HR: 14:25h
AN: H12F-04    [PDF]
TI: A Complementary Evaporation Approach to Scalar Roughness Length Estimation
AU: * Crago, R
EM: rcrago@bucknell.edu
AF: Bucknell University, Department of Civil and Environmental Engineering, Lewisburg, PA 17837 United States
AU: Crowley, R W
EM: rcrowley@bucknell.edu
AF: Bucknell University, Department of Civil and Environmental Engineering, Lewisburg, PA 17837 United States
AB: The difference between momentum and scalar roughness lengths has been well-established both theoretically and experimentally. Accurate experimental estimates of the scalar roughness length require knowledge of the actual scalar concentration at the surface, which is rarely known and is generally poorly defined for vegetation canopies. However, estimates of the scalar roughness length for water vapor can be made using the advection-aridity model for evaporation for cases in which the evaporation is known. These estimates require no knowledge of surface characteristics except the momentum roughness length. Based on the complementary relationship between actual and potential evaporation, the advection-aridity equation is only likely to be valid under conditions of minimal advection. Data from a grassland site at CASES-97, collected by Russell Qualls (University of Idaho), were screened to ensure that only data representing minimal advection conditions were retained. The scalar roughness length for water vapor was determined from the advection-aridity equation, and its dependence upon land surface characteristics was investigated.
DE: 1818 Evapotranspiration
DE: 1833 Hydroclimatology
DE: 1836 Hydrologic budget (1655)
SC: Hydrology [H]
MN: 2003 Fall Meeting