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Temperature regimes and turbulent heat fluxes across a heterogeneous canopy in an Alaskan boreal forest
Author(s) -
Starkenburg Derek,
Fochesatto Gilberto J.,
Cristóbal Jordi,
Prakash Anupma,
Gens Rudiger,
Alfieri Joseph G.,
Nagano Hirohiko,
Harazono Yoshinobu,
Iwata Hiroki,
Kane Douglas L.
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd022338
Subject(s) - canopy , atmospheric sciences , environmental science , sensible heat , black spruce , taiga , heat flux , planetary boundary layer , eddy covariance , tree canopy , turbulence , boreal , flux (metallurgy) , heat transfer , meteorology , ecology , geology , geography , ecosystem , chemistry , physics , mechanics , organic chemistry , biology
We evaluate local differences in thermal regimes and turbulent heat fluxes across the heterogeneous canopy of a black spruce boreal forest on discontinuous permafrost in interior Alaska. The data were taken during an intensive observing period in the summer of 2013 from two micrometeorological towers 600 m apart in a central section of boreal forest, one in a denser canopy (DC) and the other in a sparser canopy, but under approximately similar atmospheric boundary layer (ABL) flow conditions. Results suggest that on average 34% of the half‐hourly periods in a day are nonstationary, primarily during night and during ABL transitions. Also, thermal regimes differ between the two towers; specifically between midnight and 0500 Alaska Standard Time (AKST) it is about 3°C warmer at DC. On average, the sensible heat flux at DC was greater. For midday periods, the difference between those fluxes exceeded 30% of the measured flux and over 30 W m −2 in magnitude more than 60% of the time. These differences are due to higher mechanical mixing as a result of the increased density of roughness elements at DC. Finally, the vertical distribution of turbulent heat fluxes verifies a maximum atop the canopy crown (2.6 h ) when compared with the subcanopy (0.6 h ) and above canopy (5.1 h ), where h is the mean canopy height. We argue that these spatial and vertical variations of sensible heat fluxes result from the complex scale aggregation of energy fluxes over a heterogeneous canopy.