Bush Emma R, Jeffery Kathryn, Bunnefeld Nils, Tutin Caroline, Musgrave Ruth, Moussavou Ghislain, Mihindou Vianet, Malhi Yadvinder, Lehmann David, Edzang Ndong Josué, Makaga Loïc, Abernethy Katharine
Faculty of Natural Sciences, University of Stirling, Stirling, UK.
Agence Nationale des Parcs Nationaux (ANPN), Libreville, Gabon.
PeerJ. 2020 Apr 14;8:e8732. doi: 10.7717/peerj.8732. eCollection 2020.
The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However, they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2,000 mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of persistent cloudiness and inability to ground-truth estimates. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests under future climate scenarios.
We have the rare opportunity to analyse a 34 year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in Gabon, western equatorial Africa. We used (generalized) linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns.
Lopé's weather is characterised by a cool, light-deficient, long dry season. Long-term climatic means have changed significantly over the last 34 years, with warming occurring at a rate of +0.25 °C per decade (minimum daily temperature) and drying at a rate of -75 mm per decade (total annual rainfall). Inter-annual climatic variability at Lopé is highly influenced by global weather patterns. Sea surface temperatures of the Pacific and Atlantic oceans have strong coherence with Lopé temperature and rainfall on multi-annual scales.
The Lopé long-term weather record has not previously been made public and is of high value in such a data poor region. Our results support regional analyses of climatic seasonality, long-term warming and the influences of the oceans on temperature and rainfall variability. However, warming has occurred more rapidly than the regional products suggest and while there remains much uncertainty in the wider region, rainfall has declined over the last three decades at Lopé. The association between rainfall and the Atlantic cold tongue at Lopé lends some support for the 'dry' models of climate change for the region. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of dry season clouds to ocean temperatures and the viability of humid evergreen forests in this dry region should the clouds disappear.
中非湿润的热带森林影响着全球气候，在全球碳循环中发挥着重要作用。然而，它们也是一种生态异常现象，尽管年总降雨量不足2000毫米，但常绿森林却在赤道西部地区占主导地位。中非的气象数据极为稀少且不完整，由于持续多云以及无法进行实地验证估算，卫星衍生数据也存在重大问题。迫切需要长期气候观测来验证区域气候和植被模型，阐明驱动气候变率的机制，并评估未来气候情景下常绿森林的生存能力。
我们有幸能够分析来自赤道非洲西部加蓬的一个长期生态研究站点——洛佩国家公园的34年降雨和温度数据集（以及较短时期的绝对湿度、风速、太阳辐射和气溶胶光学厚度）。我们使用（广义）线性混合模型和频谱分析来评估季节和年际变化、长期趋势以及海洋对当地天气模式的影响。
洛佩的天气特点是凉爽、光照不足且旱季漫长。在过去34年里，长期气候均值发生了显著变化，变暖速度为每十年+0.25℃（最低日气温），变干速度为每十年-75毫米（年总降雨量）。洛佩的年际气候变率受全球天气模式的高度影响。太平洋和大西洋的海表面温度在多年尺度上与洛佩的温度和降雨有很强的相关性。
洛佩的长期天气记录此前未曾公开，在这样一个数据匮乏的地区具有很高的价值。我们的结果支持了对气候季节性、长期变暖以及海洋对温度和降雨变率影响的区域分析。然而，变暖速度比区域模型显示的要快，尽管该更广泛区域仍存在许多不确定性，但过去三十年里洛佩的降雨量有所下降。洛佩降雨与大西洋冷舌之间的关联为该地区气候变化的“干旱”模型提供了一些支持。在气候迅速变暖和变干的背景下，迫切需要研究旱季云层对海洋温度的敏感性，以及如果云层消失，这片干旱地区湿润常绿森林的生存能力。
