中国大地形东侧霾空间分布“避风港”效应及其“气候调节”影响下的年代际变异

“Harbor” effect of large topography on haze distribution in eastern China and its climate modulation on decadal variations in haze

研究发现中国区域霾日空间分布的大地形影响与季节特征显著,在西风带背景下高原大地形东侧背风坡可构成＂避风港＂效应,其可能是中国东部区域霾日高频区域性分布重要的影响因素之一;中国区域冬季为霾日高频时段,春、夏、秋季大部分区域为霾日数低频区,但近10年大气污染物排放持续加剧,中国东部霾高发时段由冬季延伸至春、秋、夏季,其呈现出大气环境恶化的＂强信号＂特征.虽然中国区域霾日数年际变化趋势主要依赖于污染源排放程度,值得注意的是虽然20世纪80,90年代中国区域CO2排放强度加大,但中国东部霾日频数年际变化却表现出波动型相对＂平稳＂缓升特征,此阶段中国东部对流层中下层出现了大气温度距平垂直结构＂上冷下暖＂的＂不稳定＂状态,其有利于中国东部大气扩散或对流;而近10年阶段中国东部出现霾天气与大气污染排放同步加剧异常变化,2001-2012年期间中国东部对流层中下层则呈＂上暖下冷＂类似＂逆温盖＂,即大气温度距平垂直结构出现年代际＂逆转＂趋势,此大气温度垂直结构年代际特征可能加剧了大气污染排放的环境影响效应,引发了中国东部大范围霾天气变异现象.

The impact of large topography on regional distribution of haze occurrences and the distinct seasonal variation of haze pollution in China are studied. The ＂harbor＂ effect on the eastern lee of the Tibetan Plateau＇s large topography on the westerlies is possibly an important factor influencing the regional distribution of haze frequency in eastern China. High haze frequency in winter and low haze frequency in spring, summer and fall are observed in China. With the enhanced pollutant emissions in China over recent 10 years, this seasonality of haze turned into indistinct with the frequent haze event extending from winter to spring, autumn and summer, implying a strong signal of atmospheric environmental degradation in China. Although the trends in interannual variations in haze occurrences largely depend on pollutant emissions in China, it is noteworthy that the interannual variation of haze pollution presented a smooth rise in eastern China from the 1980 s to the 1990 s asynchronously with the increased CO2 emission in China, and during the two decades, the anomalous pattern of ＂upper cooling and bottom warming＂ air temperature in the middle and lower troposphere similarly to the unstable stratification is favorable to air pollutant diffusion and convection. while the haze events in eastern China was synchronously significantly intensified with the sharp increasing CO2 emissions in China over recent more than 10 years, when the ＂shield＂ of temperature inversion in the middle and lower troposphere is found with an interdecadal reversion in anomalies of vertical temperature over eastern China during the period C（2001–2012）, which could aggravate the environmental effects of air pollutant emissions leading to the anomalous haze weather in a large region over eastern China.