Use of 315 nm Channel Data of the Sky Radiometer to Estimate the Columnar Ozone Concentration : A Preliminary Study

The sky radiometer is a ground-based instrument implemented to investigate the characteristics of not only aerosols but also clouds and water vapor. This study is the first attempt to bring this instrument in use to estimate the columnar ozone concentration (U). A method and preliminary results related to the estimation of U using the 315-nm-channel data of the sky radiometer are presented. The proposed method consists of calculating the calibration constant for direct intensity at 315 nm wavelength, F-0 (315 nm), using in situ observation data, which is an alternative of the traditional Langley method, and estimating U. The temporal values of U at Chiba, Japan for the period of January-April, 2013 were estimated, and they were compared with values observed by the ozone monitoring instrument (OMI). The agreement was satisfactory during the initial observation period; however, the values from the sky radiometer were observed to be gradually overestimated with time. The study suggests that the temporal change of F-0 (315 nm) is the important factor to be considered while estimating U values for long-term observations and that F-0 (315 nm) must be periodically determined. The study further discusses the uncertainties associated with the estimated U due to the uncertainties in the values of input parameters.