Dust:

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Dust Data and Sources
Dr Richard Washington University of Oxford Dr
Martin Todd University College London
Prof Andrew Goudie University of Oxford Dr Mike
Bithell University of Cambridge
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Outline

• Dust Data
• Surface based synops (from GCOS, 117 stations,
  3hrly 1980-2000)
• Surface based synops (from local Met Agencies)
• TOMS AI data
• IDDI
• Shuttle Photographs, NOAA images etc
• Climate Data and Trajectory modelling
• Reanalysis Data (NCEP and ERA-15) 3D winds
• 25 point forward trajectory clusters
• every 6 hours for 10days, 1979-1998
• Determine regional transport corridors
• Re-circulation
• Interannual variability

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Nr Missing Months 1980-2000
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Nr Missing Months 1980-2000
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Nr Missing Months 1980-2000
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Nr Missing Months 1980-2000
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GCOS Data Compared with locally Obtained Data
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In Salah visibility 80-00
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Outline

• Dust Data
• Surface based synops (from GCOS, 117 stations)
• Surface based synops (from local Met
  Agencies) Niger, Chad, Algeria, Mali, Mari
• TOMS AI data
• IDDI
• Shuttle Photographs, NOAA images etc
• Climate Data and Trajectory modelling
• Reanalysis Data (NCEP and ERA-15) 3D winds
• 25 point forward trajectory clusters
• every 6 hours for 10days, 1979-1998
• Determine regional transport corridors
• Re-circulation

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Niger visibility 70-00
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NDjamena, Chad Haze Vs Obs Rainfall By season
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Bilma, Niger sandstorms Vs TOMS by season
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North African Surface Dust storms Correlation TOMS
1980-2000
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Bilma surface visibility Vs TOMS (march 1980-2000)
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Outline

• Dust Data
• Surface based synops (from GCOS, 117 stations)
• Surface based synops (from local Met
  Agencies) Niger, Chad, Algeria, Mali, Mari
• TOMS AI data
• IDDI
• Shuttle Photographs, NOAA images etc
• Climate Data and Trajectory modelling
• Reanalysis Data (NCEP and ERA-15) 3D winds
• 25 point forward trajectory clusters
• every 6 hours for 10days, 1979-1998
• Determine regional transport corridors
• Re-circulation

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REOF2 of TOMS AI monthly anomalies for the period
1980-05/93 and 1997-2000
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REOF3 of TOMS AI monthly anomalies for the period
1980-05/93 and 1997-2000
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REOF5 of TOMS AI monthly anomalies for the period
1980-05/93 and 1997-2000
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REOF6 of TOMS AI monthly anomalies for the period
1980-05/93 and 1997-2000
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REOF7 of TOMS AI monthly anomalies for the period
1980-05/93 and 1997-2000
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REOF8 of TOMS AI monthly anomalies for the period
1980-05/93 and 1997-2000
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Apr
Potential Sand Flux overlay TOMS q 2.61 U3
pg 1 (1-U/U)(1U/U)2
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Sahel TOMS (white contours), potential sand flux
(black contours), with DEM (colour). LTM for JFM
80-00.
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Central Asia TOMS (white contours), potential
sand flux (black contours), with DEM (colour).
Long term mean for 80-00.
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Correlation of monthly visibility anomalies at
Nouakchott (Mauritania) with global NCEP derived
potential sand flux for 1980-2000
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Correlation of monthly visibility anomalies at
Bobo-Dioulasso (Burkina Faso) with global NCEP
derived potential sand flux for 1980-2000
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Outline

• Dust Data
• Surface based synops (from GCOS, 117 stations)
• Surface based synops (from local Met
  Agencies) Niger, Chad, Algeria, Mali, Mari
• TOMS AI data
• IDDI
• Shuttle Photographs, NOAA images etc
• Climate Data and Trajectory modelling
• Reanalysis Data (NCEP and ERA-15) 3D winds
• 25 point forward trajectory clusters
• every 6 hours for 10days, 1979-1998
• Determine regional transport corridors
• Re-circulation

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Djouf region
Bodele
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Parcel trajectory climatology May
(1979-98) Bodele depression (17.5N, 17E)
54 of trajectories cross the 15W meridian
27 of trajectories remain over N. Africa
21 of trajectories remain over Sahara (gt 15N)
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Parcel trajectory climatology June
(1979-98) Bodele depression (17.5N, 17E)
79 of trajectories cross the 15W meridian
13 of trajectories remain over N Africa
9 of trajectories remain over Sahara (gt 15N)
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Parcel trajectory climatology Dec
(1979-98) Bodele depression (17.5N, 17E)
66 of trajectories cross the 15W meridian
23 of trajectories remain over N. Africa
6 of trajectories remain over Sahara (gt 15N)
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Dust Recycling potential
May
July
June
Dec
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Parcel trajectory climatology May
(1979-98) Bodele depression (17.5N, 17E)
Mean 0-15N
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Parcel trajectory climatology Dec
(1979-98) Bodele depression (17.5N, 17E)
Mean 0-15N
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TOMS AI over Bodele region (15-17N, 16-18E)
mean
May 1991
May 1989
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May 1991
Height (hPa)
Lat.
Long.
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May 1989
Height (hPa)
Lat.
Long.
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Djouf region
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TOMS AI over Djouf region (17.5-22.5N, 2.5-7.5W)
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Parcel trajectory density climatology July
(1979-98) Djouf region (17.5-22.5N, 2.5-7.5W)
After days 3 5 10
trajectories crossing the 15W meridian
33 66 83
trajectories remain over Sahara (gt 15N lt 30N)
69 33 6
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Annual TOMS AI over Djouf region
Annual CMAP precipitation over Djouf region
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Conclusions

• Surface Synops GCOS data expensive and patchy
• Surface Synops from Met Agencies
• Synops-TOMS AI sensible but weak
• Major mineral dust source regions identified from
  TOMS AI data Bodele and Djouf
• Trajectory modelling allows definition of dust
  transport corridors
• Pronounced seasonal cycle and interannual
  variability

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Parcel trajectory climatology May
(1979-98) Bodele depression (17.5N, 17E)
500hPa
40N
40E
10S
80W
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Parcel trajectory density climatology July
(1979-98) Djouf region (17.5-22.5N, 2.5-7.5W)
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West of 15W
Over Atlantic
Over Sahara gt15N lt30N
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Parcel trajectory climatology May
(1979-93) Bodele depression (17.5N, 17E)
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TOMS mean AI May 1980-93
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Parcel trajectory climatology July
(1979-98) Bodele depression (17.5N, 17E)
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Parcel trajectory density climatology July
(1979-98) Djouf region (17.5-22.5N, 2.5-7.5W)
Mean 10-25N
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