渤海气溶胶时空分布研究

TEMPORAL AND SPATIAL DISTRIBUTIONS OF AEROSOLS OVER THE BOHAI SEA

利用2003—2008年在渤海所测的212组气溶胶数据,研究了气溶胶光学厚度(AOT)、浑浊度系数(β)和ngstrm指数α的时空分布规律,并初步探讨了气溶胶特征参数之间的关系。结果表明,在时间分布方面,渤海气溶胶光学厚度、浓度和粒径尺度在一天中的变化比较小,中午AOT较大,10点左右AOT较小。从6月份到9月份,AOT、β和α的范围和均值均呈下降趋势;3月份AOT、β和α均明显小于六、8、9月份的对应值。离岸25km之内的大部分地区,AOT随离岸距离的增大而减小;但25km以外,气溶胶变化没有规律。比较而言,气溶胶AOT和β变化比较一致。浑浊度系数(浓度因子)β比ngstrm指数(尺度因子)α对气溶胶光学厚度AOT的影响更明显,AOT和β的关系可采用一阶线性回归方程表示。

Aerosol optical thickness （AOT） data between 2003 to 2008 obtained using a ship-based multiband sun photometer were taken to study the temporal and spatial distributions and the influencing factors of AOT, turbidity coefficient （fl）, and Angstrom exponent （a） over the Bohai Sea. We obtained a total of 212 datasets from eight cruises and two fix-point measurements. There were 72 datasets in 2003, 21datasets in 2004, 98 datasets in 2005, and 21 datasets in 2008. Intra-day variations of AOT,β, and a were inconspicuous. The mean values and ranges of AOT,β, and α decreased from June to September. The values of AOT,β, and a in June, August and September were larger than those in March due to smog, sandstorm, and ocean moisture. In most areas within 25 km offshore, AOT and/3 decreased with increasing distance from shore. However, the variation of a did not show a clear trend. Over the Bohai Sea, the influence of β on AOT was more significant than a. The relationship between AOT and/3 was described by AOT = 2.52×β＋ 0.07 when a is greater than 0.8, and he relationship became AOT = 1.20×β＋ 0.16 when a is smaller than 0.8. We classified the aerosols into two types based on whether a was greater than 0.8. The influence of small changes in aerosol particle size on AOT may be ignored for certain types of aerosols.