Accession Number : AD0289020

Title :   SURFACE ENERGY BALANCE IN ARID LANDS AGRICULTURE

Corporate Author : AGRICULTURAL RESEARCH SERVICE TEMPE ARIZ WATER CONSERVATION LAB

Personal Author(s) : VAN BAVEL,C.H.M. ; FRITSCHEN,L.J.

Report Date : NOV 1962

Pagination or Media Count : 1

Abstract : The energy balance of bare surfaces was studied. Though the disposition of net radiation over a 24-hour period depends markedly on the moisture content of the surface, in most cases there was a net heat loss to the air. During the late afternoon and the early hours of darkness, energy was gained by a wet or moist surface from the air to offset latent heat losses. The indisputable and direct results of energy balance measurements are at variance with temperature profile studies, the latter often indicating a sensible heat flow close to the surface-in the lower 50 cm-opposed to that found from the energy balance. Conventional turbulent exchange ideas seem unapplicable under the circumstances of measurement. A direct physical analysis of evaporation from the surface showed the necessity of simultaneous and frequent measurement of soil temperature and moisture content in great detail. A preliminary set of data indicates that further studies can be made with success. Data obtained over an emerging grass crop indicate that compared with wet, bare soil, reflection is less and net radiation is greater but, nevertheless, evaporation is smaller owing to increased transfer of heat to the air. (Author)

Descriptors :   *ENERGY, *MICROMETEOROLOGY, *WATER, AIR, ATMOSPHERES, CLIMATE, HEAT, IRRIGATION SYSTEMS, METEOROLOGY, MOISTURE, TEMPERATURE

Distribution Statement : APPROVED FOR PUBLIC RELEASE