Spectral estimates of net radiation and soil heat flux

Conventional methods of measuring surface energy balance are point measurements and represent only a small area. Remote sensing offers a potential means of measuring outgoing fluxes over large areas at the spatial resolution of the sensor. The objective of this study was to estimate net radiation (Rn) and soil heat flux (G) using remotely sensed multispectral data acquired from an aircraft over large agricultural fields. Ground-based instruments measured Rn and G at nine locations along the flight lines. Incoming fluxes were also measured by ground-based instruments. Outgoing fluxes were estimated using remotely sensed data. Remote Rn, estimated as the algebraic sum of incoming and outgoing fluxes, slightly underestimated Rn measured by the ground-based net radiometers. The mean absolute errors for remote Rn minus measured Rn were less than 7%. Remote G, estimated as a function of a spectral vegetation index and remote Rn, slightly overestimated measured G; however, the mean absolute error for remote G was 13%. Some of the differences between measured and remote values of Rn and G are associated with differences in instrument designs and measurement techniques. The root mean square error for available energy (Rn - G) was 12%. Thus, methods using both ground-based and remotely sensed data can provide reliable estimates of the available energy which can be partitioned into sensible and latent heat under nonadvective conditions.

[1]  W. Brutsaert.  On a derivable formula for long-wave radiation from clear skies , 1975 .

[2]  Samuel N. Goward,et al.  Deriving surface albedo measurements from narrow band satellite data , 1987 .

[3]  R. Jackson.  Total reflected solar radiation calculated from multi-band sensor data , 1984 .

[4]  Ray D. Jackson,et al.  Evapotranspiration calculated from remote multispectral and ground station meteorological data , 1985 .

[5]  Brent Clothier,et al.  ESTIMATION OF SOIL HEAT FLUX FROM NET RADIATION DURING THE GROWTH OF ALFALFA , 1986 .

[6]  Ray D. Jackson,et al.  Net radiation calculated from remote multispectral and ground station meteorological data , 1985 .

[7]  C. B. Tanner,et al.  Evaporation from a Drying Soil , 1967 .

[8]  Craig S. T. Daughtry,et al.  Estimation of the soil heat flux/net radiation ratio from spectral data , 1990 .

[9]  Jerry L. Hatfield,et al.  Evaluation of canopy temperature—evapotranspiration models over various crops , 1984 .

[10]  Ray D. Jackson,et al.  Thermal radiation from the atmosphere , 1969 .

[11]  Alfredo Huete,et al.  Assessment of vegetation and soil water regimes in partial canopies with optical remotely sensed data. , 1990 .

[12]  Ray D. Jackson,et al.  Net radiation — soil heat flux relations as influenced by soil water content variations , 1975 .

[13]  G. Campbell,et al.  USE OF PELTIER COOLERS AS SOIL HEAT FLUX TRANSDUCERS. , 1985 .

[14]  M. S. Moran,et al.  Obtaining Surface Reflectance Factors from Atmospheric and View Angle Corrected SPOT-1 HRV Data , 1990 .

[15]  D. Baldocchi,et al.  WATER USE EFFICIENCY IN A SOYBEAN FIELD: INFLUENCE OF PLANT WATER STRESS* , 1985 .

[16]  Marvin E. Bauer,et al.  Effects of nitrogen fertilizer on growth and reflectance characteristics of winter wheat , 1986 .

[17]  W. Brutsaert.  Evaporation into the atmosphere , 1982 .

[18]  M. Bauer,et al.  Influence of solar illumination angle on soybean canopy reflectance. , 1982, Applied optics.

[19]  Donald R. Satterlund,et al.  An improved equation for estimating long‐wave radiation from the atmosphere , 1979 .

[20]  K. Ranson,et al.  Scene Shadow Effects on Multispectral Response , 1987, IEEE Transactions on Geoscience and Remote Sensing.

[21]  S. Idso,et al.  Analysis of an empirical model for soil heat flux under a growing wheat crop for estimating evaporation by an infrared-temperature based energy balance equation , 1987 .