Canopy temperatures were measured on durum wheat grown in six differentially irrigated plots. Soil water content was measured by using a neutron-scattering technique at two locations within each plot. Water contents, in 20-cm increments to 160 cm, were determined two to five times per week. Using a sliding cubic smoothing technique, we calculated daily water contents and thus water depletion rates for the entire growing season. Canopy temperatures were measured daily between 1330 and 1400 hours. Air temperatures measured at 150 cm above the soil surface were subtracted from the canopy temperatures to form the difference Tc – Ta. The summation of Tc – Ta over time yielded a factor termed the ‘stress degree day’ (SDD). The SDD concept shows promise as an indicator for determining the times and amounts of irrigations. An expression relating evapotranspiration (ET) to net radiation and Tc – Ta was simplified and tested by using ET measurements with a lysimeter. The expression was used to predict water use by wheat in the six plots. Predicted ET and measured water used agreed reasonably well. The expression may be useful in determining amounts of irrigation water to apply.

Wheat canopy temperature: A practical tool for evaluating water requirements

Crop coefficient and ratio of transpiration to evapotranspiration of winter wheat and maize in a semi-humid region

In this paper we review the current status for deriving land surface temperatures (LSTs) by remote sensing from satellites in the thermal infrared. Because of its widespread use and global applicability, we concentrate on the Advanced Very High Resolution Radiometer (AVHRR). The theoretical framework and methodologies used to derive LSTs are reviewed and amplified. Practical algorithms are described and their accuracy and application critically evaluated through sensitivity studies and by inter‐comparison. The important effects of the atmosphere, surface emissivity and instrument noise are considered and the current practice for removing these effects is specified. The accuracy currently attainable from the AVHRR for the LST algorithms studied lies between 1 and 2 K, depending critically upon the surface characteristics and the atmospheric structure. Suggestions about what improvements could be made to reduce the errors in LST estimation from space and the directions of future research are summar...

Thermal remote sensing of land surface temperature from satellites: Current status and future prospects

Calculating potential and actual evaporation from a bare soil surface by simulation of concurrent flow of water and heat

Emissivity measurements of several soils and vegetation types in the 8-14, μm Wave band: Analysis of two field methods

The temperature of a naturally exposed, bare wet soil surface was measured with a narrow bandpass infrared radiation thermometer. Corrections were made for actual sky radiance and for surface emittance, the latter also determined in the field. When used to calculate evaporation rates with a Dalton-type equation containing a log-law wind function (drag coefficient × windspeed), excellent agreement was found with lysimeter values on both an hourly and daily basis. The results demonstrate the feasibility of surface temperature measurements and support the validity of the log law for describing transfer in the surface layer.

Evaporation from a Wet Soil Surface Calculated from Radiometrically Determined Surface Temperatures

: The report deals with the measurement of surface temperature under field conditions using an infrared radiometer with a bandpass of 600 to 1300/cm (16 - 7.5 microns). The usefulness of such a method in measuring latent and sensible heat flux over a wet, bare soil surface is explored. A review is given of similar work reported by others and of available methods for using surface temperatures in flux calculations. The theory of infrared thermometry is extensively reviewed and the necessity of measuring surface emittance and sky radiance is explained. A description is given of experimental methods for the calibration of the radiation thermometer, the measurement of surface emittance and of sky radiance, the latter employing a standard surface of which the temperature is monitored. Also, an account is given of equipment and methods for routine measurement of surface temperatures in the field. On three days in the spring of 1966, a comparison was made of measured and calculated evaporation. The measurements were obtained with weighable lysimeters and the calculations based upon radiometrically obtained surface temperatures. The agreement was excellent, proving the adequacy of the log-law transfer function relating vapor gradient to vapor flux. This function can be stated simply as the product of windspeed and drag coefficient. A comparison of similarly computed sensible heat flux with residual values for the same quantity obtained from the energy balance proved inconclusive. This result is attributed mainly to the incidence of vertical divergence of sensible heat flux and to the inequality of transfer coefficients for momentum and sensible heat. (Author)

Remote measurement of surface temperature and its application to energy balance and evaporation studies of bare soil surfaces.

Radiometric Surface Temperature Measurements and Fluctuations in Sky Radiant Emittance in the 600 to 1300 cm−1 Waveband 1


 The use of fiber-optic-sensing technology for the evaluation of completion efficiency, primary cement sheath integrity, and offset well interference has become more prevalent in recent years. In addition, the use of a fiber-optic cable for microseismic monitoring as opposed to traditional wireline-conveyed geophones was recently introduced. Various fiber deployment methods have been developed over the years to allow operators to make rapid decisions in real-time based on distributed acoustic sensing (DAS), distributed temperature sensing (DTS), and microseismic data, all provided by a small fiber- optic cable deployed in the well and monitored at surface via sophisticated interrogation equipment.
 Historically, fiber-optic cables were deployed in a permanent configuration, strapped to the production casing, in a manner similar to a standard control line, and deployed with the casing prior to cementing. Permanent fiber has become simpler and cost effective over time and provides valuable near wellbore information - and there are continuous developments to keep reducing that cost and complexity. Some operator focus has been less on the monitoring of the completion efficiency metrics and more on understanding the cross well interference data provided from fiber. As a result, operators have looked to other, temporary-type deployment options for fiber.
 Two typical temporary deployments are via coiled-tubing and an armored fiber-optic cable. For the first method, a fiber-optic cable is fed into a coiled-tubing reel and then deployed downhole to monitor the strain when the well is impacted or closely impacted by a hydraulic fracture from an adjacent well. An armored fiber-optic cable deployment is similar to electric wireline in that it is installed in the well during pump down or with a wireline tractor.
 Both these options are viable and readily available; however, they include supplementary expenses in terms of equipment required to convey the fiber into the well. In addition, the surface footprint required during the conveyance and monitoring phases of the operation is substantial with crane(s), a coiled-tubing unit or wireline unit, and associated on-location equipment required during the job. Figure 1 depicts a wireline-conveyed fiber operation in conjunction with fracturing operations. Additional equipment in the form of a wireline truck and extra crane are highlighted in yellow. In contrast, a wellsite where disposable fiber is being deployed is shown in Figure 2. Once the fiber is landed, the pump units are removed and only a trailer and crew pickup remain on-site.
 Figure 1 Typical fracturing operation, wireline-conveyed fiber
 Figure 2 Typical offset well monitoring wellsite, disposable fiber
 This paper will discuss a new, low-cost option now available to conduct cross well monitoring and microseismic evaluation of offset completions using a disposable optical fiber that requires minimal equipment to deploy into the wellbore, reduces surface impact during the operational phase, provides quality strain information with excellent quality microseismic data when compared to other fiber-optic deployment methods, and is able to be disposed of at the conclusion of the operation with no detriments or impediments to the completion of the well it has been deployed in. This fiber was successfully deployed for the first time in the Marcellus Shale for Chesapeake Energy with minimal operational disturbance and reduced costs when compared to similar technologies. It was demonstrated to provide valuable data for the purposes of understanding the impact of hydraulic fracturing on far-field communication and evaluating both the temporal fracture response and zonal impact caused by structural changes across the lateral.

Application of Disposable Fiber Technology to Evaluate Far-Field Communication and Fracture Performance in the Marcellus Shale

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Evaporation from a Wet Soil Surface Calculated from Radiometrically Determined Surface Temperatures

Remote measurement of surface temperature and its application to energy balance and evaporation studies of bare soil surfaces.

Radiometric Surface Temperature Measurements and Fluctuations in Sky Radiant Emittance in the 600 to 1300 cm−1 Waveband 1

Application of Disposable Fiber Technology to Evaluate Far-Field Communication and Fracture Performance in the Marcellus Shale