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  • American Geophysical Union (AGU)  (5)
  • 1
    Online Resource
    Online Resource
    Free‐air CO 2 enrichment and soil nitrogen effects on energy balance and evapotranspiration of wheat
    American Geophysical Union (AGU) ; 1999
    In:  Water Resources Research Vol. 35, No. 4 ( 1999-04), p. 1179-1190
    Details
    In: Water Resources Research, American Geophysical Union (AGU), Vol. 35, No. 4 ( 1999-04), p. 1179-1190
    Abstract: In order to determine the likely effects of the increasing atmospheric CO 2 concentration on future evapotranspiration, ET, plots of field‐grown wheat were exposed to concentrations of 550 µ mol/mol CO 2 (or 200 µ mol/mol above current ambient levels of about 360 µ mol/mol) using a free‐air CO 2 enrichment (FACE) facility. Data were collected for four growing seasons at ample water and fertilizer (high N) and for two seasons when soil nitrogen was limited (low N). Measurements were made of net radiation, R n ; soil heat flux; air and soil temperatures; canopy temperature, T s ; and wind speed. Sensible heat flux was calculated from the wind and temperature measurements. ET, that is, latent heat flux, was determined as a residual in the energy balance. The FACE treatment increased daytime T s about 0.6° and 1.1°C at high and low N, respectively. Daily total R n was reduced by 1.3% at both levels of N. Daily ET was consistently lower in the FACE plots, by about 6.7% and 19.5% for high and low N, respectively.
    Type of Medium: Online Resource
    ISSN: 0043-1397 , 1944-7973
    URL: Article
    DOI: 10.1029/1998WR900115
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
    detail.hit.zdb_id: 2029553-4
    detail.hit.zdb_id: 5564-5
    SSG: 13
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Surface energy balance estimates at local and regional scales using optical remote sensing from an aircraft platform and atmospheric data collected over semiarid rangelands
    American Geophysical Union (AGU) ; 1994
    In:  Water Resources Research Vol. 30, No. 5 ( 1994-05), p. 1241-1259
    Details
    In: Water Resources Research, American Geophysical Union (AGU), Vol. 30, No. 5 ( 1994-05), p. 1241-1259
    Abstract: Remotely sensed data in the visible, near‐infrared, and thermal‐infrared wave bands were collected from a low‐flying aircraft during the Monsoon '90 field experiment. Monsoon '90 was a multidisciplinary experiment conducted in a semiarid watershed. It had as one of its objectives the quantification of hydrometeorological fluxes during the “monsoon” or wet season. The remote sensing observations along with micrometeprological and atmospheric boundary layer (ABL) data were used to compute the surface energy balance over a range of spatial scales. The procedure involved averaging multiple pixels along transects flown over the meteorological and flux (METFLUX) stations. Average values of the spectral reflectance and thermal‐infrared temperatures were computed for pixels of order 10 −1 to 10 1 km in length and were used with atmospheric data for evaluating net radiation ( R n ), soil heat flux ( G ), and sensible ( H ) and latent ( LE ) heat fluxes at these same length scales. The model employs a single‐layer resistance approach for estimating H that requires wind speed and air temperature in the ABL and a remotely sensed surface temperature. The values of R n and G are estimated from remote sensing information together with near‐surface observations of air temperature, relative humidity, and solar radiation. Finally, LE is solved as the residual term in the surface energy balance equation. Model calculations were compared to measurements from the METFLUX network for three days having different environmental conditions. Average percent differences for the three days between model and the METFLUX estimates of the local fluxes were about 5% for R n , 20% for G and H , and 15% for LE . Larger differences occurred during partly cloudy conditions because of errors in interpreting the remote sensing data and the higher spatial and temporal variation in the energy fluxes. Minor variations in modeled energy fluxes were observed when the pixel size representing the remote sensing inputs changed from 0.2 to 2 km. Regional scale estimates of the surface energy balance using bulk ABL properties for the model parameters and input variables and the 10‐km pixel data differed from the METFLUX network averages by about 4% for R n , 10% for G and H , and 15% for LE . Model sensitivity in calculating the turbulent fluxes H and LE to possible variations in key model parameters (i.e., the roughness lengths for heat and momentum) was found to be fairly significant. Therefore the reliability of the methods for estimating key model parameters and potential errors needs further testing over different ecosystems and environmental conditions.
    Type of Medium: Online Resource
    ISSN: 0043-1397 , 1944-7973
    URL: Article
    DOI: 10.1029/93WR03038
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1994
    detail.hit.zdb_id: 2029553-4
    detail.hit.zdb_id: 5564-5
    SSG: 13
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Canopy temperature as a crop water stress indicator
    American Geophysical Union (AGU) ; 1981
    In:  Water Resources Research Vol. 17, No. 4 ( 1981-08), p. 1133-1138
    Details
    In: Water Resources Research, American Geophysical Union (AGU), Vol. 17, No. 4 ( 1981-08), p. 1133-1138
    Abstract: Canopy temperatures, obtained by infrared thermometry, along with wet‐ and dry‐bulb air temperatures and an estimate of net radiation were used in equations derived from energy balance considerations to calculate a crop water stress index (CWSI). Theoretical limits were developed for the canopy air temperature difference as related to the air vapor pressure deficit. The CWSI was shown to be equal to 1 ‐ E / E p , the ratio of actual to potential evapotranspiration obtained from the Penman‐Monteith equation. Four experimental plots, planted to wheat, received postemergence irrigations at different times to create different degrees of water stress. Pertinent variables were measured between 1340 and 1400 each day (except some weekends). The CWSI, plotted as a function of time, closely paralleled a plot of the extractable soil water in the 0‐ to 1.1‐m zone. The usefulness and limitations of the index are discussed.
    Type of Medium: Online Resource
    ISSN: 0043-1397 , 1944-7973
    URL: Article
    DOI: 10.1029/WR017i004p01133
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1981
    detail.hit.zdb_id: 2029553-4
    detail.hit.zdb_id: 5564-5
    SSG: 13
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Venusian bow shock as seen by the ASPERA-4 ion instrument on Venus Express : OCCUPATIONAL WEIGHTING
    American Geophysical Union (AGU) ; 2010
    In:  Journal of Geophysical Research: Space Physics Vol. 115, No. A9 ( 2010-09), p. n/a-n/a
    Details
    In: Journal of Geophysical Research: Space Physics, American Geophysical Union (AGU), Vol. 115, No. A9 ( 2010-09), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2009JA014826
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2010
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    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2016813-5
    detail.hit.zdb_id: 2016810-X
    detail.hit.zdb_id: 2403298-0
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Modeling subauroral polarization streams equatorward of the plasmapause footprints
    American Geophysical Union (AGU) ; 2006
    In:  Journal of Geophysical Research Vol. 111, No. A10 ( 2006-10-13)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 111, No. A10 ( 2006-10-13)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2005JA011457
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2006
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    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2016813-5
    detail.hit.zdb_id: 2016810-X
    detail.hit.zdb_id: 2403298-0
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
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