Satellite passive microwave detection of North America start of season

► Vegetation optical depth (VOD) allows for near daily global phenology monitoring. ► We calculated VOD start of season (SOS) metrics for North America from 2004 to 2007. ► VOD, NDVI and LAI SOS temporal offsets coincided with climatic constraints on NPP. ► SOS offsets also coincided with regional vegetation physiology and biomass. ► VOD provides new phenology information for carbon, water and energy cycle studies.