Seasonal and interannual variation in water vapor and heat fluxes in a West Siberian continental bog

Abstract

[1] The seasonal and interannual variation in the energy fluxes of a West Siberian continental bog were measured from April to October in 1999 and 2000 using the eddy covariance method. The energy balance closure rate (=[ sensible + latent heat fluxes]/ [ available energy]) ranged from similar to 0.8 to 0.9 and showed a better energy balance and less scattering using the soil heat flux estimated from an area-averaged soil thermal parameter rather than from a plot-based measurement. The net radiation (R-n) increased drastically after snowmelt because the surface albedo (a) dropped from its highest value to its lowest value over the course of the snowmelt. The snowmelt water raised the water table (z(wt)) to its highest level; it then gradually decreased. The seasonal and interannual variation in a, which ranged from 0.09 - 0.19, depended on z(wt), because surface wetness was closely related to zwt through the capillary uptake of Sphagnum moss. The seasonal variation in the latent heat flux ( lE) was similar to that in R-n. The largest lE was observed in the middle of June, and was similar to 120 Wm(-2) (4.2 mm d(-1)) in both years. Conversely, the sensible heat flux ( H) did not show an obvious seasonal pattern and was lower than lE during the growing season. The Bowen ratio (B-r) in the early growing season was 0.57 and 0.60, and the values in the peak growing season were 0.65 and 0.78, in 1999 and 2000, respectively. The lower B-r was related to the higher z(wt); specifically, it was due to the wetter surface conditions. An interannual comparison of the monthly mean atmospheric water vapor deficit (deltae) and lE showed a significant relationship with a higher lE observed in the year with a higher deltae. Therefore in the bog studied the interannual variation in the water vapor flux was controlled mainly by z(wt) and deltae