Classification of Ascension Island and Natal ozonesondes using self-organizing maps
Classification of Ascension Island and Natal ozonesondes using self-organizing maps
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DOI：
10.1029/2011jd016573
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发表时间：
2012-02-17
影响因子：
4.4
通讯作者：
Schmidlin, F. J.
中科院分区：
文献类型：
--
作者：
Jensen, Anders A.;Thompson, Anne M.;Schmidlin, F. J.
来自气球载臭氧探测仪的臭氧轮廓被用于卫星算法的开发以及化学-气候模式的初始化、同化和评估。这些廓线应用中的一个重要问题是如何最好地处理变化，在这种变化中，不同的光化学和动力影响可导致廓线对流层段的臭氧混合比在一天内变化2-3倍。聚类技术是实现剖面数据统计分类的理想方法，我们将自组织映射应用于热带对流层SHADOZ数据，假设数据将根据对臭氧的各种影响进行排序，即生物质燃烧、气象条件和平流层或热带外入侵等人为来源。1998年至2009年阿森松岛(512个剖面，S 7.98度，西经14.42度)和巴西纳塔尔(425个剖面，S 5.42度，西经35.38度)的SHADOZ剖面的自组织地图已经确定，这种地图使用学习算法来揭示数据集的最显著特征。2×2自组织图创建了4个星系团，显示出与自由对流层平均臭氧的偏离既包括非洲季节性生物质燃烧造成的臭氧增加，也包括未受污染的边界层空气对流上升造成的局部臭氧减少。扩展到4x4的自组织图显示了生物质燃烧如何影响阿森松岛对流层臭氧的年度循环，并捕捉到阿森松岛和纳塔尔臭氧的季节性。阿森松岛和纳塔尔在两个地点使用4x4自组织地图进行比较，显示出对流层中臭氧的相似之处，但显示出对流层低层臭氧的差异，这是因为阿森松岛更接近非洲生物质燃烧，而且比纳塔尔更受平均Walker环流下降的影响，对流活动较少。
Ozone profiles from balloon-borne ozonesondes are used for development of satellite algorithms and in chemistry-climate model initialization, assimilation and evaluation. An important issue in the application of these profiles is how best to treat variations where varying photochemical and dynamical influences can cause the ozone mixing ratio in the tropospheric segments of the profile to change by of a factor of 2-3 within a day. Clustering techniques are an ideal way to approach the statistical classification of profile data and we apply self-organizing maps to tropical tropospheric SHADOZ data, hypothesizing that the data will sort according to various influences on ozone, namely anthropogenic sources like biomass burning, meteorological conditions, and stratospheric or extra-tropical intrusions. Self-organizing maps, that use a learning algorithm to reveal the most prominent features of a data set according to a specified number of clusters, have been determined for the 1998-2009 SHADOZ profiles over Ascension Island (512 profiles, 7.98 degrees S, 14.42 degrees W) and Natal, Brazil (425 profiles, 5.42 degrees S, 35.38 degrees W). The 2 x 2 self-organizing map, which creates 4 clusters, reveals that deviations from the average ozone in the free troposphere include both increased ozone resulting from seasonal biomass burning in Africa and locally reduced ozone brought about by convective lifting of unpolluted boundary-layer air. Expanding to a 4 x 4 self-organizing map shows how biomass burning influences the yearly cycle of tropospheric ozone at Ascension Island and captures the seasonality of ozone at both Ascension Island and Natal. Comparing Ascension Island and Natal using a 4 x 4 self-organizing map at each site reveals similarities in mid-tropospheric ozone, but shows differences in lower-tropospheric ozone due to Ascension Island being closer to African biomass burning and more affected by descent from the mean Walker circulation, with less convective activity, than Natal.