%0 Journal Article
%T Revised eddy covariance flux calculation methodologies 每 effect on urban energy balance
%A Annika Nordbo
%A Leena Jˋrvi
%A Timo Vesala
%J Tellus B
%D 2012
%I Co-Action Publishing
%R 10.3402/tellusb.v64i0.18184
%X Eddy covariance (EC) measurements of turbulent fluxes of momentum, sensible heat and latent heat 每 in addition to net radiation measurements 每 were conducted for three consecutive years in an urban environment: Helsinki, Finland. The aims were to: (1) quantify the detection limit and random uncertainty of turbulent fluxes, (2) assess the systematic error caused by EC calculation-procedure choices on the energy balance residual and (3) report the energy balance of the world's northernmost urban flux station. The mean detection limits were about 10% of the observed flux, and the random uncertainty was 9每16%. Of all fluxes, the latent heat flux 每 as measured with a closed-path gas analyser 每 was most prone to systematic calculation errors due to water vapour interactions with tube walls: using a lag window that is too small can cause a 15% lack of data (due to the dependency of lag time on relative humidity) and omitting spectral corrections can cause on average a 26% underestimation of the flux. The systematic errors in EC calculation propagate into the energy balance residual and can be larger than the residual itself: for example, omitting spectral corrections overestimates the residual by 13% or 18% on average, depending on the analyser.
%K eddy covariance
%K urban
%K energy balance
%K flux uncertainty
%K flux error
%U http://www.tellusb.net/index.php/tellusb/article/view/18184/pdf_1