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arXiv 1509.03419physics.ao-ph
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沿海热带降水与大尺度大气的关系

On the relationship of coastal tropical rainfall and the large-scale atmosphere

Martin Bergemann, Christian Jakob, Todd P. Lane

摘要:

热带沿海地区的降雨通常是由与地形直接相关的环流形成的,如陆地-海洋和/或山脉-谷风风。在许多地区,受沿海影响的降雨量占总降雨量的一半以上。参数化对流的天气和气候模式在热带沿海地区的降雨量中产生很大的误差,最常见的是低估了陆地上的降雨量,高估了海洋上的降雨量。建立在一个算法,以客观地识别降雨与陆海相互作用,我们调查沿海地区的降雨和大尺度大气之间的关系是否不同于在公海或内陆地区。我们结合3小时卫星降雨量的估计与再分析的大规模大气状态的估计。我们发现,当按降雨强度分组时,热带地区中等强度的沿海降雨发生在更稳定的条件和更干燥的大气中,并且与开阔海洋和内陆同行相比,与较小的大尺度辐合相关。总体而言,降雨量的依赖性的大尺度状态是显着较弱的降雨时,沿海地区的影响。我们的研究结果表明,对流在天气和气候模式的代表性必须迎合的大到小尺度的关系在海岸附近的特殊字符,而不是依赖于全球范围内的一套共同的规则。

英文摘要:

Rainfall in coastal areas of the tropics is often shaped by the presence of circulations directly associated with the topography, such as land-sea and/or mountain-valley breezes. In many regions the coastally-affected rainfall consitutes more than half of the overall rainfall received. Weather and climate models with parametrized convection produce large errors in rainfall in tropical coastal regions, most commonly underestimating rainfall over land and overestimating it over the ocean. Building on an algorithm to objectively identify rainfall that is associated with land-sea interaction we investigate whether the relationship between rainfall in coastal regions and the large-scale atmosphere differs from that over the open ocean or over inland areas. We combine 3-hourly satellite estimates of rainfall with estimates of the large-scale atmospheric state from reanalyses. We find that when grouped by rainfall intensity, medium-intensity coastal rainfall in the tropics occurs in more stable conditions and drier atmospheres and is associated with less large-scale convergence than its open-ocean and inland counterparts. Overall, the dependence of the amount of rainfall on the large-scale state is significantly weaker when the rainfall is coastally influenced. Our findings indicate that the representation of convection in weather and climate models must cater for the special character of the large-to-small scale relationship near coasts rather than rely on a common set of rules across the globe.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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