Convection over Tropical Africa and the Atlantic Ocean during Northern Summer. Part II: Modulation by Easterly Waves
Convection over Tropical Africa and the Atlantic Ocean during Northern Summer. Part II: Modulation by Easterly Waves
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北夏季热带非洲和大西洋上空的对流。
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发表时间：
1990
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通讯作者：
J. Duvel
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作者：
J. Duvel
摘要：利用气象卫星数据和欧洲中期天气预报中心 (ECMWF) 分析，我们研究了三个夏季（1983-85 年 6 月、7 月、8 月和 9 月）的东风波及其与西非和热带大西洋上空云量的关系。对 2.8-5.1 天范围内低层经向风的频谱分析显示，西非海岸附近 20°N 处有最大波幅。 8 月和 9 月期间波幅比 6 月和 7 月期间更大，并且第二个极大值出现在 7.5°N 附近。波的平均结构和相关云调制的复合揭示了观测到的云量和 ECMWF 分析之间的一致关系。云量波调制的相位很大程度上取决于响应平均气候条件变化的地理位置。然而，这个阶段在四个大的陆地和海洋区域中变化很大，分别以北纬 7.5° 和 17.5° 为中心，为此我们推导出垂直坐标...
Abstract Using Meteosat data and European Centre for Medium-range Weather Forecast (ECMWF) analyses, we examine easterly waves and their relation with the cloudiness over West Africa and the tropical Atlantic Ocean for three summers (June, July, August and September 1983-85). Spectral analysis of the low-level meridional wind in the 2.8–5.1 day band reveals maximum wave amplitude near the West African coast at 20°N. During August and September the wave amplitude is larger than during June and July and a secondary maximum appears around 7.5°N. Composites of the mean structure of the wave and the associated cloud modulation reveal consistent relationship between observed cloudiness and ECMWF analyses. The phase of the wave modulation of the cloudiness is strongly dependent on the geographical location in response to changes in the mean climatological conditions. This phase varies however grossly in four large land and ocean regions, centered at 7.5° and 17.5°N, respectively, for which we derive vertical cro...