深圳市灰霾的城郊差别及成因分析

ANALYSIS OF CAUSES FOR THE DIFFERENCES OF HAZE IN URBAN AND SUBURBAN AREAS OF SHENZHEN

利用2011年深圳国家基本气象站及自动气象站的能见度、相对湿度和大气成分资料,分析了深圳市区和郊区灰霾特征、差异及成因。结果表明,灰霾天气市区多于郊区,春季、夏季、秋季是短历时灰霾出现频次最高,而冬季是长历时灰霾出现频次最高,主要是由于冬季易产生灰霾的大尺度天气系统影响时间长造成的。市区和郊区的年总灰霾时数日变化规律不同,市区呈"双峰型",在早晚交通高峰期出现最大值;郊区呈"单峰型",在午后出现最大值,主要原因是市区和郊区气溶胶可溶性离子日变化特征不同。午后,郊区年总灰霾时数竟然比市区多,原因有两方面:(1)由于郊区沿海海盐粒子在午后强烈的氧化作用下,通过氯损耗产生了更多的气溶胶细粒子;(2)郊区沿海午后湿度明显高于市区,细粒子的吸湿增长比市区更强,因此灰霾出现概率比市区大。

Based on the data of visibility, relative humidity and atmospheric composition in 2011 from National Basic Meteorological Station and automatic meteorological stations in Shenzhen, the causes for differences in the diurnal variation of haze in urban and suburban areas are analyzed. The results show that the number of hazy days in the urban area is higher than that in the suburban area. In spring, summer and autumn, hazes with short duration occur most frequently, but in winter hazes with long duration are with the highest frequency of occurrence, mainly due to the extended influence of large-scale synoptic systems most suitable for haze to form. Diurnal variations of haze differ in urban from those in suburban areas. There are two peaks of occurrence frequency in the urban area, with the maximum appearing in the rush hours of morning and evening. The suburban diurnal variation of occurrence frequency is single-peak, with the maximum appearing in the afternoon. The main reason is that the diurnal variations of aerosols are different in the urban from the suburban area. The suburban haze occurs more frequently than the urban haze in the afternoon. First, stronger oxidation produced a considerable amount of aerosols because of the loss of Chlorine in the suburban area than in the urban area. Second, humidity in the suburban area was significantly higher than in the urban area in the afternoon, so fine particles absorbed more moisture to grow than in the urban area.