Seasonality of African Precipitation from 1996 to 2009

Liebmann, Brant; Bladé, Ileana; Kiladis, George N.; Carvalho, Leila M. V.; Senay, Gabriel B.; Allured, Dave; Leroux, Stéphanie; Funk, Chris

doi:10.1175/jcli-d-11-00157.1

Cited by 180 publications

(212 citation statements)

References 42 publications

Supporting

Mentioning

186

Contrasting

Unclassified

Order By: Relevance

“…Liebmann et al [35] report two annual peaks in precipitation for large areas along the Guinea Coast, which would support our first explanation given above that the bimodality in this region is real. Herrmann and Mohr [39] refer to this bimodality as a single wet season with two rainfall peaks.…”

Section: Average Length Of Growing Periodsupporting

confidence: 85%

“…The distribution of bimodal seasons in Africa has also been evaluated from gridded rainfall and temperature products [35,39]. Liebmann et al [35] report two annual peaks in precipitation for large areas along the Guinea Coast, which would support our first explanation given above that the bimodality in this region is real.…”

Section: Average Length Of Growing Periodmentioning

confidence: 71%

See 1 more Smart Citation

Length of Growing Period over Africa: Variability and Trends from 30 Years of NDVI Time Series

2013

View full text Add to dashboard Cite

Abstract:The spatial distribution of crops and farming systems in Africa is determined by the duration of the period during which crop and livestock water requirements are met. The length of growing period (LGP) is normally assessed from weather station data-scarce in large parts of Africa-or coarse-resolution rainfall estimates derived from weather satellites. In this study, we analyzed LGP and its variability based on the 1981-2011 GIMMS NDVI3g dataset. We applied a variable threshold method in combination with a searching algorithm to determine start-and end-of-season. We obtained reliable LGP estimates for arid, semi-arid and sub-humid climates that are consistent in space and time. This approach effectively mapped bimodality for clearly separated wet seasons in the Horn of Africa. Due to cloud contamination, the identified bimodality along the Guinea coast was judged to be less certain. High LGP variability is dominant in arid and semi-arid areas, and is indicative of crop failure risk. Significant negative trends in LGP were found for the northern part of the Sahel, for parts of Tanzania and northern Mozambique, and for the short rains of eastern Kenya. Positive trends occurred across western Africa, in southern Africa, and in eastern Kenya for the long rains. Our LGP analysis provides useful information for the mapping of farming systems, and to study the effects of climate variability and other drivers of change on vegetation and crop suitability.

show abstract

Section: Average Length Of Growing Periodsupporting

confidence: 85%

Section: Average Length Of Growing Periodmentioning

confidence: 71%

Length of Growing Period over Africa: Variability and Trends from 30 Years of NDVI Time Series

2013

View full text Add to dashboard Cite

show abstract

“…In fact, the maximum precipitation rate occurs from May-October and the minimum during November-April [28]. However, Andersen et al [27] consider the periods June-November and December-May as wet and dry seasons in the basin, while Liebmann et al [15] argue that the southern coast of WA experiences a wet season beginning in early March and its duration decreasing latitudinally to the north. During the boreal summer, an intense heat low develops over the Western Sahara [22].…”

Section: Study Areamentioning

confidence: 99%

“…Studies of climate variability in WA show the seasonal rainfall migration during the boreal summer [15,16] and a reduction in accumulated rainfall over the last century [17][18][19][20]. These phenomena have affected stream discharges and both are considered a partial feedback of the land-cover degradation in the watershed [21].…”

Section: Introductionmentioning

confidence: 99%

The Niger River Basin Moisture Sources: A Lagrangian Analysis

2017

View full text Add to dashboard Cite

Abstract:The Niger River basin (NRB) is located in the important climatic region of the African Sahel. In this study we use the Lagrangian tridimensional model FLEXPART v9.0 to identify and characterise the moisture sources for the NRB. This method allows the integration of the budget of evaporation minus precipitation over 10-day backward trajectories, thereby identifying the origins of the air masses residing over the NRB. The analysis was performed for the 35-year period from 1980 to 2014, which allowed us to identify the main semi-annual climatological moisture sources of the NRB, for November-April (NDJFMA) (dry season) and May-October (MJJASO) (wet season), and to quantify the respective moisture uptakes. Throughout the year, the NRB main moisture sources are located on the tropical eastern North Atlantic Ocean near Africa, the tropical eastern South Atlantic Ocean in the Gulf of Guinea, in the regions surrounding the Sahel and in the Mediterranean Sea. The extents of these sources vary between dry and wet seasons. In NDJFMA two regions appear in the east of the basin, which then join up, forming a larger source to the northeast of the basin in MJJASO, when three other less important moisture sources can be seen in central-equatorial Africa, the tropical western Indian Ocean and the Persian Gulf. In NDJFMA the majority of the moisture uptake comes from the NRB itself but then, later in MJJASO, when the precipitation increases over the basin the greatest uptake of moisture occurs over the tropical eastern South Atlantic Ocean, northeast Africa and the NRB, which suggests that these are the effective sources of precipitation in the basin in overall terms. The seasonal moisture uptake quantification over the moisture sources of the NRB, reveals that largest fraction of moisture income to the basin from outside its boundaries. Despite providing moisture to the NRB the source located in the tropical eastern North Atlantic Ocean does not contribute that much to precipitation in the basin. A daily (ten-day) backward analysis shows the importance of the moisture uptake within the NRB and from near moisture sources during the first few (backward) days, while the Atlantic Ocean sources and the Mediterranean became more important during the last five (backward) days of the analysis.

show abstract

“…The assessment of rainfall metrics capturing the seasonal variability and the associated impact on growing season ANPP requires daily rainfall records and a robust methodology that is able to extract the timing (onset and cessation) and duration of the wet season (Dunning et al, 2016;Liebmann et al, 2012). The availability and quality of such data, and uncertainties in methods to extract the rainfall seasonality, have complicated regionally scaled studies on this topic (Fitzpatrick et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

et al. 2018

View full text Add to dashboard Cite

Abstract. Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy-rainfall events, longer dry spells, and a shifted timing of the wet season. Yet the aboveground net primary productivity (ANPP) in drylands is usually explained by annual-rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tested the importance of rainfall metrics in the wet season (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days, and heavy-rainfall events) for growing season ANPP. We focused on the Sahel and northern Sudanian region (100-800 mm yr −1 ) and applied daily satellite-based rainfall estimates (CHIRPS v2.0) and growing-season-integrated normalized difference vegetation index (NDVI; MODIS) as a proxy for ANPP over the study period: 2001-2015. Growing season ANPP in the arid zone (100-300 mm yr −1 ) was found to be rather insensitive to variations in the seasonal-rainfall metrics, whereas vegetation in the semi-arid zone (300-700 mm yr −1 ) was significantly impacted by most metrics, especially by the number of rainy days and timing (onset and cessation) of the wet season. We analysed critical breakpoints for all metrics to test if vegetation response to changes in a given rainfall metric surpasses a threshold beyond which vegetation functioning is significantly altered. It was shown that growing season ANPP was particularly negatively impacted after > 14 consecutive dry days and that a rainfall intensity of ∼ 13 mm day −1 was detected for optimum growing season ANPP. We conclude that the number of rainy days and the timing of the wet season are seasonal-rainfall metrics that are decisive for favourable vegetation growth in the semiarid Sahel and need to be considered when modelling primary productivity from rainfall in the drylands of the Sahel and elsewhere.

show abstract

Seasonality of African Precipitation from 1996 to 2009

Cited by 180 publications

References 42 publications

Length of Growing Period over Africa: Variability and Trends from 30 Years of NDVI Time Series

Length of Growing Period over Africa: Variability and Trends from 30 Years of NDVI Time Series

The Niger River Basin Moisture Sources: A Lagrangian Analysis

Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

Contact Info

Product

Resources

About