Knowledge Resource Center for Ecological Environment in Arid Area
| 中国地表蒸散和干旱时空变化遥感分析 | |
| 其他题名 | Study on the Spatial and Temporal Variation of the Land Surface Evapotranspiration and Drought in China by Using the Remote Sensing Data |
| 侯英雨 | |
| 出版年 | 2008 |
| 学位类型 | 博士 |
| 导师 | 田国良 |
| 学位授予单位 | 中国科学院遥感与数字地球研究所 |
| 中文摘要 | 本文主要基于长时间序列卫星遥感数据集以及同期地面气象要素估算我国旬地表蒸散，分析了我国地表蒸散的时空变化规律及其与气候的关系，建立了基于蒸散亏缺指数的干旱评价指标，研究了我国1982-2000年干旱发生发展的时空格局。\n遥感数据提供了不同尺度的空间信息。利用遥感数据估算地表蒸散的方法主要有直接经验法、能量平衡法、间接法三种，本文采用的地表蒸散估算模型属于能量平衡法。通过与同类模型(SEBS)模拟结果以及地面观测结果的对比分析表明，它们具有较好的一致性。\n空气温度是地表蒸散遥感估算模型最重要的参数之一。本文使用的卫星遥感数据集是十天晴空合成数据。为了解决地面观测空气温度与卫星过境时间的同步问题，本文建立了稀疏植被地区和高覆盖植被地区的空气温度遥感反演方法。在稀疏植被区，按照地形差异，根据不同季节的NOAA-AVHRR无云干扰的LST资料和相应时间段的地面气象站点1.5m处空气温度观测资料， 分别建立了不同高程类型的LST与空气温度Ta的统计模型。在高植被覆盖区域，利用NDVI-LST特征空间几何关系来估算空气温度。验证结果表明，本文提出的一套空气温度遥感估算方法具有较高的精度。\n近几十年来我国气候状况、地表土地覆盖和土地利用等发生明显变化，地表区域蒸散量也必然随之发生变化。本文基于估算的地表蒸散数据集，分析了20年我国地表蒸散的时空分布及其年际和季节性变化。结果表明：（1）我国年实际蒸散状况空间差异特征明显，西藏、东北、华北年蒸散比较高；（2）我国月蒸散季节性变化规律差异明显，其中华北、黄淮、江淮月蒸散季节性变化曲线呈明显的双峰结构，江汉、西南呈一弱一强的双峰结构；江南、华南月蒸散具很强的季节性变化特征，其变化曲线呈明显单峰结构；（3）1982-2000年，我国大部地区年蒸散的年际波动性较强，基本呈下降趋势，其中有33%的陆地区域地表年蒸散呈显著减少趋势。（4）20年来我国不同地区年蒸散和月蒸散的变化趋势在时空分布上存在明显的差异性：区域不同、植被覆盖类型不同，地表蒸散的变化规律也不同；（5）不同地区、不同植被类型、不同季节的蒸散年际变化与气候 \n因子（温度、降水）相关强度不一样。 \n本文利用估算的1982－2000年的旬地表蒸散数据集，设计了蒸散亏缺指数（ETDI）作为农业干旱的评价指标。通过与地面观测的土壤相对湿度、干旱灾害、降水亏缺指数的对比分析，我们发现：蒸散亏缺指数与土壤相对湿度、帕尔默干旱指数、降水亏缺指数、干旱灾情监测数据等具有较高的相关性。因此本文设计的蒸散亏缺指数能够用来监测农业干旱的发生、发展状况。\n本文利用计算的1982－2000年的旬地表蒸散亏缺指数作为干旱评价指标，研究和分析了20年来我国干旱状况的空间格局和强度在时间和空间上的变化规律。结果发现：（1）20年来，我国发生干旱频次比较高且分布密集的区域主要有四个：西北干旱区、黄淮海干旱区、华南干旱区、西南干旱区。（2）全国干旱的时空分布区域差异性和季节性差异性非常明显：春季和冬季，全国大部地区发生干旱的频次相对较少，夏季和秋季干旱发生次数明显偏多。（3）20年来全国平均单位面积年发生干旱次数呈上升趋势，但1995-2000年，则呈明显下降趋势；（4）20年来，不同季节发生干旱频次的变化过程也不同，春季发生干旱的次数呈明显增加趋势；夏季发生干旱的次数看不出明显的增减趋势；秋季发生干旱的次数呈微弱的上升趋势，但1996－2000年呈明显的下降趋势；冬季干旱发生次数也看不出明显的增减趋势。 |
| 英文摘要 | In this thesis, the two-decade’s land surface evapotranspiration has been estimated by using the long term satellite remote sensing datasets and meteorological datasets, then the spatial and temporal variation characteristics of the evapotranspiration and its’ response to the climate factors has been analyzed. The drought severity index has been defined based on the evapotranspiration deficit index and then the spatial and temporal pattern of the drought’s occurrence and evolution during 1982 to 2000 has been studied. \nSatellite remote sensing data provides a lot of spatial information about the land surface in different scales. There are mainly three kinds of method for estimating the land surface evapotranspiration by using remote sensing data, which are directly experiential algorithm, energy balance algorithm and the indirectly algorithm. The algorithm for evapotranspiration estimation involved in this thesis belongs to the kind of the energy balance algorithm. The results of evapotranspiration estimation model developed in this paper are similar and accordant to the outputs of the other same kind remote sensing evapotranspiration algorithm (such as SEBS). The some sensible heat flux and latent heat flux data observed from ground was also used for validation. \nAir temperature (Ta) is one of the key parameters for the remote sensing evapotranspiration algorithm. The satellite remote sensing data used in the thesis is the ten-day cloud free composite datasets. In order to solve the problem of non- synchronization between the satellite remote sensing observations and the ground meteorological observations, the models for inversing the Ta in the rare and dense vegetation covering regions have been developed separately. In the rare vegetation covering regions, Ta estimation models have been setup base on the relationships between LST retrieved from NOAA-AVHRR and Ta observed on ground. In the dense vegetation covering regions, Ta estimation models have been setup based on the geometric relation of the NDVI-LST characteristics space. Validations results show that Ta estimation methods developed in this thesis have a high accuracy. \nThe characteristics of spatial and temporal distribution as well as the annual and seasons’ variation of land surface evapotranspiration have been analyzed by using the estimated two-decade’s evapotranspiration datasets. The results show: (1) The difference of spatial distribution of evapotranspiration is obvious in China. The evapotranspiration is higher in Tibet, northeast China and northern China. (2) The characteristics of intra-annual variation of evapotranspiration is obvious. The monthly evapotranspiration curve has two strong peaks in northern China, Huanghuai and Jianghuai regions, and it has one weak peak and one strong peak in Jianghan region and southwest China. The intra-annual variation in southern China is very strong and the monthly evapotranspiration curve shows single peak. (3) During 1982 to 2000, the yearly evapotranspiration’s variation is great but the trends are decreasing as a whole. The area of yearly evapotranspiration decreased markedly is up to amount of 33% in total area in China. (4) The yearly and monthly evapotranspiration spatial and temporal variations trends have significant difference in different regions. (5) The relationship between the yearly evapotranspiration and the climate factors (such as temperature, precipitation) is great different in inter-regions, as well as inter-seasons.\nIn this thesis, EvapoTranspiration Deficit Index （ETDI）has been defined as the drought evaluation indicator by using the estimated two-decade evapotranspiration datasets from 1982 to 2000. By comparison ETDI to the relative soil moisture, Palm drought index and precipitation deficit, the results show that the ETDI has a stronger relationship to them. It indicates that ETDI can be used for monitoring the agriculture drought occurrence and evaluation. \nThe spatial and temporal patterns of drought severity have been analyzed by using the two-decade ETDI as drought assessment indicator during 1982-2000. The results show that: (1) In the recent 20 years, drought occur very frequently and densely in four main regions: northwest China arid region, Huanghuaihai arid region, southern China arid region and southwest China arid region. (2) The regional and seasonal difference of drought variation is remarkable in China. The frequency of drought ccurrence in spring and winter is low in most China, but inversely, it is very high in summer and autumn. (3) The frequency of drought occurrence in unit areas in China has an increasing trend. However, from 1995 to 2000, the frequency of drought occurrence has an obvious decreasing trend. (4) The inter-annual variations of the seasonal drought occurrence frequency are also different in the recent 20 years. There \nare strong increasing trends for drought occurrence in spring and weak increasing trends in autumn, but there are no clear trends for drought occurrence in summer and winter. |
| 中文关键词 | 地表蒸散 ; 卫星遥感 ; 蒸散亏缺指数 ; 干旱监测 ; 时空变化 |
| 英文关键词 | Land Surface Evapotranspiration Satellite Remote Sensing EvapoTranspiration Deficit Index (ETDI) Drought Monitoring Spatial and Temporal Variation |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 地图学与地理信息系统 |
| 来源机构 | 中国科学院遥感应用研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286712 |
| 推荐引用方式 GB/T 7714 | 侯英雨. 中国地表蒸散和干旱时空变化遥感分析[D]. 中国科学院遥感与数字地球研究所,2008. |
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