Üllar Rannik

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At present a network of over 100 field sites are measuring carbon dioxide, water vapor and sensible heat fluxes between the biosphere and atmosphere, on a nearly continuous basis. Gaps in the long term measurements of evaporation and sensible heat flux must be filled before these data can be used for hydrological and meteorological applications. We adapted(More)
Heightened awareness of global change issues within both science and political communities has increased interest in using the global network of eddy covariance flux towers to more fully understand the impacts of natural and anthropogenic phenomena on the global carbon balance. Comparisons of net ecosystem exchange (FNEE) responses are being made among(More)
| Lagrangian stochastic models and algorithms are constructed and justi ed for solving the footprint problem, namely, the problem of calculation of the mean concentration and the ux of particles at a xed point released from a source arbitrarily situated in the space. The direct and adjoint Monte Carlo algorithms are suggested, and rigorous justi cations are(More)
[1] Eddy covariance aerosol flux measurements were conducted at the Mace Head coastal station in the North East Atlantic. Footprint and micrometeorological analysis under clean marine air mass conditions indicated that fluxes representative of open ocean conditions could be derived during high tide conditions and an oceanic fetch. Sea-spray fluxes were(More)
| Forward and backward stochastic Lagrangian trajectory simulation methods are developed to calculate the footprint and cumulative footprint functions of concentration and ®uxes in the case when the ground surface has an abrupt change of the roughness height. The statistical characteristics to the stochastic model are extracted numerically from a closure(More)
This paper provides the first steps toward a regional-scale analysis of carbon (C) budgets. We explore the ability of the ecosystem model BIOME-BGC to estimate the daily and annual C dynamics of four European coniferous forests and shifts in these dynamics in response to changing environmental conditions. We estimate uncertainties in the model results that(More)
[1] Long-term measurements of sensible and latent heat and carbon dioxide fluxes were performed over a boreal lake in southern Finland using the direct micrometeorological eddy covariance (EC) technique. The water column was sampled weekly for dissolved carbon dioxide, and the CO2 flux was estimated also applying the concentration gradient method.(More)
M. Boy, T. Petäjä, M. Dal Maso, Ü. Rannik, J. Rinne, P. Aalto, A. Laaksonen, P. Vaattovaara, J. Joutsensaari, T. Hoffmann, J. Warnke, M. Apostolaki, E. G. Stephanou, M. Tsapakis, A. Kouvarakis, C. Pio, A. Carvalho, A. Römpp, G. Moortgat, C. Spirig, A. Guenther, J. Greenberg, P. Ciccioli, and M. Kulmala Dept. of Physical Sciences, University of Helsinki,(More)