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<br />001473 <br /> <br /> <br />IV.a <br /> <br />Some of the relationships of downward fluxes of radiation involve <br />properties of clOUds not always observed; however, current work in cloud <br />physics may make it pOSSible to extend the validity of these relationships. <br />Another clllss of relationships includes those that !lIight be developed <br />between radiation fluxes and conditions at the earth's surface, such as <br />daily m~ air temperature. These relationships are valid as long as <br />the balance between radiative and advective forces remains the same; <br />unfortunately, the climate-generating forces are not always in bal.ance but <br />may shift radically with changes in daily weather. The balance between <br />radiative Ilnd advective influences also varies spatially with changes in <br />ventilation, i.e., the intermingling of surface and upper air caused by <br />topographic roughness. Therefore, relationships between any radiation <br />nux and meteorological measurements derived at a particular station <br />call1lot be extended too far away from that station. <br /> <br />These' considerations suggest that attempts to fill gaps in radiation <br />data will be most successful for a few !lIissing days of record, wllere <br />relationships to various meteorological factors can be develOped at that <br />place and in that weather situation. Attempts to fill long gaps in a <br />record becQme risky. Attempts to :fill spatial gaps between radiation <br />stations, nm.ch-needed as they are by" reason of coarseness of the network" <br />should be ~l:ln:fined to the same elimatic region, to weather situations <br />bringing the same type of cloudiness, and to the same topographic arellll. <br /> <br />In co#lusion, it mgy be said that the radiative heat transfers offer <br />at least as Dl\l.oh danger that the hydrologist will fall into errors of use <br />and interp:retlltion as does any other hydrologic fllctor. Also, that the <br />temptation: is so large because data are sparse. In qdrologic fa;ctors <br />such as precipitation, many sources of error have beeh identified by past <br />workers, who also have developed procedures for !lIinimizing them. Radiation <br />has a shorter history; not all the possible errors have yet been identified, <br />and few have been studied enough that procedures for lninimizing them are <br />available. Tlle hydrologist wishing to employ radiative-heat factors in h,is <br />investigat:j.on should be prepared to work in developing and testing p:rocecWrEls, <br />for assuring quality of data and for filling gaps in the record. . <br />