Investigation of the wet removal rate of black carbon in East Asia: validation of a below- and in-cloud wet removal scheme in FLEXible PARTicle (FLEXPART) model v10.4
Investigation of the wet removal rate of black carbon in East Asia: validation of a below- and in-cloud wet removal scheme in FLEXible PARTicle (FLEXPART) model v10.4
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DOI：
10.5194/acp-20-13655-2020
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发表时间：
2020-11-13
影响因子：
6.3
通讯作者：
Pisso, Ignacio
中科院分区：
文献类型：
--
作者：
Choi, Yongjoo;Kanaya, Yugo;Pisso, Ignacio
了解大气黑碳（BC）的全球分布对于揭示其气候效应至关重要。然而，由于有关去除过程的信息不足，关于BC运输的模拟仍然存在很大的不确定性。我们根据2010-2016年期间在三个代表性背景地点（韩国的白翎和五山以及日本的诺托）进行的长期测量，评估了东亚BC的湿去除率。平均湿去除率，由传输效率（TE）表示，即，2010年至2016年，在东亚，未沉积的BC颗粒在运输过程中的比例估计为0.73。根据沿着轨迹的累积降水量与TE的关系，中国东部和华北地区的湿去除效率较低，韩国和日本较高，这意味着大气质量输送过程中老化过程和暴露于云下和云内清除条件的频率的重要性。此外，湿清除在冬季和夏季分别表现出最高和最低的效率，虽然在夏季的最低去除效率主要是与减少BC老化过程，因为在云清除条件占主导地位。BC的平均半衰期和e-折叠寿命分别为2.8和7.1 d，这与以前的研究相似，但这些值根据每个站点的地理位置和气象条件而有所不同。接下来，通过比较TE从FLEXible PARTicle（FLEXPART）拉格朗日传输模式（版本10.4），我们诊断的清除系数（s（-1））的云下和云内清除方案中实现的FLEXPART。与测量值相比，FLEXPART的总体中位TE（0.91）被高估，这意味着模型模拟中的湿清除系数被低估。云下清除系数的测量值的中位数比根据FLEXPART方案计算的值低1.7倍。另一方面，与测量值相比，FLEXPART方案计算的云内清除系数的总体中值被高度低估了1个数量级。人工神经网络分析表明，云内清除过程中应考虑对流有效位能，以改善东亚地区BC湿清除的代表性区域差异。本研究首次提出了一种有效而直接的湿清除方案（包括在云下）的评价方法，通过引入TE沿着与不准确的排放清单的影响排除。
Understanding the global distribution of atmospheric black carbon (BC) is essential for unveiling its climatic effect. However, there are still large uncertainties regarding the simulation of BC transport due to inadequate information about the removal process. We accessed the wet removal rate of BC in East Asia based on long-term measurements over the 2010-2016 period at three representative background sites (Baengnyeong and Gosan in South Korea and Noto in Japan). The average wet removal rate, represented by transport efficiency (TE), i.e., the fraction of undeposited BC particles during transport, was estimated to be 0.73 in East Asia from 2010 to 2016. According to the relationship between accumulated precipitation along trajectory and TE, the wet removal efficiency was lower in East and North China but higher in South Korea and Japan, implying the importance of the aging process and frequency of exposure to below- and in-cloud scavenging conditions during air mass transport. Moreover, the wet scavenging in winter and summer showed the highest and lowest efficiency, respectively, although the lowest removal efficiency in summer was primarily associated with a reduced BC aging process because the in-cloud scavenging condition was dominant. The average half-life and e-folding lifetime of BC were 2.8 and 7.1 d, respectively, which is similar to previous studies, but those values differed according to the geographical location and meteorological conditions of each site. Next, by comparing TE from the FLEXible PARTicle (FLEXPART) Lagrangian transport model (version 10.4), we diagnosed the scavenging coefficients (s(-1)) of the below- and in-cloud scavenging scheme implemented in FLEXPART. The overall median TE from FLEXPART (0.91) was overestimated compared to the measured value, implying the underestimation of wet scavenging coefficients in the model simulation. The median of the measured below-cloud scavenging coefficient showed a lower value than that calculated according to FLEXPART scheme by a factor of 1.7. On the other hand, the overall median of the calculated in-cloud scavenging coefficients from the FLEXPART scheme was highly underestimated by 1 order of magnitude, compared to the measured value. From an analysis of artificial neural networks, the convective available potential energy, which is well known as an indicator of vertical instability, should be considered in the in-cloud scavenging process to improve the representative regional difference in BC wet scavenging over East Asia. For the first time, this study suggests an effective and straightforward evaluation method for wet scavenging schemes (both below and in cloud), by introducing TE along with excluding effects from the inaccurate emission inventories.