal SO₂ background value (∼1 ppb) in the troposphere. We also measured O₃ concentrations from 13 December 2000 to 06 January 2001 and investigated O₃ diurnal variation during a 24-hour period on November 24, 2000. A high O₃ concentration of about 250 ppb was observed in late December 2000.