中国能见度长期变化及区域特征分析

为找出中国不同类型观测站点能见度的变化特征及其影响因素，对中国350余个气象观测站29年（1980-2008年）的能见度观测数据进行了分析，并使用人口密度分布数据对观测站点进行分类。结果表明，我国大气能见度在1980年后呈现缓慢下降趋势，整体表现出西高东低的特征，且东部能见度逐年下降趋势显著。能见度下降地区多集中于气候湿润或人口密度较高的地区，且人口越密集，能见度恶化程度越显著，低能见度事件发生频率越高。我国西北，包括内蒙、新疆等人口密度较小、气候较为干燥的地区，其能见度呈现逐年好转的趋势，这可能与我国北方地区沙尘暴次数减少及强度减弱有关。我国华南能见度下降幅度最为显著，人为经济生产活动可能是造成这一现象最主要的原因，而我国华北和华东的能见度变化的区域协同性正逐渐增强，从一个侧面反映了该地区所面临的区域性污染加重的现象。

Analysis of Regional Characteristics and Long-Term Variations of Visibility in China

An analysis of visibility in China from 1980 to 2008 was conducted based on 29 years’ data that was collected from over 350 meteorological observation stations. In order to find out the trends and influencing factors of visibility from different areas, grid-based population density was also used to classify different types of stations. Results show that visibility decreased steadily after 1980, especially in Eastern China. This kind of decrease usually happened in areas that have high population density and relative humidity (RH). The amplitude and frequency of visibility decline have a good relativity with the population that surrounded the observational station. However, results of Northwest China shows an increase in regional visibility, especially in the areas with a relatively low RH and low population, such as Inner Mongolia and Xinjiang. This might be caused by the decrease in frequency and intensity of sand storm in recent years. The decrease of visibility in South China is the most significant, which might be caused by economical production activities. The regional correlations of visibility between different observational sites showed an obvious increase in Northern and Eastern China, which reflects the aggravation of regional pollution in these areas.