Moisture budget analysis of SST-driven decadal Sahel precipitation variability in the twentieth century

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• 作者：Catherine Pomposi ; Yochanan Kushnir ; Alessandra Giannini
• 关键词：Sahel precipitation ; Sea surface temperatures ; Atmospheric moisture budget ; Monsoon
• 刊名：Climate Dynamics
• 出版年：2015
• 出版时间：June 2015
• 年：2015
• 卷：44
• 期：11-12
• 页码：3303-3321
• 全文大小：11,708 KB
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• 作者单位：Catherine Pomposi (1)
  Yochanan Kushnir (2)
  Alessandra Giannini (3)
  
  1. Department of Earth and Environmental Sciences, Columbia University, 61 Route 9W, 143 Monell, Palisades, NY, 10964, USA
  2. Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, 104B Oceanography, Palisades, NY, 10964, USA
  3. International Research Institute for Climate and Society, 61 Route 9W, 109 Monell, Palisades, NY, 10964, USA
  
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geophysics and Geodesy
  Meteorology and Climatology
  Oceanography
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-0894

文摘

It is well known that the Sahel region of Africa is impacted by decadal scale variability in precipitation, driven by global sea surface temperatures. This work demonstrates that the National Center for Atmospheric Research’s Community Atmosphere Model, version 4 is capable of reproducing relationships between Sahelian precipitation variability and Indian and Atlantic Ocean sea surface temperature variations on such timescales. Further analysis then constructs a moisture budget breakdown using model output and shows that the change in precipitation minus evaporation in the region is dominated by column integrated moisture convergence due to the mean flow, with the convergence of mass in the atmospheric column mainly responsible. It is concluded that the oceanic forcing of atmospheric mass convergence and divergence to a first order explains the moisture balance patterns in the region. In particular, the anomalous circulation patterns, including net moisture divergence by the mean and transient flows combined with negative moisture advection, together explain the drying of the Sahel during the second half of the twentieth century. Diagnosis of moisture budget and circulation components within the main rainbelt and along the monsoon margins show that changes to the mass convergence are related to the magnitude of precipitation that falls in the region, while the advection of dry air is associated with the maximum latitudinal extent of precipitation.