@article{mathers_robarge_walker_sayde_heitman_2024, title={Laboratory observations for examining estimates of soil dry surface layer thickness with parsimonious models}, volume={7}, ISSN={["2150-3435"]}, DOI={10.1080/02626667.2024.2373249}, journal={HYDROLOGICAL SCIENCES JOURNAL}, author={Mathers, Cara and Robarge, Wayne and Walker, John and Sayde, Chadi and Heitman, Joshua}, year={2024}, month={Jul} }
 @article{carvalho_howard_crozier_johnson_sayde_chinn_godfrey iii_heitman_2024, title={Water use and radiation balance of miscanthus and corn on marginal land in the coastal plain region of North Carolina}, volume={16}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.13182}, abstractNote={Abstract Miscanthus is a perennial grass that can yield substantial amounts of biomass in land areas considered marginal. In the Coastal Plain region of North Carolina, marginal lands are typically located in coarse‐textured soils with low nutrient retention and water‐holding capacity, and high erosivity potential. Little is known about miscanthus water use under these conditions. We conducted a study to better understand the efficiency with which miscanthus uses natural resources such as water and radiant energy to produce harvestable dry biomass in comparison to corn, a typical commodity crop grown in the region. We hypothesized that under non‐limiting soil water conditions, miscanthus would have greater available energy and water use rates owing to its greater leaf area, thus leading to greater agronomic yields. Conversely, these effects would be negated under drought conditions. Our measurements showed that miscanthus intercepted more radiant energy than corn, which led to greater albedo (by 0.05), lower net radiation (by 4% or 0.4 MJ m −2 day −1 ), and lower soil heat flux (by 69% or 1.0 MJ m −2 day −1 ) than corn on average. Consequently, miscanthus had greater available energy (by 7% or 0.6 MJ m −2 day −1 ) and water use rates (by 14% or 0.5 mm day −1 ) than corn throughout the growing season on average, which partially confirmed our hypothesis. Greater water use rates and radiation interception by miscanthus did not translate to greater water‐use (1.5 g kg −1 vs. 1.6 g kg −1 ) and radiation‐use (0.9 g MJ −1 vs. 1.1 g MJ −1 ) efficiencies than corn. Compared to literature values, our data indicated that water and radiation availability were not limiting at our study site. Thus, it is likely that marginal land features present at the Coastal Plain region such as low soil fertility and high air temperatures throughout the growing season may constrain agronomic yields even if soil water and radiant energy are non‐limiting.}, number={8}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Carvalho, Henrique D. R. and Howard, Adam M. and Crozier, Carl R. and Johnson, Amy M. and Sayde, Chadi and Chinn, Mari S. and Godfrey III, Edward E. and Heitman, Joshua L.}, year={2024}, month={Aug} }
 @article{hatley_shehata_sayde_castro-bolinaga_2023, title={High-Resolution Monitoring of Scour Using a Novel Fiber-Optic Distributed Temperature Sensing Device: A Proof-of-Concept Laboratory Study}, volume={23}, ISSN={1424-8220}, url={https://doi.org/10.3390/s23073758}, DOI={10.3390/s23073758}, abstractNote={Scour events can severely change the characteristics of streams and impose detrimental hazards on any structures built on them. The development of robust and accurate devices to monitor scour is therefore essential for studying and developing mitigation strategies for these adverse consequences. This technical note introduces a novel scour-monitoring device that utilizes new advances in the fiber-optic distributed temperature sensing (FO-DTS) technology. The novel FO-DTS scour-monitoring device utilizes the differential thermal responses of sediment, water, and air media to a heating event to accurately identify the locations of the interfaces between them. The performance of the device was tested in a laboratory flume under flow conditions with water velocities ranging from 0 m/s to 0.16 m/s. In addition, the effect of the measurement duration on the device’s measurement accuracy was also investigated. The FO-DTS scour-monitoring device managed to detect the sediment–water and water–air interfaces with average absolute errors of 1.60 cm and 0.63 cm, respectively. A measurement duration of fewer than 238 s was sufficient to obtain stable measurements of the locations of the sediment–water and water–air interfaces for all the tested flow conditions.}, number={7}, journal={SENSORS}, author={Hatley, Rebecca and Shehata, Mahmoud and Sayde, Chadi and Castro-Bolinaga, Celso}, year={2023}, month={Apr}, pages={3758} }
 @article{shehata_gentine_nelson_sayde_2023, title={Optimization of the number and locations of the calibration stations needed to monitor soil moisture using distributed temperature sensing systems: A proof-of-concept study}, volume={620}, ISSN={["1879-2707"]}, DOI={10.1016/j.jhydrol.2023.129449}, abstractNote={The single-probe heat-pulse (SPHP) technique combined with the Fiber-optic Distributed Temperature Sensing (DTS) technology can offer novel high-resolution measurements of soil moisture (θ) over spatial scales ranging from several centimeters to several kilometers. However, the key limitation of this method is in obtaining the calibration relationship between θ and soil thermal conductivity (λ) across a specific field. In a previous study, a new methodology using a Gaussian processes model was presented to account for the spatial variability in the λ-θ relationship. The model aggregated θ measurements from soil moisture sensors scattered over the SPHP transect with the corresponding DTS λ measurements at their locations. In this study, a novel methodology is tested to optimize the number and locations of soil moisture sensors required to account for the spatial variability of the λ-θ relationship to achieve higher accuracy from the SPHP technique. The proposed methodology utilizes hierarchical clustering to analyze the information contained in the spatial structure of the SPHP measurements as the soil dries from a nearly-saturated condition. The proposed methodology was tested using data from a field in Oklahoma. Monte-Carlo simulation was performed to validate the performance of the proposed methodology. The predictions obtained from the proposed methodology resulted in θ measurements accuracy comparable to those obtained from the 10% best Monte-Carlo iterations of randomly assigned soil moisture locations. This study demonstrates that the proposed methodology is more efficient than the traditional practice of randomly spreading calibration soil moisture sensors along the SPHP transect.}, journal={JOURNAL OF HYDROLOGY}, author={Shehata, Mahmoud and Gentine, Pierre and Nelson, Natalie and Sayde, Chadi}, year={2023}, month={May} }
 @article{shehata_gentine_nelson_sayde_2022, title={Characterizing soil water content variability across spatial scales from optimized high-resolution distributed temperature sensing technique}, volume={612}, ISSN={["1879-2707"]}, DOI={10.1016/j.jhydrol.2022.128195}, abstractNote={Fiber-optic Distributed Temperature Sensing, when combined with the Single-probe Heat-pulse technique can measure soil moisture (θ) across spatial scales. The key limitation of this system is in obtaining the relationship between soil thermal conductivity (λ) and θ for a specific field. Using the Department of Energy Atmospheric Radiation Measurement (ARM) site, this study tested a new methodology to account for the spatial variability in the λ-θ relationship using a Gaussian processes model. The resulting accurate θ measurements (RMSE = 0.03 m3m−3) were used to characterize the spatial variability of θ across scales and to develop an empirical equation that can correct for the changes in the θ spatial variability observed at different spatial resolutions. In addition, the number of required samples to accurately characterize θ and its variability over scales ranging from 5 m and 350 m were estimated. These findings provide key information to scale soil moisture from centimeters to hundreds of meters for process understanding.}, journal={JOURNAL OF HYDROLOGY}, author={Shehata, Mahmoud and Gentine, Pierre and Nelson, Natalie and Sayde, Chadi}, year={2022}, month={Sep} }
 @article{shehata_heitman_sayde_2022, title={High-Resolution Field Measurement of Soil Heat Capacity and Changes in Soil Moisture Using a Dual-Probe Heat-Pulse Distributed Temperature Sensing Approach}, volume={58}, ISSN={["1944-7973"]}, DOI={10.1029/2021WR031680}, abstractNote={AbstractIncreasing interest in studying the variability of soil water content and its spatial scale dependency necessitates the development of new techniques to accurately monitor soil water over a wide range of spatial scales. Distributed Temperature Sensing (DTS) techniques offer unprecedented opportunities to measure temperature with a spatial resolution of a few centimeters over several kilometers, which can be used to measure soil moisture. This study is the first of its kind that investigates under field conditions the feasibility of combining the Dual‐Probe Heat‐Pulse (DPHP) technique with the DTS technology to measure soil thermal properties and variation in soil moisture. A field experiment was conducted over a 30 m transect in the Lake Wheeler Field laboratory in Raleigh, NC. Three different DPHP sensors were constructed from combinations of different fiber optic cables and heating elements and were tested to assess their performance and the effect of their construction characteristics on their accuracy. Measurements were taken over different soil moisture conditions and the system performance was compared against independent soil water content sensors. The system was able to track changes in soil water content with a mean RMSE of 0.02 m3 m−3 using the optimal DPHP sensor. The key advantage of the tested system is that it does not need any site‐specific calibrations typically required for other DTS‐based systems. The findings of this study provide some practical information and measures that need to be taken for successful DTS‐DPHP construction and application under field conditions.}, number={6}, journal={WATER RESOURCES RESEARCH}, author={Shehata, Mahmoud and Heitman, Joshua and Sayde, Chadi}, year={2022}, month={Jun} }
 @article{cheng_li_argentini_sayde_gentine_2020, title={A Model for Turbulence Spectra in the Equilibrium Range of the Stable Atmospheric Boundary Layer}, volume={125}, ISBN={2169-8996}, DOI={10.1029/2019JD032191}, abstractNote={AbstractStratification can cause turbulence spectra to deviate from Kolmogorov's isotropic 
 power law scaling in the universal equilibrium range at high Reynolds numbers. However, a consensus has not been reached with regard to the exact shape of the spectra. Here we propose a shape of the turbulent kinetic energy and temperature spectra in horizontal wavenumber for the equilibrium range that consists of three regimes at small Froude number: the buoyancy subrange, a transition region, and the isotropic inertial subrange through dimensional analysis and substantial revision of previous theoretical approximation. These spectral regimes are confirmed by various observations in the atmospheric boundary layer. The representation of the transition region in direct numerical simulations will require large‐scale separation between the Dougherty‐Ozmidov scale and the Kolmogorov scale for strongly stratified turbulence at high Reynolds numbers, which is still challenging computationally. In addition, we suggest that the failure of Monin‐Obukhov similarity theory in the very stable atmospheric boundary layer is due to the fact that it does not consider the buoyancy scale that characterizes the transition region.}, number={5}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Cheng, Yu and Li, Qi and Argentini, Stefania and Sayde, Chadi and Gentine, Pierre}, year={2020} }
 @article{shehata_heitman_ishak_sayde_2020, title={High-Resolution Measurement of Soil Thermal Properties and Moisture Content Using a Novel Heated Fiber Optics Approach}, volume={56}, ISSN={["1944-7973"]}, DOI={10.1029/2019WR025204}, abstractNote={AbstractHydrological parameters are scale dependent. Efficient monitoring techniques capable of measuring hydrological parameters, such as soil moisture content (θ), over a wide range of spatial scales are essential for understanding the complexity of water and energy movement across the landscape. Techniques to measure θ over spatial scales in the range from centimeters to thousands of meters, however, are sorely lacking. Recent improvements in the distributed temperature sensing (DTS) technology supported the development of novel techniques to fill that gap. However, improvements in the accuracy and applicability of DTS techniques are still needed. This study investigates the possibility of improving the accuracy of the fiber optics dual‐probe heat‐pulse (FO‐DPHP) DTS technique by using a new design to maintain the spacing between the FO‐DPHP probes and by introducing a novel data interpretation approach. The accuracy of the novel FO‐DPHP design was tested at different θ in a sand column experiment. The FO‐DPHP measurements obtained using traditional and novel data interpretation approaches were compared against independent measurements from several calibrated soil water content (EC5) sensors. Monte‐Carlo analyses were also performed to assess the impact of DTS measurement errors on the accuracy achieved using the data interpretation approaches. The novel design and data interpretation approach allowed for accurate measurements of soil thermal properties and θ without the need to perform a hard‐to‐achieve soil‐specific calibration. Measured θ had mean errors and standard deviations <0.03 and <0.01 m3 m−3, respectively, for moisture conditions ranging from dry to near saturation. The standard deviation in the measured heat capacity was <0.01 MJ m−3 K−1.}, number={7}, journal={WATER RESOURCES RESEARCH}, author={Shehata, Mahmoud and Heitman, Joshua and Ishak, Joseph and Sayde, Chadi}, year={2020}, month={Jul} }
 @article{pfister_lapo_sayde_selker_mahrt_thomas_2019, title={Classifying the nocturnal atmospheric boundary layer into temperature and flow regimes}, volume={145}, ISSN={["1477-870X"]}, DOI={10.1002/qj.3508}, abstractNote={We propose a classification scheme for nocturnal atmospheric boundary layers and apply it to investigate the spatio‐temporal structure of air temperature and wind speed in a shallow valley during the Shallow Cold Pool Experiment. This field campaign was the first to collect spatially continuous temperature and wind information at high resolution (1 s, 0.25 m) using the distributed temperature sensing technique across a 220 m long transect at three heights (0.5, 1.0, 2.0 m). The night‐time classification scheme was motivated by a surface energy balance and used a combination of static stability, wind regime and longwave radiative forcing as quantities to determine physically meaningful boundary‐layer regimes. Out of all potential combinations of these three quantities, 14 night‐time classes contained observations, of which we selected three for detailed analysis and comparison.The three classes represent a transition from mechanical to radiative forcing. The first night class represents conditions with strong dynamic forcing caused by locally induced lee turbulence dominating near‐surface temperatures across the shallow valley. The second night class was a concurrence of enhanced dynamic mixing due to significant winds at the valley shoulders and cold‐air pooling at the bottom of the shallow valley as a result of strong radiative cooling. The third night class was characteristic of weak winds eliminating the impact of mechanical mixing but emphasizing the formation and pooling of cold air at the valley bottom.The proposed night‐time classification scheme was found to sort the experimental data into physically meaningful regimes of surface flow and transport. It is suitable to stratify short‐ and long‐term experimental data for ensemble averaging and to identify case studies.}, number={721}, journal={QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY}, author={Pfister, Lena and Lapo, Karl and Sayde, Chadi and Selker, John and Mahrt, Larry and Thomas, Christoph K.}, year={2019}, month={Apr}, pages={1515–1534} }
 @article{a high resolution measurement of the morning abl transition using distributed temperature sensing and an unmanned aircraft system_2018, url={http://dx.doi.org/10.1007/s10652-017-9569-1}, DOI={10.1007/s10652-017-9569-1}, journal={Environmental Fluid Mechanics}, year={2018}, month={Jun} }
 @article{cheng_sayde_li_basara_selker_tanner_gentine_2017, title={Failure of Taylor's hypothesis in the atmospheric surface layer and its correction for eddy-covariance measurements}, volume={44}, ISSN={0094-8276}, url={http://dx.doi.org/10.1002/2017GL073499}, DOI={10.1002/2017gl073499}, abstractNote={AbstractTaylors' frozen turbulence hypothesis suggests that all turbulent eddies are advected by the mean streamwise velocity, without changes in their properties. This hypothesis has been widely invoked to compute Reynolds averaging using temporal turbulence data measured at a single point in space. However, in the atmospheric surface layer, the exact relationship between convection velocity and wave number k has not been fully revealed since previous observations were limited by either their spatial resolution or by the sampling length. Using Distributed Temperature Sensing (DTS), acquiring turbulent temperature fluctuations at high temporal and spatial frequencies, we computed convection velocities across wave numbers using a phase spectrum method. We found that convection velocity decreases as k−1/3 at the higher wave numbers of the inertial subrange instead of being independent of wave number as suggested by Taylor's hypothesis. We further corroborated this result using large eddy simulations. Applying Taylor's hypothesis thus systematically underestimates turbulent spectrum in the inertial subrange. A correction is proposed for point‐based eddy‐covariance measurements, which can improve surface energy budget closure and estimates of CO2 fluxes.}, number={9}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Cheng, Yu and Sayde, Chadi and Li, Qi and Basara, Jeffrey and Selker, John and Tanner, Evan and Gentine, Pierre}, year={2017}, month={May}, pages={4287–4295} }
 @article{sigmund_pfister_sayde_thomas_2017, title={Quantitative analysis of the radiation error for aerial coiled-fiber-optic distributed temperature sensing deployments using reinforcing fabric as support structure}, volume={10}, ISSN={1867-8548}, url={http://dx.doi.org/10.5194/amt-10-2149-2017}, DOI={10.5194/amt-10-2149-2017}, abstractNote={Abstract. In recent years, the spatial resolution of fiber-optic distributed temperature sensing (DTS) has been enhanced in various studies by helically coiling the fiber around a support structure. While solid polyvinyl chloride tubes are an appropriate support structure under water, they can produce considerable errors in aerial deployments due to the radiative heating or cooling. We used meshed reinforcing fabric as a novel support structure to measure high-resolution vertical temperature profiles with a height of several meters above a meadow and within and above a small lake. This study aimed at quantifying the radiation error for the coiled DTS system and the contribution caused by the novel support structure via heat conduction. A quantitative and comprehensive energy balance model is proposed and tested, which includes the shortwave radiative, longwave radiative, convective, and conductive heat transfers and allows for modeling fiber temperatures as well as quantifying the radiation error. The sensitivity of the energy balance model to the conduction error caused by the reinforcing fabric is discussed in terms of its albedo, emissivity, and thermal conductivity. Modeled radiation errors amounted to −1.0 and 1.3 K at 2 m height but ranged up to 2.8 K for very high incoming shortwave radiation (1000 J s−1 m−2) and very weak winds (0.1 m s−1). After correcting for the radiation error by means of the presented energy balance, the root mean square error between DTS and reference air temperatures from an aspirated resistance thermometer or an ultrasonic anemometer was 0.42 and 0.26 K above the meadow and the lake, respectively. Conduction between reinforcing fabric and fiber cable had a small effect on fiber temperatures (< 0.18 K). Only for locations where the plastic rings that supported the reinforcing fabric touched the fiber-optic cable were significant temperature artifacts of up to 2.5 K observed. Overall, the reinforcing fabric offers several advantages over conventional support structures published to date in the literature as it minimizes both radiation and conduction errors.
                    }, number={6}, journal={Atmospheric Measurement Techniques}, publisher={Copernicus GmbH}, author={Sigmund, Armin and Pfister, Lena and Sayde, Chadi and Thomas, Christoph K.}, year={2017}, month={Jun}, pages={2149–2162} }
 @article{benítez-buelga_rodríguez-sinobas_sánchez calvo_gil-rodríguez_sayde_selker_2016, title={Calibration of soil moisture sensing with subsurface heated fiber optics using numerical simulation}, volume={52}, ISSN={0043-1397}, url={http://dx.doi.org/10.1002/2015WR017897}, DOI={10.1002/2015wr017897}, abstractNote={AbstractThe heat pulse probe method can be implemented with actively heated fiber optics (AHFO) to obtain distributed measurements of soil water content (θ) by using reported soil thermal responses measured by Distributed Temperature Sensing (DTS) and with a soil‐specific calibration relationship. However, most reported applications have been calibrated to homogeneous soils in a laboratory, while inexpensive efficient in situ calibration procedures useful in heterogeneous soils are lacking. Here we employed the Hydrus 2‐D/3‐D code to define a soil‐specific calibration curve. We define a 2‐D geometry of the fiber optic cable and the surrounding soil media, and simulate heat pulses to capture the soil thermal response at different soil water contents. The model was validated in an irrigated field using DTS data from two locations along the FO deployment in which reference moisture sensors were installed. Results indicate that θ was measured with the model‐based calibration with accuracy better than 0.022 m3 m−3.}, number={4}, journal={Water Resources Research}, publisher={American Geophysical Union (AGU)}, author={Benítez-Buelga, Javier and Rodríguez-Sinobas, Leonor and Sánchez Calvo, Raul and Gil-Rodríguez, María and Sayde, Chadi and Selker, John S.}, year={2016}, month={Apr}, pages={2985–2995} }
 @article{mapping high-resolution soil moisture and properties using distributed temperature sensing data and an adaptive particle batch smoother_2016, url={http://dx.doi.org/10.1002/2016wr019031}, DOI={10.1002/2016wr019031}, abstractNote={This study demonstrated a new method for mapping high‐resolution (spatial: 1 m, and temporal: 1 h) soil moisture by assimilating distributed temperature sensing (DTS) observed soil temperatures at intermediate scales. In order to provide robust soil moisture and property estimates, we first proposed an adaptive particle batch smoother algorithm (APBS). In the APBS, a tuning factor, which can avoid severe particle weight degeneration, is automatically determined by maximizing the reliability of the soil temperature estimates of each batch window. A multiple truth synthetic test was used to demonstrate the APBS can robustly estimate soil moisture and properties using observed soil temperatures at two shallow depths. The APBS algorithm was then applied to DTS data along a 71 m transect, yielding an hourly soil moisture map with meter resolution. Results show the APBS can draw the prior guessed soil hydraulic and thermal properties significantly closer to the field measured reference values. The improved soil properties in turn remove the soil moisture biases between the prior guessed and reference soil moisture, which was particularly noticeable at depth above 20 cm. This high‐resolution soil moisture map demonstrates the potential of characterizing soil moisture temporal and spatial variability and reflects patterns consistent with previous studies conducted using intensive point scale soil moisture samples. The intermediate scale high spatial resolution soil moisture information derived from the DTS may facilitate remote sensing soil moisture product calibration and validation. In addition, the APBS algorithm proposed in this study would also be applicable to general hydrological data assimilation problems for robust model state and parameter estimation.}, journal={Water Resources Research}, year={2016}, month={Oct} }
 @article{cosh_ochsner_mckee_dong_basara_evett_hatch_small_steele-dunne_zreda_et al._2016, title={The Soil Moisture Active Passive Marena, Oklahoma, In Situ Sensor Testbed (SMAP-MOISST): Testbed Design and Evaluation of In Situ Sensors}, volume={15}, ISSN={1539-1663}, url={http://dx.doi.org/10.2136/vzj2015.09.0122}, DOI={10.2136/vzj2015.09.0122}, abstractNote={Core Ideas
Soil moisture sensors have varying accuracies that can be improved with calibration.
In situ sensors require scaling to improve their representativeness of large areas.
Soil moisture sensors in profile have decreasing ability to accurately represent the surface soil moisture.
In situ soil moisture monitoring networks are critical to the development of soil moisture remote sensing missions as well as agricultural and environmental management, weather forecasting, and many other endeavors. These in situ networks utilize a variety of sensors and installation practices, which confounds the development of a unified reference database for satellite calibration and validation programs. As part of the Soil Moisture Active Passive Mission, the Marena, Oklahoma, In Situ Sensor Testbed (SMAP‐MOISST) was initiated to perform inter‐comparisons and study sensor limitations. Soil moisture sensors that are deployed in major monitoring networks were included in the study, along with new and emerging technologies, such as the Cosmic Ray Soil Moisture Observing System (COSMOS), passive/active distributed temperature sensing (DTS), and global positioning system reflectometers (GPSR). Four profile stations were installed in May of 2010, and soil moisture was monitored to a depth of 1 m on an hourly basis. The four stations were distributed within a circular domain of approximately 600 m diameter, adequate to encompass the sensing range of COSMOS. The sensors included in the base station configuration included the Stevens Water Hydra Probe, Campbell Scientific 616 and 229, Decagon EC‐TM, Delta‐T Theta Probe, Acclima, and Sentek EnviroSMART capacitance system. In addition, the Pico TRIME system and additional time‐domain reflectometry (TDR) systems were deployed when available. It was necessary to apply site‐specific calibration to most sensors to reach an RMSE below 0.04 m3 m−3. For most sensor types, a single near surface sensor could be scaled to represent the areal‐average of a field domain by simple linear regression, resulting in RMSE values around 0.03 m3 m−3.}, number={4}, journal={Vadose Zone Journal}, publisher={Wiley}, author={Cosh, Michael H. and Ochsner, Tyson E. and McKee, Lynn and Dong, Jingnuo and Basara, Jeffrey B. and Evett, Steven R. and Hatch, Christine E. and Small, Eric E. and Steele-Dunne, Susan C. and Zreda, Marek and et al.}, year={2016}, pages={0} }
 @article{sayde_thomas_wagner_selker_2015, title={High-resolution wind speed measurements using actively heated fiber optics}, volume={42}, ISSN={0094-8276}, url={http://dx.doi.org/10.1002/2015GL066729}, DOI={10.1002/2015gl066729}, abstractNote={AbstractWe present a novel technique to simultaneously measure wind speed (U) at thousands of locations continuously in time based on measurement of velocity‐dependent heat transfer from a heated surface. Measuring temperature differences between paired passive and actively heated fiber‐optic (AHFO) cables with a distributed temperature sensing system allowed estimation of U at over 2000 sections along the 230 m transect (resolution of 0.375 m and 5.5 s). The underlying concept is similar to that of a hot wire anemometer extended in space. The correlation coefficient between U measured by two colocated sonic anemometers and the AHFO were 0.91 during the day and 0.87 at night. The combination of classical passive and novel AHFO provides unprecedented dynamic observations of both air temperature and wind speed spanning 4 orders of magnitude in spatial scale (0.1–1000 m) while resolving individual turbulent motions, opening new opportunities for testing basic theories for near‐surface geophysical flows.}, number={22}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Sayde, Chadi and Thomas, Christoph K. and Wagner, James and Selker, John}, year={2015}, month={Nov}, pages={10,064–10,073} }
 @article{benítez-buelga_sayde_rodríguez-sinobas_selker_2014, title={Heated Fiber Optic Distributed Temperature Sensing: A Dual-Probe Heat-Pulse Approach}, volume={13}, ISSN={1539-1663}, url={http://dx.doi.org/10.2136/vzj2014.02.0014}, DOI={10.2136/vzj2014.02.0014}, abstractNote={Implementation of the dual‐probe heat‐pulse (DPHP) approach for measurement of volumetric heat capacity (C) and water content (θ) with distributed temperature sensing heated fiber optic (FO) systems presents an unprecedented opportunity for environmental monitoring (e.g., simultaneous measurement at thousands of points). We applied uniform heat pulses along a FO cable and monitored the thermal response at adjacent cables. We tested the DPHP method in the laboratory using multiple FO cables at a range of spacings. The amplitude and phase shift in the heat signal with distance was found to be a function of the soil volumetric heat capacity. Estimations of C at a range of moisture contents (θ = 0.09– 0.34 m3 m−3) suggest the feasibility of measurement via responsiveness to the changes in θ, although we observed error with decreasing soil water contents (up to 26% at θ = 0.09 m3 m−3). Optimization will require further models to account for the finite radius and thermal influence of the FO cables. Although the results indicate that the method shows great promise, further study is needed to quantify the effects of soil type, cable spacing, and jacket configurations on accuracy.}, number={11}, journal={Vadose Zone Journal}, publisher={Wiley}, author={Benítez-Buelga, Javier and Sayde, Chadi and Rodríguez-Sinobas, Leonor and Selker, John S.}, year={2014}, pages={0} }
 @article{sayde_buelga_rodriguez-sinobas_el khoury_english_van de giesen_selker_2014, title={Mapping variability of soil water content and flux across 1-1000 m scales using the Actively Heated Fiber Optic method}, volume={50}, ISSN={0043-1397}, url={http://dx.doi.org/10.1002/2013WR014983}, DOI={10.1002/2013wr014983}, abstractNote={AbstractThe Actively Heated Fiber Optic (AHFO) method is shown to be capable of measuring soil water content several times per hour at 0.25 m spacing along cables of multiple kilometers in length. AHFO is based on distributed temperature sensing (DTS) observation of the heating and cooling of a buried fiber‐optic cable resulting from an electrical impulse of energy delivered from the steel cable jacket. The results presented were collected from 750 m of cable buried in three 240 m colocated transects at 30, 60, and 90 cm depths in an agricultural field under center pivot irrigation. The calibration curve relating soil water content to the thermal response of the soil to a heat pulse of 10 W m−1 for 1 min duration was developed in the lab. This calibration was found applicable to the 30 and 60 cm depth cables, while the 90 cm depth cable illustrated the challenges presented by soil heterogeneity for this technique. This method was used to map with high resolution the variability of soil water content and fluxes induced by the nonuniformity of water application at the surface.}, number={9}, journal={Water Resources Research}, publisher={American Geophysical Union (AGU)}, author={Sayde, Chadi and Buelga, Javier Benitez and Rodriguez-Sinobas, Leonor and El Khoury, Laureine and English, Marshall and van de Giesen, Nick and Selker, John S.}, year={2014}, month={Sep}, pages={7302–7317} }
 @inproceedings{broda_sayde_selker_aubertin_blessent_2013, place={Montréal, QC, Canada}, title={Using temperature as a tracer for analyzing the response of a capillary barrier in waste rock}, volume={29}, booktitle={66th Canadian Geotechnical Conference}, author={Broda, S. and Sayde, C. and Selker, J. and Aubertin, M. and Blessent, D.}, year={2013} }
 @inproceedings{hillyer_sayde_2010, place={Phoenix, Arizona}, title={A Web Based Advisory Service For Optimum Irrigation Management}, DOI={10.13031/2013.35837}, abstractNote={When irrigation is optimized to maximize net economic returns, some level of deficit irrigation is required. However, the theoretical, technical, and practical challenges associated with deficit irrigation scheduling are far more complex than conventional (full) irrigation. Oregon State University and the NRCS have cooperatively developed a web-based application for optimum irrigation management. This system, Irrigation Management Online (IMO), explicitly analyzes irrigation efficiency, accounts for spatial variability of soil properties and irrigation uniformity, performs simultaneous scheduling for all fields in the farm, accounts for energy use and its associated costs, and uses both ET and soil moisture measurements to enhance the accuracy of the irrigation schedules. IMO has been developed specifically to support irrigation management when either water supplies or delivery system capacities are limited. To mitigate the complexities of irrigation constraints the system has been designed so that the irrigation manager is an integral part of the irrigation optimization procedure.}, number={IRR10-9854}, booktitle={5th National Decennial Irrigation Conference Proceedings}, publisher={American Society of Agricultural and Biological Engineers}, author={Hillyer, C. and Sayde, C.}, year={2010}, month={Dec}, pages={5–8} }
 @article{sayde_gregory_gil-rodriguez_tufillaro_tyler_van de giesen_english_cuenca_selker_2010, title={Feasibility of soil moisture monitoring with heated fiber optics}, volume={46}, ISSN={0043-1397}, url={http://dx.doi.org/10.1029/2009WR007846}, DOI={10.1029/2009wr007846}, abstractNote={Accurate methods are needed to measure changing soil water content from meter to kilometer scales. Laboratory results demonstrate the feasibility of the heat pulse method implemented with fiber optic temperature sensing to obtain accurate distributed measurements of soil water content. A fiber optic cable with an electrically conductive armoring was buried in variably saturated sand and heated via electrical resistance to create thermal pulses monitored by observing the distributed Raman backscatter. A new and simple interpretation of heat data that takes advantage of the characteristics of fiber optic temperature measurements is presented. The accuracy of the soil water content measurements varied approximately linearly with water content. At volumetric moisture content of 0.05 m3/m3 the standard deviation of the readings was 0.001 m3/m3, and at 0.41 m3/m3 volumetric moisture content the standard deviation was 0.046 m3/m3. This uncertainty could be further reduced by averaging several heat pulse interrogations and through use of a higher‐performance fiber optic sensing system.}, number={6}, journal={Water Resources Research}, publisher={American Geophysical Union (AGU)}, author={Sayde, Chadi and Gregory, Christopher and Gil-Rodriguez, Maria and Tufillaro, Nick and Tyler, Scott and van de Giesen, Nick and English, Marshall and Cuenca, Richard and Selker, John S.}, year={2010}, month={Jun} }
 @inproceedings{sayde_gitelman_hillyer_el khoury_2010, place={Phoenix, Arizona}, title={Reducing the uncertainty of soil moisture water determinations}, DOI={10.13031/2013.35842}, abstractNote={Scientific irrigation scheduling often relies on calculated ET to estimate daily soil moisture water depletion. Since the resulting estimates of soil water content are uncertain, and become increasingly uncertain as ET estimation errors accumulate over a period of time, it is common practice to measure soil water periodically to correct the soil water content estimates. But soil water content measurements are also subject to substantial error. While both ET-based estimates and field measurements of soil water content provide useful information, neither is sufficiently accurate for purposes of precise irrigation management. An algorithm for minimizing uncertainty of soil water content determinations is presented. Based on Bayesian decision analysis, the algorithm integrates information from ET estimates and soil water content measurements to derive a posterior estimation of soil water status that has the potential to provide a better basis for irrigation decisions.}, number={IRR10-9853IRR10-9853}, booktitle={5th National Decennial Irrigation Conference Proceedings}, publisher={American Society of Agricultural and Biological Engineers}, author={Sayde, C. and Gitelman, A. and Hillyer, C. and El Khoury, L.}, year={2010}, month={Dec}, pages={IRR10–9853} }
 @inproceedings{hillyer_english_abourached_sayde_hutchinson_busch_2009, title={A Web-Based Advisory Service for Optimum Irrigation Management}, ISBN={9780784410363}, url={http://dx.doi.org/10.1061/41036(342)407}, DOI={10.1061/41036(342)407}, abstractNote={The optimum (profit maximizing) level of irrigation water use is usually less than the yield maximizing level, particularly when water has an associated opportunity cost. However, the amount of analysis required to implement a profit maximizing strategy is usually too time consuming to be practical for most farmers. Furthermore the practical operational constraints imposed on typical irrigation practices are usually too complicated to be fully encapsulated in software. Oregon State University and the NRCS have cooperatively developed a web-based, user-directed application for optimum irrigation management. This system has already completed two years of field trails and has a demonstrated capacity for delivering conventional irrigation schedules. The system is now entering a second phase of development where we are adding new analytical tools that enable easy generation of optimum irrigation schedules. This system, known as Irrigation Management Online (IMO), explicitly analyzes irrigation efficiency and yield reductions for deficit irrigation, performs simultaneous, conjunctive scheduling for all fields in the farm that share a limited water supply, and employs both ET and soil moisture measurements in a Bayesian decision analysis to enhance the accuracy of the irrigation schedules. To mitigate the complexities of irrigation constraints the system has been designed so that the user is an integral part of the irrigation optimization procedure.}, booktitle={World Environmental and Water Resources Congress 2009}, publisher={American Society of Civil Engineers}, author={Hillyer, Charles and English, Marshall and Abourached, Carole and Sayde, Chadi and Hutchinson, Kent and Busch, John}, year={2009}, month={May} }
 @inproceedings{sayde_selker_english_2009, place={Great Rivers, MO}, title={Measuring Soil Moisture in a Heterogeneous Field}, ISBN={9780784410363}, url={http://dx.doi.org/10.1061/41036(342)439}, DOI={10.1061/41036(342)439}, abstractNote={This paper explores the theoretical basis, preliminary experimental results and potential benefits of using fiber optic technology for distributed measurement of field soil moisture. This technology determines soil moisture content by measurement of soil thermal response to a heat pulse. With a resolution of 1 m along a fiber optic cable this technique is capable of literally hundreds of measurements along a single cable installed at a specific depth. The technology is still under development at the time of this writing, but the indications are that it can quantify soil water variability with relatively high accuracy at moderate cost.}, booktitle={World Environmental and Water Resources Congress 2009}, publisher={American Society of Civil Engineers}, author={Sayde, Chadi and Selker, John and English, Marshall}, year={2009}, month={May} }
 @inproceedings{english_sayde_gitelman_el khoury_2008, place={Honolulu, Hawaii}, title={A Feedback System to Optimize Crop Water Use Estimates in Irrigation Scheduling}, ISBN={9780784409763}, url={http://dx.doi.org/10.1061/40976(316)104}, DOI={10.1061/40976(316)104}, abstractNote={This paper deals with errors in estimation of soil water depletion inirrigation management. Such errors can reduce net economic returns to water, increase economic risk and motivate risk averse farm managers to adopt less profitable strategies. Two common methods of estimating depletion are discussed, one based on cumulative ET the other on soil moisture measurements. Both are characterized by significant uncertainty. It is common practice to rely on one or the other of these estimators for irrigation scheduling. This paper proposes an alternative approach that utilizes both estimators in combination. Rather than treating them as deterministic quantities, they are treated as random variables. The probability distributions of each are combined in a Bayesian analysis to derive a probability distribution of depletion, which then provides a better basis for irrigation decisions.}, booktitle={World Environmental and Water Resources Congress 2008}, publisher={American Society of Civil Engineers}, author={English, Marshall and Sayde, Chadi and Gitelman, Alix and El Khoury, Laureine}, year={2008}, month={May} }
 @inproceedings{sayde_khoury_gitelman_english_2008, place={Providence, Rhode Island}, title={Optimizing estimates of soil moisture for irrigation scheduling}, DOI={10.13031/2013.25158}, abstractNote={Irrigation scheduling commonly involves a water balance analysis in which daily estimates of ET are used to compute cumulative soil water depletion, and occasional soil moisture measurements are used to ‘correct’ the estimate of depletion. However, both ET estimates and soil moisture measurements are characterized by significant uncertainty, and both produce uncertain estimates of depletion. When water use is not limited the problem of uncertainty can be avoided by maintaining soil moisture at higher than critical levels, relying on moisture measurements to decide when to irrigate, and keeping some soil water in reserve as a hedge against uncertainty. On the other hand, deficit irrigation, an increasingly common strategy for maximizing net economic returns to limited water, must be managed differently. Deficit irrigation strategies allow the crop to be stressed to some degree,which implies there will be no soil moisture held in reserve. But errors in management of crop stress can be costly.}, number={084699084699}, booktitle={Proceedings of the 2008 ASABE Annual International Meeting}, publisher={American Society of Agricultural and Biological Engineers}, author={Sayde, C. and Khoury, L. and Gitelman, A. and English, M.}, year={2008}, month={Jun} }
 @inproceedings{abourached_hillyer_sayde_english_bush_2007, place={Minneapolis, Minnesota}, title={A web-based advisory service for optimum irrigation management}, number={072253}, booktitle={Proceedings of the 2007 ASABE Annual International Meeting}, publisher={American Society of Agricultural and Biological Engineers}, author={Abourached, C. and Hillyer, C. and Sayde, C. and English, M. and Bush, J.}, year={2007}, pages={1–12} }