Identifying method of ozone enhancement and multi-scale characteristics of ozone change in the mid-upper troposphere over South China

Not only there are fewer studies on the influence of subtropical upper jet stream on the ozone distribution in the mid- and upper troposphere over South China, but also there is no comprehensive method to identify the ozone enhancement in the mid- and upper troposphere using the conventional meteorological and satellite data. Ozone enhancement and loss were observed in the mid- and upper troposphere over Lin'an, Kunming and Hong Kong on 27 and 29 March 2001 using the electric chemical cell (ECC) ozonesondes, and the upper tropospheric ozone enhances over Hong Kong on 29 March 1996 and over Lin'an on 13 April 2001. Based on the data of NCEP reanalyses and final analyses, GMS-5 water vapor imagery, the enhanced ozone source and the multi-scale characteristics of ozone change in the mid- and upper troposphere over South China are analyzed. Furthermore, the sufficient conditions of meteorological fields are proposed as follows to identify ozone enhancement in the mid- and upper troposphere over South China in springtime: dark areas in the water vapor imagery of satellite, convergent areas on the left of upper jet stream, upper frontal areas, and high PV(>= 1 PVU) areas in the mid- and upper troposphere. The results show that the enhanced ozone in the mid- and upper troposphere over South China is from stratosphere through the folding dynamic tropopause or broken thermal tropopause in the cases of Hong Kong 29 March 1996, Kunming 27 March 2001, Lin'an 29 March and 13 April 2001. For the case of Hong Kong on 27 and 29 March 2001, the enhanced ozone comes from stratosphere over midlatitudes and the low ozone is from the air mass over tropical ocean. Not only the minima and maxima of the ozone vertical distribution can indicate the multi-scale characteristic of ozone change, but also the case of Lin'an on 27 March 2001 shows that the atmospheric multi-scale circulations have an obvious impact on the vertical ozone distribution by means of the analyses of potential vorticity distribution and the GMS-5 water vapor images. The results in this paper also indicate that the intrusion of stratospheric air to the mid- and upper troposphere occurs not only in the higher latitudes but also in the lower latitudes (in this paper over Kunming and Hong Kong) over South China.