| In this study, we reconstructed haze climate data series of the past 53 years by use the visibility and relative humidity data of the 146 stations in Yangtze River Delta area (YRD) from 1961 to 2013, we also discussed the climate characteristics and change law and result reasons of haze days in YRD from both time and space scales. The main contents include the following four aspects:1) Reconstruction of haze climate data series in YRD. By using daily four times visibility (02:00,08:00,14:00 and 20:00) and weather phenomena data and daily average relative humidity data of 10 stations in Shanghai from January 1,1961 to December 31,2013, we reconstructed the history haze climate data series of 10 stations in Shanghai. Over the past 53 years, the number of haze daily recorded maximumed in Xujiahui and annual average reached 55.9d, and Nanhui and Jiading reached the least, annual average reached 7.0d, the reconstructed haze days reached the maximum in Jinshan, with an average of 38.Od, Baoshan reached the least average of 2.7d. The reconstructed haze days sequence was significantly correlated with the recorded haze days sequence at the 0.05 level in Nanhui station, but in the rest of the station the correlation between reconstructed haze days sequence and recorded haze days sequence are significantly related at the 0.001 level, suggesting that morphological changes between the reconstructed haze climate data sequence and the recorded value exited a better consistency. By using daily four times visibility data, daily relative humidity data and daily weather phenomenon datas of 146 meteorological stations in YRD during 1961 to 2013, the YRD haze climate data series was also rebuilted.2) Studies of characteristics and evolution of haze in YRD. We studied the haze temporal changes by using methods of statistic analysis in YRD, and the spatial and temporal variation of haze days in Shanghai were also analyzed. During 1961 to 2013, the number of haze days showing a overall trend of gradual increase in YRD. The number of regional haze up to date in 2013, is 46.Od, but in 1965 and 1967, it is the minimum of 1.1 d. Over the past 53 years, the haze days increased significantly with a linear trend of 7.1d per 10 years, and during 1991 to 2013, the number of haze days increased significantly at 6.5d per 10 years. During 1961 to 2013, haze days in Shanghai had an annual average of 55.5d, and they were the least in 1965, with an annual average of 0.7d. Over the past 53 years, the haze days increased in a linear trend of 6.0d per 10 years significantly, while they increased significantly in a linear trend of 4.6d per 10 years during the 1961 to 1980. During the period from 1981 to 2003. the haze days increased significantly with a linear trend of 13.4d per 10 years, and haze days showing a decrease trend after 2003.3) Studies the effect of changes of atmosphere pollution on haze. As for Shanghai over the past 11 years, haze days were mainly in Decemeber, November and January, followed by February and June, and no haze days arised in September. From the annual distribution of haze days, haze day appeared most in 2008, followed by 2007 and 2009, haze days reached the least in 2002 and 2005. Air qualities in haze day of each month were mainly slight contamination, good or slightly polluted. The haze days that air quality is excellent only appeared on January 29 in 2008 and March 15 in 2010. The haze days that moderate air quality pollution arise on November 20 and 21 in 2001, and December 23 in 2003. The haze day that moderate heavy pollution arise on December 24 in 2003. The haze with heavy pollution appeared on January 19,2007, the concentrations of PM10, SO2 and NO2 of that day were 0.513,0.1955 and 0.1232 mg/m3 respectively.4) The effect of climate and weather conditions changes on haze days. Relationships between haze days and wind speeds, wind directions, rainfall, temperature, pressure are discussed, and the connections between haze days and ground temperature inversion were analysised by using the ground temperature inversion datasat at 08 and 20 in Shanghai. Results showed that the highest frequency of haze were days with daily mean wind speed at 0.0-2.0m/s, with an average of 53.4%, followed by days with the daily average wind speed of 2.1-4.0 m/s, with the occurrence frequency of haze is 43.4%, when daily average wind speed more than 6.1 m/s, haze days did not appear. In the non-haze days, the highest frequency of daily average wind speed is 2.1-4.0m/s, with an average 63.7%, followed by the daily average wind speed of 0.0-2.0m/s and 4.1-6.0m/s, accounting for 18.8% and 16.1% of the total non-haze days respectively. We also analyzed the differences in temperature field, geopotential height, relative humidity field, vertical velocity,925hPa wind field,850hPa wind field in the haze day processes and cleaning processes, as well as the 925hPa wind changes, and meteorological fields time-elevation profile of several typical haze process. |
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