Mediterranean and Southwest Asia Dust Plume, March 16-22, 1999
Observations:
1200Z Surface Observations, Med, 16-23 March, 1999: dust mobilized along
coast and in Libya and Egypt as surface low moves across N. Africa.
Strong NNW winds cause dust storms over central Egypt on the 20th.
6-hourly Surface Observations, East Med:
dust arrives in the westerly and southwesterly flow ahead of low on 19th, lasts through 21, reaching as far north as Turkey.
6-hourly Surface Observations, SW Asia
: dust reaches eastern Saudi Arabia and Kuwait on 21st, and western Iran on 22nd.
Lowest visibilities from 18Z on 20st through 12Z on 22nd all are in NW winds and progress
from Jordan to Kuwait.
There are strong southerly winds across the region ahead of the cold front, but
no low visibilities are associated with those winds.
6-hourly NOGAPS Med Loop
: surface low (lower-left plot) moves across the Med bringing high midday
W and SW surface winds
on the 18th, and high W and NW winds on the 19th and 20th giving a pulsing
nature to the high friction velocities (lower-right plot) and dust production.
This is also apparent in the Mid-East surface
observations (above) though that periodicity may be due to more observations being available
in daytime. Strong NNW winds in central Egypt and Sudan also on the 20th.
6-hourly NOGAPS SW Asia Loop
: Strong southerlies over Arabian Peninsula from 12z on 19th through 00Z on 21st.
Friction velocities exceed the threshold (60 cm/s, red shading in lower-right plots)
but surface observations do not show mobilization.
Friction velocities are greater than 40 cm/s (solid contour) in the northwesterlies
behind the cold front, but not high enough (> 60 cm/s) to lift dust.
Features seen in TOMS imagery are apparent in NAAPS simulation,
especially the timing and location of the plume across the eastern
Mediterranean on the 18th and 19th.
