Abstract
In this paper we present one year of meteorological and flux measurements obtained near Ny-Ålesund, Spitsbergen. Fluxes are derived by the eddy covariance method and by a hydrodynamic model approach (HMA) as well. Both methods are compared and analyzed with respect to season and mean wind direction. Concerning the wind field we find a clear distinction between 3 prevailing regimes (which have influence on the flux behavior) mainly caused by the topography at the measurement site. Concerning the fluxes we find a good agreement between the HMA and the eddy covariance method in cases of turbulent mixing in summer but deviations at stable conditions, when the HMA almost always shows negative fluxes. Part of the deviation is based on a dependence of HMA fluxes on friction velocity and the influence of the molecular boundary layer. Moreover, the flagging system of the eddy covariance software package TK3 is briefly revised. A new quality criterion for the use of fluxes obtained by the eddy covariance method, which is based on integral turbulence characteristics, is proposed.
Highlights
Climate in the Arctic is known to show stronger variability in surface temperature than elsewhere in the Northern hemisphere, a phenomenon which is called “Arctic amplification” [1, 2]
Concerning the fluxes we find a good agreement between the hydrodynamic model approach (HMA) and the eddy covariance method in cases of turbulent mixing in summer but deviations at stable conditions, when the HMA almost always shows negative fluxes
Several topics are obvious at first view on these plots: both figures show that the results of the HMA are limited in the negative temperature range in the way that positive sensible heat fluxes in the negative temperature range are not or only partially possible
Summary
Climate in the Arctic is known to show stronger variability in surface temperature than elsewhere in the Northern hemisphere, a phenomenon which is called “Arctic amplification” [1, 2]. Another way to calculate the sensible heat flux, not often used but quite sophisticated, is a hydrodynamic three-layer model approach, developed originally for flux measurements above sea-water by Foken [14, 15], first applied above snow by Sodemann and Foken [29], and used for flux calculations in NyAlesund by Luers and Bareiss [12] and Jocher [30] This approach uses the temperature difference between surface and measurement height and a profile coefficient Γ, which is derived by separated integrating over the very small molecular boundary layer (
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