Shallow stratocumulus clouds created below the base of the Saharan Air Layer by the action of Saharan dust

Pavel Kishcha, Arlindo da Silva, Boris Starobinets, Pinhas Alpert

Research output: Contribution to journalConference articlepeer-review


Previous studies showed that, over the global ocean, there is no noticeable hemispheric asymmetry in cloud fraction (CF). This cloud symmetry contributes to the balance in solar radiation reaching the sea surface in the Northern and Southern hemispheres. By contrast, over the tropical Atlantic, the CF hemispheric asymmetry takes place. The tropical Atlantic (30N – 30S) is frequently affected by
Saharan dust intrusions. Based on MODIS cloud fraction data during a ten-year study period, we found that these dust intrusions contribute to significant cloud cover up to 0.8 – 0.9 along the Saharan Air Layer (SAL). The area of SAL with significant CF is characterized by limited precipitation, indicating that clouds along the SAL are not developed enough. Meteorological conditions below the
temperature inversion at the SAL base include high atmospheric humidity and the presence of large amounts of settling dust particles together with marine aerosols. Being below the temperature inversion and acting as efficient CCN, Saharan dust particles coated with sea-salt contribute to the formation of shallow stratocumulus clouds. Significant cloud fraction under the base of SAL, together
with clouds over the Atlantic Inter-tropical Convergence Zone, contributes to the 20% hemispheric CF asymmetry between the tropical North and South Atlantic. Saharan dust is also the major contributor to the pronounced hemispheric aerosol asymmetry over the tropical Atlantic, based on MERRAero aerosol reanalysis data. These two factors could lead to an imbalance in strong solar radiation (which reaches the sea surface between the tropical North and South Atlantic), affecting
climate formation in the tropical Atlantic.
Original languageEnglish
Pages (from-to)62-66
Number of pages5
StatePublished - 2016
EventDUST 2016: 2nd International Conference on Atmospheric Dust - Castellaneta Marina, Taranto, Italy
Duration: 12 Jun 201617 Jun 2016
Conference number: DUST 2016


  • Clouds
  • Desert dust
  • Sahara
  • Ocean


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