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Minimum temperature surveys based on near‐surface air temperature measurements and airborne thermal scanner data

1986; Wiley; Volume: 6; Issue: 4 Linguagem: Inglês

10.1002/joc.3370060407

2374-7412

J. D. Kalma, G. Laughlin, A. A. Green, Martin O'Brien,

Urban Heat Island Mitigation

Abstract Minimum air temperature measurements and airborne thermal scanner measurements of apparent surface temperature were obtained in a regional frost risk study in gently undulating grazing country in the Southern Tablelands of New South Wales, Australia. The minimum air temperature data obtained at 7 sites on 100 nights have been used to derive a predictive relationship between temperature lapse rate and night‐time wind speed and net radiation loss. An extended network was used on 30 nights using an additional 24 sites. Excellent agreement was observed between the lapse rates collected from both the 7‐station and 31‐station networks on 24 nights. Maps of minimum air temperature across the region have been obtained for selected individual nights using Laplacian smoothing spline functions based on elevation and map co‐ordinates. Thermal scanner data were obtained with an aircraft on two nights and the paper presents detailed comparisons between apparent surface temperature data and minimum air temperatures obtained from the regional maps. These comparisons have made it possible to successfully distinguish between broad topographic controls and the effect of local surface characteristics, especially in the case of high‐resolution thermal scanner data. Such local controls include the effects of trees, surface water and various man‐made features, as well as very local topographic features such as narrow depressions, which are only noticeable from site surveys and detailed aerial photography. It is concluded that thermal imagery is an important aid in understanding spatial distribution patterns of night‐time air temperatures and hence in regional frost risk assessment.