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Evaluation of empirical expressions for the estimation of hourly and daily totals of atmospheric longwave emission under all sky conditions

1979; Wiley; Volume: 105; Issue: 446 Linguagem: Inglês

10.1002/qj.49710544620

1477-870X

A. John Arnfield,

Climate variability and models

Abstract Measurements of hourly totals of atmospheric longwave emission, made during summer and autumn seasons in southern Ontario, are used to evaluate the performance of several empirical estimation equations. Under clear sky conditions, the formulae of Swinbank and of Idso and Jackson gave similar results, with daily totals estimated to within measurement error, but with systematic deviations in hourly values which resembled those reported in earlier studies. The timing of these errors, however, suggests that previous hypotheses for such deviations may be invalid. The accuracy of estimates made with the formula of Brunt depended very strongly upon the regression parameters selected. Under all sky conditions, use of the Idso and Jackson formula, with adjustment for cloud type and amount following Bolz, yielded estimates of variable accuracy on an hourly basis, but daily (and similar period) totals are estimated with an error similar to that of the original measurements.