中国东北地区地表反照率对气候变化的响应与反馈遥感监测分析

Surface albedo is a critical geographical parameter that is widely used in studies of earth's radiation and surface energy budget. The surface broadband albedo is defined as the ratio of the surface upwelling to the downward flux of shortwave solar radiation over the upward semi-hemispherical space. It is one of the controlling parameters of the surface energy budget equation, which affects the input and relocation of solar energy over the Earth’s surfaces. The global land surface albedo changes with natural processes and human activities, such as deforestation, desertification, wildfire, and the decreasing of northern-hemisphere snow coverage. These changes in surface albedo also influence regional and global weather in which even tiny variations of surface albedo can feedback to the climate system and affect the global and regional climate patterns. The temporal and spatial variation is closely related to the global climate change and regional weather system due to the albedo feedback mechanism. As an efficient tool for monitoring the surfaces of the Earth, remote sensing is widely used for deriving long-term surface broadband albedo with various geostationary and polar-orbit satellite platforms in recent decades. Although encouraging achievements have been acquired, the current surface broadband albedo products still suffer from the problems of product accuracy, temporal resolution, and data integrity, especially in the seasonal snow-covered regions (e.g. Northeast of China). In this proposal, we aim to determine how surface albedo responses to the natural processes and human activities, and improve our knowledge about the responses and feedbacks of surface albedo to global climate change with satellite-derived surface albedo product. Firstly, a new method for estimating surface albedo over seasonal snow-covered regions, which incorporates the advantages of BRDF angular modeling method and direct-estimation algorithm will be developed. Then, a long-term, high temporal resolution surface albedo product of Northeast of China can be generated with satellite observations. Finally, the responses and feedbacks of surface albedo to climate change will be evaluated with the satellite-derived surface albedo dataset.

地表反照率是辐射与能量平衡研究中的重要地表特征参量，决定着地球表层与大气之间辐射能量的分配过程。在全球气候变化和人类活动影响加剧的背景下，地表反照率正发生着显著的变化，因此分析地表反照率对全球气候变化的响应与反馈机制具有科学研究意义和现实应用价值。近几十年来，基于卫星遥感观测数据估算地表反照率成为研究的热点。但是现有地表反照率遥感估算方法在季节性降雪区存在时间分辨率较低、稳定性较差等问题。本研究拟以中国东北地区为研究区域，发展一套适合于季节性降雪区的地表反照率遥感估算方法，提高地表反照率产品的时间分辨率和估算精度，生成中国东北地区长时间序列、高时间分辨率的地表反照率产品。并在该数据集的基础上，分析中国东北地区地表反照率对气候变化的响应与反馈机制，明确地表反照率对自然过程和人类活动的响应程度。

地表反照率是辐射与能量平衡研究的关键地表特征参量，决定着地气系统中辐射能量的分配过程。在全球气候变化和人类活动影响加剧的背景下，地表反照率正在发生着显著的变化，因此分析地表反照率对全球气候变化的响应与反馈机制具有重要的科学研究意义。但是现有地表反照率遥感估算方法在季节性降雪区存在时间分辨率较低、稳定性较差等问题，影响了季节性降雪区(如中国东北地区)地表反照率数据集的分析与应用。本项目发展了一套适用于季节性降雪区的地表反照率遥感估算方法，提高地表反照率产品的时间分辨率、估算精度和时空连续完整性，发展了基于卫星数据的地表反照率数据集生成关键技术，初步明确了中国东北地区地表反照率对气候变化的响应与反馈机制。研究发现中国东北地区在1982~2015年反照率整体呈现增加趋势(+0.0037/decade)，反照率距平存在周期性振荡现象，积雪覆盖变化与区域土地覆盖/利用变化共同增强了地表反照率变化的强度，呼伦贝尔草原、大兴安岭东部、松嫩平原区、三江平原和辽河平原等区域地表反照率呈现显著上升趋势，而大兴安岭、小兴安岭东部、辽西丘陵等区域反照率呈现显著下降趋势。本项目研究结果将为地表反照率遥感数据集生成和区域气候变化应对等领域提供技术方法和理论支撑，有力推动地表反照率数据集生成与应用研究的发展。