The timing of spring initiates an important period for resource availability for large trophic webs within ecosystems, including forage for grazing animals, flowers for pollinators, and the higher trophic levels that depend on these resources. Spring timing is highly variable across space, being influenced strongly by the departure of snow cover (i.e. snowmelt timing, in locations with a seasonal snowpack), climate, weather, elevation, and latitude. When spring timing occurs along a gradient (e.g. spring arriving later in higher elevations of mountainous terrain), the organisms that rely on spring resources often migrate to maintain an optimal position for spring resources – a phenomenon known as ‘surfing the green wave.’ While this behavior has been observed by tracking animals, there have been no studies to quantify the green wave as a movement across space and time. Furthermore, considering that snowmelt timing has moderate power to explain green-up timing for a given location, we ask the question: does snowmelt velocity predict green wave velocity? Here, we introduce the first continental maps of snowmelt and green wave velocity for North America from 2001 to 2016 as derived from the MODIS MCD12Q2 phenology dataset. We show that both snowmelt and green wave velocities are influenced strongly by topography, including slope and aspect. Furthermore, we quantify the relationships between snowmelt and green wave velocities according to three variables: direction, speed, and distance traveled. We conclude that mountainous ecoregions, such as the western North American cordillera, have the highest correspondence between snowmelt and green wave velocities, compared to flatter regions such as the Great Plains and tundra. This work will be of interest to wildlife ecologists, biologists, and land managers who seek to conserve migratory animals and the ecosystems that support them.

春季的时机为生态系统中大型营养网的资源可利用性提供了一个重要时期，其中包括放牧动物的饲料，传粉媒介的花以及依赖这些资源的较高营养级。春季时间在整个空间中变化很大，受积雪的离开（即融雪时间，在季节性积雪的地区），气候，天气，海拔和纬度的强烈影响。当春季时间沿着一个梯度发生时（例如，春季后来到达更高海拔的山区），依赖春季资源的生物通常会迁移以维持春季资源的最佳位置-这种现象被称为“冲浪绿浪”。通过跟踪动物已经观察到这种行为，尚无研究将绿浪量化为跨时空运动。此外，考虑到融雪时间具有适度的能力来解释给定位置的绿化时间，我们提出一个问题：融雪速度能预测绿波速度吗？在这里，我们介绍了从MODIS MCD12Q2物候数据集得出的2001年至2016年北美的第一幅融雪和绿浪速度的大陆图。我们显示融雪和绿浪的速度都受地形（包括坡度和坡向）的强烈影响。此外，我们根据三个变量（方向，速度和行进距离）来量化融雪和绿浪速度之间的关系。我们得出的结论是，山区生态区，例如北美西部山脉，与平坦地区（例如大平原和冻原）相比，融雪和绿浪速度之间的对应关系最高。这项工作将吸引寻求保护候鸟和支持它们的生态系统的野生生物生态学家，生物学家和土地管理者。