【作者】 郑文武；

【导师】 曾永年；

【作者基本信息】 中南大学 ， 地图制图学与地理信息工程， 2012， 博士

【摘要】 在全球气候变化的背景下,由于城市地表覆盖的急剧变化以及人类活动热排放的增强,城市热环境急剧恶化。城市热岛效应已经成为广泛关注的城市环境问题,地理学、生态学和环境学等众多学科领域就有关城市热岛的空间特征、形成机制进行了广泛深入的研究,但这些研究甚少涉及到蒸散发。由于蒸散发是城市表面水循环和能量循环中重要且难以估算的分量,也是城市热环境研究的重要参数之一,对城市地表蒸散发的模拟和动态监测研究具有重大的科学意义和实用价值,有助于更深入地理解城市热环境问题的形成机理,为城市热环境问题缓解对策的制定提供参考。本文以长沙市核心城区为研究区,基于城市地表能量平衡特征,提出了城市蒸散发遥感反演的多源平行模型,对模型的参数化方案进行了研究,并基于多源遥感数据进行了模型的实验研究,通过与气象站点数据的对比分析以及与P-M模型和SEBAL模型反演结果的对比分析,论证了算法的有效性,最后,分析了土地覆盖空间结构及变化对城市地表能量平衡影响和蒸散发变化对城市热环境的影响。研究结果表明：(1)由于城市多源平行遥感蒸散发反演模型发展了传统的二源平行模型,考虑了城市地表能量平衡特征,在多源遥感数据的支持下,城市多源平行遥感蒸散发反演算法能够获得较好的结果。与气象站实测数据相比,结果偏差最大值为1.0mm,最小值为0.1mm,与彭曼模型计算结果相比,不同的土地覆盖类型均存在一定程度的低估,裸地低估程度最大,但不超过20%,反演结果与基于SEBAL模型估算结果具有很好的相关性,植被区相关性最大。(2)从蒸散发的角度分析了土地覆盖变化对城市热环境的影响,研究表明：不同土地覆盖类型上蒸散发差异明显,土地覆盖的变化导致了显著地蒸散发变化；城市热岛效应的强度与地表蒸散发之间存在明显的负相关关系,城市扩展过程中,蒸散发空间分布特征发生了显著变化,并导致了城市热岛效应加剧。1993-2005年林地向建设用地的转化导致了蒸散发显著减少；林地向农田转化也在一定程度上导致了蒸散发的减少,以轻微减少为主；农田向建设用地转化的区域分布广泛,农田向建设用地转化的区域的蒸散发明显减少,农田向林地转化的区域的蒸散发明显增加,但主要表现为轻微增加。无城市热岛效应和表现不明显的区域蒸散发较大,热岛效应表现强和极强的区域蒸散发也相对最低,城市热岛效应的强度与地表蒸散发之间存在明显的负相关关系。通过对城市热岛效应对蒸散发变化响应的分析发现：1993年的热岛效应指数分级图显示热岛效应主要发生于中心城区,空间聚集特征明显,1993-2005年研究区热岛效应表现较强的区域大幅扩展；在蒸散发急剧减少的条件下,城市热岛效应表现出明显的增强趋势,但主要以轻微增强为主。更多还原

【Abstract】 In the context of global climate change, because of drastic changes in urban land cover and enhancement of anthropogenic heat release, the urban heat environment deteriorated sharply. The urban heat island effect is becoming one of major urban environmental problems and has been widely concerned. Some subjects such as geography, ecology and environmental science, carried out extensive and in-depth research, the study includes the spatial characteristics and formation mechanism of the urban heat island. However, these studies rarely related to the evapotranspiration. Evapotranspiration is one of the important parameters which are used urban surface water cycle and energy cycle research, and is one of the important parameters in urban thermal environment study. It is of great scientific significance and practical value to study the evapotranspiration simulation and dynamic monitoring of the urban land surface and it contribute to a deeper understanding of the environmental problems of urban heat formation mechanism.In this paper, the core urban area of Changsha City was selected as study area. Firstly, a new algorithm called multi-source parallel model based on the urban surface energy balance characteristics has been proposed. Secondly, some parameterization methods for the model have been studied, and the inversion result of this algorithm is validated by comparison with the data of meteorological stations and estimation results of P-M model and SEBAL algorithm. Finally, the influence of land covers spatial structure and change on evapotranspiration of urban land surface, and the influence of evapotranspiration changes on the urban thermal environment have been analyzed.The results show that:(1) In support of multi-source remote sensing data, the inversion result of multi-source parallel model is satisfactory. Compared with the weather station measured data, the maximum bias is1.0mm, and the minimum bias is0.1mm. Compared with result of P-M model, different land cover types are present to a certain degree of underestimation, and the relative deviation does not exceed20%, compared with result of SEBAL algorithm, two results share good relations and the relation in vegetation area get maximum value.(2) Land cover changes resulted in a significant change in evapotranspiration. Conversions of forest land to building land from1993to2005resulted in significant reductions in evapotranspiration, and conversions of forest land to farmland in the same period resulted reductions in evapotranspiration, but the reduction degrade is mainly slight. Conversions of farmland to building land are widely distributed, and resulted in significant reductions in evapotranspiration. Conversions of farmland to forest land resulted in significant evapotranspiration increase.(3) Correlation between the intensity of urban heat island and surface evapotranspiration shows obvious negative correlation. From1993to2005, the area of urban region is significantly expanded, and the spatial distribution characteristics of evapotranspiration changed significantly, and resulted in the urban heat island effect exacerbated. The evapotranspiration in the region where urban heat island effect is not obvious is relatively high, and the evapotranspiration in the region where urban heat island effect is strong is relatively low, a significant negative correlation between the intensity of urban heat island and evapotranspiration can be found. From the classification map of heat island intensity in1993, it can be found that heat island effect mainly occurred in the central urban area, and the characteristic of spatial aggregation is obvious. The region of high heat island intensity expanded significantly from1993to2005, in the conditions of significant reduction of evapotranspiration, the heat island intensity obvious enhanced, but area slightly enhanced accounted for the main part.更多还原