珠江三角洲秋季臭氧干沉降特征的数值模拟

利用区域化学传输模式WRF-Chem对2014年10月珠江三角洲臭氧干沉降特征进行模拟，结果表明：臭氧干沉降通量呈现明显的时空分布差异，日间平均沉降通量[0.68μg/（m²·s）]明显大于夜间[0.21μg/（m²·s）]；同时，珠江三角洲城区的臭氧沉降通量及日较差均比周边植被覆盖区小.受NO_x和VOCs等前体物以及各气象要素场的综合影响，臭氧浓度日变化具有明显的单峰型分布特征，在14：00~15：00达到峰值，秋季臭氧浓度高值区位于珠江三角洲主要排放源下风向区域的广佛交界、江门及中山东部等地区；臭氧的干沉降速率也具有明显的时空变化特征：从07：00~08：00的0.27cm/s开始迅速增大，10：00~16：00基本保持在0.60cm/s左右，17：00开始平缓减小至午夜的0.21cm/s左右；干沉降速率的变化主要受空气动力学阻抗R_a、粘性副层阻抗R_b以及表面阻抗R_c影响，研究表明夜间的干沉降速率主要受R_a影响，而日间R_c起主要作用.这3种阻抗分别受大气稳定度、摩擦速度和下垫面土地利用类型影响，在珠江三角洲区域亦表现出明显的时空变化特征.

Numerical simulation of ozone dry deposition characteristics in autumn over the Pearl River Delta region,China

The regional chemical transport model WRF-Chem was used to simulate the spatial and temporal characteristics of O₃ dry deposition flux in the Pearl River Delta (PRD) region in October 2014. The results show obvious spatial and temporal differences of ozone dry deposition flux: the mean flux in the daytime [0.68μg/(m²·s)] was higher than that in the night time [0.21μg/(m²·s)]; the O₃ deposition flux and its diurnal variation in the urban areas are smaller than those in the sub-urban areas. Moreover, the O₃ concentrations had obvious daily single-peak distribution characteristics which influenced by the precursors such as NO_x and VOCs, as well as the meteorological conditions. The peaks generally occur during 14:00~15:00, and the high concentrations were mainly located in the Guangfo junction、Jiangmen city and east Zhongshan city. The dry deposition velocity of O₃ also present significant spatial and temporal variations. It increased rapidly from 0.27cm/s during 07:00~08:00 to a relatively stable value 0.60cm/s during 10:00~16:00; and then decreased slowly to 0.21cm/s from 17:00 to midnight. The dry deposition velocity was mainly affected by three types of resistances: the aerodynamic resistance (R_a), sublayer resistance(R_b) and canopy resistance(R_c). Our results show that the dry deposition velocity at night was mainly affected by R_a, while in the daytime R_c played a major role. These three resistances were mainly influenced by the stability、the friction velocity and the landuse type of the underlying surface.