A Study on Aerosol Optical Properties in an Urban Atmosphere of Nagoya, Japan
A Study on Aerosol Optical Properties in an Urban Atmosphere of Nagoya, Japan
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DOI：
10.2151/jmsj.87.19
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发表时间：
2009-02-01
影响因子：
3.1
通讯作者：
Takamura, Tamio
中科院分区：
文献类型：
--
作者：
Khatri, Pradeep;Ishizaka, Yutaka;Takamura, Tamio
2004年7月23日至9月4日在日本名古屋城市大气中对气溶胶的物理和光学特性进行了观测。这些观测数据进行了分析，以了解城市气溶胶对大气热量收支的影响。在我们的观测区域的气溶胶被发现是非常低的平均单次散射ω 0.72的光吸收。这种光吸收气溶胶的存在能够显着影响欧米茄的日周期，表明这种气溶胶对大气热收支的重要作用。提出了一种估算干气溶胶折射率和密度的算法，该算法得到的平均折射率和密度分别为1.53-0.038i和1.7gcm（-3）。亚微米（d < 1.0 μ m）气溶胶对总气溶胶质量浓度和散射系数的贡献率分别为81%和95%，表明亚微米气溶胶对大气辐射传输过程的重要作用。地面和大气层顶的辐射强迫效率（RFE）、大气强迫效率（AFE）和地面加热率的24小时平均值分别为-71.8 +/- 12.3 Wm（-2）、+2.5 +/- 6.8 Wm（-2）、74.4 +/- 19.0 Wm（-2）和2.46 +/- 0.61 K/天。研究表明，增加黑碳（BC）质量分数可以通过在大气中捕获更多能量（或增加AFE）来有效地增加表面加热速率。据观察，如果BC质量分数变得大于类似于0.05（或ω变得小于类似于0.75），则在我们的研究区域上的气溶胶可以在TOA处具有正RFE。此外，该研究表明，BC质量分数增加0.1可以分别使TOA处的RIFE增加类似于15.8 Wm（-2），使表面处的RFE减少类似于30.4 Wm（-2），并且使表面处的加热速率增加类似于1.39 K/天。
An observation of physical and optical properties of aerosols was carried out in an urban atmosphere of Nagoya, Japan from 23 July to 4 September 2004. Such observed data were analyzed to understand urban aerosol effects on atmospheric heat budget. Aerosols over our observation area were found to be highly light absorptive with a very low mean single scattering albedo (omega) of 0.72. The presence of such light absorbing aerosols was capable to significantly influence the diurnal cycle of omega, indicating important roles of such aerosols on atmospheric heat budget. An algorithm was developed to estimate the refractive index and density of dry aerosols, and such algorithm produced the mean values of refractive index and density of 1.53-0.038i and 1.7 gcm(-3), respectively. Sub micron (d < 1.0 mu m) aerosols were observed to contribute total aerosol mass concentration and scattering coefficient for aerosols less than 10.0 mu m in diameter by similar to 81% and similar to 95%, indicating the important roles of sub micron aerosols on atmospheric radiative transfer process. The 24 hours mean values of radiative forcing efficiency (RFE) at surface and top of the atmosphere (TOA), atmospheric forcing efficiency (AFE), and heating rate at surface were -71.8 +/- 12.3 Wm(-2), +2.5 +/- 6.8 Wm(-2), 74.4 +/- 19.0 Wm(-2) and 2.46 +/- 0.61 K/day, respectively. The study suggested that an increase of black carbon (BC) mass fraction Could effectively increase the heating rate at surface by trapping more energy (or increasing AFE) in the atmosphere. It was observed that aerosols over our study area could have a positive RFE at TOA if BC mass fraction becomes greater than similar to 0.05 (or omega becomes smaller than similar to 0.75). Further, the study suggested that an increase of BC mass fraction by 0.1 could increase RIFE at TOA by similar to 15.8 Wm(-2), decrease RFE at surface by similar to 30.4 Wm(-2) and increase heating rate at the surface similar to 1.39 K/day, respectively.