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

Abstract

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 Plateaus 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 1980s to the 1990s 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.