Researches in heat budget for snow accreting boreal forests

以下是岩手县盛冈市森林的降雪量和降雪量的测量结果。无冠雪森林的反照率随太阳天顶角的增大而增大，随云量的增大而减小。而且，随着冠雪比的增大，它也增大，但其关系是非线性的。降雪后，冠雪比呈指数下降。万年青林林冠截留量大，落叶林林冠截留量无明显差异，通过计算土壤温度，研究了气象条件和土壤参数对霜深的影响。此外，我们还研究了积雪和森林对霜冻深度的影响。结果表明，积雪深度和积雪的热性质对霜层厚度敏感，而土壤含水量和森林密度对霜层厚度不敏感，提出了利用可见光和近红外波段数据获取积雪和森林密度信息的方法。这是盆栽幼树光谱测量和模型计算的结果。在此基础上，提出了一种估算感热通量的合适方法，即利用最佳视角下的辐射温度估算感热通量。该方法在宫城县Kogota的稻田进行了验证。

Following are results of measurements of albedo and snowfall at a forest in Morioka, Iwate Prefecture. Albedo of forest without crown snow becomes large with increasing solar zenith angle and becomes small with increasing cloud amount. Moreover, it increases with the increase of crown-snow ratio, but its relationship is nonlinear. After snowfall the crown-snow ratio decreases exponentially. The amount of crown-intercepted snow is large in dense evergreen forest, while there is no difference among deciduous forests.Dependency of frost depth on meteorological conditions and on soil parameters has been investigated after the calculation of soil temperature. Moreover, we investigated the influence of snow cover and forest on the frost depth. The result is that the frost depth is sensitive to snow depth and thermal property of snow, and not sensitive to soil water content and forest density.We proposed a method to obtain the imformation about snow cover and forest density using visible and near infrared radiation band data. It is a result of spectral measurement with potted young trees and model calculations. Furthermore, a proper method for estimating sensible heat flux was proposed, which is using radiometric temperature measured at optimum viewing angle. This method was validated at a rice paddy field in Kogota, Miyagi Prefecture.