Knowledge Resource Center for Ecological Environment in Arid Area
| 黄土高原半干旱区雨养农田陆气能量水分过程观测与模拟研究 | |
| 其他题名 | Observation and simulation of water, energy exchange in a rain-fed cropland over the semiarid area of Loess Plateau |
| 陈星 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 余晔 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 陆地和大气之间的能量水分交换过程决定了水循环、边界层的发展，并最终影响区域甚至全球气候，气候模式对这一过程较为敏感，尤其是在陆地和大气耦合较强的半干旱区，而能量水分交换过程在不同陆地类型、不同植被功能型间有着明显差异，农田作为一种被人类改变的土地利用类型，其能量水分交换过程不同于自然植被并且在大多数模式中没有得到准确的表达。本论文利用2010年12月至2012年11月在中国科学院平凉陆面过程与灾害天气观测研究站获得的气象观测资料和涡动系统观测资料，分析了黄土高原半干旱区雨养农田的气象要素、地表辐射和能量通量的季节和年际变化特征，研究了造成雨养农田蒸散发量逐日变化和年际差异的气象因素和生物因素，并选择了3种不同的下垫面时期，分析了不同时期影响陆气间能量分配的因素，最后利用CLM4.5陆面模式模拟了2011年4-10月农田陆气间能量的分配过程并对模式模拟性能进行了评估。得到如下结果：（1）研究站点的主导能量通量有较大的月际波动和年际差异。在年度尺度上，2010年12月-2011年11月，正午净辐射的最大消耗者为感热，其占净辐射约35%，而2011年12月-2012年11月，最大消耗者为潜热，其占净辐射约40%。两年平均正午潜热占比分别为32%和40%，低于灌溉农田。在冬小麦快速生长季（3-5月），这两年平均正午潜热占比分别为34%和46%，远低于灌溉冬小麦田，研究站点的潜热过程受到了水分的限制。（2）研究的两个年度的年蒸散发量分别为547.4 mm和667.0 mm。日蒸散发量在0.09 mm d-1至6.0 mm d-1之间波动。表面导度从0.17 mm s-1到30 mm s-1以上，极大值出现在降雪或降水之后，最大可达31.8 mm s-1。研究站点的蒸散发量高于同等甚至更高降水和净辐射条件下的草地、森林以及湿地站点，与同等降水条件下的农田相当，略低于灌溉农田。（3）大气的水分需要是控制研究站点蒸散发量逐日变化的最主要因素，实际年蒸散发量只占潜在蒸散发量的56%（2010年12月-2011年11月）和65%（2011年12月-2012年11月），蒸散发受到水分胁迫，土壤含水量改变了蒸散发对大气需要的响应率。研究站点的降水供应和大气的需要并不匹配，尤其在冬小麦生长季，春季干旱导致水分胁迫较为严重，降低了冬小麦的气孔导度，从而抑制了蒸散发。而在冬小麦收割之后，几乎不再受水分胁迫。（4）植被状况对蒸散发的控制程度仅次于大气的水分需要。植被状况的不同造成了蒸散发与土壤湿度之间关系的非线性。冬小麦具有很高的蒸腾能力，而土壤的蒸发能力较低，观测到的最大日蒸散发量出现在冬小麦生长季而非雨季。农业生产缩短了地表覆盖植被的时间，从而降低了潜热通量的占比，并且通过改变下垫面状况改变了影响能量分配的因素。（5）在冬小麦生长季的5-6月，决定能量分配的土壤含水量阈值约为0.11 m3 m-3，高于这一阈值时，潜热通量占主导。在冬小麦收割后的7-8月，土壤部分裸露，决定能量分配的土壤含水量阈值提高至约0.13 m3 m-3。在作物全部收割后的10-11月，虽然土壤含水量高于决定能量分配的阈值，潜热通量大于感热通量，但因缺少蒸腾作用，在同等土壤含水量情况下潜热与感热通量之间的差异小于作物收割前。在生长季，水分供应的缺乏抑制了潜热通量，导致大气水汽压差较大，大气水汽压差是潜热通量变化的结果而不是原因，而在土壤水分较为充裕的10-11月，在不受土壤水分胁迫的状况下，大气水汽压差的增加能够促使潜热通量增加，并且在同等净辐射情况下，大气水汽压差越高，分配给潜热通量的能量越多。感热通量随地气温差的增加而增加，其随地气温差增长的速率在5-6月更高，在10-11月较低。风速与潜热通量仅在10-11月作物收割以后有显著的相关关系，此时有利的湍流扩散条件可以提高土壤蒸发。（6）CLM4.5陆面模式模拟的感热通量和土壤热通量高于观测值，而潜热通量的模拟值低于观测值，尤其在冬小麦生长期间的4-6月，模拟的潜热通量比观测值低约39.4至88.3 W m-2，可能是由于模拟的植被蒸腾量偏低。CLM4.5模式高估了土壤蒸发，低估了植被蒸腾，其对潜热通量（蒸散发）各分量的表述不适用于研究站点。未耦合作物模式的CLM4.5模式不能准确反映所研究农田的植被状况及其物候变化，模拟的总初级生产力对环境状况的响应也与观测有偏差，从而导致植被蒸腾模拟出现偏差。 本论文的观测分析和模式评估结果为进一步改进陆面模式中的农作物模块提供了基础。 |
| 英文摘要 | The exchange of water and energy between the land surface and the atmosphere determines the hydrological cycle, boundary layer development, and the regional or even global climate. Climate models are sensitive to the surface energy partitioning especially in the semi-arid area which is the hotspot in the climate change. Surface energy partitioning varies greatly with land surface and plant functional type. Crop cultivation, representing the major land-use practice of human, could affect the water and energy exchange, however, most earth system models either ignore or represent cultivation in a simple way and do not account for the real crop phenology, physiology and management.In this study, meteorological and flux measurements collected at the Pingliang Land Surface Process & Severe Weather Research Station,CAS from December 2010 to November 2012 were used to analyzed the seasonal and interannnual variability of the radiation and the energy fluxes over a rain-fed cropland in the semi-arid of Loess Plateau. The biotic and abiotic factors of evaportranspiration (ET) were studied. Combined with the sensible heat fluxes (Hs), the factors in surface energy partitioning over three different underlying surfaces were investigated. Finally, the performance of CLM4.5 model in energy partitioning was evaluated in the studied rain-fed agroecosystem. The results show that:(1) The main consumer of the available energy varied among different months and years. On an annual scale, the largest consumer of midday net radiation was sensible (latent) heat flux in 2010-2011 (2011-2012), which accounted for about 35% (40%) of the net radiation (Rn). The average midday ratios of latent heat flux (LE) to Rn were about 32% and 40%, respectively, which were lower than some irrigated croplands. During the rapid growing season of winter wheat (March to May), the average midday LE/Rn were about 34% and 46%, respectively, which were much lower than other croplands. The evapotranspiration was suppressed due to the water stress, especially during the growing season.(2) The annual ETs were 547.4 mm and 667.0 mm, and the daily ET ranged from 0.09 mm d-1 to 6.0 mm d-1. The surface conductance fluctuated from 0.17 mm s-1 to above 30 mm s-1, with the maximum of 31.8 mm s-1 occurring after rain or snow. Annual ET in the study site was higher than the grassland, forest and wetland sites with equal or even higher precipitation and net radiation, and was comparable to other cropland with equal precipitation, however, slightly lower than some irrigated cropland.(3) The day to day variation of ET was mainly controlled by the demand of atmosphere in the study site. However, the daily ET only accounted for about 56% and 65% of the potential ET in the two studied years, respectively. Soil moisture changed the response rate of ET to the demand of atmosphere. The water demand of atmosphere and the water supply was mismatching, especially during the growing season of winter wheat. The water stress was different among different months, which was serious during the growing season and was absent after the harvest.(4) Vegetation played the second role in controlling ET and caused the nonlinear and nonmonotonic relationship between soil moisture and ET. The transpiration of winter wheat was powerful, while the soil evaporation was relatively low, so the maximum daily ET occurred during the growing season of winter wheat, not during the rainly season. Agricultural activities shortened the period when surface was covered with vegetation, which decreased the ratio of LE to Rn, and altered the factors in energy partitioning.(5) During May to June with the winter wheat, the water stress threshold value of energy partitioning was about 0.11 m3 m-3, above which LE was the main consumer. While, during July to August with some bare soil after winter wheat harvest, the water stress threshold value increased to about 0.13 m3 m-3. When the crop was harvested totally from Octorber to November, though the soil moisture was above the water stress threshold value, the difference between LE and Hs was smaller than that before harvest, due to the lack of transpiration. During the growing season, ET was suppressed due to water stress, as a result, the vapor pressure deficit (VPD) was high. While, during Octorber to November with high soil moisture, the increasing of VPD could improve the ET and more energy was used by LE. The sensible heat flux increased with the difference between surface temperature and air temperature. And the increasing rate of Hs with the difference between surface temperature and air temperature was higher in May and June, and lower in Octorber and November. Wind speed showed significant relationship with LE only during Octorber and November when the crop was harvested totally, indicating that the soil evaporation increased with turbulent activity.(6) The CLM4.5 overestimated the sensible heat flux and soil heat flux, while underestimated the latent heat flux, especially during the growing season of winter wheat (April to June), which was likely due to the underestimation of transpiration. The unmanaged cropland in CLM4.5 was biased in the crop phenology, and the relationship between gross primary production and the environment factors in the studied agroecosystem. These results from observation and numerical simulations in the study could help to improve the crop model in land surface models. |
| 中文关键词 | 黄土高原 ; 农田 ; 蒸散发 ; 能量分配 ; CLM模式 |
| 英文关键词 | Loess Plateau Cropland Evapotranspiration Energy partition CLM model |
| 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/2XILL650/287706 |
| 推荐引用方式 GB/T 7714 | 陈星. 黄土高原半干旱区雨养农田陆气能量水分过程观测与模拟研究[D]. 中国科学院大学,2016. |
| 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 |
| [陈星]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [陈星]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [陈星]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。
