scholarly journals Overview of the Dust and Biomass-burning Experiment and African Monsoon Multidisciplinary Analysis Special Observing Period-0

2008 ◽  
Vol 113 ◽  
Author(s):  
J. M. Haywood ◽  
J. Pelon ◽  
P. Formenti ◽  
N. Bharmal ◽  
M. Brooks ◽  
...  
Keyword(s):  
Biomass Burning ◽  
African Monsoon ◽  
Multidisciplinary Analysis

scholarly journals Remote sensing of the land surface during the African Monsoon Multidisciplinary Analysis (AMMA)

2011 ◽  
Vol 12 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Laurent Kergoat ◽  
Manuela Grippa ◽  
Alain Baille ◽  
Laurence Eymard ◽  
Roselyne Lacaze ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Land Surface ◽  
African Monsoon ◽  
Multidisciplinary Analysis

scholarly journals Driftsonde Observations to Evaluate Numerical Weather Prediction of the Late 2006 African Monsoon

2013 ◽  
Vol 52 (4) ◽  
pp. 974-995 ◽  
Author(s):  
Philippe Drobinski ◽  
Fatima Karbou ◽  
Peter Bauer ◽  
Philippe Cocquerez ◽  
Christophe Lavaysse ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Numerical Weather Prediction ◽  
Vertical Structure ◽  
Weather Prediction ◽  
Meridional Wind ◽  
Numerical Weather Prediction Model ◽  
African Monsoon ◽  
Easterly Waves ◽  
Numerical Weather ◽  
Multidisciplinary Analysis

AbstractDuring the international African Monsoon Multidisciplinary Analysis (AMMA) project, stratospheric balloons carrying gondolas called driftsondes capable of dropping meteorological sondes were deployed over West Africa and the tropical Atlantic Ocean. The goals of the deployment were to test the technology and to study the African easterly waves, which are often the forerunners of hurricanes. Between 29 August and 22 September 2006, 124 sondes were dropped over the seven easterly waves that moved across Africa into the Atlantic between about 10° and 20°N, where almost no in situ vertical information exists. Conditions included waves that developed into Tropical Storm Florence and Hurricanes Gordon and Helene. In this study, a selection of numerical weather prediction model outputs has been compared with the dropsondes to assess the effect of some developments in data assimilation on the quality of analyses and forecasts. By comparing two different versions of the Action de Recherche Petite Echelle Grande Echelle (ARPEGE) model of Météo-France with the dropsondes, first the benefits of the last data assimilation updates are quantified. Then comparisons are carried out using the ARPEGE model and the Integrated Forecast System (IFS) model of the European Centre for Medium-Range Weather Forecasts. It is shown that the two models represent very well the vertical structure of temperature and humidity over both land and sea, and particularly within the Saharan air layer, which displays humidity below 5%–10%. Conversely, the models are less able to represent the vertical structure of the meridional wind. This problem seems to be common to ARPEGE and IFS, and its understanding still requires further investigations.

scholarly journals Peroxy radical observations over West Africa during the AMMA 2006 campaign: Photochemical activity in episodes of formation of convective systems on the basis of radical measurements

2009 ◽  
Vol 9 (1) ◽  
pp. 1585-1619 ◽  
Author(s):  
M. D. Andrés-Hernández ◽  
D. Kartal ◽  
L. Reichert ◽  
J. P. Burrows ◽  
J. Meyer Arnek ◽  
...  
Keyword(s):  
West Africa ◽  
Biomass Burning ◽  
Peroxy Radical ◽  
Photochemical Activity ◽  
Back Trajectory ◽  
Peroxy Radicals ◽  
Air Masses ◽  
Convective Systems ◽  
Mixing Ratios ◽  
Multidisciplinary Analysis

Abstract. Peroxy radical measurements made on board the DLR-Falcon research aircraft over West Africa within the African Monsoon Multidisciplinary Analysis (AMMA) campaign during the 2006 wet monsoon are presented in this study. The analysis of data focuses on the photochemical activity of air masses sampled during episodes of intense convection and biomass burning. Generally, the total sum of peroxy radical mixing ratios, measured in the outflow of convective clouds, are quite variable but occasionally are coupled with the NO variations indicating the coexistence, or simultaneously emission of NOx, with a potential radical precursor (i.e., formaldehyde, acetone or peroxides) which has likely been transported to higher atmospheric layers. Based on the measurements, significant O3 production rates up to 2 ppb/h in the MCS outflow are estimated by using a box model with simplified chemistry. Peroxy radicals having mixing ratios around 20–25 pptv and with peak values of up to 60–70 pptv are measured within biomass burning plumes, detected at the coast in Ghana. Calculations of back-trajectory densities confirm the origin of these air masses being a biomass burning region at southern latitudes and close to the Gulf of Guinea, according to satellite pictures. Measured peroxy radical concentrations agree reasonably with modelled estimations taking into account simple local chemistry. Moreover the vertical profiles taken at the aircraft base in Ouagadougou, Burkina Faso, indicate the common feature of having maximum concentrations between 2 and 4 km, in agreement with other literature values obtained under similar conditions.

scholarly journals Impact of West African Monsoon convective transport and lightning NO<sub>x</sub> production upon the upper tropospheric composition: a multi-model study

2010 ◽  
Vol 10 (2) ◽  
pp. 2245-2302 ◽  
Author(s):  
B. Barret ◽  
J. E. Williams ◽  
I. Bouarar ◽  
X. Yang ◽  
B. Josse ◽  
...  
Keyword(s):  
West African Monsoon ◽  
Convective Transport ◽  
West African ◽  
Lightning Activity ◽  
African Monsoon ◽  
Model Study ◽  
Multidisciplinary Analysis ◽  
Low Concentrations ◽  
The Tropics ◽  
The Impact

Abstract. Within the African Monsoon Multidisciplinary Analysis (AMMA), we investigate the impact of nitrogen oxides produced by lightning (LiNOx) and convective transport during the West African Monsoon (WAM) upon the composition of the upper troposphere (UT) in the tropics. For this purpose, we have performed simulations with 4 state-of-the-art chemistry transport models involved within AMMA, namely MOCAGE, TM4, LMDz-INCA and p-TOMCAT. The model intercomparison is complemented with an evaluation of the simulations based on both spaceborne and airborne observations. The baseline simulations show important differences between the UT CO and O3 distributions simulated by each of the 4 models when compared to measurements of the African latitudinal transect from the MOZAIC program and to distributions measured by the Aura/MLS spaceborne sensor. We show that such model discrepancies can be explained by differences in the convective transport parameterizations and, more particularly, the altitude reached by convective updrafts (ranging between ~200–125 hPa). Concerning UT O3, the majority of models exhibit low concentrations compared to both MOZAIC and MLS observations south of the equator, with good agreement in the Northern Hemisphere. Sensitivity studies are performed to quantify the effect of deep convective transport and the influence of LiNOx production on the UT composition. These clearly indicate that the CO maxima and the elevated O3 concentrations south of the equator are due to convective uplift of air masses impacted by Southern African biomass burning, in agreement with previous studies. Moreover, during the WAM, LiNOx from Africa are responsible for the highest UT O3 enhancements (10–20 ppbv) over the tropical Atlantic between 10° S–20° N. Differences between models are primarily due to the performance of the parameterizations used to simulate lightning activity which are evaluated using spaceborne observations of flash frequency. Combined with comparisons of in-situ NO measurements we show that the models producing the highest amounts of LiNOx over Africa during the WAM (INCA and p-TOMCAT) capture observed NO profiles with the best accuracy, although they both overestimate lightning activity over the Sahel.

scholarly journals Ozone budget in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) campaign

2009 ◽  
Vol 9 (2) ◽  
pp. 6979-7032
Author(s):  
M. Saunois ◽  
C. E. Reeves ◽  
C. Mari ◽  
J. G. Murphy ◽  
D. J. Stewart ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lower Troposphere ◽  
Atmospheric Measurements ◽  
Air Masses ◽  
African Monsoon ◽  
Mixing Ratios ◽  
Budget Analysis ◽  
Multidisciplinary Analysis ◽  
Ozone Maximum ◽  
Research Aircraft

Abstract. A bi-dimensional latitudinal-vertical meterological model coupled with O3-NOx-VOC chemistry is used to reproduce the distribution of ozone and precursors in the boundary layer over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) campaign as observed on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft. The model reproduces the increase of ozone mixing ratios in the boundary layer observed between the forested region south of 13° N and the Sahelian area northward. Sensitivity and budget analysis reveals that the intertropical convergence zone is a moderate source of O3 rich-air in the boundary layer due to convective downdrafts. Dry deposition drives the ozone minimum over the vegetated area. The combination of high NOx emissions from soil north of 13° N and northward advection by the monsoon flux of VOC-enriched air masses contributes to the ozone maximum simulated at higher latitudes. Simulated OH exhibit a well marked latitudinal gradient with minimum concentrations over the vegetated region where the reactions with biogenic compounds predominate. The model underestimates the observed OH mixing ratios, however this model discrepancy has slight effect on ozone budget and does not alter the conclusions.

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