African Monsoon Multidisciplinary Analysis: an integrated project for understanding of the West African climate system and its human dimension

Abstract. The latest version of RegCM4 with CLM4.5 as land surface scheme was used to assess the performance and the sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West Africa domain from November 2002 to December 2004, at spatial resolution of 50 km × 50 km and involved five (5) convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using respectively data from the Climate Research Unit (CRU) and Global Precipitation Climatology Project (GPCP) during June to September (rainy season). Quantitative assessment of the sensitivity tests were carried out using the mean bias, the pattern correlation coefficient, the root mean square difference, the probability density function of the temperature bias and the Taylor diagram. Results revealed a better performance of the configuration with Emanuel convection scheme to simulate the spatial and temporal variability of the temperature and the precipitation. Therefore, the configuration of RegCM4 with CLM4.5 as land surface model and implementing Emanuel convective scheme is recommended for the study of the West African climate system.

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Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) wet season campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-6135-2009 ◽

2009 ◽

Vol 9 (16) ◽

pp. 6135-6155 ◽

Cited By ~ 35

Author(s):

M. Saunois ◽

C. E. Reeves ◽

C. H. Mari ◽

J. G. Murphy ◽

D. J. Stewart ◽

...

Keyword(s):

Boundary Layer ◽

Monsoon Season ◽

Trace Gases ◽

Lower Troposphere ◽

West African ◽

Atmospheric Measurements ◽

The West ◽

African Monsoon ◽

Enhanced Production ◽

Multidisciplinary Analysis

Abstract. Ozone and its precursors were measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the monsoon season 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) campaign. One of the main features observed in the west African boundary layer is the increase of the ozone mixing ratios from 25 ppbv over the forested area (south of 12° N) up to 40 ppbv over the Sahelian area. We employ a two-dimensional (latitudinal versus vertical) meteorological model coupled with an O3-NOx-VOC chemistry scheme to simulate the distribution of trace gases over West Africa during the monsoon season and to analyse the processes involved in the establishment of such a gradient. Including an additional source of NO over the Sahelian region to account for NO emitted by soils we simulate a mean NOx concentration of 0.7 ppbv at 16° N versus 0.3 ppbv over the vegetated region further south in reasonable agreement with the observations. As a consequence, ozone is photochemically produced with a rate of 0.25 ppbv h−1 over the vegetated region whilst it reaches up to 0.75 ppbv h−1 at 16° N. We find that the modelled gradient is due to a combination of enhanced deposition to vegetation, which decreases the ozone levels by up to 11 pbbv, and the aforementioned enhanced photochemical production north of 12° N. The peroxy radicals required for this enhanced production in the north come from the oxidation of background CO and CH4 as well as from VOCs. Sensitivity studies reveal that both the background CH4 and partially oxidised VOCs, produced from the oxidation of isoprene emitted from the vegetation in the south, contribute around 5–6 ppbv to the ozone gradient. These results suggest that the northward transport of trace gases by the monsoon flux, especially during nighttime, can have a significant, though secondary, role in determining the ozone gradient in the boundary layer. Convection, anthropogenic emissions and NO produced from lightning do not contribute to the establishment of the discussed ozone gradient.

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Investigating the West African Climate System Using Global/Regional Climate Models

Bulletin of the American Meteorological Society ◽

10.1175/1520-0477(2002)083<0583:itwacs>2.3.co;2 ◽

2002 ◽

Vol 83 (4) ◽

pp. 583-595 ◽

Cited By ~ 18

Author(s):

Gregory S. Jenkins ◽

Andre Kamga ◽

Adamou Garba ◽

Arona Diedhiou ◽

Vernon Morris ◽

...

Keyword(s):

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

West African ◽

Climate System ◽

The West ◽

African Climate

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On What Scale Can We Predict the Agronomic Onset of the West African Monsoon?

Monthly Weather Review ◽

10.1175/mwr-d-15-0274.1 ◽

2016 ◽

Vol 144 (4) ◽

pp. 1571-1589 ◽

Cited By ~ 6

Author(s):

Rory G. J. Fitzpatrick ◽

Caroline L. Bain ◽

Peter Knippertz ◽

John H. Marsham ◽

Douglas J. Parker

Keyword(s):

West Africa ◽

Noise Analysis ◽

West African Monsoon ◽

West African ◽

New Method ◽

The West ◽

African Monsoon ◽

Spatial Consistency ◽

Local Stakeholders ◽

Local Rainfall

Abstract Accurate prediction of the commencement of local rainfall over West Africa can provide vital information for local stakeholders and regional planners. However, in comparison with analysis of the regional onset of the West African monsoon, the spatial variability of the local monsoon onset has not been extensively explored. One of the main reasons behind the lack of local onset forecast analysis is the spatial noisiness of local rainfall. A new method that evaluates the spatial scale at which local onsets are coherent across West Africa is presented. This new method can be thought of as analogous to a regional signal against local noise analysis of onset. This method highlights regions where local onsets exhibit a quantifiable degree of spatial consistency (denoted local onset regions or LORs). It is found that local onsets exhibit a useful amount of spatial agreement, with LORs apparent across the entire studied domain; this is in contrast to previously found results. Identifying local onset regions and understanding their variability can provide important insight into the spatial limit of monsoon predictability. While local onset regions can be found over West Africa, their size is much smaller than the scale found for seasonal rainfall homogeneity. A potential use of local onset regions is presented that shows the link between the annual intertropical front progression and local agronomic onset.

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A Lagrangian perspective on stable water isotopes during the West African Monsoon

10.1002/essoar.10506628.1 ◽

2021 ◽

Author(s):

Christopher Johannes Diekmann ◽

Matthias Schneider ◽

Peter Knippertz ◽

Andries Jan de Vries ◽

Stephan Pfahl ◽

...

Keyword(s):

West African Monsoon ◽

West African ◽

Water Isotopes ◽

Stable Water Isotopes ◽

The West ◽

African Monsoon

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A hydrological onset and withdrawal index for the West African monsoon

Theoretical and Applied Climatology ◽

10.1007/s00704-008-0022-8 ◽

2008 ◽

Vol 96 (1-2) ◽

pp. 179-189 ◽

Cited By ~ 7

Author(s):

G. A. Dalu ◽

M. Gaetani ◽

M. Baldi

Keyword(s):

West African Monsoon ◽

West African ◽

The West ◽

African Monsoon

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Sensitivity study of the regional climate model RegCM4 to different convective schemes over West Africa

Earth System Dynamics ◽

10.5194/esd-9-1261-2018 ◽

2018 ◽

Vol 9 (4) ◽

pp. 1261-1278 ◽

Cited By ~ 7

Author(s):

Brahima Koné ◽

Arona Diedhiou ◽

N'datchoh Evelyne Touré ◽

Mouhamadou Bamba Sylla ◽

Filippo Giorgi ◽

...

Keyword(s):

West Africa ◽

Land Surface ◽

West African ◽

Cold Bias ◽

The West ◽

Land Surface Scheme ◽

African Climate ◽

Sensitivity Studies ◽

Surface Scheme ◽

Convective Scheme

Abstract. The latest version of RegCM4 with CLM4.5 as a land surface scheme was used to assess the performance and sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West African domain from November 2002 to December 2004 at a spatial resolution of 50 km × 50 km and involved five convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using data from the Climate Research Unit (CRU), Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measurement Mission (TRMM) during June to September (rainy season), while the simulated atmospheric dynamic was compared to ERA-Interim data. It is worth noting that the few previous similar sensitivity studies conducted in the region were performed using BATS as a land surface scheme and involved less convective schemes. Compared with the previous version of RegCM, RegCM4-CLM also shows a general cold bias over West Africa whatever the convective scheme used. This cold bias is more reduced when using the Emanuel convective scheme. In terms of precipitation, the dominant feature in model simulations is a dry bias that is better reduced when using the Emanuel convective scheme. Considering the good performance with respect to a quantitative evaluation of the temperature and precipitation simulations over the entire West African domain and its subregions, the Emanuel convective scheme is recommended for the study of the West African climate system.

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