Investigating The Temporal And Spatial Variability Of Total Ozone Column In The Yangtze River Delta Using Satellite Data:1978-2013

From 1970s, the fact that the decrease total ozone column (TOC) affected by human activities has been confirmed by many observations. The decrease of TOC bring a lot of negative impact on climate and environment and the observation of TOC became the focus of attention.Due to the lack of continuous and well-covered ground-based TOC measurements, little is known about the Yangtze River Delta. The content of this paper is the temporal and spatial variability of total ozone column in the Yangtze River Delta (YRD) from 1978 to 2013. In the study, we first convert the Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) TOC data into the same mode by format conversion, data resampling and data clipping. And then we analyze the latitudinal difference and longitudinal difference of TOC in YRD using spatial analysis method. After that we analyze the TOC variability from three time scale including long-term variation, seasonal variation and short-term variation by using least square fitting and temporal autocorrelation method.And we get the following conclusion:There is a obvious latitudinal differences of TOC in YRD. With the increasing of latitude, the mean value of TOC increases. And these variability presents a notable annual cycle of the seasons which is larger in winter or spring and smaller in summer or autumn. These differences have maximum values 13.0% in February (4.4DU/degree) and minimum values 2.8% in August. The major reason is that the Brewer-Dobson Circulation control north hemisphere mid-latitudes in winter and spring.There is also a TOC longitudinal differences in YRD. With the increasing of longitude, the mean value of TOC increases, but the longitudinal differences is much less than latitudinal. The mean gradient of longitudinal differences is only 0.3DU/degree all the year round. In addition, these longitudinal differences present a annual cycle of the seasons, ranging from 1.5% to 4.2%. The maximum values are in the late winter or early spring and the minimum values in summer. The longitudinal differences are influenced by the low value center in the Tibetan Plateau and the high value center in northeast of the China.The TOC in YRD from 1978-2013 present a downward trend. Because of the lack of data, in this paper we divided the total period into two sub-periods to analyze its long-term variability. From 1978 to 2013, the slope for the whole series is (-6.5±0.3)DU/decade. This deline trend is influenced by ozone depleting substance emitted by human activities. And the volcanic eruptions of El Chichon and Pinatubo lead to the sharp drop of TOC from 1982-1984 and 1991-1994. For 2004-2013, the decline of TOC has slowed,which is about (-1.8±0.4)DU/decade. This means after the signing of "Montreal Protocol", the measures to reduce the emission of ozone depleting substance have begun to show their effects.As for seasonal variability, the trend of TOC shows a sine distribution over the YRD, with maximum in late spring or early summer and minimum in late autunm or early winter. This variability is mainly affected by photochemical equilibrium of ozone and Brewer-Dobson Circulation.The day-to-day variability of YRD presents a notable annual cycle with maximum values in Feburary and minimum values in August or September. These variability is mainly influenced by the different frequency of weather system’s crossing in different season.The short-term system memory of TOC can be used to predict the variability of TOC in the future. The short-term system memory of YRD has a rapid drop in the first 12 days, and then decrease below the decorrelation benchmarck(1/e) at the 40th day.