Influences of relative humidity on aerosol optical properties and aerosol radiative forcing during ACE-Asia
Influences of relative humidity on aerosol optical properties and aerosol radiative forcing during ACE-Asia
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DOI：
10.1016/j.atmosenv.2006.03.036
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发表时间：
2006-07
影响因子：
5
通讯作者：
Soon-chang Yoon;Jiyoung Kim
中科院分区：
文献类型：
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作者：
Soon-chang Yoon;Jiyoung Kim
对韩国高山和 ACE-Asia 期间 C-130 飞机上的现场测量进行了分析，以研究相对湿度 (RH) 对气溶胶光学特性和辐射强迫的影响。高山超级站点气溶胶化学成分的时间变化高度依赖于气团输送路径和源区。东亚地区春季RH分布具有很大的时空变化。 C-130 飞机上的 RH 剖面测量显示混合层高度约为 2 公里。环境相对湿度下的气溶胶散射系数（σsp）比干燥相对湿度（RH<40%）下大大提高。从气溶胶光学和辐射传输模型研究中，我们发现 RH 大大增强了消光和散射系数。相对湿度的单散射反照率在较长波长中也会发生敏感变化。尽管在给定相对湿度下，不对称参数 (g) 随波长而减小，但不对称参数 (g) 随相对湿度逐渐增大。 550nm 和 RH 50% 下的气溶胶光学深度 (AOD) 在不同的 RH 水平 70、80、90 和 95% 下分别增加到因子 1.24、1.51、2.16 和 3.20。地表、TOA 和大气的日平均气溶胶辐射强迫随着 RH 的增加而增加，因为由于气溶胶颗粒的吸湿性增长，AOD 随 RH 的增加而增加。这一结果意味着对流层低层中水溶性或亲水颗粒引起的吸湿性增长可能会显着改变地表和 TOA 处的气溶胶辐射强迫的大小。然而，地表、TOA和大气的日平均辐射强迫效率随着相对湿度的增加而降低。强迫效率随相对湿度的降低是由于气溶胶光学深度随相对湿度的增加速率大于气溶胶辐射强迫随相对湿度的增加速率。
In situ measurements at Gosan, South Korea, and onboard C-130 aircraft during ACE-Asia were analyzed to investigate the influence of relative humidity (RH) on aerosol optical properties and radiative forcing. The temporal variation of aerosol chemical composition at the Gosan super-site was highly dependent on the air mass transport pathways and source region. RH in the springtime over East Asia were distributed with very high spatial and temporal variation. The RH profile onboard C-130 aircraft measurements exhibits a mixed layer height of about 2km. Aerosol scattering coefficient (σsp) under ambient RH was greatly enhanced as compared with that at dry RH (RH<40%). From the aerosol optical and radiative transfer modeling studies, we found that the extinction and scattering coefficients are greatly enhanced with RH. Single scattering albedo with RH is also sensitively changed in the longer wavelength. Asymmetry parameter (g) is gradually increased with RH although g decreases with wavelength at a given RH. Aerosol optical depth (AOD) at 550nm and RH of 50% increased to factors 1.24, 1.51, 2.16, and 3.20 at different RH levels 70, 80, 90, and 95%, respectively. Diurnal-averaged aerosol radiative forcings for surface, TOA, and atmosphere were increased with RH because AOD was increased with RH due to hygroscopic growth of aerosol particles. This result implies that the hygroscopic growth due to water-soluble or hydrophilic particles in the lower troposphere may significantly modify the magnitude of aerosol radiative forcing both at the surface and TOA. However, the diurnal-averaged radiative forcing efficiencies at the surface, TOA, and atmosphere were decreased with increasing RH. The decrease of the forcing efficiency with RH results from the fact that increasing rate of aerosol optical depth with RH is greater than the increasing rate of aerosol radiative forcing with RH.