Evidence of the impact of deep convection on reactive Volatile Organic Compounds in the upper tropical troposphere during the AMMA experiment in West Africa
Evidence of the impact of deep convection on reactive Volatile Organic Compounds in the upper tropical troposphere during the AMMA experiment in West Africa
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西非 AMMA 实验期间深对流对热带对流层上层活性挥发性有机化合物影响的证据
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
P. Perros
中科院分区：
文献类型：
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作者：
J. Bechara;A. Borbon;C. Jambert;A. Colomb;P. Perros
抽象的。2006年8月，在非洲季风多学科分析(AMMA)实地试验期间，首次在西非上空收集了大量活性痕量气体数据集。在ATR-42和猎鹰-20两架法国飞机上，用一种新的仪器AMOVOC(机载挥发性有机化合物测量)测量了挥发性有机化合物(C5-C9的VOC)。本研究的目的是(1)研究西非热带地区VOC的分布特征；(2)确定深对流对热带对流层上层(UT)VOC分布和化学的影响；(3)研究其时空扩展特征。实验策略包括在中尺度对流系统(MCS)下风向0至12公里高度和云底进行采样。西非的生物和人为VOC分布明显受南北排放梯度的影响。最丰富的VOC异戊二烯在森林中的含量最高(1.26 ppb)，而苯在城市地区的含量最高(0.11 ppb)。首先，利用CO、O_3和相对湿度的多种物理化学示踪方法区分对流和非对流气团。然后，采用了基于VOC观测的其他工具(示踪剂比率、排放指标和光化学时钟)，以在化学、空间和时间基础上描述深对流的特征。VOC垂直廓线呈“C”型趋势，表明富VOC气团是通过深对流系统从地表输送到UT的。对流外流中的VOC混合比高达背景水平的两倍，即使是反应性的和短期的VOC(例如，在12公里高度的异戊二烯高达0.19 ppb)也是如此，并且取决于地面排放类型。结果表明，UT空气质量反应性由非对流条件下的0.52%S−1提高到对流条件下的0.95%S−1。对流出流中包含的边界层空气的比例估计为40±15%。计算出0~12公里高度的垂直输送时间尺度为25±10分钟。这些结果描述了西非发生的深部对流，并为区域/全球模式中的热带对流参数化提供了相关信息。
Abstract. A large dataset of reactive trace gases was collected for the first time over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) field experiment in August 2006. Volatile Organic Compounds (VOC from C5–C9) were measured onboard the two French aircrafts the ATR-42 and the Falcon-20 by a new instrument AMOVOC (Airborne Measurement Of Volatile Organic Compounds). The goal of this study is (i) to characterize VOC distribution in the tropical region of West Africa (ii) to determine the impact of deep convection on VOC distribution and chemistry in the tropical upper troposphere (UT) and (iii) to characterize its spatial and temporal extensions. Experimental strategy consisted in sampling at altitudes between 0 and 12 km downwind of Mesoscale Convective Systems (MCS) and at cloud base. Biogenic and anthropogenic VOC distribution in West Africa is clearly affected by North to South emission gradient. Isoprene, the most abundant VOC, is at maximum level over the forest (1.26 ppb) while benzene reaches its maximum over the urban areas (0.11 ppb). First, a multiple physical and chemical tracers approach using CO, O3 and relative humidity was implemented to distinguish between convective and non-convective air masses. Then, additional tools based on VOC observations (tracer ratios, proxy of emissions and photochemical clocks) were adapted to characterize deep convection on a chemical, spatial and temporal basis. VOC vertical profiles show a "C-shaped" trend indicating that VOC-rich air masses are transported from the surface to the UT by deep convective systems. VOC mixing ratios in convective outflow are up to two times higher than background levels even for reactive and short-lived VOC (e.g. isoprene up to 0.19 ppb at 12 km-altitude) and are dependent on surface emission type. As a consequence, UT air mass reactivity increases from 0.52 s−1 in non-convective conditions to 0.95 s−1 in convective conditions. Fractions of boundary layer air contained in convective outflow are estimated to be 40 ± 15%. Vertical transport timescale is calculated to be 25 ± 10 min between 0 to 12 km altitude. These results characterize deep convection occurring over West Africa and provide relevant information for tropical convection parameterization in regional/global models.
AMMA 2006 期间西非的过氧自由基观测：对流系统流出中的光化学活动
影响因子：
6.3
作者：
Andrés- Hernández;Kartal;Reichert;Burrows;Meyer Arnek;Lichtenstern;Schlager
通讯作者：
Schlager