Peachtree Creek is a gaged watershed that has experienced a substantial increase in urbanization. The relationships of runoff to rainfall were studied for total annual flows, low flows, and peak flows. For each type of flow the relationship in the later, more urbanized period was compared to that in the earlier, less urbanized period. An increase in total runoff in wet years was observed as urbanization increased, but a decrease occurred during dry years. For low flows a similar decrease of runoff in dry years was found. An increase in peak runoff was observed over most of the range of precipitation. Increasing peak flows and declining low flows can be adequately explained by urban hydrologic theoryshed. which focuses on the effects of urban impervious surfaces upon direct runoff and infiltration. However, a decline of total runoff in dry years can be explained only by taking into account evapotranspiration as well. The concept of advectively assisted urban evapotranspiration, previously discovered by climatologists, is needed to explain such a loss of total runoff. Urban hydrologic theory must take into account vegetation and evapotranspiration, as well as impervious surfaces and their direct runoff, to explain the magnitude of total annual flows and low flows. Urban stormwater management should address the restoration of low flows, as well as the control of floods.

The coverage provided by the existing solar radiation monitoring network for British Columbia and adjacent areas in western Canada is assessed and found to be inadequate. It is generally advantageous to use a numerical solar radiation model at available sites to augment the observed values, although this is not a complete solution to the problem. It is also shown that the ability to extrapolate solar radiation data from measurement and modelling locations is strongly determined by the general nature of the synoptic weather conditions. In addition, the use of solar radiation extrapolations is restricted by problems involving homogeneity and isotropy assumptions.Les auteurs presentent une evaluation de la distribution des stations en Colombie britannique et les aires adjacents du Canada de I'ouest mesurant la radiation solaire; ils en concluent que le reseau actuel est inadequat. 11s soulignent I'avantage d'emprunter un modele numerique pour caracteriser la radiation solaire aux sites disponibles, afin d'augmenter les donnees observees. Neanmoins, cela ne represente pas pour les auteurs une solution complete du probleme. 11s demontrent que le caractere general des conditions meteorologiques synoptiques determine fortement la possibilite d'une extrapolation de la distribution de la radiation solaire, derivee des donnees mesurees et des modeles adoptes aux sites specifiques. Finalement, ils etablissent que certains problemes concernant les hypotheses d'homogeneite et d'isotropie imposent leur tour des limites a I'utilite de la methode d'extrapolation pour decrire la radiation solaire.

Common perception is that tornadoes travel in paths from the southwest quadrant of directions toward the northeast. This study examines path directions for 6,194 tornadoes that occurred in the eastern two‐thirds of the United States during the twenty‐three‐year period 1980–2002. At the national scale, nearly 70 percent of tornadoes included in the study propagated from the west, west‐southwest, and southwest, with west‐southwest being the highest frequency origin direction. Nevertheless, distinct seasonal and regional variations were found. In central and northern areas of the country, a more westerly or northwesterly path origin prevails during late spring and summer. The midtropospheric flow, convective typology, and synoptic patterns of tornado outbreaks are thought to contribute to the distributions observed in the climatology.

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