Performance Analysis and Projected Changes of Agroclimatological Indices Across West Africa Based on High‐Resolution Regional Climate Model Simulations

Abstract

In this study, we analyze a set of agroclimatological indices across West Africa and assess their projected changes for the future. We apply the regional climate model CCLM (COnsortium for Small-scale MOdelling in CLimate Mode) with a high spatial resolution of 0.11 ∘ (approximately 12 km) under current and future climate conditions, based on the emission scenario RCP4.5. The focus is on purely rainfall-based indices, that is, the onset (ORS), the cessation (CRS), and the length of the rainy season (LRS) and the joint rainfall-and temperature-based indices, that is, growing degree days (GDD) and the water availability (WAV), derived for maize, sorghum, and pearl millet across Guinea, Savanna, and Sahel. For the present, in general, the CCLM compares well to observations, represented by three different products. However, CCLM shows limitations in the representation of the CRS over Guinea with a delay of >30 days and the GDD and WAV over Sahel with biases up to 30% and 70% for all crops. For the future climate projections, ORS, CRS, and LRS are expected to be delayed up to 2 weeks for most regions, in particular for the period 2071-2100. The GDD is expected to increase by around 8% till 2021-2050 and by around 5% till 2071-2100 for all crops. The WAV is expected to be decreased by up to 10% in 2021-2050, and by up to 24% in 2071-2100 in Sahel, and <12% over Guinea and Savanna in both periods. In particular, we evaluate the added value of the high-resolution CCLM information for decision support in agricultural management. Key Points:• CCLM model results were evaluated in terms of agricultural indices for cropping of maize, sorghum, and pearl millet across three different agroecological zones in West Africa • High-resolution future climate projections indicate a shortening of the rainy seasons by approximately 2 weeks in the Sahel region till the end of the century • The projected decreases (increases) of rainfall (temperature) over the Sahel region would negatively impact on water availability (WAV) and growing degree days (GDD)

Seasonal Forecasting of the Onset of the Rainy Season in West Africa

“…Another reason is the uncertainty coming from the reference products used for comparison. This is shown e.g., by [51] for the calculation of the ORS dates for West Africa. Figure 6 also shows strong variations of the forecast performance of the ORS dates for the different years indicated by the mean and the spread of the box-plot diagrams.…”

“…Since many other ORS approaches rely on binary logics, [17] introduced fuzzy rules for a more smoothed transition of the applied conditions. This ORS fuzzy-logic were used by several other investigations, as well [2,51]. The membership functions of the fuzzy rules used in this study are shown in Figure 5.…”

Exploring assumptions in crop breeding for climate resilience: opportunities and principles for integrating climate model projections

“…We considered short-, medium-and long-duration maize crops, requiring 500, 1000 and 1500 GDDs, respectively, to reach maturity. These thresholds span the wide variety of GDD requirements reported in the literature for maize, from 100 to 1500 (Dieng et al 2018;Moeletsi and Walker 2013;Moeletsi and Walker 2012;Tsimba et al 2013).…”

“…A maximum, or upper, temperature threshold is not always used in the calculation of GDDs; however, we have chosen to use one as maize is sensitive to high temperatures (Lobell et al 2011). Various temperature thresholds are reported in the literature for maize, varying from 30°C for optimal temperatures to 45.3°C for maximum temperature (Dieng et al 2018; Food and Agriculture Organization of the United Nations 2007; Lobell et al 2011). We chose 35°C as the maximum temperature threshold, following Dieng et al (2018), as a balance between the reported thresholds.…”

Exploring the Potential of the Cost-Efficient TAHMO Observation Data for Hydro-Meteorological Applications in Sub-Saharan Africa

“…An interruption of the monsoon or a wrong predicted onset of the rainy season may lead to yield reductions. These effects can become more frequent as a consequence of climate change [11,12]. The population in BF is particularly vulnerable as approximately 80% is involved in the agricultural sector, which is dominated by subsistence farming.…”