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William E Reifsnyder

This year marks the 100th anniversary of the beginning of the scientific study of forest meteorology: the year 1873 marked the publication of Ebermayer's monograph, Die Physikalischen Einwirkungen des Waldes auf Luft und Boden. The state of knowledge from that time until 1957 when the first AMS Workshop on Agricultural Meteorology was held is reviewed.

In assessing the future of forest meteorology, a number of important questions must be answered. Who needs it and how can it be used? How can knowledge of forest meteorology be used for predictive purposes by the forester and ecologist? What are the most promising directions for forest meteorology research to take in the decade ahead? What are the major unsolved problems?

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Paul E. Waggoner and William E. Reifsnyder

Abstract

The proposed model synthesizes profiles of temperature, humidity and evaporation in a canopy of leaves from meteorological conditions at canopy top, from the temperature and humidity at the soil surface, from a leaf dimension, from the vertical distribution of leaf area and stomatal resistance, and from observations or extinction coefficients for ventilation and radiation within the canopy under steady-state conditions. The exchange of sensible and latent heat in a canopy stratum is required to be equal to the absorption of radiation by the leaves in that stratum. Further, the difference between strata in their potential for sensible and latent heat exchange is related both to leaf temperature and to the fluxes and diffusive resistances between the leaves. Leaf temperatures, evaporation and sensible heat exchange, and air temperatures within the canopy that meet these requirements were calculated by successive approximation. The microclimate and evaporation of a red clover and of a barley canopy were simulated, and changes in evaporation from a canopy following moderate changes in stomatal resistance were explained by the model.

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Edward A. Brotak and William E. Reifsnyder

Abstract

Fifty-two major wildland fires in the eastern half of the United States were analyzed to determine the synoptic situations involved. Three-fourths of the fires were found near surface frontal areas. The vast majority of fires were associated with the eastern portion of small-amplitude but intense short-wave troughs at 500 mb. A lack of moisture advection at 850 mb inhibits precipitation which normally accompanies these systems. This lack of precipitation in association with strong low-level winds found in these regions produces dangerous fire conditions at the surface. Such situations are shown to occur rarely.

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