Drought detection and assessment with solar-induced chlorophyll fluorescence in summer maize growth period over North China Plain

•Severe drought occurred in summer maize growth period of 2014 in North China Plain.•Solar-induced chlorophyll fluorescence (SIF) has close linear relationship with GPP.•SIF is more sensitive to drought than reflectance-based vegetation indices.•Assessed by SIF, crop GPP decreased by 10.6% in counties with severe drought.