Showing papers by "John L. Monteith published in 1960"

The carbon-dioxide flux over a field of sugar beet

Abstract: The difference of CO2 concentration at two heights above a sugar beet crop was measured with a sensitive infra-red gas analyser. The ratio of evaporation to humidity gradient and of total heat flux to wet-bulb temperature gradient gave a transport number for calculating CO2 flux, assumed proportional to CO2 gradient and wind speed. In August and September 1958 there was often a constant upward flux at night (mean 0·05 mg cm−2 hr−1) attributed to respiration by plants and soil micro-organisms; but during daylight, photosynthesis gave a downward flux varying with solar radiation and reaching a maximum of 0·4 mg cm−2 hr−1. From 31 July to 11 September the net downward flux of atmospheric CO2 was 158 ± 29 mg cm−2 compared with an uptake of 217 ± 38 mg cm−2 estimated from dry matter increase of sampled plants. During October there was a net upward flux of 4·9 mg cm−2 day−1 attributed to a striking increase in amount of CO2 produced in the soil.

The performance of a Gunn‐Bellani radiation integrator

Abstract: An alcohol-filled Gunn-Bellani radiation integrator, exposed at Rothamsted from June to December 1958, gave weekly distillation totals that were a linear function of short-wave radiation on a horizontal surface above a limit of 500 cal cm−2 week−1. Laboratory experiments with both alcohol- and water-filled models reveal a threshold radiation intensity which can be estimated from the properties of the distilling fluid and the partial pressure of air within the instruments. Distillation is negligible below the threshold, but above, it is proportional to the excess radiation. Because the relation between absorbed heat and radiation incident on a horizontal surface depends on solar altitude and on the proportions of direct and diffuse radiation, it is difficult to predict field response from laboratory data.

Micrometeorology in relation to plant and animal life.

Abstract: SUMMARY Micrometeorology is the study of atmospheric processes at the earth's surface. If the leaves of plants and the skins of animals are regarded as extensions of that surface, micrometeorological principles can help the biologist to investigate the influence of physical environment on living material. Two examples are considered in illustration. First, the surface temperature of plants and animals and the cooling produced by evaporation are discussed in terms of heat-balance equations. Second, it is shown that the uptake of carbon dioxide by a field crop can be measured by a micrometeorological technique.