RAPID: Initial Assessment of IPCC AR5 Multi-model Ensembles for Hydroclimatic Features at Global and Regional Scales

这是政府间气候变化专门委员会第五次评估报告（IPCC AR5）中鼓励对气候模式模拟进行诊断分析的致同事信（NSF 11-006）资助的16个快速响应（Rapid）项目之一。在这些项目中进行的研究预计将导致更详细的模式相互比较，更好地理解稳健模式行为，更好地理解和量化未来气候模拟中的不确定性。本项目研究了为AR5准备的模式模拟中水文气候的变化，利用观测数据集评估了模式在降水、蒸散发、土壤湿度和径流等变量中的表现。需要解决的一个关键问题是土地利用和土地覆盖变化（LULC）的影响，预计这对区域空间尺度上的水文循环具有重要意义。1700 - 2000年间，全球自然植被面积减少了45%，而农业用地面积增加了500%。此外，在模式敏感性研究中还发现了LULCC的一些影响，包括由于地表反照率增加导致的全球和区域气候的辐射冷却、由于蒸散发减少导致的区域变暖以及由于土地覆盖变化导致的CO2排放导致的全球变暖。为AR5准备的模拟总集是第一个单独包括对LULC响应的模拟，因此可以通过比较由LULC、温室气体增加和其他强迫因子强迫的模式模拟来评估这种潜在重要强迫的气候影响。因此，这项资助下的工作将探索气候模式模拟重要水文气候变量的能力，以及这些变量受LULC影响的程度。该项目的更广泛影响在于它对IPCC第五次评估报告的支持，该报告旨在向全球决策者提供有关气候变化及其后果的信息。决策者将受益于对用于预测全球变暖导致的气候变化的气候模式质量的评估，以及对区域和全球尺度上LULC对气候（特别是水文循环）影响的评估。

This is one of 16 Rapid Response (RAPID) projects funded as the result of a Dear Colleague Letter (NSF 11-006) encouraging diagnostic analyses of climate model simulations prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Research conducted in these projects is expected to lead to more detailed model intercomparisons, better understanding of robust model behaviors, and better understanding and quantification of uncertainty in future climate simulations.This project examines changes in hydroclimate in model simulations prepared for the AR5, using observational datasets to evaluate model performance in variables including precipitation, evapotranspiration, soil moisture, and runoff. A key issue to be addressed is the effect of land use and land cover change (LULC), which is expected to be significant for the hydrological cycle on regional spatial scales. Between 1700 and 2000, the global extent of natural vegetation decreased by 45%, and agricultural land area increased by 500%. In addition, a number of LULCC impacts have been found in model sensitivity studies, including radiative cooling of global and regional climate as a result of increase in surface albedo, regional warming due to decrease in evapotranspiration, and global warming due to CO2 emission from land cover change. The simulation ensemble prepared for the AR5 is the first of its kind to include simulations of the response to LULC alone, so that the climatic impact of this potentially important forcing can be assessed through comparisons of model simulations forced by LULC, greenhouse gas increases, and other forcing factors. Thus, work under this grant will explore both the ability of climate models to simulate important hydroclimate variables and the extent to which these variables are affected by LULC.The broader impact of the project lies in its support of the IPCC AR5, which is intended to provide information on climate change and its consequences to decision makers worldwide. Decision makers will benefit from an assessment of the quality of the climate models used to project climate changes due to global warming, as well as an evaluation of the impact of LULC on climate (particularly the hydrological cycle) at regional and global scales.