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Development of a daily soil moisture product for the period of2002–2011 in Chinese mainland

Science China Earth Sciences 2020年第8期63卷 1113-1125页

作者： Kun YANG Yingying CHEN Jie HE Long ZHAO Hui LU Jun QIN Donghai ZHENG Xin LI Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing 100084China National Tibetan Plateau Data Center Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China School of Geographical Sciences Southwest UniversityChongqing 400715China

soil moisture is an essential climate variable(ECV) concerned widely. Due to its high spatial variability, it is costly to measure soil moisture at tens of kilometers scale. In this study, a ten-year(2002–2011) daily soil moisture dataset at 0.25° spatial resolution for Chinese mainland was produced through assimilating the Advanced Microwave Scanning Radiometer for Earth Observing System(AMSR-E) brightness temperature(TB) data into a land surface model(LSM). The obtained soil moisture data was evaluated against soil moisture-measuring networks deployed in two wet areas and one dry area of the Tibetan Plateau.The results show that for the wet areas the accuracy of the soil moisture product obtained from the assimilation is considerably higher than that of both AMSR-E official soil moisture products and land surface simulation results, and for the dry area their accuracy is comparable to each other. The spatial pattern of the soil moisture from the new product is consistent with that of soil porosity from an independent survey-based dataset, further confirming the credibility of the new product. According to this product, the transition regions in China show stronger seasonal variation of soil moisture than dry and wet regions, and drier regions have stronger inter-annual variability of soil moisture than wetter regions, particularly during transitional seasons(spring and autumn). The soil moisture product is accessible at the National Tibetan Plateau Data Center.

关键词： soil moisture Microwave signal Data assimilation Spatiotemporal variability Tibetan Plateau

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An integrated methodology for soil moisture analysis using multispectral data in Mongolia

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Geo-Spatial Information Science 2017年第1期20卷 46-55页

作者： Enkhjargal Natsagdorj Tsolmon Renchin Martin Kappas Batchuluun Tseveen Chimgee Dari Oyunbileg Tsend Ulam-Orgikh Duger NUM-ITC-UNESCO Laboratory for Space Science and Remote Sensing National University of MongoliaUlaanbaatarMongolia Cartography GIS&Remote Sensing DepartmentInstitute of GeographyGeorg-August University GoettingenGoettingenGermany Department of Environment and Forest Engineering National University of MongoliaUlaanbaatarMongolia Department of Statistics National University of MongoliaUlaanbaatarMongolia School of Agroecology Mongolian University of Life SciencesUlaanbaatarMongolia

soil moisture(SM)content is one of the most important environmental variables in relation to land surface climatology,hydrology,and ecology.Long-term SM data-sets on a regional scale provide reasonable information about climate change and global warming specific regions.The aim of this research work is to develop an integrated methodology for SM of kastanozems soils using multispectral satellite data.The study area is Tuv(48°40′30″N and 106°15′55″E)province in the forest steppe zones in Mongolia.In addition to this,land surface temperature(LST)and normalized difference vegetation index(NDVI)from Landsat satellite images were integrated for the assessment.Furthermore,we used a digital elevation model(DEM)from ASTER satellite image with 30-m resolution.Aspect and slope maps were derived from this DEM.The soil moisture index(SMI)was obtained using spectral information from Landsat satellite data.We used regression analysis to develop the model.The model shows how SMI from satellite depends on LST,NDVI,DEM,Slope,and Aspect in the agricultural area.The results of the model were correlated with the ground SM data in Tuv province.The results indicate that there is a good agreement between output SM and SM of ground truth for agricultural area.Further research is focused on moisture mapping for different natural zones in Mongolia.The innovative part of this research is to estimate SM using drivers which are vegetation,land surface temperature,elevation,aspect,and slope in the forested steppe area.This integrative methodology can be applied for different regions with forest and desert steppe zones.

关键词： Remote sensing Landsat soil moisture ground truth measurement modeling

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Applicability of cosmic-ray neutron sensor for measuring soil moisture at the agricultural-pastoral ecotone in northwest China

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Science China Earth Sciences 2020年第11期63卷 1730-1744页

作者： Xingyan TAN Lanhui ZHANG Chansheng HE Yuzuo ZHU Zhibo HAN Xuliang LI Key Laboratory of West China's Environmental System(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China Department of Geography Western Michigan UniversityKalamazooMI 49008USA

Accurate monitoring of soil moisture is crucial in hydrological and ecological studies.Cosmic-ray neutron sensors(CRNS)measure area-average soil moisture at field scale,filling a spatial scale gap between in-situ observations and remote sensing measurements.However,its applicability has not been assessed in the agricultural-pastoral ecotone,a data scarce semiarid and arid region in Northwest China(APENC).In this study,we calibrated and assessed the CRNS(the standard N0 method)estimates of soil moisture.Results show that Pearson correlation coefficient,RP,and the root mean square error(RMSE)between the CRNS soil moisture and the gravimetric soil moisture are 0.904 and less than 0.016 m3 m–3,respectively,indicating that the CRNS is able to estimate the area-average soil moisture well at our study site.Compared with the in-situ sensor network measurements(ECH2O sensors),the CRNS is more sensitive to the changes in moisture in its footprint,which overestimates and underestimates the soil moisture under precipitation and dry conditions,respectively.The three shape parameters a0,a1,a2 in the standard calibration equation(N0 method)are not well suited to the study area.The calibrated parameters improved the accuracy of the CRNS soil moisture estimates.Due to the lack of low gravimetric soil moisture data,performance of the calibrated N0 function is still poor in the extremely dry conditions.Moreover,aboveground biomass including vegetation biomass,canopy interception and widely developed biological soil crusts adds to the uncertainty of the CRNS soil moisture estimates.Such biomass impacts need to be taken into consideration to further improve the accuracy of soil moisture estimation by the CRNS in the data scarce areas such as agricultural-pastoral ecotone in Northwest China.

关键词： soil moisture Cosmic-ray neutron sensor In-situ observations The agricultural-pastoral ecotone in Northwest China(APENC)

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Comparison of the effects of soil moisture and El Nino on summer precipitation in eastern China

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Science China Earth Sciences 2020年第2期63卷 267-278页

作者： Juan ZHOU Zhiyan ZUO Xinyao RONG State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences

The effects of spring soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China(YRNC) and El Ni?o on the East Asian summer monsoon(EASM) and precipitation in eastern China, as well as the relevant mechanisms, are investigated using the modified atmospheric model ECHAM5 coupled with the Common Land Model. These models are the atmospheric and land components of the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM). The simulations show that both soil moisture anomalies in eastern China and El Ni?o sea surface temperature(SST) anomalies have significant influences on the EASM, with the effect of soil moisture being slightly greater than that of the El Ni?o. However, the impacts of soil moisture on EASM and rainfall in eastern China are markedly different from those of the El Ni?o. Wetter(drier) soil over the YRNC corresponds to less(more) precipitation over northern and southeastern China, and more(less) precipitation over the Yangtze River basin and northeastern China, as well as a strengthened(weakened) and westward-shifted(eastward-shifted) West Pacific Subtropical High and a deepened(shallower) East Asian trough, representing a weakened(strengthened) EASM pattern. During El Ni?o developing summers, an anomalous anticyclone extends from northeastern to northern China, and an anomalous cyclone occupies the middle and lower reaches of the Yangtze River and southern China. Concurrently, the West Pacific Subtropical High is anomalously weaker than normal. As a result,rainfall anomalously increases over the lower reaches of the Yangtze River and southern China, and decreases over northern and northeastern China. In El Ni?o decaying summers, there is an anomalous cyclone over northeastern China and an anomalous anticyclone over southern China. The convergence of southerly airflow and northerly winds leads to enhanced rainfall around northern China and the middle reaches of the Yangtze River, and reduced rainfall over other re

关键词： soil moisture El Nino East Asian summer monsoon Precipitation Numerical simulation

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Analysis of soil moisture variation by forest cover structure in lower western Himalayas, India

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Journal of Forestry Research 2013年第2期24卷 317-324页

作者： J. V. Tyagi Nuzhat Qazi S. P. Rai M. P. Singh National Institute of Hydrology Forest Research Institute

soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill streams and have experienced degradation in forest cover due to grazing, deforestation and other human activities. This change in forest cover is likely to alter the soil moisture regime and, consequently, flow regimes in streams. The effect of change in forest cover on soil moisture regimes of this dry region has not been studied through long term field observations. We monitored soil matric potentials in two small watersheds in the lower western Himalaya of India. The watersheds consisted of homogeneous land covers of moderately dense oak forest and moderately degraded mixed oak forest. Observations were recorded at three sites at three depths in each watershed at fortnightly intervals for a period of three years. The soil moisture contents derived from soil potential measurements were analyzed to understand the spatial, temporal and profile variations under the two structures of forest cover. The analysis revealed large variations in soil moisture storage at different sites and depths and also during different seasons in each watershed. Mean soil moisture storage during monsoon, winter and summer seasons was higher under dense forest than under degraded forest. Highest soil moisture content occurred at shallow soil profiles, decreasing with depth in both watersheds. A high positive correlation was found between tree density and soil moisture content. Mean soil moisture content over the entire study period was higher under dense forest than under degraded forest. This indicated a potential for soil water storage under well managed oak forest. Because soil water storage is vital for sustenance of low flows, attention is needed on the management of oak forests in the Himalayan region.

关键词： soil moisture oak forest soil matric potential tree density degraded forest

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Variability of soil moisture and Its Relationship with Surface Albedo and soil Thermal Parameters over the Loess Plateau

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Advances in Atmospheric Sciences 2009年第4期26卷 692-700页

作者：管晓丹黄建平郭铌闭建荣王国印 Key Laboratory for Semi-Arid Climate Change of the Ministry of Education College of Atmospheric SciencesLanzhou University Institute of Arid Meteorology China Meteorological Administration

Data from July 2006 to June 2008 observed at SACOL （Semi-Arid Climate and Environment Observatory of Lanzhou University, 35.946°N, 104.137°E, elev. 1961 m）, a semi-arid site in Northwest China, are used to study seasonal variability of soil moisture, along with surface albedo and other soil thermal parameters, such as heat capacity, thermal conductivity and thermal diffusivity, and their relationships to soil moisture content. The results indicate that surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. The heat capacity, the soil thermal diffusivity, and soil thermal conductivity show large variations between Julian day 90-212 and 450-578. The soil thermal conductivity is found to increase as a power function of soil moisture. soil heat capacity and soil thermal diffusivity increase with increases in soil moisture. The SACOL observed soil moisture are also used to validate the AMSR-E/AQUA retrieved soil moisture and there is good agreement between them. The analysis of the relationship between satellite retrieved soil moisture and precipitation suggests that the variability of soil moisture depends on the variation of precipitation over the Loess Plateau.

关键词： soil moisture surface albedo soil heat capacity soil thermal conductivity soil thermal diffusivity AMSR-E soil moisture product Loess Plateau

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Relating soil moisture and air temperature to evapotranspiration fluxes during inter-storm periods at a Mediterranean experimental site

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Journal of Arid Land 2015年第1期7卷 27-36页

作者： Antonia LONGOBARDI Elina KHAERTDINOVA Department of Civil Engineering University of Salerno Department of Production Safety and Industrial Ecology Ufa State Aviation Technical University

The assessment of the water losses by actual evapotranspiration plays a very important role in water resources management, especially in particular environments suffering soil water stresses and water shortages. The rationales of this study are the scarcity of experimental data, the difficulties in the measurement of direct and continuous evapotranspiration fluxes, and the switching between controls by climate and soil water availability. The temporal patterns of observed soil moisture and air temperature of over three years at an experimental site in southern Italy have been analysed to investigate the relation between them and the actual evapotranspiration volume, estimated using the soil water budget method. To this end, an event-based empirical analysis has been performed, exploring the relation between the mentioned variables. One of the major findings of the explorative phase is the qualitative and quantitative identification of the switching between climate and soil water balance as the controls over actual evapotranspiration at the experimental site. This threshold process has then been modelled at the event and sub-event scale, establishing simple empirical equations to predict actual evapotranspiration losses as a function of soil water content. Multilevel-recorded data also allowed the investigation of the importance of soil depth.

关键词： evapotranspiration soil moisture event scale empirical analysis Italy

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Plant population and weeds influence stalk insects, soil moisture, and yield in rainfed sunflowers

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Insect Science 2007年第5期14卷 425-435页

作者： JAWWAD A. QURESHI PHILLIP W. STAHLMAN J. P. MICHAUD Department of Entomology Kansas State University Agricultural Research Center Hays Kansas USA Department of Agronomy Kansas State University Agricultural Research Center Hays Kansas USA

Insect infestation, soil moisture, and yield were examined in populations of≈33 140 plants/ha （low） and ≈ 40 340 plants/ha （high） of an oilseed sunflower, Helianthus annuus L, cv. ＇ Triumph 660CL＇ with two levels of weediness. Less weedy plots resulted from the application of herbicide combination of S-metolachlor and sulfentrazone, whereas more weedy plots resulted from application of sulfentrazone alone. Among the 12 weed species recorded, neither plant numbers nor biomass differed between crop plant densities. Larvae of the stalk-boring insects Cylindrocopturus adspersus （Coleoptera： Curculionidae） and Mordellistena sp. （Coleoptera： Mordellidae） were less abundant in high density sunflowers, ostensibly due to reduced plant size. However, the same effect was not observed for Dectes texanus （Coleoptera： Cerambycidae） or Pelochrista womanana （Lepidoptera： Tortricidae）, two other stalk-boring insects. soil moisture was highest in low density and lowest in the high density sunflowers that were less weedy. Stalk circumference, head diameter, and seed weight were reduced for sunflower plants with short interplant distances （mean = 20 cm apart） compared to plants with long interplant distances （mean = 46 cm apart）. These three variables were greater in less weedy plots compared with more weedy plot〉 and positively correlated with interplant distance. Yields on a per-hectare basis paralleled those on a per-plant basis but were not different among treatments. The agronomic implications of planting density are discussed in the context of weed and insect management.

关键词： Cylindrocopturus adspersus Dectes texanus Mordellistena sp. neutron probe Pelochrista womanana plant population soil moisture sunflower yield weed control

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Estimating the soil moisture Profile by Assimilating Near-Surface Observations with the Ensemble Kalman Filter (EnKF)

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Advances in Atmospheric Sciences 2005年第6期22卷 936-945页

作者：张述文李吴睿张卫东邱崇践李新 School of Atmospheric Sciences Lanzhou University Lanzhou 730000 Key Laboratory of Arid Climatic Changing and Reducing Disaster of Gansu Province Lanzhou 7300203 Key Laboratory of Arid Climatic Changing and Reducing Disaster of Gansu Province Lanzhou 730020 School of Physical Sciences and Technology Lanzhou University Lanzhou 730000 Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000

The paper investigates the ability to retrieve the true soil moisture profile by assimilating near-surface soil moisture into a soil moisture model with an ensemble Kalman filter （EnKF） assimilation scheme, including the effect of ensemble size, update interval and nonlinearities in the profile retrieval, the required time for full retrieval of the soil moisture profiles, and the possible influence of the depth of the soil moisture observation. These questions are addressed by a desktop study using synthetic data. The ＂true＂ soil moisture profiles are generated from the soil moisture model under the boundary condition of 0.5 cm d^-1 evaporation. To test the assimilation schemes, the model is initialized with a poor initial guess of the soil moisture profile, and different ensemble sizes are tested showing that an ensemble of 40 members is enough to represent the covariance of the model forecasts. Also compared are the results with those from the direct insertion assimilation scheme, showing that the EnKF is superior to the direct insertion assimilation scheme, for hourly observations, with retrieval of the soil moisture profile being achieved in 16 h as compared to 12 days or more. For daily observations, the true soil moisture profile is achieved in about 15 days with the EnKF, but it is impossible to approximate the true moisture within 18 days by using direct insertion. It is also found that observation depth does not have a significant effect on profile retrieval time for the EnKF. The nonlinearities have some negative influence on the optimal estimates of soil moisture profile but not very seriously.

关键词： soil moisture ensemble Kalman filter insertion land data assimilation

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Evaluating the Capabilities of soil Enthalpy, soil moisture and soil Temperature in Predicting Seasonal Precipitation

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Advances in Atmospheric Sciences 2018年第4期35卷 445-456页

作者： Changyu ZHAO Haishan CHEN Shanlei SUN Key Laboratory of Meteorological Disaster Ministry of Education (KLME)/International Joint Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD)Nanjing University of Information Science and Technology (NUIST) School of Atmospheric Science Nanjing University of Information Science and Technology (NUIST)

soil enthalpy （H） contains the combined effects of both soil moisture （w） and soil temperature （T） in the land surface hydrothermal process. In this study, the sensitivities of H to w and T are investigated using the multi-linear regression method. Results indicate that T generally makes positive contributions to H, while w exhibits different （positive or negative） impacts due to soil ice effects. For example, w negatively contributes to H if soil contains more ice; however, after soil ice melts, w exerts positive contributions. In particular, due to lower w interannual variabilities in the deep soil layer （i.e., the fifth layer）, H is more sensitive to T than to w. Moreover, to compare the potential capabilities of H, w and T in precipitation （P） prediction, the Huanghe-Huaihe Basin （HHB） and Southeast China （SEC）, with similar sensitivities of H to w and T, are selected. Analyses show that, despite similar spatial distributions of H-P and T-P correlation coefficients, the former values are always higher than the latter ones. Furthermore, H provides the most effective signals for P prediction over HHB and SEC, i.e., a significant leading correlation between May H and early summer （June） P. In summary, H, which integrates the effects of T and w as an independent variable, has greater capabilities in monitoring land surface heating and improving seasonal P prediction relative to individual land surface factors （e.g., T and w）.

关键词： seasonal precipitation prediction land surface process soil enthalpy soil moisture soil temperature

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