Impacts of anthropogenic forcing and internal variability at the watershed scale - going from the daily to the hourly time scale

人类活动对辐射强迫的影响导致的气候变化现已得到充分确认。除了预计的地表温度升高外，这些变化还将影响水循环的所有主要组成部分，包括不同空间和时间尺度上降雨的变化和强度。对这些变化影响的认识主要来自大气环流和地球系统模型。然而，由于与可用计算能力相关的限制，直到最近，这些模型的输出大多数都是在每日时间步长下可用的。因此，日以下规模的变化记录较少。尽管如此，高分辨率区域气候模式（允许或不允许对流）的发布表明，对于短时间和强降雨，人为强迫的影响将更大。因此，我们可以预测对小流域的水文响应是快速和可比拟的对流降水系统的不成比例的影响。同样，我们也可以预测，在小流域（<1000平方公里），与融雪相关的洪水的影响会减少到与夏秋降水相关的洪水。在水文学方面，这些结果表明对小型农村和城市化流域的重大影响。由于两个主要原因，对这些流域水文的人为强迫变化的潜在影响研究很少：1-北美没有可靠的亚日时间步长水文气象数据库（以及世界上大多数国家，除少数欧洲国家外）对这些流域进行足够数量的研究; 2.仍然很少有气候模式的主要输出（例如温度和降水）是在亚日时间步长上提供的。这项研究计划的具体目标是通过使用我们的研究实验室和其他地方开发的工具和方法来填补这一知识空白，以研究气候变化在日常时间步长对中小流域的影响。这些工具和方法将与使用新的数据库和具有高时空分辨率的气候模型的输出相结合，从而能够处理对小时时间步长及以下的中小流域的研究。

Climate change resulting from the anthropogenic impact on radiative forcing is now well established. In addition to increases in projected surface temperatures, the changes will affect all major components of the water cycle, including variability and intensity of rainfall at various spatial and temporal scales. The knowledge of the impacts of these changes comes largely from general circulation and earth system models. However, due to the limitations related to the available computing power, the outputs of these models have mostly been available at the daily time-step until recently. Changes at the sub-daily scales are therefore less well documented. Nevertheless, releases of higher-resolution regional climate models (convection-permitting or not) indicate that the impacts of anthropogenic forcing will be greater for short-duration and intense rainfall. We can thus predict a disproportionate impact on small watersheds whose hydrological response is rapid and commensurable with that of convective precipitation systems. Similarly, we can also predict a decrease in the impact of snowmelt related floods to those related to summer fall precipitation over small watersheds (<1000 km2). In hydrology, these results point to major impacts towards small rural and urbanized watersheds. The potential impacts of anthropogenic forcing change on the hydrology of these basins have been poorly studied for two main reasons: 1-There is no reliable hydrometeorological database at sub-daily time steps in North America (as well as in the majority of the world, except for a few European countries) to study these watersheds in sufficient numbers; 2-There are still few climate models whose main outputs (e.g. temperature and precipitation) are available at the sub-daily time steps. This research program specifically aims to fill this knowledge gap by using the tools and methodologies developed within our research laboratory and elsewhere to study the impacts of climate change at the daily time step on small to medium-size watersheds. These tools and methods will be combined with the use of new databases and outputs of climate models with high temporal and spatial resolution to thus be able to tackle the study of small to mdieum-size watersheds up to the hourly time step and below.