Impact of West African Monsoon convective transport and lightning NO x production upon the upper tropospheric composition: a multi-model study
Impact of West African Monsoon convective transport and lightning NO x production upon the upper tropospheric composition: a multi-model study
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西非季风对流输送和闪电氮氧化物产生对对流层上层成分的影响：多模型研究
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发表时间：
2010
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通讯作者：
J. Cammas
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作者：
B. Barret;J. Williams;I. Bouarar;Xin Yang;B. Josse;K. Law;M. Pham;E. L. Flochmoën;C. Liousse;V. Peuch;G. Carver;J. Pyle;B. Sauvage;P. Velthoven;H. Schlager;C. Mari;J. Cammas
抽象。在非洲季风多学科分析（AMMA），我们调查的影响产生的氮氧化物的闪电（LiNOx）和对流输送在西非季风（WAM）后的组成上对流层（UT）在热带地区。为此，我们进行了模拟与4个国家的最先进的化学传输模型中涉及AMMA，即MOCAGE，TM 4，LMDz-INCA和p-TOMCAT。模型相互比较的补充与评价的模拟的基础上，航天器和机载观测。基线模拟显示出重要的差异之间的UT CO和O3的分布模拟的4个模型相比，从MOZAIC程序和FOM的光环/MLS星载传感器的测量。我们表明，这种模型差异可以通过对流输送参数化的差异来解释，更具体地说，是对流上升气流达到的高度（范围在~200-125 hPa之间）。关于UT O3，模型表现出良好的协议与主要观察到的功能。然而，大多数模式模拟低O3浓度相比，MOZAIC和Aura/MLS观测赤道以南，而在北方半球的浓度相当高。进行敏感性研究，以量化深对流输送的效果和对UT组合物的LiNOx生产的影响。这些清楚地表明，CO最大值和赤道以南的O3浓度升高是由于对流抬升的空气质量的影响，南部非洲生物质燃烧，与以前的研究一致。此外，在WAM期间，来自非洲的LiNOx负责在10° S-20° N之间的热带大西洋上最高的UT O3增强（10-20 ppbv）。模型之间的差异主要是由于用于模拟闪电活动的参数化的性能，使用星载观测的闪光频率进行评估。结合现场NO测量结果的比较，我们发现，在WAM（印加和p-TOMCAT）期间在非洲产生最高量的LiNOx的模型捕获观察到的NO配置文件具有最好的准确性，虽然他们都高估了萨赫勒地区的闪电活动。
Abstract. Within the African Monsoon Multidisciplinary Analysis (AMMA), we investigate the impact of nitrogen oxides produced by lightning (LiNOx) and convective transport during the West African Monsoon (WAM) upon the composition of the upper troposphere (UT) in the tropics. For this purpose, we have performed simulations with 4 state-of-the-art chemistry transport models involved within AMMA, namely MOCAGE, TM4, LMDz-INCA and p-TOMCAT. The model intercomparison is complemented with an evaluation of the simulations based on both spaceborne and airborne observations. The baseline simulations show important differences between the UT CO and O3 distributions simulated by each of the 4 models when compared to measurements from the MOZAIC program and fom the Aura/MLS spaceborne sensor. We show that such model discrepancies can be explained by differences in the convective transport parameterizations and, more particularly, the altitude reached by convective updrafts (ranging between ~200–125 hPa). Concerning UT O3, the models exhibit a good agreement with the main observed features. Nevertheless the majority of models simulate low O3 concentrations compared to both MOZAIC and Aura/MLS observations south of the equator, and rather high concentrations in the Northern Hemisphere. Sensitivity studies are performed to quantify the effect of deep convective transport and the influence of LiNOx production on the UT composition. These clearly indicate that the CO maxima and the elevated O3 concentrations south of the equator are due to convective uplift of air masses impacted by Southern African biomass burning, in agreement with previous studies. Moreover, during the WAM, LiNOx from Africa are responsible for the highest UT O3 enhancements (10–20 ppbv) over the tropical Atlantic between 10° S–20° N. Differences between models are primarily due to the performance of the parameterizations used to simulate lightning activity which are evaluated using spaceborne observations of flash frequency. Combined with comparisons of in-situ NO measurements we show that the models producing the highest amounts of LiNOx over Africa during the WAM (INCA and p-TOMCAT) capture observed NO profiles with the best accuracy, although they both overestimate lightning activity over the Sahel.