Knowledge Resource Center for Ecological Environment in Arid Area
| 中国西北西部土壤湿度的微波遥感及其对气候变化的响应研究 | |
| 其他题名 | Soil Moisture Estimate from Microwave Remote Sensing and Its Response to Climate Change in the West-northwestern Region of China |
| 王磊 | |
| 出版年 | 2009 |
| 学位类型 | 博士 |
| 导师 | 文军 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 土壤湿度维系着陆地上的生命，是陆地植物生长的基本条件。对于地球科学领域，它还有着其他重要作用：土壤湿度不仅是联系地表和大气间水和能量交换的重要纽带，而且也控制着降雨过程中地表径流及渗透的分配比例。本文以中国西北西部为研究区，利用先进微波扫描辐射计（AMSR-E）亮温数据估算土壤湿度，并研究土壤湿度变化及其对气候变化的响应，主要内容和结论如下：\n 第一：利用2002-2008年暖季（4-10月）AMSR-E的6.9GHz通道亮温数据，基于一阶辐射传输方程，发展了一个适用于干旱区的土壤湿度估算模型，以此重建了中国西北西部地表土壤湿度序列。其中，借助于土壤湿度与微波极化指数（MPDI）之间的特殊关系，对地表粗糙度进行了参数化，此参数化过程是建立本文土壤湿度估算模型的关键。经验证，重建的土壤湿度序列接近于实际情况，并能运用于其他科学研究。\n 第二：利用AMSR-E亮温数据和一次典型降水天气过程的降水观测数据，发展了一个降水估计模型。首先，用逐步判别分析方法判别降雨像元。然后，用降水散射指数估算降水率。结果表明：降水散射指数大于3.0K时，降水率与散射指数之间存在线性关系。经验证，估算的降水率与观测值较接近，均方根误差为2.1mm/h，估算效果较好。最终结果表明，估算土壤湿度与降水在时空分布上可以相互印证。\n 第三：分析了中国西北西部7个农业实验站1981-2001年土壤湿度观测资料，结果表明：进入上世纪90年代，多数站点的土壤明显干化，个别站还存在突变现象。进一步研究表明，西北西部土壤湿度与局地降水、蒸发、相对湿度等气侯因子相关不明显，而与气温有着显著的负相关，这主要是由于土壤湿度与气温之间存在负反馈过程。\n 第四：利用逐月土壤湿度产品资料，分析了研究区土壤湿度变化及其对气候变化的响应。由于AMSR-E产品时间序列相对较短、部分时空不连续，选取1948-2007年NOAA气候预测中心（CPC）制作的0-10cm土壤湿度产品作为AMSR-E资料的补充和延伸。结果表明：整个中国西北西部土壤湿度呈增加趋势，气候趋势倾向率为0.16%/10a，并有2-7、11、21年周期震荡。其中，北疆、天山一带及南疆西部地区的土壤湿度为明显增加趋势（>0.2%/10a）。REOF分析结果表明，研究区土壤湿度变化分为5种典型格局，其中中西部格局（MW）代表了中国西北西部土壤湿度变化的典型格局，与全区月平均土壤湿度序列的相关系数高达0.462。土壤湿度变化与区域气候存在明显的响应：无论是前期的气温还是降水对后期的土壤湿度都有明显影响，但土壤湿度对后期的气温和降水影响却小得多。研究还发现，土壤的干湿变化与ENSO（厄尔尼诺-南方涛动，El Niño-Southern Oscillation）有着密切的联系，典型的ENSO暖（冷）事件对应研究区湿润（干旱）状况，SSTA与滞后11月的土壤湿度变化有着高度的相关性。北疆、东疆和塔克拉玛干沙漠中部一带为SSTA的敏感区，其中，艾比湖、古尔班通古特沙漠以及东疆哈密一带为高度敏感区。土壤湿度对ENSO的响应主要源自于降水对ENSO的响应。 |
| 英文摘要 | Soil moisture sustains life over land and practically enables vegetation growth. For many Earth science disciplines, it has many other roles. It is a key link to water and energy budget between the land surface and the atmosphere. It also controls the partitioning of rainfall into runoff and infiltration. This paper focuses on soil moisture deriving from the Advanced Microwave Scanning Radiometer for EOS（AMSR-E）and its response to climate over west-northwestern region of China. \n First, 7 years (during the warm period over 2002-2008) of the AMSR-E data taken at a frequency of 6.9 GHz for night observations at both polarizations are processed and used to obtain 7 years of surface soil moisture dataset for an arid area, in west-northwestern China. This soil moisture dataset can contribute to better understanding the climate change and forecast modeling for this area. Based on the first-order radiative transfer model calculation, a unique model for estimating surface soil moisture over the study area is developed. Considering extremely complex topography over the study area, we have to present a parameterization of surface roughness at the 6.9GHz and spatial resolution of the AMSR-E using the annual minimum Microwave Polarization Difference Index (MPDI). Validations are made, indicating the soil moisture product derived from the AMSR-E is realistic and acceptable.\n Second, for initial purpose to validate the dynamics estimated soil moisture during rainfall events, a rainfall algorithm is also developed for this region from the AMSR-E measurements. The algorithm attempts to use all 12 channels on the AMSR-E instrument and applies a two-step method calibrated over 11 days of hourly rain-gauge data. Stepwise Discriminant Analysis (SDA) is first used to optimally estimate rain pixels based on all 12 channels, although only three channels are found to be necessary. Next, a rain predicator scattering index is used to estimate rain rates. A linear relationship between the rain rates and the scattering index above the threshold of 3.0K is constructed with a simple approximately linear function. The estimated rain rates are compared with the nearly simultaneous ground gauge measurements, and a good relationship is found between the two, with a 2.1mm h-1 root-mean-square error, indicating that the algorithm works well.\n Third, the characteristics of gravimetric soil moisture vertical distribution, temporal variation and its response to the local climate change are analyzed using ground measurements over west-northwestern China. The results show soil has been getting dry at most sites since 1990s and abrupt change is found in two sites (Tulufan and Wulanwusu). The soil-drying trend is mainly controlled by air temperature. The main reason is that a negative feedback mechanism exists between soil moisture and air temperature. Furthermore, there is response between soil moisture and climate. Negative correlation generally exists between soil moisture and temperature. A little of response is found between soil moisture and precipitation.\n Finally, the estimated soil moisture combined with the Climate Prediction Center (CPC) soil moisture is used for climate application. The 0-10cm soil moisture variability over 1948–2007 in the study area is investigated. For entire region as a whole a significant increasing trend in mean moisture availability is observed, with strong decadal (11-year, 21-year) and interannual (2-7-year) variations. Five moisture-related spatial patterns are objectively defined using Rotated Empirical Orthogonal Function (REOF) analysis. These patterns are related to distinct geographical areas and are associated with distinct temporal variations. Furthermore, it is found that dry and wet soil conditions are closely related to the shift in El Niño-Southern Oscillation (ENSO). Warm and cold events are generally corresponding to wet and dry soil conditions, respectively. Sea surface temperature anomaly (SSTA) is highest related to 11-month lagged monthly soil moisture. These findings will facilitate predicting soil moisture conditions in the study area. Lastly, sensitivity analysis indicates that the northern and eastern parts of Xinjiang together with middle of the Taklimakan Desert are the sensitive regions to 11-month leading SSTA. |
| 中文关键词 | 中国西北西部 ; 土壤湿度 ; 微波遥感 ; AMSR-E ; 气候变化 ; 响应 |
| 英文关键词 | West-northwestern region of China Soil moisture Microwave remote sensing AMSR-E Climate change Respo |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 大气物理学与大气环境 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286757 |
| 推荐引用方式 GB/T 7714 | 王磊. 中国西北西部土壤湿度的微波遥感及其对气候变化的响应研究[D]. 中国科学院寒区旱区环境与工程研究所,2009. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [王磊]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [王磊]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [王磊]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
