中文摘要：

利用1998--2008年广东省广州、东莞和增城的常规气象资料及2004年6月10日-2008年12月30日 Micaps3．0的K指数、沙氏指数和L指数资料，重点分析了这三个地方10—12月的灰霾天气变化特征。研究结果表明，增城的能见度比例主要集中在大于10km的范围内，空气质量最好，东莞的空气质量最差。广州和东莞10-12月的能见度等级百分比分布形态类似，轻微灰霾天气所占频率较大，其中10月占的比例最高。并提出垂直交换系数试图对污染物的垂直输送能力进行评估，进而尝试对灰霾天气进行预报。结果表明当垂直交换系数小于15000时，城市容易出现灰霾天气，反之则说明该地的空气质量较为良好。

英文摘要：

Based on the data from the conventional weather stations in Guangzhou, Dongguan and Zengcheng during 1998--2008 and the Kindex, Sindex, Lindex from Micaps 3.0 during 2004--2008, the occurrence frequencies of haze in the three regions are analyzed. In our results, the air quality of Zengcheng, having visibility higher than 10 km, is the best while that of Dongguan is the worst. Guangzhou and Dongguan show similar patterns on the percentage distributions of visibility. They are primarily in light pollution which has the greatest occurrence in October. Following Wu et al. where the Vector Sum Technique was used in the assessment of horizontal transmission capacity, this paper attempts to use the vertical exchange index to evaluate the vertical transmission capacity and tries to predict haze. Our results indicate that haze is likely to happen when the vertical exchange coefficient is smaller than 15,000. Otherwise, it is a high visibility day.