Accession Number:

ADA196409

Title:

Estimating Evapotranspiration of an Irrigated Surface from Upwind and Downwind Vertical Profiles of Temperature and Humidity

Descriptive Note:

Master's thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1988-01-01

Pagination or Media Count:

92.0

Abstract:

Evapotranspiration ET and the contribution of horizontal advection of sensible heat were predicted for an irrigated surface in arid regions from upwind and downwind vertical profiles of temperature and humidity. Measurements were made of atmospheric temperature and specific humidity to a height of 70 meters at the upwind and downwind sides of an irrigated alfalfa field with dry upwind conditions. The depth of air whose temperature and humidity profiles were distorted by the irrigated surface defined a control volume. Total ET was estimated via a vapor budget method which essentially calculated the input of water vapor into the control volume. The amount of energy used in ET which was contributed by sensible heat advection was estimated by calculating the amount of internal energy depleted from the control volume. Simultaneous estimates of ET were made with an eddy correlation system, located near the center of the field. The depth of air modified by the irrigated crop averaged 10 for specific humidity and 15 for temperature during the light winds encountered in this study. ET estimates from the vapor budget method compared well with eddy correlation results. Deviation between the two estimates averaged 43 wsq m 7. 2. Calculations of the depletion of internal energy in the control volume indicated that, in this study, horizontal advection of sensible heat contributed from 35-86 of the total energy used in ET.

Subject Categories:

  • Agricultural Engineering
  • Meteorology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE