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1

Analysis and modeling of soil moisture in Jiangsu, China  

NASA Astrophysics Data System (ADS)

There are large uncertainties in the observation of soil moisture. This study compares the two observation datasets of soil moisture data, including automatic and manual measurements, in Jiangsu Province, China from 2010 to 2012. More than 30 automatic monitoring instruments of soil moisture have been installed in Jiangsu since 2010. However, the automatic stations show various uncertainties, including improper site selection, such as shallow soil depth on rocks, underground river, and artificial soil. Compared to the manual observations, the values of automatic observations usually are lower, except for over saturation condition. With increasing soil depths, soil moisture of automatic observation becomes more stable with less variance and shows larger discrepancies with manual observations. Automatic measurements have greater advantage in temporal and spatial coverage, and indicate better relationship with observed precipitation patterns. At eight depths from 10 cm to 100 cm, manual soil moisture observations largely fluctuate than automatic ones, especially under relatively dry conditions. In general, observation errors in automatic measurements need careful analysis, and automatic measurements with quality control are more accurate in representing real soil moisture, and are less influenced by precipitation conditions. Also, the observed soil moisture data is used to evaluate the simulated soil moisture using the Weather Research and Forecasting (WRF) model and the global forecast system (GFS) model in July, 2012. Both models select the Noah land surface model and produce soil moisture for four layers. Several extremely dry periods are also investigated to predict potential drought using soil moisture.

Yuan, H.; Sun, R.; Fei, Q.

2013-12-01

2

Analysis of Soil Moisture Changes in Europe during a Single Growing Season in a New ECMWF Soil Moisture Assimilation System  

E-print Network

Analysis of Soil Moisture Changes in Europe during a Single Growing Season in a New ECMWF Soil This study aims at stimulating the development of soil moisture data assimilation systems in a direction concerning the systematic nature of soil moisture data assimilation experiments over Europe during

Haak, Hein

3

Parameter Sensitivity in LSMs: An Analysis Using Stochastic Soil Moisture Models and ELDAS Soil Parameters  

E-print Network

Parameter Sensitivity in LSMs: An Analysis Using Stochastic Soil Moisture Models and ELDAS Soil as well as model evaluation requires a realistic representation of soil moisture in land surface models (LSMs). However, soil moisture in LSMs is sensitive to a range of uncertain input parameters

Haak, Hein

4

Analysis of soil moisture memory from observations in Europe  

NASA Astrophysics Data System (ADS)

Soil moisture is known to show distinctive persistence characteristics compared to other quantities in the climate system. As soil moisture is governing land-atmosphere feedbacks to a large extent, its persistence can provide potential to improve seasonal climate predictions. So far, many modeling studies have investigated the nature of soil moisture memory, with consistent, but model-dependent results. This study investigates soil moisture memory in long-term observational records based on data from five stations across Europe. We investigate spatial and seasonal variations in soil moisture memory and identify their main climatic drivers. Also, we test an existing framework and introduce an extension thereof to approximate soil moisture memory and evaluate the contributions of its driving processes. At the analyzed five sites, we identify the variability of initial soil moisture divided by that of the accumulated forcing over the considered time frame as a main driver of soil moisture memory that reflects the impact of the precipitation regime and of soil and vegetation characteristics. Another important driver is found to be the correlation of initial soil moisture with subsequent forcing that captures forcing memory as it propagates to the soil and also land-atmosphere interactions. Thereby, the role of precipitation is found to be dominant for the forcing. In contrast to results from previous modeling studies, the runoff and evapotranspiration sensitivities to soil moisture are found to have only a minor influence on soil moisture persistence at the analyzed sites. For the central European sites, the seasonal cycles of soil moisture memory display a maximum in late summer and a minimum in spring. An opposite seasonal cycle is found at the analyzed site in Italy. High soil moisture memory is shown to last up to 40 days in some seasons at most sites. Extremely dry or wet states of the soil tend to increase soil moisture memory, suggesting enhanced prediction potential during extreme events at most sites considered in this study.

Orth, R.; Seneviratne, S. I.

2012-08-01

5

Microwave soil moisture measurements and analysis  

NASA Technical Reports Server (NTRS)

An effort to develop a model that simulates the distribution of water content and of temperature in bare soil is documented. The field experimental set up designed to acquire the data to test this model is described. The microwave signature acquisition system (MSAS) field measurements acquired in Colby, Kansas during the summer of 1978 are pesented.

Newton, R. W.; Howell, T. A.; Nieber, J. L.; Vanbavel, C. H. M. (principal investigators)

1980-01-01

6

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

E-print Network

Soil Moisture Memory in AGCM Simulations: Analysis of Global Land­Atmosphere Coupling Experiment 2006) ABSTRACT Soil moisture memory is a key aspect of land­atmosphere interaction and has major implications for seasonal forecasting. Because of a severe lack of soil moisture observations on most

Haak, Hein

7

Soil moisture-temperature coupling: A multiscale observational analysis  

NASA Astrophysics Data System (ADS)

Land-atmospheric interactions are complex and variable in space and time. On average soil moisture-temperature coupling is expected to be stronger in transition zones between wet and dry climates. During heatwaves anomalously high coupling may be found in areas of soil moisture deficit and high atmospheric demand of water. Here a new approach is applied to satellite and in situ observations towards the characterization of regions of intense soil moisture-temperature coupling, both in terms of climatology and anomalies during heatwaves. The resulting average summertime coupling hot spots reflect intermediate climatic regions in agreement with previous studies. Results at heatwave-scale suggest a minor role of soil moisture deficit during the heatwave of 2006 in California but an important one in the 2003 event in Western Europe. Progress towards near-real time satellite products may allow the application of the approach to aid prediction and management of warm extremes.

Miralles, D. G.; van den Berg, M. J.; Teuling, A. J.; de Jeu, R. A. M.

2012-11-01

8

Midlatitude soil moisture: an experimental and modeling analysis  

NASA Astrophysics Data System (ADS)

Soil moisture has a key role for the internal dynamics of ecohydrological systems and for their relationships with the climate system. At continental midlatitudes, soil moisture was recognized as a key variable in determining the strength of summer droughts (Ferranti and Viterbo, 2006). Lack of observations of soil moisture (and evapotranspiration) has been recognized as a main limitation to further progress, e.g. in the field of land-atmosphere interactions (Seneviratne and Stckli, 2008). Obtaining soil moisture estimates from indirect observations is therefore very important. Here we compare direct measurement of soil moisture and different modeling approaches. Soil water data at hourly temporal resolution were collected from 2005 to present in the monitoring station located in Grugliasco, Torino (campus of the Agricultural Faculty of University of Torino, Italy). The station is located in the northwestern part of the Po Valley. The site is equipped with an automatic meteorological station, an automatic TDR station with 160 vertical probes ranging from 150 mm to 2000 mm length, and 80 mercury column tensiometers. The vegetation at the site is composed of grasses and grapevines. The dataset is compared with the output of a simple punctual model for soil moisture averaged over the active soil layer. The model includes infiltration, evapotranspiration, runoff and leakage. Rainfall, atmospheric pressure and temperature and wind velocity at the site are used as external input of the model. The model allows a detailed temporal description of soil moisture dynamics, with resolution of a few hours, comparable with the temporal resolution of the data. The importance of the various mechanisms of the soil water balance, and the model sensitivity to the different parameters are tested against the data observed. References: Ferranti, L. and P. Viterbo, J. Climate, 19, 3659-3680 (2006). Seneviratne, S.I., and R. Stckli, In: Climate Variability and Extremes during the Past 100 years, Brnnimann et al. (eds.), Adv. Global Change Research, 33, Springer Verlag (2008).

Baudena, M.; Bevilacqua, I.; Canone, D.; Ferraris, S.; Previati, M.; Provenzale, A.

2009-04-01

9

A meta-analysis of the response of soil moisture to experimental warming  

NASA Astrophysics Data System (ADS)

Soil moisture is an important variable for regulating carbon, water and energy cycles of terrestrial ecosystems. However, numerous inconsistent conclusions have been reported regarding the responses of soil moisture to warming. In this study, we conducted a meta-analysis for examination of the response of soil moisture to experimental warming across global warming sites including several ecosystem types. The results showed that soil moisture decreased in response to warming treatments when compared with control treatments in most ecosystem types. The largest reduction of soil moisture was observed in forests, while intermediate reductions were observed in grassland and cropland, and they were both larger than the reductions observed in shrubland and tundra ecosystems. Increases (or no change) in soil moisture also occurred in some ecosystems. Taken together, these results showed a trend of soil drying in most ecosystems, which may have exerted profound impacts on a variety of terrestrial ecosystem processes as well as feedbacks to the climate system.

Xu, Wenfang; Yuan, Wenping; Dong, Wenjie; Xia, Jiangzhou; Liu, Dan; Chen, Yang

2013-12-01

10

A Multiscale Analysis of Soil Moisture-Temperature Coupling  

NASA Astrophysics Data System (ADS)

Land-atmospheric interactions are complex and variable in space and time. On average soil moisture-temperature coupling is expected to be stronger in transition zones between wet and dry climates. During heatwaves anomalously high coupling may be found in areas of soil moisture deficit and high atmospheric demand of water. Here a new approach is applied to satellite and in situ observations towards the characterization of regions of intense soil moisture-temperature coupling, both in terms of climatology and anomalies during heatwaves. We estimate two energy balances - one based on actual evaporation and one based on potential evaporation - and analyze their differential skill in explaining the dynamics of air temperature. The approach is applied to recently-developed satellite-based evaporation (GLEAM) and temperature fields from reanalysis (ERA-Interim). The resulting average summertime global hot spots reflect intermediate climatic regions in agreement with previous studies. Results of the coupling during the 2003 heatwave event in Europe are in agreement with past experiments using regional climate models; maximum coupling is found over central France. Much lower coupling is found in the 2006 event in United States, especially over California were soil moisture deficit is suggested to have played an insignificant role in the peak of temperatures.

Miralles, D. G.; van den Berg, M. J.; Teuling, R.; De Jeu, R. A.

2012-12-01

11

Similarity Analysis between near surface soil moisture and streamflow during recession events in an alpine catchment  

NASA Astrophysics Data System (ADS)

Spatial and temporal variability of near surface soil moisture is important for understanding streamflow generation in high altitude mountain catchments since antecedent soil moisture plays an important role in the timing of runoff. For relatively small to medium sized catchments, the spatial variability of near surface soil moisture is hard to capture with remote sensing techniques and distributed point measurements are needed. Linking local measurements of soil moisture with integrating catchment scale streamflow measurements remains a great challenge in hydrological modeling. Since 2008, an alpine watershed of 20.4 km2 has been intensively monitored in the Swiss Alps, with a deployment of a network of wireless meteorological stations, measuring soil moisture along with other meteorological forcings. The discharge is monitored at three different sites. We present some preliminary results from a statistical analysis linking the spatial variation of the soil moisture, measured at 20 and 40 cm, with the variation of the streamflow in the particular case of recession events. A classic parameterization of recession events relating the variation of the discharge dQ-dt to the discharge Q by |dQ-dt|? Q? is used and transposed to soil moisture data. The parameterized soil moisture variation is then partitioned into runoff and evapotranspiration leading to better knowledge of local processes at the hillslope scale.

Mutzner, Raphael; Weijs, Steven V.; Rinaldo, Andrea; Parlange, Marc B.

2013-04-01

12

Multiscale analysis of surface soil moisture dynamics in a mesoscale catchment utilizing an integrated ecohydrological model  

NASA Astrophysics Data System (ADS)

Soil moisture is one of the fundamental variables in hydrology, meteorology and agriculture, influencing the partitioning of solar energy into latent and sensible heat flux as well as the partitioning of precipitation into runoff and percolation. Numerous studies have shown that in addition to natural factors (rainfall, soil, topography etc.) agricultural management is one of the key drivers for spatio-temporal patterns of soil moisture in agricultural landscapes. Interactions between plant growth, soil hydrology and soil nitrogen transformation processes are modeled by using a dynamically coupled modeling approach. The process-based ecohydrological model components of the integrated decision support system DANUBIA are used to identify the important processes and feedbacks determining soil moisture patterns in agroecosystems. Integrative validation of plant growth and surface soil moisture dynamics serves as a basis for a spatially distributed modeling analysis of surface soil moisture patterns in the northern part of the Rur catchment (1100 sq km), Western Germany. An extensive three year dataset (2007-2009) of surface soil moisture-, plant- (LAI, organ specific biomass and N) and soil- (texture, N, C) measurements was collected. Plant measurements were carried out biweekly for winter wheat, maize, and sugar beet during the growing season. Soil moisture was measured with three FDR soil moisture stations. Meteorological data was measured with an eddy flux station. The results of the model validation showed a very good agreement between the modeled plant parameters (biomass, green LAI) and the measured parameters with values between 0.84 and 0.98 (Willmotts index of agreement). The modeled surface soil moisture (0 - 20 cm) showed also a very favorable agreement with the measurements for winter wheat and sugar beet with an RMSE between 1.68 and 3.45 Vol.-%. For maize, the RMSE was less favorable particularly in the 1.5 months prior to harvest. The modeled soil moisture remained in contrast to the measurements very responsive to precipitation with high soil moisture after precipitation events. This behavior indicates that the soil properties might have changed due to the formation of a surface crust or seal towards the end of the growing season. Spatial soil moisture patterns were investigated using a grid resolution of 150 meter. Spatial autocorrelation was computed on a daily basis using patterns of soil texture as well as transpiration and precipitation indices as co-variables. Spatial patterns of surface soil moisture are mostly determined by the structure of the soil properties (soil type) during winter, early growing season and after harvest of all crops. Later in the growing season, after establishment of a closed canopy the dependence of the soil moisture patterns on soil texture patterns becomes smaller and diminishes quickly after precipitation events, due to differences of the transpiration rate of the different crops. When changing the spatial scale of the analysis, the highest autocorrelation values can be found on a grid cell size between 450 and 1200 meters. Thus, small scale variability of transpiration induced by the land use pattern almost averages out, leaving the larger scale structure of soil properties to explain the soil moisture patterns.

Korres, W.; Reichenau, T. G.; Schneider, K.

2012-12-01

13

Soil Moisture Workshop  

NASA Technical Reports Server (NTRS)

The Soil Moisture Workshop was held at the United States Department of Agriculture National Agricultural Library in Beltsville, Maryland on January 17-19, 1978. The objectives of the Workshop were to evaluate the state of the art of remote sensing of soil moisture; examine the needs of potential users; and make recommendations concerning the future of soil moisture research and development. To accomplish these objectives, small working groups were organized in advance of the Workshop to prepare position papers. These papers served as the basis for this report.

Heilman, J. L. (editor); Moore, D. G. (editor); Schmugge, T. J. (editor); Friedman, D. B. (editor)

1978-01-01

14

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

15

A soil moisture budget analysis of Texas using basic climatic data  

E-print Network

A SOIL MOISTURE BUDGET ANALYSIS OF TEXAS USING BASIC CLIMATIC DATA A Thesis by RONALD PAUL LO~ Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... May 1989 Major Subject: Meteorology A SOIL MOISTURE BUDGET ANALYSIS OF TEXAS USING BASIC CLIMATIC DATA A Thesis RONALD PAUL LOWTHER Approved as to style and content by: John F. Gn iIIts (Chair of Committee) Gerald R. North (Member) Ru If J...

Lowther, Ronald Paul

2012-06-07

16

Frequency analysis of Earth Observation and hydrological model estimations of evapotranspiration and soil moisture  

NASA Astrophysics Data System (ADS)

Evapotranspiration and Soil Moisture are important variables for water resources management on the catchment level. However, to accurately measure these variables is difficult, if not impossible. Ground station measurements are reliable, but it is mostly not possible and costly to provide adequate spatial coverage of the catchment. Earth observation data does provide this spatial coverage and becomes accessible at lower costs. The algorithms to interpret satellites imagery have been evolving. Also spatially distributed hydrological models provide the estimates of Evapotranspiration and Soil Moisture covering the catchment. However, also hydrological models need validation. In this paper state-of-the-art recent estimates (2013) from the three information sources for Evapotranspiration and Soil Moisture are compared on the basis of sample locations and frequency analysis for the Rijnland area in the Netherlands.

Song, Yang; Hartanto, Isnaeni; Alexandridis, Thomas; van Andel, Schalk Jan; Solomatine, Dimitri

2014-05-01

17

Analysis and estimation of soil moisture at the catchment scale using EOFs  

Microsoft Academic Search

Soil moisture patterns and dynamics are important for numerous applications such as flood forecasting, climate modeling, and management of agricultural lands. Unfortunately, widespread observations of soil moisture are not currently available at the spatial scale of most of these applications. Given these data limitations and the complexity of soil moisture dynamics, there is a need to gain a better understanding

Mark A. Perry; Jeffrey D. Niemann

2007-01-01

18

GLOBE Videos: Soil Characterization - Soil Moisture (18:23 min)  

NSDL National Science Digital Library

This video describes how to select a soil moisture study site and sampling strategy, and identifies what laboratory instruments will be needed to complete a soil moisture analysis. Students are shown collecting soil moisture data and asking questions about what soil moisture data might tell them about the environment. The resource includes a video and a written transcript, and is supported by the Soil Moisture Protocol in the GLOBE Teacher's Guide. This is one of five videos about soils in the 24-part instructional video series describing scientific protocols used by GLOBE (Global Learning and Observation to Benefit the Environment), a worldwide, hands-on, K-12 school-based science education program.

19

4, 25872624, 2007 Soil moisture  

E-print Network

HESSD 4, 2587­2624, 2007 Soil moisture dynamics and runoff generation processes T. Blume et al System Sciences Use of soil moisture dynamics and patterns for the investigation of runoff generation 4, 2587­2624, 2007 Soil moisture dynamics and runoff generation processes T. Blume et al. Title Page

Paris-Sud XI, Université de

20

5, 935969, 2008 Soil moisture  

E-print Network

HESSD 5, 935­969, 2008 Soil moisture temporal patterns and variation A. Longobardi Title Page Observing soil moisture temporal variability under fluctuating climatic conditions A. Longobardi Department #12;HESSD 5, 935­969, 2008 Soil moisture temporal patterns and variation A. Longobardi Title Page

Paris-Sud XI, Université de

21

Soil Moisture Memory in Climate Models  

NASA Technical Reports Server (NTRS)

Water balance considerations at the soil surface lead to an equation that relates the autocorrelation of soil moisture 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) persistence in the atmospheric forcing, as perhaps induced by land atmosphere feedback. Geographical variations in the relative strengths of these factors, which can be established through analysis of model diagnostics and which can be validated to a certain extent against observations, lead to geographical variations in simulated soil moisture memory and thus, in effect, to geographical variations in seasonal precipitation predictability associated with soil moisture. The use of the equation to characterize controls on soil moisture memory is demonstrated with data from the modeling system of the NASA Seasonal-to-Interannual Prediction Project.

Koster, Randal D.; Suarez, Max J.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

22

Soil moisture detection from Skylab  

NASA Technical Reports Server (NTRS)

An investigation was designed for the Skylab satellite to determine the feasibility of remote sensing of the soil moisture content of the surface from various microwave sensors. Skylab data for the experiment were collected during passes 5, 10, 16, and 38 across the two test sites selected in eastern Kansas and western Texas. Pass 38 covered both test sites giving five data sets for the analysis. As Skylab data were being taken the moisture content of the soil was sampled by ground crews for each 2.5 centimeter depth from the surface to 15 centimeters at interval of about six kilometers along two different routes along the test sites. This resulted in a total of 2250 soil moisture samples corresponding to different locations and six different depths. Skylab data were collected by passive microwave radiometers at wavelengths of 2.1 and 21 centimeters by the S193 and S194 microwave sensors. An active microwave system also collected scatterometer data at a wavelength of 2.1 centimeters. The analysis of microwave data has revealed that the longer wavelength L-Band passive radiometer gives the best correlation with soil moisture content of the upper 2.5 centimeter depth of soil.

Eagleman, J. R.; Lin, W. C.

1975-01-01

23

Catchment scale validation of SMOS and ASCAT soil moisture products using hydrological modeling and temporal stability analysis  

NASA Astrophysics Data System (ADS)

Since soil moisture is an important influencing factor of the hydrological cycle, knowledge of its spatio-temporal dynamics is crucial for climate and hydrological modeling. In recent years several soil moisture data products from satellite information have become available with global coverage and sub-monthly resolution. Since the remote sensing of soil moisture is an indirect measurement method and influenced by a large number of factors (e.g. atmospheric correction, vegetation, soil roughness, etc.), a comprehensive validation of the resulting soil moisture products is required. However, the coarse spatial resolution of these products hampers the comparison with point-scale in situ measurements. Therefore, upscaling of in situ to the scale of the satellite data is needed. We present the validation results of the soil moisture products of the years 2010-2012 retrieved from the Soil Moisture and Ocean Salinity (SMOS) and the Advanced Scatterometer (ASCAT) for the Rur and Erft catchments in western Germany. For the upscaling of in situ data obtained from three test sites of the Terrestrial Environmental Observatories (TERENO) initiative we used the hydrological model WaSiM ETH. Correlation of the SMOS product to modeled and upscaled soil moisture resulted in a mean correlation coefficient of 0.28 whereas for ASCAT a correlation coefficient of 0.50 was obtained. However, for specific regions the SMOS product showed similar correlation coefficients as the ASCAT product. While for ASCAT correlation was mainly dependent on topography and vegetation, SMOS was also influenced by radiofrequency interferences in our study area. Both products show dry biases as compared to the soil moisture reference. However, while SMOS showed relatively constant bias values, ASCAT bias is variable throughout the year. As an additional validation method we performed a temporal stability analysis of the retrieved spatio-temporal soil moisture data. Through investigation of mean relative differences of soil moisture for every pixel, their standard deviations and their rankings, we analyzed the temporal persistence of spatial patterns. Our results show high standard deviations for both SMOS and ASCAT soil moisture products as compared to modeled soil moisture, indicating a lower temporal persistence. The consistence of ranks of mean relative differences was low for SMOS and relative ASCAT soil moisture compared to modeled soil moisture, while ASCAT soil moisture, converted to absolute values, showed higher rank consistence.

Rtzer, K.; Montzka, C.; Bogena, H.; Wagner, W.; Kerr, Y. H.; Kidd, R.; Vereecken, H.

2014-11-01

24

A global analysis of satellite derived and DGVM surface soil moisture products  

NASA Astrophysics Data System (ADS)

Soil moisture availability is important in regulating photosynthesis and controlling land surface-climate feedbacks at both the local and global scale. Recently, global remote-sensing datasets for soil moisture have become available. In this paper we assess the possibility of using remotely sensed soil moisture (AMSR-E) to evaluate the results of the process-based vegetation model ORCHIDEE during the period 2003-2004. We find that the soil moisture products of AMSR-E and ORCHIDEE correlate well, in particular when considering the root zone soil moisture of ORCHIDEE. However, the root zone soil moisture in ORCHIDEE consistently overestimated the temporal autocorrelation relative to AMSR-E and in situ measurements. This may be due to the different vertical depth of the two products, to the uncertainty in precipitation forcing in ORCHIDEE, and to the fact that the structure of ORCHIDEE consisting of a single-layer deep soil, does not allow simulation of the proper cascade of time scales that characterize soil drying after each rain event. We conclude that assimilating soil moisture in ORCHIDEE using AMSR-E with the current hydrological model may significantly improve the soil moisture dynamics in ORCHIDEE.

Rebel, K. T.; de Jeu, R. A. M.; Ciais, P.; Viovy, N.; Piao, S. L.; Kiely, G.; Dolman, A. J.

2011-04-01

25

Soil-moisture ground truth, Hand County, South Dakota  

NASA Technical Reports Server (NTRS)

Soil samples were taken in the field and carefully preserved in taped metal containers for later laboratory gravimetric analysis to determine soil-moisture content. The typical sampling pattern used in this mission is illustrated, and the soil types encountered on the soil-moisture lines are summarized. The actual soil-moisture data were tabulated by range, township and section. Soil-moisture data obtained in fields of winter wheat and spring wheat are briefly summarized.

Jones, E. B.

1976-01-01

26

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

27

Assessing representative soil moisture at watershed scale of Maqu catchment using spatio-temporal statistical analysis  

NASA Astrophysics Data System (ADS)

In this study the temporal stability concept by Vachaud et al. (1985) is selected to evaluate a soil moisture measuring network in the Maqu catchment (3200 km2) in the north eastern part of the Tibetan plateau. The network serves for validation of coarse scale (25-50 km) satellite soil moisture products and comprises 20 stations with probes installed at depths of 5, 10, 20, 40, 80 cm. Besides identifying the Representative Mean Soil Moisture (RMSM) station for each respective probe depth, we applied the concept to a time series of satellite based moisture products from the Advance Microwave Scanning Radiometer (AMSR-E) to evaluate if a RMSM pixel can be identified from the pixels that overlay the catchment. Analysis in this study serve to evaluate how well the satellite based moisture estimates match to observation at the RMSM stations for respective depths. We aim to evaluate if the RMSM can be estimated by the satellite product so to broaden the procedure to validate satellite images. We used moisture data for the year 2009 for which data is available at 15 minutes interval using ECH2O EC-TM probes. For each probe depth a Mean Relative Difference (MRD) plot is created to identify stations that are characterized by mean, wet and dry moisture conditions. The spearman non-parametric test and pearson's correlation coefficient test are used to analyze the temporal persistence of the ranks of the measuring stations. The analysis is applied to each probe depth to evaluate the effect of the measuring depth on determining the catchment RMSM. Similar analysis is carried out on the satellite soil moisture observations that cover a full hydrological year to identify a RMSM pixel. The result of the analysis on the network showed that the station that indicates RMSM changes for each probe depth and thus a single station that indicates the catchment RMSM cannot be identified. Results on identifying a RMSM pixel shows that such pixel can be identified, however in our case, a station is not available in the pixel footprint area to evaluate if a RMSM station coincides with the RMSM pixel. Therefore, the network may require optimization to represent catchment average moisture conditions. So to evaluate how well station based RMSM is represented by a satellite time series, we inter-compared the time series of the RMSM station at respective probe depths to the time series of the single pixels that overlay the station. We calculated the Root Mean Square Error and Bias for all probe depth and results indicate that satellite observations best match to observations indicating RMSM for probes installed at 20 cm depth. The study also showed that for selecting the RMSM station in the Maqu catchment a minimum observation period should cover an annual cycle with clear dry and wet seasons.

Bhatti, H. A.; Rientjes, T. H. M.; Verhoef, W.

2012-04-01

28

The Global Soil Moisture Data Bank - Benchmark Soil Moisture Observations  

NASA Astrophysics Data System (ADS)

Soil moisture is a crucial component of the global hydrological cycle. Summer desiccation is a potential threat from some climate model simulations of global warming, but actual in situ soil moisture observations are needed to examine long term soil moisture changes as well as to develop accurate land surface models. Here we present a set of benchmark in situ soil moisture observations, from long-term observing programs in the United States, Europe, and Asia. The longest time series started in 1958, the same year as the Keeling Mauna Loa CO2 record, and is based on gravimetric observations from 141 stations at agricultural fields with winter and spring cereal crops in the Ukraine with a temporal resolution of 10 days (3 measurements per month) during the growing period, from April 8 to October 28. We discuss methods of observation, of quality control, and of achieving homogeneity. Shorter records from other locations will also be presented. These benchmark soil moisture observations are being used by the international research community to study climate change, as ground truth for remote sensing, to develop and evaluate land surface models, and to evaluate general circulation model and reanalysis calculations of soil moisture variations. While land data assimilation of remotely-sensed forcing and soil moisture, utilizing a validated land surface model, will be necessary to produce a global soil moisture data set, this goal cannot be achieved without these actual in situ observations.

Robock, A.; Vinnikov, K.; Li, H.

2005-12-01

29

Impact of elevated atmospheric CO2 on soil moisture: a meta-analysis  

NASA Astrophysics Data System (ADS)

The dynamics of soil moisture and vegetation productivity interact with and affect each other in many ecosystems. Therefore understanding soil moisture changes and the underlying mechanisms under climate change is important to predict future plant-water interactions and consequent hydrological responses. In this study, we aim to quantify and compare soil moisture under ambient and elevated CO2 treatment in different ecosystems. We used meta-analytic techniques to test the responses under different climate regimes, vegetation types, soil textures, and management types. We found a consistent increase in soil moisture under elevated CO2 treatment, and the effect is stronger in water-limited systems. The results suggest that CO2 enrichment may stimulate a decrease in stomatal conductance in plants, hence lead to a decrease of transpiration rate and higher soil water content.

Lu, X.; Wang, L.; McCabe, M. F.; Leung, M.

2013-12-01

30

Soil moisture: Some fundamentals. [agriculture - soil mechanics  

NASA Technical Reports Server (NTRS)

A brief tutorial on soil moisture, as it applies to agriculture, is presented. Information was taken from books and papers considered freshman college level material, and is an attempt to briefly present the basic concept of soil moisture and a minimal understanding of how water interacts with soil.

Milstead, B. W.

1975-01-01

31

Statistical analysis of simulated global soil moisture and its memory in an ensemble of CMIP5 general circulation models  

NASA Astrophysics Data System (ADS)

Soil moisture and its memory can have a strong impact on near surface temperature and precipitation and have the potential to promote severe heat waves, dry spells and floods. To analyze how soil moisture is simulated in recent general circulation models (GCMs), soil moisture data from a 23 model ensemble of Atmospheric Model Intercomparison Project (AMIP) type simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are examined for the period 1979 to 2008 with regard to parameterization and statistical characteristics. With respect to soil moisture processes, the models vary in their maximum soil and root depth, the number of soil layers, the water-holding capacity, and the ability to simulate freezing which all together leads to very different soil moisture characteristics. Differences in the water-holding capacity are resulting in deviations in the global median soil moisture of more than one order of magnitude between the models. In contrast, the variance shows similar absolute values when comparing the models to each other. Thus, the input and output rates by precipitation and evapotranspiration, which are computed by the atmospheric component of the models, have to be in the same range. Most models simulate great variances in the monsoon areas of the tropics and north western U.S., intermediate variances in Europe and eastern U.S., and low variances in the Sahara, continental Asia, and central and western Australia. In general, the variance decreases with latitude over the high northern latitudes. As soil moisture trends in the models were found to be negligible, the soil moisture anomalies were calculated by subtracting the 30 year monthly climatology from the data. The length of the memory is determined from the soil moisture anomalies by calculating the first insignificant autocorrelation for ascending monthly lags (insignificant autocorrelation folding time). The models show a great spread of autocorrelation length from a few months in the tropics, north western Canada, eastern U.S. and northern Europe up to few years in the Sahara, the Arabian Peninsula, continental Eurasia and central U.S. Some models simulate very long memory all over the globe. This behavior is associated with differences between the models in the maximum root and soil depth. Models with shallow roots and deep soils exhibit longer memories than models with similar soil and root depths. Further analysis will be conducted to clearly divide models into groups based on their inter-model spatial correlation of simulated soil moisture characteristics.

Wi, Felix; Stacke, Tobias; Hagemann, Stefan

2014-05-01

32

SOIL MOISTURE CHARACTERISTICS IN UPPER PART OF HINDON RIVER CATCHMENT  

E-print Network

1 SOIL MOISTURE CHARACTERISTICS IN UPPER PART OF HINDON RIVER CATCHMENT C. P. Kumar* Vijay Kumar the field and laboratory determination of soil moisture characteristics and their variation along the Hindon analysis. Key Words : Soil Moisture, Hydraulic Conductivity, Retention Curve, Soil Water Pressure

Kumar, C.P.

33

Airborne microwave remote sensing of soil moisture  

E-print Network

Clellan [3]. Plots of permittivity vs. volumetric soil moisture (amount of water in a given volume of soil) demonstrated similar permittivities for moisture less than transition regardless of the. soil type. The slope of the per- mittivity versus moisture...Clellan [3]. Plots of permittivity vs. volumetric soil moisture (amount of water in a given volume of soil) demonstrated similar permittivities for moisture less than transition regardless of the. soil type. The slope of the per- mittivity versus moisture...

Black, Quentin Robert

2012-06-07

34

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

National Technical Information Service (NTIS)

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 estimat...

A. S. Jones, C. L. Combs, M. Sengupta, T. Lakhankar, T. H. Vonder Haar

2010-01-01

35

Radar scattering and soil moisture  

NASA Technical Reports Server (NTRS)

Research is being conducted on microwave scattering from vegetation. The objective is to develop techniques for measuring parameters of the vegetation canopy (such as biomass) needed for understanding global biogeochemical cycles and to develop techniques for correcting microwave measurements of soil moisture for the effects of the vegetation canopy. Measurements of vegetation and soil moisture are important for understanding the environment on a global scale. For example, moisture in the soil is an important, highly variable, element in the global hydrologic cycle. The hydrologic cycle, in turn, is strongly coupled to weather and climate through moisture (and energy) fluxes at the surface. The amount and distribution of vegetation is an important element in biogeochemical cycles; and knowledge of both the vegetation canopy and soil moisture is of practical importance in agricultural management. These theories are examined.

Levine, D. M.; Neill, P. O.

1988-01-01

36

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

NASA Astrophysics Data System (ADS)

This study explores the teleconnection of two climatic patterns, namely the El Nio-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), with hydrological processes over the Pearl River basin in southern China, particularly on a sub-basin-scale basis. 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 the 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 for inferences on the occurrence of extreme hydrological events (e.g., floods and droughts).

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

2014-04-01

37

Soil moisture controls beyond the Darcy scale  

NASA Astrophysics Data System (ADS)

Processes controlling soil moisture distribution beyond the Darcy scale have not yet been adequately explored. Akin to the presence of certain soil moisture thresholds at the Darcy scale beyond which processes like vapor flow, film flow and capillary flow become more dominating than the others, it is hypothesized that similar thresholds may exist for the coarser scale. Coarse scale soil moisture distribution is known to depend on different processes like infiltration, interception, stem flow, sub-surface flow etc. These processes occur due to heterogeneity in physical factors, namely, soil, vegetation, topography and meteorological factors. This study evaluates the quantitative relative contribution of different physical factors (% sand, % clay, elevation, slope, flow accumulation and leaf area index) on the structure of soil moisture at different scales (1.6, 3.2, 6.4, 12.8 and 25.6 km) and determines the presence of certain scale based ';thresholds' at which the relationship between physical controls and soil moisture distribution changes. Coarse change maps representing soil moisture change at different time scales were generated using airborne soil moisture data collected during various soil moisture campaigns (SGP97, SMEX02 and SMEX04) to assess the nature of drying/wetting dynamics that exist in a particular region. Wavelet analysis was conducted on these change maps and physical factors and scale based correlations between soil moisture dynamics and physical factors were determined. The study has been conducted over 3 hydro-climates (humid, sub-humid and semi-arid) to assess the transferability of these results across hydro-climates. It has been found that within a particular hydro-climate, it may be possible to define fuzzy threshold boundaries at which different physical factors (and related physical processes) become dominant. However, across hydro-climates the results are not transferable. It indicates that the composition of heterogeneity of a particular hydro-climate (i.e. combination of topography, soil and vegetation) influences the effect that each physical factor has on the soil moisture distribution. Thus, the influence of physical factors on soil moisture distribution is non-linear. However, the effect of different physical factors within a hydro-climate itself is dependent upon the spatial support scale of analysis.

Gaur, N.; Mohanty, B.

2013-12-01

38

A soil moisture budget analysis of Texas using basic climatic data while assuming a possible warming trend across the state  

E-print Network

Evapotranspiration and Temperature 3. A Control Soil Moisture Budget . B, A Soil Moisture Budget Based on a Warming Trend 26 28 29 35 37 CHAFIER IV. PRESENTATION OF THE RESULTS A. Soil Moisture Regime 1. Relationship Between MMP and MMT . 2. Relationship... Evapotranspiration and Temperature 3. A Control Soil Moisture Budget . B, A Soil Moisture Budget Based on a Warming Trend 26 28 29 35 37 CHAFIER IV. PRESENTATION OF THE RESULTS A. Soil Moisture Regime 1. Relationship Between MMP and MMT . 2. Relationship...

Bjornson, Brian Matthew

2012-06-07

39

Soil moisture variability across climate zones  

Microsoft Academic Search

Variability in soil moisture is controlled by temporal variability in atmospheric conditions and spatial variability in land-surface conditions. Observations of soil moisture have revealed a variety of patterns generally, in semiarid regions variance increased as mean soil moisture content increased, in humid regions variance decreased as mean soil moisture content increased, and in temperate regions variance peaked at intermediate

Justin E. Lawrence; George M. Hornberger

2007-01-01

40

Soil moisture variability across climate zones  

Microsoft Academic Search

Variability in soil moisture is controlled by temporal variability in atmospheric conditions and spatial variability in land-surface conditions. Observations of soil moisture have revealed a variety of patterns - generally, in semiarid regions variance increased as mean soil moisture content increased, in humid regions variance decreased as mean soil moisture content increased, and in temperate regions variance peaked at intermediate

Justin E. Lawrence; George M. Hornberger

2007-01-01

41

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

E-print Network

Sensitivity of LISEM predicted catchment discharge to initial soil moisture content of soil profile: Soil moisture Infiltration Rainfall-runoff Sensitivity analysis LISEM s u m m a r y This study conducts a broad sensitivity analysis, taking into account the influence of initial soil moisture content in two

Loon, E. Emiel van

42

Method for evaluating moisture tensions of soils using spectral data  

NASA Technical Reports Server (NTRS)

A method is disclosed which permits evaluation of soil moisture utilizing remote sensing. Spectral measurements at a plurality of different wavelengths are taken with respect to sample soils and the bidirectional reflectance factor (BRF) measurements produced are submitted to regression analysis for development therefrom of predictable equations calculated for orderly relationships. Soil of unknown reflective and unknown soil moisture tension is thereafter analyzed for bidirectional reflectance and the resulting data utilized to determine the soil moisture tension of the soil as well as providing a prediction as to the bidirectional reflectance of the soil at other moisture tensions.

Peterson, John B. (Inventor)

1982-01-01

43

Analysis and mapping of field-scale soil moisture variability using high-resolution, ground-based data during the  

E-print Network

Analysis and mapping of field-scale soil moisture variability using high-resolution, ground and temporal scales. To achieve a better accounting of the water and energy budgets at the land different hydrologic and climatic conditions and at different hierarchical space scales and timescales

Mohanty, Binayak P.

44

Estimating Daily Surface Soil Moisture Using a Daily Diagnostic Soil Moisture Equation  

E-print Network

Estimating Daily Surface Soil Moisture Using a Daily Diagnostic Soil Moisture Equation Feifei Pan1 moisture for scheduling irri- gation: errors in the estimated soil moisture are cumulative and frequent recalibrations are needed. A simple and robust approach to estimation of daily soil moisture using a daily

Pan, Feifei

45

Hydrologic applications of SAR derived soil moisture  

NASA Technical Reports Server (NTRS)

The MACHYDRO-90 was a multi-sensor aircraft campaign conducted to study drainage basin hydrology and the role of soil moisture in defining hydrologic characteristics and patterns. The results from the synthetic aperture radar (SAR) are presented. Data were collected over a period in which the soil conditions changed from dry to wet and then through a drying period which was close to ideal. Radar backscatter data are compared to detailed soil moisture samples taken to define soil moisture gradients within a watershed. The analysis also includes 40-MHz bandwidth SAR data, which provide very high spatial resolution. It is shown these data can be interpreted for hydrology and their application to hydrologic modeling is discussed.

Engman, Edwin T.

1992-01-01

46

Streamflow Data Assimilation for Soil Moisture Prediction  

E-print Network

Streamflow Data Assimilation for Soil Moisture Prediction by Christoph Rüdiger Diplom on archival quality paper ­ #12;#12;Preface Page i Abstract Soil moisture is an important variable in and between the soil and the atmosphere. However, obtaining reliable information on soil moisture is difficult

Walker, Jeff

47

Vadose Zone Journal Soil Moisture Retrieval Using  

E-print Network

Vadose Zone Journal Soil Moisture Retrieval Using Ground-Based L-Band Passive Microwave in a grassland at the NOAA-CREST­Soil Moisture Advanced Radiometric Testbed (CREST-SMART) facility, which includes a mobile L-band dual-polarized radiometer with an in situ soil tem- perature and soil moisture

Krakauer, Nir Y.

48

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

49

Evaluation of Reanalysis Soil Moisture Simulations Using Updated Chinese Soil Moisture Observations  

E-print Network

Evaluation of Reanalysis Soil Moisture Simulations Using Updated Chinese Soil Moisture Observations 2004) ABSTRACT Using 19 yr of Chinese soil moisture data from 1981 to 1999, the authors evaluate soil) over China. R-2 shows improved interannual variability and better seasonal patterns of soil moisture

Robock, Alan

50

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

51

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

52

Microstrip Ring Resonator for Soil Moisture Measurements  

NASA Technical Reports Server (NTRS)

Accurate determination of spatial soil moisture distribution and monitoring its temporal variation have a significant impact on the outcomes of hydrologic, ecologic, and climatic models. Development of a successful remote sensing instrument for soil moisture relies on the accurate knowledge of the soil dielectric constant (epsilon(sub soil)) to its moisture content. Two existing methods for measurement of dielectric constant of soil at low and high frequencies are, respectively, the time domain reflectometry and the reflection coefficient measurement using an open-ended coaxial probe. The major shortcoming of these methods is the lack of accurate determination of the imaginary part of epsilon(sub soil). In this paper a microstrip ring resonator is proposed for the accurate measurement of soil dielectric constant. In this technique the microstrip ring resonator is placed in contact with soil medium and the real and imaginary parts of epsilon(sub soil) are determined from the changes in the resonant frequency and the quality factor of the resonator respectively. The solution of the electromagnetic problem is obtained using a hybrid approach based on the method of moments solution of the quasi-static formulation in conjunction with experimental data obtained from reference dielectric samples. Also a simple inversion algorithm for epsilon(sub soil) = epsilon'(sub r) + j(epsilon"(sub r)) based on regression analysis is obtained. It is shown that the wide dynamic range of the measured quantities provides excellent accuracy in the dielectric constant measurement. A prototype microstrip ring resonator at L-band is designed and measurements of soil with different moisture contents are presented and compared with other approaches.

Sarabandi, Kamal; Li, Eric S.

1993-01-01

53

Measurement Scheduling for Soil Moisture Sensing  

E-print Network

INVITED P A P E R Measurement Scheduling for Soil Moisture Sensing: From Physical Models to Optimal energy consumption is presented; the paper is grounded in the physics of soil moisture. By David I Shuman of monitoring soil moisture evolution using a wireless network of in situ sensors. Continuously sampling

Mahajan, Aditya

54

2, 417448, 2005 Soil moisture-runoff  

E-print Network

HESSD 2, 417­448, 2005 Soil moisture-runoff relation at the catchment scale K. Scipal et al. Title Sciences Discussions Soil moisture-runoff relation at the catchment scale as observed with coarse Commons License. 417 #12;HESSD 2, 417­448, 2005 Soil moisture-runoff relation at the catchment scale K

Boyer, Edmond

55

The Soil Moisture Active Passive (SMAP) Mission  

Microsoft Academic Search

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. SMAP will make global measurements of the soil moisture present at the Earth's land surface and will distinguish frozen from thawed land surfaces. Direct observations of soil moisture and freeze\\/thaw state from

Dara Entekhabi; Eni G. Njoku; Peggy E. O'Neill; Kent H. Kellogg; Wade T. Crow; Wendy N. Edelstein; Jared K. Entin; Shawn D. Goodman; Thomas J. Jackson; Joel Johnson; John Kimball; Jeffrey R. Piepmeier; Randal D. Koster; Neil Martin; Kyle C. McDonald; Mahta Moghaddam; Susan Moran; Rolf Reichle; J. C. Shi; Michael W. Spencer; Samuel W. Thurman; Leung Tsang; Jakob Van Zyl

2010-01-01

56

Optimum Radar Parameters for Mapping Soil Moisture  

Microsoft Academic Search

The radar response to soil moisture content was experimentally determined for each of three bare fields with considerably different surface roughnesses at eight frequencies in the 2-8 GHz band for HH and VV polarizations. Analysis of the data indicates that the effect of roughness on the radar backscattering coefficient can be minimized by proper choice of the radar parameters. If,

Fawwaz Ulaby; Percy Batlivala

1976-01-01

57

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

58

Role of soil moisture in maintaining droughts  

NASA Technical Reports Server (NTRS)

The influence of soil moisture on the persistence of an ongoing drought was investigated. The case study of drought of the summer of 1980 was selected. The difference in the simulation of two identical twin runs: one with the climatological normal soil moisture and the other with anomalous soil moisture for drought conditions, were examined on the mean monthly circulation. It is found that a reduction in soil moisture did produce a corresponding reduction in precipitation. The pattern of the rainfall anomaly however, was not identical to the soil moisture (evapotranspiration) anomaly but had a good resemblance with observations.

Sud, Y. C.; Smith, W. E.

1984-01-01

59

The North American Soil Moisture Database  

NASA Astrophysics Data System (ADS)

Soil moisture is an important variable in the climate system, yet in situ observations of soil moisture are not prevalent in most regions of the world. The Soil Moisture and Ocean Salinity (SMOS) satellite recently launched by the European Space Agency and NASA's Soil Moisture Active and Passive (SMAP) mission underscore the need for better in situ soil moisture data for validation and accuracy assessment. The North American Soil Moisture Database is a harmonized and quality-controlled soil moisture dataset that is being developed to support investigations of land-atmosphere interactions, validating the accuracy of soil moisture simulations in global land surface models, and describing how soil moisture influences climate on seasonal to interannual timescales. Currently the database is comprised of well over 1,300 soil moisture observation stations from more than 20 networks in the United States. The data is subjected to rigorous quality control procedures. Upon completion, the database will consist of homogenized and standardized soil moisture data products that will be published on a dedicated website and made available to the scientific community to support research efforts such as EaSM, SMAP and SMOS.

Ford, T.; Quiring, S.

2012-12-01

60

Vegetation Effects on Soil Moisture Estimation  

NASA Technical Reports Server (NTRS)

Several successful algorithms have been developed to estimate soil moisture of bare surfaces. We previously reported a new algorithm using the tilted Bragg approximation. However, these algorithms are only applicable to bare surfaces. When vegetation is present, soil moisture is typically underestimated by bare surface algorithms. In order to derive soil moisture under vegetation, we have to understand the complex scattering process due to vegetation. Our main interest is to retrieve the global soil moisture information using Hydros L-band polarimetric radar data. The Hydros mission will provide the first global view of land soil moisture using L-band radar and radiometer. The unique characteristics of the Hydros data are the availability of the low resolution soil moisture information from radiometer data and the continuous time series radar data collected at the same incidence angle. In this paper, we will examine a potential inversion algorithm to retrieve soil moisture under vegetation canopies using Hydros L-band polarimetric radar data.

Kim, Yunjin; van Zyl, Jakob

2004-01-01

61

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

62

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 Ohs 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 Ohs 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 Ohs 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.

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

2010-12-01

63

Models of soil moisture dynamics in ecohydrology: A comparative study  

E-print Network

Models of soil moisture dynamics in ecohydrology: A comparative study Andrew J. Guswa Picker, infiltration, and evapotranspiration. A simple model for soil moisture dynamics, which does not resolve spatial moisture; 1875 Hydrology: Unsaturated zone; KEYWORDS: ecohydrology, soil moisture, transpiration, modeling

Guswa, Andrew J.

64

The impact of soil moisture inhomogeneities on modification of a mesoscale convective system: a budget-based model analysis  

NASA Astrophysics Data System (ADS)

In order to investigate the sensitivity of a mesoscale convective system (MCS) to soil moisture inhomogeneities in West Africa cloud-resolving simulations with the COSMO-Model initialized with European Centre for Medium-range Weather Forecasts analyses data were performed. Three scenarios were investigated: homogeneous soil type and soil moisture (HOM) and homogeneous soil type with a north-south oriented band of two degrees width with reduced soil moisture (BANDT) and with increased soil moisture (BANDM). In all experiments an MCS developed east of the band in the late afternoon. Precipitation related to the MCS was continuously strong in HOM. When the MCS approached the band with reduced soil moisture in BANDT precipitation decreased because of higher convective inhibition (CIN) ahead of the band. Reaching the drier band precipitation increased again. The moist band in BANDM caused an increase of precipitation ahead of the band and a decrease in the area with higher soil moisture caused by very high CIN values. Soil moisture inhomogeneities induced thermal circulations which led to modified conditions in the lower troposphere and to changes in CIN and accounted for the modification of precipitation of an MCS. In BANDT, precipitating cells already developed in the western part of the dry band in the late afternoon, where convergence, generated by thermal circulations and supported by downward mixing of momentum from the African Easterly Jet, triggered convection.

Adler, Bianca; Gantner, Leonhard; Kalthoff, Norbert

2010-05-01

65

A simplified bi-dimensional variational analysis of soil moisture from screen-level observations in a mesoscale numerical weather-prediction model  

Microsoft Academic Search

The analysis of soil moisture for the initialization of a mesoscale numerical weather-prediction (NWP) model is considered subject to operational constraints, both in terms of computational cost and data availability. A variational technique is used to analyse the soil moisture by assimilating screen-level observations of temperature and relative humidity. We consider a simplified bi-dimensional (z and t) variational approach (simplified

G. Balsamo; F. Bouyssel; J. Noilhan

2004-01-01

66

Soil Moisture Monitorization Using GNSS Reflected Signals  

E-print Network

The use of GNSS signals as a source of opportunity for remote sensing applications, GNSS-R, has been a research area of interest for more than a decade. One of the possible applications of this technique is soil moisture monitoring. The retrieval of soil moisture with GNSS-R systems is based on the variability of the ground dielectric properties associated to soil moisture. Higher concentrations of water in the soil yield a higher dielectric constant and reflectivity, which incurs in signals that reflect from the Earth surface with higher peak power. Previous investigations have demonstrated the capability of GPS bistatic scatterometers to obtain high enough signal to noise ratios in order to sense small changes in surface reflectivity. Furthermore, these systems present some advantages with respect to others currently used to retrieve soil moisture. Upcoming satellite navigation systems, such as the European Galileo, will represent an excellent source of opportunity for soil moisture remote sensing for vario...

Egido, Alejandro; Caparrini, Marco; Martin, Cristina; Farres, Esteve; Banque, Xavier

2008-01-01

67

Electrical methods of determining soil moisture content  

NASA Technical Reports Server (NTRS)

The electrical permittivity of soils is a useful indicator of soil moisture content. Two methods of determining the permittivity profile in soils are examined. A method due to Becher is found to be inapplicable to this situation. A method of Slichter, however, appears to be feasible. The results of Slichter's method are extended to the proposal of an instrument design that could measure available soil moisture profile (percent available soil moisture as a function of depth) from a surface measurement to an expected resolution of 10 to 20 cm.

Silva, L. F.; Schultz, F. V.; Zalusky, J. T.

1975-01-01

68

ERS scatterometer surface soil moisture analysis of two sites in the south and north of the Sahel region of West Africa  

NASA Astrophysics Data System (ADS)

SummaryThe analysis of feedback effects between continental surfaces and the atmosphere is a key element in the understanding of African monsoon dynamics. For this reason, the monitoring of surface parameters, in particular soil moisture, is essential. Satellite remote sensing appears to be the most suitable means of obtaining data relevant to such parameters. The present paper presents the results of statistical analysis of soil moisture products based on data recorded by the ERS scatterometer, over the period 1992-2006, from two sites in Niger and Mali in the Sahel climatic region. Soil moisture products were validated over these two sites using ground data measurements and ASAR/ENVISAT estimations. The soil moisture distribution during the monsoon period is described, and the temporal correlation between estimated soil moisture levels is computed. Finally, the dynamics of cells corresponding to precipitation events and high surface moisture values were evaluated in the studied regions, thereby revealing variations during the monsoon period as well as site specific trends.

Zribi, M.; Pard, M.; De Rosnay, P.; Baup, F.; Boulain, N.; Descroix, L.; Pellarin, T.; Mougin, E.; Ottl, C.; Decharme, B.

2009-08-01

69

Root Zone Soil Moisture Retrieval Using Streamflow and Surface Moisture Data Assimilation in Nested Catchments  

E-print Network

Root Zone Soil Moisture Retrieval Using Streamflow and Surface Moisture Data Assimilation in Nested; Remote Sensing; Soil Moisture; Streamflow EXTENDED ABSTRACT Correct knowledge of soil moisture to the control that soil moisture exerts on the latent and sensible heat flux transfer between the land surface

Walker, Jeff

70

Development of an Aquarius Soil Moisture Product  

NASA Astrophysics Data System (ADS)

Aquarius observations over land offer a new resource for measuring soil moisture from space. Our objective in this investigation is to exploit the large amount of land observations that Aquarius acquires and extend the mission scope to land applications through the retrieval of soil moisture. This research increases the value and impact of the Aquarius mission by including a broader scientific community, allowing the exploration of new algorithm approaches that exploit the active-passive observations, and will contribute to a better understanding of the Earth's climate and water cycle. The first stage of our Aquarius soil moisture research focused on the use of the radiometer data because of the extensive heritage that this type of observations has in soil moisture applications. The calibration of the Aquarius radiometer over the entire dynamic range is a key element for the successful implementation of the soil moisture algorithm. Results to date indicate that the Aquarius observations are well calibrated for ocean targets but have a warm bias over land. This bias needed to be addressed if the Aquarius observations are to be used in land applications. Our approach was to use the gain and offsets computed using the Soil Moisture Ocean Salinity (SMOS) comparisons to adjust the Aquarius brightness temperatures. The Single Channel Algorithm (SCA) was implemented using the Aquarius observations. SCA is also the baseline algorithm for the SMAP radiometer-only soil moisture product. Aquarius radiometer observations from the three beams (after bias/gain modification) along with the National Centers for Environmental Prediction (NCEP) surface temperature model forecast were then used to estimate soil moisture. Ancillary data inputs required for using the SCA are vegetation water content, land surface temperature, and several soil and vegetation parameters derived based on land cover. The spatial patterns of the soil moisture estimates are consistent with the climatology and with the other satellite missions (Advanced Microwave Scanning Radiometer-E and SMOS). The soil moisture and temperature products were validated using in situ observations from the Little Washita and Little River watershed soil moisture networks. Results show good performance by the algorithm for these land surface conditions for the period of August 2011-June-2013 (RMSE=0.031 m3/m3, Bias=0.007 m3/m3, and R=0.855). The validated radiometer soil moisture product will serve as a baseline for continuing research on both active and combined passive-active soil moisture algorithms. The soil moisture product was implemented as part of the routine Aquarius data processing and will be available from National Snow and Ice Data Center both in swath and gridded formats in the near future. Acknowledgement: USDA is an equal opportunity employer.

Bindlish, R.; Jackson, T. J.; Zhao, T.; Cosh, M. H.

2013-12-01

71

On the spatial scaling of soil moisture  

Microsoft Academic Search

The spatial scale of soil moisture measurements is often inconsistent with the scale at which soil moisture predictions are needed. Consequently a change of scale (upscaling or downscaling) from the measurements to the predictions or model values is needed. The measurement or model scale can be defined as a scale triplet, consisting of spacing, extent and support. Spacing refers to

Gnter Blschl

1999-01-01

72

Soil moisture retrievals: where are we?  

NASA Astrophysics Data System (ADS)

Soil moisture is one of the most important variables regarding climate evolution ans plays a major role in the transfers between the soil and the atmosphere ([1]). Soil moisture needs to be considered as a global variable to improve our global comprehension of the climate. Several approaches have been developed to either model soil moisture or to retrieve it from satellite data. The European Center for Medium range Weather Forecasting (ECMWF) provides global maps of modeled soil moisture but there exists also regional climate models such as SIM, ???. Recently, satellite missions, specially designed for soil moisture monitoring such as the Soil Moisture and Ocean Salinity,(SMOS) have been proposed. SMOS was indeed successfully launched in November 2009 and SMAP (Soil Moisture Active Passive) is scheduled for launch in November 2014. Several algorithms have been created to retrieve soil moisture from higher frequencies measurements obtained from existing satellites such as : SMMR (1978-87), SSM/I (1987), AMSR-E (2004), ERS-ASCAT (1991-2006). Even if their lowest frequencies (5-20 GHz) are not the most suitable for soil moisture retrievals (very sensitive to vegetation growth and atmosphere), it remains a valuable time series from 1979 until now. All these products are obtained at a coarse resolution (typically around 50 km) and it is not always straight-forward to relate them to point measurements for the validation purposes especially at a global scale. It is thus necessary to validate coarse scale soil moisture estimates with model outputs or area representative points. SMOS validation has been performed on a number of sites but it is also necessary to inter-compare with other existing products (satellite products and model outputs) to identify the overall behavior at the global scale. The present paper deals with this topic.

Kerr, Y.; Leroux, D.; Richaume, P.; Wigneron, J. P.; Mialon, A.; Mahmoodi, A.; Bitar, A. Al; Novello, N.; Gruhier, C.; Pellarin, T.; Rudiger, C.; Lawrence, H.; De rosnay, P.; Albergel, C.

2012-04-01

73

Comparison of SMOS and AMSR-E retrieved soil moisture with the field measured soil moisture data in South India  

NASA Astrophysics Data System (ADS)

This study focuses on the comparison of soil moisture products from Soil Moisture and Ocean Salinity (SMOS) satellite with field measurements and other remote sensing products over an small experimental watershed in the Kabini river basin in South India. SMOS ascending and descending orbits are considered from April, 2010 till August, 2010. Period will be eventually extended to latest available data till paper presentation. The measured data comprises of periodic measurement in 50 plots (2 readings in each plot) and hourly soil moisture data at a metrological station on the site. The plots used for measurement of soil moisture have various types of crop, soil, topography, which is useful for providing a representative soil moisture comparable to the 40 km resolution SMOS data. The measured hourly soil moisture data is useful in providing the knowledge of temporal variability. Comparison with AMSR-E derived soil moisture products are also done. Apart from the satellite retrieved data, the soil moisture data from European Centre for Medium-Range Weather Forecasts (ECMWF) is also compared with field measured data. The retrieved soil moisture from SMOS satellite shows better dynamics than AMSR-E which have a low variability. On the other hand results show an overestimation in the ECMWF analysis product used as initial guess for SMOS retrievals. The data from this site is being used to retrieve surface soil moisture using RADARSAT-2, EVISAT and would be used for CAL/VAL of Radar Imaging SATellite (RISAT-1) an upcoming C-Band SAR mission from Indian Space Research Organization (ISRO).

Tomer, S. K.; Bitar, A. A.; Sekhar, M.; Kerr, Y. H.; Merlin, O.; Bandyopadhyay, S.; Mohan, S.

2010-12-01

74

ORIGINAL ARTICLE Using GPS multipath to measure soil moisture fluctuations  

E-print Network

ORIGINAL ARTICLE Using GPS multipath to measure soil moisture fluctuations: initial results Abstract Measurements of soil moisture are important for studies of climate and weather forecasting, flood prediction, and aquifer recharge studies. Although soil moisture mea- surement networks exist, most

Small, Eric

75

Investigation of remote sensing techniques of measuring soil moisture  

NASA Technical Reports Server (NTRS)

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 experiment during which passive microwave measurements were acquired to validate these models, and evaluation of previously acquired aircraft microwave measurements. The development of a root zone soil water and soil temperature profile model and the calibration and evaluation of gamma ray attenuation probes for measuring soil moisture profiles are considered. The analysis of spatial variability of soil information as related to remote sensing is discussed as well as the implementation of an instrumented field site for acquisition of soil moisture and meteorologic information for use in validating the soil water profile and soil temperature profile models.

Newton, R. W. (principal investigator); Blanchard, A. J.; Nieber, J. L.; Lascano, R.; Tsang, L.; Vanbavel, C. H. M.

1981-01-01

76

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

77

Sensitivity of Soil Respiration to Variability in Soil Moisture and Temperature in a Humid Tropical Forest  

PubMed Central

Precipitation and temperature are important drivers of soil respiration. The role of moisture and temperature are generally explored at seasonal or inter-annual timescales; however, significant variability also occurs on hourly to daily time-scales. We used small (1.54 m2), throughfall exclusion shelters to evaluate the role soil moisture and temperature as temporal controls on soil CO2 efflux from a humid tropical forest in Puerto Rico. We measured hourly soil CO2 efflux, temperature and moisture in control and exclusion plots (n?=?6) for 6-months. The variance of each time series was analyzed using orthonormal wavelet transformation and Haar-wavelet coherence. We found strong negative coherence between soil moisture and soil respiration in control plots corresponding to a two-day periodicity. Across all plots, there was a significant parabolic relationship between soil moisture and soil CO2 efflux with peak soil respiration occurring at volumetric soil moisture of approximately 0.375 m3/m3. We additionally found a weak positive coherence between CO2 and temperature at longer time-scales and a significant positive relationship between soil temperature and CO2 efflux when the analysis was limited to the control plots. The coherence between CO2 and both temperature and soil moisture were reduced in exclusion plots. The reduced CO2 response to temperature in exclusion plots suggests that the positive effect of temperature on CO2 is constrained by soil moisture availability. PMID:24312508

Wood, Tana E.; Detto, Matteo; Silver, Whendee L.

2013-01-01

78

Retrieving pace in vegetation growth using precipitation and soil moisture  

NASA Astrophysics Data System (ADS)

The complexity of interactions between the biophysical components of the watershed increases the challenge of understanding water budget. Hence, the perspicacity of the continuum soil-vegetation-atmosphere's functionality still remains crucial for science. This study targeted the Texas Gulf watershed and evaluated the behavior of vegetation covers by coupling precipitation and soil moisture patterns. Growing season's Normalized Differential Vegetation Index NDVI for deciduous forest and grassland were used over a 23 year period as well as precipitation and soil moisture data. The role of time scales on vegetation dynamics analysis was appraised using both entropy rescaling and correlation analysis. This resulted in that soil moisture at 5 cm and 25cm are potentially more efficient to use for vegetation dynamics monitoring at finer time scale compared to precipitation. Albeit soil moisture at 5 cm and 25 cm series are highly correlated (R2>0.64), it appeared that 5 cm soil moisture series can better explain the variability of vegetation growth. A logarithmic transformation of soil moisture and precipitation data increased correlation with NDVI for the different time scales considered. Based on a monthly time scale we came out with a relationship between vegetation index and the couple soil moisture and precipitation [NDVI=a*Log(% soil moisture)+b*Log(Precipitation)+c] with R2>0.25 for each vegetation type. Further, we proposed to assess vegetation green-up using logistic regression model and transinformation entropy using the couple soil moisture and precipitation as independent variables and vegetation growth metrics (NDVI, NDVI ratio, NDVI slope) as the dependent variable. The study is still ongoing and the results will surely contribute to the knowledge in large scale vegetation monitoring. Keywords: Precipitation, soil moisture, vegetation growth, entropy Time scale, Logarithmic transformation and correlation between soil moisture and NDVI, precipitation and NDVI. The analysis is performed by combining both scenes 7 and 8 data. Schematic illustration of the two dimension transinformation entropy approach. T(P,SM;VI) stand for the transinformation contained in the couple soil moisture (SM)/precipitation (P) and explaining vegetation growth (VI).

Sohoulande Djebou, D. C.; Singh, V. P.

2013-12-01

79

SMALT - Soil Moisture from Altimetry project  

NASA Astrophysics Data System (ADS)

Soil surface moisture is a key scientific parameter; however, it is extremely difficult to measure remotely, particularly in arid and semi-arid terrain. This paper outlines the development of a novel methodology to generate soil moisture estimates in these regions from multi-mission satellite radar altimetry. Key to this approach is the development of detailed DRy Earth ModelS (DREAMS), which encapsulate the detailed and intricate surface brightness variations over the Earths land surface, resulting from changes in surface roughness and composition. DREAMS have been created over a number of arid and semi-arid deserts worldwide to produce historical SMALT timeseries over soil moisture variation. These products are available in two formats - a high resolution track product which utilises the altimeters high frequency content alongtrack and a multi-looked 6 gridded product at facilitate easy comparison/integeration with other remote sensing techniques. An overview of the SMALT processing scheme, covering the progression of the data from altimeter sigma0 through to final soil moisture estimate, is included along with example SMALT products. Validation has been performed over a number of deserts by comparing SMALT products with other remote sensing techniques, results of the comparison between SMALT and Metop Warp 5.5 are presented here. Comparisons with other remote sensing techniques have been limited in scope due to differences in the operational aspects of the instruments, the restricted geographical coverage of the DREAMS and the low repeat temporal sampling rate of the altimeter. The potential to expand the SMALT technique into less arid areas has been investigated. Small-scale comparison with in-situ and GNSS-R data obtained by the LEiMON experimental campaign over Tuscany, where historical trends exist within both SMALT and SMC probe datasets. A qualitative analysis of unexpected backscatter characteristics in dedicated dry environments is performed with comparison between Metop ASCAT and altimeter sigma0 over Saharan Africa. Geographical correlated areas of agreement and disagreement corresponding to underlying terrain are identified. SMALT products provide a first order estimation of soil moisture in areas of very dry terrain, where other datasets are limited. Potential to improve and expand the technique has been found, although further work is required to produce products with the same accuracy confidence as more established techniques. The data are made freely available to the scientific community through the website http://tethys.eaprs.cse.dmu.ac.uk/SMALT

Smith, Richard; Benveniste, Jrme; Dinardo, Salvatore; Lucas, Bruno Manuel; Berry, Philippa; Wagner, Wolfgang; Hahn, Sebastian; Egido, Alejandro

80

Soil Moisture Measurement System For An Improved Flood Warning  

NASA Astrophysics Data System (ADS)

Precipitation-runoff processes are correlated with the catchment's hydrological pre- conditions that are taken into account in some hydrological models, e.g. by pre- precipitation index. This statistically generated variable is unsuitable in case of ex- treme flood events. Thus a non-statistical estimation of the catchment's preconditions is of tremendous importance for an improvement in reliability of flood warning. This can be achieved by persistent operational observation of the catchment's soil mois- ture condition. The soil moisture acts as a state variable controlling the risk of surface runoff, which is assumed to provoke critical floods. Critical soil moisture conditions can be identified by measurements in certain areas representative for the catchment. Therefore a measurement arrangement that does not effect the structure of soils is realised with twin rod probes. Spatial resolution algorithms result in soil moisture profiles along the probe rods. In this set up a quasi three dimensional soil moisture distribution can be interpolated with point measurements of up to 47 twin rod probes per cluster, connected via multiplexer. The large number of probes per cluster is of use for detailed observation of small-scaled moisture variability. As regionalized grid cell moisture the cluster information calibrates the default, state depending soil moisture distribution of the catchment. This distribution is explained by diverse soil moisture influencing properties, which are found by Landsat satellite image. Therefore the im- age is processed with principal component analysis to extract the soil moisture distri- bution. The distribution is calibrated by the detailed measurements, acting as ground based truth. Linear multiple regression operated on the calibrated distribution identi- fies the mentioned properties. In this fashion the catchment status can be determined and combined with precipitation forecasts, thus allowing for the comprehensive risk calculation of critical floods.

Schaedel, W.; Becker, R.

81

Large scale measurements of soil moisture for validation of remotely sensed data: Georgia soil moisture experiment of 2003*  

E-print Network

Large scale measurements of soil moisture for validation of remotely sensed data: Georgia soil August 2005; accepted 18 August 2005 Abstract A series of soil moisture experiments were conducted of soil moisture and temperature collected during SMEX03 GA. A network of in situ soil moisture

82

SMEX02: Field scale variability, time stability and similarity of soil moisture  

E-print Network

for intermediate soil moisture range. Time stability analysis showed that an appropriately selected single samplingSMEX02: Field scale variability, time stability and similarity of soil moisture Jennifer M. Jacobsa 2004 Abstract Evaluation of air- or space-borne remote sensors measuring soil moisture requires

Mohanty, Binayak P.

83

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

E-print Network

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

Ni-Meister, Wenge

84

Calibration of remotely sensed soil moisture  

Microsoft Academic Search

All remotely sensed soil moisture data have to be calibrated by reference measurements on ground. The gravimetric sampling (oven drying) is not suitable. It is time consuming, expensive, and destroys the site. Also the neutron probe has less and less acceptance. The remaining possibility is the dielectric moisture determination by rf or microwaves. The optimal measuring frequency for such a

Alexander Brandelik; Christof Huebner

1995-01-01

85

Radar Mapping of Surface Soil Moisture  

NASA Technical Reports Server (NTRS)

Intended as an overview aimed at potential users of remotely sensed spatial distributions and temporal variations of soil moisture, this paper begins with an introductory section on the fundamentals of radar imaging and associated attributes.

Ulaby, F. T.; Dubois, P. C.; van Zyl, J.

1997-01-01

86

The Soil Moisture Active Passive (SMAP) Mission  

E-print Network

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. SMAP will make global measurements of ...

Entekhabi, Dara

87

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.; Dfossez, P.

2009-04-01

88

Overview of soil moisture measurements with neutrons  

NASA Astrophysics Data System (ADS)

Soil moisture measurements are useful for hydrological and agricultural applications. Soil moisture can be measured with a range of in-situ sensors in the soil, such as probes based on the difference in dielectric permittivity of wet and dry soil. At a large scale of tenths of kilometres, soil moisture can be measured with microwave remote sensing from satellites. At the intermediate scale, detection methods such as GPS reflectometry and the use of cosmic rays have been developed recently. One of the principles that can be used to measure soil moisture, is the difference in behaviour of neutrons in wet and dry soil. Neutrons are massive, electrically neutral particles that transfer their energy easily to light atoms, such as hydrogen. Therefore, in wet soil, neutrons lose their energy quickly. In dry soil, they scatter elastically from the heavy atoms and can be detected. The amount of detected neutrons is therefore inversely correlated with the amount of hydrogen in the soil. In this research we look for an overview of the possibilities to measure soil moisture with neutrons and how neutrons can be detected. Neutrons can be used to measure at the point scale and at a larger scale of approximately 1 km. We discuss in-situ measurements, in which a neutron source is put into the soil. Immediately next to the source is a detector, that counts the amount of neutrons that scatters back if the soil is dry. At a larger scale or measurement volume, we discuss the measurement of soil moisture with neutrons from cosmic rays. Cosmic rays are charged particles, accelerated by astrophysical sources (such as a Supernova). When the particles enter the atmosphere, they interact with the atmospheric atoms and form a shower. At sea level, we find several types of particles, such as muons and neutrons. We discuss why neutrons would be more useful for soil moisture measurements than other particles and how the use of cosmic-ray neutrons influences the measurement volume. Here we present an overview of the principles of soil moisture measurements at different scales with neutrons.

Hendriks, Aagje; Steele-Dunne, Susan; van de Giesen, Nick

2014-05-01

89

Soil-moisture ground truth, Hand County, South Dakota  

NASA Technical Reports Server (NTRS)

Soil types were determined from the Soil Survey of Hand County, South Dakota. The soil types encountered on the soil moisture lines are summarized. The actual soil moisture data are presented. The data have been divided by range, township and section. The soil moisture data obtained in fields of winter wheat and spring wheat are briefly summarized.

Jones, E. B.

1976-01-01

90

Soil Moisture and the Drought in Texas Todd Caldwell  

E-print Network

Soil Moisture and the Drought in Texas Todd Caldwell Bridget Scanlon Michael Young Di Long Water;Soil Moisture and the Drought in Texas I. How is drought linked to water resources? II. Where does soil moisture fit into the picture? III. How are we modeling soil moisture? IV. How are can we validate

Yang, Zong-Liang

91

REGULAR ARTICLE Decoupling litter barrier and soil moisture influences  

E-print Network

REGULAR ARTICLE Decoupling litter barrier and soil moisture influences on the establishment microhabitats with experimentally varied levels of soil moisture and leaf litter. Results Soil moisture-dependent limits on seed production. Conclusions The interactive effects of varied levels of soil moisture and leaf

Bahn, Volker

92

ERS scatterometer surface soil moisture analysis of two sites in the south and north of the Sahel region of West Africa  

Microsoft Academic Search

summary The analysis of feedback effects between continental surfaces and the atmosphere is a key element in the understanding of African monsoon dynamics. For this reason, the monitoring of surface parameters, in particular soil moisture, is essential. Satellite remote sensing appears to be the most suitable means of obtaining data relevant to such parameters. The present paper presents the results

M. Zribi; M. Pard; P. De Rosnay; F. Baup; N. Boulain; L. Descroix; T. Pellarin; E. Mougin; C. Ottl; B. Decharme

2009-01-01

93

Microwave remote sensing of soil moisture  

NASA Technical Reports Server (NTRS)

Knowledge of soil moisture is important to many disciplines, such as agriculture, hydrology, and meteorology. Soil moisture distribution of vast regions can be measured efficiently only with remote sensing techniques from airborne or satellite platforms. At low microwave frequencies, water has a much larger dielectric constant than dry soil. This difference manifests itself in surface emissivity (or reflectivity) change between dry and wet soils, and can be measured by a microwave radiometer or radar. The Microwave Sensors and Data Communications Branch is developing microwave remote sensing techniques using both radar and radiometry, but primarily with microwave radiometry. The efforts in these areas range from developing algorithms for data interpretation to conducting feasibility studies for space systems, with a primary goal of developing a microwave radiometer for soil moisture measurement from satellites, such as EOS or the Space Station. These efforts are listed.

Shiue, J. C.; Wang, J. R.

1988-01-01

94

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

95

Validation of Soil Moisture and Ocean Salinity (SMOS) Soil Moisture over Watershed Networks in the U.S.  

E-print Network

1 Validation of Soil Moisture and Ocean Salinity (SMOS) Soil Moisture over Watershed Networks and a variety of retrieval methods over the past two decades. The most recent source of soil moisture is the European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. A thorough validation must

Paris-Sud XI, Université de

96

Characterization of the spatial-temporal variability of soil moisture by remote sensing  

NASA Astrophysics Data System (ADS)

Characterization of spatial and temporal variabilities of soil moisture, spectral formalism of soil moisture estimation and sampling error simulation study were conducted to understand soil moisture field and to establish global monitoring strategy. Linear relation between soil moisture and porosity is dramatically improved with increasing pixel size although linear relation between soil moisture and soil properties is very weak. The relation between field variance and aggregation area follows power law between log scale 4 and 7. Scaling analysis indicates that the power law exponent becomes smaller with increasing area, which allows the assumption that the soil moisture field is stationary in large area. Variogram analysis shows that the stationarity of soil moisture field is changed by meteorological condition. Spectrum of soil moisture field shows there is no dominant spatial frequency. Two-dimensional correlogram of the soil moisture and brightness temperature fields shows strong anisotropy. Correlation structure of the soil moisture field is changed by drying or rainfall process. Average correlation length of the soil moisture consists of Long'-14km and Lat'-36km. Autoregressive exogenous model (ARX) with lag-1 correlation coefficient 0.9 is suggested for temporal soil moisture model. The Monsoon '90 soil moisture data indicate that diurnal cycle causes 1--4% sampling error. (5 a.m.--9a.m.: 1%, 1 p.m.--3 p.m.: 4%). North-Nakamoto formalism (1989) was used to compute the sampling error for the soil moisture field estimation. The space-time discrete design filter was evaluated and it is applicable to all kinds of sampling design. Missing temporal measurements in SGP '97 soil moisture field make it difficult to estimate the spectra directly from observed record. The soil moisture spectrum was estimated using rainfall and soil moisture models tuned parameter to SGP '97 data. Estimated sampling error of daily electronically scanned thinned army radiometer (ESTAR) soil moisture sampling 2.6%. Soil moisture data were generated by using rainfall and soil moisture model that considered the diurnal cycle and topographic effects with parameters tuned to SGP '97 data. Partial coverage caused greater sampling errors than temporal gaps. The larger the capacity for holding water, the less sampling error is generated. Block random installation gets more accurate data than random installation of soil moisture gages. The greater the loss coefficient, the greater the sampling errors. Sampling error linearly increased with increasing diurnal cycle amplitude.

Kim, Gwangseob

1999-11-01

97

Remote sensing applications to hydrology: soil moisture  

Microsoft Academic Search

Passive and active microwave remote sensing instruments are capable of measuring the surface soil moisture (0-5 cm) and can be implemented on high altitude platforms, e.g. spacecraft, for repetitive large area observations. The amount of water present in a soil affects its dielectric properties. The dielectric properties, along with several other physical characteristics, determine the microwave measurement. In addi tion,

T. J. JACKSON; J. SCHMUGGE; E. T. ENGMAN

1997-01-01

98

Using Polarimetric SAR Data to Infer Soil Moisture from Surfaces with Varying Subsurface Moisture Profiles  

NASA Technical Reports Server (NTRS)

A time-series approach is used to estimate the moisture content-based on polarimetric SAR data. It is found that under the assumption of constant soil moisture, empirically observed relationships between radar backscatter and moisture are only half as sensitive to moisture as compared to actual radar data. A numerical finite element method is used to calculate the radar backscatter for rough soils with arbitrarily varying soil moisture as a function of depth. Several instance of drying and wetting moisture profiles are considered and the radar backscatter is calculated in each case. Radar backscatter is found to crucially depend on the soil moisture variation in the top half wavelength of soil.

Khankhoje, Uday K.; van Zyl, Jakob; Kim, Yunjin; Cwik, Thomas

2012-01-01

99

Evaluation of the Soil Moisture Active Passive Mission (SMAP) merged radar-radiometer soil moisture algorithm  

Microsoft Academic Search

The Soil Moisture Active Passive (SMAP) mission is recommended by the U.S. National Research Council Committee on Earth Science and Applications from Space. The SMAP mission is under development with a target launch date in late 2014. The SMAP mission will provide high resolution (~9 km) soil moisture product at a global extent. The SMAP instrument architecture incorporates an L-band

N. Das; D. Entekhabi; E. G. Njoku

2010-01-01

100

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

101

A soil moisture network in Switzerland: Analyses from the Swiss Soil Moisture Experiment  

NASA Astrophysics Data System (ADS)

Soil moisture is an essential terrestrial variable as it strongly affects land-surface fluxes with consequent impact on runoff generation, temperature, and evapotranspiration. Measurements of soil moisture are crucial to investigate processes in hydrology as well as in climate and environmental science. However, soil moisture is still not routinely measured and there is a lack of observations in many parts of the world. Within the Swiss Soil Moisture Experiment (SwissSMEX, www.iac.ethz.ch/url/research/SwissSMEX) the large-scale and long-term SwissSMEX soil moisture network was established in 2008/2010 in Switzerland. The network has a spatial extent of about 150x210 km and consists of overall 19 sites at 17 different locations, including 14 grassland, 4 forest, and 1 arable land site. For each site measurements of soil moisture and soil temperature down to 120 cm, as well as detailed information about the topography, soil characteristics, and the main meteorological variables are available. The analyses conducted using the SwissSMEX soil moisture data set provide helpful insights on the performance of soil moisture sensors, distinction in soil moisture behavior across different land covers, as well as on the spatio-temporal dynamics of soil moisture. Here we present the design of the SwissSMEX soil moisture network as well as an overview on the analyses based on the developed data set. As for any measurements the performance of the sensor is important, we will focus on the evaluation of the applied capacitance-based 10HS (Decagon Devises, United States) soil moisture sensor. Its measurements agreed well for low volumetric water contents using both laboratory and field measurements. A considerable limitation is found in the decreasing sensitivity of sensor reading for volumetric water contents variations above 0.4 m3/m3. In addition, the applicability of a laboratory calibration function is limited due to a dependency of the sensor on soil characteristics. However, with site-specific calibration functions the measurement error of the 10HS sensor can be decreased and the day-to-day variability of soil moisture is captured (Mittelbach et al., 2011). Furthermore, we present a comparison of soil moisture recession over grassland and nearby forest sites with consequent impact on evapotranspiration, as well as on the spatio-temporal variability of soil moisture within the network using 14 grassland sites (Mittelbach et al. 2012). Reference: Mittelbach, H., F. Casini, I. Lehner, A.J. Teuling, and S.I. Seneviratne, 2011: Soil moisture monitoring for climate research: Evaluation of a low-cost soil moisture sensor in the framework of the Swiss Soil Moisture Experiment (SwissSMEX). Journal of Geophysical Research, 1616, D05111. Mittelbach, H. and S.I. Seneviratne, 2012: A new perspective on the spatio-temporal variability of soil moisture: Temporal dynamics versus time invariant contributions. Submitted to HESS.

Mittelbach, H.; Lehner, I.; Teuling, A. J.; Seneviratne, S. I.

2012-04-01

102

Response of spectral vegetation indices to soil moisture in grasslands and shrublands  

USGS Publications Warehouse

The relationships between satellite-derived vegetation indices (VIs) and soil moisture are complicated because of the time lag of the vegetation response to soil moisture. In this study, we used a distributed lag regression model to evaluate the lag responses of VIs to soil moisture for grasslands and shrublands at Soil Climate Analysis Network sites in the central and western United States. We examined the relationships between Moderate Resolution Imaging Spectroradiometer (MODIS)-derived VIs and soil moisture measurements. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) showed significant lag responses to soil moisture. The lag length varies from 8 to 56 days for NDVI and from 16 to 56 days for NDWI. However, the lag response of NDVI and NDWI to soil moisture varied among the sites. Our study suggests that the lag effect needs to be taken into consideration when the VIs are used to estimate soil moisture. ?? 2011 Taylor & Francis.

Zhang, L.; Ji, L.; Wylie, B.K.

2011-01-01

103

Satellite Soil Moisture Remote Sensing and Data Assimilation  

E-print Network

Slide 1/68 Satellite Soil Moisture Remote Sensing and Data Assimilation: Brief History & Current Status Satellite Soil Moisture Remote Sensing and Data Assimilation: Brief History & Current Status X Moisture Retrievals 4. Soil Moisture Data Assimilation 5. SM Data Research Plan Slide 2/68 #12;Slide 3

Kuligowski, Bob

104

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

105

Soil Moisture Experiments 2003 (SMEX03)  

NASA Astrophysics Data System (ADS)

A series of large-scale soil moisture field experiments have been conducted over the past decade. These have been successful at addressing a broad range of science question, focusing technology development and demonstration, and providing educational experiences for undergraduate and graduate students. Soil Moisture Experiments 2003 (SMEX03) will focus on satellite based soil moisture products. The NASA Aqua and Japanese ADEOS-II Advanced Microwave Scanning Radiometer (AMSR) Programs are committed to developing and providing daily soil moisture products. This is the first time that this challenging task has ever been attempted. The wide range of vegetation conditions that have to be dealt with, due to the global coverage and multi-temporal observations, exceed those that have been evaluated in previous investigations. For these reasons, validation is critical to the AMSR soil moisture product development and acceptance. SMEX03 will provide validation data for a wide range of vegetation conditions ranging from well-understood grass and wheat in Oklahoma to new observations of the Amazon rainforests. In addition it will provide a test bed for other new satellite instruments such as the Envisat ASAR and aircraft based prototype satellite instruments. SMEX03 will be conducted at U.S. sites in Oklahoma, Georgia and Alabama in June and July and Brazil in September.

Jackson, T. J.

2002-12-01

106

Radar measurement of soil moisture content  

NASA Technical Reports Server (NTRS)

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 was used to measure the return at 10 frequency points across the 4-8 GHz band, at different look angles, and for all polarization combinations. The results indicate that the radar response to soil moisture content is highly dependent on the surface roughness, microwave frequency, and look angle. The response seems to be linear over the range 15%-30% moisture content for all angles, frequencies, polarizations and surface conditions.

Ulaby, F. T.

1973-01-01

107

Soil moisture needs in earth sciences  

NASA Technical Reports Server (NTRS)

The author reviews the development of passive and active microwave techniques for measuring soil moisture with respect to how the data may be used. New science programs such as the EOS, the GEWEX Continental-Scale International Project (GCIP) and STORM, a mesoscale meteorology and hydrology project, will have to account for soil moisture either as a storage in water balance computations or as a state variable in-process modeling. The author discusses future soil moisture needs such as frequency of measurement, accuracy, depth, and spatial resolution, as well as the concomitant model development that must proceed concurrently if the development in microwave technology is to have a major impact in these areas.

Engman, Edwin T.

1992-01-01

108

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

109

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

110

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

111

Advanced microwave soil moisture studies. [Big Sioux River Basin, Iowa  

NASA Technical Reports Server (NTRS)

Comparisons of low level L-band brightness temperature (TB) and thermal infrared (TIR) data as well as the following data sets: soil map and land cover data; direct soil moisture measurement; and a computer generated contour map were statistically evaluated using regression analysis and linear discriminant analysis. Regression analysis of footprint data shows that statistical groupings of ground variables (soil features and land cover) hold promise for qualitative assessment of soil moisture and for reducing variance within the sampling space. Dry conditions appear to be more conductive to producing meaningful statistics than wet conditions. Regression analysis using field averaged TB and TIR data did not approach the higher sq R values obtained using within-field variations. The linear discriminant analysis indicates some capacity to distinguish categories with the results being somewhat better on a field basis than a footprint basis.

Dalsted, K. J.; Harlan, J. C.

1983-01-01

112

Assessment of SMOS soil moisture retrieval parameters using tau-omega algorithms for soil moisture deficit estimation  

NASA Astrophysics Data System (ADS)

Soil Moisture and Ocean Salinity (SMOS) is the latest mission which provides flow of coarse resolution soil moisture data for land applications. However, the efficient retrieval of soil moisture for hydrological applications depends on optimally choosing the soil and vegetation parameters. The first stage of this work involves the evaluation of SMOS Level 2 products and then several approaches for soil moisture retrieval from SMOS brightness temperature are performed to estimate Soil Moisture Deficit (SMD). The most widely applied algorithm i.e. Single channel algorithm (SCA), based on ?-? is used in this study for the soil moisture retrieval. In ?-?, the soil moisture is retrieved using the Horizontal (H) polarisation following Hallikainen dielectric model, roughness parameters, Fresnel's equation and estimated Vegetation Optical Depth (?). The roughness parameters are empirically calibrated using the numerical optimization techniques. Further to explore the improvement in retrieval models, modifications have been incorporated in the algorithms with respect to the sources of the parameters, which include effective temperatures derived from the European Center for Medium-Range Weather Forecasts (ECMWF) downscaled using the Weather Research and Forecasting (WRF)-NOAH Land Surface Model and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) while the ? is derived from MODIS Leaf Area Index (LAI). All the evaluations are performed against SMD, which is estimated using the Probability Distributed Model following a careful calibration and validation integrated with sensitivity and uncertainty analysis. The performance obtained after all those changes indicate that SCA-H using WRF-NOAH LSM downscaled ECMWF LST produces an improved performance for SMD estimation at a catchment scale.

Srivastava, Prashant K.; Han, Dawei; Rico-Ramirez, Miguel A.; O'Neill, Peggy; Islam, Tanvir; Gupta, Manika

2014-11-01

113

Thermal inertia approach to mapping of soil moisture and geology  

Microsoft Academic Search

The application of thermal inertia mapping, using satellite and airborne thermal infrared data together with broadband visible imagery, to soil moisture and geological mapping is examined. Results of a simulation of the effects of soil moisture, clay\\/sand content and porosity on the thermal properties of soils are presented. Thermal inertia is found to display a strong dependence on soil moisture

D. A. Pratt; C. D. Ellyett

1979-01-01

114

ESTIMATION OF GROUND WATER RECHARGE USING SOIL MOISTURE BALANCE APPROACH  

E-print Network

ESTIMATION OF GROUND WATER RECHARGE USING SOIL MOISTURE BALANCE APPROACH C. P. Kumar* ABSTRACT is the principal means for replenishment of moisture in the soil water system and recharge to ground water at the upper boundary, the antecedent soil moisture conditions, the water table depth and the soil type

Kumar, C.P.

115

Derivation of Soil Moisture Retention Characteristics from Saturated Hydraulic Conductivity  

E-print Network

1 Derivation of Soil Moisture Retention Characteristics from Saturated Hydraulic Conductivity C. P systems require knowledge of the relationships between soil moisture content (), soil water pressure (h involved field and laboratory determination of soil moisture characteristics along the Hindon river in its

Kumar, C.P.

116

RESEARCH ON REGIONAL SPATIAL VARIABILITY OF SOIL MOISTURE BASED ON  

E-print Network

RESEARCH ON REGIONAL SPATIAL VARIABILITY OF SOIL MOISTURE BASED ON GIS Yongcun Fan 1,* , Changli dynamics properties, soil moisture content is an important factor of soil fertility which counts for much of soil moisture measurement was introduced. Its main job includes the use of differential GPS technology

Paris-Sud XI, Université de

117

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.; Cantn, Y.; Lzaro, R.; Rodriguez-Caballero, E.; Domingo, F.

2012-04-01

118

Soil moisture - precipitation feedbacks in observations and models (Invited)  

NASA Astrophysics Data System (ADS)

There is considerable uncertainty about the strength, geographical extent, and even the sign of feedbacks between soil moisture and precipitation. Whilst precipitation trivially increases soil moisture, the impact of soil moisture, via surface fluxes, on convective rainfall is far from straight-forward, and likely depends on space and time scale, soil and synoptic conditions, and the nature of the convection itself. In considering how daytime convection responds to surface fluxes, large-scale models based on convective parameterisations may not necessarily provide reliable depictions, particularly given their long-standing inability to reproduce a realistic diurnal cycle of convection. On the other hand, long-term satellite data provide the potential to establish robust relationships between soil moisture and precipitation across the world, notwithstanding some fundamental weaknesses and uncertainties in the datasets. Here, results from regional and global satellite-based analyses are presented. Globally, using 3-hourly precipitation and daily soil moisture datasets, a methodology has been developed to compare the statistics of antecedent soil moisture in the region of localised afternoon rain events (Taylor et al 2012). Specifically the analysis tests whether there are any significant differences in pre-event soil moisture between rainfall maxima and nearby (50-100km) minima. The results reveal a clear signal across a number of semi-arid regions, most notably North Africa, indicating a preference for afternoon rain over drier soil. Analysis by continent and by climatic zone reveals that this signal (locally a negative feedback) is evident in other continents and climatic zones, but is somewhat weaker. This may be linked to the inherent geographical differences across the world, as detection of a feedback requires water-stressed surfaces coincident with frequent active convective initiations. The differences also reflect the quality and utility of the soil moisture datasets outside of sparsely-vegetated regions. No evidence is found for afternoon convection developing preferentially above locally moister soils. Higher resolution datasets are used to provide a clearer relationship between soil moisture patterns and convective initiation in both the Sahel (Taylor et al 2011) and Europe. The observations indicate a preference for convection to initiate on soil moisture gradients, consistent with many high resolution numerical studies. The ability of models to capture the observed relationships between soil moisture and rainfall in the Sahel has been evaluated. This focuses on models run at different resolutions, and with convective parameterisations switched on or off, and highlights issues associated with the parameterisation of convection. Taylor, C.M., Gounou, A., Guichard, F., Harris, P.P., Ellis, R.J.,Couvreux, F., and M. De Kauwe. 2011, Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns, Nature Geoscience, 4, 430-433, doi:10.1038/ngeo1173 Taylor, C.M., de Jeu, R.A.M., Guichard, F., Harris, P.P, and W.A. Dorigo. 2012, Afternoon rain more likely over drier soils, Nature, 489, 423-426, doi:10.1038/nature11377

Taylor, C.

2013-12-01

119

Characterization of soil moisture responses on a hillslope to sequential rainfall events during late autumn and spring  

Microsoft Academic Search

In this study, the results of intensive soil moisture monitoring and analysis are reported in order to highlight the seasonal differences in hydrological processes on a hillslope scale. A soil monitoring system for a steep hillslope was designed and installed to monitor the temporal features of soil moisture with respect to the terrain attributes. Comparison of soil moisture analyses for

Sanghyun Kim

2009-01-01

120

Soil Moisture Prediction Using Support Vector Machines  

Microsoft Academic Search

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

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

2006-01-01

121

Sensitivity of rainfall excess to antecedent soil moisture and soil hydraulic properties  

NASA Technical Reports Server (NTRS)

A sensitivity analysis to determine the impact of antecedent soil moisture and soil hydraulic properties on rainfall excess volumes was performed. That the spatial distribution of surface soil moisture at the beginning of a storm must be correctly defined if physically-based hydrologic models are to properly partition the rainfall into portions that enter the soil and portions that become available for surface runoff. This statement is especially true for those rainfall events that occur on a routine or frequent basis. Thus, the quality of the results of continuous accounting models used to estimate the replenishment of foil moisture storage from rainfall are closely tied to the quality of information on the soil moisture in the surface layers at the beginning of the storm event.

Wilkening, H. A.

1982-01-01

122

The spatial and temporal organization of soil moisture.  

E-print Network

??Runoff, infiltration, evaporation and transpiration and-at climatic scales-precipitation are hydrologic processes that strongly depend on soil moisture. From a descriptive viewpoint, soil moisture is. characterized (more)

Vogel, Gregor Klaus

2012-01-01

123

The spatial and temporal organization of soil moisture  

E-print Network

Runoff, infiltration, evaporation and transpiration and-at climatic scales-precipitation are hydrologic processes that strongly depend on soil moisture. From a descriptive viewpoint, soil moisture is. characterized by an extremely high degree...

Vogel, Gregor Klaus

2012-06-07

124

Soil moisture and soil-litter mixing effects on surface litter decomposition: A controlled environment assessment  

E-print Network

Soil moisture and soil-litter mixing effects on surface litter decomposition: A controlled temperatures and low moisture conditions. Here, we tested how soil- litter mixing and soil moisture interact to changes in PLFAs during the initial stages of decomposition in the constant soil moisture experiment

Archer, Steven R.

125

Minimizing the Impact of Measurement Uncertainty in Predicting Profile Soil Moisture from Noisy Surface Measurements  

NASA Astrophysics Data System (ADS)

Soil moisture is an important hydrological state variable which influences the partition between infiltration and runoff, provides thermal inertia in the climate system and strongly influences the distribution of vegetation. Unfortunately, accounting for the high space-time variability of soil moisture resulting from the inherent heterogeneity of soil, topography and land cover is still a weakness in many hydrological models. This limitation can be partially overcome with recent technological advances, such as the Soil Moisture and Ocean Salinity (SMOS) mission and the Advanced Microwave Scanning Radiometer- EOS (AMSR-E) soil moisture products. SMOS and AMSR-E have allowed for operational observations of coarse scale distributed soil moisture in the top 5cm of soil with a realized accuracy between 0.03 and 0.10 cm3cm-3. Despite these advances, a gap in the data still exists with respect to soil moisture in the root zone, which is more strongly related to many hydrological processes than surface soil moisture. The shallow penetration and uncertain nature of satellite soil moisture measurements gives rise to a requirement for methods to extrapolate profile soil moisture from uncertain surface soil moisture measurements. The extension of surface soil moisture into the root zone is typically accomplished through the assimilation of surface soil moisture into a hydrological model, where the covariance matrix and model physics update the soil profile. Artificial neural networks provide an efficient alternative to classical model data assimilation and can provide robust estimates of root zone soil moisture based on high-order non-linear data interactions. The presented research will contrast rootzone soil moisture predicted from feed forward neural networks, a numerical Richards equation model (HYDRUS-1D) and the prior models with assimilated noisy surface measurements using the Ensemble Kalman Filter (EnKF). A sensitivity analysis reveals that artificial neural networks are less impacted by uncertain surface measurements than model predictions and data assimilation minimizes the impact of all soil moisture extension methods at all levels of uncertainty. Artificial neural networks also have a run time advantage over a comparable model method by predicting soil moisture in a time span which is an order of magnitude faster than the model. Due to the importance of root zone soil moisture in bio-hydro-meteorological cycles, it is expected that accurate estimates of profile soil moisture will enhance energy flux and runoff partitioning in future hydrological applications.

Kornelsen, K. C.; Paulin, C. D.

2012-12-01

126

Plan of research for integrated soil moisture studies. Recommendations of the Soil Moisture Working Group  

NASA Technical Reports Server (NTRS)

Soil moisture information is a potentially powerful tool for applications in agriculture, water resources, and climate. At present, it is difficult for users of this information to clearly define their needs in terms of accuracy, resolution and frequency because of the current sparsity of data. A plan is described for defining and conducting an integrated and coordinated research effort to develop and refine remote sensing techniques which will determine spatial and temporal variations of soil moisture and to utilize soil moisture information in support of agricultural, water resources, and climate applications. The soil moisture requirements of these three different application areas were reviewed in relation to each other so that one plan covering the three areas could be formulated. Four subgroups were established to write and compile the plan, namely models, ground-based studies, aircraft experiments, and spacecraft missions.

1980-01-01

127

Absolute versus temporal anomaly and percent of saturation soil moisture spatial variability for six networks worldwide  

NASA Astrophysics Data System (ADS)

analysis of the spatial-temporal variability of soil moisture can be carried out considering the absolute (original) soil moisture values or relative values, such as the percent of saturation or temporal anomalies. Over large areas, soil moisture data measured at different sites can be characterized by large differences in their minimum, mean, and maximum absolute values, even though in relative terms their temporal patterns are very similar. In these cases, the analysis considering absolute compared with percent of saturation or temporal anomaly soil moisture values can provide very different results with significant consequences for their use in hydrological applications and climate science. In this study, in situ observations from six soil moisture networks in Italy, Spain, France, Switzerland, Australia, and United States are collected and analyzed to investigate the spatial soil moisture variability over large areas (250-150,000 km2). Specifically, the statistical and temporal stability analyses of soil moisture have been carried out for absolute, temporal anomaly, and percent of saturation values (using two different formulations for temporal anomalies). The results highlight that the spatial variability of the soil moisture dynamic (i.e., temporal anomalies) is significantly lower than that of the absolute soil moisture values. The spatial variance of the time-invariant component (temporal mean of each site) is the predominant contribution to the total spatial variance of absolute soil moisture data. Moreover, half of the networks show a minimum in the spatial variability for intermediate conditions when the temporal anomalies are considered, in contrast with the widely recognized behavior of absolute soil moisture data. The analyses with percent saturation data show qualitatively similar results as those for the temporal anomalies because of the applied normalization which reduces spatial variability induced by differences in mean absolute soil moisture only. Overall, we find that the analysis of the spatial-temporal variability of absolute soil moisture does not apply to temporal anomalies or percent of saturation values.

Brocca, L.; Zucco, G.; Mittelbach, H.; Moramarco, T.; Seneviratne, S. I.

2014-07-01

128

Soil moisture controls on temperature sensitivity of soil organic carbon decomposition for a mesic grassland  

Microsoft Academic Search

We examined relationships between soil moisture and the temperature sensitivity of decomposition of labile soil organic carbon at a central North American grassland. For soils collected from shallow, xeric uplands, temperature sensitivity was greatest at intermediate soil moisture. For soils collected from the deeper, mesic lowlands, temperature sensitivity increased with increasing soil moisture. For example, lowland soils incubated at 75%

Joseph M. Craine; Theodore M. Gelderman

2011-01-01

129

Sensitivity of satellite microwave and infrared observations to soil moisture at a global scale: Relationship of satellite observations to in situ soil moisture measurements  

Microsoft Academic Search

This study presents a systematic and integrated analysis of the sensitivity of the available satellite observations to in situ soil moisture measurements. Although none of these satellites is optimized for land surface characterization, before the launches of the SMOS- and HYDROS-dedicated missions they are the only potential sources of global soil moisture measurements. The satellite observations include passive microwave emissivities,

Catherine Prigent; Filipe Aires; William B. Rossow; Alan Robock

2005-01-01

130

Estimates of monthly mean soil moisture for 1979-1989  

NASA Technical Reports Server (NTRS)

This technical report presents estimated monthly mean global soil moisture distributions for 1979-1989. The soil moisture datasets were prepared as part of the boundary conditions for an atmospheric general circulation model (GEOS-1). Also included are the 11-year averages of monthly mean soil moisture, surface air temperature, monthly total precipitation, evapotranspiration, and potential evapotranspiration. The standard deviation of the monthly mean soil moisture is provided as a measure of year-to-year variability.

Schemm, J.; Schubert, S.; Terry, J.; Bloom, S.

1992-01-01

131

Global High Resolution Soil Moisture Product from the Soil Moisture Active Passive (SMAP) Mission  

NASA Astrophysics Data System (ADS)

The SMAP mission is under development with a target launch date in late 2014. The SMAP mission will provide high resolution (~9 km) and frequent revisit (2-3 days) soil moisture product at a global extent. The SMAP instrument architecture incorporates an L-band (1.26 GHz) radar and an L-band (1.41 GHz) radiometer that share a single feedhorn and parabolic mesh reflector. The SMAP radiometer and radar instruments are capable of measuring surface soil moisture under moderate vegetation cover individually, however, the instruments suffer from limitations on spatial resolution (radiometer) and sensitivity (radar), respectively. To overcome the limitations of the individual passive and active approaches, the SMAP mission will combine the two data streams to generate an active-passive intermediate resolution and accuracy soil moisture product. The baseline active-passive algorithm disaggregates the coarse resolution (~36 km) radiometer brightness temperature (Tb) measurements using the spatial pattern within the radiometer footprint as inferred from the high resolution coincident radar co-pol and cross-pol backscatter measurements, and then inverts the disaggregated Tb to retrieve soil moisture.Studies are conducted to evaluate the baseline and optional active-passive algorithms at a global extent using a SMAP orbit simulator that provides capability for end-to-end simulation environment. Various aspects of the baseline active/passive algorithm are evaluated that are to be included in the 9 km global soil moisture product. Soil moisture retrieval results from global-extent study area demonstrate that the mission will meet its requirements of global coverage with an accuracy of <0.04 cm3/cm3 in soil moisture for region below 5 kg/m2 vegetation water content having ~9 km spatial and 3 days temporal resolution.The presentation will introduce the scientific community on the SMAP combined active-passive soil moisture product by especially focusing on product accuracy, retrieval characteristics, flags, retrieval thresholds and masks. SMAP

Das, N. N.; Entekhabi, D.; Njoku, E. G.

2013-12-01

132

Analysis of ASAR Wide Swath Mode time series for the retrieval of soil moisture in mountainous areas  

NASA Astrophysics Data System (ADS)

Soil moisture is a key element in the global cycles of water, energy, and carbon. Knowledge on the spatial and temporal distribution of the soil moisture content (SMC) is therefore essential for a number of hydrological applications as well as earth sciences like meteorology or climatology (Heathman et al., 2003). In the last few years there has been an increasing interest towards the estimation of SMC at local scales using active microwave sensors (Barret et al., 2009). Compared to passive microwave sensors, SAR offers the potential to provide data at high spatial resolution (modern sensors can acquire images with up to approximately 1 m), which is particularly important in mountainous areas. So far, these areas have been considered only marginally in research and only pioneer studies can be found in the literature (Brocca et al., 2012; Bertoldi et al. 2013). In this work we analyzed the temporal and spatial dynamics of the surface SMC (0 - 5 cm depth) on the basis of ground data collected by fixed meteorological stations located in the emerging Long-Term Ecological Research (LTER) site Mazia Valley (Province of Bolzano, South Tyrol, Italy), SAR data from ENVISATs ASAR sensor, wide swath (WS) mode (acquired between 2005 and 2012), and SMC estimates from the hydrological model GEOtop (Endrizzi et al., 2013). The SMC retrieval process was based on the support vector regression (SVR) method introduced by Pasolli et al. (2011). The training of the algorithm was based on data acquired in 2010. Furthermore, the SAR backscatter and derived SMC have been compared with time-series derived from the distributed hydrological model GEOtop. The differences in terms of temporal and spatial dynamic have been analyzed. The main goal of this work is to evaluate the spatial and temporal patterns of SAR derived SMC at field scale and to correlate them with ground information. This is a preparatory study to establish a methodology for the retrieval of SMC with high spatial and temporal sampling and to improve retrieval accuracies by integrating temporal information from different sources of ancillary data and from SAR time-series. It was found that the dynamics of both, temporal and spatial SMC patterns obtained from various data sources (ASAR, GEOtop and meteorological stations), show a similar general temporal behaviour that indicates the robustness of the retrieval algorithm with ASAR WS. However, depending on land cover, soil type and local topographic conditions different spatial patters can be found between SMC estimations coming from ASAR and from the GEOtop model. Introducing information on the temporal behaviour of the SAR signal proves to be a promising method for increasing the confidence and accuracy in estimating SMC, complementing hydrological model predictions. Following steps were identified as critical for the retrieval process: the topographic correction and geocoding of SAR data and the calibration of the meteorological stations. Both factors can have significant influence on the quality of SMC estimation. The accuracy of meteorological input and soil parameterization were identified as the most crucial challenges for SMC derived from hydrological modeling. References Barrett, B. W., E. Dwyer, and P. Whelan. "Soil moisture retrieval from active spaceborne microwave observations: An evaluation of current techniques." Remote Sensing 1, no. 3 (2009): 210-242. Bertoldi, G., S. Della Chiesa, C. Notarnicola, L. Pasolli, G. Niedrist, and U. Tappeiner. "Estimation of soil moisture patterns in mountain grasslands by means of SAR RADARSAT 2 images and hydrological modeling." Journal of Hydrology (2014). under revision. Brocca, L., A. Tarpanelli, T. Moramarco, F. Melone, S. M. Ratto, M. Cauduro, S. Ferraris et al. "Soil Moisture Estimation in Alpine Catchments through Modeling and Satellite Observations." Vadose Zone Journal (2013). Endrizzi, S., S. Gruber, M. Dall'Amico, and R. Rigon. "GEOtop 2.0: simulating the combined energy and water balance at and below the land surface accounting for soil fr

Greifeneder, Felix; Notarnicola, Claudia; Cuozzo, Giovanni; Spindler, Nadine; Bertoldi, Giacomo; Della Chiesa, Stefano; Niedrist, Georg; Stamenkovic, Jelena; Wagner, Wolgang

2014-05-01

133

Influences of soil moisture and vegetation on convective precipitation forecasts  

E-print Network

Influences of soil moisture and vegetation on convective precipitation forecasts over the United National Laboratory, Upton, New York, USA Abstract This study investigates the influences of soil moisture (NARR) data were used as initial and boundary conditions. We also used an adjusted soil moisture

Robock, Alan

134

Application of the Preisach model in soil-moisture hysteresis  

E-print Network

Application of the Preisach model in soil-moisture hysteresis Denis Flynn, Hugh McNamara, Philip O- teresis effects in the relation between water retention and soil-moisture ten- sion. Special, one parameter, classes of Preisach operators are proposed to construct models of the soil-moisture hysteresis

Schellekens, Michel P.

135

SOIL MOISTURE ESTIMATION USING REMOTE SENSING Jeffrey Walker1  

E-print Network

SOIL MOISTURE ESTIMATION USING REMOTE SENSING Jeffrey Walker1 and Paul Houser2 1 Lecturer, Dept Sciences Branch, NASA Goddard Space Flight Center, Maryland, USA Abstract Knowledge of soil moisture high spatial and temporal variability. To overcome the land surface model limits on soil moisture

Walker, Jeff

136

Integrating soil moisture and groundwater into climate models  

E-print Network

Integrating soil moisture and groundwater into climate models Nir Krakauer nkrakauer@ccny.cuny.edu http://www-ce.ccny.cuny.edu/nir/ #12;Talk outline Motivation Soil moisture and climate Irrigation use and climate #12;Soil moisture -climate feedbacks S E ­T (+/­)P S (direct, local) S E P

Krakauer, Nir Y.

137

Use of passive microwave remote sensing to monitor soil moisture  

E-print Network

Review Use of passive microwave remote sensing to monitor soil moisture Jean-Pierre Wignerona January 1998) Abstract - Surface soil moisture is a key variable to describe the water and energy exchanges at the land surface/atmos- phere interface. However, soil moisture is highly variable both

Paris-Sud XI, Université de

138

Feasibility of Soil Moisture Estimation using Passive Distributed Temperature Sensing  

E-print Network

Feasibility of Soil Moisture Estimation using Passive Distributed Temperature Sensing S.C. Steele sensing, temperature, fiber-optic, soil moisture, vadose zone 1 #12;Abstract Through its role in the energy and water balances at the land surface, soil moisture is a key state variable in surface hydrology

Selker, John

139

Feasibility of soil moisture estimation using passive distributed temperature sensing  

E-print Network

Click Here for Full Article Feasibility of soil moisture estimation using passive distributed at the land surface, soil moisture is a key state variable in surface hydrology and landatmosphere interactions. Point observations of soil moisture are easy to make using established methods such as time

Selker, John

140

MEASUREMENT OF SOIL MOISTURE WITH SYNTHETIC APERTURE RADAR1  

E-print Network

MEASUREMENT OF SOIL MOISTURE WITH SYNTHETIC APERTURE RADAR1 J. P. Kerekes and S. C. Crocker Lincoln the use of Synthetic Aperture Radar (SAR) data in the measurement of soil moisture content in small area of soil moisture contentover small areas at various subsurface depths and under three surface cover

Kerekes, John

141

A Reactive Soil Moisture Sensor Network: Design and Field Evaluation  

E-print Network

A Reactive Soil Moisture Sensor Network: Design and Field Evaluation Rachel Cardell-Oliver Keith of soil moisture and evaluates its effectiveness. A novel feature of our solution is its reactivity to the environment: when rain falls and soil moisture is changing rapidly, measurements are collected frequently

Cardell-Oliver, Rachel

142

Asymmetric Recovery from Wet versus Dry Soil Moisture Anomalies  

Microsoft Academic Search

The energy and moisture state in the soil and new-surface atmosphere evolve due to fluxes that are themselves a function of these states. Because the soil moisture and temperature are negatively correlated (dry warm or cool moist), physical mechanisms that tend to restore each state individually (soil moisture control of evaporation and temperature dependence of saturation specific humidity, for example)

Kaye L. Brubaker; Dara Entekhabi

1996-01-01

143

Overview of the Hydros radar soil moisture algorithm  

NASA Technical Reports Server (NTRS)

In this paper, we will describe the Hydors algorithms to derive soil moisture from L-band polarimetric radar measurements. the baseline Hydros radar algorithm to estimate soil moisture is composed of three steps: land classification, preliminary soil moisture estimation, and final time-series improvement.

Kim, Yunjin; van Zyl, Jakob

2005-01-01

144

Modelling The Soil Moisture - Rainfall Feedback: Multiple Regional Climate Equilibria  

Microsoft Academic Search

In this study we investigate the soil moisture - rainfall feedback using a regional cli- mate model (RegCM). Numerical experiments are performed with perpetual day forc- ing for the 1993 summer flood conditions over North America. Each simulation is initialized under different soil moisture conditions. In one set of simulations, the soil moisture is fully interactive, while in the second

J. S. Pal; E. A. B. Eltahir; F. Giorgi

2002-01-01

145

Summer soil moisture regulated by precipitation frequency in China  

Microsoft Academic Search

Drought is one of the most important but least understood issues in global environmental changes. Decrease in soil moisture is an indicator of drought. Here, we analyze summer (June-August) soil moisture measurement data across 50 sites in China in order to investigate the linkage between climate change and drought. At the country scale, a significant decrease in summer soil moisture

Shilong Piao; Lei Yin; Xuhui Wang; Philippe Ciais; Shushi Peng; Zehao Shen; Sonia I. Seneviratne

2009-01-01

146

Soil moisture inferences from thermal infrared measurements of vegetation temperatures  

NASA Technical Reports Server (NTRS)

Thermal infrared measurements of wheat (Triticum durum) canopy temperatures were used in a crop water stress index to infer root zone soil moisture. Results indicated that one time plant temperature measurement cannot produce precise estimates of root zone soil moisture due to complicating plant factors. Plant temperature measurements do yield useful qualitative information concerning soil moisture and plant condition.

Jackson, R. D. (principal investigator)

1981-01-01

147

Radiometric Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Temperature,  

E-print Network

Radiometric Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Temperature, and Canopy Water of micrometeorology and soil moisture, the radiometric sensi- tivities to vegetation canopy temperature, soil moisture

Sarabandi, Kamal

148

Microwave soil moisture estimation in humid and semiarid watersheds  

NASA Technical Reports Server (NTRS)

Land surface hydrologic-atmospheric interactions in humid and semi-arid watersheds were investigated. Active and passive microwave sensors were used to estimate the spatial and temporal distribution of soil moisture at the catchment scale in four areas. Results are presented and discussed. The eventual use of this information in the analysis and prediction of associated hydrologic processes is examined.

O'Neill, P. E.; Jackson, T. J.; Chauhan, N. S.; Seyfried, M. S.

1993-01-01

149

Towards an integrated soil moisture drought monitor for East Africa  

NASA Astrophysics Data System (ADS)

Drought in East Africa is a recurring phenomenon with significant humanitarian impacts. Given the steep climatic gradients, topographic contrasts, general data scarcity, and, in places, political instability that characterize the region, there is a need for spatially distributed, remotely derived monitoring systems to inform national and international drought response. At the same time, the very diversity and data scarcity that necessitate remote monitoring also make it difficult to evaluate the reliability of these systems. Here we apply a suite of remote monitoring techniques to characterize the temporal and spatial evolution of the 2010-2011 Horn of Africa drought. Diverse satellite observations allow for evaluation of meteorological, agricultural, and hydrological aspects of drought, each of which is of interest to different stakeholders. Focusing on soil moisture, we apply triple collocation analysis (TCA) to three independent methods for estimating soil moisture anomalies to characterize relative error between products and to provide a basis for objective data merging. The three soil moisture methods evaluated include microwave remote sensing using the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) sensor, thermal remote sensing using the Atmosphere-Land Exchange Inverse (ALEXI) surface energy balance algorithm, and physically-based land surface modeling using the Noah land surface model. It was found that the three soil moisture monitoring methods yield similar drought anomaly estimates in areas characterized by extremely low or by moderate vegetation cover, particularly during the below-average 2011 long rainy season. Systematic discrepancies were found, however, in regions of moderately low vegetation cover and high vegetation cover, especially during the failed 2010 short rains. The merged, TCA-weighted soil moisture composite product takes advantage of the relative strengths of each method, as judged by the consistency of anomaly estimates across independent methods. This approach holds potential as a remote soil moisture-based drought monitoring system that is robust across the diverse climatic and ecological zones of East Africa.

Anderson, W. B.; Zaitchik, B. F.; Hain, C. R.; Anderson, M. C.; Yilmaz, M. T.; Mecikalski, J.; Schultz, L.

2012-04-01

150

Towards an integrated soil moisture drought monitor for East Africa  

NASA Astrophysics Data System (ADS)

Drought in East Africa is a recurring phenomenon with significant humanitarian impacts. Given the steep climatic gradients, topographic contrasts, general data scarcity, and, in places, political instability that characterize the region, there is a need for spatially distributed, remotely derived monitoring systems to inform national and international drought response. At the same time, the very diversity and data scarcity that necessitate remote monitoring also make it difficult to evaluate the reliability of these systems. Here we apply a suite of remote monitoring techniques to characterize the temporal and spatial evolution of the 2010-2011 Horn of Africa drought. Diverse satellite observations allow for evaluation of meteorological, agricultural, and hydrological aspects of drought, each of which is of interest to different stakeholders. Focusing on soil moisture, we apply triple collocation analysis (TCA) to three independent methods for estimating soil moisture anomalies to characterize relative error between products and to provide a basis for objective data merging. The three soil moisture methods evaluated include microwave remote sensing using the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) sensor, thermal remote sensing using the Atmosphere-Land Exchange Inverse (ALEXI) surface energy balance algorithm, and physically based land surface modeling using the Noah land surface model. It was found that the three soil moisture monitoring methods yield similar drought anomaly estimates in areas characterized by extremely low or by moderate vegetation cover, particularly during the below-average 2011 long rainy season. Systematic discrepancies were found, however, in regions of moderately low vegetation cover and high vegetation cover, especially during the failed 2010 short rains. The merged, TCA-weighted soil moisture composite product takes advantage of the relative strengths of each method, as judged by the consistency of anomaly estimates across independent methods. This approach holds potential as a remote soil moisture-based drought monitoring system that is robust across the diverse climatic and ecological zones of East Africa.

Anderson, W. B.; Zaitchik, B. F.; Hain, C. R.; Anderson, M. C.; Yilmaz, M. T.; Mecikalski, J.; Schultz, L.

2012-08-01

151

Microwave Soil Moisture Retrieval Under Trees  

NASA Technical Reports Server (NTRS)

Soil moisture is recognized as an important component of the water, energy, and carbon cycles at the interface between the Earth's surface and atmosphere. Current baseline soil moisture retrieval algorithms for microwave space missions have been developed and validated only over grasslands, agricultural crops, and generally light to moderate vegetation. Tree areas have commonly been excluded from operational soil moisture retrieval plans due to the large expected impact of trees on masking the microwave response to the underlying soil moisture. Our understanding of the microwave properties of trees of various sizes and their effect on soil moisture retrieval algorithms at L band is presently limited, although research efforts are ongoing in Europe, the United States, and elsewhere to remedy this situation. As part of this research, a coordinated sequence of field measurements involving the ComRAD (for Combined Radar/Radiometer) active/passive microwave truck instrument system has been undertaken. Jointly developed and operated by NASA Goddard Space Flight Center and George Washington University, ComRAD consists of dual-polarized 1.4 GHz total-power radiometers (LH, LV) and a quad-polarized 1.25 GHz L band radar sharing a single parabolic dish antenna with a novel broadband stacked patch dual-polarized feed, a quad-polarized 4.75 GHz C band radar, and a single channel 10 GHz XHH radar. The instruments are deployed on a mobile truck with an 19-m hydraulic boom and share common control software; real-time calibrated signals, and the capability for automated data collection for unattended operation. Most microwave soil moisture retrieval algorithms developed for use at L band frequencies are based on the tau-omega model, a simplified zero-order radiative transfer approach where scattering is largely ignored and vegetation canopies are generally treated as a bulk attenuating layer. In this approach, vegetation effects are parameterized by tau and omega, the microwave vegetation opacity and single scattering albedo. One goal of our current research is to determine whether the tau-omega model can work for tree canopies given the increased scatter from trees compared to grasses and crops, and. if so, what are effective values for tau and omega for trees.

O'Neill, P.; Lang, R.; Kurum, M.; Joseph, A.; Jackson, T.; Cosh, M.

2008-01-01

152

Temperature dependence of soil-moisture characteristics  

SciTech Connect

A method has been developed for rapid, transient measurement of hysteretic soil-moisture characteristics of as function of temperature. While a varying soil-water pressure was imposed on a thin sample by means of flexible membranes held in firm contact with the soil, water content theta was measured by gamma-ray attenuation, and matric potential Psi was measured with tensiometers. The applied pressure was cycled through a program designed to obtain drying, wetting, and scanning curves. Isothermal characteristics were measured for glass beads, Plainfield sand, and an undisturbed core of Plano silt loam at several temperatures in the 4/sup 0/ to 50/sup 0/C range. A model that represents the hysteresis and temperature dependence of these results has been developed. The results obtained from the present experiments are consistent with the assumption that both the effectiveness and the concentration of surfactants in soil water are greater in warmer soil.

Nimmo, J.R.

1983-01-01

153

Synergies and complementarities between ASCAT and SMOS soil moisture products  

NASA Astrophysics Data System (ADS)

Soil moisture is a critical variable in many kinds of applications including agriculture, water management, meteorology or climatology. This is especially true in the Mediterranean context, where soil moisture plays an important role in water resources management and hydrometeorological risks such as floods and droughts. Unfortunately, this variable is not widely observed in situ, so we lack data on its time evolution and spatial structure. Remote sensing has been used to estimate surface soil moisture because it provides comprehensive data over large surfaces. In this study we compared two different surface soil moisture remote sensing products; one derived from active microwave data of the ASCAT scatterometer instrument onboard METOP and the other from passive microwave data of the SMOS mission the first dedicated to estimate soil moisture. SMOS measuring frequency (1.4 GHz) is theoretically more suited to measure soil moisture than ASCAT measuring frequency (5.255 GHz) because of its lower vegetation effects. On the other hand, ASCAT- like instruments have been providing measurements for more than 2 decades and have been a key input in building the CCI Soil Moisture Variable. In order to get the best global soil moisture products it is thus essential to understand their respective performances and restrictions. The comparison has been carried out in Catalonia where we have implemented the SURFEX/ISBA land-surface model, which we forced with the SAFRAN meteorological analysis system. A downscaling algorithm has been also implemented and validated over the area to provide SMOS derived soil moisture fields at 1 km spatial resolution. Catalonia is located in the northeast of the Iberian Peninsula and its climate is typically Mediterranean, mild in winter and warm in summer. The Pyrenees and the neighbouring areas have a high-altitude climate, with minimum temperatures below 0 C, annual rainfall above 1000 mm and abundant snow during the winter. Along the coast, the climate is mild and temperate with temperatures increasing from north to south, while the rain behaves the opposite way. The hinterland, far from the sea, has a continental Mediterranean climate, with cold winters and very hot days in summer. Precipitation in Catalonia is very variable spatially and temporally. As a consequence, precipitation is very unevenly distributed within the year and it is also very variable from year to year. The range of altitudes covers over 3,000 metres and the major relief feature are the Pyrenees. Given its varied landscape, in which plains alternate with mountainous areas, Catalonia has a wide range of bioclimatic habitats. The comparison concerns ASCAT soil moisture product and SMOS at its native and increased resolution versus the hydrological model outputs. The comparison shows in general good agreement for both ASCAT and SMOS on the temporal series simulated over flat, non irrigated areas which are not close to the sea. This result gives us confidence, as both methods of estimating the soil moisture (simulation and remote sensing) are very different. However, the comparison also shows the limitations of the different products. On the one hand, SMOS has difficulties in areas close to the sea and in areas with steep relief. On the other hand, the hydrological model is not able to simulate non natural processes such as irrigation. ASCAT, in its turn, shows some limitations over agriculture surfaces where it shows an increase of soil moisture from June to October clearly correlated with vegetation cycle but seems to show better performances in areas close to the sea.

Escorihuela, Maria Jose; Quintana, Pere; Merlin, Olivier

2014-05-01

154

Characteristics of global and regional drought, 19502000: Analysis of soil moisture data from off-line simulation of the terrestrial hydrologic cycle  

Microsoft Academic Search

Drought occurrence is analyzed over global land areas for 1950-2000 using soil moisture data from a simulation of the terrestrial water cycle with the Variable Infiltration Capacity (VIC) land surface model, which is forced by an observation based meteorological data set. A monthly drought index based on percentile soil moisture values relative to the 50-year climatology is analyzed in terms

Justin Sheffield; Eric F. Wood

2007-01-01

155

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

156

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

E-print Network

Observed Soil Moisture Feifei Pan1 ; Christa D. Peters-Lidard2 ; and Anthony W. King3 Abstract: Soil.g., drainage, runoff, soil moisture, evaporation, and evapo- transpiration. With information about soil PSD, we can estimate almost all soil hydraulic properties e.g., saturated soil moisture, field capacity

Pan, Feifei

157

Quantifying Shrink Swell Capacity of Soil Using Soil Moisture Isotherms  

NASA Astrophysics Data System (ADS)

Vertisols, soils instinctively known for their expansive clays that cause them to have a high shrink swell potential, cover 2.4% of the earths ice-free land. In the United States these expansive soils can cause upwards of 6 billion in damages to pavements, foundations, and utility lines annually (Brady & Weil, 2010). Because of this, it is especially important that a soils ability to shrink and swell is well characterized when making engineering decisions. One traditional method for measuring a soil's expansive potential, the Coefficient of Linear Extensibility (COLE), can take weeks to months to complete (Grossman et al., 1968; Schafer and Singer, 1976b). Use of soil moisture isotherms, or the Soil Moisture Characteristic Curve (SMCC), in recent research has shown that the slope of the SMCC is related to a soils swelling potential (McKeen, 1992). The goal of this research is to evaluate the robustness of the relationship between the SMCC and COLE for a set of well-characterized test soils with COLE ranging from 0 to 0.176. If expansive potential can be reliably predicted from the SMCC, then data from recently developed automatic soil moisture isotherm generators could be used to characterize expansive potential with a fraction of the time and effort necessary for traditional techniques.

Rivera, L. D.; Cobos, D. R.; Campbell, C. S.; Morgan, C.

2013-12-01

158

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

159

Dynamics of deep soil moisture in response to vegetational restoration on the Loess Plateau of China  

NASA Astrophysics Data System (ADS)

The limitation of soil water in semiarid regions restricts the formation of a good cover of vegetation. The Loess Plateau in China, well known for its severe soil erosion, has a thick loessial soil that holds substantial volumes of water and provides the basis of a sustainable restoration of vegetation. Our limited understanding of the dynamics of deep soil moisture, however, could lead to the mismanagement of soil-water resources or could even misguide the policies of vegetational reconstruction. To evaluate the temporal response of deep soil moisture in different types of revegetation, we observed soil moisture to a depth of 340 cm in four plots, planted with Korshinsk peashrub (KOP), purple alfalfa (ALF), native plants (natural fallow, NAF), and millet (MIL), on 15 measurement events from 2010 to 2012. Our analysis provided four main conclusions. (1) The quantitative difference of potential evapotranspiration and actual precipitation resulted in natural deficits of soil moisture. The dynamics of deep soil moisture, however, were mainly dominated by the type of vegetation. Deep soils in plots of KOP and ALF became drier than the soil in plots of NAF and MIL. (2) Deep soil moisture in KOP and ALF was weakly variable. Correlations of time series of soil moisture between the upper and lower layers tended not to be significant. Dried soil layer, a special hydrological phenomenon, had formed in the plots. (3) The correlation between variances of soil moisture and the corresponding mean values were not always significantly positive due to the influence of vegetational type, observational depth, and date. (4) Fallow may be the best cover for achieving adequate hydrological sustainability of the soil. These results are expected to help improve the understanding of the response of deep soil moisture to vegetational restoration and to provide insight into the dynamics of deep soil moisture influenced by vegetation on loessial slopes.

Jia, Yu-Hua; Shao, Ming-An

2014-11-01

160

DInSAR measurement of soil moisture  

Microsoft Academic Search

Differential interferometric sythetic aperture radar (DInSAR) measurements using the European Remote Sensing 2 (ERS-2) satellite in a high-plains region of Colorado show intriguing spatial variations in millimeter-scale path-length change that may correspond to variations in soil moisture of a few percent by volume, in both farm fields and uncultivated terrain. The observed signal is hypothesized to result from both changes

Matt Nolan; Dennis R. Fatland; Larry Hinzman

2003-01-01

161

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

162

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

163

Microwave remote sensing of soil moisture: elimination of texture effect  

Microsoft Academic Search

In view of the influence of soil texture on microwave radiation, an attempt is made to eliminate the textural effects on the microwave reflectivity\\/emission. To determine the appropriate soil moisture parameter that minimizes the textural influences on microwave radiation from soils, soil moisture is expressed in terms of gravimetric and volumetric units and percentage of field capacity (Mfc ) and

P. V. N. Rao; C. S. Raju; K. S. Rao

1990-01-01

164

Prediction of trafficability and workability from soil moisture deficit  

Microsoft Academic Search

The relationship between the strength of field soils, under grass ley and winter wheat, and soil moisture deficit has been monitored over an 18 month period. The soil types selected represent a range of agricultural soils commonly found in Europe. Strong correlations were found to exist between moisture deficit and penetration resistance. This relationship has been used to develop a

R. Earl

1997-01-01

165

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

166

Optimizing Soil Moisture Sampling Locations for Validation Networks for SMAP  

NASA Astrophysics Data System (ADS)

Soil Moisture Active Passive satellite (SMAP) is scheduled for launch on Oct 2014. Global efforts are underway for establishment of soil moisture monitoring networks for both the pre- and post-launch validation and calibration of the SMAP products. In 2012 the SMAP Validation Experiment, SMAPVEX12, took place near Carman Manitoba, Canada where nearly 60 fields were sampled continuously over a 6 week period for soil moisture and several other parameters simultaneous to remotely sensed images of the sampling region. The locations of these sampling sites were mainly selected on the basis of accessibility, soil texture, and vegetation cover. Although these criteria are necessary to consider during sampling site selection, they do not guarantee optimal site placement to provide the most efficient representation of the studied area. In this analysis a method for optimization of sampling locations is presented which combines the state-of-art multi-objective optimization engine (non-dominated sorting genetic algorithm, NSGA-II), with the kriging interpolation technique to minimize the number of sampling sites while simultaneously minimizing the differences between the soil moisture map resulted from the kriging interpolation and soil moisture map from radar imaging. The algorithm is implemented in Whitebox Geospatial Analysis Tools, which is a multi-platform open-source GIS. The optimization framework is subject to the following three constraints:. A) sampling sites should be accessible to the crew on the ground, B) the number of sites located in a specific soil texture should be greater than or equal to a minimum value, and finally C) the number of sampling sites with a specific vegetation cover should be greater than or equal to a minimum constraint. The first constraint is implemented into the proposed model to keep the practicality of the approach. The second and third constraints are considered to guarantee that the collected samples from each soil texture categories or vegetation cover types are statistically meaningful. The proposed model is applied to the radar images from the Passive Active L-band System (PALS) collected during (SMAPVEX12). SMAPVEX12 lasted for 47 days, during which soil moisture varied significantly. The proposed model was applied to all of the collected images (17 images) during this time span. Optimized sampling site characteristics will be analyzed with surface characteristics and the trade off between the number of samples and estimated sampling error examined.

Roshani, E.; Berg, A. A.; Lindsay, J.

2013-12-01

167

Ultrasonic Velocity Variations with Soil Composition for Moisture Measurement  

NASA Technical Reports Server (NTRS)

Soil moisture content may be measured by many methods, but the presently available techniques all have drawbacks when used in ground truth measurements for remote sensing. Ultrasonic velocity varies with soil moisture content, and may be used as the basis of a new measurement technique. In order to characterize a sensor capable of field use, soil particle size distribution data are compared to ultrasonic velocity in a variety of soils over a wide moisture range.

Metzl, R.; Choi, J.; Aggarwal, M. D.; Manu, A.

1998-01-01

168

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

169

Inferring Land Surface Model Parameters for the Assimilation of Satellite-Based L-Band Brightness Temperature Observations into a Soil Moisture Analysis System  

NASA Technical Reports Server (NTRS)

The Soil Moisture and Ocean Salinity (SMOS) satellite mission provides global measurements of L-band brightness temperatures at horizontal and vertical polarization and a variety of incidence angles that are sensitive to moisture and temperature conditions in the top few centimeters of the soil. These L-band observations can therefore be assimilated into a land surface model to obtain surface and root zone soil moisture estimates. As part of the observation operator, such an assimilation system requires a radiative transfer model (RTM) that converts geophysical fields (including soil moisture and soil temperature) into modeled L-band brightness temperatures. At the global scale, the RTM parameters and the climatological soil moisture conditions are still poorly known. Using look-up tables from the literature to estimate the RTM parameters usually results in modeled L-band brightness temperatures that are strongly biased against the SMOS observations, with biases varying regionally and seasonally. Such biases must be addressed within the land data assimilation system. In this presentation, the estimation of the RTM parameters is discussed for the NASA GEOS-5 land data assimilation system, which is based on the ensemble Kalman filter (EnKF) and the Catchment land surface model. In the GEOS-5 land data assimilation system, soil moisture and brightness temperature biases are addressed in three stages. First, the global soil properties and soil hydraulic parameters that are used in the Catchment model were revised to minimize the bias in the modeled soil moisture, as verified against available in situ soil moisture measurements. Second, key parameters of the "tau-omega" RTM were calibrated prior to data assimilation using an objective function that minimizes the climatological differences between the modeled L-band brightness temperatures and the corresponding SMOS observations. Calibrated parameters include soil roughness parameters, vegetation structure parameters, and the single scattering albedo. After this climatological calibration, the modeling system can provide L-band brightness temperatures with a global mean absolute bias of less than 10K against SMOS observations, across multiple incidence angles and for horizontal and vertical polarization. Third, seasonal and regional variations in the residual biases are addressed by estimating the vegetation optical depth through state augmentation during the assimilation of the L-band brightness temperatures. This strategy, tested here with SMOS data, is part of the baseline approach for the Level 4 Surface and Root Zone Soil Moisture data product from the planned Soil Moisture Active Passive (SMAP) satellite mission.

Reichle, Rolf H.; De Lannoy, Gabrielle J. M.

2012-01-01

170

Effects of Mulches on Soil Properties and Tomato Production I. Soil Temperature, Soil Moisture and Marketable Yield  

Microsoft Academic Search

The effects of hay, compost, plastic and paper mulches on soil temperature, soil moisture and yield of paste tomato were evaluated on five farms in Virginia. Organic mulches reduced afternoon soil temperature and maintained higher soil moisture levels than other treatments. Black plastic mulch increased soil temperatures by 12C, but sometimes resulted in lower soil moisture levels in early summer,

Mark W. Schonbeck; Gregory K. Evanylo

1998-01-01

171

A simulation study of scene confusion factors in sensing soil moisture from orbital radar  

NASA Technical Reports Server (NTRS)

Simulated C-band radar imagery for a 124-km by 108-km test site in eastern Kansas is used to classify soil moisture. Simulated radar resolutions are 100 m by 100 m, 1 km by 1km, and 3 km by 3 km. Distributions of actual near-surface soil moisture are established daily for a 23-day accounting period using a water budget model. Within the 23-day period, three orbital radar overpasses are simulated roughly corresponding to generally moist, wet, and dry soil moisture conditions. The radar simulations are performed by a target/sensor interaction model dependent upon a terrain model, land-use classification, and near-surface soil moisture distribution. The accuracy of soil-moisture classification is evaluated for each single-date radar observation and also for multi-date detection of relative soil moisture change. In general, the results for single-date moisture detection show that 70% to 90% of cropland can be correctly classified to within +/- 20% of the true percent of field capacity. For a given radar resolution, the expected classification accuracy is shown to be dependent upon both the general soil moisture condition and also the geographical distribution of land-use and topographic relief. An analysis of cropland, urban, pasture/rangeland, and woodland subregions within the test site indicates that multi-temporal detection of relative soil moisture change is least sensitive to classification error resulting from scene complexity and topographic effects.

Ulaby, F. T. (principal investigator); Dobson, M. C.; Moezzi, S.; Roth, F. T.

1983-01-01

172

Quantifying mesoscale soil moisture with the cosmic-ray rover  

NASA Astrophysics Data System (ADS)

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 mobile cosmic-ray probe, or cosmic-ray rover, an instrument similar to the recently developed COSMOS probe, but bigger and mobile. This study explores the challenges and opportunities for making maps of soil moisture over large areas using the cosmic-ray rover. In 2012, soil moisture was mapped 22 times in a 25 km x 40 km survey area of the Tucson Basin at 1 km 2 resolution, i.e., at a scale comparable to that of a pixel for the Soil Moisture and Ocean Salinity (SMOS) satellite mission. The soil moisture distribution is influenced mainly by climatic variations, notably by the North American monsoon, which resulted in a systematic change in the regional variance as a function of the mean soil moisture.

Chrisman, Bobby B.

173

Use of Ultrasonic Technology for Soil Moisture Measurement  

NASA Technical Reports Server (NTRS)

In an effort to improve existing soil moisture measurement techniques or find new techniques using physics principles, a new technique is presented in this paper using ultrasonic techniques. It has been found that ultrasonic velocity changes as the moisture content changes. Preliminary values of velocities are 676.1 m/s in dry soil and 356.8 m/s in 100% moist soils. Intermediate values can be calibrated to give exact values for the moisture content in an unknown sample.

Choi, J.; Metzl, R.; Aggarwal, M. D.; Belisle, W.; Coleman, T.

1997-01-01

174

Limiting relations between soil moisture and soil texture with implications for measured, modeled and remotely sensed estimates  

Microsoft Academic Search

The relation between near surface soil moisture (s) and the similar media scaling factor (?) is shown to follow a power law in four limiting cases: long time flux limited infiltration, short time flux limited infiltration into dry soil, long time soil limited evaporation, and long time soil limited transpiration. The exponents of these relations are derived from dimensional analysis

G. D. Salvucci

1998-01-01

175

Limiting relations between soil moisture and soil texture with implications for measured, modeled and remotely sensed estimates  

Microsoft Academic Search

The relation between near surface soil moisture (s) and the similar media scaling factor (alpha) is shown to follow a power law in four limiting cases: long time flux limited infiltration, short time flux limited infiltration into dry soil, long time soil limited evaporation, and long time soil limited transpiration. The exponents of these relations are derived from dimensional analysis

G. D. Salvucci

1998-01-01

176

On the spatio-temporal dynamics of soil moisture at the field scale  

NASA Astrophysics Data System (ADS)

In this paper, we review the state of the art of characterizing and analyzing spatio-temporal dynamics of soil moisture content at the field scale. We discuss measurement techniques that have become available in recent years and that provide unique opportunities to characterize field scale soil moisture variability with high spatial and/or temporal resolution. These include soil moisture sensor networks, hydrogeophysical measurement techniques, novel remote sensing platforms, and cosmic ray probes. Techniques and methods to analyze soil moisture fields are briefly discussed and include temporal stability analysis, wavelet analysis and empirical orthogonal functions. We revisit local and non-local controls on field scale soil moisture dynamics and discuss approaches to model these dynamics at the field scale. Finally, we address the topic of optimal measurement design and provide an outlook and future research perspectives.

Vereecken, H.; Huisman, J. A.; Pachepsky, Y.; Montzka, C.; van der Kruk, J.; Bogena, H.; Weihermller, L.; Herbst, M.; Martinez, G.; Vanderborght, J.

2014-08-01

177

Soil moisture effects on the carbon isotope composition of soil respiration  

E-print Network

Soil moisture effects on the carbon isotope composition of soil respiration Claire L. Phillips1) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture. In a first experiment, we examined the effects of soil moisture on total respired d13 CO2 by growing Douglas

178

UNCORRECTEDPROOF 1 Towards deterministic downscaling of SMOS soil moisture using MODIS derived soil  

E-print Network

UNCORRECTEDPROOF 1 Towards deterministic downscaling of SMOS soil moisture using MODIS derived soil online xxxx Keywords: Downscaling Disaggregation Soil moisture Evaporative fraction NAFE SMOS MODIS 10 11 A deterministic approach for downscaling 40 km resolution Soil Moisture and Ocean Salinity (SMOS) 12 observations

Boyer, Edmond

179

Influence of soil moisture on sulphur oxidation in brown earth soils exposed to atmospheric pollution  

Microsoft Academic Search

Laboratory studies were conducted to determine the influence of soil moisture on S oxidation in atmospheric-polluted brown earth soils. Elemental S was oxidized to sulphate over a wide range of soil moisture treatments (10%60% w\\/w), but occurred optimally at around 40%50% soil moisture content (0.08 MPa). Thiosulphate and tetrathionate were found only in soils incubated at low moisture contents. S-oxidation

Wendy Nevell; M. Wainwright

1987-01-01

180

Relating TRMM precipitation radar land surface backscatter response to soil moisture in the Southern United States  

NASA Astrophysics Data System (ADS)

SummarySoil moisture is an important variable in the hydrological cycle and plays a vital role in agronomy, meteorology, and hydrology. It regulates the exchange of water and heat between land surface and atmosphere and thus plays an important role in the development of weather patterns. It is difficult to obtain a comprehensive spatio-temporal map of soil moisture because of expensive installation of soil moisture measuring instruments. In this paper, a model to estimate soil moisture ( m s) using Tropical Rainfall Measuring Mission Precipitation Radar (TRMMPR) backscatter ( ?) and Normalized Difference Vegetation Index (NDVI) is developed for the Southern United States. Soil moisture data from Soil and Climate Analysis Network (SCAN) stations is used to calibrate and validate the model. The estimated values of m s compare well with the ground measurements of soil moisture. The model works well for various landcovers but works best for low density vegetated areas (closed shrubland). All the soil moisture estimates in this landcover have an absolute error of less than 8%. The model performance deteriorates with increase in vegetation density (crops and forest). Overall, the model performance is satisfactory for all landcover types with RMSE less than 6.3% and absolute error of 10% or less for 90% of the estimates. Estimation of soil moisture over a large area with low error provides another use of TRMMPR data.

Puri, Sumit; Stephen, Haroon; Ahmad, Sajjad

2011-05-01

181

[Research on the method for rapid detection of soil moisture content using spectral data].  

PubMed

Spectroscopy technique is one of the qualitative and quantitative analytical techniques developed quickly in recent years. The spectral analysis is a fast and non-destructive method and has been used in many fields such as oil industry, food industry and so on. In the present paper, the spectral band sensitive to soil moisture content was found from the visible/near infrared spectra and a monadic linear regression model based on the data of sensitive spectral band was applied to develop a method for rapid detection of soil moisture content. The spectral data of 52 soil samples were collected by using FieldSpec HandHeld spectroradiometer made by ASD (Analytical Spectral Device) company in the US, and the data of soil moisture content were obtained by experiment. The spectral band sensitive to soil moisture content was achieved by correlation coefficient method. Then, the data of sensitive spectral band were used to build monadic linear regression model of soil moisture content. Finally, the model was employed for the prediction of soil moisture content. Correlation coefficient (r) of prediction and root mean square error of prediction (RMSEP) were used as the evaluation standards. The results indicated that the r and RMSEP for the prediction of soil moisture content were 0.966 5 and 0.012 1 respectively. Thus, it is concluded that the method used in this paper is an available method for the rapid detection of soil moisture content based on the visible/near-infrared spectra. PMID:19455797

Song, Tao; Bao, Yi-Dan; He, Yong

2009-03-01

182

Understanding tree growth in response to moisture variability: Linking 32 years of satellite based soil moisture observations with tree rings  

NASA Astrophysics Data System (ADS)

Climate change induced drought variability impacts global forest ecosystems and forest carbon cycle dynamics. Physiological drought stress might even become an issue in regions generally not considered water-limited. The water balance at the soil surface is essential for forest growth. Soil moisture is a key driver linking precipitation and tree development. Tree ring based analyses are a potential approach to study the driving role of hydrological parameters for tree growth. However, at present two major research gaps are apparent: i) soil moisture records are hardly considered and ii) only a few studies are linking tree ring chronologies and satellite observations. Here we used tree ring chronologies obtained from the International Tree ring Data Bank (ITRDB) and remotely sensed soil moisture observations (ECV_SM) to analyze the moisture-tree growth relationship. The ECV_SM dataset, which is being distributed through ESA's Climate Change Initiative for soil moisture covers the period 1979 to 2010 at a spatial resolution of 0.25. First analyses were performed for Mongolia, a country characterized by a continental arid climate. We extracted 13 tree ring chronologies suitable for our analysis from the ITRDB. Using monthly satellite based soil moisture observations we confirmed previous studies on the seasonality of soil moisture in Mongolia. Further, we investigated the relationship between tree growth (as reflected by tree ring width index) and remotely sensed soil moisture records by applying correlation analysis. In terms of correlation coefficient a strong response of tree growth to soil moisture conditions of current April to August was observed, confirming a strong linkage between tree growth and soil water storage. The highest correlation was found for current April (R=0.44), indicating that sufficient water supply is vital for trees at the beginning of the growing season. To verify these results, we related the chronologies to reanalysis precipitation and temperature datasets. Precipitation was important during both the current and previous growth season. Temperature showed the strongest correlation for previous (R=0.12) and current October (R=0.21). Hence, our results demonstrated that water supply is most likely limiting tree growth during the growing season, while temperature is determining its length. We are confident that long-term satellite based soil moisture observations can bridge spatial and temporal limitations that are inherent to in situ measurements, which are traditionally used for tree ring research. Our preliminary results are a foundation for further studies linking remotely sensed datasets and tree ring chronologies, an approach that has not been widely investigated among the scientific community.

Albrecht, Franziska; Dorigo, Wouter; Gruber, Alexander; Wagner, Wolfgang; Kainz, Wolfgang

2014-05-01

183

A methodology for initializing soil moisture in a global climate model: Assimilation of near-surface soil moisture observations  

Microsoft Academic Search

Due to its long-term persistence, accurate initialization of land surface soil moisture infully-coupled global climate models has the potential to greatly increase the accuracy ofclimatological and hydrological prediction. To improve the initialization of soil moisture in theNASA Seasonal-to-Interannual Prediction Project (NSIPP), a one-dimensional Kalman filter hasbeen developed to assimilate near-surface soil moisture observations into the catchment-basedland surface model used by

Jeffrey P. Walker; Paul R. Houser

2001-01-01

184

MoistureMap: A soil moisture monitoring, prediction and reporting system for sustainable land and water management  

E-print Network

9 MoistureMap: A soil moisture monitoring, prediction and reporting system for sustainable land soil moisture at high resolution is critical for achieving sustainable land and water management. The fundamental limitation is that spatial and temporal variation in soil moisture is not well known, nor easy

Walker, Jeff

185

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

186

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

187

A microwave systems approach to measuring root zone soil moisture  

NASA Technical Reports Server (NTRS)

Computer microwave satellite simulation models were developed and the program was used to test the ability of a coarse resolution passive microwave sensor to measure soil moisture over large areas, and to evaluate the effect of heterogeneous ground covers with the resolution cell on the accuracy of the soil moisture estimate. The use of realistic scenes containing only 10% to 15% bare soil and significant vegetation made it possible to observe a 60% K decrease in brightness temperature from a 5% soil moisture to a 35% soil moisture at a 21 cm microwave wavelength, providing a 1.5 K to 2 K per percent soil moisture sensitivity to soil moisture. It was shown that resolution does not affect the basic ability to measure soil moisture with a microwave radiometer system. Experimental microwave and ground field data were acquired for developing and testing a root zone soil moisture prediction algorithm. The experimental measurements demonstrated that the depth of penetration at a 21 cm microwave wavelength is not greater than 5 cm.

Newton, R. W.; Paris, J. F.; Clark, B. V.

1983-01-01

188

A Multi-Scale Soil Moisture and Freeze-Thaw Monitoring Network on the Third Pole  

NASA Astrophysics Data System (ADS)

Multi-sphere interactions over the Tibetan Plateau directly impact its surrounding climate and environment at a variety of spatial/temporal scales. Remote sensing and modeling are expected to provide hydro-meteorological data needed for these process studies, but in situ observations are required to support their calibration and validation. For this purpose, we established a dense monitoring network on central Tibetan Plateau to measure two state variables (soil moisture and temperature) at three spatial scales (1.0, 0.3, 0.1 degree) and four soil depths (0~5cm, 10cm, 20cm, and 40cm). The experimental area is characterized by low biomass, large soil moisture dynamic range and typical freeze-thaw cycle. The network consists of 56 stations with their elevation varying over 4470 ~ 4950 m. Soil texture and soil organic matters are measured at each station, as auxiliary parameters of this network. In order to guarantee continuous and high-quality data, tremendous efforts have been made to protect the data logger from soil water intrusion, to calibrate soil moisture sensors, and to upscale the point measurements. As the highest soil moisture network in the world, our network meets the requirement for evaluating a variety of soil moisture products and for soil moisture scaling. It also directly contributes to the "water-ice-air-ecosystem-human" interaction theme of the "Third Pole Environment" Program. The data will be publicized via the International Soil Moisture Network. Publication: Zhao, L., K. Yang, J. Qin, Y-Y Chen, W-J Tang, C. Montzka, H. Wu, C-G Lin, M-L Han, and H. Vereecken., 2012: Spatiotemporal analysis of soil moisture observations within a Tibetan mesoscale area and its implication to regional soil moisture measurements, Journal of Hydrology DOI: 10.1016/j.jhydrol.2012.12.033.

Yang, Kun; Qin, Jun; Zhao, Long; Chen, Yingying; Han, Menglei

2013-04-01

189

Preferential states in soil moisture and climate dynamics  

PubMed Central

Summer precipitation in continental midlatitude regions is significantly contributed by local recycling, i.e., by moisture returning to the atmosphere through evapotranspiration from the same region. On the other hand, reduced soil moisture availability may limit evapotranspiration rates with effects on the planetary boundary layer dynamics through the partitioning between sensible and latent heat fluxes. Thus, a dependence may exist between precipitation and antecedent soil moisture conditions. Here we provide theoretical and experimental evidence in support of the hypothesis that in continental regions summer soil moisture anomalies affect the probability of occurrence of subsequent precipitation. Owing to these feedbacks, two preferential states may arise in summer soil moisture dynamics, which thus tend to remain locked either in a dry or a wet state, whereas intermediate conditions have low probability of occurrence. In this manner, such landatmosphere interactions would explain the possible persistence of summer droughts sustained by positive feedbacks in response to initial (spring) surface moisture anomalies. PMID:15184676

D'Odorico, Paolo; Porporato, Amilcare

2004-01-01

190

Preferential states in soil moisture and climate dynamics.  

PubMed

Summer precipitation in continental midlatitude regions is significantly contributed by local recycling, i.e., by moisture returning to the atmosphere through evapotranspiration from the same region. On the other hand, reduced soil moisture availability may limit evapotranspiration rates with effects on the planetary boundary layer dynamics through the partitioning between sensible and latent heat fluxes. Thus, a dependence may exist between precipitation and antecedent soil moisture conditions. Here we provide theoretical and experimental evidence in support of the hypothesis that in continental regions summer soil moisture anomalies affect the probability of occurrence of subsequent precipitation. Owing to these feedbacks, two preferential states may arise in summer soil moisture dynamics, which thus tend to remain locked either in a "dry" or a "wet" state, whereas intermediate conditions have low probability of occurrence. In this manner, such land-atmosphere interactions would explain the possible persistence of summer droughts sustained by positive feedbacks in response to initial (spring) surface moisture anomalies. PMID:15184676

D'Odorico, Paolo; Porporato, Amilcare

2004-06-15

191

SMOS Soil moisture Cal val activities  

NASA Astrophysics Data System (ADS)

SMOS, successfully launched on November 2, 2009, uses an L Band radiometer with aperture synthesis to achieve a good spatial resolution.. It was developed and made under the leadership of the European Space Agency (ESA) as an Earth Explorer Opportunity mission. It is a joint program with the Centre National d'Etudes Spatiales (CNES) in France and the Centro para el Desarrollo Tecnologico Industrial (CDTI) in Spain. SMOS carries a single payload, an L band 2D interferometric,radiometer in the 1400-1427 MHz protected band. This wavelength penetrates well through the vegetation and with the atmosphere being almost transparent, it enables us to infer both soil moisture and vegetation water content. SMOS achieves an unprecedented spatial resolution of 50 km at L-band maximum (43 km on average) with multi angular-dual polarized (or fully polarized) brightness temperatures over the globe and with a revisit time smaller than 3 days. SMOS is now acquiring data and has undergone the commissioning phase. The data quality exceeds what was expected, showing very good sensitivity and stability. The data is however very much impaired by man made emission in the protected band, leading to degraded measurements in several areas including parts of Europe and China. Many different international teams are now performing cal val activities in various parts of the world, with notably large field campaigns either on the long time scale or over specific targets to address the specific issues. These campaigns take place in various parts of the world and in different environments, from the Antarctic plateau to the deserts, from rain forests to deep oceans. SMOS is a new sensor, making new measurements and paving the way for new applications. It requires a detailed analysis of the data so as to validate both the approach and the quality of the retrievals, and allow for monitoring and the evolution of the sensor. To achieve such goals it is very important to link efficiently ground measurement to satellite measurements through field campaigns and related airborne acquisitions. Comparison with models and other satellite products are necessary. It is in this framework that CESBIO has been involved with many groups to assess the data over many areas in close collaboration. This paper aims at summarising briefly the results (presented in detail in other presentations) to give a general overview and a general first taste of SMOS' performance, together with the identified gaps and next steps to be taken. This presentation could be the general introduction to Cal Val activities.

Kerr, Y.; Mialon, A.; Bitar, A. Al; Leroux, D.; Richaume, P.; Gruhier, C.; Berthon, L.; Novello, N.; Rudiger, C.; Bircher, S.; Wigneron, J. P.; Ferrazzoli, P.; Rahmoune, R.

2012-04-01

192

Timescales of Soil Moisture Anomalies: Results from Two GCMs  

NASA Technical Reports Server (NTRS)

Soil moisture anomalies dissipate over timescales that may span weeks to months. Characterizing the geographical and seasonal variations in these timescales can have important practical benefit; significant soil moisture "memory" allows long-lead forecasts of soil moisture, which have been found in recent studies to be essential for useful Ion--lead forecasts of precipitation in many regions. In this talk, we will present and compare the soil moisture timescales derived in two separate general circulation model (GCM) studies. Both studies employ multiple ensembles of short-term climate simulations. Timescales at a given point are effectively estimated by determining how quickly the soil moisture distribution generated in one ensemble of simulations (characterized by a unique set of initial soil moisture conditions) approaches that produced by another ensemble (characterized by a different set of initial soil moisture conditions). The talk will include a discussion of why the timescales produced by the two GCMs differ in some regions, and it will also describe the impact of soil moisture memory on simulated precipitation.

Koster, Randal D.; Milly, P. C. D.; Schlosser, C. Adam; Suarez, Max J.

1999-01-01

193

Preferential States in Continental Soil Moisture and Climate Dynamics  

Microsoft Academic Search

Summer precipitation in continental midlatitude regions is significantly contributed by local recycling, i.e. by moisture returning to the atmosphere as water vapor through evapotranspiration from the same region. In the summer months, soil moisture availability may limit water vapor fluxes from the soil surface to the planetary boundary layer, with important effects on the regional climate. It has been argued

P. D'Odorico; N. Pipino; A. Porporato

2003-01-01

194

Using similarity of soil texture and hydroclimate to enhance soil moisture estimation  

NASA Astrophysics Data System (ADS)

Estimating soil moisture typically involves calibrating models to sparse networks of in situ sensors, which introduces considerable error in locations where sensors are not available. We address this issue by calibrating parameters of a parsimonious soil moisture model, which requires only antecedent precipitation information, at gauged locations and then extrapolating these values to ungauged locations via a hydroclimatic classification system. Fifteen sites within the Soil Climate Analysis Network (SCAN) containing multiyear time series data for precipitation and soil moisture are used to calibrate the model. By calibrating at 1 of these 15 sites and validating at another, we observe that the best results are obtained where calibration and validation occur within the same hydroclimatic class. Additionally, soil texture data are tested for their importance in improving predictions between calibration and validation sites. Results have the largest errors when calibration-validation pairs differ hydroclimatically and edaphically, improve when one of these two characteristics are aligned, and are strongest when the calibration and validation sites are hydroclimatically and edaphically similar. These findings indicate considerable promise for improving soil moisture estimation in ungauged locations by considering these similarities.

Coopersmith, E. J.; Minsker, B. S.; Sivapalan, M.

2014-08-01

195

COMPARISON OF AMSRE AND MSMMN SOIL MOISTURE For each location shown in figure 2, the soil moisture timeseries for 2005 from the colocated AMSRE  

E-print Network

COMPARISON OF AMSRE AND MSMMN SOIL MOISTURE For each location shown in figure 2, the soil moisture timeseries for 2005 from the colocated AMSRE grid has been compared to the MSMMN soil moisture (see figure 3 of an area average. In general, comparison of the timeseries of pointbased and areaaveraged soil moisture

Walker, Jeff

196

SEASONAL SOIL MOISTURE PREDICTION USING A CLIMATE-PLANT-SOIL COUPLED AGROECOSYSTEM WATER MANAGEMENT MODEL  

E-print Network

distribution of the forecast. We use observed soil moisture data from four SCAN sites: Ames, IA (42°00' N 933.13 SEASONAL SOIL MOISTURE PREDICTION USING A CLIMATE-PLANT-SOIL COUPLED AGROECOSYSTEM WATER moisture prediction is a critical factor for economic decision-making in agriculture. The national outlook

Takle, Eugene S.

197

Soil moisture determination study. [Guymon, Oklahoma  

NASA Technical Reports Server (NTRS)

Soil moisture data collected in conjunction with aircraft sensor and SEASAT SAR data taken near Guymon, Oklahoma are summarized. In order to minimize the effects of vegetation and roughness three bare and uniformly smooth fields were sampled 6 times at three day intervals on the flight days from August 2 through 17. Two fields remained unirrigated and dry. A similar pair of fields was irrigated at different times during the sample period. In addition, eighteen other fields were sampled on the nonflight days with no field being sampled more than 24 hours from a flight time. The aircraft sensors used included either black and white or color infrared photography, L and C band passive microwave radiometers, the 13.3, 4.75, 1.6 and .4 GHz scatterometers, the 11 channel modular microwave scanner, and the PRT5.

Blanchard, B. J.

1979-01-01

198

Diurnal variation of diazinon volatilization: soil moisture effects.  

PubMed

Diurnal variations in diazinon volatilization were monitored in three field experiments conducted with differing soil moisture contents. The highest flux rates in all experiments were recorded just after diazinon application, but the magnitudes of those initial rates differed according to the soil moisture content, with wetter soil producing a higher rate: 5.6 10(-4) ?g cm(-2) min(-1) for initial soil moisture above field capacity, 8.3 10(-5) ?g cm(-2) min(-1) for initial soil moisture at field capacity, and 2.5 10(-5) ?g cm(-2) min(-1) for initially very dry soil. Volatilization decreased during the first day in the two experiments with initially wet soils but remained relatively constant in the experiment with initially dry soil. The volatilization rate during the first night for the wettest soil remained about an order-of-magnitude higher than that observed for driest soil. When the surface dried in the experiment conducted at the intermediate water content, the volatilization rate and temporal pattern transitioned and became similar to that observed for the initially dry soil. Around noon of the second day, a daily maximum value was observed in the volatilization rate for wet soil, whereas a minimum value was observed for the dry soil, resulting in an order-of magnitude difference. This study demonstrates the importance of soil moisture on emissions of pesticides to the atmosphere. PMID:21319734

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

2011-03-15

199

Soil moisture responses to vapour pressure deficit in polytunnel-grown tomato under soil moisture triggered irrigation control  

NASA Astrophysics Data System (ADS)

The aim of this work has been to investigate soil-to-atmosphere water transport in potted tomato plants by measuring and processing high-resolution soil moisture data against the environmental driver of vapour pressure deficit (VPD). Whilst many researchers have successfully employed sap flow sensors to determine water uptake by roots and transport through the canopy, the installation of sap flow sensors is non-trivial. This work presents an alternative method that can be integrated with irrigation controllers and data loggers that employ soil moisture feedback which can allow water uptake to be evaluated against environmental drivers such as VPD between irrigation events. In order to investigate water uptake against VPD, soil moisture measurements were taken with a resolution of 2 decimal places - and soil moisture, air temperature and relative humidity measurements were logged every 2 minutes. Data processing of the soil moisture was performed in an Excel spread sheet where changes in water transport were derived from the rate of change of soil moisture using the Slope function over 5 soil moisture readings. Results are presented from a small scale experiment using a GP2-based irrigation controller and data logger. Soil moisture feedback is provided from a single SM300 soil moisture sensor in order to regulate the soil moisture level and to assess the water flow from potted tomato plants between irrigation events. Soil moisture levels were set to avoid drainage water losses. By determining the rate of change in soil moisture between irrigation events, over a 16 day period whilst the tomato plant was in flower, it has been possible to observe very good correlation between soil water uptake and VPD - illustrating the link between plant physiology and environmental conditions. Further data is presented for a second potted tomato plant where the soil moisture level is switched between the level that avoids drainage losses and a significantly lower level. This data illustrates the possibility that rate-of-change of soil moisture and VPD measurement could be employed to highlight plant stress conditions.

Goodchild, Martin; Khn, Karl; Jenkins, Dick

2014-05-01

200

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Dependence of bare soil albedo on soil moisture on  

E-print Network

on soil moisture on the moraine of the Zongo glacier (Bolivia): implications for land surface modeling S SOIL ALBEDO ON SOIL MOISTURE Abstract. Although the dependence of bare soil albedo on soil moisture. This allows us to enhance the model's ability to capture the fast changes in surface soil moisture

Paris-Sud XI, Université de

201

Assessing vertical soil moisture dynamics using multi-frequency GPR common-midpoint soundings  

NASA Astrophysics Data System (ADS)

SummarySoil moisture measurement techniques are of utmost importance to vadose zone hydrologists. Surface hydrogeophysical methods, such as ground-penetrating radar (GPR), have the capacity to provide field-scale soil moisture information across a range of depth scales. This paper presents an extensive field study using multi-frequency (i.e., 225 MHz, 450 MHz, 900 MHz) GPR common-midpoint (CMP) soundings to monitor a complete annual cycle of soil moisture conditions at three distinct sites. We examine the use of normal-moveout (NMO) velocity analysis applied to CMP data for monitoring highly dynamic vertical soil moisture conditions in a mid-latitude climate consisting of wetting/drying and freeze/thaw cycles with varying degrees of magnitude and vertical velocity gradient. NMO velocity analysis is used to construct interval-velocity-depth models at a fixed location collected every 1-4 weeks. These time-lapse models are combined to construct temporal interval-velocity fields, which are converted into soil moisture content using an appropriate petrophysical relationship. Using these moisture fields, we were able to characterize the vertical distribution and dynamics of soil moisture in the shallow vadose zone. Although the use of multiple antenna frequencies provided varying investigation depths and vertical resolving capabilities, optimal characterization of soil moisture conditions was obtained with high-frequency 900 MHz antennas. The integration of direct ground wave and NMO velocity data from a single CMP sounding allowed us to better refine the shallow soil moisture profile and underlying vadose zone conditions during seasonal wetting, drying and freezing cycles. This study demonstrates the capacity of GPR to characterize vertical moisture dynamics, and highlights the importance of collecting high-resolution data along the air-soil interface to resolve the water content profile from the surface down to the deeper vadose zone conditions.

Steelman, Colby M.; Endres, Anthony L.

2012-05-01

202

Assimilation of soil moisture using Ensemble Kalman Filter  

NASA Astrophysics Data System (ADS)

In this work, a soil moisture data assimilation scheme was developed based on the Community Land Model Version 3.0 (hereafter CLM) and Ensemble Kalman Filter. Soil moisture in the 1st soil layer was assimilated into CLM to evaluate the improvements of land surface process simulation. The results indicated that the assimilation system could improve the model accuracy effectively. It can transfer the variations of shallow soil layer's moisture to the deep soil and make great improvements to the soil water and heat status in an overall level. The system could improve the soil moisture accuracy from the 1st soil layer to the 6th soil layer by 50%. According to this experiment, the transfer depth of soil moisture was from 40 cm to 60 cm. After assimilation, the correlation coefficient of latent heat flux observation and simulation increased from 0.68 to 0.91 and the RMSE dropped from 86.7 W/m2 to 45.7 W/m2. For the sensible heat flux, the correlation coefficient increased from 0.69 to 0.80 and the RMSE reduced from 105.1 W/m2 to 71.3 W/m2. It was feasible and significant to assimilate soil moisture remote sensing products.

Du, Juan; Liu, Chaoshun; Gao, Wei

2014-10-01

203

An observing system simulation experiment for soil moisture measurements from the SMAP radiometer  

E-print Network

The Soil Moisture Active Passive (SMAP) satellite, to be launched in 2013, will use both radiometer and radar data to estimate soil moisture. Improved soil moisture knowledge has many applications in hydroclimatology, ...

Konings, Alexandra Georges

2009-01-01

204

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 an average of 1.7 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 m3 m-3 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 (SMOS) with deeper measurements from the cosmic-ray rover. The interpolated soil moisture and soil moisture profiles allow for basin-wide mass balance calculation of evapotranspiration, which amounted to 241 mm in 2012. Generating soil moisture maps with a cosmic-ray rover at this intermediate scale may help in the calibration and validation of satellite soil moisture data products and may also aid in various large-scale hydrologic studies.

Chrisman, B.; Zreda, M.

2013-12-01

205

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

206

Use of Calibrated vs. Uncalibrated Soil Moisture Networks for Validation of Soil Moisture at Passive Microwave Remote Sensing Footprint Scales  

NASA Astrophysics Data System (ADS)

Passive microwave remote sensing missions have been designed to obtain soil moisture estimates within an accuracy of 0.04 m3 m-3 volumetric soil moisture. These missions, however, are dependent on validation, which is obtained from established soil moisture networks. Soil moisture networks provide a basis for validation of passive microwave remote sensing estimate of soil moisture at scales typically larger than 302 km2. Networks have been established globally at varying spatial resolutions, which aid in the validation process. One such network was established for the Canadian Experiment for Soil Moisture in 2010 (CanEx-SM10). During this campaign, in situ soil moisture sensors were installed in 28 agricultural fields. A study was conducted to determine if each of the 28 in situ stations were representative of the mean field soil moisture for their corresponding fields. In order to determine this, intensive soil moisture measurements were made at 14 points along two transects in each of the 28 fields during six different days of the CanEx-SM10 campaign. The 14 measurements within the field allowed for calibration of the individual network sites. Additionally, the spatial scale of the 28 fields provided the opportunity to validate the soil moisture network as a whole, at the scale of a passive microwave footprint. Many soil moisture networks do not benefit from intensive ground based sampling for calibration, which is both time and labor intensive. As a result, this study examines the error associated with using uncalibrated vs. calibrated network information for validation of soil moisture retrieved at the spatial resolution of AMSR-E and SMOS satellite missions. At the field-scale, this study examines the number of samples required to validate the in situ soil moisture stations, but also investigates the number of network sites required in both a calibrated and uncalibrated scenario to be within the allowable error associated with the current passive microwave missions of 0.04 m3 m-3 volumetric soil moisture. It is demonstrated that this network, when uncalibrated, indicates a much higher number of sites are required to be within the allowable error for the passive microwave missions at a 95% confidence level than for the calibrated network.

Berg, A. A.; Rowlandson, T. L.; Impera, S.

2012-12-01

207

Remotely sensed soil moisture input to a hydrologic model  

NASA Technical Reports Server (NTRS)

The possibility of using detailed spatial soil moisture maps as input to a runoff model was investigated. The water balance of a small drainage basin was simulated using a simple storage model. Aircraft microwave measurements of soil moisture were used to construct two-dimensional maps of the spatial distribution of the soil moisture. Data from overflights on different dates provided the temporal changes resulting from soil drainage and evapotranspiration. The study site and data collection are described, and the soil measurement data are given. The model selection is discussed, and the simulation results are summarized. It is concluded that a time series of soil moisture is a valuable new type of data for verifying model performance and for updating and correcting simulated streamflow.

Engman, E. T.; Kustas, W. P.; Wang, J. R.

1989-01-01

208

Soil moisture and the persistence of North American drought  

NASA Technical Reports Server (NTRS)

Numerical sensitivity experiments on the effects of soil moisture on North American summertime climate are performed using a 12-layer global atmospheric general circulation model. Consideration is given to the hypothesis that reduced soil moisture may induce and amplify warm, dry summers of midlatitude continental interiors. The simulations resemble the conditions of the summer of 1988, including an extensive drought over much of North America. It is found that a reduction in soil moisture leads to an increase in surface temperature, lower surface pressure, increased ridging aloft, and a northward shift of the jet stream. It is shown that low-level moisture advection from the Gulf of Mexico is important in the maintenance of persistent soil moisture deficits.

Oglesby, Robert J.; Erickson, David J., III

1989-01-01

209

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

210

Temporal persistence and stability of surface soil moisture in a semi-arid watershed  

Microsoft Academic Search

Satellite soil moisture products, such as those from Advanced Microwave Scanning Radiometer (AMSR), require diverse landscapes for validation. Semi-arid landscapes present a particular challenge to satellite remote sensing validation using traditional techniques because of the high spatial variability and potentially rapid rates of temporal change in moisture conditions. In this study, temporal stability analysis and spatial sampling techniques are used

Michael H. Cosh; Thomas J. Jackson; Susan Moran; Rajat Bindlish

2008-01-01

211

Prefractal scaling of apparent soil moisture estimated from vertical planes of Vertisol pit images  

NASA Astrophysics Data System (ADS)

Image analysis could be a useful tool for investigating the spatial patterns of apparent soil moisture at multiple resolutions. The objectives of the present work were (i) to define apparent soil moisture patterns from vertical planes of Vertisol pit images and (ii) to describe the scaling of apparent soil moisture distribution using fractal parameters. Twelve soil pits (0.70 m long x 0.60 m width x 0.30 m depth) were excavated on a bare Mazic Pellic Vertisol. Six of them were excavated in April/2011 and six pits were established in May/2011 after three days of a moderate rainfall event. Digital photographs were taken from each Vertisol pit using a KodakTM digital camera. The mean image size was 1600 x 945 pixels with one physical pixel ? 373 ?m of the photographed soil pit. Each soil image was analyzed using two prefractal scaling exponents, box counting (capacity) dimension (DBC) and interface fractal dimension (Di), and three prefractal scaling coefficients, the total number of boxes intercepting the foreground pattern at a unit scale (A), fractal lacunarity at the unit scale (?1) and Shannon entropy at the unit scale (S1). All prefractal scaling parameters identified significant differences between both sets of spatial patterns. Fractal lacunarity was the best discriminator between apparent soil moisture patterns. Soil image interpretation with prefractal parameters can be incorporated within site-specific agriculture toolbox. While fractal exponents condense information on space filling characteristics of the pattern, prefractal coefficients represent the investigated soil property as seen through a higher resolution microscope. In spite of some computational and practical limitations, image analysis of apparent soil moisture patterns could be used in connection with traditional soil moisture sampling, which always renders punctual estimates. Key words: Image analysis, fractal scaling, apparent soil moisture, Vertisols Acknowledgements This work has been partially funded by project AGL2010-21501/AGR (MICINN)

Cumbrera, R.; Tarquis, A. M.; Gasc, G.; Milln, H.

2012-04-01

212

Validation of soil moisture and surface fluxes in EURO-CORDEX simulations as part of a land-atmosphere coupling analysis  

NASA Astrophysics Data System (ADS)

Land-atmosphere coupling is highly important to understand e.g. many of the processes involved in regional climate change and its impacts. A main science question is in which way the land surface influences the atmosphere and how the strength of this coupling may be quantified. Such complex land-atmosphere interactions are e.g. sensitive to small scale surface heterogeneities that are better captured by higher resolution regional climate model runs that are supposed to provide an added value when it comes to the reproduction of extremes and associated impacts. As part of a land-atmosphere coupling analysis, where we investigate the coupling strength and its spatial and temporal variability based on ERA-Interim re-analysis driven multiscale EURO-CORDEX (Coordinated Regional Climate Downscaling Experiment) validation runs, the present study shows, how well the spatial patterns and temporal evolutions of surface moisture and surface energy fluxes are reproduced in these simulations. The analysis is done on a subset of eight WRF RCM simulations that are part of the EURO-CORDEX ensemble. We evaluate daily model results from 1990 to 2008 at spatial resolutions of about 48 km (EUR-44) and 12 km (EUR-11) for the complete European model domain. The model simulations are compared to the Essential Climate Variables (ECV) Soil Moisture satellite data product of the ESA Climate Change Initiative regridded with a nearest neighbor resampling to the EUR-44 and the EUR-11 grid, respectively. Due to data coverage, the data intercomparison is done on a grid-cell-basis for all individual days with a matching satellite observation for annual and seasonal time spans. Related to the soil moisture-temperature feedback this quantity is highly important for flux partitioning. In order to evaluate those fluxes and thereby the reproduction of boundary layer processes by the models, latent and sensible heat fluxes are compared for individual locations against flux tower measurements of the FLUXNET dataset. An important prerequisite for a valid intercomparison is e.g. a match of the dominant land use as used by the land surface schemes in the RCMs with the station site. As most RCMs in the intercomparison use the NOAH LSM with MODIS land use and USGS GTOPO topographic data, our intercomparison does not necessarily give an information on the quality of the LSM but is rather intended to investigate the overall effects of the complex interplay of several processes.

Knist, Sebastian; Goergen, Klaus; Keune, Jessica; Poorthuis, Lukas; Colette, Augustin; Margarida Cardoso, Rita; Fealy, Rowan; Fernandez, Jesus; Garcia-Diez, Markel; Katragkou, Eleni; Mayer, Stephanie; Soares, Pedro; Sobolowski, Stefan; Vautard, Robert; Sarrach-Wagi, Kirsten; Wulfmeyer, Volker; Simmer, Clemens

2014-05-01

213

A Time Series Approach for Soil Moisture Estimation  

NASA Technical Reports Server (NTRS)

Soil moisture is a key parameter in understanding the global water cycle and in predicting natural hazards. Polarimetric radar measurements have been used for estimating soil moisture of bare surfaces. In order to estimate soil moisture accurately, the surface roughness effect must be compensated properly. In addition, these algorithms will not produce accurate results for vegetated surfaces. It is difficult to retrieve soil moisture of a vegetated surface since the radar backscattering cross section is sensitive to the vegetation structure and environmental conditions such as the ground slope. Therefore, it is necessary to develop a method to estimate the effect of the surface roughness and vegetation reliably. One way to remove the roughness effect and the vegetation contamination is to take advantage of the temporal variation of soil moisture. In order to understand the global hydrologic cycle, it is desirable to measure soil moisture with one- to two-days revisit. Using these frequent measurements, a time series approach can be implemented to improve the soil moisture retrieval accuracy.

Kim, Yunjin; vanZyl, Jakob

2006-01-01

214

Improvement of hydrologic model soil moisture predictions using SEBAL evapotranspiration estimates  

NASA Astrophysics Data System (ADS)

Soil moisture conditions influence practically all aspects of Army activities and are increasingly affecting its systems and operations. Regional distributions of high resolution soil moisture data will provide critical information on operational mobility, penetration, and performance of landmine and UXO sensors. The US Army Corps of Engineers (USACE) developed the Gridded Surface/Subsurface Hydrologic Analysis (GSSHA), which is a grid-based two-dimensional hydrologic model that has been effectively applied to predict soil moisture conditions. GSSHA computes evapotranspiration (ET) using the Penman-Monteith equation. However, lack of reliable spatially-distributed meteorological data, particularly in denied areas, makes it difficult to reliably predict regional ET and soil moisture distributions. SEBAL is a remote sensing algorithm that computes spatio-temporal patterns of ET using a surface energy balance approach. SEBAL has been widely accepted and tested throughout the world against lysimeter, eddy-covariance and other field measurements. SEBAL estimated ET has shown good consistency and agreement for irrigated fields, rangelands and arid riparian areas. The main objective of this research is to demonstrate improved GSSHA soil moisture and hydrological predictions using SEBAL estimates of ET. Initial results show that the use of SEBAL ET and soil moisture estimates improves the ability of GSSHA to predict regional soil moisture distributions, and reduces uncertainty in runoff predictions.

Hendrickx, Jan M. H.; Pradhan, Nawa R.; Hong, Sung-ho; Ogden, Fred L.; Byrd, Aaron R.; Toll, David

2009-05-01

215

NASA Giovanni: A Tool for Visualizing, Analyzing, and Inter-Comparing Soil Moisture Data  

NASA Technical Reports Server (NTRS)

There are many existing satellite soil moisture algorithms and their derived data products, but there is no simple way for a user to inter-compare the products or analyze them together with other related data (e.g., precipitation). An environment that facilitates such inter-comparison and analysis would be useful for validation of satellite soil moisture retrievals against in situ data and for determining the relationships between different soil moisture products. The latter relationships are particularly important for applications users, for whom the continuity of soil moisture data, from whatever source, is critical. A recent example was provided by the sudden demise of EOS Aqua AMSR-E and the end of its soil moisture data production, as well as the end of other soil moisture products that had used the AMSR-E brightness temperature data. The purpose of the current effort is to create an environment, as part of the NASA Giovanni family of portals, that facilitates inter-comparisons of soil moisture algorithms and their derived data products.

Teng, William; Rui, Hualan; Vollmer, Bruce; deJeu, Richard; Fang, Fan; Lei, Guang-Dih

2012-01-01

216

Estimation of Soil Moisture Profile using a Simple Hydrology Model and Passive Microwave Remote Sensing  

NASA Technical Reports Server (NTRS)

Soil moisture is an important component of analysis in many Earth science disciplines. Soil moisture information can be obtained either by using microwave remote sensing or by using a hydrologic model. In this study, we combined these two approaches to increase the accuracy of profile soil moisture estimation. A hydrologic model was used to analyze the errors in the estimation of soil moisture using the data collected during Huntsville '96 microwave remote sensing experiment in Huntsville, Alabama. Root mean square errors (RMSE) in soil moisture estimation increase by 22% with increase in the model input interval from 6 hr to 12 hr for the grass-covered plot. RMSEs were reduced for given model time step by 20-50% when model soil moisture estimates were updated using remotely-sensed data. This methodology has a potential to be employed in soil moisture estimation using rainfall data collected by a space-borne sensor, such as the Tropical Rainfall Measuring Mission (TRMM) satellite, if remotely-sensed data are available to update the model estimates.

Soman, Vishwas V.; Crosson, William L.; Laymon, Charles; Tsegaye, Teferi

1998-01-01

217

A Comparison of Methods for a Priori Bias Correction in Soil Moisture Data Assimilation  

NASA Technical Reports Server (NTRS)

Data assimilation is being increasingly used to merge remotely sensed land surface variables such as soil moisture, snow and skin temperature with estimates from land models. Its success, however, depends on unbiased model predictions and unbiased observations. Here, a suite of continental-scale, synthetic soil moisture assimilation experiments is used to compare two approaches that address typical biases in soil moisture prior to data assimilation: (i) parameter estimation to calibrate the land model to the climatology of the soil moisture observations, and (ii) scaling of the observations to the model s soil moisture climatology. To enable this research, an optimization infrastructure was added to the NASA Land Information System (LIS) that includes gradient-based optimization methods and global, heuristic search algorithms. The land model calibration eliminates the bias but does not necessarily result in more realistic model parameters. Nevertheless, the experiments confirm that model calibration yields assimilation estimates of surface and root zone soil moisture that are as skillful as those obtained through scaling of the observations to the model s climatology. Analysis of innovation diagnostics underlines the importance of addressing bias in soil moisture assimilation and confirms that both approaches adequately address the issue.

Kumar, Sujay V.; Reichle, Rolf H.; Harrison, Kenneth W.; Peters-Lidard, Christa D.; Yatheendradas, Soni; Santanello, Joseph A.

2011-01-01

218

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

2011-06-01

219

Use of TRMM Microwave Imager (TMI) to characterize soil moisture for the Little River Watershed  

Microsoft Academic Search

Soil moisture plays a critical role in many hydrological processes including infiltration, evaporation, and runoff. Additionally, soil moisture has a direct effect on weather patterns. Satellite based passive microwave sensors offer an effective way to observe soil moisture data over vast areas, and there are currently several satellite systems that detect soil moisture. Long-term in situ (field) measurements of soil

J. E. Cashion; V. Lakshmi; D. Bosch

2003-01-01

220

Stable or unstable wetting fronts in water repellent soils effect of antecedent soil moisture content  

E-print Network

Stable or unstable wetting fronts in water repellent soils ± effect of antecedent soil moisture wetting; Preferential ¯ow; Critical soil moisture content 1. Introduction Simulation models are widely.V. All rights reserved. P I I S 0 1 6 7 - 1 9 8 7 ( 9 8 ) 0 0 0 8 2 - 8 #12;wetting fronts in soils may

Walter, M.Todd

221

Soil moisture variation in relation to topography and land use in a hillslope catchment of the Loess Plateau, China  

NASA Astrophysics Data System (ADS)

The profile characteristics and the temporal dynamics of soil moisture variation were studied at 26 locations in Da Nangou catchment (3.5 km 2) in the loess area of China. Soil moisture measurements were performed biweekly at five depths in the soil profile (0-5, 10-15, 20-25, 40-45 and 70-75 cm) from May to October 1998 using Delta-T theta probe. Soil moisture profile type and temporal variation type and their relationship to topography and land use were identified by detrended canonical correspondence analysis (DCCA) and correlation analysis. The profile distribution of time-averaged soil moisture content can be classified into three types i.e. decreasing-type, waving-type and increasing-type. The profile features of soil moisture (e.g. profile gradient and profile variability) are influenced by different environmental factors. The profile type of soil moisture is only attributed to land use while profile gradient and profile variability of soil moisture is mainly related to land use and topography (e.g. landform type and slope). The temporal dynamics of layer-averaged soil moisture content is grouped into three types including three-peak type, synchro-four-peak type and lagged-four-peak type. These types are controlled by topography rather than by land use. The temporal dynamic type of soil moisture shows significant correlation with relative elevation, slope, aspect, while temporal variance displays significant relation with slope shape. The mean soil moisture is related to both the profile and dynamics features of soil moisture and is controlled by both land use and topography (e.g. aspect, position, slope and relative elevation). The spatial variability of soil moisture across landscape varies with both soil depths and temporal evolution.

Qiu, Yang; Fu, Bojie; Wang, Jun; Chen, Liding

2001-01-01

222

1. Now at INNOVIM, LLC., NOAA/NWS/NCEP/Climate Prediction Center, College Park, MD Impacts of Soil Moisture Ocean Salinity (SMOS) Soil Moisture Initialization on Convection1  

E-print Network

Moisture Ocean Salinity (SMOS) Soil Moisture Initialization on Convection1 Forecasting in the U.S. Great of short term forecasts of precipitation, temperature, and dewpoint to soil43 moisture initialization with soil moisture values from the North American Regional45 Reanalysis (NARR) dataset and with those

Robock, Alan

223

Is soil moisture initialization important for seasonal to decadal predictions?  

NASA Astrophysics Data System (ADS)

The state of soil moisture can can have a significant impact on regional climate conditions for short time scales up to several months. However, focusing on seasonal to decadal time scales, it is not clear whether the predictive skill of global a Earth System Model might be enhanced by assimilating soil moisture data or improving the initial soil moisture conditions with respect to observations. As a first attempt to provide answers to this question, we set up an experiment to investigate the life time (memory) of extreme soil moisture states in the coupled land-atmosphere model ECHAM6-JSBACH, which is part of the Max Planck Institute for Meteorology's Earth System Model (MPI-ESM). This experiment consists of an ensemble of 3 years simulations which are initialized with extreme wet and dry soil moisture states for different seasons and years. Instead of using common thresholds like wilting point or critical soil moisture, the extreme states were extracted from a reference simulation to ensure that they are within the range of simulated climate variability. As a prerequisite for this experiment, the soil hydrology in JSBACH was improved by replacing the bucket-type soil hydrology scheme with a multi-layer scheme. This new scheme is a more realistic representation of the soil, including percolation and diffusion fluxes between up to five separate layers, the limitation of bare soil evaporation to the uppermost soil layer and the addition of a long term water storage below the root zone in regions with deep soil. While the hydrological cycle is not strongly affected by this new scheme, it has some impact on the simulated soil moisture memory which is mostly strengthened due to the additional deep layer water storage. Ensemble statistics of the initialization experiment indicate perturbation lengths between just a few days up to several seasons for some regions. In general, the strongest effects are seen for wet initialization during northern winter over cold and humid regions, while the shortest memory is found during northern spring. For most regions, the soil moisture memory is either sensitive to wet or to dry perturbations, indicating that soil moisture anomalies interact with the respective weather pattern for a given year and might be able to enhance or dampen extreme conditions. To further investigate this effect, the simulations will be repeated using JSBACH with prescribed meteorological forcing to better disentangle the direct effects of soil moisture initialization and the atmospheric response.

Stacke, Tobias; Hagemann, Stefan

2014-05-01

224

Remote monitoring of soil moisture using airborne microwave radiometers  

NASA Technical Reports Server (NTRS)

The current status of microwave radiometry is provided. The fundamentals of the microwave radiometer are reviewed with particular reference to airborne operations, and the interpretative procedures normally used for the modeling of the apparent temperature are presented. Airborne microwave radiometer measurements were made over selected flight lines in Chickasha, Oklahoma and Weslaco, Texas. Extensive ground measurements of soil moisture were made in support of the aircraft mission over the two locations. In addition, laboratory determination of the complex permittivities of soil samples taken from the flight lines were made with varying moisture contents. The data were analyzed to determine the degree of correlation between measured apparent temperatures and soil moisture content.

Kroll, C. L.

1973-01-01

225

Soil Moisture Profile Estimation From Active Microwave Earth Observations  

NASA Astrophysics Data System (ADS)

This paper discusses the potential of retrieving information about the soil moisture profile from measurements of the surface soil moisture content through active mi- crowave observations of the Earth. In a series of laboratory experiments using multi- frequency radar observations of bare surfaces, Mancini et al. (1999) have shown that accurate surface soil moisture retrieval by means of C and L band active microwave observations is feasible. Hoeben and Troch (2000) combined active microwave obser- vations of the surface soil moisture content and 1D dynamic modeling of the unsat- urated zone in a data assimilation framework to show that this allows the retrieval of the root zone soil moiture profile. They showed that even in the presence of model and observation noise and infrequent observations, accurate retrieval of the entire soil moisture profile is possible for bare soil. Van Loon and Troch (2002) developed a ro- bust 4D data assimilation procedure applicable at the catchment scale. Their 4DDA is based on Tikhonov regularization or generalized cross-validation. Recently, this pro- cedure has been extended to operate in recursive mode, making the algorithm more general applicable for soil moisture data assimilation at the catchment scale. Possible applications of this algorithm in the context of ENVISAT ASAR instrument will be discussed.

Troch, P. A.; van Loon, E. E.

226

Evaluation of multi-model simulated soil moisture in NLDAS-2  

NASA Astrophysics Data System (ADS)

The North American Land Data Assimilation System (NLDAS) phase 2 (NLDAS-2) has generated 31-years (1979-2008) of water and energy products from four state-of-the-art land surface models (Noah, Mosaic, SAC, VIC). The soil moisture data from these models have been used for operational drought monitoring activities, but so far have not yet been comprehensively evaluated. In this study, three available in situ soil moisture observation data sets in the United States were used to evaluate the model-simulated soil moisture for different time scales varying from daily to annual. First, we used the observed multiple layer monthly and annual mean soil moisture from the Illinois Climate Network to evaluate 20-years (January 1985-December 2004) of model-simulated soil moisture in terms of skill and analysis of error statistics. Second, we utilized 6-years (1 January 1997-31 December 2002) of daily soil moisture observed from 72 sites over the Oklahoma Mesonet network to assess daily and monthly simulation skill and errors for 3 model soil layers (0-10 cm, 10-40 cm, 40-100 cm). Third, we extended the daily assessment to sites over the continental United States using 8-years (1 January 2002-31 December 2009) of observations for 121 sites from the Soil Climate Analysis Network (SCAN). Overall, all models are able to capture wet and dry events and show high skill (in most cases, anomaly correlation is larger than 0.7), but display large biases when compared to in situ observations. These errors may come from model errors (i.e., model structure error, model parameter error), forcing data errors, and in situ soil moisture measurement errors. For example, all models simulate less soil moisture due to lack of modeled irrigation and ground water processes in Illinois, Oklahoma, and the other Midwest states.

Xia, Youlong; Sheffield, Justin; Ek, Michael B.; Dong, Jiarui; Chaney, Nathaniel; Wei, Helin; Meng, Jesse; Wood, Eric F.

2014-05-01

227

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

228

Neutron Measurement of Surface Soil M,oisture  

Microsoft Academic Search

A neutron probe design for the measurement of surface soil moisture is de- scribed. The probe consists of a single BF8 tube, a Ra-Be source in a gamma shield and a plastic shield which serves also as a sandard. Adequate accuracy and sensitivity are reported when surface soil is homogeneous. When surface soil is stratified the interpretation of measure- ments

1961-01-01

229

The dynamic interplay between roots and soil moisture  

Microsoft Academic Search

Although water uptake by roots in the soil has been investigated in numerous studies, it is still not clear which is the main factor controlling the uptake, especially under non-uniform soil moisture distribution or intermediately wet soil. Root activity or root compensation factors are frequently used to adjust 1-D root water uptake models to observations. However, they are fitting parameters,

Sarah Garre; Jan Vanderborght; Mathieu Javaux; Harry Vereecken

2010-01-01

230

Soil Albedo in Relation to Soil Color, Moisture and Roughness  

NASA Astrophysics Data System (ADS)

Land surface albedo is the ratio of reflected to incident solar radiation. It is a function of several surface parameters including soil color, moisture, roughness and vegetation cover. A better understanding of albedo and how it changes in relation to variations in these parameters is important in order to help improve our ability to model the effects of land surface modifications on climate. The objectives of this study were (1) To determine empirical relationships between smooth bare soil albedo and soil color, (2) To develop statistical relationships between albedo and ground-based thematic mapper (TM) measurements of spectral reflectances, (3) To determine how increased surface roughness caused by tillage reduces bare soil albedo and (4) To empirically relate albedo with TM data and other physical characteristics of mixed grass/shrubland sites at Walnut Gulch Watershed. Albedos, colors and spectral reflectances were measured by Eppley pyranometer, Chroma Meter CR-200 and a Spectron SE-590, respectively. Measurements were made on two field soils (Gila and Pima) at the Campus Agricultural Center (CAC), Tucson, AZ. Soil surface roughness was measured by a profile meter developed by the USDA/ARS. Additional measurements were made at the Maricopa Agricultural Center (MAC) for statistical model testing. Albedos of the 15 smooth, bare soils (plus silica sand) were determined by linear regression to be highly correlated (r^2 = 0.93, p > 0.01) with color values for both wet and dry soil conditions. Albedos of the same smooth bare soils were also highly correlated (r^2>=q 0.86, p > 0.01) with spectral reflectances. Testing of the linear regression equations relating albedo to soil color and spectral reflectances using the data from MAC showed a high correlation. A general nonlinear relationship given by y = 8.366ln(x) + 37.802 r^2 = 0.71 was determined between percent reduction in albedo (y) and surface roughness index (x) for wet and dry Pima and Gila field soils. Measurements of albedo, color and spectral reflectance at the Walnut Gulch Watershed indicated that albedo values were highly correlated with percent rock & gravel, color value and reflectance data (TM bands 1-4).

Fontes, Adan Fimbres

231

Improvement of hydrologic model soil moisture predictions using SEBAL evapotranspiration estimates  

Microsoft Academic Search

Soil moisture conditions influence practically all aspects of Army activities and are increasingly affecting its systems and operations. Regional distributions of high resolution soil moisture data will provide critical information on operational mobility, penetration, and performance of landmine and UXO sensors. The US Army Corps of Engineers (USACE) developed the Gridded Surface\\/Subsurface Hydrologic Analysis (GSSHA), which is a grid-based two-dimensional

Jan M. H. Hendrickx; Nawa R. Pradhan; Sung-Ho Hong; Fred L. Ogden; Aaron R. Byrd; David Toll

2009-01-01

232

Overview of the Aqua\\/AMSR-E 2003 soil moisture experiment in Brazil (SMEX03 Brazil)  

Microsoft Academic Search

This study presents an overview of the field design and satellite data analysis strategy of the Brazilian SMEX03 (Soil Moisture Experiment in 2003) campaign. The goal of the SMEX03 Brazil is to validate existing algorithms to retrieve soil moisture from Aqua\\/AMSR-E data under tropical savanna vegetation cover. The test site corresponded to the Barreiras region, located in the western part

E. E. Sano; E. D. Assad; T. J. Jackson; W. Crow; A. Hsu

2004-01-01

233

Data Assimilation of Cosmic-ray Derived Soil Moisture  

NASA Astrophysics Data System (ADS)

Soil moisture predicted by numerical models plays a key role in weather and seasonal climate projections. Nevertheless, intermediate-scale soil moisture measurements have been difficult to obtain due to small-scale heterogeneity of soil water content, making upscaling measurements to areas comparable to land surface model (LSM) grid size problematic. Real-time integrated soil moisture measurements at spatial scales of a few hundreds of meters and effective depth of tens of centimeters are now available from the COsmic-ray Soil Moisture Observing System (COSMOS). This paper describes the initial efforts to implement the data assimilation framework of COSMOS observations applied to LSMs. A physically-based and analytic model that calculates the above-ground fast neutron intensity from LSM-derived soil moisture profiles is introduced here. The COsmic-ray Soil Moisture Interaction Code (COSMIC) includes a description of (a) degradation of the incoming high energy neutron flux, (b) creation of fast neutrons at each depth in the soil, and (c) degradation of the resulting fast neutrons before they reach the soil surface. COSMIC has been implemented into the Data Assimilation Research Testbed (DART) in order to update the soil moisture status of the NOAH LSM given COSMOS fast neutron intensity measurements. Preliminary results show the soil water dynamics in NOAH being improved when compared to a network of 180 point-scale sensors placed within the COSMOS sensor footprint for a site near Tucson (Arizona). Comparison of surface energy and water fluxes are also shown for a number of selected COSMOS sites co-located with Ameriflux towers.

Rosolem, R.; Shuttleworth, W. J.; Arellano, A. F.; Hoar, T. J.; Zeng, X.; Zreda, M.; Franz, T. E.

2012-12-01

234

ReproducedfromSoilScienceSocietyofAmericaJournal.PublishedbySoilScienceSocietyofAmerica.Allcopyrightsreserved. Post-fire Soil Water Repellency: Persistence and Soil Moisture Thresholds  

E-print Network

ScienceSocietyofAmerica.Allcopyrightsreserved. Post-fire Soil Water Repellency: Persistence and Soil Moisture Thresholds Lee H. MacDonald* and Edward on the persistence of soil water repellency and the soil moisture threshold at which water were the primary over time and identify on soil water repellency because of the large variability soil moisture

MacDonald, Lee

235

Preferential states in soil moisture and climate dynamics  

Microsoft Academic Search

Summer precipitation in continental midlatitude regions is significantly contributed by local recycling, i.e., by moisture returning to the atmosphere through evapotranspiration from the same region. On the other hand, reduced soil moisture availability may limit evapotranspiration rates with effects on the planetary boundary layer dynamics through the partitioning between sensible and latent heat fluxes. Thus, a dependence may exist between

Paolo D'Odorico; Amilcare Porporato

2004-01-01

236

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

237

Soil moisture variation patterns observed in Hand County, South Dakota  

NASA Technical Reports Server (NTRS)

Soil moisture data were taken during 1976 (April, June, October), 1977 (April, May, June), and 1978 (May, June, July) Hand County, South Dakota as part of the ground truth used in NASA's aircraft experiments to study the use of microwave radiometers for the remote sensing of soil moisture. The spatial variability observed on the ground during each of the sampling events was studied. The data reported are the mean gravimetric soil moisture contained in three surface horizon depths: 0 to 2.5, 0 to 5 and 0 to 10 cm. The overall moisture levels ranged from extremely dry conditions in June 1976 to very wet in May 1978, with a relatively even distribution of values within that range. It is indicated that well drained sites have to be partitioned from imperfectly drained areas when attempting to characterize the general moisture profile throughout an area of varying soil and cover type conditions. It is also found that the variability in moisture content is greatest in the 0 to 2.5 cm measurements and decreases as the measurements are integrated over a greater depth. It is also determined that the sampling intensity of 10 measurements per km is adequate to estimate the mean moisture with an uncertainty of + or - 3 percent under average moisture conditions in areas of moderate to good drainage.

Jones, E. B.; Owe, M.; Schmugge, T. J. (principal investigators)

1981-01-01

238

Exploring spatiotemporal patterns and physical controls of soil moisture at various spatial scales  

NASA Astrophysics Data System (ADS)

Soil moisture variability of various spatial scales is analyzed based on empirical orthogonal function (EOF) method using soil moisture datasets with various spatial resolutions: 1 km eco-hydrological model simulation, 0.25 passive microwave (Advanced Microwave Scanning Radiometer for the Earth Observing System, AMSR-E) dataset, and 0.5 land surface model simulation from Climate Predictor Center (CPC). All three datasets generate EOFs that explain similar variances with those generated from in situ observations from agro-meteorological network. Using AMSR-E product and eco-hydrological model simulation, it is found that the primary spatial pattern of soil moisture obtained from watershed scale has a strong connection to topographic attributes, followed by soil texture and rainfall variability, as suggested by the correlation between the primary EOF mode (EOF1) of soil moisture and landscape attributes. However, the EOF analysis of both AMSR-E and CPC datasets at regional scale reaches the conclusion that soil texture indices, such as sand and clay content, is of higher importance to soil moisture EOF1 spatial pattern (explaining 61 % variance) than topography is. Furthermore, correlation between soil moisture EOF1 and soil property is higher in spring than in autumn, which indicates that soil water-holding and drainage capabilities are more important under dry conditions. At national scale, the combined effects of topographic feature and soil property are clearly exhibited in EOF1. The study results reveal that different emphases should be placed on accurate acquisition of landscape attributes for soil moisture estimation according to various spatial scales.

Qiu, Jianxiu; Mo, Xingguo; Liu, Suxia; Lin, Zhonghui

2014-10-01

239

Soil moisture from temperature measurements at the Earth's surface, update  

NASA Technical Reports Server (NTRS)

Soil moisture budgets at the Earth's surface were investigated based on soil and atmospheric temperature variations. A number of data sets were plotted and statistically analyzed in order to accentuate the existence and the characteristics of mesoscale soil temperature extrema variations and their relations to other parameters. The correlations between diurnal temperature extrema for air and soil in drought and non-drought periods appear to follow different characteristic patterns, allowing an inference of soil moisture content from temperature data. The recovery of temperature extrema after a precipitation event also follows a characteristic power curve rise between two limiting values which is an indicator of evaporation rates. If these indicators are applied universally to regional temperature data, soil moisture content or drought conditions can be inferred directly from temperature measurements.

Welker, J. E.

1984-01-01

240

Measurement of soil moisture trends with airborne scatterometers  

NASA Technical Reports Server (NTRS)

The author had identified the following significant results. Repeated looks at surfaces that maintain constant roughness can provide an estimate of soil moisture in the surface, when appropriate radar look angles are used. Significant influence due to differences in soil moisture can be detected in the 13.3 GHz and 1.6 GHz scatterometer returns. Effects of normal crop densities have little influence on the surface soil moisture estimate, when appropriate look angles are used. It appears that different look angles are optimum for different frequencies to avoid effects from vegetation. Considering the frequency and look angles used on the Seasat-A imaging radar, differences in soil moisture should produce as much as 9 db difference in return on that system.

Blanchard, B. J. (principal investigator)

1978-01-01

241

Soil moisture and evapotranspiration predictions using Skylab data  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Multispectral reflectance and emittance data from the Skylab workshop were evaluated for prediction of evapotranspiration and soil moisture for an irrigated region of southern Texas. Wavelengths greater than 2.1 microns were required to spectrally distinguish between wet and dry fallow surfaces. Thermal data provided a better estimate of soil moisture than did data from the reflective bands. Thermal data were dependent on soil moisture but not on the type of agricultural land use. The emittance map, when used in conjunction with existing models, did provide an estimate of evapotranspiration rates. Surveys of areas of high soil moisture can be accomplished with space altitude thermal data. Thermal data will provide a reliable input into irrigation scheduling.

Myers, V. I. (principal investigator); Moore, D. G.; Horton, M. L.; Russell, M. J.

1975-01-01

242

A New International Network for in Situ Soil Moisture Data  

NASA Astrophysics Data System (ADS)

The International Soil Moisture Network (ISMN) is a new data-hosting center where globally available ground-based soil moisture measurements are collected, harmonized, and made available to users through a Web interface (http://www.ipf.tuwien.ac.at/insitu). As the first international initiative of its kind, the ISMN will play a crucial role in globally assessing the quality of soil moisture estimates from spaceborne microwave sensors and land surface models; in uncovering how the hydrological cycle integrates with land, the atmosphere, and the ocean; and in studying climate change. The ISMN is fully operational and currently hosts soil moisture data from more than 500 stations spanning 18 different networks. For scientific use, access to the data is free of charge.

Dorigo, Wouter; van Oevelen, Peter; Wagner, Wolfgang; Drusch, Matthias; Mecklenburg, Susanne; Robock, Alan; Jackson, Thomas

2011-04-01

243

The NASA Soil Moisture Active Passive (SMAP) mission: Overview  

E-print Network

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. Its mission design consists of L-band ...

O'Neill, Peggy

244

A Microwave Systems Approach to Measuring Root Zone Soil Moisture.  

National Technical Information Service (NTIS)

Computer microwave satellite simulation models were developed and the program was used to test the ability of a coarse resolution passive microwave sensor to measure soil moisture over large areas, and to evaluate the effect of heterogeneous ground covers...

R. W. Newton, J. F. Paris, B. V. Clark

1983-01-01

245

Sensitivity of seasonal weather prediction and extreme precipitation events to soil moisture initialization uncertainty using SMOS soil moisture products  

NASA Astrophysics Data System (ADS)

Sensitivity of seasonal weather prediction and extreme precipitation events to soil moisture initialization uncertainty using SMOS soil moisture products (1) S. Khodayar, (2) A. Coll, (2) E. Lopez-Baeza (1) Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), Karlsruhe Germany (2) University of Valencia. Earth Physics and Thermodynamics Department. Climatology from Satellites Group Soil moisture is an important variable in agriculture, hydrology, meteorology and related disciplines. Despite its importance, it is complicated to obtain an appropriate representation of this variable, mainly because of its high temporal and spatial variability. SVAT (Soil-Vegetation-Atmosphere-Transfer) models can be used to simulate the temporal behaviour and spatial distribution of soil moisture in a given area and/or state of the art products such as the soil moisture measurements from the SMOS (Soil Moisture and Ocean Salinity) space mission may be also convenient. The potential role of soil moisture initialization and associated uncertainty in numerical weather prediction is illustrated in this study through sensitivity numerical experiments using the SVAT SURFEX model and the non-hydrostatic COSMO model. The aim of this investigation is twofold, (a) to demonstrate the sensitivity of model simulations of convective precipitation to soil moisture initial uncertainty, as well as the impact on the representation of extreme precipitation events, and (b) to assess the usefulness of SMOS soil moisture products to improve the simulation of water cycle components and heavy precipitation events. Simulated soil moisture and precipitation fields are compared with observations and with level-1(~1km), level-2(~15 km) and level-3(~35 km) soil moisture maps generated from SMOS over the Iberian Peninsula, the SMOS validation area (50 km x 50 km, eastern Spain) and selected stations, where in situ measurements are available covering different vegetation cover and soil types. Additionally, measurements from an L-band radiometer from ESA (European Space Agency), ELBARA-II, installed in the area to monitor SMOS validation conditions over a vineyard crop are available. Furthermore, MODIS, LANDSAF and SMOS products are used to define realistic initial conditions for sensitivity simulations. The results of these simulations are investigated, compared and conclusions drawn. The investigation covers the autumn period of 2012, September to November, and we will particularly focus on selected stages where extreme rain events occurred in our study area.

Khodayar-Pardo, Samiro; Lopez-Baeza, Ernesto; Coll Pajaron, M. Amparo

246

Soil Moisture Dynamics under Corn, Soybean, and Perennial Kura Clover  

NASA Astrophysics Data System (ADS)

Rising global food and energy consumption call for increased agricultural production, whereas rising concerns for environmental quality call for farming systems with more favorable environmental impacts. Improved understanding and management of plant-soil water interactions are central to meeting these twin challenges. The objective of this research was to compare the temporal dynamics of soil moisture under contrasting cropping systems suited for the Midwestern region of the United States. Precipitation, infiltration, drainage, evapotranspiration, soil water storage, and freeze/thaw processes were measured hourly for three years in field plots of continuous corn (Zea mays L.), corn/soybean [Glycine max (L.) Merr.] rotation, and perennial kura clover (Trifolium ambiguum M. Bieb.) in southeastern Minnesota. The evapotranspiration from the perennial clover most closely followed the temporal dynamics of precipitation, resulting in deep drainage which was reduced up to 50% relative to the annual crops. Soil moisture utilization also continued later into the fall under the clover than under the annual crops. In the annual cropping systems, crop sequence influenced the soil moisture dynamics. Soybean following corn and continuous corn exhibited evapotranspiration which was 80 mm less than and deep drainage which was 80 mm greater than that of corn following soybean. These differences occurred primarily during the spring and were associated with differences in early season plant growth between the systems. In the summer, soil moisture depletion was up to 30 mm greater under corn than soybean. Crop residue also played an important role in the soil moisture dynamics. Higher amounts of residue were associated with reduced soil freezing. This presentation will highlight key aspects of the soil moisture dynamics for these contrasting cropping systems across temporal scales ranging from hours to years. The links between soil moisture dynamics, crop yields, and nutrient leaching will also be examined.

Ochsner, T.; Venterea, R. T.

2009-12-01

247

Soil moisture under contrasted atmospheric conditions in Eastern Spain  

NASA Astrophysics Data System (ADS)

Soil moisture plays a key role on the recently abandoned agriculture land where determine the recovery and the erosion rates (Cerd, 1995), on the soil water repellency degree (Bod et al., 2011) and on the hydrological cycle (Cerd, 1999), the plant development (Garca Fayos et al., 2000) and the seasonality of the geomorphological processes (Cerd, 2002). Moreover, Soil moisture is a key factor on the semiarid land (Ziadat and Taimeh, 2013), on the productivity of the land (Qadir et al., 2013) and soils treated with amendments (Johnston et al., 2013) and on soil reclamation on drained saline-sodic soils (Ghafoor et al., 2012). In previous study (Azorin-Molina et al., 2013) we investigated the intraannual evolution of soil moisture in soils under different land managements in the Valencia region, Eastern Spain, and concluded that soil moisture recharges are much controlled by few heavy precipitation events; 23 recharge episodes during 2012. Most of the soil moisture recharge events occurred during the autumn season under Back-Door cold front situations. Additionally, sea breeze front episodes brought isolated precipitation and moisture to mountainous areas within summer (Azorin-Molina et al., 2009). We also evidenced that the intraanual evolution of soil moisture changes are positively and significatively correlated (at p<0.01) with the amount of measured precipitation. In this study we analyze the role of other crucial atmospheric parameters (i.e., temperature, relative humidity, global solar radiation, and wind speed and wind direction) in the intraanual evolution of soil moisture; focussing our analyses on the soil moisture discharge episodes. Here we present 1-year of soil moisture measurements at two experimental sites in the Valencia region, one representing rainfed orchard typical from the Mediterranean mountains (El Teularet-Sierra de Enguera), and a second site corresponding to an irrigated orange crop (Alcoleja). Key Words: Soil Moisture Discharges, Intraannual changes, Atmospheric parameters, Eastern Spain Acknowledgements The research projects GL2008-02879/BTE, LEDDRA 243857 and RECARE FP7 project 603498 supported this research. References: Azorin-Molina, C., Connell, B.H., Baena-Calatrava, R. 2009. Sea-breeze convergence zones from AVHRR over the Iberian Mediterranean Area and the Isle of Mallorca, Spain. Journal of Applied Meteorology and Climatology 48 (10), 2069-2085. Azorin-Molina, C., Vicente-Serrano, S. M., Cerd, A. 2013. Soil moisture changes in two experimental sites in Eastern Spain. Irrigation versus rainfed orchards under organic farming. EGU, Geophysical Research Abstracts, EGU2013-13286. Bod, M.B., Mataix-Solera, J., Doerr, S.H. & Cerd, A. 2011. The wettability of ash from burned vegetation and its relationship to Mediterranean plant species type, burn severity and total organic carbon content. Geoderma, 160, 599-607. 10.1016/j.geoderma.2010.11.009 Cerd, A. 1995. Soil moisture regime under simulated rainfall in a three years abandoned field in Southeast Spain. Physics and Chemistry of The Earth, 20 (3-4), 271-279. Cerd, A. 1999. Seasonal and spatial variations in infiltration rates in badland surfaces under Mediterranean climatic conditions. Water Resources Research, 35 (1) 319-328. Cerd, A. 2002. The effect of season and parent material on water erosion on highly eroded soils in eastern Spain. Journal of Arid Environments, 52, 319-337. Garca-Fayos, P. Garca-Ventoso, B. Cerd, A. 2000. Limitations to Plant establishment on eroded slopes in Southeastern Spain. Journal of Vegetation Science, 11- 77- 86. Ghafoor, A., Murtaza, G., Rehman, M. Z., Saifullah Sabir, M. 2012. Reclamation and salt leaching efficiency for tile drained saline-sodic soil using marginal quality water for irrigating rice and wheat crops. Land Degradation & Development, 23: 1 -9. DOI 10.1002/ldr.1033 Johnston, C. R., Vance, G. F., Ganjegunte, G. K. 2013. Soil properties changes following irrigation with coalbed natural gas water: role of water treatments, soil amendments and land suitability.

Azorin-Molina, Csar; Cerd, Artemi; Vicente-Serrano, Sergio M.

2014-05-01

248

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

249

The NASA Soil Moisture Active Passive (SMAP) mission: Overview  

Microsoft Academic Search

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. Its mission design consists of L-band radiometer and radar instruments sharing a rotating 6-m mesh reflector antenna to provide high-resolution and high-accuracy global maps of soil moisture and freeze\\/thaw state every 2-3

Peggy O'Neill; Dara Entekhabi; Eni G. Njoku; Kent H. Kellogg

2010-01-01

250

Climate variability effects on spatial soil moisture dynamics  

Microsoft Academic Search

We investigate the role of interannual climate variability on spatial soil moisture variability dynamics for a field site in Louvain-la-Neuve, Belgium. Observations were made during 3 years under intermediate (1999), wet (2000), and extremely dry conditions (2003). Soil moisture variability dynamics are simulated with a comprehensive model for the period 1989-2003. The results show that climate variability induces non-uniqueness and

Adriaan J. Teuling; Franois Hupet; Remko Uijlenhoet; Peter A. Troch

2007-01-01

251

Climate variability effects on spatial soil moisture dynamics  

Microsoft Academic Search

We investigate the role of interannual climate variability on spatial soil moisture variability dynamics for a field site in Louvain-la-Neuve, Belgium. Observations were made during 3 years under intermediate (1999), wet (2000), and extremely dry conditions (2003). Soil moisture variability dynamics are simulated with a comprehensive model for the period 19892003. The results show that climate variability induces non-uniqueness and

Adriaan J. Teuling; Franois Hupet; Remko Uijlenhoet; Peter A. Troch

2007-01-01

252

SMOS CATDS Level 3 products, Soil Moisture and Brightness Temperature  

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 the surface soil moisture and the ocean salinity. The CNES (Centre National d'Etudes Spatiales) has developed the CATDS (Centre Aval de Traitement des Donnes SMOS) ground segment. The CATDS provides temporal synthesis products (referred to as level 3) of soil moisture, which are now covering the whole SMOS period, i.e. since January 2010. These products have different time resolutions: daily products, 3-day global products (insuring a complete coverage of the Earth surface), 10-day composite products, and monthly averaged products. Moreover, a new product provides brightness temperatures at H and V polarizations which are computed at fixed incidence angles every 5 degrees. As the instrument measures L-band brightness temperatures at the antenna frame (X/Y polarizations), a rotation is applied to transform the observations to V/H polarizations. All the CATDS products are presented in the NetCDF format and on the EASE grid (Equal Area Scalable Earth grid) with a spatial resolution of ~ 25*25 km2 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-day window. The use of many revisits is expected to improve the retrieved soil moisture. This communication aims at presenting the soil moisture and brightness temperature products from the CATDS as well as the other geophysical parameters retrieved, such as the vegetation optical depth or the dielectric constant of the surface. SMOS Level 3 soil moisture. 3-days aggregation product, the best estimation of soil moisture is chosen.

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

2012-12-01

253

The COsmic-ray Soil Moisture Observing System (COSMOS): a non-invasive, intermediate scale soil moisture measurement network  

Microsoft Academic Search

Soil moisture at a horizontal scale of ca. 600 m averaged over depths of 15-70 cm can be inferred from measurements of cosmic-ray neutrons that are generated within air and soil, moderated mainly by hydrogen atoms in the soil, and emitted back to the atmosphere where they are measured. These neutrons are sensitive to water content changes, largely insensitive to

Marek Zreda; W. James Shuttleworth; Chris Zweck; Xubin Zeng; Ty Ferre

2010-01-01

254

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. PMID:23112582

Dente, Laura; Su, Zhongbo; Wen, Jun

2012-01-01

255

Coupling soil moisture and precipitation observations for predicting hourly runoff at small catchment scale  

NASA Astrophysics Data System (ADS)

The importance of soil moisture is recognized in rainfall-runoff processes. This study quantitatively investigates the use of soil moisture measured at 10, 20, and 40 cm soil depths along with rainfall in predicting runoff. For this purpose, two small sub-catchments of Tiber River Basin, in Italy, were instrumented during periods of October 2002-March 2003 and January-April 2004. Colorso Basin is about 13 km2 and Niccone basin 137 km2. Rainfall plus soil moisture at 10, 20, and 40 cm formed the input vector while the discharge was the target output in the model of generalized regression neural network (GRNN). The model for each basin was calibrated and tested using October 2002-March 2003 data. The calibrated and tested GRNN was then employed to predict runoff for each basin for the period of January-April 2004. The model performance was found to be satisfactory with determination coefficient, R2, equal to 0.87 and Nash-Sutcliffe efficiency, NS, equal to 0.86 in the validation phase for both catchments. The investigation of effects of soil moisture on runoff prediction revealed that the addition of soil moisture data, along with rainfall, tremendously improves the performance of the model. The sensitivity analysis indicated that the use of soil moisture data at different depths allows to preserve the memory of the system thus having a similar effect of employing the past values of rainfall, but with improved GRNN performance.

Tayfur, Gokmen; Zucco, Graziano; Brocca, Luca; Moramarco, Tommaso

2014-03-01

256

Can Your Global Climate Modeling Project Use a Global Soil Moisture Data Set?  

Microsoft Academic Search

Soil moisture is a critical component of the hydrological cycle and plays an important role in determining land surface \\/ atmosphere interactions. However, scientists currently lack sufficient observational data to characterize large scale soil moisture distributions. The GLOBE Soil Moisture Project aims to mobilize the global K-12 with the larger scientific community to participate in periodic, near-surface, gravimetric soil moisture

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

2002-01-01

257

ON THE RELATIONSHIP BETWEEN MEAN AND VARIANCE OF SOIL MOISTURE FIELDS1  

E-print Network

ON THE RELATIONSHIP BETWEEN MEAN AND VARIANCE OF SOIL MOISTURE FIELDS1 Feifei Pan and Christa D in the literature related to the relationship between mean and variance (or standard deviation) of soil moisture fields. Some studies found an increase in soil moisture variance with decreasing mean soil moisture

Pan, Feifei

258

SPECIAL ISSUE A statistical retrieval algorithm for root zone soil moisture  

E-print Network

SPECIAL ISSUE A statistical retrieval algorithm for root zone soil moisture Ralf Lindau & Clemens for the estimation of root zone soil moisture is presented. Global fields of the soil moisture within the uppermost dominated by the spatial variability of the long-term mean soil moisture, while the temporal variability

Lindau, Ralf

259

Soil moisture initialization for climate prediction: Assimilation of scanning multifrequency microwave radiometer  

E-print Network

Soil moisture initialization for climate prediction: Assimilation of scanning multifrequency microwave radiometer soil moisture data into a land surface model Wenge Ni-Meister,1 Paul R. Houser,2 soil moisture state initialization. However, initial soil moisture state prediction skill can

Ni-Meister, Wenge

260

The Influence of Antecedent Soil Moisture on Springtime Runoff in the Sierra Nevada Mountains  

NASA Astrophysics Data System (ADS)

As the changing climate influences precipitation, air temperature, and snowmelt, measurements in the Sierra Nevada are illustrating the contribution of antecedent soil moisture on the timing and volume of springtime runoff. Delays in runoff correspond to low antecedent soil moisture from the preceding fall when snow fell on dry soil. In the Tuolumne River streamgage at the Little Grand Canyon just above Hetch Hetchy reservoir, no delay occurred between runoff and snowmelt in 2007 when the soil was wetter due to a cooler summer and fall rains. However, a 26-day delay in runoff was observed after the onset of snowmelt in 2008 when the soil was drier than the preceding fall at the time of the first snowfall due to a hotter and drier summer. If soils are dry prior to snowfall then the soil moisture is first replenished by springtime snowmelt, which not only delays runoff, but also reduces runoff volume to less than that estimated from snow pack. Typical runoff forecasts rely heavily on snow survey data and snowpack conditions, and the exclusion of soil moisture data could lead to an overestimate of the amount of runoff and compromise reservoir operations. In an average snowfall year, for example, the Kaweah Basin in the southern Sierra Nevada could lose as much as 20 percent of its snow water equivalent and the Merced Basin could lose 12 percent of its snow water equivalent simply to recharge soil moisture. Analyses of measured soil moisture in the Sierra Nevada, corresponding high elevation streamflow records, regional hydrologic modeling, and analysis of future climate projections to define the nature of summer and fall temperature and precipitation, will be used to illustrate the important role antecedent soil moisture plays in the timing and volume of springtime runoff in a changing climate.

Flint, A. L.; Flint, L. E.; Dettinger, M. D.

2009-12-01

261

Impact of the soil hydrology scheme on simulated soil moisture memory  

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 state and temporal variation of the regional climate. Identifying those regions can help to improve predictability in seasonal to decadal climate forecasts. In order to accurately simulate soil moisture memory and associated soil moisture-atmosphere interactions, an adequate representation of soil hydrology is required. The present study investigates how different setups of a soil hydrology scheme affect soil moisture memory simulated by the global climate model of the Max Planck Institute for Meteorology, ECHAM6/JSBACH. First, the standard setup is applied in which soil water is represented by a single soil moisture reservoir corresponding to the root zone. Second, a new five layer soil hydrology scheme is introduced where not only the root zone is differentiated into several layers but also layers below are added. Here, three variants of the new scheme are utilized to analyse how different characteristics of the soil hydrology and the associated fluxes influence soil moisture memory. Soil moisture memory of the different setups is analysed from global ECHAM6/JSBACH simulations forced by observed SST. Areas are highlighted where the regional climate seems to be sensitive to the improved representation of soil hydrology in the new setup and its variants. Results indicate that soil moisture memory is generally enlarged in regions during the dry season where a soil moisture buffer is present below the root zone due to the 5-layer scheme. This effect is usually enhanced when this buffer is increased. Memory tends to be weakened (strengthened) where bare soil evaporation is increased (decreased), especially in semi-arid regions and wet seasons. For some areas, this effect is compensated by a decreased (increased) transpiration.

Hagemann, Stefan; Stacke, Tobias

2014-06-01

262

Preliminary results of SAR soil moisture experiment, November 1975  

NASA Technical Reports Server (NTRS)

The experiment was performed using the Environmental Research Institute of Michigan's (ERIM) dual-frequency and dual-polarization side-looking SAR system on board a C-46 aircraft. For each frequency, horizontally polarized pulses were transmitted and both horizontally and vertically polarized return signals were recorded on the signal film simultaneously. The test sites were located in St. Charles, Missouri; Centralia, Missouri; and Lafayette, Indiana. Each test site was a 4.83 km by 8.05 km (3 mile by 5 mile) rectangular strip of terrain. Concurrent with SAR overflight, ground soil samples of 0-to-2.5 cm and 0-to-15 cm layers were collected for soil moisture estimation. The surface features were also noted. Hard-copy image films and the digital data produced via optical processing of the signal films are analyzed in this report to study the relationship of radar backscatter to the moisture content and the surface roughness. Many difficulties associated with processing and analysis of the SAR imagery are noted. In particular, major uncertainty in the quantitative analysis appeared due to the difficulty of quality reproduction of digital data from the signal films.

Choudhury, B. J.; Chang, A. T. C.; Schmugge, T. J.; Salomonson, V. V.; Wang, J. R.

1979-01-01

263

NASA Giovanni: A Tool for Visualizing, Analyzing, and Inter-comparing Soil Moisture Data  

NASA Technical Reports Server (NTRS)

There are many existing satellite soil moisture algorithms and their derived data products, but there is no simple way for a user to inter-compare the products or analyze them together with other related data. An environment that facilitates such inter-comparison and analysis would be useful for validation of satellite soil moisture retrievals against in situ data and for determining the relationships between different soil moisture products. As part of the NASA Giovanni (Geospatial Interactive Online Visualization ANd aNalysis Infrastructure) family of portals, which has provided users worldwide with a simple but powerful way to explore NASA data, a beta prototype Giovanni Inter-comparison of Soil Moisture Products portal has been developed. A number of soil moisture data products are currently included in the prototype portal. More will be added, based on user requirements and feedback and as resources become available. Two application examples for the portal are provided. The NASA Giovanni Soil Moisture portal is versatile and extensible, with many possible uses, for research and applications, as well as for the education community.

Teng, William; Rui, Hualan; Vollmer, Bruce; deJeu, Richard; Fang, Fan; Lei, Guang-Dih; Parinussa, Robert

2014-01-01

264

Soil moisture determination by means of the data driven models  

NASA Astrophysics Data System (ADS)

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 is eligible, depends on a variety of factors such as accuracy, cost, and ease of use. One of the most important hydro physical characteristics of soil is water retention curve (WRC), which is input to various hydraulic and hydrological models and reflects the energy dependence of soil water and the water content, e.g. the relationship between soil moisture and moisture potential. The method of determining the water retention curve points in laboratory conditions is very expensive, time consuming and labor intensive. In soil physics, therefore, were developed methods for determining soil hydro physical characteristics from easier obtained characteristics - soil granularity composition, organic matter content and bulk density. For these models (or relations) have been established title pedotransfer functions (PTF). These functions specify different soil characteristics and properties from relationship with another. The submitted work compares the creation of such functional dependencies using neural networks, hybrid self-organizing map (SOM) and support vector machines (SVM) model and standard multi-linear regression method. The SVMs formulate a quadratic optimization problem that avoids local minima problems, which makes them often superior to traditional (iterative) learning algorithms such as multi-layer perceptron (MLP) type of neural network. Input data are taken from Zahorsk lowland in Slovakia. It was taken 140 soil samples from various localities of Zahorsk lowland on finding soil characteristics and on the expression of water retention curve points. Sandy soils are prevailing in this area. Main input data were percentage of granularity categories I to IV according to Kopecky method, reduced volume weight (?d) and measured humidity for potentials hw = -2.5; -56, -209, -558, -976, -3060, -15300 cm specified in laboratory in the overpressure equipment for testing the regression made with abovementioned methods. To compare the results between measured and modeled data by various data driven methods, was accomplished an analysis using correlation coefficient and other statistical characteristics. This evaluation revealed most accurate results by using hybrid SOM-SVM model, in comparison with a conventional multi-layer artificial neural networks, multi-linear regression and standalone SVM model. Greater stability and need of less time devoted to calculations was observed in computation using SVM methodology, since the MLP training sometimes stuck in a local minimum so the training process has to be reset and run many times. This work was supported by the Slovak Research and Development Agency under the contract No. LPP-0319-09.

Cisty, Milan; Suchar, Martin; Bajtek, Zbynek

2010-05-01

265

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

266

Soil Moisture Active/Passive (SMAP) Mission concept  

NASA Astrophysics Data System (ADS)

Soil Moisture Active/Passive (SMAP) Mission is one of the first satellites being developed by NASA in response to the National Research Council's Decadal Survey. SMAP will make global measurements of the moisture present at Earth's land surface and will distinguish frozen from thawed land surfaces. Direct observations of soil moisture and freeze/thaw state from space will allow better estimates of water and energy transfers between Earth's surface and atmosphere, which are primary driving factors for weather and climate. Soil moisture measurements are also of great importance in assessing flooding potential and as input to flood prediction models. Conversely, observations of widespread low soil moisture levels can provide early warning of drought conditions, reduced water supply and crop loss. SMAP observations can help mitigate these natural hazards, resulting in potentially great economic and social benefits. SMAP freeze/thaw timing observations will also reduce a major uncertainty in quantifying the global carbon balance and will help resolve the problem of the missing carbon sink. The SMAP mission concept would utilize L-band radar and radiometry. These instruments will share a rotating 6-meter mesh antenna to provide high-resolution and high-accuracy global maps of soil moisture and freeze/thaw state every two to three days.

Entekhabi, D.; Jackson, T. J.; Njoku, E.; O'Neill, P.; Entin, J.

2008-08-01

267

Fractal scaling of apparent soil moisture estimated from vertical planes of Vertisol pit images  

NASA Astrophysics Data System (ADS)

SummaryImage analysis could be a useful tool for investigating the spatial patterns of apparent soil moisture at multiple resolutions. The objectives of the present work were (i) to define apparent soil moisture patterns from vertical planes of Vertisol pit images and (ii) to describe the scaling of apparent soil moisture distribution using fractal parameters. Twelve soil pits (0.70 m long 0.60 m width 0.30 m depth) were excavated on a bare Mazic Pellic Vertisol. Six of them were excavated in April/2011 and six pits were established in May/2011 after 3 days of a moderate rainfall event. Digital photographs were taken from each Vertisol pit using a Kodak digital camera. The mean image size was 1600 945 pixels with one physical pixel ?373 ?m of the photographed soil pit. Each soil image was analyzed using two fractal scaling exponents, box counting (capacity) dimension (DBC) and interface fractal dimension (Di), and three prefractal scaling coefficients, the total number of boxes intercepting the foreground pattern at a unit scale (A), fractal lacunarity at the unit scale (?1) and Shannon entropy at the unit scale (S1). All the scaling parameters identified significant differences between both sets of spatial patterns. Fractal lacunarity was the best discriminator between apparent soil moisture patterns. Soil image interpretation with fractal exponents and prefractal coefficients can be incorporated within a site-specific agriculture toolbox. While fractal exponents convey information on space filling characteristics of the pattern, prefractal coefficients represent the investigated soil property as seen through a higher resolution microscope. In spite of some computational and practical limitations, image analysis of apparent soil moisture patterns could be used in connection with traditional soil moisture sampling, which always renders punctual estimates.

Cumbrera, Ramiro; Tarquis, Ana M.; Gasc, Gabriel; Milln, Humberto

2012-07-01

268

Potential Soil Moisture Products from the Aquarius Radiometer and Scatterometer Using an Observing System Simulation Experiment  

SciTech Connect

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 United States, 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 RMSEs 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 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 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, Yan [I.M. Systems Group at NOAA/NCEP/EMC; Feng, Xia [George Mason University; Houser, Paul [George Mason University; Anantharaj, Valentine G [ORNL; Fan, Xingang [Western Kentucky University, Bowling Green; De Lannoy, Gabrielle [Ghent University, Belgium; Zhan, Xiwu [NOAA/NESDIS Center for Satellite Applications and Research; Dabbiru, Lalitha [Mississippi State University (MSU)

2013-01-01

269

Effect of ambient gases and soil moisture regimes on carbohydrate translocation in kidneybean plants grown in pots in Riyadh, KSA  

Microsoft Academic Search

This study designated to examine the effect of elevated gases in four localities of Riyadh City on carbohydrate for parts of kidneybean plants (Phaseolous vulgaris L.) grown in pots under two soil moisture regimes (well-watered vs. restricted water). Carbohydrate analysis results showed increases in kidneybean samples under well-watered conditions compared to restricted soil moisture. Most kidneybean samples at Embasses site

Fahad Al-Qurainy

270

Soil Moisture Drought in China, 19502006 Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Beijing, China  

E-print Network

Soil Moisture Drought in China, 1950­2006 AIHUI WANG Nansen-Zhu International Research Centre from which agricultural drought severities and durations were estimated. A cluster analysis method and severity­area­duration (SAD) algorithm were applied to the soil moisture data to characterize drought

271

Influence of Soil Moisture on Soil Gas Vapor Concentration for Vapor Intrusion  

PubMed Central

Abstract Mathematical models have been widely used in analyzing the effects of various environmental factors in the vapor intrusion process. Soil moisture content is one of the key factors determining the subsurface vapor concentration profile. This manuscript considers the effects of soil moisture profiles on the soil gas vapor concentration away from any surface capping by buildings or pavement. The open field soil gas vapor concentration profile is observed to be sensitive to the soil moisture distribution. The van Genuchten relations can be used for describing the soil moisture retention curve, and give results consistent with the results from a previous experimental study. Other modeling methods that account for soil moisture are evaluated. These modeling results are also compared with the measured subsurface concentration profiles in the U.S. EPA vapor intrusion database. PMID:24170970

Shen, Rui; Pennell, Kelly G.; Suuberg, Eric M.

2013-01-01

272

Development of a Satellite Systems for Measuring Soil Moisture  

NASA Technical Reports Server (NTRS)

The science need for remotely sensed soil moisture has been well established in the hydrologic, climate change and weather forecasting communities. There also have been a number of programs that have demonstrated the feasibility of using long wave microwave sensors for estimating soil moisture. These have ranged from truck mounted sensors, to intensive airborne campaigns with science objectives. Based on this history of truck and aircraft experiments, the science community has settled on a soil moisture product that meets the following criteria: a two day global repeat, a measured layer of 5 cm of soil, a footprint of 20 to 30 km, and an absolute accuracy of +/- 4% volumetric soil moisture. The principal sensor to accomplish this is an L-band passive microwave radiometer. A soil moisture mission is being proposed for the NASA Earth Systems Science Pathfinder (ESSP) mission which has very real constraints of a limited budget which includes the launch vehicle, and a three year award to launch time schedule. This paper describes ways to solve the very large antenna challenge, and the criteria used to choose the final design for an ESSP proposal. The paper also discusses the alternatives considered to obtain the necessary ancillary data for characterizing the surface roughness, the surface temperature and the attenuation affects of vegetation.

Engman, Edwin T.

1998-01-01

273

Advances, experiences, and prospects of the International Soil Moisture Network  

NASA Astrophysics Data System (ADS)

In 2009, the International Soil Moisture Network (ISMN; http:www.ipf.tuwien.ac.at) was initiated as a platform to support calibration and validation of soil moisture products from remote sensing and land surface models, and to advance studies on the behavior of soil moisture over space and time. This international initiative is fruit of continuing coordinative efforts of the Global Energy and Water Cycle Experiment (GEWEX) in cooperation with the Group of Earth Observation (GEO) and the Committee on Earth Observation Satellites (CEOS). The decisive financial incentive was given by the European Space Agency (ESA) who considered the establishment of the network critical for optimizing the soil moisture products from the Soil Moisture and Ocean Salinity (SMOS) mission. The ISMN collects and harmonizes ground-based soil moisture data sets from a large variety of individually operating networks and makes them available through a centralized data portal. Meanwhile, almost 6000 soil moisture data sets from over 1300 sites, distributed among 34 networks worldwide, are contained in the database. The steadily increasing number of organizations voluntarily contributing to the ISMN, and the rapidly increasing number of studies based on the network show that the portal has been successful in reaching its primary goal to promote easy data accessibility to a wide variety of users. Recently, several updates of the system were performed to keep up with the increasing data amount and traffic, and to meet the requirements of many advanced users. Many datasets from operational networks (e.g., SCAN, the US Climate Reference Network, COSMOS, and ARM) are now assimilated and processed in the ISMN on a fully automated basis in near-real time. In addition, a new enhanced quality control system is currently being implemented. This presentation gives an overview of these recent developments, presents some examples of important scientific results based on the ISMN, and sketches an outlook for mid- to long-term operation.

Dorigo, W.; van Oevelen, P. J.; Drusch, M.; Wagner, W.; Scipal, K.; Mecklenburg, S.

2012-12-01

274

Effects of soil moisture stress on evapotranspiration partitioning  

Microsoft Academic Search

Crop canopy decreases with increased soil moisture stress. Therefore, the soil evaporation (E) during the growing season will be affected. Leaf area index (LAI) and ground cover (GC) of cowpeas (Vigna sinensis, L.) were measured during the growing season on a line source sprinkler irrigation system receiving different amounts of irrigation to develop a function to predict LAI under different

A. R. Sepaskhah; S. Ilampour

1995-01-01

275

Advanced ground truth for remote sensing of soil moisture  

Microsoft Academic Search

The increase in accuracy of soil moisture retrieval from radar data requires a complete and accurate ground truth for calibration and verification. In order to support microwave backscattering models, one has to provide reliable permittivity and volumetric water content profiles of the soil. The conventional methods do not meet these requirements. The gravimetric sampling does not even deliver the volumetric

Alexander Brandelik; Christof Huebner

1995-01-01

276

Fate of spilled xylene as influenced by soil moisture content  

Microsoft Academic Search

Barrel size undisturbed monoliths of Weswood silt loam soil (Fluventic Ustochrept) were collected, instrumented, equilibrated at desired moisture contents, and treated with xylene by spilling it on the soil surface. Volatilization of xylene was measured using a chamber equipped with a granular activated carbon (GAC) vapor trap. Leachate was collected daily under - 33 kPa tension with a GAC vapor

M. W. Aurelius; K. W. Brown

1987-01-01

277

Soil Moisture: The Hydrologic Interface Between Surface and Ground Waters  

NASA Technical Reports Server (NTRS)

A hypothesis is presented that many hydrologic processes display a unique signature that is detectable with microwave remote sensing. These signatures are in the form of the spatial and temporal distributions of surface soil moisture. The specific hydrologic processes that may be detected include groundwater recharge and discharge zones, storm runoff contributing areas, regions of potential and less than potential evapotranspiration (ET), and information about the hydrologic properties of soils. In basin and hillslope hydrology, soil moisture is the interface between surface and ground waters.

Engman, Edwin T.

1997-01-01

278

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 1 Disaggregation of SMOS Soil Moisture  

E-print Network

IEEEProof IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 1 Disaggregation of SMOS Soil MoisturePATCh) is an algorithm dedicated to the dis-5 aggregation of soil moisture observations using high-resolution6 soil temperature data. DisPATCh converts soil temperature fields7 into soil moisture fields given a semi

Paris-Sud XI, Université de

279

Spatiotemporal analyses of soil moisture from point to footprint scale in two different hydroclimatic regions  

NASA Astrophysics Data System (ADS)

This paper presents time stability analyses of soil moisture at different spatial measurement support scales (point scale and airborne remote sensing (RS) footprint scale 800 m 800 m) in two different hydroclimatic regions. The data used in the analyses consist of in situ and passive microwave remotely sensed soil moisture data from the Southern Great Plains Hydrology Experiments 1997 and 1999 (SGP97 and SGP99) conducted in the Little Washita (LW) watershed, Oklahoma, and the Soil Moisture Experiments 2002 and 2005 (SMEX02 and SMEX05) in the Walnut Creek (WC) watershed, Iowa. Results show that in both the regions soil properties (i.e., percent silt, percent sand, and soil texture) and topography (elevation and slope) are significant physical controls jointly affecting the spatiotemporal evolution and time stability of soil moisture at both point and footprint scales. In Iowa, using point-scale soil moisture measurements, the WC11 field was found to be more time stable (TS) than the WC12 field. The common TS points using data across the 3 year period (2002-2005) were mostly located at moderate to high elevations in both the fields. Furthermore, the soil texture at these locations consists of either loam or clay loam soil. Drainage features and cropping practices also affected the field-scale soil moisture variability in the WC fields. In Oklahoma, the field having a flat topography (LW21) showed the worst TS features compared to the fields having gently rolling topography (LW03 and LW13). The LW13 field (silt loam) exhibited better time stability than the LW03 field (sandy loam) and the LW21 field (silt loam). At the RS footprint scale, in Iowa, the analysis of variance (ANOVA) tests show that the percent clay and percent sand are better able to discern the TS features of the footprints compared to the soil texture. The best soil indicator of soil moisture time stability is the loam soil texture. Furthermore, the hilltops (slope 0%-0.45%) exhibited the best TS characteristics in Iowa. On the other hand, in Oklahoma, ANOVA results show that the footprints with sandy loam and loam soil texture are better indicators of the time stability phenomena. In terms of the hillslope position, footprints with mild slope (0.93%-1.85%) are the best indicators of TS footprints. Also, at both point and footprint scales in both the regions, land use-land cover type does not influence soil moisture time stability.

Joshi, Champa; Mohanty, Binayak P.; Jacobs, Jennifer M.; Ines, Amor V. M.

2011-01-01

280

NASA's Soil Moisture Active Passive (SMAP) Mission and Opportunities for Applications Users  

E-print Network

Water in the soilboth its amount (soil moisture) and its state (freeze/thaw)plays a key role in water and energy cycles, in weather and climate, and in the carbon cycle. Additionally, soil moisture touches upon human ...

Brown, Molly E.

281

Sensitivity of Severe Convective Storms to Soil Moisture and Lower Atmospheric Water Vapor  

NASA Astrophysics Data System (ADS)

Numerous studies have examined the sensitivity of the atmospheric state to soil moisture on time scales of up to a day. Dry line intensity, lower tropospheric water vapor content, and precipitation have all been shown through modeling studies to be affected by modest perturbations to upstream soil moisture content and subsequent lower atmospheric water vapor. Since all of these aspects could be associated with convection, a high-impact forecast event that exhibits rapid nonlinear error growth, it is reasonable to expect that irrigation practices might influence severe convective storms. Understanding the link between soil moisture and specific convective elements could have broad implications for severe weather forecasting, and could reveal the degree to which irrigation-induced storm-scale inadvertent weather modification exists. This work examines the sensitivity to soil moisture and lower atmospheric water vapor content of a severe convective storm that struck Moore, Oklahoma, USA on May 20th, 2013, killing 24 people. While adjoint sensitivity analysis that employs the tangent linear version of a numerical weather prediction model might be used to examine convective sensitivities to soil moisture, the strong nonlinearity associated with these events likely renders this technique inaccurate. Alternatively, the approach here utilizes backward trajectory analysis to identify the regions up to a day prior to which the storm might be sensitive. Once the regions are identified, an ensemble of model forecasts is created by varying initial soil moisture to reveal the degree to which perturbations must be made to influence the downstream storm. Subsequent comparisons are made between the required soil moisture perturbations and realistic soil water values added through irrigation.

Ancell, Brian; Nauert, Christian

2014-05-01

282

Poor Soil Wettability: Does moisture alter measurement results?  

NASA Astrophysics Data System (ADS)

Poor soil wettability is a global problem, creating challenges to agriculture by plant drought stress and to soil stability in natural environments. Events that lead to poor soil wettability are varied, including natural and manmade events such as forest fires, hot dry environments, poor soil management or the application of post-consumer materials. Even though options offered in the literature for amelioration of the symptoms of hydrophobicity greatly differ, the basic techniques used to identify hydrophobic soil have changed very little over the past half-century. Recently, however, scientists have begun to question what these traditional techniques are actually measuring. One of the areas of interest is the relationship of hydrophobicity to moisture content, also termed reversible or seasonal hydrophobicity. Many studies suggest that changes in the organic matter structure as it is exposed to soil moisture leads to a reduction of the surface energy of particle surfaces. This study further complements that work by investigating how testing methods and soil-sample treatment impact water sorption of hydrophobic media, so as to make it appear that the surface energy has changed. The understanding of this phenomenon can lead to improved techniques for testing of hydrophobicity soil and also for soil management in agricultural areas by understanding the impact of soil moisture regimes on wettability.

Dragila, M. I.; Woolverton, P.; Horneck, D.; Kleber, M.

2013-12-01

283

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

284

Determination of soil moisture distribution from impedance and gravimetric measurements  

NASA Technical Reports Server (NTRS)

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 buried at these locations. The objective of this exercise was to test the hypothesis that the soil impedance is sensitive to the moisture content of the soil and that the imaginary part (that is, capacitive reactance) can be used to calculate the volumetric water content of the soil. These measurements were compared with gravimetric samples collected at these locations by the FIFE staff science team.

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

1992-01-01

285

Preparing for NASA's Soil Moisture Active Passive (SMAP) Mission  

NASA Astrophysics Data System (ADS)

Soil Moisture Active/Passive (SMAP) Mission is one of the first satellites being developed by NASA in response to the National Research Council's Decadal Survey. SMAP will make global measurements of the moisture present at Earth's land surface and will distinguish frozen from thawed land surfaces. Direct observations of soil moisture and freeze/thaw state from space will allow better estimates of water and energy transfers between Earth's surface and atmosphere, which are primary driving factors for weather and climate. Soil moisture measurements are also of great importance in assessing flooding potential and as input to flood prediction models. Conversely, observations of widespread low soil moisture levels can provide early warning of drought conditions, reduced water supply and crop loss. SMAP observations can help mitigate these natural hazards, resulting in potentially great economic and social benefits. SMAP freeze/thaw timing observations will also reduce a major uncertainty in quantifying the global carbon balance and will help resolve the problem of the missing carbon sink. The SMAP mission concept would utilize L-band radar and radiometry. These instruments will share a rotating 6-meter mesh antenna to provide high-resolution and high-accuracy global maps of soil moisture and freeze/thaw state every two to three days. Soil moisture products at 3, 10 and 40 km resolutions will be derived. These will both complement and extend the records of the ESA SMOS mission and offer an order of magnitude improvement in spatial resolution. SMAP is currently in Phase A and scheduled for a 2013 launch. The science teams will be focusing on algorithm development and validation over the next few years. These efforts will be described.

Jackson, T.; Entekhabi, D.; Njoku, E.; O'Neill, P.; Entin, J.

2009-04-01

286

Remote sensing of soil moisture with microwave radiometers  

NASA Technical Reports Server (NTRS)

Results are presented that were derived from measurements made by microwave radiometers during the March 1972 and February 1973 flights of National Aeronautics and Space Administration (NASA) Convair-9900 aircraft over agricultural test sites in the southwestern part of United States. The purpose of the missions was to study the use of microwave radiometers for the remote sensing of soil moisture. The microwave radiometers covered the 0.8- to 21-cm wavelength range. The results show a good linear correlation between the observed microwave brightness temperature and moisture content of the 0- to 1-cm layer of the soil. The results at the largest wavelength (21 cm) show the greatest sensitivity to soil moisture variations and indicate the possibility of sensing these variations through a vegetative canopy. The effect of soil texture on the emission from the soil was also studied and it was found that this effect can be compensated for by expressing soil moisture as a percent of field capacity for the soil. The results were compared with calculations based on a radiative transfer model for layered dielectrics and the agreement is very good at the longer wavelengths. At the shorter wavelengths, surface roughness effects are larger and the agreement becomes poorer.

Schmugge, T.; Wilheit, T.; Webster, W., Jr.; Gloerson, P.

1976-01-01

287

Hydrological connectivity drives microbial responses to soil moisture (Invited)  

NASA Astrophysics Data System (ADS)

Biogeochemical models generally fit microbial responses to moisture with smooth functions--as soils dry, processes slow. Microbial physiology, in contrast, has focused on how cells synthesize organic solutes to remain hydrated. Increasingly, however, we recognize that drying affects soil processes through resource constraints that develop when hydrological connection breaks down and organisms and resources become isolated in disconnected water pockets. Thus, microbial activity is regulated by abrupt breaks in connectivity and resources become unavailable to synthesize organic osmolytes; i.e. both biogeochemical models and pure-culture physiology perspectives are flawed. Hydrological connectivity fails before microbes become substantially stressed and before extracellular enzymes become inactive. Thus, resources can accumulate in dry soils, even as microbial activity shuts down because of resource limitation. The differential moisture responses of enzymes, organisms, and transport explains why microbial biomass and extractable C pools increase through the dry summer in California annual grasslands, why the size of the respiration pulse on rewetting increases with the length of drought, and even why soils from a wide range of biomes show the same relative response to soil moisture. I will discuss the evidence that supports the hydrological connectivity hypothesis for soil microbial moisture responses, how it affects a range of ecosystem processes, and how we can use it to develop simple, yet mechanistically rich, models of soil dynamics.

Schimel, J.

2013-12-01

288

Toward an Operational Bare Soil Moisture Mapping Using TerraSAR-X Data Acquired  

E-print Network

1 Toward an Operational Bare Soil Moisture Mapping Using TerraSAR-X Data Acquired Over Agricultural moisture in agricultural areas. Empirical relationships between TerraSAR-X signal and soil moisture were that the mean error on the soil moisture estimation is less than 4% regardless of the TerraSAR-X configuration

Paris-Sud XI, Université de

289

IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 1 Assessing the SMOS Soil Moisture Retrieval  

E-print Network

IEEEProof IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 1 Assessing the SMOS Soil Moisture Retrieval Moisture4 and Ocean Salinity (SMOS) forward model parameters for soil5 moisture retrieval was assessed at 1 soil moisture9 from the airborne observations, and then to interpret the differ-10 ences between

Paris-Sud XI, Université de

290

Soil moisture initialization for climate prediction: Characterization of model and observation errors  

E-print Network

Soil moisture initialization for climate prediction: Characterization of model and observation; accepted 15 April 2005; published 12 July 2005. [1] While it has been shown that soil moisture data moisture observations to provide optimal climate model surface and root zone soil moisture initialization

Ni-Meister, Wenge

291

An evaluation of the spatial resolution of soil moisture information  

NASA Technical Reports Server (NTRS)

Rainfall-amount patterns in the central regions of the U.S. were assessed. The spatial scales of surface features and their corresponding microwave responses in the mid western U.S. were investigated. The usefulness for U.S. government agencies of soil moisture information at scales of 10 km and 1 km. was ascertained. From an investigation of 494 storms, it was found that the rainfall resulting from the passage of most types of storms produces patterns which can be resolved on a 10 km scale. The land features causing the greatest problem in the sensing of soil moisture over large agricultural areas with a radiometer are bodies of water. Over the mid-western portions of the U.S., water occupies less than 2% of the total area, the consequently, the water bodies will not have a significant impact on the mapping of soil moisture. Over most of the areas, measurements at a 10-km resolution would adequately define the distribution of soil moisture. Crop yield models and hydrological models would give improved results if soil moisture information at scales of 10 km was available.

Hardy, K. R.; Cohen, S. H.; Rogers, L. K.; Burke, H. H. K.; Leupold, R. C.; Smallwood, M. D.

1981-01-01

292

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

293

Distribution of soil and leaf water potentials of mature grapefruit trees under three soil moisture regimes  

E-print Network

DISTRIBUTION OF SOIL AND LEAF WATER POTENTIALS OF MATURE GRAPEFRUIT TREES UNDER THREE SOIL MOISTURE REGIMES A Thesis by SANMUGAM AHEMBARANATHAN PRATHAPAP, Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE May 1982 Major Subject; Agricultural Engineering DISTRIBUTION OF SOIL AND LEAF WATER POTENTIALS OF MATURE GRAPEFRUIT TREES UNDER THREE SOIL MOISTURE REGIMES A Thesis by SANMUGAM AHEMBARANATHAN PRATHAPAR...

Prathapar, Sanmugam Ahembaranathan

2012-06-07

294

NASA Soil Moisture Active Passive (SMAP) Mission Formulation  

NASA Technical Reports Server (NTRS)

The Soil Moisture Active Passive (SMAP) Mission is one of the first Earth observation satellites being formulated by NASA in response to the 2007 National Research Council s Earth Science Decadal Survey [1]. SMAP s measurement objectives are high-resolution global measurements of near-surface soil moisture and its freeze-thaw state. These measurements would allow significantly improved estimates of water, energy and carbon transfers between the land and atmosphere. The soil moisture control of these fluxes is a key factor in the performance of atmospheric models used for weather forecasts and climate projections. Soil moisture measurements are also of great importance in assessing flooding and monitoring drought. Knowledge gained from SMAP s planned observations can help mitigate these natural hazards, resulting in potentially great economic and societal benefits. SMAP measurements would also yield high resolution spatial and temporal mapping of the frozen or thawed condition of the surface soil and vegetation. Observations of soil moisture and freeze/thaw timing over the boreal latitudes will contribute to reducing a major uncertainty in quantifying the global carbon balance and help resolve an apparent missing carbon sink over land. The SMAP mission would utilize an L-band radar and radiometer sharing a rotating 6-meter mesh reflector antenna (see Figure 1) [2]. The radar and radiometer instruments would be carried onboard a 3-axis stabilized spacecraft in a 680 km polar orbit with an 8-day repeating ground track. The instruments are planned to provide high-resolution and high-accuracy global maps of soil moisture at 10 km resolution and freeze/thaw at 3 km resolution, every two to three days (see Table 1 for a list of science data products). The mission is adopting a number of approaches to identify and mitigate potential terrestrial radio frequency interference (RFI). These approaches are being incorporated into the radiometer and radar flight hardware and ground processing designs.

Entekhabi, Dara; Njoku, Eni; ONeill, Peggy; Kellogg, Kent; Entin, Jared

2011-01-01

295

A Method for Estimating Soil Moisture from ERS Scatterometer and Soil Data  

Microsoft Academic Search

The potential of using ERS Scatterometer data for soil moisture monitoring over the Ukraine is investigated. The ERS Scatterometer is a C-band radar with a spatial resolution of 50 km and a high temporal sampling rate. An algorithm for estimating the surface soil moisture content is applied to 6 years of data. A qualitative comparison with meteorological observations and auxiliary

Wolfgang Wagner; Guido Lemoine; Helmut Rott

1999-01-01

296

Improved Understanding of Soil Surface Roughness Parameterization for L-Band Passive Microwave Soil Moisture Retrieval  

Microsoft Academic Search

Surface roughness parameterization plays an important role in soil moisture retrieval from passive microwave observations. This letter investigates the parameterization of surface roughness in the retrieval algorithm adopted by the Soil Moisture and Ocean Salinity mission, making use of experimental airborne and ground data from the National Airborne Field Experiment held in Australia in 2005. The surface roughness parameter is

Rocco Panciera; Jeffrey P. Walker; Olivier Merlin

2009-01-01

297

Transient soil moisture profile of a water-shedding soil cover in north Queensland, Australia  

NASA Astrophysics Data System (ADS)

In current agricultural and industrial applications, soil moisture determination is limited to point-wise measurements and remote sensing technologies. The former has limitations on spatial resolution while the latter, although has greater coverage in three dimensions, but may not be representative of real-time hydrologic conditions of the substrate. This conference paper discusses the use of elongated soil moisture probes to describe the transient soil moisture profile of water-shedding soil cover trial plots in north Queensland, Australia. Three-metre long flat ribbon cables were installed at designed depths across a soil cover with substrate materials from mining activities comprising of waste rocks and blended tailings. The soil moisture measurement is analysed using spatial time domain reflectometry (STDR) (Scheuermann et al., 2009) Calibration of the flat ribbon cable's soil moisture measurement in waste rocks is undertaken in a glasshouse setting. Soil moisture retention and outflows are monitored at specific time interval by mass balance and water potential measurements. These data sets together with the soil hydrologic properties derived from laboratory and field measurements are used as input in the numerical code on unsaturated flow, Hydrus2D. The soil moisture calculations of the glasshouse calibration using this numerical method are compared with results from the STDR soil moisture data sets. In context, the purpose of the soil cover is to isolate sulphide-rich mine wastes from atmospheric interaction as oxidation and leaching of these materials may result to acid and metalliferous drainage. The long term performance of a soil cover will be described in terms of the quantities and physico-chemical characteristics of its outflows. With the soil moisture probes set at automated and pre-determined measurement time intervals, it is expected to distinguish between macropore and soil moisture flows during high intensity rainfall events and, also continuously update data sets on soil moisture retention, especially during long periods of drought. As such, description of the soil cover water balance will be more elaborate as the soil moisture profile will be described in terms of temporal and spatial variability. Moreover, this field data set can lend support on the evaluation of the potential use of mine wastes as cover materials with respect to their hydrologic and geochemical properties.

Gonzales, Christopher; Baumgartl, Thomas; Scheuermann, Alexander

2014-05-01

298

BOREAS HYD-6 Ground Gravimetric Soil Moisture Data  

NASA Technical Reports Server (NTRS)

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-6 team collected several data sets related to the moisture content of soil and overlying humus layers. This data set contains percent soil moisture ground measurements. These data were collected on the ground along the various flight lines flown in the Southern Study Area (SSA) and Northern Study Area (NSA) during 1994 by the gamma ray instrument. The data are available in tabular ASCII files. The HYD-06 ground gravimetric soil moisture data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Carroll, Thomas; Knapp, David E. (Editor); Hall, Forrest G. (Editor); Peck, Eugene L.; Smith, David E. (Technical Monitor)

2000-01-01

299

Heated distributed temperature sensing for field scale soil moisture monitoring.  

PubMed

Characterizing both spatial and temporal soil moisture (?) dynamics at site scales is difficult with existing technologies. To address this shortcoming, we developed a distributed soil moisture sensing system that employs a distributed temperature sensing system to monitor thermal response at 2 m intervals along the length of a buried cable which is subjected to heat pulses. The cable temperature response to heating, which is strongly dependent on soil moisture, was empirically related to colocated, dielectric-based ? measurements at three locations. Spatially distributed, and temporally continuous estimates of ? were obtained in dry conditions (?? 0.31) using this technology (root mean square error [RMSE] = 0.016), but insensitivity of the instrument response curve adversely affected accuracy under wet conditions (RMSE = 0.050). PMID:22463129

Striegl, Arlen M; Loheide, Steven P

2012-01-01

300

Patterns and scaling properties of surface soil moisture in an agricultural landscape: An ecohydrological modeling study  

NASA Astrophysics Data System (ADS)

Soil moisture is a key variable in hydrology, meteorology and agriculture. Soil moisture, and surface soil moisture in particular, is highly variable in space and time. Its spatial and temporal patterns in agricultural landscapes are affected by multiple natural (precipitation, soil, topography, etc.) and agro-economic (soil management, fertilization, etc.) factors, making it difficult to identify unequivocal cause and effect relationships between soil moisture and its driving variables. The goal of this study is to characterize and analyze the spatial and temporal patterns of surface soil moisture (top 20 cm) in an intensively used agricultural landscape (1100 km2 northern part of the Rur catchment, Western Germany) and to determine the dominant factors and underlying processes controlling these patterns. A second goal is to analyze the scaling behavior of surface soil moisture patterns in order to investigate how spatial scale affects spatial patterns. To achieve these goals, a dynamically coupled, process-based and spatially distributed ecohydrological model was used to analyze the key processes as well as their interactions and feedbacks. The model was validated for two growing seasons for the three main crops in the investigation area: Winter wheat, sugar beet, and maize. This yielded RMSE values for surface soil moisture between 1.8 and 7.8 vol.% and average RMSE values for all three crops of 0.27 kg m-2 for total aboveground biomass and 0.93 for green LAI. Large deviations of measured and modeled soil moisture can be explained by a change of the infiltration properties towards the end of the growing season, especially in maize fields. The validated model was used to generate daily surface soil moisture maps, serving as a basis for an autocorrelation analysis of spatial patterns and scale. Outside of the growing season, surface soil moisture patterns at all spatial scales depend mainly upon soil properties. Within the main growing season, larger scale patterns that are induced by soil properties are superimposed by the small scale land use pattern and the resulting small scale variability of evapotranspiration. However, this influence decreases at larger spatial scales. Most precipitation events cause temporarily higher surface soil moisture autocorrelation lengths at all spatial scales for a short time even beyond the autocorrelation lengths induced by soil properties. The relation of daily spatial variance to the spatial scale of the analysis fits a power law scaling function, with negative values of the scaling exponent, indicating a decrease in spatial variability with increasing spatial resolution. High evapotranspiration rates cause an increase in the small scale soil moisture variability, thus leading to large negative values of the scaling exponent. Utilizing a multiple regression analysis, we found that 53% of the variance of the scaling exponent can be explained by a combination of an independent LAI parameter and the antecedent precipitation.

Korres, W.; Reichenau, T. G.; Schneider, K.

2013-08-01

301

Soils âField Characterization, Collection, and Laboratory Analysis  

NSDL National Science Digital Library

Field characterization of soil profiles in coniferous and deciduous settings; sample collection of soils from different horizons; laboratory analysis of soil moisture, soil organic carbon (by loss on ignition), and grain size distribution (by sieving)

Biswas, Abir

302

Soil moisture as signal and noise in SAR interferometry  

NASA Astrophysics Data System (ADS)

The possibility of measuring changes in soil moisture with differential SAR interferometry (DInSAR) was conclusively demonstrated in the first seminal paper on the repeat-pass technique using SeaSat's L-band sensor (Gabriel et al, 1989). There they confirmed that apparent increases and decreases of the soil surfaces of farm fields corresponded exactly with irrigation patterns. Since that time, the DInSAR technique has become a huge success but its application to soil moisture has been largely overlooked. Here we present theory, laboratory work, and satellite measurements that suggest that microwave penetration depth varies smoothly with soil moisture in nearly any soil and can therefore be used as a proxy for it, unlike clay swelling which occurs in a small percentage of soils and is too complex to model adequately. We find from the literature that the relationship between soil moisture and penetration depth is non-linear and indicates that a change of 5% volumetric water content (VWC) should cause between 1 and 50 mm of change in C-band penetration depth depending on initial VWC. Recent experimental measurements of this relationship within an anechoic chamber confirm this non-linear relationship and confirm that the expected magnitudes are sufficient for DInSAR measurement. We also present ERS-2 results that show intriguing spatial variations in millimeter-scale path-length change that correlate with hydrological features such as stream channels and watershed boundaries. Detection of these subtle signals was facilitated using a digital elevation model with high vertical accuracy, which we use to demonstrate that a real, ground-based signal can be found at the 0.5 mm level. Our latest research is focused on using various point scatterer techniques to construct long time-series of soil moisture maps using both ERS and Radarsat data. We conclude that penetration depth may be a viable proxy for measuring soil moisture, and that one reason the signal is often overlooked is that it is usually overwhelmed by errors caused by topographic uncertainties. Soil moisture may also be a significant, and previously unrecognized, source of noise in the measurement of subtle deformation signals or the creation of DEMs using repeat-pass interferometry.

Nolan, M.; Rabus, B.; Ferretti, A.; Morrison, K.; Khadhra, K.

2005-12-01

303

Moisture Relations of Some Texas Soils.  

E-print Network

is affecter!, to a. consicleralsle extent, bp the relative moistness of tlie soil. The experiments reported in the present bulletin were designed to snpplcment the other work, hj- showing thc condition of n~oisture of tbe soils at various intervals.... ................................................ ...................................................... Houstonblackclay Yazooclay ............................................................. Houstonloam ........................................................... J~OISTURE EEI;-~TIONS OF' SOIIE TEXAS SOILS. 31 The gain in 1911 varies from 0 to 3.7 bushels...

Fraps, G. S. (George Stronach)

1915-01-01

304

Improving runoff prediction through the assimilation of the ASCAT soil moisture product  

NASA Astrophysics Data System (ADS)

The role and the importance of soil moisture for meteorological, agricultural and hydrological applications is widely known. Remote sensing offers the unique capability to monitor soil moisture over large areas (catchment scale) with, nowadays, a temporal resolution suitable for hydrological purposes. However, the accuracy of the remotely sensed soil moisture estimates has to be carefully checked. The validation of these estimates with in-situ measurements is not straightforward due the well-known problems related to the spatial mismatch and the measurement accuracy. The analysis of the effects deriving from assimilating remotely sensed soil moisture data into hydrological or meteorological models could represent a more valuable method to test their reliability. In particular, the assimilation of satellite-derived soil moisture estimates into rainfall-runoff models at different scales and over different regions represents an important scientific and operational issue. In this study, the soil wetness index (SWI) product derived from the Advanced SCATterometer (ASCAT) sensor onboard of the Metop satellite was tested. The SWI was firstly compared with the soil moisture temporal pattern derived from a continuous rainfall-runoff model (MISDc) to assess its relationship with modeled data. Then, by using a simple data assimilation technique, the linearly rescaled SWI that matches the range of variability of modelled data (denoted as SWI*) was assimilated into MISDc and the model performance on flood estimation was analyzed. Moreover, three synthetic experiments considering errors on rainfall, model parameters and initial soil wetness conditions were carried out. These experiments allowed to further investigate the SWI potential when uncertain conditions take place. The most significant flood events, which occurred in the period 2000-2009 on five subcatchments of the Upper Tiber River in Central Italy, ranging in extension between 100 and 650 km2, were used as case studies. Results reveal that the SWI derived from the ASCAT sensor can be conveniently adopted to improve runoff prediction in the study area, mainly if the initial soil wetness conditions are unknown.

Brocca, L.; Melone, F.; Moramarco, T.; Wagner, W.; Naeimi, V.; Bartalis, Z.; Hasenauer, S.

2010-07-01

305

Improving runoff prediction through the assimilation of the ASCAT soil moisture product  

NASA Astrophysics Data System (ADS)

The role and the importance of soil moisture for meteorological, agricultural and hydrological applications is widely known. Remote sensing offers the unique capability to monitor soil moisture over large areas (catchment scale) with, nowadays, a temporal resolution suitable for hydrological purposes. However, the accuracy of the remotely sensed soil moisture estimates has to be carefully checked. The validation of these estimates with in-situ measurements is not straightforward due the well-known problems related to the spatial mismatch and the measurement accuracy. The analysis of the effects deriving from assimilating remotely sensed soil moisture data into hydrological or meteorological models could represent a more valuable method to test their reliability. In particular, the assimilation of satellite-derived soil moisture estimates into rainfall-runoff models at different scales and over different regions represents an important scientific and operational issue. In this study, the soil wetness index (SWI) product derived from the Advanced SCATterometer (ASCAT) sensor onboard of the Metop satellite was tested. The SWI was firstly compared with the soil moisture temporal pattern derived from a continuous rainfall-runoff model (MISDc) to assess its relationship with modeled data. Then, by using a simple data assimilation technique, the linearly rescaled SWI that matches the range of variability of modelled data (denoted as SWI*) was assimilated into MISDc and the model performance on flood estimation was analyzed. Moreover, three synthetic experiments considering errors on rainfall, model parameters and initial soil wetness conditions were carried out. These experiments allowed to further investigate the SWI potential when uncertain conditions take place. The most significant flood events, which occurred in the period 2000-2009 on five subcatchments of the Upper Tiber River in central Italy, ranging in extension between 100 and 650 km2, were used as case studies. Results reveal that the SWI derived from the ASCAT sensor can be conveniently adopted to improve runoff prediction in the study area, mainly if the initial soil wetness conditions are unknown.

Brocca, L.; Melone, F.; Moramarco, T.; Wagner, W.; Naeimi, V.; Bartalis, Z.; Hasenauer, S.

2010-10-01

306

Effect of moisture on alachlor retention in the soil  

E-print Network

in air-dry Sawyer fine sandy loam than in air-dry IIiller clay at 38 C and 2Fio relative humidity. As moisture increased to approximately 60fo field capacity, soil type differences became negligible, as sufficient moisture vras tI en available... Niller clay or Sawyer fine sandy loam (her- after referred to as clay or fine sandy loam) was pas od through a No. 10 seive to remove lumps and plant residue. Pifty-ml beakers or 4 ~ 5 x 1. 0 cm metal dishe were filled level with the soil. All exper...

Hargrove, Raford Stanley

2012-06-07

307

Remote monitoring of soil moisture using airborne microwave radiometers  

E-print Network

REMOTE MONITORING OF SOIL MOISTURE USING AIRBORNE MICROWAVE RADIOMETERS A Thesis by CHARLES LINDSEY J(ROLL Submitted to the Graduate College of Texas A)M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... August 1973 Major Subject: Electrical Engineering REMOTE MONITORING OF SOIL MOISTURE USING AIRBORNE MICROWAVE RADIOMETERS A Thesis by CHARLES LINDSEY KROLL Approved as to style and content by: man o Co mrtt Hca o D artmc c Ill l c r Mem e Member...

Kroll, Charles Lindsey

2012-06-07

308

Determination of Soil Moisture by the Method of Multiple Electrodes.  

E-print Network

; 1 ? Fig. 5. Top plan view of electr odes in position , s how ing t he resistance measurements. used in determining oil m oisture. DETERMINATION OF SOIL MOISTURE BY MULTIPLE ELE TRODES 17 wher R1 i the r i tan b tween lceh?odt? ? 1 and '2, H:! i...; 1 ? Fig. 5. Top plan view of electr odes in position , s how ing t he resistance measurements. used in determining oil m oisture. DETERMINATION OF SOIL MOISTURE BY MULTIPLE ELE TRODES 17 wher R1 i the r i tan b tween lceh?odt? ? 1 and '2, H:! i...

McCorkle, W. H.

1931-01-01

309

A soil moisture availability model for crop stress prediction  

E-print Network

December 1983 Major Subject: Bioengineering A SOIL MOISTURE AVAILABILITY MODEL FOR CROP STRESS PREDICTION A Thesis by ROGER F RANKI IN GAY, JR. Approved as to style and content by: te . . arpe (Co-Chairman of Committee) s1n 1 U (Co... December 1983 Major Subject: Bioengineering A SOIL MOISTURE AVAILABILITY MODEL FOR CROP STRESS PREDICTION A Thesis by ROGER F RANKI IN GAY, JR. Approved as to style and content by: te . . arpe (Co-Chairman of Committee) s1n 1 U (Co...

Gay, Roger Franklin

2012-06-07

310

ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture  

NASA Technical Reports Server (NTRS)

The measurement of soil moisture from space requires putting relatively large microwave antennas in orbit. Aperture synthesis, an interferometric technique for reducing the antenna aperture needed in space, offers the potential for a practical means of meeting these requirements. An aircraft prototype, electronically steered thinned array L-band radiometer (ESTAR), has been built to develop this concept and to demonstrate its suitability for the measurement of soil moisture. Recent flights over the Walnut Gulch Watershed in Arizona show good agreement with ground truth and with measurements with the Pushbroom Microwave Radiometer (PBMR).

Le Vine, D. M.; Griffis, A.; Swift, C. T.; Jackson, T. J.

1992-01-01

311

Soil Moisture Response to a Changing Climate in Arctic Regions  

NASA Astrophysics Data System (ADS)

Soil moisture is the land surface hydrologic variable that most strongly affects land-atmosphere moisture and energy fluxes. In Arctic regions, these interactions are complicated by the role of permafrost. Especially in northern regions, soil moisture therefore is important not only as a hydrological storage component, also as a result of its strong influence on the hydrological cycle through controls on energy fluxes such as evaporative heat flux, phase change in thawing of permafrost, and effects on thermal conductivity. With projected increases in surface temperature and decreases in surface moisture levels that may be associated with global warming, it is likely that the active layer thickness will increase, leading to subtle but predictable ecosystem responses such as vegetation changes. Field measurements of soil moisture have been collected on the North Slope of Alaska, with emphasis upon establishing macro and micro-topographic influences. Sites were installed in the foothill regions and on the coastal plain of the Kuparuk River basin. Spatially distributed model simulations are being conducted across a range of scales. Preliminary results indicate macro-topographic gradients greatly impact the importance of lateral versus vertical fluxes. Micro-topographic differences affect the small spatial scale differences in soil moisture, but have less impact upon flux direction. Permafrost in arctic regions exerts a significant influence on soil moisture through controls on vegetation and drainage. In relatively flat areas where the frozen layer is near the surface, the soil moisture contents are usually quite high. These areas have relatively high evapotranspiration and sensible heat transfer, but quite low conductive heat transfers due to the insulative properties of thick organic soils. As in more temperate regions, watershed morphology exerts strong controls on hydrological processes; however unique to arctic watersheds are complications arising from the short-term active layer dynamics and longer-term permafrost dynamics. As the active layer becomes thicker throughout the summer, it has a greater capacity to store water, resulting in a time-varying basin response to storm events. As the season progresses, the stream recession rates increase as more hillslope water flows through the soil rather than as overland flow. Peak flows are also more attenuated as the active layer increases in thickness or as permafrost areal extent decreases.

Hinzman, L. D.; Kane, D. L.; Lettenmaier, D.; Yang, D.; Zhao, Y.

2002-12-01

312

Influence of land use on soil moisture spatial-temporal variability and monitoring  

NASA Astrophysics Data System (ADS)

In this study, the influence of land use on soil moisture dynamics is investigated for monitoring purposes. To this end, 23 measurement campaigns were carried out during a period of 8 months at 5 sites located in central Italy, within a catchment of ?6 km2. The sites are characterized by different land uses: grassland, woodland (holm oak and hornbeam) olive grove and cropland. Soil moisture was measured with a portable Time Domain Reflectometer for a layer depth of 15 cm under the soil surface. The optimization of the monitoring scheme was addressed through a statistical and temporal stability analysis. Notwithstanding the significant differences in the land use, the temporal patterns of the field-mean soil moisture of the different sites were very similar while the spatial variability, expressed through the coefficient of variation, was found slightly higher (average value equal to 0.27) than that obtained from previous sampling campaigns on the same area but on sites characterized by a homogeneous soil use. The maximum number of required samples, to estimate the areal mean soil moisture within an accuracy of 2% vol/vol, was found ranging between 7 and 11 at the field scale and equal to 20 at the catchment scale. The temporal stability analysis allowed to identify the grassland site as the most representative of the catchment-mean soil moisture behavior (coefficient of determination, R2 = 0.96). Therefore, even though the heterogeneity of the land use increases the spatial variability (as expected), soil moisture exhibits a significant temporal stability and its large scale monitoring from few observations is still feasible.

Zucco, G.; Brocca, L.; Moramarco, T.; Morbidelli, R.

2014-08-01

313

Downscaling Satellite Soil Moisture Estimates in the Southern Great Plains through a  

E-print Network

2009 #12;Motivation · Soil moisture () is a key variable controlling energy and water fluxes among soil predictions over the ARM CART site derived from 32-km (vs 1 km) soil moisture data and (b) decomposition water storage over portions of the ARM CART region is sufficiently depleted to allow for soil moisture

Vivoni, Enrique R.

314

Root Zone Soil Moisture Assessment Using Passive Microwave Remote Sensing and Distributed Hydrologic Modeling  

Microsoft Academic Search

Soil moisture is a fundamental state variable and it varies spatially due to topography, soil, precipitation variability and landuse-landcover, and temporally, due to difference in hydrologic characteristics and controls. Estimation of profile soil moisture using remotely sensed land surface moisture data with the combination of forward soil hydrologic modeling is very promising. This integrated method may become resourceful solution to

N. N. Das; B. Mohanty

2004-01-01

315

Temporal Stability of Soil Moisture and Radar Backscatter Observed by the Advanced Synthetic Aperture Radar (ASAR)  

Microsoft Academic Search

The high spatio-temporal variability of soil moisture is the result of atmospheric forcing and redistribution processes related to terrain, soil, and vegetation characteristics. Despite this high variability, many field studies have shown that in the temporal domain soil moisture measured at specific locations is correlated to the mean soil moisture content over an area. Since the measurements taken by Synthetic

Wolfgang Wagner; Carsten Pathe; Marcela Doubkova; Daniel Sabel; Annett Bartsch; Stefan Hasenauer; Gnter Blschl; Klaus Scipal; Jos Martnez-Fernndez

2008-01-01

316

Forty-five years of observed soil moisture in the Ukraine: No summer desiccation (yet)  

E-print Network

Forty-five years of observed soil moisture in the Ukraine: No summer desiccation (yet) Alan Robock present the longest data set of observed soil moisture available in the world, 45 yr of gravimetrically- observed plant available soil moisture for the top 1 m of soil, observed every 10 days for April

Robock, Alan

317

22.4 IMPACTS OF PERTURBED SOIL MOISTURE CONDITIONS ON SHORT RANGE ENSEMBLE VARIABILITY  

E-print Network

22.4 IMPACTS OF PERTURBED SOIL MOISTURE CONDITIONS ON SHORT RANGE ENSEMBLE VARIABILITY Christian J (1981) the soil moisture is the soil parameter of primary importance in determining the partition, Lanicci et al. (1987) explored how the soil moisture distribution is important in the development

Hamill, Tom

318

SOIL MOISTURE RETENTION CHARACTERISTICS AND HYDRAULIC CONDUCTIVITY FOR DIFFERENT AREAS IN INDIA IN SELECTED STATES  

E-print Network

SOIL MOISTURE RETENTION CHARACTERISTICS AND HYDRAULIC CONDUCTIVITY FOR DIFFERENT AREAS IN INDIA systems require knowledge of the relationships between soil moisture content (), soil water pressure (h the approximate soil moisture retention curve at the places where only saturated hydraulic conductivity data

Kumar, C.P.

319

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

E-print Network

Soil moisture variability of root zone profiles within SMEX02 remote sensing footprints Minha Choi 31 July 2006 Available online 20 September 2006 Abstract Remote sensing of soil moisture effectively provides soil moisture at a large scale, but does not explain highly heterogeneous soil mois- ture

320

An analytical method for predicting surface soil moisture from rainfall observations  

E-print Network

content in the upper several meters of soil that is available for plant growth. It affects land surfaceAn analytical method for predicting surface soil moisture from rainfall observations Feifei Pan for estimating surface soil moisture directly from rainfall data is proposed and studied. Soil moisture dynamics

Pan, Feifei

321

An inverse method for estimating the spatial variability of soil textures from observed soil moisture fields  

Microsoft Academic Search

Soil texture (sand, clay, silt 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. To study water cycle regionally or globally, we must have a regional or global soil texture database. At the present stage, three soil geographic data

F. Pan; A. W. King; M. J. Sale

2003-01-01

322

SMEX02: Field scale variability, time stability and similarity of soil moisture  

Microsoft Academic Search

Evaluation of air- or space-borne remote sensors measuring soil moisture requires strategic ground-based sampling. As part of the Soil Moisture Experiment 2002 (SMEX02), daily surface soil moisture sampling at 90140 locations were conducted in four fields in Walnut Creek watershed, Iowa. Various combinations of soils, vegetation, and topography characterize the fields. Depending on the field's characteristics and soil moisture content,

Jennifer M. Jacobs; Binayak P. Mohanty; En-Ching Hsu; Douglas Miller

2004-01-01

323

Effectiveness of vertical moisture barriers in highway pavements on expansive soils  

E-print Network

chosen for this study in order to study the effectiveness of vertical moisture barriers in controlling the development of roughness. The moisture condition (suction) in the subgrade soils was measured using either thermal moisture sensors or thermocouple...

Jayatilaka, Ranasinghege

2012-06-07

324

Multi-scale analysis of the impact of increased spatial resolution of soil moisture and atmospheric water vapour on convective precipitation  

NASA Astrophysics Data System (ADS)

The distribution of water vapour in the planetary boundary layer (PBL) and its development over time is one of the most important factors affecting precipitation processes. Despite the dense radiosonde network deployed during the Convective and Orographically-induced Precipitation Study (COPS), the high spatial variability of the water vapour field was not well resolved with respect to the detection of the initiation of convection. The first part of this investigation focuses on the impact of an increased resolution of the thermodynamics and dynamics of the PBL on the detection of the initiation of convection. The high spatial resolution was obtained using the synergy effect of data from the networks of radiosondes, automatic weather stations, synoptic stations, and especially Global Positioning Systems (GPSs). A method is introduced to combine GPS and radiosonde data to obtain a higher resolution representation of atmospheric water vapour. The gained spatial resolution successfully improved the representations of the areas where deep convection likelihood was high. Location and timing of the initiation of convection were critically influenced by the structure of the humidity field in the boundary-layer. The availability of moisture for precipitation is controlled by a number of processes including land surface processes, the latter are strongly influenced by spatially variable fields of soil moisture (SM) and land use. Therefore, an improved representation of both fields in regional model systems can be expected to produce better agreement between modelled and measured surface energy fluxes, boundary layer structure and precipitation. SM is currently one of the least assessed quantities with almost no data from operational monitoring networks available. However, during COPS an innovative measurement approach using a very high number of different SM sensors was introduced. The network consisted of newly developed low-cost SM sensors installed at 43 stations. Each station was equipped with sensors at three different depth (5, 20 and 50cm) simultaneously measuring SM and soil temperature. Within the framework of this work, a strategy to study the effects of SM, evapotranspiration and water vapour in the PBL on convective precipitation is applied on different scales, from local to regional. The SM and atmospheric fields are compared to their related representation within the COSMO-CLM, high-resolution regional model applied in the climate mode. The optimized fields are used for initialization of the model runs to study the impact of surface and PBL processes on convective precipitation. The combination of dense observations with COSMO-CLM simulations permits a rigorous analysis of the water transfer process chain from SM and fluxes to convective initiation and precipitation. This work constitutes a central part of the overall COPS strategy by thorough analysis of the measurement and model data and aims to improve the QPF by better process representation in the regional model COSMO-CLM.

Khodayar, S.; Schaedler, G.; Kalthoff, N.

2010-09-01

325

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

326

Macrofauna assemblage composition and soil moisture interact to affect soil ecosystem functions  

NASA Astrophysics Data System (ADS)

Changing climatic conditions and habitat fragmentation are predicted to alter the soil moisture conditions of temperate forests. It is not well understood how the soil macrofauna community will respond to changes in soil moisture, and how changes to species diversity and community composition may affect ecosystem functions, such as litter decomposition and soil fluxes. Moreover, few studies have considered the interactions between the abiotic and biotic factors that regulate soil processes. Here we attempt to disentangle the interactive effects of two of the main factors that regulate soil processes at small scales - moisture and macrofauna assemblage composition. The response of assemblages of three common temperate soil invertebrates (Glomeris marginata Villers, Porcellio scaber Latreille and Philoscia muscorum Scopoli) to two contrasting soil moisture levels was examined in a series of laboratory mesocosm experiments. The contribution of the invertebrates to the leaf litter mass loss of two common temperate tree species of contrasting litter quality (easily decomposing Fraxinus excelsior L. and recalcitrant Quercus robur L.) and to soil CO2 fluxes were measured. Both moisture conditions and litter type influenced the functioning of the invertebrate assemblages, which was greater in high moisture conditions compared with low moisture conditions and on good quality vs. recalcitrant litter. In high moisture conditions, all macrofauna assemblages functioned at equal rates, whereas in low moisture conditions there were pronounced differences in litter mass loss among the assemblages. This indicates that species identity and assemblage composition are more important when moisture is limited. We suggest that complementarity between macrofauna species may mitigate the reduced functioning of some species, highlighting the importance of maintaining macrofauna species richness.

Collison, E. J.; Riutta, T.; Slade, E. M.

2013-02-01

327

Influence of Soil Moisture on Microbial Activity in a Primary Acidification of Pyritic Soils  

NASA Astrophysics Data System (ADS)

Soil moisture had a grate influence on soil acidification in pyritic soils. The acidification was occurred by chemical and bacterial processes of pyrite oxidation. It was reported that the bacterial oxidation was accelerated by soil moisture at near the condition of plastic limited. We investigated the accelerated soil moisture condition by matric potential and changes of bacterial activity using a soil taken from polder land of the Lake Nakaumi. Six levels of soil moisture conditions were prepared by drying. The samples were incubated at 30oC with keeping these moistures, and populations of Gram-positive and -negative bacteria (GPB and GNB) and Thiobacillus ferrooxidans (total, adsorbed and free forms) were determined. Soil acidification was accelerated at the moisture range from -6.0kPa to -35kPa while drying at 5.4g/h of evaporation rate. Samples drying at 12.0g/h ceased acidifying over -35kPa. On the other hand, a drop of pH value was accelerated at -35kPa when the samples was kept under their moisture conditions. The moisture condition seemed to be suitable for bacterial oxidation. The major bacteria under most of the moisture conditions were GPB, but T. ferrooxidans, one of GNB, was predominated at -35kPa. Under this moisture condition, the growth rate of T. ferrooxidans was highest and the population of GPB decreased during the exponential growth stage of T. ferrooxidans. Acidification of the soil seemed to be depending on proliferation of T. ferrooxidans not on the cell number of T. ferrooxidans. The growth rate of both absorbed and free forms of T. ferrooxidans was highest at -35kPa of all soil moisture conditions. The survival rate of T. ferrooxidans was highest at -3.5kPa and that of the free forms decreased at -35kPa. At -3,000kPa the absorbed forms of T. ferrooxidans had very small population and then decreased. The free forms were not detected. These data indicated that growth habitat of T. ferrooxidans were influenced by soil moisture. The accelerated moisture condition of -35kPa had a uniqueness on the bacterial populations and was suitable for proliferation of T. ferrooxidans. These results showed that high growth rate of T. ferrooxidans had a great influence on high rate of acidification in pyritic soils. The mechanism supposed to be that motility of the bacteria was influenced by shrinkage level of soil matrix and also that the environment was suitable for getting their energy to keep them alive.

Ueno, K.; Adachi, T.

2004-12-01

328

Plants and their relationship to soil moisture and tracer movement  

SciTech Connect

To obtain a better understanding of the mechanisms for possible movement of radionuclides or other toxic materials from waste burial sites in arid to semiarid regions, changes in soil moisture and tracer (Co, Cs, Sr, and tritium) movement were compared for bare vs vegetated soils. During the course of two growing seasons, comparing vegetated with bare soils, plant transpiration processes significantly reduced the soil moisture. In the vegetated soils, most of the Co, Cs, and Sr remained in the region of original emplacement. In bare soils, Co and Cs underwent minimum movement, but the peak concentration of Sr moved downward. For all tracers in the vegetated soils, there was some evidence that slight amounts of tracer had been absorbed in the plant roots and brought to the surface through plant translocation processes. In all cases, there was no significant upward movement of Co, Cs, and Sr. For tritium, the vegetated soils, compared with the bare soils, retained the maximum inventories near the original emplacement location. Although all soils showed some tritium loss, it was greatest in the vegetated soils. A literature review associated with the experiment indicated that plant species alone does not determine rooting depth, rate of transpiration, nutrient uptake, and other plant-associated processes. Environmental conditions are just as important as plant species and must be included in modeling plant-related effects. More data are needed on the effects of tracer concentration, soil water composition, variations in precipitation with time and intensity, evaporation rates, variations in soil composition, soil microorganisms, other invertebrates and vertebrates that inhabit soils, litter decay, and colloid movement on contaminant movement under conditions of unsaturated flow.

Perkins, B.; DePoorter, G.L.

1985-11-01

329

Potential application of satellite radar to monitor soil moisture  

NASA Technical Reports Server (NTRS)

The microwave backscattering characteristics of soils as a function of moisture content are reviewed as a basis for the evaluation of the applicability of satellite radar to soil moisture determinations. Results of experiments showing the dependence of the complex dielectric constant, power reflection coefficient and backscattering coefficient of soil on its volumetric moisture content are presented. Results of a research program using the truck-mounted University of Kansas microwave active spectrometer to determine if, by the proper choice of sensor frequency, polarization and incidence, the sensor dynamic range in response to moisture variations may be greater than its response to other variations are considered in detail, and the optimum conditions of frequency (between 4 and 5 GHz), angular incidence (between 7 and 20 deg from nadir) and polarization (HH) obtained are indicated. An empirical model for the backscattering coefficient as a function of gravimetric moisture content derived on the basis of the experimental data is presented, and it is noted that available airborne and spaceborne data confirm the results of the ground-based sensors.

Ulaby, F. T.; Bradley, G. A.; Dobson, M. C.

1981-01-01

330

Analysis of surface moisture variations within large field sites  

NASA Technical Reports Server (NTRS)

A statistical analysis was made on ground soils to define the general relationship and ranges of values of the field moisture relative to both the variance and coefficient of variation for a given test site and depth increment. The results of the variability study show that: (1) moisture variations within any given large field area are inherent and can either be controlled nor reduced; (2) neither a single value of the standard deviation nor coefficient of variation uniquely define the variability over the complete range of mean field moisture contents examined; and (3) using an upper bound standard deviation parameter clearly defines the maximum range of anticipated moisture variability. 87 percent of all large field moisture content standard deviations were less than 3 percent while about 96 percent of all the computed values had an upper bound of sigma=4 percent for these intensively sampled fields. The limit of accuracy curves of mean soil moisture measurements for large field sites relative to the required number of samples were determined.

Bell, K. R.; Blanchard, B. J.; Witczak, M. W.; Schmugge, T. J.

1979-01-01

331

Potential for Remotely Sensed Soil Moisture Data in Hydrologic Modeling  

NASA Technical Reports Server (NTRS)

Many hydrologic processes display a unique signature that is detectable with microwave remote sensing. These signatures are in the form of the spatial and temporal distributions of surface soil moisture and portray the spatial heterogeneity of hydrologic processes and properties that one encounters in drainage basins. The hydrologic processes that may be detected include ground water recharge and discharge zones, storm runoff contributing areas, regions of potential and less than potential ET, and information about the hydrologic properties of soils and heterogeneity of hydrologic parameters. Microwave remote sensing has the potential to detect these signatures within a basin in the form of volumetric soil moisture measurements in the top few cm. These signatures should provide information on how and where to apply soil physical parameters in distributed and lumped parameter models and how to subdivide drainage basins into hydrologically similar sub-basins.

Engman, Edwin T.

1997-01-01

332

A Flexible Moisture Content Probe for Unsaturated Soil Column Experiments  

SciTech Connect

A commercially available soil moisture capacitance probe was modified by replacing rigid electrode traces with non-intrusive, flexible circuit board trace electrodes that can be attached to the interior of soil column walls. This new design minimizes soil packing difficulties and potential bias in flow pathways commonly associated with rigid probe installations in column experiments. Testing showed that the modified probe design provides reproducible output independent of sample bulk density. The electrical conductivity of the pore-water solution, however, affects the probe response. For cases where the specific conductance of the pore-water solution is constant, the probe can be calibrated. The flexible electrodes offer a simple means of minimizing sensor intrusion into laboratory soil columns while providing reproducible voltage output that is a function of moisture content.

E. D. Mattson; K. E. Baker; C. D. Palmer; J. M Svoboda

2006-05-01

333

The GLOBE Soil Moisture Project's examination of a low-technology method for measuring gravimetric soil moisture  

Microsoft Academic Search

GLOBE (see http:\\/\\/www.globe.org) is an NSF-funded effort that supports a worldwide hands-on, primary and secondary school-based science and education program. The GLOBE Soil Moisture Project (see http:\\/\\/www.hwr.arizona.edu\\/globe\\/sci\\/SM\\/SMC\\/) is a subset of the overall Program, and aims to mobilize GLOBE-participating students worldwide to collect near-surface (i.e. 0-5 cm and 10 cm below ground surface) gravimetric soil moisture data twice a year.

M. P. L. Whitaker; T. P. A. Ferre; B. Nijssen; J. Washburne

2003-01-01

334

Methodology for Predicting Near Surface Soil Moisture.  

National Technical Information Service (NTIS)

A comprehensive model of soil-water dynamics, a 'wetting front' model, was developed and tested. The model represents a variety of flow processes including infiltration, redistribution, drainage and evaporation. The accuracy of the model was tested by com...

G. M. Hornberger, R. B. Clapp, B. J. Cosby

1984-01-01

335

Conservation and Utilization of Soil Moisture.  

E-print Network

below normal rainfall always indicated poor crops. Good to excellent crops have been produced in the dry years of 1924, 1927, 1931 and 1947 with the benefit of timely rainfall oisture stored in the soil during the previous season. ~tal rainfall... below normal rainfall always indicated poor crops. Good to excellent crops have been produced in the dry years of 1924, 1927, 1931 and 1947 with the benefit of timely rainfall oisture stored in the soil during the previous season. ~tal rainfall...

Burnett, Earl; Fisher, C. E.

1953-01-01

336

Observing soil moisture temporal variability under fluctuating climatic conditions  

Microsoft Academic Search

The paper focuses on the observation of interannual and intra-annual climate variability impact on soil moisture temporal patterns and variation, for an experimental site located in Southern Italy and characterized by a typical Mediterranean climate. Analysed data consist of three years soil water content time series measured during the period 2004-2007, under intermediate (2004\\/2005), wet (2005\\/2006) and dry (2006\\/2007) climatological

A. Longobardi

2008-01-01

337

Impact of a Merged Precipitation Data on Global Soil Moisture Variability  

NASA Technical Reports Server (NTRS)

Accurate soil moisture information has proved to be important to climate simulations and climate and weather forecasts. However, many difficulties exist that limit our understanding of soil moisture distribution and variability. One of them is the lack of accurate precipitation with appropriate spatial and temporal resolution. Precipitation as an input forcing to the land surface greatly influences soil moisture characteristics and variability. To improve precipitation data quality, an algorithm has been developed to generate a spatially and temporally continuous 3-hourly global precipitation data for the period of 1987 to present. This precipitation product is a combination of the precipitation from Special Sensor Microwave Imager (SSMI) with the Goddard Earth Observing System-1 Data Assimilation System (GEOS-1 DAS) employing a Physical-space Statistical Analysis System (PSAS). In this study we investigate the impact of this merged/analyzed precipitation data on the global soil moisture variability using an Off-line Land-surface GEOS Assimilation (OLGA) system. Two OLGA integrations starting from 1987 to 1993 are performed forced with the analyzed and GEOS-1 DAS precipitation respectively. We examine the spatial and temporal characteristics of soil moisture variability in response to the analyzed precipitation. The influence of this merged precipitation on the soil moisture variability and regional hydrological budget is estimated throughout the comparison with the results forced with the GEOS-1 DAS precipitation only. In the OLGA the sut@-grid scale horizontal heterogeneity is explicitly represented on the tile space. This provides a means to assess the role of the surface moisture heterogeneity in the interaction with the surface atmosphere and surface hydrological budget, and to validate OLGA results at tile space with in situ observation. ABRACOS (Anglo-Brazilian Amazonian Climate Observation Study), FIFE (First ISLSCP Field Experiment) I and HAPEX data will be used in the validation.

Yang, Runhua; Houser, Paul R.

1999-01-01

338

A comparison of soil moisture sensors for space flight applications  

NASA Technical Reports Server (NTRS)

Plants will be an important part of future long-term space missions. Automated plant growth systems require accurate and reliable methods of monitoring soil moisture levels. There are a number of different methods to accomplish this task. This study evaluated sensors using the capacitance method (ECH2O), the heat-pulse method (TMAS), and tensiometers, compared to soil water loss measured gravimetrically in a side-by-side test. The experiment monitored evaporative losses from substrate compartments filled with 1- to 2-mm baked calcinated clay media. The ECH2O data correlated well with the gravimetric measurements, but over a limited range of soil moisture. The averaged TMAS sensor data overstated soil moisture content levels. The tensiometer data appeared to track evaporative losses in the 0.5- to 2.5-kPa range of matric potential that corresponds to the water content needed to grow plants. This small range is characteristic of large particle media, and thus high-resolution tensiometers are required to distinguish changing moisture contents in this range.

Norikane, J. H.; Prenger, J. J.; Rouzan-Wheeldon, D. T.; Levine, H. G.

2005-01-01

339

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

340

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 Qubec, 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

341

Inter-Comparison of Retrieved and Modelled Soil Moisture and Coherency of Remotely Sensed Hydrology Data  

NASA Astrophysics Data System (ADS)

A neural network algorithm has been developed for the retrieval of Soil Moisture (SM) from global satellite observations. The algorithm estimates soil moisture from a synergy of passive and active microwave, infrared and visible satellite observations in order to capture the different SM variabilities that the individual sensors are sensitive to. The advantages and drawbacks of each satellite observation have been analysed and the information type and content carried by each observation have been determined. A global data set of monthly mean soil moisture for the 1993-2000 period has been computed with the neural network algorithm (Kolassa et al., in press, 2012). The resulting soil moisture retrieval product has then been used in an inter-comparison study including soil moisture from (1) the HTESSEL model (Balsamo et al., 2009), (2) the WACMOS satellite product (Liu et al., 2011), and (3) in situ measurements from the International Soil Moisture Network (Dorigo et al., 2011). The analysis showed that the satellite remote sensing products are well-suited to capture the spatial variability of the in situ data and even show the potential to improve the modelled soil moisture. Both satellite retrievals also display a good agreement with the temporal structures of the in situ data, however, HTESSEL appears to be more suitable for capturing the temporal variability (Kolassa et al., in press, 2012). The use of this type of neural network approach is currently being investigated as a retrieval option for the SMOS mission. Our soil moisture retrieval product has also been used in a coherence study with precipitation data from GPCP (Adler et al., 2003) and inundation estimates from GIEMS (Prigent et al., 2007). It was investigated on a global scale whether the three observation-based datasets are coherent with each other and show the expected behaviour. For most regions of the Earth, the datasets were consistent and the behaviour observed could be explained with the known hydrological processes. In addition, a regional analysis was conducted over several large river basins, including a detailed analysis of the time-lagged correlations between the three datasets and the spatial propagation of observed signals. Results appear consistent with the knowledge of the hydrological processes governing the individual basins. References Adler, R.F., G.J. Huffman, A. Chang, R. Ferraro, P. Xie, J. Janowiak, B. Rudolf, U. Schneider, S. Curtis, D. Bolvin, A. Gruber, J. Susskind, and P. Arkin (2003), The Version 2 Global Precipita- tion Climatology Project (GPCP) Monthly Precipitation Analysis (1979-Present).J. Hydrometeor., 4,1147-1167. Balsamo, G., Viterbo, P., Beljaars, A., van den Hurk, B., Hirschi, M., Betts, A. and Scipa,l K. (2009) A Revised Hydrology for the ECMWF Model: Verification from Field Site to Terrestrial Water Storage and Impact in the Integrated Forecast System, J. Hydrol., 10, 623-643 Dorigo, W. A., Wagner, W., Hohensinn, R., Hahn, S., Paulik, C., Xaver, A., Gruber, A., Drusch, M., Mecklenburg, S., van Oevelen, P., Robock, A., and Jackson, T. (2011), The International Soil Moisture Network: a data hosting facility for global in situ soil moisture measurements, Hydrol. Earth Syst. Sci., 15, 1675-1698 Kolassa, J., Aires, F., Polcher, J., Prigent, C., and Pereira, J. (2012), Soil moisture Retrieval from Multi-instrument Observations: Information Content Analysis and Retrieval Methodology (2012), J. Geophys. Res., Liu, Y. Y., Parinussa, R. M., Dorigo, W. A., De Jeu, R. A. M., Wagner, W., van Dijk, A. I. J. M., McCabe, M. F., and Evans, J. P.(2011), Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals, Hydrol. Earth Syst. Sci., 15, 425-436. Prigent, C., F. Papa, F. Aires, W. B. Rossow, and E. Matthews (2007), Global inundation dy- namics inferred from multiple satellite observations, 1993-2000, J. Geophys. Res., 112, D12107, doi:10.1029/2006JD007847.

Kolassa, Jana; Aires, Filipe

2013-04-01

342

Seasonal soil moisture patterns in contrasting habitats in the Willamette Valley, Oregon  

EPA Science Inventory

Changing seasonal soil moisture regimes caused by global warming may alter plant community composition in sensitive habitats such as wetlands and oak savannas. To evaluate such changes, an understanding of typical seasonal soil moisture regimes is necessary. The primary objective...

343

Ground truth report 1975 Phoenix microwave experiment. [Joint Soil Moisture Experiment  

NASA Technical Reports Server (NTRS)

Direct measurements of soil moisture obtained in conjunction with aircraft data flights near Phoenix, Arizona in March, 1975 are summarized. The data were collected for the Joint Soil Moisture Experiment.

Blanchard, B. J.

1975-01-01

344

Measuring and Modeling Interactions Between Groundwater, Soil Moisture, and Plant Transpiration in Natural and Agricultural Ecosystems  

E-print Network

Measuring and Modeling Interactions Between Groundwater, Soil Moisture, and Plant Transpiration Transpiration in Natural and Agricultural Ecosystems � 2009 by Gretchen Rose Miller #12;1 Abstract Measuring and Modeling Interactions Between Groundwater, Soil Moisture, and Plant Transpiration in Natural

Rubin, Yoram

345

The Soil Moisture Active and Passive Mission (SMAP): Science and Applications  

E-print Network

The soil moisture active and passive mission (SMAP) will provide global maps of soil moisture content and surface freeze/thaw state. Global measurements of these variables are critical for terrestrial water and carbon cycle ...

Entekhabi, Dara

346

Fostering applications opportunities for the NASA Soil Moisture Active Passive (SMAP) mission  

E-print Network

The NASA Soil Moisture Active Passive (SMAP) Mission will provide global observations of soil moisture and freeze/thaw state from space. We outline how priority applications contributed to the SMAP mission measurement ...

Moran, M. Susan

347

Development and Application of a Soil Moisture Downscaling Method for Mobility Assessment.  

National Technical Information Service (NTIS)

Soil moisture is a critical variable for many Army activities including mobility assessments. Several methods can be used to produce soil moisture patterns at an intermediate resolution (grid cells with approximately 1 km linear dimension). However, mobil...

J. D. Niemann, M. L. Coleman

2011-01-01

348

Modeling and application of soil moisture at varying spatial scales with parameter scaling  

E-print Network

The dissertation focuses on characterization of subpixel variability within a satellite-based remotely sensed coarse-scale soil moisture footprint. The underlying heterogeneity of coarse-scale soil moisture footprint is masked by the area...

Das, Narendra Narayan

2009-05-15

349

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

350

The COsmic-ray Soil Moisture Observing System (COSMOS): a non-invasive, intermediate scale soil moisture measurement network  

NASA Astrophysics Data System (ADS)

Soil moisture at a horizontal scale of ca. 600 m averaged over depths of 15-70 cm can be inferred from measurements of cosmic-ray neutrons that are generated within air and soil, moderated mainly by hydrogen atoms in the soil, and emitted back to the atmosphere where they are measured. These neutrons are sensitive to water content changes, largely insensitive to soil chemistry, and their intensity is inversely correlated with hydrogen content of the soil. The measurement with a neutron detector placed above the ground takes minutes to hours, permitting high-resolution, long-term monitoring of undisturbed soil moisture. The ability to provide non-invasive, precise, rapid and continuous measurements over a large footprint make the method suitable for calibration and validation (cal/val) of satellite microwave instruments, such as SMOS and SMAP. We envision three types of cal/val activities. In the first, multiple probes would be installed over the satellite microwave footprint to provide average soil moisture continuously. Given the disparity between the microwave footprint (40 km) and the cosmic-ray footprint (0.6 km), this approach would require a large number of probes, and may be too expensive. The second approach would use a smaller number of stationary probes that would be relocated every hour or so, or probes mounted on moving vehicles, to cover a microwave pixel within a short time. This approach would provide snapshots of soil moisture rather than continuous coverage, but would require a small number of probes and be inexpensive. The third approach would utilize the COsmic-ray Soil Moisture Observing System (COSMOS), which comprises initially a network of 50 probes (to provide a proof of concept) and subsequently 500 probes distributed across the contiguous USA. Additional COSMOS probes are also being deployed on an experimental basis in Australia, Europe, and China. SMOS data could be compared with the changing spatio-temporal pattern of continental soil moisture as sampled by initially 50, subsequently 500 COSMOS probes, ultimately providing a continental scale validation mechanism.

Zreda, Marek; Shuttleworth, W. James; Zweck, Chris; Zeng, Xubin; Ferre, Ty

2010-05-01

351

Simultaneous estimation of both soil moisture and model parameters using particle filtering method through the assimilation of microwave signal  

Microsoft Academic Search

Soil moisture is a very important variable in land surface processes. Both field moisture measurements and estimates from modeling have their limitations when being used to estimate soil moisture on a large spatial scale. Remote sensing is becoming a practical method to estimate soil moisture globally; however, the quality of current soil surface moisture products needs to be improved in

Jun Qin; Shunlin Liang; Kun Yang; Ichiro Kaihotsu; Ronggao Liu; Toshio Koike

2009-01-01

352

SIR-C Measurements of Soil Moisture, Vegetation and Surface Roughness and their Hydrological Application  

NASA Technical Reports Server (NTRS)

The objectives of the study are: (1) Analysis of SIR-C/X-SAR response to soil moisture, vegetation and surface roughness and development of an algorithm to retrieve these parameters; (2) Combination of the visible and near-infrared data and the SIR-C/X-SAR data to improve the range and accuracy of vegetation classification; (3) Testing of theoretical models for microwave propagation with SIR-C/X-SAR and microwave radiometric measurements over rough surfaces; and (4) Evaluation of a water balance model using SIR-C/X-SAR derived soil moisture values and other ancillary data. Progress, significant results and future plans are presented.

Wang, James R.

1996-01-01

353

Effects of Soil Moisture on the Temperature Sensitivity of Soil Heterotrophic Respiration: A Laboratory Incubation Study  

PubMed Central

The temperature sensitivity (Q10) of soil heterotrophic respiration (Rh) is an important ecological model parameter and may vary with temperature and moisture. While Q10 generally decreases with increasing temperature, the moisture effects on Q10 have been controversial. To address this, we conducted a 90-day laboratory incubation experiment using a subtropical forest soil with a full factorial combination of five moisture levels (20%, 40%, 60%, 80%, and 100% water holding capacity - WHC) and five temperature levels (10, 17, 24, 31, and 38C). Under each moisture treatment, Rh was measured several times for each temperature treatment to derive Q10 based on the exponential relationships between Rh and temperature. Microbial biomass carbon (MBC), microbial community structure and soil nutrients were also measured several times to detect their potential contributions to the moisture-induced Q10 variation. We found that Q10 was significantly lower at lower moisture levels (60%, 40% and 20% WHC) than at higher moisture level (80% WHC) during the early stage of the incubation, but became significantly higher at 20%WHC than at 60% WHC and not significantly different from the other three moisture levels during the late stage of incubation. In contrast, soil Rh had the highest value at 60% WHC and the lowest at 20% WHC throughout the whole incubation period. Variations of Q10 were significantly associated with MBC during the early stages of incubation, but with the fungi-to-bacteria ratio during the later stages, suggesting that changes in microbial biomass and community structure are related to the moisture-induced Q10 changes. This study implies that global warmings impacts on soil CO2 emission may depend upon soil moisture conditions. With the same temperature rise, wetter soils may emit more CO2 into the atmosphere via heterotrophic respiration. PMID:24647610

Zhou, Weiping; Hui, Dafeng; Shen, Weijun

2014-01-01

354

Upscaling of field-scale soil moisture measurements using distributed land surface modeling  

Microsoft Academic Search

Accurate coarse-scale soil moisture information is required for robust validation of current- and next-generation soil moisture products derived from spaceborne radiometers. Due to large amounts of land surface and rainfall heterogeneity, such information is difficult to obtain from existing ground-based networks of soil moisture sensors. Using ground-based field data collected during the Soil Moisture Experiment in 2002 (SMEX02), the potential

Wade T. Crow; Dongryeol Ryu; James S. Famiglietti

2005-01-01

355

Spatial variability and its scale dependency of observed and modeled soil moisture over different climate regions  

NASA Astrophysics Data System (ADS)

Past studies on soil moisture spatial variability have been mainly conducted at catchment scales where soil moisture is often sampled over a short time period; as a result, the observed soil moisture often exhibited smaller dynamic ranges, which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness) of in situ soil moisture, modeled and satellite-retrieved soil moisture obtained in a warm season (198 days) were examined over three large climate regions in the US. The study found that spatial moments of in situ measurements strongly depend on climates, with distinct mean, spatial variability and skewness observed in each climate zone. In addition, an upward convex shape, which was revealed in several smaller scale studies, was observed for the relationship between spatial variability of in situ soil moisture and its spatial mean when statistics from dry, intermediate, and wet climates were combined. This upward convex shape was vaguely or partially observable in modeled and satellite-retrieved soil moisture estimates due to their smaller dynamic ranges. Despite different environmental controls on large-scale soil moisture spatial variability, the correlation between spatial variability and mean soil moisture remained similar to that observed at small scales, which is attributed to the boundedness of soil moisture. From the smaller support (effective area or volume represented by a measurement or estimate) to larger ones, soil moisture spatial variability decreased in each climate region. The scale dependency of spatial variability all followed the power law, but data with large supports showed stronger scale dependency than those with smaller supports. The scale dependency of soil moisture variability also varied with climates, which may be linked to the scale dependency of precipitation spatial variability. Influences of environmental controls on soil moisture spatial variability at large scales are discussed. The results of this study should be useful for diagnosing large scale soil moisture estimates and for improving the estimation of land surface processes.

Li, B.; Rodell, M.

2013-03-01

356

Spatial variability and its scale dependency of observed and modeled soil moisture under different climate conditions  

NASA Astrophysics Data System (ADS)

Past studies on soil moisture spatial variability have been mainly conducted in catchment scales where soil moisture is often sampled over a short time period. Because of limited climate and weather conditions, the observed soil moisture often exhibited smaller dynamic ranges which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness) of in situ soil moisture measurements (from a continuously monitored network across the US), modeled and satellite retrieved soil moisture obtained in a warm season (198 days) were examined at large extent scales (>100 km) over three different climate regions. The investigation on in situ measurements revealed that their spatial moments strongly depend on climates, with distinct mean, spatial variability and skewness observed in each climate zone. In addition, an upward convex shape, which was revealed in several smaller scale studies, was observed for the relationship between spatial variability of in situ soil moisture and its spatial mean across dry, intermediate, and wet climates. These climate specific features were vaguely or partially observable in modeled and satellite retrieved soil moisture estimates, which is attributed to the fact that these two data sets do not have climate specific and seasonal sensitive mean soil moisture values, in addition to lack of dynamic ranges. From the point measurements to satellite retrievals, soil moisture spatial variability decreased in each climate region. The three data sources all followed the power law in the scale dependency of spatial variability, with coarser resolution data showing stronger scale dependency than finer ones. The main findings from this study are: (1) the statistical distribution of soil moisture depends on spatial mean soil moisture values and thus need to be derived locally within any given area; (2) the boundedness of soil moisture plays a pivoting role in the dependency of soil moisture spatial variability/skewness on its mean (and thus climate conditions); (3) the scale dependency of soil moisture spatial variability changes with climate conditions.

Li, B.; Rodell, M.

2012-09-01

357

The effect of soil moisture levels on evapotranspiration from cotton and grain sorghum  

E-print Network

OF TABLES Table Page The Coefficients, c and K, Calculated for Sampling Intervals with No Rainfall Using Both Exponential and Uniform Soil Moisture Depletion. . . . . . . . . . 22 II . Data for the Regression of Soil Moisture and Pan Evaporation... on the Coefficients, c and K 24 III . Correlation Coefficients and Their Probability Levels for the Correlation Between the Soil Moisture Accretion and tl-. e Uniform Daily Soil Moisture Depletion 44 Correlaticn Coeffictents and Their Probability Levels...

Schneider, Arland David

2012-06-07

358

Use of soil moisture depletion models and rainfall probability in predicting the irrigation requirements of crops  

E-print Network

fulfillment of requirements for the degree of MASTER OF SCIFiVCE Z!ay 1969 )Zajor Subject: Agricultural Engineering USE OF SOIL MOISTURE DEPLETION MODELS AND RAINFALL PROBABILITY IN PREDICTING THE IRRIGATION REQUIREMENTS OF CROPS A Thesis by Wilfredo P... of the Philippines Directed by: Dr. E. A. Uiler A continuous soil moisture accounting model based on soil moisture depletion equations and soil moisture depletion constants was developed. The model was adapted to an 18. 6-acre experimental watershed and was used...

David, Wilfredo P

2012-06-07

359

Soil microbial community responses to antibiotic-contaminated manure under different soil moisture regimes.  

PubMed

Sulfadiazine (SDZ) is an antibiotic frequently administered to livestock, and it alters microbial communities when entering soils with animal manure, but understanding the interactions of these effects to the prevailing climatic regime has eluded researchers. A climatic factor that strongly controls microbial activity is soil moisture. Here, we hypothesized that the effects of SDZ on soil microbial communities will be modulated depending on the soil moisture conditions. To test this hypothesis, we performed a 49-day fully controlled climate chamber pot experiments with soil grown with Dactylis glomerata (L.). Manure-amended pots without or with SDZ contamination were incubated under a dynamic moisture regime (DMR) with repeated drying and rewetting changes of >20 % maximum water holding capacity (WHCmax) in comparison to a control moisture regime (CMR) at an average soil moisture of 38 % WHCmax. We then monitored changes in SDZ concentration as well as in the phenotypic phospholipid fatty acid and genotypic 16S rRNA gene fragment patterns of the microbial community after 7, 20, 27, 34, and 49 days of incubation. The results showed that strongly changing water supply made SDZ accessible to mild extraction in the short term. As a result, and despite rather small SDZ effects on community structures, the PLFA-derived microbial biomass was suppressed in the SDZ-contaminated DMR soils relative to the CMR ones, indicating that dynamic moisture changes accelerate the susceptibility of the soil microbial community to antibiotics. PMID:24743980

Reichel, Rdiger; Radl, Viviane; Rosendahl, Ingrid; Albert, Andreas; Amelung, Wulf; Schloter, Michael; Thiele-Bruhn, Sren

2014-07-01

360

The role of biological soil crusts in soil moisture dynamics in two semiarid ecosystems with contrasting soil textures  

NASA Astrophysics Data System (ADS)

The interplant soil surfaces in most arid and semiarid ecosystems are covered by biological soil crusts (BSCs). These crusts regulate water inputs and losses through soils and play major roles in local hydrological regimes. In recent years, the role of BSCs in infiltration and runoff has gained increasing importance and better knowledge of 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 hardly been studied, so their effects on these processes remain unknown. The aim of this study was to explore the influence of BSCs on soil moisture regimes in the top layer of the soil in two semiarid ecosystems in SE Spain with different particle-size distributions. At both study sites, soil moisture was monitored at 0.03 and 0.10 m under two types of BSCs, a cyanobacteria-dominated BSC and a lichen-dominated BSC, and in adjacent soils where they had been removed. Our results showed that during wet soil periods, removal of BSCs led to decreased soil moisture, especially in the upper layer (0.03 m), compared to soils covered by BSCs. Decrease in soil moisture was more noticeable after removal of lichens than cyanobacterial BSCs, and more so in fine than in coarse-textured soils. Soil water loss was also generally faster in soils with no BSCs than in soils covered by them. However, no difference was found in soil moisture under either crusted or scalped soils during soil drying periods. The type of BSC influenced soil moisture differently depending on soil water content. During wet soil periods, soil water loss was faster and soil moisture lower under cyanobacterial than under lichen BSCs. On the contrary, during soil drying periods, soils covered by lichens lost water faster and showed lower moisture than those covered by cyanobacteria. Our results show the major role of the presence of BSCs, as well as the types, in soil water content in semiarid ecosystems.

Chamizo, Sonia; Cantn, Yolanda; Lzaro, Roberto; Domingo, Francisco

2013-05-01

361

Microbiology and Moisture Uptake of Desert Soils  

Microsoft Academic Search

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

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

2005-01-01

362

Dielectric properties of soils as a function of moisture content  

NASA Technical Reports Server (NTRS)

Soil dielectric constant measurements are reviewed and the dependence of the dielectric constant on various soil parameters is determined. Moisture content is given special attention because of its practical significance in remote sensing and because it represents the single most influential parameter as far as soil dielectric properties are concerned. Relative complex dielectric constant curves are derived as a function of volumetric soil water content at three frequencies (1.3 GHz, 4.0 GHz, and 10.0 GHz) for each of three soil textures (sand, loam, and clay). These curves, presented in both tabular and graphical form, were chosen as representative of the reported experimental data. Calculations based on these curves showed that the power reflection coefficient and emissivity, unlike skin depth, vary only slightly as a function of frequency and soil texture.

Cihlar, J.; Ulaby, F. T.

1974-01-01

363

Assessing the soil texture specific sensitivity of simulated soil moisture to projected climate change by SVAT modelling  

NASA Astrophysics Data System (ADS)

Climate change is assumed to have a regionally specific impact on the soil moisture regime. The impact of climate change on the soil moisture can be expected to depend on the soil texture. Since soil moisture observations are not available operationally, models can be used to elaborate such sensitivity. In this study, a soil vegetation atmosphere transfer scheme (SVAT) was applied to virtual soil columns to assess the soil texture specific sensitivity of simulated soil moisture to projected climate change. For each of the 31 soil texture classes of the German soil texture classification, long term simulations were carried out based on observed and scenario based climate data representing five different climate regions in Germany. The simulation results indicate that soil moisture regimes considerably differ from region to region and among different soil texture classes. Different soil texture classes showed different sensitivities of soil moisture with respect to projected climate change. While differences in soil moisture between current conditions and SRES climate scenarios were largest for silt soils, they were smallest for clay soils for continental as well as humid climates. Sand and loam soils behaved intermediately, showing a moderate sensitivity. The results also showed that soil texture specific sensitivity of soil moisture to climate change was largest for soils which were not affected by groundwater (no capillary rise). With an increasing influence of groundwater, differences between soil texture classes decreased. In contrast, increasing vegetation density, rooting depths and transpiration demand induced an increasing sensitivity of soil moisture to climate change except for continental climates. This study indicates that validated, physical based soil hydrological models serve as suitable tools to assess the response of soil moisture to changing climate conditions. Based on virtual soil columns, modelling experiments systematically reveal soil texture dependent sensitivities which can hardly be identified in real world studies due to limited availability and accessibility of the wide spectrum of different soil textures.

Bormann, H.

2012-04-01

364

Spatio-temporal evolution and time-stable characteristics of soil moisture within remote sensing footprints with varying soil,  

E-print Network

Spatio-temporal evolution and time-stable characteristics of soil moisture within remote sensing measure soil moisture at the footprint scale, a scale of several hundred square meters or kilometers of within-footprint variability of soil moisture are needed to determine the factors governing hydrologic

Mohanty, Binayak P.

365

A stochastic differential equation approach to soil moisture  

NASA Astrophysics Data System (ADS)

The dynamics of water within the unsaturated root zone of the soil are represented by a pair of stochastic differential equations (SDE's), one representing the so-called surplus state of the moisture and the other the deficit condition. The inputs to the model are the climatically controlled random infiltration events and evapotranspiration which are modeled as a compound Poisson process and a Wiener (Brownian motion) process, respectively. The solutions to these SDE's are not in close-form but sample functions are obtained by numerical integration. The moment properties of the soil moisture evolution process have also been derived analytically including the mean, variance, covariance and autocorrelation functions. To illustrate the model, climatic parameters representing the surplus and deficit cases and properties of clay loam soil have been used to numerically derived the corresponding sample functions. With proper selection of all the parameters, physically realistic sample trajectories can be obtained for the model.

Mtundu, N. D.; Koch, R. W.

1987-06-01

366

Stochastic Soil Moisture Estimation and Forecasting for Irrigated Fields  

NASA Astrophysics Data System (ADS)

A methodology is developed for estimating and forecasting soil water depletion and crop evapotranspiration, with explicit consideration of modeling errors and stochastic inputs. The water balance of an irrigated field and a time series model for reference crop evapotranspiration are formulated in state-space form, with soil moisture depletion and reference evapotranspiration as state variables. The Kalman filter is used to generate estimates and forecasts of the state variables, together with statistical information on their associated errors. Model calibration and validity tests are performed with two independent data sets from locations in Colorado. Each set includes several years of reference crop evapotranspiration data calculated from climatological observations, one season of soil moisture measurements, and concurrent irrigation applications. The estimates, forecasts, and error covariance information provided by the model can allow irrigation decisions to be made with explicit consideration of the inherent risks of crop damage or failure under limitations in water, energy, labor, and capital.

Aboitiz, Martin; Labadie, John W.; Heermann, Dale F.

1986-02-01

367

The effect of soil moisture on mineral nitrogen, soil electrical conductivity, and pH  

Microsoft Academic Search

Inorganic nitrogen in the soil is the source of N for non-legume plants. Rapid methods for monitoring changes in inorganic N concentrations would be helpful for N nutrient management. The effect of varying soil moisture content on soil mineral nitrogen, electrical conductivity (EC), and pH were studied in a laboratory experiment. Soil NO3-N increased as soil water-filled pore space (WFPS)

Rui Zhang; Brian J. Wienhold

2002-01-01

368

Performance of soil moisture retrieval algorithms using multiangular L band brightness temperatures  

Microsoft Academic Search

The Soil Moisture and Ocean Salinity (SMOS) mission of the European Space Agency was successfully launched in November 2009 to provide global surface soil moisture and sea surface salinity maps. The SMOS single payload is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS), an L band two-dimensional aperture synthesis interferometric radiometer with multiangular and polarimetric imaging capabilities. SMOS-derived soil moisture

M. Piles; A. Camps; M. Vall-llossera; A. Monerris; M. Talone; J. M. Sabater

2010-01-01

369

Temporal and spatial soil moisture change pattern detection using multi-temporal Radarsat SCANSAR images  

Microsoft Academic Search

The research has been done to derive the soil moisture information at local scale by using single polarization, single frequency sensors such as ERS-1\\/2, Radarsat, and JERS-1. There is a need to develop a technique to estimate soil moisture information from these currently available data sources at both regional and local scales. In this study, a soil moisture change detection

Yang Hu; Jiancheng Shi; Li Zhen; Huadong Guo; Zhongjun Zhang

2003-01-01

370

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

371

Towards the assimilation of scatterometer derived soil moisture in the ECMWF numerical weather prediction model  

Microsoft Academic Search

The European Centre for Medium-Range Weather Forecasts (ECMWF) currently prepares the assimilation of soil moisture data derived from advanced scatterometer (ASCAT) measurements. ASCAT is part of the METOP satellite payload launched in November 2006 and will assure the operational provision of soil moisture information until at least 2020. In several studies it has been shown that soil moisture derived from

Klaus Scipal; Matthias Drusch; Stefan Hasenauer; Wolfgang Wagner; Alexander Jann

372

Cross evaluation of in-situ, synthetic and remotely sensed surface soil moisture in southwestern France  

Microsoft Academic Search

A long term data acquisition effort of profile soil moisture is currently underway at 12 automatic weather stations located in southwestern France. The SMOSMANIA profile soil moisture network has several objectives including: (i) the validation of the operational soil moisture products of Mto-France, produced by the hydrometeorological model SIM, (ii) the validation of new versions of the land surface model

Clement Albergel; Jean-Christophe Calvet; Eric Martin; Stefan Hasenauer; Naemi Vahid; Wolfgang Wagner; Patricia de Rosnay

2010-01-01

373

Spatiotemporal analyses of soil moisture from point to footprint scale in two different hydroclimatic regions  

E-print Network

Spatiotemporal analyses of soil moisture from point to footprint scale in two different] This paper presents time stability analyses of soil moisture at different spatial measurement support scales soil moisture data from the Southern Great Plains Hydrology Experiments 1997 and 1999 (SGP97 and SGP99

374

On the value of soil moisture measurements in vadose zone hydrology: A review  

E-print Network

On the value of soil moisture measurements in vadose zone hydrology: A review H. Vereecken,1 J. A of soil moisture measurements in vadose zone hydrology with a focus on the field and catchment scales. This review is motivated by the increasing ability to measure soil moisture with unprecedented spatial

Vrugt, Jasper A.

375

UNCORRECTEDPROOF 1 A sequential model for disaggregating near-surface soil moisture observations  

E-print Network

UNCORRECTEDPROOF 1 A sequential model for disaggregating near-surface soil moisture observations 2 12 Available online xxxx 131415 16 Keywords: 17 Disaggregation 18 Soil moisture 19 Fractal 20 Scaling microwave-derived soil moisture from 40 km to 4 km 27resolution using MODIS (Moderate Imaging

Paris-Sud XI, Université de

376

Hysteresis of soil moisture spatial heterogeneity and the "homogenizing" effect of vegetation  

E-print Network

Hysteresis of soil moisture spatial heterogeneity and the "homogenizing" effect of vegetation 16 September 2010. [1] By partitioning mass and energy fluxes, soil