Dust and the low‐level circulation over the Bodélé Depression, Chad: Observations from BoDEx 2005

Dust plays an important role in climate, recognition of which has led to a concentrated research effort in field campaigns, development and analysis of remotely sensed data, and modeling to better understand dust. There have, however, been very few direct surface-based field measurements from key dust source regions. The Bodele, Chad, has been shown to be one of the premier sources of dust in the world. This paper reports on the Bodele Field Experiment (BoDEx 2005) which took place during February and March 2005 and presents the first surface-based measurements of the circulation over the Bodele. On the basis of Pilot Balloon and AWS data, we confirm the existence of the Bodele Low Level Jet (LLJ) and show that winds undergo a strong diurnal cycle such that strongest surface winds typically occur in the midmorning when momentum is mixed downward in turbulence induced by radiative heating. In contrast, the core of the LLJ, near 500 m, peaks during the evening and is weakest during the day. The LLJ was present on all days during BoDEx 2005, but winds at the surface reached speeds necessary for large-scale dust entrainment on only a few days. The winds strength during the main dust plume event of BoDEx (10–12 March 2005) was in the bottom third of March plume events of the last 4 years. Pathways of dust transport from the Bodele using a trajectory model show potential advection of dust over the west African coastline within 5 days.

[1]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[2]  Günther Zängl,et al.  Diurnal circulation of the Bolivian Altiplano. Part II Theoretical and model investigations , 2005 .

[3]  Olga V. Kalashnikova,et al.  Ability of multiangle remote sensing observations to identify and distinguish mineral dust types : Optical models and retrievals of optically thick plumes : Quantifying the radiative and biogeochemical impacts of mineral dust , 2005 .

[4]  Renjian Zhang,et al.  Ground observations of a strong dust storm in Beijing in March 2002 , 2005 .

[5]  Cyril Moulin,et al.  Understanding the long‐term variability of African dust transport across the Atlantic as recorded in both Barbados surface concentrations and large‐scale Total Ozone Mapping Spectrometer (TOMS) optical thickness , 2005 .

[6]  Richard Washington,et al.  Atmospheric controls on mineral dust emission from the Bodélé Depression, Chad: The role of the low level jet , 2005 .

[7]  Yoram J. Kaufman,et al.  Dust transport and deposition observed from the Terra‐Moderate Resolution Imaging Spectroradiometer (MODIS) spacecraft over the Atlantic Ocean , 2005 .

[8]  H. Hayami.  Behavior of secondary inorganic species in gaseous and aerosol phases measured in Fukue Island, Japan, in dust season , 2005 .

[9]  Jan H. Schween,et al.  Diurnal Circulation of the Bolivian Altiplano. Part I: Observations , 2005 .

[10]  Irina N. Sokolik,et al.  Characterization of east Asian dust outbreaks in the spring of 2001 using ground‐based and satellite data , 2005 .

[11]  C. Hueglin,et al.  Saharan dust events at the Jungfraujoch: detection by wavelength dependence of the single scattering albedo and first climatology analysis , 2004 .

[12]  C. Zender,et al.  Quantifying mineral dust mass budgets:Terminology, constraints, and current estimates , 2004 .

[13]  Meteorological events and transport patterns in ACE‐Asia , 2004 .

[14]  O. Boucher,et al.  The aerosol-climate model ECHAM5-HAM , 2004 .

[15]  Zorka Vukmirović,et al.  Contribution of dust transport and resuspension to particulate matter levels in the Mediterranean atmosphere , 2004 .

[16]  D. Orevi.  Contribution of dust transport and resuspension to particulate matter levels in the Mediterranean atmosphere , 2004 .

[17]  Pinhas Alpert,et al.  Vertical distribution of Saharan dust based on 2.5-year model predictions , 2004 .

[18]  Giorgio Fiocco,et al.  Direct radiative forcing of Saharan dust in the Mediterranean from measurements at Lampedusa Island and MISR space-borne observations , 2004 .

[19]  Yoram J. Kaufman,et al.  Direct wind measurements of Saharan dust events from Terra and Aqua satellites , 2004 .

[20]  N. Mahowald,et al.  Sensitivity of TOMS aerosol index to boundary layer height: Implications for detection of mineral aerosol sources , 2004 .

[21]  Mian Chin,et al.  Long-term simulation of global dust distribution with the GOCART model: correlation with North Atlantic Oscillation , 2004, Environ. Model. Softw..

[22]  A. Smedman,et al.  Effects of shear sheltering in a stable atmospheric boundary layer with strong shear , 2004 .

[23]  David S. Covert,et al.  Variability of aerosol optical properties derived from in situ aircraft measurements during ACE‐Asia , 2003 .

[24]  Detection of dust plumes and their sources in northeastern Libya , 2003 .

[25]  Sundar A. Christopher,et al.  Longwave radiative forcing of Saharan dust aerosols estimated from MODIS, MISR, and CERES observations on Terra , 2003 .

[26]  Peter J. Lamb,et al.  African Droughts and Dust Transport to the Caribbean: Climate Change Implications , 2003, Science.

[27]  Didier Tanré,et al.  Modeling the radiative impact of mineral dust during the Saharan Dust Experiment (SHADE) campaign , 2003 .

[28]  P. Formenti,et al.  Radiative properties and direct radiative effect of Saharan dust measured by the C-130 aircraft during SHADE: 1. Solar spectrum , 2003 .

[29]  Jonathan P. Taylor,et al.  Radiative properties and direct effect of Saharan dust measured by the C‐130 aircraft during Saharan Dust Experiment (SHADE): 2. Terrestrial spectrum , 2003 .

[30]  P. Formenti,et al.  Measurement and modeling of the Saharan dust radiative impact: Overview of the Saharan Dust Experiment (SHADE) , 2003 .

[31]  N. Mahowald,et al.  Sensitivity study of meteorological parameters on mineral aerosol mobilization, transport, and distribution , 2003 .

[32]  C. Zender,et al.  Mineral Dust Entrainment and Deposition (DEAD) model: Description and 1990s dust climatology , 2003 .

[33]  R. Washington,et al.  Dust-Storm Source Areas Determined by the Total Ozone Monitoring Spectrometer and Surface Observations , 2003 .

[34]  Jean-François Léon,et al.  Mineral dust sources in the surroundings of the north Indian Ocean , 2003 .

[35]  M. Heimann,et al.  Impact of vegetation and preferential source areas on global dust aerosol: Results from a model study , 2002 .

[36]  Michael W. Douglas,et al.  The South American low‐level jet east of the Andes during the 1999 LBA‐TRMM and LBA‐WET AMC campaign , 2002 .

[37]  O. Boucher,et al.  A satellite view of aerosols in the climate system , 2002, Nature.

[38]  C. Moulin,et al.  TOMS and METEOSAT satellite records of the variability of Saharan dust transport over the Atlantic during the last two decades (1979–1997) , 2002 .

[39]  O. Torres,et al.  ENVIRONMENTAL CHARACTERIZATION OF GLOBAL SOURCES OF ATMOSPHERIC SOIL DUST IDENTIFIED WITH THE NIMBUS 7 TOTAL OZONE MAPPING SPECTROMETER (TOMS) ABSORBING AEROSOL PRODUCT , 2002 .

[40]  Paul Ginoux,et al.  A Long-Term Record of Aerosol Optical Depth from TOMS Observations and Comparison to AERONET Measurements , 2002 .

[41]  N. Middleton,et al.  Saharan dust storms: nature and consequences , 2001 .

[42]  B. Holben,et al.  A dust outbreak episode in sub‐Sahel West Africa , 2001 .

[43]  M. Chin,et al.  Sources and distributions of dust aerosols simulated with the GOCART model , 2001 .

[44]  Yoram J. Kaufman,et al.  Full year cycle of desert dust spectral optical thickness and precipitable water vapor over Alexandria, Egypt , 2001 .

[45]  Michel Legrand,et al.  Satellite detection of dust using the IR imagery of Meteosat: 1. Infrared difference dust index , 2001 .

[46]  J. Lelieveld,et al.  Saharan dust in Brazil and Suriname during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) - Cooperative LBA Regional Experiment (CLAIRE) in March 1998 , 2001 .

[47]  G. Kallos,et al.  Saharan dust contributions to PM10 and TSP levels in Southern and Eastern Spain , 2001 .

[48]  Barak Herut,et al.  Dry atmospheric inputs of trace metals at the Mediterranean coast of Israel (SE Mediterranean): sources and fluxes , 2001 .

[49]  J. Penner,et al.  Aerosols, their Direct and Indirect Effects , 2001 .

[50]  M. Legrand,et al.  Dust Variability over Northern Africa and Rainfall in the Sahel , 2000 .

[51]  Sandy P. Harrison,et al.  Dust sources and deposition during the last glacial maximum and current climate: A comparison of model results with paleodata from ice cores and marine sediments , 1999 .

[52]  S. H. Melfi,et al.  Validation of the Saharan dust plume conceptual model using lidar, meteosat, and ECMWF Data , 1999 .

[53]  K. Stahr,et al.  The importance of source region identification and their properties for soil-derived dust : The case of Harmattan dust sources for Eastern West Africa , 1999 .

[54]  P. Devara,et al.  Atmospheric aerosol–cloud-stability relationship as observed with optical and radio remote sensing techniques , 1998 .

[55]  A. Chappell,et al.  Soil flux (loss and gain) in southwestern Niger and its agricultural impact , 1998 .

[56]  A. Avila,et al.  Mineralogical composition of African dust delivered by red rains over northeastern Spain , 1997 .

[57]  P. Bhartia,et al.  Global distribution of UV-absorbing aerosols from Nimbus 7/TOMS data , 1997 .

[58]  A. Lacis,et al.  The influence on climate forcing of mineral aerosols from disturbed soils , 1996, Nature.

[59]  N. Kubilay,et al.  Trace elements in atmospheric particulates over the Eastern Mediterranean; Concentrations, sources, and temporal variability , 1995 .

[60]  P. Seibert,et al.  A study of an outstanding Saharan dust event at the high-alpine site Jungfraujoch, Switzerland , 1995 .

[61]  I. Fung,et al.  Modeling of mineral dust in the atmosphere: Sources, transport, and optical thickness , 1994 .

[62]  Michael Garstang,et al.  Saharan dust in the Amazon Basin , 1992 .

[63]  Nick Middleton,et al.  The changing frequency of dust storms through time , 1992 .

[64]  Sylvie Joussaume,et al.  Three-dimensional simulations of the atmospheric cycle of desert dust particles using a general circulation model , 1990 .

[65]  A. Barnston,et al.  Classification, seasonality and persistence of low-frequency atmospheric circulation patterns , 1987 .

[66]  T. Carlson,et al.  The Large-Scale Movement of Saharan Air Outbreaks over the Northern Equatorial Atlantic , 1972 .