| |
|---|---|
 (134Kb)
|
80,163,000 Yen (FY2000; 40,010,000Yen)
The flux of carbon dioxide has been compared between the micro-meteorological eddy covariance method and the change of column concentration trapped in the temperature inversion at nighttime at Tomakomai, Hokkaido in August 2000. The accumulation of carbon dioxide in a temperature inversion by the respiration of forest ecosystem has been measured by a tethered balloon equipped with a sampling tube obtaining the altitude distribution up to 120 m. The distribution up to 2100 m has been obtained on board of a model aircraft equipped by an NDIR carbon dioxide sensor. The latter has been operated from early morning and the uptake of carbon dioxide in the temperature inversion by forest ecosystem has been evaluated. The nighttime respiration value thus obtained was more than twice of the value from micro-meteorological method, and the early morning photosynthesis was equivalent each other.
The flux of CO2 has been observed at Takayama site since 1998 with eddy covariance method. The Takayama site is located over a hill in the complex terrain, however, many kinds of disturbance induced by the complex terrain may influence the obtained data. The relations between local wind system and CO2 flux, local wind system and CO2 concentration, and turbulent fluxes and wind direction were investigated. The amount of nighttime CO2 flux measured at 27-m tower highly depends on the stability of the boundary layer. Observed momentum flux and latent heat flux depend on the wind direction. When the wind direction is westerly, latent heat flux should be underestimated, because relatively dry air, which is brought up along a steep cliff at the west side of the tower, intrudes into the surface layer. The CO2 concentration attains the daily maximum value at mid night due to the advection of local down slope wind.
CO2 flux, NEP, complex terrain, CO2 concentration change, mesoscale model