Saharan Dust Sources and their World Trajectories - A review in memory of J. Barkan (deceased 27 May 2020)

Barkan investigated the synoptics of dust trajectories to Europe, Arctic, E. & W. Mediterranean, and the Atlantic Ocean (Barkan et al. 2004). His most recent research just before he passed away Barkan studied the outstanding Red Snow Event in Eastern Europe on March 2018. In April 2018 the European media published in great headlines a strange occurrence. Red colored snow fell in Bulgaria, Rumania, Ukraine and what was most interesting to the media, was reported in the mountains around Sochi the location of the former winter Olympic Games. Barkan showed that the phenomenon of the red snow in southwestern Europe is the result of a cold trough which penetrated from the north toward the central Mediterranean and Saharan Africa, together with its movement eastward. Consequently, a strong southwesterly flow formed along the eastern flank of the trough. This flow transported a large amount of red Saharan dust which upon mixing with the snowfall in the area painted the snow red (Barkan and Alpert, 2020). In this case the trough developed further east which is not a common occurrence. This has caused heavy dust storms in central Sahara near the most ample dust sources (Barkan, Kutiel and Alpert, 2004). So, it will be shown that the transported dust reached the area together with snow flakes and probably painted it in red or brown.

Another interesting study by late Barkan is on the difference in the synoptic situation between years with a large amount of dust and years with relatively small amount, in the Sahara- this was examined for 1979-1992 (Barkan and Alpert, 2008). For every month the dustiest and the non-dustiest year were chosen and the average of the three months in the season of these years was examined. The examination was made for the atmospheric variables: wind flow, wind velocity, geopotential height and temperature, at the 700 hPa level. The data used were the daily aerosol index from the TOMS satellite born instrument and the daily NCEP/NCAR reanalysis data of the variables mentioned above between the years 1979-1992.

 Other interesting studies will be reviewed including, a novel climatic index for the total Saharan dust being discovered as the Sun insolation; a unique case-study of near-circular Saharan dust transport over the Atlantic Ocean; and dust as a potential tracer for the flow over different topographical shapes employing MODIS-Terra observations.

References:

• Barkan, P. Kishcha, H. Kutiel, and P. Alpert, "The Synoptics of Dust Intrusion Days from the African Continent into the Atlantic Ocean", J. Geophys. Res., Vol. 109, No. D8, D08201=2010.1029/2003JD004416=20, 2004.
• Barkan, H. Kutiel and P. Alpert, "Climatology of dust sources over the North African region, based on TOMS data", Indoor-Built Environ., Vol. 13, 407-419, 2004.
• Barkan, P. Alpert, H. Kutiel, and P. Kishcha,"The Synoptics of dust transportation days from Africa toward Italy and Central Europe", J. Geophy. Res., 110, doi:10.1029/2003 JD004416, 2005.
• Alpert, J. Barkan, and P. Kishcha, "A potential climatic index for total Saharan dust: the Sun insolation", J Geophy. Res., 111, D01103, doi:10.1029/2005JD006105, 2006.