Influence of Source/Sink Distributions to the Flux-Profile Relationships Observed in a Black Spruce Forest
Abstract
The flux-profile relationships are fundamental to determine turbulent fluxes. In the surface layer, normalized gradients have been expressed as universal functions of the atmospheric stability. However, in the roughness sublayer, observed normalized gradients are systematically smaller than that expected from the universal functions, and there is no consensus to solve the problem. On the other hand, the normalized gradient becomes larger than that expected from the universal functions for the surface layer in the vicinity of source/sink (Coppin et al., 1986, Boundary-Layer Meteorol., 35, 167-191). Clarifying what affects the flux- profile relationships in the roughness sublayer is important to determine fluxes by the gradient method, especially for low concentration gasses. We examined seasonal variations of the flux-profile relationship using observed momentum, sensible heat, water vapor and carbon dioxide in a black spruce forest (64°52'N, 147°51'W) in Fairbanks, Alaska, USA. In this site, the source/sink distributions for water vapor and carbon dioxide changed from understory in early spring to overstory in summer, whereas those for momentum and sensible heat did not change significantly. The flux-profile relationships reflected the seasonal characteristics of the source/sink distributions of the canopy. The result suggests that when applying the gradient method to determine the flux, it is necessary to determine the turbulent transfer coefficient by conditionally selecting the data which reflected the same source/sink distributions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H11A0720I
- Keywords:
-
- 0315 Biosphere/atmosphere interactions (0426;
- 1610);
- 0428 Carbon cycling (4806);
- 1610 Atmosphere (0315;
- 0325);
- 1631 Land/atmosphere interactions (1218;
- 1843;
- 3322);
- 1818 Evapotranspiration