Mid-Pliocene West African Monsoon rainfall as simulated in the PlioMIP2 ensemble
Mid-Pliocene West African Monsoon rainfall as simulated in the PlioMIP2 ensemble
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DOI：
10.5194/cp-17-1777-2021
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发表时间：
2021-08-27
影响因子：
4.3
通讯作者：
Brady, Esther C.
中科院分区：
文献类型：
--
作者：
Berntell, Ellen;Zhang, Qiong;Brady, Esther C.
上新世中期暖期（mPWP，与320万年前相似）被认为是最近的一个以温暖气候状态为特征的时期，与现代地理环境相似，大气CO2浓度与400 ppmv相似，因此经常被认为是近期气候预测的有趣类比。古环境重建表明，西非地表温度升高，热带沙漠减少，气候湿润，西非季风（WAM）增强。利用上新世模式比对项目（PlioMIP2）第二阶段的模式结果，通过与工业化前时期的对照模拟进行比较，分析了上新世期间WAM降水的变化。整体数据显示，西非和撒哈拉地区的夏季降雨量强劲增加，平均增加2.5毫米/天，而赤道大西洋地区的降雨量则减少。90%的模式显示撒哈拉地区异常变暖和撒哈拉热低压加深，导致WAM增强和进入非洲大陆的季风流量增加。在使用耦合模式相互比较项目（CMIP3和CMIP5）的第3和第5阶段的未来预估中，也可以看到撒哈拉的类似变暖。虽然先前对未来预测的研究表明，萨赫勒地区的干湿对比是西向东的，但PlioMIP2模拟表明，该地区在温暖气候下降雨量均匀增加，其特征是温室气体强迫增加。我们注意到，这种影响将进一步取决于植被对二氧化碳强迫的长期响应。
The mid-Pliocene warm period (mPWP; similar to 3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar to modern geography and similar to 400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indicate higher surface temperatures, decreasing tropical deserts, and a more humid climate in West Africa characterized by a strengthened West African Monsoon (WAM). Using model results from the second phase of the Pliocene Modelling Intercomparison Project (PlioMIP2) ensemble, we analyse changes of the WAM rainfall during the mPWP by comparing them with the control simulations for the pre-industrial period. The ensemble shows a robust increase in the summer rainfall over West Africa and the Sahara region, with an average increase of 2.5 mm/d, contrasted by a rainfall decrease over the equatorial Atlantic. An anomalous warming of the Sahara and deepening of the Saharan Heat Low, seen in >90% of the models, leads to a strengthening of the WAM and an increased monsoonal flow into the continent. A similar warming of the Sahara is seen in future projections using both phase 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). Though previous studies of future projections indicate a west-east drying-wetting contrast over the Sahel, PlioMIP2 simulations indicate a uniform rainfall increase in that region in warm climates characterized by increasing greenhouse gas forcing. We note that this effect will further depend on the long-term response of the vegetation to the CO2 forcing.