scispace - formally typeset
Search or ask a question

Showing papers by "John L. Monteith published in 1961"


Journal ArticleDOI
TL;DR: In this article, the authors measured short-wave radiation S, reflected shortwave radiation α S and net radiation R were measured over bare soil and crops from 1957 to 1959, and deduced from the observed linear dependence of R on S in the absence of cloud.
Abstract: Incoming short-wave radiation S, reflected short-wave radiation α S and net radiation R were measured over bare soil and crops from 1957 to 1959, and net long-wave radiation (L) was deduced from For grass, α increased from 0·23 at solar elevation 60° to 0·28 at 20° with daily mean 0·26. For bare soil, the corresponding increase was from 0·16 to 0·19 with mean 0·17. In mid-June, L for bare soil decreased from – 0·1 cal cm−2 min−1 during the night to – 0·4 cal cm−2 min−1 in the early afternoon. For long grass, in August, the corresponding change was from – 0·05 to – 0·22 cal cm−2 min−1. Under clear skies the incoming long-wave component varied much less than the outgoing component, and net flux L was closely related to surface temperature. With a heating coefficient β = – dL/dR, the observed linear dependence of R on S in the absence of cloud may be expressed as Where, formally, R = L0 when S = 0. For grass, sugar beet and potatoes, β lay between 0·15 and 0·22 with a variation which may depend on wind speed rather than on crop. The value for dry bare soil was higher (0·41) because there was greater surface heating. Measurements under clear skies and over grass at Cambridge and Kew agree well with Rothamsted values (β = 0·22, L0 = – 5·9 cal cm−2 hr−1). Over Nebraska prairie, β = 0·25, L0 = – 4·5 cal cm−2 hr−1 from selected observations during Projects Great Plains and Prairie grass.

185 citations


Journal ArticleDOI
TL;DR: From radiation measurements at Kew Observatory (tabulated by Lonnqvist), the effective emissivity of the atmosphere e, defined as the ratio of incoming long-wave radiation to black-body radiation at screen temperature, can be related to optical path m (cm) by as mentioned in this paper.
Abstract: From radiation measurements at Kew Observatory (tabulated by Lonnqvist), the effective emissivity of the atmosphere e, defined as the ratio of incoming long-wave radiation to black-body radiation at screen temperature, can be related to optical path m (cm) by With standard deviation ± 0·018. The relation between m and surface vapour pressure e (mb) found from Belasco's (1952) air mass analysis is giving almost the same as Brunt's equation from Benson data. Net long-wave radiation L over short grass can be calculated from where c is fractional cloudiness; σTA is black-body radiation at screen temperature; ΔL1 is a correction for the difference between TA and cloud-base temperature; and ΔL2 for the difference between TA and surface radiative temperature. From Roach's Kew data, ΔL1 = – 18 cal cm−2 day−1 and ΔL2 varies with season from – 12 cal cm−2 day−1 (December) to + 20 cal cm−2 day−1 (June). Throughout the British Isles, annual mean L with c = 0 is close to – 200 cal cm−2 day−1, and for real values of c Estimated annual net (total) radiation is 29 k cal cm−2 with little variation over the British Isles.

96 citations