Abstract. Global climate models have difficulties to simulate the northward extension of the monsoonal precipitation over north Africa during the mid-Holocene as revealed by proxy data. A common feature of these models is that they usually operate on too coarse grids to explicitly resolve convection, but convection is the most essential mechanism leading to precipitation in the west African monsoon region. Here, we investigate how the representation of tropical deep convection in the ICON climate model affects the meridional distribution of monsoonal precipitation during the mid-Holocene, by comparing regional simulations of the summer monsoon season (July to September, JAS) with parameterized (40 km-P) and explicitly resolved convection (5 km-E). The spatial distribution and intensity of precipitation, are more realistic in the explicitly resolved convection simulations than in the simulations with parameterized convection. However, in the JAS-mean the 40 km-P simulation produces more precipitation and extents further north than the 5 km-E simulation, especially between 12° N and 17° N. The higher precipitation rates in the 40 km-P simulation are consistent with a stronger monsoonal circulation over land. Furthermore, the atmosphere in the 40 km-P simulation is less stably stratified and notably moister. The differences in atmospheric water vapor are the result of substantial differences in the probability distribution function of precipitation and its resulting interactions with the land surface. The parametrization of convection produces light and large-scale precipitation, keeping the soils moist and supporting the development of convection. In contrast, less frequent but locally intense precipitation events lead to high amounts of runoff in explicitly resolved convection simulations. The stronger runoff inhibits the moistening of the soil during the monsoon season and limits the amount of water available to evaporation.

中文翻译：

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对流表示对全新世西非季风的影响

摘要。全球气候模型很难模拟全新世中期中北部非洲季风降水向北扩展。这些模型的一个共同特点是它们通常在过于粗糙的网格上运行以无法明确解决对流问题，但是对流是导致西非季风区域降水的最重要机制。在这里，我们通过比较夏季季风季节（7月至9月，JAS）与参数化（40 km）的区域模拟，研究了ICON气候模式中热带深对流的表示如何影响全新世中期的季风降水的子午分布。 -P）和明确解决的对流（5 km-E）。降水的空间分布和强度，在显式解析的对流模拟中比在带参数化对流的模拟中更现实。但是，在JAS-mean中，40 km-P模拟比5 km-E模拟产生更多的降水和向北延伸的区域，特别是在12°N和17°N之间。40 km-P模拟中较高的降水速率是与更强的季风环流相一致。此外，在40 km-P模拟中的大气分层较不稳定，并且明显潮湿。大气中水汽的差异是降水及其与陆地表面相互作用的概率分布函数存在实质差异的结果。对流的参数化产生轻度和大范围的降水，保持土壤湿润并支持对流的发展。相反，在明确解析的对流模拟中，频率较低但局部强度较大的降水事件导致大量径流。较强的径流抑制了季风季节土壤的湿润，并限制了可蒸发的水量。