Sahel dust zone and synoptic background

Klose, Martina; Shao, Yaping; Karremann, Melanie K.; Fink, Andreas H.

doi:10.1029/2010gl042816

Cited by 81 publications

(56 citation statements)

References 17 publications

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“…The dust may than be transported towards the Atlantic Ocean and beyond. Klose et al (2010) show that about half of dust suspended over the Sahel may be linked to a pressure pattern typical of Harmattan surges: a low over the Arabian Peninsula and the Azores High expanding eastwards into the continent. The mass of dust emission associated with cyclones has not been estimated before.…”

Section: S Fiedler Et Al: Dust Emission Associated With Depressionsmentioning

confidence: 99%

How important are atmospheric depressions and mobile cyclones for emitting mineral dust aerosol in North Africa?

et al. 2014

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Abstract. This study presents the first quantitative estimate of the mineral dust emission associated with atmospheric depressions and mobile cyclones in North Africa. Atmospheric depressions are automatically tracked at 925 hPa based on ERA-Interim data from the European Centre for MediumRange Weather Forecasts for [1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002][2003][2004][2005][2006][2007][2008]. A set of filter criteria is applied to identify mobile cyclones, i.e. migrating and long-lived cyclones. The shorter term cyclone is used as a synonym for mobile cyclones. Dust emission is calculated with a dust emission model driven by 10 m winds and soil moisture from ERA-Interim. Emission peaks during winter and spring with spatial averages of 250-380 g m −2 per month. Comparison of the dust source activation frequency from the model against SEVIRI satellite observation shows a good agreement in the Bodélé Depression but differences in the north and west of North Africa. Depressions are abundant, particularly in summer when the Saharan heat low is situated over West Africa and during spring in the lee of the Atlas Mountains. Up to 90 % (55 % annually and spatially averaged) of dust emission occurs within 10 degrees of these depressions, with embedded mechanisms such as nocturnal low-level jets playing a role. Cyclones are rarer and occur primarily north of 20 • N in spring in agreement with previous studies and over summertime West Africa consistent with near-surface signatures of African Easterly Waves. Dust emission within 10 degrees of cyclones peaks over Libya with up to 25 % in spring. Despite the overall small contribution of 4 % annually and spatially averaged, cyclones coincide with particularly intense dust emission events exceeding the climatological mean by a factor of four to eight. Soil moisture weakens dust emission during cyclone passage by about 10 %.

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Section: S Fiedler Et Al: Dust Emission Associated With Depressionsmentioning

confidence: 99%

How important are atmospheric depressions and mobile cyclones for emitting mineral dust aerosol in North Africa?

et al. 2014

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“…Arbuszewski et al in a research entitled "Studying the Effect of Tropical Convergence Zone on Aerosols" have shown that air masses of dust are fully associated with the location of ITCZ [5]. Seasonal variation in the spatial distribution of aerosols over Africa and nearby oceans is related to the large-scale atmospheric circulation, which is manifested by seasonal changes in the position of the intertropical convergence zone [6] and subsequent variations in the location and intensity of circulation centers [7] [8] [9]. The ITCZ is characterized by the convergence of dry northeasterly trade winds blowing over the Sahara, the so-called Harmattan winds, and humid south easterly winds originating farther south over the tropical Atlantic Ocean [7].…”

Section: Introductionmentioning

confidence: 99%

Annual Fluctuations and Displacements of Inter Tropical Convergence Zone (ITCZ) within the Range of Atlantic Ocean-India

Lashkari¹,

Mohammadi²,

Keikhosravi³

2017

OJE

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Inter Tropical Convergence Zone (ITCZ) is one of the major systems in making the general circulation of atmosphere. Many climatologists believe that the starting point of the general circulation of atmosphere is from this system. It seems that the annual displacement of this system is coordinated with the sun. In this study we have tried to investigate the annual and seasonal displacement of this system within the range of Middle East, especially within the range of longitude of Iran in a long period of time (statistical period of 66 years). This is the first study in the field of ITCZ monthly and annual longterm changes in Iran. In this study, not only his exact position on Africa and South West Asia ITCZ is determined, it also shows the change in the period of 66 years. These results can also be used on regional climate changes. For this purpose topographic and surface level pressure maps are 1000 and 850 hpa and they were approximately extracted monthly for 12 months of the year from 1948 to 2013 and also they were extracted from the National Oceanic and Atmospheric Administration Site in America within the range of 30˚ west to 110˚ east, and they were extracted by using the flow map of location (ITCZ). Due to the sudden displacement in the ITCZ bar path in the two seasons of summer and winter, on the Middle East region, the direct impact of this displacement on sudden changes of seasons, the start and end of untimely rains, its impacts on agricultural products and water recourses of the country so all these reasons are essential that this phenomenon should be studied carefully. Studies have shown that ITCZ is not a coordinated solar system and its displacement is not coordinate with the apparent annual displacement of the sun. October is the only month of ITCZ that within the range of 10 northern degrees in all the ranges of longitude 20˚ west to 110˚ east has an approximate orbital shape. In 6 months of the year (from November to April) (ITCZ) within the range of 30˚ east or 110˚ east, it is entirely located in the Southern Hemisphere and on the contrary in 5 months from May to September (ITCZ) within the range of 30˚ 13east to 110˚ east, it is entirely located in the Northern Hemisphere. And in this period, ITCZ has its highest Northern movement on the Earth. So that at the foot of the Himalayas it moves to 30˚ north. Within the range of Africa, ITCZ never enters the Southern Hemisphere at any time of the year. And the interesting phenomenon of severe refraction in the way of ITCZ, during the cold period, is within the range of Ethiopia and ITCZ has approximately redirected for Meridian and enters the Southern Hemisphere.

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“…In similar studies of other regions, Klose [26] found that the Sahel dust zone corresponds well to the convergence zone located to the north of the African monsoon trough. However, Fiedler et al [27] highlighted that depressions are abundant and associated with 55% of the annual amount of dust emissions over North African dust sources.…”

Section: Introductionmentioning

confidence: 79%

The Synoptic Patterns Associated with Spring Widespread Dusty Days in Central and Eastern Saudi Arabia

Awad¹,

Mashat²

2014

Atmosphere

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Four synoptic regimes were identified as accompanying the widespread dust in central and eastern Saudi Arabia. The widespread cases of dust were classified based on the value and spread of the aerosol index data from the TOMS aerosol index (TOMS AI) satellite over the area of interest. The synoptic regimes of these dust cases were recognized using the Empirical Orthogonal Function (EOF) analysis of their mean sea level pressure (SLP), which was obtained from the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) Reanalysis Project dataset. The variations of the analyzed SLP of these four regimes appeared as meridional distributions for the first two regimes and zonal distributions for the second two regimes. A surface synoptic study of the first two regimes showed that the most significant features were either a strong low-pressure system over the eastern region or a strong high-pressure system over the western region. The synoptic features for the less significant regimes (the second two regimes) were characterized by the interaction between the northern high-pressure belt, which shifted northward because of the significant regime decrease, and the southern low-pressure belt. In addition, the upper synoptic study showed that the upper synoptic systems support the surface systems. Moreover, the study showed that the surface northerly wind over the eastern Arabian Peninsula is the dominant wind during strong dust activity, whereas the surface southerly wind is dominant during weak dust activity. OPEN ACCESSAtmosphere 2014, 5 890

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Sahel dust zone and synoptic background

Cited by 81 publications

References 17 publications

How important are atmospheric depressions and mobile cyclones for emitting mineral dust aerosol in North Africa?

How important are atmospheric depressions and mobile cyclones for emitting mineral dust aerosol in North Africa?

Annual Fluctuations and Displacements of Inter Tropical Convergence Zone (ITCZ) within the Range of Atlantic Ocean-India

The Synoptic Patterns Associated with Spring Widespread Dusty Days in Central and Eastern Saudi Arabia

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