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1

Soil Moisture  

NSDL National Science Digital Library

NOAA's Climate Prediction Center offers this useful data site on soil moisture across the US. Soil moisture data are provided here as color contour maps that represent calculated soil moisture, anomalies, and percentiles for the most recent day, monthly, and twelve-month time periods. Also provided here are 25-year average soil moisture & soil wetness summaries. In addition to providing recent and historical data, the Soil Moisture site features soil moisture forecasts for two-week, monthly, and seasonal intervals, based on the National Weather Service Medium Range Forecast (MRF) and the Constructed Analog on Soil Moisture (CAS).

2000-01-01

2

Soil Moisture  

NSDL National Science Digital Library

This Flash animation renders the pattern of soil moisture storage at the surface. The increase/decrease in soil moisture are especially apparent for the in Africa because of the annual north-south march of the wet InterTropical Convergence Zone (ITC). In the Flash format, the animation can easily be rewound or paused to stress important points.

Climvis.org

3

Long term analysis of PALS soil moisture campaign measurements for global soil moisture algorithm development  

Technology Transfer Automated Retrieval System (TEKTRAN)

An important component of satellite-based soil moisture algorithm development and validation is the comparison of coincident remote sensing and in situ observations that are typically provided by intensive field campaigns. The planned NASA Soil Moisture Active Passive (SMAP) mission has unique requi...

4

Rank Stability Analysis of Surface and Profile Soil Moisture  

Technology Transfer Automated Retrieval System (TEKTRAN)

Although several studies have examined the spatial and rank stability of soil moisture at the surface layer (0-5cm) with the purpose of estimating large scale mean soil moisture, the integration of the rank stability of profile (0-60cm) soil moisture has not been fully considered. This research comb...

5

Soil moisture  

Microsoft Academic Search

Infiltration continues to occupy the attention of soil physicists and engineers. A theoretical and experimental analysis of the effect of surface sealing on infiltration by Edwards and Larson [1969] showed that raindrops reduced the infiltration rate by as much as 50% for a two-hour period of infiltration. The effect of raindrops on the surface infiltration rate of soils has been

L. L. Boersma; D. Kirkham; D. Norum; R. Ziemer; J. C. Guitjens; J. Davidson; J. N. Luthin

1971-01-01

6

Analysis of Large Scale Spatial Variability of Soil Moisture Using a Geostatistical Method  

PubMed Central

Spatial and temporal soil moisture dynamics are critically needed to improve the parameterization for hydrological and meteorological modeling processes. This study evaluates the statistical spatial structure of large-scale observed and simulated estimates of soil moisture under pre- and post-precipitation event conditions. This large scale variability is a crucial in calibration and validation of large-scale satellite based data assimilation systems. Spatial analysis using geostatistical approaches was used to validate modeled soil moisture by the Agriculture Meteorological (AGRMET) model using in situ measurements of soil moisture from a state-wide environmental monitoring network (Oklahoma Mesonet). The results show that AGRMET data produces larger spatial decorrelation compared to in situ based soil moisture data. The precipitation storms drive the soil moisture spatial structures at large scale, found smaller decorrelation length after precipitation. This study also evaluates the geostatistical approach for mitigation for quality control issues within in situ soil moisture network to estimates at soil moisture at unsampled stations.

Lakhankar, Tarendra; Jones, Andrew S.; Combs, Cynthia L.; Sengupta, Manajit; Vonder Haar, Thomas H.; Khanbilvardi, Reza

2010-01-01

7

McMaster Mesonet soil moisture dataset: description and spatio-temporal variability analysis  

NASA Astrophysics Data System (ADS)

This paper introduces and describes the hourly high resolution soil moisture dataset continuously recorded by the McMaster Mesonet located in the Hamilton-Halton Watershed in Southern Ontario, Canada. The McMaster Mesonet consists of a network of time domain reflectometer (TDR) probes collecting hourly soil moisture data at six depths between 10 cm and 100 cm at nine locations per site spread across four sites in the 1250 km2 watershed. The sites for the soil moisture arrays are designed to further improve understanding of soil moisture dynamics in a cold and snowy climate and to capture soil moisture transitions in areas that have different topography, soil and land-cover. The McMaster Mesonet soil moisture constitutes a unique database in Canada because of its high spatio-temporal resolution. In order to provide some insight into the dominant processes at the McMaster Mesonet sites a spatio-temporal and temporal stability analysis were conducted to identify spatio-temporal patterns in the data and to suggest some physical interpretation of soil moisture variability. It was found that the seasonal Canadian climate causes a transition in soil moisture patterns at seasonal time scales. During winter and early spring months, and at the meadow sites, soil moisture distribution is governed by topographic redistribution, whereas following efflorescence in the spring and summer, soil moisture spatial distribution at the forested site was equally dominated by vegetation canopy. Analysis of short-term temporal stability revealed that the relative difference between sites was maintained unless there was significant rainfall (> 20 mm) or wet conditions a priori. Following a disturbance in the spatial soil moisture distribution due to wetting, the relative soil moisture pattern re-emerged in 18 to 24 h. Access to the McMaster Mesonet data can be provided by visiting http://www.hydrology.mcmaster.ca.

Kornelsen, K. C.; Coulibaly, P.

2012-12-01

8

Spatio-temporal analysis of a long-term global soil moisture dataset  

NASA Astrophysics Data System (ADS)

It is a well known truth that soil moisture plays an essential role within the hydrological cycle and the climate system. Therefore a deeper knowledge and understanding of soil moisture behaviour, changes and pattern is of major interest. This contribution introduces a statistical approach to recognize spatio-temporal patterns within a long-term global soil moisture data set. The great potential of satellites to detect soil moisture on a global and continuous scale is well-known and in particular microwave remote sensing is recognized to work as the most efficient instrument for acquiring soil moisture information. The current study is based on a long-term global soil moisture data set, the ESA CCI soil moisture data set (http://www.esa-soilmoisturee-cci.org). It was developed by combining data derived from active and passive microwave satellite-based sensors, profiting from the advantages of both retrieval techniques. The ESA CCI soil moisture data set provides soil moisture information for more than three decades and can easily be extended with products from current and future satellite missions. Relative dynamics and long term changes of the original satellite derived retrievals are preserved in the CCI product, thus a valuable basis for long-term analysis is given. By applying a cluster algorithm to monthly and seasonal means of the combined CCI data regions with similar temporal soil moisture patterns are created. The plausibility of the resulting groups is verified by comparison with land cover classifications and climate classes. Besides, special care has been taken of the treatment of missing values as their existences causes difficulties when statistical methods are applied. In this study various methods for missing value imputation are discussed to provide as much meaningful data as input for the following cluster analysis as possible. Overall, the described analysis of soil moisture product is expected to improve our knowledge and understanding of soil moisture behaviour and the quality of the used product.

Xaver, Angelika; Dorigo, Wouter A.

2013-04-01

9

Improving long-term global precipitation dataset using multi-sensor surface soil moisture retrievals and the soil moisture analysis rainfall tool (SMART)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Using multiple historical satellite surface soil moisture products, the Kalman Filtering-based Soil Moisture Analysis Rainfall Tool (SMART) is applied to improve the accuracy of a multi-decadal global daily rainfall product that has been bias-corrected to match the monthly totals of available rain g...

10

Analysis of large scale spatial variability of soil moisture using a geostatistical method.  

PubMed

Spatial and temporal soil moisture dynamics are critically needed to improve the parameterization for hydrological and meteorological modeling processes. This study evaluates the statistical spatial structure of large-scale observed and simulated estimates of soil moisture under pre- and post-precipitation event conditions. This large scale variability is a crucial in calibration and validation of large-scale satellite based data assimilation systems. Spatial analysis using geostatistical approaches was used to validate modeled soil moisture by the Agriculture Meteorological (AGRMET) model using in situ measurements of soil moisture from a state-wide environmental monitoring network (Oklahoma Mesonet). The results show that AGRMET data produces larger spatial decorrelation compared to in situ based soil moisture data. The precipitation storms drive the soil moisture spatial structures at large scale, found smaller decorrelation length after precipitation. This study also evaluates the geostatistical approach for mitigation for quality control issues within in situ soil moisture network to estimates at soil moisture at unsampled stations. PMID:22315576

Lakhankar, Tarendra; Jones, Andrew S; Combs, Cynthia L; Sengupta, Manajit; Vonder Haar, Thomas H; Khanbilvardi, Reza

2010-01-25

11

Soil Moisture Assessment by Means of Compressional and Shear Wave Velocities: a Theoretical Analysis  

Microsoft Academic Search

This paper deals with the problem of measuring the moisture of agricultural soils by an accurate theoretical method valid for different kinds of soils in different physical conditions. In this work we propose a theoretical analysis based on the propagation of seismic waves in a complex medium as the agricultural soil is. Particularly we prove that the use of both

F. Adamo; G. Andria; F. Attivissimo; L. Fabbiano; N. Giaquinto

2006-01-01

12

Analysis of spatiotemporal soil moisture patterns at the catchment scale using a wireless sensor network  

NASA Astrophysics Data System (ADS)

Soil water content plays a key role in partitioning water and energy fluxes and controlling the pattern of groundwater recharge. Despite the importance of soil water content, it is not yet measured in an operational way at larger scales. The aim of this paper is to present the potential of real-time monitoring for the analysis of soil moisture patterns at the catchment scale using the recently developed wireless sensor network SoilNet [1], [2]. SoilNet is designed to measure soil moisture, salinity and temperature in several depths (e.g. 5, 20 and 50 cm). Recently, a small forest catchment Wüstebach (~27 ha) has been instrumented with 150 sensor nodes and more than 1200 soil sensors in the framework of the Transregio32 and the Helmholtz initiative TERENO (Terrestrial Environmental Observatories). From August to November 2009, more than 6 million soil moisture measurements have been performed. We will present first results from a statistical and geostatistical analysis of the data. The observed spatial variability of soil moisture corresponds well with the 800-m scale variability described in [3]. The very low scattering of the standard deviation versus mean soil moisture plots indicates that sensor network data shows less artificial soil moisture variations than soil moisture data originated from measurement campaigns. The variograms showed more or less the same nugget effect, which indicates that the sum of the sub-scale variability and the measurement error is rather time-invariant. Wet situations showed smaller spatial variability, which is attributed to saturated soil water content, which poses an upper limit and is typically not strongly variable in headwater catchments with relatively homogeneous soil. The spatiotemporal variability in soil moisture at 50 cm depth was significantly lower than at 5 and 20 cm. This finding indicates that the considerable variability of the top soil is buffered deeper in the soil due to lateral and vertical water fluxes. Topographic features showed the strongest correlation with soil moisture during dry periods, indicating that the control of topography on the soil moisture pattern depends on the soil water status. Interpolation using the external drift kriging method demonstrated that the high sampling density allows capturing the key patterns of soil moisture variation in the Wüstebach catchment. References: [1] Bogena, H.R., J.A. Huisman, C. Oberdörster, H. Vereecken (2007): Evaluation of a low-cost soil water content sensor for wireless network applications. Journal of Hydrology: 344, 32- 42. [2] Rosenbaum, U., Huisman, J.A., Weuthen, A., Vereecken, H. and Bogena, H.R. (2010): Quantification of sensor-to-sensor variability of the ECH2O EC-5, TE and 5TE sensors in dielectric liquids. Accepted for publication in Vadose Zone Journal (09/2009). [3] Famiglietti J.S., D. Ryu, A. A. Berg, M. Rodell and T. J. Jackson (2008), Field observations of soil moisture variability across scales, Water Resour. Res. 44, W01423, doi:10.1029/2006WR005804.

Bogena, Heye R.; Huisman, Johan A.; Rosenbaum, Ulrike; Weuthen, Ansgar; Vereecken, Harry

2010-05-01

13

Soil Moisture Time Series Analysis for a Hillslope located Gwangneung National Arboretum  

Microsoft Academic Search

Understanding the hydrological processes at a hillslope scale can be achieved through intensive in situ monitoring of an intermediate hydrologic variable, soil moisture, during rainfall events. A soil monitoring system was installed to efficiently represent the spatial and temporal features of soil moisture for a hillslope located Gwangneung national Arboretum in South Korea. The soil moisture responses to sequential rainfall

S. Kim; M. Son; J. Kim; D. Lee; S. Moon

2007-01-01

14

Analysis of polarimetric RADARSAT2 images for soil moisture retrieval in an alpine catchment  

NASA Astrophysics Data System (ADS)

Soil moisture estimation is one of the most challenging problems in the context of biophysical parameter estimation from remotely sensed data. Typically, microwave signals are used thanks to their well known sensitivity to variations in the water content of soil. However, other target properties such as soil roughness and the presence of vegetation affect the microwave signals, thus increasing the complexity of the estimation problem. The latter problem becomes even more complex when we move on mountain areas, such as the Alps, where the high heterogeneity of the topographic condition further affect the signals acquired by remote sensors. In this paper, we explore the use of polarimetric RADARSAT2 SAR images for the estimation of soil moisture content in an alpine catchment. In greater detail, we first exploit field measurements and ancillary data to carry out an analysis on the sensitivity of the SAR signal to the moisture content of soil and other target properties, such as topography and vegetation/land-cover heterogeneity, that characterize the mountain environment. On the basis of the findings emerged from this analysis, we propose a technique for estimating moisture content of soils in these challenging operative conditions. This technique is based on the Support Vector Regression algorithm and the integration of ancillary data. Preliminary results are discussed both in terms of accuracy over point measurements and effectiveness in handling spatially distributed data.

Pasolli, L.; Notarnicola, C.; Bruzzone, L.; Bertoldi, G.; Niedrist, G.; Tappainer, U.; Zebisch, M.; Del Frate, F.; Laurin, G. V.

2010-10-01

15

Measuring soil moisture  

NASA Astrophysics Data System (ADS)

A recent aerial field experiment of the National Aeronautics and Space Administration carried out above farmland near Ames, Iowa, could help scientists to develop a remote global soil moisture observing system over most of the Earth's non-forested and unfrozen regions.During the experiment, which lasted from 25 June to 8 July scientists and engineers measured soil moisture content with remote sensing techniques that included a passive and active L- and S-band microwave instrument about 1.1 kilometers above ground, and an airborne synthetic aperture radar flying at an altitude of about 7.9 kilometers.

Showstack, Randy

16

Soil Moisture Memory in AGCM Simulations: Analysis of Global Land Atmosphere Coupling Experiment (GLACE) Data  

Microsoft Academic Search

Soil moisture memory is a key aspect of land-atmosphere interaction and has major implications for seasonal forecasting. Because of a severe lack of soil moisture observations on most continents, existing analyses of global-scale soil moisture memory have relied previously on atmospheric general circulation model (AGCM) experiments, with derived conclusions that are probably model dependent. The present study is the first

Sonia I. Seneviratne; Randal D. Koster; Zhichang Guo; Paul A. Dirmeyer; Eva Kowalczyk; David Lawrence; Ping Liu; Cheng-Hsuan Lu; David Mocko; Keith W. Oleson; Diana Verseghy

2006-01-01

17

Optional Soil Moisture Sensor Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the water content of soil based on the electrical resistance of soil moisture sensors. Students install soil moisture sensors in holes that are 10 cm, 30 cm, 60 cm, and 90 cm deep. They take daily readings of soil moisture data by connecting a meter to the sensors and using a calibration curve to determine the soil water content at each depth.

The GLOBE Program, University Corporation for Atmospheric Research (UCAR)

2003-08-01

18

A simulated soil moisture based drought analysis for the United States  

NASA Astrophysics Data System (ADS)

Droughts have severe economic, environmental and social impacts. Timely determination of the current level of drought may aid the decision making process in reducing the impacts from drought. In this study, high-resolution, land surface hydrology simulations using the Variable Infiltration Capacity (VIC) model are used to derive a hydrologically based drought index. Soil moisture data from a retrospective simulation from 1950 to 1999 over the continental United States are used to develop probability distributions of monthly average soil moisture, and the relative position of soil moisture fields within the historic distribution provides a measure of drought in relation to the long-term behavior. The index is able to identify the major drought events during the latter part of the twentieth century and shows good agreement with the time series of U.S. drought from two Palmer Drought Severity Index (PDSI) data sets. On average, 30% of the United States experienced dry conditions (<10% soil moisture quantile) during 1950-1999, peaking at over 70% coverage at the height of the 1950s drought. Many dry events exhibit long-term persistence, especially in the West, which is important in terms of the cumulative impacts. The physical basis of the model allows the index to take into account a number of processes, which contribute to the development of drought, such as snow accumulation and melt that other indices ignore or treat unsatisfactorily. Furthermore, the high spatial and temporal resolution of the simulations ensure that the drought index is able to allow for the effects of short-term changes in meteorology as well as longer-term climate variations, and resolve the high spatial variability in soil moisture and drought occurrence. The potential for implementing the analysis in an operational mode exists by using data from the near real-time simulations within the North American Land Data Assimilation System (NLDAS).

Sheffield, Justin; Goteti, Gopi; Wen, Fenghua; Wood, Eric F.

2004-12-01

19

[Real-time analysis of soil moisture, soil organic matter, and soil total nitrogen with NIR spectra].  

PubMed

The grey-brown alluvial soil in northern China was selected as research object, and the feasibility and possibility of real-time analyzing soil para-fueter with NIR spectroscopic techniques were explored. One hundred fifty samples were collected from a winter wheat farm. NIR absorbance spectra were rapidly measured under their original conditions by a Nicolet Antaris FT-NIR analyzer. Three soil parameters, namely soil moisture, SOM (soil organic matter) and TN (total nitrogen) content, were analyzed. For soil moisture content, a linear regression model was available, using 1920 nm wavelength with correlation coefficient of 0.937, so that the results obtained could be directly used to real-time evaluate soil moisture. SOM content and TN content were estimated with a muviaiple linear regression model, 1870 and 1378 nm wavelengths were selected in the SOM estimate model, and 2262 and 1888 nrameter wavelengths were selected in the TN estimate model. The results showed that soil SOM and TN contents can be evaluated by using NIR absorbance spectra of soil samples. PMID:16830746

Sun, Jian-ying; Li, Min-zan; Zheng, Li-hua; Hu, Yong-guang; Zhang, Xi-jie

2006-03-01

20

An analysis of soil moisture dynamics using multi-year data from a network of micrometeorological observation sites  

NASA Astrophysics Data System (ADS)

Soil moisture data, obtained from four AmeriFlux sites in the US, were examined using an ecohydrological framework. Sites were selected for the analysis to provide a range of plant functional type, climate, soil particle size distribution, and time series of data spanning a minimum of two growing seasons. Soil moisture trends revealed the importance of measuring water content at several depths throughout the rooting zone; soil moisture at the surface (0 10 cm) was approximately 20 30% less than that at 50 60 cm. A modified soil moisture dynamics model was used to generate soil moisture probability density functions at each site. Model calibration results demonstrated that the commonly used soil matric potential values for finding the vegetation stress point and field content may not be appropriate, particularly for vegetation adapted to a water-controlled environment. Projections of future soil moisture patterns suggest that two of the four sites will become severely stressed by climate change induced alterations to the precipitation regime.

Miller, Gretchen R.; Baldocchi, Dennis D.; Law, Beverly E.; Meyers, Tilden

2007-05-01

21

A New Model of Dielectric Analysis for Measurement Soil Moisture Water Content  

NASA Astrophysics Data System (ADS)

Measurement of soil water content (?) has become an important part of the analysis of various fields of study, especially those involving irrigation in agriculture, forestry, hydrology and land activity. The models for measuring soil water content (?) is usually based on the permittivity (?) value. Many previous studies have been proposed e.g., Top et al. 1980; Roth et al. 1992; Malicki et al. 1996; and Robinson et al. 2005. Measurements using electromagnetic methods typically utilize permittivity parameters to determine water content in the soil. This method was used due to the significantly of differences permittivity between soil and water. In this study, a new model of dielectric analysis for measurement soil moisture water content is proposed and then compared with the existing models as the performance evaluation of the model. Result obtained shows that the new proposed model fits secondary experimental data reasonably well over a wide range of soil types. It is therefore suggested the new proposed model be used for the measurement of soil water content.

Mukhlisin, Muhammad; Saputra, Almushfi; Raihan Taha, Mohd

2013-04-01

22

Global Soil Moisture Data Bank  

NSDL National Science Digital Library

This Data Bank is a collection of more than 400 observations of primarily Asian soil moisture. The data are freely available, and can be used for studying patterns of soil moisture variation, developing and testing land surface models, and ground truth for remote sensing.

1995-01-01

23

Soil moisture memory in AGCM simulations: Analysis of Global Land-Atmosphere Coupling Experiment (GLACE) Data  

NASA Astrophysics Data System (ADS)

A period of heavy rainfall or prolonged drought can produce an anomaly in soil moisture that may take weeks or months to dissipate. The fact that the soil can "remember" a wet or dry anomaly long after the conditions responsible for the anomaly are forgotten by the atmosphere is a key aspect of land-atmosphere interactions and has major implications for seasonal forecasting. The Global Land-Atmosphere Coupling Experiment (GLACE) is a recent project investigating the strength of land-atmosphere coupling in Atmospheric General Circulation Models (AGCMs). As part of this experiment, three ensembles of simulations spanning June 1-August 31 have been conducted by a number of different models, using different specifications for the land-atmosphere coupling (full coupling, partial coupling, and no coupling). The present study investigates the soil moisture memory characteristics of the control experiments (with full coupling). Thus, in essence, the memory characteristics of a number of different models, all doing the same experiment and producing the same type of output, are objectively compared and contrasted. Koster and Suarez (2001) derived an equation that relates the autocorrelation of soil moisture (soil moisture memory) in climate models to 1) seasonality in the statistics of the atmospheric forcing, 2) the variation of evaporation with soil moisture, 3) the variation of runoff with soil moisture, and 4) correlation between the atmospheric forcing and antecedent soil moisture, which reflects both the memory of the external forcing and land-atmosphere feedbacks. Here, we use the equation to analyze soil moisture memory in the investigated AGCMs. The results show that the differences in regional soil moisture memory between the studied AGCMs can indeed be related in part to intermodel differences in these four controls.

Seneviratne, S. I.; Koster, R. D.; Guo, Z.; Dirmeyer, P.

2004-05-01

24

Analysis and modeling of space-time organization of remotely sensed soil moisture  

NASA Astrophysics Data System (ADS)

The characterization and modeling of the spatial variability of soil moisture is an important problem for various hydrological, ecological, and atmospheric processes. A compact representation of interdependencies among soil moisture distribution, mean soil moisture, soil properties and topography is necessary. This study attempts to provide such a compact representation using two complimentary approaches. In the first approach, we develop a stochastic framework to evaluate the influence of spatial variability in topography and soil physical properties, and mean soil moisture on the spatial distribution of soil moisture. Topography appears to have dominant control on soil moisture distribution when the area is dominated by coarse-texture soil or by mixed soil with small correlation scale for topography (i.e., small lambdaZ). Second, soil properties is likely to have dominant control on soil moisture distribution for fine-texture soil or for mixed soil with large lambda Z. Finally, both topography and soil properties appear to have similar control for medium-texture soil with moderate value of lambda Z. In the second approach, we explore the recent developments in Artificial Neural Network (ANN) to develop nonparametric space-time relationships between soil moisture and readily available remotely sensed surface variables. We have used remotely sensed brightness temperature data in a single drying cycle from Washita '92 Experiment and two different ANN architectures (Feed-Forward Neural Network (FFNN), Self Organizing Map (SOM)) to classify soil types into three categories. The results show that FFNN yield better classification accuracy (about 80%) than SOM (about 70% accuracy). Our attempt to classify soil types into more than three categories resulted in about 50% accuracy when a FFNN was used and even lesser accuracy when a SOM was used. To classify soil into more than three groups and to explore the limits of classification accuracy, this study suggests the use of multiple-drying-cycle brightness temperature data. We have performed several experiments with FFNN models and the results suggest that the maximum achievable classification accuracy through the use of multiple-drying-cycle brightness temperature is about 80%. It appears that the requirement of rapidly changing decision boundary, in the case of space-time evolution of brightness temperature over large areas, will restrict the FFNN model to yield better accuracy. Motivated by these observations, we have used a simple prototype-based classifier, known as 1-NN model, and achieved 86% classification accuracy for six textural groups. A comparison of error regions predicted by both models suggests that, for the given input representation, maximum achievable accuracy for classification into six soil texture types is about 94%. (Abstract shortened by UMI.)

Chang, Dyi-Huey

25

Assimilation of SMOS brightness temperatures in the ECMWF EKF for the analysis of soil moisture  

NASA Astrophysics Data System (ADS)

Since November 2nd 2009, the European Centre for Medium-Range Weather Forecasts (ECMWF) has being monitoring, in Near Real Time (NRT), L-band brightness temperatures measured by the Soil Moisture and Ocean Salinity (SMOS) satellite mission of the European Space Agency (ESA). The main objective of the monitoring suite for SMOS data is to systematically monitor the difference between SMOS observed brightness temperatures and the corresponding model equivalent simulated by the Community Microwave Emission Model (CMEM), the so-called first guess departures. This is a crucial step, as first guess departures is the quantity used in the analysis. The ultimate goal is to investigate how the assimilation of SMOS brightness temperatures over land improves the weather forecast skill, through a more accurate initialization of the global soil moisture state. In this presentation, some significant results from the activities preparing for the assimilation of SMOS data are shown. Among these activities, an effective data thinning strategy, a practical approach to reduce noise from the observed brightness temperatures and a bias correction scheme are of special interest. Firstly, SMOS data needs to be significantly thinned as the data volume delivered for a single orbit is too large for the current operational capabilities in any Numerical Weather Prediction system. Different thinning strategies have been analysed and tested. The most suitable one is the assimilation of SMOS brightness temperatures which match the ECMWF T511 (~40 km) reduced Gaussian Grid. Secondly, SMOS observational noise is reduced significantly by averaging the data in angular bins. In addition, this methodology contributes to further thinning of the SMOS data before the analysis. Finally, a bias correction scheme based on a CDF matching is applied to the observations to ensure an unbiased dataset ready for assimilation in the ECMWF surface analysis system. The current ECMWF operational soil moisture analysis system is based on a point-wise Extended Kalman Filter (EKF). This system assimilates proxy surface observations, i.e., 2 m air temperature and relative humidity to analyse the soil moisture state. Recent developments have also made it possible to assimilate remote sensing data coming from active and passive instruments. In particular, the ECMWF EKF can also assimilate data from the Advanced Scatterometer (ASCAT) onboard METOP-A and, more recently, from SMOS brightness temperatures observations. The first preliminary assimilation results will be shown. The analysis fields will be evaluated through comparison to in-situ data from different regions.

Munoz-Sabater, Joaquin

2012-07-01

26

Analysing soil moisture reactions to precipitation for soil moisture regionalization  

NASA Astrophysics Data System (ADS)

Storage and turnover of water in soils have an important impact on processes of runoff generation. To consider soil moisture in precipitation-runoff-models data with high spatial and temporal resolution are required. In a mesoscale catchment (about 300 km2) in the hilly landscape of the Sauerland (Western-Germany) an online monitoring network collects data by 48 pF-meters and four precipitation collectors. Because data is generated discrete in time and space at a few sites an upscaling for every point in time from local point measurements to the mesoscale is necessary. Our approach to regionalize the actual soil moisture not only interpolates the measurements of observed random variables like classic geostatistical methods do, e.g. kriging interpolations, but uses locally variable properties of the study area that support our estimation. Such properties are on the one hand temporally constant parameters like land use, soil properties and topography from satellite images, soil maps and a digital elevation model and on the other hand temporally variable parameters derived from solar radiation data and precipitation time series. The regionalization model thus incorporates results of these time series, such as the time between a precipitation event and the depth-dependent soil moisture reaction. In order to achieve this, precipitation time series are separated into events and soil moisture time series are divided into intervals of increasing, decreasing and constant soil moisture. Intervals of time series with decreasing soil moisture are matched to previous precipitation events. Then characteristic attributes like the time between a precipitation event and the depth-dependent decreasing soil moisture are calculated. The results are used to develop a soil moisture regionalization model based on temporally constant and dynamic parameters. The nonlinear relation between these parameters and soil moisture are learned from given data, e.g. by an artificial neural network. In our paper the results of analysing precipitation and soil moisture time series are shown, as well as the application of the regionalization model of soil moisture on a mesoscale catchment.

Engels, S.; Marschner, B.; Zepp, H.

2012-04-01

27

An analysis of the soil moisture-rainfall feedback, based on direct observations from Illinois  

Microsoft Academic Search

Many global and regional climate modeling studies have demonstrated the importance of the initial soil water condition in their simulations of regional rainfall distribution. However, none of these modeling studies has been tested against directly observed data. This study tests the hypothesis that soil saturation is positively correlated with subsequent precipitation by analyzing a 14-year soil moisture data set from

Kirsten L. Findell; Elfatih A. B. Eltahir

1997-01-01

28

Teleconnection analysis of runoff and soil moisture over the Pearl River basin in South China  

NASA Astrophysics Data System (ADS)

This study explores the teleconnection of two climatic patterns, namely the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), with hydrological processes over the Pearl River basin in South China. The Variable Infiltration Capacity (VIC) model is used to simulate the daily hydrological processes over the basin for the study period 1952-2000, and then, using the simulation results, the time series of the monthly runoff and soil moisture anomalies for its ten sub-basins are aggregated. Wavelet analysis is performed to explore the variability properties of these time series at 49 timescales ranging from 2 months to 9 yr. Use of wavelet coherence and rank correlation method reveals that the dominant variabilities of the time series of runoff and soil moisture are basically correlated with IOD. The influences of ENSO on the terrestrial hydrological processes are mainly found in the eastern sub-basins. The teleconnections between climatic patterns and hydrological variability also serve as a reference basis for inferences on the occurrence of extreme hydrological events (e.g. floods and droughts).

Niu, J.; Chen, J.; Sivakumar, B.

2013-09-01

29

^ MEB passive crowave soil moisture retrieval algorithm  

Microsoft Academic Search

e abstract article i nfo 11 12 Soil moisture will be mapped globally by the European Soil Moisture and Ocean Salinity (SMOS) mission to 13 be launched in 2009. The expected soil moisture accuracy will be 4.0%v\\/v. The core component of the SMOS 14 soil moisture retrieval algorithm is the L- ^ band Microwave Emission of the Biosphere (L- ^

Rocco Panciera; Jeffrey P. Walker; Jetse D. Kalma; Edward J. Kim; Pierre Wigneron

30

Parameter Estimation And Sensitivity Analysis for Root Zone Soil Moisture in SVAT Models.  

NASA Astrophysics Data System (ADS)

Accurate knowledge of root zone soil moisture is crucial in hydrology, micrometeorology and agriculture for estimating energy and moisture fluxes at the land surface. Soil Vegetation Atmosphere Transfer (SVAT) models are typically used to simulate energy and moisture transport in soil and vegetation, and estimate these fluxes at the land surface and in the vadose zone. Coupling an SVAT model with a vegetation model allows inclusion of canopy effects on the fluxes, without relying on observations or empirical functions. An SVAT model, viz. Land Surface Process (LSP) model, has been coupled with a widely used crop-growth model, Decision Support System for Agrotechnology Transfer (DSSAT). The LSP-DSSAT was calibrated for a growing season of sweet corn in North Central Florida, using extensive field observations from the second Microwave Water and Energy Balance Experiment (MicroWEX-2). In this research, we address uncertainty of parameters in the LSP-DSSAT model, due to uncertainty in forcings and initial conditions, and due to accumulated errors from numerical computation. We also conduct sensitivity analyses to identify key model parameters to which the root zone soil moisture estimates are most sensitive. We will present a stochastic approach to estimate correlations between the parameters and root zone soil moisture.

Judge, J.; Agrawal, D.; Graham, W. D.

2008-05-01

31

Sensitivity Analysis of Satellite Rainfall Forcing and Land-surface Model Parameter Uncertainty on Soil Moisture Prediction  

NASA Astrophysics Data System (ADS)

A sensitivity analysis was carried out to investigate the uncertainty in the simulation of soil moisture by integrating a land surface model, forced with hydro-meteorological data. The study seeks to address the characterization of two sources of uncertainty: 1) errors in the rainfall estimation from sensor observations; and, 2) the land surface model parametric error, which manifests as non-uniqueness in soil hydraulic parameters. The study is conducted in the Oklahoma region, which presents a good coverage by weather radars, multi-year satellite rainfall products and in-situ meteorological and soil moisture measurement stations. The land surface model that has been chosen is the NASA Catchment Land Surface Model (CLSM; Koster et al., 2000). The framework to characterize the parametric error is represented by the generalized likelihood uncertainty estimation (GLUE) technique. The forcing rainfall uncertainty is analyzed through an error model included in the NASA Land Data Assimilation System (LDAS), which is applied to satellite rainfall fields to obtain an ensemble of equiprobable realizations of precipitation. The perturbed precipitation fields are propagated through CLSM to produce multiple ensembles of soil moisture. This numerical experiment allows us to quantify the propagation of uncertainty from rainfall to soil moisture prediction, accounting for the two main error sources, i.e. rainfall forcing and land surface model parameterizations. In previous studies we have shown how satellite-rainfall error alone can impact soil moisture uncertainty. Results from this study will complement these initial findings to quantify the relative impact of rainfall vs modeling error and the combined uncertainty on the prediction of soil moisture.

Maggioni, V.; Anagnostou, E. N.; Reichle, R. H.

2010-12-01

32

Global Soil Moisture Data Bank  

NSDL National Science Digital Library

From the Department of Environmental Sciences at Rutgers, The State University of New Jersey, highlights of this site include data sets from soil moisture observation stations in Eurasia (including China, India, Mongolia, and the former Soviet Union) as well as the slightly less exotic locales of Iowa and Illinois. These data sets are available by clicking on a map of Eurasia and the two US states. Links to other data sets include those for Australia, Brazil, Europe, Russia and Ukraine, and the US. The site also offers abstracts and full-text papers on soil moisture research. Finally, additional sections lead to carefully selected links for model calculations, related projects, and soil moisture measurements.

33

A simulated soil moisture based drought analysis for the United States  

Microsoft Academic Search

Droughts have severe economic, environmental and social impacts. Timely determination of the current level of drought may aid the decision making process in reducing the impacts from drought. In this study, high-resolution, land surface hydrology simulations using the Variable Infiltration Capacity (VIC) model are used to derive a hydrologically based drought index. Soil moisture data from a retrospective simulation from

Justin Sheffield; Gopi Goteti; Fenghua Wen; Eric F. Wood

2004-01-01

34

Sprinkler Irrigation and Soil Moisture Uniformity  

Microsoft Academic Search

Uniformity of soil moisture under sprinkler irrigation is important for plant quality; however, sprinkler systems are typically gauged by the uniformity of application above the crop canopy. The objectives of this study were to measure and analyze both application uniformity with catch cans and soil moisture uniformity to quantify the relationship. Under testing on bare soil and turfgrass, soil moisture

Michael D. Dukes; Melissa B. Haley; Stephen A. Hanks

35

A soil moisture climatology of Illinois  

Microsoft Academic Search

Ten years of soil moisture measurements (biweekly from March through September and monthly during winter) within the top 1 m of soil at 17 grass-covered sites across Illinois are analyzed to provide a climatology of soil moisture for this important Midwest agricultural region. Soil moisture measurements were obtained with neutron probes that were calibrated for each site. Measurement errors are

Steven E. Hollinger; Scott A. Isard

1994-01-01

36

Interactive Analysis Tools for the Soil Moisture and Ocean Salinity (SMOS) mission  

NASA Astrophysics Data System (ADS)

The Interactive Analysis Tools (IAT) is a set of software elements that ESA has developed in the context of the SMOS mission ground segment. These IAT will be used off-line by different SMOS users according to the needs of each team like: sensor monitoring (instrument commissioning team), problem investigation (Data Processing Ground Segment team), calibration and validation support (Expert Support Laboratories), long term monitoring and data analysis (Calibration and Expertise Centre team). The poster will present an overview and description of the main functionalities of the IATs available to the user community. In particular the IATs considered are the following: the L1 processor prototype that provides Geolocated Calibrated Brightness temperature on antenna frame (L1c data) from the raw digital correlation measured by the sensor. The L2 Sea surface salinity prototype that provides geolocated Sea salinity measurements retrieved by the L1c data. The L2 Soil Moisture prototype that provides geolocated Soil Moisture measurements retrieved by the L1c data. The SMOS Data Viewer that provides browse functionality for all the SMOS data products and auxiliary file. Specific visualization functions are also available for L1 and L2 in order to proper analyze the data content. The SMOS Global Mapping Tool (GMT) that provides averaged maps over a user defined time period (e.g one week, one month) of the key parameters available in the L1 and L2 data as well as maps of derived parameters like the first Stokes and the polarization index. The SMOS Comparison Tool (SCoT) that provides data comparison between different L1 products. SCoT can be used in the context of L1 processor test acceptance (to verified the operational processor vs the prototype) and in the context of scientific analysis in order to compare L1 data processed with different configuration parameters. The SMOSBox developed as module extensions of the existing BEAM tool. SMOSBox provides tools to analyse L1b, L1c and L2 data. In particular will be available: advances plots: density plots, contour plots, 3-D plots, computation of derived quantities like Stokes parameter and pseudo L3 salinity maps and specific L2 data export function in NetCDF format.

Crapolicchio, R.; Delwart, S.; Zundo, M.

2009-04-01

37

Analysis of reflected Global Positioning System (GPS) signals from land for soil moisture determination and topography mapping  

NASA Astrophysics Data System (ADS)

GPS signals reflected from the ocean surface have been used in remote sensing applications to determine sea-state and wind speed. Studies show that, with rougher surfaces, GPS signal pulses scatter more, which creates weaker and wider pulses at the receiver. Based on this model, the correlation between soil moisture, topography, and GPS signals was studied using reflections off the ground. The data used for the study were gathered during two flights in 1998 and 2001 around Austin, Texas and Albuquerque, New Mexico and later processed at Langley Research Center. The power of the signals were analyzed and plotted over Digital Elevation Models (DEMs) and Landsat7 images (near- and mid-infrared bands) to interpret the correlation of signal behavior with topography. In addition, the received signal's conduct was correlated with soil moisture data obtained from the Department of Agriculture's Soil Climate Analysis Network (SCAN) sites at Prairie View (Texas) and Adams Ranch (New Mexico). The strengths of the reflected signals were observed larger near known bodies of water and farmlands where soil moisture levels are known to be high. In general, for flat lands, the power of the signals and soil moisture contents appeared to have a close-to-linear relationship. In addition, the received pulses widened when reflected over rapid-changing topography in Texas, but any relationship among these was not perceived in New Mexico. Further studies are needed to obtain a definite relationship among soil moisture and reflected signal strength and to introduce satellite position in the signal-topography study.

Torres, Omar; Katzberg, Stephen J.

2002-09-01

38

Logging effects on soil moisture losses  

Treesearch

Title: Logging effects on soil moisture losses ... of soil moisture within the surface 15 feet by an isolated mature sugar pine and an adjacent uncut ... required for the wetting front to progress through the unsaturated zone above the water table.

39

Soil Moisture Retrieval from Aquarius  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aquarius observations over land offer an unprecedented opportunity to provide a value-added product, land surface soil moisture, which will contribute to a better understanding of the Earth’s climate and water cycle. Additionally, Aquarius will provide the first spaceborne data that can be used to a...

40

Numerical studies on soil moisture distributions in heterogeneous catchments  

Microsoft Academic Search

The paper deals with numerical studies of basin-scale dynamics of soil moisture in arbitrarily heterogeneous conditions (i.e., in presence of heterogeneity of climate, soil, vegetation and land use). Its relevance stems from comparative analysis of the probabilistic structure of spatially averaged soil moisture fields with the corresponding exact solutions of the underlying simplified stochastic point processes. The probabilistic structure of

T. Settin; G. Botter; I. Rodriguez-Iturbe; A. Rinaldo

2007-01-01

41

Analysis of soil moisture trends in the Salt River watershed of central Arizona  

Microsoft Academic Search

In this investigation, we generate estimates of soil moisture for the Salt River basin on which the expanding city of Phoenix,\\u000a Arizona relies upon for nearly half of its water supply. While previous empirical studies have produced mixed results concerning\\u000a recent drought trends in the southwestern USA, our results support the many numerical climate models which predict that this\\u000a region

Bohumil M. Svoma; Robert C. Balling Jr; Andrew W. Ellis

2010-01-01

42

Determination of the thermal conductivity of sands under varying moisture, drainage\\/wetting, and porosity conditions- applications in near-surface soil moisture distribution analysis  

Microsoft Academic Search

A class of problems in hydrology and remote sensing requires improved understanding of how water and heat flux boundary conditions affect the soil moisture processes in the shallow subsurface near the land\\/atmospheric interface. In these systems, a clear understanding of how variations in water content, soil drainage\\/wetting and porosity conditions affect the soil's thermal behavior is needed for the accurate

Kathleen M. Smits; Toshihiro Sakaki; Anuchit Limsuwat; Tissa H. Illangasekare

43

Satellite observed preferential states in soil moisture  

NASA Astrophysics Data System (ADS)

This study presents observational evidence for the existence of preferential states in soil moisture content. Recently there has been much debate about the existence, location and explanations for preferential states in soil moisture. A number of studies have provided evidence either in support or against the hypothesis of a positive feedback mechanism between soil moisture and subsequent precipitation in certain regions. Researchers who support the hypothesis that preferential states in soil moisture holds information about land atmosphere feedback base their theory on the impact of soil moisture on the evaporation process. Evaporation recycles moisture to the atmosphere and soil moisture has a direct impact on the supply part of this process but also on the partitioning of the available energy for evaporation. According to this theory, the existence of soil moisture bimodality can be used as an indication of possible land-atmosphere feedbacks, to be compared with model simulations of soil moisture feedbacks. On the other hand, other researchers argue that seasonality in the meteorological conditions in combination with the non-linearity of soil moisture response alone can induce bimodality. In this study we estimate the soil moisture bimodality at a global scale as derived from the recently available 30+ year ESA Climate Change Initative satellite soil moisture dataset. An Expectation-Maximization iterative algorithm is used to find the best Gaussian Mixture Model, pursuing the highest likelihood for soil moisture bimodality. With this approach we mapped the regions where bi-modal probability distribution of soil moisture appears for each month for the period between 1979-2010. These bimodality areas are analyzed and compared to maps of model simulations of soil moisture feedbacks. The areas where more than one preferential state exists compare surprisingly well with the map of land-atmosphere coupling strength from model simulations. This approach might therefore be useful as an additional tool to further enhance our knowledge on land-atmosphere interactions.

Vilasa, Luis U.; De Jeu, Richard A. M.; Dolman, Han A. J.; Wang, Guojie

2013-04-01

44

Propagation of soil moisture memory into the climate system  

NASA Astrophysics Data System (ADS)

Soil moisture is known for its integrative behaviour and resulting memory characteristics. Associated anomalies can persist for weeks or even months into the future, making initial soil moisture an important potential component in weather forecasting. This is particularly crucial given the role of soil moisture for land-atmosphere interactions and its impacts on the water and energy balances on continents. We present here an analysis of the characteristics of soil moisture memory and of its propagation into runoff and evapotranspiration in Europe, based on available measurements from several sites across the continent and expanding a previous analysis focused on soil moisture [1]. We identify the main drivers of soil moisture memory at the analysed sites, as well as their role for the propagation of soil moisture persistence into runoff and evapotranspiration memory characteristics. We focus on temporal and spatial variations in these relationships and identify seasonal and latitudinal differences in the persistence of soil moisture, evapotranspiration and runoff. Finally, we assess the role of these persistence characteristics for the development of agricultural and hydrological droughts. [1] Orth and Seneviratne: Analysis of soil moisture memory from observations in Europe; submitted to J. Geophysical Research.

Orth, R.; Seneviratne, S. I.

2012-04-01

45

Soil moisture prediction over the Australian continent  

Microsoft Academic Search

Summary This paper describes an attempt to model soil moisture over the Australian continent with an integrated system of dynamic models and a Geographic Information System (GIS) data base. A land surface scheme with improved treatment of soil hydrological processes is described. The non-linear relationships between soil hydraulic conductivity, matric potential and soil moisture are derived from the Broadbridge and

Y. Shao; L. M. Leslie; R. K. Munro; P. Irannejad; W. F. Lyons; R. Morison; D. Short; M. S. Wood

1997-01-01

46

Relating Soil Moisture to TRMMPR Backscatter in Southern United States  

NASA Astrophysics Data System (ADS)

Soil Moisture is an important variable in hydrological cycle. It plays a vital role in agronomy, meteorology, and hydrology. In spite of being an important variable, soil moisture measuring stations are sparse. This is due to high cost involved in the installation of dense network of measuring stations required to map a comprehensive spatio-temporal behavior of soil moisture. Hence, there is a need to develop an alternate method to measure soil moisture. This research relates soil moisture (SM) to backscatter (?°) obtained from Tropical Rainfall Measuring Mission Precipitation Radar (TRMMPR) and Normalized Difference Vegetation Index (NDVI) obtained from Advanced Very High Resolution Radiometer. SM data is obtained from Soil Climate Analysis Network (SCAN). ?° measurements are normalized at an incidence angle of 10° at which it has the highest sensitivity to SM. An empirical model that relates SM to normalized ?° and NDVI is developed. NDVI takes into account the different vegetation densities. The relationship between model variables is approximated to be linear. The model is applied to data from 1998 to 2008 where 75% of the data is used for calibration and the remaining 25% for validation. Figure 1 shows the comparison of observed and modeled soil moisture for a site with low vegetation. Even though the model underestimates the soil moisture content, it captures the signal well and produces peaks similar to the observed soil moisture. The model performs well with a correlation of 0.71 and root mean square error of 4.0%. The accuracy of the model depends on vegetation density. Table 1 summarizes the model performance for different vegetation densities. The model performance decreases with the increase in vegetation as the leaves in the vegetation canopy attenuate the incident microwaves which reduces the penetration depth and subsequently the sensitivity to soil moisture. This research provides a new insight into the microwave remote sensing of soil moisture. Figure 1. Plot of observed vs. modeled soil moisture. Table 1. Soil moisture model performance based on different vegetation densities.

Puri, S.; Stephen, H.; Ahmad, S.

2009-12-01

47

Analysis of influencing factors on soil moisture content in karst areas: A case study in Guizhou province, China  

Microsoft Academic Search

Karst rocky desertification is a typical type of land degradation in the southwestern China. It has great ecological and economical implications for the local people. In this study, the effect of some influencing factors (precipitation, relative humidity, temperature, hillside slope and vegetation type) on soil moisture content were investigated. The soil moisture content increased with the increase of the precipitation.

Guo Yingqing; Su Weici; He Tairong; Teng Jianzhen

2010-01-01

48

New Approaches for Soil Moisture Analysis over Complex Arctic Environments with PALSAR/ALOS  

NASA Astrophysics Data System (ADS)

Frozen ground is a sensitive indicator of how our home planet is changing. In this study, the relevance of L-band Synthetic Aperture Radar (SAR) data for extracting information on frozen ground is presented. Specifically, the study focused on the characterization of a permafrost active layer using polarimetric ALOS PALSAR imagery in two locations in Alaska: the Kobuk river valley and the Arctic National Wildlife Refuge. The adequacy between polarimetric EM model and radar data has been studied for a long time, especially over bare agricultural fields (Oh et al., 1992). The assessment of residual liquid water can be realized by means of a bare soil EM backscattering model. Over natural wild land areas such as the Arctic tundra, new approaches have to be proposed in order to tackle the effect of the vegetation and other irrelevant effects (sensor calibration, multiple scattering terms, etc.). As a result, traditional soil moisture retrieval has shown limited accuracy for operational use, even though promising methods have been recently investigated (Mattia et al., 2006; Verhoest et al., 2007). Two methodologies based on multi-temporal acquisitions are proposed in this study. In regards to the uncertainties of the vegetation effect or other irrelevant mechanisms, a first methodology is proposed in this study. An optimization on the Oh’s weights (Oh, 2004) and full-polarimetric PALSAR data is carried out by using priori information provided by the Advanced Microwave Scanning Radiometer (AMSR-E) onboard the Aqua satellite. By tuning PALSAR data and Oh’s weights, the effects of vegetation are counterbalanced. This method was tested over the Arctic National Wildlife Refuge (ANWR). The optimization results are found to be in good agreement with theoretical aspects: vegetation induces an increase of cross-polarized channel (anisotropic effect) and a decrease of co-polarized channels (attenuation mechanism). The soil moisture variation can be then retrieved in a consistent manner. The second methodology does not use any priori information from AMSR-E sensor to reduce the uncertainties. Over the second test site, the Kobuk river valley, nine single-polarized HH PALSAR scenes were used, four being acquired during the thawing period and five during the frozen period. Since the soil moisture content during the frozen events is close to zero, the roughness was estimated through the inversion of Oh’s model, assuming also some effects (e.g., Fresnel refraction) due to the overlying snow cover. In this assessment, the uncertainties about the snow densities and the soil moistures were modeled and integrated into the retrieval approach. The retrieved soil roughness and its associated uncertainty estimates based on the data acquired during the frozen season were further used to derive moisture variation during the thawing period.

Longépé, N.; Necsoiu, M.; Tadono, T.; Shimada, M.

2010-12-01

49

IMPROVING HYDROLOGICAL FORECASTING USING SPACEBORNE SOIL MOISTURE RETRIEVALS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Using existing data sets of passive microwave spaceborne soil moisture retrievals, streamflow, and precipitation for 26 basins in the United States Southern Great Plains, a 5-year analysis is performed to quantify the value of soil moisture retrievals derived from the Tropical Rainfall Mission (TRMM...

50

Soil moisture from operational meteorological satellites  

Microsoft Academic Search

In recent years, unforeseen advances in monitoring soil moisture from operational satellite platforms have been made, mainly\\u000a due to improved geophysical retrieval methods. In this study, four recently published soil-moisture datasets are compared\\u000a with in-situ observations from the REMEDHUS monitoring network located in the semi-arid part of the Duero basin in Spain.\\u000a The remotely sensed soil-moisture products are retrieved from

Wolfgang Wagner; Vahid Naeimi; Klaus Scipal; Richard de Jeu; José Martínez-Fernández

2007-01-01

51

Soil Type Dependent Moisture-Respiration Relations Derived from Soil Incubation Data  

NASA Astrophysics Data System (ADS)

One of the most important factors affecting soil carbon mineralization is soil moisture. Moisture affects soil respiration either by being a limiting factor itself (affecting mobility and osmotic potential) or by limiting oxygen diffusion. The general relation between soil moisture and the production of CO2, integrated into all major soil carbon models, can vary largely between soils. However, a lack of information concerning its variation across soil types has led to most models applying simple moisture functions not validated by data. The uncertainties associated to such simplifications may result in wrong predictions of soil carbon stock changes. Soil incubations in the laboratory are well suited for obtaining precise relationships between variables, avoiding the problem of confounded or uncontrolled variables common in the field. Using multiple datasets from soil incubation studies, we performed an analysis with the aim of uncovering relations between moisture effects on soil respiration and a range of soil characteristics. We compiled data from multiple sources where soil moisture varied and was monitored along with respiration. Using, as a common unit, the relative increase in soil respiration for each per cent increase in moisture, we were able to calculate means and confidence intervals along the moisture axis and, most importantly, to relate the relative respiration change to soil physical characteristics. We found significant relations between soil characteristics (bulk density, pore space, organic carbon and texture) and the moisture effect on soil respiration, with such relations being strongly dependent on the moisture range and the type of measure used (gravimetric, volumetric, water potential, etc.). Most soil properties showed both fixed effects and interactions with moisture when fitting linear regression models. The relations obtained from regression analysis deviate significantly from those used currently in many soil carbon models, indicating the possibility of considerable errors in current soil carbon predictions.

Moyano, F. E.; Vasilyeva, N.; Chenu, C.

2011-12-01

52

Space-time soil moisture variability for two different land use types: analysis at the plot scale  

NASA Astrophysics Data System (ADS)

Understanding space-time soil moisture variability at various scales is a key issue in hydrological research. At the plot scale soil moisture variability is expected to be explained by physical factors such as soil hydraulic properties, local topography and vegetation cover. This study aims to: i) characterize the spatial and temporal variability of soil moisture at the plot scale at two soil depths and for two different types of land use (meadow and vineyard); ii) investigate the role of vegetation cover on the seasonal variability of soil moisture; iii) assess the capability of a dynamic model to explain soil moisture variability and the control exerted by land use. The work is based on soil moisture data collected on a plot (about 200 m2) in Grugliasco (Po River basin, Northern Italy) by means of Time Domain Reflectometry (TDR) measurements. The plot is divided into two subplots: one covered by grapevine plants, the other covered homogeneously by grass. The soil is sandy, the slope is about 1%, and there is a buffer grass area about 20 m wide around the measurement field. The characteristics of the site allow to isolate the contribution of soil hydraulic properties and land use to space-time soil moisture variability. We used the data of 40 probes distributed in the two subplots, vertically inserted into the soil at 0-30 cm and 0-60 cm depths. Precipitation and temperature are recorded continuously on site. Statistics were computed based on soil moisture measurements collected continuously at daily time step over three years (2006-2008). Results show that soil moisture spatial patterns at the two sampling depths are highly correlated for both land uses. Higher values of mean soil moisture at 0-60 cm depth with respect to 0-30 cm for both types of land use likely reflect the evaporation processes affecting more the surface layer. Spatial mean soil moisture is always higher in the vineyard than in the meadow (especially at 0-30 cm depth), implying the influence of vegetation cover during the growing season. An exponential equation fits well the relationship between the spatial coefficient of variation and the mean soil moisture. An increasing variability of the coefficient of variation is observed during periods with high potential evapotranspiration rates (June-August). This is more evident for the grass site at 0-30 cm depth, highlighting again the important shading effect performed by the grapevine leaves. The application of a simple soil moisture dynamic model reveals a general good capability to capture soil moisture temporal dynamics at the plot scale. Moreover, the model reproduces consistently the observed relationships between soil moisture spatial mean and variability. Thus, the model provides a preliminary link between physical processes and statistical variability patterns. Keywords: soil moisture, plot scale, space-time variability, land use.

Zuecco, Giulia; Borga, Marco; Penna, Daniele; Canone, Davide; Ferraris, Stefano

2013-04-01

53

The international soil moisture network: A data hosting facility for global in situ soil moisture measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

In situ measurements of soil moisture are invaluable for calibrating and validating land surface models and satellite-based soil moisture retrievals. In addition, long-term time series of in situ soil moisture measurements themselves can reveal trends in the water cycle related to climate or land co...

54

Estimating Soil Moisture by Feel and Appearance  

Microsoft Academic Search

Prior to the collection of samples for estimating soil moisture, the producer must determine the soil type, texture and available water holding capacity of each layer sampled. Soil texture, which is the relative amounts of sand, silt, and clay contained in soil, plays an important role in determining the amount of water a soil will hold. The portion of water

Sandy Loam; Fine Sandy Loam

55

Estimating of the Soil Moisture in Brazil  

NASA Astrophysics Data System (ADS)

Soil moisture is a key variable in soil-atmosphere transfer processes. Soil moisture can be measured by direct and indirect techniques. Those methods are time consuming and impractical over large areas, such as Brazil. For this reason, soil moisture is generally estimated from the amount of water entering or draining from the soil profile by the water balance method. In this work, a soil water balance for Brazil was developed, using a new approximation that takes into account the spatial variability of soil characteristics. The water balance model used a simple equation, which is a function of the water availability, rainfall and potential evapotranspiration. The maximum soil water storage was derived from the field capacity and the wilting point using a pedo-transfer function (PTF). PTF allows the estimation of soil hydraulic properties from basic soil data, such as texture, organic carbon and bulk density. The evapotranspiration was estimated using the Penman-Monteith method. Based on the vegetation parameters provided by the SiB model, the potential evapotranspiration was calculated for the main Brazilian biomes, as defined in SiB. The mean soil moisture for the period 1971-1990 was derived combining historical rainfall data and evapotranspiration estimates. From the soil moisture climatology, regions with higher/lower soil moisture availability during El Nino (1982-1983)/La Nina (1988-1989) episodes were identified.

Rossato, Luciana

2002-01-01

56

Soil moisture estimation from soil spectral characteristics in a precision farming environment  

NASA Astrophysics Data System (ADS)

Soil moisture is a critical component of numerous agricultural systems, including crop growth, and precision farming. Consequently, understanding how soil moisture varies across the field is important for planning and management of those systems. However, accurate, detailed maps of soil moisture are difficult to obtain from in situ measurements. This work addresses the variability of soil moisture, the impact of moisture variability on crop yield, and the potential of optical remote sensing for soil moisture monitoring. Two fields were sampled for surface and near-surface soil moisture and reflectance throughout the growing season. These data were studied to estimate variability in soil moisture, to determine the relationship between moisture and corn yield, and to quantify the relationship between surface reflectance and surface moisture. Analysis of the spatial structure of soil moisture revealed that the geospatial characteristics of the moisture patterns were similar from one date to another. While there was no strong correlation between moisture patterns and topographic indices, analysis indicated that plan curvature may be important for understanding surface moisture spatial variation. Temporal stability of moisture patterns was studied to identify optimal sampling points for field-average soil moisture. These points tended to be in areas that were neutral in aspect and plan curvature compared to the field average. Investigation of the relationship between moisture and corn yield indicated that there may be useful information in early (roughly from germination to within two weeks of planting) surface soil moisture measurements for interpreting variation in crop yield. Spectral reflectance data were analyzed in conjunction with surface moisture data to determine the nature of the relationship between the two. For one of the fields, the strongest relationship between reflectance and surface moisture was between 550 and 620 nm. For the other, the strongest relationship was around 945 nm. Finally, a combination of spectral data and limited moisture data was used to create moisture maps. Use of a cokriging technique generated more detailed soil moisture maps than the limited data alone. This method shows potential for development as part of a data fusion technique to generate moisture maps from a minimum of samples.

Kaleita, Amy Leigh

57

Spatial and temporal variability of soil moisture and climate variability  

NASA Astrophysics Data System (ADS)

This research investigates the spatial and temporal variability of soil moisture as related to large scale climate variability. A three layer hydrological model VIC-3L (Variable Infiltration Capacity Model -C 3 layers) was used in the Colorado River Basin over a 50 year period. The simulation focused on the soil moisture generation between January 1950 and December 2002 at daily time step. Simulation was performed on 1/8 degree resolution for the water balance model. Using wavelet analysis, temporal soil moisture was compared to the Palmer Drought Severity Index (PDSI), precipitation, and streamflow to determine whether deep soil moisture was an indicator of climate extremes. Principle component analysis (PCA) was performed to evaluate the spatial variability soil moisture response to climate variability. Wavelet coherency analysis and PCA analysis for the Colorado River Basin indicate a strong relationship between droughts and the deep soil moisture. Relationships between soil moisture and other large scale climate patterns (e.g., ENSO, PDO, sea surface temperatures) are also evaluated.

Tang, C.; Piechota, T.

2005-12-01

58

SOIL MOISTURE ESTIMATION USING REMOTE SENSING  

Microsoft Academic Search

Knowledge of soil moisture content in the root zone is important throughout a wide range of environmental applications, yet adequate monitoring or modelling of this parameter, particularly at larger spatial scales, is difficult due to its high spatial and temporal variability. To overcome the land surface model limits on soil moisture estimation accuracy, point measurement spatial coverage limits, and microwave

Jeffrey Walker; Paul Houser

59

Improved understanding of soil moisture variability dynamics  

Microsoft Academic Search

Different trends of soil moisture variability with mean moisture content have been reported from field observations. Here we explain these trends for three different data sets by showing how vegetation, soil and topography controls interact to either create or destroy spatial variance. Improved understanding of these processes is needed for the transformation of point-scale measurements and parameterizations to scales required

Adriaan J. Teuling; Peter A. Troch

2005-01-01

60

Soil Moisture Information And Thermal Microwave Emission  

Microsoft Academic Search

This paper presents theoretical and experimental results that demonstrate the depth to which soil moisture can be directly measured using microwave radiometers. The experimental results also document the effect of uniform surface roughness on the response of thermal microwave emission to soil moisture. Experimental measurements were executed in July 1980 at the Texas A&M University Research Farm near College Station,

Richard W. Newton; Quentin Robert Black; Shahab Makanvand; Andrew J. Blanchard; Buford Randall Jean

1982-01-01

61

Gravity changes, soil moisture and data assimilation  

Microsoft Academic Search

Remote sensing holds promise for near-surface soil moisture and snow mapping, but current techniques do not directly resolve the deeper soil moisture or groundwater. The benefits that would arise from improved monitoring of variations in terrestrial water storage are numerous. The year 2002 saw the launch of NASA's Gravity Recovery And Climate Experiment (GRACE) satellites, which are mapping the Earth's

J. Walker; R. Grayson; M. Rodell; K. Ellet

2003-01-01

62

How representative are point soil moisture measurements?  

NASA Astrophysics Data System (ADS)

Spatially representative soil moisture is needed to understand land-atmosphere coupling, evapotranspiration, runoff and floods, precipitation, ecosystem and nutrient dynamics, and droughts. But assessments of area-average soil moisture are fraught with difficulties that are due to the combination of limited applicability of measurement methods and the innate spatial variability, at various scales, of soil properties, land-surface characteristics and hydroclimatic factors. Because soil moisture is difficult to measure over area, point measurements have been widely used instead. A fundamental and practical question is: how representative are point measurements of soil moisture? Many previous field studies that assessed variability used indirect methods and a small number of usually depth-integrated samples. We made soil moisture measurements on thousands of samples collected from tens of sites with multiple 30-cm deep moisture profiles obtained within an area 400 m in diameter at each site. Within each area soil moisture is highly variable, with the ratio of highest to lowest value ranging between 1.8 and 12, and the ratio of profile averages ranging from 1.2 to 4.1. The shapes of the profiles are inconsistent, too: within the same site soil moisture profiles show decreasing trends with depth, or increasing, or are flat or irregular. The absence of obvious pattern, combined with the observed large spatial variability, suggests that single measurements at a point are not representative of the surrounding area. To assess the importance of the local variability, we compared the variances computed for each of the 400-m areas with the total variance for all data from all sites. The variance at the 400-m scale makes up on average 40% and as much as 85% of the variance at the continental scale. This result shows that point measurements of soil moisture are unreliable as a measure of soil moisture at any spatial scale. [Acknowledgement: The COSMOS project is supported by the US National Science Foundation.

Zreda, Marek; Franz, Trenton; Desilets, Darin; Zeng, Xubin; Zweck, Chris

2013-04-01

63

Uncertainty in SMAP Soil Moisture Measurements Caused by Dew  

Microsoft Academic Search

Soil moisture is an important reservoir of the hydrologic cycle that regulates the exchange of moisture and energy between the land surface the atmosphere. Two satellite missions will soon make the first global measurements of soil moisture at the optimal microwave wavelength within L-band: ESA's Soil Moisture and Ocean Salinity (SMOS) mission; and NASA's Soil Moisture Active-Passive (SMAP) mission. SMAP

B. K. Hornbuckle; A. Kruger; T. L. Rowlandson; S. D. Logsdon; A. Kaleita; S. H. Yueh

2009-01-01

64

Soil moisture variability within remote sensing pixels  

SciTech Connect

This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. This paper addresses the question of soil moisture variation within the field of view of a remote sensing pixel. Remote sensing is the only practical way to sense soil moisture over large areas, but it is known that there can be large variations of soil moisture within the field of view of a pixel. The difficulty with this is that many processes, such as gas exchange between surface and atmosphere can vary dramatically with moisture content, and a small wet spot, for example, can have a dramatic impact on such processes, and thereby bias remote sensing data results. Here the authors looked at the impact of surface topography on the level of soil moisture, and the interaction of both on the variability of soil moisture sensed by a push broom microwave radiometer (PBMR). In addition the authors looked at the question of whether variations of soil moisture within pixel size areas could be used to assign errors to PBMR generated soil moisture data.

Charpentier, M.A.; Groffman, P.M. (Univ. of Rhode Island, Kingston (United States))

1992-11-30

65

Dynamic Thermocapacitive Soil-Moisture Sensor.  

National Technical Information Service (NTIS)

Measurement of soil moisture using wire wound strip heaters inserted in the soil is recommended as a convenient and accurate method that eliminates collection of soil samples and their tedious processing. Sensors can be packed in soil which is then dried ...

B. S. Zalivadnyy

1972-01-01

66

Relationships between Climate Variability, Drought and Model Soil Moisture  

NASA Astrophysics Data System (ADS)

This research investigates the interannual variability of soil moisture as related to large scale climate variability. A three layer hydrological model VIC -3L (Variable Infiltration Capacity Model - 3 layers) was used in the Colorado River Basin and Mississippi River Basin over a 50 year period. The simulation focuses on the soil moisture generation and simulation have been developed between January 1950 and December 2002 at daily time step. Simulation was performed on 1/8 degree resolution for the water balance model of both basins and shows the interannual variability of deep soil moisture. Using wavelet analysis, deep soil moisture is compared to the Palmer Drought Severity Index (PDSI), precipitation, and streamflow to determine whether deep soil moisture is an indicator of climate extremes. Wavelet and coherency analysis for the Colorado River Basin and the upper Mississippi River basin indicate a strong relationship between droughts and the deep soil moisture. Relationships between soil moisture and other large scale climate variability (e.g., ENSO, PDO, sea surface temperatures) are also evaluated.

Tang, C.; Piechota, T.

2004-12-01

67

Validation of SMOS and ASCAT Soil Moisture Products - Time Series Analysis in the Rur and Erft Catchments  

NASA Astrophysics Data System (ADS)

As soil moisture is an important driver for various climatic and hydrological processes, area-wide time series of soil moisture data are important for numerical weather predictions, for example at the European Centre for Medium-Range Weather Forecasts (ECMWF), as well as for climate and hydrological modeling. The Soil Moisture and Ocean Salinity (SMOS) satellite, launched in 2009, is an attempt to provide global soil moisture data in the required temporal resolution. SMOS records brightness temperatures in the L-Band at 1.4 GHz, which are converted into soil moisture through inverse modeling. This study uses reprocessed SMOS Level 2 soil moisture data from the year 2010 for a long-term validation in the Rur and Erft catchments in Northrhine-Westfalia, Germany. They are compared to time-series of soil moisture derived from Advanced Scatterometer (ASCAT) data. ASCAT is a real-aperture radar that measures surface backscattering coefficients in the C-band at 5.255 GHz with a resolution of 30 to 50 km. Through a time series-based change detection approach relative soil moisture is retrieved from the backscattering coefficients, which is then converted to absolute soil moisture with data on soil properties. The individual accuracy and suitability of both datasets for the further use in numerical weather prediction and hydrological modeling are analyzed with the help of a soil moisture reference calculated by WaSiM ETH, a grid-element-based hydrological model. The model was calibrated with soil moisture data from the wireless sensor network at two test sites in the study area. Regression between the in situ data and the model values shows good results, despite a small bias, with an overall RMSE coefficient of 0.05. Time-series of the observed and modeled data also indicate a good agreement. A first comparison of SMOS data with the soil moisture reference does not show a high correlation. Furthermore, the temporal development of the data is different for SMOS soil moisture and the reference. A strong bias can be observed for the whole period: SMOS shows constantly lower values of soil moisture than the reference data. Partition into ascending and descending nodes does not show better results. Calculation of RMSE for every SMOS footprint over the whole period displays smaller values in the northern part of the study area than in the southern part. That can be due to the mountainous terrain but also to the dense vegetation with much forest in this area. When comparing a L-band radiometer like SMOS and a C-band scatterometer like ASCAT, disparities in the time series can occur because of different vegetation penetration abilities and soil penetration depths, distinct sensitivities to surface roughness, and sensitivity to radio frequency interferences (RFI).

Rötzer, K.; Montzka, C.; Bogena, H.; Wagner, W.; Kidd, R.; Vereecken, H.

2012-04-01

68

An Investigation of Soil Moisture Dynamics Using FLUXNET Data  

Microsoft Academic Search

Soil moisture data, obtained from four FLUXNET sites in the US, were examined using an ecohydrological framework. Sites were selected for the analysis to provide a range of plant functional type, climate, and soil grain size distribution. Data at a selected site included at least two years of measurements of volumetric soil water content, air temperature, precipitation, atmospheric pressure, net

G. R. Miller; D. D. Baldocchi

2005-01-01

69

Equilibrium Moisture and Density Conditions in Colorado Subgrade Soils.  

National Technical Information Service (NTIS)

The report is an analysis of moisture-density information from Colorado and other areas of the nation and world. The objective of the study was to develop a basis for predicting equilibrium moisture and density values of subsurface soils in highway cuts a...

1968-01-01

70

Towards the estimation root-zone soil moisture via the simultaneous assimilation of thermal and microwave soil moisture retrievals  

NASA Astrophysics Data System (ADS)

The upcoming deployment of satellite-based microwave sensors designed specifically to retrieve surface soil moisture represents an important milestone in efforts to develop hydrologic applications for remote sensing observations. However, typical measurement depths of microwave-based soil moisture retrievals are generally considered too shallow (top 2-5 cm of the soil column) for many important water cycle and agricultural applications. Recent work has demonstrated that thermal remote sensing estimates of surface radiometric temperature provide a complementary source of land surface information that can be used to define a robust proxy for root-zone (top 1 m of the soil column) soil moisture availability. In this analysis, we examine the potential benefits of simultaneously assimilating both microwave-based surface soil moisture retrievals and thermal infrared-based root-zone soil moisture estimates into a soil water balance model using a series of synthetic twin data assimilation experiments conducted at the USDA Optimizing Production Inputs for Economic and Environmental Enhancements (OPE 3) site. Results from these experiments illustrate that, relative to a baseline case of assimilating only surface soil moisture retrievals, the assimilation of both root- and surface-zone soil moisture estimates reduces the root-mean-square difference between estimated and true root-zone soil moisture by 50% to 35% (assuming instantaneous root-zone soil moisture retrievals are obtained at an accuracy of between 0.020 and 0.030 m 3 m -3). Most significantly, improvements in root-zone soil moisture accuracy are seen even for cases in which root-zone soil moisture retrievals are assumed to be relatively inaccurate (i.e. retrievals errors of up to 0.070 m 3 m -3) or limited to only very sparse sampling (i.e. one instantaneous measurement every eight days). Preliminary real data results demonstrate a clear increase in the R2 correlation coefficient with ground-based root-zone observations (from 0.51 to 0.73) upon assimilation of actual surface soil moisture and tower-based thermal infrared temperature observations made at the OPE 3 study site.

Li, Fuqin; Crow, Wade T.; Kustas, William P.

2010-02-01

71

Soil moisture mapping for aquarius  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aquarius is the first satellite to provide both passive and active L-band observations of the Earth. In addition, the instruments on Satelite de Aplicaciones Cientificas-D (SAC-D) provide complementary information for analysis and retrieval algorithms. Our research focuses on the retrieval of soil m...

72

Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles  

PubMed Central

In the past decades, many studies on soil moisture retrieval from SAR demonstrated a poor correlation between the top layer soil moisture content and observed backscatter coefficients, which mainly has been attributed to difficulties involved in the parameterization of surface roughness. The present paper describes a theoretical study, performed on synthetical surface profiles, which investigates how errors on roughness parameters are introduced by standard measurement techniques, and how they will propagate through the commonly used Integral Equation Model (IEM) into a corresponding soil moisture retrieval error for some of the currently most used SAR configurations. Key aspects influencing the error on the roughness parameterization and consequently on soil moisture retrieval are: the length of the surface profile, the number of profile measurements, the horizontal and vertical accuracy of profile measurements and the removal of trends along profiles. Moreover, it is found that soil moisture retrieval with C-band configuration generally is less sensitive to inaccuracies in roughness parameterization than retrieval with L-band configuration.

Lievens, Hans; Vernieuwe, Hilde; Alvarez-Mozos, Jesus; De Baets, Bernard; Verhoest, Niko E.C.

2009-01-01

73

Sensitivity analysis of C- and Ku-band synthetic aperture radar data to soil moisture content in a semiarid region  

NASA Astrophysics Data System (ADS)

In this study, the sensitivity of the C-band (5.3 GHz) with a 23sp° incidence angle and the Ku-band (14.85 GHz) with 35sp° ,\\ 55sp° , and 75sp° incidence angles to surface soil moisture content from a semiarid region were evaluated. To obtain an improved soil moisture estimation, a practical technique to reduce the influence of soil roughness and vegetation in the SAR data was developed in a study area located in the Walnut Gulch Experimental Watershed, a representative site of shrub- and grass-dominated rangelands of the southwestern part of the United States. To correct for soil roughness effects, the C-band radar backscattering coefficients sigmasp° from a wet season image were subtracted from sigmasp° derived from a dry season image. The assumption was that, in semiarid regions, the SAR data from the dry season was dependent only on the soil roughness effects. To correct for vegetation effects, an empirical relation between sigmasp° and leaf area index was used, the latter derived from Landsat Thematic Mapper data. The results showed that when both soil roughness and vegetation effects were corrected for, the sensitivity of sigmasp° to soil moisture improved substantially. The sensitivity of sigmasp° to soil moisture was also evaluated in agricultural fields with bare soil and periodic roughness components (planting row and furrow structures). Four types of SAR system configurations were analyzed: C-band with a 23sp° incidence angle and Ku-band with 35sp° ,\\ 55sp° , and 75sp° incidence angles. The test sites were located at the University of Arizona's Maricopa Agricultural Center, south of Phoenix, Arizona. The results showed that the sensitivity of sigmasp° to soil moisture was strongly dependent upon the field conditions. The SAR signal was nearly insensitive to soil moisture for furrowed fields (furrow spacing ˜95 cm; amplitude ˜22 cm), but for fields with planting row structures (row spacing ˜24 cm; amplitude ˜2 cm), the SAR data was sensitive to soil moisture, particularly with the C-band at a 23sp° incidence angle and the Ku-band with a 35sp° incidence angle, regardless of the row direction.

Sano, Edson Eyji

74

Soil moisture estimation from radar altimetry  

NASA Astrophysics Data System (ADS)

The climate of West African Sahel is controlled by a complex system of interactions between the atmosphere, biosphere and hydrosphere, known as the West African monsoon. The rainfall dynamics at various spatial and temporal scales, which have a strong impact on human activities, are mainly governed by surface conditions - vegetation cover and soil moisture. This important parameter of the hydrological cycle is poorly described at regional, continental or global scale. Space-borne sensors exhibit a strong potential for the study of continental surfaces. Radar altimetry, initially developed to make accurate measurements of ocean topography, is commonly used for the survey of ice sheets and river stages. Several studies showed that changes in snow cover, soil water content and vegetation properties are responsible for variations of the backscatter response. Over the Sahel region, maxima of the backscatter coefficients are correlated to rain events. We present the results of an analysis of the backscatter coefficients from Topex/Poseidon and ENVISAT/RA-2 over the Gourma site (Mali) and compare them with in- situ and satellite measurements of precipitation, soil moisture and vegetation.

Mougin, E.; Frappart, F.; Famiglietti, J. S.

2006-12-01

75

Snow cover and soil moisture in mountains  

NASA Astrophysics Data System (ADS)

Soil moisture is an important parameter of the climate system. It constrains evapotranspiration of plants and it functions as a storage of water, giving it an economic value, e.g. for agriculture. Furthermore, soil moisture is an important factor for predicting flood risk. In mountainous areas with a seasonal snow cover, the spatial distribution of snow depth is strongly influencing the spatial variation of soil moisture. To assess potential flooding situations during snow melt and rain on snow events in particular but for any heavy precipitation event in the mountains, it is important to understand the influence of the snow cover on soil status with respect to liquid and solid water. Only if this is known, the reaction of the soil i.e. amount of runoff, storage or melt, on additional water input can be assessed. For an operational assessment of the soil moisture state in the Swiss Alps at 140 measurement sites for snow and avalanche forecasting (IMIS network), the SNOWPACK model has been extended with a soil module, solving the Richards equation for the matrix flow. The modelling is validated with vertical profile measurements of soil moisture at meteorological stations in an Alpine catchment near Davos, Switzerland. It was found that the combination of a physical based snowpack model with a Richards equation solver seems to provide an adequate description of soil moisture fluctuations, especially in near surface layers. Soil moisture fluctuations, both measured and modelled, are strongly reduced when a snow cover is present. The measurements also revealed a strong increase in soil moisture, accompanied by a daily cycle in soil moisture during snow melt, extending down to 120cm depth. When soil properties from literature were assumed for the soil type in the vertical profile, the daily cycle in the model during snow melt was restricted mainly to the top layers, while observations show also a reaction in deeper layers. These observations are consistent with the assumption of the existence of preferential flow paths, which are not modelled by the Richards equation. This discrepancy between observations and model results during the melt phase may cause an underestimation of the soil storage capacity and an overestimation of the surface run-off in the model.

Wever, N.; Lehning, M.

2012-04-01

76

Soil moisture estimation with limited soil characterization for decision making  

NASA Astrophysics Data System (ADS)

Many decisions in agriculture are conditional to soil moisture. For instance in wet conditions, farming operations as soil tillage, organic waste spreading or harvesting may lead to degraded results and/or induce soil compaction. The development of a tool that allows the estimation of soil moisture is useful to help farmers to organize their field work in a context where farm size tends to increase as well as the need to optimize the use of expensive equipments. Soil water transfer models simulate soil moisture vertical profile evolution. These models are highly sensitive to site dependant parameters. A method to implement the mechanistic soil water and heat flow model (the TEC model) in a context of limited information (soil texture, climatic data, soil organic carbon) is proposed [Chanzy et al., 2008]. In this method the most sensitive model inputs were considered i.e. soil hydraulic properties, soil moisture profile initialization and the lower boundary conditions. The accuracy was estimated by implementing the method on several experimental cases covering a range of soils. Simulated soil moisture results were compared to soil moisture measurements. The obtained accuracy in surface soil moisture (0-30 cm) was 0.04 m3/m3. When a few soil moisture measurements are available (collected for instance by the farmer using a portable moisture sensor), significant improvement in soil moisture accuracy is obtained by assimilating the results into the model. Two assimilation strategies were compared and led to comparable results: a sequential approach, where the measurement were used to correct the simulated moisture profile when measurements are available and a variational approach which take moisture measurements to invert the TEC model and so retrieve soil hydraulic properties of the surface layer. The assimilation scheme remains however heavy in terms of computing time and so, for operational purposed fast code should be taken to simulate the soil moisture as with the Ross model [Ross, 2003, Crevoisier et al, 2009]. To meet the decision support context, we evaluated the model ability of evaluating the soil moisture level in comparison to a moisture threshold that splits soil conditions into desirable and undesirable cases. This threshold depends on soil properties, the farming operation and equipment characteristics. We evaluate the rate of making good decisions using either the TEC model with and without soil moisture measurements or an empirical algorithm that simulate the decision processes followed by farmers, currently. This later is a reference case that allows appreciating the adding value of using soil water transfer models. We found a significant improvement with a rate of success, which increases from 65% with the reference case to 90% when using the model with soil moisture assimilation. Chanzy, A., Mumen M., Richard, G.. (2008), Accuracy of top soil moisture simulation using a mechanistic model with limited soil characterization, Water Resources Research, 44(3), W03432. Crevoisier, D., Chanzy, A., Voltz M. (2009), Evaluation of the Ross Fast Solution of Richards' Equation in Unfavourable Conditions for Standard Finite Element Methods, Advances in Water Ressources, In revision. Ross, P. J. (2003). Modeling soil water and solute transport - Fast, simplified numerical solutions. Agronomy Journal 95:1352-1361.

Chanzy, A.; Richard, G.; Boizard, H.; Défossez, P.

2009-04-01

77

The spatial distribution of surface soil moisture in a small forested watershed in British Columbia, Canada  

NASA Astrophysics Data System (ADS)

Soil moisture is intimately linked to transpiration and various ecological and biological processes. Understanding soil moisture patterns will help to assess the spatial variation of these processes. Average soil moisture of the top 20 cm of the soil was measured at 116 locations in a 1-ha forested watershed in the UBC Malcolm Knapp Research Forest. Measurements were taken with a Hydrosense time domain reflectometer between August 2007 and May 2009. The data showed clear and distinctive wet and dry states. During and after summer storms, the transition between the wet and dry states occurred within approximately 8 days. Temporal stability analysis showed persistence in the soil moisture pattern, with topography as the key control on the soil moisture distribution. The wetter regions were located in areas close to the stream, and in areas of topographic convergence. Detailed moisture pattern analysis showed that in response to summer storms soil moisture increased at a faster rate on upper slope areas than at lower elevations. Similarly, soil moisture at the upper slope areas decreased faster afterwards. Soil moisture measurements on the hillslopes showed a lower correlation between slope position and soil moisture. The soil moisture pattern at the hillslopes was also less persistent than the pattern for the whole watershed. This suggests that the topographic control on soil moisture may be influenced by scale.

Chin, K. S.; Tromp-van Meerveld, H. J.

2009-12-01

78

The moisture response of soil heterotrophic respiration: interaction with soil properties  

NASA Astrophysics Data System (ADS)

Soil moisture is of primary importance for predicting the evolution of soil carbon stocks and fluxes, both because it strongly controls organic matter decomposition and because it is predicted to change at global scales in the following decades. However, the soil functions used to model the heterotrophic respiration response to moisture have limited empirical support and introduce an uncertainty of at least 4% in global soil carbon stock predictions by 2100. The necessity of improving the representation of this relationship in models has been highlighted in recent studies. Here we present a data-driven analysis of soil moisture-respiration relations based on 90 soils. With the use of linear models we show how the relationship between soil heterotrophic respiration and different measures of soil moisture is consistently affected by soil properties. The empirical models derived include main effects and moisture interaction effects of soil texture, organic carbon content and bulk density. When compared to other functions currently used in different soil biogeochemical models, we observe that our results can correct biases and reconcile differences within and between such functions. Ultimately, accurate predictions of the response of soil carbon to future climate scenarios will require the integration of soil-dependent moisture-respiration functions coupled with realistic representations of soil water dynamics.

Moyano, F. E.; Vasilyeva, N.; Bouckaert, L.; Cook, F.; Craine, J.; Curiel Yuste, J.; Don, A.; Epron, D.; Formanek, P.; Franzluebbers, A.; Ilstedt, U.; Kätterer, T.; Orchard, V.; Reichstein, M.; Rey, A.; Ruamps, L.; Subke, J.-A.; Thomsen, I. K.; Chenu, C.

2012-03-01

79

The moisture response of soil heterotrophic respiration: interaction with soil properties  

NASA Astrophysics Data System (ADS)

Soil moisture is of primary importance for predicting the evolution of soil carbon stocks and fluxes, both because it strongly controls organic matter decomposition and because it is predicted to change at global scales in the following decades. However, the soil functions used to model the heterotrophic respiration response to moisture have limited empirical support and introduce an uncertainty of at least 4 % in global soil carbon stock predictions by 2100. The necessity of improving the representation of this relationship in models has been highlighted in recent studies. Here we present a data-driven analysis of soil moisture-respiration relations based on 90 soils. With the use of linear models we show how the relationship between soil heterotrophic respiration and different measures of soil moisture is consistently affected by soil properties. The empirical models derived include main and moisture interaction effects of soil texture, organic carbon content and bulk density. When compared to other functions currently used in different soil biogeochemical models, we observe that our results can correct biases and reconcile differences within and between such functions. Ultimately, accurate predictions of the response of soil carbon to future climate scenarios will require the integration of soil-dependent moisture-respiration functions coupled with realistic representations of soil water dynamics.

Moyano, F. E.; Vasilyeva, N.; Bouckaert, L.; Cook, F.; Craine, J.; Curiel Yuste, J.; Don, A.; Epron, D.; Formanek, P.; Franzluebbers, A.; Ilstedt, U.; Kätterer, T.; Orchard, V.; Reichstein, M.; Rey, A.; Ruamps, L.; Subke, J.-A.; Thomsen, I. K.; Chenu, C.

2011-12-01

80

Soil Moisture Prediction Using Support Vector Machines  

NASA Astrophysics Data System (ADS)

Herein, a recently developed methodology, Support Vector Machines (SVMs), is presented and applied to the challenge of soil moisture prediction. Support Vector Machines are derived from statistical learning theory and can be used to predict a quantity forward in time based on training that uses past data, hence providing a statistically sound approach to solving inverse problems. The principal strength of SVMs lies in the fact that they employ Structural Risk Minimization (SRM) instead of Empirical Risk Minimization (ERM). The SVMs formulate a quadratic optimization problem that ensures a global optimum, which makes them superior to traditional learning algorithms such as Artificial Neural Networks (ANNs). The resulting model is sparse and not characterized by the "curse of dimensionality." Soil moisture distribution and variation is helpful in predicting and understanding various hydrologic processes, including weather changes, energy and moisture fluxes, drought, irrigation scheduling, and rainfall/runoff generation. Soil moisture and meteorological data are used to generate SVM predictions for four and seven days ahead. Predictions show good agreement with actual soil moisture measurements. Results from the SVM modeling are compared with predictions obtained from ANN models and show that SVM models performed better for soil moisture forecasting than ANN models.

Kashif Gill, M.; Asefa, Tirusew; Kemblowski, Mariush W.; McKee, Mac

2006-08-01

81

Remote detection of bare soil moisture using a surface-temperature-based soil evaporation transfer coefficient  

NASA Astrophysics Data System (ADS)

An approach for estimating soil moisture is presented and tested by using surface-temperature-based soil evaporation transfer coefficient ( ha), a coefficient recently proposed through the equation ha = ( Ts - Ta)/( Tsd - Ta) , where Ts, Tsd, and Ta are land surface temperature (LST), reference soil (dry soil without evaporation) surface temperature, and air temperature respectively. Our analysis and controllable experiment indicated that ha closely related to soil moisture, and therefore, a relationship between field soil moisture and ha could be developed for soil moisture estimation. Field experiments were carried out to test the relationship between ha and soil moisture. Time series Aqua-MODIS images were acquired between 11 Sep. 2006 and 1 Nov. 2007. Then, MODIS derived ha and simultaneous measured soil moisture for different soil depths were used to establish the relations between the two variables. Results showed that there was a logarithmic relationship between soil moisture and ha ( P < 0.01). These logarithmic models were further validated by introducing another ground-truth data gathered from 46 meteorological stations in Hebei Province. Good agreement was observed between the measured and estimated soil moisture with RMSE of 0.0374 cm 3/cm 3 and 0.0503 cm 3/cm 3 for surface energy balance method at two soil depths (10 cm and 20 cm), with RMSE of 0.0467 cm 3/cm 3 and 0.0581 cm 3/cm 3 for maximum temperature method at two soil depths. For vegetated surfaces, the ratio of ha and NDVI suggested to be considered. The proposed approach has a great potential for soil moisture and drought evaluation by remote sensing.

Zhao, Shaohua; Yang, Yonghui; Qiu, Guoyu; Qin, Qiming; Yao, Yunjun; Xiong, Yujiu; Li, Chunqiang

2010-10-01

82

Estimating groundwater recharge through tills: a sensitivity analysis of soil moisture budgets and till properties in Ireland  

Microsoft Academic Search

The study highlights the dangers of limiting recharge calculations in humid climates to meteorological and soil considerations.\\u000a It highlights the importance of developing a conceptual understanding of the influence of geology on recharge mechanisms and\\u000a recharge rates. Uncertainties in recharge estimates through tills are examined by a study of the available literature, combined\\u000a with sensitivity analyses of soil moisture budget

Vincent P. Fitzsimons; Bruce D. R. Misstear

2006-01-01

83

Mapping surface soil moisture with microwave radiometers  

Microsoft Academic Search

Summary Water stored in the soil serves as a reservoir for the evapotranspiration (ET) process on land surfaces, therefore knowledge of the soil moisture content is important for partitioning the incoming solar radiation into latent and sensible heat components. There is no remote sensing technique which directly observes the amount of water in this reservoir, however microwave remote sensing at

T. Schmugge; T. J. Jackson

1994-01-01

84

Soil moisture deficiencies in puddled pastures  

Microsoft Academic Search

The effects of a period of heavy animal treading in wet weather on the subsequent moisture status of two pasture topsoils were investigated in replicated trials on medium-textured alluvial soils. The surface soil was found to be significantly denser in the heavily-trodden plots than in the untrodden controls for as long as six months after the treading. The higher density

M. W. Gradwell

1966-01-01

85

Soil moisture - resistivity relation at the plot and catchment scale  

NASA Astrophysics Data System (ADS)

The key role played by soil moisture in both Global Hydrological Cycle and Earth Radiation Budget has been claimed by numerous authors during past decades. The importance of this environmental variable is evident in several natural processes operating in a wide range of spatial and temporal scales. At continental and regional scales soil moisture influences the evapotranspiration process and so acts indirectly on the climate processes; at middle scale is one of the major controls of the infiltration-runoff soil response during rainfall events; at small scales the knowledge of soil moisture evolution is crucial for precision agriculture and the associated site-specific management practices. However, soil moisture exhibits an high temporal and spatial variability and this is even more evident in the vadose zone. Thus, in order to better understand the soil moisture dynamics it is desirable to capture its behavior at different temporal and/or spatial scales. Traditional in situ methods to measure soil moisture like TDR can be very precise and allows an high temporal resolution. Recently, the application in field of geophysical methods for capturing soil moisture spatial and temporal variations has demonstrated to be a promising tool for hydro-geological studies. One of the major advantages relies on the capability to capture the soil moisture variability at larger scales, that is decametric or hectometric scale. In particular, this study is based on the simultaneous application of the electrical resistivity and the TDR methods. We present two study cases that differ from each other by both spatial and temporal resolution. For the first one, simultaneous measurements obtained during four different period of the year and carried out within a test catchment (~60 km2) in Umbria region (central Italy) were analyzed. The second case concerns almost three months of simultaneous measurements carried out in a small test site ( <200 m2), located in the garden of IMAA-CNR institute in Tito Scalo (south Italy). One measurement every two days were performed on average, in particular 44 sampling events during 80 days. In both case we present a correlation and a regression analysis conducted both on punctual measurements and on their spatial averages. The results show that the resistivity method can be conveniently applied for soil moisture retrieval with a fairly good accuracy. The capability of this technique to obtain information for the whole soil profile suggests its use to better investigate the role of soil moisture dynamics at catchment scale and its influence on the rainfall-runoff processes.

Calamita, Giuseppe; Perrone, Angela; Satriani, Antonio; Brocca, Luca; Moramarco, Tommaso

2010-05-01

86

Validation of Coarse Resolution Microwave Soil Moisture Products  

Microsoft Academic Search

The strong relationship between soil moisture content and the soil dielectric constant offers a direct way of measuring soil moisture with microwave sensors. Global coarse-resolution soil moisture datasets are currently retrieved from active microwave spaceborne instruments (AMI onboard ERS and ASCAT on Metop-A) and in the near future from dedicated passive microwave satellite sensors (SMOS). This article summarizes recent soil

Zoltan Bartalis; Wolfgang Wagner; Craig Anderson; Hans Bonekamp; Vahid Naeimi; Stefan Hasenauer

2008-01-01

87

Effects of soil moisture on the diurnal pattern of pesticide emission: Numerical simulation and sensitivity analysis  

NASA Astrophysics Data System (ADS)

Accurate prediction of pesticide volatilization is important for the protection of human and environmental health. Due to the complexity of the volatilization process, sophisticated predictive models are needed, especially for dry soil conditions. A mathematical model was developed to allow simulation of the diurnal variation of pesticide volatilization as affected by soil-water content, the air-solid interface partition coefficient, soil-water retention function and soil surface resistance processes. The model formulation considered two possible water retention functions and two soil surface resistance functions. To test the model, simulations were performed for ten successive days of drying under typical semi-arid summer conditions following application of the pesticide diazinon to either a loam or sand soil. Results showed that the temporal variation and magnitude of diazinon emission were strongly affected by the air-solid interface partition coefficient, soil-water content and the surface resistance function. The model was capable of simulating complex diurnal patterns in the peak emission rates which are caused by changes in soil water content and air-solid partitioning. The water retention function formulation had only a minor effect on the simulated water content and volatilization rates, whereas the soil surface resistance function significantly influenced the volatilization rate. Neither the water retention function nor the soil surface resistance formulation had a significant effect on the simulated soil temperature.

Reichman, Rivka; Yates, Scott R.; Skaggs, Todd H.; Rolston, Dennis E.

2013-02-01

88

Passive Microwave Observations of Soil Moisture and Dew in Soil Moisture Experiments 2005 (SMEX05)  

Microsoft Academic Search

Microwave remote sensing can provide reliable measurements of surface soil moisture. However, there are a few land surface features that have a perturbing influence on the soil moisture retrievals. A lack of appropriate observations and physical characterization of target parameters contribute to retrieval problems. Also, some of these effects are relatively small and can be difficult to separate from other

J. Du; T. J. Jackson; R. Bindlish; M. H. Cosh; L. Li; B. K. Hornbuckle

2009-01-01

89

Soil Moisture Profile Effect on Radar Signal Measurement  

PubMed Central

The objective of this paper is to analyze the behaviour of a backscattered signal according to soil moisture depth over bare soils. Analysis based on experimental vertical moisture profiles and ASAR/ENVISAT measurements has been carried out. A modified IEM model with three permittivity layers (0-1cm, 1-2cm, 2-5cm) has been developed and used in this study. Results show a small effect of moisture profile on the backscattered signal (less than 0.5dB). However, measurements and simulations have provided a more detailed insight into the behaviour of the radar signal and have shown that it was important to consistently use the same protocol when performing ground truth measurements of soil moisture.

Le Morvan, Aurelie; Zribi, Mehrez; Baghdadi, Nicolas; Chanzy, Andre

2008-01-01

90

Comparing soil moisture memory in satellite observations and models  

NASA Astrophysics Data System (ADS)

A major obstacle to a correct parametrization of soil processes in large scale global land surface models is the lack of long term soil moisture observations for large parts of the globe. Currently, a compilation of soil moisture data derived from a range of satellites is released by the ESA Climate Change Initiative (ECV_SM). Comprising the period from 1978 until 2010, it provides the opportunity to compute climatological relevant statistics on a quasi-global scale and to compare these to the output of climate models. Our study is focused on the investigation of soil moisture memory in satellite observations and models. As a proxy for memory we compute the autocorrelation length (ACL) of the available satellite data and the uppermost soil layer of the models. Additional to the ECV_SM data, AMSR-E soil moisture is used as observational estimate. Simulated soil moisture fields are taken from ERA-Interim reanalysis and generated with the land surface model JSBACH, which was driven with quasi-observational meteorological forcing data. The satellite data show ACLs between one week and one month for the greater part of the land surface while the models simulate a longer memory of up to two months. Some pattern are similar in models and observations, e.g. a longer memory in the Sahel Zone and the Arabian Peninsula, but the models are not able to reproduce regions with a very short ACL of just a few days. If the long term seasonality is subtracted from the data the memory is strongly shortened, indicating the importance of seasonal variations for the memory in most regions. Furthermore, we analyze the change of soil moisture memory in the different soil layers of the models to investigate to which extent the surface soil moisture includes information about the whole soil column. A first analysis reveals that the ACL is increasing for deeper layers. However, its increase is stronger in the soil moisture anomaly than in its absolute values and the first even exceeds the latter in the deepest layer. From this we conclude that the seasonal soil moisture variations dominate the memory close to the surface but these are dampened in lower layers where the memory is mainly affected by longer term variations.

Stacke, Tobias; Hagemann, Stefan; Loew, Alexander

2013-04-01

91

Multifrequency Microwave Radiometer Measurements of Soil Moisture  

Microsoft Academic Search

Ground-based microwave radiometer experiments were performed to investigate the effects of moisture, temperature, and roughness on microwave emission from bare soils. Measurements were made at frequencies of 0.6-0.9, 1.4, and 10.7 GHz using van-mounted radiometers to observe prepared soil sites in Kern County, CA. The sites were instrumented for monitoring soil characteristics and surface meteorological conditions. Brightness temperature variations of

Eni G. Njoku; Peggy E. O'Neill

1982-01-01

92

An electrical recording soil moisture tensiometer  

Microsoft Academic Search

Summary  An automatically recording soil moisture tensiometer was produced by substituting the usual mercury manometer by an electrical\\u000a pressure transducer. Like other tensiometers and unlike the neutron probe, this instrument samples relatively small volumes\\u000a of soil. In tests, individual recording tensiometers gave results repeatable to 0.002 bar even in moist soils and responded\\u000a twice as quickly as standard tensiometers. As a

J. D. Deans; R. Milne

1978-01-01

93

Impact of soil hydraulic parameter uncertainty on soil moisture modeling  

NASA Astrophysics Data System (ADS)

For simulations in basins where soil information is limited to soil type maps, a methodology is presented to quantify the uncertainty of soil hydraulic parameters arising from within-soil-class variability and to assess the impact of this uncertainty on soil moisture modeling. Continuous pedotransfer functions were applied to samples with different texture within each soil class to construct discrete probability distributions of the soil hydraulic parameters. When propagating the parameter distributions through a hydrologic model, a wide range of simulated soil moisture was generated within a single soil class. The pedotransfer function was found to play a crucial role in assessing the uncertainty in the modeled soil moisture, and the geographic origin of the pedotransfer function (region specific versus nonregion specific) highly affected the range and shape of the probability distribution of the soil hydraulic parameters. Furthermore, the modeled soil moisture distribution was found to be non-Gaussian. An accurate uncertainty assessment therefore requires the characterization of its higher-order moments. As an extension of this research, we have shown that applying continuous region-specific pedotransfer functions to the central point of a soil class is a better alternative to standard (often nonregion-specific) class pedotransfer functions for determining an average set of soil hydraulic parameters.

Loosvelt, Lien; Pauwels, Valentijn R. N.; Cornelis, Wim M.; de Lannoy, GabriëLle J. M.; Verhoest, Niko E. C.

2011-03-01

94

Analysis of shallow soil moisture flux adjacent to the Area 5 radioactive waste management site  

Microsoft Academic Search

Hazardous waste requires significant isolation from the biosphere. Shallow land burial of radioactive waste is currently employed at Area 5 of the Nevada Test Site to prevent release of impounded radioactive materials. Soil covers have been proposed to limit the infiltration of precipitation into the waste. Appropriate design for these covers depends on knowledge of infiltration in the soils intended

William Albright; Scott Tyler; Sam Hokett

1997-01-01

95

Soil Moisture Estimation Using Inexpensive Radios  

NASA Astrophysics Data System (ADS)

Technological advances and changes in licensing have made small, inexpensive radio modules commonplace. Today, these radios are used in a large number of wireless data- and control applications. A novel approach is to view such radio modules not only as communication devices, but also as small, inexpensive sources of radio frequency (RF) energy, which are useful for devising unconventional sensors. We have explored the possibility of using buried radios and the resulting RF links as distributed soil moisture sensors. We conducted a number of experiments that record the RF attenuation of the links over time. Estimating RF attenuation is straightforward, since the radio modules provide a received signal strength indication (RSSI). To provide reference data, we installed several time-domain reflectometry (TDR) soil moisture probes with accompanying temperature probes to monitor changes in soil moisture and soil temperature. We collocated tipping bucket rain gauges for monitoring rain events. We employed RF modules that operate at 900 MHz. Rather than burying the radios, we lowered the antennas into 2.5 cm PVC pipes that we drove into the ground to a depth of 60 cm. We seal both ends of the PVC pipe to prevent water from entering the tube. Our experimental data shows a clear relationship between soil moisture and RF attenuation. We developed a simple, yet effective, mathematical model to relate changes in RF attenuation to changes in soil moisture. One can easily achieve reliable links 2-3 m long, and we believe the technique holds promise as an economical method for distributed/integrated soil moisture estimation.

Niemeier, J. J.; Kruger, A.

2011-12-01

96

Impact of SMOS soil moisture data assimilation on NCEP-GFS forecasts  

NASA Astrophysics Data System (ADS)

Soil moisture is one of the few critical land surface state variables that have long memory to impact the exchanges of water, energy and carbon between the land surface and atmosphere. Accurate information about soil moisture status is thus required for numerical weather, seasonal climate and hydrological forecast as well as for agricultural production forecasts, water management and many other water related economic or social activities. Since the successful launch of ESA's soil moisture ocean salinity (SMOS) mission in November 2009, about 2 years of soil moisture retrievals has been collected. SMOS is believed to be the currently best satellite sensors for soil moisture remote sensing. Therefore, it becomes interesting to examine how the collected SMOS soil moisture data are compared with other satellite-sensed soil moisture retrievals (such as NASA's Advanced Microwave Scanning Radiometer -AMSR-E and EUMETSAT's Advanced Scatterometer - ASCAT)), in situ soil moisture measurements, and how these data sets impact numerical weather prediction models such as the Global Forecast System of NOAA-NCEP. This study implements the Ensemble Kalman filter in GFS to assimilate the AMSR-E, ASCAT and SMOS soil moisture observations after a quantitative assessment of their error rate based on in situ measurements from ground networks around contiguous United States. in situ soil moisture measurements from ground networks (such as USDA Soil Climate Analysis network - SCAN and NOAA's U.S. Climate Reference Network -USCRN) are used to evaluate the GFS soil moisture simulations (analysis). The benefits and uncertainties of assimilating the satellite data products in GFS are examined by comparing the GFS forecasts of surface temperature and rainfall with and without the assimilations. From these examinations, the advantages of SMOS soil moisture data products over other satellite soil moisture data sets will be evaluated. The next step toward operationally assimilating soil moisture and other land observations into GFS will also be discussed.

Zhan, X.; Zheng, W.; Meng, J.; Dong, J.; Ek, M.

2012-04-01

97

The International Soil Moisture Network: a data hosting facility for global in situ soil moisture measurements  

NASA Astrophysics Data System (ADS)

In situ measurements of soil moisture are invaluable for calibrating and validating land surface models and satellite-based soil moisture retrievals. In addition, long-term time series of in situ soil moisture measurements themselves can reveal trends in the water cycle related to climate or land cover change. Nevertheless, on a worldwide basis the number of meteorological networks and stations measuring soil moisture, in particular on a continuous basis, is still limited and the data they provide lack standardization of technique and protocol. To overcome many of these limitations, the International Soil Moisture Network (ISMN; http://www.ipf.tuwien.ac.at/insitu) was initiated to serve as a centralized data hosting facility where globally available in situ soil moisture measurements from operational networks and validation campaigns are collected, harmonized, and made available to users. Data collecting networks share their soil moisture datasets with the ISMN on a voluntary and no-cost basis. Incoming soil moisture data are automatically transformed into common volumetric soil moisture units and checked for outliers and implausible values. Apart from soil water measurements from different depths, important metadata and meteorological variables (e.g., precipitation and soil temperature) are stored in the database. These will assist the user in correctly interpreting the soil moisture data. The database is queried through a graphical user interface while output of data selected for download is provided according to common standards for data and metadata. Currently (status January 2011), the ISMN contains data of 16 networks and more than 500 stations located in the North America, Europe, Asia, and Australia. The time period spanned by the entire database runs from 1952 until the present, although most datasets have originated during the last decade. The database is rapidly expanding, which means that both the number of stations and the time period covered by the existing stations are still growing. Hence, it will become an increasingly important resource for validating and improving satellite-derived soil moisture products and studying climate related trends. As the ISMN is animated by the scientific community itself, we invite potential networks to enrich the collection by sharing their in situ soil moisture data.

Dorigo, W. A.; Wagner, W.; Hohensinn, R.; Hahn, S.; Paulik, C.; Drusch, M.; Mecklenburg, S.; van Oevelen, P.; Robock, A.; Jackson, T.

2011-02-01

98

The International Soil Moisture Network: a data hosting facility for global in situ soil moisture measurements  

NASA Astrophysics Data System (ADS)

In situ measurements of soil moisture are invaluable for calibrating and validating land surface models and satellite-based soil moisture retrievals. In addition, long-term time series of in situ soil moisture measurements themselves can reveal trends in the water cycle related to climate or land cover change. Nevertheless, on a worldwide basis the number of meteorological networks and stations measuring soil moisture, in particular on a continuous basis, is still limited and the data they provide lack standardization of technique and protocol. To overcome many of these limitations, the International Soil Moisture Network (ISMN; http://www.ipf.tuwien.ac.at/insitu) was initiated to serve as a centralized data hosting facility where globally available in situ soil moisture measurements from operational networks and validation campaigns are collected, harmonized, and made available to users. Data collecting networks share their soil moisture datasets with the ISMN on a voluntary and no-cost basis. Incoming soil moisture data are automatically transformed into common volumetric soil moisture units and checked for outliers and implausible values. Apart from soil water measurements from different depths, important metadata and meteorological variables (e.g., precipitation and soil temperature) are stored in the database. These will assist the user in correctly interpreting the soil moisture data. The database is queried through a graphical user interface while output of data selected for download is provided according to common standards for data and metadata. Currently (status May 2011), the ISMN contains data of 19 networks and more than 500 stations located in North America, Europe, Asia, and Australia. The time period spanned by the entire database runs from 1952 until the present, although most datasets have originated during the last decade. The database is rapidly expanding, which means that both the number of stations and the time period covered by the existing stations are still growing. Hence, it will become an increasingly important resource for validating and improving satellite-derived soil moisture products and studying climate related trends. As the ISMN is animated by the scientific community itself, we invite potential networks to enrich the collection by sharing their in situ soil moisture data.

Dorigo, W. A.; Wagner, W.; Hohensinn, R.; Hahn, S.; Paulik, C.; Xaver, A.; Gruber, A.; Drusch, M.; Mecklenburg, S.; van Oevelen, P.; Robock, A.; Jackson, T.

2011-05-01

99

On the assimilation of satellite derived soil moisture in numerical weather prediction models  

NASA Astrophysics Data System (ADS)

Satellite derived surface soil moisture data sets are readily available and have been used successfully in hydrological applications. In many operational numerical weather prediction systems the initial soil moisture conditions are analysed from the modelled background and 2 m temperature and relative humidity. This approach has proven its efficiency to improve surface latent and sensible heat fluxes and consequently the forecast on large geographical domains. However, since soil moisture is not always related to screen level variables, model errors and uncertainties in the forcing data can accumulate in root zone soil moisture. Remotely sensed surface soil moisture is directly linked to the model's uppermost soil layer and therefore is a stronger constraint for the soil moisture analysis. Three data assimilation experiments with the Integrated Forecast System (IFS) of the European Centre for Medium-range Weather Forecasts (ECMWF) have been performed for the two months period of June and July 2002: A control run based on the operational soil moisture analysis, an open loop run with freely evolving soil moisture, and an experimental run incorporating bias corrected TMI (TRMM Microwave Imager) derived soil moisture over the southern United States through a nudging scheme using 6-hourly departures. Apart from the soil moisture analysis, the system setup reflects the operational forecast configuration including the atmospheric 4D-Var analysis. Soil moisture analysed in the nudging experiment is the most accurate estimate when compared against in-situ observations from the Oklahoma Mesonet. The corresponding forecast for 2 m temperature and relative humidity is almost as accurate as in the control experiment. Furthermore, it is shown that the soil moisture analysis influences local weather parameters including the planetary boundary layer height and cloud coverage. The transferability of the results to other satellite derived soil moisture data sets will be discussed.

Drusch, M.

2006-12-01

100

Soil moisture profiles from multifrequency radar data at basin scale  

Microsoft Academic Search

Multifrequency radar data are used to investigate the possibility offered by microwave remote sensing in estimating soil moisture on bare soil fields. Surface soil moisture values obtained from the inversion of a theoretical scattering model for the MAC-Europe '91 airborne campaign are compared with sampled ground measures of soil moisture for the Virginiolo experimental catchment (Tuscany, Italy). The radar signal

O. Bolognani; M. Mancini; R. Rosso

1996-01-01

101

Gravity changes, soil moisture and data assimilation  

NASA Astrophysics Data System (ADS)

Remote sensing holds promise for near-surface soil moisture and snow mapping, but current techniques do not directly resolve the deeper soil moisture or groundwater. The benefits that would arise from improved monitoring of variations in terrestrial water storage are numerous. The year 2002 saw the launch of NASA's Gravity Recovery And Climate Experiment (GRACE) satellites, which are mapping the Earth's gravity field at such a high level of precision that we expect to be able to infer changes in terrestrial water storage (soil moisture, groundwater, snow, ice, lake, river and vegetation). The project described here has three distinct yet inter-linked components that all leverage off the same ground-based monitoring and land surface modelling framework. These components are: (i) field validation of a relationship between soil moisture and changes in the Earth's gravity field, from ground- and satellite-based measurements of changes in gravity; (ii) development of a modelling framework for the assimilation of gravity data to constrain land surface model predictions of soil moisture content (such a framework enables the downscaling and disaggregation of low spatial (500 km) and temporal (monthly) resolution measurements of gravity change to finer spatial and temporal resolutions); and (iii) further refining the downscaling and disaggregation of space-borne gravity measurements by making use of other remotely sensed information, such as the higher spatial (25 km) and temporal (daily) resolution remotely sensed near-surface soil moisture measurements from the Advanced Microwave Scanning Radiometer (AMSR) instruments on Aqua and ADEOS II. The important field work required by this project will be in the Murrumbidgee Catchment, Australia, where an extensive soil moisture monitoring program by the University of Melbourne is already in place. We will further enhance the current monitoring network by the addition of groundwater wells and additional soil moisture sites. Ground-based gravity measurements will also be made on a monthly basis at each monitoring site. There will be two levels of modelling and monitoring; regional across the entire Murrumbidgee Catchment (100,000 km2), and local across a small sub-catchment (150 km2).

Walker, J.; Grayson, R.; Rodell, M.; Ellet, K.

2003-04-01

102

The Temperature Dependence of Soil Moisture Characteristics of Agricultural Soils  

Microsoft Academic Search

The temperature dependence of static and dynamic characteristics of four soils: glass beads, Plainfield sand, Plano silt loam, and Elkmound sandy loam were explored. Gain -factor model was employed for quantifying the temperature dependences. The study required novel methods and technologies which were developed and employed for the rapid, and transient measurement of soil-moisture characteristics of these soils. A pressurized

Amir Salehzadeh

1990-01-01

103

Dependence of Extreme Daily Maximum Temperatures on Antecedent Soil Moisture in the Contiguous United States during Summer  

Microsoft Academic Search

The paper presents an analysis of the dependence of summertime daily maximum temperature on antecedent soil moisture using daily surface observations from a selection of stations in the contiguous United States and daily time series of soil moisture computed with a simple local water balance model. The computed soil moisture time series are offered as an alternative to Palmer's soil

Imke Durre; John M. Wallace; Dennis P. Lettenmaier

2000-01-01

104

The role of biological soil crusts on soil moisture  

NASA Astrophysics Data System (ADS)

In water-limited ecosystems, water becomes the most important driver for plant productivity. In these systems, spatial distribution of water resources is not random but organized into a mosaic of water-depletion areas linked to water-accumulation areas. In other words, water is transferred from interplant patches that act as source areas to vegetation patches that act as sinks of this resource. Thus, structure and functioning of interplant patches have a decisive role in water redistribution and distribution patterns of vegetation. Soil surface in the interplant spaces of most arid and semiarid ecosystems is covered by biological soil crusts (BSCs). These organisms regulate water fluxes into and through soils and play major roles in local hydrological processes. In the last years, the role of these organisms in infiltration and runoff has gained increased importance and a better knowledge about their effects on these processes has been acquired. However, the role of BSCs in other important components of the water balance such as evaporation or soil moisture has been scarcely studied, so that their effects on these processes remain unknown. The objective of this work is to examine the influence of BSCs on soil moisture regimes in the top profile of the soil in two semiarid ecosystems of SE Spain with contrasting soil texture and where BSCs are well-represented. Soil moisture content at 0.03 and 0.10 m was monitored under two representative types of BSCs, a dark cyanobacteria-dominated BSC and a light-coloured lichen-dominated BSC, and in soils where these BSCs were removed by scraping, at both study sites. Our results show that, under high water conditions, removal of BSCs leads to a decrease in soil moisture compared to soils covered by BSCs. Decrease in soil moisture due to BSC removal namely affects moisture in the upper layer of the soil (0.03 m), but has little impact in deeper soil (0.10 m). Evaporation is also generally faster in soils with no BSCs than in soils covered by them. The type of BSC influences soil moisture in a different way depending on soil water conditions. Under high water content conditions, soil water loss is faster and soil moisture content lower under cyanobacterial than under lichen BSCs, due to higher infiltration promoted by lichens. On the contrary, under low water content conditions, lichen-crusted soils dry out faster and exhibit less moisture than cyanobacteria-crusted ones, attributed to the larger porosity and subsequent greater evaporative losses in lichen- than in cyanobacteria-crusted soils. We found higher moisture in coarse-textured soils than in fine-textured ones, despite the higher water retention capacity of the latter soils. More favourable conditions in the coarser soils, which had greater organic matter content, aggregate stability and were subject to less water stress due to its proximity to the coast, seems to contribute to this increased soil moisture content. BSCs therefore play an important role on the maintenance of water availability in the interplant spaces, thereby strongly affecting soil physical and biological processes, and the potential for emergence establishment and survival of plants in semiarid ecosystems.

Chamizo, S.; Cantón, Y.; Lázaro, R.; Rodriguez-Caballero, E.; Domingo, F.

2012-04-01

105

An Investigation of Soil Moisture Dynamics Using FLUXNET Data  

NASA Astrophysics Data System (ADS)

Soil moisture data, obtained from four FLUXNET sites in the US, were examined using an ecohydrological framework. Sites were selected for the analysis to provide a range of plant functional type, climate, and soil grain size distribution. Data at a selected site included at least two years of measurements of volumetric soil water content, air temperature, precipitation, atmospheric pressure, net radiation, and latent heat flux. The Rosetta database program, based on pedo-transfer functions, was used to generate water retention curves from site soil grain size distributions. Using these curves and plant parameters found in the literature, ranges for each critical soil moisture point were determined. For all sites, the hydroscopic point (Sh) and wilting point (Sw) had the smallest range, while more uncertainty was associated with the stress point (S*) and field content (Sfc). Soil moisture trends revealed the importance of measuring water content at several depths throughout the rooting zone; soil moisture at the surface (above 10 cm) was around 20 to 30 percent less than that at 50 to 60 cm. Frequently, the surface soil moisture would fall below Sw while remaining between S* and Sw at deeper intervals. While daily variability of soil moisture was high due to the timing of precipitation events, yearly variability was lower than anticipated. However, a broader range of years should be examined to confirm this finding. A steady state soil moisture dynamics model was used to generate soil moisture probability density functions (pdfs) at each site. The model was altered to accommodate the year-round growing seasons at two of the sites, a compromise between a fully transient model and the typical steady state model. The modeled pdfs were then compared to histograms generated from the measured data. Model accuracy depended heavily on proper parameter selection. Most parameters could be found using available FLUXNET data for the site, however, S* and Sfc were not known with sufficient certainty. A simple inversion technique was used to find these parameters and calibrate the model. The inversion results demonstrated that the commonly used soil matric potential values for finding S* and Sfc may not be appropriate.

Miller, G. R.; Baldocchi, D. D.

2005-12-01

106

Modeling soil heating and moisture transport under extreme conditions  

Treesearch

Description: Heating any soil during a sufficiently intense wildfire or ... of the soil specific heat, thermal conductivity, and the water retention curve, as well as ... soil water potential and soil moisture at extremely low soil moisture contents (i.e., ... progress on modeling soil evaporation and heating under conditions of high ...

107

Effects of soil moisture on the diurnal pattern of pesticide emission: Numerical simulation and sensitivity analysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

Accurate prediction of pesticide volatilization is important for the protection of human and environmental health. Due to the complexity of the volatilization process, sophisticated predictive models are needed, especially for dry soil conditions. A mathematical model was developed to allow simulati...

108

Sensitivity of LISEM predicted catchment discharge to initial soil moisture content of soil profile  

Microsoft Academic Search

This study conducts a broad sensitivity analysis, taking into account the influence of initial soil moisture content in two soil layers, layer depths, event properties, and two infiltration models. A distributed hydrology and soil erosion model (LISEM) is used. Using the terrain data from the Catsop research catchment and two different rainfall events, the sensitivity of discharge is investigated for

Vahedberdi Sheikh; Emiel van Loon; Rudi Hessel; Victor Jetten

2010-01-01

109

Radar measurement of soil moisture content  

Microsoft Academic Search

The effect of soil moisture on the radar backscattering coefficient was investigated by measuring the 4-8 GHz spectral response from two types of bare-soil fields: slightly rough and very rough, in terms of the wavelength. An FM-CW radar system mounted atop a 75-ft truck-mounted boom was used to measure the return at 10 frequency points across the 4-8 GHz band,

FAWWAZ T. ULABY

1974-01-01

110

Estimation of Soil Moisture from Diurnal Surface Temperature Observations.  

National Technical Information Service (NTIS)

A coupled heat and moisture balance model was used to determine the thermal inertia of a grass covered top soil under different meteorological conditions. Relations between thermal inertia and soil moisture were established using the De Vries models for t...

A. A. Vandegriend P. J. Camillo

1986-01-01

111

Estimating Surface Soil Moisture in Simulated AVIRIS Spectra.  

National Technical Information Service (NTIS)

Soil albedo is influenced by many physical and chemical constituents, with moisture being the most influential on the spectra general shape and albedo. Without moisture, the intrinsic or matrix reflectance of dissimilar soils varies widely due to differen...

M. L. Whiting L. Li S. L. Ustin

2005-01-01

112

Microwave soil moisture retrieval under trees  

Technology Transfer Automated Retrieval System (TEKTRAN)

During 2007 a field experiment was conducted with a goal of optimizing microwave soil moisture retrieval algorithms for small to medium deciduous trees. After initial field checkout in Fall 2006, the ComRAD microwave truck instrument system was deployed to a test site with several stands of deciduo...

113

Heated optical fiber to measure soil moisture  

Microsoft Academic Search

To provide definitive answers to open questions about coupled heat and moisture fluxes in a field soil during the diurnal cycle, a large lysimeter experiment began in the summer 2010. The homogeneously filled lysimeter is weighed by high precision balances to evaluate the evaporation, while a set of sensors has been installed to monitor the vertical profile of volumetric water

F. Ciocca; M. B. Parlange; N. van de Giesen; I. Lunati

2010-01-01

114

The Soil Moisture and Ocean Salinity mission  

Microsoft Academic Search

Surface soil moisture is a key variable of water and energy exchanges at the land surface\\/atmosphere interface. But currently there are no means to assess it on a global and timely fashion. Similarly, our current knowledge of sea surface salinity is very reduced. One way to overcome this issue would be to use an adequate space-borne instrument. The most promising

Y. H. Kerr; P. Waldteufel; J.-P. Wigneron; M. Berger

2003-01-01

115

BOREAS HYD-1 Volumetric Soil Moisture Data.  

National Technical Information Service (NTIS)

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-1 team made measurements of volumetric soil moisture at the Southern Study Area (SSA) and Northern Study Area (NSA) tower flux sites in 1994 and at selected tower flux sites in 1995-97. Differ...

R. H. Cuenca S. F. Kelly D. E. Stangel

2000-01-01

116

Soil Moisture Survey Experiment at Phoenix, Arizona.  

National Technical Information Service (NTIS)

An aerial survey employing the measurement of natural terrestrial gamma radiation was carried out over farm lands east of Phoenix, Arizona, on March 18, 1975. The purpose of the survey was to determine soil moisture by detecting differences in the terrest...

E. L. Feimster A. E. Fritzsche C. Jupiter

1975-01-01

117

Soil moisture as an indicator of weather extremes  

NASA Astrophysics Data System (ADS)

In this paper, we investigate floods and droughts in the Upper Mississippi basin over a 50-year period (1950-1999) using a hydrological model (Variable Infiltration Capacity Model - 3 Layer). Simulations have been carried out between January 1950 and December 1999 at daily time-step and 1/8° spatial resolution for the water budget and at hourly time-step and 1° spatial resolution for the energy balance. This paper will provide valuable insights to the slow response components of the hydrological cycle and its diagnostic/predictive value in the case of floods and droughts. The paper compares the use of the Palmer Drought Severity Index against the anomalies of the third layer soil moisture for characterizing droughts and floods. Wavelet and coherency analysis is performed on the soil moisture, river discharge, precipitation and PDSI time series confirm our hypothesis of a strong relationship between droughts and the third layer soil moisture.

Lakshmi, Venkat; Piechota, Thomas; Narayan, Ujjwal; Tang, Chunling

2004-06-01

118

SMOS CATDS level 3 Soil Moisture products  

NASA Astrophysics Data System (ADS)

The ESA's (European Space Agency) SMOS (Soil Moisture and Ocean Salinity) mission, operating since november 2009, is the first satellite dedicated to measuring surface soil moisture and ocean salinity. The CNES (Centre National d'Etudes Spatiales) has developed a ground segment for the SMOS data, known as the CATDS (Centre Aval de Traitement des Données SMOS). Operational since June 2011, it provides data referred to as level 3 products at different time resolutions: daily products, 3 days global products insuring a complete coverage of the Earth surface, 10-days composite products, and monthly averages products. These products are presented in the NetCDF format on the EASE grid (Equal Area Scalable Earth grid) with a spatial resolution of ~ 25*25 km2. Having global maps at different time resolutions is of interest for different applications such as agriculture, water management, climatic events (especially droughts and floods) or climatology. The soil moisture level 3 algorithm is based on ESA's (European Space Agency) level 2 retrieval scheme with the improvement of using several overpasses (3 at most) over a 7-days window. The benefit of using many revisits is expected to improve the retrieved soil moisture. Along with the surface soil moisture, other geophysical parameters are retrieved such as the vegetation optical depth or the dielectric constant of the surface. The aim of this communication is to present the first results from the CATDS dataset and all the different data available. Comparisons with in situ data at different sites will be presented to assess the quality of these data. A comparison with the ESA level 2 SMOS products will also be shown to better understand the difference between these dataset, in terms of quality, coverage, applications and use. We will also present how the CATDS data can capture some special events. For instance, the dataset will be compared with meteorological events (rain events), or extreme events such as droughts or floods.

Berthon, L.; Mialon, A.; Bitar, A. Al; Cabot, F.; Kerr, Y. H.

2012-04-01

119

Information and complexity measures applied to observed and simulated soil moisture time series  

Microsoft Academic Search

Time series of soil moisture-related parameters provide important insights into the functioning of soil water systems. Analysis of patterns within such time series has been used in several studies. The objective of this work was to compare patterns in observed and simulated soil moisture contents to understand whether modelling leads to a substantial loss of information or complexity. The time

Feng Pan; Yakov A. Pachepsky; Andrey K. Guber; Robert L. Hill

2011-01-01

120

SoilNet - A Zigbee based soil moisture sensor network  

NASA Astrophysics Data System (ADS)

Soil moisture plays a key role in partitioning water and energy fluxes, in providing moisture to the atmosphere for precipitation, and controlling the pattern of groundwater recharge. Large-scale soil moisture variability is driven by variation of precipitation and radiation in space and time. At local scales, land cover, soil conditions, and topography act to redistribute soil moisture. Despite the importance of soil moisture, it is not yet measured in an operational way, e.g. for a better prediction of hydrological and surface energy fluxes (e.g. runoff, latent heat) at larger scales and in the framework of the development of early warning systems (e.g. flood forecasting) and the management of irrigation systems. The SoilNet project aims to develop a sensor network for the near real-time monitoring of soil moisture changes at high spatial and temporal resolution on the basis of the new low-cost ZigBee radio network that operates on top of the IEEE 802.15.4 standard. The sensor network consists of soil moisture sensors attached to end devices by cables, router devices and a coordinator device. The end devices are buried in the soil and linked wirelessly with nearby aboveground router devices. This ZigBee wireless sensor network design considers channel errors, delays, packet losses, and power and topology constraints. In order to conserve battery power, a reactive routing protocol is used that determines a new route only when it is required. The sensor network is also able to react to external influences, e.g. such as rainfall occurrences. The SoilNet communicator, routing and end devices have been developed by the Forschungszentrum Juelich and will be marketed through external companies. We will present first results of experiments to verify network stability and the accuracy of the soil moisture sensors. Simultaneously, we have developed a data management and visualisation system. We tested the wireless network on a 100 by 100 meter forest plot equipped with 25 end devices each consisting of 6 vertically arranged soil moisture sensors. The next step will be the instrumentation of two small catchments (~30 ha) with a 30 m spacing of the end devices. juelich.de/icg/icg-4/index.php?index=739

Bogena, H. R.; Weuthen, A.; Rosenbaum, U.; Huisman, J. A.; Vereecken, H.

2007-12-01

121

The interrelationship of meteorological factors, soil moisture and plant growth  

Microsoft Academic Search

A thorough review of literature pertaining to the role of soil moisture in the interrelationships between meteorological factors and plant growth has been presented. In arid and semi-arid areas crop yields are closely related to the supply of soil moisture during the growing season. Direct measurements of soil moisture are laborious, costly or sometimes unpracticable. Unless sufficiently replicated they do

W. Baier

1965-01-01

122

REMOTE SENSING OF SOIL MOISTURE USING MICROWAVE TECHNIQUES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture mapping using remote sensing will become a reality in this decade. Soil moisture has been difficult to measure and map using conventional ground based technologies. Microwave remote sensing based soil moisture retrieval has been demonstrated using tower and aircraft instruments, howev...

123

Validation of Advanced Microwave Scanning Radiometer Soil Moisture Products  

Microsoft Academic Search

Validation is an important and particularly challenging task for remote sensing of soil moisture. A key issue in the validation of soil moisture products is the disparity in spatial scales between satellite and in situ observations. Conventional measurements of soil moisture are made at a point, whereas satellite sensors provide an integrated area\\/volume value for a much larger spatial extent.

Thomas J. Jackson; Michael H. Cosh; Rajat Bindlish; Patrick J. Starks; David D. Bosch; Mark Seyfried; David C. Goodrich; Mary Susan Moran; Jinyang Du

2010-01-01

124

Groundwater influences on soil moisture and surface evaporation  

Microsoft Academic Search

Soil hydrological processes play an important role in land-atmosphere system. In most climate models, these processes are described by soil moisture variations in the first 2 m of soil resulting from precipitation, evaporation, and transpiration. Groundwater effects on soil moisture variations and surface evaporation are either neglected or not explicitly treated. Although groundwater may have a small effect on soil

X. Chen; Q. Hu

2004-01-01

125

Effect of Temperature, Moisture, and Soil Texture on DCPA Degradation  

Microsoft Academic Search

Turf managers sometimes experience poor or early loss of control of targeted weeds, even when herbicides are applied at recommended rates. This study was conducted to determine the influence of soil temperature and moisture on the rate of DCPA (dimethyl tetrachloroterephthalate) degradation in soil. The effect of six soil temperatures, three soil moistures, and three soil textures on the degradation

J. S. Choi; T. W. Fermanian; David J. Wehner; L. A. Spomer

1988-01-01

126

Equivalent steady soil moisture profile and the time compression approximation in water balance modeling  

Microsoft Academic Search

The definition of preevent soil moisture profile and time compression analysis are critical components in water balance models that are based on realistic infiltration\\/exfiltration relations and include profile redistribution of vadose zone moisture. In this paper, detailed analysis of these two fundamental components of water balance modeling is presented. Numerical integration of the governing equations for liquid moisture flow in

Guido Daniel Salvucci; Dara Entekhabi

1994-01-01

127

Development of a measurement operator for cosmic ray soil moisture observations  

NASA Astrophysics Data System (ADS)

Cosmic ray sensors measure neutron fluxes close to the earth surface. Effective absorption of energetic cosmic rays by hydrogen nuclei in the soil establishes a direct relationship between measured neutron flux and soil moisture content. Using this relationship, cosmic ray sensors are becoming increasingly popular for measuring soil moisture content at the field scale. The interesting aspect of the measurement is that the average soil moisture content (with diameter around 600 m and a vertical depth up to 70 cm) over a larger scale can be obtained (Zreda et al., 2008). However, the relation between the spatial distribution of soil moisture content in the footprint of a cosmic ray probe and the measured number of neutron counts is non-linear and the exact relationship is still subject to uncertainty. The soil moisture monitoring network SoilNet (Bogena et al. 2010) established in the framework of the TERENO project offers an excellent opportunity to compare soil moisture measurements and neutron counts and improve the calibration of cosmic ray probes. The established relation between the two methods is a non-linear measurement operator in a data assimilation framework. Here soil moisture contents measured in Rollesbroich (Eifel, Germany) at 83 locations and 3 depths (5, 20 and 50 cm) were used to calibrate a cosmic ray probe. First results of the analysis to illustrate the influence of soil moisture heterogeneity in the cosmic ray footprint, the relation between mean soil moisture content and vertical footprint, as well as the causes for deviations between soil moisture content measured by a cosmic ray probe and by SoilNet will be shown. It will be demonstrated that a good correspondence between measured soil moisture contents by TDR or FDR and soil moisture estimated with a cosmic ray probe for a period of a few months does not guarantee a good fit at other times of the year.

Baatz, R.; Bogena, H.; Hendricks-Franssen, H.-J.; Huisman, J. A.; Montzka, C.; Vereecken, H.

2012-04-01

128

SMOS validation of soil moisture and ocen salinity (SMOS) soil moisture over watershed networks in the U.S.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Estimation of soil moisture at large scale has been performed using several satellite-based passive microwave sensors and a variety of retrieval methods. The most recent source of soil moisture is the European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. A thorough validation must b...

129

On the structure of soil moisture time series in the context of land surface models  

Microsoft Academic Search

Root-zone soil moisture is addressed as a key variable controlling surface water and energy balances. Particular focus is applied to the soil moisture controls on wet-end drainage and dry-end transpiration, and the integrated effects of these controls on the structure of soil moisture time series. Analysis is centered on data collected during a pair of field experiments, where a site

J. D. Albertson; G. Kiely

2001-01-01

130

Assessing Soil Moisture Regimes with Traditional and New Methods  

Microsoft Academic Search

individual precipitation events, but shallow enough to show seasonal variations. Soil moisture regime classes are required by U.S. soil taxonomy The lack of data on the actual long-term daily soil and other classification systems. Soil moisture regimes are based on long-term daily data of soil water content, which are as a rule estimated moisture requires the characterization of the pedoclimate

Edoardo A. C. Costantini; Fabio Castelli; Salvatore Raimondi; Paolo Lorenzoni

2002-01-01

131

Soil Moisture Prediction During Freeze and Thaw Using a Coupled Heat and Moisture Flow Model.  

National Technical Information Service (NTIS)

A coupled heat flow and moisture flow model (FROSTB) was used to simulate large scale freeze-thaw experiments to assess its ability to predict soil moisture conditions during freeze and thaw. The experimental data consists of temperature and soil moisture...

S. R. Bigi S. A. Shoop

1994-01-01

132

Radar Retrieval of Surface and Deep Soil Moisture and Effect of Moisture Profile on Inversion Accuracy  

Microsoft Academic Search

We study the retrieval of surface and deep moisture of bare soil from noisy radar observations using simulated anneal- ing. Due to moisture variations with depth, we model bare soil with a stratified dielectric profile with a rough surface on top. Small perturbation method (SPM) is used as the forward model. We use the full moisture profile for radar data

Alireza Tabatabaeenejad; Mahta Moghaddam

2011-01-01

133

COsmic-ray Soil Moisture Observing System (COSMOS): soil moisture and beyond  

NASA Astrophysics Data System (ADS)

COSMOS, a project funded by the US National Science Foundation, was designed to measure average soil moisture in the top 10-70 cm of soil over the horizontal footprint of approximately 700 m by measuring cosmic-ray neutrons in air above the ground surface. It is in its fourth, final, year of the feasibility phase in which 60 neutron probes have been installed in the USA to provide continental-scale soil moisture data. The cosmic-ray neutron probe responds to all sources of hydrogen present within the footprint. Therefore, in addition to soil moisture, other pools of hydrogen can be measured; these include atmospheric water vapor, organic matter in soil, water in soil minerals, biomass water (including hydrogen bound in cellulose), and snow on the ground and on the canopy. All these pools of hydrogen form the "total surface moisture" that is measured by COSMOS probes. The first four pools are measured independently (water vapor) or are implicitly included in the probe calibration (water in minerals and organic matter, biomass water). The other two can be separated from one another to produce time series of soil moisture and snow water equivalent. Work is in progress to assimilate neutron data into land-surface models, to produce soil moisture profiles, to validate satellite soil moisture products (the current SMOS mission and the future SMAP mission), to measure temporal variations in biomass, and to measure area-average unsaturated hydraulic properties of soils. Separately, mobile COSMOS probe, called COSMOS rover, is being developed. COSMOS rover can be used to map soil moisture over large areas or along long transects. Cosmic-ray sensing of moisture at the land surface has gained popularity outside of the USA. Approximately 60 probes have been purchased in addition to the 60 probes in the COSMOS project. Funds for additional 80 probes, most of them in Germany, have been secured, and large new proposals will be submitted in the USA and Australia in 2013. These probes form an embryonic global COSMOS network, and an international community of scientists interested in cosmic-ray sensing is emerging. Acknowledgement: The COSMOS project is supported by the US National Science Foundation.

Zreda, Marek; Shuttleworth, William J.; Zeng, Xubin; Zweck, Chris; Franz, Trenton; Rosolem, Rafael

2013-04-01

134

Soil moisture retrieval from satellite images and its application to heavy rainfall simulation in eastern China  

NASA Astrophysics Data System (ADS)

The soil water index (SWI) from satellite remote sensing and the observational soil moisture from agricultural meteorological stations in eastern China are used to retrieve soil moisture. The analysis of correlation coefficient (CORR), root-mean-squaxe-error (RMSE) and bias (BIAS) shows that the retrieved soil moisture is convincible and close to the observation. The method can overcome the difficulties in soil moisture observation on a large scale and the retrieved soil moisture may reflect the distribution of the real soil moisture objectively. The retrieved soil moisture is used as an initial scheme to replace initial conditions of soil moisture (NCEP) in the model MM5V3 to simulate the heavy rainfall in 1998. Three heavy rainfall processes during 13-14 June, 18-22 June, and 21-26 July 1998 in the Yangtze River valley are analyzed. The first two processes show that the intensity and location of simulated precipitation from SWI are better than those from NCEP and closer to the observed values. The simulated heavy rainfall for 21-26 July shows that the update of soil moisture initial conditions can improve the model's performance. The relationship between soil moisture and rainfall may explain that the stronger rainfall intensity for SWI in the Yangtze River valley is the result of the greater simulated soil moisture from SWI prior to the heavy rainfall date than that from NCEP, and leads to the decline of temperature in the corresponding area in the heavy rainfall days. Detailed analysis of the heavy rainfall on 13-14 June shows that both land-atmosphere interactions and atmospheric circulation were responsible for the heavy rainfall, and it shows how the SWI simulation improves the simulation. The development of mesoscale systems plays an important role in the simulation regarding the change of initial soil moisture for SWI.

Zhao, D. M.; Su, B. K.; Zhao, M.

2006-03-01

135

HCMM/Soil Moisture Experiment.  

National Technical Information Service (NTIS)

Progress in the compilation and analysis of airborne and ground data to determine the relationship between the maximum surface minus maximum air temperature differential (delta Tsa) and available water (PAW) is reported. Also, results of an analysis of HC...

J. Cihlar

1980-01-01

136

Soil moisture retrieval from AMSR-E  

Microsoft Academic Search

The Advanced Microwave Scanning Radiometer (AMSR-E) on the Earth Observing System (EOS) Aqua satellite was launched on May 4, 2002. The AMSR-E instrument provides a potentially improved soil moisture sensing capability over previous spaceborne radiometers such as the Scanning Multichannel Microwave Radiometer and Special Sensor Microwave\\/Imager due to its combination of low frequency and higher spatial resolution (approximately 60 km

Eni G. Njoku; Thomas J. Jackson; Venkataraman Lakshmi; Tsz K. Chan; Son V. Nghiem

2003-01-01

137

Microwave Soil Moisture Retrieval Under Trees  

Microsoft Academic Search

During 2007 a field experiment was conducted with a goal of optimizing microwave soil moisture retrieval algorithms for small to medium deciduous trees. After initial field checkout in Fall 2006, the ComRAD microwave truck instrument system was deployed to a test site with several stands of deciduous paulownia trees. A joint effort of NASA\\/GSFC and George Washington University, ComRAD consists

Peggy O'Neill; Roger H. Lang; Mehmet Kurum; Alicia T. Joseph; Michael H. Cosh; Thomas J. Jackson

2008-01-01

138

The added value of spaceborne passive microwave soil moisture retrievals for forecasting rainfall-runoff partitioning  

NASA Astrophysics Data System (ADS)

Using existing data sets of spaceborne soil moisture retrievals, streamflow and precipitation for 26 basins in the United States Southern Great Plains, a 5-year analysis is performed to quantify the value of soil moisture retrievals derived from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) X-band (10.7 GHz) radiometer for forecasting storm event-scale runoff ratios. The predictive ability of spaceborne soil moisture retrievals is objectively compared to that obtainable using only available rainfall observations and the antecedent precipitation index (API). The assimilation of spaceborne observations into an API soil moisture proxy is demonstrated to add skill to the forecasting of land surface response to precipitation.

Crow, W. T.; Bindlish, R.; Jackson, T. J.

2005-09-01

139

Evolution of physical controls for soil moisture in humid and subhumid watersheds  

NASA Astrophysics Data System (ADS)

The covariability of soil moisture with soil, vegetation, topography, and precipitation is linked by physical relationships. The influence of each of these interdependent physical controls on soil moisture spatial distribution depends on the nature of heterogeneity present in the domain and evolves with time and scale. This paper investigates the effect of three physical controls, i.e., topography (slope), vegetation (type), and soil (texture), on soil moisture spatial distribution in the Little Washita and Walnut Creek watersheds in Oklahoma and Iowa, respectively, at two support scales. Point-support-scale data collected from four soil moisture campaigns (SMEX02, SMEX03, SMEX05, and CLASIC07) and airborne-scale data from three soil moisture campaigns (SGP97, SGP99, and SMEX02) were used in this analysis. The effect of different physical controls on the spatial mean and variability of soil moisture was assessed using Kruskal-Wallis and Shannon entropy respectively. It was found that at both (point and airborne) support scales, nonuniform precipitation (forcing) across the domain can mask the effect of the dominant physical controls on the soil moisture distribution. In order to isolate land-surface controls from the impact of forcing, the effect of precipitation variability was removed. After removing the effect of precipitation variability, it was found that for most soil moisture conditions, soil texture as opposed to vegetation and topography is the dominant physical control at both the point and airborne scales in Iowa and Oklahoma. During a very wet year (2007), however, the effect of topography on the soil moisture spatial variability overrides the effect of soil texture at the point support scale. These findings are valuable for developing any physically based scaling algorithms to upscale or downscale soil moisture between the point and watershed scales in the studied watersheds in humid and subhumid regions of the Great Plains of USA. These results may also be used in designing effective soil moisture field campaigns.

Gaur, Nandita; Mohanty, Binayak P.

2013-03-01

140

Planning for a Soil Moisture Satellite Mission  

NASA Astrophysics Data System (ADS)

SMAP Algorithms & Cal/Val Workshop; Oxnard, California, 9-11 June 2009; The Soil Moisture Active and Passive (SMAP) mission aims to gather high-resolution global soil moisture and freeze/thaw state data, which should enable improvements to weather and climate forecasts, flood prediction and drought monitoring, and estimations of net carbon dioxide (CO2) uptake in forested regions. Targeted for launch in 2014, SMAP is one of four missions recommended by the U.S. National Research Council Committee on Earth Science and Applications From Space for launch in the early part of the next decade (Earth Science and Applications From Space: National Imperatives for the Next Decade and Beyond, Natl. Acad. Press, 2007). The SMAP mission concept utilizes an L-band (1.20-1.41 gigahertz) radar and a radiometer that share a rotating 6-meter mesh reflector antenna to provide high-resolution and high-accuracy global maps of soil moisture and freeze/thaw state every 2-3days.

Moghaddam, Mahta; Jackson, Thomas

2009-09-01

141

NASA's Soil Moisture Active Passive (SMAP) observatory  

NASA Astrophysics Data System (ADS)

The Soil Moisture Active Passive (SMAP) mission, one of the first-tier missions recommended by the 2007 U.S. National Research Council Committee on Earth Science and Applications from Space, was confirmed in May 2012 by NASA to proceed into Implementation Phase (Phase C) with a planned launch in October 2014. SMAP will produce high-resolution and accurate global maps of soil moisture and its freeze/thaw state using data from a non-imaging synthetic aperture radar and a radiometer, both operating at L-band. Major challenges addressed by the observatory design include: (1) achieving global coverage every 2-3 days with a single observatory; (2) producing both high resolution and high accuracy soil moisture data, including through moderate vegetation; (3) using a mesh reflector antenna for L-band radiometry; (4) minimizing science data loss from terrestrial L-band radio frequency interference; (5) designing fault protection that also minimizes science data loss; (6) adapting planetary heritage avionics to meet SMAP's unique application and data volume needs; (7) ensuring observatory electromagnetic compatibility to avoid degrading science; (8) controlling a large spinning instrument with a small spacecraft; and (9) accommodating launch vehicle selection late in the observatory's development lifecycle.

Kellogg, K.; Thurman, S.; Edelstein, W.; Spencer, M.; Chen, Gun-Shing; Underwood, M.; Njoku, E.; Goodman, S.; Jai, Benhan

142

Heated optical fiber to measure soil moisture  

NASA Astrophysics Data System (ADS)

To provide definitive answers to open questions about coupled heat and moisture fluxes in a field soil during the diurnal cycle, a large lysimeter experiment began in the summer 2010. The homogeneously filled lysimeter is weighed by high precision balances to evaluate the evaporation, while a set of sensors has been installed to monitor the vertical profile of volumetric water content, capillary pressure and temperature. In addition, an innovative technique, which employs a heated optical fiber, is placed in the first meter of the soil profile, where the temperature and water-content fluctuations concentrate. The optical fiber (with a total length of thirty meters) is installed on a large spiral, which slowly penetrates the soil. Using the heat pulse method, the fiber allows us to obtain a distributed measure of soil moisture. The experimental setup offers the possibility of comparing optical-fiber measurements with data obtained from the frequency domain reflectometry sensors placed at the same depths. We present a validation of the effectiveness of this new technique to measure soil water content. Results of the application of the heat pulse method to study energy and mass balances are presented.

Ciocca, F.; Parlange, M. B.; van de Giesen, N.; Lunati, I.

2010-12-01

143

Modification of Soil Temperature and Moisture Budgets by Snow Processes  

Microsoft Academic Search

Snow cover significantly influences the land surface energy and surface moisture budgets. Snow thermally insulates the soil column from large and rapid temperature fluctuations, and snow melting provides an important source for surface runoff and soil moisture. Therefore, it is important to accurately understand and predict the energy and moisture exchange between surface and subsurface associated with snow accumulation and

X. Feng; P. Houser

2006-01-01

144

Uncertainty in SMAP Soil Moisture Measurements Caused by Dew  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture is an important reservoir of the hydrologic cycle that regulates the exchange of moisture and energy between the land surface the atmosphere. Two satellite missions will soon make the first global measurements of soil moisture at the optimal microwave wavelength within L-band: ESA's So...

145

Impacts of vegetation and cold season processes on soil moisture and climate relationships over Eurasia  

NASA Astrophysics Data System (ADS)

A number of modeling studies have addressed soil moisture persistence and its effects on the atmosphere. Such analyses are particularly valuable for seasonal to interannual prediction. In this study, we perform an observation-based study to further investigate the impacts of vegetation and cold season processes on soil moisture persistence and climate feedbacks. The joint analysis of independent meteorological, soil moisture and land cover measurements, without the use of a model, in the former Soviet Union provides a unique look at soil moisture-climate relationships at seasonal to interannual timescales. Averaged data over the growing season show a strong consistency between soil moisture and precipitation over grassland dominant regions, suggesting that precipitation anomalies are a dominant control of soil moisture at interannual timescales. Investigation of soil moisture persistence at the seasonal timescale shows a strong correlation between soil moisture in spring and the subsequent precipitation in summer over forest dominant regions and between cold season precipitation accumulation in winter and soil moisture in the following spring. Our findings can be explained by the theory proposed by Koster and Suarez (2001) and are consistent with the results from other modeling studies. Although it is hard to obtain the statistical meaningful conclusions because of the short data records, our results show the potential role of vegetation and cold season processes in land-atmosphere interactions. Further modeling studies and analyses using long in situ data records are necessary to fully verify our results.

Dong, Jiarui; Ni-Meister, Wenge; Houser, Paul R.

2007-05-01

146

Microbiology and Moisture Uptake of Desert Soils  

NASA Astrophysics Data System (ADS)

We have initiated an interdisciplinary study of the microbiology and water content of desert soils to better understand microbial activity in extreme arid environments. Water is the one constituent that no organism can live without; nevertheless, there are places on Earth with an annual rainfall near zero that do support microbial ecosystems. These hyperarid deserts (e.g. Atacama and the Antarctic Dry Valleys) are the closest terrestrial analogs to Mars, which is the subject of future exploration motivated by the search for life beyond Earth. We are modeling the moisture uptake by soils in hyperarid environments to quantify the environmental constraints that regulate the survival and growth of micro-organisms. Together with the studies of moisture uptake, we are also characterizing the microbial population in these soils using molecular and culturing methods. We are in the process of extracting DNA from these soils using MoBio extraction kits. This DNA will be used as a template to amplify bacterial and eukaryotic ribosomal DNA to determine the diversity of the microbial population. We also have been attempting to determine the density of organisms by culturing on one-half strength R2A agar. The long-range goal of this research is to identify special adaptations of terrestrial life that allow them to inhabit extreme arid environments, while simultaneously quantifying the environmental parameters that enforce limits on these organisms' growth and survival.

Kress, M. E.; Bryant, E. P.; Morgan, S. W.; Rech, S.; McKay, C. P.

2005-12-01

147

SMOS rehearsal campaign 2008: Data analysis and soil moisture retrieval using the L-MEB model at the Upper Danube anchor site  

NASA Astrophysics Data System (ADS)

In spring 2008 the SMOS rehearsal campaign took place over parts of Europe. Within the Upper Danube anchor test site, situated mainly in southern Germany, extensive ground based measurements of soil moisture and other parameters were taken in addition to the airborne L-band radiometer data collected. Within the framework of SMOS cal/val activities at the Upper Danube anchor site a coupled SVAT-radiative transfer model was developed for modelling soil moisture and the resulting microwave emissions. In the present study it is used to retrieve soil moisture from the radiometer data. The hydrological processes are simulated with the SVAT model PROMET, whilst the microwave emission of the land areas are simulated using the L-MEB model which is also part of ESA's SMOS Level 2 processor. To study the sensitivity of the radiometer data to the measured soil moisture and to test the L-MEB retrieval performance a soil moisture retrieval of the radiometer data is performed using an iterative inversion approach. First results of the soil moisture retrieval are discussed and presented. Comparisons of the retrieved soil moisture against ground measurements are given and the uncertainty assessed.

Schlenz, F.; Loew, A.; Dall'Amico, J.; Mauser, W.

2009-04-01

148

Quantifying mesoscale soil moisture with the cosmic-ray rover  

NASA Astrophysics Data System (ADS)

Soil moisture governs the surface fluxes of mass and energy and is a major influence on floods and drought. Existing techniques measure soil moisture either at a point or over a large area many kilometers across. To bridge these two scales we used the cosmic-ray rover, an instrument similar to the recently developed COSMOS probe, but bigger and mobile. This paper explores the challenges and opportunities for mapping soil moisture over large areas using the cosmic-ray rover. In 2012, soil moisture was mapped 22 times in a 25 km × 40 km survey area of the Tucson Basin at 1 km2 resolution, i.e., a survey area extent comparable to that of a pixel for the Soil Moisture and Ocean Salinity (SMOS) satellite mission. The soil moisture distribution is dominated by climatic variations, notably by the North American monsoon, that results in a systematic increase in the standard deviation, observed up to 0.022 m3 m-3, as a function of the mean, between 0.06 and 0.14 m3 m-3. Two techniques are explored to use the cosmic-ray rover data for hydrologic applications: (1) interpolation of the 22 surveys into a daily soil moisture product by defining an approach to utilize and quantify the observed temporal stability producing an average correlation coefficient of 0.82 for the soil moisture distributions that were surveyed and (2) estimation of soil moisture profiles by combining surface moisture from satellite microwave sensors with deeper measurements from the cosmic-ray rover. The interpolated soil moisture and soil moisture profile estimates allow for basin-wide mass balance calculation of evapotranspiration, totaling 241 mm for the year 2012. Generating soil moisture maps with cosmic-ray rover at this intermediate scale may help in the calibration and validation of satellite campaigns and may also aid in various large scale hydrologic studies.

Chrisman, B.; Zreda, M.

2013-06-01

149

Impact of soil hydraulic parameter uncertainty on soil moisture modeling  

Microsoft Academic Search

the geographical origin of a PTF has a high impact on the pdf of the SHPshigher-order moments should be included when assessing the soil moisture pdfcentral point is an alternative to standard SHPs to determine an average SHP set

Lien Loosvelt; Valentijn R. N. Pauwels; Wim M. Cornelis; Gabriëlle J. M. De Lannoy; Niko E. C. Verhoest

2011-01-01

150

Temporal dynamics and spatial heterogeneity of soil moisture in a northern temperate deciduous forest  

NASA Astrophysics Data System (ADS)

Soil moisture in forest environments is variable both in time and space, strongly influencing water and energy fluxes between the land surface and the atmosphere. However, few continuous, deep profile soil moisture datasets exist for temperate forest environments. Our study has initiated measurements of soil moisture in a heterogeneous deciduous forest environment of Northern Michigan in April 2009. Our research site is at the Forest Accelerated Succession ExperimenT (FASET) at the University of Michigan Biological Station (UMBS) where canopy structure was manipulated to represent a large disturbance and a successional phase shift by girdling all mid-successional canopy-dominant aspen and birch trees over 33 Ha. The nearby UMBS-AmeriFlux tower site serves as the un-manipulated control. In total, forty four sensors were deployed at four different locations. They provide half-hourly data on soil water content and temperature over the 3m-deep profiles at multiple depths ( 5, 15, 30, 60, 100, 200 and 300cm). In this study, we examine the temporal dynamics of deep-profile soil moisture and correlation between near-surface and deeper layer soil moisture. Through the analysis of data over the observational period we demonstrate that soil moisture was influenced by differences in canopy structure. Specifically, deep soil moisture (integrated over the root zone or deeper than 300 cm) has been consistently larger at the experimental than at the control site. Furthermore, correlation analysis between near-surface soil moisture and deeper layer soil moisture over the four sites provides inferences pointing to the non-uniqueness of the relationship that has an important implication for remotely sensed near-surface soil moisture. In addition to continuous point measurements, periodic observations of near-surface soil moisture during growing-season were conducted at two nested 50m X 50m plots and at long transects in the footprints of the AmeriFlux and FASET towers. This dataset was used to characterize the evolution of spatial heterogeneity of soil moisture states in the forest environment. By combining high resolution point-scale soil moisture profile data with periodic near-surface soil moisture measurements, this study has also examined the representativeness of point-scale measurement with regards to the spatially mean soil moisture state.

He, L.; Ivanov, V. Y.; Vogel, C. S.; Bohrer, G.; Moghaddam, M.

2010-12-01

151

Soil moisture-vegetation-precipitation feedback over North America: Its sensitivity to soil moisture climatology  

NASA Astrophysics Data System (ADS)

Our previous studies examined how vegetation feedback at the seasonal time scale influenced the impact of soil moisture anomalies (SMAs) on subsequent summer precipitation with a modified version of the coupled Community Atmosphere Model-Community Land Model 3 that includes a predictive phenology scheme. Here we investigate the climatology sensitivity of soil moisture-vegetation-precipitation feedback using the same model as the baseline model (BASE) and its derivative with modifications to the model runoff parameterization as the experiment model (EXP), in which we eliminate the subsurface lateral drainage to reduce the known dry biases of BASE. With vegetation feedback ignored, precipitation is more sensitive to wet SMAs than dry SMAs in BASE; opposite to BASE, the wetter mean soil moisture in EXP leads to higher sensitivity of precipitation to dry SMAs than to wet SMAs. However, in both BASE and EXP, the impact of dry SMAs on subsequent precipitation persists longer than the impact of wet SMAs. With vegetation feedback included, EXP shows a positive feedback between vegetation and precipitation following both dry and wet SMAs in summer, while BASE shows a positive feedback following wet SMAs only, with no clear signal following dry SMAs due to dry soil biases. In BASE, the magnitude of precipitation changes due to vegetation feedback is comparable to that due to soil moisture feedback when more realistic SMAs are applied. In addition, a major difference is found in spring when the vegetation impact on subsequent precipitation is negative and significant in BASE, but not significant in EXP.

Kim, Yeonjoo; Wang, Guiling

2012-09-01

152

3.6 INVERSE ESTIMATION OF SOIL MOISTURE AND SURFACE ENERGY BUDGET FROM IN-SITU SOIL TEMPERATURE DATA  

Microsoft Academic Search

Because soil thermal properties depend on soil moisture, soil temperature is strongly controlled by soil moisture. This provides a possibility to derive soil moisture from soil temperature measurements. Following this motive, this study develops a system to inversely estimate soil moisture profile from soil temperature profile. The forward model is a single-source land surface model to simulate land surface and

Kun Yang; Toshio Koike; Baisheng Ye

2004-01-01

153

Soil moisture profile variability in land-vegetation- atmosphere continuum  

Microsoft Academic Search

Soil moisture is of critical importance to the physical processes governing energy and water exchanges at the land-air boundary. With respect to the exchange of water mass, soil moisture controls the response of the land surface to atmospheric forcing and determines the partitioning of precipitation into infiltration and runoff. Meanwhile, the soil acts as a reservoir for the storage of

Wanru Wu

2000-01-01

154

Root Zone Soil Moisture Forecasting Using Multivariate Relevance Vector Machines  

Microsoft Academic Search

Root zone soil moisture at depths of 1 and 2 meters are forecasted four days into the future. Prediction of soil moisture can be of paramount importance owing to its applicability in soil water balance calculations, modeling of various hydrometeorological, ecological, and biogeochemical factors, and initialization of various land-atmosphere models. In this study, we propose a new multivariate output prediction

B. Zaman; M. McKee

2009-01-01

155

Volatilization of EPTC as affected by soil moisture  

Microsoft Academic Search

Volatilization is an important process that controls the dissipation of pesticides after field application. Soil moisture plays an important role in controlling the volatilization of pesticides. However, the extent of this role is unclear. This study was conducted to determine how soil moisture affects the sorption capacity and vapor loss of EPTC (S-ethyl dipropyl carbamothioate) from two soils, Weswood clay

Liqun Fu

1998-01-01

156

Simulation of soil moisture and its variability in East Asia  

Microsoft Academic Search

Soil moisture and related hydrological process play an important role in regional and global climates. However, large-scale and long-term observation of soil moisture is sparse. In this study, the latest NCAR Community Land Model is used to simulate regional soil moisture in East Asia for recent 25 years with the atmospheric forcing provided by NCEP\\/DOE reanalysis. A 50-year simulation has

Chuanli Du; Wanli Wu; Xiaodong Liu; Wei Gao

2006-01-01

157

Propagation of soil moisture memory to runoff and evapotranspiration  

NASA Astrophysics Data System (ADS)

As a key variable of the land-climate system soil moisture is a main driver of runoff and evapotranspiration under certain conditions. Soil moisture furthermore exhibits outstanding memory (persistence) characteristics. Also for runoff many studies report distinct low frequency variations that represent a memory. Using data from over 100 near-natural catchments located across Europe we investigate in this study the connection between soil moisture memory and the respective memory of runoff and evapotranspiration on different time scales. For this purpose we use a simple water balance model in which dependencies of runoff (normalized by precipitation) and evapotranspiration (normalized by radiation) on soil moisture are fitted using runoff observations. The model therefore allows to compute memory of soil moisture, runoff and evapotranspiration on catchment scale. We find considerable memory in soil moisture and runoff in many parts of the continent, and evapotranspiration also displays some memory on a monthly time scale in some catchments. We show that the memory of runoff and evapotranspiration jointly depend on soil moisture memory and on the strength of the coupling of runoff and evapotranspiration to soil moisture. Furthermore we find that the coupling strengths of runoff and evapotranspiration to soil moisture depend on the shape of the fitted dependencies and on the variance of the meteorological forcing. To better interpret the magnitude of the respective memories across Europe we finally provide a new perspective on hydrological memory by relating it to the mean duration required to recover from anomalies exceeding a certain threshold.

Orth, R.; Seneviratne, S. I.

2012-10-01

158

Tibetan Plateau Soil moisture products Intercomparison and the field observations  

NASA Astrophysics Data System (ADS)

It is well known that soil moisture plays an important role in hydrological and climate modeling. With an average elevation exceeding 4,000, Tibetan Plateau land-surface water and energy cycles greatly influence the Asian Monsoon, and global atmosphere general circulations. A set of accurate soil moisture data of Tibetan Plateau can provide observational information for the studies of land-atmosphere interaction. In this paper, we firstly compared three categories of passive microwave remote sensing of soil moisture data sets using AMSR-E over Tibet Plateau with CEOP in situ observations of 6 stations. These three sets of soil moisture data included NASA NSIDC AMSR-E soil moisture products (Enjoku, et al., 2003), and NASA-VUA (the Vrije Universiteit Amsterdam) soil moisture products (Owe et al., 2008) and soil moisture data sets developed by CAS IRSA (Institute of Remote Sensing and Applications) of China (Shi et al, 2010). All the comparisons are for Year 2003, when the observational data was available. The results show that the soil moisture data set of CAS-IRSA is closer to the observations than NASA-VUA products. AMSR-E has the worst accuracy with little seasonal variation. NASA-VUA consistently overestimate soil moisture than the other two satellite products and in situ measurements. To look at the regional characteristics of the soil moisture products over the entire plateau, we areal-averaged soil moisture for an area covers latitude 25 °N to 38°N, and longitude from 77 °E to 98°E. NCEP reanalysis soil moisture data at 0-10cm with 1°spatial resolution, and soil moisture output from RAMS default run at 25 km spatial scale over Tibet plateau (Qi, et al., 2010) are also included in this comparison. The results show that soil moistures produced by NCEP reanalysis and RAMS have clear seasonal cycles, and are in good agreement with observations. NASA-VUA products displayed more realistic seasonal changes than CAS-IRSA product, but overestimate soil moisture at the regional scale. In summary, satellite remotely-sensed soil moisture products over Tibetan Plateau need to be further improved and evaluated before they can be useful for Tibetan Plateau climate related applications.

Qi, Y.; Lu, L.; Jiang, L.; Tao, J.; Du, J.; Shi, J.

2010-12-01

159

Footprint-scale soil moisture spatial-temporal variability and implications for satellite validation  

NASA Astrophysics Data System (ADS)

Soil moisture is an important boundary variable that controls land surface processes, including interactions with climate, weather, biogeochemical and ecological phenomena. Remote sensing will ultimately provide appropriate spatial coverage of moisture content fields for use in Earth system monitoring and research. However, considerable spatial variability in moisture content exists within remote sensing footprints, and errors in ground-based estimates of footprint means are largely unquantified. This research characterizes soil moisture variability within a number of aircraft- and satellite-footprint-scale sites and quantifies the related uncertainty in ground-based estimates of the footprint mean. The footprint sites are located in Iowa and Oklahoma, and are associated with the SGP97, SGP99, SMEX02, and SMEX03 experiments, which aimed to validate airborne (ESTAR, PSR) and space-borne (AMSR-E) microwave radiometers. In chapter 2, soil moisture spatial variability is characterized with varying surface wetness conditions across scales from 2.5 m to about 50 km. Ground-based soil moisture measurements from SGP and SMEX experiments are employed for the analysis. Results revealed a preferential pattern of soil moisture variability with mean moisture content and scale of the soil moisture field. In chapter 3, the scaling behavior of soil moisture variability with support scale was examined. The semi-variogram function of soil moisture was deployed to reproduce log variance versus log support. Results indicated the existence of a multi-scale nested correlation structure of soil moisture, which resulted in a piece-wise decaying pattern of log variance with increasing log support. In chapter 4, high-resolution soil moisture images from airborne radiometers were utilized to characterize more detailed features of footprint-scale soil moisture distributions. A mixture of Gaussian distributions was proposed to fit the observed footprint-scale soil moisture distributions and the benefits of the mixture model were discussed. In chapter 5, ground-based measurements of soil moisture were combined with the antecedent precipitation index (API) to improve the accuracy of validation data. Ground-based validation data from a limited number of samples were improved by utilizing the API with a Gaussian mixture model. However, direct upscaling of point measurements by correcting bias of the API did not improve the accuracy of the footprint-scale mean estimate. Implications of the results of this study and suggestions for future research are presented in chapter 6.

Ryu, Dongryeol

160

Root zone soil moisture from the assimilation of screen-level variables and remotely sensed soil moisture  

Microsoft Academic Search

In most operational NWP models, root zone soil moisture is constrained using observations of screen-level temperature and relative humidity. While this generally improves low-level atmospheric forecasts, it often leads to unrealistic model soil moisture. Consequently, several NWP centers are moving toward also assimilating remotely sensed near-surface soil moisture observations. Within this context, an EKF is used to compare the assimilation

C. S. Draper; J.-F. Mahfouf; J. P. Walker

2011-01-01

161

Entropy theory for movement of moisture in soils  

NASA Astrophysics Data System (ADS)

An entropy theory is formulated for one-dimensional movement of moisture in unsaturated soils in the vertically downward direction. The theory is composed of five parts: (1) Tsallis entropy, (2) principle of maximum entropy, (3) specification of information on soil moisture in terms of constraints, (4) maximization of the Tsallis entropy, and (5) derivation of the probability distributions of soil moisture. The theory is applied to determine the soil moisture profile under three conditions: (1) the moisture is maximum at the soil surface and decreases downward to a minimum value at the bottom of the soil column (it may be near the water table); (2) the moisture is minimum at the soil surface and increases downward to a maximum value at the end of the soil column (this case is the opposite of case 1); and (3) the moisture at the soil surface is low and increases downward up to a distance and then decreases up to the bottom (this case combines case 2 and case 1). The entropy-based soil moisture profiles are tested using experimental observations reported in the literature, and properties of these profiles are enumerated.

Singh, Vijay P.

2010-03-01

162

Passive microwaves for soil moisture monitoring  

NASA Astrophysics Data System (ADS)

Since SMMR launched in 1978) to SMOS (launched in 2009) several missions have attempted describing the soil moisture, an important component of the water cycle. This could be a unique data set to see climatic trends, if coupled with other means as all the sensors (namely SMMR, SSM/I, ERS SCAT, Envisat ASCAT, AMSR, and now SMOS) have different times of over pass, different frequencies and possibluy even different measurement approaches. The rationale here is to inter-calibrate all the sensors available and try to operate a seamless transition correcting all the artifacts. The paper presents our two prong approach. On one hand we intercalibrate using reference targets the SMMR - SSM/I - AMSR series, deriving an empirical adjustment law for time of over pass and slight frequency differences, while, on the other hand we inter-compare over well monitored sites the behaviour of all available sensors and possibly algorithms. Finally, in the framework of the preparation of the SMOS mission we analyse over a reference site different ways to spatialise point information of a smos like pixel. During the oral presentation we will give the results gained through this approach and the problems encountered as well as potential ways to solve them. The results are intercompared with other similar approaches and long term soil moisture evolution shown on different areas.

Kerr, Yann; Leroux, Delphine; Juglea, Silvia; Gruhier, Claire; Mialon, Arnaud; Cabot, François

2010-05-01

163

Dissecting soil moisture-precipitation coupling  

NASA Astrophysics Data System (ADS)

The ability of soil moisture to affect precipitation (SM-P) can be dissected into the ability of soil moisture to affect evapotranspiration (ET; SM-ET) and the ability of ET to affect precipitation (ET-P). SM-ET is a local process that is relatively easy to quantify, but ET-P includes nonlocal atmospheric processes and is more complex. Here, ET-P is quantified both locally and remotely with a back-trajectory method for water vapor transport, using corrected reanalysis data. It is found that, for SM-P and ET-P, local impact is greater than that from remote for most land areas with significant local impacts. By examining the responses of the three metrics (SM-ET, ET-P, and SM-P) to climate variations over different climate regimes, we show that SM-ET is the principal factor that determines the spatial pattern and variation of SM-P. For climatologically wet regions, SM-ET and SM-P are higher during dry periods, and vice versa for climatologically dry regions. All three metrics show highest values over the transitional zones.

Wei, Jiangfeng; Dirmeyer, Paul A.

2012-10-01

164

Spatial and temporal variability of soil moisture on the field with and without plants*  

NASA Astrophysics Data System (ADS)

Spatial and temporal variability of the natural environment is its inherent and unavoidable feature. Every element of the environment is characterized by its own variability. One of the kinds of variability in the natural environment is the variability of the soil environment. To acquire better and deeper knowledge and understanding of the temporal and spatial variability of the physical, chemical and biological features of the soil environment, we should determine the causes that induce a given variability. Relatively stable features of soil include its texture and mineral composition; examples of those variables in time are the soil pH or organic matter content; an example of a feature with strong dynamics is the soil temperature and moisture content. The aim of this study was to identify the variability of soil moisture on the field with and without plants using geostatistical methods. The soil moisture measurements were taken on the object with plant canopy and without plants (as reference). The measurements of soil moisture and meteorological components were taken within the period of April-July. The TDR moisture sensors covered 5 cm soil layers and were installed in the plots in the soil layers of 0-0.05, 0.05-0.1, 0.1-0.15, 0.2-0.25, 0.3-0.35, 0.4-0.45, 0.5-0.55, 0.8-0.85 m. Measurements of soil moisture were taken once a day, in the afternoon hours. For the determination of reciprocal correlation, precipitation data and data from soil moisture measurements with the TDR meter were used. Calculations of reciprocal correlation of precipitation and soil moisture at various depths were made for three objects - spring barley, rye, and bare soil, at the level of significance of p<0.05. No significant reciprocal correlation was found between the precipitation and soil moisture in the soil profile for any of the objects studied. Although the correlation analysis indicates a lack of correlation between the variables under consideration, observation of the soil moisture runs in particular objects and of precipitation distribution shows clearly that rainfall has an effect on the soil moisture. The amount of precipitation water that increased the soil moisture depended on the strength of the rainfall, on the hydrological properties of the soil (primarily the soil density), the status of the plant cover, and surface runoff. Basing on the precipitation distribution and on the soil moisture runs, an attempt was made at finding a temporal and spatial relationship between those variables, employing for the purpose the geostatistical methods which permit time and space to be included in the analysis. The geostatistical parameters determined showed the temporal dependence of moisture distribution in the soil profile, with the autocorrelation radius increasing with increasing depth in the profile. The highest values of the radius were observed in the plots with plant cover below the arable horizon, and the lowest in the arable horizon on the barley and fallow plots. The fractal dimensions showed a clear decrease in values with increasing depth in the plots with plant cover, while in the bare plots they were relatively constant within the soil profile under study. Therefore, they indicated that the temporal distribution of soil moisture within the soil profile in the bare field was more random in character than in the plots with plants. The results obtained and the analyses indicate that the moisture in the soil profile, its variability and determination, are significantly affected by the type and condition of plant canopy. The differentiation in moisture content between the plots studied resulted from different precipitation interception and different intensity of water uptake by the roots. * The work was financially supported in part by the ESA Programme for European Cooperating States (PECS), No.98084 "SWEX-R, Soil Water and Energy Exchange/Research", AO-3275.

Usowicz, B.; Marczewski, W.; Usowicz, J. B.

2012-04-01

165

A nonlinear coupled soil moisture-vegetation model  

NASA Astrophysics Data System (ADS)

Based on the physical analysis that the soil moisture and vegetation depend mainly on the precipitation and evaporation as well as the growth, decay and consumption of vegetation a nonlinear dynamic coupled system of soil moisture-vegetation is established. Using this model, the stabilities of the steady states of vegetation are analyzed. This paper focuses on the research of the vegetation catastrophe point which represents the transition between aridness and wetness to a great extent. It is shown that the catastrophe point of steady states of vegetation depends mainly on the rainfall P and saturation value v0, which is selected to balance the growth and decay of vegetation. In addition, when the consumption of vegetation remains constant, the analytic solution of the vegetation equation is obtained.

Liu, Shikuo; Liu, Shida; Fu, Zuntao; Sun, Lan

2005-06-01

166

Microwave Backscatter Dependence on Surface Roughness, Soil Moisture, and Soil Texture: Part II-Vegetation-Covered Soil  

Microsoft Academic Search

Results are presented of an experimental investigation to determine the relationship between radar backscatter coefficient ¿° and soil moisture for vegetation-covered soil. These results extend a previous report which showed the experimental relationship between ¿° and soil moisture for bare soil [1]. It is shown that the highest correlation between ¿° and soil moisture is 0.92 for the combined response

Fawwaz Ulaby; Gerald Bradley; Myron Dobson

1979-01-01

167

Soil moisture and temperature profile effects on microwave emission at low frequencies  

Microsoft Academic Search

Soil moisture and temperature vertical profiles vary quickly during the day and may have a significant influence on the soil microwave emission. The objective of this work is to quantify such an influence and the consequences in soil moisture estimation from microwave radiometric information. The analysis is based on experimental data collected by the ground-based PORTOS radiometer at 1.4, 5.05,

Suresh Raju; André Chanzy; Jean-Pierre Wigneron; Jean-Christophe Calvet; Yann Kerr; Laurent Laguerre

1995-01-01

168

Microwave Backscatter Dependence on Surface Roughness, Soil Moisture, and Soil Texture: Part I-Bare Soil  

Microsoft Academic Search

This is the first in a series of two papers on the use of active microwave remote sensing for measuring the moisture content of bare (Part I) and vegetation-covered (Part II) soil. An experimental program was conducted to evaluate the response of the backscattering coefficient to soil moisture content as a means to specify radar system parameters for future airborne

FAWWAZ T. ULABY; Percy Batlivala; Myron Dobson

1978-01-01

169

Airborne GPS bistatic radar soil moisture measurements during SMEX02  

Microsoft Academic Search

To further investigate the potential for remotely sensing soil moisture using the L-band GPS bistatic radar concept, a GPS bistatic radar participated for the first time in airborne measurements during the Soil Moisture Experiment 2002 (SMEX02) in Ames, Iowa. A 12 channel GPS navigation receiver was modified to perform bistatic radar measurements and mounted on the JPL PALS instrument. The

D. Masters; S. Katzberg; P. Axelrad

2003-01-01

170

Inflatable antenna microwave radiometer for soil moisture measurement  

Microsoft Academic Search

Microwave measurements of soil moisture are not being obtained at the required spatial Earth resolution with current technology. The Low Earth Orbit Microwave Radiometry Workshop held in Hampton, Virginia, identified measurements of soil moisture at a resolution of 10 km as the general science driver. Recently, new novel designs for lightweight reflector systems have been developed using deployable inflatable antenna

B. M. Kendall; M. C. Bailey; L. C. Schroeder

1995-01-01

171

A Computer-Based Soil Moisture Monitoring and Hydrating System  

Microsoft Academic Search

A computer-based soil moisture monitoring and hydrating system is described in this paper. This system is made of two major components: the sensing unit, and the main station. The sending unit can be located out in a lawn or field, while the main station can be located close to the sprinkler system control. This system provides soil moisture measurements, and

J.-N. Juang; D. U. Ekong; C. Carlson; W. Longsdorf; M. Miller

2007-01-01

172

WindSat Soil Moisture Algorithm and Validation  

Technology Transfer Automated Retrieval System (TEKTRAN)

A WindSat land algorithm that retrieves global soil moisture and vegetation water content simultaneously using the physically-based multi-channel maximum-likelihood estimation was developed and evaluated. The retrievals agree well with soil moisture climatology, and in-situ data collected from a ser...

173

Remote Sensing of Soil Moisture With Microwave Radiometers  

Microsoft Academic Search

Microwave radiometry has been used for the remote sensing of soil moisture in a series of aircraft flights over an agricultural test area in the vicinity of Phoenix, Arizona. The radiometers covered the wavelength range 0.8-21 cm. Ground truth in the form of gravimetric measurements of the soil moisture in the top 15 cm were obtained for 200 fields at

T. Schmugge; P. Gloersen; T. Wilheit; F. Geiger

1974-01-01

174

Satellite remote sensing of soil moisture in Illinois, United States  

Microsoft Academic Search

To examine the utility of using satellite passive microwave observations to measure soil moisture over large regions, we conducted a pilot study using the scanning multichannel microwave radiometer (SMMR) on Nimbus-7, which operated from 1978 to 1987, and actual in situ soil moisture observations from the state of Illinois, United States, which began in 1981. We examined SMMR midnight microwave

Konstantin Y. Vinnikov; Alan Robock; Shuang Qiu; Jared K. Entin; Manfred Owe; Bhaskar J. Choudhury; Steven E. Hollinger; Eni G. Njoku

1999-01-01

175

SOIL MOISTURE EXPERIMENTS 2004 AND 2005 RESULTS AND PLANS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Soil Moisture Experiments (SMEX) series of field campaigns was designed to address research priorities of several programs involving satellite remote sensing of surface soil moisture. These include the Advanced Scanning Microwave Radiometer (AMSR) on Aqua, the Windsat on Coriolis, and future mis...

176

The Soil Moisture and Ocean Salinity Mission - An Overview  

Microsoft Academic Search

The Soil Moisture and Ocean Salinity (SMOS) mission is the European Space Agency's (ESA) second Earth Explorer Opportunity mission. The scientific objectives of the SMOS mission directly respond to the current lack of global observations of soil moisture and ocean salinity, two key variables used in predictive hydrological, oceanographic and atmospheric models. The paper will give an overview on the

Susanne Mecklenburg; Yann Kerr; Achim Hahne

2008-01-01

177

An adaptive ensemble Kalman filter for soil moisture data assimilation  

Microsoft Academic Search

In a 19-year twin experiment for the Red-Arkansas river basin we assimilate synthetic surface soil moisture retrievals into the NASA Catchment land surface model. We demonstrate how poorly specified model and observation error parameters affect the quality of the assimilation products. In particular, soil moisture estimates from data assimilation are sensitive to observation and model error variances and, for very

Rolf H. Reichle; Wade T. Crow; Christian L. Keppenne

2008-01-01

178

Estimating soil moisture based on image processing technologies  

Microsoft Academic Search

Soil moisture is a critical factor to crop growth. Due to the facts of drought and less rain in northern China, it is necessary to introduce water controlled irrigating. Therefore, estimating soil moisture distribution rapidly and accurately is very important for decision making of water saving irrigating. This study took a farmland in Beijing as the experiment field. The aerial

Lihua Zheng; Minzan Li; Jianying Sun; Xijie Zhang; Peng Zhao

2005-01-01

179

The Soil Moisture Active/Passive Mission (SMAP)  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Soil Moisture Active/Passive (SMAP) mission will deliver global views of soil moisture content and its freeze/thaw state that are critical terrestrial water cycle state variables. Polarized measurements obtained with a shared antenna L-band radar and radiometer system will allow accurate estima...

180

Integrated Measurement of Soil Moisture by Use of Radio Waves.  

National Technical Information Service (NTIS)

An integrated value of soil moisture can be determined by measuring the attenuation of vertically-polarized surface radio waves that are propagated over the ground between a transmitting and receiving antenna. Soil moisture values in the root-zone region ...

D. G. Chadwick

1973-01-01

181

Soil Moisture and the Persistence of North American Drought  

Microsoft Academic Search

We describe numerical sensitivity experiments exploring the effects of soil moisture on North American summertime climate using the NCAR CCMI, a 12-layer global atmospheric general circulation model. In particular. the hypothesis that reduced soil moisture may help induce and amplify warm, dry summers over midlatitude continental interiors is examined. Equilibrium climate statistics are computed for the perpetual July model response

Robert J. Oglesby; David J. Erickson III

1989-01-01

182

Exploiting equilibrium tendencies of soil moisture dynamics for parameter estimation  

Microsoft Academic Search

dt ) conditioned on mois- ture level is equal to zero. Applying this principle to the water balance equations allows direct, empirical estimation of the relation between soil moisture and total water loss (the sum of drainage d, evapotranspiration et, and runoff ro) from precipitation measurements conditionally averaged according to soil moisture level; and (2) the variance of the sum

Guido D. Salvucci; Marisa Gioiso

183

Soil Moisture and Drought Variability in the Upper Colorado River Basin  

NASA Astrophysics Data System (ADS)

This research investigates the interannual variability of soil moisture as related to large-scale climate variability. In addition, a study of the spatial and temporal soil moisture in the Upper Colorado River Basin is presented. A three layer hydrological model VIC-3L (Variable Infiltration Capacity Model C 3 layers) was used in the Upper Colorado River Basin over a 50-year period. Model calibration was conducted between the VIC-3L modeled streamflow and observed streamflow from five stations. Model verification was analyzed by comparing calculated soil moisture from the VIC-3L model with that from the Climate Prediction Center (CPC). Using wavelet analysis, deep soil moisture was compared to the Palmer Drought Severity Index (PDSI), precipitation, and streamflow to determine whether deep soil moisture is an indicator of climate extremes. Wavelet and coherency analysis for the Upper Colorado River Basin indicated a strong relationship between the PDSI, climate variability and the deep soil moisture. Lastly, the spatial and temporal soil moisture were analyzed by GIS map analysis, linear correlation, and t-test methods.

Tang, C.; Piechota, T.

2006-12-01

184

Validation of soil moisture in Brazil using SMEX03 data  

NASA Astrophysics Data System (ADS)

The goal of this work was to validate surface soil moisture products as derived from Advanced Microwave Scanning Radiometer - AMSR-E (C and X bands) sensor observations for cerrado region in Brazil, using Soil Moisture Experiment 2003 (SMEX03) data. These data were collected in Barreiras city, Bahia state, during the first two weeks of December 2003. The soil moisture derived from AMSR-E sensor was retrieved from the Land Parameter Retrieval Model (LPRM), which was developed by researchers from NASA and the Vrije University Amsterdam. The comparison of time series of the soil moisture showed that the AMSR-E C band and observational data set both give a similar seasonal pattern for cerrado region, presenting a high coefficient of determination (R) for C and X bands. From the results we concluded that the region with cerrado vegetation has a strong potential to retrieve reliable surface soil moisture.

Rossato, L.; de Jeu, R.; Alvalá, R.

2009-04-01

185

SOIL TEMPERATURE AND FALL FREEZE-THAW EFFECTS ON INFILTRATION AND SOIL MOISTURE MOVEMENT  

Microsoft Academic Search

The quantity of spring snowmelt infiltration and runoff depends on the antecedent soil moisture conditions at the time of soil freezing. Determining the soil moisture status at any particular time during the freezing process requires an understanding of vertical distribution of liquid and frozen water content within the soil profile. This study investigated the effects of soil freezing and thawing

F. C. Kahimba

2006-01-01

186

What is the philosophy of modelling soil moisture movement?  

NASA Astrophysics Data System (ADS)

In laboratory, the soil moisture movement in the different soil textures has been analysed. From field investigation, at a spot, the soil moisture movement in the root zone, vadose zone and shallow aquifer has been explored. In addition, on ground slopes, the interflow in the near surface soil layers has been studied. Along the regions near river reaches, the expansion and shrink of the saturated area due to rainfall occurrences have been observed. From those previous explorations regarding soil moisture movement, numerical models to represent this hydrologic process have been developed. However, generally, due to high heterogeneity and stratification of soil in a basin, modelling soil moisture movement is rather challenging. Normally, some empirical equations or artificial manipulation are employed to adjust the soil moisture movement in various numerical models. In this study, we inspect the soil moisture movement equations used in a watershed model, SWAT (Soil and Water Assessment Tool) (Neitsch et al., 2005), to examine the limitations of our knowledge in such a hydrologic process. Then, we adopt the features of a topographic-information based on a hydrologic model, TOPMODEL (Beven and Kirkby, 1979), to enhance the representation of soil moisture movement in SWAT. Basically, the results of the study reveal, to some extent, the philosophy of modelling soil moisture movement in numerical models, which will be presented in the conference. Beven, K.J. and Kirkby, M.J., 1979. A physically based variable contributing area model of basin hydrology. Hydrol. Science Bulletin, 24: 43-69. Neitsch, S.L., Arnold, J.G., Kiniry, J.R., Williams, J.R. and King, K.W., 2005. Soil and Water Assessment Tool Theoretical Documentation, Grassland, soil and research service, Temple, TX.

Chen, J.; Wu, Y.

2009-12-01

187

Dependence of Soil Respiration on Soil Temperature and Soil Moisture in Successional Forests in Southern China  

Microsoft Academic Search

The spatial and temporal variations in soil respiration and its relationship with biophysical factors in for- ests near the Tropic of Cancer remain highly uncertain. To contribute towards an improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured in three succes- sional subtropical forests at the Dinghushan Nature Reserve (DNR) in southern China from March

Xu-Li Tang; Guo-Yi Zhou; Shu-Guang Liu; De-Qiang Zhang; Shi-Zhong Liu; Jiong Li; Cun-Yu Zhou

2006-01-01

188

Soil moisture retrieval from space: the Soil Moisture and Ocean Salinity (SMOS) mission  

Microsoft Academic Search

Microwave radiometry at low frequencies (L-band: 1.4 GHz, 21 cm) is an established technique for estimating surface soil moisture and sea surface salinity with a suitable sensitivity. However, from space, large antennas (several meters) are required to achieve an adequate spatial resolution at L-band. So as to reduce the problem of putting into orbit a large filled antenna, the possibility

Yann H. Kerr; Philippe Waldteufel; Jean-Pierre Wigneron; Jean-Michel Martinuzzi; Michael Berger

2001-01-01

189

The areal distribution of soil moisture under sprinkler irrigation  

Microsoft Academic Search

The areal distributions of soil water content under varying uniformities of sprinkler water application were observed on two different soil types, to quantify the relationship between the subsurface distribution of soil moisture and water application on the ground surface. Field experimental results showed evidence of the importance of redistribution of the unevenly applied surface water. The water within the soil

Jiusheng Li; Hiroshi Kawano

1996-01-01

190

Assimilation of streamflow and in situ soil moisture data into operational distributed hydrologic models: Effects of uncertainties in the data and initial model soil moisture states  

NASA Astrophysics Data System (ADS)

We assess the potential of updating soil moisture states of a distributed hydrologic model by assimilating streamflow and in situ soil moisture data for high-resolution analysis and prediction of streamflow and soil moisture. The model used is the gridded Sacramento (SAC) and kinematic-wave routing models of the National Weather Service (NWS) Hydrology Laboratory's Research Distributed Hydrologic Model (HL-RDHM) operating at an hourly time step. The data assimilation (DA) technique used is variational assimilation (VAR). Assimilating streamflow and soil moisture data into distributed hydrologic models is new and particularly challenging due to the large degrees of freedom associated with the inverse problem. This paper reports findings from the first phase of the research in which we assume, among others, perfectly known hydrometeorological forcing. The motivation for the simplification is to reduce the complexity of the problem in favour of improved understanding and easier interpretation even if it may compromise the goodness of the results. To assess the potential, two types of experiments, synthetic and real-world, were carried out for Eldon (ELDO2), a 795-km 2 headwater catchment located near the Oklahoma (OK) and Arkansas (AR) border in the U.S. The synthetic experiment assesses the upper bound of the performance of the assimilation procedure under the idealized conditions of no structural or parametric errors in the models, a full dynamic range and no microscale variability in the in situ observations of soil moisture, and perfectly known univariate statistics of the observational errors. The results show that assimilating in situ soil moisture data in addition to streamflow data significantly improves analysis and prediction of soil moisture and streamflow, and that assimilating streamflow observations at interior locations in addition to those at the outlet improves analysis and prediction of soil moisture within the drainage areas of the interior stream gauges and of streamflow at downstream cells along the channel network. To assess performance under more realistic conditions, but still under the assumption of perfectly known hydrometeorological forcing to allow comparisons with the synthetic experiment, an exploratory real-world experiment was carried out in which all other assumptions were lifted. The results show that, expectedly, assimilating interior flows in addition to outlet flow improves analysis as well as prediction of streamflow at stream gauge locations, but that assimilating in situ soil moisture data in addition to streamflow data provides little improvement in streamflow analysis and prediction though it reduces systematic biases in soil moisture simulation.

Lee, Haksu; Seo, Dong-Jun; Koren, Victor

2011-12-01

191

On the effects of hydrological model structure on soil moisture data assimilation  

NASA Astrophysics Data System (ADS)

Nowadays, satellite sensors allow obtaining soil moisture estimates at global scale with an adequate temporal and spatial resolution, thereby offering a theoretical chance to improve flood-forecasting systems based on rainfall-runoff models. In fact, the knowledge of antecedent soil moisture conditions plays a crucial role in predicting catchment response to rainfall events. In the literature, several studies have focused on the assimilation of soil moisture data into hydrological models. The results of these studies tend to show that an improvement in discharge and soil moisture forecasts can be obtained when the assimilated information originates from accurate in situ measurements. When dealing with the assimilation of remote sensing-derived soil moisture data, the reported results are more controversial. There is no doubt that the performances of soil moisture data assimilation studies depend on many factors: data assimilation scheme, hydrological model structure, accuracy and resolution of soil moisture data. As of today, these dependences are not well understood and the disparity of outcomes in past studies arguably reflects the differences in the design of the experiments. In this general context, the aim of this study is to investigate the effects of hydrological model structures on soil moisture data assimilation performance. The analysis focuses on the vertical "stratification" of the soil column in a conceptual hydrological model. We consider multiple structures that differ by the number of soil reservoirs and their respective sizes. The recently introduced SUPERFLEX hydrological modelling framework is used to this end. In fact, this framework allows building and modifying multiple hydrological models by combining three basic building blocks: reservoirs, lag functions and junctions. As a data assimilation scheme, the particle filter was considered. The area of interest is the Alzette catchment (1200 km2), located in Luxembourg, while the analysed period spans from 2005 to 2011. The results of our study provide some insights on model structure requirements supporting an optimal usage of in situ measured and remotely sensed soil moisture data for operational hydrology.

Corato, Giovanni; Matgen, Patrick; Giustarini, Laura; Fenicia, Fabrizio

2013-04-01

192

Geophysical mapping of variations in soil moisture  

NASA Astrophysics Data System (ADS)

The geophysical investigation of soil characteristics is a matter of great actuality for agricultural, hydrogeological, geotechnical or archaeological purposes. The geophysical mapping of soil quality is subject of a recently started scientific project in Romania: "Soil investigation and monitoring techniques - modern tools for implementing the precision agriculture in Romania - CNCSIS 998/2009". One of the first studied soil parameter is moisture content, in irrigated or non-irrigated agricultural areas. The geophysical techniques employed in two areas located within the Romanian Plain, Prahova and Buzau counties, are the following: - electromagnetic (EM), using the EM38B (Geonics) conductivity meter for getting areal distribution of electric conductivity and magnetic susceptibility; - electric resistivity tomography (ERT), using the SuperSting (AGI) multi-electrode instrument for getting in-depth distribution of electric resistivity. The electric conductivity mapping was carried out on irrigated cultivated land in a vegetable farm in the Buzau county, the distribution of conductivity being closely related to the soil water content due to irrigation works. The soil profile is represented by a chernozem with the following structure: Am (0 - 40 cm), Bt (40-150 cm), Bt/C (150-170 cm), C (starting at 170 cm). The electromagnetic measurements showed large variations of this geophysical parameter within different cultivated sectors, ranging from 40 mS/m to 85 mS/m. The close association between conductivity and water content in this area is illustrated by such geophysical measurements on profiles situated at ca 50 m on non-irrigated land, displaying a mean value of 15 mS/m. This low conductivity is due to quite long time interval, of about three weeks, without precipitations. The ERT measurements using multi-electrode acquisition systems for 2D and 3D results, showed by means of electric resistivity variations, the penetration of water along the cultivated rows from the drip system. The mean depth of water penetration is about 0.5 m, while the depth level where the irrigation water is accumulating in a continuous wet layer is about 0.7 m. Magnetic susceptibility measurements performed on the soil profile in this area showed highest values on the Am layer, an important decrease within the Bt layer, followed by a weak increase toward the C layer. Electric conductivity and magnetic susceptibility measurements were carried out on profiles crossing non-irrigated cultivated areas in the Prahova county. The variations of electric conductivity, ranging between 10 and 30 mS/m is considered to be related mainly to the moisture content. Highest values of electric conductivity, greater than 50 mS/m, correlated with anomalies of magnetic susceptibility, were recorded over buried metallic pipes of various sizes, the cultivated land being located between an oil refinery and green-houses.

Ioane, Dumitru; Scradeanu, Daniel; Chitea, Florina; Garbacea, George

2010-05-01

193

Is Regional Root Reinforcement Controlled by Soil Moisture Variability?  

NASA Astrophysics Data System (ADS)

Climate change will alter the amount, type (i.e., snow vs. rain), and timing of precipitation that controls many hazardous Earth surface processes, including debris flows. Most GCMs agree that as climate warms the frequency of extreme precipitation will increase across the globe. Debris flow events triggered by heavy precipitation will likely also increase. Precipitation also affects the resistance to debris flow initiation by controlling belowground plant hydraulic architecture (e.g. root frequency, diameter distribution, tensile strength). Quantifying the links between precipitation, below ground properties, and the processes that initiate debris flows are therefore critical to understanding future hazard. To explore these links, we conducted a field experiment in the Coweeta Hydrologic Laboratory by excavating 12 soil pits (~1 m3), from two topographies (noses, hollows), and two tree species (Liriodendron tulipifera and Betula lenta). For each species and topography, we collected all biomass from five soil depths and measured soil moisture at 30, 60, and 90cm depth. For each depth we also measured root tensile strength, root cellulose content. Where we collected soil moisture data, we also measured root and soil hydraulic conductivity. Our data show a link between soil moisture content and root biomass distribution; root biomass is more evenly distributed through the soil column in hollows compared to noses. This relationship is consistent with the hypothesis that more consistent soil moisture in hollows allows plant roots to access resources from deeper within the soil column. This physiologic control has a significant effect on root cohesion, with trees on noses (or lower average soil moisture) providing greater root cohesion close to the surface, but considerably less cohesion at depth. Root tensile strength correlated with local daily soil moisture rather than the long term differences represented by noses and hollows. Daily soil moisture affected the amount of "bound water" (water present in the cell wall), which in turn affected the strength of the cellulose fibrils that provide tensile strength. This phenomenon, which is the reason any wet wood is weaker than dry wood, results in a 50% difference in root tensile strength within the range of soil moisture measured in the field. We used a one-dimensional finite difference model to explore the effects of soil moisture on root cohesion. Our model shows that changes in the distribution of root biomass represent the primary control on root cohesion (representing up to 50% of intra-specific variability in root cohesion). Local changes in soil moisture result in ~20% change in the overall root cohesion. Our work suggest a feed-forward process in precipitation (and thus soil moisture), root strength changes, and debris flow hazard.

Hales, T.; Ford, C. R.

2011-12-01

194

Evaluation of ECMWF's soil moisture analyses using observations on the Tibetan Plateau  

NASA Astrophysics Data System (ADS)

An analysis is carried out for two hydrologically contrasting but thermodynamically similar areas on the Tibetan Plateau, to evaluate soil moisture analysis based on the European Centre for Medium-Range Weather Forecasts (ECMWF) previous optimum interpolation scheme and the current point-wise extended Kalman filter scheme. To implement the analysis, this study used two regional soil moisture and soil temperature networks (i.e., Naqu and Maqu) on the Tibetan Plateau. For the cold-semiarid Naqu area, both ECMWF soil moisture analyses significantly overestimate the regional soil moisture in the monsoon seasons. For the cold-humid Maqu network area, the ECMWF products have comparable accuracy as reported by previous studies in the humid monsoon period. The comparisons were made among the liquid soil moisture analysis from ECMWF, the ground station's measurements and the satellite estimates from the Advanced Scatterometer sensor. The results show reasonable performances of the ECMWF soil moisture analyses (i.e., both optimum interpolation and extended Kalman filter products) and the Advanced Scatterometer level 2 products, when compared to the in situ measurements.

Su, Z.; Rosnay, P.; Wen, J.; Wang, L.; Zeng, Y.

2013-06-01

195

Soil moisture estimation in a semiarid watershed using RADARSAT-1 satellite imagery and genetic programming  

NASA Astrophysics Data System (ADS)

Soil moisture is a critical element in the hydrological cycle especially in a semiarid or arid region. Point measurement to comprehend the soil moisture distribution contiguously in a vast watershed is difficult because the soil moisture patterns might greatly vary temporally and spatially. Space-borne radar imaging satellites have been popular because they have the capability to exhibit all weather observations. Yet the estimation methods of soil moisture based on the active or passive satellite imageries remain uncertain. This study aims at presenting a systematic soil moisture estimation method for the Choke Canyon Reservoir Watershed (CCRW), a semiarid watershed with an area of over 14,200 km2 in south Texas. With the aid of five corner reflectors, the RADARSAT-1 Synthetic Aperture Radar (SAR) imageries of the study area acquired in April and September 2004 were processed by both radiometric and geometric calibrations at first. New soil moisture estimation models derived by genetic programming (GP) technique were then developed and applied to support the soil moisture distribution analysis. The GP-based nonlinear function derived in the evolutionary process uniquely links a series of crucial topographic and geographic features. Included in this process are slope, aspect, vegetation cover, and soil permeability to compliment the well-calibrated SAR data. Research indicates that the novel application of GP proved useful for generating a highly nonlinear structure in regression regime, which exhibits very strong correlations statistically between the model estimates and the ground truth measurements (volumetric water content) on the basis of the unseen data sets. In an effort to produce the soil moisture distributions over seasons, it eventually leads to characterizing local- to regional-scale soil moisture variability and performing the possible estimation of water storages of the terrestrial hydrosphere.

Makkeasorn, Ammarin; Chang, Ni-Bin; Beaman, Mark; Wyatt, Chris; Slater, Charles

2006-09-01

196

Research on the Spatial Variability of Soil Moisture  

NASA Astrophysics Data System (ADS)

China is a country seriously suffering from the lack of water resource, especially the north of China (a dense area) where there are more agricultural production than other places in China. Therefore, some have become most important problems which should be settled down right now for precision agriculture: saving the water of agriculture, optimizing the water for cropland as well as making use of soil moisture effectively. To realise the potential of soil-moisture, protect the water source , strengthen the management of the soil moisture of farm, design the irrigation and drainage, monitor the soil-moisture, etc. ,the data collection of soil moisture and the study on how to could provide the far-reaching and academic significance of guidance together with higher regional and practical use value. The IDW, Spline and Kriging in the Spatial Analyst of ArcGIS 9.0 are applied on drawing the distributing map of soil moisture and it also offers the theoretical foundation for the connection between studying soil moisture and enhancing the yield.

Zhang, Changli; Liu, Shuqiang; Zhang, Xianyue; Tan, Kezhu

197

Rock Fraction Effects on the Surface Soil Moisture Estimates From L-Band Radiometric Measurements  

Microsoft Academic Search

1. ABSTRACT Although soil holds a small percentage of the total Earth's water budget, surface soil moisture plays an important role in the water cycle and the global climate. Two space missions are now being developed to map soil moisture at global scale: the European Space Agency's Soil Moisture and Ocean Salinity (SMOS), and NASA's Soil Moisture Active and Passive

Alessandra Monerris; Mercè Vall-Llossera; Adriano Camps; Maria Piles

2008-01-01

198

High-resolution soil moisture mapping in Afghanistan  

NASA Astrophysics Data System (ADS)

Soil moisture conditions have an impact upon virtually all aspects of Army activities and are increasingly affecting its systems and operations. Soil moisture conditions affect operational mobility, detection of landmines and unexploded ordinance, natural material penetration/excavation, military engineering activities, blowing dust and sand, watershed responses, and flooding. This study further explores a method for high-resolution (2.7 m) soil moisture mapping using remote satellite optical imagery that is readily available from Landsat and QuickBird. The soil moisture estimations are needed for the evaluation of IED sensors using the Countermine Simulation Testbed in regions where access is difficult or impossible. The method has been tested in Helmand Province, Afghanistan, using a Landsat7 image and a QuickBird image of April 23 and 24, 2009, respectively. In previous work it was found that Landsat soil moisture can be predicted from the visual and near infra-red Landsat bands1-4. Since QuickBird bands 1-4 are almost identical to Landsat bands 1- 4, a Landsat soil moisture map can be downscaled using QuickBird bands 1-4. However, using this global approach for downscaling from Landsat to QuickBird scale yielded a small number of pixels with erroneous soil moisture values. Therefore, the objective of this study is to examine how the quality of the downscaled soil moisture maps can be improved by using a data stratification approach for the development of downscaling regression equations for each landscape class. It was found that stratification results in a reliable downscaled soil moisture map with a spatial resolution of 2.7 m.

Hendrickx, Jan M. H.; Harrison, J. Bruce J.; Borchers, Brian; Kelley, Julie R.; Howington, Stacy; Ballard, Jerry

2011-05-01

199

Temperature sensitivity of boreal soil respiration across a soil moisture gradient  

NASA Astrophysics Data System (ADS)

Soil temperature and moisture are the primary controls over soil respiration, and are often used to model soil respiration over multiple spatial and temporal scales. Accurate quantification and prediction of soil respiration is particularly important in boreal ecosystems where soils contain large stores of organic carbon; however, the interaction of soil temperature and moisture as controls on soil respiration is complex and not completely understood. Here we present an investigation of the temperature sensitivity of soil respiration (measured as CO2 efflux) at six sites spanning a range of elevations and soil moisture conditions across a boreal forest hillslope. This study tests our hypothesis that temperature sensitivity of soil respiration is greatest at intermediate soil moisture, where moisture conditions do not limit CO2 efflux either through desiccation stress (at low moisture conditions) or through diffusive resistance (at high moisture conditions). Temperature sensitivity, quantified as the Q10 (the ratio of efflux at one soil temperature divided by efflux at a temperature ten degrees cooler), ranged from 1.7 to 2.3 at the sites we investigated. Contrary to the global trend of increasing Q10 at lower soil temperatures, we find greater temperature sensitivity at sites with warmer mean growing season soil temperatures, and intermediate mean growing season soil moisture content. To assess the broader applicability of these results we report temperature sensitivities of boreal soil respiration from other studies across varying soil conditions. Our results indicate that future warmer boreal soil temperatures, which will likely be coupled with drier soil conditions, will increase temperature sensitivity of soil respiration in regions with high soil moisture, but decrease temperature sensitivity of soil respiration in regions with intermediate or dry moisture conditions.

Kelsey, K.; Wickland, K. P.; Striegl, R. G.

2011-12-01

200

The Murrumbidgee soil moisture monitoring network data set  

NASA Astrophysics Data System (ADS)

This paper describes a soil moisture data set from the 82,000 km2 Murrumbidgee River Catchment in southern New South Wales, Australia. Data have been archived from the Murrumbidgee Soil Moisture Monitoring Network (MSMMN) since its inception in September 2001. The Murrumbidgee Catchment represents a range of conditions typical of much of temperate Australia, with climate ranging from semiarid to humid and land use including dry land and irrigated agriculture, remnant native vegetation, and urban areas. There are a total of 38 soil moisture-monitoring sites across the Murrumbidgee Catchment, with a concentration of sites in three subareas. The data set is composed of 0-5 (or 0-8), 0-30, 30-60, and 60-90 cm average soil moisture, soil temperature, precipitation, and other land surface model forcing at all sites, together with other ancillary data. These data are available on the World Wide Web at http://www.oznet.org.au.

Smith, A. B.; Walker, J. P.; Western, A. W.; Young, R. I.; Ellett, K. M.; Pipunic, R. C.; Grayson, R. B.; Siriwardena, L.; Chiew, F. H. S.; Richter, H.

2012-07-01

201

The impact of land surface temperature on soil moisture anomaly detection from passive microwave observations  

NASA Astrophysics Data System (ADS)

For several years passive microwave observations have been used to retrieve soil moisture from the Earth's surface. Low frequency observations have the most sensitivity to soil moisture, therefore the current Soil Moisture and Ocean Salinity (SMOS) and future Soil Moisture Active and Passive (SMAP) satellite missions observe the Earth's surface in the L-band frequency. In the past, several satellite sensors such as the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and WindSat have been used to retrieve surface soil moisture using multi-channel observations obtained at higher microwave frequencies. While AMSR-E and WindSat lack an L-band channel, they are able to leverage multi-channel microwave observations to estimate additional land surface parameters. In particular, the availability of Ka-band observations allows AMSR-E and WindSat to obtain coincident surface temperature estimates required for the retrieval of surface soil moisture. In contrast, SMOS and SMAP carry only a single frequency radiometer and therefore lack an instrument suited to estimate the physical temperature of the Earth. Instead, soil moisture algorithms from these new generation satellites rely on ancillary sources of surface temperature (e.g. re-analysis or near real time data from weather prediction centres). A consequence of relying on such ancillary data is the need for temporal and spatial interpolation, which may introduce uncertainties. Here, two newly-developed, large-scale soil moisture evaluation techniques, the triple collocation (TC) approach and the Rvalue data assimilation approach, are applied to quantify the global-scale impact of replacing Ka-band based surface temperature retrievals with Modern Era Retrospective-analysis for Research and Applications (MERRA) surface temperature output on the accuracy of WindSat and AMSR-E based surface soil moisture retrievals. Results demonstrate that under sparsely vegetated conditions, the use of MERRA land surface temperature instead of Ka-band radiometric land surface temperature leads to a relative decrease in skill (on average 9.7%) of soil moisture anomaly estimates. However the situation is reversed for highly vegetated conditions where soil moisture anomaly estimates show a relative increase in skill (on average 13.7%) when using MERRA land surface temperature. In addition, a pre-processing technique to shift phase of the modelled surface temperature is shown to generally enhance the value of MERRA surface temperature estimates for soil moisture retrieval. Finally, a very high correlation (R2 = 0.95) and consistency between the two evaluation techniques lends further credibility to the obtained results.

Parinussa, R. M.; Holmes, T. R. H.; Yilmaz, M. T.; Crow, W. T.

2011-10-01

202

Long-term soil moisture variability from a new P-E water budget method  

NASA Astrophysics Data System (ADS)

Basin-scale soil moisture is traditionally estimated using either land-surface model forced by observed meteorological variables or atmospheric moisture convergence from atmospheric analysis and observed runoff. Interannual variability from such methods suffer from major uncertainties due to the sensitivity to small imperfections in the land-surface model or the atmospheric analysis. Here we introduce a novel P-E method in estimating basin-scale soil moisture, or more precisely apparent land water storage (AWS). The key input variables are observed precipitation and runoff, and reconstructed evaporation. We show the results for the tropics using the example of the Amazon basin. The seasonal cycle of diagnosed soil moisture over the Amazon is about 200mm, compares favorably with satellite estimate from the GRACE mission, thus lending confidence both in this method and the usefulness of space gravity based large-scale soil moisture estimate. This is about twice as large as estimates from several traditional methods, suggesting that current models tend to under estimate the soil moisture variability. One of the advantage of the P-E method is to retrive long-term variability of the basin-scale soil moisture (including interannual and decadal time scales), which can provide valuable information to understand climate variability and to predict future climate condition. However, validation on reconstructed evaporation is very difficult due to lack of observation. The interannual variability in AWS in the Amazon basin is about 150mm, also consistent with GRACE data, but much larger than model results. We also apply this P-E method to the midlatitude Mississippi basin and discuss the impact of major 20th century droughts such as the dust bowl period on the long-term soil moisture variability. The results suggest the existence of soil moisture memories on decadal time scales, significantly longer than typically assumed seasonal timescales.

Zeng, N.; Yoon, J.; Mariotti, A.; Swenson, S. C.

2006-05-01

203

The Predictability of Soil Moisture and Near-Surface Temperature in Hindcasts of the NCEP Seasonal Forecast Model.  

NASA Astrophysics Data System (ADS)

Using the NCEP-DOE reanalysis (R-2) soil wetness and the NCEP Seasonal Forecast System, seasonal predictability of the soil moisture and near-surface temperature, and the role of land surface initial conditions are examined. Two sets of forecasts were made, one starting from climatological soil moisture as initial condition and the other from R-2 soil moisture analysis. Each set consisted of 10-member ensemble runs of 7-month duration. Initial conditions were taken from the first 5 days of April, 12 h apart, for the 1979-96 period.The predictive skill of soil moisture was found to be high over arid/semiarid regions. The model prediction surpassed the persisted anomaly forecast, and the soil moisture initial condition was essential for skillful predictions over these areas. Over temperate zones with more precipitation, and over tropical monsoon regions, the predictive skill of the soil moisture declined steeply in the first 3-4 months. This is due to the difficulties in predicting precipitation accurately. In contrast, the situation was very different over tropical South America where tropical SST forcing controlled the precipitation and where the model simulated the precipitation well. The forecast starting from climatological soil moisture approached the forecast skill of initial soil moisture in 3-4 months; after that the effect of initial soil moisture information tended to disappear.The near-surface temperature anomaly forecast was closely related to the soil moisture anomaly forecast, but the skill was lower. The verification of temperature made against the U.S. 344 climate division data indicated that the improvement in the forecast skill was not an artifact of the R-2 soil moisture analysis.It was suggested that the equatorial Pacific SST anomaly had an impact on the soil moisture anomaly over the continental United States during the first month of integration, and then it contributed positively toward the prediction of near-surface temperature during the following months.

Kanamitsu, Masao; Lu, Cheng-Hsuan; Schemm, Jae; Ebisuzaki, Wesley

2003-02-01

204

The GLOBE Soil Moisture Campaign's Light Bulb Oven  

Microsoft Academic Search

The GLOBE Soil Moisture Campaign (SMC) (www.hwr.arizona.edu\\/globe\\/sci\\/SM\\/SMC) has developed a light bulb oven to provide a low budget, low-technology method for drying soil samples. Three different soils were used to compare the ability of the light bulb oven to dry soils against a standard laboratory convection oven. The soils were: 1) a very fine sandy loam (the \\

M. P. Whitaker; D. Tietema; T. P. Ferre; B. Nijssen; J. Washburne

2003-01-01

205

Soil moisture determination by means of the data driven models  

Microsoft Academic Search

Information's about soil water content are in the planning of water resources and management very valuable. Modeling and predicting soil water transfer is very important in agriculture or hydrology - e.g. for purposes of the effective irrigation management. Many tried and proven methods of estimating or measuring soil moisture are available. The choice of the method which in particular case

Milan Cisty; Martin Suchar; Zbynek Bajtek

2010-01-01

206

Nonlinear Dynamics of Soil Moisture and Mineral Nitrogen  

Microsoft Academic Search

We investigate the behavior of simple dynamical systems describing the temporal dynamics of soil moisture, plant growth, soil organic matter, and mineral nitrogen. The equilibrium condition of the deterministic system are analyzed as a function of the climate, soil, and vegetation parameters, along with the possible bifurcations of the system to regimes of periodic or aperiodic oscillations. Particular attention is

A. Porporato; P. D'Odorico; S. Manzoni; I. Rodriguez-Iturbe

2003-01-01

207

Some aspects of the cation status of soil moisture  

Microsoft Academic Search

Summary An alcohol displacement method is used to obtain equilibrium soil solutions from three soils set up over a moisture content range of 25–10,000 per cent. A considerable change of concentration of ions occurs with time of contact between the soil and its solution phase, equilibrium being attained between 30 to 40 days. A decreasing cation concentration gradient was demonstrated

P. Moss

1963-01-01

208

Determination of soil moisture distribution from impedance and gravimetric measurements  

Microsoft Academic Search

Daily measurements of the soil dielectric properties at 5 and 10 cm were obtained at five locations throughout the First ISLSCP Field Experiment (FIFE) test site during the 1987 intensive field campaigns (IFCs). An automated vector voltmeter was used to monitor the complex electrical impedance, at 10 MHz, of cylindrical volumes of soil delineated by specially designed soil moisture probes

Stephen G. Ungar; Robert Layman; Jeffrey E. Campbell; John Walsh; Harlan J. McKim

1992-01-01

209

Soil moisture changes under shrub cover (rosmarinus officinalis) and cleared shrub as response to precipitation in a semiarid environment: Stemflow effects  

Microsoft Academic Search

Variations in soil moisture after rainfall under Rosmarinus officinalis L and cleared shrub (prior cover R. officinalis) were analyzed. The results from the General Linear Model analysis showed the relevance of shrub plant cover on soil water infiltration in depth. A threshold of about 15–18 mm of rainfall was established, above which soil moisture changes tended to be positive. Moisture

J. Bellot

1997-01-01

210

Remote sensing techniques for soil moisture and agricultural drought monitoring  

NASA Astrophysics Data System (ADS)

Drought is the most complex and least understood of all natural hazards, affecting more people than any other hazard. Soil moisture is a primary indicator for agricultural drought. This dissertation is aimed at evaluating and investigating soil moisture and drought monitoring using remote sensing techniques. Recent technological advances in remote sensing have shown that soil moisture can be measured by a variety of remote sensing techniques, each with its own strengths and weaknesses. This research is designed to combine the strengths of optical/infrared as well as microwave remote sensing approaches for soil moisture estimation. A soil moisture estimation algorithm at moderate resolution was developed based on the well known 'Universal Triangle' relation by using MODIS land parameters as well as ground measured soil moisture. Though lower in spatial resolution, AMSR-E microwave measurements provides daily global soil moisture of the top soil layer, which are typically less affected by clouds, making them complementary to MODIS measurements over regions of clouds. Considering that the 'Universal Triangle' approach for soil moisture estimation is based on empirical relations which lack solid physical basis, a new physics based drought index, the Normalized Multi-band Drought Index (NMDI) was proposed for monitoring soil and vegetation moisture from space by using one near-infrared (NIR) and two shortwave infrared (SWIR) channels. Typical soil reflectance spectra and satellite acquired canopy reflectances are used to validate the usefulness of NMDI. Its ability for active fire detection has also been investigated using forest fires burning in southern Georgia, USA and southern Greece in 2007. Combining information from multiple NIR and SWIR channels makes NMDI a most promising indicator for drought monitoring and active fire detecting. Given the current technology, satellite remote sensing can only provide soil moisture measurements for the top soil profile, and these near-surface soil moisture must be related to the complete soil moisture profile in the unsaturated zone in order to be useful for hydrologic, climatic and agricultural studies. A new numerical method was presented to solve the governing equation for water transport in unsaturated soil by matching physical and numerical diffusion. By applying a new numerical scheme with which to discrete the kinematic wave equation on the space-time plane, this method shows the capability to simulate the physical diffusion of the diffusive wave with the numerical diffusion generated in the difference solution under certain conditions. Compared with other numerical methods with the first-order finite differences scheme, this method has enhanced the solution precision to the second order. An example application shows a good agreement with the observed data and suggests this new approach can be appropriate for soil moisture profile estimation. By combining the proposed soil moisture and drought estimation techniques, the daily soil moisture profile at high resolution can be gained, and is thus expected to be helpful not only in drought monitoring and active fire detecting, but also in agricultural applications and climate studies.

Wang, Lingli

211

Are superconducting gravimeters expensive soil moisture probes?  

NASA Astrophysics Data System (ADS)

This paper investigates hydrological processes and their influence on gravity at the underground geodynamic Membach station (eastern Belgium), where absolute (AG) and superconducting (SG) gravity measurements have been performed since 1996. Seasonal and short term effects are observed. A comprehensive hydrogeological investigation regarding the influence of variations in local and regional water mass on gravity measurements is presented for observations taken near the station. Applying a regional water storage model, the gravity contribution due to the elastic deformation of the Earth is derived. In addition, the Newtonian gravity effect induced by the local water mass variations is calculated, using soil moisture observations taken at the ground surface (about 48 m above the gravimeters). The computation of this gravimetric effect is based on a digital elevation model with spatially discretized rectangular prisms. The obtained results are compared with the observations of gravity. We find that the seasonal variations and shorter period effects depend on the local changes (about 100 m around the gravimeter) in hydrology. This result shows the sensitivity of SG observations to very local water storage changes. This may be useful e.g. to constrain the water budget in local systems like karst aquifers.

van Dam, T.; van Camp, M.; Vanclooster, M.; Dassargues, A.

2007-12-01

212

Assessment of Potential AMSR-E Soil Moisture Disaggregation Using Scatterometer Observations  

NASA Astrophysics Data System (ADS)

Advanced Microwave Scanning Radiometer (AMSR-E) on the NASA's Aqua platform has been providing land surface variables such as soil moisture in near real-time since 2002. A fundamental ongoing issue with the satellite estimates, as with any satellite passive microwave sensor, is their coarse spatial scale and how to downscale them to spatial resolutions compatible with a wider range of applications. Disaggregation techniques based on a synergism between passive and active microwave observations have shown promising results. However the available radar systems have limited temporal and spatial coverage in the mid-latitudes where soil moisture is important. Most of the disaggregation methodologies are based on temporal change detection in soil moisture. Another alternative is the QuikSCAT scatterometer, which offers daily observations with a 2.225km ground pixel size for the enhanced backscattering coefficient product. This may be a desirable option that offers a long-term data set with high temporal resolution for developing downscaling technique for disaggregation of radiometer derived soil moisture estimates (i.e. AMSR-E). QuikSCAT backscatter sensitivity to soil moisture was studied over the National Airborne Field Experiment 2006 (NAFE"06) area located in the south-eastern part of Australia. The domain encompasses a wide range of ground conditions including flood irrigation. Point comparisons between QuikSCAT backscattering coefficients and AMSR-E soil moisture revealed the greatest sensitivity of QuikSCAT backscatter to soil moisture over the Kyeamba study area, which was mostly grazing land. North-south and east-west oriented transect lines for a variety soil moisture conditions were also examined. Overall, the QuikSCAT backscatter and AMSR-E soil moisture show similar trends. However the larger variability of the backscatter values was evident in more of the transect lines. As a result, further analysis of the impact of NDVI and vegetation type is needed. The proposed assimilation of radiometer and scatterometer obtained observations will result into high temporal and fine spatial resolution soil moisture product. Aquarius, due for launch in 2009, carries on board both instruments. On that way exploring the possibility of combining AMSR-E and QuikSCAT observations can be beneficial for Aquarius by building more knowledge on the soil moisture temporal and spatial variability and by improving the available soil moisture and disaggregation algorithms.

Lakshmi, V.; Mladenova, I. E.; Jackson, T.; Long, D.

2007-12-01

213

High dielectric constant microwave probes for sensing soil moisture  

Microsoft Academic Search

Implantable soil moisture sensors suitable for long-term monitoring of moisture in highway subgrades and for similar applications are needed. Two candidate designs of microwave sensors (operating range 4 to 6 GHz) have been investigated for such applications. One design uses the fringing field of a low-loss dielectric slab waveguide (relative dielectric constant of 25) to obtain good resolution for finely

J. R. Birchak; C. G. Gardner; J. E. Hipp; J. M. Victor

1974-01-01

214

Light, Soil Moisture, and Tree Reproduction in Hardwood Forest Openings.  

National Technical Information Service (NTIS)

Light, soil moisture, and tree reproduction were measured at five positions in six openings on each of three aspects in southern Illinois. Amount of light received was clearly related to position in the openings, opening size, and aspect. More moisture wa...

L. S. Minckler J. D. Woerheide R. C. Schlesinger

1973-01-01

215

Residual Soil Moisture below the Root Zone in Southern  

Microsoft Academic Search

Work of others has indicated that, with conversion of watershed vegetation from chaparral to grasses and forbs, there would be water svings at the end of the summer dry season because of residual soil moisture left by the shallow-rooted annuals. Such residual moisture, with subsequent deep percolation, would eventually be carried downward to the water table. Two techniques were developed

California Watersheds

1963-01-01

216

An instrument for measuring soil moisture by neutron scattering  

Microsoft Academic Search

At the Swedish Meteorological and Hydrological Institute the neutron method has for some years been used for studies on soil moisture by means of a Danish apparatus. This report deals with the measuring equipment, sources of error, calibration technique, etc. The moisture probe is equipped with a 5 mC Ac-Be neutron source, combined with a scintillation crystal of Lithium Iodide

Todor Milanov

217

Soil moisture variability of root zone profiles within SMEX02 remote sensing footprints  

NASA Astrophysics Data System (ADS)

Remote sensing of soil moisture effectively provides soil moisture at a large scale, but does not explain highly heterogeneous soil moisture characteristics within remote sensing footprints. In this study, field scale spatio-temporal variability of root zone soil moisture was analyzed. During the Soil Moisture Experiment 2002 (SMEX02), daily soil moisture profiles (i.e., 0 6, 5 11, 15 21, and 25 31 cm) were measured in two fields in Walnut Creek watershed, Ames, Iowa, USA. Theta probe measurements of the volumetric soil moisture profile data were used to analyze statistical moments and time stability and to validate soil moisture predicted by a simple physical model simulation. For all depths, the coefficient of variation of soil moisture is well explained by the mean soil moisture using an exponential relationship. The simple model simulated very similar variability patterns as those observed. As soil depth increases, soil moisture distributions shift from skewed to normal patterns. At the surface depth, the soil moisture during dry down is log-normally distributed, while the soil moisture is normally distributed after rainfall. At all depths below the surface, the normal distribution captures the soil moisture variability for all conditions. Time stability analyses show that spatial patterns of sampling points are preserved for all depths and that time stability of surface measurements is a good indicator of subsurface time stability. The most time stable sampling sites estimate the field average root zone soil moisture value within ±2.1% volumetric soil moisture.

Choi, Minha; Jacobs, Jennifer M.

2007-04-01

218

Spatial patterns of soil moisture connected to monthly-seasonal ...  

Treesearch

... and precipitation variability are investigated by identifying the coupled patterns of the ... of one variable which are closely connected to variability of the other. ... by using soil moisture in the form of its coupled SVD patterns with precipitation.

219

Soil moisture-temperature relationships: results from two field experiments  

NASA Astrophysics Data System (ADS)

This paper analyses data from two field experiments in Chickasha, Oklahoma, and Tifton, Georgia, carried out in July 1999 and June 2000 respectively. The observations on soil moisture at two depths, viz. 0-2·5 and 0-5·0 cm, surface temperature, and temperatures at 1, 5 and 10 cm depths are analysed. The relationship between the soil moisture and the temperature variability in time is examined as a function of vegetation type and location. Results from these experiments show that, during drydown, surface temperature shows an increase that corresponds to a decrease in the soil moisture. Linear models for prediction of soil moisture (at both depths) using surface temperature observations are examined. Copyright

Lakshmi, Venkat; Jackson, Thomas J.; Zehrfuhs, Diane

2003-10-01

220

Device Comparison for Determining Field Soil Moisture Content.  

National Technical Information Service (NTIS)

During the period May 2010-August 2010, researchers of the U.S. Army Engineer Research and Development Center in Vicksburg, MS tested the effectiveness of various devices in determining the moisture content of soil for horizontal construction. These tests...

I. E. Berney J. D. Kyzar L. O. Oyelami

2011-01-01

221

Investigation of Remote Sensing Techniques of Measuring Soil Moisture.  

National Technical Information Service (NTIS)

Major activities described include development and evaluation of theoretical models that describe both active and passive microwave sensing of soil moisture, the evaluation of these models for their applicability, the execution of a controlled field exper...

R. W. Newton A. J. Blanchard J. L. Nieber R. Lascano L. Tsang

1981-01-01

222

Changes in Soil Moisture in CO2 Climate Studies.  

National Technical Information Service (NTIS)

Simulated changes in soil moisture in numerical studies of the effect of CO2 on climate are assessed. Reasons for discrepancies between the simulated changes are explored. Although the changes may appear inconsistent, the same physical mechanisms (for exa...

J. F. B. Mitchell

1986-01-01

223

SMOS CP34 soil moisture and ocean salinity maps  

Microsoft Academic Search

This paper presents the soil moisture and ocean salinity maps from the SMOS mission generated operationally by the Spanish SMOS Level 3 and 4 data processing center (CP34) and experimentally by the SMOS Barcelona Expert Center (SMOS-BEC).

C. Gabarro; J. Ballabrera; A. Turiel; J. Martinez; M. Umbert; F. Perez; N. Hoareau; M. Portabella; V. Gonzalez; J. Gourrion; S. Guimbard; M. Piles; A. Camps; M. Vall-llossera

2012-01-01

224

ANALYSIS AND MAPPING OF FIELD-SCALE SOIL MOISTURE VARIABILITY USING HIGH-RESOLUTION, GROUND-BASED DATA DURING THE SOUTHERN GREAT PLAINS 1997 (SGP97) HYDROLOGY EXPERIMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture is an important state variable in the hydrologic cycle, and its spatiotemporal distribution depends on many geophysical processes operating at different spatial and temporal scales. To achieve a better accounting of the water and energy budgets at the land-atmosphere boundary, it is n...

225

Impact of improved soil moisture on the ECMWF precipitation forecast in West Africa  

NASA Astrophysics Data System (ADS)

West Africa is a region of strong coupling between soil moisture and precipitation and where numerical weather prediction of precipitation generally exhibits poor skill. This region has been the focus of the African Monsoon Multidisciplinary Analysis - Land-surface Model Intercomparison Project in which the European Medium-Range Weather Forecasts (ECMWF) land surface scheme—among others—has been driven offline by accurate meteorological forcing in order to produce improved soil moisture estimates. The impact of these improved initial conditions for soil moisture on the short-range precipitation forecast is examined with the ECMWF Integrated Forecast System. While direct and beneficial impact of a more realistic soil moisture is obtained for accumulated precipitation in the regions over the coast of the Gulf of Guinea and eastern Sahel, over the rest of the Sahel the impact is detrimental or neutral.

Agustí-Panareda, A.; Balsamo, G.; Beljaars, A.

2010-10-01

226

Extraction of soil moisture information from SAR satellite data  

Microsoft Academic Search

Relating to the global climate change prediction, hydrologists are interested in large-scale hydrological processes, particularly in evapotranspiration processes as an interaction between the land surface and the atmosphere. Soil moisture is an important factor controlling the evapotranspiration process. SAR data of E ERS-1 and J ERS-1 are expected to provide large-scale soil moisture information which can be incorporated into a

T. Nakaegawa; G. Fuchigami; M. Koike; T. Oki; K. Musiake

1993-01-01

227

Field observations of soil moisture variability across scales  

Microsoft Academic Search

In this study, over 36,000 ground-based soil moisture measurements collected during the SGP97, SGP99, SMEX02, and SMEX03 field campaigns were analyzed to characterize the behavior of soil moisture variability across scales. The field campaigns were conducted in Oklahoma and Iowa in the central USA. The Oklahoma study region is sub-humid with moderately rolling topography, while the Iowa study region is

James S. Famiglietti; Dongryeol Ryu; Aaron A. Berg; Matthew Rodell; Thomas J. Jackson

2008-01-01

228

Mapping Root Zone Soil Moisture Using Remotely Sensed Optical Imagery  

Microsoft Academic Search

Field-based soil moisture measurements are cumbersome. Remote sensing techniques based on active or passive microwave data have limitations. This paper presents and validates a new method based on land surface energy balances using remotely sensed optical data ~including thermal infrared!, which allows field and landscape-scale mapping of soil moisture depth-averaged through the root zone of existing vegetation. Root zone depth

Christopher A. Scott; Wim G. M. Bastiaanssen; Mobin-ud-Din Ahmad

2003-01-01

229

Do soil moisture thresholds explain wet and dry states?  

NASA Astrophysics Data System (ADS)

Variable source area (VSA) hydrology is a useful tool to discriminate between areas in a catchment that do and do not make a significant contribution to streamflow. Saturation excess runoff is an important factor in VSA that has often been determined by topography. Recent investigations that indicate wet and dry states (where flow is assumed to be either horizontally or vertically dominant) strongly determine runoff response have focused on spatial patterns. Consequently, the threshold between wet and dry states has been difficult to determine. With high temporal resolution data from the Corin Catchment in temperate, south-eastern Australia, we investigated if thresholds for switching between wet and dry states existed and how they could be explained. Soil moisture, relative humidity and tension data at a 30 min interval were collected from several field sites over about 1 y, including a period of flooding rains. Four tensiometers and two soil moisture probes at two depths (30 and 60 cm) were installed at each field site. One field site was selected for analysis because air bubbles, instrument failure and pest damage rendered data from the other field sites incomplete or unacceptable. Horizontal, vertical and mixed flows, neither vertically or horizontally dominated, i.e. minimal water movement, were determined from the difference in tension between vertical and horizontal planes. Flow was classified as the same direction as the plane if the difference was greatest amongst all tensiometers on that plane, otherwise flow was considered mixed. The field site was relatively wet, i.e. < -50 kPa, and soil moisture distributions were similar irrespective of flow. Horizontal flow was the most infrequent, occurring on 12 days over short contiguous periods (median = 1.5 h, maximum 13 h) and in most hours of the day except afternoon. In contrast, vertical flow occurred on 227 days (median = 3.5 h, maximum 399.5 h). Horizontal flow occurred when prior and current relative humidity (RH) exceeded 75 and 71 %, respectively; vertical and mixed flow commenced when prior/current RH exceeded 21.5 - 36 %. A soil moisture threshold between wet and dry states could not be identified. This may be because the field site was in only one state, or additional other factors explain switching between wet and dry states. We hypothesise that horizontal flows are transpiration dependent, occurring during or after rainfall when transpiration is low. Further analysis is presented.

Henry, J.; Vervoort, R. W.; Adams, M. A.

2011-12-01

230

Inverse Method for Estimating the Spatial Variability of Soil Particle Size Distribution from Observed Soil Moisture  

SciTech Connect

Soil particle size distribution (PSD) (i.e., clay, silt, sand, and rock contents) information is one of critical factors for understanding water cycle since it affects almost all of water cycle processes, e.g., drainage, runoff, soil moisture, evaporation, and evapotranspiration. With information about soil PSD, we can estimate almost all soil hydraulic properties (e.g., saturated soil moisture, field capacity, wilting point, residual soil moisture, saturated hydraulic conductivity, pore-size distribution index, and bubbling capillary pressure) based on published empirical relationships. Therefore, a regional or global soil PSD database is essential for studying water cycle regionally or globally. At the present stage, three soil geographic databases are commonly used, i.e., the Soil Survey Geographic database, the State Soil Geographic database, and the National Soil Geographic database. Those soil data are map unit based and associated with great uncertainty. Ground soil surveys are a way to reduce this uncertainty. However, ground surveys are time consuming and labor intensive. In this study, an inverse method for estimating mean and standard deviation of soil PSD from observed soil moisture is proposed and applied to Throughfall Displacement Experiment sites in Walker Branch Watershed in eastern Tennessee. This method is based on the relationship between spatial mean and standard deviation of soil moisture. The results indicate that the suggested method is feasible and has potential for retrieving soil PSD information globally from remotely sensed soil moisture data.

Pan, Feifei [University of Texas; Peters-lidard, Christa D. [NASA Goddard Space Flight Center; King, Anthony Wayne [ORNL

2010-11-01

231

A simple nudging scheme to assimilate ASCAT soil moisture data in the WRF model  

NASA Astrophysics Data System (ADS)

The present work shows results obtained in a numerical experiment using the WRF (Weather and Research Forecasting, www.wrf-model.org) model. A control run where soil moisture is constrained by GFS global analysis is compared with a test run where soil moisture analysis is obtained via a simple nudging scheme using ASCAT data. The basic idea of the assimilation scheme is to "nudge" the first level (0-10 cm below ground in NOAH model) of volumetric soil moisture of the first-guess (say ?(b,1) derived from global model) towards the ASCAT derived value (say ^? A). The soil moisture analysis ?(a,1) is given by: { ? + K (^?A - ? ) l = 1 ?(a,1) = ?(b,l) (b,l) l > 1 (b,l) (1) where l is the model soil level. K is a constant scalar value that is user specified and in this study it is equal to 0.2 (same value as in similar studies). Soil moisture is critical for estimating latent and sensible heat fluxes as well as boundary layer structure. This parameter is, however, poorly assimilated in current global and regional numerical models since no extensive soil moisture observation network exists. Remote sensing technologies offer a synoptic view of the dynamics and spatial distribution of soil moisture with a frequent temporal coverage and with a horizontal resolution similar to mesoscale NWP model. Several studies have shown that measurements of normalized backscatter (surface soil wetness) from the Advanced Scatterometer (ASCAT) operating at microwave frequencies and boarded on the meteorological operational (Metop) satellite, offer quality information about surface soil moisture. Recently several studies deal with the implementation of simple assimilation procedures (nudging, Extended Kalman Filter, etc...) to integrate ASCAT data in NWP models. They found improvements in screen temperature predictions, particularly in areas such as North-America and in the Tropics, where it is strong the land-atmosphere coupling. The ECMWF (Newsletter No. 127) is currently implementing and testing an EKF for combining conventional observations and remote sensed soil moisture data in order to produce a more accurate analysis. In the present work verification skills (RMSE, BIAS, correlation) of both control and test run are presented using observed data collected by International Soil Moisture Network. Moreover improvements in temperature predictions are evaluated.

Capecchi, V.; Gozzini, B.

2012-04-01

232

The impact of land surface temperature on soil moisture anomaly detection from passive microwave observations  

Microsoft Academic Search

For several years passive microwave observations have been used to retrieve soil moisture from the Earth's surface. Low frequency observations have the most sensitivity to soil moisture, therefore the current Soil Moisture and Ocean Salinity (SMOS) and future Soil Moisture Active and Passive (SMAP) satellite missions observe the Earth's surface in the L-band frequency. In the past, several satellite sensors

R. M. Parinussa; T. R. H. Holmes; M. T. Yilmaz; W. T. Crow

2011-01-01

233

Soil moisture sensor intercomparisons at the SMAP marena in situ testbed  

Technology Transfer Automated Retrieval System (TEKTRAN)

In May 2010, a soil moisture sensor intercomparison study was begun in Marena, Oklahoma. This effort is designed to serve as a foundation for incorporating diverse soil moisture networks into the Soil Moisture Active Passive (SMAP) Calibration and Validation program. Various soil moisture sensors, w...

234

Application of observation operators for field scale soil moisture averages and variances in agricultural landscapes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture is a key variable in understanding hydrologic processes and energy fluxes at the land surface. In spite of developing technologies for in-situ soil moisture measurements and increased availability of remotely sensed soil moisture data, scaling issues between soil moisture observations ...

235

Moisture retention of a swelling soil under capillary and overburden pressures  

Microsoft Academic Search

The moisture content in a rigid soil varies with capillary pressure. On the other hand the moisture retention properties of a swelling soil are functions of capillary pressure and overburden pressure. An unloaded moisture retention curve for a swelling soil can be determined following the same laboratory procedures used for the rigid soils. Determination of the moisture contents due to

Ata-ur-Rehman Tariq; Deanna S. Durnford

1997-01-01

236

Denitrification under different cultivated plants: effects of soil moisture tension, nitrate concentration, and photosynthetic activity  

Microsoft Academic Search

Plant effects on the denitrification rate were investigated in pot experiments at different soil moisture tensions and nitrate concentrations. Nitrate concentrations and the soil moisture tension were regulated immediately before each measurement. The effects of the plants on denitrification rates were dependent on the soil moisture tension. At a low soil moisture tension (-7 cm H2O), there was a 10-fold

L. R. Bakken

1988-01-01

237

The impact of land surface temperature on soil moisture anomaly detection from passive microwave observations  

Microsoft Academic Search

For several years passive microwave observations have been used to retrieve soil moisture from the Earth's surface. Low frequency observations have the most sensitivity to soil moisture, therefore the modern Soil Moisture and Ocean Salinity (SMOS) and future Soil Moisture Active and Passive (SMAP) satellite missions observe the Earth's surface in the L-band frequency. In the past, several satellite sensors

R. M. Parinussa; T. R. H. Holmes; W. T. Crow

2011-01-01

238

Validation of SMOS Soil Moisture Products over the Maqu and Twente Regions  

PubMed Central

The validation of Soil Moisture and Ocean Salinity (SMOS) soil moisture products is a crucial step in the investigation of their inaccuracies and limitations, before planning further refinements of the retrieval algorithm. Therefore, this study intended to contribute to the validation of the SMOS soil moisture products, by comparing them with the data collected in situ in the Maqu (China) and Twente (The Netherlands) regions in 2010. The seasonal behavior of the SMOS soil moisture products is generally in agreement with the in situ measurements for both regions. However, the validation analysis resulted in determination coefficients of 0.55 and 0.51 over the Maqu and Twente region, respectively, for the ascending pass data, and of 0.24 and 0.41, respectively, for the descending pass data. Moreover, a systematic dry bias of the SMOS soil moisture was found of approximately 0.13 m3/m3 for the Maqu region and 0.17 m3/m3 for the Twente region for ascending pass data. Several factors might have affected the retrieval accuracy, such as the presence of Radio Frequency Interference (RFI), the use of inaccurate land cover information and the presence of frozen soils not correctly detected in winter. Improving the RFI filtering method and the quality of the retrieval algorithm inputs, such as land surface temperature and land cover, would certainly improve the accuracy of the retrieved soil moisture.

Dente, Laura; Su, Zhongbo; Wen, Jun

2012-01-01

239

Validation of SMOS soil moisture products over the Maqu and Twente regions.  

PubMed

The validation of Soil Moisture and Ocean Salinity (SMOS) soil moisture products is a crucial step in the investigation of their inaccuracies and limitations, before planning further refinements of the retrieval algorithm. Therefore, this study intended to contribute to the validation of the SMOS soil moisture products, by comparing them with the data collected in situ in the Maqu (China) and Twente (The Netherlands) regions in 2010. The seasonal behavior of the SMOS soil moisture products is generally in agreement with the in situ measurements for both regions. However, the validation analysis resulted in determination coefficients of 0.55 and 0.51 over the Maqu and Twente region, respectively, for the ascending pass data, and of 0.24 and 0.41, respectively, for the descending pass data. Moreover, a systematic dry bias of the SMOS soil moisture was found of approximately 0.13 m(3)/m(3) for the Maqu region and 0.17 m(3)/m(3) for the Twente region for ascending pass data. Several factors might have affected the retrieval accuracy, such as the presence of Radio Frequency Interference (RFI), the use of inaccurate land cover information and the presence of frozen soils not correctly detected in winter. Improving the RFI filtering method and the quality of the retrieval algorithm inputs, such as land surface temperature and land cover, would certainly improve the accuracy of the retrieved soil moisture. PMID:23112582

Dente, Laura; Su, Zhongbo; Wen, Jun

2012-07-25

240

Impact of diverse tillage on soil moisture dynamics  

NASA Astrophysics Data System (ADS)

The influences of traditional and reduced tillage on the water content dynamics of two soils were investigated in a long-term field experiment under nearly the same meteorological conditions for a winter wheat monoculture during three years. In addition to the moisture changes, the basic physicochemical properties, water retention, differential porosity and hydraulic conductivity of the investigated soils were measured. The results have shown the dependence between moisture and the tillage system applied for both types of soil. The soil water content was higher under reduced tillage in comparison to traditional management.

S?awi?ski, C.; Cymerman, J.; Witkowska-Walczak, B.; Lamorski, K.

2012-07-01

241

Comparison of convective precipitation in COSMO model runs by variation of the initial soil moisture fields  

NASA Astrophysics Data System (ADS)

The prediction of convective precipitation is still a challenging task. Advances in this field of research are especially important in tropical regions like West Africa where mesoscale convective systems predominantly evoke the precipitation of the rainy season. In the sparsely vegetated area of the Sahel, land-atmosphere feedbacks are known to play a crucial role in the physics of the evolution of convective systems. Recent work implies particularly the importance of soil moisture. However, information about the soil moisture for West Africa comprises a great uncertainty. A case study from the AMMA campaign (African Monsoon Multidisciplinary Analyses) was chosen to evaluate the model runs effectuated with COSMO. To examine the impact of soil moisture uncertainty on the model precipitation, the original soil moisture field of the special AMMA reanalysis experiment of the ECMWF was replaced with several other soil moisture fields. Those were the ECMWF operational analysis, the GME analysis, the ALMIP experiment (AMMA Land Surface Model Intercomparison Project) and the AMSR-E soil moisture fields. They proved to produce a significant model spread in the precipitation sum after 36 hours associated with large differences in the domain averaged convection related parameters like CAPE and boundary layer conditions as well as surface fluxes. Compared to the global forecasts from GME and IFS, all high resolution model runs initialized from the same meteorological fields as the global models show a considerable improvement of the simulated precipitation sum in regard to the available precipitational observations.

Klüpfel, V.; Kalthoff, N.; Gantner, L.

2010-09-01

242

Atmospheric controls on soil moisture-boundary layer interactions  

NASA Astrophysics Data System (ADS)

This thesis addresses the question of how the early morning atmospheric thermodynamic structure affects the interaction between the soil moisture state and the growth and development of the boundary layer (BL), leading to the triggering of convection. It is concluded that in mid-latitudes, for matters of convective triggering and response to land surface conditions, the critical portion of the atmosphere-approximately 1 to 3 km above the ground surface-is independent of geographic location and local synoptic setting. As long as the low levels of the troposphere are relatively humid but not extremely close to saturation, a negative feedback between soil moisture and rainfall is likely when the early morning temperature lapse rate in this region is dry adiabatic; a positive feedback is likely when it is moist adiabatic; and when there is a temperature inversion in this region, deep convection cannot occur, independent of the soil moisture. Additionally, when the low levels of the troposphere are extremely dry or very close to saturation, the occurrence of convection is determined solely by the atmospheric conditions. Essential characteristics of the temperature structure of the early-morning atmosphere are captured by a new thermodynamic measure, the Convective Triggering Potential (CTP), developed to distinguish between soundings favoring rainfall over dry soils from those favoring rainfall over wet soils. A one-dimensional model of the planetary boundary layer (BL) and surface energy budget has been modified to allow the growing BL to entrain air from an observed atmospheric sounding. The model is used to analyze the impact of soil saturation on BL development and the triggering of convection in different atmospheric settings. Analyses of CTP-HIlow scatter plots from radiosonde stations across the contiguous 48 United States reveal that positive feedbacks are likely in much of the eastern half of the country. Use of the 1D BL model at four additional stations confirms that the CTP-HI low framework used in this nationwide analysis is valid for regions far removed from Illinois, where it was originally developed. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.) (Abstract shortened by UMI.)

Findell, Kirsten Lynn

2001-11-01

243

SCAT/ASCAT Soil Moisture Data: Enhancements in the TU Wien Method for Soil Moisture Retrieval From ERS and METOP Scatterometer Observations  

NASA Astrophysics Data System (ADS)

Active microwave remote sensing observations of the scatterometers onboard the European Remote Sensing (ERS) and METeorological OPerational (METOP) satellites have been proven to be valuable for monitoring surface soil moisture globally using the so-called TU Wien change detection method. The METOP satellite series carrying ASCAT (Advanced Scatteromer) instrument for the next 15 years will ensure the continuity of soil moisture retrieval from scatterometers' data for more than 30 years considering the available ERS-1&2 Scatterometer (SCAT) observations dataset. With the aim of implementing a near real-time system for operational soil moisture remote sensing at EUMETSAT, the Institute of Photogrammetry and Remote Sensing at Vienna University of Technology (TU Wien) has developed an improved soil moisture retrieval algorithm to cope with some of the limitations found in the earlier method. The new algorithm has been implemented on a discrete global grid with 12.5 km quasi-equal grid spacing and includes a correction method to reduce azimuthal anisotropy of backscatter signal, new techniques for calculation of the model parameters and incorporates a comprehensive error modeling. The error analysis provides not only the quality information about the product but also facilitates accurate determination of historically driest/wettest conditions during the retrieval process. Enhancements made in the TU Wien retrieval algorithm result in a more uniform performance of the model and, consequently, a spatially consistent soil moisture product with a better spatial resolution.

Naeimi, V.; Wagner, W.; Bartalis, Z.

2009-05-01

244

A plateau scale soil moisture and soil temperature observatory for quantifying uncertainties in coarse resolution satellite products  

NASA Astrophysics Data System (ADS)

A plateau scale soil moisture and soil temperature observatory is established on the Tibetan Plateau for quantifying uncertainties in coarse resolution satellite products of soil moisture and soil temperature. The observatory consists of three regional networks across the Tibetan Plateau and provides reliable measurements of mean and variance in soil moisture and soil temperature of representative areas comparable in size to coarse satellite footprints. Using these in-situ measurements, a analysis is carried out to assess the reliability of several satellite products derived from AMSR-E and ASCAT data by three retrieval algorithms (henceforth the AMSR-E products, the ASCAT-L2 products and the ITC-model retrievals) for the first time. For the cold semiarid Naqu area, AMSR-E and ASCAT-L2 products overestimate significantly the regional soil moisture in the monsoon seasons. The ITC-model retrievals are closer to the in-situ measurements but the dynamics in the retrieved time series needs further investigation. The use of these datasets is therefore not recommended for cold semiarid conditions on the Tibetan Plateau. For the cold humid Maqu network area AMSR-E and ASCAT-L2 products have comparable accuracy as reported by previous studies in the humid monsoon period. AMSR-E products significantly overestimate and ASCAT-L2 products underestimate the soil moisture in the winter period. The ITC-model retrievals underestimate the soil moisture in general. It is concluded that global coarse resolution soil moisture products are useful but exhibit till now unreported uncertainties in cold and semiarid regions - use of them would be critically enhanced if uncertainties can be quantified and reduced using in-situ measurements.

Su, Z.; Wen, J.; Dente, L.; van der Velde, R.; Wang, L.; Ma, Y.; Yang, K.; Hu, Z.

2011-01-01

245

Impacts of Spatial Scaling Errors on Soil Moisture Retrieval Accuracy at L-Band  

Microsoft Academic Search

In the near future, data from two microwave remote sensors at L-band will enable estimation of near-surface soil moisture. The European Space Agency's Soil Moisture and Salinity Mission (SMOS) launched in November 2009, and NASA is developing a new L-band soil moisture mission named Soil Moisture Active\\/Passive (SMAP). Soil moisture retrieval theory is well-established, but many details of its application,

William L. Crosson; Ashutosh S. Limaye; Charles A. Laymon

2010-01-01

246

Soil Moisture Variability and Critical Moisture Levels at Big Meadows, Shenandoah National Park, Virginia  

NASA Astrophysics Data System (ADS)

Variability in soil moisture is controlled by temporal variability in atmospheric conditions and spatial variability in land surface conditions. Patterns relating the mean moisture content in a field to the variance have been studied using assumed random variations in the land surface variables. Although purely random calculations may describe the relationship between mean and variance, observed spatial patterns are affected strongly by non-random patterns in soil properties and in topography. We used a soil moisture balance model at 75 points at Big Meadows, an upland wetland in Shenandoah National Park, Virginia and captured the land surface variability using soil conductivity measured with an infiltrometer along with slope and aspect derived from a DEM. We calibrated the model using volumetric moisture content measurements made with a TDR probe. We used a series of numerical experiments to examine the effects of rainfall variability on the spatial distribution of soil moisture. A study of critical water stress periods is of particular importance at Big Meadows because this area is extensively used during summer months. To explore how normal climate variability affects the amount of time soil moisture is below the critical moisture content, ?c, we ran the model for 3 drought years and 3 wet years. We used stochastically derived time series to reproduce local precipitation and temperature patterns. To explore potential impacts of climate change: we (1) held the total annual precipitation constant, increased the magnitude and decreased the intensity of storms, and we (2) increased the mean annual temperature by 5 degrees C. On average, vegetation is stressed 76.3% of the year in wet years, 80.5% of the year in drought years, and 78.1% of the year in climate change years.

Lawrence, J. E.; Hornberger, G. M.

2006-12-01

247

The Presence of Plants Alters the Effect of Soil Moisture on Soil C Decomposition in Two Different Soil Types  

NASA Astrophysics Data System (ADS)

While it is well known that soil moisture directly affects microbial activity and soil C decomposition, it is unclear if the presence of plants alters these effects through rhizosphere processes. We studied soil moisture effects on soil C decomposition with and without sunflower and soybean. Plants were grown in two different soil types with soil moisture contents of 45 and 85% of field capacity in a greenhouse experiment. We continuously labeled plants with depleted 13C, which allowed us to separate plant-derived CO2-C from original soil-derived CO2-C in soil respiration measurements. We observed an overall increase in soil-derived CO2-C efflux in the presence of plants (priming effect) in both soils with on average a greater priming effect in the high soil moisture treatment (60% increase in soil-derived CO2-C compared to control) than in the low soil moisture treatment (37% increase). Greater plant biomass in the high soil moisture treatment contributed to greater priming effects, but priming effects remained significantly higher after correcting for plant biomass. Possibly, root exudation of labile C may have increased more than plant biomass and may have become more effective in stimulating microbial decomposition in the higher soil moisture treatment. Our results indicate that changing soil moisture conditions can significantly alter rhizosphere effects on soil C decomposition.

Dijkstra, F. A.; Cheng, W.

2005-12-01

248

A Coupled Soil Moisture and Surface Temperature Prediction Model.  

NASA Astrophysics Data System (ADS)

A model for soil moisture and soil surface temperature prediction for bare soil is considered in this paper. In describing evaporation rate. soil structure and moisture were taken into account as much as possible. Soil moisture prediction was carried out using Sellers' method. Hydraullic properties were determined both known values for the given type of soil and the empirical equations of Clapp and Hornberger. Soil surface temperature prediction were made using the `force-restore' method. Sensible and latent heat fluxes were determined using a resistance representation taking into consideration atmospheric stability.The model results were compared with some field data of soil temperature and latent and sensible heat fluxes. The agreement between the model-calculated and the observed heat fluxes was fairly good. Soil moisture and temperature prediction were satisfactory, although an excessive drying occurred at the beginning of a five-day simulation period. Some sensitivity analyses were also made. The model formulation of latent heat flux was compared with the formulation of Philip. Tests were made for different values of `mean temperature' in the restore term.Furthermore, the model is applicable for the calculation of sensible and latent heat fluxes provided that net radiation, air temperature, humidity, and wind velocity at screen height are available.

Ács, F.; Mihailovi, D. T.; Rajkovi, B.

1991-06-01

249

Correcting for forecast bias in soil moisture assimilation with the ensemble Kalman filter  

NASA Astrophysics Data System (ADS)

Land surface models are usually biased in at least a subset of the simulated variables even after calibration. Bias estimation may therefore be needed for data assimilation. Here, in situ soil moisture profile observations in a small agricultural field were merged with Community Land Model (CLM2.0) simulations using different algorithms for state and forecast bias estimation with and without bias correction feedback. Simple state updating with the conventional ensemble Kalman filter (EnKF) allows for some implicit forecast bias correction. It is possible to estimate the soil moisture bias explicitly and derive superior soil moisture estimates with a generalized EnKF that uses a simple persistence model for the bias and assumes that the a priori bias error covariance is proportional to the a priori state error covariance. For the case of bi-weekly assimilation of the entire profile of soil moisture observations, bias estimation and correction typically reduces the RMSE in soil moisture (over the standard EnKF without bias correction) by around 60 percent. However, under the above assumptions, significant improvements are limited to state variables for which observations are available. Therefore, it is crucial to measure the state variables of interest. The best variant for state and bias estimation depends on the nature of the model bias and the output of interest to the user. In a model that is only biased for soil moisture, large and frequent increments for soil moisture updating may be required, which in turn may negatively impact the water balance and output fluxes. It is then better to post-process the soil moisture with the bias analysis without updating the model state.

de Lannoy, GabriëLle J. M.; Reichle, Rolf H.; Houser, Paul R.; Pauwels, Valentijn R. N.; Verhoest, Niko E. C.

2007-09-01

250

Seasonality in ENSO-related precipitation, river discharges, soil moisture, and vegetation index in Colombia  

NASA Astrophysics Data System (ADS)

An analysis of hydrologic variability in Colombia shows different seasonal effects associated with El Niño/Southern Oscillation (ENSO) phenomenon. Spectral and cross-correlation analyses are developed between climatic indices of the tropical Pacific Ocean and the annual cycle of Colombia's hydrology: precipitation, river flows, soil moisture, and the Normalized Difference Vegetation Index (NDVI). Our findings indicate stronger anomalies during December-February and weaker during March-May. The effects of ENSO are stronger for streamflow than for precipitation, owing to concomitant effects on soil moisture and evapotranspiration. We studied time variability of 10-day average volumetric soil moisture, collected at the tropical Andes of central Colombia at depths of 20 and 40 cm, in coffee growing areas characterized by shading vegetation ("shaded coffee"), forest, and sunlit coffee. The annual and interannual variability of soil moisture are highly intertwined for the period 1997-1999, during strong El Niño and La Niña events. Soil moisture exhibited greater negative anomalies during 1997-1998 El Niño, being strongest during the two dry seasons that normally occur in central Colombia. Soil moisture deficits were more drastic at zones covered by sunlit coffee than at those covered by forest and shaded coffee. Soil moisture responds to wetter than normal precipitation conditions during La Niña 1998-1999, reaching maximum levels throughout that period. The probability density function of soil moisture records is highly skewed and exhibits different kinds of multimodality depending upon land cover type. NDVI exhibits strong negative anomalies throughout the year during El Niños, in particular during September-November (year 0) and June-August (year 0). The strong negative relation between NDVI and El Niño has enormous implications for carbon, water, and energy budgets over the region, including the tropical Andes and Amazon River basin.

Poveda, GermáN.; Jaramillo, Alvaro; Gil, Marta MaríA.; Quiceno, Natalia; Mantilla, Ricardo I.

2001-08-01

251

Potential soil moisture products from the Aquarius radiometer and scatterometer using an observing system simulation experiment  

NASA Astrophysics Data System (ADS)

Using an Observing System Simulation Experiment (OSSE), we investigate the potential soil moisture retrieval capability of the National Aeronautics and Space Administration (NASA) Aquarius radiometer (L-band 1.413 GHz) and scatterometer (L-band, 1.260 GHz). We estimate potential errors in soil moisture retrievals and identify the sources that could cause those errors. The OSSE system includes: (i) a land surface model in the NASA Land Information System, (ii) a radiative transfer and backscatter model, (iii) a realistic orbital sampling model and (iv) an inverse soil moisture retrieval model. We execute the OSSE over a 1000 × 2200 km2 region in the central US, including the Red and Arkansas river basins. Spatial distributions of soil moisture retrieved from the radiometer and scatterometer are close to the synthetic truth. High root mean square errors (RMSEs) of radiometer retrievals are found over the heavily vegetated regions, while large RMSE of scatterometer retrievals are scattered over the entire domain. The temporal variations of soil moisture are realistically captured over a sparely vegetated region with correlations 0.98 and 0.63, and RMSEs 1.28% and 8.23% vol vol-1 for radiometer and scatterometer, respectively. Over the densely vegetated region, soil moisture exhibits larger temporal variation than the truth, leading to correlation 0.70 and 0.67 respectively, and RMSEs 9.49% and 6.09% vol vol-1 respectively. The domain averaged correlations and RMSEs suggest that radiometer is more accurate than scatterometer in retrieving soil moisture. The analysis also demonstrates that the accuracy of the retrieved soil moisture is affected by vegetation coverage and spatial aggregation.

Luo, Y.; Feng, X.; Houser, P.; Anantharaj, V.; Fan, X.; De Lannoy, G.; Zhan, X.; Dabbiru, L.

2012-07-01

252

Can the ASAR Global Monitoring Mode Product Adequately Capture Spatial Soil Moisture Variability?  

NASA Astrophysics Data System (ADS)

Global soil moisture (SM) monitoring in the past several decades has been undertaken mainly at coarse spatial resolution, which is not adequate for addressing small-scale phenomena and processes. The currently operational Advanced Microwave Scanning Radiometer (NASA) and future planned missions such as the Soil Moisture and Ocean Salinity (ESA) and the Soil Moisture Active Passive (NASA) will remain resolution limited. Finer scale soil moisture estimates can be achieved either by down-scaling the available coarse resolution radiometer and scatterometer (i.e. ERS1/2, ASCAT) observations or by using high resolution active microwave SAR type systems (typical resolution is in the order of meters). Considering the complex land surface - backscatter signal interaction, soil moisture inversion utilizing active microwave observations is difficult and generally needs supplementary data. Algorithms based on temporal change detection offer an alternative less complex approach for deriving (and disaggregating coarse) soil moisture estimates. Frequent monitoring and low frequency range along with a high pixel resolution are essential preconditions when characterizing spatial and temporal soil moisture variability. An alternative active system that meets these requirements is the Advance Synthetic Aperture Radar (ASAR) on ENVISAT [C-band, global, 1 km in Global Monitoring (GM) Mode]. The Vienna University of Technology (TU Wien) has developed a 1 km soil moisture product using the temporal change detection approach and the ASAR GM. The TU Wien SM product sensitivity was evaluated at two scales: point (using in situ data from permanent soil moisture stations) and regional [using ground measured data and aircraft estimates derived from the Polarimetric L-band Microwave Radiometer (PLMR)] over the National Airborne Field Experiment (NAFE'05) area located in the Goulburn catchment, SE Australia. The month long (November 2005) campaign was undertaken in a region predominantly covered by grasslands and partly by forests and croplands. Point scale analysis revealed high ASAR sensitivity and adequate response to changes in moisture conditions (R = 0.69 and RMSE = 0.08 v/v). Regional analysis was performed at several different spatial resolutions (1 km to 25 km). ASAR exhibited high noise level and significant wet bias. Increase in pixel size resulted in improving R and RMSE from R = 0.59 and RMSE = 0.14 to R = 0.91 and RMSE = 0.05 at 1 km and 25 km respectively; however, despite the reasonable statistical agreement at 1 km, the soil moisture spatial patterns clearly visible in the PLMR images, the later were verified with ground data, were lacking in the ASAR product.

Mladenova, I.; Lakshmi, V.; Walker, J.; Panciera, R.; Wagner, W.; Doubkova, M.

2008-12-01

253

Short and long-term patterns of soil moisture in alpine tundra  

Microsoft Academic Search

Time domain reflectometry (TDR), a nondestructive technique for monitoring water content of soils, was used to measure volumetric soil moisture in three different communities in the alpine tundra during the summer of 1992. Data were converted to gravimetric estimates in order to allow comparison with 20 yr of records of gravimetric data, some of which date back to 1953. Analysis

R. V. Taylor; T. R. Seastedt

1994-01-01

254

What perspective in remote sensing of soil moisture for hydrological applications by coarse-resolution sensors  

NASA Astrophysics Data System (ADS)

Soil moisture is a key state variable in hydrology, it controls the proportion of rainfall that infiltrates, runoff and evaporates from the land. For hydrological applications, soil moisture monitoring at catchment scale is required and, for that, microwave remote sensing sensors might be used. However, due to their coarse-spatial resolution, the skepticism on the suitability to retrieve the soil moisture at catchment scale takes still place. This work attempts to bring out if coarse resolution sensors for soil moisture monitoring can have some perspectives for hydrological applications. Two soil moisture products derived from the Advanced SCATterometer (ASCAT) and the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) are used for this purpose. The analysis is addressed by investigating: (i) the reliability of product data in the estimation of the wetness conditions of a catchment antecedent to rainfall events, and (ii) the benefit on runoff prediction if data are assimilated into a rainfall-runoff model. Rainfall-runoff observations are taken from several catchments in Italy and Luxembourg for testing. Results reveal that ASCAT and AMSR-E soil moisture products can be conveniently used to improve runoff prediction thus opening new important challenges and opportunities for the use of this new sources of data in the operational hydrology.

Brocca, Luca; Melone, Florisa; Moramarco, Tommaso; Wagner, Wolfgang

2011-10-01

255

One-Dimensional Soil Moisture Profile Retrieval by Assimilation of Near-Surface Measurements: A Simplified Soil Moisture Model and Field Application  

Microsoft Academic Search

The Kalman filter assimilation technique is applied to a simplified soil moisture model for retrieval of the soil moisture profile from near-surface soil moisture measurements. First, the simplified soil moisture model is developed, based on an approximation to the Buckingham-Darcy equation. This model is then used in a 12- month one-dimensional field application, with updating at 1-, 5-, 10-, and

JEFFREY P. W ALKER; GARRY R. WILLGOOSE; JETSE D. KALMA

2000-01-01

256

The effect of soil moisture upon the atmospheric and soil temperature near the air-soil interface  

Microsoft Academic Search

The soil and atmospheric boundary layers, considered as a coupled, non-steady state, heat-moisture transfer system, is analyzed to examine the effects of soil moisture variations upon the temperature distributions of the air layer near the ground and the underlying soil. The exchange coefficient for the air is approximated by the Keyps formula; the soil diffusion equations follow the theory of

Wilford G. Zdunkowski; Jan Paegle; James P. Reilly

1975-01-01

257

Future Soil Moisture Satellite Missions and Research Needs  

NASA Astrophysics Data System (ADS)

During the coming decade, launches of a number of satellite microwave sensors will provide new and unique opportunities for acquiring global information on the amount and distribution of surface soil moisture and its frozen/thawed state. This new information will provide potentially significant enhancements to the predictive capabilities of numerical weather and climate models as well as improved capabilities for monitoring and predicting floods, droughts, and other natural hazards. The development focus has been on L-band (1.4 GHz) passive microwave sensors (radiometers) as the basis for new satellite mission concepts since these instruments are uniquely suited to acquiring soil moisture information over a wide range of vegetation and heterogeneous terrain, and under nearly all weather conditions. Active microwave sensors (radars) can provide higher spatial resolution measurements and, in combination with passive sensors, enhanced information on surface moisture and its freeze/thaw condition. The soil moisture and surface freeze/thaw state together control the `surface resistance' to water and energy exchanges at the surface. Among the new soil moisture mission concepts under consideration for launch in ~2005 or later are the Soil Moisture and Ocean Salinity (SMOS) and Hydrosphere States (HYDROS) missions, and higher-resolution follow-on missions. These missions use different but complementary technological approaches to surface soil moisture sensing. In the nearer term, launches of the Advanced Scanning Microwave Radiometers (AMSRs) on the NASA EOS-Aqua and National Space Development Agency of Japan ADEOS-II satellites in 2002, and similar instruments to be launched in subsequent years as part of Department of Defense and National Polar-orbiting Operational Environmental Satellite System (NPOESS) programs, will provide new C-band (~6.9 GHz) data that will be useful for soil moisture monitoring under more limited vegetation and environmental conditions. There are many opportunities, and research needs, to be addressed in developing innovative approaches to utilization of the new satellite-derived data. Issues include development of new processing and retrieval algorithms, methods for jointly assimilating satellite-derived and in-situ data into hydrologic models, and validation of derived soil moisture data and products. An overview of the current soil moisture mission and planning status, and ongoing and needed research, will be provided in this paper.

Njoku, E. G.; Jackson, T. J.; O'Neill, P. E.

2001-12-01

258

Airborne Synthetic Aperture Radar Study of Soil Moisture at Mars Analogs  

NASA Astrophysics Data System (ADS)

Hypotheses involving water have been proposed for Martian surface processes such as gullies, duracrust cementation and dark slope streaks. Future SAR missions capable of detecting soil moisture could test these hypotheses, but standard soil moisture retrieval techniques for SAR data such as the Integral Equation Method (IEM) are not applicable to Mars due to the current lack of high resolution surface roughness data. Another approach would be to conduct repeat passes, where surface roughness is assumed to be constant and changes in backscatter are related to changes in soil moisture. This study was undertaken to determine optimal parameters for detecting soil moisture at Mars analog sites. Quad-polarized C, L and P band AIRSAR data at 11m slant resolution were collected at four sites: a fluvial plain near Cameron, AZ; artificial recharge basins near Tucson, AZ and gullies in San Juan Mountains, CO and Death Valley, CA. Soil moisture was measured at a range of depths (0-40cm) with gravimetric sampling and over a large spatial extent with Time Domain Reflectometry (TDR). For a homogenous unvegetated sand bar at Cameron, a significant correlation (< 0.025 level of significance in a t-distribution test) was found for L-VV and L-TP with soil moisture at 0 cm depth, C-HV had a weaker correlation (< 0.05 level of significance) to 0 cm moisture on both the sand bar and the unvegetated surface of a recharge basin. The lack of response to deeper moisture in this study cannot discount the potential for detecting deeper moisture on Mars if the radar wavelength is long enough to penetrate a desiccated upper layer. Further analysis of the gully sites and TDR data will also be presented.

Doggett, T.; Greeley, R.; Baker, V.; Chien, S.; Davies, A.; Dohm, J.; Ferre, T.; Hinnel, A.; Rucker, D.; Williams, K.

2004-05-01

259

Application of the Preisach Model to Soil-moisture Hysteresis  

NASA Astrophysics Data System (ADS)

An examination of the physics of the land phase of the hydrological cycle shows that the most important non-linearities occur in the unsaturated zone of the soil. These have been studied using switched boundary conditions applied to the one-dimensional form of Richards differential equation, modelling the wetting and drying of a column of bare or vegetated soil, at a scale of roughly one meter. However, the strongly non-linear hysteretic property of the soil moisture characteristic is usually ignored. Smooth non-linear differential, or integro-differential, operators cannot reproduce soil-moisture hysteresis. The classical Preisach Model is presented and applied to the quantitative description of soil-moisture scanning curves. The Preisach model is a deterministic, rate independent non-linear operator with return-point memory and congruent loops. Special, one parameter, classes of Preisach operators are proposed as models of soil-moisture hysteresis for particular soils. The results of fitting these operators to laboratory and field data, taken from the Grenoble GRIZZLY Soil Database, are presented and discussed.

O'Kane, J.; Pokrovskii, A.; Krejci, P.; Haverkamp, R.

2003-12-01

260

Dependence of soil respiration on soil temperature and soil moisture in successional forests in Southern China  

USGS Publications Warehouse

The spatial and temporal variations in soil respiration and its relationship with biophysical factors in forests near the Tropic of Cancer remain highly uncertain. To contribute towards an improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured in three successional subtropical forests at the Dinghushan Nature Reserve (DNR) in southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared in successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season (April-September) and with low rates in the cool dry season (October-March). Soil respiration measured at these forests showed a clear increasing trend with the progressive succession. Annual mean (?? SD) soil respiration rate in the DNR forests was (9.0 ?? 4.6) Mg CO2-C/hm2per year, ranging from (6.1 ?? 3.2) Mg CO2-C/hm2per year in early successional forests to (10.7 ?? 4.9) Mg CO2-C/hm2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation in DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture increased with progressive succession processes. This increase is caused, in part, by abundant respirators in advanced-successional forest, where more soil moisture is needed to maintain their activities. ?? 2006 Institute of Botany, Chinese Academy of Sciences.

Tang, X. -L.; Zhou, G. -Y.; Liu, S. -G.; Zhang, D. -Q.; Liu, S. -Z.; Li, J.; Zhou, C. -Y.

2006-01-01

261

Validation of surface soil moisture from AMSR-E using auxiliary spatial data in the transboundary Indus Basin  

NASA Astrophysics Data System (ADS)

Information on soil moisture is vital to describe various hydrological processes. Soil moisture parameters are normally measured using buried sensors in the soil. Alternatively, spatial and temporal characteristics of surface soil moisture are estimated through satellites. Advanced Microwave Scanning Radiometer on the Earth Observing System (AMSR-E) is one of such satellites that estimate surface soil moisture in an operational context. These estimates need validation prior to use in various hydrological and water management applications. Such validations are normally carried out using field measurements of soil moisture. This is not technically feasible in vast river basins such as the Indus Basin and for pixel sizes of 25 km × 25 km with non-homogeneous soils and land use. Therefore, AMSR-E data interpreted with Njoku model and posted by the National Snow and Ice Data Center (NSIDC) for the Indus Basin is evaluated by comparing it against auxiliary spatial data. The auxiliary data exists of (i) land use, (ii) rainfall from the Tropical Rainfall Measuring Mission (TRMM) satellite, (iii) seasonality of vegetation from SPOT-Vegetation and (iv) saturated water content (?sat) inferred from soil maps. A strong relationship was observed between rainfall and surface soil moisture in the land use class "rainfed". Spearman's rank correlation coefficient (rs) between the soil moisture and rainfall ranged from 0.14 to 0.55 with a mean of 0.36. For irrigated land uses, rs ranged from -0.04 to 0.52 with a mean of 0.29 due to control of soil moisture by irrigation water supply. The temporal analysis of soil moisture data with vegetation time series showed resemblance with growth phenology. Higher Pearson's correlation coefficient (r) between the soil moisture and vegetation development was found for time lags of a few weeks. The daily maximum values estimated by AMSR-E ranged from 0.08 to 0.38 cm3 cm-3. The maximum values were near, but below ?sat limits for different soil types. AMSR-E captured the flooding processes during July and August 2010 by showing the soil moisture values to approximate the saturated soil moisture content for areas that are reported to be flooded. This suggests that the absolute AMSR-E soil moisture data from NSIDC are accurate in the upper range of land wetness.It is concluded that AMSR-E surface soil moisture data exhibits spatio-temporal behavior, and the trends agree with auxiliary spatial data sets.

Cheema, M. J. M.; Bastiaanssen, W. G. M.; Rutten, M. M.

2011-07-01

262

Determination of chemical availability of cadmium and zinc in soils using inert soil moisture samplers  

Microsoft Academic Search

A rapid method for extracting soil solutions using porous plastic soil-moisture samplers was combined with a cation resin equilibration based speciation technique to look at the chemical availability of metals in soil. Industrially polluted, metal sulphate amended and sewage sludge treated soils were used in our study. Cadmium sulphate amended and industrially contaminated soils all had > 65% of the

Bruce P. Knight; Amar M. Chaudri; Steve P. McGrath; Kenneth E. Giller

1998-01-01

263

Horizontal and vertical variability of soil moisture in savanna ecosystems  

NASA Astrophysics Data System (ADS)

Soil moisture is a key hydrological variable that mediates the interactions between climate, soil, and vegetation dynamics in water-limited ecosystems. Because of the importance of water limitation in savannas, a number of theoretical models of tree-grass coexistence have been developed which differ in their underlying assumptions about the ways in which trees and grasses access and use soil moisture. However, clarification of the mechanisms that allow savanna vegetation to persist as a mixture of grasses and trees remains a vexing problem in both hydrological and vegetation science. A particular challenge is the fact that the spatial pattern of vegetation is both a cause and effect of variation in water availability in semiarid ecosystems. At landscape to regional scales, climatic and geologic constraints on soil moisture availability are primary determinants of vegetation structural pattern. However, at local to landscape scales the patchy vegetation structural mosaic serves to redistribute the availability of soil moisture in ways that have important consequences for structural dynamics and community composition. In this regard, the emerging field of ecohydrology is well suited to investigate questions concerning couplings between the patchy structural mosaic of savanna vegetation and the kinds self-organizing dynamics known to exist in other light and nutrient-limited vegetation systems. Here we address the role of patchy vegetation structure through the use of a lumped model of soil moisture dynamics that accounts for the effect of tree canopy on the lateral and vertical distribution of soil moisture. The model includes mechanisms for the drying of the ground surface due to soil evaporation in the sites with no tree cover, and for the lateral water uptake due to root invading areas with no canopy cover located in the proximity of trees. The model, when applied to a series of sites along a rainfall gradient in southern Africa, is able to explain the cover fractions observed in this region.

Caylor, K.; D'Odorico, P.; Rodriguez-Iturbe, I.

2004-12-01

264

Evaluation of microwaves soil moisture products based on two years of ground measurements over a Sahelian region.  

NASA Astrophysics Data System (ADS)

Microwaves remote sensing is a promising approach to measure soil moisture values and variations. Soil moisture is a very important variable which strongly interacts with soil-vegetation-atmosphere fluxes. This is particularly true in Sahelian region with monsoon climatic system. From active or passive microwaves measurements of backscatter coefficients or brightness temperatures, soil moisture products are derived. Soil moisture products evaluation is essential to improve algorithm and inform users on the products quality (eg quality of soil moisture products variability or absolutes). This study aims to evaluate and to intercompare five soil moisture products from active and passive microwaves sensors. The study is performed for 2005-2006, for a 1 x 3 degrees longitude-latitude window located in Sahel (14-17N and 0-1W). In addition an accurate validation is conducted for specific locations based on ground measurements available in this region. It uses the Gourma (Mali) soil moisture measurements network installed in the framework of the African Monsoon Multidisciplinary Analysis (AMMA) program. The soil moisture network has been organized in order to validate remotely sensed soil moisture for the future Soil Moisture an Ocean Salinity (SMOS) mission. Three stations located on sandy dune systems have been selected according to their location along the North-South climatic gradient. They provide continuous soil moisture measurements at 15-minute time step and at 5-cm depth for 2005-2006. Five soil moisture products provided by three different sensors are considered. 1) From the Advanced Microwave Scanning Radiometer on Earth Observing System (AMSR-E), two soil moisture products are used: the National Snow and Ice Data Center product and the Amsterdam University product. 2) From the Wind Scatterometer, on European Remote Sensing (ERS) satellite, two soil moisture products are evaluated: the Vienna University of Technology and the Zribi et al 2007 products. 3) The soil moisture product obtained by the Amsterdam University from the Tropical Rainfall Measuring Mission satellite mission (TMI sensor -TRMM Microwave Imager) is also evaluated. AMSR-E and TRMM/TMI are passive microwave sensors while ERS/SCAT is an active microwave sensor. Soil moisture product comparison and evaluation investigates both spatial and temporal variations of soil moisture as well as absolutes values. Consistency of soil moisture spatial distributions between the products is addressed. It is shown that there is generally a good agreement, in term of spatial distribution of soil moisture over the considered region, between the products during the monsoon season. In contrast products consistency is poorer during the dry season. Statistical correlations between ground measurements and satellite products are significant for all products, (best results is R2=0.85 for the AMSR-E university of Amsterdam product). But all the soil moisture products considered over-estimate absolute soil moisture values, particularly during the dry season. Mean RMSE is around 5% in volumetric soil moisture content. Important differences between products based on data from same sensor are also highlighted in this study.

Gruhier, C.; de Rosnay, P.; Kerr, Y.; Kergoat, L.

2008-12-01

265

Active and passive microwave remote sensing of soil moisture  

NASA Astrophysics Data System (ADS)

This study focuses on the development of a consistent methodology for soil moisture inversion from Synthetic Aperture Radar (SAR) data using the Integral Equation Model (Fung et al., 1992) without the need to prescribe time-varying land-surface attributes as constraining parameters. Specifically, the dependence of backscatter coefficient on the soil dielectric constant, surface roughness height and correlation length was investigated. The IEM was used in conjunction with an inversion model to retrieve soil moisture using multi-frequency and multi-polarization data (L, C and X-Bands) simultaneously. The results were cross-validated with gravimetric observations obtained during the Washita '94 field experiment in the Little Washita Watershed, Oklahoma. The average error in the estimated soil moisture was of the order of 3.4%, which is comparable to that expected due to noise in the SAR data. The retrieval algorithm performed very well for low incidence angles and over bare soil fields, and it deteriorated slightly for vegetated areas, and overall for very dry soil conditions. The IEM was originally developed for scattering from a bare soil surface, and therefore the vegetation effects are not explicitly incorporated in the model. We coupled a semi-empirical vegetation scattering parameterization to our multi-frequency soil moisture inversion algorithm. This approach allows for the explicit representation of vegetation backscattering effects without the need to specify a large number of parameters. The retrieval algorithm performed well for vegetated conditions when a land-use based vegetation parameterization was used. The explicit incorporation of land-use in the parameterization scheme is equivalent to incorporating the effect of vegetation structure in the soil moisture estimates obtained using the SAR observations. ESTAR images of brightness temperature obtained during the same period were inverted independently for soil moisture. The results at individual sampling sites were first compared against gravimetric soil moisture observations for Washita '94, and the RMS errors for both applications were between 3% and 4%. Subsequently, we investigated the use of high resolution SAR-derived soil moisture fields to estimate sub-pixel variability in ESTAR derived fields. The effect of sub-pixel variability of various land surface properties (namely soil moisture, soil texture, soil temperature, and vegetation). The results demonstrated the linear scaling behavior of ESTAR based soil moisture estimates. We also investigated the problem of consistency between the two systems. Estimated and observed brightness temperature fields were compared and analyzed to establish the aggregation kernel inherent to ESTAR, i.e., how the instrument actually processes/integrates sub-pixel variability. The scaling properties of both SAR and ESTAR at all frequencies were investigated and the results indicated that both sensors demonstrated fractal behavior. The results suggested that the two systems can be used to complement each other, and there is a potential to downscale ESTAR observations for high resolution soil moisture estimation, using only one SAR frequency (e.g. L-band).

Bindlish, Rajat

2000-10-01

266

Determinants of SGP97 Surface Soil Moisture Patterns from ESTAR and NOAH  

NASA Astrophysics Data System (ADS)

Recently, Peters-Lidard and coworkers published an analysis of modeled and measured soil moisture during the Washita '92 and '94 field campaigns suggesting that the spatial scaling of soil moisture is controlled in wet periods by processes controlling infiltration (e.g., including rainfall pattern, soil and vegetation properties) and in dry periods by processes controlling drainage and evaporation (e.g., soils, topography and vegetation properties). We will present recent work that further explores these issues in the context of the month-long Southern Great Plains '97 hydrology experiment (SGP97), during which daily soil moisture images at an 800 m resolution were derived from brightness temperature measurements obtained with the airborne L band ESTAR microwave radiometer. This set of images, which compared favorably with in-situ volumetric soil moisture measurements, forms the basis of this study, along with the NOAH land surface model (developed by NOAA/NCEP, Oregon State University, the Air Force Weather Agency, and the Office of Hydrology). In this study, the NOAH model is applied with and without enhancements representing topography for comparisons to the spatial pattern of ESTAR-derived soil moisture estimates over the 11,000 square kilometer SGP97 test region. Results for both wet and dry periods will be presented and discussed in the context of the controlling processes described above.

Peters-Lidard, C. D.; O'Neill, P. E.; Hsu, A.

2002-05-01

267

Soil electromagnetic parameters as functions of frequency, soil density, and soil moisture  

Microsoft Academic Search

Measurements are made to determine the conductivity and dielectric constants of a gray clay loam and a reddish-brown clay loam. The measurements are made as a function of soil density (from 1.2 g\\/cm3to 1.8 g\\/cm3), soil moisture (from 0 percent to 20 percent of the dry soil weight), and excitation frequency (from 30 MHz to 4 GHz), using standard transmission

J. E. Hipp

1974-01-01

268

Soil moisture retrieval by active/passive microwave remote sensing data  

NASA Astrophysics Data System (ADS)

This study develops a new algorithm for estimating bare surface soil moisture using combined active / passive microwave remote sensing on the basis of TRMM (Tropical Rainfall Measuring Mission). Tropical Rainfall Measurement Mission was jointly launched by NASA and NASDA in 1997, whose main task was to observe the precipitation of the area in 40 ° N-40 ° S. It was equipped with active microwave radar sensors (PR) and passive sensor microwave imager (TMI). To accurately estimate bare surface soil moisture, precipitation radar (PR) and microwave imager (TMI) are simultaneously used for observation. According to the frequency and incident angle setting of PR and TMI, we first need to establish a database which includes a large range of surface conditions; and then we use Advanced Integral Equation Model (AIEM) to calculate the backscattering coefficient and emissivity. Meanwhile, under the accuracy of resolution, we use a simplified theoretical model (GO model) and the semi-empirical physical model (Qp Model) to redescribe the process of scattering and radiation. There are quite a lot of parameters effecting backscattering coefficient and emissivity, including soil moisture, surface root mean square height, correlation length, and the correlation function etc. Radar backscattering is strongly affected by the surface roughness, which includes the surface root mean square roughness height, surface correlation length and the correlation function we use. And emissivity is differently affected by the root mean square slope under different polarizations. In general, emissivity decreases with the root mean square slope increases in V polarization, and increases with the root mean square slope increases in H polarization. For the GO model, we found that the backscattering coefficient is only related to the root mean square slope and soil moisture when the incident angle is fixed. And for Qp Model, through the analysis, we found that there is a quite good relationship between Qpparameter and root mean square slope. So here, root mean square slope is a parameter that both models shared. Because of its big influence to backscattering and emissivity, we need to throw it out during the process of the combination of GO model and Qp model. The result we obtain from the combined model is the Fresnel reflection coefficient in the normal direction gama(0). It has a good relationship with the soil dielectric constant. In Dobson Model, there is a detailed description about Fresnel reflection coefficient and soil moisture. With the help of Dobson model and gama(0) that we have obtained, we can get the soil moisture that we want. The backscattering coefficient and emissivity data used in combined model is from TRMM/PR, TMI; with this data, we can obtain gama(0); further, we get the soil moisture by the relationship of the two parameters-- gama(0) and soil moisture. To validate the accuracy of the retrieval soil moisture, there is an experiment conducted in Tibet. The soil moisture data which is used to validate the retrieval algorithm is from GAME-Tibet IOP98 Soil Moisture and Temperature Measuring System (SMTMS). There are 9 observing sites in SMTMS to validate soil moisture. Meanwhile, we use the SMTMS soil moisture data obtained by Time Domain Reflectometer (TDR) to do the validation. And the result shows the comparison of retrieval and measured results is very good. Through the analysis, we can see that the retrieval and measured results in D66 is nearly close; and in MS3608, the measured result is a little higher than retrieval result; in MS3637, the retrieval result is a little higher than measured result. According to the analysis of the simulation results, we found that this combined active and passive approach to retrieve the soil moisture improves the retrieval accuracy.

Wu, Shengli; Yang, Lijuan

2012-09-01

269

Influence of soil moisture and microbial activity on pendimethalin degradation  

Microsoft Academic Search

)-3,4-dimethyl-2,6-dinitroaniline, is a selective pre-emergence herbicide used extensively for control of large variety of grasses and broadleaf weeds in several crops including wheat (Triticum aestivum L.), soybean (Glycin max(L) Marr), peas (Pisum sativum) and various vegetable crops (Sprankle 1974). Persistence of herbicides, in general, is influenced by soil type, soil temperature, soil moisture and cultivation practices. It was observed (Zimdahl

G. Kulshrestha; S. B. Singh

1992-01-01

270

Towards a continuous operational system to estimate the root-zone soil moisture from intermittent remotely sensed surface moisture  

Microsoft Academic Search

A study has been carried out to develop and evaluate a system to estimate soil moisture content in the root-zone using active microwaves from the European Remote Sensing Satellite, ERS-1, to measure moisture content in the top 10 cm of the soil profile. Two permanent grass sites in the UK with contrasting soil types, clayey and sandy, were selected for

R. Ragab

1995-01-01

271

Pathways of soil moisture controls on boundary layer dynamics  

NASA Astrophysics Data System (ADS)

Soil moisture controls on precipitation are now receiving significant attention in climate systems because the memory of their variability is much slower than the memory of the fast atmospheric processes. We propose a new model that integrates soil water dynamics, plant hydraulics and stomatal responses to water availability to estimate root water uptake and available energy partitioning, as well as feedbacks to boundary layer dynamics (in terms of water vapor and heat input to the atmospheric system). Using a simplified homogenization technique, the model solves the intrinsically 3-D soil water movement equations by two 1-D coupled Richards' equations. The first resolves the radial water flow from bulk soil to soil-root interface to estimate root uptake (assuming the vertical gradients in moisture persist during the rapid lateral flow), and then it solves vertical water movement through the soil following the radial moisture adjustments. The coupling between these two equations is obtained by area averaging the soil moisture in the radial domain (i.e. homogenization) to calculate the vertical fluxes. For each vertical layer, the domain is discretized in axi-symmetrical grid with constant soil properties. This is deemed to be appropriate given the fact that the root uptake occurs on much shorter time scales closely following diurnal cycles, while the vertical water movement is more relevant to the inter-storm time scale. We show that this approach was able to explicitly simulate known features of root uptake such as diurnal hysteresis of canopy conductance, water redistribution by roots (hydraulic lift) and downward shift of root uptake during drying cycles. The model is then coupled with an atmospheric boundary layer (ABL) growth model thereby permitting us to explore low-dimensional elements of the interaction between soil moisture and ABL states commensurate with the lifting condensation level.

Siqueira, M.; Katul, G.; Porporato, A.

2007-12-01

272

The impact of different soil moisture and soil compaction on the growth of triticale root system  

Microsoft Academic Search

Effects of different soil moisture (soil drought and waterlogging) and soil compaction (1.33 and 1.50 g·cm?3) on the growth and morphological traits of the root system were studied in four breeding forms and seven cultivars of triticale.\\u000a Morphological changes, including the restriction of root extension, expansion and proliferation of laterals roots, occur in\\u000a plants grown in different soil moisture and

Stanis?aw Grzesiak; Maciej T. Grzesiak; W?adys?aw Filek; Tomasz Hura; Joanna Stabry?a

2002-01-01

273

FOSMEX: Forest Soil Moisture Experiments With Microwave Radiometry  

Microsoft Academic Search

The microwave Forest Soil Moisture Experiment (FOSMEX) was performed at a deciduous forest site at the Research Centre Julich (Germany). An L- and an X-band radiometer were mounted 100 m above ground and directed to the canopy. The measurements consist of dual- and single-polarized L- and X-band data and simultaneously recorded ground moisture, temperature, and meteorological data. The canopy L-band

Massimo Guglielmetti; Mike Schwank; Christian Matzler; Christoph Oberdorster; Jan Vanderborght; Hannes Fluhler

2008-01-01

274

Impact of the soil hydrology scheme on simulated soil moisture memory in a GCM  

NASA Astrophysics Data System (ADS)

Soil moisture-atmosphere feedback effects play an important role in several regions of the globe. For some of these regions, soil moisture memory may contribute significantly to the development of the regional climate. Identifying those regions can help to improve predictability in seasonal to decadal climate forecasts. The present study investigates how different setups of the soil hydrology scheme affect soil moisture memory simulated by the global climate model of the Max Planck Institute for Meteorology (MPI-M), ECHAM6/JSBACH. First, the standard setup applied for the CMIP5 exercise is used, in which soil water is represented by a single soil moisture reservoir. Second, a new five soil layer hydrology scheme is utilized where the previous bucket soil moisture now corresponds to the root zone soil moisture. In the standard setup, transpiration may access the whole soil moisture that is exceeding the wilting point over vegetated areas. However, in the five layer scheme, soil water below the root zone cannot be accessed by transpiration directly, but only be transported upwards into the root zone by diffusion following the Richard's equation. Thus, this below the root zone, which is not present in the standard setup, can act as buffer in the transition between wet and dry periods. A second notable difference between the two setups is the formulation of bare soil evaporation. In the standard setup, it may only occur if the whole soil moisture bucket is almost completely saturated, while in the new setup, it depends only on the saturation of the upper most soil layer. As the latter is much thinner than the root zone (bucket), bare soil evaporation can occur more frequently, especially after rainfall events. For the second setup, two further variants are considered: one where the bare soil evaporation was modified and one where a new parameter dataset of soil water holding capacities was used. Soil moisture memory of the different setups will be analysed from global ECHAM6/JSBACH simulations forced by AMIP2 SST. Areas will be highlighted where the regional climate seems to be sensitive to the improved representation of soil hydrology in the new setup and its variants. First results indicate that soil moisture memory effects play a role in regions where a soil moisture buffer is present below the root zone.

Hagemann, Stefan; Stacke, Tobias

2013-04-01

275

Microwave remote sensing and GIS for monitoring surface soil moisture and estimation of soil properties  

Microsoft Academic Search

Passive microwave remote sensing and a geographic information system (GIS) were employed for monitoring and quantifying spatial and temporal variability of surface soil moisture over the Little Washita drainage basin, Oklahoma, USA, between 10 and 18 June 1992. Daily microwave measurements at a ground resolution of 200 m were obtained from airborne ESTAR instrument. Surface soil moisture values were derived

NANDISH M. MATTIKALLI; EDWIN T. ENGMAN

1997-01-01

276

Soil Moisture-Atmosphere Feedbacks on Atmospheric Tracers: The Effects of Soil Moisture on Precipitation and Near-Surface Chemistry  

NASA Astrophysics Data System (ADS)

The atmospheric component is described by rapid fluctuations in typical state variables, such as temperature and water vapor, on timescales of hours to days and the land component evolves on daily to yearly timescales. This dissertation examines the connection between soil moisture and atmospheric tracers under varying degrees of soil moisture-atmosphere coupling. Land-atmosphere coupling is defined over the United States using a regional climate model. A newly examined soil moisture-precipitation feedback is identified for winter months extending the previous summer feedback to colder temperature climates. This feedback is driven by the freezing and thawing of soil moisture, leading to coupled land-atmosphere conditions near the freezing line. Soil moisture can also affect the composition of the troposphere through modifying biogenic emissions of isoprene (C5H8). A novel first-order Taylor series decomposition indicates that isoprene emissions are jointly driven by temperature and soil moisture in models. These compounds are important precursors for ozone formation, an air pollutant and a short-lived forcing agent for climate. A mechanistic description of commonly observed relationships between ground-level ozone and meteorology is presented using the concept of soil moisture-temperature coupling regimes. The extent of surface drying was found to be a better predictor of ozone concentrations than temperature or humidity for the Eastern U.S. This relationship is evaluated in a coupled regional chemistry-climate model under several land-atmosphere coupling and isoprene emissions cases. The coupled chemistry-climate model can reproduce the observed soil moisture-temperature coupling pattern, yet modeled ozone is insensitive to changes in meteorology due to the balance between isoprene and the primary atmospheric oxidant, the hydroxyl radical (OH). Overall, this work highlights the importance of soil moisture-atmosphere coupling for previously neglected cold climate regimes, controlling isoprene emissions variability, and providing a processed-based description of observed ozone-meteorology relationships. From the perspective of ozone air quality, the lack of sensitivity of ozone to meteorology suggests a systematic deficiency in chemistry models in high isoprene emission regions. This shortcoming must be addressed to better estimate tropospheric ozone radiative forcing and to understanding how ozone air quality may respond to future warming.

Tawfik, Ahmed B.

277

A methodology to determine soil moisture movement due to thermal gradients  

Microsoft Academic Search

Moisture and heat migration through the soil mass is an important consideration for the safety of electrical gadgets buried in the soil mass. Continuous passage of current through these gadgets increases their temperature, which may result in redistribution or migration of the moisture in the surrounding soil mass. Excessive changes in the soil moisture may lead to its thermal instability,

S. Krishnaiah; D. N. Singh

2003-01-01

278

First approximations of soil moisture retention curves using the filter-paper method  

Microsoft Academic Search

Relationships between gravimetric soil moisture content (w) and matric potential (), and between volumetric soil moisture content (v) and pressure head (h) were approximated for the unsaturated zone on Long Island, New York. Soil samples were collected from two sites using a hand auger. The soil moisture content was determined using the filter-paper (wf) and gravimetric (w) methods, respectively. The

Duke U. Ophori; Beena Maharjan

2000-01-01

279

Estimation of Drainage and Evapotranspiration from Time Series of Soil Moisture, Potential Evaporation, and Precipitation  

Microsoft Academic Search

A previous study demonstrated that the dependence of soil water outflow on soil moisture can be estimated by averaging precipitation conditioned on soil moisture. The methodology is non parametric and relies only on the assumed stationarity of the soil moisture time series. Here we present a method for partitioning out the evapotranspiration component of total outflow. One goal is to

G. D. Salvucci; M. Gioioso

2003-01-01

280

Evaluation of the SMOS L-MEB passive microwave soil moisture retrieval algorithm  

Microsoft Academic Search

Soil moisture will be mapped globally by the European Soil Moisture and Ocean Salinity (SMOS) mission to be launched in 2009. The expected soil moisture accuracy will be 4.0 %v\\/v. The core component of the SMOS soil moisture retrieval algorithm is the L-band Microwave Emission of the Biosphere (L-MEB) model which simulates the microwave emission at L-band from the soil–vegetation

Rocco Panciera; Jeffrey P. Walker; Jetse D. Kalma; Edward J. Kim; Kauzar Saleh; Jean-Pierre Wigneron

2009-01-01

281

Using Soil Moisture as a Guide in Controlling the Amount of Irrigated Water on Grass Lawns  

NASA Astrophysics Data System (ADS)

Soil moisture content is one of the factors that controls the infiltration capacity of soils. Precipitation and irrigation increase soil moisture which in turn reduces infiltration capacity. This results in increased runoff during subsequent storm events. Increased stormwater runoff may cause adverse environmental problems such as increased soil erosion, increased bed and suspended loads in streams, and increased non-point source pollution. Monitoring soil moisture on irrigated plots can be used as a guide for efficient use of irrigated water. Thus, irrigation systems only will be turned on when soil moisture falls below a threshold value for the respective soil type. However, landscapers at Northern Kentucky University (NKU) schedule the irrigation of grass lawns without taking into consideration the level of soil moisture. This has resulted in incidences of irrigation of the lawns during or immediately after a heavy storm event. Effective monitoring of the soil moisture of irrigated fields has been shown to help in controlling cost of irrigation and conserving valuable resources. This can be achieved by using instruments such as tensiometers and neutron probes to monitor soil moisture (Manning, 1992). On an irrigated field such as a grass lawn, the ideal condition will be to maintain soil moisture between field capacity and wilting point. The objective of this study is to investigate the effect of soil texture and slope on the amount of irrigated water used on selected grass lawns on NKU campus at Highland Heights, Kentucky. The grass lawns were selected based on low slope (0 to 10¬0), medium slope (10¬0 to 15¬0), and high slope (more than 15¬0 ). Two plots were selected for each slope category. The soil texture of each grass lawn was determined by performing standard particle size distribution analysis of samples taken during the installation of the tensiometers. A survey instrument and a GIS software were used to analyze the slopes. The tensiometers were monitored daily and NKU Grounds Department was advised to irrigate those plots only when the soil moisture fell below a specified threshold level. The threshold value was between 70 and 80 centibars for the range of soil textures at the site. Temperature and precipitation data were gathered from NKU's Department of Physics and Geology weather center and the Northern Kentucky Airport Weather Station. The second low slope plot (LSII) has the highest percent sand of 40% whilst the second medium slope (MSII) has the lowest sand of 30%. Although the textures of the low slope plots are significantly different, there was not much difference between the moisture readings. However, a slight difference in the texture of the high slope plots tends to affect water infiltration and moisture retention capacities. It takes longer for water to infiltrate the finer grained, high slope plot but it retains the moisture longer once it is saturated. Air temperatures of 850 F and above was the controlling factor as all plots dried faster even after irrigation or precipitation. Overall, the soil moisture monitoring resulted in less amount of irrigated water use; less than half the normal amount.

Boateng, S.; Koenig, J.

2007-05-01

282

Monitoring the Global Soil Moisture Climatology Using GLDAS/LIS  

NASA Astrophysics Data System (ADS)

Soil moisture plays a crucial role in the terrestrial water cycle through governing the process of partitioning precipitation among infiltration, runoff and evaporation. Accurate assessment of soil moisture and other land states, namely, soil temperature, snowpack, and vegetation, is critical in numerical environmental prediction systems because of their regulation of surface water and energy fluxes between the surface and atmosphere over a variety of spatial and temporal scales. The Global Land Data Assimilation System (GLDAS) is developed, jointly by NASA Goddard Space Flight Center (GSFC) and NOAA National Centers for Environmental Prediction (NCEP), to perform high-quality global land surface simulation using state-of-art land surface models and further minimizing the errors of simulation by constraining the models with observation- based precipitation, and satellite land data assimilation techniques. The GLDAS-based Land Information System (LIS) infrastructure has been installed on the NCEP supercomputer that serves the operational weather and climate prediction systems. In this experiment, the Noah land surface model is offline executed within the GLDAS/LIS infrastructure, driven by the NCEP Global Reanalysis-2 (GR2) and the CPC Merged Analysis of Precipitation (CMAP). We use the same Noah code that is coupled to the operational NCEP Global Forecast System (GFS) for weather prediction and test bed versions of the NCEP Climate Forecast System (CFS) for seasonal prediction. For assessment, it is crucial that this uncoupled GLDAS/Noah uses exactly the same Noah code (and soil and vegetation parameters therein), and executes with the same horizontal grid, landmask, terrain field, soil and vegetation types, seasonal cycle of green vegetation fraction and surface albedo as in the coupled GFS/Noah and CFS/Noah. This execution is for the 25-year period of 1980-2005, starting with a pre-execution 10-year spin-up. This 25-year GLDAS/Noah global land climatology will be used for both climate variability assessment and as a source of land initial conditions for ensemble CFS/Noah seasonal hindcast experiments. Finally, this GLDAS/Noah climatology will serve as the foundation for a global drought/flood monitoring system that includes near realtime daily updates of the global land states.

Meng, J.; Mitchell, K.; Wei, H.; Gottschalck, J.

2006-05-01

283

Soil moisture and vegetation memories in a cold, arid climate  

NASA Astrophysics Data System (ADS)

Continental climate is established as a result of a complex interplay between the atmosphere and various land-surface systems such as the biosphere, soil, hydrosphere, and cryosphere. These systems function as climate memory, allowing the maintenance of interannual atmospheric anomalies. In this paper, we present new observational evidence of an interseasonal moisture memory mechanism mediated by the land surface that is manifested in the coupled cold and arid climate of Mongolia. Interannual anomalies of soil moisture and vegetation due to rainfall during a given summer are maintained through the freezing winter months to the spring, acting as an initial condition for subsequent summer land-surface and rainfall conditions. Both the soil moisture and vegetation memories were prominent over the eastern part of the Mongolian steppe zone (103-112°E and 46-50°N). That is, the cold-season climate with low evapotranspiration and strong soil freezing acts to prolong the decay time scale of autumn soil moisture anomalies to 8.2 months that is among the longest in the world. The vegetation also has a memory of the similar time scale, likely because the large rootstock of the perennial plants dominant in the Mongolian steppe may remain alive, retain belowground biomass anomalies during the winter, and have an impact on the initial vegetation growth during the spring.

Shinoda, Masato; Nandintsetseg, Banzragch

2011-10-01

284

Scatterometer-Derived Soil Moisture Calibrated for Soil Texture With a One-Dimensional WaterFlow Model  

Microsoft Academic Search

Current global satellite scatterometer-based soil moisture retrieval algorithms do not take soil characteristics into account. In this paper, the characteristic time length of the soil water index has been calibrated for ten sampling frequencies and for different soil conductivity associated with 12 soil texture classes. The calibration experiment was independently performed from satellite observations. The reference soil moisture data set

Remko de Lange; Rob Beck; Nick van de Giesen; Jan Friesen; Allard de Wit; Wolfgang Wagner

2008-01-01

285

De-noising of microwave satellite soil moisture time series  

NASA Astrophysics Data System (ADS)

The use of satellite soil moisture data for scientific and operational hydrologic, meteorological and climatological applications is advancing rapidly due to increasing capability and temporal coverage of current and future missions. However evaluation studies of various existing remotely-sensed soil moisture products from these space-borne microwave sensors, which include AMSR-E (Advanced Microwave Scanning Radiometer) on Aqua satellite, SMOS (Soil Moisture and Ocean Salinity) mission and ASCAT (Advanced Scatterometer) on MetOp-A satellite, found them to be significantly different from in-situ observations, showing large biases and different dynamic ranges and temporal patterns (e.g., Albergel et al., 2012; Su et al., 2012). Moreover they can have different error profiles in terms of bias, variance and correlations and their performance varies with land surface characteristics (Su et al., 2012). These severely impede the effort to use soil moisture retrievals from multiple sensors concurrently in land surface modelling, cross-validation and multi-satellite blending. The issue of systematic errors present in data sets should be addressed prior to renormalisation of the data for blending and data assimilation. Triple collocation estimation technique has successfully yielded realistic error estimates (Scipal et al., 2008), but this method relies on availability of large number of coincident data from multiple independent satellite data sets. In this work, we propose, i) a conceptual framework for distinguishing systematic periodic errors in the form of false spectral resonances from non-systematic errors (stochastic noise) in remotely-sensed soil moisture data in the frequency domain; and ii) the use of digital filters to reduce the variance- and correlation-related errors in satellite data. In this work, we focus on the VUA-NASA (Vrije Universiteit Amsterdam with NASA) AMSR-E, CATDS (Centre National d'Etudes Spatiales, CNES) SMOS and TUWIEN (Vienna University of Technology) ASCAT data sets to identify two types of errors that are spectrally distinct. Based on a semi-empirical model of soil moisture dynamics, we consider possible digital filter designs to improve the accuracy of their soil moisture products by reducing systematic periodic errors and stochastic noise. We describe a methodology to design bandstop filters to remove artificial resonances, and a Wiener filter to remove stochastic white noise present in the satellite data. Utility of these filters is demonstrated by comparing de-noised data against in-situ observations from ground monitoring stations in the Murrumbidgee Catchment (Smith et al., 2012), southeast Australia. Albergel, C., de Rosnay, P., Gruhier, C., Muñoz Sabater, J., Hasenauer, S., Isaksen, L., Kerr, Y. H., & Wagner, W. (2012). Evaluation of remotely sensed and modelled soil moisture products using global ground-based in situ observations. Remote Sensing of Environment, 118, 215-226. Scipal, K., Holmes, T., de Jeu, R., Naeimi, V., & Wagner, W. (2008), A possible solution for the problem of estimating the error structure of global soil moisture data sets. Geophysical Research Letters, 35, L24403. Smith, A. B., Walker, J. P., Western, A. W., Young, R. I., Ellett, K. M., Pipunic, R. C., Grayson, R. B., Siriwardena, L., Chiew, F. H. S., & Richter, H. (2012). The Murrumbidgee soil moisture network data set. Water Resources Research, 48, W07701. Su, C.-H., Ryu, D., Young, R., Western, A. W., & Wagner, W. (2012). Inter-comparison of microwave satellite soil moisture retrievals over Australia. Submitted to Remote Sensing of Environment.

Su, Chun-Hsu; Ryu, Dongryeol; Western, Andrew; Wagner, Wolfgang

2013-04-01

286

[Effect of soil moisture on prediction of soil total nitrogen using NIR spectroscopy].  

PubMed

As one of the most important components of soil liutrient, it is necessary to obtain the soil total nitrogen(STN)content in precision agriculture. It is a feasible method to predict soil total nitrogen content based on NIRS. However, the effect of soil moisture content (SMC) on the prediction of STN is very serious. In the present research, the effect of SMC was discussed from qualitative analysis and quantitative analysis by the Fourier spectrum analyzer MATRIX_I. Firstly, sixty soil samples with different STN and SMC were scanned by the MATRIX_I. It was found that the reflectince of soil samples in near infrared region decreased with the increase in SMC. Subsequently, Moisture absorbance index (MAI) was proposed by the diffuse of absorbance at the wavelengths of 1 450 and 1 940 nm to classify soil properties and then correction factor was present Finally, the STN forecasting model with BP NN method was established by the revised absorbance data at the six wavelengths of 940, 1 050, 1,100, 1,200, 1,300 and 1,550 nm. The model was evaluated by correlation coefficient of Rc, correlation coefficient of Rv, root mean square error of calibration (RMSEC), root mean square error of validation (RMSEP) and residual prediction deviation (RPD). Compared with the model obtained from original spectral data, both the accuracy and the stability were improved. The new model was with Rc of 0.86, Rv of 0.81, RMSEC of 0.06, RMSEP of 0.05, and RPD of 2.75. With the first derivative of the revised absorbance, the RPD became 2.90. The experiments indicated that the method could eliminate the effect of SMC on the prediction of STN efficiently. PMID:23705431

An, Xiao-Fei; Li, Min-Zan; Zheng, Li-Hua; Liu, Yu-Meng; Sun, Hong

2013-03-01

287

TEMPORAL STABILITY OF PROFILE SOIL MOISTURE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Validation of satellite estimates of surface soil water content and verification of model simulations of sub-surface soil water content over large land areas cannot be accomplished in a timely, cost-effective manner using traditional manual sampling techniques. This study analyzes the temporal stab...

288

[Investigation of polarization characteristics of soil surface with low vegetation cover and different soil moisture].  

PubMed

Compared with the spectral detection method, polarization detection could obtain more information of the target. For example, the polarization detection could be applied to interpret the refractive index and the surface roughness of the object, or retrieve the soil moisture, etc. Polarization detection provides a new approach to quantitative retrieval of soil moisture, and this is very important in agriculture, hydrology, meteorology and ecology. The polarization characteristics of soil surface with low vegetation cover,which is a example of mixed pixel in remote sensing, were researched with experiments, and the relationship between the polarization characteristics and soil moisture was also explored. The results showed that the polarization characteristics of soil surface with low vegetation cover are mainly determined by the area of bare soil, and are strongly relevant with the soil moisture. For the results of experiments in this paper, the IDOLP of soil surface with low vegetation cover increased with increasing soil moisture when the viewing angle of instrument was between 20 degree and 60 degree, while the incident angle of light source was fixed at 40 degree. This paper offered a new method to retrieve moisture content of soil with low vegetation cover. PMID:21284189

Zhang, Qiao; Sun, Xiao-bing; Hong, Jin

2010-11-01

289

Soil moisture monitoring for climate research: Evaluation of a low-cost sensor in the framework of the Swiss Soil Moisture Experiment (SwissSMEX) campaign  

Microsoft Academic Search

Soil moisture measurements are essential to understand land surface–atmosphere interactions. In this paper we evaluate the performance of the low-cost 10HS capacitance sensor (Decagon Devices, United States) using laboratory and field measurements. Measurements with 10HS sensors of volumetric water content (VWC, Vol.%), integrated absolute soil moisture (millimeters) over the measured soil column, and the loss of soil moisture (millimeters) for

Heidi Mittelbach; Francesca Casini; Irene Lehner; Adriaan J. Teuling; Sonia I. Seneviratne

2011-01-01

290

Moisture Controls on Trace Gas Fluxes in Semiarid Riparian Soils  

Microsoft Academic Search

Variability in seasonal soil moisture (SM) and temperature (T) can alter ecosystem\\/atmosphere exchange of the trace gases carbon di- oxide (CO2), nitrous oxide (N2O), and methane (CH4). This study re- ports the impact of year-round SM status on trace gas fluxes in three semiarid vegetation zones, mesquite (30 g organic C kg 21 soil), open\\/ forb (6 g organic C

Jean E. T. McLain; Dean A. Martens

2006-01-01

291

Influence of soil moisture on C incorporation and preservation in soil  

NASA Astrophysics Data System (ADS)

Sequestration of atmospheric C into soil is only mediated by plant. Plant leaf can use atmospheric C by photosynthesis, thereafter this C is translocated into soil through plant root exudates and root fragments. With changing climatic conditions like decreasing rainfall especially during growing seasons of plants, water availability is thought to raise as limiting factor for plant growth and thus sequestration of C. However, little is known about the pathway of translocation of C from atmosphere to soil at different moisture regimes. To quantify atmospheric C incorporation in plant and its preservation into soil via the rhizosphere, a laboratory experiment on Juncus effusus, which is adapted to very moist conditions, was conducted. The plants were kept at levels of 70 and 100% soil moisture (relative to field capacity, which was adjusted daily to a difference of 30% between high and low moisture levels) for several months. C uptake by plants and translocation towards soil was traced 3, 7, 14 and 21 days after 14CO2 pulse labeling in bulk carbon and lipid fractions of plants and soils. J. effusus produced higher leaf and root biomass at 100% moisture as compared to 70% soil moisture. Consequently, rhizosphere-dry mass increased with increasing root biomass. Considering whole pot (plant & soil together), 14C proportion of shoots decreased and that of roots increased successively from 3 to 21 days after labelling due to translocation of C from shoots to roots. 14C content of rhizosphere was observed to be highest at day 14 after labeling at 100% soil moisture, implied an exceptional increase of root exudates, whereas root exudation was less in 70% soil moisture. As a result of C translocation from roots to soil, 14C content of soil increased until day 7 after labeling. Thereafter, soil 14C content decreased more sharply with time at 100% soil moisture than at 70% moisture. Moreover, to gain quantitative knowledge of 14C preservation, a comparatively recalcitrant C fraction, lipid-14C, was also measured. J. effusus leaf, grown at 70% soil moisture; showed higher percentage of lipid-14C of organic C, probably to protect higher loss of water through respiration. Similarly, rhizosphere and soil lipid-14C content were also high under 70% soil moisture, probably because of lower diffusion of root exudates at 70% soil moisture as compared to that at 100% soil moisture. With these result it can be concluded that incorporation of 14C in soil was high in 100% soil moisture but preservation, of bulk C and in the form of lipid-14C, was higher under 70% than that of 100% soil moisture. This clearly explains commonly lower C contents in dry vs. wet soils, where the latter benefit from improved C incorporation, whereas preservation might be less pronounced.

Majumder, B.; Gocke, M.; Kuzyakov, Y.; Wiesenberg, G.

2012-04-01

292

Assimilation of streamflow and soil moisture observations in a distributed physically-based hydrological model  

NASA Astrophysics Data System (ADS)

Data assimilation techniques not only enhance model simulations and predictions, they also give the opportunity to pose a diagnostic on both model and observations used in the assimilation process. The goal of this research is to assimilate streamflow and soil moisture in a distributed physically-based hydrological model, CATHY (CATchment HYdrology). The study site is the des Anglais Watershed, a 690-km2 river basin located in southern Québec, Canada. An ensemble Kalman filter was used to assimilate streamflow observations at the basin outlet and at interior locations, as well as soil moisture at different depths (15, 45, and 90 cm) measured with probes (6 stations) and surface soil moisture estimated from radar remote sensing. The use of a Latin hypercube sampling instead of the Monte Carlo method to generate the ensemble reduced the size of ensemble, and therefore the calculation time. An important issue in data assimilation is the estimation of error covariance matrices. Different post-assimilation diagnostics, based on innovations (observation-minus-background), analysis residuals (observation-minus-analysis) and analysis increments (analysis-minus-background) were used to evaluate assimilation optimality. A calibration approach was performed to determine the standard deviation of model parameters, forcing data and observations that lead to optimal assimilations. The analysis of innovations showed a lag between the model prediction and the observation during rainfall events. The assimilation of streamflow observations (outlet or interior locations) corrected this discrepancy. The assimilation of outlet streamflow observations improved the Nash-Sutcliffe efficiencies (NSE) at both outlet and interior point locations. The structure of the state vector used in this study allowed the assimilation of outlet streamflow observations to have an impact over streamflow simulations at interior point locations. Indeed, the state vector contains the outlet streamflow (Qout) and the incoming streamflow (Qin), since both these informations are used by the Muskingum-Cunge surface routing equation in CATHY. However, assimilation of streamflow observations increased systematically the soil moisture values simulated at 15 and 45 cm. The combined assimilation of outlet streamflow and soil moisture improved the NSE of streamflow without degrading the simulation of soil moisture. Moreover, the assimilation of streamflow and soil moisture observations from one station (at 45 cm depth) appeared to have a similar impact on soil moisture simulations compared to a combined assimilation of streamflow and soil moisture observations from five stations. Finally, it was found that the frequency of the assimilation of soil moisture observations has a greater impact on the results than the spatial coverage of the assimilation: assimilation of daily soil moisture measured with probes at six stations gives better results than the assimilation of surface soil moisture estimated from radar remote sensing 8 times over the course of a summer season.

Trudel, M.; Leconte, R.; Paniconi, C.

2012-04-01

293

Soil Moisture Retrieval From ASAR Measurements Over Natural Surfaces With a Large Roughness Variability.  

National Technical Information Service (NTIS)

In this work, the accuracy of soil moisture retrieved from ASAR data over bare or sparsely vegetated surfaces is investigated by means of a simulation study. The soil moisture retrieval method is based on an optimization algorithm that appropriately inver...

F. Mattia G. Pasquariello G. Satalino L. Dente

2005-01-01

294

Soil Moisture and Vegetation Effects on GPS Reflectivity From Land  

NASA Astrophysics Data System (ADS)

While originally designed as a navigation system, the GPS signal has been used to achieve a number of useful scientific measurements. One of these measurements utilizes the reflection of the GPS signal from land to determine soil moisture. The study of GPS reflections is based on a bistatic configuration that utilizes forward reflection from the surface. The strength of the GPS signal varies in proportion to surface parameters such as soil moisture, soil type, vegetation cover, and topography. This paper focuses on the effects of soil water content and vegetation cover on the surface based around a reflectivity. A two-part method for calibrating the GPS reflectivity was developed that permits the comparison of the data with surface parameters. The first part of the method relieves the direct signal from any multipath effects, the second part is an over-water calibration that yields a reflectivity independent of the transmitting satellite. The sensitivity of the GPS signal to water in the soil is shown by presenting the increase in reflectivity after rain as compared to before rain. The effect of vegetation on the reflected signal is also presented by the inclusion of leaf area index as a fading parameter in the reflected signal from corn and soy bean fields. The results are compared to extensive surface measurements made as part of the Soil Moisture Experiment 2002 (SMEX 2002) in Iowa and SMEX 2003 in Georgia.

Torres, O.; Grant, M. S.; Bosch, D.

2004-12-01

295

The soil moisture active passive (SMAP) mission and validation  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Soil Moisture Active Passive (SMAP) satellite will be launched by the National Aeronautics and Space Administration in October 2014. This satellite is the culmination of basic research and applications development over the past thirty years. During most of this period, research and development o...

296

Introduction to Soil Moisture Experiments 2004 (SMEX04)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Land surface antecedent boundary conditions may control the onset and intensity of the summer monsoon rainfall in the southwestern U.S. and northern Mexico. The influence of the land surface is relayed through surface evaporation and associated surface cooling (dependent on soil moisture), terrain, ...

297

A microwave imaging circular setup for soil moisture information  

Microsoft Academic Search

Soil moisture is an important parameter for understanding fluid flow modelling as well as the water uptake by plants roots. A microwave scanner is presently being designed to demonstrate the potentiality of a non-invasive microwave imaging system for volumetric water content monitoring. After briefly describing the setup, the numerical tools which are needed for the modelling and the inversion of

Raphael Lencrerot; A. Litman; H. Tortel; J.-M. Geffrin

2007-01-01

298

Soil Temperature and Moisture Errors in Operational Eta Model Analyses  

Microsoft Academic Search

Proper partitioning of the surface heat fluxes that drive the evolution of the planetary boundary layer in numerical weather prediction models requires an accurate specification of the initial state of the land surface. The National Centers for Environmental Prediction (NCEP) operational Eta Model is used to produce land surface analyses by continuously cycling soil temperature and moisture fields. These fields

Christopher M. Godfrey; David J. Stensrud

2008-01-01

299

Validation of the ASAR Global Monitoring Mode Soil Moisture Product  

Technology Transfer Automated Retrieval System (TEKTRAN)

It is well established in literature that integration of land surface variables such as soil moisture into forecasting models will lead to improved hydrologic prediction. Furthermore, most hydrological processes are best monitored at spatial scales of 1 km or higher. However, current and future pas...

300

NASA Soil Moisture Active Passive (SMAP) Mission: Overview.  

National Technical Information Service (NTIS)

The Soil Moisture Active Passive (SMAP) mission is one of the first Earth observation satellites being developed by NASA in response to the National Research Council.s Decadal Survey (1). Its mission design consists of L-band radiometer and radar instrume...

D. Entekhabi E. Njoku K. Kellogg P. O'Neill

2011-01-01

301

An evaluation of soil moisture models for countermine application  

Microsoft Academic Search

The focus of this study is the evaluation of emerging soil moisture models as they apply to infrared, radar, and acoustic sensors within the scope of countermine operations. Physical, chemical, and biological processes changing the signature of the ground are considered. The available models were not run in-house, but were evaluated by the theory by which they were constructed and

George L. Mason

2004-01-01

302

The development of HJ SAR soil moisture retrieval algorithm  

Microsoft Academic Search

Four satellites with S-band synthetic aperture radar (SAR) onboard, along with four optical satellites, form the Huan Jing (HJ) constellation, which consists of the Chinese Environment and Disaster Monitoring Satellites that are designed for fast monitoring of the dynamics of soil moisture and other environmental variables. A 24-hour revisit time of the future four HJ SAR satellites enables an estimation

Jinyang Du; Jiancheng Shi; Ruijing Sun

2010-01-01

303

Retrieving near-surface soil moisture from Radarsat SAR data  

NASA Astrophysics Data System (ADS)

On the basis of six Radarsat synthetic aperature radar (SAR) images acquired over the Paddle River Basin, Alberta, and 1350 field soil moisture data collected from nine selected sites of the basin in the same days, this study demonstrated the feasibility of retrieving near-surface soil moisture (5-10 cm depth) from Radarsat SAR data. Between two retrieval algorithms, a linear regression and the theoretical integral equation model (IEM) of Fung et al. [1992], the results indicate that IEM performed consistently better than the regression model. However, the performance of both models generally deteriorates when the basin is nearly saturated, which is the case for September 10 and 27, 1996, with a basin saturation level of 82 and 75%, respectively. With respect to Radarsat's configuration and IEM's surface parameters, it is found that radar backscattering ?0 is highly sensitive to the surface rms height, especially for a relatively smooth surface and a Gaussian correlation function. From the semivariogram of measured soil moisture and ?0 it is found that the homogeneity assumption of spatial interpolation as a function of distance lag breaks down only at a distance lag of about 200-275 m. Apparently, spatial interpolation methods based on this assumption can only interpolate soil moisture meaningfully for single land use plots of several hundred meters in size.

Biftu, Getu Fana; Gan, Thian Yew

1999-05-01

304

Future Soil Moisture Satellite Missions and Research Needs  

Microsoft Academic Search

During the coming decade, launches of a number of satellite microwave sensors will provide new and unique opportunities for acquiring global information on the amount and distribution of surface soil moisture and its frozen\\/thawed state. This new information will provide potentially significant enhancements to the predictive capabilities of numerical weather and climate models as well as improved capabilities for monitoring

E. G. Njoku; T. J. Jackson; P. E. O'Neill

2001-01-01

305

SYLAB L BAND MICROWAVE OBSERVATIONS OF SOIL MOISTURE REVISITED  

Technology Transfer Automated Retrieval System (TEKTRAN)

In preparing for future L band passive microwave soil moisture satellite missions, investigators have employed ground, aircraft and satellite sensors. Of the satellite sensors, there has been only one instrument that provides any heritage at L band, the Skylab S-194 instrument that operated in the 1...

306

TRMM Microwave Imager soil moisture mapping and flooding during CLASIC  

Technology Transfer Automated Retrieval System (TEKTRAN)

Passive microwave remote sensing has the potential to contribute to flood risk and impact assessment through the direct relationship between emissivity and soil moisture/standing water. Lower frequencies have greater potential because the impacts of atmospheric and vegetation attenuation are minimiz...

307

Concerning the Relationship between Evapotranspiration and Soil Moisture  

Microsoft Academic Search

Evapotranspiration observations have traditionally been scaled by potential evapotranspiration as a means of unifying the soil moisture-evapotranspiration relationship under a variety of meteorological conditions. However, this scaling alone does not unify the relationship during the drying. supply-limited phase. In this paper, a second scaling parameter is identified which applies to this phase of evapotranspiration. The parameter is a maximum sustainable,

Peter J. Wetzel; Jy-Tai Chang

1987-01-01

308

The International Soil Moisture Network - A data hosting facility for in situ soil moisture measurements in support of SMOS cal/val  

NASA Astrophysics Data System (ADS)

In situ soil moisture observations are crucial for validating SMOS and other satellite based soil moisture products. In order to support valid conclusions about the accuracy of such products the in situ soil moisture observations used need to be available for many locations worldwide and have to be intercomparable. So far, the latter requirement is usually not met as the different locally and regionally operating networks apply neither a standard measurement technique nor a standard protocol. The need for international cooperation in constructing centralized and homogenized global soil moisture data sets has been recognized by the international community. To support the validation of satellite soil moisture products the International Soil Moisture Working Group (ISMWG) has suggested constructing a standardized global data base of in-situ soil moisture measurements. Further, the creation of multi-source soil moisture datasets, including in situ observations, was included in the GEO 2009-2011 Work Plan under sub-task WA-08-01a led by GEWEX (Global Energy and Water Cycle Experiment) and ESA (European Space Agency). As fruit of this initiative and in support of SMOS calibration and validation activities, ESA decided to support the development of the International Soil Moisture Network. The International Soil Moisture Network is a web based data hosting facility for collecting and redistributing in situ soil moisture measurements from existing soil moisture networks. Incoming data are carefully checked for their quality and homogenized before being stored in the database. A web interface allows the user to easily query and download the data. Special care has been taken to make downloads compliant with international data and metadata standards such as GEWEX CEOP, ISO 19115, and INPIRE of the European Commission. This presentation provides insight in the design considerations, implementation, functionalities and outputs of the data hosting facility. The International Soil Moisture Network can be accessed at: http://www.ipf.tuwien.ac.at/insitu

Dorigo, Wouter; Hahn, Sebastian; Hohensinn, Roland; Paulik, Christoph; Wagner, Wolfgang; Drusch, Matthias; van Oevelen, Peter

2010-05-01

309

Modeling canopy transpiration using time series analysis: A case study illustrating the effect of soil moisture deficit on Pinus taeda  

Microsoft Academic Search

Bulk sap flow measurements are widely used to assess and model the hydrological process of canopy transpiration (Ec); however, common analysis techniques of these data do not identify and\\/or incorporate time lag effects, multiple variables affecting canopy transpiration at different temporal scales or thresholds, and interactions of environmental variables. Here, we describe how autoregressive-integrated-moving average (ARIMA) time series models can

Chelcy R. Ford; Carol E. Goranson; Robert J. Mitchell; Rodney E. Will; Robert O. Teskey

2005-01-01

310

Radon diffusion coefficients in soils of varying moisture content  

NASA Astrophysics Data System (ADS)

Radon is a naturally occurring radioactive gas that is generated in the Earth's crust and is free to migrate through soil and be released to the atmosphere. Due to its unique properties, soil gas radon has been established as a powerful tracer used for a variety of purposes, such as exploring uranium ores, locating geothermal resources and hydrocarbon deposits, mapping geological faults, predicting seismic activity or volcanic eruptions and testing atmospheric transport models. Much attention has also been given to the radiological health hazard posed by increased radon concentrations in the living and working environment. In order to exploit radon profiles for geophysical purposes and also to predict its entry indoors, it is necessary to study its transport through soils. Among other factors, the importance of soil moisture in such studies has been largely highlighted and it is widely accepted that any measurement of radon transport parameters should be accompanied by a measurement of the soil moisture content. In principle, validation of transport models in the field is encountered by a large number of uncontrollable and varying parameters; laboratory methods are therefore preferred, allowing for experiments to be conducted under well-specified and uniform conditions. In this work, a laboratory technique has been applied for studying the effect of soil moisture content on radon diffusion. A vertical diffusion chamber was employed, in which radon was produced from a 226Ra source, was allowed to diffuse through a soil column and was finally monitored using a silicon surface barrier detector. By solving the steady-state radon diffusion equation, diffusion coefficients (D) were determined for soil samples of varying moisture content (m), from null (m=0) to saturation (m=1). For dry soil, a D value of 4.1×10-7 m2s-1 was determined, which increased moderately by a factor of ~3 for soil with low moisture content, i.e. up to m ~0.2. At higher water fractions, a decrease in D was initiated and became particularly pronounced approaching complete saturation; at m =0.9, D was as low as 2×10-9 m2s-1. A series of field experiments has also been conducted using alpha-track CR-39 detectors to follow the moisture-dependence of radon diffusion through soil under natural conditions. Diffusion coefficients were determined as a function of surface soil moisture assuming a one-dimensional diffusive radon transport model. Comparison between results obtained by the two methods showed that laboratory studies may provide a good indication of radon diffusion coefficients to be expected in the field. However, values determined in the field were systematically lower than those assessed in the laboratory. This finding could be attributed to soil-dependent parameters, such as differences in pore space geometry between the soil used in laboratory experiments and the undisturbed soil. In the latter case, the higher degree of compaction imposes a more tortuous pathway to soil gas, while at the same time the diffusive gas flux is hindered by local-scale zones of higher bulk density or water content.

Papachristodoulou, C.; Ioannides, K.; Pavlides, S.

2009-04-01

311

Estimation of spatial soil moisture averages in a large gully of the Loess Plateau of China through statistical and modeling solutions  

NASA Astrophysics Data System (ADS)

Three-year root zone soil water datasets in a large gully were used for analysis. Considerable soil moisture time stability existed in the large gully. Time-stale locations were showed temporally robust by cross validation. Spatial averages were reliably estimated by only a few randomly selected locations. A simple model was developed and well reproduced soil moisture time series.

Gao, Xiaodong; Wu, Pute; Zhao, Xining; Wang, Jiawen; Shi, Yinguang; Zhang, Baoqing; Tian, Lei; Li, Hongbing

2013-04-01

312

Soil moisture control over autumn season methane flux, Arctic Coastal Plain of Alaska  

NASA Astrophysics Data System (ADS)

Two shortfalls in estimating current and future seasonal budgets of methane efflux in Arctic regions are the paucity of non-summer measurements and an incomplete understanding of the sensitivity of methane emissions to changes in tundra moisture. A recent study in one Arctic region highlighted the former by observing a previously unknown large methane pulse during the onset of autumn soil freeze. This study addresses these research gaps by presenting an analysis of eddy covariance measurements of methane efflux and supporting environmental variables during the autumn season of 2009 and associated soil freeze-in period at our large-scale water manipulation site near Barrow, Alaska (the Biocomplexity Experiment). We found that methane emissions during the autumn were closely tied to liquid soil moisture in the top 30 cm of soil. Declines in soil moisture between manipulated wet, intermediate, and dry conditions as well as through time during the soil freeze-in period led to corresponding declines in methane efflux. During the period of soil freeze-in (from 23 September to 28 October), we estimate that our wet section emitted 623 mg CH4 m-2 while the dry section emitted only 253 mg CH4 m-2, the average of which represents 18 % of net emissions from the typically measured growing season. We did not find evidence for a pulse in methane emissions during soil freeze at this site. Results from this study imply that future changes in tundra moisture will have a large effect on methane emissions in this region, and changes which span the saturation point are likely to have the largest effect. We speculate that changes in autumn soil moisture are also likely to affect winter emissions via the insulative effects of ice on winter soil temperature and liquid soil moisture availability after bulk soil freeze. Further research should expand the use of eddy covariance methane flux measurements to investigate ecosystem-level effects of tundra moisture on autumn and winter methane emissions in this and other Arctic regions.

Sturtevant, C. S.; Oechel, W. C.; Zona, D.; Emerson, C. E.

2011-07-01

313

Dynamic soil moisture monitoring in shendong mining area using Temperature Vegetation Dryness Index  

Microsoft Academic Search

As a method to analyze the soil moisture, the NDVI-Ts space has aroused much attention. The paper uses the method of TVDI which calculated from the NDVI-Ts space to monitor the soil moisture status of Shendong mining area which is located in arid and semiarid area in Northwest China from 6 September to 8 November. The soil moisture status come

Ying Liu; Weiyu Ma; Hui Yue; Hu Zhao

2011-01-01

314

Remote sensing of an agricultural soil moisture network in Walnut Creek, Iowa  

Technology Transfer Automated Retrieval System (TEKTRAN)

The calibration and validation of soil moisture remote sensing products is complicated by the logistics of installing a soil moisture network for a long term period in an active landscape. Usually soil moisture sensors are added to existing precipitation networks which have as a singular requiremen...

315

Evaluation of SMAP Level 2 Soil Moisture Algorithms Using SMOS Data.  

National Technical Information Service (NTIS)

The objectives of the SMAP (Soil Moisture Active Passive) mission are global measurements of soil moisture and land freeze/thaw state at 10 km and 3 km resolution, respectively. SMAP will provide soil moisture with a spatial resolution of 10 km with a 3-d...

A. Colliander E. Njoku J. C. Shi M. Cosh P. O'Neill R. Bindlish S. Chan T. Zhao T. J. Jackson Y. Kerr

2011-01-01

316

The SMAP In Situ Soil Moisture Sensor Testbed: Comparing in situ sensors for satellite validation  

Technology Transfer Automated Retrieval System (TEKTRAN)

One of the most valuable tools in validating satellite based soil moisture estimates, such as those from the Soil Moisture Active Passive (SMAP) mission are large scale in situ networks. Global validation involves networks operated by many different organizations. Existing in situ soil moisture netw...

317

Evaluation of the SMAP radiometer lever 2 pre-launch soil moisture algorithms using SMOS data  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objectives of the upcoming SMAP (Soil Moisture Active Passive) satellite mission include global measurements of soil moisture at 40 km, 10 km and 3 km resolutions with a 3-day revisit time at an accuracy of 0.04 m3/m3. The 40 km resolution soil moisture product is based primarily on the passiv...

318

Relationships between oceanic-atmospheric patterns and soil moisture in the Upper Colorado River Basin  

NASA Astrophysics Data System (ADS)

We examine the relationships between oceanic-atmospheric patterns and soil moisture. Soil moisture in the UCRB has strong correlation with SSTs in normal years. PDO positively influences UCRB soil moisture in all three weather conditions. ENSO displays different results in in-phase and 1-year lead time analyses. AMO displays similar results in in-phase and 1-year lead time analyses.

Tang, Chunling; Piechota, Thomas C.; Chen, Dong

2011-12-01

319

High resolution change estimation of soil moisture and its assimilation into a land surface model  

Microsoft Academic Search

Near surface soil moisture plays an important role in hydrological processes including infiltration, evapotranspiration and runoff. These processes depend non-linearly on soil moisture and hence sub-pixel scale soil moisture variability characterization is important for accurate modeling of water and energy fluxes at the pixel scale. Microwave remote sensing has evolved as an attractive technique for global monitoring of near surface

Ujjwal Narayan

2006-01-01

320

Validation of the ASAR Global Monitoring Mode Soil Moisture Product Using the NAFE'05 Data Set  

Microsoft Academic Search

The Advanced Synthetic Aperture Radar (ASAR) Global Monitoring (GM) mode offers an opportunity for global soil moisture (SM) monitoring at much finer spatial resolution than that provided by the currently operational Advanced Microwave Scanning Radiometer for the Earth Observing System and future planned missions such as Soil Moisture and Ocean Salinity and Soil Moisture Active Passive. Considering the difficulties in

Iliana Mladenova; Venkat Lakshmi; Jeffrey P. Walker; Rocco Panciera; Wolfgang Wagner; Marcela Doubkova

2010-01-01

321

Evaluation of Hyperspectral, Infrared Temperature and Radar Measurements for Monitoring Surface Soil Moisture  

Microsoft Academic Search

Remote sensing techniques for monitoring soil moisture were tested by comparing hyperspectral reflectance and spectral indexes; surface temperature (Ts) and thermal indexes; and normalized radar backscatter to soil moisture. A laboratory study indicated that hyperspectral reflectance and Ts were sensitive to surface soil moisture (r2 range from 0.72

Ross Bryant; David Thoma; Susan Moran; Chandra Holifield; David Goodrich; Tim Keefer; Ginger Paige

322

SOIL MOISTURE EXPERIMENTS 2004 AND 2005 FOR EVALUATION OF VEGETATION WATER CONTENT WITH MODIS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Soil Moisture Experiment 2004 (SMEX04) and Soil Moisture Experiment 2005 (SMEX05) were conducted to test algorithms in support of Aqua AMSR-E and the future HYDROS mission. Vegetation Water Content is a major uncertainty for retrieval of soil moisture from microwave data, and MODIS shortwave in...

323

Modeling Soil Moisture in the Mojave Desert  

USGS Publications Warehouse

The Mojave Desert is an arid region of southeastern California and parts of Nevada, Arizona, and Utah; the desert occupies more than 25,000 square miles (fig. 1). Ranging from below sea level to over 5,000 feet (1,524 m) in elevation, the Mojave Desert is considered a ?high desert.? On the west and southwest it is bounded by the Sierra Nevada, the San Gabriel, and the San Bernardino Mountains. These imposing mountains intercept moisture traveling inland from the Pacific Ocean, producing arid conditions characterized by extreme fluctuations in daily temperatures, strong seasonal winds, and an average annual precipitation of less than six inches. The Mojave Desert lies farther south and at a lower elevation than the cooler Great Basin Desert and grades southward into the even lower and hotter Sonoran Desert.

Miller, David M.; Hughson, Debra; Schmidt, Kevin M.

2008-01-01

324

Evidence of soil moisture control of energy partitioning with vegetation  

NASA Astrophysics Data System (ADS)

The seminal works by Dooge, Linear Theory of Hydrologic Systems, and Eagleson, Dynamic Hydrology, have shaped and guided hydrologists, and hydrology, over the past 30 years. Both Dooge and Eagleson were interested in the controlling mechanisms of hydrologic processes, including evapotranspiration. Their investigations into the switching mechanisms for control of soil evaporation and persistence and feedback in partitioning of latent and sensible heat fluxes as a function of soil moisture conditions have been leading contributions in these areas of study. Long-term, 20-min frequency data from the Oregon Evapotranspiration Investigation Plot (ETIP) from spring, summer and fall periods, including a special summer dry-down experiment, are analyzed for impacts of soil moisture content on daily Bowen ratio and daily ratio of measured grass evapotranspiration to a Penman-Monteith reference evapotranspiration. The gradual shift in partitioning of available energy between latent and sensible heat fluxes within a growing vegetative canopy with fully developed root zone illustrates the complexity of the processes and the difficulty of determining control processes compared to bare soil conditions with no vegetation. A full suite of data for radiation balance, soil parameters and moisture content, latent and sensible heat fluxes and micrometeorological parameters over a 125-day period in 1992 are exploited. Encompassed within these data is a special 30-day summer dry-down experiment.

Cuenca, R. H.; O Kane, J. P.

2003-04-01

325

Characteristics of soil moisture in permafrost observed in East Siberian taiga with stable isotopes of water  

Microsoft Academic Search

Soil moisture and its isotopic composition were observed at Spasskaya Pad experimental forest near Yakutsk, Russia, during summer in 1998, 1999, and 2000. The amount of soil water (plus ice) was estimated from volumetric soil water content obtained with time domain reflectometry. Soil moisture and its 18O showed large interannual variation depending on the amount of summer rainfall. The soil

A. Sugimoto; D. Naito; N. Yanagisawa; K. Ichiyanagi; N. Kurita; J. Kubota; T. Kotake; T. Ohata; T. C. Maximov; A. N. Fedorov

2003-01-01

326

NDVI and EVI Estimation of Root Zone Soil Moisture in East Texas  

Microsoft Academic Search

The soil surface layer is a critical boundary between land and atmosphere, and soil moisture is a critical condition affecting interaction of land surface and atmosphere. The root zone can be defined as the top 100 cm of the soil layer. Remotely sensed data can indirectly measure soil moisture, but the signal only penetrates the top few centimeters, so soil

Mark T. Schnur

327

Effect of concentration, moisture and soil type on the dissipation of flufenacet from soil.  

PubMed

Effect of concentration, moisture and soil type on dissipation of flufenacet from soil has been studied under laboratory condition. The treated soil samples (1 and 10 microg/g levels) were incubated at 25+/-1 degrees C. The effect of moisture was studied by maintaining the treated soil samples (10 microg/g level) at field capacity and submerged condition. In general, flufenacet persisted for 60-90 days at lower and beyond 90 days at high rate. The dissipation of flufenacet from soil followed first order kinetics with half-life (DT50) values ranging from 10 to 31 days. The dissipation of flufenacet was faster at low rate than high rate of application. The slow dissipation at high rate could be attributed to inhibition of microbial activity at high rate. There was little overall difference in rate of dissipation in Ranchi and Nagpur soil maintained at field capacity and submerged condition moisture regimes. In Delhi soil net dissipation was faster under field capacity moisture than submerged condition. Soil types greatly influenced the dissipation of flufenacet. Dissipation was fastest in Delhi soil (DT50 10.1-22.3 days) followed by Ranchi soil (DT50 10.5-24.1 days) and least in Nagpur soil (DT50 29.2-31.0 days). The difference in dissipation could be attributed to the magnitude of adsorption and desorption of flufenacet in these soils. PMID:12108696

Gupta, Suman; Gajbhiye, Vijay T

2002-06-01

328

Using soil temperature and moisture to predict forest soil nitrogen mineralization  

Microsoft Academic Search

Due to the importance of N in forest productivity ecosystem and nutrient cycling research often includes measurement of soil N transformation rates as indices of potential availability and ecosystem losses of N. We examined the feasibility of using soil temperature and moisture content to predict soil N mineralization rates (Nmin) at the Coweeta Hydrologic Laboratory in the southern Appalachians. We

Jennifer D. Knoepp; Wayne T. Swank

2002-01-01

329

Tensiometer and method of determining soil moisture potential in below-grade earthen soil  

Microsoft Academic Search

A portable tensiometer to in situ determine below-grade soil moisture potential of earthen soil includes, a) a body having opposing first and second ends and being adapted for complete insertion into earthen soil below grade; b) a porous material provided at the first body end, the porous material at least in part defining a fluid chamber within the body at

Joel M. Hubbell; James B. Sisson

1997-01-01

330

Tensiometer and method of determining soil moisture potential in below-grade earthen soil  

Microsoft Academic Search

A portable tensiometer to in-situ determine below-grade soil moisture potential of earthen soil includes, (a) a body having opposing first and second ends and being adapted for complete insertion into earthen soil below grade; (b) a porous material provided at the first body end, the porous material at least in part defining a fluid chamber within the body at the

J. M. Hubbell; J. B. Sisson

1997-01-01

331

SOIL MOISTURE NEUTRON PROBE CALIBRATION AND USE IN FIVE SOILS OF UZBEKISTAN  

Technology Transfer Automated Retrieval System (TEKTRAN)

The soil moisture neutron probe (SMNP) is a key tool in measurements of crop water use, necessary for accurate irrigation and minimization of salinization; but it is not useful in all soils. We showed that the SMNP could be accurately field calibrated at five locations in Uzbekistan, in soils rangin...

332

Improving the Airborne Remote Sensing of Soil Moisture: Estimating Soil Effective Temperature  

Microsoft Academic Search

Obtaining measurements of the near-surface soil water content from passive microwave observations requires knowledge of the soil effective temperature, which is a function of the soil temperature and moisture profiles. Detailed information on these profiles is not available from airborne remote sensing, but the effective temperature can be estimated via thermal infrared observations of the land surface. Current estimation techniques

Paul M. O'Neill; Remy Dehaan; Jeffrey P. Walker; Iain Hume

333

Adopting Drought Indices for Estimating Initial Soil Moisture for Land Surface Models  

NASA Astrophysics Data System (ADS)

We studied the use of two drought indices: Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI) for developing regional soil moisture estimates. Soil moisture availability has a significant impact on environmental processes at different scales. Errors in initializing soil moisture tend to have high persistence and cause bias in the results for both short-term weather as well as climate outlooks. However, regionally representative soil moisture is a difficult parameter to estimate. Soil moisture measurements are limited, and often point-based, with significant spatial variability. Therefore development of simple approaches for estimation of soil moisture on a regional scale is of immediate importance for the atmospheric science community. SPI and PDSI variations are compared for three North Carolina climate divisions: mountains, central piedmont, and the coastal plains, for a period of five years. Results suggest SPI is better representative than PDSI for short time scale precipitation changes that introduce mesoscale variability. Soil moisture observations were also made concurrently to assess the covariance between the drought indices, precipitation, and soil moisture changes. When compared with observed soil moisture values, results suggest SPI can be used as an indicator of soil wetness at a regional scale. SPI has good coherence with the soil wetness variability. A regression equation for estimating soil moisture based on SPI is proposed and tested. This relation can be used for developing soil moisture estimates over a model domain.

Sims, A. P.; Niyogi, D. S.; Raman, S.

2001-05-01

334

Time Series Prediction Model of Soil Moisture Based on Wavelet DeNoising  

Microsoft Academic Search

Soil moisture is one of the most important factors which affect crop yields directly. In recent years, although upland field area increased not too much, agricultural water resources utilization increased which has led to a waste of water resources in Sanjiang Plain. In order to solve the above problem, wavelet de-noising theory and time series analysis are adopted to analyze

Peng Shengmin; Li Tianxiao; Wang Fulin

2009-01-01

335

The objectives and rationale of the Soil Moisture and Ocean Salinity (SMOS) mission  

Microsoft Academic Search

This paper will describe the SMOS concept in terms of instrument (characteristics) investigates the main aspects of the retrieval capabilities of the 2D microwave interferometer for monitoring soil moisture, vegetation biomass and surface temperature. The analysis is based on model inversion taking into account the instrument characteristics. The standard error of estimate of the surface variables is computed as a

Yann H. Kerr; Philippe Waldteufel; Jean-Pierre Wigneron; M. Berger

2001-01-01

336

Determination of the Sea Surface Salinity Error Budget in the Soil Moisture and Ocean Salinity Mission  

Microsoft Academic Search

The Soil Moisture and Ocean Salinity mission will provide sea surface salinity maps over the oceans, beginning in late 2009. In this paper an ocean salinity error budget is described, an analysis needed to identify the magnitude of the error sources associated with the retrieval. Instrumental, external noise sources, and geophysical errors have been analyzed, stressing their relative impact. This

Roberto Sabia; Adriano Camps; Marco Talone; Mercè Vall-Llossera

2010-01-01

337

Evaluation of SMOS L2 soil moisture data over the Eastern Poland using ground measurements  

NASA Astrophysics Data System (ADS)

Validation of SMOS products is vital for their further use in the study of climate and hydrology. Several authors [1,2] have recently evaluated SMOS soil moisture data with an aid of in-situ observations of soil moisture. Collow and Robock have reported a dry bias as compared to in situ observations. Since their results are not much conclusive, they call for further studies using more data. Bircher and co-authors have also noted significant discrepancies between Danish network and SMOS soil moisture. SWEX_POLAND soil moisture network consists of 9 stations located in Eastern Poland. These stations are located on the areas representing variety types of land use: meadows, cultivated fields, wetlands and forests. We have expanded our analysis, as presented in the EGU 2012, using data from all network stations. Similarly as before, we have used three methods in our comparison studies: the Bland-Altman method, concordance correlation coefficient and total deviation index. Using these methods we have confirmed a fair/moderate agreement of SMOS L2 SM data and network observations. Like the other authors we have also noted the significant biases in SMOS soil moisture. However, the general trends in dynamics of soil moisture revealed by SMOS, the SWEX_POLAND network and referred to GLDAS, are in a considerable relevancy. We have shown that the SMOS satellite measurements are reliable, so can be used to detect areas of dry and moist soil. In Poland the trends indicating the growth of agricultural droughts are depicted by SMOS L2 very well, even better than national drought services for the agriculture. It is worth to note that the year 2011 was more variable and drier than the 2010 for Poland. Moreover, SMOS data prove the well-known property of central Poland to be drier than the rest of the country. It is expected that further mitigation of RFI contamination in Poland will be available due to the cooperation of ESA SMOS to the national spectrum control services (UKE). Therefore, we confirm that SMOS is a very valuable source of data, which is going to be used on regional studies related to the climate in Poland. 1. Collow, T.W., A. Robock, J. B. Basara, and B. G. Illston (2012), Evaluation of SMOS retrievals of soil moisture over the central United States with currently available in situ observations, J. Geophys. Res., 117, D09113, doi:10.1029/2011JD017095. 2. Bircher, S., Skou, N., Jensen, K. H.,. Walker, J. P and Rasmussen L. (2012), A soil moisture and temperature network for SMOS validation in Western Denmark, Hydrol. Earth Syst. Sci., 16, 1445-1463, doi:10.5194/hess-16-1445-2012

Usowicz, Jerzy; ?ukowski, Mateusz; S?omi?ski, Jan; Stankiewicz, Krystyna; Usowicz, Bogus?aw; Lipiec, Jerzy; Marczewski, Wojciech

2013-04-01

338

[Spatial heterogeneity of soil moisture after raining at forest-grassland landscape boundary in hilly area of Loess Plateau].  

PubMed

Soil moisture is a main factor limiting vegetation restoration in semi-arid region. In this paper, the spatial variability of different layers soil moisture after raining at the forest-grassland boundary in hilly area of Loess Plateau were studied by traditional and geostatistical analysis methods. The results showed that the moisture content in surface (0 - 10 cm) and subsurface soil layer (10 - 20 cm) of grassland was higher than that of forestland. The two layers soil moisture content at forest-grassland boundary showed a small variation but an obvious ecological distribution. By using moving split-window techniques, it was obtained that the width of edge influence in surface and subsurface layer was 8 and 6 m, respectively. Geostatistical analyses showed that the spatial distribution of two layers soil moisture had a pure nugget effect in grassland, linear model in forestland, and spherical model in forest-grassland boundary. The spatial heterogeneity of two layers soil moisture was higher at forest-grassland boundary than at forestland and grassland, which had a stronger spatial dependence and autorelation. Kriging maps expressed the spatial structural characters. The distribution of soil moisture in two layers showed a strip shape near forest edge, and a patch shape far from the edge. PMID:16355767

You, Wenzhong; Zeng, Dehui; Liu, Mingguo; Song, Xide; Ye, Yaohui; Zhang, Yong

2005-09-01

339

Soil moisture-temperature feedbacks at meso-scale during summer heat waves over Western Europe  

NASA Astrophysics Data System (ADS)

This paper investigates the impact of soil moisture-temperature feedback during heatwaves occurring over France between 1989 and 2008. Two simulations of the weather research and forecasting regional model have been analysed, with two different land-surface models. One resolves the hydrology and is able to simulate summer dryness, while the other prescribes constant and high soil moisture and hence no soil moisture deficit. The sensitivity analysis conducted for all heatwave episodes highlights different soil moisture-temperature responses (1) over low-elevation plains, (2) over mountains and (3) over coastal regions. In the plains, soil moisture deficit induces less evapotranspiration and higher sensible heat flux. This has the effect of heating the planetary boundary layer and at the same time of creating a general condition of higher convective instability and a slight increase of shallow cloud cover. A positive feedback is created which increases the temperature anomaly during the heatwaves. In mountainous regions, enhanced heat fluxes over dry soil reinforce upslope winds producing strong vertical motion over the mountain slope, first triggered by thermal convection. This, jointly to the instability conditions, favors convection triggering and produces clouds and precipitation over the mountains, reducing the temperature anomaly. In coastal regions, dry soil enhances land/sea thermal contrast, strengthening sea-breeze circulation and moist cold marine air advection. This damps the magnitude of the heatwave temperature anomaly in coastal areas, expecially near the Mediterranean coast. Hence, along with heating in the plains, soil dryness can also have a significant cooling effect over mountains and coastal regions due to meso-scale circulations.

Stéfanon, Marc; Drobinski, Philippe; D'Andrea, Fabio; Lebeaupin-Brossier, Cindy; Bastin, Sophie

2013-05-01

340

Evaluation of microwaves soil moisture products based on two years of ground measurements over a Sahelian region  

Microsoft Academic Search

Microwaves remote sensing is a promising approach to measure soil moisture values and variations. Soil moisture is a very important variable which strongly interacts with soil-vegetation-atmosphere fluxes. This is particularly true in Sahelian region with monsoon climatic system. From active or passive microwaves measurements of backscatter coefficients or brightness temperatures, soil moisture products are derived. Soil moisture products evaluation is

C. Gruhier; P. de Rosnay; Y. Kerr; L. Kergoat

2008-01-01

341

Validation of surface soil moisture from AMSR-E using auxiliary spatial data in the transboundary Indus Basin  

Microsoft Academic Search

Information on soil moisture is vital to describe various hydrological processes. Soil moisture parameters are normally measured using buried sensors in the soil. Alternatively, spatial and temporal characteristics of surface soil moisture are estimated through satellites. Advanced Microwave Scanning Radiometer on the Earth Observing System (AMSR-E) is one of such satellites that estimate surface soil moisture in an operational context.

M. J. M. Cheema; W. G. M. Bastiaanssen; M. M. Rutten

2011-01-01

342

Soil Moisture Sensing Controller and Optimal Estimator (SoilSCaPE): An in-situ Wireless Sensor Network for Validation of Spaceborne Soil Moisture Estimates (Invited)  

NASA Astrophysics Data System (ADS)

We develop technologies for dynamic and near-real-time validation of space-borne soil moisture measurements, in particular those from the NASA Soil Moisture Active and Passive (SMAP) mission. Soil moisture fields are functions of variables that change over time scales of minutes to days or weeks, and across the range of spatial scales from a few meters to several kilometers. We develop a sensor placement policy based on nonstationary spatial statistics of soil moisture, and for each location, develop dynamic scheduling policies based on physical models of soil moisture temporal dynamics and microwave sensor models for heterogeneous landscapes. Furthermore, we relate the ground-based estimates of the true mean to the space-based estimates through a physics-based statistical aggregation procedure enabled by remote sensing and hydrologic landscape simulators. An integrated communication and actuation platform is developed and used to command the sensors and transmit their data to a base station in real time. Full-scale field experiments are planned (and some underway) in coordination with SMAP calibration/validation experiments to prototype the validation system. This paper summarizes the latest status of these developments, including the description of a nearly full-scale system prototype recently installed in Oklahoma. This first SoilSCaPE multi-hop network includes 20 wireless end devices each with 4 in-situ soil moisture sensors, 4 wireless routers, and a single wireless coordinator. The data from the network are uploaded to a web server via a 3G link.

Moghaddam, M.; Liu, M.; Wu, X.; Li, K.; Burgin, M.; Goykhman, Y.; Wang, Q.; Shuman, D.; Nayyar, A.; Teneketzis, D.; Entekhabi, D.

2010-12-01

343

The Soil Moisture Active and Passive (SMAP) Mission: Improving Science Application Tools and Research  

NASA Astrophysics Data System (ADS)

NASA depends on the science community to identify and prioritize leading-edge scientific questions and the observations required to answer them. The Soil Moisture Active and Passive (SMAP) Mission has been identified as a priority for NASA's Science Mission Directorate through the most recent decadal survey. Following launch in 2014, SMAP will deliver global maps of soil moisture content and surface freeze/thaw state. Global measurements of these variables are critical for terrestrial hydrologic and carbon cycle applications. The SMAP observatory consists of two multipolarization L-band sensors, a radar and radiometer that share a deployable mesh reflector antenna. The combined observations from the two sensors will allow accurate estimation of soil moisture at spatial scales. The wide-swath (1000 km) measurements will allow global mapping of soil moisture and freeze/thaw state with a 2-3 day revisit frequency and 1-2 day revisit in boreal latitudes. The synergy of active and passive observations enables measurements of soil moisture and freeze/thaw state with unprecedented resolution, sensitivity, area coverage and revisit frequency. SMAP data are valuable for both scientific research and practical applications. SMAP has the potential to drive a diverse range of novel research in drought and flood guidance, agricultural productivity estimation, weather forecasting, climate prediction, human health risk analysis and defense systems. The accuracy, resolution, and global coverage of SMAP soil moisture and freeze/thaw measurements will provide new information for many science and applications disciplines. A SMAP Applications Team will explore ways to measure interaction and integration of SMAP data with the Emergency Management User community of Maryland in order to produce quantitative metrics related to long-term projects, milestone completion, and movement of SMAP products into routine operations for emergency response.

Escobar, V. M.; Brown, M. E.; Moran, S. M.

2011-12-01

344

On the dynamics of soil moisture vegetation and erosion: Implications of stochastic climate forcing  

NASA Astrophysics Data System (ADS)

Landscapes are observable manifestations of dynamic interactions between climatic, hydrologic, geomorphic, and ecosystem processes. As such, understanding landscape system response to fluctuations and changes in climatic forcing is necessary to predict impacts of future climate change on landscapes, and interpret geological records as indicators of past climate. We develop a simple stochastic model for climate, soil moisture, vegetation and runoff erosion dynamics driven by the Poisson pulse rainfall model. In the model, runoff generation, moisture losses due to drainage and evapotranspiration, and vegetation growth and mortality are related to vegetation cover and soil moisture state. We apply this model to investigate the sensitivity of soil moisture, grass cover and erosion potential to rainfall variability (Rvar) and mean annual precipitation (MAP). In general, under fixed MAP and rainfall rate, both soil moisture and grass cover increase, reach a maximum, and then decrease as Rvar increases. Erosion potential tends to increase with reduced vegetation cover. Analysis of existing data suggests power-law dependence between both Rvar and interstorm period with MAP. When climate is characterized in this manner, the model shows both long-term mean soil moisture and vegetation cover increase with increasing MAP. Erosion potential, however, initially increases with increasing MAP, but reaches a peak and subsequently decreases as MAP grows large. Similar behavior between measured sediment yields and MAP have been reported in the literature for a range of climatic conditions. We find that the degree of nonlinear dependence between Rvar and MAP exerts an important control on the shape of the relationship between erosion potential and MAP. Results underscore the importance of coupled soil, vegetation and climate dynamics on erosion rates.

Istanbulluoglu, E.; Bras, R. L.; Flores, A. N.

2004-12-01

345

Soil moisture surpasses elevated CO2 and temperature as a control on soil carbon dynamics in a multi-factor climate change experiment  

SciTech Connect

Some single-factor experiments suggest that elevated CO2 concentrations can increase soil carbon, but few experiments have examined the effects of interacting environmental factors on soil carbon dynamics. We undertook studies of soil carbon and nitrogen in a multi-factor (CO2 x temperature x soil moisture) climate change experiment on a constructed old-field ecosystem. After four growing seasons, elevated CO2 had no measurable effect on carbon and nitrogen concentrations in whole soil, particulate organic matter (POM), and mineral-associated organic matter (MOM). Analysis of stable carbon isotopes, under elevated CO2, indicated between 14 and 19% new soil carbon under two different watering treatments with as much as 48% new carbon in POM. Despite significant belowground inputs of new organic matter, soil carbon concentrations and stocks in POM declined over four years under soil moisture conditions that corresponded to prevailing precipitation inputs (1,300 mm yr-1). Changes over time in soil carbon and nitrogen under a drought treatment (approximately 20% lower soil water content) were not statistically significant. Reduced soil moisture lowered soil CO2 efflux and slowed soil carbon cycling in the POM pool. In this experiment, soil moisture (produced by different watering treatments) was more important than elevated CO2 and temperature as a control on soil carbon dynamics.

Garten Jr, Charles T [ORNL; Classen, Aimee T [ORNL; Norby, Richard J [ORNL

2009-01-01

346

Above and below-ground response to soil moisture change on an alpine wetland ecosystem in the Qinghai-Tibetan Plateau, China  

Microsoft Academic Search

Climate change is expected to affect plant communities worldwide. However, less is known about the consequences of global warming-induced decrease of soil moisture on alpine wetland ecosystem in the Qinghai-Tibetan Plateau. To determine response of natural alpine wetland community to decrease of soil moisture, we did a gradient analysis of soil moisture by sequence space-series variation. We used sequence space-series

G.-L. Wu; W. Li; L.-P. Zhao; Z.-H. Shi; Z.-P. Shangguan

2011-01-01

347

Evaporation From a Bare Soil Evaluated Using a Soil Water Transfer Model and Remotely Sensed Surface Soil Moisture Data  

Microsoft Academic Search

Daily surface soil moisture data, obtained with a C band scatterometer on a bare soil, provide the upper boundary condition for a numerical soil water transfer model. The model uses an implicit finite difference scheme to solve the nonlinear Richards equation. The soil is represented by two layers differing in hydraulic conductivity. Following calibration by comparison of calculated and measured

L. Prevot; R. Bernard; O. Taconet; D. Vidal-Madjar; J. L. Thony

1984-01-01

348

Short- and long-term patterns of soil moisture in alpine tundra  

SciTech Connect

Time domain reflectometry (TDR), a nondestructive technique for monitoring water content of soils, was used to measure volumetric soil moisture in three different communities in the alpine tundra during the summer of 1992. Data were converted to gravimetric estimates in order to allow comparison with 20 yr of records of gravimetric data, some of which date back to 1953. Analysis for growing-season trends indicated progressive depletion of soil moisture in all three community types studied. Using a liner model, mesic meadows showed the strongest seasonal decline and wet meadows the weakest. Curvilinear fits of the data suggested midsummer minima in xeric and mesic meadows and a midsummer maximum in wet meadows. Average summer soil moisture values for xeric meadows during the 1953-1964 interval were lower than those made in later years. This result may reflect sample site difference, but is consistent with a directional trend in increasing precipitation over this interval. Average summer soil moisture content of xeric meadows was correlated with annual precipitation, but not growing season (June-August) rainfall; this pattern was only discernible with the 20 yr data set. 35 refs., 2 figs., 3 tabs.

Taylor, R.V. (Univ. of New Mexico, Albuquerque, NM (United States)); Seastedt, T.R. (Univ. of Colorado, Boulder, CO (United States))

1994-02-01

349

Synergy between passive (SMOS) and active (RADARSAT-2) microwave soil moisture over Berambadi, India  

NASA Astrophysics Data System (ADS)

This study presents comparison and analysis towards blending of the SMOS derived soil moisture and RADARSAT-2 derived soil moisture over the Berambadi watershed, South India. SMOS (Soil Moisture and Ocean Salinity) satellite from ESA has a passive microwave L-Band sensor providing acquisition at ~40 km resolution and less than 3 days temporal resolution. RADARSAT-2 is an active microwave sensor from (CSA) operating in C-Band at a decametric spatial resolution and 24 days temporal resolution. Both satellites are all-weather satellites. SMOS is less impacted by roughness effects as it operates in passive mode at L-Band compared to RADARSAT-2, which on the other hand has a significantly higher spatial resolution. Twenty four images of RADARSAT-2 and SMOS-L2UDP soil moisture product, along with extensive field data collected in field campaigns during 2010-2012 in the framework of the ongoing AMBHAS (Assimilation of Multi-satellite data at Berambadi watershed for Hydrology And land Surface experiment) project were used in the analysis. A non parametric algorithm based on the CDF transformation method was developed to retrieve the soil moisture from RADARSAT-2 backscatter coefficient at a spatial resolution of 100 m. This product is validated using a random sampling procedure to divide the data into calibration and validation set each one consisting of 12 images. The developed algorithm provided a good estimate of the surface soil moisture with a RMSE of 0.05 m3 m-3. Then the validated RADARSAT-2 soil moisture maps were upscaled to compare with the SMOS data. Eight upscaling strategies were considered, taking into account the surface heterogeneity in terms of texture (clay sand), surface cover (forest, land cover) and SMOS mean antenna pattern. The strategies use linear combination of the different parameters. Significant differences were observed between the eight strategies. The RMSE and coefficient of determination of the different strategies varied between 0.06-0.09 m3 m-3 and 0.3-0.9 respectively. The best comparisons with a RMSE of 0.06 m3 m-3 and a coefficient of determination of 0.7 were obtained for upscaling strategies that include land cover effect. This result was used in the development of a downscaling procedure to merge the spatial information from RADARSAT-2 with the temporal dynamics from SMOS acquisitions. In order to implement this method the persistence of the spatial patterns in the RADARSAT-2 soil moisture map were evaluated by inspecting the spatiotemporal correlation coefficient across the two years, which was approximately 0.55. The impact of rain and farming activities were also taken into consideration in the analysis of the spatial heterogeneity. This study shows the potential synergy between the use of active/passive microwave soil moisture retrievals for spatial and temporal down-scaling of soil moisture. This study also shows the potential synergies between SMOS and SMAP (Soil Moisture Active Passive) mission from NASA due to launch in 2015 since SMAP will make active L-band acquisitions.

Tomer, Sat Kumar; Bitar, Ahmad Al; Sekhar, Muddu; Merlin, Olivier; Bandyopadhyay, Soumya; Kerr, Yann

2013-04-01

350

An Improved Technique for dry Soil Moisture Release Curves to Determine Soil Mineralogical and Physical Properties  

NASA Astrophysics Data System (ADS)

Soil moisture release curves (MRC) or moisture sorption isotherms, which relate the amount of water in soil to its water potential or water activity, have many applications in soil physics and geotechnical engineering including determining soil water flow, specific surface area, swelling potential, and clay mineralogy and activity. Although research showing MRC for various soils dates back more than 50 years, limitations with the measurement technique have made developing MRC time consuming and inaccurate, especially in dry soils. Recently, an instrument was developed to create moisture sorption isotherms for various food and pharmaceutical products. The objective of this research was to investigate its use in soils for obtaining MRC in dry soils simply and accurately. Several different soil types were tested in the instrument from pure sand to bentonite and smectite clays. From the MRC of these soils, we were able to develop good correlations between actual and derived clay activity, surface area, and swelling potential. In addition, we were able to see hysteresis in dry soil water uptake for all soils, including sand. According to our tests, this new instrument will provide a powerful tool to investigate several soil physical properties simply and accurately.

Campbell, G. S.; Campbell, C. S.; Cobos, D. R.

2008-12-01

351

The influence of soil moisture on magnetic susceptibility measurements  

NASA Astrophysics Data System (ADS)

An important methodological question for magnetic susceptibility measurements is if a variation of the soil conductivity, as a result of a change in soil moisture, influences the measured susceptibility values. An answer to this question is essential because an accurate magnetic susceptibility mapping requires a grid of comparable magnetic susceptibility values, which indicate the magnetic iron-mineral contents of the soils. Therefore, in the framework of the MAGPROX project (EU-Project EVK2-CT-1999-00019), the study aims at investigating the influence of soil moisture and the possible correlation between magnetic susceptibility and electric conductivity. This approach was realised by model experiments in the laboratory and a field monitoring experiment, which was performed in an analogical manner as the model. For the laboratory experiment, a plastic tub with a water in- and outflow system and installed lines of electrodes was used. The measurements were carried out with layers of different magnetic material within the experimental sand formation under varying water saturation conditions. For the field experiment, which was carried out from July to December 2003, two test sites were selected. The magnetic susceptibility was measured by means of the recently developed vertical soil profile kappa meter SM400 and a commonly used Bartington MS2D probe. The electric resistivity was recorded using a 4-point light system (laboratory) and a ground conductivity meter EM38 (field). The knowledge of the resistivity of the sand formation enabled an estimation of porosity and water saturation in consideration of the Archie equations. The laboratory experiment results showed a very slight variation of measured magnetic susceptibility under different degrees of moisture, indicating mainly the influence from the diamagnetic contribution of the water volume. A measurement error in connection with the measurement method, for example caused by an interfering effect of soil conductivity variations, was not found. The authors conclude, that in practical use of the investigated instruments for topsoil magnetic susceptibility mapping in the field, the influence of soil moisture and resulting soil conductivity can be neglected, especially compared to the influence of the contact between measurement loop and soil. The study presented here verifies the magnetic susceptibility data reproducibility and comparability, which provides the basis for magnetic susceptibility monitoring. Additionally, new application approaches of magnetic susceptibility measurements were proposed, which show again the versatility and the potential of the method.

Maier, G.; Scholger, R.; Schön, J.

2006-06-01

352

Response of heterotrophic soil respiration to changes in moisture: what do data and theory tell us?  

NASA Astrophysics Data System (ADS)

Soil moisture strongly affects the dynamics of soil organic matter­­ and is central to predict changes in soil carbon stocks from site to global scales. Despite its importance in controlling soil carbon transformations, the mechanisms involved are still poorly represented in models, mostly as highly simplified empirical relationships. To improve such representations we approached the problem in two ways: First, a synthesis analysis of laboratory data was performed to explore the variability of moisture effects on heterotrophic respiration across soil types. Second, we used theory and established relationships to build a semi-mechanistic model that predicts the response of soil heterotrophic respiration to changes in moisture and its dependence on soil properties. With the first approach, statistical models of the response of soil heterotrophic respiration to moisture were obtained. The inclusion of soil properties (clay, bulk density and organic matter) as predictor variables improved the agreement between model results and observations. These models are useful to visualize the change in the response across different soil types. They thus improve over other commonly used empirical relationships, but because they remain a statistical approximation based on linear regressions they are potentially biased and could lead to systematic errors in predictions. In the second approach we explored the theory linking gas diffusivity and heterotrophic respiration in soils, as well as the effect of soil clay content, pore space, organic matter and temperature. The advantage of a mechanistically based model is that it can be modified or expanded to test different theories or processes, and extrapolation of predictor variables will not usually lead to unrealistic predictions. Observations and model predictions from the two approaches are shown to agree in many points, e.g. in the influence of soil clay content. But both the empirical and the more mechanistic model are unable to explain much of the variability in the data and fail to reproduce nonlinear responses such as the Birch effect. We conclude that a more complete theoretical basis is needed to represent the full range of soil moisture responses in a unifying model, further validated with new experimental data.

Moyano, Fernando; Manzoni, Stefano; Chenu, Claire

2013-04-01

353

Using Remotely-Sensed Estimates of Soil Moisture to Infer Spatially Distributed Soil Hydraulic Properties  

NASA Astrophysics Data System (ADS)

Near-surface soil moisture is a critical component of land surface energy and water balance studies encompassing a wide range of disciplines. However, the processes of infiltration, runoff, and evapotranspiration in the unsaturated (vadose) zone of the soil are not easy to estimate or predict because of the difficulty in accurately representing soil texture and hydraulic properties in land surface and hydrologic models. This study approaches the problem of parameterizing soils from a unique perspective based on components originally developed for semi-operational estimation of soil moisture for vehicle mobility assessments. Estimates of 0-5 cm soil moisture derived from radar imagery were acquired over the Walnut Gulch watershed in Arizona. The resultant fields of soil moisture were then used to calibrate a land surface model and infer information on the soil hydraulic properties of the region. Specifically, a well-established parameter estimation routine was incorporated into the Noah land surface model, and run at very high spatial resolutions during the Monsoon 90 field experiment. Optimizations of sand, clay, and silt percentages for each soil type were then related to specific hydraulic parameters using pedotransfer functions. By estimating a more continuous range of widely applicable soil properties such as sand and clay percentages, rather than prescribing soil texture classes or attempting multi-objective optimizations over large parameter sets as in previous studies, the accuracy and consistency of the resulting properties could be more easily assessed. In addition, the strong influence of temporal and spatial patterns in precipitation is addressed, and the methodology is tested using a more recent radar-based soil moisture product and independent dataset at Walnut Gulch. Overall, results demonstrate the potential for this method to gain physically meaningful information on soil properties given limited microwave retrievals from remote sensing.

Santanello, J. A.; Peters-Lidard, C.; Garcia, M.; Mocko, D.

2006-05-01

354

Some aspects of the cation status of soil moisture  

Microsoft Academic Search

Summary In a previous paper it was shown that the equilibrium between the soil and its solution phase only remained undisturbed over the field range of moisture content but became disturbed once this range was exceeded. Values of pK-1\\/2p(Ca+Mg) increased with dilution. Equilibration studies with water and calcium chloride solutions (0.002–0.10M) showed that there was an increasing release of potassium

P. Moss

1963-01-01

355

Soil moisture dynamics of calcareous grassland under elevated CO 2  

Microsoft Academic Search

Water relations of nutrient-poor calcareous grassland under long-term CO2 enrichment were investigated. Understanding CO2 effects on soil moisture is critical because productivity in these grasslands is water limited. In general, leaf conductance\\u000a was reduced at elevated CO2, but responses strongly depended on date and species. Evapotranspiration (measured as H2O gas exchange) revealed only small, non-significant reductions at elevated CO2, indicating

Pascal A. Niklaus; D. Spinnler; C. Körner

1998-01-01

356

WindSat Global Soil Moisture Retrieval and Validation  

Microsoft Academic Search

A physically based six-channel land algorithm is developed to simultaneously retrieve global soil moisture (SM), vegetation water content (VWC), and land surface temperature. The algorithm is based on maximum-likelihood estimation and uses dual-polarization WindSat passive microwave data at 10, 18.7, and 37 GHz. The global retrievals are validated at multispatial and multitemporal scales against SM climatologies, in situ network data,

Li Li; Peter W. Gaiser; Bo-Cai Gao; Richard M. Bevilacqua; Thomas J. Jackson; Eni G. Njoku; Christoph Rudiger; Jean-Christophe Calvet; Rajat Bindlish

2010-01-01

357

Soil Moisture Sensing via Swept Frequency Based Microwave Sensors  

PubMed Central

There is a need for low-cost, high-accuracy measurement of water content in various materials. This study assesses the performance of a new microwave swept frequency domain instrument (SFI) that has promise to provide a low-cost, high-accuracy alternative to the traditional and more expensive time domain reflectometry (TDR). The technique obtains permittivity measurements of soils in the frequency domain utilizing a through transmission configuration, transmissometry, which provides a frequency domain transmissometry measurement (FDT). The measurement is comparable to time domain transmissometry (TDT) with the added advantage of also being able to separately quantify the real and imaginary portions of the complex permittivity so that the measured bulk permittivity is more accurate that the measurement TDR provides where the apparent permittivity is impacted by the signal loss, which can be significant in heavier soils. The experimental SFI was compared with a high-end 12 GHz TDR/TDT system across a range of soils at varying soil water contents and densities. As propagation delay is the fundamental measurement of interest to the well-established TDR or TDT technique; the first set of tests utilized precision propagation delay lines to test the accuracy of the SFI instrument’s ability to resolve propagation delays across the expected range of delays that a soil probe would present when subjected to the expected range of soil types and soil moisture typical to an agronomic cropping system. The results of the precision-delay line testing suggests the instrument is capable of predicting propagation delays with a RMSE of +/?105 ps across the range of delays ranging from 0 to 12,000 ps with a coefficient of determination of r2 = 0.998. The second phase of tests noted the rich history of TDR for prediction of soil moisture and leveraged this history by utilizing TDT measured with a high-end Hewlett Packard TDR/TDT instrument to directly benchmark the SFI instrument over a range of soil types, at varying levels of moisture. This testing protocol was developed to provide the best possible comparison between SFI to TDT than would otherwise be possible by using soil moisture as the bench mark, due to variations in soil density between soil water content levels which are known to impact the calibration between TDR’s estimate of soil water content from the measured propagation delay which is converted to an apparent permittivity measurement. This experimental decision, to compare propagation delay of TDT to FDT, effectively removes the errors due to variations in packing density from the evaluation and provides a direct comparison between the SFI instrument and the time domain technique of TDT. The tests utilized three soils (a sand, an Acuff loam and an Olton clay-loam) that were packed to varying bulk densities and prepared to provide a range of water contents and electrical conductivities by which to compare the performance of the SFI technology to TDT measurements of propagation delay. For each sample tested, the SFI instrument and the TDT both performed the measurements on the exact same probe, thereby both instruments were measuring the exact same soil/soil-probe response to ensure the most accurate means to compare the SFI instrument to a high-end TDT instrument. Test results provided an estimated instrumental accuracy for the SFI of +/?0.98% of full scale, RMSE basis, for the precision delay lines and +/?1.32% when the SFI was evaluated on loam and clay loam soils, in comparison to TDT as the bench-mark. Results from both experiments provide evidence that the low-cost SFI approach is a viable alternative to conventional TDR/TDT for high accuracy applications.

Pelletier, Mathew G.; Karthikeyan, Sundar; Green, Timothy R.; Schwartz, Robert C.; Wanjura, John D.; Holt, Greg A.

2012-01-01

358

Comparison of soil moisture penetration depths for several bare soils at two microwave frequencies and implications for remote sensing  

Microsoft Academic Search

Microwave brightness temperature measurements were made over three different bare soils at frequencies of 5 GHz (?=6 cm) and 1.67 GHz (?=18 cm) to compare differences in penetration depth according to texture, soil moisture, and wavelength. The soil plots were wetted, and circularly polarized microwave measurements were made during the dry-down cycle. Soil profile temperature and profile moisture content were

Manfred Owe; Adriaan A. Van de Griend

1998-01-01

359

Sensitivity of simulated soil heterotrophic respiration to temperature and moisture reduction functions  

Microsoft Academic Search

In this study, the influence of different soil temperature and moisture reduction functions for scaling decomposition rates of soil organic matter on the prediction of CO2 production and fluxes was analysed. For this purpose, soil temperature and moisture reduction functions of six soil carbon decomposition models (CANDY, CENTURY, DAISY, PATCIS, ROTHC, and SOILCO2) were implemented in the modified SOILCO2-ROTHC model.

J. Bauer; M. Herbst; J. A. Huisman; L. Weihermüller; H. Vereecken

2008-01-01

360

Soil moisture gradients and controls on a southern Appalachian hillslope from drought through recharge  

Microsoft Academic Search

Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and topographic features are the two general physio-graphic factors controlling soil moisture on hillslopes, studies have shown conflicting results regarding which factor is more important. The relative importance of topographic and soil property

J. A. Yeakley; W. T. Swank; L. W. Swift; G. M. Hornberger; H. H. Shugart

1998-01-01

361

Moisture control over atmospheric CH 4 consumption and CO 2 production in diverse Alaskan soils  

Microsoft Academic Search

Moisture is an important control on atmospheric CH4 consumption and CO2 production in soil. Wet conditions limit these microbial activities by restricting CH4 and O2 diffusion and dry conditions limit microbial activity due to physiological water stress. We examined the relationship between soil moisture and these biogeochemical activities in five Alaskan soils with varying physical properties. Three expressions of soil

Jay Gulledge; Joshua P Schimel

1998-01-01

362

Stability of banded vegetation patterns under seasonal rainfall and limited soil moisture storage capacity  

Microsoft Academic Search

The delicate equilibrium of soil moisture and biomass may become unstable under water scarcity conditions causing banded vegetation patterns to form on hillsides of semi-arid catchments. Soil related processes that induce instability (namely: soil moisture advection and diffusion), have been evaluated numerically for different rainfall regimes. This study addresses the combined influence of some relevant soil characteristics, and the effect

Nadia Ursino; Samuel Contarini

2006-01-01

363

Active and passive microwave measurements of soil moisture in FIFE  

SciTech Connect

This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. This paper reports on the application of active and passive microwave measurement systems to the simultaneous determination of soil moisture. These systems have been tested on common targets very few times. Here C and X band scatterometer data from a helicopter base is compared with L band push broom microwave radiometer (PBMR) data taken from the NASA C-130 aircraft. The regions sampled over FIFE encompass areas with different surface treatments. The scatterometers proved to be sensitive to soil moisture over most of the areas studied, while the radiometer lost sensitivity in regions which had been unburned for years, and which thus had substantial dead organic accumulation. The correlation of soil moisture and backscattered signal was observed to increase with off normal angles.

Wang, J.R. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Gogineni, S.P.; Ampe, J. (Univ. of Kansas, Lawrence (United States))

1992-11-30

364

Effects of soil moisture variations on deposition velocities above vegetation.  

SciTech Connect

The parameterized subgrid-scale surface flux (PASS) model provides a simplified means of using remote sensing data from satellites and limited surface meteorological information to estimate the influence of soil moisture on bulk canopy stomatal resistances to the uptake of gases over extended areas. PASS-generated estimates of bulk canopy stomatal resistance were used in a dry deposition module to compute gas deposition velocities with a horizontal resolution of 200 m for approximately 5000 km{sup 2} of agricultural crops and rangeland. Results were compared with measurements of O{sub 3} flux and concentrations made during April and May 1997 at two surface stations and from an aircraft. The trend in simulated O{sub 3} deposition velocity during soil moisture drydown over a period of a few days matched the trend observed at the two surface stations. For areas under the aircraft flight paths, the variability in simulated O{sub 3} deposition velocity was substantially smaller than the observed variability, while the averages over tens of kilometers were usually in agreement within 0.1 cm s{sup -1}. Model results indicated that soil moisture can have a major role in deposition of O{sub 3} and other substances strongly affected by canopy stomatal resistance.

Wesely, M. L.; Song, J.; McMillen, R. T.; Meyers, T. P.; Environmental Research; Northern Illinois Univ.; National Oceanic and Atmospheric Administration

2001-01-01

365

Wireless soil moisture sensor networks for environmental monitoring and irrigation  

NASA Astrophysics Data System (ADS)

Dependable spatial-temporal soil parameter data is required for informed decision making in precision farming and hydrological applications. Wireless sensor networks are seen as a key technology to satisfy these demands. Hence, research and development focus is on reliable outdoor applications. This comprises sensor design improvement, more robust communication protocols, less power consumption as well as better deployment strategies and tools. Field trials were performed to investigate and iteratively improve wireless sensor networks in the above-mentioned areas. They accounted for different climate conditions, soil types and salinity, irrigation practices, solar power availability and also for different radio spectrum use which affects the reliability of the wireless links. E.g. 868 MHz and 2.4 GHz wireless nodes were compared in the field with regard to range. Furthermore a low-cost soil moisture sensor was developed to allow for large-scale field experiments. It is based on the measurement of the high frequency dielectric properties of the soil. Two agricultural sites were equipped with 80 sensors and 20 wireless nodes each. The soil moisture data is collected in regular intervals, aggregated in a base station and visualized through a web-based geographical information system. The complete system and results of field experiments are presented.

Hübner, Christof; Cardell-Oliver, Rachel; Becker, Rolf; Spohrer, Klaus; Jotter, Kai; Wagenknecht, Tino

2010-05-01

366

Measurement of daily spectral soil albedo over France from MODIS and MSG: comparison with soil moisture derived from ASCAT observations  

NASA Astrophysics Data System (ADS)

Surface albedo determines the partition of energy between land surface and atmosphere, which is a crucial parameter for climate studies. In particular, consistency of coarse scale soil background albedo data set is required to improve the radiative scheme in land surface modeling. As an important component of land surface, soil albedo depends on soil moisture, soil roughness, mineral content, tillage, etc. It can change rapidly at hourly or daily basis, revealing the variation of the state variables, particularly soil moisture. Over dense vegetation areas, radiation interactions exist between the soil background and the bottom of canopy, which adds to the difficulty to yield a clear separation between the respective soil and vegetation attributes. With the advent of a new-generation of Earth observing sensor systems, consistent sets of surface albedo products are regularly distributed at global and regional scales within expected accuracy, particularly MODIS and SEVIRI, which provides the potential of generating soil albedo from satellite observations. The objective of this study is to derive soil background albedo from MODIS and SEVIRI data sets over France. A procedure was developed to derive a MODIS albedo on a daily basis in combining TERRA and AQUA observations and in considering the MODIS BRDF model at the appropriate dates. A novel 1D radiative transfer approach is applied to disentangle soil background albedo and vegetation albedo by using the albedo and LAI data sets of MODIS and SEVIRI. This background albedo from satellite observations is made evolving with the use of a Kalman filter approach. In order to generate a predictive model, temporal trajectories of soil background albedo are extracted for each soil mapping unit and further clustered into several clusters by using k-mean method. The temporal coherence of the resulting soil background albedos was assessed with satellite and in-situ rainfall and soil moisture observations. It comes out that the derived soil background albedo compares favorably with the chronology of precipitation rates recorded by TRMM Multi-Satellite Precipitation Analysis (TMPA), ASCAT soil moisture products, and also with measurements by rain gauges at 12 anchor stations of the SMOSMANIA network during 2007-2010.

Liu, S.; Roujean, J. L.; Kaptue, A.; Carrer, D.; Lafont, S.; Parrens, M.; Szczypta, C.; Calvet, J. C.

2012-04-01

367

Assimilation of surface soil moisture into a multilayer soil model: design and evaluation at local scale  

NASA Astrophysics Data System (ADS)

Land surface models (LSM) have improved considerably in the last two decades. In this study, the ISBA LSM soil diffusion scheme is used (with 11 soil layers represented). A Simplified Extended Kalman Filter (SEKF) allows surface soil moisture (SSM) to be assimilated in the multi-layer LSM in order to constrain deep soil moisture. In parallel, the same simulations are performed using the ISBA LSM with 2 soil layers (a thin surface layer and a bulk reservoir). Simulations are performed over a 3 yr period (2003-2005) for a bare soil field in southwestern France, at the SMOSREX experimental site. Analyzed soil moisture values correlate better with soil moisture observations when the ISBA LSM soil diffusion scheme is used. The Kalman gain is greater from the surface to 45 cm than below this limit. For dry periods, corrections introduced by the assimilation scheme mainly affect the first 25 cm of soil whereas weaker corrections impact the total soil column for wet periods. Such seasonal corrections cannot be described by the two-layer ISBA LSM. Sensitivity studies performed with the multi-layer LSM show improved results when SSM (0-6 cm) is assimilated into the second layer (1-5 cm) than into the first layer (0-1 cm). The introduction of vertical correlations in the background error covariance matrix is also encouraging. Using a yearly CDF-matching scheme for bias correction instead of matching over the three years permits the seasonal variability of the soil moisture content to be better transcribed. An assimilation experiment has also been performed by forcing ISBA-DF with a local forcing setting precipitation to zero. This experiment shows the benefit of the SSM assimilation for correcting inaccurate atmospheric forcing.

Parrens, M.; Mahfouf, J.-F.; Barbu, A.; Calvet, J.-C.

2013-07-01

368

Detecting causation mechanisms of soil moisture patterns in Germany  

NASA Astrophysics Data System (ADS)

Detecting trends, feedbacks, and causation mechanisms in hydrometeorologic variables such as soil moisture is a challenging task because of the nonlinear dynamics of the atmosphere-land-vegetation system, the assimilation of noisy observations, and the structural and parametric uncertainty of land surface models (LSM). Quite often, wrong conclusions can be drawn because uncorrelated variables may be assumed to have no causal relationship with presupposed predictors. The main goal of this study is to test whether a significant "Granger causality" (Granger 1969) exist between monthly soil moisture fields over Germany and large-scale circulation patterns, characterized by anomalies of sea level pressure over the Northern Hemisphere or geopotential height and atmospheric humidity over Europe. The advantage of this testing framework stems from the fact that it is based on predictability instead of correlation to identify causation, as it is the case with standard correlation-based approaches. Two contrasting modeling paradigms, the land surface NOAH model and the process-based hydrologic model mHM (Samaniego et al. 2012) are employed to estimate daily soil moisture over Germany during the period from 1989 to 2009. WRF/NOAH was forced with ERA-Interim data at the boundary of the EURO-CORDEX Region (www.meteo.unican.es/wiki/cordexwrf) with a spatial resolution of 0.11°. To ease comparison, mHM was also forced with daily precipitation and temperature fields generated by WRF during the same period at 4×4 km resolution. Main physiographic characteristics in NOAH such as land cover and soil texture are represented with a 1×1 km MODIS data set and a single horizon, coarse resolution FAO soil map with 16 soil texture classes, respectively. The multiscale parameter regionalization technique (MPR, Samaniego et al. 2010) embedded in mHM allows to estimate effective model parameters based on detailed input data (100×100 m) obtained from Corine land cover and soil texture fields for various horizons comprising 72 classes. mHM global parameters, in contrast with those of NOAH, were obtained by closing the water balance in major German river basins. For the "Granger causality" test, variables such as sea level pressure or geopotential height at 500 hPa (dss.ucar.edu/datasets/ds010.0/, data-portal.ecmwf.int/data/d/interim_daily) are used as predictor fields including the lagged values of these variables. Results indicate that the subgrid variability of the land surface properties and the parametrization schemes have greater influence on soil moisture simulations. Mann-Kendall tests performed with mHM data indicated the existence of a negative trend (p-value 5%) in soil moisture during summer months which is the consequence of observed downward trend in precipitation and upward trend in temperature. On the contrary, soil moisture simulations in winter months did not exhibited significant trends. The Granger-causation mechanisms of these trends are under investigation.

Samaniego, Luis; Kumar, Rohini; Zink, Matthias; Warrach-Sagi, Kirsten; Wulfmeyer, Volker

2013-04-01

369

On the Soil Roughness Parameterization Problem in Soil Moisture Retrieval of Bare Surfaces from Synthetic Aperture Radar  

Microsoft Academic Search

Synthetic Aperture Radar has shown its large potent ial for retrieving soil moisture maps at regional scales. However, since th e backscattered signal is determined by several surface characteristics, the retrieval of s oil moisture is an ill-posed problem when using single configuration imagery. Unless accurate surface roughness parameter values are available, retrieving soil moisture from radar back scatter usually

Niko E. C Verhoest; Hans Lievens; Wolfgang Wagner; Jesús Álvarez-Mozos; M. Susan Moran; Francesco Mattia

2008-01-01

370

Radiobrightness thermal inertia sensing of soil and canopy moistures for grassland areas  

Microsoft Academic Search

Radiobrightness thermal inertia (RTI) can be used to estimate the moisture content of prairie grassland and agricultural soils. Moisture increases the apparent thermal inertia' of soil by increasing its thermal conductivity, density, and specific heat. Apparent thermal inertia is further increased by evapotranspiration during the day and by condensation at night. Increasing moisture content causes a decrease in microwave emissivity.

E. J. Kim; A. W. England

1995-01-01

371

Soil moisture's underestimated role in climate change impact modelling in low-energy systems.  

PubMed

Shifts in precipitation regimes are an inherent component of climate change, but in low-energy systems are often assumed to be less important than changes in temperature. Because soil moisture is the hydrological variable most proximally linked to plant performance during the growing season in arctic-alpine habitats, it may offer the most useful perspective on the influence of changes in precipitation on vegetation. Here we quantify the influence of soil moisture for multiple vegetation properties at fine spatial scales, to determine the potential importance of soil moisture under changing climatic conditions. A fine-scale data set, comprising vascular species cover and field-quantified ecologically relevant environmental parameters, was analysed to determine the influence of soil moisture relative to other key abiotic predictors. Soil moisture was strongly related to community composition, species richness and the occurrence patterns of individual species, having a similar or greater influence than soil temperature, pH and solar radiation. Soil moisture varied considerably over short distances, and this fine-scale heterogeneity may contribute to offsetting the ecological impacts of changes in precipitation for species not limited to extreme soil moisture conditions. In conclusion, soil moisture is a key driver of vegetation properties, both at the species and community level, even in this low-energy system. Soil moisture conditions represent an important mechanism through which changing climatic conditions impact vegetation, and advancing our predictive capability will therefore require a better understanding of how soil moisture mediates the effects of climate change on biota. PMID:23749628

le Roux, Peter Christiaan; Aalto, Juha; Luoto, Miska

2013-08-13

372

Soil Moisture Conditions in Four Types of Forests in Kampong Thom, Cambodia  

Microsoft Academic Search

Soil moisture conditions were observed in four types of forest in central Cambodia, where dry evergreen forests are distributed\\u000a widely, to investigate differences of soil moisture in each forest and to clarify relationships between forest types and soil\\u000a moisture conditions. Observations revealed that soil water contents were high during the rainy season in dry deciduous forest\\u000a (DDF) and mixed forest

Makoto Araki; Jumpei Toriyama; Seiichi Ohta; Mamoru Kanzaki; Eriko Ito; Bora Tith; Sopheavuth Pol; Sopheap Lim; Saret Khorn; Phearak Pith; Seila Det

373

Impact of Soil Moisture Dynamics on ASAR ?o Signatures and Its Spatial Variability Observed over the Tibetan Plateau  

PubMed Central

This paper reports on the analysis of a 2.5 year-long time series of ASAR wide swath mode (WSM) observations for characterizing the soil moisture dynamics. The employed ASAR WSM data set consists of 152 VV-polarized scenes acquired in the period between April 2005 and September 2007 over the Naqu river basin located on the Tibetan Plateau. For four different spatial domains, with areas of 30×30 km2, 5×5 km2 and (two domains of) 1×1 km2, the mean backscatter (?o) and the standard deviation (stdev) have been computed for each ASAR acquisition. Comparison of the mean ?o values with the stdev values results in a specific triangular distribution of data points for all spatial domains. Analysis of the mean ?o and stdev with respect to in-situ soil moisture measurements demonstrates that this triangular shaped distribution can be explained by soil moisture dynamics during monsoon and winter periods. This shows that the relationship between the spatial mean soil moisture and variability is not uniquely defined and may change throughout seasons. Downscaling of coarse resolution soil moisture products should, therefore, be ideally based on additional near real time data sources. In this context, the presented results could form a basis for the development of SAR-based soil moisture downscaling methodologies.

van der Velde, Rogier; Su, Zhongbo; Ma, Yaoming

2008-01-01

374

Soil moisture retrieval from WindSat using the single channel algorithm toward a blended global soil moisture product from multiple microwave sensors  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture has long been recognized as one of the critical land surface initial conditions for numerical weather, climate hydrological predictions, particularly for transition zones between dry and humid climates. However, none of the currently existing soil moisture products has been used operat...

375

Initializing numerical weather prediction models with satellite-derived surface soil moisture: Data assimilation experiments with ECMWF's Integrated Forecast System and the TMI soil moisture data set  

Microsoft Academic Search

Satellite-derived surface soil moisture data sets are readily available and have been used successfully in hydrological applications. In many operational numerical weather prediction systems the initial soil moisture conditions are analyzed from the modeled background and 2 m temperature and relative humidity. This approach has proven its efficiency to improve surface latent and sensible heat fluxes and consequently the forecast

M. Drusch

2007-01-01

376

Soil Moisture Retrieval Using an L-Band Synthetic Apeture Radiometer During The Soil Moisture Experiments 2003 (SMEX03) and 2004 (SMEX04)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture retrievals made using data from the airborne L-band microwave radiometer, 2D-STAR, over a wide range of land cover types are presented. The 2D-STAR was flown over six regional-scale sites during soil moisture experiments in 2003 and 2004. Four sites located in Alabama, Georgia, Arizona...

377

Retrieval of soil moisture from passive and active L\\/S band sensor (PALS) observations during the Soil Moisture Experiment in 2002 (SMEX02)  

Microsoft Academic Search

The Soil Moisture Experiments in 2002 (SMEX02) were conducted in Iowa between June 25th and July 12th, 2002. A major aim of the experiments was examination of existing algorithms for soil moisture retrieval from active and passive microwave remote sensors under high vegetation water content conditions. The data obtained from the passive and active L and S band sensor (PALS)

Ujjwal Narayan; Venkat Lakshmi; Eni G. Njoku

2004-01-01

378

An examination of direct ground wave soil moisture monitoring over an annual cycle of soil conditions  

Microsoft Academic Search

Direct ground wave (DGW) measurements obtained with ground-penetrating radar have been used in a number of previous studies to estimate volumetric water content in the shallow soil zone; however, these studies have generally involved controlled field experiments or measurements collected across limited natural ranges of soil moisture conditions. To further investigate the capacity of this method, we have undertaken an

Colby M. Steelman; Anthony L. Endres

2010-01-01

379

Temperature and soil moisture interactively affected soil net N mineralization in temperate grassland in Northern China  

Microsoft Academic Search

Intact soil cores from three adjacent sites (Site A: grazed, Site B: fenced for 4 years, and Site C: fenced for 24 years) were incubated in the laboratory to examine effects of temperature, soil moisture, and their interactions on net nitrification and N mineralization rates in the Inner Mongolia grassland of Northern China. Incubation temperature significantly influenced net nitrification and

Changhui Wang; Shiqiang Wan; Xuerong Xing; Lei Zhang; Xingguo Han

2006-01-01