• Published : 2000.07.01


A spectral formalism was applied to quantify the sampling errors due to spatial and/or temporal gaps in soil moisture measurements. The lack of temporal measurements of the two-dimensional soil moisture field makes it difficult to compute the spectra directly from observed records. Therefore, the space-time soil moisture spectra derived by stochastic models of rainfall and soil moisture was used in their record. Parameters for both models were tuned with Southern Great Plains Hydrology Experiment(SGP'97) data and the Oklahoma Mesonet data. The structure of soil moisture data is discrete in space and time. A design filter was developed to compute the sampling errors for discrete measurements in space and time. This filter has the advantage in its general form applicable for all kinds of sampling designs. Sampling errors of the soil moisture estimation during the SGP'97 Hydrology Experiment period were estimated. The sampling errors for various sampling designs such as satedlite over pass and point measurement ground probe were estimated under the climate condition between June and August 1997 and soil properties of the SGP'97 experimental area. The ground truth design was evaluated to 25km and 50km spatial gap and the temporal gap from zero to 5 days.



  1. Blackman, R.B., and Tuckey, J.W., (1959). The Measurement of Power Spectra. Dover Publication
  2. Eltahir, E.A.B. (1998). 'A soil moisture-rainfall feedback mechanism, 1, Theory and observations.' Water Resour. Res., Vol. 34, No. 4, pp, 765-776
  3. Engman, E.T, (1990). 'Progress in microwave remote sensing of soil moisture, Cana. J. Remote Sensing ' Vol. 16, pp. 6-14
  4. Entekhabi, D. and Rodriguez-Iturbe, I. (1994). 'Analytical framework for the characterization of the space-time variability of soil moisture.' Advances in Water Resources, Vol. 17, pp. 25-45
  5. Jackson, T.J., Engman, E.T. and Schiebe, F.R.. (1993). 'Washita'92 experiment description, in Hydrology Data Report, edited by T. J. Jackson and F. R. Schiebe, National Agricultural Water Quality Laboratory.' 93(I)
  6. Jackson T.J. and Le Vine, D.E. (1996). 'Mapping surface soil moisture using an aircraft-based passive microwave instrument: algorithm and example.' J. Hydrology., Vol. 184, pp. 85-99
  7. Lin, D.-S., Wood, E.F., Troch, P.A., Mancini, M, and Jackson, T.J. (1994). 'Comparisons of remotely sensed and model-simulated soil moisture over a heterogeneous watershed, Remote Sens. Environ.' Vol. 48, pp. 150-171
  8. North, G.R. and Nakamoto, S. (1989). 'Formalism for comparing rain estimation designs.' J. Atmos. Ocean. Tech., Vol. 6, pp. 985-992<0985:FFCRED>2.0.CO;2
  9. Rind. D. (1982). 'The influence of ground moisture conditions in North America on summer climate as modeled in the GISS GCM.' Monthly Weather Review, Vol. 100, pp. 501-526<1487:TIOGMC>2.0.CO;2
  10. Rodriguez-Iturbe, I., Entekhabi, D. and Bras, R.L. (1991a). 'Nonlinear dynamics of soil moisture at climate scales 1.Stochastic analysis.' Water Resour. Res., Vol. 27, No. 8, pp. 1899-1906
  11. Rodriguez-Iturbe, I., Entekhabi, D., Lee, J.S. and Bras, R.L. (1991b). 'Nonlinear dynamics of soil moisture at climate scales 2. Chaotic analysis.' Water Resour. Res., Vol. 27, No. 8, pp. 1907-1915
  12. Shukla, D.A. and Mintz, Y. (1982). 'The influence of land-surface evaporation on Earth's climate' Science, Vol. 215, pp. 1498-1501
  13. Valdes, J.B., Diaz-Granados, M. and Bras, R.L. (1990). 'A derived PDF for the initial soil moisture in a catchment.' J. Hydrology, Vol. 113, pp. 163-176
  14. Waymire, E., Gupta, V.K. and Rodriguez-Iturbe, I. (1984). 'A spectral theory of rainfall intensity at the $meso-{\beta}$ scale.' Water Resour. Res., Vol. 20, No. 10, pp. 1453-1465
  15. Wood, E.F., Lin, D.-S., Mancini, M., Thongs, D., Troch, P.A., Jackson, T.J., Famiglietti, J.S. and Engman, E.T. (1993). 'Intercomparisons between passive and active microwave remote sensing, and hydrological modeling for soil moisture.' Adv. Space Res. Vol. 13, No. 5, pp. 167-176
  16. Yu, C, Warrick, A.W., Conklin, M.H., Young, M.H. and Zreda, M. (1997). 'Two- and three-parameter calibration of time domain reflecrometry for soil moisture measurement.' Water Resour. Res., Vol. 33, No. 10, pp. 2417-2421
  17. Zheng, X. and Eltahir, E.A.B. (1998). 'A soil moisture-rainfall feedback mechanism., 2, Numerical experiments.' Water Resour. Res., Vol. 34, No 4, pp. 777-785