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The formation of a large summertime Saharan dust plume: Convective and synoptic-scale analysis.

Roberts AJ, Knippertz P - J Geophys Res Atmos (2014)

Bottom Line: Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex.The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool.Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

View Article: PubMed Central - PubMed

Affiliation: School of Earth and Environment, University of Leeds Leeds, UK.

ABSTRACT

Haboobs are dust storms produced by the spreading of evaporatively cooled air from thunderstorms over dusty surfaces and are a major dust uplift process in the Sahara. In this study observations, reanalysis, and a high-resolution simulation using the Weather Research and Forecasting model are used to analyze the multiscale dynamics which produced a long-lived (over 2 days) Saharan mesoscale convective system (MCS) and an unusually large haboob in June 2010. An upper level trough and wave on the subtropical jet 5 days prior to MCS initiation produce a precipitating tropical cloud plume associated with a disruption of the Saharan heat low and moistening of the central Sahara. The restrengthening Saharan heat low and a Mediterranean cold surge produce a convergent region over the Hoggar and Aïr Mountains, where small convective systems help further increase boundary layer moisture. Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex. The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool. Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

No MeSH data available.


Related in: MedlinePlus

Same as Figure 3 but at 0000 UTC 10 June and including fields over southern Europe.
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fig05: Same as Figure 3 but at 0000 UTC 10 June and including fields over southern Europe.

Mentions: Figure 5 not only shows the same synoptic fields from ERA Interim and TRMM rainfall estimates as in Figure 3 but also shows southern Europe for 0000 UTC 10 June. The 200 hPa winds, 200 hPa geopotential, mean sea-level pressure, and TRMM rainfall show the presence of a midlatitude cyclone and trough over the Iberian Peninsula. The stream of the subtropical jet over West Africa is predominantly zonal, the northward bulge in the ITD is still present, and the rainfall associated with the MCS can be seen over Algeria, Niger, Mali, and Burkina Faso. The midlatitude cyclone produces a secondary low south of the Atlas Mountains through lee cyclogenesis. This deforms the Saharan heat low, which creates southwesterly flow over Algeria and northern Mali, which provides a mechanism for dust transport out of the Sahara toward the Mediterranean. SEVIRI dust images (not shown) show the stretching of the dust plume and northward transport of dust throughout 10 and 11 June.


The formation of a large summertime Saharan dust plume: Convective and synoptic-scale analysis.

Roberts AJ, Knippertz P - J Geophys Res Atmos (2014)

Same as Figure 3 but at 0000 UTC 10 June and including fields over southern Europe.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4379907&req=5

fig05: Same as Figure 3 but at 0000 UTC 10 June and including fields over southern Europe.
Mentions: Figure 5 not only shows the same synoptic fields from ERA Interim and TRMM rainfall estimates as in Figure 3 but also shows southern Europe for 0000 UTC 10 June. The 200 hPa winds, 200 hPa geopotential, mean sea-level pressure, and TRMM rainfall show the presence of a midlatitude cyclone and trough over the Iberian Peninsula. The stream of the subtropical jet over West Africa is predominantly zonal, the northward bulge in the ITD is still present, and the rainfall associated with the MCS can be seen over Algeria, Niger, Mali, and Burkina Faso. The midlatitude cyclone produces a secondary low south of the Atlas Mountains through lee cyclogenesis. This deforms the Saharan heat low, which creates southwesterly flow over Algeria and northern Mali, which provides a mechanism for dust transport out of the Sahara toward the Mediterranean. SEVIRI dust images (not shown) show the stretching of the dust plume and northward transport of dust throughout 10 and 11 June.

Bottom Line: Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex.The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool.Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

View Article: PubMed Central - PubMed

Affiliation: School of Earth and Environment, University of Leeds Leeds, UK.

ABSTRACT

Haboobs are dust storms produced by the spreading of evaporatively cooled air from thunderstorms over dusty surfaces and are a major dust uplift process in the Sahara. In this study observations, reanalysis, and a high-resolution simulation using the Weather Research and Forecasting model are used to analyze the multiscale dynamics which produced a long-lived (over 2 days) Saharan mesoscale convective system (MCS) and an unusually large haboob in June 2010. An upper level trough and wave on the subtropical jet 5 days prior to MCS initiation produce a precipitating tropical cloud plume associated with a disruption of the Saharan heat low and moistening of the central Sahara. The restrengthening Saharan heat low and a Mediterranean cold surge produce a convergent region over the Hoggar and Aïr Mountains, where small convective systems help further increase boundary layer moisture. Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex. The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool. Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

No MeSH data available.


Related in: MedlinePlus