The data contain time series of optical-equivalent snow grain size (r_opt) retrieved from airborne spectral surface albedo measurements North of Greenland during PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project) in spring 2018. The data of three flights were measured under cloudless, low Sun, and partly rough surface conditions. Snow r_opt was retrieved from two wavelength approaches based on spectral surface albedo data using (i) the albedo ratio between 1280 nm and 1100 nm wavelength (ratio-method), and (ii) the surface albedo at 1700 nm (1700nm-method). The corresponding spectral surface albedo (also included in the data set) was derived from measurements by the Spectral Modular Airborne Radiation measurement sysTem (SMART) mounted on the Polar 5 research aircraft operated by AWI.