首页> 美国政府科技报告 >THE USE OF SUB-ARCTIC BOGS AS NATURAL CLIMATIC INDICATORS
【24h】

THE USE OF SUB-ARCTIC BOGS AS NATURAL CLIMATIC INDICATORS

机译:亚北极沼泽作为自然气候指标的应用

获取原文

摘要

The physical interaction of the atmosphere and the ground surface has been investigated in a particular attempt to derive climatic temperature values from a very limited amount of observed soil temperature data. A model is proposed in which the Fourier equation pertaining to the sinusoidal variation of temperature in a homogeneous medium has been used to generate soil temperature profiles at a given time, which are compared to observed tempera¬ture profiles.nThe temperature profile prescribed by the model is an expo¬nentially damped cosine function in the vertical direction with its shape determined by three parameters:the mean annual soil temperature, the surface temperature amplitude, and the thermal diffusivity of the ground. Since the model is non-linear with respect to the parameters, and linear least squares techniques may not be used, an alternate statistical method of determining a set of least squares estimates of the parameters developed. The agreements between the observed and statistically generated tempera-ture profiles is examined for a number of cases in bogs in the north central United States and Canada. Sphagnum bogs were chosen because they are nearly vertically homogeneous, and because they represent a land form common to a broad latitudinal range. It is concluded that the values of the three parameters that are estimated by the model are physically valid. Furthermore, it is shown that the amount of Information obtained from a single soil temperature profile is equivalent to that obtained by recording soil temperatures at two fixed depths over a period of a year.nThe effects of a winter snov cover, frozen ground, and non-homogeneous ground material on the observed temperature profiles, and the implications of the estimated parameters with regard to the annual course of the air temperature are evaluated and discus¬sed. It is found that an extensive winter snov cover will alter the observed temperature field in the ground such that the boun¬dary conditions of the courier equation are no longer satisfied.nThe estimated annual course of temperature at the ground sur¬face agrees quite well with observed air temperatures at nearby stations during summer, but exceeds the observed air temperatures appreciably in winter. Based on the cases studied it can be assumed however, that the estimated parameters accurately repre¬sent the temperature field within the ground. This technique there¬fore has important applications in the field of phytoclimatology. With respect to temperature variations, sphagnum bogs have been shown to serve very well as natural climatic indicators.

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号