Insolation and net long-wave radiation off the Oregon coast

Abstract

Insolation, net radiation, and various oceanic and atmospheric variables were measured at sites 13 and about 120 km off the coast of Oregon in July and August 1973. A total often 24‐hour stations were occupied. The daily mean net solar radiation ranged from 0.10 to 0.40 cal cm−2 min−1, and large spatial variations of radiation in this upwelling region were present. The daily mean values were not closely related to the proportion of sky covered with clouds, but a mean from all the stations was in reasonable agreement with one cloud formula. The net long‐wave radiation varied from about −0.01 cal cm−2 min−1 under overcast skies to −0.10 cal cm−2 min−1 under clear skies. Daily mean values appear closely related to cloud amount, and a cloud factor of 1 ‐ 0.9C, as suggested by previous workers, seems appropriate for stratocumulus clouds. The measured clear‐sky net long‐wave radiation is appreciably less than that given by numerous widely used formulas but is supported by other observations and by a formula derived by Anderson.

Variations in oceanic net long-wave radiation caused by atmospheric thermal structure

“…This paper presents data, however, which suggest that appreciable variations in net long-wave radiation result from varying upper air temperature structure. Net long-wave radiation under clear skies was measured with a net radiometer (described by Reed and Halpern [1975] Table 1 iists the observed net long-wave radiation under clear skies near the times that the profiles shown in Figure 1 were obtained. (The other two clear sky observations off Oregon (given by Reed and Halpern [1975]) near the times of flights that revealed profiles similar to, but somewhat warmer than, the profile of August 22 (Figure 1) had irradiances of -0.090 and -0.095 cal cm -2 min -x.)…”

“…Net long-wave radiation under clear skies was measured with a net radiometer (described by Reed and Halpern [1975] Table 1 iists the observed net long-wave radiation under clear skies near the times that the profiles shown in Figure 1 were obtained. (The other two clear sky observations off Oregon (given by Reed and Halpern [1975]) near the times of flights that revealed profiles similar to, but somewhat warmer than, the profile of August 22 (Figure 1) had irradiances of -0.090 and -0.095 cal cm -2 min -x.) It is of course true that the measurements of radiation and the air thermal profiles are not really synoptic; even off Africa, though, it seems doubtful, because of the similarity of the profiles before and after the Copyright ¸ 1975 by the American Geophysical Union.…”

On estimating the atmospheric longwave flux at the ocean surface from ship meteorological reports

“…Relatively little work has been carried out thus far on the evaluation of the various bulk formulae using direct measurements of longwave radiation made at sea. Reed and Halpern [1975], Reed [1976], and Simpson and Paulson [1979] carded out preliminary studies using measurements in the over short periods, typically 10 days, but were unable to reach any firm conclusions, given the limited nature of the data sets being considered. More recently, the performance of a group of bulk formulae has been assessed in separate studies based o n larger sets of cruise data by Katsaros [1990] and Bignarni et al…”

Variability of net longwave radiation over the eastern North Pacific Ocean

“…The prediction of net longwave radiative heat flux thus requires consideration of the contributions by three components: the sea surface, clouds, and the atmosphere. There have been several previous experiments which have measured LWT• over the sea surface [Swinbank, 1963' Charnell, 1967' Paltridge, 1969' Schooley, 1969' Reed and Halpern, 1975' Reed, 1975' Simpson and Paulson, 1979, hereafter $P, 1979. Also Lind et al [1984] have measured downwelling longwave irradiance over the North Atlantic Ocean.…”