Improved climatological precipitation characteristics over West Africa at convection-permitting scales
Improved climatological precipitation characteristics over West Africa at convection-permitting scales
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DOI：
10.1007/s00382-019-04759-4
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发表时间：
2019-08-01
期刊：
影响因子：
4.6
通讯作者：
Wilcox, Catherine
中科院分区：
文献类型：
--
作者：
Berthou, Segolene;Rowell, David P.;Wilcox, Catherine
西非的气候是独特的，具有挑战性的重现使用标准分辨率的气候模式作为一个大部分的降水来自有组织的深对流。首次在泛非洲区域进行了为期10年（1997-2006）的区域4.5公里对流允许模拟。4.5公里的模拟（CP 4A）进行了比较，25 x40公里对流参数化模式（R25）在西非。CP 4A显示平均降水量增加，这导致西非季风成熟阶段的改善，但早期和后期的恶化。与中尺度对流系统相联系的短时强降水事件增多，降水率的分布得到改善。因此，CP 4A模式在每日和次每日时间尺度上显示出更好的干湿期代表性。降雨的日循环得到改善，这影响季风的日循环并增加萨赫勒地区的水分辐合。虽然发现了不足之处，与模型开发的影响，这个对流允许模型提供了一个更可靠的降水分布比对流参数化的对应在每日和次每日的时间尺度。因此，对流允许尺度将有助于解决降水分布在未来将如何变化的关键问题。
The West African climate is unique and challenging to reproduce using standard resolution climate models as a large proportion of precipitation comes from organised deep convection. For the first time, a regional 4.5km convection permitting simulation was performed on a pan-African domain for a period of 10years (1997-2006). The 4.5km simulation (CP4A) is compared with a 25x40km convection-parameterised model (R25) over West Africa. CP4A shows increased mean precipitation, which results in improvements in the mature phase of the West African monsoon but deterioration in the early and late phases. The distribution of precipitation rates is improved due to more short lasting intense rainfall events linked with mesoscale convective systems. Consequently, the CP4A model shows a better representation of wet and dry spells both at the daily and sub-daily time-scales. The diurnal cycle of rainfall is improved, which impacts the diurnal cycle of monsoon winds and increases moisture convergence in the Sahel. Although shortcomings were identified, with implications for model development, this convection-permitting model provides a much more reliable precipitation distribution than its convection-parameterised counterpart at both daily and sub-daily time-scales. Convection-permitting scales will therefore be useful to address the crucial question of how the precipitation distribution will change in the future.