Changes in snow parameterization over typical vegetation in the Northern Hemisphere

Abstract

Seasonal snow is sensitive to climate change, and is always taken as a signal of local climate changes. As changes in snow differ locally in their characteristics, it is necessary to detect the effects of snow on different land cover types. The middle and high latitudes of the Northern Hemisphere are located in a vast area of seasonal snow, experiencing snow accumulation and snowmelt stages each year. This study found that selected land cover types (open shrubland, evergreen needleleaf forest, and mixed forest) possess unique relationship curves between the snow cover fraction and snow depth. This has resulted in the northward shrinking of open shrubland and expansion of evergreen needleleaf forest and mixed forest, thereby further modulating local ecological systems. However, such changes in the snow process are not reproduced well by model parameterizations, and a faster melting process in the snowmelt stage will occur owing to the effects of global warming not being properly considered in such parametrization schemes. This inability to properly simulate the change in the snow process will affect the understanding of the ecological impacts of snowmelt in spring.摘要季节性降雪对气候变化很敏感, 常被当作气候变化的信号. 由于其局地特征差异显著, 不同下垫面类型的积雪过程也不尽相同. 北半球中高纬度的典型下垫面 (开阔灌丛, 常绿针叶林和混交林) 在积雪覆盖率和雪深之间有着独特的关系曲线, 这种关系不仅代表了积雪过程和融雪过程的特征变化, 更能用于模式进行积雪预测. 研究发现, 北半球中高纬度的增温改变了积雪参数化关系, 进一步影响了局地能量和水循环, 造成开阔灌丛的北缩和常绿针叶林及混交林的扩张. 然而, 目前模式中的积雪参数化并不能很好地再现全球变暖影响下融雪阶段出现的加速融化过程, 并且进一步影响对春季融雪的生态影响的理解.