| キャベツ畑のアルベドの特性. Characteristics of Albedo Over a Cabbage Field | |||||||||||
Abstract | |||||||||||
| To make clear the characterisitics of albedo for a cabbage field, incoming and reflected short wave radiations were measured with the ratio of green canopy area, the dry spell days and the extraterrestrial radiation ratio. Data were obtained for 57 days from 1 September 1982 to 27 October 1982, but data for 22 rainy days were excluded from the analysis. Results obtained from the data set of the cabbage field were compared with the results from the potato field which has been reported in a previous paper (Nakayama et al, 1984). The albedo for the cabbage field was affected considerably by the ratio of green canopy area (i. e., percentage of the area covered with green canopy to the total field area), as well as that of the potato field. The dry spell days (i. e., the number of fine and cloudy days following a rainy day which has more than 15 mm/day of rainfall) had little effect on the albedo because the soil surface was maintained in a wet condition throughout the obeservation period. The effect of the extraterrestrial radiation ratio on albedo for the cabbage field was slightly larger than that for the potato field. A multiple regression equation to estimate the albedo for cabbage field was derived as Eq. (1). Altough this equation represented the albedo well for the cabbage field, it was very different from similar type of equation for the potato field, Eq. (2). By comparing both albedos for cabbage and potato in detail, it was found that the difference between the both equations was due to the partiality of the data, such as the cabbage data did not include the data under the condition of dry soil surface and the potato data included only a small amount of data under wet soil condition in the early growing season. On the assumption that there is no essential difference between both cabbage and potato data, a new multiple regression equation was derived as Eq. (3) by combining both data. It seems likely that this new regression equation has wide applicability for the estimation of albedo for crop fields. | |||||||||||
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