中国东部海陆热力差异与华南冬季雾霾的气候学关联

根据中国东部冬季海陆热力分异和耦合作用关系，构建了纬向海陆热力差异指标。从大气环流和降水角度，揭示了局地海陆热力差异对中国东部相对湿度变化的影响。基于此，探讨了局地海陆热力差异与华南地区冬季雾霾形成、转化和趋势变化的气候学关联。结果表明：冬季海陆热力对比显著的耦合区位于华南地区和菲律宾海东部海域，形成的局地海陆热力差异具有约17 a左右的年代际变化，20世纪80年代初其由强转弱的趋势突变明显。局地海陆热力差异增强时，华南地区冬季东北风异常加强，由东中国海（渤海、黄海和东海）及日本海向华南地区的水汽输送和降水也呈现增强趋势，这有利于华南地区相对湿度的异常增加。受局地海陆热力差异调控，华南地区偏湿期和偏干期约以17 a的周期交替出现。20世纪80年代之前的偏湿期，华南地区雾日条件湿度基本保持不变，之后环境相对湿度逐渐降低，引起雾日偏少。由于华南地区本底（平均）相对湿度更利于霾的形成，在污染物排放或迁移累积增强的情形下，相对湿度的降低抑制霾向雾的转化，使得雾日持续减少，而霾日趋于增加，特别在21世纪初的偏干峰值期霾日增加速率达到最高。21世纪20年代华南地区相继进入偏干期，气候变暖导致饱和比湿加大，未来霾天气趋多趋强、持续时间长等极端特性和高危险性特点将更为突显。

The Climatological Association of Sea-land Thermal Contrast in Eastern China with Winter Fog and Haze in South China

Based on sea-land thermal contrast and coupling relationship in winter, a local zonal sea-land thermal difference (SLTD) index was constructed. From the perspective of atmospheric circulation and precipitation, this article reveals the influence of the SLTD on relative humidity (RH) in eastern China, and further discusses the climatological association with the formation, transformation and trend changes of winter fog and haze in South China. The results show that, in winter, the coupling region with significant sea-land thermal contrast is located in south China region and the eastern part of the Philippine Sea. The SLTD has a decadal change of about 17 years, and the trend shift from strengthening into weakening in the early 1980s was obvious. As the SLTD increases, the winter northeast wind in South China is abnormally enhanced, and the moisture transport from the east China seas and the Sea of Japan to South China and rainfall are also strengthened, which is conducive to the abnormal increase of RH in South China. Under the modulation of the SLTD, the wet period and dry period in South China alternated with cycle of about 17 years. In the wet period before 1980s, the RH in fog days in south China remained basically unchanged. The environmental RH tended to decrease at the beginning of the 1980s, which caused less fog days. Due to the background of RH in South China is more conducive to the formation of haze in the case of the pollutant discharge or migration accumulation increase, the reduction of RH inhibits the transformation of haze into fog, making fog days continue to decrease while haze days to increase with highest rate especially in the dry peak period after 2000. Since 2020s, South China has subsequently entered a dry period, the increase in saturation specific humidity caused by climate warming is more likely to cause extreme and dangerous characteristics such as stronger and longer duration of haze weather in the future.