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William P. Lowry

Abstract

The author reexamines Klein's (1948) quantitative statements relating clear-sky direct-beam solar radiation to altitude for the lower troposphere, which are of the form (transmissivity) = B + A log (altitude). Klein's summaries are judged to be the best general statements on the subject previously published, but the author proposes a different empirical formulation which is based on more direct physical reasoning and which yields a better statistical fit when applied to Klein's data. The author also proposes, for informal adoption, two standard soundings (moist and dry) of zenith path clear-sky direct-beam transmissivity τp as a function of pressure p in the form ln(Cτp ) = InM + Np, where C is a constant with value near 0.975, the approximate transmissivity just below the high atmospheric ozone layer. For use in estimations of transmissivity tp with nonzero zenith angles, the author presents, as part of his proposal, altitude-dependent estimators for the adjustment parameter ap , suggested by Williams (1976) in the form lntp = (secZ) ln[τ p + a p ln(secZ)] where Z is the zenith angle.

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William P. Lowry

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Doubt exists among atmospheric scientists about current estimates of local and regional effects of urbanization on climate, but not generally about the existence of these urban effects. This paper presents a framework for discussion of various estimators, uses the framework to make the case for a particular estimator, and then uses the framework to examine possible shortcomings of other estimators which appear in the literature. The measure recommended consists of differences between observations, from urban and pre-urban periods, first stratified by synoptic weather type. The measures whose shortcomings are examined are 1) contemporaneous urban-rural differences, 2) contemporaneous upwind-downwind differences, 3) contemporaneous urban-regional ratios, 4) time trends of differences and ratios and 5) contemporaneous weekday-weekend differences. The paper is designated as a “problem analysis” because its goal is general facilitation of discussion about the problem of empirical estimation of urban effects on climate.

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William P. Lowry

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During 53 days in the summer of 1966 continuous hygrothermograph records were obtained at 6 points along a north-south transect of the 11-km wide Valsetz Basin in the Oregon Coast Range. The 6 records sampled both north and south aspects and nearly the full range of elevations between 300 and 900 m above msl in the basin. Hourly values of temperature and relative humidity were tabulated from the charts, converted to values of potential temperature and mixing ratio, and put on punched cards. The period of record was divided into three relatively dissimilar types of day, and hourly mean cross-sections of potential temperature and mixing ratio were drawn for each type. Only comparatively minor variations superimposed on a basic nocturnal pattern and a basic daytime pattern of cross-section distinguish the three types of day. .Principal causes of the variations are nocturnal accumulation of cold air on the basin floor, nocturnal heating at ridge top levels associated with subsidence inversion, anti higher midday rates of evapotranspiration on south-facing slopes than on north-facing slopes.

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William P. Lowry

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In order to provide basic information on micrometeorology as related to forest-fire weather and forest regeneration, a series of measurements was made in the central Oregon Coast Range. Net radiation flux, soil heat storage, and evaporation were calculated from observations, while turbulent flux was considered the residual of these three. Based on published energy-budget data from situations in which advection was considered absent, an estimate was made of what the turbulent flux would have been at these Oregon stations in the absence of the sea breeze. Differences between these hypothetical values and the observed values are termed the “total advection effect” and are separated into vertical and horizontal components.

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William P. Lowry

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William P. Lowry

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William P. Lowry

This paper presents an abbreviated review of the literature concerning the relationship of evaporative moisture-loss rate to soil-moisture content. Results from a variety of sources appear to fall into four major types of curve expressing this relationship. The author compares these types and concludes that three of them are mutually supporting and represent special cases of the same process. The fourth type is considered contradictory. It is concluded further that the search for a neat, concise, general statement of the relationship under consideration is probably futile.

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William P. Lowry

A scheme was required for interpretation of wind data collected manually in rough terrain. In response to this need, an analysis technique was developed in which “synoptic” pairs of observations from two stations were combined and summarized in an index number. This technique is described and its application to the original problem presented. Application to three other types of analyses is described and discussed.

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William P. Lowry
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William P. Lowry
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