Over stralingsmetingen, de warmtebalans en de verdamping van gras
1959
Scholte Ubing, D.W.
Different terms of the energy balance at the surface were discussed. Regression formulae for calculation of net radiation from cloudiness, vapour pressure and temperature were discussed. This type of formula may be used even for short periods by allowing for cloudiness during the night.Different types of net radiometers, including the 'poor man's radiometer' were compared.The evapotranspiration of grass was calculated from the water balance of the root zone. Moisture content of the soil at various depths (max. 75 cm) was calculated from thermal conductivity measurements by a non-stationary method.The ratio of potential evaporation to that of an 'open thin waterlayer' (E 0 ) varies with net radiation. An average value of 0.67 was found.Of the net radiant heat flux density, 75-80% was used for evaporation and about 25-20 % for heating the soil and air. No influence of cutting the grass was observed.There was a difference in water uptake from field soil and from soil in a Popov pot.Evaporation under conditions of moisture stress was still dependent on the net radiation and thus on potential evaporation. This also applied to the yields observed.
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