Abstracts for the 5th International GAME Conf.

3-5 October 2001

Aichi Trade Center

Nagoya Japan

Study on Energy and Mass Transfers from Leaf to Canopy Scales in Larch Forest of Eastern Siberia

Atsuhiro Takahashi (1), Tetsuya Hiyama (2), Takeshi Ohta (3), Takashi Kuwada (4), Shuko Hamada (5), Yoshihiro Fukushima (6)

A vegetation-atmosphere interaction model was developed to estimate momentum, energy, and mass flux at forest canopy. The aerodynamic roughness lengths are parameterized by leaf-scale transfer coefficients, wind velocity profile, and leaf area density. If leaf-scale transfer coefficients are determined uniquely, roughness lengths depend on only leaf area density. Wind velocity profile is calculated with the data of leaf area density. Leaf-scale stomatal conductance was functioned in terms of micrometeorological factors such as solar radiation, surface temperature to be integrated to canopy-scale roughness length for latent heat flux and CO2 flux. We used Jarvis'(1976) model for estimating stomatal conductance, which is a function of the solar radiation and the surface temperature. Needed parameters are determined by using directly measured stomatal conductance. The effect of vapor pressure deficit is not considered in this analysis. After fitting these parameters, stomatal conductance calculated by Jarvis' model has good agreement with observed one. We compared the estimated results from the model with the observed data in two days with different meteorological condition. The data were obtained from the tower established in a larch forest of Eastern Siberia. Under condition of cold temperature and enough solar radiation, most of the effective energy was distributed to upward sensible heat flux. Calculated flux has very good agreement with the observed one under such condition. On this contrast, when the air temperature was high and enough solar radiation was supplied, evapotranspiration becomes larger. In this case, the agreement between calculated and observed fluxes was worse around noon when the solar radiation was strong. The calculation made flux underestimate during strong solar radiation. Although the problem of representative in measurement was remained, this disagreement could be caused by activated lower vegetation and evaporation at forest floor. In sparse canopy such as Eastern Siberia, solar radiation can penetrate easily into canopy layer and turbulent transport can occur efficiently, so that lower canopy layer and ground might affect for energy and mass fluxes significantly. Modeling of under story fluxes would be mportant in future works. We also applied a multi-layer model which calculates energy budget at each multi-divided layer within the canopy. Leaves were classified into sunlit and shaded leaves. Sunlit leaves acted as source both for sensible and latent heat fluxes. Shaded leaves were almost only the source of latent heat flux. The input effective energy was much larger at sunlit leaves than at shaded leaves, but total area of shaded leaves was much larger than those of sunlit leaves. The contribution of shaded leaves was not negligible and actually took role as source of latent heat flux. It suggests that the distribution and clumping of leaves within the canopy are important for determination of the ratio of sunlit/shaded leaves and influence the energy distribution for whole canopy.

Submittal Information

Name : Date :
    Atsuhiro Takahashi
    30-May-01-00:34:16
Organization : Theme :
    Graduate school of science, Nagoya university
    Theme 2
Address : Presentation :
    Furo-cho, Chikusa-ku, Nagoya 464-8601
    Poster or oral
Country : Abstract ID :
    JAPAN
    T2AT30May01003416
Phone : Fax :
    +81-52-789-3474
    +81-52-789-3436
E-mail :
    atsuhiro@ihas.nagoya-u.ac.jp