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Recent climate warming in the Arctic requires improvements in permafrost and carbon cycle monitoring, accomplished here by setting up long-term observation sites with high-quality in situ measurements of turbulent atmospheric energy fluxes applying the eddy covariance method and/or laser scintillometry in Arctic landscapes. Accurate quantification and well-adapted parameterizations of turbulent energy fluxes, e.g., during neutral to stable stratified conditions, are a fundamental problem in soil-snow-ice-vegetation-atmosphere interaction studies. We present results from the Arctic Turbulence Experiment (ARCTEX-2006) performed on the island of Svalbard, Norway, during the winter/spring transition 2006 that focus on data correction and quality assessment, on synoptic weather conditions, as well as site-specific micrometeorological features. A quality assessment and data correction adapted to the environmental conditions of polar regions demonstrates that specific measurement errors common at a high Arctic landscape could be minimized. We discuss the role of the intermittency of the turbulent atmospheric fluctuation of momentum and scalars, the existence of a disturbed vertical temperature profile (sharp inversion layer) close to the surface, and the relevance of possible free convection events for the snow or ice melt in the Arctic spring at Svalbard. Recommendations and improvements regarding the interpretation of eddy flux data as well as the arrangement of the instrumentation under polar distinct exchange conditions and (extreme) weather situations are presented. [ABSTRACT FROM AUTHOR]

The observed rapid climate warming in the Arctic requires improvements in permafrost and carbon cycle monitoring, accomplished by setting up long-term observation sites with high-quality in-situ measurements of turbulent heat, water and carbon fluxes as well as soil physical parameters in Arctic landscapes. But accurate quantification and well adapted parameterizations of turbulent fluxes in polar environments presents fundamental problems in soil-snow-ice-vegetation-atmosphere interaction studies. One of these problems is the accurate estimation of the surface or aerodynamic temperature T(0) required to force most of the bulk aerodynamic formulae currently used. Results from the Arctic-Turbulence-Experiment (ARCTEX-2006) performed on Svalbard during the winter/spring transition 2006 helped to better understand the physical exchange and transport processes of energy. The existence of an atypical temperature profile close to the surface in the Arctic spring at Svalbard could be proven to be one of the major issues hindering estimation of the appropriate surface temperature. Thus, it is essential to adjust the set-up of measurement systems carefully when applying flux-gradient methods that are commonly used to force atmosphere-ocean/land-ice models. The results of a comparison of different sensible heat-flux parameterizations with direct measurements indicate that the use of a hydrodynamic three-layer temperature-profile model achieves the best fit and reproduces the temporal variability of the surface temperature better than other approaches. [ABSTRACT FROM AUTHOR]

In early May 2006 a record high air pollution event was observed at Ny-Ålesund, Spitsbergen. An atypical weather pattern established a pathway for the rapid transport of biomass burning aerosols from agricultural fires in Eastern Europe to the Arctic. Atmospheric stability was such that the smoke was constrained to low levels, within 2 km of the surface during the transport. A description of this smoke event in terms of transport and main aerosol characteristics can be found in Stohl et al. (2007). This study puts emphasis on the radiative effect of the smoke. The aerosol number size distribution was characterised by lognormal parameters as having an accumulation mode centered around 165-185 nm and almost 1.6 for geometric standard deviation of the mode. Nucleation and small Aitken mode particles were almost completely suppressed within the smoke plume measured at Ny-Ålesund. Chemical and microphysical aerosol information obtained at Mt. Zeppelin (474 m a.s.l) was used to derive input parameters for a one-dimensional radiation transfer model to explore the radiative effects of the smoke. The daily mean heating rate calculated on 2 May 2006 for the average size distribution and measured chemical composition reached 0.55 K day-1 at 0.5 km altitude for the assumed external mixture of the aerosols but showing much higher heating rates for an internal mixture (1.7 K day-1). In comparison a case study for March 2000 showed that the local climatic effects due to Arctic haze, using a regional climate model, HIRHAM, amounts to a maximum of 0.3 K day-1 of heating at 2 km altitude (Treffeisen et al., 2005). [ABSTRACT FROM AUTHOR]