Analysis of tropospheric ozone long-term changing trends and affecting factors over northern China
CHEN Xi;HUANG FuXiang;XIA XueQi;CAO Jing;XU XiaoBing;School of Earth Sciences and Resources,China University of Geosciences;National Satellite Meteorological Center;Guangzhou Meteorological Satellite Ground Station;Chinese Academy of Meteorological Sciences;
The tropospheric ozone is an important pollutant composition and greenhouse gas, of which the generation process is often closely related to the photochemical reaction of pollutant gases discharged by human activities, thereby leading to great influences on global climate change, human health, plant and crop growth, and so on. In this paper, long-time series of tropospheric ozone datasets for the period of 1979–2013 are used to investigate the long-term trends of the tropospheric ozone in northern China, and quantitatively assess the influences of major impact factors on ozone changes, while combining the effects analysis of tropopause height change on the column of the tropospheric ozone during the same period. From the decadal scale, it can be seen that the tropospheric ozone long-term trends in northern China over 30 years showed significant differences in the different seasons. Among them, the summer tropospheric ozone presented a growth trend with the growth rate of 1.28 DU/10 a, while the winter data showed a downward trend with the decline rate of 1.46 DU/10 a, and spring and autumn showed volatility characteristics and downward trend in their fluctuations. From the distribution of the different months of the year, it can be seen that the maximum occurred in the summer, commonly at 50 DU, followed by the mean of the spring at around 40 DU, then the mean of the autumn at about 35 DU. The winter minimum mean is around 26 DU. In northern China the major impact factors of tropospheric ozone include solar, ENSO and QBO. The influence of the solar cycle from trough to peak can generally reach 5–6 DU, the effect of precipitation is 5–6 DU, and the effect of ENSO is 1–2 DU, while that of QBO in most cases is less than 2 DU. The NCEP tropopause height data are used to analyze the northern China tropopause height variation, and the results show that there is no significant change in the northern China tropopause height from the decadal time scale, only a significant variation in the different seasons of the year. It is shown that the changes in tropopause height and tropospheric ozone are closely related, and the correlation coefficient R=0.826. The analysis showed that the tropopause height annual cycle changes had a significant impact on the annual cycle of the tropospheric ozone; however, the tropopause height did not exhibit significant decadal trends, thus having little effect on the tropospheric ozone changing trends at decadal time scale.