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Weakened seasonality of the African rainforest precipitation in boreal winter and spring driven by tropical SST variabilities
Geoscience Letters ( IF 4 ) Pub Date : 2021-06-07 , DOI: 10.1186/s40562-021-00192-w
Xin-Yue Wang , Jiang Zhu , Meijiao Xin , Chentao Song , Yadi Li , Yi Zhou , Xichen Li

Precipitation in the equatorial African rainforest plays an important role in both the regional hydrological cycle and the global climate variability. Previous studies mostly focus on the trends of drought in recent decades or long-time scales. Using two observational datasets, we reveal a remarkable weakening of the seasonal precipitation cycle over this region from 1979 to 2015, with precipitation significantly increased in the boreal winter dry season (~ 0.13 mm/day/decade) and decreased in the boreal spring wet season (~ 0.21 mm/day/decade), which account for ~ 14% (the precipitation changes from 1979 to 2015) of their respective climatological means. We further use a state-of-the-art atmospheric model to isolate the impact of sea surface temperature change from different ocean basins on the precipitation changes in the dry and wet seasons. Results show that the strengthening precipitation in the dry season is mainly driven by the Atlantic warming, whereas the weakening precipitation in the wet season can be primarily attributed to the Indian Ocean. Warming Atlantic intensifies the zonal circulation over the African rainforest, strengthening moisture convergence and intensifying precipitation in the boreal winter dry season. Warming Indian Ocean contributes more to reducing the zonal circulation and suppressing the convection in the boreal spring wet season, leading to an opposite effect on precipitation. This result has important implication on local ecology as well as global climate system.

中文翻译:

热带海温变化导致北半球冬春季非洲雨林降水季节性减弱

赤道非洲雨林的降水在区域水文循环和全球气候变率中都起着重要作用。以往的研究主要集中在近几十年或长期尺度上的干旱趋势。使用两个观测数据集,我们揭示了从 1979 年到 2015 年该地区季节性降水周期的显着减弱,北方冬季旱季(~0.13 毫米/天/十年)的降水量显着增加,而在北方春季雨季降水量减少(~ 0.21 mm/day/decade),占各自气候平均值的~14%(1979年至2015年的降水变化)。我们进一步使用最先进的大气模型来隔离来自不同海洋盆地的海面温度变化对旱季和雨季降水变化的影响。结果表明,旱季降水增强主要受大西洋变暖驱动,而雨季降水减弱主要归因于印度洋。大西洋变暖加剧了非洲热带雨林的纬向环流,加强了北方冬季旱季的水分汇聚和降水。印度洋变暖对减少纬向环流和抑制北春季湿季对流的贡献更大,对降水产生相反的影响。这一结果对当地生态和全球气候系统具有重要意义。而雨季降水减弱主要归因于印度洋。大西洋变暖加剧了非洲热带雨林的纬向环流,加强了北方冬季旱季的水分汇聚和降水。印度洋变暖对减少纬向环流和抑制北春季湿季对流的贡献更大,对降水产生相反的影响。这一结果对当地生态和全球气候系统具有重要意义。而雨季降水减弱主要归因于印度洋。大西洋变暖加剧了非洲热带雨林的纬向环流,加强了北方冬季旱季的水分汇聚和降水。印度洋变暖对减少纬向环流和抑制北春季湿季对流的贡献更大,对降水产生相反的影响。这一结果对当地生态和全球气候系统具有重要意义。印度洋变暖对减少纬向环流和抑制北春季湿季对流的贡献更大,对降水产生相反的影响。这一结果对当地生态和全球气候系统具有重要意义。印度洋变暖对减少纬向环流和抑制北春季湿季对流的贡献更大,对降水产生相反的影响。这一结果对当地生态和全球气候系统具有重要意义。
更新日期:2021-06-07
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