Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data
Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data
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DOI：
10.5194/acp-5-311-2005
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发表时间：
2004-06
影响因子：
6.3
通讯作者：
B. Sauvage;V. Thouret;J. Cammas;F. Gheusi;G. Athier;P. Nédélec
中科院分区：
文献类型：
--
作者：
B. Sauvage;V. Thouret;J. Cammas;F. Gheusi;G. Athier;P. Nédélec
抽象的。我们分析了 MOZAIC 计划在 1997 年 4 月至 2003 年 3 月期间记录的赤道非洲臭氧观测数据，提供了第一个源自该地区大陆实地数据的臭氧气候学数据。三维流线强烈表明臭氧月平均垂直剖面的特征、赤道非洲上空对流层最持久的环流模式（每月）如哈马坦、非洲东急流、生物质燃烧产生的臭氧前体排放的贸易和区域之间的联系。在每个半球的生物质燃烧季节，对流层低层呈现出增强的臭氧层（即 12 月至 2 月几内亚湾海岸上空的臭氧浓度为 70 ppbv，6 月至 8 月刚果上空的臭氧浓度为 85 ppbv）。臭氧月平均垂直剖面的特征与季节性动力强迫确定的区域流态明显相关。燃烧季节几内亚湾沿岸的平均臭氧剖面的特点是系统性的高臭氧浓度低于 650hPa；这是由于哈马坦和 AEJ 输送了逆风火灾产生的污染物。将高臭氧限制在对流层低层是由于哈马坦的高稳定性和阻碍有效垂直混合的撒哈拉反气旋。相比之下，在中部非洲当地旱季（六月至八月）观察到的臭氧增强不仅出现在对流层低层，而且出现在整个对流层。此外，这项研究强调了几内亚湾海岸地区和刚果南部地区之间每半年出现一次的联系。雨季地区的垂直剖面显示，由于位于相反的旱季半球的火灾产生的生物质燃烧产物，对流层低层的臭氧增强。
Abstract. We analyze ozone observations recorded over Equatorial Africa between April 1997 and March 2003 by the MOZAIC programme, providing the first ozone climatology deriving from continental in-situ data over this region. Three-dimensional streamlines strongly suggests connections between the characteristics of the ozone monthly mean vertical profiles, the most persistent circulation patterns in the troposphere over Equatorial Africa (on a monthly basis) such as the Harmattan, the African Easterly Jet, the Trades and the regions of ozone precursors emissions by biomass burning. During the biomass burning season in each hemisphere, the lower troposphere exhibits layers of enhanced ozone (i.e. 70 ppbv over the coast of Gulf of Guinea in December-February and 85 ppbv over Congo in June-August). The characteristics of the ozone monthly mean vertical profiles are clearly connected to the regional flow regime determined by seasonal dynamic forcing. The mean ozone profile over the coast of Gulf of Guinea in the burning season is characterized by systematically high ozone below 650hPa ; these are due to the transport by the Harmattan and the AEJ of the pollutants originating from upwind fires. The confinement of high ozone to the lower troposphere is due to the high stability of the Harmattan and the blocking Saharan anticyclone which prevents efficient vertical mixing. In contrast, ozone enhancements observed over Central Africa during the local dry season (June-August) are not only found in the lower troposphere but throughout the troposphere. Moreover, this study highlights a connection between the regions of the coast of Gulf of Guinea and regions of Congo to the south that appears on a semi annual basis. Vertical profiles in wet-season regions exhibit ozone enhancements in the lower troposphere due to biomass burning products transport from fires situated in the opposite dry-season hemisphere.