Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic
Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic
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DOI：
10.5194/amt-14-6723-2021
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发表时间：
2021-10-20
影响因子：
3.8
通讯作者：
Tobo, Yutaka
中科院分区：
文献类型：
--
作者：
Ohata, Sho;Mori, Tatsuhiro;Tobo, Yutaka
长期测量大气中的黑碳（BC）的质量浓度是必要的，以调查其排放，运输和沉积的变化。然而，根据仪器的不同，与BC相关的参数，如气溶胶吸收系数（B（abs））已被测量。北极地区B（绝对值）的大多数地面测量都是通过基于滤光片的吸收光度计进行的，其中包括粒子烟尘吸收光度计、连续光吸收光度计、风速计和多角度吸收光度计。通过假定质量吸收截面的值（MAC; M-BC = B（abs）/MAC），可以将测量的B（abs）转换为BC的质量浓度（M-BC）。然而，B（绝对值）转换为M-BC的准确性尚未得到充分评估。在这里，我们介绍了一种系统的方法，用于从这些仪器测量的B（绝对值）和独立测量的M-BC推导MAC值。在该方法中，使用具有加热入口的基于过滤器的吸收光度计（COS-MOS）测量M-BC。COSMOS衍生的M-BC（M-BC（COSMOS））可追溯到严格校准的单粒子烟尘光度计（SP2），M-BC（COSMOS）的绝对准确度此前已被证明在亚洲和北极地区约为15%。应用该方法的必要条件是测量的B（abs）与独立测量的M-BC的高度相关性和回归斜率的长期稳定性，表示为MAC（cor）（从相关性导出的MAC）。一般来说，加拿大的阿勒特、斯瓦尔巴德群岛的新奥勒松、阿拉斯加的巴罗（NOAA巴罗天文台）、芬兰的帕拉斯图恩图里和日本的奥勒松的B（abs-）M（BC）（COSMOS）相关性很高（每小时数据的r（2）= 0.76-0.95），并且稳定长达10年。我们成功地估计了这些仪器的MAC（cor）值（每小时数据在550 nm波长下为10.8- 15.1 m（2）g（-1）），这些MAC（cor）值可用于从这些站点测量的B（abs）中获得M-BC的误差约束估计，即使在过去，当COSMOS测量没有进行。由于该方法估算的北极各站点M-BC绝对值相互一致，适用于北极M-BC时空变化的研究和数值模式计算性能的评价。
Long-term measurements of atmospheric mass concentrations of black carbon (BC) are needed to investigate changes in its emission, transport, and deposition. However, depending on instrumentation, parameters related to BC such as aerosol absorption coefficient (b(abs)) have been measured instead. Most ground-based measurements of b(abs) in the Arctic have been made by filter-based absorption photometers, including particle soot absorption photometers (PSAPs), continuous light absorption photometers (CLAPs), Aethalometers, and multi-angle absorption photometers (MAAPs). The measured b(abs) can be converted to mass concentrations of BC (M-BC) by assuming the value of the mass absorption cross section (MAC; M-BC = b(abs)/MAC). However, the accuracy of conversion of b(abs) to M-BC has not been adequately assessed. Here, we introduce a systematic method for deriving MAC values from b(abs) measured by these instruments and independently measured M-BC. In this method, M-BC was measured with a filter-based absorption photometer with a heated inlet (COS-MOS). COSMOS-derived M-BC (M-BC (COSMOS)) is traceable to a rigorously calibrated single particle soot photometer (SP2), and the absolute accuracy of M-BC (COSMOS) has been demonstrated previously to be about 15% in Asia and the Arctic. The necessary conditions for application of this method are a high correlation of the measured b(abs) with independently measured M-BC and long-term stability of the regression slope, which is denoted as MAC(cor) (MAC derived from the correlation). In general, b(abs-)M(BC) (COSMOS) correlations were high (r(2) = 0.76-0.95 for hourly data) at Alert in Canada, Ny-Alesund in Svalbard, Barrow (NOAA Barrow Observatory) in Alaska, Pallastunturi in Finland, and Fukue in Japan and stable for up to 10 years. We successfully estimated MAC(cor) values (10.8-15.1m(2) g(-1) at a wavelength of 550 nm for hourly data) for these instruments, and these MAC(cor) values can be used to obtain error-constrained estimates of M-BC from b(abs) measured at these sites even in the past, when COSMOS measurements were not made. Because the absolute values of M-BC at these Arctic sites estimated by this method are consistent with each other, they are applicable to the study of spatial and temporal variation in M-BC in the Arctic and to evaluation of the performance of numerical model calculations.