ITD Diurnal Cycle

B. Pospichal, D. Bou Karam , S. Crewell, C. Flamant, A. Hünerbein, O. Bock, F. Saïd (2009): Diurnal cycle of the inter-tropical discontinuity over West Africa analysed by remote sensing and mesoscale modelling, submitted to QJRMS.


Abstract

 

The diurnal cycle of the Inter-tropical discontinuity (ITD), i.e. the interface at the ground between the moist monsoon air and the dry Harmattan air, is an important factor in the West African monsoon system. During the whole year of 2006, high resolution ground-based remote-sensing measurements have been performed in the area of Djougou, Benin which made it possible to observe the ITD and the associated sharp gradient of temperature and humidity in detail.

 

In order to extend the point measurements to a 3D view of the ITD and to enhance the knowledge of the processes around the ITD, the mesoscale atmospheric model MesoNH has been run for a 84-hours period in April 2006. In addition Meteosat infrared observations have been used to determine the ITD position and its movement. From these observations a northward propagation of the moist air front (ITD) of 8-12 m s-1 has been calculated.

 

The model turned out to match well with the observations: For example, the time of front arrival in Djougou is simulated with a maximum error of about 1 hour and the speed of the ITD is consistent with Meteosat images. This agreement suggests the use of the model to further describe processes in the lower atmosphere.

 

Keywords: AMMA, West African Monsoon, Low level jet, MesoNH

International Meetings

2010


Schwendike J., D. Bou Karam, S. Crumeyrolle, C. Flamant, S.C. Jones, M. Schmidberger, F. Solmon, T. Stanelle, B. Voge, H. Vogel (2010): Mineral dust transport over West Africa in 2006, AMS 29th Conference on Hurricanes and Tropical Meteorology, 10–14 May 2010, Tucson, Arizona, USA.


Bou Karam D., C. Flamant, A. Evan, J. Cuesta and E. Williams (2010): The radiative impact of airborne dust on the Saharan cyclone on February 2007, European Geosciences Union, General Assembly, 1-7 May 2010, Vienna, Austria.


Bou Karam D., E. Williams, M. McGraw-Herdeg, M. Janiga, J. Cuesta, C. Flamant and C. Thorncroft (2010): Dusty gust fronts at synoptic scale, initiated and maintained by moist convection over the Sahara desert, European Geosciences Union, General Assembly, 1-7 May 2010, Vienna,  Austria.


Williams E., M. Donovan, Z. J. Luo, C. Kessinger, C. Huaqing, N. Rehak, D. Megenhardt, M. Steiner, D. Bou Karam (2010): Diameters of Cumulonimbi over Land and Ocean and Their Dependence on Cloud Base Height, AMS annual meeting, 17-20 January 2010, Atlanta, Georgia, USA.


Bou Karam D., C. Flamant, P. Tulet (2010): Estimate of dust emissions in the intertropical discontinuity region of the West African Monsoon, AMS annual meeting, 17-20 January 2010, Atlanta, Georgia, USA.


Bou Karam D., C. Flamant, A. Evan, J. Cuesta and E. Williams (2010): The radiative impact of airborne dust on the Saharan cyclone on February 2007, AMS annual meeting, 17-20 January 2010, Atlanta, Georgia, USA.


Bou Karam D., E. Williams, M. McGraw-Herdeg, M. Janiga, J. Cuesta, C. Flamant and C. Thorncroft (2010): Dusty gust fronts at synoptic scale, initiated and maintained by moist convection over the Sahara desert, AMS annual meeting, 17-20 January 2010, Atlanta, Georgia, USA.



2009



Bou Karam D., E. Williams, M. McGraw-Herdeg, M. Janiga, J. Cuesta, C. Flamant and C. Thorncroft (2009): Dusty gust fronts at synoptic scale, initiated and maintained by moist convection over the Sahara desert, AGU Fall meeting, 14-18 Dec 2009, San Francisco, California, USA.


Bou Karam D., C. Flamant, J. Cuesta, J. Pelon, E. Williams (2009): CALIPSO observations on dust emission and transport associated with Saharan depressions: The February 2007 case, CALIPSO/CloudSat Science Workshop, 27-31 July 2009, Madison, Wisconsin, USA.


Bou Karam D., E. Williams, M. McGraw-Herdeg, M. Janiga, J. Cuesta, C. Flamant and C. Thorncroft (2009): Dusty gust fronts at synoptic scale, initiated and maintained by moist convection over the Sahara desert, CALIPSO/CloudSat Science Workshop, 27-31 July 2009, Madison, Wisconsin, USA.


Bou Karam D., C. Flamant, P. Tulet, J. Pelon (2009): Dust emissions and transport in the intertropical discontinuity region of the west African Monsoon, 3rdInternational AMMA Conference, 20-24 July 2009, Ouagadougou, Burkina Faso.


Bou Karam D., C. Flamant, P. Tulet, J-P. Chaboureau M. Chong and E. Williams (2009): Dry cyclogenesis in the intertropical discontinuity region of the west African Monsoon, European Geosciences Union, General Assembly, 19-24 April 2009, Vienna, Austria.


Bou Karam D., C. Flamant, J. Pelon (2009): CALIPSO observations on the dynamic of dust plumes in the intertropical discontinuity region of West Africa, European Geosciences Union, General Assembly, 19-24 April 2009, Vienna, Austria.


2008


Bou Karam D., C. Flamant, P. Tulet, J-P. Chaboureau (2008): Mesoscale modelling of dust emissions over the Sahel associated with the West African Monsoon intertropical discontinuity, Atelier de Modélisation de l’Atmosphère, Météo France, 22-24 January 2008, Toulouse, France.


Bou Karam D., C. Flamant, J. Pelon, J. Cuesta (2008): CALIPSO observations and mesoscale modelling on dust emissions and transport over the Sahel associated with the West African Monsoon Inter Tropical Discontinuity CALIPSO Science Team meeting, Centre National des Etudes Spatiales (CNES), 11-14 Mars 2008, Paris, France.


Bou Karam D., C. Flamant, P. Knippertz, P. Tulet (2008): A newly identified mechanism for dust emissions over the Sahel associated with the West African Monsoon inter-tropical discontinuity region European Geosciences Union, General Assembly, 14-18 April 2008, Vienna, Austria.


Bou Karam D., C. Flamant, J. Pelon, J-P. Chaboureau (2008): CALIPSO observations and mesoscale modelling on dust emissions and transport over the Sahel associated with the West African Monsoon Intertropical discontinuity, European Geosciences Union, General Assembly, 14-18 April 2008, Vienna, Austria.


Pospichal B., D. Bou Karam, S. Crewell, C. Flamant (2008): Diurnal cycle of the ITD before the onset of the WAM over Benin: ground-based measurements and mesoscale modelling, European Geosciences Union, General Assembly, 14-18 April 2008, Vienna, Austria.


Bou Karam D., C. Flamant, P. Knippertz, O. Reitebuch, M. Chong, A. Dabas, J. Pelon (2008): A newly identified mechanism for dust emissions over the Sahel associated with the West African Monsoon inter-tropical discontinuity, 24th International Laser Radar Conference (ILRC), 23-27 June 2008, Boulder, Colorado, USA.


2007


Bou Karam D., C. Flamant, P. Tulet, J-P. Chaboureau (2007): Numerical modelling of Saharan dust impact on the atmospheric dynamics in the Bodélé depression,European Geosciences Union, General Assembly, 16-20 April 2007, Vienna, Austria.


Bou Karam D., C. Flamant, P. Tulet, J-P. Chaboureau (2007): Saharan dust lofting by Harmattan and monsoon flows convergence: Numerical Modelling and Lidar observations, European Geosciences Union, General Assembly, 16-20 April 2007, Vienna, Austria.


Bou Karam D., C. Flamant, J. Pelon, J-P. Chaboureau, P. Tulet (2007): Saharan dust uptakes associated with the inter-tropical discontinuity dynamics: CALIPSO observations and numerical modelling, CALIPSO Science Team meeting, June 2007, San Francisco, California, USA.



Bou Karam D., C. Flamant, J. Pelon, J-P. Chaboureau, P. Tulet (2007): Saharan dust uptakes associated with the inter-tropical discontinuity dynamics: CALIPSO observations and numerical modelling, Symposium de Lille, 22-26 October 2007, Lille, France.


Bou Karam D., C. Flamant, P. Tulet, P. Knippertz (2007): Saharan dust uptakes associated with the inter-tropical discontinuity dynamics: Airborne Lidar observations and numerical modelling, African Monsoon Multidisciplinary Analyses ( AMMA) 2nd International Conference, 26-30 November 2007, Karlsruhe, Germany.



Bou Karam D., C. Flamant, P. Tulet, J-P. Chaboureau, P. Knippertz (2007): Dust emissions over the Sahel associated with the West African Monsoon density current behavior in the inter-tropical discontinuity region, American Geophysical Union, 10-14 December 2007, San Francisco, California, USA.