Moisture transport and water vapour budget over the Sahara Desert
Moisture transport and water vapour budget over the Sahara Desert
复制标题
DOI：
10.1002/joc.7614
复制
发表时间：
2022-03
期刊：
影响因子：
--
通讯作者：
Li Zhuo;Liming Zhou
中科院分区：
文献类型：
--
作者：
Li Zhuo;Liming Zhou
以前的研究表明，撒哈拉和阿拉伯沙漠的近地表温度在气候变暖中被放大，这被称为沙漠放大（DA）。DA可能与水蒸气增加相关的大规模温室效应有关。在最干燥的沙漠中，由于水分的可用性非常有限，两个关键的问题没有得到回答，即沙漠中的水分来源以及热力学和动力学过程对水分输送变化的相对贡献。在这项研究中，大气水蒸气收支撒哈拉沙漠1981-2020年进行了分析，以解决这两个问题。结果表明，自1981年以来，撒哈拉沙漠上空的水汽含量显著增加，主要是在北方夏季和对流层中低层。水汽收支分析表明，在北方夏季，大部分增加的水汽通过沙漠北方边界的增强的偏北入流输送到撒哈拉沙漠，而其他边界都是输出通道。向北向内的水汽输送与对流层低层的高压脊和撒哈拉高压有关。进一步的分析表明，动力和热力因素共同作用导致了北方边界向内水汽通量的增加，而与环流形势变化相关的动力分量则主导了其年际变化。对流层低层环流形势的变化主要表现为阿拉伯半岛低压的向西伸和对流层低层撒哈拉高压的加强，这两种环流形势的变化都有助于偏北向内水汽输送的增加。
Previous studies documented that near‐surface temperatures over the Sahara and Arabian deserts have been amplified in a warming climate, which is termed desert amplification (DA). DA has been linked possibly to the large‐scale greenhouse effects associated with increasing water vapour. With very limited moisture availability over the driest desert, two key questions unanswered are the desert moisture sources and the relative contributions of thermodynamic and dynamic processes to the changes in moisture transport. In this study, the atmospheric water vapour budget over the Sahara Desert from 1981–2020 is analysed to address these two questions. Results indicate that the water vapour content over the Sahara Desert has increased significantly since 1981, primarily during the boreal summer and in the lower to middle troposphere. The water vapour budget analysis indicates that in the boreal summer, most of the added moisture is transported into the Sahara Desert through the intensifying northerly inflow across the northern boundary of the desert, while the other boundaries are all export channels. The northerly inward moisture transport is associated with the ridge in the lower troposphere and the Saharan high above the lower troposphere. Further analysis indicates that both dynamic and thermodynamic factors contribute to the increase of the inward moisture flux at the northern boundary, while the associated interannual variability is dominated by the dynamic component related to the circulation pattern changes. The changes of the circulation pattern in the lower troposphere are manifested as the westward extension of the low over the Arabian Peninsula and as the strengthening of the Saharan high above the lower troposphere, both contributing to the increase of the northerly inward moisture transport.