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51 Spatially Resolved Measurements of Evapotranspiration by Lidar

Part 5. Remote Sensing

  1. William E Eichinger

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa056

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Eichinger, W. E. 2006. Spatially Resolved Measurements of Evapotranspiration by Lidar. Encyclopedia of Hydrological Sciences. 5:51.

Author Information

  1. University of Iowa, IIHR Hydroscience and Engineering, Iowa City, IA, US

Publication History

  1. Published Online: 15 APR 2006

Abstract

Spatially resolved estimates of evapotranspiration may be made over an area of about a square kilometer, with relatively fine (25 m) spatial resolution, derived from three-dimensional measurements of water vapor concentration made by a scanning Raman lidar. The method is based upon the Monin–Obukhov similarity theory applied to spatially and temporally averaged data. The method has been applied at several locations to produce maps of the spatial distribution of evapotranspiration rates at regular intervals throughout the day. The estimates of evapotranspiration rates made compare favorably with estimates made using eddy correlation methods. The method is limited in that it assumes that the surface roughness, friction velocity, and Obukhov length are assumed constant over the examined areas. Values for the friction velocity and Obukhov length are required from conventional point instruments. The three-dimensional water vapor concentration and the evaporation maps can be used in a wide variety of ways to study the spatial variations in evapotranspiration caused by changes in soil type and moisture content, canopy type, and topography.

Keywords:

  • lidar;
  • Raman;
  • evapotranspiration;
  • evaporation;
  • mixing ratio;
  • heterogeneity