近50年中国霾年代际特征及气象成因

根据1961-2013年全国745个国家基准站的长期观测资料，分析中国霾日数年代际变化特征及可能的气象成因。结果表明:近50年来，中国霾天气主要集中在东部从华南到华北的大部分地区，霾日数呈增加趋势。秋冬两季是霾天气发生最频繁、变化最明显的两个季节。中国东部淮河以南地区秋冬两季霾日数在2000年前呈增加趋势，其后增加趋势变得较为平缓，20世纪90年代前霾日数与近地面风速呈显著负相关关系，90年代后则与大气相对湿度呈显著负相关关系，随着90年代前近地面风速减小和90年代后大气相对湿度降低，该区域霾日数表现出明显的增加趋势。中国东部从淮河到华北大部分地区秋冬两季霾日数1980年后增加趋势变得不明显，这可能与该区域近地面风速和大气相对湿度的变化趋势较为平缓有关。

Interdecadal Variation of Haze Days over China with Atmospheric Causes in Recent 50 Years

Characteristics of interdecadal variations of haze days over China and plausible meteorological causes during 1961 to 2013 are analyzed, using observations from 745 meteorological stations in China. Results show that most haze weather occurs over the east part of China from South China to North China where haze days exhibit an increasing trend especially in economically developed areas,such as North China, the Huanghuai and Jianghuai Plains. Haze days are fewer in large parts of Northeastern China and Western China, and haze days show decreasing tendency in these regions. Generally, haze days are more frequent in autumn and winter than those in spring and summer. Also, autumn and winter are seasons that variation of haze days is most significant. Haze days occur more frequently in January and December than other months. The first mode of EOF reflects a monotonically increasing trend in the east part of China. The second mode shows that the region from South China to the Huaihe River and the region from the Huaihe River to North China present opposite variation tendency of phase. Focusing on regions from South China to the Huaihe River and from the Huaihe River to North China, haze days show an increasing trend year by year over the region from South China to the Huaihe River in autumn and winter before 2000, and then the trend is smoother. In the region from the Huaihe River to North China, however, haze days change gently in recent 30 years in autumn and winter. The variation of haze days relate to surface wind speed and relative humidity. Haze days show a significant negative relationship with surface wind speed before 1990s. Haze days may be influenced by variations of east wind in the region from South China to the Huaihe River in autumn, while northeast wind in the winter. For region from the Huaihe River to North China, haze days is concerned with south wind in autumn, while haze days have nothing to do with wind in winter. The relativity between haze days and surface wind speed weakens, but haze days have significant relationship with relative humidity after 1990s. Haze days experience an increasing tendency because of the reduced surface wind before 1990s and the decrease of relative humidity after 1990s over the region from South China to the Huaihe River in autumn and winter. In comparison, haze days show moderate variations in the region from the Huaihe River to North China, which are probably related to the moderate variability in surface speed and relative humidity in autumn and winter.