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 tests the importance of seasonal rainfall metrics (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days and heavy rainfall events) on growing season ANPP. We focus on the Sahel and north-Sudanian region (100–800 mm year−1) and apply daily satellite based rainfall estimates (RFE-2.0) and growing season integrated NDVI (MODIS) as a proxy for ANNP over the study period 2001–2015. Growing season ANPP in the arid zone (100–300 mm year−1) was found to be rather insensitive to variations in the seasonal rainfall metrics, whereas vegetation in the semi-arid zone (300–700 mm year−1) was significantly impacted by most metrics, especially by the number of rainy days and timing (start and cessation) of the wet season. We analyzed critical breakpoints for all metrics, showing that growing season ANPP is particularly negatively impacted after > 10 consecutive dry days and that a rainfall intensity of 7 mm day−1 is detected for optimum growing season ANPP. We conclude that number of rainy days and the timing of the wet season are seasonal rainfall metrics being decisive for favorable vegetation growth in semi-arid Sahel which needs to be considered when modelling primary productivity from rainfall in the dryland's of Sahel and elsewhere.
RELATIONSHIP BETWEEN RAINY DAYS, MEAN DAILY INTENSITY AND SEASONAL RAINFALL IN MAHARASTHRA
