Observations of Surface Water Extent for the Elephant Butte Reservoir in New Mexico

Since the launch of NASA’s Terra satellite in December 1999 the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer has made more than two dozen of observations of the Elephant Butte Reservoir located on the Rio Grande river in central New Mexico. The first observations were in June 2000 and the most recent were in May 2005. This period includes low water levels resulting from the the recent drought conditions and the earlier full high water conditions in 2000. There was about a 25 m change in water level during this time. The area of the reservoir was estimated for each of these scenes and compared with known water levels. The ASTER data were the Level 2 products which include both the visible reflectance and the thermal infrared (surface temperature). Both spectral regions provide good contrasts between water and surrounding land. This contrast makes the area estimation straightforward. There was a large range in surface water area observed from 30,000 km2 to more than 75,000 km2. An approximately linear relation between area and water level was found

TIMS observations of surface emissivity in HAPEX-Sahel

The Thermal Infrared Multispectral Scanner (TIMS) was flown on the NASA C-130 aircraft for a series of 12 flights during HAPEX-Sahel at altitudes ranging from 0.25 to 6 km (0.6 to 15 m resolution). TIMS provides coverage of the 8 to 12 micrometer thermal infrared band in 6 contiguous channels. Thus it is possible to observe the spectral behavior of the surface emissivity over this wavelength interval

Enoxaparin therapy for arterial thrombosis in infants with congenital heart disease

Objective: To investigate efficacy and safety of enoxaparin for catheter-related arterial thrombosis in infants with congenital heart disease. Design: Prospective observational study. Setting: Pediatric Intensive Care and Cardiology Unit at the University Children's Hospital of Zurich. Patients: Acohort of 32 infants aged 0-12 months treated with enoxaparin for catheter-related arterial thrombosis from 2002 to 2005. Measurements: Dose requirements of enoxaparin, resolution of thrombosis by Doppler ultrasound, and bleeding complications. Results: Catheter-related arterial thrombosis was located in the iliac/femoral arteries in 31 (97%) infants and aorta in 1 infant, and was related to indwelling catheters and cardiac catheterization in 17 (53%) and 15 (47%) cases, respectively. Newborns required increased doses of enoxaparin to achieve therapeutic anti-FXa levels (mean 1.62 mg/kg per dose) compared with infants aged 2-12 months (mean 1.12 mg/kg per dose; p = 0.0002). Complete resolution of arterial thrombosis occurred in 29 (91%) infants at amean of 23 days after initiation of enoxaparin therapy. Partial or no resolution was observed in 1 (3%) and 2 (6%) infants, respectively, at amean follow-up time of 4.3 months. Bleeding complications occurred in 1 (3%) infant. Conclusion: Enoxaparin is efficient and safe for infants with congenital heart disease and catheter-related arterial thrombosis, possibly representing avalid alternative to the currently recommended unfractionated hepari

Using Distributed Temperature Sensing to monitor field scale dynamics of ground surface temperature and related substrate heat flux

We present one of the first studies of the use of Distributed Temperature Sensing (DTS) along fibre-optic cables to purposely monitor spatial and temporal variations in ground surface temperature (GST) and soil temperature, and provide an estimate of the heat flux at the base of the canopy layer and in the soil. Our field site was at a groundwater-fed wet meadow in the Netherlands covered by a canopy layer (between 0-0.5 m thickness) consisting of grass and sedges. At this site, we ran a single cable across the surface in parallel 40 m sections spaced by 2 m, to create a 40×40 m monitoring field for GST. We also buried a short length (≈10 m) of cable to depth of 0.1±0.02 m to measure soil temperature. We monitored the temperature along the entire cable continuously over a two-day period and captured the diurnal course of GST, and how it was affected by rainfall and canopy structure. The diurnal GST range, as observed by the DTS system, varied between 20.94 and 35.08◦C; precipitation events acted to suppress the range of GST. The spatial distribution of GST correlated with canopy vegetation height during both day and night. Using estimates of thermal inertia, combined with a harmonic analysis of GST and soil temperature, substrate and soil-heat fluxes were determined. Our observations demonstrate how the use of DTS shows great promise in better characterising area-average substrate/soil heat flux, their spatiotemporal variability, and how this variability is affected by canopy structure. The DTS system is able to provide a much richer data set than could be obtained from point temperature sensors. Furthermore, substrate heat fluxes derived from GST measurements may be able to provide improved closure of the land surface energy balance in micrometeorological field studies. This will enhance our understanding of how hydrometeorological processes interact with near-surface heat fluxes

Soil Moisture Sensing with Microwave Radiometers

The large difference between the dielectric constant of water and dry soils produces a strong dependence of the dielectric properties, and thus emissivity, of wet soils on their moisture content in the microwave (50 \u3e X \u3e 1 cm) region of the electromagnetic spectrum. This change in emissivity with soil moisture content can be measured remotely with microwave radiometers. The variation of emissivity with soil moisture is dependent on the wavelength (A) of observation, soil type, surface roughness and vegetative cover. These dependencies are discussed both theoretically and experimentally. Results obtained from aircraft and spacecraft platforms are presented which give a positive indication of the utility of this remote measurement technique

Soil moisture estimation using L-band radiometry

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Radiometry at infrared wavelengths for agricultural applications

Measurements of thermal radiation at infrared wavelengths (7-14 μm) yield much information about the land surface. The primary use of these observations is for surface temperature determination as the emissivity is usually close to one. For this purpose it is fortuitous that the peak in the thermal emission occurs in an atmospheric transmission window. In additions there are variations in the emissivity of minerals and soils in the 7-14-μm region which can be interpreted for identification purposes. The emissivity for vegetative canopies has been found to be close to one with little spectral variation. Applications of the derived surface temperature to study the surface energy balance and to estimate the energy fluxes from the land surface are discussed. The basic concepts of the energy balance at the land surface are presented along with an example of how remotely sensed surface brightness temperatures can be used to estimate the sensible heat and to estimate plant water use. The example is from the Monsoon 90 experiment conducted over an arid watershed in the state of Arizona in the United States. In this case, surface temperatures derived from an aircraft thermal infrared sensor and vegetation and land use characteristics derived from a Landsat TM image were used in a two-source model to predict the surface heat fluxes. The agreement with ground measurements is reasonably good for the 3 days of observations. (© Inra/Elsevier, Paris.)Applications agricoles de la radiométrie infrarouge. Les mesures de radiation thermique aux longueurs d'ondes infrarouges (7 à 14 μm) fournissent une riche information concernant la surface des terres. Ces observations sont utilisées en premier lieu pour déterminer la température de surface, puisque l'émissivité en est généralement proche. Dans ce cas il arrive par hasard que le pic dans l'émission thermique se trouve dans la fenêtre de transmission atmosphérique. En outre il y a des variations de l'émissivité des minéraux et des sols dans la bande 7 à 14 μm, qui peuvent être interprétées dans des buts d'identification. On a trouvé que l'émissivité des canopées de la végétation était proche de la valeur un, avec une petite variation spectrale. On discute des applications de la température de surface dérivée à l'étude de l'équilibre énergétique de surface et à l'estimation des flux d'énergie envoyé par la surface des terres. Les concepts de base de l'équilibre énergétique à la surface des terres sont présentés avec un exemple qui montre comment les températures de brillance de surface télédétectées peuvent être utilisées pour estimer la chaleur sensible et l'utilisation de l'eau par la plante. L'exemple est tiré de l'expérience Mousson 90 qui a été faite au-dessus d'une ligne de partage des eaux en région aride, dans l'état d'Arizona. Dans ce cas, les températures de surface provenant du détecteur infrarouge thermique de l'avion et les caractéristiques de la végétation et de l'utilisation des terres provenant de l'image Landsat TM ont été utilisées dans un modèle à deux sources pour prédire les flux de chaleur de surface. Les résultats concordent assez bien avec les mesures de terrain faites durant les trois jours d'observation. (© Inra/Elsevier, Paris.