Long term Total Ozone Comparisons Between Space based and Ground based Observations at 4 Sites in China

The observed total ozone differences between ground based data and available satellite products over Xianghe, Kunming, Waliguan and Longfengshan are analyzed. The absolute differences of total ozone between space based and ground based observations are-5—10 DU. And the relatives differences (RD) is—5%—4%, fitting the normal distribution of 0.05 significance. Compared with the ground based observation, the precision of TOMS (Total Ozone Mapping Spectrophotometer) version total ozone is better than that of DOAS (Differential Optical Absorption Spectroscopy). Total ozone RDs are statistically similar at Xianghe and Longfengshan where total ozone is high, while the similarity of RDs are also detected at low total ozone region Kunming and Waliguan. The regional similarities also indicate in the sensitivity validations of total ozone RDs to the SZA (solar zenith angle) and total ozone references. The integrated total ozone dataset with the ground based and TOMS as well as OMI observations in the 4 proxy sites also reflect the substantial depletion of global total ozone event around 1993. An eventual recover trend emerged in Xianghe, Kunming, and Longfengshan during 1995—1996, but the recover trend in Waliguan doesn't occur until 2001. The inter comparisons also reveal the quality information of ground based total ozone observations. For example, due to Brewer grating scratches in 2000—2006, total ozone observation from Longfengshan intends to be lower at high SZA conditions, which has been reflected in the RDs sensitivity validation to SZA. The increasing total ozone difference between Dobson#075 and OMI or SCIAMACHY products since 2007 needs further investigation.