南疆盆地沙尘气溶胶光学特性及我国沙尘天气强度划分标准的研究

依据气溶胶光学厚度测量原理,利用布设于塔里木盆地腹地塔中和盆地西南边缘和田气象站的2部CE318自动跟踪太阳光度计于2002年6月至2003年11月期间的探测结果,结合地面气象实测资料,分析了南疆盆地大气气溶胶的光学特性。同时结合我国已有的沙尘气溶胶光学特性的研究成果,初步提出了依据气溶胶光学厚度判断沙尘天气强度的标准。结果表明:塔中、和田气溶胶光学厚度随波长的增大多呈现减小趋势,塔中个别季节有些例外;2站气溶胶光学厚度的日变化基本保持对称的抛物线形,在春、夏季尤为明显;Angstrom浑浊度系数β的拟合曲线显示β随能见度增大而减小,波长指数α随能见度的变化趋势说明弱沙尘天气下,大气中主要弥漫着小粒径的气溶胶颗粒,而强沙尘天气则以大粒径为主;沙尘气溶胶光学厚度随晴空、浮尘、扬沙、沙尘暴依次增加;沙尘天气发生时,气溶胶光学厚度的临界值基本为晴空值的两倍,沙漠地区气溶胶光学厚度≥1.1206,北京≥0.3174。而发生沙尘暴的阈值则有很大不同,沙漠区气溶胶光学厚度至少 > 3.0,北京由于大气污染等因素,其判断沙尘暴发生的阈值为1.9982。另外笔者认为AOD与水平能见度之比值能够较全面地考虑水平和垂直两个方向的要素变化,衡量沙尘天气强度更具有合理意义,值得更深一步的探讨。

Research on Dust Aerosol Optical Properties in South Tarim Basin and Classification of Different Dusty Weather in China

Two sets of sun photometer CE318 were separately located in Tazhong meteorological station in the middle of Tarim basin and Hetian station in the south of the basin, they were used to monitor aerosol from Jun., 2002 to Nov., 2003. Based on the retrieval principles of aerosol optical property and combination with surface observational data, some interesting results and elementary classification criteria of different dusty weather according to aerosol optical depth (AOD) had been obtained and were presented as the following.The AOD at Hetian and Tazhong mainly decreased inversely with the growth of wavelength throughout the year except for Tazhong in spring, autumn and winter. At the same time, the diurnal variation curve of AOD at the two stations showed a symmetry parabola in each season, especially obvious in spring and summer. The values of AOD at Tazhong and Hetian were relatively high during summer half-year and low in Oct. and Dec. The simulated curve of Angstrom turbidity parameter β varying with visibility indicated that they varied in a contrary way and concentration of aerosol particles was high under heavy dusty weather condition. It was proved by the relation between wavelength index α and visibility that radius of large number of particles under heavy dusty weather was bigger than that of the light. The classification standard of different dusty weather was suggested as below: when AOD was higher than or equal to1.1206, it implied that dusty weather was likely to occur; if AOD≥3.0, sandstorm will take place. The aforementioned classification standards are suitable for desert areas while unsuitable for city such as Beijing where the air pollution is very severe. The two threshold values in Beijing are 0.3174 and 1.9982, respectively. In addition, the authors considered that the ratio of AOD to visibility could roundly reflect the factor change in both horizontal and vertical directions, so it was reasonable to measure the intensity of dusty weather.