那曲流域季节冻土区土壤水热动态变化分析

鉴于青藏高原冻土区土壤水热动态变化过程对高寒区气候变化、植被演替及退化等方面的研究意义重大。基于2019年9月10日～2020年8月10日那曲流域4个监测站点分层土壤温度和湿度数据,探讨了冻融过程中土壤水热的变化规律及土壤水分和温度间的互作效应。结果表明,那曲流域季节冻土区在冻结过程期、完全冻结期、融化过程期、完全融化期土壤含水率呈现降低—稳定—升高—波动的变化趋势。冻结过程中,土壤水在温度梯度的作用下开始向冻结锋面运移并补充冻结锋面以下的土壤水分,各层土壤含水率均有所下降;融化过程中季节冻土呈现双向消融特征,各层土壤含水率上升,小唐古拉山、措玛乡、那曲大桥、香茂乡分别在20、35、10、50cm土壤水分高值区。土壤在冻结过程中处于放热状态,表层土壤温度较深层小,而融化过程处于吸热状态,表层土壤温度较深层大。随着土层深度增加,气温对土壤温度的影响越来越小,表层土壤温度变化速率均较深层大。5、10、20、35、50cm土层土壤温度与土壤含水率呈正相关关系,确定性系数R2分别为0.596、0.500、0.499、0.304、0.414。研究结果为及时明晰青藏高原土壤水热动态变化状况提供了一定的理论依据。     

土壤水热耦合模型在三江源冻土活动层水热变化中的应用

为揭示青海三江源区水文活动规律,描述季节性冻土分布区内冻、融变化过程中土壤内部热量交换和水分迁移等物理过程,采用有限体积法离散热传导方程和非饱和土壤水运动方程并对其进行耦合求解,建立了冻土区土壤水热耦合模型。利用2005～2007年间9个测站的土壤水热观测资料,从不同角度分析了冻土活动层内的土壤水热特征,对土壤融化深度、表层土壤温度及表层土壤含水量等变化过程的模拟验证结果表明,该模型的模拟结果符合当地的水热运动规律。并定量分析检验了模型方法的有效性,揭示了三江源区的土壤水热运动规律,为该地区的生态系统服务提供了有力的支持。     

青藏高原土壤冻融对地表辐射特征的影响分析

利用黄河源区气候与环境综合观测研究站.2006年10月1日～2007年4月30日的辐射和5cm土壤温度和湿度资料研究了土壤冻融对地表辐射特征的影响,结果表明:土壤冻结降低了土壤中的液态水含量,致使冻结阶段地表反照率大于冻结前的值,也大于土壤融化后的值;受总辐射和地表反照率共同作用,整个冻融过程中反射辐射可区分为两个比较明显的阶段;土壤冻结减缓了地表温度降低的速率,相应地减缓了地表长波辐射和大气逆辐射降低的速率;整个冻融过程中净辐射变化与总辐射的变化比较相近,在冻结阶段,地表反照率大于冻结前的值,也大于融化后的值,因此冻结阶段的净辐射值也更小一些。     

粉质粘土冻融过程中水热迁移特性的实验研究

当利用土壤源热泵供暖时,地埋管周围的土壤有时会形成冻土.为了研究土壤冻融过程中的水热迁移特性,使用足尺冻融实验台,对哈尔滨地区粉质粘土进行了冻融实验.实验结果显示土壤在冻结过程中水分迁移量与冻结速率成反比关系,已冻结区域的含水率基本不发生变化;沿冻结方向分为水分聚集区、输运区和水源区,聚集区在冻融实验前后含水率变化最大,输运区在冻融实验前后含水率变化最小;土壤在冻融状态转换的过程中,会出现含水率突变的现象,变化强度与冻融速率成正比关系.     

改进的SIMHYD模型在黄河源区高寒气候的适应性研究

气候变暖使得区域水文循环过程加快,尤其在高纬度、高海拔地区,温度升高将使积雪、冰川融水量增加,这将给高寒区的水资源管理带来一定的挑战。以黄河上游的高寒气候区为研究对象,先采用5年滑动平均法从流域干燥指数(P/P_(ET))序列中识别出流域水资源最枯、最丰时段;然后,采用度日因子方法耦合SIMHYD模型,提出一种改进的SIMHYD模型(简称SIMHYD_snow模型);最后,对比评估SIMHYD_snow与传统SIMHYD模型的水文模拟过程,并揭示二者在月尺度水资源量评估上的差异。结果表明,黄河源区水资源整体呈"由丰转枯再转丰"的时程变化特征,1990年代最枯;改进的SIMHYD_snow模型显著提高了非汛期水文模拟精度,且湿润期更优;传统SIMHYD模型低估了非汛期的径流量,高估了汛前径流量。研究结果可为高寒气候区流域水资源量的精准评估提供重要的支撑。     

基于随机森林算法的冻融期土壤蒸发预报模型研究

以山西省晋中盆地大田土壤蒸发实测数据和气象站监测资料为例,采用2017~2018年冻融期土壤蒸发实测数据作为因变量、影响冻融期土壤蒸发的9个因素作为自变量,利用随机森林算法构建了冻融期土壤蒸发预报模型,并对冻融期三个阶段影响土壤蒸发的因素进行了重要度评价。结果表明,冻融期土壤蒸发的预测值与实测值的平均相对误差为5.7%,均方误差为0.055,模型预测精度较高,拟合效果较好,所建立的模型适用于冻融期土壤蒸发的预报;不稳定冻结期对土壤蒸发影响较大的为地表土壤含水率和太阳辐射,稳定冻结期为降水和地表土壤含水率,消融解冻期为降水、地表土壤含水率和水面蒸发量。     

相变对土壤自然温度场影响研究

利用土壤水热耦合迁移方程,首次考虑土壤和大气温度场的年周期性变化,建立有相变影响的土壤传热物理、数学模型,将土壤冻结过程是否考虑相变的数值模拟结果进行对比分析。模拟结果表明有相变时土壤温度随时间变化的曲线不再为光滑的余弦曲线,土壤冻结初期和融化过程相对于无相变土壤都有温度的平缓持续段;进入冻结期后有相变的土壤温度整体高于无相变的土壤,随着深度的增加,此温度差值增大。将模拟结果与实测值进行对比分析表明,得出该文给出的模型及计算方法基本正确,但还应考虑冰的阻抗作用。     

藏北高原地区和西北干旱区地表能量季节变化特征对比分析

基于中日合作研究项目"全球协调加强观测计划之亚澳季风青藏高原试验"(CAMP/Tibet,2001～2005年)和大型野外观测试验国家重点基础研究发展规划项目中的"西北干旱区陆气相互作用试验"(DHEX,2000-2003年) 1a年的观测数据资料分析研究了干旱区地表能量,即净辐射通量、感热通量、潜热通量和土壤热通量。得到一些有关地表能量的新认识,最后还提出并讨论了计算地表能量通量的方法及其优缺点。     

中国昼夜降水特征的空间分异规律

降水昼夜分配的时空特征,是干旱半干旱地区降水资源有效性的重要影响因素。我国昼夜降水空间分异复杂,在雨强、高程、季相等方面的规律还有待进一步研究。为此,采用空间分区、高程分带、雨强分级、季相对比等方法,基于全国839个气象站点1951～2019年的降水资料,研究了我国昼夜降水特征的空间分异规律。结果表明,在空间分区上,我国可划分为受夜间冷却和山谷风效应的青藏及周边夜雨典型区、受辐射对流效应的秦-淮以南昼雨典型区、秦-淮以北降水昼夜相对均衡区;在垂直分异方面,青藏高原及周边山地最为明显,年夜间降水量的高程递减率大于昼间,昼夜差异随海拔升高而减弱;降水的雨强特征为中高雨强降水比重大,尤其是青藏东缘中高强度夜雨显著;季相规律为青藏及西南地区月降水均为夜雨大于昼雨,而南方4～10月昼雨典型。我国昼夜降水特征的空间分异规律,可作为农业与生态水资源气候评估的参考,对山洪预警也有重要意义。     

陆面水文模式Noah-LSM在赣江上游区的适用性研究

为合理评估未来气候变化下赣江上游区的水文响应机制,基于赣江上游峡山水文站以上集水区域6个气象站点1961～2014年逐日气象资料和2008～2014年中国陆面数据同化系统土壤含水率产品,采用NoahLSM陆面水文模式进行历史流量和土壤含水率过程模拟,评估Noah-LSM在赣江上游区的适用性。结果表明,Noah-LSM模拟的率定期和验证期日流量模拟过程确定性系数分别为0.857、0.750,模拟的土壤含水率过程与中国陆面数据同化系统产品基本吻合。Noah-LSM能合理模拟研究区的流量和土壤含水率过程,且在赣江上游区具有良好的适用性。     

地表覆盖对季节性冻融期土壤水分特征的影响

为探求不同地表覆盖下非饱和冻融土壤介质中土壤水分的迁移转化规律,于2013年11月10日~2014年3月22日在山西省晋中市东阳镇进行季节性冻融期系列田间试验。结果表明,地表覆盖有效地减少了地表土壤水分的蒸发,削弱了土壤含水率的波动幅度,但不同冻融阶段不同地表覆盖地块的土壤水分有所差异。与裸地(LD)相比,冻结阶段,秸杆覆盖(JG)和地膜覆盖(DM)显著增加了地表以下0~10cm土壤墒情,且DM比JG保墒效果好;融化前期,秸秆覆盖阻碍了融雪水的直接入渗,JG对土层的蓄水保墒作用不明显;融化后期,秸秆覆盖削弱了风速对地表土壤水分的影响,抑制了表土蒸发,对土层具有保墒作用。整个冻融期,DM始终对土层具有保墒作用,且其保墒效果较JG好。地表覆盖有效地减弱了地表以下0~20cm土壤含水率的波动幅度,随着土壤深度的加大,覆盖措施对土壤含水率的影响逐渐减弱。DM土壤水分随时间的变化态势与LD相似程度较高。从储水保墒角度出发,冻融期DM覆盖更具现实意义。研究成果可为北方冬春季节土地利用及管理提供指导。     

土壤温度和水分日变化实验

在露天和温室两种条件下 ,对 2 0 0mm× 5 0mm (高×半径 )的土壤床中温度和水分的日变化规律进行了实验研究。结果表明 :1)土壤温度随着太阳辐射和大气温度的周期性变化而呈现出周期性变化 ,随着深度的增加 ,温度变化的滞后效应越明显 ;2 )夏天的白天大部分时间中 ,土壤浅层的温度高于深层的温度 ;从下午的某个时间至第二天日出 ,这种现象则相反 ;3 )云层夺太阳幅射的阻挡 ,对土壤表层的温度有较大的影响 ,而对较深处影响不大 ;4)由于有遮阳设施 ,温度中土壤的最高温度要比露天情况下低 ;5 )从傍晚开始 ,土壤中的水蒸汽出现冷凝 ,浅层土壤中水蒸汽开始冷凝的时间比深层早 ,露天下土壤中水蒸汽的冷凝现象比温室中更明显     

Household energy consumption patterns in agricultural zone,pastoral zone and agro-pastoral transitional zone in eastern part of Qinghai-Tibet Plateau

Despite the rapid development in fossil fuel, biomass is still the main energy resource in rural China. However, the research on household energy consumption on the Qinghai-Tibet Plateau is limited. We investigated the differences in household energy consumption pattern, the influencing factors of fuel type choice, and the willingness to use clean energy in agricultural, pastoral and agro-pastoral transitional zones in eastern part of Qinghai-Tibet Plateau. Information was collected through Participatory Rural Appraisal (PRA) and Physical Monitoring (PM). We found that biomass was the main energy resource in pastoral regions while fossil energy was the main fuel in agricultural regions. Energy consumption per capita in pastoral regions was higher than that in agricultural regions in our study area, and annual household energy consumption in pastoral regions was much higher than the provincial average. Altitude, livelihood and education level were main factors affecting domestic fuel type choice, while altitude and household size were two factors determining energy consumption per capita. The use of biomass as fuel could have negative influence on the material cycle in ecosystem and affect the carbon budget on the Qinghai-Tibet Plateau. Householders were willing to use clean energy and most interviewees chose electricity as their favorite fuel type. Therefore, the modern utilization of biomass and the exploration of renewable energy are promising in future energy development in eastern part of Qinghai-Tibet Plateau. However, energy transition might be constrained by poor local transportation and traditional consumption habit of indigenous community.     

不同环境条件下土壤温度日变化的计算模拟

应用多孔介质中传热传质的数学模型，对夏天和冬天，环境风速分别为4m／s和1m／s以及环境相对湿度分别为35％和85％这3种情况下高为500mm，半径为250mm的圆柱土壤床中温度的日变化进行了比较。根据数值模拟的结果绘出土壤中不同深度处温度的日变化曲线表明：(1)土壤中各点的温度随气温和土壤表面获得的辐射能的周期性变化而呈周期性变化；(2)随着深度的增加，土壤温度受气温和太阳辐射的影内变小，温度变化的滞后效应越来越明显；(3)在夏天，一天的大部分时间土壤表层的温度高于深层的温度，冬天则恰恰相反；(4)风速对土壤表层的温度影内较大。风速越大，土壤温度降低得越多；(5)干燥气候下，由于土壤水分的蒸发制冷作用，一天中土壤各点的温度低于湿润气候下相应各点的温度，土壤表层尤为明显。     

Measurement of ice movement in water using electrical capacitance tomography

The permafrost with the highest altitude and largest area in the mid and low latitude is located in the Qinghai-Tibet Plateau. As most frozen soils contain ice particles which are very sensitive to temperature and other external parameters, thus influencing the stability of the embankment in permafrost regions, it is very important to develop techniques to prevent damages to railway embankments due to thaw settlement. In this paper, the electrical capacitance sensors are designed to study the freezing front movement in a vessel and ice movement in water, which is the first step to apply the ECT system to the study of frozen soil. Two sensor arrangements are put into use. First, the traditional closed electrode sensors are put into use. In this arrangement, the electrodes are attached to the outside of the pipe or vessel, and the cross-sectional distribution of ice and water could be reconstructed from the capacitances measured. Also, the ice moving track at the cross section could be reflected thoroughly. Since the traditional closed electrode sensors can not meet the needs of measuring the ice freezing front movement, a new electrode sensors structure, that is, the unclosed electrode sensors are designed to satisfy the specific test of frozen soil. In this arrangement, several pairs of electrodes are arranged along the height of the vessel. A sudden decrease in the measured capacitance is observed when the freezing front advances past the electrodes. Therefore, according to the capacitance variation, the ice movement can be reflected. In summary, electrical capacitance tomography has the advantages of being non-intrusive. With different electrode sensor arrangement, ice movement and ice freezing front can be obtained. The electrical capacitance sensor system can be applied to investigate the complicated phenomena in frozen soil.     

Performance of solar chimney power plant in Qinghai-Tibet Plateau

A solar chimney power plant (SCPP) is proposed to be built in Qinghai-Tibet Plateau where there is abundant solar radiation, high direct solar radiation low atmospheric temperature, large diurnal temperature range, and lots of salt lakes working as heat storage system, which can help to improve the power output of SCPP. The plant is expected to power local railway traffic lines and act as a solar power base to supply power for national development. The performance of the SCPP that will be built in Qinghai-Tibet Plateau is analyzed and power potential estimated by developing a simple mathematical model. It is found that SCPP if built in the plateau can produce twice more power than an SCPP built on the same latitude of other regions. The yearly power potential for SCPP in Qinghai-Tibet Plateau is estimated to be 86.8 million TJ. When 10–20% of the plateau land is used for the SCPP, the yearly power output may reach 8.7 million TJ to 17.4 million TJ, accounting for 10.7–21.3% of China's energy consumption in 2008 which stood at 81.6 million TJ. It is found that the SCPP in the plateau can support local and national development together with other renewable energy resources such as hydroelectric power and wind power.     

太阳辐照下湿份分层土壤中热湿传输的数值模拟

考虑温度对土壤湿分迁移的影响，建立描述存在干饱和层时的土壤热湿传递的数学模型，并就自然环境和恒定太阳辐照下两种情况进行数值模拟，获得不同环境条件下土壤中温度和湿分分布以及水分蒸发的动态特性，分析干饱和土壤层对土壤热湿迁移与水分蒸发以及温度对土壤湿分传输的影响。     

Long-term water balance and sustainable production of Miscanthus energy crops in the Loess Plateau of China

Sustainable production of second-generation energy crops on marginal land holds a great potential for renewable energy development. Because a vast area of marginal land is located in the arid and semiarid regions of the world, water shortage is the most serious environmental limitation. In this study, we developed a water balance model to address the question of whether Miscanthus energy crops can be sustainably produced in the Loess Plateau of China, a region of more than 60 million hectares particularly abundant in semiarid marginal land. The simulation of 20-year soil water content in bare soil, the winter wheat field, and the Miscanthus field across the Loess Plateau suggested that the long-term production of Miscanthus would not cause water depletion in deep soil. This finding addressed a serious concern that growing high-biomass plants in the Loess Plateau might lead to deep-soil water depletion, which was suggested to be the cause of previous failure of afforestation. Planting Miscanthus was effective in reducing surface runoff and consequently preventing water and soil loss in this heavily eroded region. The model and analyses illustrated where in the Loess Plateau this perennial energy crop could be produced with stable and sufficient yield.     

中国干旱频率分析分区探讨

干旱频率分析是水资源规划设计和旱灾风险管理的基础,其分析指标的合理选取依赖于不同下垫面的空间特征。选择降雨、气温、日照时数、高程、土壤类型和年径流深等影响干旱的主要因素描述不同地理区域干旱现象在气象、地貌和水资源等因素上的空间差异,并基于这些因素的空间差异性和相似性,采用定性和定量相结合的方法对中国干旱频率分区进行了研究。通过在地理信息系统平台上构建分区因子图层,并利用等值线叠加法划分出10个在空间上具有相似性的地理区域作为中国干旱频率分析的一级大区,为中国不同区域选择适宜指标进行干旱频率分析提供了参考。     

Estimation of global solar radiation in arid and semi-arid climates of East and West Iran

In Iran, most of the models used so far, have provided solar estimation for a few specific locations based on the short-term solar observations. Using different radiation models, (e.g. Sabbagh, Paltridge–Proctor, Daneshyar) and various input parameters (e.g. cloud cover, sunshine duration, relative humidity, temperature, and altitude) we developed a general height-depended formula for the prediction of the direct and diffuse monthly average daily solar radiation for 64 mountainous arid and semi-arid locations in West and East Iran. The models mentioned are modified and new coefficients are defined for the diffuse component based on the long-term observed diffuse data. Model results are validated against up to 13-year daily solar observations at 10 solar radiation sites. In comparison with the previous studies, the newly developed method performs more accurate estimation (less than 3% MPE error) in the arid and semi-arid regions. Comparison of the model results indicates that calibration of the coefficients made to the diffuse formula against the longer period experimental data can improve the estimations of global solar radiation.