2000-2011年中国地表比辐射率时空格局及影响因素分析

Spatial-Temporal Patterns and Important Factors Driving and Surface Emissivity in China, 2000-2011

地表比辐射率是影响地表长波辐射收支的重要物理参数和生态参数。本文通过对EOS—MODIS卫星地表比辐射率产品（MOD11A2）的时空特征分析，得到2000—2011年12年中国地表比辐射率数据集的时空分布特征。结果表明，全国地表比辐射率取值区间较小，仅为0．9610-0．9760。土地覆被类型的空间分布决定了比辐射率的空间格局特征，不同土地覆被类型的比辐射率以沙地最小，冰雪和水体最高，而且耕地要明显高于自然植被。2000-2011年地表比辐射率变化总体上以降低趋势为主，但在我国西北部的新疆和青海等地区变化较为复杂，部分地区表现出明显的增加趋势。在6个气候区内，地表比辐射率从高到低顺序依次为：暖温带湿润区〉中温带湿润区〉中温带半干旱区〉热带亚热带湿润区〉青藏高原区〉中温带干旱区。积雪可以显著增加地表比辐射率，在中温带干旱区，可使比辐射率值从0．964升高到0．967左右。不同气候区无雪情况下比辐射率年内变化规律并不相同，呈现出各自独有的变化特征，以中温带干旱区比辐射率年内变化最为明显。但所有气候区的比辐射率年际差异较小，没有显著的变化趋势。

Surface emissivity is an important physical and ecological parameter that affects surface long wave radiation budgets and energy balance. Influential factors include vegetation cover, soil moisture, ice and snow. Based on spatial and temporal characteristics analysis of EOS-MODIS satellite surface emissivity products （MOD11A2）, we obtained 12-year spatial-temporal pattems in land surface emissivity in China. The results showed that the emissivity value distribution range is small, only 0.9619-0.9760 across the whole country. Sandy had the minimum emissivity values, and ice and water had maximum values. Residential areas showed a lower surface emissivity than that of the surrounding areas, between 0.9641-0.9680 and forming clear plaques of settlements. Emissivity declined from 2000-2011 across the whole country. However, some areas showed increases, but the opposite signal appeared in the mountains. Surface emissivity for climate zones descended in the order： warm temperate zone humid region 〉 middle temperate zone humid region 〉 middle temperate zone semi-arid region 〉 tropical and subtropical zone humid region 〉 Tibetan Plateau region 〉 middle temperate zone arid region. Snow significantly increased surface emissivity in the middle temperate zone arid region where emissivity increased from 0.964 to 0.967. Snow-free emissivity had different variation characteristic across the six climate zones. For example, in the middle temperate zone arid region, surface emissivity increased with the emergence of vegetation. However, surface emissivity showed the opposite characteristic in the middle temperate zone humid region.